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Soilmass Deformation Simulator Experiment Investigation under Water-Soil's Long-Term Chemical Interaction and Certain Load in Urban
This paper general have summarized the inner connection among city region, underground water environmental variation and soil structural strength, have defined the mini scale structure concept of the soil. On the basis of the four basic forms of water-soil interaction, this paper have discussed the mechanism of water-soil's chemical interaction. From the chemical action angle which is easy to be
Yi Nianping; Zhang Xingui; Qin Junqing
Dynamics of the water-pipeline-soil interaction
Pipeline designers must be able to predict the pipeline response to ocean forces in terms of motion amplitude, accumulated displacements, stresses in the steel pipe, and the number of stress oscillations. The mathematical model presented here takes into account the complex environmental and pipeline conditions affecting a pipeline's response to dynamic water-pipe-seabed interaction. The described analysis yields time histories of
K. Karal; S. A. Halvorsen
Influence of fungal-soil water interactions on phytophthora root rot of alfalfa
Phytophthora root rot of alfalfa (Medicago sativa L.) is a serious problem in wet soils. This disease is caused by Phytophthora megasperma f. sp. medicaginis. The influence of soil-water interactions with P. megasperma f. sp. medicaginis and other factors on the severity of phytophthora root rot of mature alfalfa plants (10¢12 weeks) was studied in greenhouse experiments. Severe and reproducible
A. K. Alva; L. E. Lanyon; K. T. Leath
Finite element modelling for water waves-soil interaction
The soil permeability and shear modulus of many marine sediments vary with depth because of consolidation under overburden pressure. However, conventional theories for wave-induced soil response have assumed a homogeneous porous seabed, with constant soil permeability and shear modulus. This paper presents a finite element model for the wave-induced soil response in a porous seabed, with variable permeability and shear
Yee Shown Lin
Dynamics of the water-pipeline-soil interaction
Pipeline designers must be able to predict the pipeline response to ocean forces in terms of motion amplitude, accumulated displacements, stresses in the steel pipe, and the number of stress oscillations. The mathematical model presented here takes into account the complex environmental and pipeline conditions affecting a pipeline's response to dynamic water-pipe-seabed interaction. The described analysis yields time histories of pipeline motion and steel pipe stresses.
Karal, K.; Halvorsen, S.A.
Gravel admix, vegetation, and soil water interactions in protective barriers: Experimental design, construction, and initial conditions
The purpose of this study is to measure the interactive effects of gravel admix and greater precipitation on soil water storage and plant abundance. The study is one of many tasks in the Protective Barrier Development Program for the disposal of Hanford defense waste. A factorial field-plot experiment was set up at the site selected as the borrow area for barrier topsoil. Gravel admix, vegetation, and enhanced precipitation treatments were randomly assigned to the plots using a split-split plot design structure. Changes in soil water storage and plant cover were monitored using neutron probe and point intercept methods, respectively. The first-year results suggest that water extraction by plants will offset gravel-caused increases in soil water storage. Near-surface soil water contents were much lower in graveled plots with plants than in nongraveled plots without plants. Large inherent variability in deep soil water storage masked any effects gravel may have had on water content below the root zone. In the future, this source of variation will be removed by differencing monthly data series and testing for changes in soil water storage. Tests of the effects of greater precipitation on soil water storage were inconclusive. A telling test will be possible in the spring of 1988, following the first wet season during which normal precipitation is doubled. 26 refs., 9 figs., 9 tabs.
Waugh, W.J.
Dynamics of the water-pipeline-soil interaction
A design engineer-oriented approach to determining the pipeline dynamic response to ocean forces accounting for complex environmental and pipeline conditions is presented. The described analysis yields time histories of pipeline motion and steel pipe stresses induced by water motion. Sinusoidal variation of normal water particle motion in time and along the pipeline, waves, flexural rigidity of pipe, damaged concrete coating,
K. Karal; S. A. Halvorsen
Barrier erosion control test plan: Gravel mulch, vegetation, and soil water interactions
Soil erosion could reduce the water storage capacity of barriers that have been proposed for the disposal of near-surface waste at the US Department of Energy's Hanford Site. Gravel mixed into the top soil surface may create a self-healing veneer that greatly retards soil loss. However, gravel admixtures may also enhance infiltration of rainwater, suppress plant growth and water extraction, and lead to the leaching of underlying waste. This report describes plans for two experiments that were designed to test hypotheses concerning the interactive effects of surface gravel admixtures, revegetation, and enhanced precipitation on soil water balance and plant abundance. The first experiment is a factorial field plot set up on the site selected as a soil borrow area for the eventual construction of barriers. The treatments, arranged in a a split-split-plot design structure, include two densities of gravel admix, a mixture of native and introduced grasses, and irrigation to simulate a wetter climate. Changes in soil water storage and plant cover are monitored with neutron moisture probes and point intercept sampling, respectively. The second experiment consists of an array of 80 lysimeters containing several different barrier prototypes. Surface treatments are similar to the field-plot experiment. Drainage is collected from a valve at the base of each lysimeter tube, and evapotranspiration is estimated by subtraction. The lysimeters are also designed to be coupled to a whole-plant gas exchange system that will be used to conduct controlled experiments on evapotranspiration for modeling purposes. 56 refs., 6 figs., 8 tabs.
Waugh, W.J.; Link, S.O. (Pacific Northwest Lab., Richland, WA (USA))
Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals
NASA Astrophysics Data System (ADS)
In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit ?18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The ?18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured ?18O values up to 1.55ē relative to pure water at 5% water content, declining to 0.49ē depletion at 30% water content. K-montmorillonite enriched measured ?18O values up to 0.86ē at 5% water content, declining to 0.11ē enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the ?18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral-water interactions.
Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald
NSDL National Science Digital Library
Trees, soil and water: Journey to Forever - health care for mountains, trees for deserts, trees for people, forest, forestry, deforestation, erosion, soil conservation, water conservation, desertification.
Addison, Keith
Interaction and independence on methane oxidation of landfill cover soil among three impact factors: water, oxygen and ammonium
To understand the influence patterns and interactions of three important environmental factors, i.e. soil water content, oxygen\\u000a concentration, and ammonium addition, on methane oxidation, the soils from landfill cover layers were incubated under full\\u000a factorial parameter settings. In addition to the methane oxidation rate, the quantities and community structures of methanotrophs\\u000a were analyzed to determine the methane oxidation capacity of
Pinjing He; Na Yang; Wenjuan Fang; Fan L³; Liming Shao
Plant interactions with changes in coverage of biological soil crusts and water regime in Mu Us Sandland, China.
Plant interactions greatly affect plant community structure. Dryland ecosystems are characterized by low amounts of unpredictable precipitation as well as by often having biological soil crusts (BSCs) on the soil surface. In dryland plant communities, plants interact mostly as they compete for water resources, and the direction and intensity of plant interaction varies as a function of the temporal fluctuation in water availability. Since BSCs influence water redistribution to some extent, a greenhouse experiment was conducted to test the hypothesis that the intensity and direction of plant interactions in a dryland plant community can be modified by BSCs. In the experiment, 14 combinations of four plant species (Artemisia ordosica, Artemisia sphaerocephala, Chloris virgata and Setaria viridis) were subjected to three levels of coverage of BSCs and three levels of water supply. The results show that: 1) BSCs affected plant interaction intensity for the four plant species: a 100% coverage of BSCs significantly reduced the intensity of competition between neighboring plants, while it was highest with a 50% coverage of BSCs in combination with the target species of A. sphaerocephala and C. virgata; 2) effects of the coverage of BSCs on plant interactions were modified by water regime when the target species were C. virgata and S. viridis; 3) plant interactions were species-specific. In conclusion, the percent coverage of BSCs affected plant interactions, and the effects were species-specific and could be modified by water regimes. Further studies should focus on effects of the coverage of BSCs on plant-soil hydrological processes. PMID:24498173
Gao, Shuqin; Pan, Xu; Cui, Qingguo; Hu, Yukun; Ye, Xuehua; Dong, Ming
Interactions between soil stability and pore water pressure as a function of the loading time during compaction test
Soil tillage and the accompanying compaction, can dramatically alter soil physical properties. Quantifying soil compaction modifications of soil bulk density is often used while interactions between hydraulic and mechanical processes are seldom addressed. The pre-compression stress value is used to predict irreversible soil deformation. We analysed the effects of mechanical stress and the time required for changes in soil strength
O. Fazekas; R. Horn
The movement of water and chemicals into and through soils has a large impact upon our environment and the entire ecosystem. Understanding these processes is of great importance in managing, utilizing, and protecting our natural resources. This software was written to enhance our...
Uncoupled axial, flexural, and circumferential pipe¢soil interaction analyses of partially supported jointed water mains
Pipelines used in the distribution of potable water are a vital part of everyday life. The pipelines buried in soil-backfill are exposed to different deleterious reactions; as a result, the design factor of safety may be significantly degraded and, consequently, pipelines may fail prematurely. Proactive pipeline management, which entails optimal maintenance, repair, or replacement strategies, helps increase the longevity of
Balvant Rajani; Solomon Tesfamariam
Interaction of Actinide Species with Microorganisms & Microbial Chelators: Cellular Uptake, Toxicity, & Implications for Bioremediation of Soil & Ground Water.
Microorganisms influence the natural cycle of major elements, including C, N, P, S, and transition metals such as Mn and Fe. Bacterial processes can also influence the behavior of actinides in soil and ground water. While radionuclides have no known biological utility, they have the potential to interact with microorganisms and to interfere with processes involving other elements such as Fe and Mn. These interactions can transform radionuclides and affect their fate and transport. Organic acids, extruded by-products of cell metabolism, can solubilize radionuclides and facilitate their transport. The soluble complexes formed can be taken up by the cells and incorporated into biofilm structures. We have examined the interactions of Pu species with bacterial metabolites, studied Pu uptake by microorganisms and examined the toxicity of Pu and other toxic metals to environmentally relevant bacteria. We have also studied the speciation of Pu(IV) in the presence of natural and synthetic chelators.
Hakim Boukhalfa Mary, P. Neu Alvin Crumbliss
Artificial Hillslopes at Biosphere 2: Exploring Soil-Water-Atmosphere-Plant Interactions in a Changing Environment
NASA Astrophysics Data System (ADS)
The partitioning of precipitation upon the land surface into evaporation, transpiration, infiltration, recharge, runoff and stream flow and subsequent controls on hydrologic storages and flow paths remains an open research question. Experimental studies to date have suffered from scale issues and uncertain boundary conditions. The Biosphere 2 Experimental Biome's unique spatial scale provides the opportunity for controlled experiments at a relevant scale, bridging the gap between controlled, laboratory-scale experiments and field experiments under natural conditions. The B2 Artificial Hillslopes Experiment is designed as a community effort. The objective of the experiment is to explore how climate, soil and vegetation interact and drive the geomorphological and biogeochemical evolution of the hydrologic system in a hillslope. Hillslopes were chosen as flow domains because they represent a fundamental landscape unit, controlling the hydrologic response of catchments. Three replications of a hillslope template with evolving vegetation cover will be exposed to controlled perturbations of climate, simulating the impact of a changing future climate. Experiments are planned to run for at least 10 years. The first phase of the experiment has included pre-construction modeling efforts in hydrology, ecology, geomorphology and geochemistry that aim at supporting the design and construction process of the artificial hillslopes as well as providing initial model predictions of the anticipated evolution of the vegetation-hillslope systems. Based on hydrologic modeling results, a zero-order watershed geometry and loamy sand texture of the soil material on a 10 deg hillslope were determined to generate a variety of hydrologic conditions favorable for geochemical weathering, plant and soil ecology. Using this hillslope configuration, the expected evolution of the hillslopes over the course of the experimental time and resulting modification of the hydrologic behavior were assessed in numerical experiments. These modeling results will be compared to future experimental data. Using artificial hillslopes in a climate-controlled environment offers exciting research opportunities to test hypotheses, validate models and observe emergent behavior, thereby advancing our understanding of critical zone processes in a changing environment.
Hopp, L.; Troch, P.; Huxman, T.; Harman, C.; Desilets, S.; Dontsova, K.; Chorover, J.; Kling, S.; Pelletier, J.; Paniconi, C.; Ivanov, V.; Jenerette, D.; Sivapalan, M.; McDonnell, J.
Maize canopies under two soil water regimes
Seasonal course of evapotranspiration and of canopy CO2 assimilation are determined by interactions among the plant, aerial, and soil factors over time and culminate in the total water requirement and primary productivity of a crop. In this study, maize was grown for two seasons in large fields under two contrasting soil water regimes (WET and DRY), and monitored for canopy
Pasquale Steduto; Theodore C Hsiao
Boron in irrigation water and its interactions with soil and plants: an example of municpal landfill leachate reuse
In several countries, leachate is successfully treated by recirculation to the vegetated landfill cover, as it contains several micro and macronutrients for plant growth. However, the proportion and concentration of some parameters can negatively affect the plant growth and soil quality in the case of high leachate input. The presented research discusses B in leachate and its interactions with soil
Maja ZUPAN?I? JUSTIN
A variety of chemical equilibrium models have been developed to help assess environmental chemistry problems, but few were specifically developed as research and teaching tools for use in conjunction with soil chemistry experiments. MANE model was developed to calculate equilibri...
Soils - Part 2: Physical Properties of Soil and Soil Water
NSDL National Science Digital Library
This lesson will help you understand the major components of the physical properties of soil. You will learn such terms as texture, aggregation, soil structure, bulk density, and porosity as it relates to soils. You will learn how soil holds and transmits water and cultural practices that enhance or degrade physical properties of the soil.[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.
Antimony interactions with heterogeneous complexants in waters, sediments and soils: A review of data obtained in bulk samples
Published studies where antimony association with colloidal and particulate phases is studied in waters, soils and sediments are reviewed. The techniques considered range from the simple calculation of partition coefficients, the application of size-based speciation methods or sequential extraction techniques to the use of more sophisticated techniques such as X-ray absorption spectroscopy (XAS). What these methods have in common is
Montserrat Filella
Hydraulic Redistribution of Soil Water in a Drained Loblolly Pine Plantation: Quantifying Patterns and Controls over Soil-to-Root and Canopy-to-Atmosphere Interactions
NASA Astrophysics Data System (ADS)
The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on water and carbon balances are not well studied. Quantification of evapotranspiration (ET), tree transpiration and their biophysical regulation are needed for assessing forest water management options. We characterized vertical variation in the diurnal and seasonal soil volumetric water content at 10 cm intervals to evaluate changes in water availability for root uptake and monitored eddy covariance ET and tree transpiration (sap flux) in a drained Loblolly pine (Pinus taeda L.) plantation. We also quantified the magnitude of hydraulic redistribution (HR), the passive movement of soil water from deep to shallow roots, to identify factors affecting the seasonal dynamics of root water uptake, root and plant water potentials and stomatal conductance. Soil water content varied with soil depth and total water use from the upper 1m peaked between 4 and 6.5 mm/day during the growing season and was strongly correlated and similar to ET (ET represented 90-95% of total water depletion). After periods of more than 10 days without rain, water extraction shifted to the deeper layers, and recharge from HR approached 0.5 mm/day in the upper 60 cm. However, the upper 30cm accounted for 40% of total water depletion from the upper 1m at peak water uptake (>4 mm/day), and increased to 65% during days of low water uptake (<2 mm/day), illustrating the contribution of deeper roots to water uptake during days of high evaporative demand. This result was supported by the fact that deep roots (from 30-50cm) accounted for 65% of the total water redistributed. Because of stomatal regulation to prevent water potentials from reaching critical values that would cause significant loss of tree hydraulic conductivity, maximum tree transpiration during high evaporative demand remained constant at around 3 mm/day. Tree transpiration represented on average 60% of ET. However, it represented only 50% of ET on days following rain events and up to 80% of ET after prolonged periods without rain. We propose that HR prevented predawn water potentials from decreasing during periods of increasing soil water deficit, therefore maintaining a constant driving force for water uptake of around 1.7 MPa. It was thought that HR was an important mechanism for maintaining shallow root function during drought and preventing total stomatal closure but our study shows that even in wet conditions with soil water potentials never dropping below -0.6 MPa, HR may play a role in wetland hydrological balance. This first approximation of the extent of HR in this ecosystem suggests that it is likely to be an important process in wet forests of North Carolina.
Domec, J.; Noormets, A.; King, J. S.; Sun, G.; McNulty, S. G.; Gavazzi, M. J.; Strickland, S.; Boggs, J. L.
Field study of gravel admix, vegetation, and soil water interactions: Protective Barrier Program Status Reprt - FY 1989
Pacific Northwest Laboratory (PNL) and Westinghouse Hanford Company (Westinghouse Hanford) are collaborating on a field study of the effects of gravel admixtures on plant growth and soil water storage in protective barriers. Protective barriers are engineered earthern covers designed to prevent water, plants, and animals from contacting buried waste and transporting contaminants to groundwater or the land surface. Some of the proposed designs include gravel admixtures or gravel mulches on the barrier surface to control soil loss by wind and runoff. The purpose of this study is to measure, in a field setting, the influence of surface gravel additions on soil water storage and plant cover. The study plots are located northwest of the Yakima Gate in the McGee Ranch old field. Here we report the status of work completed in FY 1989 on the creation of a data management system, a test of water application uniformity, field calibration of neutron moisture gages, and an analysis of the response of plants to various combinations of gravel admixtures and increased rainfall. 23 refs., 11 figs., 6 tabs.
Waugh, W.J.; Thiede, M.E.; Kemp, C.J.; Cadwell, L.L. Link, S.O.
Soil and Human Interactions in Maya Wetlands
NASA Astrophysics Data System (ADS)
Since the early 1990s, we have studied Maya interaction with soils in Mexico, Belize, Guatemala, and elsewhere. We studied upland and lowland soils, but here we focus on seasonal or 'Bajo' wetlands and perennial wetlands for different reasons. Around the bajos, the ancient Maya focused on intensive agriculture and habitation despite the difficulties their Vertisol soils posed. For the perennial wetlands, small populations spread diffusely through Mollisol and Histisol landscapes with large scale, intensive agro-ecosystems. These wetlands also represent important repositories for both environmental change and how humans responded in situ to environmental changes. Work analyzing bajo soils has recorded significant diversity but the soil and sediment record shows two main eras of soil instability: the Pleistocene-Holocene transition as rainfall fluctuated and increased and tropical forest pulsed through the region, and the Maya Preclassic to Classic 3000 to 1000 BP as deforestation, land use intensity, and drying waxed and waned. The ancient Maya adapted their bajo soil ecosystems successfully through agro-engineering but they also withdrew in many important places in the Late Preclassic about 2000 BP and Terminal Classic about 1200 BP. We continue to study and debate the importance of perennial wetland agro-ecosystems, but it is now clear that Maya interaction with these soil landscapes was significant and multifaceted. Based on soil excavation and coring with a broad toolkit of soil stratigraphy, chemistry, and paleoecology from 2001 to 2013, our results show the ancient Maya interacted with their wetland soils to maintain cropland for maize, tree crops, arrow root, and cassava against relative sea level rise, increased flooding, and aggradation by gypsum precipitation and sedimentation. We have studied these interactions across an area of 2000 km2 in Northern Belize to understand how Maya response varied and how these soil environments varied over time and distance. Most areas dealt with water table rise and gypsum aggradation from extremely sulfur- and calcium-rich water sources. Thus far we have evidence for Archaic to Classic aggradation (5000 BP to the present) and Classic period fields and canals as mostly piecemeal attempts by the Maya to adapt to these and other environmental changes. Wetland fields were mainly Classic period systems (1500 to 1000 BP) but varied from long- to short-lived. We found one example of a very Late/Terminal Classic (c. 1200 BP), preplanned reclamation project on a floodplain. One system had some reoccupation in the Postclassic about 800 BP. These findings and a recent discovery in Campeche, MX display the burgeoning evidence for intricate Maya connections with tropical wetland soils.
Beach, Timothy; Luzzadder-Beach, Sheryl
Boron isotopes in different grain size fractions: Exploring past and present water-rock interactions from two soil profiles (Strengbach, Vosges Mountains)
NASA Astrophysics Data System (ADS)
In the present study, we test the ability of B isotopes to trace past and present weathering reactions in the case of two forest soils formed by a polyphasic sequence involving early hydrothermal alteration of the bedrock and pedogenesis. We provide B chemical and isotopic compositions in two 2-m soil profiles sampled in the Strengbach watershed (Vosges, France). The two soils belong to different soil series, an ochreous podzol (Haplorthod) and a brown acidic soil (dystrochrept), developed on the same granitic bedrock but differently affected by hydrothermal alteration. Separated granulometric fractions and bulk soil samples have been analyzed. Coarse particles are mostly composed of primary minerals and show a clear anti-correlation between ?11B and Mg/Al, reflecting various grades of the early hydrothermal alteration. The finest particles (clay-size fractions) deviate from this "hydrothermal" trend and are diagnostic of pedogenic processes occurring after B exchange with the surrounding 11B-rich soil solution. Examination of the B distribution in different particle size fractions also indicates that B is transferred from the coarse sand fraction in deeper soil layers to the clay fraction in the upper layers. The intermediate size fractions are found to play only a secondary role in the soil-forming reactions. The two soils show distinct B isotope profiles, which are consistent with the different pedogenic processes that govern their formation. In the podzolic soil, ?11B can be explained by a simple model in which pedogenesis occurs by continuous dissolution of primary minerals and precipitation of secondary ones. In the brown acid soil, a more complex model that includes the precipitation of clay minerals in the deep horizon and their gradual dissolution in the upper soil layers accounts for the observed results. Additionally, residual hydrothermal illites are more resistant to weathering and are found in the clay fraction where they were directly inherited from the dislocation of coarser grains in which they were encapsulated. On a broader scale, the large B isotopic fractionation during water-rock interactions greatly facilitates the quantification of matter exchange between soil solutions and solids and the determination of global weathering rates. The data from the present study demonstrate that the determination of B isotopes in different particle size fractions can reveal the relative importance of source and process effects during weathering.
Lemarchand, D.; Cividini, D.; Turpault, M.-P.; Chabaux, F.
Container Soil-Water Reactions.
ERIC Educational Resources Information Center
Presented is an activity that illustrates the relationship between the soil found in containers and soil in the ground including the amount of air and water found in each. Sponges are used to represent soil. Materials, procedures, and probable results are described. (KR)
Spomer, L. Art; Hershey, David R.
Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2
Elevated CO2 interacts with soil water and microsite to affect soil microbesFungal biomarkers indicate active metabolism of newer C under elevated CO2Soil water availability is key to Mojave Desert soil C and nutrient cycles
V. L. Jin; S. M. Schaeffer; S. E. Ziegler; R. D. Evans
Antimony interactions with heterogeneous complexants in waters, sediments and soils: A review of data obtained in bulk samples
NASA Astrophysics Data System (ADS)
Published studies where antimony association with colloidal and particulate phases is studied in waters, soils and sediments are reviewed. The techniques considered range from the simple calculation of partition coefficients, the application of size-based speciation methods or sequential extraction techniques to the use of more sophisticated techniques such as X-ray absorption spectroscopy (XAS). What these methods have in common is that they are applied directly to bulk samples and that, with the exception of XAS, they give operationally defined results, which are very often difficult to interpret and compare. In the case of the extraction methods, which are the most commonly used, this difficulty is compounded by the tendency of many authors to endlessly modify the experimental procedures. Antimony does not seem to associate to any significant extent with colloidal and particulate phases in waters. However, at the same time, it appears not to be easily extractable from soils where, even if it is usually present to a certain extent in 'iron oxide' fractions in sequential extraction methods, most remains in the so called 'residual' fraction. Unfortunately, the direct application of XAS techniques to real environmental samples, which could help to clarify antimony binding by solid phases, is precluded in most systems because of their insensitivity; only a few heavily polluted systems have been studied so far using these techniques. In these studies antimony is present as Sb(V) in soils and significantly bound by iron oxide phases.
Filella, Montserrat
Interaction of Herbicides and Soil Microorganisms.
National Technical Information Service (NTIS)
The introduction of microorganisms with specific degradative capacities into the soil was shown to be a possible means of ridding the soil of contaminating chemicals. An investigation of the interactions of soil microorganisms and several groups of herbic...
Soil¢water characteristic curves of Singapore residual soils
Soil¢water characteristic curves were obtained for a number of Singapore residual soil samples. Soil samples were obtained from the two main residual soil formations, the Jurong sedimentary formation and the Bukit Timah granitic formation, at various depths. The effect of weathering on the shape of the soil¢water characteristic curve is examined. As the test procedure in obtaining the soil¢water characteristic
S. S. Agus; E. C. Leong; H. Rahardjo
Soil Moisture Data Assimilation in Soil Water Flow Modeling
Soil water flow modeling has multiple applications. This modeling is based on simplifications stemming from both conceptual uncertainty and lack of detailed knowledge about parameters. Modern soil moisture sensors can provide detailed information about changes in soil water content in time and with depth. This information can be used for data assimilation in soil water flow modeling. The ensemble Kalman
Y. A. Pachepsky; A. Guber; D. Jacques; F. Pan; M. van Genuchten; R. E. Cady; T. J. Nicholson
Estimating soil water retention using soil component additivity model
NASA Astrophysics Data System (ADS)
Soil water retention is a major soil hydraulic property that governs soil functioning in ecosystems and greatly affects soil management. Data on soil water retention are used in research and applications in hydrology, agronomy, meteorology, ecology, environmental protection, and many other soil-related fields. Soil organic matter content and composition affect both soil structure and adsorption properties; therefore water retention may be affected by changes in soil organic matter that occur because of both climate change and modifications of management practices. Thus, effects of organic matter on soil water retention should be understood and quantified. Measurement of soil water retention is relatively time-consuming, and become impractical when soil hydrologic estimates are needed for large areas. One approach to soil water retention estimation from readily available data is based on the hypothesis that soil water retention may be estimated as an additive function obtained by summing up water retention of pore subspaces associated with soil textural and/or structural components and organic matter. The additivity model and was tested with 550 soil samples from the international database UNSODA and 2667 soil samples from the European database HYPRES containing all textural soil classes after USDA soil texture classification. The root mean square errors (RMSEs) of the volumetric water content estimates for UNSODA vary from 0.021 m3m-3 for coarse sandy loam to 0.075 m3m-3 for sandy clay. Obtained RMSEs are at the lower end of the RMSE range for regression-based water retention estimates found in literature. Including retention estimates of organic matter significantly improved RMSEs. The attained accuracy warrants testing the 'additivity' model with additional soil data and improving this model to accommodate various types of soil structure. Keywords: soil water retention, soil components, additive model, soil texture, organic matter.
Zeiliger, A.; Ermolaeva, O.; Semenov, V.
Effect of burning temperature on water repellency and aggregate stability in forest soils under laboratory conditions
Soil water repellency is usually modified after wildfires by the combustion of soil organic matter and plant residues, and is considered to be the cause of important changes in the hydrological response of burned soils. In this research, the interactions between burning temperature, soil water content, water repellency and stability of aggregates have been studied. Samples collected from soils under
Lorena M. Zavala; Arturo J. P. Granged; Antonio Jordßn; Gema Bßrcenas-Moreno
A new model for humic materials and their interactions with hydrophobic organic chemicals in soil-water or sediment-water systems
A generalized model of humic materials in soils and sediments, which is consistent with their observed properties, is presented. This model provides a means of understanding the interaction of hydrophobic pollutants with humic materials. In this model, it is proposed that the humic materials in soils and sediments consist of a number of different oligomers and simple compounds which result from the partial degradation of plant remains. These degradation products are stabilized by incorporation into humic aggregates bound together by weak bonding mechanisms, such as hydrogen bonding, pi bonding, and hydrophobic interactions. The resulting structures are similar to micelles or membranes, in which the interiors of the structures are hydrophobic and the exteriors are hydrophilic. Hydrophobic compounds will partition into the hydrophobic interiors of the humic micelles or "membrane-like" structures. ?? 1986.
Wershaw, R. L.
SOIL & WATER MANAGEMENT & CONSERVATION Landscape and Conservation Management Effects on Hydraulic Properties of a Claypan Soil Toposequence
Information on the effects of landscape and its interaction with management on soil hydraulic properties is scarce. Our objective was to investigate the effects and interactions of landscape position and conservation management systems (e.g., reduced tillage or permanent grass) on soil bulk density, saturated hydraulic conductivity (Ksat), soil water retention, and pore-size distributions for claypan soils in central Missouri. Landscape
S. H. Anderson; E. J. Sadler; K. A. Sudduth
Can the soil properties affect the O and H isotopic composition of the soil water?
NASA Astrophysics Data System (ADS)
Understanding the dynamic of the soil water content is of primary importance since it is the vector of the matter exchange between soil and the other compartments of watersheds. The soil water is the phase, which is best suited to characterize the current dynamics in the soil and to provide information on mid- to long-term soil processes. Oxygen and Hydrogen stable isotopes of water are now currently used in hydrological studies to inform on water mixing and residence time in the soil and greatly contribute to improve our understanding of soil-water interactions. However, as of today the influence of biogeochemical processes on the spatio-temporal variability of ?18O and ?D of the soil solutions was rarely quantified. The Oxygen and Hydrogen exchanges between the soil water and the other soil compartments (living organisms, mineral, exchange capacity, organic matter) are still poorly studied and require deeper investigations. For instance, the weathering of silicate minerals produces O2+ in the soil solution, exchange capacity in acidic soils releases quantity of H+ in the soil solution and the degradation of the organic matter could also impact the Oxygen and Hydrogen isotope ratios of the soil water. But, are we able to quantify the contribution of these different processes to the Oxygen and Hydrogen isotopic composition of the soil water? In order to address this question, we set up a laboratory experiment with one liter soil columns of a 2mm-sieved and air-dried soil. The goal of the experiment was to observe the variation of the water Oxygen and Hydrogen isotopic composition at two different depths of these soil columns starting from the field capacity to the complete drying of the soil. Water with a known isotopic composition was used to saturate the soil matrix and we observed the deviation from this initial composition at the different depths during the drying of the soil using ceramic cup lysimeters. Three steps of saturation were applied during the entire experiment. The deviation from the initial isotopic composition becomes significant in the soil waters at the different depths after two weeks of experiment and increases until reaching a threshold at the end of the experiment. After each new saturation step, the isotopic composition of the input water is not conserved anymore in the collected solutions and increases instantaneously. This observation may illustrate the potential for the soil bio-physico-chemical activities to contribute to the O and H composition of the soil water. These preliminary results allowed us to evaluate the contribution of the evaporation process in the Oxygen and Hydrogen isotopic fractionation and to deduce the potential contribution of soil compartments.
Hissler, Christophe; Legout, Arnaud; Barnich, Franńois; Stoll, Martine; Klaus, Julian
Water Extraction from Martian Soil
NASA Astrophysics Data System (ADS)
With the projected growth in space exploration, several milestones have been set for future space programs. One milestone in particular is the landing of a human on the planet Mars. However, one major barrier to the successful placement of persons on Mars is a lack of water on the Martian surface. Because of the massive quantity of water that would be necessary for a mission to Mars, it is not possible to transport the amount necessary from Earth to Mars. Water would be necessary for human consumption as well as a base for jet propulsion fuel. Past unmanned missions to Mars, such as the Viking missions of the 1970's, have revealed the presence of small quantities of water in Martian soil. Research has determined that the water in the soil can be recovered when the soil is heated to a temperature between 200 C and 500 C. Team JFEET has designed a system with the capability to extract water from the soil of Mars, and then meter and deliver the water to a storage tank for later use.
Wiens, J.; Bommarito, F.; Blumenstein, E.; Ellsworth, M.; Cisar, T.; McKinney, B.; Knecht, B.
Analytical solution for soil water redistribution during evaporation process.
Simulating the dynamics of soil water content and modeling soil water evaporation are critical for many environmental and agricultural strategies. The present study aims to develop an analytical solution to simulate soil water redistribution during the evaporation process. This analytical solution was derived utilizing an exponential function to describe the relation of hydraulic conductivity and water content on pressure head. The solution was obtained based on the initial condition of saturation and an exponential function to model the change of surface water content. Also, the evaporation experiments were conducted under a climate control apparatus to validate the theoretical development. Comparisons between the proposed analytical solution and experimental result are presented from the aspects of soil water redistribution, evaporative rate and cumulative evaporation. Their good agreement indicates that this analytical solution provides a reliable way to investigate the interaction of evaporation and soil water profile. PMID:24355839
Teng, Jidong; Yasufuku, Noriyuki; Liu, Qiang; Liu, Shiyu
Nature of water molecular bridging of the soil organic matter
NASA Astrophysics Data System (ADS)
Soil is a complex anisotropic and porous system consisting of both inorganic and organic parts, air and water, inhabited and successively transformed by soil biota. Processes of soil formation are influenced by several factors. Among the most important factors belong the inorganic and organic input materials, which are mixed and transformed during soil formation. As a result, specific interactions and interrelationships develop between soil compartments. Although, they are important for soil function and its stability, they are still not well understood. This work deals with water molecule bridges (WaMB), as one of those interactions, and their relation to organic matter functioning. Differential scanning calorimetry (DSC) belongs to the family of methods of thermal analysis, i.e. it uses heat as a probe of the sample's nature. In soil science, the application of this common method is quite rare. In our previous works, DSC revealed a physical stabilization of organic matter segments in soils by development of WaMB. Results suggested the development of those bridges at ambient temperature accompanied with condensation of water into small nanodroplets. In another work, we found out that water, evaporating at the same temperature as WaMB transition occurs, correlates with the activity of soil microorganisms measured via CO2respiration. In this work, the enthalpy and kinetic parameters of water evaporation are studied in two kinds of soil: in clay-rich chernozem soils originating from Siberia and a histosol collected in Germany. We discuss the details of application of DSC, experimental arrangement and advantages and disadvantages of this approach. It is shown that enthalpy of evaporation can be used for understanding the nature of water binding in soils with well-developed aggregates. In contrast, the evaporation of water from histosol, without a typical soil texture, is more complicated because of diffusion processes. Further, the connection between enthalpy of evaporation and soil microbiological activity is discussed.
Kucerik, Jiri; Siewert, Christian; Quilesfogel-Esparza, Claudia; Schaumann, Gabriele E.
Earthworm Interactions with Soil Enzymes
\\u000a As one of the dominant members of soil fauna, earthworms fulfill significant tasks in the soil ecosystem by participating\\u000a in the physico-chemical processes of the soil, such as organic matter cycles, nutrient transformations, and modifications\\u000a in soil structure. These processes are also directed by the activities and amounts of the enzymes produced by soil microorganisms\\u000a that inhabit a wide range
Ridvan Kizilkaya; Ayten Karaca; Oguz Can Turgay; Sema Camci Cetin
Macroscopic modeling of plant water uptake: soil and root resistances
NASA Astrophysics Data System (ADS)
The macroscopic physically-based plant root water uptake (RWU) model, based on water-potential-gradient formulation (Vogel et al., 2013), was used to simulate the observed soil-plant-atmosphere interactions at a forest site located in a temperate humid climate of central Europe and to gain an improved insight into the mutual interplay of RWU parameters that affects the soil water distribution in the root zone. In the applied RWU model, the uptake rates are directly proportional to the potential gradient and indirectly proportional to the local soil and root resistances to water flow. The RWU algorithm is implemented in a one-dimensional dual-continuum model of soil water flow based on Richards' equation. The RWU model is defined by four parameters (root length density distribution, average active root radius, radial root resistance, and the threshold value of the root xylem potential). In addition, soil resistance to water extraction by roots is related to soil hydraulic conductivity function and actual soil water content. The RWU model is capable of simulating both the compensatory root water uptake, in situations when reduced uptake from dry layers is compensated by increased uptake from wetter layers, and the root-mediated hydraulic redistribution of soil water, contributing to more natural soil moisture distribution throughout the root zone. The present study focusses on the sensitivity analysis of the combined soil water flow and RWU model responses in respect to variations of RWU model parameters. Vogel T., M. Dohnal, J. Dusek, J. Votrubova, and M. Tesar. 2013. Macroscopic modeling of plant water uptake in a forest stand involving root-mediated soil-water redistribution. Vadose Zone Journal, 12, 10.2136/vzj2012.0154.
Vogel, Tomas; Votrubova, Jana; Dohnal, Michal; Dusek, Jaromir
Modeling the Soil Water and Energy Balance of a Mixed Grass Rangeland and Evaluating a Soil Water Based Drought Index in Wyoming
NASA Astrophysics Data System (ADS)
Soil water content plays an important role in the complex interaction between terrestrial ecosystems and the atmosphere. Automated soil water content sensing is increasingly being used to assess agricultural drought conditions. A one-dimensional vertical model that calculates incoming solar radiation, canopy energy balance, surface energy balance, snow pack dynamics, soil water flow, snow-soil heat exchange is applied to calculate water flow and heat transport in a Rangeland soil located near Lingel, Wyoming. The model is calibrated and validated using three years of measured soil water content data. Long-term average soil water content dynamics are calculated using a 30 year historical data record. The difference between long-term average soil water content and observed soil water content is compared with plant biomass to evaluate the usefulness of soil water content as a drought indicator. Strong correlation between soil moisture surplus/deficit and plant biomass may prove our hypothesis that soil water content is a good indicator of drought conditions. Soil moisture based drought index is calculated using modeled and measured soil water data input and is compared with measured plant biomass data. A drought index that captures local drought conditions proves the importance of a soil water monitoring network for Wyoming Rangelands to fill the gap between large scale drought indices, which are not detailed enough to assess conditions at local level, and local drought conditions. Results from a combined soil moisture monitoring and computer modeling, and soil water based drought index soil are presented to quantify vertical soil water flow, heat transport, historical soil water variations and drought conditions in the study area.
Engda, T. A.; Kelleners, T. J.; Paige, G. B.
Across-scale patterning of plant-soil¢water interactions surrounding tree islands in Southern Everglades landscapes
The freshwater Everglades is a complex system containing thousands of tree islands embedded within a marsh-grassland matrix.\\u000a The tree island-marsh mosaic is shaped and maintained by hydrologic, edaphic and biological mechanisms that interact across\\u000a multiple scales. Preserving tree islands requires a more integrated understanding of how scale-dependent phenomena interact\\u000a in the larger freshwater system. The hierarchical patch dynamics paradigm provides
Erin J. HananMichael; Michael S. Ross
Soil water dynamics in an oak stand
Soil water dynamics under a mixed stand of mature sessile and pedunculate oaks were studied both under natural conditions and during imposed water shortages in a lysimeter. Root densities of each species were described in situ by counting roots in the trench surrounding the dry plot. Soil water contents and potentials, and pre-dawn leaf water potentials (?wp) were monitored during
N. Brķda; A. Granier; F. Barataud; C. Moyne
Soil Moisture Data Assimilation in Soil Water Flow Modeling
NASA Astrophysics Data System (ADS)
Soil water flow modeling has multiple applications. This modeling is based on simplifications stemming from both conceptual uncertainty and lack of detailed knowledge about parameters. Modern soil moisture sensors can provide detailed information about changes in soil water content in time and with depth. This information can be used for data assimilation in soil water flow modeling. The ensemble Kalman filter appears to be an appropriate method for that. Earlier we demonstrated ensemble simulations of soil water flow by using sets of pedotransfer functions (empirical relationships between soil hydraulic properties and soil basic properties, such as particle size distribution, bulk density, organic carbon content, etc.). The objective of this work was to apply the data assimilation with the ensemble Kalman filter to soil water flow modeling, using soil water content monitoring with TDR probes and an ensemble of soil water flow models parameterized with different pedotransfer functions. Experiments were carried out at the Bekkevoort site, Belgium. Sixty time domain reflectometry (TDR) probes with two rods) were installed along the trench in loamy soil at 12 locations with 50-cm horizontal spacing at five depths (15, 35, 55, 75, and 95 cm). Water content and weather parameters were monitored for one year with 15 min frequency. Soil water flow was simulated using the HYDRUS6 software. Mean daily means of water contents at the observation depths were the measurements used in data assimilation. Eighteen pedotransfer functions for water retention and one for hydraulic conductivity were applied to generate ensembles to evaluate the uncertainty in simulation results, whereas the replicated measurements at each of measurement depths were used to characterize the uncertainty in data. Data assimilation appeared to be very efficient. Even assimilating measurements at a single depth provided substantial improvement in simulations at other observation depths. Results on selecting one best depth or two best depths will be presented. Best depths appear to be different depending on whether simulations are carried out to estimate soil water dynamics in root zone or to estimate infiltration losses beyond this zone. Soil moisture sensor data assimilation in soil flow modeling allows one to avoid multiparametric calibration and correct simulation on the go which can be beneficial in many applications, Using pedotransfer functions in ensemble Kalman filter results in the effective data assimilation in soil water flow modeling.
Pachepsky, Y. A.; Guber, A.; Jacques, D.; Pan, F.; van Genuchten, M.; Cady, R. E.; Nicholson, T. J.
Soil Water and Temperature System (SWATS) Handbook
The soil water and temperature system (SWATS) provides vertical profiles of soil temperature, soil-water potential, and soil moisture as a function of depth below the ground surface at hourly intervals. The temperature profiles are measured directly by in situ sensors at the Central Facility and many of the extended facilities of the SGP climate research site. The soil-water potential and soil moisture profiles are derived from measurements of soil temperature rise in response to small inputs of heat. Atmospheric scientists use the data in climate models to determine boundary conditions and to estimate the surface energy flux. The data are also useful to hydrologists, soil scientists, and agricultural scientists for determining the state of the soil.
Bond, D
Modeling soil water movement with water uptake by roots
Soil water movement with root water uptake is a key process for plant growth and transport of water and chemicals in the soil-plant\\u000a system. In this study, a root water extraction model was developed to incorporate the effect of soil water deficit and plant\\u000a root distributions on plant transpiration of annual crops. For several annual crops, normalized root density distribution
Jinquan Wu; Renduo Zhang; Shengxiang Gui
Understanding Dynamic Soil Water Repellency and its Hydrological Implications
NASA Astrophysics Data System (ADS)
The adverse effects of water repellent soils on vadose zone hydrology are being increasingly identified worldwide in both rural and urban landscapes. Among the affected landscapes are agricultural fields, forests, effluent application sites, golf greens, wetlands, and wildfire sites. In spite of cross-discipline research efforts put forth in recent years, understanding of fundamental parameters controlling soil water behaviour in these systems is lacking. This is due, in part, to inherent complexities of water repellent soil systems and logistical shortcomings of methods commonly used by researchers in-situ and in the lab. As a result, modeling flow in these systems has further proven to be a difficult task. The objectives of our study were 1) to systematically measure and quantify water infiltration and distribution in dynamic water repellent systems and 2) to identify fundamental hydraulic behaviours that lead to the expression of changes in soil water repellency. To achieve this, we combined techniques to elucidate soil- water interactions at a post-wildfire site. Field tests and subsequent lab work reveal essential hydrological information on fire-affected water repellent soils at variable scales and under different burn conditions. Through the use of traditional and newer techniques, our work shows unique and previously unreported behaviour of soil water in these systems. We also address limitations of current field methods used to study repellency and associated infiltration behaviours.
Beatty, S. M.; Smith, J. E.
A minimalist probabilistic description of root zone soil water
The probabilistic response of depth-integrated soil water to given climatic forcing can be described readily using an existing supply-demand-storage model. An apparently complex interaction of numerous soil, climate, and plant controls can be reduced to a relatively simple expression for the equilibrium probability density function of soil water as a function of only two dimensionless parameters. These are the index of dryness (ratio of mean potential evaporation to mean precipitation) and a dimensionless storage capacity (active root zone soil water capacity divided by mean storm depth). The first parameter is mainly controlled by climate, with surface albedo playing a subsidiary role in determining net radiation. The second is a composite of soil (through moisture retention characteristics), vegetation (through rooting characteristics), and climate (mean storm depth). This minimalist analysis captures many essential features of a more general probabilistic analysis, but with a considerable reduction in complexity and consequent elucidation of the critical controls on soil water variability. In particular, it is shown that (1) the dependence of mean soil water on the index of dryness approaches a step function in the limit of large soil water capacity; (2) soil water variance is usually maximized when the index of dryness equals 1, and the width of the peak varies inversely with dimensionless storage capacity; (3) soil water has a uniform probability density function when the index of dryness is 1 and the dimensionless storage capacity is large; and (4) the soil water probability density function is bimodal if and only if the index of dryness is <1, but this bimodality is pronounced only for artificially small values of the dimensionless storage capacity.
Milly, P. C. D.
Soil Structure Interaction in Different Seismic Environments.
National Technical Information Service (NTIS)
The current strong interest in nuclear power and the concerns regarding the seismic safety of the facilities involved has generated the development of improved methods of seismic soil-structure interaction analysis. Presented is a plane-strain method for ...
A. Gomez-Masso, H. B. Seed, J. Lysmer, J. C. Chen
Verification of Soil-Structure Interaction Methods.
National Technical Information Service (NTIS)
Soil-structure interaction (SSI) methods currently used by industry to evaluate the seismic response of nuclear power plant facilities are reviewed with the aim of evaluating those areas of uncertainty which still exist in the analytic approaches. The pri...
C. A. Miller, C. J. Costantino, A. J. Philippacopoulos, M. Reich
A modified soil water based Richards equation for layered soils
NASA Astrophysics Data System (ADS)
Most Soil-Vegetation-Atmosphere-Transfer (SVAT) models like TERRA-ML (implemented e.g. in the CCLM model (www.clm-community.eu)) use the soil moisture based Richards equation to simulate vertical water fluxes in soils, assuming a homogeneous soil type. Recently, high-resolution soil type datasets (e.g. B³K 1000, only for Germany (Federal Institute for Geosciences and Natural Resources, BGR, www.bgr.bund.de) or Harmonized World Soil Database (HWSD, version 1.1, FAO/IIASA/ISRIC/ISSCAS/JRC, March 2009)) have been developed. Deficiencies in the numerical solution of the soil moisture based Richards equation may occur if inhomogeneous soil type data is implemented, because there are possibly discontinuities in soil moisture due to various soil type characteristics. One way to fix this problem is to use the potential based Richards equation, but this may lead to problems in conservation of mass. This presentation will suggest a possible numerical solution of the soil moisture based Richards equation for inhomogeneous soils. The basic idea is to subtract the equilibrium state of it from soil moisture fluxes. This should reduce discontinuities because each soil layer aspires the equilibrium state and therefore differences might be of the same order. First sensitivity studies have been done for the Main river basin, Germany.
