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In the Italian Alps, local climate, topography and soil play a dominant role in pasture distribution. In this study, pre-existent layers of spatial data were used to identify the geographical locations of the main pasture communities (macrotypes) dominating these mountainous areas and to characterize them environmentally. The influence of the environment on macrotype distribution was assessed by principal component analysis (PCA) and a kernel density estimation (KDE) on nine explanatory variables extracted from soil–topography–climatic gridded maps. Results indicated the reliability of the method. The ecological description disentangled from PCA and KDE analysis fitted well with the ecological exigencies of seven macrotypes, identified as most representative in terms of their extent, ecological and pastoral importance across the Alps. This was more evident for high-altitude communities and xeric species, but less evident for the more ubiquitous, mixed or fragmented macrotypes. The results show that three main environmental regions can be distinguished across the area: a relatively wet and cold region located at the highest altitudes dominated by mountainside pasture macrotypes; an intermediate area comprising macrotypes without any marked environmental needs; and relatively dry and warm areas at the lowest altitudes dominated by xeric species and rich semi-natural grasslands. Method strengths, weaknesses and possible applications of the results are discussed.
Efficient soil P cycling is essential for promoting optimal and sustainable grassland growth. The soil biological community is regarded as an important source of available P to the plant community. However, the effects of P fertilization on the soil biota are unclear. This study aimed to investigate the effects of P fertilization on plant and soil biological communities in two intensively managed grassland sites that had been receiving mineral-based P fertilization over a 14-year period. Both pastures had been frequently cut and harvested for plant material and had received only inorganic fertilizers from the establishment of the trial. Both sites were sampled four times from October 2009 to April 2011 and plant and a range of soil biological parameters were determined at each sampling period. The main findings of this study showed that soil chemical measures, such as labile inorganic P and total P concentrations, and plant yield and P contents responded as expected to P fertilization. However, all soil biological parameters either showed no response or inconsistent responses to P fertilization over the experimental period. This study indicates that intensive management regimes, for example intensive plant harvesting and fertilizer regimes, appear to override the relationship between plant and soil biological communities with respect to their response to P fertilization, and thus their productivity is apparently not predicated upon biotic activity.
Atmospheric carbon dioxide (CO2), global mean temperature and interannual variability in temperature and rainfall are expected to increase significantly by the end of the 21st century. To review the effects of these factors on forage quality, we carried out a meta-analysis of climate manipulation experiments. The first notable result was a lack of effect of elevated CO2 on structural carbohydrates and digestibility. Elevated CO2 increased the total non-structural carbohydrates of forage tissues by an average of 25% and decreased forage nitrogen (N) content by 8%. Increased legume abundance in multispecies swards can, however, maintain N concentration in the harvested biomass. There were no consistent effects of warming on contents of N, water-soluble and structural carbohydrates, or on digestibility. We highlight the continuum in the effect of water availability, from drought to irrigation, with a curvilinear increase of forage N as water availability decreased. Digestibility increased, on average, by 7% with drought, but with strong experimental variations. The review places special emphasis on discussion of the specificities of mountain and Mediterranean grasslands, the former being limited by low temperature, the latter by drought and heat. Elevated CO2 decreased forage N content in mountain areas and in temperate plains alike. It increased N content by an average of 3% in Mediterranean areas; this could be due to shifts in vegetation communities under elevated CO2 or to a greater concentration of N in plant tissues under drought conditions. Further experiments are needed to investigate the effects of combined factors, including extreme climatic events.
Perennial ryegrass (Lolium perenne L.) evaluation trials are often conducted under simulated grazing to identify the most productive cultivars. It is unclear whether simulated grazing identifies the most productive cultivar for animal-grazed swards. Ten cultivars were established as plots and managed concurrently under simulated grazing (SG), animal grazing (AG) and conservation (CON). The experiment lasted 3 years with dry-matter (DM) off-take, digestibility, tiller density and ground-cover score recorded in all years. A good relationship existed between DM off-take under SG and CON (R2 = 0·73). The relationship between SG and AG was strongest in year 2 and 3 (R2 = 0·53 and 0·55 respectively). High DM production was observed in SG swards in year 1; this was weakly related to the DM production of the AG sward. Across the 3 years, the CON treatment had higher yields than either of the other two treatments and was poorly correlated to DM yield under AG, confirming that cultivars should be evaluated under a similar defoliation frequency to their intended use. Tiller density declined quickest under CON and slowest under AG. Some reranking of cultivars occurred between defoliation managements. The results show that simulated grazing is a useful indicator of DM yield performance of animal-grazed swards.
Above-ground net primary production (ANPP) and precipitation-use efficiency (PUE) are key factors that can clarify the response of grassland ecosystem carbon and water cycles to ongoing climate change. The variations of ANPP and PUE were analysed based on long-term in situ observations of a species-rich alpine meadow in the north-eastern Qinghai-Tibetan Plateau from 1981 to 2010. ANPP and PUE increased markedly over time. ANPP was significantly controlled by post-growing season length (from 1 September to the end of growing season in the previous year, R2 = 0·31, P < 0·01). Regression trees showed that air temperature during October of the previous year played a predominant role in ANPP annual variations. Results indicated that a strong thermal-lagging effect on ANPP variations was present in the alpine meadow ecosystem. ANPP variations were undetectable during wet, normal and dry years (P = 0·25). Our finding supported the hypothesis that temporal site-specific ANPP variations were less regulated by a single factor. The temporal PUE declined linearly with increasing annual precipitation, and the slope was obviously steeper than that of spatial patterns. More ANPP variability in an alpine meadow under warming conditions might occur via community transition in the north-eastern Qinghai-Tibetan Plateau.
Studies have shown that yield responses of grass leys to phosphorus (P) fertilization vary considerably and initial soil test P (STP) does not always predict such variation. To identify the sources of variation in dry-matter (DM) yield responses to P, we used a meta-analysis to review quantitatively 38 Finnish field experiments on various soil types and growth conditions and to develop yield-response models. The major sources of variation in the yield responses to annually applied P were soil type, soil acidity (for organic soils), initial STP and control yields fertilized with nitrogen (N) and potassium (K). According to Mitscherlich-type exponential models, the maximum yield increases due to P fertilization in the low-STP class were 18% over the control on mineral soils and 28% on organic soils. However, only about 40% of the variation in yield could be attributed to annual fertilizer P applications. Control yields explained about 25% of variation in yield responses to P fertilization, and P addition became less efficient with increasing control yields, which were associated with rising N rates. While applied P leads to infrequent or small yield responses on mineral soils, other practices to increase grass yields should be prioritized, including optimal N fertilization. On moderately acidic organic soils that show clearly lower P responses than do similar but less acidic soils, liming should be the first step to increase yields. Moreover, the models derived in this work indicate that revising P fertilizer recommendations in Finland would avoid unnecessary application at non-responsive STP levels.
Analysis of exposed silage face surface area was conducted to better understand and provide feed management recommendations as well as evaluate potential compliance needs related to volatile organic compound emissions. Policy was developed by the San Joaquin Valley Air Pollution Control District (District) to restrict exposed surface area of silage piles to 199·7 m2 per farm if only one pile was exposed or 399·5 m2 per farm if more than one pile was exposed. Exposed surface area on piles of silages at 20 dairies was quantified to determine impacts of these surface area restrictions. Herd size ranged from 490 to 7,200 milking cows, and the number of exposed piles ranged from one to four per farm as maize and/or wheat silage. Surface area of piles was quantified based on pile measurements and geometric shapes. The measured value was compared to the estimated value using the District 'online calculator'. The District calculator used inputs for base length and height with assumed constant relationships between base and top lengths. Five of 43 piles had >199·7 m2 of exposed surface area. Sixteen of 20 dairies with more than one exposed surface complied with the exposed surface area restriction. On average, the District calculator overestimated surface areas by 11·6% ± 14·8 (range −57·7 to 38·4%). Pile measurements and use of geometric shapes provide a more precise method to quantify exposed surface area. This will be of particular use for those operators who utilize the District calculator and find their exposed areas out of compliance.
Understanding the flowering cycles of perennial warm-season grass species may be very important to the design of management practices and breeding. However, developmental dynamics are not well understood. As most plant traits associated with flowering dynamics do not follow a normal distribution, the use of general linear models to describe and compare these variables might be misleading. The aims of this study were (i) to find a methodology to compare panicle accumulation curves and (ii) to estimate heritabilities for flowering curve attributes. Panicle counts were recorded during a complete flowering cycle on a diverse collection of dallisgrass (Paspalum dilatatum). We compared the efficiency of different linear mixed models based on whole plot or individual plant data; then, we adjusted nonlinear regression curves for individual plants to estimate several curve attributes and compared this approach to the area under the curve. Finally, we calculated the broad-sense heritabilities of the estimated curve parameters. The following reproductive curve attributes were obtained: panicle production potential, panicle accumulation rate and days until 3, 5, 10 and 15 panicles. We found that monitoring individual plants is more efficient when studying flowering attributes. Significant differences among genotypes for several flowering cycle attributes were found. Heritabilities were very high for all flowering cycle initiation and duration attributes. We also showed that the number of days until the emergence of a given low number of panicles can be used as a highly heritable measure to characterize flowering cycles.
Nitrate () leaching is an environmental and health concern. In grazed pasture systems, leaching primarily occurs beneath animal urine patch areas due to high nitrogen (N) loading and the inability of pasture plants to capture all of this N. This study investigated the relative importance of plant growth and root architecture to recover soil N. Herbage N recovery, dry matter (DM) yield and root architecture, following injections of 15N-enriched urea at different soil depths (5, 25 and 45 cm), were measured for Italian ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.) grown in soil monolith lysimeters (18 cm diameter × 70 cm depth) under simulated South Island, New Zealand winter temperature and light levels. Total herbage N uptake and DM yield were on average 24 and 48% greater in L. multiflorum than F. arundinacea respectively. Root length density (cm cm−3 soil) in the 5- to 25-cm-depth horizon was similar between species. In the 25- to 45-cm-depth horizon, F. arundinacea roots were found at higher densities than L. multiflorum. In the 45- to 65-cm-depth horizon, root length density was fourfold to ninefold higher for F. arundinacea than L. multiflorum, but N uptake efficiency was greater in L. multiflorum (0·48 mg 15N m−1 root) than F. arundinacea (0·09 mg 15N m−1 root). The results suggest that deep F. arundinacea roots are relatively inactive during the winter period and confirm that plant growth is more important than root architecture (e.g. deep roots) to recover soil N and ultimately reduce nitrate leaching losses.
