FIELD OF THE INVENTION 
     The present invention relates to an irrigation control system, and, more particularly, to a system and method for managing water and other substances in plant root zones. 
     BACKGROUND OF THE INVENTION 
     Irrigation has been practiced for thousands of years and not much has changed in how it is practiced. Irrigation had been limited to water movement by gravity, animal and human power, and then later windmills and steam engines were employed to move water as those technologies developed. The development of the internal combustion engine enabled by the use of steel and large dams having been enabled by the use of concrete has provided the reservoirs and the devices to move stored water great distances to be applied to fields. These technologies also enabled deep wells and pumps to draw water up from the depths of aquifers such as the Ogallala aquifer in the south central United States. Steel pipes carry the water to the ends of the fields for furrow irrigation or above the fields for pivot irrigation. These technologies have been in place since the 1960&#39;s. Water movement under human control was supplemented by automatic control in the 1970&#39;s and 1980&#39;s which is further enabled by developments in microprocessors and sensors which can provide a signal that a measured amount of water has been delivered to a certain point in the field or that a certain amount of water had been applied to the field. 
     Water control has evolved into field water management in the 1990&#39;s and early 2000&#39;s. Point monitoring and control of water became distributed control thanks to the development of wired and wireless networks and global positioning systems (GPS). Field data collection, weather data collection and site specific irrigation control could be performed at different locations. 
     What is needed in the art is a new and cost efficient method and apparatus for managing water. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fluid distribution control system that is dependent upon the need of a plant, based on a three-dimensional estimate of needs and for estimating those needs at a future time period. 
     The invention comprises, in one form thereof, a method for managing substances in a plant root zone, including the steps of providing a fluid distribution system, controlling the fluid distribution system, modeling the plant root zone, and distributing the substances thereto. The fluid distribution system is associated with an agricultural area. The fluid distribution system is controlled by way of a controller. The plant root zone is modeled for a plurality of locations in the agricultural area. The modeling step incorporates a desired three-dimensional distribution of the substances for each of the plurality of locations for a future time period. Substances are distributed to the plurality of locations by way of the fluid distribution system under control of the controller. The controller is dependent upon the desired three-dimensional distribution and the future time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative irrigation system illustrated in a perspective view thereof utilizing an embodiment of the control method and apparatus of the present invention; 
         FIG. 2  illustrates an agricultural area having zones in which the irrigation system of  FIG. 1  is utilized; and 
         FIG. 3  is a schematic illustration of an embodiment of components of the system and informational inputs used by an embodiment of the method of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and more particularly to  FIGS. 1-3  there is illustrated an irrigation system  10  having a movement system  12  and a distribution system  14  including pipes  16  and nozzles  18 . Although irrigation system  10  is illustrated as a pivot type of system other types of irrigation systems are also contemplated including, for example, drip tape irrigation as well as any other type. Irrigation system  10  moves across agricultural area  20  by way of movement system  12 . Distribution system  14  has water and other substance delivered through pipes  16  and out nozzles  18  under the control of a controller system  50 . As irrigation system  10  moves across various sub-areas  22  and crosses boundaries  24  different portions of irrigation system  10  are activated by activating individual nozzles  18  to respond to the three dimensional needs of the crops growing in agricultural area  20  in the different sub-areas  22  as irrigation system  10  moves in agricultural area  20 . As a nozzle  18  crosses a boundary  24 , control system  50  alters the output of that nozzle  18  to correspond to the particular need in the plant root zones of the particular sub-area. 
     Although sub-areas  22  have been shown having boundaries  24 , the representation shown in  FIG. 2  is for the ease of illustration and it is to be understood that the location of boundaries  24  may be separately established for both soil model  68  as well as crop model  72 . For example, one sub-area may be used for soil model  68  that corresponds to a particular soil makeup, and a different sub-area shape may be used for crop model  72  that is based on genetic and performance information  74  for the crop. Moisture sensors  64 , which may be located at some of the nodes, represented by the ‘+’ symbol in  FIG. 2 , may also contribute to the definition of boundaries  24  for either crop model  72  or soil model  68  since the models are effected by the three dimensional moisture distribution. Sub-areas  22  are fluid in that they are established based on inputs received by controller  52  and result in the selection of the amount of water  58 , the amount of substances  60 , the duration and flow rate delivered to a particular sub-area  22  by irrigation system  10 . 