Kalinka, F.; Ahrens, B.
Methods for determining actual soil water repellence
In this paper we describe a simple and quick method for determining the presence of water repellency in a soil by using a small core sampler (1.5 cm in diameter, 25 cm long) and applying the water drop penetration time (WDPT) test at different depths on the sandy soil cores. Obtained results provide spatial distribution patterns of water repellency in
L. W. Dekker; C. J. Ritsema; K. Oostindie; D. Moore; J. G. Wesseling
Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA
Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds
Samuel B. McLaughlin; Stan D Wullschleger; G. Sun; M. Nosal
Mechanics of wheel-soil interaction
NASA Technical Reports Server (NTRS)
An approximate theory for wheel-soil interaction is presented which forms the basis for a practical solution to the problem. It is shown that two fundamental observations render the problem determinate: (1) The line of action of the resultant of radial stresses acting at the wheel soil interface approximately bisects the wheel-soil contact angle for all values of slip. (2) A shear stress surface can be hypothesized. The influence of soil inertia forces is also evaluated. A concept of equivalent cohesion is introduced which allows a convenient experimental comparison for both cohesive and frictional soils. This theory compares favorably with previous analyses and experimental data, and shows that soil inertia forces influencing the motion of a rolling wheel can be significant.
Houland, H. J.
NSDL National Science Digital Library
Many waterways are considered polluted due, at least in part, to excessive amounts of phosphorus. This topic-in-depth delves into the issues surrounding phosphorus in the environment. First, Larry G. Bundy at the University of Wisconsin - Madison provides a slide show about phosphorus's presence in soils (1). Students can discover the agronomic need for phosphorus, its effects on water quality and management issues. The second web site, created by the University of Florida Cooperative Extension Service, offers a great overview of how wetlands affect the retention, cycling, and release of phosphorus in wetlands (2). Users will find a straightforward diagram of the phosphorus cycle in wetlands. Next, Manitoba Agriculture, Food, and Rural Initiatives present the reasons for careful management of phosphorus in fertilizers, manure, detergents, sewage, and industrial waste (3). The web site effectively summarizes how phosphorus gets into the surface water and negatively influences the environment. Developed by the USGS, the fourth web site addresses the pollution concerns surrounding agricultural landscapes (4). Visitors can learn about the amounts and effects of the erosion of phosphorus, as well as nitrogen and pesticides, on nearby streams and lakes. Next, the Minnesota Environmental Partnership discusses why Minnesota has restricted the use of phosphorus-containing fertilizers on lawns (5). Visitors can discover tips for buying fertilizers and how to deal with the leftovers. The sixth web site describes the USDA's Agricultural Research Service's findings that residue from water-treatment processes may increase soil's capacity to adsorb phosphorus (6). Users can discover how this may help reduce the transport of phosphorus into the watershed, especially in sandy soils. Next, the Australian Government's National Eutrophication Management Program presents its research examining phosphorus erosion, external things that affect its movement, predictive capabilities, and ways to reduce its movement (7). Visitors can learn about the researchers' discoveries that phosphorus can enter waterways through the subsoil. Lastly, the Minnesota Department of Agriculture describes the concept of a watershed and how they influence water quality (8). Users can find out how to reduce the amount of phosphorus entering nearby streams and lakes and how to help their watershed.
Uptake and Hydraulic Redistribution of Soil Water in a Natural Forested Wetland and in two Contrasting Drained Loblolly Pine Plantations: Quantifying Patterns over Soil-to-Root and Canopy-to-Atmosphere Interactions
NASA Astrophysics Data System (ADS)
The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on water and carbon balances are not well studied. Quantification of evapotranspiration (ET), tree transpiration and their biophysical regulation are needed for assessing forest water management options. We characterized vertical variation in the diurnal and seasonal soil volumetric water content at 10 cm intervals to evaluate changes in water availability for root uptake and monitored eddy covariance ET and tree transpiration (sap flux) in three contrasting loblolly pine (Pinus taeda L.) stands. Those stands included a 50- yr-old wetland natural regeneration (NG), a 17-yr-old drained mid-rotation plantation (MP) and a 5-yr-old drained plantation (YP) in eastern North Carolina. We also quantified the magnitude of hydraulic redistribution (HR), the passive movement of soil water from deep to shallow roots, to identify factors affecting the seasonal dynamics of root water uptake, root and plant water potentials and stomatal conductance. In NG, soil water content was always at full saturation and total tree water use peaked between 6-7 mm/day, and this stand was used as reference. In MP, soil water content varied with soil depth and total water use from the upper 1m peaked between 4 and 6.5 mm/day during the growing season and was strongly correlated and similar to ET (ET represented 90-95% of total water depletion). In YP, soil water used was limited to the upper 30 cm and was strongly affected by summer drought by declining progressively from 0.9 mm/day in spring to 0.4 m/day in September. After periods of more than 10 days without rain, water extraction in MP shifted to the deeper layers, and recharge from HR approached 20% of ET. During days of high evaporative demand, water use in MP was comparable to NG thanks to HR and to the contribution of deeper roots to water uptake. In YP, HR never contributed for more than 8% of ET. There was no HR in NG. Tree transpiration represented on average 60% and 40% of ET in MP and YP, respectively. However, in MP it represented only 50% of ET on days following rain events and up to 80% of ET after prolonged periods without rain. In MP, we propose that HR prevented soil water potentials from decreasing during periods of increasing soil water deficit, therefore maintaining a constant driving force for water uptake. In MP, HR was an important mechanism for maintaining shallow root function during drought and preventing total stomatal closure. Our study shows that HR prevented soil water potentials from dropping below -0.6 MPa, and played a role in wetland hydrological balance by increasing water uptake in MP to level close to those of trees growing on pure wetlands (NG).
Domec, J.; King, J. S.; Noormets, A.; Sun, G.; McNulty, S. G.; Gavazzi, M. G.; Treasure, E.; Boggs, J. L.
Soil-Plant-Water Environment Research.
National Technical Information Service (NTIS)
A number of field observations were made within an actively growing crop environment. The observations included soil water movement, evapotranspiration rates, plant canopy temperatures, and water use predictions based on plant and meteorological condition...
M. L. Horton C. G. Carlson L. R. Stone
Porosity and Water Flow in Soils
NSDL National Science Digital Library
Three different types of sediments will be taken and the porosity and water flow rate for each type will be determined. From this activity, students will understand concepts of porosity and water flow through soil material.
Gautam, Tej
Soil water hydrology: simulation for water balance computations
Soil moisture occurs as the result of the climatic, crop, and soil processes which impact water on a vegetated landscape. This complex and highly dynamic water supply provides the water upon which the vast majority of the world food supply depends. Most importantly, it is as variable within and between years and location as the variables which determine its occurrence.
America's Soil and Water: Condition and Trends.
ERIC Educational Resources Information Center
A review of conditions and trends regarding soil and water resources of rural nonfederal lands of the United States is presented in this publication. Maps, charts, and graphs illustrate the data collected on various aspects of soil and water use and practice. Topic areas considered include: (1) land use patterns; (2) classes of land; (3)ģ
Investigation of soil-atmosphere interaction in pyroclastic soils
NASA Astrophysics Data System (ADS)
Development of a physical model to estimate soil-atmosphere interaction of a layer.Quantification of infiltration and evaporation across a pyroclastic layer surface.Evaporation obtained by monitoring weight changes and energetic terms.Actual evaporation always significant compared with infiltration even during winter.Validation of traditional approaches suitable to estimate evaporation.
Rianna, Guido; Pagano, Luca; Urciuoli, Gianfranco
Increasing Efficiency of Water Use in Agriculture through Management of Soil Water Repellency to Optimize Soil and Water Productivity
NASA Astrophysics Data System (ADS)
Water's ability to infiltrate and disperse in soils, and soil's ability to receive, transport, retain, filter and release water are important factors in the efficient use of water in agriculture. Deteriorating soil conditions, including development of soil water repellency, negatively impact hydrological processes and, consequently, the efficiency of rainfall and irrigation. Soil water repellency is increasingly being identified in diverse soils and cropping systems. Recently research has been conducted on the use of novel soil surfactants (co-formulations of alkyl polyglycoside and block copolymer surfactants) to avoid or overcome soil water repellency and enhance water distribution in soils. Results indicate that this is an effective and affordable approach to maintaining or restoring soil and water productivity in irrigated cropping systems. Results from studies conducted in Australia and the United States to determine how this technology modifies soil hydrological behavior and crop yields will be presented. A range of soils and various crops, including potatoes, corn, apples and grapes, were included. Several rates were compared to controls for effect on soil moisture levels, soil water distribution, and crop yield. An economic analysis was also conducted in some trials. Treatments improved rootzone water status, significantly increased crop yield and quality, and in some cases allowed significant reductions in water requirements. Where assessed, a positive economic return was generated. This technology holds promise as a strategy for increasing efficiency of water use in agriculture.
Moore, Demie; Kostka, Stan; McMillan, Mica; Gadd, Nick
Hygrometric Measurement of Soil Water Potential
NASA Astrophysics Data System (ADS)
Knowledge of soil water potential as a function of water content is required to make unsaturated flow and transport predictions. Although numerous methods are available to measure soil water potential, they are largely difficult and time consuming procedures. The goal of the research is to develop a hygrometric method that will perform satisfactorily with minimal required hardware or technician time. The volume of a drop of saline water will change due to evaporation or condensation until its salinity, and hence osmotic potential, is equal to the water potential in the adjacent gas phase. This relationship is exploited by our method to measure soil moisture potential. To begin, a drop of KCl solution with known mass and KCL concentration is placed adjacent to a soil sample with known water content inside a hermetically sealed container. The mass of the KCl drop is recorded over time with an electronic balance. As thermodynamic equilibrium is achieved, the mass of water within the KCl drop changes until its osmotic potential is equal to the capillary potential of water within the soil sample. After the mass of the KCl drop reaches equilibrium, the KCl concentration is calculated, which enables direct determination of the water potential within the soil sample. Unlike transient hygrometric measurements of water potential using psychrometers, no calibration is required.
Butler, C. D.; Tyner, J. S.
mySoil: Crowd-Sourcing Soil Water Repellency Data to Create a Global Assessment
NASA Astrophysics Data System (ADS)
Soil water repellency (SWR) alters the way water interacts with soil by impacting hydrological and biogeochemical cycling to an extent which is not yet fully understood. Most studies have focused on SWR in specific environments and habitats, mostly in Mediterranean climates, but SWR has been increasingly observed in a range of habitats from the tropics to the northern latitudes. To better assess the distribution of this phenomenon, we propose using citizen science to create a means of crowd-sourcing SWR data from around the globe using the mySoil app. The water drop penetration time (WDPT) test, in which the length of time a drop of water remains on the soil surface is measured and a corresponding qualitative water repellency class is assigned to the soil, provides useful data and is easy to use. We propose adding a simple, standardised WDPT protocol to the mySoil app and web portal so both academics and non-scientists can contribute to the collection of SWR data from around the world. The protocol would include guidelines on drop size and the number of drops to apply, and would encourage inclusion of details such as vegetation cover, soil moisture conditions, last rainfall, and broad habitat. By initially engaging with researchers to create a back bone of respondents, we believe we can develop a global assessment that will reveal the distribution of the SWR phenomenon.
Hallin, Ingrid; Robinson, David A.; Doerr, Stefan H.; Douglas, Peter; Lawley, Russell; Shelley, Wayne; Urbanek, Emilia
Transport of Water in Frozen Soil. I. Experimental Determination of Soil - Water Diffusivity under Isothermal Conditions.
National Technical Information Service (NTIS)
A new experimental method for measuring the soil-water diffusivity of frozen soil under isothermal conditions is introduced. The theoretical justification of the method is presented and the feasibility of the method is demonstrated by experiments conducte...
Y. Nakano A. R. Tice J. L. Oliphant T. F. Jenkins
Interaction between Diclofenac and Soil Humic Acids
The interaction between the non-steroidal anti-inflammatory drug diclofenac and standard humic acids (HAs) in bulk solution was studied using two complementary analytical methods: UV-Visible spectroscopy and square wave voltammetry. The observed UV-Vis spectra and Ip\\/V curves suggested that, at our experimental conditions, albeit both substances being negatively charged at pH 6.5, interaction between the pharmaceutical and the soil humic acids
Alja Margon; Arnold Pastrello; Davide Mosetti; Pierpaolo Cantone; Liviana Leita
Soil-water characteristics of constructed mine soils and associated undisturbed soils in southwestern North Dakota
The effects of mining and reclamation on water movement and retention were determined from measurements of bulk density, aggregate stability, water retention and hydraulic conductivity on both undisturbed and reclaimed (constructed) soils. A soil root growth environment model was modified and used to estimate potential productivity of constructed soils. Bulk density was significantly higher in the top 60 cm of constructed soils than in similar undisturbed soils. A pronounced increase in bulk density was observed at the interface between first and second lift materials. The bulk density values of constructed soils decreased with time, especially in the tillage layer. Available water-holding capacities (AWC) of constructed soils were similar to those of comparable soils. Changes in bulk density affect macropore space but not available water-holding capacities. Low AWC's were measured for soil materials containing degraded lignite. Aggregate-size distribution in constructed soils tends to be the same as in the soil materials used in their construction, but total aggrega contents tend to be 30 to 50% lower than in undisturbed soils. The hydraulic conductivity of constructed soils is highly correlated with and consistently one order of magnitude lower than that of comparable undisturbed soils. Measured soil properties were used to estimate potential productivity by use of a soil root growth based productivity index model. Potential benefits of this index model include: (1) elimination of problems associated with the use of reference areas such as climate variability and management practices, (2) design of constructed soils for best use of available materials and (3) identification of potential limiting soil conditions in constructed soils both before and immediately after reclamation.
Wollenhaupt, N.C.
The soil water balance in a mosaic of clumped vegetation
NASA Astrophysics Data System (ADS)
The spatio-temporal distribution of soil moisture influences the plant growth and the distribution of terrestrial vegetation. This effect is more evident in arid and semiarid ecosystems where the interaction between individuals and the water limited conditions play a fundamental role, providing environmental conditions which drive a variety of non-linear ecohydrological response functions (such as transpiration, photosynthesis, leakage). In this context, modeling vegetation patterns at multiple spatial aggregation scales is important to understand how different vegetation structures can modify the soil water distribution and the exchanged fluxes between soil and atmosphere. In the present paper, the effect of different spatial vegetation patterns, under different climatic scenarios, is investigated in a patchy vegetation mosaic generated by a random process of individual tree canopies and their accompanying root system. Vegetation pattern are generated using the mathematical framework proposed by Caylor et al. (2006) characterized by a three dimensional stochastic vegetation structure, based on the density, dispersion, size distribution, and allometry of individuals within a landscape. A Poisson distribution is applied to generate different distribution of individuals paying particular attention on the role of clumping on water distribution dynamics. The soil water balance is evaluated using the analytical expression proposed by Laio et al. (2001) to explore the influence of climate and vegetation patterns on soil water balance steady-state components (such as the average rates of evaporation, the root water uptake and leakage) and on the stress-weighted plant water uptake. Results of numerical simulations show that clumping may be beneficial for water use efficiency at the landscape scale. References Caylor, Kelly K., P. D'Odorico and I. Rodriguez Iturbe: On the ecohydrology of structurally heterogeneous semiarid landscape. Water Resour. Res., 28, W07424, 2006. Laio, F., A. Porporato, L., Ridolfi and I. Rodriguez Iturbe: Plants in water controlled ecosystems: Active role in hydrological processes and response to water stress, II. Probabilistic soil moisture dynamics, Adv. Water Resour., 24(7), 707-723,2001.
Pizzolla, Teresa; Manfreda, Salvatore; Caylor, Kelly; Gioia, Andrea; Iacobellis, Vito
Water retention, hydraulic conductivity of hydrophilic polymers in sandy soil as affected by temperature and water quality
NASA Astrophysics Data System (ADS)
SummaryHydrophilic polymers can swell by absorbing huge volumes of water or aqueous solutions. This property has led to many practical applications of these new materials, particularly in arid regions for improving water retention in sandy soils and the water supply to plants grown on them. The effects of two hydrophilic polymers, carboxymethylcellulose (RF) and isopropyl acrylamide (BF) on the water holding capacity and saturated hydraulic conductivity ( KS) of a sandy soil at varying soil temperature and water quality were evaluated. The RF was less efficient in absorbing water than BF, but the efficiency of BF in retaining water was negatively affected by its thermo-sensitivity and the quality of water. The temperature dependence of the water absorption was not clear for the soils treated with RF, whereas, the efficiency of BF treatment in absorbing water decreased significantly ( P < 0.05) with increasing soil temperature. The dependence of the KS on soil temperature differed with the type of hydrophilic polymer used. The KS of the control soil remained nearly constant as the soil temperature increased. The KS of the BF treated soil increased significantly ( P < 0.05) and linearly with increasing soil temperature, while that of soil treated with RF showed a quadratic response. The soil-absorbent mixtures exhibited different water retention characteristics under different soil temperature conditions. The increase in soil temperature did not affect the water retention characteristics curve of the control. The effect of soil temperature on the water potential curve of the soil treated with RF was not clear particularly when the temperature increased from 25 to 35 ░C. The water potential curve for soil-BF mixtures showed that the water content value at field capacity shifted from 0.21 to 0.10 cm 3 cm -3 for 0.1% and from 0.27 to 0.12 cm 3 cm -3 for 0.2%, as the soil temperature increased from 15 to 35 ░C. This implies that the soil-BF absorbent mixtures would release some moisture as the soil temperature would increase from 15 to 35 ░C, and this water could be lost by percolation or taken up by plant. It was found that available water content increased up to four times with RF as compared to control soil whereas it increased up to five times with BF treatment. At high temperature, the difference was much reduced except for RF at 0.2%. This understanding of the characteristics of the absorbents and the interactions among absorbents, soil, and temperature would be of help in water management in sandy soil.
Andry, H.; Yamamoto, T.; Irie, T.; Moritani, S.; Inoue, M.; Fujiyama, H.
Spatial and Statistical Similarities of Local Soil Water Fluxes
at the soil surface beneath a constant-rate rainfall simu- lator to measure cumulative water storage with time. Understanding the spatial and statistical distribution of soil water These authors estimated the local water flux from the flux in a field is fundamental for stochastic modeling soil water flow and chemical transport in spatially variable soils. The objective of slope of water
Bing Cheng Si
Soil Chapter-Soils as Sponges: How Much Water does Soil Hold?
NSDL National Science Digital Library
Students determine the moisture content of a sponge after squeezing the water out of the sponge, and allowing water to evaporate from the sponge. Students also measure the amount of water that has evaporated from the soil samples. This learning resource is part of the Soils chapter of the GLOBE Teacher's Guide, and is supported by the GLOBE soils protocols. GLOBE (Global Learning and Observation to Benefit the Environment) is a worldwide, hands-on, K-12 school-based science education program.
Acid-base characteristics of the Grass Pond watershed in the Adirondack Mountains of New York State, USA: interactions among soil, vegetation and surface waters
NASA Astrophysics Data System (ADS)
Grass Pond watershed is located within the southwestern Adirondack Mountain region of New York State, USA. This region receives some of the highest rates of acidic deposition in North America and is particularly sensitive to acidic inputs due to many of its soils having shallow depths and being generally base poor. Differences in soil chemistry and tree species between seven subwatersheds were examined in relation to acid-base characteristics of the seven major streams that drain into Grass Pond. Mineral soil pH, stream water BCS (base-cation surplus) and pH exhibited a positive correlation with sugar maple basal area (p = 0.055; 0.48 and 0.39, respectively). Black cherry basal area was inversely correlated with stream water BCS, ANC (acid neutralizing capacity)c and NO3- (p = 0.23; 0.24 and 0.20, respectively). Sugar maple basal areas were positively associated with watershed characteristics associated with the neutralization of atmospheric acidic inputs while in contrast, black cherry basal areas showed opposite relationships to these same watershed characteristics. Canonical correspondence analysis indicated that black cherry had a distinctive relationship with forest floor chemistry apart from the other tree species, specifically a strong positive association with forest floor NH4, while sugar maple had a distinctive relationship with stream chemistry variables, specifically a strong positive association with stream water ANCc, BCS and pH. Our results provide evidence that sugar maple is acid-intolerant or calciphilic tree species and also demonstrate that black cherry is likely an acid-tolerant tree species.
McEathron, K. M.; Mitchell, M. J.; Zhang, L.
Acid-base characteristics of the Grass Pond watershed in the Adirondack Mountains of New York State, USA: interactions between soil, vegetation and surface waters
NASA Astrophysics Data System (ADS)
Grass Pond watershed is located within the Southwestern Adirondack Mountain region of New York State, USA. This region receives some of the highest rates of acidic deposition in North America and is particularly sensitive to acidic inputs due to many of its soils having shallow depths and being generally base-poor. Differences in soil chemistry and tree species between seven subwatersheds were examined in relation to acid-base characteristics of the seven major streams that drain into Grass Pond. Mineral soil pH, stream water BCS and pH exhibited a positive correlation with sugar maple basal area (p = 0.055; 0.48 and 0.39, respectively). Black cherry basal area was inversely correlated with stream water BCS, ANCc and NO3- (p = 0.23; 0.24 and 0.20, respectively). Sugar maple basal areas were positively correlated with watershed characteristics associated with the neutralization of atmospheric acidic inputs while in contrast, black cherry basal areas showed opposite relationships to these same watershed characteristics. Canonical Correspondence Analysis indicated that black cherry had a distinctive relationship with forest floor chemistry apart from the other tree species, specifically a strong positive association with forest floor NH4 while sugar maple had a distinctive relationship with stream chemistry variables, specifically a strong positive association with stream water ANCc, BCS and pH. Our results provide evidence that sugar maple is acid-intolerant or calciphilic tree species and also demonstrate that black cherry is likely an acid-tolerant tree species.
McEathron, K. M.; Mitchell, M. J.; Zhang, L.
Transient soil moisture profile of a water-shedding soil cover in north Queensland, Australia
NASA Astrophysics Data System (ADS)
In current agricultural and industrial applications, soil moisture determination is limited to point-wise measurements and remote sensing technologies. The former has limitations on spatial resolution while the latter, although has greater coverage in three dimensions, but may not be representative of real-time hydrologic conditions of the substrate. This conference paper discusses the use of elongated soil moisture probes to describe the transient soil moisture profile of water-shedding soil cover trial plots in north Queensland, Australia. Three-metre long flat ribbon cables were installed at designed depths across a soil cover with substrate materials from mining activities comprising of waste rocks and blended tailings. The soil moisture measurement is analysed using spatial time domain reflectometry (STDR) (Scheuermann et al., 2009) Calibration of the flat ribbon cable's soil moisture measurement in waste rocks is undertaken in a glasshouse setting. Soil moisture retention and outflows are monitored at specific time interval by mass balance and water potential measurements. These data sets together with the soil hydrologic properties derived from laboratory and field measurements are used as input in the numerical code on unsaturated flow, Hydrus2D. The soil moisture calculations of the glasshouse calibration using this numerical method are compared with results from the STDR soil moisture data sets. In context, the purpose of the soil cover is to isolate sulphide-rich mine wastes from atmospheric interaction as oxidation and leaching of these materials may result to acid and metalliferous drainage. The long term performance of a soil cover will be described in terms of the quantities and physico-chemical characteristics of its outflows. With the soil moisture probes set at automated and pre-determined measurement time intervals, it is expected to distinguish between macropore and soil moisture flows during high intensity rainfall events and, also continuously update data sets on soil moisture retention, especially during long periods of drought. As such, description of the soil cover water balance will be more elaborate as the soil moisture profile will be described in terms of temporal and spatial variability. Moreover, this field data set can lend support on the evaluation of the potential use of mine wastes as cover materials with respect to their hydrologic and geochemical properties.
Gonzales, Christopher; Baumgartl, Thomas; Scheuermann, Alexander
Fly ash dynamics in soil-water systems
Studies regarding the effluents and coal ashes (or fly ash) resulting from coal burning are numerous, but their disposal and interactions with the soil and water systems and their detailed environmental impact assessment with concrete status reports on a global scale are scanty. Fly ash dynamics in soil and water systems are reviewed. After detailing the physical composition of fly ash, physicochemical changes in soil properties due to fly ash amendment are summarized. Areas covered include texture and bulk density, moisture retention, change in chemical equilibria, and effects of fly ash on soil microorganisms. Plant growth in amended soils is discussed, as well as plant uptake and accumulation of trace elements. In order to analyze the effect of fly ash on the physicochemical properties of water, several factors must be considered, including surface morphology of fly ash, pH of the ash sluice water, pH adjustments, leachability and solubility, and suspended ash and settling. The dynamics of fly ash in water systems is important due to pollution of groundwater resources from toxic components such as trace metals. Other factors summarized are bioaccumulation and biomagnification, human health effects of contaminants, and the impact of radionuclides in fly ash. Future research needs should focus on reduction of the environmental impact of fly ash and increasing utilization of fly ash as a soil amendment. 110 refs., 2 figs., 10 tabs.
Sharma, S.; Fulekar, M.H.; Jayalakshmi, C.P. (Energy and Environment Group, New Delhi (India))
The interaction between soil erosion and soil organisms in temperate agroecosystems: nematode redistribution in tramlines
NASA Astrophysics Data System (ADS)
Arable agriculture presents a unique set of challenges, and one of the most important is soil erosion. Whilst policy and practice look towards sustainable intensification of production to ensure food security, fundamental gaps in our understanding still exist. The physical processes involved in the detachment, transport and deposition of soil are well characterised but further research considering chemical and nutrient transport, fertiliser and pesticide losses, and environmental impacts to downstream environments is still required. Furthermore the interaction between soil erosion and soil organisms have largely been ignored, even though soil organisms serve a myriad of functions essential in the provision of soil ecosystem goods and services. Here we present the findings of a field-scale experiment into soil biotic redistribution undertaken at the James Hutton Institute's Balruddery Farm, Scotland (Link Tramlines Project XDW8001). Farm vehicle-tyre wheelings left in arable fields (tramlines) to enable crop spraying during the crop growth cycle have been identified as key transport pathways for sediment and associated nutrients. We tested the hypothesis that soil organisms were also transported by tramline erosion. During the winter of 2012/13 an experiment was undertaken to measure soil organism export from unbound hillslope plots subject to four different tramline treatments set out in a randomised block design. We used soil nematodes as a model organism as they are ubiquitous and sensitive to disturbance and an established indicator taxa of biological and physico-chemical changes in soil. Tramline treatments included a control tyre (conventional tractor tyre), a control tyre with a sown tramline, a low pressure tyre with sown tramline, and a control tyre with a spiked harrow. Post-event sampling of rainfall events was undertaken, and a range of variables measured in the laboratory. The spiked harrow treatment produced the greatest overall reductions in nematode export with 95% less nematodes exported, compared with the control treatment. We observed wholesale non-selective transport of all nematode trophic groups present in the soil. The findings of this experiment are twofold. Firstly, we demonstrate that soil organisms are transported by erosion processes and confirm that tramlines are key hydrological pathways. Secondly, we highlight practical on-farm solutions that have potential to decrease soil organism losses. These results provide important baseline information to improve our understanding of soil erosion impacts to the wider soil ecosystem. The results help to inform soil and water conservation measures for sustainable agriculture.
Baxter, Craig; Rowan, John S.; McKenzie, Blair M.; Neilson, Roy
Black Carbon - Soil Organic Matter abiotic and biotic interactions
NASA Astrophysics Data System (ADS)
Wildfires, prescribed burns and the use of char as a soil amendment all add large quantities of black carbon to soils, with profound, yet poorly understood, effects on soil biology and chemical-physical structure. We will present results emerging from our black carbon program, which addresses questions concerning: 1) black carbon-soil organic matter interactions, 2) char decomposition and 3) impacts on microbial community structure and activities. Our understanding derives from a complementary set of post-fire black carbon field surveys and laboratory and field experiments with grass and wood char amendments, in which we used molecular (i.e., BPCA, PLFA) and isotopic (i.e., 13C and 15N labelled char) tracers. Overall, emerging results demonstrate that char additions to soil are prone to fast erosion, but a fraction remains that increases water retention and creates a better environment for the microbial community, particularly favoring gram negative bacteria. However, microbial decomposition of black carbon only slowly consumes a small fraction of it, thus char still significantly contributes to soil carbon sequestration. This is especially true in soils with little organic matter, where black carbon additions may even induce negative priming.
Cotrufo, Francesca; Boot, Claudia; Denef, Karolien; Foster, Erika; Haddix, Michelle; Jiang, Xinyu; Soong, Jennifer; Stewart, Catherine
Polymer-water interaction studies
NASA Astrophysics Data System (ADS)
Polymer water interactions were investigated. The following interactions were studied: (1) water absorption and desorption kinetics in EVA and PVB; (2) humidity dependence of electrical properties of EVA and PVB; (3) plasticizer effects in PVB; and (4) radiation effects in PVB and EVA.
Orehotsky, J.
Polymer-water interaction studies
NASA Technical Reports Server (NTRS)
Polymer water interactions were investigated. The following interactions were studied: (1) water absorption and desorption kinetics in EVA and PVB; (2) humidity dependence of electrical properties of EVA and PVB; (3) plasticizer effects in PVB; and (4) radiation effects in PVB and EVA.
Orehotsky, J.
Effects of soil water content on soil respiration in forests and cattle pastures of eastern Amazonia
The effect of soil water content on efflux of CO2 from soils has been described by linear, logarithmic, quadratic, and parabolic functions of soil water expressed as matric potential, gravimetric and volumetric water content, water holding capacity, water-filled pore space, precipitation indices, and depth to water table. The effects of temperature and water content are often statistically confounded. The objectives
Eric A. Davidson; Louis V. Verchot; J. Henrique CattŌnio; Ilse L. Ackerman; J. E. M. Carvalho
Interactive effects of plant species diversity and elevated CO2 on soil biota and nutrient cycling.
Terrestrial ecosystems consist of mutually dependent producer and decomposer subsystems, but not much is known on how their interactions are modified by plant diversity and elevated atmospheric CO2 concentrations. Factorially manipulating grassland plant species diversity and atmospheric CO2 concentrations for five years, we tested whether high diversity or elevated CO2 sustain larger or more active soil communities, affect soil aggregation, water dynamics, or nutrient cycling, and whether plant diversity and elevated CO2 interact. Nitrogen (N) and phosphorus (P) pools, symbiotic N2 fixation, plant litter quality, soil moisture, soil physical structure, soil nematode, collembola and acari communities, soil microbial biomass and microflora community structure (phospholipid fatty acid [PLFA] profiles), soil enzyme activities, and rates of C fluxes to soils were measured. No increases in soil C fluxes or the biomass, number, or activity of soil organisms were detected at high plant diversity; soil H2O and aggregation remained unaltered. Elevated CO2 affected the ecosystem primarily by improving plant and soil water status by reducing leaf conductance, whereas changes in C cycling appeared to be of subordinate importance. Slowed-down soil drying cycles resulted in lower soil aggregation under elevated CO2. Collembola benefited from extra soil moisture under elevated CO2, whereas other faunal groups did not respond. Diversity effects and interactions with elevated CO2 may have been absent because soil responses were mainly driven by community-level processes such as rates of organic C input and water use; these drivers were not changed by plant diversity manipulations, possibly because our species diversity gradient did not extend below five species and because functional type composition remained unaltered. Our findings demonstrate that global change can affect soil aggregation, and we advocate that soil aggregation should be considered as a dynamic property that may respond to environmental changes and feed back on other ecosystem functions. PMID:18229849
Niklaus, P A; Alphei, J; Kampichler, C; Kandeler, E; K÷rner, C; Tscherko, D; Wohlfender, M
Influence of soil pH on properties of the soil-water interface
NASA Astrophysics Data System (ADS)
Surface characteristics of soils are one of the main factors controlling processes at the soil-water interface like wetting, sorption or dissolution processes and, thereby, have a high impact on natural soil functions like habitat, filter, buffer, storage and transformation functions. Since surface characteristics, like wettability or repellency, are not static soil properties but continuously changing, the relevant processes and mechanisms are in the focus of the presented study. These mechanisms help to gain further insight into the behaviour of soil and its dynamics under changing environmental conditions. The influence of water content, relative air humidity and drying temperature on soil water repellency has been investigated in many studies. In contrast, few studies have systematically investigated the relationship between soil water repellency (SWR) and soil pH. Several studies found alkaline soils to be less prone to SWR compared to acidic soils (e.g., CerdÓ, and Doerr 2007; Mataix-Solera et al. 2007). Furthermore, SWR has been successfully reduced in acidic soils by increasing soil pH via liming (e.g., Karnok et al. 1993; Roper 2005). However, SWR has also been reported in calcareous soils in the Netherlands (Dekker and Jungerius 1990), California, USA (Holzhey 1968) and Spain (Mataix-Solera and Doerr 2004). The hypothesis that the pH may control repellency via changes in the variable surface charge of soil material has not yet been tested. Previously it has been shown that it is necessary to eliminate the direct influence of changes in soil moisture content so that the unique relationship between pH and SWR can be isolated (Bayer and Schaumann 2007). A method has been developed which allows adjustment of the pH of soils with low moisture content via the gas phase with minimal change in moisture content. The method was applied to 14 soil samples from Germany, Netherlands, the UK and Australia, using the water drop penetration time (WDPT) as the indicator of SWR. Sessile drop and Wilhelmy plate contact angles (CAsess and CAwpm resp.) were measured on the four samples from Germany and the data correlated with those of WDPT. The titratable surface charge of these four soils was measured at selected pH values using a particle charge detector (PCD). Changes in SWR with soil pH were found to be influenced by the density and type of sites able to interact with protons at the available surfaces of organic and mineral materials in soil. The maximum SWR occurred for soil at natural pH and where the charge density was minimal. As pH increased, negative surface charge increased due to deprotonation of sites and WDPT decreased. Two types of behaviour were observed: Those in which (i) WDPT shortened with decreasing pH and ii) WDPT was sensibly constant with decreasing pH. The data suggest that the availability and relative abundance of proton active sites at mineral surfaces, and those at organic functional groups influence the behaviour. Bayer, J. V. and G. E. Schaumann (2007). Hydrological processes 21(17): 2266 - 2275. CerdÓ, A. and S. H. Doerr (2007). Hydrological Processes 21(17): 2325-2336. Dekker, L. W. and P. D. Jungerius (1990). Dunes of the European coasts, Catena-Verlag. 18: 173-183. Holzhey, C. S. (1968). Symposium on water repellent soils, Riverside, California. Karnok, K. A., E. J. Rowland, et al. (1993). Agronomy Journal 85(5): 983-986. Mataix-Solera, J., V. Arcenegui, et al. (2007). Hydrological Processes 21(17): 2300-2309. Mataix-Solera, J. and S. H. Doerr (2004). Geoderma 118(1-2): 77-88. Roper, M. M. (2005). Australian Journal of Soil research 43: 803-810.
Diehl, Doerte
Soil water balance scenario studies using predicted soil hydraulic parameters
NASA Astrophysics Data System (ADS)
Pedotransfer functions (PTFs) have become a topic drawing increasing interest within the field of soil and environmental research because they can provide important soil physical data at relatively low cost. Few studies, however, explore which contributions PTFs can make to land-use planning, in terms of examining the expected outcome of certain changes in soil and water management practices. This paper describes three scenario studies that show some aspects of how PTFs may help improve decision making about land management practices. We use an exploratory research approach using simulation modelling to explore the potential effect of alternative solutions in land management. We: (i) evaluate benefits and risks when irrigating a field, and the impact of soil heterogeneity; (ii) examine which changes can be expected (in terms of soil water balance and supply) if organic matter content is changed as a result of an alternative management system; (iii) evaluate the risk of leaching to deeper horizons in some soils of Hungary. Using this research approach, quantitative answers are provided to what if? type questions, allowing the distinction of trends and potential problems, which may contribute to the development of sustainable management systems.
Nemes, A.; W÷sten, J. H. M.; Bouma, J.; Vßrallyay, G.
Ad Hoc Modeling of Root Zone Soil Water with Landsat Imagery and Terrain and Soils Data
Agricultural producers require knowledge of soil water at plant rooting depths, while many remote sensing studies have focused on surface soil water or mechanistic models that are not easily parameterized. We developed site-specific empirical models to predict spring soil water content for two Montana ranches. Calibration data sample sizes were based on the estimated variability of soil water and the
Joel B. Sankey; Rick L. Lawrence; Jon M. Wraith
DIVISION S-6ŚSOIL & WATER MANAGEMENT & CONSERVATION Soil Water Retention as Related to Topographic Variables
long been routinely used in soil mapping (Northcote, 1954). Geomorphometry was proposed as a data source Digital elevation models were proposed and used as a data source to predict soil properties (Moore et al., 1993; McKenzie to estimate soil properties. This study evaluated variability of texture and water retention of soils for a gently sloping 3.7-ha field located and Austin,
A. Pachepsky; D. J. Timlin; W. J. Rawls
Tank-farm construction: Tank-soil interaction in tank-farm construction
This article illustrates examples of tank-soil interaction as a result of utilization of the above concepts. The need to address tank-soil interaction arises due to concern for two phenomena, namely, stability and settlement. If adequate soil bearing is not available, soil will move out from under the tank causing the tank to fail. Settlement of soil can create stresses leading to rupture of tank bottom, shell buckling, or ovality of tank which can inhibit the movement of the roof in floating-roof tanks. This article surveyed the interaction of tank and soil as the result of soil-improvement approaches. The soil improvement is time dependent. Tank-soil interaction should be monitored by using geotechnical instrumentation and evaluation methods to fulfill two underlying objectives. One, the bearing capacity of soil at any time during the soil improvement program should be higher than applied load. Two, the magnitude and the rate of soil settlement should be such that it does not detrimentally affect the structural integrity of the tank. The soil behavior should be monitored with respect to pore water pressure, vertical settlement, and lateral movement. The tank behavior should be monitored with respect to bottom rupture, shell buckling, ovality, roof binding, and failure of ringwall foundation.
Ahmed, S.
Interactions between arbuscular mycorrhizal fungi and soil bacteria
The soil environment is interesting and complicated. There are so many interactions taking place in the soil, which determine\\u000a the properties of soil as a medium for the growth and activities of plants and soil microorganisms. The soil fungi, arbuscular\\u000a mycorrhiza (AM), are in mutual and beneficial symbiosis with most of the terrestrial plants. AM fungi are continuously interactive\\u000a with
Mohammad Miransari
Laboratory study on the interaction between herbicides and sediments in water systems
Interaction between herbicides and sediments in water systems is an important process occurring in water, which influences the behaviour of the herbicides in water. This paper reports on the sorption of herbicides norflurazon, oxadiazon and trifluralin on soil and the interaction between the herbicides and sediments under stirred and non-stirred conditions. The sorption coefficients of the herbicides on soils are
G.-G Ying; B Williams
The very extensive literature on phosphorus (P) sorption studies is reviewed with the intention of selecting rate constants and other parameter values for the constituent equations in a soil P dynamics model. Processes considered are fast reversible sorption of P onto surface sites, and slow reactions which deposit P at depth below surfaces of iron or aluminium oxide minerals in
M. B. McGechan
Predicting soil-water and soil-air transport properties and their effects on soil-vapor extraction efficiency
Accurate prediction of water and air transport parameters in variably saturated soil is necessary for modeling of soil-vapor extraction (SVE) at soil sites contaminated with volatile organic chemicals (VOCs). An expression for predicting saturated water permeability (k{sub 1,s}) in undisturbed soils from the soil total porosity and the field capacity soil-water content was developed by fitting a tortuous-tube fluid flow
Tjalfe G. Poulsen; Per Moldrup; Toshiko Yamaguchi; P. Schjoenning; Jens Aage Hansen
Soil and xylem water potential and soil water content in contrasting Pinus contorta ecosystems, Southeastern Wyoming, USA
The relationships between volumetric soil water content (?), in situ soil water potential (?soil) and predawn xylem pressure potential (?predawn) were quantified in four contrasting lodgepole pine ecosystems in Wyoming, USA. On three of the sites, changes in ?soil correlated closely with ?predawn, but on a porous soil derived from coarse granitic parent material, ?predawn declines occurred much sooner than
T. J. Fahey; D. R. Young
Ecohydrology of root zone water fluxes and soil development in complex semiarid rangelands
In semiarid complex terrain, the landscape creates spatial niches for different types of vegetation through the effects of aspect, slope and curvature on the water and energy balance at the soil surface. The ecohydrology of rangelands is defined by the interaction of soils, plants and climate occurring on a topographic surface. While these interactions have been studied for subtle terrain,
Hugo A. Gutiķrrez-Jurado; Enrique R. Vivoni; J. Bruce J. Harrison; Huade Guan
Battelle completes three-year study of pipe-soil interaction
It has been recognized in recent years that understanding pipe-soil interaction is a key aspect of designing pipelines and risers for deep water and severe operating conditions. Incorrect prediction of pipe-soil interaction may lead to excessive pipeline movement and overstressing of the lower pipeline riser elbow and other key components. Unsafe designs may result from a lack of understanding of this interaction. Battelle's Petroleum Technology Center in Houston, Texas, has completed a three-year study of offshore pipe-soil interaction and its impact on pipeline and riser design. This article reviews the conduct and results of the study.
Not Available
Stable or unstable wetting fronts in water repellent soils ¢ effect of antecedent soil moisture content
Dry water repellent soils are known to inhibit water infiltration, ultimately forcing water to flow via preferential paths through the vadose zone. To study water flow and transport in a water repellent sandy soil, a bromide tracer experiment had been carried out, which started in the fall after winter wheat had been sown. Despite the uniform tracer application, soil core
Coen J Ritsema; John L Nieber; Louis W Dekker; T. S. Steenhuis
Soil Water: Advanced Crop and Soil Science. A Course of Study.
ERIC Educational Resources Information Center
The course of study represents the fourth of six modules in advanced crop and soil science and introduces the agriculture student to the topic of soil water. Upon completing the three day module, the student will be able to classify water as to its presence in the soil, outline the hydrological cycle, list the ways water is lost from the soil,ģ
Miller, Larry E.
Soil water management implications during the constant rate and the falling rate stages of soil evaporation
Desorptivity is a soil physical term used to describe the ability of soil to lose water by evaporation. Theoretically, it has been established that evaporation of water from soil during the falling rate stage, when water becomes limiting, is proportional to the square root of time. The proportionality constant is called desorptivity. Using ten soils with different textures from different
Mensah Bonsu
Soil water repellency patterns following long-term irrigation with waste water in a sandy calcareous soil, SE Spain
One of the consequences of long-term irrigation with waste water can be the development of soil water repellency (WR). Its emergence can affect soil-water balance, irrigation efficiency and crop yield. Water repellency development has been suggested to be controlled by parameters such as organic matter quantity and type present in the waste water, soil properties (particularly the texture), and the
J. Mataix-Solera; L. GarcĒa-Irles; A. Morugßn; S. H. Doerr; F. GarcĒa-Orenes; I. Atanassova; M. A. Navarro; H. Ayguadķ
Water repellency and critical soil water content in a dune sand
Assessments of water repellency of soils are commonly made on air-dried or oven-dried samples, without considering the soil water content. The objectives of this study were to examine the spatial and temporal variability of soil water content, actual water repellency over short distances, and the variations in critical soil water contents. Between 22 April and 23 November 1999, numerous samples
Louis W. Dekker; Stefan H. Doerr; Klaas Oostindie; Apostolos K. Ziogas; Coen J. Ritsema
Reflectance of Vegetation, Soil, and Water.
National Technical Information Service (NTIS)
The author has identified the following significant results. Reflectance of crop residues, that are important in reducing wind and water erosion, was more often different from bare soil in band 4 than in bands 5, 6, or 7. The plant parameters leaf area in...
C. L. Wiegand
Soil and Water Conservation Activities for Scouts.
ERIC Educational Resources Information Center
The purpose of the learning activities outlined in this booklet is to help Scouts understand some conservation principles which hopefully will lead to the development of an attitude of concern for the environment and a commitment to help with the task of using and managing soil, water, and other natural resources for long range needs as well asģ
Soil Conservation Service (USDA), Washington, DC.
Heat Exchange in Air, Water, and Soil
NSDL National Science Digital Library
The Earth is composed, at least at the surface, of soil/rock, water, and air. How do the heat exchange properties of these three very different substances compare, and what effect, if any, do they have on climate and weather? This activity represents a so
Eichinger, John
Cactus extract increases water infiltration rates in two soils
Polyacrylamides (PAM) and polysaccharides can be used as soil amendments to improve soil physical properties, including infiltration of water into soil. Mucilage from prickly pear cactus contains large polysaccharides. Two experiments were done to test the hypothesis that pretreating columns of soil with cactus extract would improve subsequent falling?head ponded infiltration of water. One experiment tested samples from a loamy
Duane Gardiner; Peter Felker; Todd Carr
An interactive software system was developed to enable decision-makers, regulators, policy-makers, scientists, consultants, and students to simulate the movement of waterand chemicals in unsaturated soils. Water movement is modeled using Richards (1931) - equation. Chemical trans...
Displacement of soil pore water by trichloroethylene
Dense nonaqueous phase liquids (DNAPLS) are important pollutants because of their widespread use as chemical and industrial solvents. An example of the pollution caused by the discharge of DNAPLs is found at the Picatinny Arsenal, New Jersey, where trichloroethylene (TCE) has been discharged directly into the unsaturated zone. This discharge has resulted in the formation of a plume of TCE-contaminated water in the aquifer downgradient of the discharge. A zone of dark-colored groundwater containing a high dissolved organic C content has been found near the point of discharge of the TCE. The colored-water plume extends from the point of discharge at least 30 m (100 feet) downgradient. Fulvic acids isolated from the colored-waters plume, from water from a background well that has not been affected by the discharge of chlorinated solvents, and from soil pore water collected in a lysimeter installed at an uncontaminated site upgradient of the study area have been compared. Nuclear magnetic resonance spectra of the fulvic acids from the colored waters and from the lysimeter am very similar, but are markedly different from the nuclear magnetic resonance spectrum of the fulvic acid from the background well. The three-dimensional fluorescence spectrum and the DOC fractionation profile of the colored groundwater and the soil pore water are very similar to each other, but quite different from those of the background water. It is proposed from these observations that this colored water is soil pore water that has been displaced by a separate DNAPL liquid phase downward to the saturated zone. 15 refs., 6 figs., 4 tabs.
