An Online Irrigation Tool for Soybean Producers in Nebraska.

More than 60% of Nebraska farmers currently have internet access and most are high speed connections. Development of SoyWater, a web-based irrigation decision aid, was motivated by such internet access availability and by recent improvements in ability to simulate and predict soybean growth stages. SoyWater offers a user-friendly feature with an intuitive graphical user interface that enables farmers to schedule irrigations only when needed based on real-time and historical weather data. Alternatively, farmers can use this tool to defer all irrigation to R3-stage (beginning pod), which is  an effective irrigation strategy in high water-holding capacity soils that are at field capacity at planting. SoyWater was developed using scripting languages (PHP and Javascript), database management system (MySQL), Google Map applications, and open source Geospatial Software. SoyWater features a direct connection to an automated weather data network (AWDN) and a simple crop-soil-water balance simulation. Required user inputs are: (1) emergence (preferred) or planting date, (2) cultivar maturity group, and (3) soil texture. Daily crop evapotranspiration is determined from actual (to date) and historical weather data from the selected weather station in “real-time” during the growing season. An irrigation trigger is determined by a user-selected water depletion threshold in the active root zone. A crop water use reporting table was designed with feedback from farmers and extension specialists to make the format easily understood. This table allows users to update their SoyWater field(s) with rainfall and irrigation amounts at any time. The phenology routine in SoySim (www.soysim.unl.edu), a soybean growth simulation model, is integrated into SoyWater to predict vegetative and reproductive developmental stages. Prediction of soybean developmental stages is critical for crop water use calculation, timing of irrigations using the R3-stage deferred irrigation approach, and other management considerations such as when to apply the last irrigation or chemicals to control of pest and diseases. SoySim- predicted V- and R-stages were validated in-situ in 22 fields across Nebraska in 2009 and 2010, with RMSE=5 days for stages V2, V3, V7, V8, V11, V15, R1, R3, R5 and R7 . Widespread use of this on-line irrigation tool is expected to improve irrigation efficiency/effectiveness in soybean, allowing increased profit arising from reduced water and energy consumption.