Mediterranean dehesas are an archetypal example of high nature value farmland in Europe. To better understand the interactions between trees and grasslands in the conservation and management of the dehesa, we measured, over 3 years, the contribution of scattered trees to the diversity and biomass dry-matter (DM) yield of the herb layer and the relationship between the herb layer (biomass and diversity interaction) and the trees. The study was based on 135 subplots representing four aspects and three distances from fifteen trees selected randomly in a plot within a dehesa in central Spain. The specific questions were the following: (i) To what extent do trees affect biomass of the herbaceous layer? (ii) What is the relationship between herbaceous layer biomass and species diversity under the influence of trees? and (iii) What are the effects of trees and small-scale topography on the herbaceous diversity? Results differed between years depending on water availability. Legume and forb DM yields were highest at the edge of the tree crown and beyond the canopy. Species richness was positively related to legume DM yield, and both were higher at the bottom of the hillside, especially in dry conditions. Given the importance of tree influence on the biomass and diversity of grasslands, maintaining proper agroforestry management practices for trees and grasslands is important for conserving dehesa diversity and productivity under the conditions of high climatic and soil variability in Mediterranean dehesas.
Biochar and hydrochar application to soil holds promise for climate change mitigation. This study provides first insights into the nutrient concentration and removal of grassland vegetation after addition of various carbon compounds together with pig slurry. Four treatments: control (no carbon application), feedstock, hydrochar and biochar from Miscanthus x giganteus were applied at a permanent grassland site near Giessen, Germany. Changes in plant functional groups, biomass production and nutrition status were monitored over 2 years. Total biomass production was not affected by the carbon amendments. However, biochar favoured growth of forbs over grasses, while legume growth was increased by all carbon amendments. The initial nutrient concentrations of the carbon compounds were enriched according to their degree of carbonization, potentially providing nutrients to plants. The plant biomass from hydro- and biochar amended plots, added up over 2 years, exhibited higher potassium concentrations compared to biomass from feedstock and control plots. All carbon amendments led to lower sodium concentrations in total biomass, compared to the control. Uncarbonized feedstock led to increased manganese concentrations in total biomass, while the concentrations of all other heavy metals were not influenced by any carbon amendment, compared to the control. From a plant and animal nutritional point of view, none of the carbon amendments reduced grassland yield or fodder quality. The study suggests that hydrochar and, even more so, biochar may provide a source of potassium to plants.
Semi-natural grasslands (SNG) are considered as bioenergy resources, either for combustion or for biogas production. To provide information on the seasonal (June–August) dynamics of herbage quantity and chemical composition, we studied the effects of factors on the proportions of four plant functional groups, chemical composition and total biomass yield at twelve sites representing three Estonian SNG types. Biomass yield increased only in alluvial meadows with the largest contribution of sedges/rushes (39%). Grasses dominated in dry-to-mesic meadows (62%) and other forbs in wooded meadows (55%). Concentration of fibre was highest in grasses and sedges/rushes (682 and 645 g NDF kg−1), and lignin was highest in legumes and other forbs (103 and 113 g kg−1). Legumes contained more C and N (447 and 25 g kg−1) and grasses more Cl (1 g kg−1). The highest concentrations of Mg, K and ash were in other forbs (4, 18 and 80 g kg−1), and Ca in legumes (16 g kg−1). The results are discussed in the context of suitability of different functional groups and SNG types for bioenergy conversion. Grasses and sedge-/rush-rich biomass are considered suitable for methane production. Biomass harvesting in July and minimizing the problems with N and Cl during combustion need to be considered. Forb-rich biomass should be pre-treated before direct combustion.
Pasture legumes are important components of both mixed farming rotations and permanent pastures in temperate climates. Breeding of two widely sown pasture legumes, subterranean clover (Trifolium subterraneum L.) and French serradella (Ornithopus sativus Brot.), is constrained by the long generation cycle, typically enabling only one generation per year. We hypothesized manipulation of culture medium and conditions would enable the development of a laboratory-based protocol for in vitro reproduction in subterranean clover and French serradella. In vitro flowering and viable seed set was induced from both species. For subterranean clover, the most effective treatment was culturing on modified MS medium with 1 μm kinetin and 0·1 m sucrose under a 100 μmol m−2 s−1 light intensity and continuous photoperiod. For French serradella, culture on a hormone-free B5 medium with 5 mm NH4Cl and 0·1 m sucrose under a 100 μmol m−2 s−1 light intensity and 20 h photoperiod was optimum. It is expected this technique will have application in accelerating generation turnover within breeding programs, for the study of factors influencing flowering in pasture legumes, and for the propagation of valuable yet enfeebled plants such as embryo-rescued hybrids.
The aim of this work was to investigate whether neutral detergent fibre (NDF) and dry-matter digestibility (DMD) are related to tall fescue accumulated forage mass (AFM) and to assess the relevance of environmental variables to predict the nutritive value of tall fescue swards. Three experiments were carried out in Pergamino, Argentina. To obtain swards with different amounts of AFM, two N levels and two irrigation regimes were applied in the spring after sowing and the autumn of the next year. In spring and autumn, AFM, NDF and DMD were measured every 10–12 days. In spring, NDF increased from 503 to 604 g kg−1, DMD decreased from 684 to 558 g kg−1 and AFM increased from 0·64 to 2·82 t DM ha−1. In autumn, NDF decreased from 543 to 442 g kg−1, DMD increased from 591 to 681 g kg−1 and AFM increased from 0·35 to 1·10 t DM ha−1. The results show that the nutritive value of tall fescue through the year is not related to the accumulation of dry matter of the sward. Nutritive value is determined by the reproductive stage in late spring and early summer, the fate of photosynthates at different times of the year and the synthesis of non-digestible compounds.
The study aimed at evaluating an effective sterilization–inoculation technique to facilitate silage research on the effect of forage microflora on fermentation variables. The sterilization effect of heating at 60°C for 3 h + 103°C for 15 h was tested on samples of grass, grass–clover, white clover and maize, pre-dried at 60°C to a dry-matter (DM) content >900 g kg−1. The ensilability of treated samples, reconstituted to original DM concentration (250–390 g kg−1), was assessed by inoculation with microfloras extracted from the original samples. Microfloral inoculants were obtained by a combination of centrifugation (15 500 g for 40 min) and filtration (0·45 and 0·22 μm pore sizes) of the supernatant. The sterilization treatment effectively sterilized the forage samples but decreased water soluble carbohydrates by 49% and N buffer solubility by 22% and increased the acid detergent insoluble N proportion of total N by 53% (P < 0·05). The reconstituted silages had 18% less lactic acid, 20% less ethanol and 37% less ammonia-N (P < 0·05), but volatile fatty acids and 2,3-butanediol did not differ from the untreated silages (P > 0·05). Counts of lactic acid bacteria, enterobacteria, clostridia, yeasts and moulds in the two silage treatments were also similar (P > 0·05). It is concluded that, despite causing chemical and physical alterations, the sterilization–inoculation technique evaluated could be a useful tool for future studies on the effects of microflora on ensiling results.
Accurate estimation of grassland biomass has been a central focus due to its importance in ecosystem processes and carbon cycles. This study aimed to examine whether the performance of soil-adjusted vegetation indices for estimating above-ground green biomass was better than that of soil-unadjusted vegetation indices in arid and semi-arid grasslands. Above-ground green biomass in desert steppe of Inner Mongolia and corresponding moderate-resolution imaging spectroradiometer (MODIS) surface reflectance 8-day composite MOD09Q1 data were collected during late September of 2013. Results showed that soil-adjusted SAVI (soil-adjusted vegetation index), MSAVI (modified soil-adjusted vegetation index), OSAVI (optimized soil-adjusted vegetation index), TSAVI (transformed soil-adjusted vegetation index), ATSAVI (adjusted transformed soil-adjusted vegetation index) and PVI (perpendicular vegetation index) did not improve estimation accuracy over soil-unadjusted simple ratio (SR) and normalized difference vegetation index (NDVI), due to low green vegetation cover (<30%) in the study area. Our results suggest that these soil-adjusted vegetation indices may be not suitable for describing green vegetation information in arid and semi-arid grasslands with low green vegetation cover (<30%).
A nonlinear optimization model of a pasture-based dairy farm, located in the Waikato region of New Zealand, is used to provide an integrated analysis of profitable stocking-rate decisions for pasture-based dairy production, across a range of alternative milk and nitrogen fertilizer prices. Previous research has identified that operating profit increases either in a linear or concave fashion as stocking rate is lifted. This study shows that both views are relevant, depending on the magnitude of milk and nitrogen fertilizer prices. A lower milk price and/or higher per-unit cost for nitrogen fertilizer reduces profit at higher stocking rates, as the cost of maintaining a larger herd through pronounced feed deficits is magnified. In contrast to previous research, nitrogen fertilizer and imported supplement are shown to be highly complementary strategies under profitable farm management. Model output demonstrates that decreasing stocking rates to reduce leaching, in most cases, will impose a cost in terms of both production and profit. Overall, this work indicates the key importance of stocking-rate decisions to profitable grazing strategies, relative to those concerning milk per cow. Nevertheless, it is the inherent linkages between stocking rate and the multiple elements of a grazing system that infers this importance, highlighting the need to carefully consider all management levers.
A significant effect of year on maize nutritive value has been reported in many studies; however, the direct effect of year on both nutritive values and fermentation traits of maize silage has not been directly investigated. During a 7-year period (2006–2012), we investigated the following variables of 597 maize silages commercially produced in bunker silos on farms in the Czech Republic: dry-matter content (DM), crude protein (CP), starch, amylase-treated neutral detergent fibre (aNDF), acid detergent fibre (ADF) and net energy lactation (NEL), as well as fermentation traits such as pH, contents of lactic acid (LA), acetic acid (AA), butyric acid (BA) and the ratio between LA and volatile fatty acids. The effect of year and DM explained 16 and 30% of the variability in nutritive and fermentation traits respectively. Although a common silage DM content was used for each year, the climatic effect of year significantly changed almost all tested variables, but particularly aNDF, ADF, starch, AA and BA. The year contribution to trait variability effect was as much as two times higher for fermentation traits (12·6%) as for nutritive value (6·1%). Temperature–precipitation relationships associated with achieved maize yield were considered as factors explaining the year effect. Temperature and precipitation averaged over the full vegetation period had low relevance to nutritive and fermentation traits. This study reveals the importance of year-to-year variation in silage nutritive value and fermentation, which could be useful for understanding the contribution of year to these changes in both field experiments and national assessments.
Crop growth is related to radiation-use efficiency (RUE), which is influenced by the nitrogen (N) status of the crop, expressed at canopy level as specific leaf N (SLN) or at plant level as N nutrition index (NNI). To determine the mechanisms through which N affects dry-matter (DM) production of forage kale, results from two experiments (N treatment range 0–500 kg ha−1) were analysed for fractional radiation interception (RI), accumulated radiation (Racc), RUE, N uptake, critical N concentration (Nc), NNI and SLN. The measured variables (DM, RI and SLN) and the calculated variables (NNI, Racc and RUE) increased with N supply. RUE increased from 0·74 and 0·89 g MJ−1 IPAR for the control treatments to 1·50 and 1·95 g MJ−1 IPAR under adequate N and water in both experiments. This represented an increase in RUE of 52–146% for the range of N treatments used in both experiments, whilst Racc increased by 9–17%, compared with the control treatments. Subsequently, the total DM yield of kale increased from 6·7 and 8 t DM ha−1 for the control treatments to ≥ 19 t DM ha−1 when ≥150 kg N ha−1 was applied. The DM yields for the 500 kg N ha−1 treatments were 25·5 and 27·6 t DM ha−1 for the two experiments. RUE increased linearly with SLN, at an average rate of 0·38 g DM MJ−1 IPAR per each additional 1 g N m−2 leaf until a maximum RUE of 1·90 g MJ−1 IPAR was reached in both experiments. There were no changes in RUE with SLN of > 2·6 g m−2 and NNI >1, implying luxury N uptake. RUE was the most dominant driver of forage kale DM yield increases in response to SLN and NNI.