Wershaw, R.L.; Aiken, G.R. [Denver Federal Center, CO (United States); Imbrigiotta, T.E. [Geological Survey, West Trenton, NJ (United States)
Fire induced changes in aggregate stability: the interacting effects of soil heating and ash leachate
NASA Astrophysics Data System (ADS)
Increases in runoff and erosion after wildfires are typically attributed to the combined effects of the loss of ground cover, water repellency and surface sealing. Surface sealing in burned areas is caused by raindrop compaction of mineral soils (structural seal formation), the clogging of soil pores by fine soil and ash, or the formation of low conductivity ash crusts (depositional seal formation). Structural sealing is more likely to occur if the fire reduces the aggregate stability of the mineral soil. Soil heating tends to reduce aggregate stability by combusting soil organic matter. Effects due to soil heating may be amplified or reduced by interactions between soil clays and ash leachate, but these effects are poorly understood. We are investigating the interacting effects of soil heating and exposure to ash leachate on the stability of soil aggregates in burned areas. During the 2011 fire season in the Rocky Mountains we collected soil samples (~1000g) from unburned areas adjacent to three recent wildfires. Soils were obtained from areas with sharply contrasting parent materials, leading to differences in the soil mineralogy. High severity ash was collected from within the burned areas. Each soil sample was divided into 6 subsamples with the first subsample acting as a control. The remaining five subsamples were heated to 100, 200, 300, 500, and 700C respectively. After heating, each subsample was split in two. Ash leachate was added to one half and DI water was added to the other half. The ash leachate was prepared by mixing 10 g of ash with 1000 mL of water in accordance with previous studies. All samples were then air dried and analyzed for porosity, bulk density, aggregate size distribution, aggregate stability and water repellency. Initial results suggest that there is an interacting effect of soil heating and exposure to ash leachate on the stability of soil aggregates, but the effect varies depending on the mineralogy of soil clays and the type of cations in the leachate. Thus, in order to predict effects of fire on soil aggregate stability it is necessary to determine not only the intensity of soil heating but also the soil clay mineralogy and the ash cation chemistry.
Balfour, V.; Hatley, D.; Woods, S.
Belastung von Boeden und Gewaessern. (Soil and water pollution).
National Technical Information Service (NTIS)
Findings of soil and water pollution studies were presented at a conference of the Arbeitsgemeinschaft Grossfroschungseinrichtungen (AGF). The problem of soil and water pollution is past of the general subject 'analysis of environmental pollution' in envi...
Impact of soil compaction upon soil water balance and maize yield estimated by the SIMWASER model
The capability of the soil water balance model SIMWASER to predict the impact of soil compaction upon the yield of maize (Zea mays L.) is tested, using the results of a field experiment on the influence of soil compaction by wheel pressure upon soil structure, water regime and plant growth. The experimental site was located on an Eutric Cambisol with
E Stenitzer; E Murer
Climate Change Impacts on Soil and Water Conservation
Planning for Extremes: Addressing Climate Change Impacts on Soil and Water Conservation, Milwaukee, Wisconsin, 1-3 November 2006 Climate change and particularly precipitation changes will affect water runoff and soil erosion from agricultural cropland, but will the change be large enough to warrant modifications in U.S. conservation policy or practice? In a 2003 report by the Soil and Water Conservation Society
Jurgen D. Garbrecht; Jean L. Steiner; Craig A. Cox
Modelling for planning soil and water conservation: a critical review
Degradation of soil and water resources, which is increasing throughout the World, is affecting directly and indirectly all the vital processes on the Earth's surface. This is partially due to non-appropriate land use planning, where soil and water conservation must be the most important components. Global climate changes may contribute to accelerate some soil and water degradation processes and their
SENT═S Ildefonso
Spatial variability constraints to modeling soil water at different scales
There is increasing interest in modeling soil water content over relatively large areas or scales. In general, the spatial variability of soil water content increases with scale, but it is not known how much or at which scales. High spatial variability constrains soil water models by reducing the accuracy of input parameters, calibration and verification data. It may also require
M Seyfried
River regulation and interactions groundwater - surface water
NASA Astrophysics Data System (ADS)
The determination of a minimum acceptable flow in a river affected by regulation is a major task in management of hydropower development. The Norwegian Water Resources and Energy Directorate (NVE), responsible for administrating the nation's water resources, requires an objective system that takes into account the needs of the developer and the rivers environment such as water quality, river biota, landscape, erosion and groundwater. A research project has been initiated with focus on interactions between groundwater and surface water. The purpose of the project is to provide the licensing authorities with tools for quantitative assessment of the effects of regulation on groundwater resources and at the same time the effect of groundwater abstraction on river flows. A small, urbanised alluvial plain (2 km^2) by the river Glomma in Central Southern Norway is used as a case study. The local aquifer consists of heterogeneous glaciofluvial and fluvial deposit, mainly sand and gravel. Two three-dimensional numerical models (Visual Modflow 3.0 and Feflow 5.0) have been used for this study. The models were calibrated with hydro-geological data collected in the field. Aquifer and river sediment has been examined by use of Ground Penetrating Radar (GPR) and soil samples collection. Preferential flow has been examined by tracer tests. Water level, temperature and electric conductivity have been recorded in both aquifer and river. Hydro-climatic regime has been analysed by statistical tools. The first task of the project is to carry out water balance studies in order to estimate the change in rate of groundwater recharge from and to the river along a normal hydrologic year with snowmelting, flood, and baseflow. The second task is to analyse the potential effect of change in the river water regime (due to regulation and consecutive clogging) on groundwater resources and their interaction with stream water.
Colleuille, H.; Wong, W. K.; Dimakis, P.; Pedersen, T. S.
Drag anchor fluke?soil interaction in clays
Finite element analysis of the fluke-soil interaction behaviour of drag anchors in undrained soil has allowed calculation of plastic yield loci for characterisation of fluke failure states. The yield loci produced are examined in terms of soil deformation mechanisms and kinematics and are incorporated into a novel method for drag anchor design.
M. F. Bransby; M. P. O'Neill; M. F. Randolph
Soil-water characteristic curves for compacted clays
Soil-water characteristic curves (SWCCs) are presented for four compacted clay barrier soils that were prepared at different compaction water contents (dry, wet, and optimum water content) and compactive efforts (standard and modified Proctor). The SWCCs were measured in the laboratory using pressure plate extractors. The shape of the SWCC depends on compaction water content and compactive effort, but compaction water
James M. Tinjum; Craig H. Benson; Lisa R. Blotz
Guidelines for soil-structure interaction analysis
This report presents engineering application guidelines for conducting seismic soil-structure interaction (SSI) analyses of nuclear power plant structures. These guidelines are largely based on the results obtained and lessons learned from the Large-Scale Seismic Test (LSST) program involving {1/4} and 1/12 scaled containment models in Lotung, Taiwan. The development of these guidelines has taken into consideration the guidelines recommended in the ASCE Standard 4--86, Seismic Analysis of Safety-Related Nuclear Structures'', and the new revision (Revision 2) of the NRC Standard Review Plan (SRP), Section 3.7.2, Seismic System Analysis.'' The guidelines presented in this report follow an approach which reckons every necessary step for characterizing and providing an adequate solution to the total SSI problem which is broken down into a series of five SSI subproblems, namely, site response problem, foundation scattering problem, structural modelling problem, foundation impedance problem, and interaction response solution problem. The four analysis methods evaluated are the lumped-parameter (soil-spring) method, the continuum-halfspace substructing (CLASSI) method, the discretized-halfspace substructing (SASSI) method, and the finite element direct (FLUSH and ALUSH) method. The approach used herein was found to be very effective for evaluating the validities of the various SSI analysis results and findings of the LSST program. The guidelines presented herein place emphasis on the general requirements, procedures, and criteria for conducting SSI analyses in an industry environment by those involved in the seismic design or performance evaluation of nuclear power plant structures and equipment. 53 refs., 17 figs.
Tseng, W.S. (International Civil Engineering Consultants, Inc., Berkeley, CA (United States)); Hadjian, A.H. (Bechtel Corp., Los Angeles, CA (United States))
Properties of soil organic matter and aqueous extracts of actually water repellent and wettable soil samples
The occurrence of water repellent spots can inhibit a homogeneous wetting progress in soil. Although the wettability is an important factor for sorption and transport processes, the knowledge about the reasons for water repellent behavior and its effects on other soil properties is still insufficient. In this study, water repellent and wettable soil samples from two urban locations were compared.
Julia Hurra▀; Gabriele E. Schaumann
Estimating soil water evaporation using radar measurements
NASA Technical Reports Server (NTRS)
Field studies were conducted to evaluate the application of radar reflectivity as compared with the shortwave reflectivity (albedo) used in the Idso-Jackson equation for the estimation of daily evaporation under overcast sky and subhumid climatic conditions. Soil water content, water potential, shortwave and radar reflectivity, and soil and air temperatures were monitored during three soil drying cycles. The data from each cycle were used to calculate daily evaporation from the Idso-Jackson equation and from two other standard methods, the modified Penman and plane of zero-flux. All three methods resulted in similar estimates of evaporation under clear sky conditions; however, under overcast sky conditions, evaporation fluxes computed from the Idso-Jackson equation were consistently lower than the other two methods. The shortwave albedo values in the Idso-Jackson equation were then replaced with radar reflectivities and a new set of total daily evaporation fluxes were calculated. This resulted in a significant improvement in computed soil evaporation fluxes from the Idso-Jackson equation, and a better agreement between the three methods under overcast sky conditions.
Sadeghi, Ali M.; Scott, H. D.; Waite, W. P.; Asrar, G.
Temporal patterns of infiltration into a water repellent soil under field conditions
NASA Astrophysics Data System (ADS)
Water repellency causes substantial economic losses for farmers in southern Australia through impacts on crop growth and weed germination. However, recent research has demonstrated that laboratory measurements of water repellency may not be a reliable indicator of the severity of symptoms experienced in the field. In particular, crop residue retention and minimal soil disturbance led to increased water repellency, but was also associated with higher soil water contents measured at strategic times of the year. Little is known about the temporal patterns of soil water storage close to the soil surface in a water repellent sand. In this research we measured soil water content at a depth of 0.05 m at 15-minute intervals from June 2011 to October 2012, under various treatment combinations of residue retention and soil disturbance. Measurements were made in both 'crop row' and 'crop inter-row' positions. For a rainfall event (9.2 mm) in March 2012, prior to crop seeding, plots previously established with no-till absorbed significantly more water (increase in soil water content of 0.074 v/v) than plots conventionally cultivated (0.038 v/v). In June 2012 (12.6 mm), 4 weeks after crop seeding, tillage was again significant, and there was a significant interaction between tillage and 'row' or 'inter-row' position. These results demonstrate the importance of crop management in modifying the response of water repellent soils to rainfall in the field.
Ward, Phil; Roper, Margaret; Micin, Shayne; Jongepier, Ramona
Physical properties and soil-water balance of key soils of the Opotiki region, North Island, New Zealand
The soil pattern of the Opotiki region consists of alluvial soils and soils derived from volcanic ash. The soils range from recent soils to gley soils and yellow-brown loams and are discussed in terms of soil physical properties and water balance. Levels of available water are generally high to very high except where root depth is restricted by high ground
W. C. Rijkse
Water movement through an experimental soil liner
A field-scale soil liner was constructed to test whether compacted soil barriers in cover and liner systems could be built to meet the U.S. EPA saturated hydraulic conductivity requirement (???1 x 10-7 cm s-1). The 8 x 15 x 0.9m liner was constructed in 15 cm compacted lifts using a 20,037 kg pad-foot compactor and standard engineering practices. Water infiltration into the liner has been monitored for one year. Monitoring will continue until water break through at the base of the liner occurs. Estimated saturated hydraulic conductivities were 2.5 x 10-9, 4.0 x 10-8, and 5.0 x 10-8 cm s-1 based on measurements of water infiltration into the liner by large- and small-ring infiltrometers and a water balance analysis, respectively. Also investigated in this research was the variability of the liner's hydraulic properties and estimates of the transit times for water and tracers. Small variances exhibited by small-ring flux data suggested that the liner was homogeneous with respect to infiltration fluxes. The predictions of water and tracer breakthrough at the base of the liner ranged from 2.4-12.6 y, depending on the method of calculation and assumptions made. The liner appeared to be saturated to a depth between 18 and 33 cm at the end of the first year of monitoring. Transit time calculations cannot be verified yet, since breakthrough has not occurred. The work conducted so far indicates that compacted soil barriers can be constructed to meet the saturated hydraulic conductivity requirement established by the U.S. EPA.A field-scale soil liner was constructed to test whether compacted soil barriers in cover and liner systems could be built to meet the U.S. EPA saturated hydraulic conductivity requirement (??? 1 ?? 10-7 cm s-1). The 8 ?? 15 ?? 0.9 m liner was constructed in 15 cm compacted lifts using a 20.037 kg pad-foot compactor and standard engineering practices. Water infiltration into the liner has been monitored for one year. Monitoring will continue until water break through at the base of the liner occurs. Estimated saturated hydraulic conductivities were 2.5 ?? 10-9, 4.0 ?? 10-8, and 5.0 ?? 10-8 cm s-1 based on measurements of water infiltration into the liner by large- and small-ring infiltrometers and a water balance analysis, respectively. Also investigated in this research was the variability of the liner's hydraulic properties and estimates of the transit times for water and tracers. Small variances exhibited by small-ring flux data suggested that the liner was homogeneous with respect to infiltration fluxes. The predictions of water and tracer breakthrough at the base of the liner ranged from 2.4-12.6 y, depending on the method of calculation and assumptions made. The liner appeared to be saturated to a depth between 18 and 33 cm at the end of the first year of monitoring. Transit time calculations cannot be verified yet, since breakthrough has not occurred. The work conducted so far indicates that compacted soil barriers can be constructed to meet the saturated hydraulic conductivity requirement established by the U.S. EPA.
Krapac, I. G.; Cartwright, K.; Panno, S. V.; Hensel, B. R.; Rehfeldt, K. R.; Herzog, B. L.
Ad Hoc Modeling of Root Zone Soil Water with Landsat Imagery and Terrain and Soils Data
Agricultural producers require knowledge of soil water at plant rooting depths, while many remote sensing studies have focused on surface soil water or mechanistic models that are not easily parameterized. We developed site-specific empirical models to predict spring soil water content for two Montana ranches. Calibration data sample sizes were based on the estimated variability of soil water and the desired level of precision for the soil water estimates. Models used Landsat imagery, a digital elevation model, and a soil survey as predictor variables. Our objectives were to see whether soil water could be predicted accurately with easily obtainable calibration data and predictor variables and to consider the relative influence of the three sources of predictor variables. Independent validation showed that multiple regression models predicted soil water with average error (RMSD) within 0.04 mass water content. This was similar to the accuracy expected based on a statistical power test based on our sample size (n = 41 and n = 50). Improved prediction precision could be achieved with additional calibration samples, and range managers can readily balance the desired level of precision with the amount of effort to collect calibration data. Spring soil water prediction effectively utilized a combination of land surface imagery, terrain data, and subsurface soil characterization data. Ranchers could use accurate spring soil water content predictions to set stocking rates. Such management can help ensure that water, soil, and vegetation resources are used conservatively in irrigated and non-irrigated rangeland systems.
Sankey, Joel B.; Lawrence, Rick L.; Wraith, Jon M.
Modeling soil¢root water transport and competition for single and mixed crops
A knowledge of above and below ground plant interactions for water is essential to understand the performance of intercropped systems. In this work, root water potential dynamics and water uptake partitioning were compared between single crops and intercrops, using a simulation model. Four root maps having 498, 364, 431 and 431 soil-root contacts were used. In the first and second
F. Lafolie; L. Bruckler; H. Ozier-Lafontaine; R. Tournebize; A. Mollier
Only one isotopic water world: relevant processes at the soil-vegetation-atmosphere interface (Invited)
The stable water isotopes of oxygen and hydrogen have been used to gain process and system knowledge about flow pathways, residence times, mixing and redistribution for many decades. In recent years the processes due to water-ecosystem interactions have become more relevant and new ideas how processes effect the isotopic signature of soil water and runoff have been postulated (e.g. Brooks
M. Weiler; K. Gimbel; R. Weber
Quantifying nonisothermal subsurface soil water evaporation
NASA Astrophysics Data System (ADS)
Accurate quantification of energy and mass transfer during soil water evaporation is critical for improving understanding of the hydrologic cycle and for many environmental, agricultural, and engineering applications. Drying of soil under radiation boundary conditions results in formation of a dry surface layer (DSL), which is accompanied by a shift in the position of the latent heat sink from the surface to the subsurface. Detailed investigation of evaporative dynamics within this active near-surface zone has mostly been limited to modeling, with few measurements available to test models. Soil column studies were conducted to quantify nonisothermal subsurface evaporation profiles using a sensible heat balance (SHB) approach. Eleven-needle heat pulse probes were used to measure soil temperature and thermal property distributions at the millimeter scale in the near-surface soil. Depth-integrated SHB evaporation rates were compared with mass balance evaporation estimates under controlled laboratory conditions. The results show that the SHB method effectively measured total subsurface evaporation rates with only 0.01-0.03 mm h-1difference from mass balance estimates. The SHB approach also quantified millimeter-scale nonisothermal subsurface evaporation profiles over a drying event, which has not been previously possible. Thickness of the DSL was also examined using measured soil thermal conductivity distributions near the drying surface. Estimates of the DSL thickness were consistent with observed evaporation profile distributions from SHB. Estimated thickness of the DSL was further used to compute diffusive vapor flux. The diffusive vapor flux also closely matched both mass balance evaporation rates and subsurface evaporation rates estimated from SHB.
Deol, Pukhraj; Heitman, Josh; Amoozegar, Aziz; Ren, Tusheng; Horton, Robert
Forecasting corn nitrogen fertilizer rate based on soil water fluctuation
The objective of this paper has been to develop a model for nitrogen(N) fertilizer rate forecasting for corn crop (Zea mays L.) based on plant available soil water (PAW) and precipitation. Crop N requirements, soil organic matter, N supplying capability of soil, or initial soil nitrate were used as the basis for N fertilizer recommendations. Often a standard average N
D. Isfan
Impacts of Evaporation from Saline Soils on Soil Hydraulic Properties and Water Fluxes
NASA Astrophysics Data System (ADS)
Saline soils are common in arid zones, where evaporation from shallow groundwater is generally the major component of the water balance. Thus, accurate quantification of soil water evaporation is crucial to improve water resource management in these regions. Evaporation from saline soils is a complex process that couples the movement of salts, heat, liquid water and water vapor. Precipitation/dissolution reactions can alter the soil structure and modify flow paths. The impact of evaporation from shallow groundwater on soil properties and water fluxes poses a major hydrologic challenge that remains to be answered. As a preliminary approach to consider these effects, we used the SiSPAT model (Simple Soil Plant Atmospheric Transfer) to represent the movement of liquid water and water vapor in a saline soil column subjected to two groundwater levels under nonisothermal conditions. To parameterize the model, we determined the hydraulic properties of the soil before performing the soil column experiments. When the SiSPAT model was run using uniform and constant hydraulic properties, it was unable to predict the moisture and thermal profiles, or the cumulative evaporation. This inability to reproduce the observed data is most likely due to alterations of the soil structure as a result of precipitation/dissolution reactions. When the soil hydraulic properties were allowed to vary in space, the model reproduced the experimental data successfully, suggesting that the structure of the initially homogeneous soil column was modified. It is thus necessary to incorporate salt precipitation to correctly simulate evaporation in saline soils.
Fierro, V.; Hernandez, M. F.; Braud, I.; Cristi Matte, F.; Hausner, M. B.; Suarez, F. I.; Munoz, J.
Seasonal and long-term effects of CO2 and O3 and their interaction with climate and soil moisture on water loss in ponderosa pine
Evapotranspiration (ET) is driven by evaporative demand, available solar energy and soil moisture as well as by physiological plant activity which may be substantially affected by elevated CO2 and O3. A multi-year study was conducted in outdoor sun-lit controlled-environment cha...
Seasonal and long-term effects of CO2 and O3 on water loss in ponderosa pine and their interaction with climate and soil moisture
Evapotranspiration (ET) is driven by evaporative demand, available solar energy and soil moisture (SM) as well as by plant physiological activity which may be substantially affected by elevated CO2 and O3. A multi-year study was conducted in outdoor sunlit-controlled environment ...
On the assessment of root and soil respiration for soils of different textures: interactions with soil moisture contents and soil CO2 concentrations
Estimates of root and soil respiration are becoming increasingly important in agricultural and ecological research, but there\\u000a is little understanding how soil texture and water content may affect these estimates. We examined the effects of soil texture\\u000a on (i) estimated rates of root and soil respiration and (ii) soil CO2 concentrations, during cycles of soil wetting and drying in the
Tjeerd J. Bouma; David R. Bryla
Soil and ground-water restoration by steam enhanced extraction
The acceleration of recovery rates of second phase liquid contaminants from the subsurface during gas or water pumping operations is realized by increasing the soil and ground-water temperature. Several methods of delivery of thermal energy to soils and ground water are possible. Of these methods, steam injection combined with ground-water pumping and vacuum extraction appears to be the most economical
Modeling soil water regime - from laboratory scale to hillslope scale
Laboratory determined soil hydraulic parameters were used for the modeling of the soil water regime at the experimental watershed Uhlirska in the Jizera Mountains, North Bohemia. The simulations were carried out for the period of May 1 to September 30 of the year 2001. The resulting space-time development of the soil water pressure was compared to the observed tensiometer data
T. Vogel; M. Cislerova; M. Sanda; M. Dohnal
Measuring and modelling water related soil-vegetation feedbacks in a fallow plot
NASA Astrophysics Data System (ADS)
Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field scale water balance. The objectives of this study are to test the potential of integrated non invasive geophysical methods and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during a controlled irrigation experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of ERT maps of soil moisture evidenced a considerably different hydrologic response to irrigation of the two plots. Local measurements of soil saturation and vegetation cover were repeated in space to evidence a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the fallow site.
Ursino, N.; Cassiani, G.; Deiana, R.; Vignoli, G.; Boaga, J.
Surface soil water content regimes: opportunities in soil science
With the qualities and properties of soil not being uniformly distributed across continents, soils are classified according to their morphological features, genesis and soil-forming processes. Because properties of soils vary across the landscape, a relationship observed at one location may not be applicable for other locations. Hence, measured data and deduced relationships are location specific and should be interpreted with
Donald R. Nielsen; Miroslav KutĒlek; Marc B. Parlange
Determination of Martian soil mineralogy and water content using the Thermal Analyzer for Planetary Soils (TAPS)
NASA Technical Reports Server (NTRS)
Physical and chemical interactions between the surface and atmosphere of Mars can be expected to embody a strong cause-and-effect relationship with the minerals comprising the martian regolith. Many of the minerals in soils and sediments are probably products of chemical weathering (involving surface/atmosphere or surface/hydrosphere reactions) that could be expected to subsequently influence the sorption of atmospheric gases and water vapor. Therefore, identification of the minerals in martian surface soils and sediments is essential for understanding both past and present interactions between the Mars surface and atmosphere. Clearly, the most definitive mineral analyses would be achieved with well-preserved samples returned to Earth-based laboratories. In advance of a Mars sample return mission, however, significant progress could be made with in situ experiments that fill current voids in knowledge about the presence or abundance of key soil minerals such as clays (layered-structured silicates), zeolites, and various salts, including carbonates. TAPS is intended to answer that challenge by providing first-order identification of soil and sediment minerals.
Gooding, James L.; Ming, Douglas W.; Allton, Judith H.; Byers, Terry B.; Dunn, Robert P.; Gibbons, Frank L.; Pate, Daniel B.; Polette, Thomas M.
Formation of Soil Water Repellency by Laboratory Burning and Its Effect on Soil Evaporation
Fire-induced soil water repellency can vary with burning conditions, and may lead to significant changes in soil hydraulic properties. However, isolation of the effects of soil water repellency from other factors is difficult, particularly under field conditions. This study was conducted to (i) investigate the effects of burning using different plant leaf materials and (ii) of different burning conditions on
Sujung Ahn; Sangjun Im
Water retention of mineral soil is often well predicted using algorithms (pedotransfer functions) with basic soil properties but the spatial variability of these properties has not been well characterized. A further source of uncertainty is that water retention by volcanic soils...
Effect of sample disturbance on soil water repellency determination in sandy soils
Effective irrigation of managed lands suffering from soil water repellency can benefit from understanding the spatial distribution of repellency in the surface soil layer at actual field conditions. We examined whether the common procedure of mixing and homogenizing samples from the soil surface layer gives representative values of field repellency. Water drop penetration time (WDPT) measurements were made for more
E. R. Graber; O. Ben-Arie; R. Wallach
Spatial and temporal soil water estimation considering soil variability and evapotranspiration uncertainty
Lack of accurate information stemming from soil variability and climatic uncertainty obstructs efficient irrigation management. State-space models of soil water balance and potential evapotranspiration were used in the application of spatial-temporal estimation methods to reduce uncertainty. Temporal soil water storage estimates and estimation errors were obtained by the Kalman filter (KF). Spatial estimates were obtained by the conditional multivariate normal
R. J. Hanks
Spatial and Temporal Soil Water Estimation Considering Soil Variability and Evapotranspiration Uncertainty
Lack of accurate information stemming from soil variability and climatic uncertainty obstructs efficient irrigation management. State-space models of soil water balance and potential evapotranspiration were used in the application of spatial-temporal estimation methods to reduce uncertainty. Temporal soil water storage estimates and estimation errors were obtained by the Kalman filter (KF). Spatial estimates were obtained by the conditional multivariate normal
Dani; R. J. Hanks
A method is presented for developing probability density functions for parameters of soil moisture relationships of capillary head and hydraulic conductivity. These soil moisture parameters are required for the assessment of water flow and solute transport in unsaturated media. T...
Surface water and groundwater interactions in coastal wetlands
NASA Astrophysics Data System (ADS)
Salt marshes are an important wetland system in the upper intertidal zone, interfacing the land and coastal water. Dominated by salt-tolerant plants, these wetlands provide essential eco-environmental services for maintaining coastal biodiversity. They also act as sediment traps and help stabilize the coastline. While they play an active role in moderating greenhouse gas emissions, these wetlands have become increasingly vulnerable to the impact of global climate change. Salt marshes are a complex hydrological system characterized by strong, dynamic interactions between surface water and groundwater, which underpin the wetland's eco-functionality. Bordered with coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur at different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil aeration conditions, which in turn affect marsh plant growth. This talk presents results and findings from recent numerical and experimental studies, focusing on the pore-water flow behaviour in the marsh soil under the influence of tides and density-gradients.
Li, Ling; Xin, Pei; Shen, Chengji
Effects of land use on temporal-spatial variability of soil water and soil-water conservation
The Loess Plateau of China suffers serious soil erosion primarily resulting from irrational land uses. Soil water plays a critical role influencing vegetation-restoration processes, but varies with temporal and spatial characteristics, of concern to many researchers. However, few studies consider the influence of deep soil water and varied weather patterns in a semi-arid region. Four vegetation types chosen for this
Chen Zeng; Mingan Shao; Quanjiu Wang; Jun Zhang
Method for Measuring Enriched Levels of Deuterium in Soil Water.
National Technical Information Service (NTIS)
This report describes procedures for analyzing hydrogen isotope ratios. Hydrogen is separated from liquid water or soil water by reacting the water with heated uranium. An isotope-ratio mass spectrometer determines the atom % deuterium in the hydrogen to ...
J. L. Oliphant T. F. Jenkins A. R. Tice
Surfactant solubilization of hydrophobic compounds in soil and water
The soil\\/water partition coefficient (Kd) of hexachlorobenzene (HCB) ranged from 220 1\\/kg to 1800 1\\/kg for eight soils having a wide range of physico-chemical properties.\\u000a Kd normalised to soil organic carbon (Koc) was found to be 28000 ▒ 4800 1\\/kg. Anionic surfactant dodecylsulphate (DS) present at concentrations above the critical\\u000a micellar concentration (CMC) caused reductions in the apparent soil\\/water partition
Ana B. Payß-Pķrez; Mohammed S. Rahman; Helle Skej°-Andresen; Bo R. Larsen
Ecohydrology of root zone water fluxes and soil development in complex semiarid rangelands
In semiarid complex terrain, the landscape creates spatial niches for\\u000a different types of vegetation through the effects of aspect, slope and\\u000a curvature on the water and energy balance at the soil surface. The\\u000a ecohydrology of rangelands is defined by the interaction of soils,\\u000a plants and climate occurring on a topographic surface. While these\\u000a interactions have been studied for subtle terrain,
Hugo A. Gutierrez-Jurado; Enrique R. Vivoni; J. Bruce J. Harrison; Huade Guan
Estimation of tree water relationships using a Soil-Tree-Atmosphere Continuum model
NASA Astrophysics Data System (ADS)
To better understand root-soil water interactions, a mature white fir (Abies concolor) and the surrounding root zone were continuously monitored (sap flow, canopy stem water potential, soil moisture, and temperature), to characterize tree hydrodynamics. We present a hydrodynamic flow model, simulating unsaturated flow in the soil and tree with stress functions controlling spatially distributed root water uptake and canopy transpiration. Using the van Genuchten functions, we parameterize the effective retention and unsaturated hydraulic conductivity functions of the tree sapwood and soil, soil and canopy stress functions, and radial root zone distribution. To parameterize the in-situ tree water relationships, we combine a numerical model with observational data in an optimization framework, minimizing residuals between simulated and measured observational data of soil and tree canopy. Using the MCMC method, the HYDRUS model is run in an iterative process that adjusts parameters until residuals are minimized. Using these optimized parameters, the HYDRUS model simulates diurnal tree water potential and sap flow as a function of tree height, in addition to spatially distributed changes in soil water storage and soil water potential.
Hopmans, Jan; Hartsough, Peter; Rings, Joerg; Kandalous, Maziar; Kamai, Tamir; Vrugt, Jasper; Simunek, Jirka
Soil CO? dynamics in a tree island soil of the Pantanal: the role of soil water potential.
The Pantanal is a biodiversity hotspot comprised of a mosaic of landforms that differ in vegetative assemblages and flooding dynamics. Tree islands provide refuge for terrestrial fauna during the flooding period and are particularly important to the regional ecosystem structure. Little soil CO? research has been conducted in this region. We evaluated soil CO? dynamics in relation to primary controlling environmental parameters (soil temperature and soil water). Soil respiration was computed using the gradient method using in situ infrared gas analyzers to directly measure CO? concentration within the soil profile. Due to the cost of the sensors and associated equipment, this study was unreplicated. Rather, we focus on the temporal relationships between soil CO? efflux and related environmental parameters. Soil CO? efflux during the study averaged 3.53 Ąmol CO? m?▓ s?╣, and was equivalent to an annual soil respiration of 1220 g C m?▓ y?╣. This efflux value, integrated over a year, is comparable to soil C stocks for 0-20 cm. Soil water potential was the measured parameter most strongly associated with soil CO? concentrations, with high CO? values observed only once soil water potential at the 10 cm depth approached zero. This relationship was exhibited across a spectrum of timescales and was found to be significant at a daily timescale across all seasons using conditional nonparametric spectral Granger causality analysis. Hydrology plays a significant role in controlling CO? efflux from the tree island soil, with soil CO? dynamics differing by wetting mechanism. During the wet-up period, direct precipitation infiltrates soil from above and results in pulses of CO? efflux from soil. The annual flood arrives later, and saturates soil from below. While CO? concentrations in soil grew very high under both wetting mechanisms, the change in soil CO? efflux was only significant when soils were wet from above. PMID:23762259
Johnson, Mark S; Couto, Eduardo GuimarŃes; Pinto, Osvaldo B; Milesi, Juliana; Santos Amorim, Ricardo S; Messias, Indira A M; Biudes, Marcelo Sacardi
Research summarized in this report focuses on the abiotic interactions of aromatic amines with whole soils in aqueous systems. This work was initiated to improve our ability to predict the mobility of aromatic amines and their potential to contaminate groundwater, and to improve...
A one-dimensional model of water flow in soil-plant systems based on plant architecture
The estimation of root water uptake and water flow in plants is crucial to quantify transpiration and hence the water exchange\\u000a between land surface and atmosphere. In particular the soil water extraction by plant roots which provides the water supply\\u000a of plants is a highly dynamic and non-linear process interacting with soil transport processes that are mainly determined\\u000a by the
Michael Janott; Sebastian Gayler; Arthur Gessler; Mathieu Javaux; Christine Klier; Eckart Priesack
Interaction between soil hydrology and boundary-layer development
A two-layer model of soil hydrology and thermodynamics is combined with a one-dimensional model of the planetary boundary layer to study various interactions between evolution of the boundary layer and soil moisture transport. Boundary-layer moistening through surface evaporation reduces the potential and actual surface evaporation as well as the boundary-layer growth. With more advanced stages of soil drying, the restricted
H.-L. Pan; L. Mahrt
Effect of antecedent soil-water content on aggregate stability and erodibility of a loess soil
NASA Astrophysics Data System (ADS)
Soil erosion processes are affected by the erodibility of the soil and by the erosivity of the rain. Aggregate stability is commonly considered as the most significant soil physical property that determines soil erodibility. Both aggregate stability and soil erodibility are commonly considered to be constant properties, without taking into account the influence of time-dependent parameters, such as antecedent soil-water content (?), being the soil-water content prior to the rainfall. The effects of rain characteristics and invariant soil properties such as texture and organic matter content on soil erosion processes are well documented. However, the effect of antecedent soil-water content on aggregate breakdown, seal formation and subsequent soil erosion is much more disputable as opposing effects have been reported. The objectives were to determine the effect of ? on aggregate stability, seal formation, runoff and soil loss. Lab experiments were conducted on a Belgian silt loam soil. Air-dried soil aggregates were subjected to antecedent soil-water contents of 0.04 (air-dry aggregates), 0.12 and 0.19 m3 m-3. Aggregate stability was determined according to the 'dry and wet sieving' method of De Leenheer and De Boodt (1959). The method starts from fixed aggregate fractions obtained from dry sieving which subsequently are prewetted and undergo a wet sieving. Runoff and soil loss was determined by means of a laboratory rainfall simulator, consisting of a rotating circular water tank, which is located at 3.20 m height and which is supplied with 90 glass capillaries serving as drop formers. A positive relationship between antecedent soil-water content and aggregate stability was found. This can be attributed to a decrease in slaking forces. On the soils with highest antecedent soil-water content an increase in aggregate stability due to prewetting prevented aggregate breakdown. As such, no seal was formed and no runoff occurred. The highest total runoff values were observed for the intermediate ?, while intermediate amounts of total runoff were noticed for the air-dry aggregates. Soil loss, however, showed a different trend: highest values were found for the lowest ?, intermediate values for the intermediate ? and no soil loss for the highest ?. We further observed that ? had no influence on the final runoff rates and on the final infiltration rate through the soil surface. In using a water discharge and stream power equation to predict sediment transport, we found a decreasing erodibility with increasing ?. We therefore suggest including ? as an additional variable to assess soil erodibility in deterministic event-based water erosion models.
Vermang, J.; Demeyer, V.; Cornelis, W. M.; Gabriels, D.
Response of cotton water stress indicators to soil salinity
A field study was conducted on cotton (Gossypium hirsutum L. c.v. Acala SJ-2) to investigate the effects of soil salinity on the responses of stress indices derived from canopy temperature, leaf diffusion resistance and leaf water potential. The four salinity treatments used in this study were obtained by mixtures of aqueduct and well water to provide mean soil water electrical
T. A. Howell; J. L. Hatfield; J. D. Rhoades; M. Meron
Oxygen isotopic composition of soil water: Quantifying evaporation and transpiration
The oxygen isotopic composition of soil water provides an extra quantitative dimension in water balance analysis which allows separation of evaporation from transpiration. Spatial and temporal variations in water content and oxygen isotopic composition in soils along an arid to humid transect in Hawaii reflect the processes of recharge by rain, mixing with antecedent moisture, and evapotranspiration. Rainwater is always
Jean C. C Hsieh; Oliver A Chadwick; Eugene F Kelly; Samuel M Savin
Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporati...
Integrating water by plant roots over spatially distributed soil salinity
In numerical simulation models dealing with water movement and solute transport in vadose zone, the water budget largely depends on uptake patterns by plant roots. In real field conditions, the uptake pattern largely changes in time and space. When dealing with soil and water salinity, most saline soils demonstrate spatially distributed osmotic head over the root zone. In order to
Mehdi Homaee; Urs Schmidhalter
Water repellent soils as they occur on UK golf greens
Water repellent soils have been identified as a major problem in the management of golf greens in the UK for over 60years. The cause of this problem has provoked much speculation, but prior to this work, no research into the possible cause of water repellent soils in the UK had been completed. One of the commonly believed links with water
C. A York; P. M Canaway
Semiempirical model of soil water hysteresis
In order to represent hysteretic soil water retention curves accurately using as few measurements as possible, a new semiempirical model has been developed. It has two postulates related to physical characteristics of the medium, and two parameters, each with a definite physical interpretation, whose values are determined empirically for a given porous medium. Tests of the model show that it provides high-quality optimized fits to measured water content vs. matric pressure wetting curves for a wide variety of media. A practical use of this model is to provide a complete simulated main wetting curve for a medium where only a main drying curve and two points on the wetting curve have been measured. -from Author
Nimmo, J. R.
Modeling distributions of water and dielectric constants around land mines in homogeneous soils
NASA Astrophysics Data System (ADS)
Many sensors for landmine detection are affected by soil water content, temperature, electrical conductivity and dielectric constant. The most important of these is water content since it directly influences the three other properties. We model water distribution around antitank mines buried in a loam and loamy sand soil under the climatic conditions of Bosnia and Kuwait. In Kuwait the loam and loamy sand have mean soil water contents of about 16 and 7 volume percent, respectively; in Bosnia, the mane water contents are higher with means of 30 and 14 volume percent in the loam and loamy sand. As a result the soil dielectric constant in Kuwait varied from about 4 to 8 in the loamy sand and from 8 to 14 in the loam. In Bosnia the higher water contents result in a soil dielectric constant from 4 to 12 in the loamy sand and from 9 to 50 in the loam. Water contents below the landmine were sometimes higher than above it. The modeling result demonstrate that a solid water content regimes and the resulting distributions of soil dielectric constants around landmines are strongly affected by the interaction between climate, soil type, and landmine geometry.
Hendrickx, Jan M.; Das, Bhabani S.; Borchers, Brian
Lepidium latifolium : plant nutrient competition-soil interactions
Exotic weeds are invading rangelands of the western United States at unprecedented rates. Understanding plant-soil relationships and competitive interactions of invasive weeds is crucial in long-term control strategies. In a greenhouse experiment, we investigated the influence of soil nutrient depletion on plant growth and plant competition between the exotic invasive weeds, Lepidium latifolium (invading wetlands) and Bromus tectorum (invading a
Robert R. Blank; Robert G. Qualls; James A. Young
Soil water repellency in north-eastern Greece with adverse effects of drying on the persistence
Many soils may be water repellent to some degree, challenging the common perception that soil water repellency is only an interesting aberration. When dry, water repellent soils resist or retard water infiltration into the soil matrix. Soil water repellency often leads to the development of unstable wetting and preferential flow paths. In the present study the persistence of water repellency
Apostolos K. Ziogas; Louis W. Dekker; Klaas Oostindie; Coen J. Ritsema
Interactions between soil thermal and hydrological dynamics in the response of Alaska ecosystems to fire disturbance
Soil temperature and moisture are important factors that control many ecosystem processes. However, interactions between soil thermal and hydrological processes are not adequately understood in cold regions, where the frozen soil, fire disturbance, and soil drainage play important roles in controlling interactions among these processes. These interactions were investigated with a new ecosystem model framework, the dynamic organic soil version of the Terrestrial Ecosystem Model, that incorporates an efficient and stable numerical scheme for simulating soil thermal and hydrological dynamics within soil profiles that contain a live moss horizon, fibrous and amorphous organic horizons, and mineral soil horizons. The performance of the model was evaluated for a tundra burn site that had both preburn and postbura measurements, two black spruce fire chronosequences (representing space-for-time substitutions in well and intermediately drained conditions), and a poorly drained black spruce site. Although space-for-time substitutions present challenges in modeldata comparison, the model demonstrates substantial ability in simulating the dynamics of ??vapotranspiration, soil temperature, active layer depth, soil moisture, and water table depth in response to both climate variability and fire disturbance. Several differences between model simulations and field measurements identified key challenges for evaluating/improving model performance that include (1) proper representation of discrepancies between air temperature and ground surface temperature; (2) minimization of precipitation biases in the driving data sets; (3) improvement of the measurement accuracy of soil moisture in surface organic horizons; and (4) proper specification of organic horizon depth/properties, and soil thermal conductivity. Copyright 2009 by the American Geophysical Union.
Yi, S.; McGuire, A. D.; Harden, J.; Kasischke, E.; Manies, K.; Hinzman, L.; Liljedahl, A.; Randerson, J.; Liu, H.; Romanovsky, V.; Marchenko, S.; Kim, Y.
Reflectance of vegetation, soil, and water
NASA Technical Reports Server (NTRS)
The author has identified the following significant results. The ability to read the 24-channel MSS CCT tapes, select specified agricultural land use areas from the CCT, and perform multivariate statistical and pattern recognition analyses has been demonstrated. The 5 optimum channels chosen for classifying an agricultural scene were, in the order of their selection the far red visible, short reflective IR, visible blue, thermal infrared, and ultraviolet portions of the electromagnetic spectrum, respectively. Although chosen by a training set containing only vegetal categories, the optimum 4 channels discriminated pavement, water, bare soil, and building roofs, as well as the vegetal categories. Among the vegetal categories, sugar cane and cotton had distinctive signatures that distinguished them from grass and citrus. Acreages estimated spectrally by the computer for the test scene were acceptably close to acreages estimated from aerial photographs for cotton, sugar cane, and water. Many nonfarmable land resolution elements representing drainage ditch, field road, and highway right-of-way as well as farm headquarters area fell into the grass, bare soil plus weeds, and citrus categories and lessened the accuracy of the farmable acreage estimates in these categories. The expertise developed using the 24-channel data will be applied to the ERTS-1 data.
Wiegand, C. L. (principal investigator)
Monitoring soil-vegetation interactions using non-invasive geophysical techniques
NASA Astrophysics Data System (ADS)
The understanding of soil-vegetation-atmosphere interactions is of utmost importance in the solution of a number of hydrological questions and practical issues, including flood control, agricultural best practice, slope stability and impacts of climatic changes. Geophysical time-lapse monitoring can greatly contribute to the understanding of these interactions particularly for its capability to map in space and time the effects of vegetation on soil moisture content. In this work we present the results of two case studies showing the potential of hydro-geophysics in this context. The first example refers to the long term monitoring of the soil static and dynamic characteristics in an experimental site located in Sardinia (Italy). The main objective of this study is to understand the effects of soil - water - plants interactions on soil water balance. A combination of time-lapse electromagnetic induction (EMI) monitoring over wide areas and localized irrigation tests monitored by electrical resistivity tomography (ERT) and TDR soil moisture measurements is here used, in order to achieve quantitative field-scale estimates of moisture content from topsoil layer. Natural gamma-ray emission mapping, texture analysis and laboratory calibration of an electrical constitutive relationship on soil samples complete the dataset. We therefore observed that the growth of vegetation, with the associated below ground allocation of biomass, has a significant impact on the soil moisture dynamics. In particular vegetation extracts a large amount of water from the soil in the hot season, but it also reduces evaporation by shadowing the soil surface. In addition, vegetation enhances the soil wetting process as the root system facilitates water infiltration, thus creating a positive feedback system. The second example regards the time-lapse monitoring of soil moisture content in an apple orchard located in the Alpine region of Northern Italy (Trento). A three-dimensional cross-hole ERT setup was created using four small-scale boreholes and a 2D array of surface electrodes. The soil response to irrigation and evapo-transpiration evidences the location of tree roots, including the influence of irrigation patterns on the root growth, and their efficiency at removing soil moisture.
Perri, M.; Cassiani, G.; Boaga, J.; Rossi, M.; Vignoli, G.; Deiana, R.; Ursino, N.; Putti, M.; Majone, B.; Bellin, A.; Blaschek, M.; Duttmann, R.; Meyer, S.; Ludwig, R.; Soddu, A.; Dietrich, P.; Werban, U.
Interactions of Liquid Propellant/LP XM46 With Soils.
National Technical Information Service (NTIS)
Development of an effective spill response plan for liquid propellant/LP XM46 (LP) required an understanding of the potential interactions between soil and the propellant. Studies were designed to characterize potential hazards of initial contact of LP wi...
J. C. Pennington C. B. Price D. Gunnison D. W. Rathburn T. E. Myers
Physical and chemical effects of biochar on natural and artificial water repellent soils
NASA Astrophysics Data System (ADS)
Water repellency (WR) affects soils worldwide. Hydrophobic compounds accumulate in soil through organic matter decomposition, microbial activity, condensation of organic compounds during vegetation fires, or through anthropogenic impacts such as oil spills. WR hinders vegetation establishment, which can lead to soil erosion and increased runoff. Biochar is currently being evaluated for its potential to increase soil carbon and as a soil amendment. To date, the effect of biochar on water repellent soils has remained largely undetermined. This study considered the potential of biochar as both a physical and chemical amendment for water repellent soils by asking two questions: does adding biochar reduce the observed degree of soil water repellency; and does biochar remove hydrophobic compounds from soil? The potential of biochar as a physical amendment to water repellent soils was evaluated by mixing 5, 10, 25 and 40% (by weight) each of coarse and fine ground biochar with two naturally water repellent soils and measuring the water drop penetration time (WDPT) for each mixture. Biochar particles beyond the range of existing soil particle diameters increased WDPT variability, which could be explained by increased surface roughness and the resulting enhancement of water repellency effects through Cassie-Baxter interactions. Overall, fine biochar was more effective at reducing water repellency: 25% w/w rendered both soils studied wettable. Removal of hydrophobic compounds by biochar was tested by mixing 1, 5, 10, 25 and 40% biochar with acid washed sand (AWS) coated with 1.2x10-5 mol octadecane and octadecanoic acid (per gram AWS, which corresponds to approximately 50 monolayers hydrophobic compound per gram AWS). Each mix stood for 1 to 30 days in a solution of pH 3, 6 or 9 before the AWS was extracted and the quantity of hydrophobic compound remaining determined by infrared spectroscopy and/or gas chromatography. Biochar successfully removed the hydrophobic compounds, even in dry conditions and independent of pH and exposure time. Results varied with the quantity of biochar added: some removal was evident with 1% and 5% biochar additions, approximately 50% of material initially deposited onto AWS was removed by 10% biochar, and ? 25% biochar removed 100% of the material present. These results suggest that biochar can reduce WR effects in soils by creating wettable pathways through water repellent soil and by removing hydrophobic compounds from soil particles.
