A Smartphone App for Scheduling Irrigation on Cotton

A smartphone app for scheduling irrigation on cotton in Georgia was developed and tested during the 2013 growing season.  The app is based on a crop-coefficient model and uses cotton crop coefficients developed by various research groups in the Southeast.  The app uses growing degree days as a trigger for changing the crop coefficient during the growing season but allows for user override based on observed phenology (first bloom, first open boll, etc.)  The model uses a check-book approach to estimate when available soil moisture has been depleted by adding precipitation and irrigation to available soil moisture and subtracting FAO-56 ET adjusted by the crop coefficient from it.  The model was used to schedule irrigation in four experimental blocks at the University of Georgia’s Stripling Irrigation Research Park (SIRP).  Soil water tension in the experimental blocks was recorded continuously with a Watermark-based soil moisture sensing system.  Despite above average rainfall during the majority of the growing season, the model performed well.