Acroceras macrum is a warm-season grass used for pastures, and it has high nutritive value. The scarce genetic and reproductive information about this grass is limiting its breeding for forage. The objective of this research was to determine the number of genotypes and cytotypes present in a collection established in Argentina, and to estimate the diversity of this species based on molecular markers, and morphological and agronomic characteristics. The number of genotypes among forty-seven accessions was determined using ISSR markers. The identified genotypes were further characterized for ploidy levels. In addition, the genetic distances among them were estimated with ISSR markers. They were also propagated and planted into the field following a randomized complete block design with four replications, and a group of sixteen morphological and agronomic variables were evaluated. A total of twenty-seven genotypes were identified in this collection; twenty-two genotypes were tetraploid (2n = 4x = 36) and five were hexaploid (2n = 6x = 54). These two cytotypes were found clearly separated by both genetic and phenotypic characteristics. Above-ground biomass, internode length, initial growth and number of spikelets per inflorescence were the most variable traits. The high diversity present in this collection will allow for the initiation of a breeding programme for A. macrum.
We evaluated the effect of row spacing on seed and forage yields in alfalfa (Medicago sativa L.) using combined seed and forage production plots, in an irrigated Mediterranean agricultural environment. We compared three row distances (20, 40 and 60 cm) in two cultivars at a seed rate of 25 kg ha−1 over a period of 4 years. We measured the seed yield and yield components as well as forage production. The 4-year average revealed an overall clean seed yield of 367 kg ha−1 declining over time, without significant differences in row distances. The number of shoots per square metre differed significantly as a function of row spacing, with averages of 357, 226 and 172 shoots m−2 for row widths of 20, 40 and 60 cm respectively. The row spacing did not affect the number of racemes per shoot (23·1), the number of pods per raceme (7·2), the number of seeds per pod (6·5) or the thousand seed weight (1·667 g). The average forage production was 20·1, 18·5 and 17·9 Mg DM ha−1 for row distances of 20, 40 and 60 cm, respectively, with higher yields associated with smaller row distances. Our data demonstrate that row spacing >20 cm does not confer any advantage to the production of alfalfa seed under irrigated Mediterranean agricultural conditions and that close spacing can significantly increase forage yields in the same environment.
A symbiosis between grasses and systemic fungal endophytes exists in both natural and agricultural grassland communities. Our objective was to examine the effects of systemic endophytes on the competitive ability of two agronomically important grass species: meadow fescue [Festuca pratensis (Huds.) syn. Schedonorus pratensis (Huds.) P. Beauv] and tall fescue [Festuca arundinacea (Schreb.) syn. Schedonorus phoenix (Scop.)]. Plants of meadow and tall fescue were grown for 48 days in replacement series of interspecific mixture with a legume (red clover, Trifolium pratense L.) in different nutrient environments in a greenhouse. Neither of the grass species gained endophyte-promoted competitive advantage over red clover in grass–clover mixtures. Endophyte infection increased the growth of meadow fescue monocultures by 89% compared to endophyte-free monocultures in high-nutrient soils, but plant competition or the cost of endophyte infection to the meadow fescue decreased the yield in resource-limited conditions. On average, endophyte-infected and endophyte-free meadow fescues produced 0·15 and 0·17 g, and 0·14 and 0·14 g dry biomass per plant in mixtures with red clover in high- and low-nutrient soils respectively. In contrast to meadow fescue, endophyte-promoted growth of tall fescue monocultures was not detected. Endophyte-infected and endophyte-free tall fescue monocultures produced 0·76 and 0·95 g biomass per pot, respectively, in the high-nutrient environment. Endophyte infection can increase the performance of the host grass, but the positive effects depend on the host species, the species composition and soil nutrient availability.
Dry grasslands are endangered habitats across Europe, and their restoration requires increasing attention, including their re-creation on arable land. We studied spontaneous colonization by eleven target species on thirty-five dry grassland sites restored with regional seed mixtures 1–13 years ago in the eastern part of the Czech Republic, a region where species-rich dry grasslands often occur in the vicinity of the restored grasslands. Occurrence of the target species (not sown in the restored grasslands) was quantified inside and outside each restored grassland up to distances of 100 and 500 m, and the distance to the nearest population outside was assessed. Data were processed using univariate (Spearman rank-correlation coefficient, generalized linear models) and multivariate (redundancy analysis) statistics. The establishment of all target species was closely related to their occurrence in the surroundings. Occurrence of species at a distance of up to 500 m, minimum distance to the nearest population and time since start of restoration significantly influenced the occurrence of all the species in the restored grasslands, while distance up to 100 m influenced all except two species. The most successful were wind-dispersed Cirsium canum and Inula salicina and, the least successful was the myrmecochorous Euphorbia virgata. Seeding regional seed mixtures may be considered an appropriate first step in the restoration of species-rich grasslands on arable land. Following diversification of the vegetation in restored grassland, spontaneous establishment of additional species may occur if the species occur in the vicinity. Results are discussed in the context of grassland restoration and agri-environmental objectives.
Two grazing experiments were conducted on non-irrigated tall fescue–subterranean clover and cocksfoot–subterranean pastures subject to summer-dry conditions in Canterbury, New Zealand, to measure the effect of low (8·3–10 ewes and their twin lambs ha−1) vs. high (13·9–20 ewes and their twin lambs ha−1) stocking rates (SR) on lamb and ewe liveweight gain in spring. In tall fescue–subterranean clover pasture, lambs grew faster at low (374 g per head d−1) than high (307 g per head d−1) SR, but total liveweight gain per ha was greater at high (12·3 kg ha−1 d−1) than low (7·5 kg ha−1 d−1) SR. In successive years in spring in cocksfoot–subterranean clover pastures, lambs grew faster at low (327, 385 g per head d−1) than high (253, 285 g per head d−1) SR but total liveweight gain per ha was greater at high (7·26, 7·91 kg ha−1) than low (5·43, 6·38 kg ha−1) SR. These studies indicate that in summer-dry areas, subterranean clover-based pastures will support high twin lamb growth rates in spring, with lower SR leading to higher lamb growth rates and more lambs reaching slaughter weights before the onset of dry conditions.
An investigation of eleven genotypes and two cultivars of Biserrula pelecinus L. (biserrula) was conducted in Western Australia to study their ecological and agronomic traits. All biserrula genotypes were productive in the 2 years of testing, with dry-matter production ranging from 3·5 to 4·9 t ha−1 and seed yield ranging from 314 to 1381 kg ha−1. Biserrula has high initial levels of hard seededness (95–100%) and a more gradual hard seed breakdown (68–92%) in summer. The high levels of hard seed decreased the seedling densities of biserrula in the second year, while were at highest levels in the third year after the plots were cropped to wheat. A further experiment was conducted to study the interaction between spray-topping and seed set. This study showed subterranean clover seed yields were more tolerant to herbicides than a number of biserrula genotypes. There were significant responses to the herbicides within the biserrula genotypes, and 95GCN59 was less affected. The rhizobium experiment showed a strong host strain/interaction and has emphasized the importance of simultaneous breeding and selection of plant germplasm run in parallel with the selection of elite strains of rhizobia such as WSM1497 to optimize nitrogen fixation.
The aim of this study was to reduce the breakdown of hybrid vigour by crossing maize × teosinte subspecies through induced tetraploidy and to improve the biomass and reproductive fertility of the induced tetraploids. To achieve this, seeds of maize breeding lines selected from an open-pollinated population 'Sargodha-2002' and a maize × teosinte cross were germinated in colchicine solution (0·25, 0·5 or 1·0%) until they had a thick radical and protruded plumule. Colchicine at 0·5% induced the highest number of tetraploids with the lowest number of chimeric plants. The induced tetraploids of maize and maize × teosinte crosses showed a significant (P ≤ 0·05) increase in leaf area (5 and 14%), total soluble solids (20 and 18%), leaf oil percentage (42 and 12%) and leaf crude protein contents (10 and 14%) in leaves relative to the diploid subspecies. Moreover, induced tetraploidy also arrested hybrid vigour by slowing down the decay of heterosis in progenies (4x) for plant height, leaf biomass and leaf oil percentage. Induced maize × teosinte hybrid tetraploids selected for frequent bivalent chromosome pairing resulted in higher seed setting cob−1 (increased 58%), pollen fertility (increased 59%) and seed setting percentage (increased 100%) than the quadrivalent variant.
The effects of boron (B) application on flower development, nectar production, germination and seed yield were investigated in organic seed crops of white clover grown in soils with <1 mg B kg−1. Application techniques of a liquid B product were studied in two field experiments in 2009–2011. Three rates of B application to the soil at sowing and three rates of B as a foliar application in the harvest year were compared with untreated control plots. None of the B treatments had a significant effect on seed yield, relative to the control. In one experiment, with a dense crop stand, the results indicated a small (10%) yield increase with B applied to the soil. Seed germination and B concentration of shoots, roots and seeds were unaffected by B application, although the soil concentration increased. In seeds with an average B concentration of 22 mg kg−1, 73% germinated as normal seedlings and 14% were assessed as hard seeds; corresponding values for seeds with an average B concentration of 17 mg kg−1 were 60 and 38% respectively. The results indicate the need for further studies of factors determining B uptake in white clover.
Alpine bluegrass (Poa alpina L.) is common in mountain areas, where it represents a valuable forage resource and is widely used for ecological restoration of disturbed landscapes. This study assessed the variation of germplasm from the Rhaetian Alps, Italy. Both seed production and morphology were examined for potential use in restoration projects and for conservation and selection purposes of local genetic resources. The effects of the ex situ growing site were also assessed in two altitude-contrasting sites. Individual populations harboured great phenotypic diversity for all traits, including seed yield, while variation among valleys of origin was less manifest. Noticeable site-specific population yield responses were observed, suggesting that the environment adopted for seed production may steer the choice of materials to be multiplied. The longer vegetative period in the lowland site, combined with environment-tailored agronomic practices, contributed to better plant growth, seed yield and survival compared to the mountain site, suggesting that seed production of this Alpine species could be feasible in a lowland environment when adequate inputs were provided. One valley (Valchiavenna) displayed high average levels of seed yield and plant vigour across growing sites, indicating its possible value as a source of germplasm suitable for resowing at high altitude.
The relevance of particular architectural characteristics for a good regrowth has not been elucidated yet in red clover. Here, we present the shoot architecture and regrowth of six red clover genotypes analysed under controlled and field conditions, with and without competition from perennial ryegrass. Among the genotypes investigated, Lemmon and Crossway displayed the highest number of nodes and branches, the highest increase in the number of nodes in the basal 7 cm and the highest outgrowth capacity of the nodes in this zone resulting in the highest dry-matter yields. Our results indicate that selecting genotypes with a high number of first-order branches, short internodes and the ability to resume growth from the nodes that remain in the uncut zone will allow the development of cultivars with good regrowth.