Hallin, Ingrid; Douglas, Peter; Doerr, Stefan H.; Bryant, Rob; Matthews, Ian; Charbonneau, Cecile
Effect of Thickness of a Water Repellent Soil Layer on Soil Evaporation Rate
NASA Astrophysics Data System (ADS)
A water repellent soil layer overlying wettable soil is known to affect soil evaporation. This effect can be beneficial for water conservation in areas where water is scarce. Little is known, however, about the effect of the thickness of the water repellent layer. The thickness of this layer can vary widely, and particularly after wildfire, with the soil temperature reached and the duration of the fire. This study was conducted to investigate the effect of thickness of a top layer of water repellent soil on soil evaporation rate. In order to isolate the thickness from other possible factors, fully wettable standard sand (300~600 microns) was used. Extreme water repellency (WDPT > 24 hours) was generated by 'baking' the sand mixed with oven-dried pine needles (fresh needles of Pinus densiflora) at the mass ratio of 1:13 (needle:soil) at 185░C for 18 hours. The thicknesses of water repellent layers were 1, 2, 3 and 7 cm on top of wettable soil. Fully wettable soil columns were prepared as a control. Soil columns (8 cm diameter, 10 cm height) were covered with nylon mesh. Tap water (50 ml, saturating 3 cm of a soil column) was injected with hypoderm syringes from three different directions at the bottom level. The injection holes were sealed with hot-melt adhesive immediately after injection. The rate of soil evaporation through the soil surface was measured by weight change under isothermal condition of 40░C. Five replications were made for each. A trend of negative correlation between the thickness of water repellent top layer and soil evaporation rate is discussed in this contribution.
Ahn, S.; Im, S.; Doerr, S.
Soil water monitoring using heated distributed temperature sensing
NASA Astrophysics Data System (ADS)
Traditionally, soil water measurements could only be obtained as point-in-time and point-in-space samples. These methods result in uncertainty in understanding the soil water dynamics of a site because of issues of scale, soil and vegetation spatial heterogeneity, and temporal variability of climatic conditions. Previous researchers have demonstrated the feasibility of obtaining distributed soil water content measurements using the heat pulse method with fiber optic temperature sensing. Numerical simulations of multiple proposed hybrid cable cross-sections guided the design and fabrication of a custom bundle of fiber optics, resistance heating conductors, and protective coatings for soil water monitoring. The conductors introduce a heat pulse to the surrounding soil, while temperature rise versus time is monitored with a Distributed Temperature Sensing (DTS) system using the fiber optics in the bundle. The temperature rise versus time response is related to the matric potential and water content of the soil surrounding the cable. In order to monitor the near-surface hydrology of a recently restored southwestern Wisconsin floodplain, the cable was buried at a depth of 20cm along a transect perpendicular to the Upper East Branch of the Pecatonica River near Barneveld, Wisconsin. Spatial variations of soil water can be readily observed with this technology as the cable spans various vegetation communities, soil types, and moisture conditions at this site. This new technology will help bridge the existing gaps of scale in soil water monitoring networks by providing high resolution, continuous measurements over large spatial scales.
Striegl, A. M.; Loheide, S. P.
Experimental and mathematical modeling of soil water and heat regime in selected soils
NASA Astrophysics Data System (ADS)
Knowledge of soil thermal (heat) properties is essential when assessing heat transport in soils. Heat regime in soils associates with many other soil processes (like water evaporation and diffusion, plant transpiration, contaminants behavior etc.). Thermal properties are needed when assessing affectivity of energy gathering from soil profiles using horizontal ground heat exchangers, which is a main goal of this study. Study is focused on measuring of thermal properties (heat capacity and heat conductivity) in representative soils of the Czech Republic. Measurements were performed on soil samples taken from the surface horizons of 11 representative soil types and from 2 soil substrates (sand and loess). The measured relationships between the heat conductivity and volumetric soil-water content were described by non-linear equations (Chung and Horton, 1987). The measured relationships between the heat capacity and volumetric soil-water content were expressed using the linear equations. The greatest values of the heat conductivity were measured in sandy soils (sandy and gravely sand substrates). The average values were obtained in soils on loess substrates. Lower values were obtained for all Cambisols (variable substrates). The lowest values were measured in Stagnic Chernozem Siltic on marlite. Opposite trend was observed for the maximal heat capacity, which was mostly impacted by water content. A soil water and heat regime within the soil profile was monitored at one location. In addition the impact of various soil cover at the soil top on soil water content and temperature was measured. Soil hydraulic properties were measured using the multistep-outflow technique. The saturated hydraulic conductivities were also measured using the Guelph permeameter. Programs HYDRUS-1D and 2D/3D were used for a mathematical interpretation of the observed soil water and heat regime. Acknowledgment: Authors acknowledge the financial support of the Technology Agency of the Czech Republic (TA02020991). Work was also partly supported by the Ministry of Agriculture of the Czech Republic (QJ1230319). Literature Chung, S.O., Horton, R. 1987. Soil heat and water flow with a partial surface mulch, Water Resour. Res., 23(12), 2175-2186, 1987.
Kodesova, Radka; Fer, Miroslav; Klement, Ales; Nikodem, Antonin; Vlasakova, Mirka; Tepla, Daniela; Jaksik, Ondrej
The Ecohydrological Interactions Between Mesquite and its Water Sources
NASA Astrophysics Data System (ADS)
Velvet mesquite (Prosopis velutina), a native woody plant to southern Arizona, USA and Sonora, Mexico, has successfully expanded its range and encroached into both upland and riparian grasslands during the 20th century. In this study, we examined the interactions between mesquite and its water sources in order to determine how the trees responded to moisture availability. This study took place in a riparian area and because the trees had access to both deep groundwater and surface water, these interactions resulted in important hydrological and ecological consequences. Surprisingly, we found that the mesquite responded to and even manipulated both surface and deep soil moisture even though they apparently had access to a stable groundwater source throughout the growing season. During dry season nights, observations of root sap flow showed that the trees moved moisture upwards in the taproot and out into the surface soils in lateral roots. As a consequence of this "hydraulic lift", diurnal soil respiration measurements showed that the soil microbes were stimulated following the nocturnal release of moisture into the near-surface regions. During rainy season nights, there was sap flow movement toward the tree in the surface lateral roots and downwards in the taproot indicating "hydraulic descent". Borehole GPR measurements of the deeper, 2 - 10 m, vadose zone moisture content increased apparently as a result of this tree-facilitated water movement. Also, hydraulic descent influenced water table elevations indicating direct groundwater recharge via plant pathways.
Scott, R. L.; Hultine, K.; Ferrķ, P.
Soybean yields and soil water status in Argentina: Simulation analysis
Recent changes in management of soybean production in Argentina may have large impacts on the soil water balance and on crop yield response. Changes in this system have included widespread adoption of a no-till management leaving crop residue on the soil surface, intensive cropping rotations (e.g. double cropping of wheat and soybean) so that the soil may not be fully
T. R. Sinclair; L. R. Salado-Navarro; Graciela Salas; L. C. Purcell
Teaching Soil and Water Conservation: A Classroom and Field Guide.
ERIC Educational Resources Information Center
Compiled in this booklet are 22 activities designed to develop awareness of the importance of conservation and the wise use of soil and moisture on croplands, grasslands, and woodlands. They have been selected by Soil Conservation Service (SCS) personnel and consultants to show that the way we manage our basic natural resources, soil and water,ģ
Foster, Albert B.; Fox, Adrian C.
Modeling soil carbon transported by water erosion processes
Long-term monitoring is needed for direct assessment of soil organic carbon (SOC), soil, and nutrient loss by water erosion on a watershed scale. However, labor and capital requirements preclude implementation of such monitoring at many locations representing principal soils and ecoregions. These considerations warrant the development of diagnostic models to assess erosional SOC loss from more readily obtained data. The
G. C. Starr; R. Lal; R. Malone; D. Hothem; L. Owens; J. Kimble
Difficulties in the evaluation and measuring of soil water infiltration
NASA Astrophysics Data System (ADS)
Soil water infiltration is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the evaluation and measurement of water infiltration rates has become indispensable for the evaluation and modeling of the previously mentioned processes. Infiltration is one of the most difficult hydrological parameters to evaluate or measure accurately. Although the theoretical aspects of the process of soil water infiltration are well known since the middle of the past century, when several methods and models were already proposed for the evaluation of infiltration, still nowadays such evaluation is not frequently enough accurate for the purposes being used. This is partially due to deficiencies in the methodology being used for measuring infiltration, including some newly proposed methods and equipments, and in the use of non appropriate empirical models and approaches. In this contribution we present an analysis and discussion about the main difficulties found in the evaluation and measurement of soil water infiltration rates, and the more commonly committed errors, based on the past experiences of the author in the evaluation of soil water infiltration in many different soils and land conditions, and in their use for deducing soil water balances under variable and changing climates. It is concluded that there are not models or methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the soil before and during the measurement. Direct "in situ" field evaluations have to be preferred in any case to indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, or through the use of stochastic models such as the SCS Curve Number Method, or of other models using empirical or physical approaches, which have demonstrated to be of limited value in most of the cases. References Philip, J. R., 1954., An infiltration equation with physical significance: Soil Sci..,v. 77, p. 153-157. Philip, J. R., 1958. The theory of infiltration, pt. 7: Soil Sci., v. 85, no. 6, p. 333-337. Pla, I.1981. Simuladores de lluvia para el estudio de relaciones suelo-agua bajo agricultura de secano en los tr¾picos. Rev. Fac. Agron. XII(1-2):81-93.Maracay (Venezuela) Pla, I. 1986. A routine laboratory index to predict the effects of soil sealing on soil and water conservation. En "Assesment of Soil Surface Sealing and Crusting". 154-162.State Univ. of Ghent.Gante (Bķlgica Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., M.C. Ramos, S. Nacci, F. Fonseca y X. Abreu. 2005. Soil moisture regime in dryland vineyards of Catalunya (Spain) as influenced by climate, soil and land management. "Integrated Soil and Water Management for Orchard Development". FAO Land and Water Bulletin 10. 41-49. Roma (Italia). Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Pla, I. 2011. Evaluaci¾n y Modelizaci¾n Hidrol¾gica para el Diagn¾stico y Prevenci¾n de "Desastres Naturales". Gesti¾n y Ambiente 14 (3): 17-22. UN-MedellĒn (Colombia). ISSN 0124.177X
Pla-SentĒs, Ildefonso
Soil Moisture-Ecosystem-Climate Interactions in a Changing Climate
NASA Astrophysics Data System (ADS)
Soil moisture is a key variable of the climate system. It constrains plant transpiration and photosynthesis in several regions of the world, with consequent impacts on the water, energy and biogeochemical cycles (e.g. Seneviratne et al. 2010). Moreover it is a storage component for precipitation and radiation anomalies, inducing persistence in the climate system. Finally, it is involved in a number of feedbacks at the local, regional and global scales, and plays a major role in climate-change projections. This presentation will provide an overview on these interactions, based on several recent publications (e.g. Seneviratne et al. 2006, Orlowsky and Seneviratne 2010, Teuling et al. 2010, Hirschi et al. 2011). In particular, it will highlight possible impacts of soil moisture-ecosystem coupling for climate extremes such as heat waves and droughts, and the resulting interconnections between biophysical and biogeochemical feedbacks in the context of climate change. Finally, it will also address recent regional- to global-scale trends in land hydrology and ecosystem functioning, as well as issues and potential avenues for investigating these trends (e.g. Jung et al. 2010, Mueller et al. 2011). References Hirschi, M., S.I. Seneviratne, V. Alexandrov, F. Boberg, C. Boroneant, O.B. Christensen, H. Formayer, B. Orlowsky, and P. Stepanek, 2011: Observational evidence for soil-moisture impact on hot extremes in southeastern Europe. Nature Geoscience, 4, 17-21, doi:10.1038/ngeo1032. Jung, M., et al., 2010: Recent decline in the global land evapotranspiration trend due to limited moisture supply. Nature, 467, 951-954. doi:10.1038/nature09396 Mueller, B., S.I. Seneviratne, et al.: Evaluation of global observations-based evapotranspiration datasets and IPCC AR4 simulations, Geophys. Res. Lett., 38, L06402, doi:10.1029/2010GL046230 Orlowsky, B., and S.I. Seneviratne, 2010: Statistical analyses of land-atmosphere feedbacks and their possible pitfalls. J. Climate, 23(14), 3918-3932 Seneviratne, S.I., T. Corti, E.L. Davin, M. Hirschi, E.B. Jaeger, I. Lehner, B. Orlowsky, and A.J. Teuling, 2010: Investigating soil moisture-climate interactions in a changing climate: A review. Earth-Science Reviews, 99, 3-4, 125-161, doi:10.1016/j.earscirev.2010.02.004 Seneviratne, S.I., D. L³thi, M. Litschi, and C. Schõr, 2006: Land-atmosphere coupling and climate change in Europe. Nature, 443, 205-209. Teuling, A.J., S.I. Seneviratne, et al. 2010: Contrasting response of European forest and grassland energy exchange to heatwaves. Nature Geoscience, 3, 722-727, doi:10.1038/ngeo950.
Seneviratne, S. I.; Davin, E.; Hirschi, M.; Mueller, B.; Orlowsky, B.; Teuling, A.
Critical water contents of hydrophobic soils in New Zealand
NASA Astrophysics Data System (ADS)
Soil water repellency is an important problem for pasture farming in New Zealand which causes low infiltration rates and increased surface runoff. However, the real extent of this issue is not yet evaluated. Water repellency is thought to appear on dry soils, when the water content falls below a critical limit. The main objectives of this study was 1) to investigate the effects of different amounts of infiltration water on hydrophobicity of three selected soils under grassland in the North island of New Zealand, and 2) to determine the critical water content for ten sites with five different soil types. In April 2011 undisturbed and disturbed soil samples from a brown, gley and organic soil have been taken from sites around Mount Taranaki. Soil water repellency was determined using the Water Droplet Penetration Time Test (WDPT) and the Molarity of Ethanol Droplet Test (MED). During the lab experiment four amounts of water were applied to the 270 cm│ samples: 400, 800, 1600 and 2400 mL . One test was performed with cold and one with hot (80 ░C) water. Each test was replicated four times. In the leachate the amount of dissolved organic carbon was analyzed. The experiments showed that only for the brown soil water repellency decreased significantly with increasing amount of infiltration water whereas for gley soils no correlation was found. Gley soil had initially a lower degree of hydrophobicity compared to the other soils. Possibly due to the higher bulk density of these soils, the carbon compounds directly surrounding the soil particles wre rearranged rather than leached. No clear pattern could be obtained for organic soils. This may be explained by the high initial carbon content of more than 20%. It may take a much greater amount of infiltration to affect hydrophobicity. The critical contact angle of investigated soils above which water repellency is moderately persistent, was 93.8░. In May 2012 ten more sites were sampled and five soil types were investigated with respect to the critical water content. Soil hydrophobicity was again tested during 4 wetting and drying cycles on 3 replicates each of disturbed and undisturbed soil samples. The tests confirmed that water repellency does not exist at high water contents. It generally starts to appear at a certain limit, increases rapidly up to a peak value and finally decreases slowly when the water content approaches 0. Critical water contents were very high in the first wetting cycle and stabilized at a rather constant level during the 2nd, 3rd and 4th wetting cycle. This phenomenon may be due to inhomogeneous water distributions within the field moist soil samples in the 1st wetting cycle and it was thus chosen to take the critical moisture content from the 2nd wetting cycle for further purposes. We found relatively broad transition zones where soils were found to be both hydrophilic and hydrophobic. Critical water contents or rather transition zones were found to differ significantly between the various soil orders and showed values between 0.34 (m│/m│) for recent soil and 0.44(m│/m│) for organic soil.
Landl, Magdalena; Holzinger, Ursula; Singh, Ranvir; Klik, Andreas
Measuring and Modelling water related soil - vegetation feedbacks in a fallow plot
NASA Astrophysics Data System (ADS)
Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field scale water balance. The objective of this study was to test the potential of integrated non invasive geophysics and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during an infiltration experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of the experimental data evidenced a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the site.
Ursino, Nadia; Cassiani, Giorgio; Deiana, Rita; Vignoli, Giulio; Boaga, Jacopo
The effects of simulated fire events on the creation and destruction of soil water repellency using vegetation and soil samples from a desert shrub grassland
Fire-induced soil water repellency has been shown to interact with aeolian processes to enhance the heterogeneity of arid landscapes. To investigate aspects of these processes, vegetation (black grama grass and creosote bush) and soil samples from a field site in the northern Chihuahuan desert of central New Mexico were prepared and heated to temperatures ranging from 100 to 600 degrees
T. M. Over; S. Pratte; B. Frost; J. Blitz
Correction of TDR-based soil water content measurements in conductive soils
Time Domain Reflectometry (TDR) is a widespread technique for measurement of soil water content (SWC). The main assumption behind the use of Time Domain Reflectometry (TDR) is of negligible losses, therefore assuming that only the real part determines the value of the TDR-measured apparent dielectric permittivity. This assumption does not hold for soils where surfaces are conductive (clay soils) or
Marco Bittelli; Fiorenzo Salvatorelli; Paola Rossi Pisa
Soil porosity characteristics and water movement under zero tillage in silty soils in Argentinian Pampas
The objective of this study was to identify pore characteristics (quantity, distribution, stability and orientation of pores) that condition water dynamics under continuous zero tillage (ZT) on silty soils of the Argentinian Rolling Pampas. Soil properties were analyzed under continuous chisel plough (CP) and ZT treatments from three trials with different duration and crop sequence. The following soil properties of
M. C. Sasal; A. E. Andriulo; M. A. Taboada
Soil-Structure Interaction. A General Method to Calculate Soil Impedance.
National Technical Information Service (NTIS)
A correct analysis of the seismic response of nuclear power plant buildings needs to take into account the soil structure interaction. The most classical and simple method consists in characterizing the soil by a stiffness and a damping function for each ...
M. Farvacque, F. Gantenbein
The potential water quality effects and economic implications of soil and water conservation practices (SWCPs) are identified. Method for estimating the effects of SWCPs on pollutant losses from croplands are presented. Mathematical simulation and linear programming models were u...
Analysis of soil and water for TATB content
A reverse-phase liquid chromatography (HPLC) method was developed for the analysis of TATB in soil samples. The soil samples were extracted with dimethylformamide (DMF). The extract was analyzed to determine the TATB content in the soil. The detection limit using this procedure was 2 parts/million (ppm) for TATB in the soil. An organic free sample of water was saturated with TATB. The water was filtered through a 0.2-{mu} filter, then injected into both a reverse-phase and normal-phase liquid chromatograph system. No peaks were detected. Therefore, the solubility of TATB in water is less than the detection limits of the chromatograph methods.
Schaffer, C.L.
Advances in Sensible Heat Balance Characterization of Soil Water Evaporation
NASA Astrophysics Data System (ADS)
Soil water evaporation intimately couples the hydrological cycle with the land-surface energy balance, making it an important driver for a wide range of terrestrial processes. To date, few methods have been available characterize soil water evaporation in detail, which has, in turn, limited capability to predict soil water evaporation processes in local and large scale models. Recent work has developed a measurement-based soil sensible heat balance (SHB) approach, capable of quantifying evaporation time and depth dynamics at a vertical scale of millimeters, near the soil surface. The SHB approach does not require detailed characterization or estimation of soil hydraulic properties, which has been a limitation in previous work. Rather it utilizes detailed measurements of the soil temperature profile and soil thermal properties from heat-pulse sensors in order to derive evaporation front dynamics. Laboratory experiments indicate that the SHB approach is precise to within <10% of independent mass balance measurements. Field tests indicate that the SHB is well correlated to lysimeter and Bowen ratio measurement approaches for bare surface conditions. Using SHB, laboratory and field experiments have characterized migration of the soil water evaporation front during multi-day drying events, and linked the shift between potential evaporation and falling rate evaporation to changes in soil surface albedo and soil moisture.
Heitman, J.; Xiao, X.; Deol, P. K.; Horton, R.; Ren, T.
The Forest as a Soil and Water Manager
NASA Astrophysics Data System (ADS)
Forests provide a vital service in regulating stream flow and protecting soil from erosion. Loss of forest cover increases erosion (by raindrop impact, surface runoff, gullies, landslides and river bank failure) and the transfer of eroded soil or sediment to the river network. It also increases annual runoff and the peak discharges of at least small to moderate flood events, and thus the sediment transporting capability of streams. Adverse impacts include reservoir sedimentation, aquatic habitat degradation and river channel instability. Sediment also greatly increases the destructive effects of floods. The forest/erosion interface takes many forms, e.g. forest fire impact, forest/landslide interaction and impact of pre-plantation activities such as ditching. However, despite decades of study, data on forests and erosion remain relatively fragmented and there is no integrated overview at regional to continental scales, e.g. at the European scale. Further, quantitative understanding does not yet match qualitative understanding and lags behind our ability to make quantitative generalizations on, for example, the impact of forest cover on water yields and flood frequencies. This presentation therefore discusses our current understanding of the effect of forest cover on water runoff and soil erosion, highlighting in particular the type of quantitative data available and the quantitative methods which are available to predict the impact of changes in forest cover, including their limitations. It also considers the type of models needed to predict the impacts of land use and climate change on soil erosion and proposes a next step in improving our predictive capability for the forest/erosion interface through an integration of existing research to provide generalizations and an overview at regional to subcontinental scales.
Bathurst, J. C.
Soil Moisture\\/ Tree Water Status Dynamics in MidLatitude Montane Forest, Southern Sierra Critical Zone Observatory, CA
As part of an effort to understand the root-water-nutrient interactions in the multi-dimensional soil\\/vegetation system surrounding large trees, in August 2008 we instrumented a mature white fir (Abies concolor) and the surrounding soil to better define the water balance in a single tree. In July 2010, we instrumented a second tree, a Ponderosa pine (Pinus ponderosa) in shallower soils on
P. C. Hartsough; A. Malazian; M. W. Meadows; K. Roudneva; J. Storch; R. C. Bales; J. W. Hopmans
A review of soil and water conservation in China
The preservation and sustainable development of soil and water resources is one of the basic principles for the development\\u000a of China. Throughout the course of history, all the social improvement and economic development are deeply concerned with\\u000a soil loss and ecological environmental protection. It is now a common sense that soil and water conservation is the safety\\u000a insurance for national
Zhang Xingchang; Shao Mingan; Li Shiqing; Peng Keshan
Stochastic analysis of soil water regime in a watershed
Hopmans, J.W. and Stricker, J.N.M., 1989. Stochastic analysis of soil water regime in a watershed. J. Hydrol., 105: 57-84. A stochastic-deterministic one-dimensional model is proposed that simulates soil water flow for variable soil hydraulic properties and variable lower boundary conditions. These variations were determined by a normalization procedure which yields a scaled mean or reference curve and a set of
Effects of water addition on soil arthropods and soil characteristics in a precipitation-limited environment
NASA Astrophysics Data System (ADS)
We investigated the effect of water addition and season on soil arthropod abundance and soil characteristics (%C, %N, C:N, moisture, pH). The experimental design consisted of 24 groups of five boxes distributed within a small aspen stand in Saskatchewan, Canada. The boxes depressed the soil to create a habitat with suitable microclimate for soil arthropods, and by overturning boxes we counted soil arthropods during weekly surveys from April to September 1999. Soil samples were collected at two-month intervals and water was added once per week to half of the plots. Of the eleven recognizable taxonomic units identified, only mites (Acari) and springtails (Collembola) responded to water addition by increasing abundance, whereas ants decreased in abundance with water addition. During summer, springtail numbers increased with water addition, whereas pH was a stronger determinant of mite abundance. In autumn, springtails were positively correlated with water and negatively correlated with mites, whereas mite abundance was negatively correlated with increasing C:N ratio, positively correlated to water addition, and negatively correlated with springtail abundance. Although both mite and springtail numbers decreased in autumn with a decrease in soil moisture, mites became more abundant than springtails suggesting a predator-prey (mite-springtail) relationship. Water had a significant effect on both springtails and mites in summer and autumn supporting the assertion that prairie soil communities are water limited.
Chikoski, Jennifer M.; Ferguson, Steven H.; Meyer, Lense
Soil water dynamics inside and outside of lysimeters
NASA Astrophysics Data System (ADS)
Lysimeters are the one and only instrument to directly measure water fluxes through the upper an lower boundary of soil profiles. This allows to close the water balance including soil water storage, deep seepage and evapotranspiration. However, lysimeters force the water flow to the vertical direction while in reality lateral water movement is deemed to play an important role in soil water dynamics especially along hillslopes. We present an approach where we monitor soil water dynamics in lysimeters and in the field at the same location of a gentle hillslope. A cylindrical soil monolith is taken leaving the surrounding soil undisturbed. The monolith is used as a weighable lysimeter while the pit in the field is equipped with the same sensors (moisture, water potential, temperature) as the lysimeter. Based on this set up, we can evaluate in how far water flow inside the lysimeter corresponds to the situation in the field. The results demonstrate that lateral flow becomes important when the water content is close to saturation. This is true at the soil surface in case of surface runoff but also at the depth of a compacted plow pan where interflow is initiated. Under unsaturated conditions, the limitation of lysimeters to 1D flow seems to be an acceptable approximation even in slopy areas.
Vogel, Hans-Joerg; Rupp, Holger; K÷hne, Max; Wollschlõger, Ute
Modeling Base Flow Soil Water Residence Times From Deuterium Concentrations
Three approaches to determining mean soil water residence times in a steep headwater catchment were investigated. The deuterium concentrations of soil water collected from 11 suction cup samplers at the Maimai M8 catchment were determined weekly for 14 weeks and the results compared with those of rainfall in the same period. Deuterium variations in the suction samples were considerably delayed
Michael K. Stewart; Jeffrey J. McDonnell
Simulating daily soil water under foothills fescue grazing with the soil and water assessment tool model (Alberta, Canada)
NASA Astrophysics Data System (ADS)
Grazing is common in the foothills fescue grasslands and may influence the seasonal soil-water patterns, which in turn determine range productivity. Hydrological modelling using the soil and water assessment tool (SWAT) is becoming widely adopted throughout North America especially for simulation of stream flow and runoff in small and large basins. Although applications of the SWAT model have been wide, little attention has been paid to the model's ability to simulate soil-water patterns in small watersheds. Thus a daily profile of soil water was simulated with SWAT using data collected from the Stavely Range Sub-station in the foothills of south-western Alberta, Canada. Three small watersheds were established using a combination of natural and artificial barriers in 1996-97. The watersheds were subjected to no grazing (control), heavy grazing (2.4 animal unit months (AUM) per hectare) or very heavy grazing (4.8 AUM ha-1). Soil-water measurements were conducted at four slope positions within each watershed (upper, middle, lower and 5 m close to the collector drain), every 2 weeks annually from 1998 to 2000 using a downhole CPN 503 neutron moisture meter. Calibration of the model was conducted using 1998 soil-water data and resulted in Nash-Sutcliffe coefficient (EF or R2) and regression coefficient of determination (r2) values of 0.77 and 0.85, respectively. Model graphical and statistical evaluation was conducted using the soil-water data collected in 1999 and 2000. During the evaluation period, soil water was simulated reasonably with an overall EF of 0.70, r2 of 0.72 and a root mean square error (RMSE) of 18.01. The model had a general tendency to overpredict soil water under relatively dry soil conditions, but to underpredict soil water under wet conditions. Sensitivity analysis indicated that absolute relative sensitivity indices of input parameters in soil-water simulation were in the following order; available water capacity > bulk density > runoff curve number > fraction of field capacity (FFCB) > saturated hydraulic conductivity. Thus these data were critical inputs to ensure reasonable simulation of soil-water patterns. Overall, the model performed satisfactorily in simulating soil-water patterns in all three watersheds with a daily time-step and indicates a great potential for monitoring soil-water resources in small watersheds.
Mapfumo, Emmanuel; Chanasyk, David S.; Willms, Walter D.
Effects of Soil and Water Content on Methyl Bromide Oxidation by the Ammonia-Oxidizing Bacterium Nitrosomonas europaeaå
Little information exists on the potential of NH3-oxidizing bacteria to cooxidize halogenated hydrocarbons in soil. A study was conducted to examine the cooxidation of methyl bromide (MeBr) by an NH3-oxidizing bacterium, Nitrosomonas europaea, under soil conditions. Soil and its water content modified the availability of NH4+ and MeBr and influenced the relative rates of substrate (NH3) and cosubstrate (MeBr) oxidations. These observations highlight the complexity associated with characterizing soil cooxidative activities when soil and water interact to differentially affect substrate and cosubstrate availabilities.
Duddleston, Khrystyne N.; Bottomley, Peter J.; Porter, Angela; Arp, Daniel J.
Scatterometer-Derived Soil Moisture Calibrated for Soil Texture With a One-Dimensional WaterFlow Model
Current global satellite scatterometer-based soil moisture retrieval algorithms do not take soil characteristics into account. In this paper, the characteristic time length of the soil water index has been calibrated for ten sampling frequencies and for different soil conductivity associated with 12 soil texture classes. The calibration experiment was independently performed from satellite observations. The reference soil moisture data set
Remko de Lange; Rob Beck; Nick van de Giesen; Jan Friesen; Allard de Wit; Wolfgang Wagner
Genetic by environment interactions affect plant-soil linkages
The role of plant intraspecific variation in plant¢soil linkages is poorly understood, especially in the context of natural environmental variation, but has important implications in evolutionary ecology. We utilized three 18- to 21-year-old common gardens across an elevational gradient, planted with replicates of five Populus angustifolia genotypes each, to address the hypothesis that tree genotype (G), environment (E), and G ū E interactions would affect soil carbon and nitrogen dynamics beneath individual trees. We found that soil nitrogen and carbon varied by over 50% and 62%, respectively, across all common garden environments. We found that plant leaf litter (but not root) traits vary by genotype and environment while soil nutrient pools demonstrated genotype, environment, and sometimes G ū E interactions, while process rates (net N mineralization and net nitrification) demonstrated G ū E interactions. Plasticity in tree growth and litter chemistry was significantly related to the variation in soil nutrient pools and processes across environments, reflecting tight plant¢soil linkages. These data overall suggest that plant genetic variation can have differential affects on carbon storage and nitrogen cycling, with implications for understanding the role of genetic variation in plant¢soil feedback as well as management plans for conservation and restoration of forest habitats with a changing climate.
Pregitzer, Clara C; Bailey, Joseph K; Schweitzer, Jennifer A
Water and methyl isothiocyanate distribution in soil after drip fumigation.
Methyl isothiocyanate (MITC) generators, such as metam sodium (Met-Na), are used for soil fumigation of agricultural land. The ban on the fumigant methyl bromide has resulted in greater use of MITC generators. To understand the efficacy of MITC, it is necessary to assess its generation and disappearance kinetics when Met-Na is applied to soil. This study evaluated the movement of water and distribution and dissipation of MITC in soil after application of Met-Na through surface drip irrigation systems. The effects of varying water application volume (25, 50, and 75 mm) and rate (1.9, 5.0, and 7.5 L h m) were evaluated in a sandy loam soil. Good fumigant distribution within the sandy loam soil was observed under medium water application amount (50 mm) with slow to intermediate drip application rates (1.9-5.0 L h m). Low water application amount (25 mm) or high application rate (7.5 L h m) did not provide adequate MITC distribution throughout the soil bed width and rooting depth. Dissipation patterns of MITC in soil in all water application amounts and rates followed first-order kinetics, with a rate constant of 0.025 ▒ 0.004 h and a half-life of 27 ▒ 3 h. Simulated water distribution through the soil profile using HYDRUS 2D/3D fitted measured field data well, and the model accurately simulated MITC fumigant distribution in the soil. PMID:24216433
Nelson, Shad D; Ajwa, Husein A; Trout, Tom; Stromberger, Mary; Yates, Scott R; Sharma, Shankar
Sensitivity and uncertainty analysis of estimated soil hydraulic parameters for simulating soil water content
NASA Astrophysics Data System (ADS)
The sensitivity and uncertainty analysis has been carried out for the scalar parameters (soil hydraulic parameters (SHPs)), which govern the simulation of soil water content in the unsaturated soil zone. The study involves field experiments, which were conducted in real field conditions for wheat crop in Roorkee, India under irrigated conditions. Soil samples were taken for the soil profile of 60 cm depth at an interval of 15 cm in the experimental field to determine soil water retention curves (SWRCs). These experimentally determined SWRCs were used to estimate the SHPs by least square optimization under constrained conditions. Sensitivity of the SHPs estimated by various pedotransfer functions (PTFs), that relate various easily measurable soil properties like soil texture, bulk density and organic carbon content, is compared with lab derived parameters to simulate respective soil water retention curves. Sensitivity analysis was carried out using the monte carlo simulations and the one factor at a time approach. The different sets of SHPs, along with experimentally determined saturated permeability, are then used as input parameters in physically based, root water uptake model to ascertain the uncertainties in simulating soil water content. The generalised likelihood uncertainty estimation procedure (GLUE) was subsequently used to estimate the uncertainty bounds (UB) on the model predictions. It was found that the experimentally obtained SHPs were able to simulate the soil water contents with efficiencies of 70-80% at all the depths for the three irrigation treatments. The SHPs obtained from the PTFs, performed with varying uncertainties in simulating the soil water contents. Keywords: Sensitivity analysis, Uncertainty estimation, Pedotransfer functions, Soil hydraulic parameters, Hydrological modelling
Gupta, Manika; Garg, Naveen Kumar; Srivastava, Prashant K.
Soil interactions with petroleum hydrocarbons: Abiotic processes
Soil and groundwater resources in many parts of the world are threatened by spilled petroleum products. These products generally consist of complex mixtures of volatile hydrocarbons with different vapor pressures. The volatilization of light hydrocarbon fractions leads to changes in viscosity and density of the residual nonaqueous liquid. This may cause changes in the transport characteristics of the porous matrix
P. Fine; E. R. Graber; B. Yaron
Coupling root architecture and pore network modeling - an attempt towards better understanding root-soil interactions
NASA Astrophysics Data System (ADS)
Understanding root-soil interactions is of high importance for environmental and agricultural management. Root uptake is an essential component in water and solute transport modeling. The amount of groundwater recharge and solute leaching significantly depends on the demand based plant extraction via its root system. Plant uptake however not only responds to the potential demand, but in most situations is limited by supply form the soil. The ability of the plant to access water and solutes in the soil is governed mainly by root distribution. Particularly under conditions of heterogeneous distribution of water and solutes in the soil, it is essential to capture the interaction between soil and roots. Root architecture models allow studying plant uptake from soil by describing growth and branching of root axes in the soil. Currently root architecture models are able to respond dynamically to water and nutrient distribution in the soil by directed growth (tropism), modified branching and enhanced exudation. The porous soil medium as rooting environment in these models is generally described by classical macroscopic water retention and sorption models, average over the pore scale. In our opinion this simplified description of the root growth medium implies several shortcomings for better understanding root-soil interactions: (i) It is well known that roots grow preferentially in preexisting pores, particularly in more rigid/dry soil. Thus the pore network contributes to the architectural form of the root system; (ii) roots themselves can influence the pore network by creating preferential flow paths (biopores) which are an essential element of structural porosity with strong impact on transport processes; (iii) plant uptake depend on both the spatial location of water/solutes in the pore network as well as the spatial distribution of roots. We therefore consider that for advancing our understanding in root-soil interactions, we need not only to extend our root models, but also improve the description of the rooting environment. Until now there have been no attempts to couple root architecture and pore network models. In our work we present a first attempt to join both types of models using the root architecture model of Leitner et al., (2010) and a pore network model presented by Raoof et al. (2010). The two main objectives of coupling both models are: (i) Representing the effect of root induced biopores on flow and transport processes: For this purpose a fixed root architecture created by the root model is superimposed as a secondary root induced pore network to the primary soil network, thus influencing the final pore topology in the network generation. (ii) Representing the influence of pre-existing pores on root branching: Using a given network of (rigid) pores, the root architecture model allocates its root axes into these preexisting pores as preferential growth paths with thereby shape the final root architecture. The main objective of our study is to reveal the potential of using a pore scale description of the plant growth medium for an improved representation of interaction processes at the interface of root and soil. References Raoof, A., Hassanizadeh, S.M. 2010. A New Method for Generating Pore-Network Models. Transp. Porous Med. 81, 391-407. Leitner, D, Klepsch, S., Bodner, G., Schnepf, S. 2010. A dynamic root system growth model based on L-Systems. Tropisms and coupling to nutrient uptake from soil. Plant Soil 332, 177-192.
Leitner, Daniel; Bodner, Gernot; Raoof, Amir
Effect of soil water content on soil thermal conductivity under field conditions
NASA Astrophysics Data System (ADS)
Knowledge of the thermal properties of soils is required in many areas of engineering, meteorology, agronomy, and ecosystem and soil science. Soil thermal conductivity varies in time and space, since it is influenced by soil properties as well as soil temperature and moisture conditions. We use the one dimensional heat conduction equation in conjunction with two-year data measured in a grass-covered field in North Carolina Piedmont to estimate soil thermal conductivity and to investigate how it is impacted by water content. In agreement with laboratory experiments reported in the literature, our results suggest that under dry conditions soil thermal conductivity increases across a relatively narrow range of soil water contents, above which a further increase in water content does not significantly change thermal conductivity. However, when soil approaches saturation, heat transfer is further improved, a fact not previously noted. This nonlinear behavior is consistent with the formation at high water contents of a continuous film of liquid water in soil aggregates of mineral and organic matter.
Vico, G.; Daly, E.; Manzoni, S.; Porporato, A.
Effects of soil pH and soil water content on prosulfuron dissipation.
The sulfonylurea herbicide prosulfuron, 1-(4-methoxy-6-methyltriazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)phenylsulfonyl]urea, is used for the selective control of broadleaf weeds in corn, sorghum, and cereal grains. To investigate its fate in soils, this study examined the effects of soil pH and water content on the rates of dissipation processes and the products formed under aerobic conditions. Radiometry and chromatography analyses were used to quantify the degradation products and bound residues formed in incubations of 10 different soils. The pH-dependent hydrolysis of the sulfonylurea bridge to form phenyl sulfonamide was the primary transformation process. Significant microbial degradation of prosulfuron occurred in 2 of the 10 soils, yielding (14)CO(2) and desmethyl prosulfuron among the major products. The time required for 50% dissipation of the herbicide (DT(50)) was determined for each soil and water content treatment. At equivalent water contents, prosulfuron DT(50) values were positively correlated with soil pH (P < 0.0001), varying from 6.5 days at pH 5.4 to 122.9 days at pH 7.9. Soil pH and water content strongly influence the fate of sulfonylurea herbicides in agricultural fields. Differences in the effect of soil water content on dissipation kinetics in a comparison of two soils were attributed to differences in soil pH, texture, and the ability of indigenous microorganisms to transform the herbicide. PMID:12009993
Hultgren, Ryan P; Hudson, Robert J M; Sims, Gerald K
Soil warming, carbon-nitrogen interactions, and forest carbon budgets.
Soil warming has the potential to alter both soil and plant processes that affect carbon storage in forest ecosystems. We have quantified these effects in a large, long-term (7-y) soil-warming study in a deciduous forest in New England. Soil warming has resulted in carbon losses from the soil and stimulated carbon gains in the woody tissue of trees. The warming-enhanced decay of soil organic matter also released enough additional inorganic nitrogen into the soil solution to support the observed increases in plant carbon storage. Although soil warming has resulted in a cumulative net loss of carbon from a New England forest relative to a control area over the 7-y study, the annual net losses generally decreased over time as plant carbon storage increased. In the seventh year, warming-induced soil carbon losses were almost totally compensated for by plant carbon gains in response to warming. We attribute the plant gains primarily to warming-induced increases in nitrogen availability. This study underscores the importance of incorporating carbon-nitrogen interactions in atmosphere-ocean-land earth system models to accurately simulate land feedbacks to the climate system. PMID:21606374
Melillo, Jerry M; Butler, Sarah; Johnson, Jennifer; Mohan, Jacqueline; Steudler, Paul; Lux, Heidi; Burrows, Elizabeth; Bowles, Francis; Smith, Rose; Scott, Lindsay; Vario, Chelsea; Hill, Troy; Burton, Andrew; Zhou, Yu-Mei; Tang, Jim
Environmental Implications of Soil Properties and Essential Nutrient Interactions, Under the Effect of Treated Municipal Wastewater
An experiment of randomized block design was conducted during 2005 in a green-house, Agrinion Greece. The effect of two variables\\u000a was studied on the interactions between essential nutrients and the soil physical and chemical properties, i.e. treated municipal\\u000a waste water (TMWW), and fresh irrigation water, denoted as ōcontrolö. The experiment was done in six replications with a total\\u000a of 2?ū?6?=?12
I. K. Kalavrouziotis; P. H. Koukoulakis
Water Repellency Effects on Water Retention in Heat Pre-treated Volcanic Ash Soil
Water repellency (WR) in soil is a common phenomenon after forest fires all over the world. It can induce hydrological problems such as preferential flow in soils and reduced water infiltration rate which in turn can lead to surface runoff and erosion. In this study, we examined the hydrophobicity for pre-heated volcanic ash soil samples with different temperatures between 60
T. Chhoden; A. Karunarathna; K. Kawamoto; T. Komatsu; P. Moldrup
Water Repellency, Infiltration and Water Retention Properties of Forest Soils Under Different Management Practices
For soils under both agricultural and forest use, management and tillage practice can have significant influence on the hydraulic properties. It is therefore supposed, that management practices are capable of altering surface runoff, water retention and flood- ing risk for river catchments. Soil water repellency (hydrophobicity) can adversely affect soil hydrological properties, e.g. reduce infiltration capacity and induce pref- erential
N. A. Wahl; O. Bens; B. Schõfer; R. F. H³ttl
Estimation of water saturated permeability of soils, using 3D soil tomographic images and pore-level transport phenomena modelling
NASA Astrophysics Data System (ADS)
There are some important macroscopic properties of the soil porous media such as: saturated permeability and water retention characteristics. These soil characteristics are very important as they determine soil transport processes and are commonly used as a parameters of general models of soil transport processes used extensively for scientific developments and engineering practise. These characteristics are usually measured or estimated using some statistical or phenomenological modelling, i.e. pedotransfer functions. On the physical basis, saturated soil permeability arises from physical transport processes occurring at the pore level. Current progress in modelling techniques, computational methods and X-ray micro-tomographic technology gives opportunity to use direct methods of physical modelling for pore level transport processes. Physically valid description of transport processes at micro-scale based on Navier-Stokes type modelling approach gives chance to recover macroscopic porous medium characteristics from micro-flow modelling. Water microflow transport processes occurring at the pore level are dependent on the microstructure of porous body and interactions between the fluid and the medium. In case of soils, i.e. the medium there exist relatively big pores in which water can move easily but also finer pores are present in which water transport processes are dominated by strong interactions between the medium and the fluid - full physical description of these phenomena is a challenge. Ten samples of different soils were scanned using X-ray computational microtomograph. The diameter of samples was 5 mm. The voxel resolution of CT scan was 2.5 Ąm. Resulting 3D soil samples images were used for reconstruction of the pore space for further modelling. 3D image threshholding was made to determine the soil grain surface. This surface was triangulated and used for computational mesh construction for the pore space. Numerical modelling of water flow through the sample was performed. Steady-state Navier-Stokes equations for incompressible laminar flows were used for that purpose. Resulting from modelling values of the soil saturated permeabilities were compared with results from measurements, made using constant head permeameter. Differences in this results were discussed. The study was partially funded from the National Science Centre (Poland) upon the contract: UMO-2011/01/B/ST10/07544.
Lamorski, Krzysztof; S?awi?ski, Cezary; Barna, Gy÷ngyi
Rock fragments induce patchy distribution of soil water repellency in burned soils
NASA Astrophysics Data System (ADS)
Forest fires are recurrent phenomena in the Mediterranean area and are one of the main causes of changes in the Mediterranean ecosystems, increasing the risk of soil erosion and desertification. Fire is an important agent which can induce important changes in the chemical and physical characteristics of soils. During wildfires, only a small part of the heat generated is transmitted to the first centimetres of the soil profile. The intensity of the changes produced in the physical and chemical characteristics of the soil depends on the temperatures reached at different soil depths, the time of residence of temperature peaks, and the stability of the different soil components. One of the soil physical properties strongly affected by fire is soil water repellency (WR). Depending on temperature, time of heating, type of soil and fuel, fire can induce, enhance or destroy soil WR. Soil WR is a key factor in controlling soil hydrology and water availability in burnt soils together with other factors as texture or aggregation. Although the occurrence and consequences of fire-induced soil WR have been deeply studied, some gaps still exist, as the influence of rock fragment cover during burning. During combustion of litter and aerial biomass, the soil surface under rock fragments is heated and reachs temperature peaks after a certain delay respect to exposed areas. In contrast, temperature peaks are longer, increasing the time of residence of high temperature. In consequence, rock fragments may change the expected spatial distribution of soil WR. Up to date, very scarce research concerns the effect of rock fragments at the soil surface on the fire-induced pattern of soil water repellency. METHODS Two experiments were carried out in this research. In the first case, an experiment was conducted in an experimental farm in Sevilla (southern Spain). The effect of a low severity prescribed fire was studied in soil plots under different rock fragment covers (0, 15, 30, 45 and 60%). Soil WR was assessed in soil samples (0-10 cm) collected monthly during 6 monhts after burning. In the second case, a fire-affected forest soil from Cala±as (Huelva, southweastern Spain) was studied. Soil plots under different fire severities (low, medium and high severity burning) and rock fragment cover classes (20-40 and 60-80%) were analyzed. Soil WR was assessed in the soil surface immediately under the vertical projection of randomly selected stones and in the middle point between these and the nearest stones. Unburned adjacent soils under similar rock fragment cover classes were used as control. All soil WR assessments were carried out using the WDPT method. RESULTS In both cases, soil WR was induced in the soil surface contacting rock fragments after burning. Severity of WR ranged between subcritical or slight (low severity burning) and strong (high severity burning). Soil WR was also found to increase with rock fragment cover, especially after moderate or high severity burning, both under and between rock fragments. It is suggested that high density of rock fragments on the soil surface create a continuous surface of high residence of temperature peaks (in agreement with GarcĒa-Moreno et al., 2013). Combustion of plant residues in oxygen depletion conditions between adjacent nearby rock fragments contributes to heat transfer to the soil surface and consequent enhanced soil WR. REFERENCES GarcĒa-Moreno, J., Gordillo-Rivero, A.J., Gil, J., Jimķnez-Morillo, N.T., Mataix-Solera, J., Gonzßlez-Pe±aloza, F.A., Granged, A.J.P., Bßrcenas-Moreno, G., Jimķnez-Pinilla, P., Lozano, E., Jordßn, A., Zavala, L.M. 2013. Do stones modify the spatial distribution of fire-induced soil water repellency? Preliminary data. Flamma, 4:76-80.