     Control system  50  includes a controller  52 , a user interface  54  and a valve system  56  that receives water from water source  58  and other substances  60  that are then sent by way of valve system  56  to distribution system  14 . Substances  60  may include nutrients, herbicides, pesticides, fungicides, nematicides, salt, minerals, dyes or other fluid borne or dissolved elements or compounds. Controller  52  receives inputs from moisture sensors  64 , evapotranspiration data  66 , soil model  68 , crop model  72 , human observations  76 , remote sensed data  78 , business rules  80  and business information  82 . Soil model  68  receives input from weather data  70  and crop model  72  receives input from genetic and performance information  74  for the particular crops being grown in agricultural area  20 . 
     Even though different crops or crops with different genetic traits may be in agricultural area  20 , for ease of understanding, agricultural area  20  will be assumed to be growing a singular crop across all sub-areas  22 . Sub-areas  22  representing different two-dimensional locations within agricultural area  20 . Three dimensional information and models for the different locations in agricultural area  20  provide insight into the needs of the plants in their root zones, which is utilized by controller  52  for the distribution of resources  58  and  60  to meet a need for a future time period. 
     The present invention controls the movement of water from water source  58  and other substances  60  through distribution system  14  with a focus on optimizing desired conditions for individual plant root zones in terms of the three-dimensional distribution of water, nutrients and other substances, such as salt. The present invention considers plant genetics, the natural environment and management options with varying outcomes and risks. It utilizes technical advances in computational hardware, crop, weather and soil modeling, water marketing, business risk assessments and global food chain management. The system and method manages substances in the plant root zones that are based upon soil models  68  for separate sub-areas  22 . Soil model  68  includes a ‘Z-direction’ model with predicted future needs at different depths for X-Y locations of the two dimensional view of  FIG. 2 . Soil model  68  is correlated with crop model  72  to determine the needs of the particular crop in terms of the depth below the surface of the ground for substances  60  as well as for water  58 . 
     Controller  52  may be a single computer, a computer with multiple processors, or a distributed processing system that is spatially distributed and networked together to work on the common task of the present method. Controller  52  can send an actuating signal to a valve system  56  that may include a number of valves controlling the flow through pipes  16  to separate individual nozzles  18  of irrigation system  10 . Valve system  56  may provide a feedback signal to controller  52  to indicate the position of the valve and/or other information such as the instant or accumulative flow through the valve. 
     Most prior art irrigation systems have one valve for the entire area being irrigated or a number of valves, each regulating water flow for a portion of the total irrigated area. If there are multiple valves, each one may be controlled individually. Management of a prior art irrigation system is done based on sensed soil moisture from soil moisture sensors, which is compared to a target value by a processor. The difference is used to determine the position of the valve for control purposes. An alternate approaches uses evapotranspiration data to estimate a water deficit. The valve is then controlled to apply water to make up this deficit. Both of these methods suffer from the same deficiencies. One is that due to sensor cost, the spatial resolution of the control inputs, such as soil moisture or evapotranspiration, is typically poor and leads to some areas being under watered and some areas being over watered. Another weakness in the prior art is that such systems are often reactive. They take current and past data into account and maybe a short term weather forecast and then react to it. A third short fall of the prior art methods is that they do not utilize remotely sensed data such as images that indicate crop coverage of soil, crop growth stage, crop biomass, crop leaf area and crop stress due to moisture or nutrient distribution. A fourth short coming is that they do not easily incorporate ground truthing from human observations. A fifth short coming is that they are not integrated with business rules and business information, which should affect application amounts due to the cost of water and the value of the water applied to the crop. If a map is used as in some prior art systems a target volume of water or nutrient is applied to each management area. The processor in such a system uses positional information to locate a given valve and then control is undertaken so that the volume of water or nutrient is applied to that area. The present invention differs from the prior art in that the valve is controlled in a way to achieve a distribution of water, nutrients and other substances, such as salt around the plant root zone, which is a three-dimensional location at a future point in time. In the present invention the use of soil models, such as SIS, crop models, weather data, business rules, business information and even remote sensed data are utilized. 