Soil occupation capacity via lateral expansion of tussocks in elephant grass (Pennisetum purpureum Schum.) may be associated with basal tillering. As grazing management alters the proportion of basal and aerial tillers in a tiller population, the hypothesis of this work was that grazing management affects tussock size and distribution with implications for plant population stability. The objective of this study was to evaluate the tiller population stability index, the proportion of basal and aerial tillers, tussock size, and the frequency of tussocks and bare ground in rotationally managed elephant grass cv. Napier. Treatments resulted from the combination of two post-grazing heights (35 and 45 cm) and two pre-grazing conditions (95% and maximum canopy light interception during regrowth – LI0·95 and LIMax) and were allocated to experimental units (850 m2 paddocks) according to a 2 × 2 factorial arrangement in a randomized complete block design, with four replications. Measurements were taken from January 2011 to April 2012. The post-grazing height treatments affected the tiller population stability index, but did not influence the pattern of tussock distribution. On the other hand, the different grazing frequencies (targets of LI pre-grazing) altered the pattern of tussock distribution and the proportion of bare ground. In general, the tiller population stability index and frequency of tussocks were higher and the frequency of bare ground lower on swards managed with the LI0·95 target relative to those managed with the LIMax target, regardless of the post-grazing height used, indicating a larger soil occupation capacity of plants under the more frequent defoliation regime. Such responses were associated with larger population of basal tillers and highlight the importance of tiller category and perennation pathway in defining patterns of plant growth and tussock distribution.
Developing sustainable grazing management systems based on perennial species is critical to preventing land degradation in marginal land classes. A field study was conducted from 2002 to 2006 to identify the impacts of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on herbage accumulation, soil seed reserve and nutritive value in a hill pasture in western Victoria, Australia. Three deferred grazing strategies were used: short-term deferred grazing (no defoliation between October and January), long-term deferred grazing (no defoliation from October to the autumn break) and optimized deferred grazing (withholding time from grazing commenced between annual grass stem elongation and seed head emergence and concluded in February/March). These treatments were applied with two fertilizer levels (with or without fertilizer at 50 kg phosphorus ha−1 and 2000 kg lime ha−1 applied in year 1 only) in a factorial arrangement and two additional treatments: continuous grazing (CG) and no grazing (NG) in year 1. The deferred grazing treatments on average produced herbage dry matter of 4773 kg ha−1, the NG produced 4583 kg ha−1 and the CG produced 3183 kg ha−1 in year 4 (2005–06) of the experiment. Deferred grazing treatments with and without fertilizer application produced an average of 5135 and 4411 kg DM ha−1 respectively. Averaged over 4 years, deferred grazing increased the germinable seed pool of perennial grasses by 200% and annual grasses by 50% (except optimized deferred grazing that considerably decreased the annual grass seed pool) compared with the CG. The best of the deferred grazing strategies increased the digestibility of pastures by 7% compared with the CG. The results demonstrated that deferred grazing from spring to autumn followed by rotational grazing could be an effective tool to increase herbage production and soil seed pool and improve the digestibility of native pastures in the steep hill country of southern Australia.
Drought stress is a major factor-limiting grass growth. The production of reactive oxygen species (ROS) increases under stress conditions and causes cell oxidative damage. This study investigated the effect of sodium nitroprusside [a nitric oxide (NO) donor] treatment on drought stress in two turfgrass species, creeping bentgrass and tall fescue. Physiological characteristics such as relative water content (RWC), ion leakage, chlorophyll and proline content, and activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) were evaluated after 40 d drought stress and in the recovery stage. Results showed that nitric oxide (NO) treatment, especially 150 μm, could maintain significantly higher RWC and reduce ion leakage under drought stress conditions in both species. Furthermore, both turfgrass species showed higher chlorophyll and proline content after drought stress period when sprayed with NO, while chlorophyll and proline content of control plants declined. Drought stress significantly reduced SOD and APX activity, while NO treatment induced higher SOD and APX activity under drought conditions. After recovery, leaf RWC returned to the control level; however, NO-sprayed plants showed higher RWC compared to controls. Both turfgrass species exhibited lower chlorophyll content at the recovery stage when exposed to severe drought stress, and NO application increased chlorophyll content compared to controls. No significant differences were found between NO treatment and control plants for proline and SOD activity, but APX activity of NO-sprayed plants was higher than in the control plants. These results suggest that foliar application of NO may alleviate drought stress in turfgrass by maintaining membrane stability and inducing antioxidant enzyme activity.
An experiment was conducted in inland northern New South Wales (NSW) to assess the response of tropical perennial grasses Chloris gayana (Rhodes grass) cv. Katambora and Digitaria eriantha (digit grass) cv. Premier and annual forage sorghum (Sorghum bicolor ssp. bicolor × S. bicolor ssp. drummondii hybrid) cv. Sweet Jumbo fertilized with five rates of nitrogen (N; 0, 50, 100, 150 and 300 kg N ha−1) and defoliated every 2 or 6 weeks over two growing seasons. Tropical perennial grasses were highly responsive to N fertilizer, while there was no significant response by forage sorghum. Herbage production of Rhodes grass increased linearly whereas digit grass had a high response at 50–100 kg N ha−1. Nitrogen-use efficiency was highest during the growing season when rainfall was higher. During this season, digit grass had the highest N efficiency (148 kg DM kg−1 N applied) at 50 kg N ha−1, and Rhodes grass (66 kg DM kg−1 N applied) at 100 kg N ha−1. Plant frequency of both perennial species increased and then stabilized at high levels (>84%, cell size 0·1 by 0·1 m) during the two growing seasons. Plant frequency of Rhodes grass declined over the winter period, but recovered within 6 weeks of commencement of the growing season. Soil nitrate levels indicated that unused nitrate moved down the soil profile during wet winters. Implications of leaching below the rooting zone are discussed.
Six dryland pastures were established at Lincoln University, Canterbury, New Zealand, in February 2002. Production and persistence of cocksfoot pastures established with subterranean, balansa, white or Caucasian clovers, and a perennial ryegrass-white clover control and a lucerne monoculture were monitored for nine years. Total annual dry-matter (10.0–18·5 t DM ha−1) and sown legume yields from the lucerne monoculture exceeded those from the grass-based pastures in all but one year. The lowest lucerne yield (10 t ha−1 yr−1) occurred in Year 4, when spring snow caused ungrazed lucerne to lodge and senesce. Cocksfoot with subterranean clover was the most productive grass-based pasture. Yields were 8·7–13·0 t DM ha−1 annually. Subterranean clover yields were 2·4–3·7 t ha−1 in six of the nine years which represented 26–32% of total annual production. In all cocksfoot-based pastures, the contribution of sown pasture components decreased at a rate equivalent to 3·3 ± 0·05% per year (R2 = 0·83) and sown components accounted for 65% of total yield in Year 9. In contrast, sown components represented only 13% of total yield in the ryegrass-white clover pastures in Year 9, and their contribution declined at 10·1 ± 0·9% per year (R2 = 0·94). By Year 9, 79% of the 6.6 t ha−1 produced from the ryegrass-white clover pasture was from unsown species and 7% was dead material. For maximum production and persistence, dryland farmers on 450–780 mm yr−1 rainfall should grow lucerne or cocksfoot-subterranean clover pastures in preference to ryegrass and white clover. Inclusion of white clover as a secondary legume component to sub clover would offer opportunities to respond to unpredictable summer rainfall after sub clover has set seed.
Feed intake and diet choice affect production efficiency in livestock. Plant waxes, in particular n-alkanes, have been used as markers to predict intake and diet preferences. Still, when n-alkane profiles of plants within mixed swards are similar, they alone may not produce reliable predictions. Including long-chain alcohols (LCOHs) may help. In this study, the reliability of predicting forage mixtures was assessed using n-alkanes and LCOH separately and in combination. Reliability was characterized as the regression of observed on predicted fescue proportion in forage mixtures and the Kulczyński similarity index. Two technicians performed extractions of n-alkanes and LCOHs of pure red clover and 'Fawn' tall fescue, and nine mixtures of them. The concentrations of n-alkanes C27, C29, C31 and C33 and alcohols C26-OH, C28-OH and C30-OH were compared among forage mixtures and between technicians. Technicians were consistent in their measures of n-alkanes (P > 0·12), but differed in their measures of C26-OH and C28-OH (P < 0·002). Longer-chained compounds were more consistently quantified. Forage delineations were not improved by C26-OH. With n-alkanes alone, estimated and actual fescue proportions closely agreed. Including LCOH offered no improvement. Despite variation in measured concentrations between technicians, fescue and red clover mixtures were reliably predicted using n-alkanes alone.
This study evaluated two potassium sorbate (PS) and sodium benzoate (SB) application rates in improving the aerobic stability of maize silage. Treatments included no additive, the addition of PS at 1 and 2 g kg−1 fresh matter (FM) and the addition of SB at 1 and 2 g kg−1 FM. Four replicates of each treatment were ensiled in 15-L plastic jars. The silages were analysed for their fermentative characteristics and were subjected to an aerobic stability test with pH and yeast and mould count measurements. Considering fermentation quality and aerobic stability, both additives were effective. The PS was more active against yeasts during aerobic exposure. When the additives were applied at 2 g kg−1, the silages were more stable (256 h, on average) than those with 1 g kg−1 (119 h, on average) and control (61 h). Aerobic deterioration was more pronounced in the controls than in the treated silages. Silages treated at 2 g kg−1 had consistent effects on pH values and yeast counts over 288 h of aerobiosis. Overall, PS and SB applied at 2 g kg−1 were more effective in improving aerobic stability.
Neither methodology nor guidelines are available for defining quality characteristics and storage conditions of seed material harvested from semi-natural grassland. Seeds from an Arrhenatherion meadow were harvested via on-site threshing and seed stripping. After determination of purity, thousand seed weight and pre-tests in a phytotron, germination-capacity trials were carried out in a greenhouse. The harvested seed material was stored for up to 3 years under different conditions: (i) room temperature 18–23°C, (ii) cooling chamber (2–5°C with 40–50% humidity) and (iii) freezer (−18°C). There was a significant impact of the tested harvesting methods on seed separation, thousand seed weight and purity, but not on the germination capacity. Different storage conditions and storage length significantly influenced the germination capacity. There were also generally higher germination values for the seed-stripping material than the on-site threshing material (ca. 70 and 60%, respectively, in the first year). Germination capacity decreased significantly with time and was <15% after 3 years. We conclude that harvested seed material from semi-natural grassland should preferably be stored under cool conditions and used within 2 years.