Gordillo-Rivero, ┴ngel; GarcĒa-Moreno, Jorge; Bßrcenas-Moreno, Gema; Jimķnez-Morillo, Nicasio T.; Mataix-Solera, Jorge; Jordßn, Antonio; Zavala, Lorena M.
26 CFR 1.175-2 - Definition of soil and water conservation expenditures.
Code of Federal Regulations, 2010 CFR
...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...
26 CFR 1.175-2 - Definition of soil and water conservation expenditures.
Code of Federal Regulations, 2013 CFR
...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...
26 CFR 1.175-1 - Soil and water conservation expenditures; in general.
Code of Federal Regulations, 2010 CFR
...2009-04-01 false Soil and water conservation expenditures; in general... ┬¦ 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...
26 CFR 1.175-1 - Soil and water conservation expenditures; in general.
Code of Federal Regulations, 2010 CFR
...2010-04-01 false Soil and water conservation expenditures; in general... ┬¦ 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...
26 CFR 1.175-1 - Soil and water conservation expenditures; in general.
Code of Federal Regulations, 2013 CFR
...2013-04-01 false Soil and water conservation expenditures; in general... ┬¦ 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...
26 CFR 1.175-2 - Definition of soil and water conservation expenditures.
Code of Federal Regulations, 2010 CFR
...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...
Citrus orchards management and soil water repellency in Eastern Spain
NASA Astrophysics Data System (ADS)
Water repellent soils are found around the world, although originally was found on fire affected soil (DeBano, 1981). However, for decades, water repellency was found to be a rare soil property. One of the pioneer research that shown that water repellency was a common soil property is the Wander (1949) publication in Science. Wander researched the water repellency on citrus groves, and since then, no information is available about the water repellency on citrus plantations. The Mediterranean soils are prone to water repellency due to the summer dry conditions (CerdÓ and Doerr, 2007). And Land Use and Land Management are key factors (Harper et al., 2000; Urbanek et al., 2007) to understand the water repellency behaviour of agriculture soils. Valencia region (Eastern Spain) is the largest exporter in the world and citrus plantations located in the alluvial plains and fluvial terraces are moving to alluvial fans and slopes where the surface wash is very active (CerdÓ et al., 2009). This research aims to show the water repellency on citrus orchards located on the sloping terrain (< 15 % angle slope). Measurement were conducted in four experimental plots located in the Canyoles River watershed to assess the soil water repellency in citrus orchards under different managements: annual addition of plant residues and manure with no tilling and no fertilizer (MNT), annual addition of plant residues with no tillage (NT), application of conventional herbicides and no tilling (HNT) and conventional tillage in June (CT). The period for each type of management ranged from 2 and 27 (MNT), 1 and 25 (NT), 2 and 27 (HNT) and 3 and 29 years (CT). At each plot, a ten points were selected every 10 cm along inter-rows and water drop penetration time test (WDTP; DeBano, 1981) was performed. The results show that the MNT treatment induced slight water repellency in citrus-cropped soils compared to other treatments. Small but significant soil water repellency was observed under NT and HNT treatments (mean WDTP 4 ▒ 4 s and 2 ▒ 2 s, respectively), which may be regarded as subcritical soil water repellency. Slight water repellency observed in soils under MNT treatment may be attributed to the input of hydrophobic organic compounds as a consequence of the addition of plant residues and organic manure. A further issue to be achieved is the study of geomorphological processes associated to sub-critical soil water repellency. The experimental setup within the citrus plantation is being supported by the research project CGL2008-02879/BTE
CerdÓ, A.; Gonzßlez Pe±aloza, F. A.; Jordßn, A.; Zavala, L. M.
Reduction of rare soil microbes modifies plant-herbivore interactions.
Rare species are assumed to have little impact on community interactions and ecosystem processes. However, very few studies have actually attempted to quantify the role of rare species in ecosystems. Here we compare effects of soil community assemblages on plant-herbivore interactions and show that reduction of rare soil microbes increases both plant biomass and plant nutritional quality. Two crop plant species growing in soil where rare microbes were reduced, had tissues of higher nutritional quality, which theoretically makes them more susceptible to pest organisms such as shoot-feeding aphids and root-feeding nematodes. Reduction of rare microbes increased aphid body size in the absence of nematodes; nematodes always reduced aphid body size independent of the soil microbial community. This study is the first to show that rare soil microbes are not redundant but may play a role in crop protection by enhancing aboveground and belowground plant defence. It remains to be tested whether these are direct effects of rare soil microbes on plants and herbivores, or indirect effects via shifts in the microbial soil community assemblages. PMID:20070364
Hol, W H Gera; de Boer, Wietse; Termorshuizen, Aad J; Meyer, Katrin M; Schneider, Johannes H M; van Dam, Nicole M; van Veen, Johannes A; van der Putten, Wim H
Measuring Low Concentrations of Liquid Water in Soil
NASA Technical Reports Server (NTRS)
An apparatus has been developed for measuring the low concentrations of liquid water and ice in relatively dry soil samples. Designed as a prototype of instruments for measuring the liquidwater and ice contents of Lunar and Martian soils, the apparatus could also be applied similarly to terrestrial desert soils and sands. The apparatus is a special-purpose impedance spectrometer: Its design is based on the fact that the electrical behavior of a typical soil sample is well approximated by a network of resistors and capacitors in which resistances decrease and capacitances increase (and, hence, the magnitude of impedance decreases) with increasing water content.
Buehler, Martin
Phosphorus runoff from two water sources on a calcareous soil.
Phosphorus (P) in irrigation runoff may enrich offsite water bodies and streams and be influenced by irrigation water quality and antecedent soil surface conditions. Runoff, soil loss, and P fractions in runoff using reverse osmosis (RO) water or mixed RO and well water (RO/ Tap) were studied in a laboratory sprinkler study to evaluate water source effects on P transport. A top- or subsoil Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid), either amended or not amended with manure and/or with cheese whey, with Olsen P from 20 to 141 mg kg(-1) and lime from 108 to 243 g kg(-1), was placed in 1.5 x 1.2 x 0.2-m-deep containers with 2.4% slope and irrigated three times from a 3-m height for 15 min, applying 20 mm of water. The first irrigation was on a dry loose surface, the second on a wet surface, and the third on a dry crusted surface. Surface (ca. 2 cm) soil samples, prior to the first irrigation, were analyzed for Olsen P, water-soluble P (Pws), and iron-oxide impregnated paper-extractable P (FeO-P) analyses. Following each irrigation we determined runoff, sediment, dissolved reactive phosphorus (DRP) in a 0.45-microm filtered sample, and FeO-P and total P in unfiltered samples. Soil surface conditions had no effect on P runoff relationships. Water source had no significant effect on the relationship between DRP or FeO-P runoff and soil test P, except for DRP in RO runoff versus water-soluble soil P (r2 = 0.90). Total P in RO runoff versus soil P were not related; but weakly correlated for RO/Tap (r2 < 0.50). Water source and soil surface conditions had little or no effect on P runoff from this calcareous soil. PMID:11476510
Aase, J K; Bjorneberg, D L; Westermann, D T
Soil-root mechanical interactions within bundles of roots
NASA Astrophysics Data System (ADS)
Root-soil mechanical interactions play an important role in strength and force redistribution in rooted soil. Recent advances in root reinforcement modeling implement detailed representation of root geometry and mechanical properties as well as root-soil mechanical interactions. Nevertheless, root-soil mechanical interactions are often considered at the single root scale ignoring interactions between neighboring roots and root bundles known to play important role in similar applications such as engineered composite material reinforcement. The objective was to quantify mechanical interactions among neighboring roots or roots network using pullout laboratory experiments and modeling. We focus on the on effects of such interactions on global pull out force of a bundle of roots via better understanding of transmission of radial stresses to soil matrix due to the friction at the interface soil-root. Additionally, we wish to predict how cumulative friction changes along a single root axis with and without branching points during the slipping out. Analytical models of fiber reinforced materials show the magnitude of bonded friction depends on three key parameters: bond modulus, maximal bond strength and difference between the Young moduli of fiber and Young moduli of matrix. Debonded friction is calculated assuming failure follows Coulomb failure that includes apparent cohesion, effective normal stress and residual root soil friction angle. We used a pullout device to measure displacement and force of individual roots and for the bundle of roots. Additionally, we monitored and detected activation of root-soil friction by six acoustic emission sensors placed on waveguide in contact with the soil matrix. Results from experiments with parallel and crossing roots demonstrated the importance of considering factors such as distance of root axis, branching points, crossing of roots and roots diameter for the behavior of bundle of roots and inclined roots during pullout. Acoustic emission measurements provided interesting insights into progressive activation of root-soil friction. These results enhance understanding of root reinforcement mechanism and enable more realistic implementation of root reinforcement modeling for stability calculation of vegetated slopes.
Giadrossich, Filippo; Schwarz, Massimiliano; Preti, Federico; Or, Dani
Modeling Base Flow Soil Water Residence Times From Deuterium Concentrations
NASA Astrophysics Data System (ADS)
Three approaches to determining mean soil water residence times in a steep headwater catchment were investigated. The deuterium concentrations of soil water collected from 11 suction cup samplers at the Maimai M8 catchment were determined weekly for 14 weeks and the results compared with those of rainfall in the same period. Deuterium variations in the suction samples were considerably delayed and diminished compared with the rainfall, indicating significant storage times and mixing with soil water. Soil matrix water at shallow levels (ś200 mm depth) in unsaturated soils was relatively responsive to fresh input, but deeper water and water near the stream subject to occasional water table rises showed much less variation. Steady state and non-steady state exponential models gave similar mean residence times, ranging from 12 to more than 100 days for different locations. Three groups of soil water response were defined, comprising shallow, medium and deep (near-stream) soil locations based on the mean residence times. The nonsteady models revealed considerable week-to-week and longer variations in mean residence time for shallow soil (SL4), but indicated that steady state models could adequately represent the system in the overall period investigated. In the third approach, model types and parameters that gave the best fits to the soil water deuterium concentrations were determined. Exponential and especially dispersion models were the most satisfactory. Weighting the input (rainfall ?D) partially or fully with the amount of rainfall gave much worse fits than with the unweighted input, showing that much of the rainfall bypasses the soil matrix. The best fitting dispersion model (designated DM2) yielded the most accurate mean residence times: 13 days for shallow soil (SL4), 42 days for soil at 400 mm depth (SL5), both at midslope locations, and 63 days for soil at 800 mm depth near the stream (SL2). Capillary flow was important for the unsaturated shallow soil (SL4), while advection and hydrodynamic dispersion (mixing) were more dominant for the periodically saturated (SL5) and the generally saturated (SL2) soils.
Stewart, Michael K.; McDonnell, Jeffrey J.
Cosmic Ray Neutron Probe Soil Water Measurements over Complex Terrain in Austria
NASA Astrophysics Data System (ADS)
The importance of surface soil water (rooting zone) has become evident with climate change affecting rainfall patterns and crop production. The use of Cosmic Ray Neutron Probe (CRNP) for measuring surface soil water has become increasingly popular. The advantage of CRNP is that it is a non-invasive technique for measuring soil water content at an area-wide scale, in contrast to more conventional, techniques which measure mainly at field scale (point level). The CRNP integrates over a circular area of ca. 600 meters in diameter, to a depth of 70 cm, giving an average value for soil water content. Cosmic radiation interacting with the Earth's atmosphere continuously generates neutrons. At Earth's surface, these neutrons interact with surface water, and are slowed down. At sub-micrometer geometrics, these neutrons affect semiconductor devices, so they can be counted, slow and fast ones separately. From the difference in numbers between fast and slow neutrons, soil water content is calculated. As first in Austria, a CRNP (CRS 1000/B model) consisting of two neutron counters (one tuned for slow, the other one for fast neutrons), data logger and an Iridium modem, has been installed at Petzenkirchen research station of the Doctoral Programme for Water Resource Systems (TU Vienna) at 48.14 latitude and 15.17 longitude, 100 km west of Vienna, in late autumn 2013. The research station is located in an undulating agricultural landscape, characterized by heavy Cambisols and Planosols, and winter wheat and barley as main crops in winter, and maize and sunflower in summer. In addition, an in-situ soil moisture network consisting of 32 stations of Time Domain Transmissivity (TDT) sensors measuring soil water at 4 depths (0.05, 0.10,0.20 and 0.50 m) over an area of 64 ha has been established. This TDT network is currently being used to validate the use of the innovative CRNP technique. First results will be shown at the EGU 2014.
Vreugdenhil, Mariette; Weltin, Georg; Kheng Heng, Lee; Wahbi, Ammar; Oismueller, Markus; Dercon, Gerd
Interaction of methane and methanol with water
Intermolecular interaction energies of methane and methanol with a water molecule are computed in the SCF approximation with a minimal basis set and with the counterpoise correction; the value for the dispersion correction is estimated by a perturbation method. The computed interaction energies for a water molecule at a large number of different positions and orientations relative to either CHŌ
G. Bolis; E. Clementi; D. H. Wertz; H. A. Scheraga; C. Tosi
Enhancement of wind erosion by fire-induced water repellency in soils: a wind tunnel study
NASA Astrophysics Data System (ADS)
Wind erosion and fire occurrences are known to affect the composition and structure of vegetation in dryland landscapes. Fires contribute to determine the dominance or co-dominance of woody plants and grasses in arid and semiarid ecosystems. Fires expose the soil surface to the erosive action of wind and also make the soil more erodible by the release of water repellent compounds from vegetation due to burning. Despite the relevance of wind erosion and fires to the dynamics of arid ecosystems, the interactions between these two processes remain poorly understood. Here by a series of wind tunnel experiments, laboratory methods and theoretical analysis, we investigate the effect of fire-induced water repellency on the soil susceptibility to wind erosion. The experiments were done using pure Ottawa sands which were artificially coated with palmitic acid, a common water repellent lipid in soils. The results indicate that fire-induced water repellency enhances soil erodibility, causing a drop in wind erosion threshold velocity. The results are explained by the effect of water repellent compounds on soil-water contact angle and on the strength of interparticle wet-bonding forces.
Ravi, S.; D'Odorico, P.; Herbert, B.; Zobeck, T.; Over, T. M.
Critical Zone Soil Properties effects on Soil Water Storage and Flux
NASA Astrophysics Data System (ADS)
Soil properties control a wide range of hydrologic processes including recharge to regional aquifers. Soil water must pass through the critical zone to contribute to ground water recharge. Deep percolation (DP) from catchments is considered to be an estimate of mountain block recharge to regional aquifers. DP is also an important term in water mass balance studies, which attempt to estimate hydrologic states and fluxes in watersheds with fractured or transmissive bedrock. Few studies estimate the magnitude of this water balance term and it is often considered negligible. The objective of this study is to estimate the timing and magnitude of DP in the 0.015 km2 Tree Line experimental catchment (TL) from the 2011 water year. The catchment, which is located within the Dry Creek Experimental Watershed, Boise, ID, contains thin sandy soil over fractured granitic bedrock. We introduce modeling methods that focus on achieving a high degree of agreement between measured and modeled catchment storage. A distributed physically-based snow energy balance model is loosely coupled to a capacitance-based soil moisture model to estimate soil storage. Measured and calculated soil model parameters, including field capacity, saturated soil moisture content, and plant extraction limits, control the flux of water through the critical zone. Variability in soil storage and soil water fluxes through the critical zone is driven by soil properties. Parameters describing a leaf area index time series are calibrated to minimize the difference between measured and modeled soil dry down in the spring. DP is estimated to be 126 mm from Dec. 13, 2010 to June 30, 2011, which is 18% of the precipitation measured during that time. Rain-on-snow events are estimated to contribute 79 mm, which is 11% of precipitation or 63% of the calculated DP.
Kormos, P. R.; McNamara, J. P.; Seyfried, M. S.; Marks, D. G.; Flores, A. N.; Marshall, H.; Williams, C. J.
Water repellent soils as they occur on UK golf greens
NASA Astrophysics Data System (ADS)
Water repellent soils have been identified as a major problem in the management of golf greens in the UK for over 60 years. The cause of this problem has provoked much speculation, but prior to this work, no research into the possible cause of water repellent soils in the UK had been completed. One of the commonly believed links with water repellent soils on UK golf greens was the activity of basidiomycete fungi. This was proposed as a possible causal factor because the symptoms expressed on the turf above affected soils, were similar in many instances to those symptoms expressed by the activity of superficial fairy rings. Since it was impractical to study superficial fairy rings, it was decided to observe other basidiomycete fairy rings (Type 1 fairy rings) to see if any water-repellence could be identified as being associated with them. Three of these rings, caused by the fungus Marasmius oreades (Bolt ex. Fr) Fr., were studied on each of the two different sites. Soil samples were removed at intervals from the centre of the rings, across the obvious symptoms of the rings (i.e. the zone of dead grass bordered on both sides by a zone of stimulated grass growth) and beyond, into the uncolonised soil. These samples were taken to the laboratory, allowed to air dry and were then tested to determine relative levels of water repellence. It was found that on the 'outside' of the fairy rings where the fungus had not yet colonised, the soils were less water repellent than they were in the other zones of the rings (i.e. the dead zone and the inner zone). In the region of the dead zone of these fairy rings, the soil was very water repellent. This may have been expected because the fungus was present in this area in large quantities and the fungus itself repels water. However, of particular interest, were the results from the inner part of the ring where the fungus had been present in the past, but where it no longer colonised the soil. In these soil samples, the rootzone soil was still very water repellent. It was concluded from the study that it was possible for basidiomycete-type fungi to effect water repellence on soils through which they have passed. Thus, this may be at least a contributory factor to the development of severely water repellent soils on UK golf greens.
York, C. A.; Canaway, P. M.
The role of waste thermal water in the soil degradation
NASA Astrophysics Data System (ADS)
Thermal water exploitation is widespread, because it is considered to a "green" renewable energy source, the transporter of the Earth crust's heat. It is suitable for very diverse purposes: balneology, heating, mineral water, municipal hot water supply, technological water, etc. After usage, large amount of thermal water becomes sewage water with high concentrations of salts, heavy metals, ammonia, nitrate, and high temperature. Besides that, most of these waters have an unfavourable ion composition. Na+ (and in some cases Mg+) is predominant among cations. A common way of treatment is to let off the waste thermal water in unlined ground channels to leak into the soil. This can cause physical and chemical soil degradation. Continouos Na+ supply occurs, that occupies the place of Ca2+ on the ion exchange surfaces. Thus, adverse effects of Na+ can appear, like formation of extreme moisture regime, peptization, liquefaction. Beside Na+, Mg2+ also helps the formation of physical degradation in the soil. High water retain and unfavourable structure evolves. Not only the physical features of the soil are touched, fertility of production sites as well. Namely sorrounding the unlined ground channels, agricultural areas are seated, so it is important to protect productivity of the soil to maintain yield. Because of the seepage of high salt concentration waters, salt accumulation can be observed near to the channel lines. The investigated sample sites are located in the Great Hungarian Plane. We determined the main pollutants of the thermal waters, and the effects to the sorrounding soils. On two selected investigation areas (Cserkesz?l?, Tiszakķcske) salt profiles and Na+ adsorption isotherms are presented to characterize soil degradation. Genetic soil types are differ on the investigated areas, so the aspect of impact is different, as well.
Balog, Kitti; Farsang, Andrea
Formation of Soil Water Repellency by Laboratory Burning and Its Effect on Soil Evaporation
NASA Astrophysics Data System (ADS)
Fire-induced soil water repellency can vary with burning conditions, and may lead to significant changes in soil hydraulic properties. However, isolation of the effects of soil water repellency from other factors is difficult, particularly under field conditions. This study was conducted to (i) investigate the effects of burning using different plant leaf materials and (ii) of different burning conditions on the formation of soil water repellency, and (iii) isolate the effects of the resulting soil water repellency on soil evaporation from other factors. Burning treatments were performed on the surface of homogeneous fully wettable sand soil contained in a steel frame (60 x 60 cm; 40 cm depth). As controls a sample without a heat treatment, and a heated sample without fuel, were also used. Ignition and heat treatments were carried out with a gas torch. For comparing the effects of different burning conditions, fuel types included oven-dried pine needles (fresh needles of Pinus densiflora), pine needle litter (litter on a coniferous forest floor, P. densiflora + P. rigida), and broad-leaf litter (Quercus mongolica + Q. aliena + Prunus serrulata var. spontanea + other species); fuel loads were 200 g, 300 g, and 500 g; and heating duration was 40 s, 90 s and 180 s. The heating duration was adjusted to control the temperature, based on previous experiments. The temperature was measured continuously at 3-second intervals and logged with two thermometers. After burning, undisturbed soil columns were sampled for subsequent experiments. Water Drop Penetration Time (WDPT) test was performed at every 1 mm depth of the soil columns to measure the severity of soil water repellency and its vertical extent. Soil water repellency was detected following all treatments. As the duration of heating increased, the thickness of the water repellent layer increased, whilst the severity of soil water repellency decreased. As regards fuel amount, the most severe soil water repellency was formed at a fuel load of 300 g. Pine needle litter formed the most severe soil water repellency and fresh pine needle formed the thickest water repellent layer, whilst broad-leaf litter did only cause water repellency on the surface of the sand. The soil evaporation rate was measured by a gravitational method at an isothermal condition. Undisturbed soil columns were sealed after adding 50 ml of tap water through the bottom. After twelve hours of stabilization, the columns were opened and covered with filter paper. The rate of soil evaporation through the soil surface was measured by the hourly weight change at 45░ C. The initial 65 hours' evaporation rate was analyzed, while the slope of cumulative evaporation over time maintained its linearity. It was found that as the thickness of the water repellent layer increased, the evaporation rate tended to decrease. These two variables showed a good correlation (Pearson's correlation coefficient =-0.8916, p=0.0170) and a large coefficient of determination (R2=0.795) in the linear regression. This suggests that a layer of water repellent soil can affect water evaporation rate and that the rate is negatively correlated with the thickness of the repellent layer.
Ahn, Sujung; Im, Sangjun
Water balance for Great Basin phreatophytes derived from eddy covariance, soil water, and water table measurements
NASA Astrophysics Data System (ADS)
SummaryThis study was conducted in the Owens Valley, California to determine the relative contribution of groundwater and soil water to evapotranspiration (ET) from phreatophytic meadow and scrub plant communities. Groundwater uptake during the growing season was estimated from the difference between ET measured using eddy covariance, and the sum of soil water depletion, precipitation, and evaporation from the water table. Total ET during the growing season (March 26 to October 15) ranged from 53 to 646 mm among all sites and years. ET during winter was small, averaging approximately 40 mm. Estimates of evaporation from the water table based on soil properties and ET measurements at night both suggested this flux was a small component of the water balance. For alkali meadows with water table depths of 1-3 m, groundwater uptake accounted for 60-81% of ET. Shrub-dominated sites had lower cover and transpiration, and relied less on groundwater than meadows. Groundwater uptake was correlated with water table depth and leaf area index ( r2 = 0.62 and 0.70, respectively) even though water table depth and vegetation cover were less correlated ( r2 = 0.44). A slightly higher correlation was observed between groundwater uptake per unit leaf area and water table depth ( r2 = 0.73). Annual ET results from this study could assist the management of groundwater pumping in areas of phreatophytic vegetation by improved accounting of the sources of ET as vegetation leaf area and water table depths vary.
Steinwand, A. L.; Harrington, R. F.; Or, D.
Soil water content and freezing temperature affect freeze¢thaw related N 2 O production in organic soil
An organic agricultural soil was exposed to freeze¢thaw cycles (FTC) using either intact soil cores or cores packed with homogenized soil. The cores were first exposed to two mild FTCs (¢1.5?░C\\/+4?░C) with soil water content being 56¢85% of the water-filled pore space (WFPS). Both intact and packed soil cores showed high N2O emissions when the soil was thawing and had
Hannu T. Koponen; Pertti J. Martikainen
Integrated use of soil physical and water isotope methods for ecohydrological characterization of desertified areas
NASA Astrophysics Data System (ADS)
Measures for monitoring desertification and soil degradation require a thorough understanding of soil physical properties and of the water balance in order to guide restoration efforts (Costantini et al. 2009). It is hypothesized that long term restoration success on degraded land depends on a series of interacting factors such as exposition, soil type, soil hydrology including lateral flow on hill-slope catenae. Recently, new soil water isotope measurement techniques have been developed (Garvelmann et al. 2012) that provide much faster and reliable stable water isotope profiles in soils. This technique yield information on groundwater recharge, soil water balance and on the origin of water available for plants, which in combination with conservative chemical tracers (chloride) can be validated. A multidisciplinary study including ecologists, soil physicists and hydrologists of the COST Action Desert Restoration Hub was carried out on four semi-arid sites in Portugal. A comparative characterization of soil physical parameters, soil water isotope and chloride profiles was performed in order to estimate pedoclimate, soil aridity, soil water balance and groundwater recharge. In combination with soil physical data a comprehensive and cross-validated characterization of pedoclimate and soil aridity was obtained. These indicators were then integrated and related to plant cover. The long-term rainfall of the four sites ranges from 512 to 638 mm, whereas air temperature is from 15.8 to 17.0░C. The De Martonne index of aridity spans from 19.3 to 24.6, pointing to semiarid to moderately arid climatic conditions. The long-term average number of days when the first 0.50 m of soil is dry ranges from 110 to 134, while the mean annual soil temperature at 0.50 m spans from 15.8 and 19.1░C. The studied profiles show different hydrological characteristics, in particular, the estimated hydraulic conductivity ranges from 0.1-1 to 10-100 Ąm/s. Three out of four profiles show a marked decrease in water permeability at 0.04, 0.20, or 0.40 m depth. Soil isotope profiles indicated that percolation beneath the root zone and groundwater recharge ranges from 21.7 mm/y to 29.7 mm/y. The recharge rate was positively related to mean annual rainfall and soil organic matter, and interestingly, increased with aridity and desertification. The difference between mean annual rainfall and percolation was positively related to plant cover and in inverse proportion to the aridity index. Our results highlight the importance of combining different methods of site characterization by soil physics, soil water isotopes and soil water chemistry (chloride) with vegetation data, providing a more specific analysis of ecohydrological conditions and their relation to ecosystem functioning and recovery potential. The field protocol applied can provide relevant information for guiding restoration strategies. Costantini, E. A. C., Urbano, F., Aramini, G., Barbetti, R., Bellino, F., Bocci, M., & Tascone, F. (2009). Rationale and methods for compiling an atlas of desertification in Italy. Land Degradation & Development, 20(3), 261-276. Garvelmann, J., K³lls, C., & Weiler, M. (2012). A porewater-based stable isotope approach for the investigation of subsurface hydrological processes. Hydrology and Earth System Sciences, 16(2), 631-640.
K³lls, Christoph; Nunes, Alice; K÷bel-Batista, Melanie; Branquinho, Cristina; Bianconi, Nadja; Costantini, Eduardo
Integrating water by plant roots over spatially distributed soil salinity
NASA Astrophysics Data System (ADS)
In numerical simulation models dealing with water movement and solute transport in vadose zone, the water budget largely depends on uptake patterns by plant roots. In real field conditions, the uptake pattern largely changes in time and space. When dealing with soil and water salinity, most saline soils demonstrate spatially distributed osmotic head over the root zone. In order to quantify such processes, the major difficulty stems from lacking a sink term function that adequately accounts for the extraction term especially under variable soil water osmotic heads. The question of how plants integrate such space variable over its rooting depth remains as interesting issue for investigators. To move one step forward towards countering this concern, a well equipped experiment was conducted under heterogeneously distributed salinity over the root zone with alfalfa. The extraction rates of soil increments were calculated with the one dimensional form of Richards equation. The results indicated that the plant uptake rate under different mean soil salinities preliminary reacts to soil salinity, whereas at given water content and salinity the "evaporative demand" and "root activity" become more important to control the uptake patterns. Further analysis revealed that root activity is inconstant when imposed to variable soil salinity. It can be concluded that under heterogeneously distributed salinity, most water is taken from the less saline increment while the extraction from other root zone increments with higher salinities never stops.
Homaee, Mehdi; Schmidhalter, Urs
The water/graphitic-carbon interaction energy
NASA Astrophysics Data System (ADS)
The water/graphitic-carbon interaction energy was obtained for a sample having a water surface site adsorption density of 13.3 ?mol m -2. The interaction energy was determined from the spreading pressure of water, its surface tension and the water contact angle and using a formula obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for contact angles 42░ and 86░ are 7.63 and 7.18 kJ mol -1 of water are similar to the water binding energies obtained from molecular dynamic simulations of water droplets on a graphite surface: 6.7-8.33 kJ mol -1.
Helmy, Ahmed K.; Ferreiro, Eladio A.; de Bussetti, Silvia G.
Unity of mechanisms of water and wind erosion of soils
NASA Astrophysics Data System (ADS)
An equation for the threshold velocity of the water or wind flow at which erosion of a homogeneous model soil begins was derived on the basis of accepted and explicitly formulated suppositions and limitations and tested using experimental data. The validity of the proposed mechanisms and equations describing the lifting force of the soil-eroding water or wind flow and the interaggregate cohesion in a model homogeneous incoherent soil was confirmed. The limit for the decrease in the threshold flow velocity with decreasing size of the soil particles (aggregates) was theoretically substantiated. The first unified equation of the threshold velocity of the water or wind flow for a homogeneous model soil in dimensionless variables was derived and experimentally justified.
Gendugov, V. M.; Glazunov, G. P.
Can soil surface sealing be a natural compensation mechanism for soil water loss under future dry conditions?
NASA Astrophysics Data System (ADS)
Physical sealing of the soil is a widespread natural process in bare soil patches between shrubs, occurring frequently in dry environments. The seal layer has significantly lower hydraulic conductivity than the underlying undisturbed soil and thus it affects significantly hydrological fluxes. The presence of seal layer has been shown previously to be a negative feedback for vegetation water availability by reducing infiltration which leads to runoff initiation and consequently, propagation of desertification processes. The seal layer, however, has also shown a positive feedback, disregarded previously, resulting from suppressed evaporation fluxes from the soil which can have a much broader impact and affect water budget of dry areas at the regional scale. This positive feedback is studied in this research with model-based analysis of both measured local climatic records and synthetic climate change scenarios. The hillslope site (0.05 KM2) is located at the LTER Lehavim site, in the Negev desert at the south of Israel (31020' N, 34045' E). Annual rainfall is 290 mm and the soils are brown lithosols and arid brown loess, prone to surface sealing. The vegetation is characterized by scattered dwarf shrubs with dominant species Sarcopoterium spinosum. A previously published, high resolution physically-based model (aggregated Hydrus 1D runs) was used. The model (3X3 m2, 8240 cells) accounts explicitly for topographic and soil hydraulic parameters. Hydraulic properties of the seal layer at the soil surface were modeled following Mualem and Assouline (1989). Simulation of measured climate records reveals the seal layer to be a positive feedback for root zone water availability during dry and averaged rainfall seasons, while being a negative feedback during higher than average rainfall amounts (increasing the mean water content in the root zone, relatively to an unsealed profile, by 39%, 19% and -11% respectively). To study the seal layer role in future drier conditions, as projected by climate models for the Mediterranean region, the hydrological model was forced with a series of synthetic rainfall storms, systematically varying the drying intervals, evaporation intensity and soil initial water content conditions. Compared to an unsealed system, the presence of a seal layer was found to be an efficient water conservation mechanism, "buffering" the effect of climatic scenarios. For the drying intervals duration of 7 and 10 days (corresponding for the averages drying intervals during an average and dry seasons), water content at the root zone under the seal was found to be 17% and 20% higher, respectively. Furthermore, the seal layer effect on root zone water storage was found to be spatially heterogeneous, as the seal layer interacts differently with local topographic parameters.
Sela, Shai; Svoray, Tal; Assouline, Shmuel
Literature Survey of Airborne Vehicles Impacting with Water and Soil: Head Injury Criteria and Severity Index Development of Computer Program KRASH.
National Technical Information Service (NTIS)
This report describes a two part study to identify KRASH code requirements for analyses of: Structure/terrain interaction; Head/structure Interaction. The literature survey of water and soil impact methodology is presented. The reports are reviewed with r...
G. Wittlin M. A. Gamon
Reliability evaluation of containments including soil-structure interaction
Soil-structure interaction effects on the reliability assessment of containment structures are examined. The probability-based method for reliability evaluation of nuclear structures developed at Brookhaven National Laboratory is extended to include soil-structure interaction effects. In this method, reliability of structures is expressed in terms of limit state probabilities. Furthermore, random vibration theory is utilized to calculate limit state probabilities under random seismic loads. Earthquake ground motion is modeled by a segment of a zero-mean, stationary, filtered Gaussian white noise random process, represented by its power spectrum. All possible seismic hazards at a site, represented by a hazard curve, are also included in the analysis. The soil-foundation system is represented by a rigid surface foundation on an elastic halfspace. Random and other uncertainties in the strength properties of the structure, in the stiffness and internal damping of the soil, are also included in the analysis. Finally, a realistic reinforced concrete containment is analyzed to demonstrate the application of the method. For this containment, the soil-structure interaction effects on; (1) limit state probabilities, (2) structural fragility curves, (3) floor response spectra with probabilistic content, and (4) correlation coefficients for total acceleration response at specified structural locations, are examined in detail. 25 refs., 21 figs., 12 tabs.
Pires, J.; Hwang, H.; Reich, M.
Impact of Soil Water Content and Core Sampler Diameter at Sampling for Dry Soil Fragment?Size Distributions
Soil conditions at sampling and the dimensions of the sample are critical factors when soil aggregation is indirectly characterized by determining the distribution of soil fragments. Our objective was to determine the effects of gravimetric soil water content and core sampler diameter (16, 54, and 84Āmm) at sampling on the dry?fragment?size distribution of two soils (Typic Paleudalf and Typic Hapludalf)
John H. Grove; Ed Perfect
Climate Change Impacts on Soil and Water Conservation
NASA Astrophysics Data System (ADS)
Planning for Extremes: Addressing Climate Change Impacts on Soil and Water Conservation, Milwaukee, Wisconsin, 1-3 November 2006 Climate change and particularly precipitation changes will affect water runoff and soil erosion from agricultural cropland, but will the change be large enough to warrant modifications in U.S. conservation policy or practice? In a 2003 report by the Soil and Water Conservation Society (SWCS), this question was answered with an emphatic yes. Impacts of projected precipitation changes on soil erosion and runoff are complex, display high regional and temporal variability, and depend on a number of nonclimatic factors, such as seasonal timing of agronomic practices and antecedent soil moisture conditions. Altogether, observed and projected changes in precipitation are believed to substantially heighten the risk of runoff, soil erosion, and related environmental consequences. This article reports on a follow-up workshop that called for a review of current approaches to estimating soil erosion and runoff on agricultural lands, enhancements to soil and water planning tools, and strengthening of conservation practices and standards.
Garbrecht, Jurgen D.; Steiner, Jean L.; Cox, Craig A.
Conservation laws for a class of soil water equations
NASA Astrophysics Data System (ADS)
In this paper, we consider a class of nonlinear partial differential equations which model soil water infiltration, redistribution and extraction in a bedded soil profile irrigated by a line source drip irrigation system. By using the nonlocal conservation theorem method and the partial Lagrangian approach, conservation laws are presented. It is observed that both approaches lead to the nontrivial and infinite conservation laws.
Ya?ar, Emrullah
As Leaching into Fresh Water from Highly Contaminated Hawaiian Soils
NASA Astrophysics Data System (ADS)
Arsenic contamination of current and former agricultural soils in Hawaii is an unfortunate legacy of plantation era agricultural practices. Here, we report an investigation of As mobility in fresh water from highly contaminated (0.8 % As) A-zone Hawaiian andisols from the Hamakua Coast of the Island of HawaiÆi. Aliquots of the same acidic soil (pH= 5.0) were exposed to fresh water for varying lengths of time and analyzed to quantify the fraction of As and other elements leached from the soil relative to concentrations determined by total digestion. A maximum of 0.04% of As and 0.05% of Fe were removed from the soils in initial rinses and multi-day leaches using 18 megaohm Millipore water, in experiments lasting up to 35 days. Arsenic concentrations were highest in initial soil rinses, indicating that a small fraction of the total As in the soil is either loosely bound or present as a fine-grained, soluble As-bearing phase. During subsequent leaching experiments, arsenic and most other inorganic ions that we analyzed for reached equilibrium after 3 days; Fe reached equilibrium concentrations after 10 days. All soil solutions contained As levels that exceeded the EPA acceptable drinking water limit of 0.01 ppm. However, contaminant transport modeling suggests that As contaminated leachates would not migrate substantially from this site, so that local isolation and storage of contaminated soils would likely be an acceptable containment method.
Niklis, N. J.; Rubin, K. H.; El-Kadi, A. I.
Soil and water conservation: Productivity and environmental protection. 3. edition
This book is a revision of a landmark book offering a broad coverage of the field of soil and water conservation while fully exploring the hazards posed by erosion, sedimentation, and pollution. Scope includes agriculture, engineering, mining, and other uses of land along with the techniques needed to conserve soil while maintaining environmental quality.
Troeh, F.R.; Hobbs, J.A.; Donahue, R.L.
Stemflow-induced processes of soil water storage
NASA Astrophysics Data System (ADS)
Compared to stemflow production studies only few studies deal with the fate of stemflow at the near-stem soil. To investigate stemflow contribution to the root zone soil moisture by young and adult babassu palms (Attalea speciosa Mart.), I studied stemflow generation, subsequent soil water percolation and root distributions. Rainfall, stemflow and perched water tables were monitored on an event basis. Perched water tables were monitored next to adult palms at two depths and three stem distances. Dye tracer experiments monitored stemflow-induced preferential flow paths. Root distributions of fine and coarse roots were related to soil water redistribution. Average rainfall-collecting area per adult palm was 6.4 m▓, but variability between them was high. Funneling ratios ranged between 16-71 and 4-55 for adult and young palms, respectively. Nonetheless, even very small rainfall events of 1 mm can generate stemflow. On average, 9 liters of adult palm stemflow were intercepted and stemflow tended to decrease for-high intensity rainfall events. Young babassu palms funneled rainfall via their fronds, directly to their subterranean stems. The funneling of rainfall towards adult palm stems, in contrast, led to great stemflow fluxes down to the soil and induced initial horizontal water flows through the soil, leading to perched water tables next to palms, even after small rainfall events. The perched water tables extended, however, only a few decimeters from palm stems. After perched water tables became established, vertical percolation through the soil dominated. To my knowledge, this process has not been described before, and it can be seen as an addition to the two previously described stemflow-induced processes of Horton overland flow and fast, deep percolation along roots. This study has demonstrated that Babassu palms funnel water to their stems and subsequently store it in the soil next to their stems in areas where coarse root length density is very high. This might partly explain the competitive position of babassu palms on pastures or secondary forests.
Germer, Sonja
Water Extractability of Trace Metals from Soils: Some Pitfalls
Water soluble and\\/or dissolved metals represent the most ecotoxicologically relevant fraction of metals in the environment. However, water extractions may be prone to errors. This study aims to evaluate the performance of 5 filters as well as Rhizon soil moisture samplers, with respect to metal adsorption and\\/or release by the filter. In addition, the effect of equilibration time on water
E. Meers; G. Du Laing; V. G. Unamuno; E. Lesage; F. M. G. Tack; M. G. Verloo
Agri-environmental policy in Germany: soil and water conservation
This paper is concerned with agri-environmental policy in Germany and focuses in particular on soil and water conservation. At first it discusses to what extent agriculture contributes to erosion and the pollution of surface waters and groundwater with nutrients and pesticides. Whereas erosion is a minor problem in Germany water pollution due to modern and intensive agriculture is of major
Peter Weingarten
Soil-Earthquake Interactions in Buyukada/ Prinkipo (Istanbul)
NASA Astrophysics Data System (ADS)
As the largest one of the nine islands comprising the Princes' Islands in the Marmara Sea, close to Istanbul, Buyukada ("Large Isle") consist of with an area of 5.46 km2. The main factor controlling the earthquake hazard for Istanbul is a complex fault system, i.e. the North Anatolian Fault zone, which in the Marmara Sea region. Recent geophysical studies have carried out that this hazard is mainly associated within two active seismogenic areas: the Central Marmara Basin and the Adalar Fault zone, located about 15-30 km south-west and south of Istanbul. Eartquake ground motion affects the structures via the state of the soils. There are several historical buildings on B³y³kada, such as the Ayia Yorgi Church and Monastery dating back to the sixth century, the Ayios Dimitrios Church, and the Hamidiye Mosque built by Abdul Hamid II and Greek Orphanage, a huge wooden building etc. The soils and buildings with characteristics of earthquakes could be caused an earthquake damage / loss. One of the most important factors in reducing the earthquake risk in urban areas due to the earthquake ground motion is to estimate gound motion level with interaction of soils. When we look at the geological structure of Buyukada, Paleozoic unites and alluvial deposit are located. Site response of alluvial deposits in Buyukada is also important for the behavior during an earthquake. Geophysical study in the study area in order to estimate the behavior of soils is carried out to obtain the dominant period (microtremor measurements) and shear wave velocity ( MASW - MAM measurements) data. Soil geophysical results is input to earthquake motion for bedrock sites, and is important to the interaction with the ground movement and the soils to estimate B³y³kaada's earthquake ground motion. In the earthquake-soil interaction, spectral acceleration is an important criterion. In this study, spectral acceleration are also estiamted for ground motion level in Princes' Islands by using several approaches.
Ozcep, Ferhat; Karabulut, Savas; Caglak, Faruk; Ozel, Oguz
Scaling in soil aggregate distribution as dependent on aggregate water content and soil compaction
NASA Astrophysics Data System (ADS)
Fractal scaling has been documented in literature for mass of dry soil aggregates. Changes in water content are known to cause shrinking or swelling in aggregates. The objective of this work was to determine (a) whether the fractal scaling will hold for aggregates at various water contents, (b) how does mass fractal dimension depend on water content if the fractal scaling holds, (c) how will soil compaction affect the scaling. Soil samples were taken from several depths of Gray Forest soil for four different levels of compaction caused by agricultural machinery passes. The aggregate bulk density was measured with the kerosene method in air-dry aggregates, at saturation, and at two intermediate water contents. The power-law scaling mass=A*(diameter)^D was applicable to aggregates from all depths in the studied water content range. Bulk density at saturation did not depend on aggregate size, and D was equal to three for all aggregate sizes studied. Both the parameter A and the mass fractal dimension D depended on water content, and the dependencies could be approximated well with linear functions. Coefficients of those linear functions reflected aggregate size and were sensitive to the degree of compaction. The observed scaling provides a succinct representation of complex structure by a small number of parameters that can be used as complements to other soil parameters to show effects of soil management on soil structure.
Guber, A.; Pachepsky, Y.
Influence of soil-structure interaction on floor response spectra
A study was undertaken to investigate the influence of soil-structure interaction on floor response spectra developed in typical nuclear power plant structures. A horizontal earthquake time history, whose spectra envelops the Regulatory Guide 1.60 criteria and is scaled to a log peak acceleration, was used as input to structural models. Two different structural stick models were used, representing typical BWR and PWR facilities. By varying the structural and soil stiffness parameters, a wide range of system behaviors were investigated. Floor response spectra, required to assess equipment qualification, were of primary interest. It was found from a variation of parameter study that the interaction soil parameters, particularly radiation damping, greatly affect the nature of the calculated responses. 2 refs., 2 figs., 2 tabs.
Costantino, C.J.; Miller, C.A.; Curreri, J.R.
Numerical analysis of kinematic soil-pile interaction
In the present study, the response of singles pile to kinematic seismic loading is investigated using the computer program SAP2000. The objectives of the study are: (1) to develop a numerical model that can realistically simulate kinematic soil-structure interaction for piles accounting for discontinuity conditions at the pile-soil interface, energy dissipation and wave propagation; (2) to use the model for evaluating kinematic interaction effects on pile response as function of input ground motion; and (3) to present a case study in which theoretical predictions are compared with results obtained from other formulations. To evaluate the effects of kinematic loading, the responses of both the free-field soil (with no piles) and the pile were compared. Time history and static pushover analyses were conducted to estimate the displacement and kinematic pile bending under seismic loadings.
Castelli, Francesco; Maugeri, Michele [Department of Civil and Environmental Engineering, University of Catania, Viale Andrea Doria no. 6, 95125, Catania (Italy); Mylonakis, George [Department of Civil Engineering, University of Patras, Rio GR-26500, Patras (Greece)
Soil Water and Temperature in Harvested and Nonharvested Pinyon-Juniper Stands.
National Technical Information Service (NTIS)
Soil water and temperature initially increased following tree removal. The duff soil microsite accumulated soil moisture and the transition microsite at the edge of the duff became depleted. The south aspect had the greatest increase in soil moisture and ...
R. L. Everett S. H. Sharrow
Soil Surface Structure: A key factor for the degree of soil water repellency
NASA Astrophysics Data System (ADS)
Despite of considerable efforts, the degree of water repellency has not always been fully explained by chemical property of soil (termed hydrophobicity). That might be because the structure of a soil surface was not considered properly, which is another main factor determining the severity of soil water repellency. Surface structure has only recently been considered in soil science, whilst it has been paid attention for several decades in materials science due to its relevance to industrial applications. In this contribution, comparison of critical contact angles measured on different surface structures (made with glass beads, glass shards and beach sands) is presented and the effect of surface structure on manifestation of soil water repellency is discussed in terms of several different variables such as the individual particles shape, and areal and structural factors of the actual surface.
