Etc-Based Smartphone Aps for Scheduling Irrigation.

Irrigation has become essential to crop production in many agricultural areas of the United States and especially across the cotton producing regions of the USA. As a result, the competition for available fresh water supplies is increasing and in some regions, cotton producers are faced with diminishing water supplies.  If irrigated agriculture is to survive in this competitive environment, we must use irrigation water efficiently and more cost-effectively.  The goal of the work described here was to develop an interactive ET-based irrigation scheduling tool for cotton which operates on a smartphone platform. The model uses meteorological data to calculate FAO 56 evapotranspiration (ETo) and a phenology-based crop coefficient (Kc) to estimate crop evapotranspiration (ETc).  The model uses ETc, precipitation from the meteorological data, and irrigation events to estimate a daily plant-available soil water balance within the crop’s root zone.  The model reports a daily root zone plant-available soil water deficit in terms of inches of water and percent of total. We converted the model into an interactive smartphone application (app) for iOS and Android operating systems. The Cotton App provides notifications to the user when actions such as irrigation are needed. For example, the Cotton App sends the user a notification when the root zone plant available soil water deficit exceeds 50% indicating that irrigation is recommended. We calibrated and validated our model during 2012 and 2013 using data from replicated plot experiments and commercial fields. Both were instrumented with soil moisture sensors which continuously monitored soil water tension. The Cotton App was released April 2014 and used to schedule irrigation in grower field during the 2014 growing season.