This study compared the forage quality of Festulolium entries of festucoid (Hykor) and loloid attributes (Felopa and Norwegian candivars) with major cultivars of the parent species perennial ryegrass and meadow fescue, and with timothy. Forage NDF, iNDF, kdNDF and DDM were analysed at vegetative stage, early heading, heading and anthesis during spring growth (SG) and two subsequent regrowths over two production years at two locations in Norway. NDF and iNDF increased and kdNDF and DDM decreased with advancing maturity, mostly expressed in SG, with negative correlations between DDM and NDF and iNDF and ADL, and strong positive correlations with kdNDF. In SG, across years and locations, the content of NDF at heading stage was 30% higher and iNDF 400% higher in stems than in leaves, while stem kdNDF was about 50% of that in leaves. In general, timothy cv. Grindstad and Festulolium cv. Hykor had the highest NDF and iNDF and the lowest kdNDF values. Loloid entries of Festulolium were quite similar to perennial ryegrass, although the tetraploid entry proved better than the others with respect to forage quality. Regarding nutritive value, the festucoid and loloid types of Festulolium should be considered separate groups. The effect of year was more pronounced than that of location, for which the ranking of entries was quite similar. Loloid Festulolium is prone to winter damage, and, although it has higher nutritive value than the parent species, its use will depend on the conditions for winter survival.
Understanding the morpho-physiological responses of forage plants is critical for successfully managing pastures; however, there is no specific method for morphogenetically assessing Arachis pintoi. The present study aimed to develop and validate mathematical models to estimate leaf area in A. pintoi to enable assessments of leaf elongation and senescence. Two experiments were performed. The first experiment used 500 A. pintoi leaves to model leaf area. Three models were used: correlation, mechanistic and empirical. A total of 336 leaflets were collected to validate the models. For the second experiment, 786 leaflet pairs were collected to test the leaf symmetry. Leaf length (L), width (W) and area (A) were measured for each leaflet in both of the experiments. The model identity test was used. The leaflet area can be estimated using the following formula: Â = W ×L × 0·25 × π. Experiment 2 showed that the initial leaflet pairs were equal, as were the terminal leaflet pairs. In conclusion, the mechanistic model should be used to estimate the leaf area for A. pintoi, and only half of each leaf can be measured.
Sainfoin is a non-bloating temperate forage legume with a moderate-to-high condensed tannin (CT) content. This study investigated whether the diversity of sainfoin accessions in terms of CT structures and contents could be related to rumen in vitro gas and methane (CH4) production and fermentation characteristics. The aim was to identify promising accessions for future investigations. Accessions differed (P < 0·0001) in terms of total gas and CH4 productions. Fermentation kinetics (i.e. parameters describing the shape of the gas production curve and half-time gas production) for CH4 production were influenced by accession (P ≤ 0·038), but not by PEG. Accession, PEG and time affected (P < 0·001) CH4 production, but accession and PEG interaction showed only a tendency (P = 0·08). Increase in CH4 due to PEG addition was not related to CT content. Further analysis of the relationships among multiple traits (nutritional composition, CT structure and CH4 production) using principal component analysis (PCA) based on optimally weighted variables revealed differences among accessions. The first two principal component axes, PC1 (57·6%) and PC2 (18·4%), explained 76·0% of the total variation among accessions. Loading of biplots derived from both PCAs made it possible to establish a relationship between the ratio of prodelphinidin:procyanidin (PD:PC) tannins and CH4 production in some accessions. The PD:PC ratio seems to be an important source of variation that is negatively related to CH4 production. These results suggested that sainfoin accessions collected from across the world exhibited substantial variation in terms of their effects on rumen in vitro CH4 production, revealing some promising accessions for future investigations.
We evaluated forage production patterns, weight gains and blood parameters when lambs (Ovis aries) and meat-goat (Caprus hircus) kids were finished on a mixed sward of cocksfoot (Dactylis glomerata L.), red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) with (SUP) and without (UNSUP) supplemental whole cottonseed (Gossypium hirsutum; WCS) in a replicated study. Botanical composition and energy/protein ratios of the sward varied with year and with time during the growing season. Swards had greater amounts of red clover relatively early and more cocksfoot later in the season. Suffolk (SX) lambs had the heaviest body weights, Katahdin (KA) lambs were intermediate, and meat-goat (GX) kids were the lightest at the end of each year. Overall body weight gain followed a trend of SX > KA > GX, and WCS supplementation increased weight gain for all animals by 18%. Only in 2008 did SUP animals have higher blood urea nitrogen levels, which may indicate less efficient use of dietary nitrogen when grazing grass–legume pastures managed for high nutritive value compared with UNSUP animals. Gossypol in WCS did not affect blood packed cell volume between SUP and UNSUP lambs and meat-goat kids. Suffolk lambs, Katahdin lambs and cross-bred Boer meat-goat kids finished on pasture with and without WCS supplementation produced desirable body weights for most ethnic markets in the USA.
Aerobic stability is an important feature in the evaluation of silages. The aims were to investigate the chemical and microbiological changes that occur in sugar-cane (Saccharum spp.) silage after aerobic exposure, to identify the major species of yeasts associated with the aerobic deterioration process and to select lactic acid bacteria (LAB) strains that can improve the aerobic stability of this silage. Fourteen wild LAB strains belonging to Lactobacillus plantarum, L. brevis and L. hilgardii were evaluated using experimental silos. Silage samples were collected at 0, 96 and 216 h after aerobic exposure to determinate the DM, WSC, pH, products of fermentation, to evaluate the silage temperatures and to identify yeast species associated with the aerobic deterioration of silage. The strains tested were able to modify the fermentative and chemical parameters and the diversity of yeasts species of silage after aerobic exposure. There was no association between the facultative or obligatory heterofermentative fermentation patterns and the increased aerobic stability of silage. Aerobic stability of sugar-cane silages was associated with high acetic acid and 1,2-propanediol concentrations. L. hilgardii UFLA SIL51 and UFLA SIL52 strains promoted an increase in aerobic stability of silage.
Forage plants constitute the primary food source for ruminants, and their aboveground growth and belowground growth depend on mineral nutrient supply. The objective of this study was to identify and quantify variation in morphology, production and nutritional status in Panicum maximum cv. Tanzânia and Stylosanthes guianensis cv. Mineirão grown with varying levels of S availability. In an experimental setting, plants of both species received rates of S calculated to reflect suboptimum, adequate and excessive levels of the element. S had a direct effect on morphology and production in both species. S limitation altered the allocation of photosynthates between the aboveground and belowground portions of Guinea grass and stylo, and was associated with lower root dry mass production. Guinea grass plants increased root surface area as an adaptive mechanism when S was limiting in the growth medium. The relative chlorophyll index of recently expanded leaves was correlated with aboveground dry mass production. After the initial growth, Guinea grass and stylo plants showed similar S requirements and use efficiency to achieve the maximum of aboveground productivity, although leguminous plants have a substantially higher capacity for store S in the shoot tissue as compared to gramineous plants growing under similar availability of S in the medium. While applying S was necessary for increasing dry mass production in both species, planting these species together is a promising strategy for guaranteeing high yields of forage with a nutritional value that satisfies the S requirements of ruminants.
Sloping fields on soils of shallow depth to tillage are commonly left uncultivated in many parts of the world. This study was conducted to compare the effects on morphological traits, dry-matter (DM) yield, legume ratio (LR), crude protein content (CP), crude protein yield (CP yield) and mineral concentrations (N, P, K, S, Ca, Cu, Fe, Mg, Mn, Na, B and Zn) of Hungarian vetch (Vicia pannonica Crantz.) and barley (Hordeum vulgare L.) grown in intercropping mixtures in response to three rates of organic solid cattle manure application (M0: 0, M1: 10, M2: 20 t ha−1). Experimentation was conducted on soils of two different soil depths [shallow (8–12 cm; low-medium erosion risk) and normal soil depth (18–22 cm; no erosion risk)] on a sloping field in the 2006–2007 and 2007–2008 growing seasons at Gumushane, Turkey. Herbage harvested on the shallow depth area had 22–73% less DM yield, 14–72% less CP yield, 6–9% greater CP content and generally higher minerals contents than herbage from the normal soil depth area. Cattle manure applications increased DM yield by about 23%, increased CP content and CP yield, and also increased the contents of most minerals in herbage of the intercropping mixtures, relative to the control, averaged over the two soil depths. It is suggested that, for areas with shallow soil depths that are prone to erosion, plant cover should be used for forage production, and that fertilization with solid cattle manure at 20 t ha−1 can support production of quality forage of acceptable DM yield.
Previous investigations have detected a directional trend in the normalized difference vegetation index (NDVI) of pastures around scattered paddock trees and identified shade from the tree as the most likely causal factor. This study uses a field experiment to quantify the effect of varying levels of shade on the above-ground biomass and NDVI of three grass species native to Australia (Microlaena stipoides, C3, shade tolerant; Austrodanthonia richardsonii, C3, prefers full sunlight, and Chloris ventricosa, C4, prefers full sunlight) in different seasons. The study demonstrates that shade had little influence on the above-ground biomass of C3 species but significantly reduced biomass in the C4 species. Until early winter, the NDVI of each species was generally significantly higher in all shaded treatments than in the no-shade treatment. This suggests that shaded plants retained a higher proportion of green biomass and/or changed leaf shape, increased leaf area and chlorophyll content. Regardless, although not proven in this experiment, it is likely shade prolonged the retention of green plant material into mid to late winter. Overall, this experiment explains the directional trends in NDVI around scattered trees found in previous work and suggests that shade from scattered trees prolongs green pasture production in a range of native grass species, without loss of C3 pasture biomass.
Little is known about the long-term effects of mineral N, P and K application on the nutritional status of mown alluvial grasslands. We asked how long-term fertilizer application affected soil chemical properties, plant species composition, herbage production, nutrient concentrations in soils and plants and balance of nutrients. Six treatments (control, PK, N50PK, N100PK, N150PK and N200PK) were investigated at the Černíkovice Experiment (Czech Republic) established in 1966 on an Alopecurus pratensis meadow, using annual application rates of 50, 100, 150 and 200 kg N, 40 kg P and 100 kg K ha−1. Data were collected and analysed for 2007, 2008 and 2009. Although fertilizers had been applied over 45 years, differences in soil chemical properties between fertilization treatments were small. The legumes Lathyrus pratensis and Trifolium repens responded highly positively to PK application, and tall grasses, A. pratensis in particular, to NPK application. Herbage quality was high in terms of content of major nutrients, and its chemical properties varied considerably between treatments, cuts and years. Mean annual herbage yield ranged from 6·1 in the control to 9·7 t ha−1 in the N200PK treatment. Herbage production was N-limited in 2007 and 2009, but not in 2008. Seasonal N agronomical efficiency ranged from 4·2 to 22·9 kg of DM herbage per kg of applied N. The herbage N:P and N:K ratios did not reflect the actual response of herbage production to N application. A negative balance between N applied and N removed in harvested herbage was recorded in all treatments. We concluded that in highly productive alluvial grasslands, mineral-rich soils can respond weakly to N, P and K application, fertilizer application modifies plant species composition and herbage production is not N-limited in all years. Nutrient ratios must be interpreted with caution for the estimation of nutrient limitation.