     Soil model  68  and crop model  72  are supplied with other data, which can include evapotranspiration data that enables a high spatial and temporal resolution estimate of current crop water needs. This estimate is three-dimensional in the root zone and includes water availability by depth and also considers soil moisture variability arising from factors within the model including, but not limited to, soil structure, crop growth stage and business rules  80  to implement techniques such as root deficit irrigation (RDI) in which crops are intentionally water stressed for a benefit at a later crop growth stage. The soil model  68  and crop model  72  may be ground truthed by entry of human observations  76  of crop or soil conditions. Controller  52  may also use soil moisture sensors  64  for ground truthing soil model  68  and evapotranspiration data  66  to calculate the amount of water entering the atmosphere from sub-areas  22 . 
     Business rules  80  and business information  82  enable water amounts to be adjusted based on crop value of incremental additions or subtractions of the recommended amounts of water  58  and substances  60 . Crop model  72  and soil model  68  run with different irrigation water amounts and application rates such as, for example, 1 inch-acre/hour for two hours versus 2 inch-acre/hour for one hour. The crop value at harvest for a given quality of the crop is part of the business information  82 . The crop value may be a single value, a function of maturity date or a complex probability distribution of value based upon crop and demand forecasts for the produced crop around the world. Models  68  and  72  are utilized along with rules  80  and information  82  to adjust water amounts so that the risk to the crop is reduced by applying more water at an earlier time to reduce a likelihood of a shortage at a critical crop growth phase in the future. Business rules  80  are also utilized by controller  52  to adjust water amounts based on alternate uses of water source  58  and/or substances  60  such as when the heat is so extreme that irrigation system  10  cannot keep up with losses and/or water source  58  and/or substances  60  may have more value being sold to other users in a market system than being consumed by irrigation system  10 . 
     User interface  54  displays a variety of audio and visual forms and may include voice synthesis delivered to a user at a remote location to a phone or various electronic displays so that information may be reported to the user by way of user interface  54 . User interface  54  may include an irrigation “dashboard” providing a summary of irrigation system  10  and the status of agricultural area  20 . Information may also be received relative to unauthorized movement of sensors  64  or even the condition of sensors  64  and other elements of mechanisms contained in irrigation system  10 . System  50  provides estimated past, present or future states of soil moisture in agricultural area  20  at various sub-areas  22 . User interface  54  allows the user to override the recommendations of controller  52  or authorize those recommendations. User interface  54  includes authentication software to ensure that only authorized users make changes to system  50 . 
     Advantageously the present invention provides for the computation of a three-dimensional soil model of the need for nutrients and/or water at various depths in sub-area portions of agricultural area  20 . Crop model  72  incorporates genetic and performance information  74  to better define the needs of the crop including such things as salt tolerance and moisture needs at various stages of maturity of the crop. Various inputs to controller  52  provide for cross checking of information, such as remotely sensed data  78 , the ground truthing by human observation  76  and/or localized moisture sensors  64  to provide levels of assurance that future needs of the plants will be properly met in the root zones of various sub-areas  22 . Soil model  68  models soil types in various sub-areas  22  or even further divided areas within agricultural area  20 . Soil model  68  incorporates the reactions of soil to current moisture and substances  60 , rates of distribution within the soil and the need for the variable rates of distribution by distribution system  14  to the crops in order to achieve the future transportation of substances  60  with water source  58  to a proper root zone level of a particular sub-area  22 . Advantageously, business rules  80  and  82  incorporate market information for the inputs into irrigation system  10  as well as the marketing value of the crop that is to be output from agricultural area  20  in order to optimize a return on investment or to reduce risk based upon future needs of the crop in agricultural area  20  as well as costs of substances  60  and water  58 . 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
A method for managing substances in a plant root zone, including the steps of providing a fluid distribution system, controlling the fluid distribution system, modeling the plant root zone, and distributing the substances thereto. The fluid distribution system is associated with an agricultural area. The fluid distribution system is controlled by way of a controller. The plant root zone is modeled for a plurality of locations in the agricultural area. The modeling step incorporates a desired three-dimensional distribution of the substances for each of the plurality of locations for a future time period. Substances are distributed to the plurality of locations by way of the fluid distribution system under control of the controller. The controller is dependent upon the desired three-dimensional distribution and the future time.