Ahn, S.; Doerr, S. H.; Douglas, P.; Bryant, R.; Hamlett, C.; McHale, G.; Newton, M.; Shirtcliffe, N.
Mediterranean shrub vegetation: soil protection vs. water availability
NASA Astrophysics Data System (ADS)
Soil Erosion and Land Degradation are closely related to the changes in the vegetation cover (Zhao et al., 2013). Although other factors such as rainfall intensiy or slope (Ziadat and Taimeh, 2013) the plant covers is the main factor that controls the soil erosion (Haregeweyn, 2013). Plant cover is the main factor of soil erosion processes as the vegetation control the infiltration and runoff generation (CerdÓ, 1998a; Kargar Chigani et al., 2012). Vegetation cover acts in a complex way in influencing on the one hand on runoff and soil loss and on the other hand on the amount and the way that rainfall reaches the soil surface. In arid and semiarid regions, where erosion is one of the main degradation processes and water is a scant resource, a minimum percentage of vegetation coverage is necessary to protect the soil from erosion, but without compromising the availability of water (Belmonte Serrato and Romero Diaz, 1998). This is mainly controlled by the vegetation distribution (CerdÓ, 1997a; Cammeraat et al., 2010; Kakembo et al., 2012). Land abandonment is common in Mediterranean region under extensive land use (CerdÓ, 1997b; GarcĒa-Ruiz, 2010). Abandoned lands typically have a rolling landscape with steep slopes, and are dominated by herbaceous communities that grow on pasture land interspersed by shrubs. Land abandonment use to trigger an increase in soil erosion, but the vegetation recovery reduces the impact of the vegetation. The goal of this work is to assess the effects of different Mediterranean shrub species (Dorycnium pentaphyllum Scop., Medicago strasseri, Colutea arborescens L., Retama sphaerocarpa, L., Pistacia Lentiscus L. and Quercus coccifera L.) on soil protection (runoff and soil losses) and on rainfall reaching soil surface (rainfall partitioning fluxes). To characterize the effects of shrub vegetation and to evaluate their effects on soil protection, two field experiments were carried out. The presence of shrub vegetation reduced runoff by at least 45% and soil loss by at least 59% in relation to an abandoned and degraded soil (bare soil) (Garcia-Estringana et al., 2010a). D. pentaphyllum, M. strasseri and C. arborescens were more effective in reducing runoff and soil loss (at least 83% and 97% respectively) than R. sphaerocarpa (45% and 59% respectively). Pisctacia Lentiscus L reduced the soil losses in 87% and the runoff rates (68%) meanwhile Quercus coccifera L reached a larger reduction (95% and 88 %) in comparison to herbicide treated agriculture soil. So, all shrub species protected the soil, but not in the same way. In relation to rainfall reaching the soil surface, great differences were observed among species, with interception losses varying between 10% for R. sphaerocarpa to greater than 36% for D. pentaphyllum and M. strasseri, and with stemflow percentages changing between less than 11% for D. pentaphyllum and M. strasseri and 20% for R. sphaerocarpa (Garcia-Estringana et al., 2010b). Rainfall interception on Pistacia Lentiscus and Quercus coccifera were 24% and 34% respectively for the two years of measurements. The integration of the effects of Mediterranean shrub vegetation on soil protection and rainfall partitioning fluxes facilitates understanding the effects of changes in vegetation type on soil and water resources. From this perspective, the interesting protective effect of D. pentpahyllum and M. strasseri, reducing intensely runoff and soil loss contrasts with the dangerous reduction in rainfall reaching the soil surface. Soil protection is essential in semiarid and arid environments, but a proper assessment of the effects on water availability is critical because of water is a scant resource in these kinds of environments. Pistacia Lentiscus and Quercus coccifera shown both a high capacity to intercept rainfall, increase infiltration and reduce the soil losses. We suggest to apply similar research programs into recently fire affected land as the role of vegetation after the fire is very dynamic (CerdÓ 1998b). Acknowledgements The research projects 07 M/0077/1998, 07 M/0023/
GarcĒa Estringana, Pablo; Nieves Alonso-Blßzquez, M.; Alegre, Alegre; CerdÓ, Artemi
Photosynthesis and Transpiration of Monterey Pine Seedlings as a Function of Soil Water Suction and Soil Temperature
Rates of photosynthesis, respiration, and transpiration of Monterey pine (Pinus radiata D. Don) were measured under controlled conditions of soil water suction and soil temperature. Air temperature, relative humidity, light intensity, and air movement were maintained constant. Rates of net photosynthesis, respiration, and transpiration decreased with increasing soil water suction. The decrease in the rates of net photosynthesis and transpiration as a function of the soil temperature at low soil water suctions may be attributed to changes in the viscosity of water. At soil water suctions larger than 0.70 bars rates of transpiration and net photosynthesis may be affected in the same proportion by changes in stomatal apertures. Images
Babalola, O.; Boersma, L.; Youngberg, C. T.
Survey of microbial enzymes in soil, water, and plant microenvironments.
Detection of microbial enzymes in natural environments is important to understand biochemical activities and to verify the biotechnological potential of the microorganisms. In the present report, 346 isolates from soil, water, and plants were screened for enzyme production (caseinase, gelatinase, amylase, carboxymethyl cellulase, and esterase). Our results showed that 89.6% of isolates produced at least one tested enzyme. A predominance of amylase in soil samples, carboxymethyl cellulase in plants, as well as esterase and gelatinase in water was observed. Interesting enzymatic profiles were found in some microenvironments, suggesting specificity of available nutrients and/or natural selection. This study revealed the potential of microorganisms present in water, soil, and plant to produce important enzymes for biotechnological exploration. A predominance of certain enzymes was found, depending on the type of environmental sample. The distribution of microbial enzymes in soil, water and plants has been little exploited in previous reports. PMID:24847390
Alves, Priscila Divina Diniz; Siqueira, Flßvia de Faria; Facchin, Susanne; Horta, Carolina Campolina Rebello; Vict¾ria, J·nia Maria Netto; Kalapothakis, Evanguedes
Survey of Microbial Enzymes in Soil, Water, and Plant Microenvironments
Detection of microbial enzymes in natural environments is important to understand biochemical activities and to verify the biotechnological potential of the microorganisms. In the present report, 346 isolates from soil, water, and plants were screened for enzyme production (caseinase, gelatinase, amylase, carboxymethyl cellulase, and esterase). Our results showed that 89.6% of isolates produced at least one tested enzyme. A predominance of amylase in soil samples, carboxymethyl cellulase in plants, as well as esterase and gelatinase in water was observed. Interesting enzymatic profiles were found in some microenvironments, suggesting specificity of available nutrients and/or natural selection. This study revealed the potential of microorganisms present in water, soil, and plant to produce important enzymes for biotechnological exploration. A predominance of certain enzymes was found, depending on the type of environmental sample. The distribution of microbial enzymes in soil, water and plants has been little exploited in previous reports.
Alves, Priscila Divina Diniz; Siqueira, Flavia de Faria; Facchin, Susanne; Horta, Carolina Campolina Rebello; Victoria, Junia Maria Netto; Kalapothakis, Evanguedes
Interactions Among Grassland Plant Species, Microbial Communities, and Soil Processes
Plant-microbial interactions are thought to be an important determinant of ecosystem processes, yet we do not know whether impacts of plant species on soil microbial community composition translate to impacts on function. We established field plots in a California annual grassland of five plant monocultures for two years to determine the effects of different plant species on the composition of
V. Eviner; M. Waldrop; E. Schwartz; J. Pett-Ridge; M. Firestone
Soil water repellency characteristic curves for soil profiles with natural organic carbon gradients
NASA Astrophysics Data System (ADS)
Soil water repellency (SWR) is a phenomenon that influences many soil hydrologic processes such as reduction of infiltration, increase in overland flow, and enhanced preferential flow. SWR has been observed in various soil types and textures, and the degree of SWR is greatly controlled by soil moisture content and levels of organic matter and clay. One of the key topics in SWR research is how to describe accurately the seasonal and temporal variation of SWR with the controlling factors such as soil moisture, organic matter, and clay contents for soil profiles with natural organic carbon gradients. In the present study, we summarize measured SWR data for soil profiles under different land uses and vegetation in Japan and New Zealand, and compared these with literature data. We introduce the contact angle-based evaluation of SWR and predictive models for soil water repellency characteristic curves, in which the contact angle is a function of the moisture content. We also discuss a number of novel concepts, including i) the reduction in the contact angle with soil-water contact time to describe the time dependence of SWR, ii) the relationship between the contact angles from the measured scanning curves under controlled wetting and drying cycles, and iii) the initial contact angles measured by the sessile drop method.
Kawamoto, Ken; M³ller, Karin; Moldrup, Per; de Jonge, Lis; Clothier, Brent; Hiradate, Syuntaro; Komatsu, Toshiko
Drainage models to predict soil water regimes in drained soils: a UK perspective
Drainage is an intervention in the natural hydrology of the soil to alter the duration of adverse (waterlogged) soil conditions. The effects of drainage can be investigated by models that predict the position of the water table at a site in the presence of drainage. An inter-related series of models, which include the van Schilfgaarde non-steady state model, that have
A. C. Armstrong; A. M. Matthews; D. A. Castle
Macrofauna assemblage composition and soil moisture interact to affect soil ecosystem functions
NASA Astrophysics Data System (ADS)
Changing climatic conditions and habitat fragmentation are predicted to alter the soil moisture conditions of temperate forests. It is not well understood how the soil macrofauna community will respond to changes in soil moisture, and how changes to species diversity and community composition may affect ecosystem functions, such as litter decomposition and soil fluxes. Moreover, few studies have considered the interactions between the abiotic and biotic factors that regulate soil processes. Here we attempt to disentangle the interactive effects of two of the main factors that regulate soil processes at small scales - moisture and macrofauna assemblage composition. The response of assemblages of three common temperate soil invertebrates (Glomeris marginata Villers, Porcellio scaber Latreille and Philoscia muscorum Scopoli) to two contrasting soil moisture levels was examined in a series of laboratory mesocosm experiments. The contribution of the invertebrates to the leaf litter mass loss of two common temperate tree species of contrasting litter quality (easily decomposing Fraxinus excelsior L. and recalcitrant Quercus robur L.) and to soil CO2 fluxes were measured. Both moisture conditions and litter type influenced the functioning of the invertebrate assemblages, which was greater in high moisture conditions compared with low moisture conditions and on good quality vs. recalcitrant litter. In high moisture conditions, all macrofauna assemblages functioned at equal rates, whereas in low moisture conditions there were pronounced differences in litter mass loss among the assemblages. This indicates that species identity and assemblage composition are more important when moisture is limited. We suggest that complementarity between macrofauna species may mitigate the reduced functioning of some species, highlighting the importance of maintaining macrofauna species richness.
Collison, E. J.; Riutta, T.; Slade, E. M.
Effect of soil water repellency on soil hydraulic properties estimated under dynamic conditions
NASA Astrophysics Data System (ADS)
SummarySoil research done over the past decades has proven that water repellent soils are widespread in all climates. Water repellency enhances the leaching of contaminants in the unsaturated zone by introducing preferential flow. In order to predict soil water fluxes in the unsaturated zone the accurate knowledge of the soil hydraulic properties (SHP) is mandatory. In this study the effect of water repellency on both imbibition and drainage SHP was studied. Inflow/outflow experiments were conducted in the laboratory for two soils and two artificially created hydrophobic mixtures. In the inflow/outflow experiments the pressure head at the bottom of the soil column was increased/decreased and the estimated SHP functions were obtained by means of inverse modeling. Inflow/outflow experiments were also conducted using ethanol instead of water in order to estimate the effect of liquid wetting properties on the estimated characteristic curves of the materials under study. The results showed that the water retention functions and the unsaturated hydraulic conductivity functions estimated from the dynamic experiments are strongly dependent on the degree of water repellency and the wetting/drying process.
Diamantopoulos, E.; Durner, W.; Reszkowska, A.; Bachmann, J.
Cooperative water-SOM interactions derived from the organic compound effect on SOM hydration
NASA Astrophysics Data System (ADS)
Interactions of water molecules with soil organic matter (SOM) may affect the ability of SOM to participate in multiple physical, chemical and biological processes. Specifically, water-SOM interactions may have a profound effect on interactions of organic compounds with SOM which is often considered as a major natural sorbent controlling the environmental fate of organic pollutants in the soil environment. Quantification of water - SOM interactions may be carried out by using water vapor sorption isotherms. However, water sorption isotherms providing macroscopic thermodynamic data do not allow examining water-SOM interactions on a microenvironment scale. The examination of water-SOM interactions in a local SOM environment may be carried out by determining the response of the SOM hydration to sorption of probe organic compounds. Recently, the model-free approach was proposed which allows quantifying effects of sorbing organic molecules on water - SOM interactions, by using relatively more available data on the effect of water activity on organic compound - SOM interactions. Therefore, this thermodynamic approach was applied to the experimental data describing sorption of organic compounds by SOM, both from the vapor and liquid phases, at various water activities. Hence, the response of water interactions with the model SOM materials such as a humic acid and an organic matter-rich peat soil to the presence of various organic sorbates was evaluated. Depending on a molecular structure of organic sorbates probing various molecular environments in SOM, the SOM-bound water may be driven in or out of the SOM sorbents. Organic compounds containing the atoms of oxygen, nitrogen or sulfur and preferring a relatively "polar" SOM microenvironment demonstrate the distinct enhancing effect on water-SOM interactions. In contrast, the "low-polarity" organic compounds, e.g., hydrocarbons or their halogen-substituted derivatives, produce a weakening effect on water-SOM interactions. Importantly, the changes in water-SOM interactions induced by the presence of organic compounds may demonstrate the cooperative behavior: (1) several water molecules may be involved in an enhanced hydration of SOM, (2) at the presence of an organic sorbate, interactions of water molecules with SOM enhance the uptake of the following water molecules. The proposed cooperative water-SOM interactions may result from a perturbation of the SOM matrix due to a sorption of organic and water molecules where a partial disrupting of molecular contacts in SOM makes easier the following SOM-water interactions thus promoting the enhanced SOM hydration.
Borisover, Mikhail
7 CFR 610.12 - Equations for predicting soil loss due to water erosion.
Code of Federal Regulations, 2010 CFR
...2010-01-01 false Equations for predicting soil loss due to water erosion. 610.12...CONSERVATION OPERATIONS TECHNICAL ASSISTANCE Soil Erosion Prediction Equations ┬¦ 610.12 Equations for predicting soil loss due to water erosion. (a)...
7 CFR 610.12 - Equations for predicting soil loss due to water erosion.
Code of Federal Regulations, 2010 CFR
...2009-01-01 false Equations for predicting soil loss due to water erosion. 610.12...CONSERVATION OPERATIONS TECHNICAL ASSISTANCE Soil Erosion Prediction Equations ┬¦ 610.12 Equations for predicting soil loss due to water erosion. (a)...
Fates and transport of PPCPs in soil receiving reclaimed water irrigation.
Fates and transport of 9 commonly found PPCPs of the reclaimed water were simulated based on the HYDRUS-1D software that was validated with data generated from field experiments. Under the default scenario in which the model parameters and input data represented the typical conditions of turf grass irrigation in southern California, the adsorption, degradation, and volatilization of clofibric acid, ibuprofen, 4-tert-octylphenol, 4-n-nonylphenol, naproxen, triclosan, diclofenac sodium, bisphenol A and estrone in the receiving soils were tracked for 10 years. At the end, their accumulations in the 90 cm soil profile varied from less than 1 ng g(-1) to about 140 ng g(-1) and their concentrations in the drainage water in the 90 cm soil depth varied from nil to ?g L(-1) levels. The adsorption and microbial degradation processes interacted to contain the PPCPs entirely within surface 40 cm of the soil profiles. Leaching and volatilization were not significant processes governing the PPCPs in the soils. The extent of accumulations in the soils did not appear to produce undue ecological risks to the soil biota. PPCPs did not represent any potential environmental harm in reclaimed water irrigation. PMID:24148973
Chen, Weiping; Xu, Jian; Lu, Sidan; Jiao, Wentao; Wu, Laosheng; Chang, Andrew C
Soil Moisture and Vegetation Water Content Retrieval Using QuikSCAT data
NASA Astrophysics Data System (ADS)
Future water resources are a critical societal impact of climate change and hydrological cycles. Current climate models uncertainties result in disagreement on whether there will be more or less water. On a global scale, there are important gaps in knowledge of where water is stored, where it is going, and how fast it is moving. Soil moisture and vegetation water content are key environmental variables on evaporation and transpiration at the land-atmosphere boundary. Radar remote sensing helps to improve our estimate of water resources globally and temporally. SMAP (Soil Moisture Active Passive) and SWOT (Surface Water Ocean Topography) are the two future NASA missions to monitor water resources and their variation spatially and temporally. Li et al. (Li. Et al. 2010) developed a physically based six-channel algorithm, which uses dual-polarization Windsat passive microwave data to retrieve soil moisture and vegetation water content. We use the retrieved soil moisture and vegetation water content using Windsat descending pass (around 6AM), and also simultaneous collocated QuikSCAT dual-polarization backscattered power to estimate different parameters of the land. The backscattered power can be written as ?pi = fbare ?grp(smi,m) + (1-fbare){ Ap ( 1-exp(-Bp Wi) ) + Cp Wi? exp(-Bp Wi) } where ?pi is the ith QuikSCAT backscatter power with polarization p, fbare is the bare surface fraction, m is soil rms. slope, ?grp is the ground backscattered power with polarization p, and smi and Wi are the retrieved soil moisture and vegetation water content using Windsat data. Ap, Cp, and Bp are the backscattering contributions from vegetation volume, canopy ground interaction, and attenuation of the canopy with polarization p, respectively. We assume all parameters remain constant for each month of different years compared to soil moisture and vegetation water content. Therefore for each point, we have 10 unknowns for HH and VV polarizations. We collect all observations of simultaneous QuikSCAT and retrieved smi and Wi for each location during the summer season and retrieve all those 10 parameters. We show how the retrieved global bare surface fraction compares well with the existing maps. These parameters are then used to estimate the soil moisture and vegetation water content for summer days of a different year using QuikSCAT backscattered power and formula above. Although QuikSCAT satellite is designed to capture sea-winds, it also collects data over land globally almost every day. Therefore, we can generate a global map of soil moisture and vegetation water content daily. We compare the retrieved values with Li et al.'s retrieval values.
Oveisgharan, S.; Haddad, Z. S.; Turk, J.; Li, L.; Rodriguez, E.
Vertical variations of soil hydraulic properties within two soil profiles and its relevance for soil water simulations
NASA Astrophysics Data System (ADS)
Numerical simulations of soil water dynamics can be valuable tools for the assessment of different soil and land management practices. For accurate simulations, the soil hydraulic properties (SHP), i.e. the hydraulic conductivity and water retention function have to be properly known. They can be either estimated from physical soil properties by pedotransfer functions (PTF) or measured. In most studies, soil profiles are analyzed and sampled with respect to their pedogenic horizons. While considerable effort has been put on horizontal spatial SHP variations, vertical changes within soil profiles have not been analyzed in detail. Therefore, the objectives of this study were (i) the SHP measurement along vertical transects within two soil profiles, (ii) to evaluate their spatial variation and correlation with physical soil properties, and (iii) to assess the impact of the SHP determination method and its spatial discretization on simulated soil water balance components. Two soils, an agriculturally used silty-loam Chernozem and a forested sandy Cambisol were sampled in 0.05 m increments along vertical transects. The parameters of a dual porosity model were derived using the evaporation method and scaling was applied to derive representative mean SHP parameters and scaling factors as a measure of spatial variability. State-space models described spatial variations of the scaling factors by physical soil properties. Simulations with HYDRUS 1D delivered the soil water balance for different climatic conditions with the SHP being estimated from horizon-wise PTFs, or discretized either sample-wise, according to the pedogenic horizons, or as hydrologically relevant units (hydropedological approach). Considerable SHP variations were found for both soil profiles. In the Chernozem, variations of the hydraulic conductivity were largest within the ploughed Ap-horizon and could be attributed to variations in soil structure (macropores). In the subsoil, soil water retention showed a gradual decrease within each horizon. The observed water retention variations could be described by state-space models that comprised the contents of clay and total carbon, whereas variations of the hydraulic conductivity were described by clay content and total porosity. The hydraulic conductivity in the Cambisol was slightly undulating throughout the profile. Here, water retention was largest in the upper part of the profile and considerably decreased within the lower part of the Bhs-horizon. Simulated soil water balance components differed distinctly between the SHP discretizations. Compared to observed soil water contents, the simulations where the SHP were given by small-scale layers or hydropedological units performed best for both experimental sites. The different SHP discretizations mainly affected the estimated drainage losses and the simulated crop transpiration under medium to dry climatic conditions. The study confirmed the importance of an adequate spatial SHP discretization. The results indicate that SHP estimations by PTFs or the standard horizon-mean sampling strategy might fail to parameterize soil water simulations, especially in structured soils. The presented hydropedological approach showed a way to receive good simulation results by reducing the SHP observation density.
Schwen, Andreas; Zimmermann, Michael; Bodner, Gernot
Prion protein interaction with soil humic substances: environmental implications.
Transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative disorders caused by prions. Animal TSE include scrapie in sheep and goats, and chronic wasting disease (CWD) in cervids. Effective management of scrapie in many parts of the world, and of CWD in North American deer population is complicated by the persistence of prions in the environment. After shedding from diseased animals, prions persist in soil, withstanding biotic and abiotic degradation. As soil is a complex, multi-component system of both mineral and organic components, it is important to understand which soil compounds may interact with prions and thus contribute to disease transmission. Several studies have investigated the role of different soil minerals in prion adsorption and infectivity; we focused our attention on the interaction of soil organic components, the humic substances (HS), with recombinant prion protein (recPrP) material. We evaluated the kinetics of recPrP adsorption, providing a structural and biochemical characterization of chemical adducts using different experimental approaches. Here we show that HS act as potent anti-prion agents in prion infected neuronal cells and in the amyloid seeding assays: HS adsorb both recPrP and prions, thus sequestering them from the prion replication process. We interpreted our findings as highly relevant from an environmental point of view, as the adsorption of prions in HS may affect their availability and consequently hinder the environmental transmission of prion diseases in ruminants. PMID:24937266
Giachin, Gabriele; Narkiewicz, Joanna; Scaini, Denis; Ngoc, Ai Tran; Margon, Alja; Sequi, Paolo; Leita, Liviana; Legname, Giuseppe
Volatile-mediated interactions between phylogenetically different soil bacteria
There is increasing evidence that organic volatiles play an important role in interactions between micro-organisms in the porous soil matrix. Here we report that volatile compounds emitted by different soil bacteria can affect the growth, antibiotic production and gene expression of the soil bacterium Pseudomonas fluorescens Pf0¢1. We applied a novel cultivation approach that mimics the natural nutritional heterogeneity in soil in which P. fluorescens grown on nutrient-limited agar was exposed to volatiles produced by 4 phylogenetically different bacterial isolates (Collimonas pratensis, Serratia plymuthica, Paenibacillus sp., and Pedobacter sp.) growing in sand containing artificial root exudates. Contrary to our expectation, the produced volatiles stimulated rather than inhibited the growth of P. fluorescens. A genome-wide, microarray-based analysis revealed that volatiles of all four bacterial strains affected gene expression of P. fluorescens, but with a different pattern of gene expression for each strain. Based on the annotation of the differently expressed genes, bacterial volatiles appear to induce a chemotactic motility response in P. fluorescens, but also an oxidative stress response. A more detailed study revealed that volatiles produced by C. pratensis triggered, antimicrobial secondary metabolite production in P. fluorescens. Our results indicate that bacterial volatiles can have an important role in communication, trophic - and antagonistic interactions within the soil bacterial community.
Garbeva, Paolina; Hordijk, Cornelis; Gerards, Saskia; de Boer, Wietse
Prion Protein Interaction with Soil Humic Substances: Environmental Implications
Transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative disorders caused by prions. Animal TSE include scrapie in sheep and goats, and chronic wasting disease (CWD) in cervids. Effective management of scrapie in many parts of the world, and of CWD in North American deer population is complicated by the persistence of prions in the environment. After shedding from diseased animals, prions persist in soil, withstanding biotic and abiotic degradation. As soil is a complex, multi-component system of both mineral and organic components, it is important to understand which soil compounds may interact with prions and thus contribute to disease transmission. Several studies have investigated the role of different soil minerals in prion adsorption and infectivity; we focused our attention on the interaction of soil organic components, the humic substances (HS), with recombinant prion protein (recPrP) material. We evaluated the kinetics of recPrP adsorption, providing a structural and biochemical characterization of chemical adducts using different experimental approaches. Here we show that HS act as potent anti-prion agents in prion infected neuronal cells and in the amyloid seeding assays: HS adsorb both recPrP and prions, thus sequestering them from the prion replication process. We interpreted our findings as highly relevant from an environmental point of view, as the adsorption of prions in HS may affect their availability and consequently hinder the environmental transmission of prion diseases in ruminants.
Giachin, Gabriele; Narkiewicz, Joanna; Scaini, Denis; Ngoc, Ai Tran; Margon, Alja; Sequi, Paolo; Leita, Liviana; Legname, Giuseppe
Fire and grazing effects on wind erosion, soil water content, and soil temperature.
Selective grazing of burned patches can be intense if animal distribution is not controlled and may compound the independent effects of fire and grazing on soil characteristics. Our objectives were to quantify the effects of patch burning and grazing on wind erosion, soil water content, and soil temperature in sand sagebrush (Artemisia filifolia Torr.) mixed prairie. We selected 24, 4-ha plots near Woodward, OK. Four plots were burned during autumn (mid-November) and four during spring (mid-April), and four served as nonburned controls for each of two years. Cattle were given unrestricted access (April-September) to burned patches (<2% of pastures) and utilization was about 78%. Wind erosion, soil water content, and soil temperature were measured monthly. Wind erosion varied by burn, year, and sampling height. Wind erosion was about 2 to 48 times greater on autumn-burned plots than nonburned plots during the dormant period (December-April). Growing-season (April-August) erosion was greatest during spring. Erosion of spring-burned sites was double that of nonburned sites both years. Growing-season erosion from autumn-burned sites was similar to nonburned sites except for one year with a dry April-May. Soil water content was unaffected by patch burn treatments. Soils of burned plots were 1 to 3 degrees C warmer than those of nonburned plots, based on mid-day measurements. Lower water holding and deep percolation capacity of sandy soils probably moderated effects on soil water content and soil temperature. Despite poor growing conditions following fire and heavy selective grazing of burned patches, no blowouts or drifts were observed. PMID:16091608
Vermeire, Lance T; Wester, David B; Mitchell, Robert B; Fuhlendorf, Samuel D
Rethinking soil and water conservation in a changing society : A case study in eastern Burkina Faso
Soil and water conservation is at the top of development agendas in Africa. Virtually every project related to agriculture or the environment has a soil and water conservation component to it and environmental protection plans are being drawn up by African governments in which soil and water conservation figures dominantly. This focus on soil and water conservation is due to
V. M. Mazzucato; D. Niemeijer
Muddy Waters: Soil Erosion and Downstream Externalities
Soil erosion and fertilizer run-off cause serious flow externalities in downstream environments through-out the world. Social costs include e.g. loss of health, life and production due to pollution and eutrophication of freshwater resources, reduced life of hydro-power plants, increased turbidity, and degradation of coral reefs and marine resources. The key optimal control models on soil capital management omit downstream externalities
Anders Ekbom; Gardner M. Brown; Thomas Sterner
Interaction between water and defective silica surfaces
We use the density functional theory method to study dry (1 x 1) {alpha}-quartz (0001) surfaces that have Frenkel-like defects such as oxygen vacancy and oxygen displacement. These defects have distinctively different effects on the water-silica interface depending on whether the adsorbent is a single water molecule, a cluster, or a thin film. The adsorption energies, bonding energies, and charge transfer or redistributions are analyzed, from which we find that the existence of a defect enhances the water molecule and cluster surface interaction by a large amount, but has little or even negative effect on water thin film-silica surface interaction. The origin of the weakening in film-surface systems is the collective hydrogen bonding that compromises the water-surface interaction in the process of optimizing the total energy. For clusters on surfaces, the lowest total energy states lower both the bonding energy and the adsorption energy.
Chen Yunwen; Cheng Haiping [Department of Physics and Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)
The impact of the soil surface properties in water erosion seen through LandSoil model sensitivity analysis
NASA Astrophysics Data System (ADS)
Quantitative models of soil redistribution at the landscape scale are the current tools for understanding space-time processes in soil and landscape evolution. But models use larger and larger numbers of variables and sometimes it becomes difficult to understand their relative importance and model behaviours in critical conditions. Sensitivity analysis (SA) is widely used to clarify models behaviours, their structure giving fundamental information to ameliorate models their selves. We tested the LandSoil model (LANDscape design for SOIL conservation under soil use and climate change) a model designed for the analysis of agricultural landscape evolution at a fine spatial resolution scale [1-10 meters] and a mid-term temporal scale [10-100 years]. LandSoil is suitable for simulations from parcel to catchment scale. It is spatially distributed, event-based, and considers water and tillage erosion processes that use a dynamic representation of the agricultural landscape through parameters such as a monthly representation of soil surface properties. Our aim was to identify most significant parameters driving the model and to highlight potential particular/singular behaviours of parameter combinations and relationships. The approach was to use local sensitivity analysis, also termed 'one-factor-at-time' (OAT) which consists of a deterministic, derivative method, inquiring the local response O to a particular input factor Pi at a specified point P0 within the full input parameter space of the model expressed as: ?O/?P = (O2-O1) / (P2-P1) The local sensitivity represents the partial derivatives of O with respect to Pi at the point P0. In the SA procedure the topographical entity is represented by a virtual hillslope on which soil loss and sensitivity are calculated. Virtual hillslope is inspired from the virtual catchment framework proposed by Cheviron at al. (2011): a fixed topology consisting of a 3X3 square pixel structure having 150 m length allowing to test different spatial configurations of the properties within the hillslope. To test the model we identified different parameters. A three-category (P,R,p) sensitivity analysis procedure was therefore found possible and appropriate to control the effects of hydrological factors (P,R) and soil-terrain parameters (p). All the analysis were done with the use of the integration of the ArcGis software structure, on which the LandSoil model is based, and the PEST model (Doherty, 2004). PESTR is an iterative, non-linear parameter analysis software platform based on the Gauss-Marquardt-Levenberg algorithm (Marquardt, 1963). The results show the relevance of the rainfall amount in simulation and some interesting interactions between parameters such soil roughness - soil crusting and soil cover.
Ciampalini, Rossano; Follain, Stķphane; Cheviron, Bruno; Le Bissonnais, Yves; Couturier, Alain; Walter, Christian
Soil water nitrate and ammonium dynamics under a sewage effluent irrigated eucalypt plantation.
Managed forests and plantations are appropriate ecosystems for land-based treatment of effluent, but concerns remain regarding nutrient contamination of ground- and surface waters. Monthly NO3-N and NH4-N concentrations in soil water, accumulated soil N, and gross ammonification and nitrification rates were measured in the second year of a second rotation of an effluent irrigated Eucalyptus globulus plantation in southern Western Australia to investigate the separate and interactive effects of drip and sprinkler irrigation, effluent and water irrigation, irrigation rate, and harvest residues retention. Nitrate concentrations of soil water were greater under effluent irrigation than water irrigation but remained <15 mg L(-1) when irrigated at the normal rate (1.5-2.0 mm d(-1)), and there was little evidence of downward movement. In contrast, NH4-N concentrations of soil water at 30 and 100 cm were generally greater under effluent irrigation than water irrigation when irrigated at the normal rate because of direct effluent NH4-N input and indirect ammonification of soil organic N. Drip irrigation of effluent approximately doubled peak NO3-N and NH4-N concentrations in soil water. Harvest residue retention reduced concentrations of soil water NO3-N at 30 cm during active sprinkler irrigation, but after 1 yr of irrigation there was no significant difference in the amount of N stored in the soil system, although harvest residue retention did enhance the "nitrate flush" in the following spring. Gross mineralization rates without irrigation increased with harvest residue retention and further increased with water irrigation. Irrigation with effluent further increased gross nitrification to 3.1 mg N kg(-1) d(-1) when harvest residues were retained but had no effect on gross ammonification, which suggested the importance of heterotrophic nitrification. The downward movement of N under effluent irrigation was dominated by NH4-N rather than NO3-N. Improving the capacity of forest soils to store and transform N inputs through organic matter management must consider the dynamic equilibrium between N input, uptake, and immobilization according to soil C status, and the effect changing microbial processes and environmental conditions can have on this equilibrium. PMID:17965391
Livesley, S J; Adams, M A; Grierson, P F
Water repellency in highly managed soils and turfgrass - How our understanding has changed in the past 20 years.
NASA Astrophysics Data System (ADS)
Over the past 20 years, a major shift has occurred in how turfgrass managers deal with soil water repellency. Initially, water management strategies focused solely on remediating localized dry spots, the visible effects of hydrophobic soils. Nearly a decade ago at this conference, a group of turfgrass scientists participated in this session on soil water repellency interacting with a broad group of soil physicists setting in motion research, collaborations and discoveries that have resulted in not only a better understanding of the implications of this phenomenon on soil hydraulic properties and plant productivity, but also, development of new strategies, particularly surfactants, to improve water capture, reduce preferential flow, increase irrigation and water use efficiency, improve performance of soil directed pesticides, reduce leaching of nitrogen, increase mineralization of organically bound nitrogen, and enhance plant tolerance to abiotic stress. It also resulted in research utilizing soil moisture measurement tools, specifically, TDR and capacitance probes, which were introduced to and accepted by soil and crop scientists working in amenity turfgrass. Within the past five years, these technologies and strategies for their effective utilization have transitioned from the research community to become accepted by turfgrass managers globally. It is the objective of this presentation to illustrate key discoveries, implications to improved water and resource utilization, and the resulting acceptance of them as new, more sustainable soil management practices.
Kostka, Stan; McMillan, Mica; Oostindie, Klaas; Dekker, Louis; Cisar, John; Leinauer, Bernd; Fidanza, Michael; Bigelow, Cale; Ritsema, Coen
Interaction of water with epoxy
The chemistries of reactants, plasticizers, solvents and additives in an epoxy paint are discussed. Polyamide additives may play an important role in the absorption of molecular iodine by epoxy paints. It is recommended that the unsaturation of the polyamide additive in the epoxy cure be determined. Experimental studies of water absorption by epoxy resins are discussed. These studies show that
Dana Auburn
Partitioning of Evapotranspiration Into Soil Evaporation and Plant Transpiration Using Isotopes of Water in Controlled Conditions
NASA Astrophysics Data System (ADS)
Rainfall recycling by evapotranspiration from continental surfaces is certainly the most unknown component of the global water cycle. This is due to the large variability of rainfall as well as the heterogeneity of these continental surfaces, both in time and space. Traditional measuring methods such as sap flow, micro lysimeter, water and energy balance estimation (Bowen ratio, eddy correlation) have been used since the 70s for a monitoring of real evapotranspiration fluxes over crops and others plant covers. A complementary method consists in using isotopic biogeochemistry. When making specific hypothesis, it is possible to identify and quantify the different sources of the atmospheric water vapour (vegetation and soil at different scales). Analysis of the heavy stable isotopic ratios of water in both liquid and vapour phases: 18O and 2H can allow determining the history of the water in the soil since the last rainfall event (infiltration, re-evaporation) or the root extraction depths. Field campaigns measurements (plants and soils), interpreted using the Keeling Plot method allowed some progress in the partition between evaporation and transpiration understanding. But the experimental design is not sufficient to mechanistically describe the water processes involved. The study of all the interactions is difficult due to the large number of controlling variables describing climate, vegetation and soil characteristics. A monolith experiment (including soil and growing plant) was carried out in a reactor called RUBIC (Reactor Used for Continental Isotopic Biogeochemistry, Bariac et al., Geochim. Cosmochim. Acta., 1991). Controlled conditions allowed a monitoring and regulation of climatic parameters (net radiation, air temperature, vapour pressure deficit, CO2 partial pressure, and wind speed). It was also necessary to fix soil (structure, texture, and water content) and vegetation (specie and seeding density) parameters. The collected data allow us to improve our understanding of the partition of evapotranspiration into soil evaporation and plant transpiration and to assess the hypothesis (often made in isotopic biochemistry) of a stationary state reached in the two reservoirs (soil and plant). These data also allow the evaluation of the hypothesis included in a transfer module of heavy stable isotopes of water within the bare soil and the plant (Braud et al., Journ. of Hydrol., 2005). The latter is coupled to a SVAT model (Soil-Plant-Atmosphere Transfer) called SiSPAT (Simple Soil Plant Atmosphere Transfer model, Braud et al., Journ. of Hydrol., 1995) and was extended to take into account isotopes transfer within the vegetation (root extraction and transpiration). The experimental design of RUBIC as well as the first modelling results will be presented.
Rothfuss, Y.; Bariac, T.; Braud, I.; Biron, P.; Richard, P.; Canale, L.; Durand, J.; Gaudet, J.
Mechanical impedance of soil crusts and water content in loamy soils
NASA Astrophysics Data System (ADS)
Soil crust development affects soil water dynamics and soil aeration. Soil crusts act as mechanical barriers to fluid flow and, as their mechanical impedance increases with drying, they also become obstacles to seedling emergence. As a consequence, the emergence of seedling cohorts (sensitive seeds) might be reduced. However, this may be of interest to be used as an effective system of weed control. Soil crusting is determined by several factors: soil texture, rain intensity, sedimentation processes, etc. There are different ways to characterize the crusts. One of them is to measure their mechanical impedance (MI), which is linked to their moisture level. In this study, we measured the evolution of the mechanical impedance of crusts formed by three loamy soil types (clay loam, loam and sandy clay loam, USDA) with different soil water contents. The aim of this communication was to establish a mathematical relationship between the crust water content and its MI. A saturated soil paste was prepared and placed in PVC cylinders (50 mm diameter and 10 mm height) arranged on a plastic tray. Previously the plastic tray was sprayed with a hydrophobic liquid to prevent the adherence of samples. The samples on the plastic tray were left to air-dry under laboratory conditions until their IM was measured. To measure IM, a food texture analyzer was used. The equipment incorporates a mobile arm, a load cell to apply force and a probe. The arm moves down vertically at a constant rate and the cylindrical steel probe (4 mm diameter) penetrates the soil sample vertically at a constant rate. The equipment is provided with software to store data (time, vertical distance and force values) at a rate of up to 500 points per second. Water content in crust soil samples was determined as the loss of weight after oven-drying (105░C). From the results, an exponential regression between MI and the water content was obtained (determination coefficient very close to 1). This methodology allows the prediction of the potential mechanical behaviour of soil crusts generated during soil drying, from initial saturated soil conditions (e.g. waterlogging conditions).
Josa March, Ramon; Verd·, Antoni M. C.; Mas, Maria Teresa
Water Drop/Bow Shock Interactions.
National Technical Information Service (NTIS)
The interaction of water drops of diameters in the range of 20 to 200 micrometers with reentry vehicle bow shocks was investigated with a microscope/Q-spoiled laser camera system. A single stream of water drops was generated on the trajectory of a Mach 12...
A. K. Hopkins E. S. Grood H. R. Taylor J. P. Barber
Effect of disturbed soil thickness on soil water use and movement under perennial grass
Soil water storage and use were measured in each of three growing seasons under crested wheatgrass (Agrophyron desertorum) grown on 0.25-, 0.5-, 0.75-, and 1.0-m thicknesses of disturbed soil. Soil profiles were constructed from Haploboroll topsoil (0.2 m for all treatments), placed over varying thicknesses of subsoil (B and C horizon materials), which in turn was placed over sodic (Sodium adsorption ratio = 30) drag-line spoil at a semiarid, steppe-land site in western North Dakota. Forage yield was 2- to 3.5-fold greater on 1.0 m soil thickness than on 0.25 m. Both total soil water potentials and root weight densities were similar in minespoil and in subsoil at the same profile depths. Root water uptake was much less from the minespoil (mean saturated hydraulic conductivity (HC) = 1 x 10 T cm/d) than from subsoil (mean HC = 0.2 cm/d). Low HC per se appeared to be the dominant factor limiting sodic minespoil as a plant growth medium because low HC resulted in less use of stored soil water from minespoil compared to subsoil. Depletion from a 120-cm profile was 0.2, 3.3, 7.9 and 9.8 cm for 0.25-, 0.50-, 0.75- and 1.0-m soil thickness, respectively. Relative differences in evapotranspiration (ET) between the 0.25-m and 1.0-m soil thickness treatments were much less than yield differences, reflecting progressively reduced water use efficiency with less soil thickness.
Merrill, S.D.; Smith, S.J.; Power, J.F.
Lithium\\/water interactions: Experiments and analysis
The interaction of molten-lithium droplets with water is studied experimentally. In one set of experiments, droplets of [approximately]10- to 15-mm diameter are injected into a vessel filled with water. The reaction is filmed, and pressure measurements are made. The initial metal and water temperatures range from 200 to 500[degrees]C and 20 to 70[degrees]C, respectively. It is found that when reactant
S. Lomperski; M. L. Corradini
Effect of Ionic Soil Stabilizers on Soil-Water Characteristic of Special Clay
NASA Astrophysics Data System (ADS)
The engineering properties of special clay are conventionally improved through the use of chemical additive such as ionic soil stabilizer (ISS). Such special clays are often referred to as stabilized or treated clays. The soil-water characteristic curves (SWCC) of special clays from Henan province and Hubei province were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-500 kPa. The SWCC results are used to interpret the special clays behavior due to stabilizer treatment. In addition, relationships were developed between the basic clay and stabilized properties such as specific surface area and pore size distribution. The analysis showed that specific surface area decreases, cumulative pore volume and average pore size diameter decrease, dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. The research data and interpretation analysis presented here can be extended to understand the water film change behaviors influencing the mechanical and physical properties of stabilized special clay soils. KEY WORDS: ionic soil stabilizer, special clay, pore size diameter, specific surface area, soil water characteristic curve, water film
Cui, D.; Xiang, W.
Priming and substrate quality interactions in soil organic matter models
NASA Astrophysics Data System (ADS)
Interactions between different qualities of soil organic matter (SOM) affecting their turnover are rarely represented in models. In this study, we propose three mathematical strategies at different levels of abstraction to represent those interactions. By implementing these strategies into the Introductory Carbon Balance Model (ICBM) and applying them to several scenarios of litter input, we show that the different levels of abstraction are applicable at different timescales. We present a simple one-parameter equation of substrate limitation that can straightforwardly be implemented into other models of SOM dynamics at decadal timescale. The study demonstrates how substrate quality interactions can explain patterns of priming effects, accelerate turnover in FACE experiments, and the slowdown of decomposition in long-term bare fallow experiments as an effect of energy limitation of microbial biomass. The mechanisms of those interactions need to be further scrutinized empirically for a more complete understanding. Overall, substrate quality interactions contribute to both understanding and quantitatively modelling SOM dynamics.
Wutzler, T.; Reichstein, M.
Arsenic transport in irrigation water across rice-field soils in Bangladesh.
Experiments were conducted to analyze processes impacting arsenic transport in irrigation water flowing over bare rice-field soils in Bangladesh. Dissolved concentrations of As, Fe, P, and Si varied over space and time, according to whether irrigation water was flowing or static. Initially, under flowing conditions, arsenic concentrations in irrigation water were below well-water levels and showed little spatial variability across fields. As flowing-water levels rose, arsenic concentrations were elevated at field inlets and decreased with distance across fields, but under subsequent static conditions, concentrations dropped and were less variable. Laboratory experiments revealed that over half of the initial well-water arsenic was removed from solution by oxidative interaction with other water-column components. Introduction of small quantities of soil further decreased arsenic concentrations in solution. At higher soil-solution ratios, however, soil contributed arsenic to solution via abiotic and biotic desorption. Collectively, these results suggest careful design is required for land-based arsenic-removal schemes. PMID:23688733
Polizzotto, Matthew L; Lineberger, Ethan M; Matteson, Audrey R; Neumann, Rebecca B; Badruzzaman, A Borhan M; Ashraf Ali, M
Water-module interaction studies
NASA Technical Reports Server (NTRS)
Mechanisms by which moisture enters photovoltaic modules and techniques for reducing such interactions are reported. Results from a study of the effectiveness of various module sealants are given. Techniques for measuring the rate and quantity of moisture ingress are discussed. It is shown that scribe lines and porous frit bridging conductors provide preferential paths for moisture ingress and that moisture diffusion by surface/interfacial paths is considerably more rapid than diffusion by bulk paths, which implies that thin-film substrate and supersubstrate modules are much more vulnerable to moist environments than are bulk-encapsulated crystalline-silicon modules. Design approaches that reduce moisture entry are discussed.
Mon, G.; Wen, L.; Ross, R., Jr.
Water-module interaction studies
NASA Astrophysics Data System (ADS)
Mechanisms by which moisture enters photovoltaic modules and techniques for reducing such interactions are reported. Results from a study of the effectiveness of various module sealants are given. Techniques for measuring the rate and quantity of moisture ingress are discussed. It is shown that scribe lines and porous frit bridging conductors provide preferential paths for moisture ingress and that moisture diffusion by surface/interfacial paths is considerably more rapid than diffusion by bulk paths, which implies that thin-film substrate and supersubstrate modules are much more vulnerable to moist environments than are bulk-encapsulated crystalline-silicon modules. Design approaches that reduce moisture entry are discussed.
Mon, G.; Wen, L.; Ross, R., Jr.
Soil and Water Management in West Africa: An Economic Analysis.
National Technical Information Service (NTIS)
Water conservation is a necessary component in efforts to raise the productivity of traditional rain-fed farming in West Africa. Soil-water balance relationships and a whole-farm modeling approach are used to estimate benefits of conservation on a typical...
J. C. Day
Recent discoveries and technological innovations in the field of soil and water conservation can be traced to the works of our predecessors. In this paper, conservation is defined broadly, to include the quality of water lower in watersheds, and is discussed according to contaminants. Within-field source prevention and reduction practices as well as off-site mitigation practices are described. Examples concerning
E. John Sadler; Kenneth A. Sudduth; Newell R. Kitchen; Robert N. Lerch; Robert J. Kremer; Earl D. Vories
Water Intake by Soil, Experiments for High School Students.