Artificial grassland establishment has been implemented in the alpine region of Qinghai–Tibetan Plateau in China as a mitigation tool against grassland degradation, one of the major environmental problems in this region. We hypothesized that both grassland degradation and artificial restoration may alter the reproductive modes of the alpine vegetation at the levels of individual species as well as plant functional groups. By investigating a long-term field study of grassland degradation and artificial restoration experiments, we found that alpine plants can maintain a highly plastic relationship between sexual and asexual reproduction, that is, the alpine plants in degraded grasslands increased their efforts towards sexual reproduction while those in artificially restored grasslands promoted their efforts in vegetative reproduction with in the year after restoration. The high reproductive plasticity of the alpine plants can be regulated through a number of mechanisms, which include changing proportion of clonal species in the plant composition, altering number ratio of sexual and vegetative propagules, shifting biomass allocation for sexual and vegetative reproduction at both individual species and functional group levels. These conclusions demonstrate how crucial it is to consider manipulation of reproductive modes needed to restore the structure and stability of degraded alpine grasslands.
The current promotion of larger areas of lucerne (Medicago sativa) production on the Loess Plateau in China prompted this study, which investigated lucerne harvesting practices by farmers and the scope for improved harvest yield and quality by optimizing harvest date, interval and height above ground. On-farm surveys were conducted to document the dominant harvesting practices used by farmers and their perceptions of barriers to adoption of alternative harvesting practices. In districts with less emphasis on livestock, less labour and inadequate facilities to store conserved lucerne, smaller areas of lucerne are grown and it is often harvested daily to meet demand from penned livestock. The consequence is that much of the lucerne is harvested either before or after flowering, resulting in suboptimal yield of biomass and crude protein. Field experiments conducted at low and high rainfall locations on the Loess Plateau over three seasons showed that delaying the start to harvest until after mid-June (the date of first flowering), while not affecting total biomass harvested for the season, does reduce leaf biomass harvested and hence crude protein concentration and yield. Lower crude protein is a consequence of a decline in both leaf percentage in harvested biomass and stem nitrogen concentration. Commencing harvests well before flowering with short (3 week) harvest intervals also penalized total and leaf biomass harvested. Raising cutting height from ground level (current farmer practice) to 50 mm (likely with the advent of mechanized harvesting) did not penalize harvested total or leaf biomass.
Perennial ryegrass pastures are the main feed for dairy cows in temperate regions. Alternatives to increase farm sustainability such as naturalized pastures have been proposed, and only limited knowledge exists regarding their potential as a forage source for grazing dairy systems. A field study was undertaken between September 2006 and September 2009 in Valdivia, Chile, to assess the effect of three pasture renovation strategies [naturalized fertilized (NFP); cultivated fertilized Lolium perenne and Trifolium repens mixture (RGWC); and cultivated fertilized Bromus valdivianus, Dactylis glomerata, Holcus lanatus, Lolium perenne and Trifolium repens mixture (MIXED)] over a naturalized degraded pasture on herbage production, botanical change and chemical composition. The three renovation strategies increased total herbage accumulation. During 2007–2008 and 2008–2009, the naturalized fertilized pasture produced similar amounts of dry matter as the cultivated fertilized mixtures. A higher grazing efficiency (the proportion of total herbage mass accumulation, removed by grazing dairy cows) was estimated for NNFP, RGWC and MIXED. Fertilization and liming increased the proportions of Lolium perenne and Bromus spp. at the expense of Agrostis capillaris and Trifolium repens. In the cultivated mixtures, the amount of Lolium perenne tended to decrease over time. Crude protein concentration and digestibility tended to be higher for naturalized fertilized and perennial ryegrass–white clover pastures throughout the experiment. These results suggest that fertilization and liming of a low-producing naturalized pasture might be a sound alternative for pasture improvement.
The presence of a woody canopy in open oak woodlands affects not only the nutrition but also the species composition of the herbaceous community. Yet, the contribution of both effects (changes in nutrient concentrations and species composition) to total resources that are captured by the herbaceous community is not well understood. We assessed the mineral nutrition (N, P, K and Ca) of three herbaceous species and the herbaceous community as well as the species composition in contrasting microhabitats (beneath trees, beneath a leguminous shrub and in open spaces). Both trees and shrubs increased the nutrient concentrations of the herbaceous species that were studied, except for Taraxacum officinale. Their effects were less consistent when the entire community was considered and depended upon the nutrient being analysed. Species richness and N, P and K concentrations were positively associated, suggesting that more nutrients are captured by the herbaceous community as diversity increases. Our results suggest a close relationship between species composition and nutritional value at the community level that may explain the discrepancies observed between both levels of analysis (species vs. community). Thus, farm-level strategies based on the whole herbaceous community may overlook processes operating at the species level, which can be relevant to achieve sustainable management.
This study examined how sheep develop a learned aversion to the annual legume biserrula (Biserrula pelecinus L.). Merino sheep were grazed on paddocks sown with either (i) biserrula, (ii) biserrula + ryegrass (Lolium rigidum Gaud.), (iii) crimson clover (Trifolium incarnatum L.), (iv) crimson clover + ryegrass or (v) ryegrass, for 4 weeks. Relative preference (Chesson–Manly selection index) was determined by offering randomly ordered monoculture plots of the three forage species. The groups of sheep were then combined into a single group and grazed a paddock containing a monoculture sward of each plant type for 5 d. Relative preference of sheep was tested again after the completion of the combined grazing. The experiment was repeated at three stages of plant phenology: vegetative, reproductive and senesced. Relative preference for biserrula was lower in sheep that had grazed the paddock sown with only biserrula compared with sheep that grazed a combination of biserrula + ryegrass, at both the vegetative (α; −0·11 vs. 0·32) and reproductive (α; 0·18 vs. 0·63) stages. At each stage of phenology, when groups were combined and grazed together, preference for biserrula became uniform. This supported the hypothesis that sheep develop an aversion to biserrula when they graze a pasture containing biserrula. However, we concluded that the familiarity of sheep with biserrula did not result in low relative preference; rather, the aversion was more likely a response to the high proportion of this plant in their diet. Social facilitation may have enabled sheep to overcome rapidly the food aversion.
Nitrogen fertilizer is applied to supplement soil nitrogen supply to maximize forage brassica crop dry-matter production. However, nitrogen fertilizer applications in excess of that required to maximize growth result in potentially toxic nitrate–nitrogen (NO3–N) concentrations in grazeable plant tissues. Three experiments, two for forage kale at Lincoln (Canterbury) and one for forage rape at Hastings (Hawke's Bay) in New Zealand were grown under different rates of nitrogen (0–500 kg N ha−1) to determine the effect of different rates of nitrogen on NO3–N content of different plant parts of the crops. One of the kale experiments was grown with either full irrigation or no rain and no irrigation over summer, hereafter referred to as summer drought. The NO3–N concentration on a whole plant (weighted average) basis increased from 0·1 mg g−1 dry matter for the control plots to 2·30 mg g−1 for the 500 kg N ha−1 plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g−1 for the 200 kg N ha−1 plots for forage rape crops. However, NO3–N concentration increased with N supply under the summer-drought plots from an average of 0·33 mg g−1 when ≤120 kg N ha−1 was applied to 2·30 mg g−1 for the 240 kg N ha−1 treatments but was unaffected by N supply under irrigation. The NO3–N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments. The NO3–N concentration was highest at the bottom of the kale stem and decreased towards the top. We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha−1 under irrigation and adjusted lower N rates for regions prone to dry summers.
Plains rough fescue (Festuca hallii [Vasey] Piper) is an important forage grass species in the Northern Great Plains of Canada. Its seed is in demand for forage production and habitat restoration, but erratic seed production limits supply. A comprehensive understanding of factors influencing flowering and seed production in this species is needed. This study evaluated the morphological and phenological variation among six ecotypes of F. hallii from Saskatchewan and Manitoba. Seeds were germinated, and seedlings were grown in the field and then transplanted to a greenhouse in November. Plants not flowering in the greenhouse were vernalized under 5°C and 8-h light for 11 weeks. In a separate experiment, plants were subjected to temperature regimes of 15/5°C, 10/0°C and 5/−5°C with day-length treatments of 12 h, 8 h and a gradually changing daylength from 12 to 8 h respectively. This study demonstrated the existence of considerable variation in morphological and phenological characteristics, and in growth and vernalization requirements among ecotypes of F. hallii. Vernalization requirements were not met for the ecotype from the Moist Mixed Grassland Ecoregion when it was grown under common conditions, whereas ecotypes from other ecoregions were vernalized in at least one of the 2 years in the field experiment. Northern ecotypes tended to flower earlier after artificial vernalization treatments. Overall, 15/5 to 5/−5°C d per night temperature regimes with photoperiods between 12 and 8 h were effective in inducing flowering. The seed source of F. hallii should be regarded as an important consideration affecting its use, both for habitat restoration and for forage production.
Slurry injection into grassland has advantages as it decreases ammonia losses, but may harm grassland plants. In two field experiments, four different types of knife/tine equipment were tested on three different grassland species (monocultures of red clover, perennial ryegrass and red fescue), with or without added mineral nitrogen (N), but without slurry application. During 2 years, in two separate experiments, the injection treatments were applied in spring or in summer to different plots. Crop damage was assessed by a range of methods. It was concluded that both the timing and the design of the knife/injector equipment had a significant influence on yield when used in grassland, with the greatest decrease in yield after spring use. Mean total yield over 2 years (no treatment = 100) for timing and species, with N added, was 94 (vertical knife), 92 (vertical and horizontal knife), 96 (double disc tine) and 94 (tubulator tine). With no N added, the relative yield decrease caused by equipment was less. Red fescue seemed to be a little more sensitive than the other species at spring treatment in one of the 2 years. Leaf area index could be useful for measuring crop damage.
Tedera (Bituminaria bituminosa vars. albomarginata and crassiuscula) is a perennial pasture species with agronomic characters ideally suited to Mediterranean climates. Tedera seed has a period of after-ripening or primary dormancy typically lasting three months, which delays assessment and breeding of elite hybrid varieties. Temperature, chemical and mechanical methods were investigated in conjunction with in vitro culture to circumvent this dormancy period across a range of parental and hybrid genotypes. Temperature treatment of T5 (Tedera accession 5) and T48 (Tedera accession 48) alone was not sufficient to break dormancy (24.0% and 14.7% germination); however, when combined with soaking in gibberellic acid (GA3) and mechanical scarification resulted in 79.7% and 84.3% germination respectively. In an effort to further improve this result for valuable hybrid genotypes, we combined mechanical scarification with removal of seed coat after imbibition and in vitro culture on B5 medium until radicle emergence. This resulted in breaking dormancy from 96% to 100% of parent seeds and 100% of hybrid seeds. Hardening the germinated F1 or F2 seedlings 4 d after first transfer to in vitro culture resulted in 100% survival of plants to soil. This procedure is now used on a routine basis in the Australian tedera breeding programme.
The plant-trait-based method is powerful for assessing ecosystem services provided by species-rich grasslands, but its use presents difficulties for stakeholders involved in field studies. Therefore, we examined whether a simplified plant-functional-type method could overcome such difficulties. A total of 1287 grasslands, spread over eight regions, were characterized according to their environmental and management factors, eight indicator (including Ellenberg) values and abundance of five previously defined grass functional types (GFTs) differing in growth strategies (fast–slow, early–late). Four related plant-community-composition descriptors indicating forage services (forage production, digestibility, distribution of herbage biomass throughout the growing season and management flexibility) responded to environmental and management factors that are correlated to indicator values. Based on GFTs, cluster analysis defined vegetation types (VTs). Their relationships to environmental and management factors (or proxies of them), forage services and species richness were subsequently analysed. Of the thirteen VTs, four consisted mainly of GFTs with a dominant fast-growth strategy and three with a slow-growth strategy. These clusters were clearly related to two stress axes (temperature and nutrients). The other six VTs consisted of a mixture of both strategies and corresponded to intermediate levels of stress and disturbance. Although simplified, the method distinguished VTs that responded consistently to environmental and management factors and provides accurate indicators of forage services.
The grass plant comprises leaf, pseudostem, true stem (including inflorescence) and dead material. These components differ in digestibility, and variations in their relative proportions can affect sward quality. The objective of this study was to determine the change in the proportion and organic matter digestibility (OMD) of leaf, pseudostem, true stem and dead components of four perennial ryegrass cultivars (two tetraploids: Astonenergy and Bealey and two diploids: Abermagic and Spelga) throughout a grazing season. The DM proportions and in vitro OMD of leaf, pseudostem, true stem and dead in all cultivars were determined during ten grazing rotations between May 2011 and March 2012. There was an interaction between rotation and cultivar for leaf, pseudostem, true stem and dead proportions. In May and June, Astonenergy had the highest leaf and lowest true stem proportion (P < 0·05). From July onwards, there was no difference in leaf or true stem proportion between cultivars. Bealey had the highest annual mean OMD (752 g kg−1) and Spelga the lowest (696 g kg−1; P < 0·05). The OMD followed the order leaf > pseudostem > true stem > dead. Bealey had the highest combined leaf and pseudostem proportion 0·92, which explains why it had the highest OMD. In this study, the tetraploid cultivars had the highest leaf and pseudostem proportion and OMD. For accurate descriptions of a sward in grazing studies and to accurately determine sward morphological composition, pseudostem should be separated from true stem, particularly during the reproductive stage when true stem is present.
Utilization of long-chain alcohols (LCOH) as diet-composition markers in sheep consuming six diets composed of improved pasture species (Lolium perenne and Trifolium repens) with heather–gorse components (Erica spp., Calluna vulgaris and Ulex gallii) was evaluated. Twenty-four adult cross-bred sheep were housed in individual stalls. Diet composition was estimated from LCOH concentrations, combined or not with alkanes and long-chain fatty acid (LCFA) data using least-squares procedures. Prior to calculations, faecal concentrations were corrected using mean treatment (faecal recovery 1, FR1) recoveries and mean recoveries across diets (FR2). Estimates were compared with those obtained without faecal correction (FR0) and known values. Large differences between plant species and plant parts were found in LCOH patterns and total LCOH concentrations. LCOH provided complementary information to that given by alkanes and LCFA. Even-chain LCOH comprised the largest fraction, representing on average 0·894 of total concentrations. Faecal recovery was incomplete and tended to increase with carbon-chain length (CCL) in a curvilinear manner (FR = −7·872 + 0·580 × CCL − 0·010 × CCL2; P < 0·001; r2 = 0·752). Diet composition influenced (P < 0·001) LCOH recovery, although variability within (CV of 9·0%) and between (CV of 13·3%) diets was low. Accuracy of estimates was influenced (P < 0·001) by faecal-correction method and markers used, and the best estimate was obtained combining LCOH and alkanes. Improvement in estimate accuracy can be achieved if suitable correction of LCOH faecal concentrations is performed prior to calculations. Results indicated that LCOH showed lower dependence than alkanes and LCFA on the use of accurate faecal-correction data.
Seven forage types (diploid and tetraploid perennial ryegrass, Italian ryegrass and hybrid ryegrass, a low-input mixture of perennial ryegrass, cocksfoot, timothy and meadow fescue, a mixture of perennial ryegrass and white clover, and monoculture of red clover) were sown in late July 2004. Each received one of four rates of dairy cattle slurry in three annual applications by trailing shoe, which supplied average nitrogen (N) inputs of 0·0, 114·9, 204·8 and 301·2 kg N ha−1 annum−1. Treatments were cut either three or four times annually over four years. Average dry-matter yield (DM) response to slurry N was 15·6 kg DM kg−1 N. Lowest recovery of slurry N was in the second application each year (after first cut). The data suggest that slurry applied to Italian ryegrass, and also to swards containing legumes on soils with high phosphorus content, will produce a lower DM response to slurry N and result in a lower slurry N recovery than on swards of perennial ryegrass or cocksfoot-dominant low-input mixtures. Apparent recovery of slurry N was low at the second cut, especially when first-cut yields had been high. To maximize slurry N recovery, application to regrowths with potentially slow rates of growth or high legume content should be avoided.
Two experiments were conducted to examine the 'long-term' effect of feed space allowance and period of access to feed on dairy cow performance. In Experiment 1, three horizontal feed space allowances (20, 40 and 60 cm cow−1) were examined over a 127-d period (14 cows per treatment). In Experiment 2, 48 dairy cows were used in a continuous design (10-week duration) 2 × 2 factorial design experiment comprising two horizontal feed space allowances (15 and 40 cm cow−1), and two periods of access to feed (unrestricted and restricted). With the former, uneaten feed was removed at 08·00 h, while feeding took place at 09·00 h. With the latter, uneaten feed was removed at 06·00 h, while feeding was delayed until 12·00 h. Mean total dry-matter (DM) intakes were 19·0, 18·7 and 19·3 kg cow−1 d−1 with the 20, 40 and 60 cm cow−1 treatments in Experiment 1, and 18·1 and 18·2 kg cow−1 d−1 with the 'restricted feeding time' treatments, and 17·8 and 18·1 kg d−1 with the 'unrestricted feeding time' treatments (15 and 40 cm respectively) in Experiment 2. None of milk yield, milk composition, or end-of-study live weight or condition score were significantly affected by treatment in either experiment (P > 0·05), while fat + protein yield was reduced with the 15-cm treatment in Experiment 2 (P < 0·05). When access to feed was restricted by space or time constraints, cows modified their time budgets and increased their rates of intake.
A study was conducted on the effect of tropospheric ozone (O3) on soft brome (Bromus hordeaceus) and the modulation of its response by nitrogen (N). Two assays were conducted using open-top chambers (OTCs). Three O3 treatments were considered: filtered air, with concentrations below background levels (charcoal-filtered air), non-filtered air (NFA) that simulates ambient O3 concentrations, and unfiltered air to which 40 nL L−1 O3 above-ambient concentrations was added (NFA+), simulating elevated values recorded in natural areas of annual pastures in the Iberian Peninsula. Three N rates were used, simulating the increase in soil N through atmospheric deposition and excreta from livestock grazing. Ozone caused an augmentation in foliar senescence, whereas green biomass was not altered; consequently, an increased senescent/green biomass ratio was produced. A stronger O3 effect was detected in the second assay compared with the first. This was related to the estimated absorbed O3 fluxes, which were double the value calculated in the former. Increasing N input enhanced biomass production, but its effectiveness was greater in the first assay, under less-favourable weather conditions and lower plant growth. In the first assay, the O3 response was modulated by N availability, which mitigated the effects of O3 to medium concentration values. In the first assay, O3 reduced the aerial/subterranean biomass ratio, caused by a positive-trend effect on roots. Foliar concentration of lignin was increased by O3, and in vitro digestibility of aerial biomass and the plant cell wall fraction tended to decrease with increasing O3.
This study evaluated the effect of two fibrolytic enzyme products, applied at baling, on the chemical composition and digestibility of alfalfa hay. Three replicate bales of alfalfa hay (82% dry matter) were produced with the application of one of five treatments including an untreated control and one of two fibrolytic enzyme products (DYC and ECO), either applied alone or in combination with a ferulic acid esterase-producing bacterial additive. The enzyme products were applied on the basis of endoglucanase activity. The neutral detergent fibre (NDF) concentration and accumulated temperature after storage of hay produced using DYC- or ECO-based treatments were greater (P < 0·05) than untreated hay, except for hay bales produced using ECO alone. Bales produced using ECO-based treatments had a greater (P < 0·05) in vitro NDF digestibility compared with untreated bales. The application of fibrolytic enzymes at baling may potentially improve NDF digestibility without negatively affecting chemical composition or increasing aerobic deterioration. However, the effects of fibrolytic enzymes varied depending on the product applied. Combining ferulic acid esterase-producing bacterial additives with fibrolytic enzymes did not improve the nutritive value of hay after storage.
Pasture herbage is a major source of minerals for livestock in pasture-based production systems. Herbage mineral concentrations vary throughout the growing season, whereas mineral supplementation to livestock is often constant. The study objectives were to analyse the seasonal variation in herbage mineral concentrations in tall fescue [Schedonorus phoenix (Scop.) Holub]-based pasture with regard to beef cattle mineral requirements and to create a statistical model to predict variation in herbage mineral concentrations across the growing season. Pasture herbage was analysed from 12 grazing systems in Virginia to determine its mineral concentration from April to October of 2008–2012. The pasture herbage, grown without fertilization, contained adequate macronutrient concentrations to meet the requirements of dry beef cows through the growing season and the requirements of lactating beef cows in April. Phosphorus supplementation appeared to be unnecessary for dry beef cows given adequate concentrations in pasture herbage. A model using month of harvest, soil moisture and relative humidity explained 75% of the variation in an aggregated mineral factor. The 90% prediction intervals indicated that N, P, K, S and Cu concentrations could be predicted within 1·35, 0·08, 0·80 and 0·07% and 3·83 mg kg−1 respectively. Prediction of herbage mineral concentrations could help to improve livestock health, reduce costs to producers and limit nutrient losses to the environment.
This work analysed the regulatory structural mechanisms involved in the competitive interactions between the annual grass Bromus willdenowii Kunth. (BW = prairie grass) and the perennial C3 grass Dactylis glomerata L. (DG = orchardgrass) during pasture establishment. Four combinations of species (pure BW, pure DG, DG flanked by BW and BW flanked by DG plants), with and without winter nitrogen fertilization, were factorially arranged in a randomized complete block design. Data were recorded at two organization levels: tillers (three tiller age cohorts) and target plants. Annual neighbours caused a decrease in the number of living leaves in tillers of intermediate age of both species. This structural regulatory mechanism led to a decrease in tiller number per plant and, therefore, restricted the development of horizontal space occupation. Annual neighbours did not cause an increase in tiller size, measured as lamina length or pseudostem height, but decreased root biomass. As a consequence, annual neighbours did not lead the hierarchy in light capture, but limited species radical colonization and competitive ability for soil resources. Winter nitrogen fertilization only affected tiller size in older tillers. These findings emphasize the importance of the cultural decisions, as sowing densities and nitrogen fertilization, to optimize pasture floristic composition.