ERIC Educational Resources Information Center
Presented are a variety of surface run-off experiments for high school students. The experiments are analogies to basic concepts about water intake, as related to water delivery, soil properties and management, floods, and conservation measures. The materials needed to perform the experiments are easily obtainable. The experiments are followed byģ
Earthworm effects on movement of water and solutes in soil
The objectives of this study were to determine and model the effects of earthworms on water and solute movement in soil. Microrelief and rainfall effects on water and solute movement were determined in packed buckets inoculated with earthworms (Aporrectodea tuberculata). A solution of Br[sup [minus
Trojan, M.D.
Soil water content and temperature induced spatial structure of heterotrophic respiration at field scale
Heterotrophic soil respiration is known to be highly variable in space and time. The spatial structure of this carbon dioxide flux strongly depends on the spatial pattern of soil water content and energy fluxes at the boundary layer between soil and atmosphere. The goal of this study was to determine the spatial variability of soil respiration, soil water content and
M. Herbst; N. Prolingheuer; A. Graf; J. A. Huisman; L. Weihermueller; J. Vanderborght; H. Vereecken
Characteristics of soil moisture in permafrost observed in East Siberian taiga with stable isotopes of water
Soil moisture and its isotopic composition were observed at Spasskaya Pad experimental forest near Yakutsk, Russia, during summer in 1998, 1999, and 2000. The amount of soil water (plus ice) was estimated from volumetric soil water content obtained with time domain reflectometry. Soil moisture and its 18O showed large interannual variation depending on the amount of summer rainfall. The soil
A. Sugimoto; D. Naito; N. Yanagisawa; K. Ichiyanagi; N. Kurita; J. Kubota; T. Kotake; T. Ohata; T. C. Maximov; A. N. Fedorov
Modelling interactions between soil evolution and diffusive surface processes
NASA Astrophysics Data System (ADS)
Bioturbation, combined with settlement under gravity, generates profiles of bulk density, porosity and hydraulic conductivity (Ksat). Rates of bioturbation are linked to rates of diffusive downslope sediment transport (creep) and rates can be compared via the increase in OSL ages of soil aggregate grains with depth. Some primary porosity is also produced by weathering of rock to saprolite, often with little reduction in bulk density but some dilation of joints. Downward percolation of rain water near the surface is controlled by the diffusion-induced decrease in porosity and Ksat, driving lateral subsurface flow in the zone of fluctuating water table, and leaving progressively less water for downward percolation. As the depth to the weathering front is varied, progressively less water is therefore available for weathering, producing the observed decrease in weathering rate with increasing soil depth. These processes are modelled by repeatedly applying a stochastic realisation of daily rainfalls for an area until the annual hydrological cycle stabilises, providing the average partition of rainfall into its components of evapotranspiration, lateral flow and downward percolation, with depth in the soil. The average hydrology is then applied to drive evolution of the weathering profile over longer time spans.
Kirkby, Mike; Johnson, Michelle; Gloor, Emanual
Measurements of soil temperature for monitoring of the soil water behavior in an embankment slope during periodic rainfall
NASA Astrophysics Data System (ADS)
One of the most common causes of slope disaster (e.g. landslide, slope failure and debris flow) is heavy rainfall. Distributions of soil moisture and soil suction stress are changed by rain water infiltration. Monitoring of soil water behavior is crucial for prediction of the slope disaster. This study focuses on soil temperatures of a slope as a detector for monitoring soil water behavior. Soil temperature is varied by soil water condition, this is, infiltrating water transports thermal energy downward and thermal property of soil is shifted by containing of soil water. The purpose of this study is to detect the changes in soil water behavior caused by infiltration of rainfalls using measurement of soil temperature. For this purpose, we had carried out the measurements of soil temperature during various rainfalls (Yoshioka et al., 2013). In addition, we measured soil temperature and soil water content at several depths in a slope of an experimental embankment during various intensities of periodic and/or continuous rainfalls. In this presentation, we represent the details of the experiments and the results. Experiments were performed using the experimental embankment at NIED in Japan, which is about 7.3 meters tall and 27 meters wide. The embankment is located in a large-scale rainfall simulator. This facility is about 73 meters long, 48 meters wide and 20 meters tall. We measured soil temperature and volumetric water contents in the slope of the embankment, meteorological condition and rain water temperature. The rainfall intensities were 30, 60, 90 and 120 mm/h. The artificial rainfalls were carried out 10th, 17th, 24th, 31st, May and 10th, 11th, 12th June, 2013. As the results, soil temperature at many points in all experimental days rose caused by rainfalls, but the temperature at some points didn't change. We had two forms of soil temperature changes; one was a steep rise and the other was a gradual rise. In the case of periodic rainfall, soil temperature at some points changed in each rainfall. The soil temperature rose greater in the rainfall with higher intensity than that in the rainfall with lower intensity. The soil temperature change has similar tendency as the volumetric water content change. Both soil temperature and volumetric water contents rose after the start of rainfalls and decreased gradually after the finish of them. These results indicated that the soil temperature change reflected the soil water behavior even when periodic rainfall occurred. Reference: Yoshioka et al. (2013) Measurement of soil temperature in the slope of an embankment using a large-scale rainfall simulator, Proceedings of the 11th SEGJ International Symposium (submitted)
Yoshioka, M.; Takakura, S.; Ishizawa, T.; Sakai, N.
Groundwater Surface Water Interaction Effects on Pesticide Persistence and Transformation Pathways
NASA Astrophysics Data System (ADS)
Historical DDT use at Point Pelee National Park (PPNP) has left a legacy of contamination found in the flora, fauna, soils, and groundwater. The transformation pathway and the rate of transformation of DDT to either DDE or DDD, and subsequent metabolites depends on many environmental factors including soil texture, soil moisture, temperature, organic carbon content, flooding, and microbial activity, (Guenzi and Beard 1968, 1976; Spencer et al. 1996; Aigner et al. 1998). Under aerobic conditions the transformation of DDT to DDE is the preferred pathway, whereas under anaerobic conditions, DDT to DDD is the preferred pathway. Also, the transformation of DDT to DDD under anaerobic conditions is faster than that for DDT to DDE under aerobic conditions. Given that one of the primary factors effecting the redox conditions of a soil is soil wetness, and that flooded soils tend to become anaerobic and reducing, it was hypothesized that there may be a relation between the dynamic nature of groundwater-surface water interactions at PPNP and the concentrations and proportions of DDT, DDE, and DDD. The soils are texturally sand and are mostly of the Brunisolic Soil Order (Inceptisols) with the Regosolic Soil Order (Entisols) on the sand dunes and the Organic Soil Order (Histosols) along the margins of the Marsh. The location of the groundwater-surface water interface coinciding with historic water levels within Lake Erie and the marsh has played a significant role.
Smith, J. E.; Crowe, A. S.; Marenco, N.
Effect of Plant-derived Hydrophobic Compounds on Soil Water Repellency in Dutch Sandy Soils
NASA Astrophysics Data System (ADS)
Soil water repellency or hydrophobicity is a common and important soil property, which may diminish plant growth and promotes soil erosion leading to environmentally undesired situations. Hydrophobic organic compounds in the soil are derived from vegetation (leaves, roots, mosses) or microorganisms (fungi, bacteria), and these compounds induce soil water repellency (SWR) and can be called SWR-biomarkers. As common hydrophobic constituents of organic matter, plant lipids are mainly from wax layers of leaves and roots, whereas cutins and suberins as aliphatic biopolyesters occur in leaves and roots, respectively. Their unique compositions in soil can indicate the original vegetation sources. To investigate the individual or combined effects of the hydrophobic compounds on SWR and their possible associations with each other, we conducted experiments to analyse the organic composition of Dutch coastal dune sandy soils in relation to SWR. DCM/MeOH solvent is used to remove solvent soluble lipids. BF3-methanol is utilized to depolymerize cutins and suberins from isopropanol/NH3 extractable organic matter. Total organic carbon (TOC) has a positive linear relation with SWR only for those soils containing low TOC (
Mao, Jiefei; Dekker, Stefan C.; Nierop, Klaas G. J.
Interactions Among Grassland Plant Species, Microbial Communities, and Soil Processes
NASA Astrophysics Data System (ADS)
Plant-microbial interactions are thought to be an important determinant of ecosystem processes, yet we do not know whether impacts of plant species on soil microbial community composition translate to impacts on function. We established field plots in a California annual grassland of five plant monocultures for two years to determine the effects of different plant species on the composition of the bulk soil microbial community and selected soil processes. Plant species were associated with distinct ecosystem process rates such as net nitrogen mineralization, nitrification, decomposition and soil respiration. Bacterial community substrate utilization profiles differed among different plant species and were related to labile soil C. DNA-based fingerprints of bacterial, ammonia oxidizer, and fungal communities did not generally differ in soils planted to different species; however, these microbial community profiles did strongly correlate to rates of decomposition. Terminal Restriction Fragment Length Polymorphism (TRFLP) analysis of soil microbial communities showed that the lupine community was distinct from the other four plant-associated communities. Phospholipid fatty acid (PLFA) patterns also failed to distinguish differences in the overall microbial communities associated with the five different moncultures. Interestingly, PLFA biomarker 16:1w5, indicative of AM fungi, differed among plant species treatments. This PLFA biomarker and bacterial TRFLP patterns were related to decomposition rates of a common litter. In summary, large functional differences were found between field plots with different plant species and the composition of the microbial communities was closely related to some of the functions assessed, independent of plant species. Only small plant-induced changes in microbial community composition were detected, yet apparently these changes had significant impact on function. Our analyses were not specifically targeted to microsites with high activity (such as rhizosphere soil) and our DNA and PLFA-based analyses included a potentially huge "dormant" community of soil microorganisms. While our analyses could detect little impact of plant species on overall microbial community profiles, a smaller active-fraction of the soil microbial community may have been more significantly affected.
Eviner, V.; Waldrop, M.; Schwartz, E.; Pett-Ridge, J.; Firestone, M.
Visualizing Clogging up of Soil Pores in the Tropical Degraded Soils and Their Impact on Green Water Productivity
NASA Astrophysics Data System (ADS)
Abstract Restrictive soil layers commonly known as hardpans restrict water and airflow in the soil profile and impede plant root growth below the plow depth. Preventing hardpans to form or ameliorate existing hardpans will allow plants root more deeply, increase water infiltration and reduce runoff, all resulting in greater amounts of water available for the crop (i.e. green water). However, there has been a lack of research on understanding the influence of transported disturbed soil particles (colloids) from the surface to the subsurface to form restrictive soil layers, which is a common occurrence in degraded soils. In this study we investigated the effect of disturbed soil particles on clogging up of soil pores to form hardpans. Unsaturated sand column experiments were performed by applying 0.04 g/ml soil water solution in two sand textures. For each experiment, soil water solution infiltration process was visualized using a bright field microscope and soil particles remained in the sand column was quantified collecting and measuring leachate at the end of the experiment in the soil and water lab of Cornell University. Preliminary results show that accumulation of significant amount of soil particles occur in between sand particles and at air water interfaces, indicating the clogging of soil pores occurs as a result of disturbed fine soil particles transported from the soil surface to the subsurface. Key Words: Soil pore clogging; Hardpans; Green water productivity Visualization of sand column experiment showing the sand column at the start of the experiment (left) and two hours after the second application in that soil particles were accumulated at the air water interfaces(right).
Tebebu, T.; Baver, C.; Stoof, C.; Steenhuis, T. S.
Zinc movement in sewage-sludge-treated soils as influenced by soil properties, irrigation water quality, and soil moisture level
A soil column study was conducted to assess the movement of Zn in sewage-sludge-amended soils. Varables investigated were soil properties, irrigation water quality, and soil moisture level. Bulk samples of the surface layer of six soil series were packed into columns, 10.2 cm in diameter and 110 cm in length. An anaerobically digested municipal sewage sludge was incorporated into the top 20 cm of each column at a rate of 300 mg ha-1. The columns were maintained at moisture levels of saturation and unsaturation and were leached with two waters of different quality. At the termination of leaching, the columns were cut open and the soil was sectioned and analyzed. Zinc movement was evaluated by mass balance accounting and correlation and regression analysis. Zinc movement in the unsaturated columns ranged from 3 to 30 cm, with a mean of 10 cm. The difference in irrigation water quality did not have an effect on Zn movement. Most of the Zn applied to the unsaturated columns remained in the sludge-amended soil layer (96.1 to 99.6%, with a mean of 98.1%). The major portion of Zn leached from the sludge-amended soil layer accumulated in the 0- to 3-cm depth (35.7 to 100%, with a mean of 73.6%). The mean final soil pH values decreased in the order: saturated columns = sludge-amended soil layer > untreated soils > unsaturated columns. Total Zn leached from the sludge-amended soil layer was correlated negatively at P = 0.001 with final pH (r = -0.85). Depth of Zn movement was correlated negatively at P = 0.001 with final pH (r = -0.91). Multiple linear regression analysis showed that the final pH accounted for 72% of the variation in the total amounts of Zn leached from the sludge-amended soil layer of the unsaturated columns and accounted for 82% of the variation in the depth of Zn movement among the unsaturated columns. A significant correlation was not found between Zn and organic carbon in soil solutions, but a negative correlation significant at P = 0.001 was found between pH and Zn (r = -0.61).
Welch, J. E.; Lund, L. J.
Collimated neutron probe for soil water content measurements
A collimated neutron probe was designed to enable mesurements in specific directions from the access tube. To determine the size and shape of soil volume affecting the neutron counts, experiments were conducted to evaluate: 1) the vertical distance of soil above and below the probe that influences neutron counts; 2) the horizontal distance away from the probe into the soil that influences neutron counts; 3) the angle of soil viewed by the probe from the collimator; and 4) the three-dimensional thermal-neutron density field. The vertical distance was ~0.5m, the horizontal distance was ~0.2m, and the angle of soil viewed by the probe from the collimator was ~120??. Thermal neutrons detected from distances or angles larger than these values influence the determination of relative water content by 5% or less. -from Authors
Klenke, J. M.; Flint, A. L.
Using cokriging, estimates and estimation variances of the gravimetric moisture content (GMC) were made using one and two additional random functions: the bare soil surface temperature and the percent sand content. Various measures of the differences and quality of the estimates ...
Soil electrical conductivity as a function of soil water content and implications for soil mapping
Apparent soil electrical conductivity (ECa) has shown promise as a soil survey tool in the Midwestern United States, with a share of this interest coming from the precision agriculture community. To fully utilize the potential of ECa to map soils, a better understanding of temporal changes in ECa is needed. Therefore, this study was undertaken to compare temporal changes in
Eric C. Brevik; Thomas E. Fenton; Andreas Lazari
Water distribution at the root-soil interface: is there more water next to roots?
NASA Astrophysics Data System (ADS)
Plants are big water movers and have a significant impact on soil water dynamics as well as on the global water cycle. Despite the relevance of root water uptake in terrestrial ecology, the movement of water from soil to roots still presents important open questions, e.g the following two. Which are the properties of the soil near the roots? And what effect do these properties have on soil plant water relations? Most models are based on brute-force spatial averaging of soil properties and assume that the bulk soil has the same properties as the rhizosphere. However, there is evidence in the literature that the rhizosphere has specific properties that may affect water and nutrient uptake (Young 1995, Gregory 2007). In order to investigate the rhizosphere hydraulic properties and their effect on soil plant water relations, we used neutron radiography and neutron tomography to image the water content distribution in soils during plant transpiration. Rectangular (quasi-2D) and cylindrical containers were filled with sandy soil and planted with lupins (Lupinus albus). Three weeks after planting, the samples were equilibrated at water potentials of -10 and 30 hPa and have been imaged for 5 days at intervals of 6 hours. At day 5 the samples were irrigated again via capillary rise and the water distribution was monitored for 4 more days. During the first day of the drying period, regions of water depletion formed around the central part of the tap root where first order laterals were present. As the soil dried up, the picture changed: instead of less water around the roots, as commonly supposed by models, we observed that more water was present around the lateral roots. Interestingly, these regions during drying were retaining high water content, but after irrigation remained markedly drier than the bulk soil. Our hypothesis is that high water content near roots during drying and lower water content during rewetting are explained by the presence of bio-polymers exuded by roots forming a hydrogel that consists of up to 99% water at very negative water potentials (Read et al. 1999). Thanks to its high water holding capacity, this hydrogel maintains a continuous hydraulic pathway across soil and roots for an extended period of time during drying. During rewetting it adversely affects water redistribution, like a storage that needs time to fill up again. These data show for the first time in situ the potential role of mucilage in controlling water dynamics in the rhizosphere and consequences for plant water extraction. Gregory P J, Roots, rhizosphere and soil: the route to a better understanding of soil science? European Journal of Soil Science, 57: 2-12, 2006. Read D P, Gregory P J, and Bell A E. Physical properties of axenic maize root mucilage. Plant and Soil, 211: 87-91, 1999. Young I M. Variation in moisture contents between bulk soil and the rhizosheath of wheat. New Phytologist, 130: 135-139, 1995.
Carminati, A.; Moradi, A.; Oswald, S.; Vetterlein, D.; Weller, U.; Vogel, H.-J.
Spatio-temporal variability of soil water content on the local scale in a Mediterranean mountain area (Vallcebre, North Eastern Spain). How different spatio-temporal scales reflect mean soil water content
NASA Astrophysics Data System (ADS)
As a result of complex human-land interactions and topographic variability, many Mediterranean mountain catchments are covered by agricultural terraces that have locally modified the soil water content dynamic. Understanding these local-scale dynamics helps us grasp better how hydrology behaves on the catchment scale. Thus, this study examined soil water content variability in the upper 30 cm of the soil on a Mediterranean abandoned terrace in north-east Spain. Using a dataset of high spatial (regular grid of 128 automatic TDR probes at 2.5 m intervals) and temporal (20-min time step) resolution, gathered throughout a 84-day period, the spatio-temporal variability of soil water content at the local scale and the way that different spatio-temporal scales reflect the mean soil water content were investigated. Soil water content spatial variability and its relation to wetness conditions were examined, along with the spatial structuring of the soil water content within the terrace. Then, the ability of single probes and of different combinations of spatial measurements (transects and grids) to provide a good estimate of mean soil water content on the terrace scale was explored by means of temporal stability analyses. Finally, the effect of monitoring frequency on the magnitude of detectable daily soil water content variations was studied. Results showed that soil water content spatial variability followed a bimodal pattern of increasing absolute variability with increasing soil water content. In addition, a linear trend of decreasing soil water content as the distance from the inner part of the terrace increased was identified. Once this trend was subtracted, resulting semi-variograms suggested that the spatial resolution examined was too high to appreciate spatial structuring in the data. Thus, the spatial pattern should be considered as random. Of all the spatial designs tested, the 10 ū 10 m mesh grid (9 probes) was considered the most suitable option for a good, time-stable estimate of mean soil water content, as no improvement was obtained with the 5 ū 5 m mesh grid (30 probes). Finally, the results of temporal aggregation showed that decreasing the monitoring frequency down to 8 h during wetting-up periods and to 1 day during drying-down ones did not result in a loss of information on daily soil water content variations.
Molina, Antonio J.; Latron, Jķr¶me; Rubio, Carles M.; Gallart, Francesc; Llorens, Pilar
Plant response to the soil environment: An analytical model integrating yield, water, soil type, and salinity
An accessible solution capable of reliably predicting plant-environmental interrelationships for variable species, climates, soils, and management options is a necessary tool for creating sustainable agriculture and environmental preservation. A mechanism-based analytical solution, the first of its kind that considers multiple environmental variables and their combined effects on plant response, was developed and tested. Water uptake by plants, water and salt
Uri Shani; Alon Ben-Gal; Effi Tripler; Lynn M. Dudley
Experiments and modeling of mobility and interaction of heavy metals in a natural soil
NASA Astrophysics Data System (ADS)
Health and environmental impacts of heavy metals are associated mostly with dissolved ions. Understanding of ion partitioning between solid and aqueous phases is therefore critical. We study the mobility and interaction of copper (Cu2+) and zinc (Zn2+) ions in laboratory-scale, natural soil columns. The experiments focus on the analysis of breakthrough curves obtained after simultaneous injection of an aqueous solution containing the two metal ions into a column packed with water-saturated soil. The soil columns are tested under aerobic and anaerobic conditions to assess the effect of redox conditions on metal mobility. The measurements show that the two metals compete for the available adsorption sites. The weaker ion (Zn2+) has lower affinity with the soil and is replaced by the stronger one (Cu2+) after a preliminary adsorption. We interpret this observed behavior by means of different models based on a set of coupled partial differential and algebraic equations, involving both aqueous and adsorbed species. Depending on the model considered, the relationship between aqueous and adsorbed ion concentrations is described by an equilibrium Gaines-Thomas formulation, a competitive Sheindorf-Rebhun-Sheintuch (SRS) isotherm, or a competitive Extended Langmuir isotherm. The system of governing equations is solved numerically and model parameters are calibrated against experimental measurements. Results show that the redox conditions can alter the capacity of the soil to retain cations migrating within the tested saturated natural soils. The Gaines-Thomas formulation best reproduces the observed behavior.
Sanchez-Vila, X.; Bianchi Janetti, E.; Dror, I.; Riva, M.; Guadagnini, A.; Berkowitz, B.
Importance of soil organic carbon on surface soil water content variability among agricultural fields
NASA Astrophysics Data System (ADS)
Improvements to the downscaling estimates of soil water content (SWC) from passive microwave retrievals require detailed knowledge of field scale influences on SWC variability. The Soil Moisture Active Passive Validation Experiment (SMAPVEX-12) field campaign provided SWC and physical properties from 50 cropland fields to assess the influence of soil organic carbon (SOC) on SOC variability in a range of SOC, SWC and soil textural class over a 6 week period. Field average SWC over the duration of the experiment was optimally predicted by combination of soil texture and SOC in all soil wetness conditions, although either %Sand or SOC separately also expressed 82% of variance in SWC over all fields covering three soil textural groups. Soil OC explained greater variance in SWC than texture in dry conditions, while texture predominated in moist conditions. The high correlation between SOC and SWC suggests soil OC may contribute to the initiatives to downscale SWC estimates from satellite to field scale where SWC data are sparse or inaccurate.
Manns, Hida R.; Berg, Aaron A.
Upscaled soil-water retention using van Genuchten's function
Soils are often layered at scales smaller than the block size used in numerical and conceptual models of variably saturated flow. Consequently, the small-scale variability in water content within each block must be homogenized (upscaled). Laboratory results have shown that a linear volume average (LVA) of water content at a uniform suction is a good approximation to measured water contents in heterogeneous cores. Here, we upscale water contents using van Genuchten's function for both the local and upscaled soil-water-retention characteristics. The van Genuchten (vG) function compares favorably with LVA results, laboratory experiments under hydrostatic conditions in 3-cm cores, and numerical simulations of large-scale gravity drainage. Our method yields upscaled vG parameter values by fitting the vG curve to the LVA of water contents at various suction values. In practice, it is more efficient to compute direct averages of the local vG parameter values. Nonlinear power averages quantify a feasible range of values for each upscaled vG shape parameter; upscaled values of N are consistently less than the harmonic means, reflecting broad pore-size distributions of the upscaled soils. The vG function is useful for modeling soil-water retention at large scales, and these results provide guidance for its application.
Green, T. R.; Constantz, J. E.; Freyberg, D. L.
Assessment of Interactions Between Stomatal Conductance, Evapotranspiration, Carbon and Irrigated Soil Salinity
Hydrological behavior and soil salinity are intricately linked in many agricultural environments. Fluxes of energy, water, and carbon dioxide are critical to the response of plants to soil salinity. A physically based plant water use model is developed to examine the problem of soil salinity as it relates to evapotranspiration and plant water uptake in an arid agricultural region. This
B. Runkle; X. Liang
Effects of organic compounds, water content and clay on the water repellency of a model sandy soil
Soil water repellency is related to organic matter and clay, and varies non-linearly with soil water content. The purpose of this study is to assess the combined effects of organic compounds, water content and clays on water repellency of a model sandy soil under wetting and drying processes. Hydrophobic stearic acid and hydrophilic glucomannan were used as the organic compounds,
D. A. L. Leelamanie; Jutaro Karube
Human interactions with ground-water
Ground-Water could be considered as an immense reservoir, from which only a certain amount of water can be withdrawn without affecting the quantity and quality of water. This amount is determined by the characteristics of the environment in which ground-water occurs and by the interactions of ground-water with precipitation, surface water, and people. It should be recognized that quantity and quality of ground-water are intimately related and should be considered accordingly. Quantity refers to usable water and water is usable for any specific purpose only so long as its quality has not deteriorated beyond acceptable limits. Thus an overall quantitative and qualitative management of ground water is inevitable, and its should also involve the uses of ground-water reservoirs for purposes other than water supply. The main objective of ground-water management is to ensure that ground-water resources will be available in appropriate time and in appropriate quantity and quality to meet the most important demands of our society. Traditional, and obvious uses of ground-water are the extraction of water for water supplies (domestic, municipal, agricultural, and industrial) and the natural discharge feeding lakes and maintaining base flow of streams. Not so obvious are the uses of ground-water reservoirs, the very framework within which ground-water occurs and moves, and in which other fluids or materials can be stored. In the last two decades, ground-water reservoirs have been intensively considered for many other purposes than water supplies. Diversified and very often conflicting uses need to be evaluated and dealt with in the most efficient way in order to determine the importance of each possible use, and to assign priorities of these uses. With rising competition for the use of ground-water reservoirs, we will also need to increase the potential for effective planning of ground-water development and protection. Man's development and use of ground-water necessarily modifies the natural conditions and the total natural system must be successfully blended with the unnatural stresses placed upon it. This can be accomplished by introducing new methods (such as ground-water zoning) in and by developing alternative strategies for ground-water management and protection. ?? 1983 D. Reidel Publishing Company.
Zaporozec, A.
Interactive effect of organic amendment and environmental factors on degradation of 1,3-dichloropropene and chloropicrin in soil.
Soil organic matter is an important factor affecting the fate of soil fumigants; therefore, the addition of organic amendments to surface soils could reduce fumigant emissions by accelerating fumigant degradation. Experiments were conducted to determine the degradation of fumigants [a mixture of cis- and trans-1,3-dichloropropene (1,3-D) and chloropicrin (CP), a similar composition as in Telone C35] in soils with organic amendment under a range of soil moisture, temperature, sterilization, and texture conditions. Degradation of the fumigants followed availability-adjusted first-order or pseudo-first-order kinetics with slower degradation of 1,3-D than CP. Increasing soil water content from 5 to 17.5% (w/w) slightly increased the degradation of 1,3-D, but not that of CP. Five different organic amendments at 5% (w/w) increased fumigant degradation 1.4-6.3-fold in this study. The degradation of both fumigants was accelerated with increasing amount of organic material (OM). Little interaction between soil moisture and OM was observed. Autoclave sterilization of soils did not reduce degradation of either fumigant; however, increasing the incubation temperature from 10 to 45 degrees C accelerated fumigant degradation 5-14 times. Soil texture did not affect 1,3-D degradation, but CP degraded more rapidly in finer-textured soil. These results suggest that OM type and rate and soil temperature are the most important factors affecting the degradation of 1,3-D and CP. PMID:19722521
Qin, Ruijun; Gao, Suduan; Ajwa, Husein; Hanson, Bradley D; Trout, Thomas J; Wang, Dong; Guo, Mingxin
Effect of the soil water content on Jatropha seedlings in a tropical climate
NASA Astrophysics Data System (ADS)
The purpose of this study was to evaluate growth, chlorophyll content, and photosynthesis in Jatropha at different levels of soil moisture. Plants were cultivated in containers and the treatments of the soil water content evaluated were: 0% (without watering), 20, 40, 60, and 80% soil water content. Plant height was statistically similar for all treatments, but the number of leaves differed significantly. Total dry matter and chlorophyll at 40, 60, and 80% soil water content were statistically similar, but different from 0 and 20% soil water content. Leaf area at 40, 60, and 80% soil water content was statistically different from 0 and 20% soil water content. The photosynthetic rate, transpiration and stomatal conductance at 60 and 80% soil water content were statistically similar but different from 0 and 20% soil water content. Water stress affected growth, chlorophyll content, photosynthetic rate, transpiration, and stomatal conductance.
Pķrez-Vßzquez, A.; Hernßndez-Salinas, G.; ┴vila-Resķndiz, C.; Valdķs-RodrĒguez, O. A.; Gallardo-L¾pez, F.; GarcĒa-Pķrez, E.; Ruiz-Rosado, O.
Solubilization and biodegradation of polycyclic aromatic hydrocarbon compounds in soil-water suspensions with surfactants
Hydrophobic organic compounds (HOCs) sorb strongly onto soil and sediment material, and the effectiveness of microbial treatment can be diminished by HOC phase partitioning and decreased substrate accessibility to microorganisms. Surfactant addition has been suggested as a technique for decreasing the interfacial tension and partitioning of the HOC with soil, and thereby increasing HOC mobility and bioavailability. However, this study indicates that nonionic surfactant solubilization of HOCs from soil may not be beneficial for the enhancement of soil bioremediation. The solubilization and microbial degradation of phenanthrene, a three-ring polycyclic aromatic hydrocarbon (PAH) compound, was examined in various soil-water systems with commercially-available surface-active agents. This was accomplished by a series of batch tests using radiolabeled techniques. The purpose of surfactant addition was to assess the effect of surfactant solubilization of PAHs on their biodegradation. For soil-water suspensions without surfactant approximately 50-60% of the phenanthrene was mineralized over the course of ten weeks. The addition of nonionic surface-active agents was observed not to be beneficial for microbial mineralization of phenanthrene in the soil-water systems, and for supra-CMC surfactant doses phenanthrene mineralization was completely inhibited for all the surfactants tested. Sub-CMC levels of surfactant in the soil-water systems generally did not have an inhibitory effect on phenanthrene mineralization, but neither did such doses serve to enhance the rate of degradation, which proceeded most rapidly in the absence of any surfactant. Companion tests suggest that the supra-CMC inhibitory effect is not a toxicity phenomenon, per se, of the surfactant or micellized PAH. An assessment of the results from the various experiments suggest that the inhibitory effect is probably related to a reversible physiological surfactant micelle-bacteria interaction.
Laha, S.
A dynamic soil water threshold for vegetation water stress derived from stomatal conductance models
In many terrestrial ecosystems, vegetation experiences limitation by different resources at different times. These resources include, among others, light, nutrients, and water. Frequently, however, leaf-level modeling frameworks that unite these limitations rely on empirical functions to scale stomatal conductance as a function of water stress. These functions use prescribed values of soil water content to mark the transition between water-stressed
Ryan E. Emanuel; Paolo D'Odorico; Howard E. Epstein
78 FR 56153 - National Environmental Policy Act: Categorical Exclusions for Soil and Water Restoration Activities
Federal Register 2010, 2011, 2012, 2013
...Act: Categorical Exclusions for Soil and Water Restoration Activities AGENCY: Forest...that restore lands negatively impacted by water control structures, disturbance events...potential environmental effects of soil and water restoration projects that are...
Some Sensitivity Analyses of an Hourly Soil-Plant Water Relations Model.
National Technical Information Service (NTIS)
Nineteen parameters representing landscape, plant, and soil characteristics were examined for their influence on midday plant water relations, daily fluxes and monthly water balance components predicted by a soil-plant-water relations model having hourly ...
R. J. Luxmoore J. L. Stolzy J. T. Holdeman
Soil Management Plan For The Potable Water System Upgrades Project
This plan describes and applies to the handling and management of soils excavated in support of the Y-12 Potable Water Systems Upgrades (PWSU) Project. The plan is specific to the PWSU Project and is intended as a working document that provides guidance consistent with the 'Soil Management Plan for the Oak Ridge Y-12 National Security Complex' (Y\\/SUB\\/92-28B99923C-Y05) and the 'Record
Developing joint probability distributions of soil water retention characteristics
A method is presented for developing probability density functions for parameters of soil moisture relationships of capillary head (h(Phi)) and hydraulic conductivity (K(Phi)). These soil moisture parameters are required for the assessment of water flow and solute transport in unsaturated media. The method employs a statistical multiple regression equations proposed in the literature for estimating (h(Phi)) or (K(Phi)) relationships using
Robert F. Carsel; Rudolph S. Parrish
Desert shrub water relations with respect to soil characteristics and plant functional type
Summary 1. Soil characteristics influence plant communities in part through water relations. Hypothetically, finer textured soils in arid climates should be associated with more negative plant and soil water potentials during drought, greater resistance of xylem to cavitation, and shallower root systems than coarse soils. 2. These hypotheses were tested by comparing the water relations of Great Basin shrubs growing
J. S. Sperry; U. G. Hacke
Soil Moisture: The Hydrologic Interface Between Surface and Ground Waters
NASA Technical Reports Server (NTRS)
A hypothesis is presented that many hydrologic processes display a unique signature that is detectable with microwave remote sensing. These signatures are in the form of the spatial and temporal distributions of surface soil moisture. The specific hydrologic processes that may be detected include groundwater recharge and discharge zones, storm runoff contributing areas, regions of potential and less than potential evapotranspiration (ET), and information about the hydrologic properties of soils. In basin and hillslope hydrology, soil moisture is the interface between surface and ground waters.
Engman, Edwin T.
DenNit ¢ Experimental analysis and modelling of soil N 2 O efflux in response on changes of soil water content, soil temperature, soil pH, nutrient availability and the time after rain event
To quantify the effects of soil temperature (Tsoil), and relative soil water content (RSWC) on soil N2O emission we measured N2O soil efflux with a closed dynamic chamber in situ in the field and from soil cores in a controlled climate chamber experiment. Additionally we analysed the effect of soil acidity, ammonium, and nitrate concentration in the field. The analysis
Sascha Reth; Kerstin Hentschel; Matthias Dr÷sler; Eva Falge
Spatial Variability of Physical Properties of a Tropical Soil. II. Soil Water Retention Curves and Hydraulic Conductivity.
National Technical Information Service (NTIS)
The characterization of a field site from the soil physics point of view, the improvement of the use of soil and water resources under a particular condition and the development of means for controlling the dynamics of soil-water movement are presented. S...
K. Reichardt P. L. Libardi S. V. Queiroz F. Grohmann
Precision and accuracy of three alternative instruments for measuring soil water content in two forest soils of the Pacific Northwest
We compared the accuracy and precision of three devices for measuring soil water content in both natural and repacked soils and evaluated their temperature sensitivity. Calibrations were developed for a capacitance instrument (ECH2O), a time domain reflectometry cable tester (CT), and a water content reflectometer (WCR) in soils collected from the Wind River and H.J. Andrews Experimental Forests. We compared
Nicole M. Czarnomski; Georgianne W. Moore; Tom G. Pypker; Julian Licata; Barbara J. Bond
Modelling the long-term effect of irrigation with gypsiferous water on soil and water resources
The use of gypsiferous mine water for irrigation of agricultural crops is a promising technology that could solve problems related to both shortage of irrigation water and disposal of effluent mine drainage. The long-term effect of irrigation with lime-treated acid mine drainage on soil properties and catchment salt load was investigated. The soil water¢salt balance-crop growth model (SWB) and the
J. G Annandale; N. Z Jovanovic; N BenadĶ; P. D Tanner
The effects of water exposure, soil conditions, and fungus exposure on hatching of the larval lone star tick, Amblyomma americanum (Acari: Ixodidae)
We examined whether water functions as a developmental cue for hatching in the lone star tick, Amblyomma americanum. The experiments examined various exposure routes to water: submersion, relative humidity and an ecologically relevant setup of moist soil along with soil fungi to mimic fungus¢egg interactions at oviposition sites. We demonstrate that eggs survive for up to a week underwater; increasing
Jay A. Yoder; Benjamin A. Rausch; Brian Z. Hedges; Sarah E. Stueber; Andrew J. Jajack; Joshua B. Benoit
Association of water spectral indices with plant and soil water relations in contrasting wheat genotypes.
Spectral reflectance indices can be used to estimate the water status of plants in a rapid, non-destructive manner. Water spectral indices were measured on wheat under a range of water-deficit conditions in field-based yield trials to establish their relationship with water relations parameters as well as available volumetric soil water (AVSW) to indicate soil water extraction patterns. Three types of wheat germplasm were studied which showed a range of drought adaptation; near-isomorphic sister lines from an elite/elite cross, advanced breeding lines, and lines derived from interspecific hybridization with wild relatives (synthetic derivative lines). Five water spectral indices (one water index and four normalized water indices) based on near infrared wavelengths were determined under field conditions between the booting and grain-filling stages of crop development. Among all water spectral indices, one in particular, which was denominated as NWI-3, showed the most consistent associations with water relations parameters and demonstrated the strongest associations in all three germplasm sets. NWI-3 showed a strong linear relationship (r(2) >0.6-0.8) with leaf water potential (psi(leaf)) across a broad range of values (-2.0 to -4.0 MPa) that were determined by natural variation in the environment associated with intra- and inter-seasonal affects. Association observed between NWI-3 and canopy temperature (CT) was consistent with the idea that genotypes with a better hydration status have a larger water flux (increased stomatal conductance) during the day. NWI-3 was also related to soil water potential (psi(soil)) and AVSW, indicating that drought-adapted lines could extract more water from deeper soil profiles to maintain favourable water relations. NWI-3 was sufficiently sensitive to detect genotypic differences (indicated by phenotypic and genetic correlations) in water status at the canopy and soil levels indicating its potential application in precision phenotyping. PMID:20639342
Gutierrez, Mario; Reynolds, Matthew P; Klatt, Arthur R
Water-Retention of Fractal Soil Models Using Continuum Percolation Theory: Tests of Hanford Site Soils
ABSTRACT,of percolation theory for flow in a fractal medium in- creases understanding of the steady-state hydraulic con- For 43 Hanford site soils, we use fractal analysis and assume propor- ductivity in the DOE Hanford Site soils. A related prob- tionality of pore radii to particle radii to generate water-retention curves, h(), from particle-size distributions. The air-entry head is lem, which
Allen G. Hunt; Glendon W. Gee
Determination of polyacrylamide in soil waters by size exclusion chromatography.
Determination of polyacrylamide (PAM) concentration in soil waters is important in improving the efficiency of PAM application and understanding the environmental fate of applied PAM. In this study, concentrations of anionic PAM with high molecular weight in soil waters containing salts and dissolved organic matter (DOM) were determined quantitatively by size exclusion chromatography (SEC) with ultraviolet (UV) absorbance detection. Polyacrylamide was separated from interferential salts and DOM on a polymeric gel column eluted with an aqueous solution of 0.05 M KH2PO4 and then detected at a short UV wavelength of 195 nm. Analysis of PAM concentrations in soil sorption supernatants, soil leachates, and water samples from irrigation furrow streams showed that SEC is an effective approach for quantifying low concentrations (0-10 mg L(-1)) of PAM in waters containing soil DOM and salts. The method has a lower detection limit of 0.02 microg and a linear response range of 0.2 to 80 mg L(-1). Precision studies gave coefficients of variation of < 1.96% (n = 4) for > 10 mg L(-1) PAM and < 12% (n = 3) for 0.2 to 3 mg L(-1) PAM. PMID:14535339
Lu, Jianhang; Wu, Laosheng; Gan, Jianying
Evapotranspiration of soil water movement in small area vegetation
NASA Astrophysics Data System (ADS)
In Greece, crops are frequently cultivated in small isolated areas in close proximity to roads and bare soils and therefore evapotranspiration is affected by local advection. Under these circumstances, oasis effect conditions are present and evapotranspiration is higher than what is expected. In this paper, the evapotranspiration and soil water dynamics of a cotton crop cultivated in small areas under the oasis effect is studied. To this end, two isolated free-drainage lysimeters cultivated with cotton in the year 2007 were used. Soil moisture of the soil profile of both the lysimeters was monitored with two capacitance water content probes. The soil water balance method was used to estimate crop evapotranspiration and corresponding crop coefficients in one of the two lysimeters. These coefficients were 75% larger than the FAO-56 crop coefficients at the mid-season stage. The FAO-56 and the derived crop coefficients were used for the simulation of the water dynamics in the second lysimeter by the SWBACROS model. The derived crop coefficients for these conditions produced much better results than the FAO-56 crop coefficients. The results were improved when crop coefficient value equal to 2.5 was used for the mid-season stage.
Paraskevas, C.; Georgiou, P.; Ilias, A.; Panoras, A.; Babajimopoulos, C.
Interaction of methane and methanol with water
Intermolecular interaction energies of methane and methanol with a water molecule are computed in the SCF approximation with a minimal basis set and with the counterpoise correction; the value for the dispersion correction is estimated by a perturbation method. The computed interaction energies for a water molecule at a large number of different positions and orientations relative to either CH/sub 4/ or CH/sub 3/OH (the latter in three different conformations) are used to derive simple analytical atom-atom pair potentials. These potentials are used elsewhere in Monte Carlo studies of the hydration of CH/sub 4/ and CH/sub 3/OH.
Bolis, G. (IBM Corp., Poughkeepsie, NY); Clementi, E.; Wertz, D.H.; Scheraga, H.A.; Tosi, C.
Hot water tolerance of soil animals: utility of hot water immersion in preventing invasions of alien soil animals
\\u000a Introduced soil animals have frequently affected native fauna on oceanic islands that have never been connected to a continental\\u000a land mass. Alien soil animals can be unintentionally introduced via transfer in potted plants or by commercial trade among\\u000a islands and continental landmasses. Hot water treatment to destroy pests has recently been used during the quarantine of ornamental\\u000a plants. To examine
Shinji Sugiura
Chromium-microorganism interactions in soils: remediation implications.
Discharge of Cr waste from many industrial applications such as leather tanning, textile production, electroplating, metallurgy, and petroleum refinery has led to large-scale contamination of land and water. Generally, Cr exists in two stable states: Cr(III) and Cr(VI). Cr(III) is not very soluble and is immobilized by precipitation as hydroxides. Cr(VI) is toxic, soluble, and easily transported to water resources. Cr(VI) undergoes rapid reduction to Cr(III), in the presence of organic sources or other reducing compounds as electron donors, to become precipitated as hydroxides. Cr(VI)-reducing microorganisms are ubiquitous in soil and water. A wide range of microorganisms, including bacteria, yeasts; and algae, with exceptional ability to reduce Cr(VI) to Cr(III) anaerobically and/or aerobically, have been isolated from Cr-contaminated and noncontaminated soils and water. Bioremediation approaches using the Cr(VI)-reducing ability of introduced (in bioreactors) or indigenous (augmented by supplements with organic amendments) microorganisms has been more successful for remediation of Cr-contaminated water than soils. Apart from enzymatic reduction, nonenzymatic reduction of Cr(VI) can also be common and widespread in the environment. For instance, biotic-abiotic coupling reactions involving the microbially formed products, H2S (the end product of sulfate reduction), Fe(II) [formed by Fe(III) reduction], and sulfite (formed during oxidation of elemental sulfur), can mediate the dissimilatory reduction of Cr(VI). Despite the dominant occurrence of enzymatic and nonenzymatic reduction of Cr(VI), natural attenuation of Cr(VI) is not taking place at a long-term contaminated site in South Australia, even 225 years after the last disposal of tannery waste. Evidence suggests that excess moisture conditions leading to saturation or flooded conditions promote the complete removal of Cr(VI) in soil samples from this contaminated site; but Cr(VI) reappears, probably because of oxidation of the Cr(III) by Mn oxides, with a subsequent shift to drying conditions in the soil. In such environments with low natural attenuation capacity resulting from reversible oxidation of Cr(III), bioeremediation of Cr(VI) can be a challenging task. PMID:12868782
Kamaludeen, Sara P B; Megharaj, Mallavarapu; Juhasz, Albert L; Sethunathan, Nabrattil; Naidu, Ravi
Soil and water conservation policies: Successes and failures
This book presents an in-depth look at soil and water conservation programs throughout the world. For as far into the future as one can see, governments will probably topple, power will continue to exchange hands, the climate will undergo continuous change, and the global economy will ebb and flow like the oceans. But for the world's many diverse countries--whether they be highly industrialized or third world--one thing will always remain constant: the need to solve the planet's pressing soil and water conservation problems, as well as implement effective policies. This book addresses: Why do some policy initiatives succeed while others fail?
Napier, T.A. [ed.
Modeling soil organic matter dynamics as affected by soil water erosion.
Soil organic carbon (SOC) stock is an important component of the global carbon (C) cycle, which has the potential to influence global climate. In this paper we presented an overview of soil organic matter (SOM) models in the context of soil erosion and discussed basic processes driving erosion-induced SOC loss. Although the mechanism of this loss is poorly understood, erosion influences SOC in two ways: redistribution of C within the watershed or ecosystem, and loss of C to the atmosphere. Erosion disperses soil, altering its microbiological activity as well as water, air and nutrient regimes. This, along with sediment enrichment, has an impact on greenhouse gas emission from soil. For most of agricultural settings, field studies suggest that cultivation along with soil erosion are the primary reasons for SOC loss. Tracing the fate of eroded C is a challenging task. Modeling is the approach taken most often. In this paper we discuss approaches used in various SOC models to assess erosion-induced C loss from soil in agricultural ecosystems. An example with Century model applied to meadow and corn-soybean rotation under chisel-till demonstrated the model's ability to respond well to different erosion scenarios. It was estimated that at soil loss rate of 10 t ha(-1) year(-1) (value often considered a threshold for maintaining productivity) 19% of the total SOC loss would be attributed to erosion after 90 years of cultivation. PMID:15031015
Polyakov, V; Lal, R
Subcritical water extraction to isolate kinetically different soil nitrogen fractions
NASA Astrophysics Data System (ADS)
Soil organic N is largely composed of inherently biologically labile proteinaceous N and its persistence in soil is mainly explained by stabilization through binding to minerals and other soil organic matter (SOM) components at varying strengths. In order to separate kinetically different soil N fractions we hypothesize that an approach, which isolates soil N fractions on the basis of bonding strength is required, rather than employing chemical agents or physical methods. We developed a sequential subcritical water extraction (SCWE) procedure at 100 ░C, 150 ░C and 200░C to isolate SOM fractions. We assessed these SCWE N fractions as predictors for aerobic and anaerobic N mineralization measured from 25 paddy soil cores in incubations. SCWE organic carbon (SCWE OC) and N (SCWE N) increased exponentially with the increase of temperature and N was extracted preferentially over OC. The efficiency of SCWE and the selectivity towards N were both lower in soils with increasingly reactive clay mineralogy. The 100-150 ░C SCWE N and the 100 ░C + 100-150 ░C SCWE N correlated slightly better with the aerobic N mineralization than soil N content. The resulting explained percentages (46-49%) are, however, too small to allow accurate fertilizer recommendations. No correlations were found between the SCWE fractions and anaerobic N mineralization rate and consequently alternative driving factors should be looked for. Nonetheless, perhaps SCWE does, still hold potential to separate kinetically different SOM pools from upland soils, in which the bio-availability of N is more likely to be a key constraint in the N mineralization process. This in contrast to the studied paddy soils, in which N mineralization appeared to be largely decoupled from SOM quantity and quality or its availability, perhaps due to an overriding control of abiotic factors on the anaerobic N mineralization process.
Sleutel, S.; Kader, M. A.; Demeestere, K.; Walgraeve, C.; Dewulf, J.; De Neve, S.
Organic compounds in hot-water-soluble fractions from water repellent soils
NASA Astrophysics Data System (ADS)
Water repellency (WR) is a soil property providing hydrophobic protection and preventing rapid microbial decomposition of organic matter entering the soil with litter or plant residues. Global warming can cause changes in WR, thus influencing water storage and plant productivity. Here we assess two different approaches for analysis of organic compounds composition in hot water extracts from accelerated solvent extraction (ASE) of water repellent soils. Extracts were lyophilized, fractionated on SiO2 (sand) and SPE cartridge, and measured by GC/MS. Dominant compounds were aromatic acids, short chain dicarboxylic acids (C4-C9), sugars, short chain fatty acids (C8-C18), and esters of stearic and palmitic acids. Polar compounds (mainly sugars) were adsorbed on applying SPE clean-up procedure, while esters were highly abundant. In addition to the removal of polar compounds, hydrophobic esters and hydrocarbons (alkanes and alkenes < C20) were extracted through desorption of complex colloids stabilized as micelles in dissolved organic carbon (DOC). Water repellency was completely eliminated by hot water under high pressure. The molecular composition of HWSC can play a critical role in stabilization and destabilization of soil organic matter (SOM), particle wettability and C dynamics in soils. Key words: soil water repellency, hot water soluble carbon (HWSC), GC/MS, hydrophobic compounds
Atanassova, Irena; Doerr, Stefan
Spatial and Temporal Soil Water Estimation Considering Soil Variability and Evapotranspiration Uncertainty
NASA Astrophysics Data System (ADS)
Lack of accurate information stemming from soil variability and climatic uncertainty obstructs efficient irrigation management. State-space models of soil water balance and potential evapotranspiration were used in the application of spatial-temporal estimation methods to reduce uncertainty. Temporal soil water storage estimates and estimation errors were obtained by the Kalman filter (KF). Spatial estimates were obtained by the conditional multivariate normal method. These spatial and temporal estimates were combined by an additional KF step that considers spatial estimates as measurements. Time-dependent soil water spatial covariance was approximated by assuming a constant correlation range and by using measurements variance to estimate the variogram "sill." Simulation and field results indicate that soil water storage estimates by the proposed method agreed better with measurements than estimates based on either spatial or temporal information only. The proposed estimation scheme can be extended to other systems with a simple physical model and a known spatial structure where only a few field measurements are available.
Or, Dani; Hanks, R. J.
Dynamics of the soil water and solute in the sodic saline soil in the Songnen Plain, China
According to the field experiment in the sodic saline soil region in the Songnen Plain, the dynamics of the soil water and\\u000a solute affected by the shallow groundwater were explored during the growing season in 2004. The results presented that, influenced\\u000a by the strongly evaporative demand, the soil water tended to transport to the upper soil layer with salt. The
Qiang Liu; Baoshan Cui; Zhifeng Yang
Soil Water Simulation and Predication Using Stochastic Models Based on LS-SVM for Red Soil Region of China
The seasonal drought and the low available soil moisture affect the agricultural production in red soil region, China. Therefore,\\u000a it is necessary to simulate and predict the dynamic changes of soil water in the field. Presently, dynamic model has been\\u000a applied to obtain the soil water information. While the simulation accuracy of dynamic model depends on many complicated parameters,\\u000a which
Jianqiang Deng; Xiaomin Chen; Zhenjie Du; Yong Zhang
[Ecological effect of hygroscopic and condensate water on biological soil crusts in Shapotou region of China].
By the method of field experiment combined with laboratory analysis, this paper studied the ecological significance of hygroscopic and condensate water on the biological soil crusts in the vegetation sand-fixing area in Shapotou region of China. In the study area, 90% of hygroscopic and condensate water was within the 3 cm soil depth, which didn' t affect the surface soil water content. The hygroscopic and condensate water generated at night involved in the exchange process of soil surface water and atmosphere water vapor, made up the loss of soil water due to the evaporation during the day, and made the surface soil water not reduced rapidly. The amount of the generated hygroscopic and condensate water had a positive correlation with the chlorophyll content of biological soil crusts, indicating that the hygroscopic and condensate water could improve the growth activity of the biological soil crusts, and thus, benefit the biomass accumulation of the crusts. PMID:23755477
Pan, Yan-Xia; Wang, Xin-Ping; Zhang, Ya-Feng; Hu, Rui
Reflectance of vegetation, soil, and water
NASA Technical Reports Server (NTRS)
There are no author-identified significant results in this report. This report deals with the selection of the best channels from the 24-channel aircraft data to represent crop and soil conditions. A three-step procedure has been developed that involves using univariate statistics and an F-ratio test to indicate the best 14 channels. From the 14, the 10 best channels are selected by a multivariate stochastic process. The third step involves the pattern recognition procedures developed in the data analysis plan. Indications are that the procedures in use are satsifactory and will extract the desired information from the data.
Wiegand, C. L. (principal investigator)
Impact of alfalfa on soil and water quality
Dominance of row crop agriculture in rolling landscapes of western and Southwestern Minnesota is identified as a primary, non-point source of sediments and associated pollutants reaching the Minnesota River. Currently as a biomass energy project, alfalfa is being promoted in western Minnesota to harvest the leaves for animal feed and stems to generate electricity. As a perennial, leguminous crop grown with minimum inputs, introduction of alfalfa in row cropped lands has potential to improve both in-situ soil productivity and downstream water quality. A field study was initiated in 1996 to compare the volume of runoff and pollutants coming from alfalfa an com-soybean fields in western Minnesota. Two pair of alfalfa and corn-soybean watersheds were instrumented at Morris in the Fall of 1996 to measure rainfall, runoff, and sample water for sediment load, phosphorus, nitrogen, biochemical oxygen demand, and chemical oxygen demand. Simulated rainfall-runoff experiments were conducted on an existing crop rotation - input management study plots at Lamberton to evaluate soil quality effects of the inclusion of alfalfa in a corn-soybean rotation under manure and fertilization management schemes. Alfalfa soil water use as a function of frequency of harvest was also monitored at Morris to evaluate the effect of cutting schedule on soil water use. During the growing season of 1997, alfalfa under a two-cut management scheme used about 25-mm (an inch) more soil water than under a three-cut schedule. The mean differences between the treatments were not significant. The conclusions drawn in this report come from analysis of data collected during one winter-summer hydrologic and crop management cycle. Continued observations through a period of at least 3-5 years is recommended to improve the instrumentation robustness and discern the variability due to climate, soil, and crop management factors.
Sharma, P.; Moncrief, J.; Gupta, S.
Analysis of soil water dynamics in an agroforestry system based on detailed soil water records from time-domain reflectometry
NASA Astrophysics Data System (ADS)
Time domain reflectometry [TDR] was used to investigate the spatial and temporal variation in surface soil water dynamics under a number of types of vegetation, including both trees and crops grown in isolation, and grown together as an agroforestry system. The installation and operation of this technique are presented, and discussed in terms of its suitability to monitor rapid fluctuations in soil-water content in a spatially heterogeneous system such as that described in this experiment. The relatively small sampling volume of each of the TDR waveguides permitted discrete measurements to be made of soil water content (?v). In the tree-only and tree+crop treatments, this revealed considerable variation in ?v resulting from spatial redistribution of rainfall under the tree canopies, with a significant input to soil close to the base of the trees being made by stemflow, i.e. water intercepted by the tree canopy and channelled down the stem. Over the experimental period (one rainy season) the TDR data suggested that net recharge to the soil profile in the sole crop system was 53 mm, almost 75% more than occurred in either of the two treatments containing trees, reflecting greater rainfall interception by the tree canopies.
Jackson, N. A.; Wallace, J. C.
The utility of surface temperature measurements for the remote sensing of surface soil water status
NASA Technical Reports Server (NTRS)
Experiments carried out on an Avondale loam soil indicated that the thermal inertia concept of soil water content detection is reasonably sound. The volumetric water contents of surface soil layers between 2 and 4 cm thick were found to be linear functions of the amplitude of the diurnal surface soil temperature wave for clear day-night periods. They were also found to be linear functions of the daily maximum value of the surface soil-air-temperature differential. Tests on three additional soils ranging from sandy loam to clay indicated that the relations determined for Avondale loam could not be accurately applied to these other soil types. When the moisture characteristic curves of each soil were used to transform water contents into pressure potentials, however, it was found that soil water pressure potential could be determined without prior knowledge of soil type, and thus its value as a potential soil water status survey tool was significantly enhanced.
Idso, S. B.; Jackson, R. D.; Reginato, R. J.; Schmugge, T. J.
Pipe-soil shear interaction stiffness in horizontal directional drilling and pipe bursting
During horizontal directional drilling and pipe bursting installations, the shear forces between the pipe and the surrounding soil play a major role in the tensile loads and stresses experienced by the pipe. The magnitudes and variations in the shear forces are controlled by the pipe-soil interaction characteristics. This paper discusses the shear interaction between the pipe and the soil during
Abdul Ghafar Chehab; Ian Moore
Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2
NASA Astrophysics Data System (ADS)
Changes in the rates of nitrogen (N) cycling, microbial carbon (C) substrate use, and extracellular enzyme activities in a Mojave Desert ecosystem exposed to elevated atmospheric CO2 suggest shifts in the size and/or functional characteristics of microbial assemblages in two dominant soil microsites: plant interspaces and under the dominant shrub Larrea tridentata. We used ester-linked phospholipid fatty acid (PLFA) biomarkers as a proxy for microbial biomass to quantify spatial and temporal differences in soil microbial communities from February 2003 to May 2005. Further, we used the 13C signature of the fossil CO2 source for elevated CO2 plots to trace recent plant C inputs into soil organic matter (SOM) and broad microbial groups using ?13C (ē). Differences between individual ?13CPLFA and ?13CSOM for fungal biomarkers indicated active metabolism of newer C in elevated CO2 soils. Total PLFA-C was greater in shrub microsites compared to plant interspaces, and CO2 treatment differences within microsites increased under higher soil water availability. Total, fungal, and bacterial PLFA-C increased with decreasing soil volumetric water content (VWC) in both microsites, suggesting general adaptations to xeric desert conditions. Increases in fungal-to-bacterial PLFA-C ratio with decreasing VWC reflected functional group-specific responses to changing soil water availability. While temporal and spatial extremes in resource availability in desert ecosystems contribute to the difficulty in identifying common trends or mechanisms driving microbial responses in less extreme environments, we found that soil water availability and soil microsite interacted with elevated CO2 to shift fungal and bacterial biomarker abundances in Mojave Desert soils.
Jin, V. L.; Schaeffer, S. M.; Ziegler, S. E.; Evans, R. D.
Soil-water characteristic curves for compacted clays
Soil-water characteristic curves (SWCCs) are presented for four compacted clay barrier soils that were prepared at different compaction water contents (dry, wet, and optimum water content) and compactive efforts (standard and modified Proctor). The SWCCs were measured in the laboratory using pressure plate extractors. The shape of the SWCC depends on compaction water content and compactive effort, but compaction water content is more important. Compaction at higher compaction water content or with greater compactive effort results in larger air entry. Also, clays with higher plasticity index have greater air-entry suction. Changes in the shape of the SWCC are consistent with changes in pore size that occur by varying compaction conditions and with the mineralogical composition of the soils. These changes in the SWCC also are reflected in the van Genuchten and Brooks-Corey parameters, which were obtained from least-squares fits to the SWCC data. Regression equations are presented that can be used to estimate the van Genuchten parameters {alpha} and n from compaction water content, compactive effort, and plasticity index.
Tinjum, J.M. [CH2M Hill, Inc., Denver, CO (United States); Benson, C.H.; Blotz, L.R. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering
Chemical kinetics of water-rock interactions
The recent literature on the kinetics of water-rock interactions is reviewed. The data are then extended to provide a quantitative framework for the description of weathering and alteration. The available experimental data on dissolution of silicates verifies quantitatively the usual mineral stability series in sedimentary petrology. The rate of hydration of carbonic acid is shown to be a possible limiting
Antonio C. Lasaga
Predawn disequilibrium between plant and soil water potentials in two cold-desert shrubs
Classical water relations theory predicts that predawn plant water potential should be in equilibrium with soil water potential\\u000a (soil ?w) around roots, and many interpretations of plant water status in natural populations are based on this expectation. We examined\\u000a this expectation for two salt-tolerant, cold-desert shrub species in glasshouse experiments where frequent watering assured\\u000a homogeneity in soil ?w and soil-root
L. A. Donovan; D. J. Grisķ; J. B. West; R. A. Pappert; N. N. Alder; J. H. Richards
Migration through soil of organic solutes in an oil-shale process water
The migration through soil of organic solutes in an oil-shale process water (retort water) was studied by using soil columns and analyzing leachates for various organic constituents. Retort water extracted significant quantities of organic anions leached from ammonium-saturated-soil organic matter, and a distilled-water rinse, which followed retort-water leaching, released additional organic acids from the soil. After being corrected for organic
Jerry A. Leenheer; Harold A. Stuber
Observing plants dealing with soil water stress: Daily soil moisture fluctuations derived from polymer tensiometers
NASA Astrophysics Data System (ADS)
Periods of soil water deficit often occur within a plant's life cycle, even in temperate deciduous and rain forests (Wilson et al. 2001, Grace 1999). Various experiments have shown that roots are able to sense the distribution of water in the soil, and produce signals that trigger changes in leaf expansion rate and stomatal conductance (Blackman and Davies 1985, Gollan et al. 1986, Gowing et al. 1990 Davies and Zhang 1991, Mansfield and De Silva 1994, Sadras and Milroy 1996). Partitioning of water and air in the soil, solute distribution in soil water, water flow through the soil, and water availability for plants can be determined according to the distribution of the soil water potential (e.g. Schr÷der et al. 2013, Kool et al. 2014). Understanding plant water uptake under dry conditions has been compromised by hydrological instrumentation with low accuracy in dry soils due to signal attenuation, or a compromised measurement range (Whalley et al. 2013). Development of polymer tensiometers makes it possible to study the soil water potential over a range meaningful for studying plant responses to water stress (Bakker et al. 2007, Van der Ploeg et al. 2008, 2010). Polymer tensiometer data obtained from a lysimeter experiment (Van der Ploeg et al. 2008) were used to analyse day-night fluctuations of soil moisture in the vicinity of maize roots. To do so, three polymer tensiometers placed in the middle of the lysimeter from a control, dry and very dry treatment (one lysimeter per treatment) were used to calculate water content changes over 12 hours. These 12 hours corresponded with the operation of the growing light. Soil water potential measurements in the hour before the growing light was turned on or off were averaged. The averaged value was used as input for the van Genuchten (1980) model. Parameters for the model were obtained from laboratory determination of water retention, with a separate model parameterization for each lysimeter setup. Results show daily fluctuations in water content changes, with both root water uptake and root water excretion. The magnitude of the water content change was in the same order for all treatments, thus suggesting compensatory uptake. References Bakker G, Van der Ploeg MJ, de Rooij GH, Hoogendam CW, Gooren HPA, Huiskes C, Koopal LK and Kruidhof H. New polymer tensiometers: Measuring matric pressures down to the wilting point. Vadose Zone J. 6: 196-202, 2007. Blackman PG and Davies WJ. Root to shoot communication in maize plants of the effects of soil drying. J. Exp. Bot. 36: 39-48, 1985. Davies WJ and Zhang J. Root signals and the regulation of growth and development of plants in drying soil. Annu. Rev. Plant Physiol. Plant Mol. Biol. 42: 55-76, 1991. Gollan T, Passioura JB and Munns R. Soil water status affects the stomatal conductance of fully turgid wheat and sunflower leafs. Aust. J. Plant Physiol. 13: 459-464, 1986. Gowing DJG, Davies WJ and Jones HG. A Positive Root-sourced Signal as an Indicator of Soil Drying in Apple, Malus x domestica Borkh. J. Exp. Bot. 41: 1535-1540, 1990. Grace J. Environmental controls of gas exchange in tropical rain forests. In: Press, M.C, J.D. Scholes and M.G. Barker (ed.). Physiological plant ecology: the 39th Symposium of the British Ecological Society. Blackwell Science, United Kingdom, 1999. Kool D, Agam N, Lazarovitch N, Heitman JL, Sauer TJ, Ben-Gal A. A review of approaches for evapotranspiration partitioning. Agricultural and Forest Meteorology 184: 56- 70, 2014. Mansfield TA and De Silva DLR. Sensory systems in the roots of plants and their role in controlling stomatal function in the leaves. Physiol. Chem. Phys. & Med. 26: 89-99, 1994. Sadras VO and Milroy SP. Soil-water thresholds for the responses of leaf expansion and gas exchange: a review. Field Crops Res. 47: 253-266, 1996. Schr÷der N, Lazarovitch N, Vanderborcht J, Vereecken H, Javaux M. Linking transpiration reduction to rhizosphere salinity using a 3D coupled soil-plant model. Plant Soil 2013, doi: 10.1007/s11104-013-1990-8 Van der Ploeg MJ, Gooren HPA, Bakker G and de Rooij GH.
van der Ploeg, Martine; de Rooij, Gerrit
[Soil water resource use limit in semi-arid loess hilly area].
Taking Caragana korshinskii as test object, and by using neutron probe, a long term observation was conducted on the soil water and plant growth during the process of vegetation restoration in semi-arid loess hilly area. The results showed that after seeding on waste land, the capability of plant community in conserving soil and water was promoted with time, with the depth of roots to absorb and use soil water increased and the soil water content reduced. Then, the dried soil layer appeared, and its deepness and thickness increased with increasing plant age. Therefore, the plant use of soil water had a limit, soil water resource use limit, i.e., the soil water storage when the deepness of dried soil layer was equal to the largest depth that rain could recharge. In the C. korshinskii woodland in semi-arid loess hilly area, the soil water resource use limit in 0-290 cm layer was 249.4 mm. When the soil water storage in woodland was close or equal to the soil water resource use limit, effective measures should be taken to decrease soil evapotranspiration or increase soil water supply to ensure the sustainable water use of plant roots. PMID:21442986
Guo, Zhong-sheng
Spatiotemporal Pattern of Root Water Uptake for Locally Differing Soil Water Availability
NASA Astrophysics Data System (ADS)
One of the important but not well known questions is how the root system of a plant respond to water scarcity, especially if there is a locally heterogeneous distribution of soil moisture or accessibility of water. However, heterogeneous water availability is a typical characteristic of soils, for example by heterogeneity of soil properties, infiltration and evaporation or competition between plant roots. On top of that, water content in soil has a large temporal dynamics. Despite these intrinsic heterogeneities of soil-plant water relations, we know little about the ways how plants respond to local environmental properties. Recently imaging and tomography methods have become available, that facilitate the measurement of spatial and temporal distribution of water content and of the root system itself, which offers the possibility to investigate also the distribution of water uptake in a plant root system. To monitor root water uptake response to local soil water availability, we used neutron radiography especially suited to detect water distribution, to non-invasively image root growth and 2-D soil water distribution as time-lapsed images. We applied a method to hydraulically partition the soil to be able to actively control the level of water available locally and at the same time to locally quantify water uptake for these heterogeneous conditions. The key results for an imaging experiment running full three weeks show topological patterns of water uptake along the root system. Moreover, under water stress, compensatory root water uptake maximizes soil water utilization in response to transpiration demand. Lupin plants were grown in 40*35*1 cm│ aluminum containers. The root zone was partitioned into twenty compartments separated by capillary barriers and divides the root system into taproot and lateral roots, and into young and old later root segments at the top, middle and bottom profile positions. Three weeks after planting, four soil-water treatments in three replaces each, were applied as: no stress (control), %50 stress (water available for 50% of the lateral roots) and 75% stress (water available for 25% of lateral roots in old and young parts in two individual treatments). Two levels of transpiration demand in 5-day periods each were also applied, interrupted by five days of recovering in between. Daily changes in soil water content and root water uptake rate in each compartment have been monitored by neutron radiography four times a day as well as daily transpiration rates. The results show a high compensatory water uptake by the root segments in the wet parts under water stress. This root compensation increases significantly with increasing portion of the root system suffering water scarcity. ; While for low transpiration demand, there was not a significant difference in transpiration rate between 50% and 25% local water availability, for higher transpiration demand transpiration demand cannot be fully compensated when water is provided for the root system locally. In respect to root topology , root segments in the top with less distance to the shoot show higher rates of water uptake then those in the lower position while the difference in local root water uptake between old and young roots is not that high.
Dara, Abbas; Moradi, Ahmad B.; Oswald, Sascha
Hysteresis and uncertainty in soil water-retention curve parameters
Accurate estimates of soil hydraulic parameters representing wetting and drying paths are required for predicting hydraulic and mechanical responses in a large number of applications. A comprehensive suite of laboratory experiments was conducted to measure hysteretic soil-water characteristic curves (SWCCs) representing a wide range of soil types. Results were used to quantitatively assess differences and uncertainty in three simplifications frequently adopted to estimate wetting-path SWCC parameters from more easily measured drying curves. They are the following: (1) ?w=2?d, (2) nw=nd, and (3) ?ws=?ds, where ?, n, and ?s are fitting parameters entering van GenuchtenÆs commonly adopted SWCC model, and the superscripts w and d indicate wetting and drying paths, respectively. The average ratio ?w/?d for the data set was 2.24▒1.25. Nominally cohesive soils had a lower ?w/?d ratio (1.73▒0.94) than nominally cohesionless soils (3.14▒1.27). The average nw/nd ratio was 1.01▒0.11 with no significant dependency on soil type, thus confirming the nw=nd simplification for a wider range of soil types than previously available. Water content at zero suction during wetting (?ws) was consistently less than during drying (?ds) owing to air entrapment. The ?ws/?ds ratio averaged 0.85▒0.10 and was comparable for nominally cohesive (0.87▒0.11) and cohesionless (0.81▒0.08) soils. Regression statistics are provided to quantitatively account for uncertainty in estimating hysteretic retention curves. Practical consequences are demonstrated for two case studies.
Likos, William J.; Lu, Ning; Godt, Jonathan W.
Interactions between phosphate and water in solution
The Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations are used to analyze the interaction between mono-methyl phosphate-ester (MMP) and its solvation environment in a combined quantum mechanical/molecular mechanical (QM/MM) framework. The solute-solvent configurations are generated using a specific parameterization of the self-consistent-charge density functional tight-binding (SCC-DFTB) model for the MMP and TIP3P for water. The NBO and NEDA calculations are done with several QM/MM partitioning schemes with the HF/6-31+G** as the QM level. Regardless of the size of the QM region, a notable amount of charge transfer is observed between MMP and the neighboring water molecules and the charge-transfer interactions are, in the NEDA framework, as important as the electric (electrostatic and polarization) components. This work illustrates that NBO based analyses are effective tools for probing intermolecular interactions in condensed phase systems.
Yang, Yang; Cui, Qiang
A method to extract soil water for stable isotope analysis
A method has been developed to extract soil water for determination of deuterium (D) and 18O content. The principle of this method is based on the observation that water and toluene form an azeotropic mixture at 84.1??C, but are completely immiscible at ambient temperature. In a specially designed distillation apparatus, the soil water is distilled at 84.1??C with toluene and is separated quantitatively in the collecting funnel at ambient temperature. Traces of toluene are removed and the sample can be analyzed by mass spectrometry. Kerosene may be substituted for toluene. The accuracy of this technique is ?? 2 and ?? 0.2???, respectively, for ??D and ??18O. Reduced accuracy is obtained at low water contents. ?? 1990.
Revesz, K.; Woods, P. H.
Dynamic vertical interaction of a foundation-soil system generated by seismic waves
NASA Astrophysics Data System (ADS)
Based on Biot's dynamic poroelastic theory, a foundation-soil interaction model is established to investigate the vertical vibrations of a rigid circular foundation on poroelastic soil excited by incident plane waves, including the fast P waves and SV waves. Scattering waves caused by the foundation and fluid-solid coupling due to the pore water in the soil are also considered in the model. The solution of the vertical vibrations of the foundation subjected to seismic waves are obtained by solving two sets of dual integral equations derived from the mixed boundary-value conditions. The different vertical vibrations of foundation rest on elastic and saturated half-space are compared. The influences of incident angle, permeability of soil and foundation mass on the vertical vibrations of the foundation are then discussed. The results show that resonant phenomenon of the foundation is observed at certain excitation frequencies; the effects of the pore water on the foundation vertical vibrations are significant. In addition, significant differences are found when the foundation is excited by P waves and SV waves, respectively.
Wang, Peng; Wang, Jun; Cai, Yuanqiang; Gu, Chuan
Multivariate analyses of water chemistry: surface and ground water interactions.
Multivariate statistical methods (MSMs) applied to ground water chemistry provide valuable insight into the main hydrochemical species, hydrochemical processes, and water flowpaths important to ground water evolution. The MSMs of principal component factor analysis (FA) and k-means cluster analysis (CA) were sequentially applied to major ion chemistry from 211 different ground water-sampling locations in the Amargosa Desert. The FA reduces the number of variables describing the system and finds relationships between major ions. The CA of the reduced system produced objective hydrochemical facies, which are independent of, but in good agreement with, lithological data. The derived factors and hydrochemical facies are innovatively presented on biplots, revealing composition of hydrochemical processes and facies, and overlaid on a digital elevation model, displaying flowpaths and interactions with geologic and topographic features in the region. In particular, a distinct ground water chemical signature is observed beneath and surrounding the extended flowpath of Fortymile Wash, presenting some contradiction to contemporary water levels along with potential interaction with a fault line. The signature surrounding the ephemeral Fortymile Wash is believed to represent the relic of water that infiltrated during past pluvial periods when the amount of runoff in the wash was significantly larger than during the current drier period. This hypothesis and aforementioned analyses are supported by the examination of available chloride, oxygen-18, hydrogen-2, and carbon-14 data from the region. PMID:18194324
Woocay, Arturo; Walton, John
Interactions between soil moisture and Atmospheric Boundary Layer at the Brazilian savana-type vegetation Cerrado
NASA Astrophysics Data System (ADS)
Before the large people influx and development of the central part of Brazil in the sixties, due to new capital BrasĒlia, Cerrado, a typical Brazilian savanna-type vegetation, used to occupy about 2 million km2, going all the way from the Amazon tropical forest, in the north of the country, to the edges of what used to be of the Atlantic forest in the southeast. Today, somewhat 50% of this area has given place to agriculture, pasture and managed forests. It is forecasted that, at the current rate of this vegetation displacement, Cerrado will be gone by 2030. Understanding how Cerrado interacts with the atmosphere and how this interaction will be modified with this land-use change is a crucial step towards improving predictions of future climate-change scenarios. Cerrado is a vegetation adapted to a climate characterized by two very distinct seasons, a wet season (Nov-Mar) and dry season (May-Ago), with April and October being transitions between seasons. Typically, based on measurements in a weather station located in Brasilia, 75% of precipitation happens in the wet-season months and only 5% during dry-season. Under these circumstances, it is clear that the vegetation will have to cope with long periods of water stress. In this work we studied using numerical simulations, the interactions between soil-moisture, responsible for the water stress, with the Atmospheric Boundary Layer (ABL). The numerical model comprises of a Soil-Vegetation-Atmosphere model where the biophysical processes are represented with a big-leaf approach. Soil water is estimated with a simple logistic model and with water-stress effects on stomatal conductance are parameterized from local measurements of simultaneous latent-heat fluxes and soil moisture. ABL evolution is calculate with a slab model that considers independently surface and entrainment fluxes of sensible- and latent- heat. Temperature tropospheric lapse-rate is taken from soundings at local airport. Simulations of 30-day dry down from saturation to complete water stress were performed and is analyzed as far how ABL respond to soil moisture changes. This provides informations about ABL behavior on the transition states. Future studies will look on how this behavior will change with the new vegetation covers.
Pinheiro, L. R.; Siqueira, M. B.
Search for Nitrifying Agents in Water and Soils as Sources of Nitrates in Surface Water.
National Technical Information Service (NTIS)
The soil and surrounding water of seventeen diverse types of watersheds were analyzed over a one-year sampling period for a variety of parameters. Terrestrial nitrifying populations were quantified. Concentrations of ammonia, nitrate, and total nitrogen a...
N. A. Phillips R. L. Todd
Amend soils with residues from water-treatment processes
This article reports that land application is emerging as a viable disposal\\/reuse method for water-treatment-process residues. In many cases, these residues actually enhance soil quality and arrest fertilizer loss. Water treatment usually generates solid residues requiring disposal. These include sludges from lime softening and related pretreatment processes and spent ion-exchange resins and adsorbents used for softening, dealkalization, and deionization of
Water and Salt Regimes of Soils: Modeling and Management.
National Technical Information Service (NTIS)
Mathematical models describing the migration of moisture and salts in the soil layers are presented in this book. The region between the exposed surface and the water-confining stratum, the aeration and total saturation zones have been examined, and the i...
E. A. Sokolenko
This investigation was initiated to study the effects of application of differing rates of manure to land on crops, soil, and runoff water. The study was conducted under field conditions in the sub-humid climate of the Northern Great Plains. Manure application rates included leve...
Controlled release formulations of acephate: Water and soil release kinetics
Controlled release formulations of insecticide acephate (O,S-dimethyl acetylphosphoramidothioate) have been prepared using commercially available polyvinyl chloride, carboxy methyl cellulose and carboxy methyl cellulose with kaolinite. Kinetics of acephate release in soil and water from the different formulations was studied in comparison with the commercially available formulation 75 DF. Release from the commercial formulation was faster than the new controlled pesticide
Keyath Nisar; Jitendra Kumar; Najam A. Shakil; Pankaj; Suresh Walia; Balraj S. Parmar
Water-stability of soil aggregates in relation to selected properties.
National Technical Information Service (NTIS)
The stability of soil aggregates in water is an important soil physical property for evaluating the potential of agricultural soils to erode and elucidating the mechanisms of soil erosion. In this study we used aggregates from 15 surface soil samples in I...
J. S. C. Mbagwu P. Bazzoffi I. Unamba Oparah
The Dual Gravimetric Hot-Air Method for Measuring Soil Water Diffusivity
The hot-air method provides rapid measurement of a soil's unsatu- rated hydraulic diffusivity function. The original method consists of blowing hot air across one end of a soil column for a short period, and then quickly extruding, dissecting, and oven drying the soil to provide the soil water content profile, which is used to calculate the soil's un- saturated hydraulic
J. S. Tyner; L. M. Arya; W. C. Wright
Farm water budgets for semiarid irrigated floodplains of northern New Mexico: characterizing the surface water-groundwater interactions
NASA Astrophysics Data System (ADS)
KEY WORDS - Hydrology, Water budget, Deep percolation, Surface water-Groundwater interactions. With the recent projections for water scarcity, water balances have become an indispensable water management tool. In irrigated floodplains, deep percolation from irrigation can represent one of the main aquifer recharge sources. A better understanding of surface water and groundwater interactions in irrigated valleys is needed for properly assessing the water balances in these systems and estimating potential aquifer recharge. We conducted a study to quantify the parameters and calculate the water budgets in three flood irrigated hay fields with relatively low, intermediate and, high water availability in northern New Mexico. We monitored different hydrologic parameters including total amount of water applied, change in soil moisture, drainage below the effective root zone, and shallow water level fluctuations in response to irrigation. Evapotranspiration was calculated from weather station data collected in-situ using the Samani-Hargreaves. Previous studies in the region have estimated deep percolation as a residual parameter of the water balance equation. In this study, we used both, the water balance method and actual measurements of deep percolation using passive lysimeters. Preliminary analyses for the three fields show a relatively rapid movement of water through the upper 50 cm of the vadose zone and a quick response of the shallow aquifer under flood irrigation. Further results from this study will provide a better understanding of surface water-groundwater interactions in flood irrigated valleys in northern New Mexico.
Gutierrez, K. Y.; Fernald, A.; Ochoa, C. G.; Guldan, S. J.
Predawn plant water potential does not necessarily equilibrate with soil water potential under well-watered conditions
Predawn leaf water potential (Ow) and xylem pressure potential (Op) are expected to be in equilibrium with the soil water potential (soil Ow) around roots of well-watered plants. We surveyed 21 plant species (desert, chaparral, and coastal salt marsh species, as well as two temperate tree and two crop species) for departures from this expectation and for two potential mechanisms
L. A. Donovan; M. J. Linton; J. H. Richards
Modeling of soil water content and soil temperature at selected U.S. and central European stations using SoilClim model
Within the presented study the SoilClim model was tested through various climatic and soil conditions. SoilClim model enables to estimate reference and actual evapotranspiration from defined vegetation cover and consequently the soil water content within two defined layers (named as Moisture control section I and II) could be deduced. The soil temperature in 0.5 m depth is also estimated (on
P. Hlavinka; M. Trnka; J. Balek; Z. Zalud; M. Hayes; M. Svoboda; J. Eitzinger
Negative pressure of stretched liquid water. Geochemistry of soil capillaries
NASA Astrophysics Data System (ADS)
Solution-mineral equilibria in the unsaturated zone above aquifers requires us to take into account the negative internal pressure of liquid water, distributed in fine pores of a partially filled medium. The proposed method affords calculation of the thermodynamic properties of capillary water by extrapolating their dependencies measured at positive pressures, into a negative pressure domain, finding supports from measurements already obtained on the stretched water. Besides Gibbs free energy, enthalpy, entropy, heat capacity, isobaric expansibility and isothermal compressibility of soil water, calculations of the dielectric constant, the water-air interfacial tension and the pH at neutrality have been established. This thermodynamic characterization of the water state in soils enables us to consider quantitatively the melting and boiling temperatures in soils or in fluid inclusions, the corresponding latent heat, or the lowering of the saturated vapour pressure in the unsaturated zone of weathering profiles. This pressure approach implies some reviewed consequences about solute species, gases and mineral solubilities, or still hydration-dehydration phenomena, in capillaries.
Mercury, Lionel; Tardy, Yves
Application of Boundary-Element Techniques for some Soil-Structure Interaction Problems.
National Technical Information Service (NTIS)
Boundary-element technique research performed to solve soil-structure interaction problems is the basis for this report. Specifically, it was designed to answer questionable situations for long hydraulic U-Lock structures erected on elastic soil. A review...
C. V. Vallabhan J. Sivakumar
Soil physical properties, water depletion and crop development under traditional and conservation tillage in southern Spain
Tillage methods affect soil physical properties and, thus, have a direct influence on the replenishment and depletion of soil water storage and crop performance. This study was conducted to determine the effects of traditional and conservation tillage on soil physical properties, soil water replenishment and depletion, and crop development and yield under southern Spanish conditions. The experiments were carried out
F. Moreno; F. PelegrĒn; J. E. Fernßndez; J. M. Murillo
Financial efficiency of major soil and water conservation measures in West Usambara highlands, Tanzania
Soil and Water Conservation (SWC) measures are needed to control soil erosion and sustain agricultural production on steep slopes of West Usambara mountains. However, the adoption by farmers of the recommended soil and water conservation measures is low and soil erosion continues to be a problem. It could well be that the reason for the low adoption is that the
A. J. M. Tenge; J. De graaff; J. P. Hella
A Manual on Conservation of Soil and Water. Appropriate Technologies for Development. R-38.
ERIC Educational Resources Information Center
In order to keep the land productive, a good conservation program is imperative. The primary purpose of soil and water conservation is to prevent soil erosion and heal its scars. This handbook explains the causes, processes, and consequences of soil erosion and depletion, and describes major soil- and water-conservation measures. This book wasģ
Peace Corps, Washington, DC. Information Collection and Exchange Div.
Influence of different plant species on water repellency in Mediterranean heathland soils
It is established that soil hydrophobicity reduces soil infiltration rates, and enhances runoff flow and soil erosion. Water repellency has been studied with special interest in coniferous and eucalyptus forests, particularly after burning, but the number of studies concerning Mediterranean heathlands is still very low. In this paper, we study the occurrence and persistence of water repellency in soil samples
Lorena MartĒnez-Zavala; Antonio Jordßn-L¾pez
Influence of soil-water ratio on the performance of slurry phase bioreactor treating herbicide contaminated soil.
The influence of soil-water ratio was studied on the performance of the slurry phase bioreactor operated in sequencing batch mode (anoxic-aerobic-anoxic microenvironments) during the bioremediation of soil contaminated with pendimethalin. The performance of the reactors was evaluated at different soil-water ratios (1:5-1:25; at soil loading rate (60 kg of soil/cum-day to 12 kg of soil/cum-day)) keeping the loading rate of pendimethalin constant (133.2 g/kg of soil-day) in six reactors and variable (66.6 g/kg of soil-day to 166.6 g/kg of soil-day) in other four reactors. At 1:20 soil-water ratio, the slurry phase system showed enhanced degradation of substrate (629 microg pendimethalin/g soil). The removal efficiency of pendimethalin in the reactors was dependent on the mass-transfer rates of the substrate from the soil to the aqueous phase. Soil-water ratio and substrate loading rates showed significant influence on the substrate portioning, substrate degradation efficiency and substrate desorption rate. PMID:17081747
Venkata Mohan, S; Ramakrishna, M; Shailaja, S; Sarma, P N
Experimental nitrogen, phosphorus, and potassium deposition decreases summer soil temperatures, water contents, and soil CO2 concentrations in a northern bog
NASA Astrophysics Data System (ADS)
Ombrotrophic peatlands depend on airborne nitrogen (N), whose deposition has increased in the past and lead to disappearance of mosses and increased shrub biomass in fertilization experiments. The response of soil water content, temperature, and carbon gas concentrations to increased nutrient loading is poorly known and we thus determined these data at the long-term N fertilization site Mer Bleue bog, Ontario, during a two month period in summer. Soil temperatures decreased with NPK addition in shallow peat soil primarily during the daytime (t-test, p<0.05) owing to increased shading, whereas they increased in deeper peat soil (t-test, p<0.05), probably by enhanced thermal conductivity. RMANOVA suggested interactions between N and PK addition in particular soil layers and strong interactions between soil temperatures and volumetric water contents (p<0.05). Averaged over all fertilized treatments, the mean soil temperatures at 5 cm depth decreased by 1.3 ░C and by 4.7 ░C (standard deviation 0.9 ░C) at noon. Water content was most strongly affected by within-plot spatial heterogeneity but also responded to both N and PK load according to RMANOVA (p<0.05). Overall, water content and CO2 concentrations in the near-surface peat (t-test, p<0.05) were lower with increasing N load, suggesting more rapid soil gas exchange. The results thus suggest that changes in bog ecosystem structure with N deposition have significant ramifications for physical parameters that in turn control biogeochemical processes.
Wendel, S.; Moore, T.; Bubier, J.; Blodau, C.
Effects of corn stalk orientation and water content on passive microwave sensing of soil moisture
NASA Technical Reports Server (NTRS)
A field experiment was conducted utilizing artificial arrangements of plant components during the summer of 1982 to examine the effects of corn canopy structure and plant water content on microwave emission. Truck-mounted microwave radiometers at C (5 GHz) and L (1.4 GHz) band sensed vertically and horizontally polarized radiation concurrent with ground observations of soil moisture and vegetation parameters. Results indicate that the orientation of cut stalks and the distribution of their dielectric properties through the canopy layer can influence the microwave emission measured from a vegetation/soil scene. The magnitude of this effect varies with polarization and frequency and with the amount of water in the plant, disappearing at low levels of vegetation water content. Although many of the canopy structures and orientations studied in this experiment are somewhat artificial, they serve to improve understanding of microwave energy interactions within a vegetation canopy and to aid in the development of appropriate physically based vegetation models.
Oneill, P. E.; Blanchard, B. J.; Wang, J. R.; Gould, W. I.; Jackson, T. J.
Soil erosion-vegetation interactions in Mediterranean-dry reclaimed mining slopes
NASA Astrophysics Data System (ADS)
Mining reclamation in Mediterranean-dry environments represents a complex task. Reclaimed mining slopes are particularly vulnerable to the effects of accelerated soil erosion processes, especially when these processes lead to the formation of rill networks. On the other hand, encouraging early vegetation establishment is perceived as indispensable to reduce the risk of degradation in these man-made ecosystems. This study shows a synthesis of soil erosion-vegetation research conducted in reclaimed mining slopes at El Moral field site (Teruel coalfield, central-east Spain). Our results highlight the role of rill erosion processes in the development of reclaimed ecosystems. Runoff routing is conditioned by the development of rill networks, maximizing the loss of water resources at the slope scale by surface runoff and altering the spatial distribution of soil moisture. As a result, the availability of water resources for plant growth is drastically reduced, affecting vegetation development. Conversely, vegetation exerts a strong effect on soil erosion: erosion rates rapidly decrease with vegetation cover and no significant rill erosion is usually observed after a particular cover threshold is reached. These interactive two-way vegetation-soil erosion relationships are further studied using a novel modeling approach that focuses on stability analysis of water-limited reclaimed slopes. Our framework reproduces two main groups of trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. This stability-analysis also facilitates the determination of threshold values for both vegetation cover and rill erosion that drive the long-term reclamation results, assisting the identification of critical situations that require specific human interventions to ensure the long-term sustainability of the restored ecosystems.
Moreno de las Heras, Mariano; Merino-MartĒn, Luis; Espigares, TĒscar; Nicolau, Josķ M.
Gravity factor of the formation of the field and capillary water capacities in soils and artificial layered soil-like bodies
The water retention capacity of soils characterizes a quasiequilibrium between the forces retaining and removing the soil water. It has been studied under field and laboratory conditions. It is shown that the gravity factor, as well as the soil particle-size distribution and structure, has an important role in determining the soil water capacity after the outflow of gravitational water. Our
A. V. Smagin; G. M. Khakimova; D. A. Khineeva; N. B. Sadovnikova
Passive regulation of soil biogeochemical cycling by root water transport
NASA Astrophysics Data System (ADS)
Surface and subsurface moisture dynamics are strongly influenced by the ability of vegetation to take up and redistribute soil moisture using hydraulic redistribution (HR). These dynamics in turn affect soil biogeochemical cycling through controls on decomposition and mineralization rates and ion transport. The goal of this study is to explore this coupling between HR and biogeochemistry using a numerical model. We examine decomposition and mineralization of organic matter and analyze whether differences in decomposition rates induced by HR influence the long-term storage of carbon in the soil and the movement of nitrate (NO 3-) and ammonium (NH 4+) in the rhizosphere. These dynamics are studied in a framework that incorporates the interaction between multiple plant species. The net effect of HR on decomposition is controlled by a trade-off between the resultant moisture and temperature states. This trade-off is conditioned by the availability of fine roots near the surface, and it impacts the long-term storage and vertical distribution of carbon in the soil. HR also impacts the transport and uptake of ions from the soil. It reduces the leaching of nitrate considerably, and, therefore facilitates the uptake of nitrate by vegetation roots. Furthermore, the magnitude and patterns of the feedbacks induced by HR are also influenced by the presence of different plant species that coexist. These results suggest that the alteration of soil moisture by plants through associated processes such as HR can have considerable impact on the below-ground biogeochemical cycling of carbon and nitrogen.
Quijano, Juan C.; Kumar, Praveen; Drewry, Darren T.
Maize canopies under two soil water regimes
The degree of coupling between the plant canopy and the atmosphere is indicative of the ability of the two systems to exchange momentum, energy, and mass. In terms of water vapor and CO2 exchange, it characterizes the extent to which stomatal and canopy conductance may control transpiration and CO2 assimilation. In the present work, the degree of coupling of maize
Pasquale Steduto; Theodore C Hsiao
Subcritical Water Extraction of Amino Acids from Atacama Desert Soils
NASA Technical Reports Server (NTRS)
Amino acids are considered organic molecular indicators in the search for extant and extinct life in the Solar System. Extraction of these molecules from a particulate solid matrix, such as Martian regolith, will be critical to their in situ detection and analysis. The goals of this study were to optimize a laboratory amino acid extraction protocol by quantitatively measuring the yields of extracted amino acids as a function of liquid water temperature and sample extraction time and to compare the results to the standard HCl vapor- phase hydrolysis yields for the same soil samples. Soil samples from the Yungay region of the Atacama Desert ( Martian regolith analog) were collected during a field study in the summer of 2005. The amino acids ( alanine, aspartic acid, glutamic acid, glycine, serine, and valine) chosen for analysis were present in the samples at concentrations of 1 - 70 parts- per- billion. Subcritical water extraction efficiency was examined over the temperature range of 30 - 325 degrees C, at pressures of 17.2 or 20.0 MPa, and for water- sample contact equilibration times of 0 - 30 min. None of the amino acids were extracted in detectable amounts at 30 degrees C ( at 17.2 MPa), suggesting that amino acids are too strongly bound by the soil matrix to be extracted at such a low temperature. Between 150 degrees C and 250 degrees C ( at 17.2 MPa), the extraction efficiencies of glycine, alanine, and valine were observed to increase with increasing water temperature, consistent with higher solubility at higher temperatures, perhaps due to the decreasing dielectric constant of water. Amino acids were not detected in extracts collected at 325 degrees C ( at 20.0 MPa), probably due to amino acid decomposition at this temperature. The optimal subcritical water extraction conditions for these amino acids from Atacama Desert soils were achieved at 200 degrees C, 17.2 MPa, and a water- sample contact equilibration time of 10 min.
Amashukeli, Xenia; Pelletier, Christine C.; Kirby, James P.; Grunthaner, Frank J.
Reliability analysis of shearwall structure with soil structure interaction
The reliability assessment of a site-dependent structural system under seismic environment is studied in this report. The stiffness parameters of the system (soil as well as structure) are considered as random variable. The random distribution of modal frequencies are obtained. A new response spectral density function is defined which include the effect of randomness of the model frequencies. A stationary random process is used to simulate the seismic excitation load along with the random operational loads. The random vibration analysis in frequency domain is used to obtain the statistical properties of the dynamic res