Beef cattle are major contributors of enteric methane (CH4) emissions in Canada. Feeding forages containing condensed tannins (CT) has been suggested as a means of reducing enteric CH4 emissions and improving production efficiency. Sainfoin (Onobrychis viciifolia) is one of the CT-containing legumes, which has also been recognized to have several additional beneficial properties. This study compared sainfoin silage (SS) and lucerne (Medicago sativa) silage (LS) with respect to animal performance, enteric CH4 production, abundance of selected rumen microbes and selected serum parameters in yearling steers during a Canadian winter. Sainfoin silage in our study contained approximately 12 g CT kg−1 dry matter (DM), a level which did not adversely affect silage palatability as steers fed SS experienced higher DM intake. However, animals fed LS and SS had similar body weight gain over the course of the trial. Feeding SS resulted in lower blood urea nitrogen concentrations and relative abundance of methanogenic archaea in rumen fluid. Yet, microbial population shifts fell short of exerting significant influence on enteric CH4 emissions. This study suggests that under western Canadian growing and animal-rearing conditions, sainfoin is not yet competitive with lucerne forage with respect to enteric CH4 emissions or animal productivity warranting further research and development.
Extending the grazing season through the production and utilization of high-quality forage is a key objective in grassland-based dairy production systems. Grazing swards to a low post-grazing sward height (PGSH) is a strategy for improving grass utilization. A grazing experiment conducted in Ireland investigated immediate and subsequent effects of PGSH on sward production, utilization and structural characteristics. Swards were grazed to 2·7 cm (severe; S1) or 3·5 cm (moderate; M1) from 10 February to 18 April 2010 (Period 1; P1). From 19 April, each P1 paddock was halved and grazed to either 3·8 cm (S2) or 4·8 cm (M2), until 30 October (Period 2; P2). The first grazing rotation was +7 d on S1 swards compared with M1 swards (45 d), due to greater herbage utilization (+0·22). Herbage production during P1 was not affected by PGSH but a severe PGSH during this period reduced subsequent herbage production: 13·9 (S1) vs. 15·5 t dry matter (DM) ha−1 (M1) by the end of the study. Leaf proportion was increased (+0·10) on S2 swards compared with M2 swards, but M2 swards produced 1·2 t DM ha−1 more herbage during P2. Despite the relatively lower level of sward utilization obtained from moderate grazing in P1 (3·5 cm) and P2 (4·5–5·0 cm), such levels of PGSH increased DM production while maintaining sward quality, compared with severe grazing (2·7 cm in P1 and 3·5–4·0 cm in P2).
Dallisgrass (Paspalum dilatatum Poir.) is a warm-season grass, native to South America. Its adoption as a pasture crop has been hindered by low seed germination and slow establishment. However, variability in germination behaviour for this species has never been systematically analysed. For Paspalum spp., dry-storage and moist cold or warm pre-conditioning treatments have been reported as effective for the relief or breaking of seed dormancy. In the present work, seed germination responses at 32°C were assayed for sixteen P. dilatatum genotypes, representing its known natural genetic variability, to two moist pre-conditioning treatments (at 5 and 20°C) and without pre-conditioning, and three seed storage periods (0, 3 and 6 months). Pre-conditioning at 20°C showed high germination percentages (>80%), with ratios equal to or higher than pre-conditioning at 5°C, suggesting that cold is not required to break dormancy. Longer storage times resulted in increases in germination responses for most of the genotypes, while other biotypes showed no effect. Biotypes Virasoro and Chirú showed a remarkably different behaviour with higher germination percentages of untreated freshly harvested seeds. Our results show that diversity for traits involved in seed germination exists among naturally occurring P. dilatatum genotypes and the characterization of these traits should be addressed during ecotype characterization and evaluation of potential domesticates of this species.
The increasing cost of commercial fertilizers and environmental problems associated with improper fertilization management have prompted the need to re-examine commercial N sources that can effectively supply N to pastures while minimizing N losses. This 3-year study evaluated the effects of selected N sources on bahiagrass (Paspalum notatum Flügge) responses, soil properties and N losses. Treatments consisted of a factorial combination of 6 N sources [(i) ammonium nitrate (AN), (ii) ammonium sulphate (AS), (iii) urea (U), (iv) urea treated with Agrotain (U + Agrotain), (v) SuperU and (vi) ammonium sulphate nitrate] and 3 N levels (0, 60 or 120 kg ha−1 year−1), replicated three times. Bahiagrass dry-matter yield (DMY), crude protein (CP) concentration, N uptake and recovery were not affected by N source, with the exception of AN that resulted in reduced DMY in 2010 compared with the other sources. Bahiagrass DMY, CP concentration, N uptake and recovery increased linearly as N levels increased. Nitrogen fertilization showed no effect on soil pH or soil N accumulation. Soil pore-water N concentrations from treatments fertilized with N were similar to the control plots indicating no threat to the environment. At the N levels evaluated in this study, selection of N source should be based on the fertilizer cost.
Livestock production is the main source of livelihood in the arid and semi-arid lands in Africa. However, desertification characterized by vegetation degradation and soil erosion is a major threat to the sustainability of land-based production systems. Native rangeland forage species Cenchrus ciliaris L. (Buffel grass/African foxtail grass), Eragrostis superba Peyr. (Maasai love grass) and Enteropogon macrostachyus (Hochst. Ex A. Rich.) Monro ex Benth. (Bush rye grass) have been used to combat desertification. The objectives of the study were to identify the best-suited native grass species to combat desertification in a semi-arid environment in Kenya and to identify the preferred grass species among the agropastoralists in the area. Percentage basal cover, plant densities and frequencies of the three grasses in pure stands and mixtures were estimated. Grass species preferences were through household survey and focus group discussion. Results showed a significant difference (P < 0·05) in plant densities and cover estimates: E. macrostachyus was ranked first; C. ciliaris and E. superba were ranked second and third respectively. The agropastoral farmers, however, preferred E. superba followed by C. ciliaris and E. macrostachyus, a reverse trend. These results suggest that the choice of grass species to combat desertification is influenced more by its contribution as a source of forage for livestock than its contribution for rehabilitation purposes.
Arundo donax L. (Poaceae), giant reed, is a rhizomatous shrubby grass that is cultivated in subtropical and warm temperate regions for a multitude of uses. Recently, it has been identified as a leading sustainable, non-food crop for lignocellulosic biofuels due to its low ecological and agronomic demands. Lack of cold hardiness may limit its diffusion into colder areas of the transition zone. The objectives of this study were to (i) quantify freeze tolerance (LT50) of cold-acclimated and non-acclimated Arundo donax L. plants using reproducible, controlled environment conditions, (ii) determine the effect of prolonged exposure to freeze stress on tolerance by keeping plants at a constant, sublethal temperature and (iii) study the relationship of non-structural carbohydrates (total soluble sugars, glucose, fructose and sucrose) and proline accumulation with cold hardiness. In vitro-propagated plants of the Honduran and Hungarian ecotypes of Arundo donax L. were chosen for this study. Cold acclimation treatment was imposed for 1 week using a controlled environment chamber set at 10°C and with a 12-h photoperiod of 200 μmol m−2 s−1 photosynthetically active radiation. Freeze tolerance ranged from −12·8°C (Honduran) to −16·4°C (Hungarian ecotype). In all the organs analysed, total soluble sugars significantly increased during cold acclimation, with concentrations between 1·8- and 4·7-fold higher than in non-acclimated plants. The higher concentrations of sugars and proline in cold-acclimated plants were positively associated with enhanced giant reed freeze tolerance (2·9°C lower). Our results confirm that during cold acclimation, metabolic changes related to increased freezing tolerance occur in giant reed.
Bromus auleticus is known for its qualities as forage but its domestication has limitations relating to seed production technology and farm-scale seed propagation. The effect of different combinations of population on the reproductive success and seed germination of a relict population of Argentina was studied. The tests used a population of Santa Fe (SF) as the recipient of pollen and three populations as donors (LP: La Pampa, ER: Entre Ríos and BA: Buenos Aires). Reproductive success was determined in plants from five pollination treatments: (i) (SFxSF), (ii) LP, (iii) ER, (iv) BA and (v) mixture of donor. Three temperature conditions were evaluated for germination: (i) 15°C, (ii) 28°C and (iii) alternating 15–28°C (12 h each). There were significant differences in reproductive success depending on the source of pollen. Seeds obtained from new genotypic combinations did not increase their weight in relation to the pollen donor. Germination behaviour was more affected by extrinsic factors (temperature) than by their genetic origin. However, under non-optimal germination conditions, seeds originating from new genotypic combinations showed a significant increase in germination percentage and germination rate. This work contributes additional knowledge to previous studies regarding the effect of pollen quality limitation on seed production and quality of B. auleticus. The results confirm the hypothesis that a mixture of genotypes from a diverse origin increases the quantity of flowers that become fruits and seed quality, which is of great importance to improved seed production and field establishment of B. auleticus.
Two additives (Silo Guard (SG) and propionic acid (PA)) were tested for their effects on the quality and aerobic security of sorghum–sudangrass hybrid silages (JC-1 and WC-2). Two sorghum–sudangrass hybrid varieties were harvested for ensiling without additives (CK) or after the following treatments: SG at 0·5% of fresh forage or PA at 0·5% of fresh forage, with three replicates per treatment. The addition of SG and PA both affected the fermentation quality and chemical composition of the silages by lowering pH and NH3-N/TN and increasing lactic acid, the LA/TA ratio, WSC and CP concentrations compared with the untreated silages. In vitro DM digestibility (IVDMD), in vitro NDF digestibility (IVNDFD) and in vitro CP digestibility (IVCPD) were increased by SG in the JC-1 silages and WC-2 silages. Both additives improved the aerobic stability of sorghum–sudangrass hybrid silages. Furthermore, the additives reduced the mould counts and the aflatoxin and zearalenone levels compared with the untreated silages following aerobic exposure. Therefore, ensiling two sorghum–sudangrass hybrid varieties resulted in high-quality silages. The addition of SG and PA improved silage quality, in vitro digestibility and aerobic security.
The morphogenetic responses of individual tillers and the composition of tiller populations throughout regrowth in response to all combinations of two post-grazing heights (35 and 45 cm) and two pre-grazing conditions (95% and maximum canopy light interception during regrowth – LI95% and LIMax) were studied in swards of elephant grass (Pennisetum purpureum Schum. cv. Napier) from November 2011 to April 2012. Swards were subjected to the same treatments from January 2011 until measurements began, to enable them to adapt to the defoliation regimes. Treatments were allocated to experimental units (850 m2 paddocks) according to a 2 × 2 factorial arrangement in a randomized complete block design, with four replications. The total number of tillers (basal + aerial) was similar for both LI pre-grazing targets. However, there was a change in the preferential growth pathway used by plants characterized by modification in the proportion of tiller classes in plant population. Swards managed with the LIMax target had a smaller population density of basal tillers and used the recruitment of aerial tillers as the main growth pathway. Although effective for maintaining stable rates of leaf elongation and senescence, such a strategy resulted in greater tiller death. Additionally, stem elongation, a consequence of the competition for light under those circumstances, resulted in differences in sward herbage mass and morphological composition with potential implications for herbage feeding value.