Irrigation Timing for Wheat Based on Climate, Crop, and Soil Data

A user‐oriented technique for timing irrigation of wheat is presented. The technique is based on actual crop evapotranspiration, initial soil moisture in the top 0.6‐m profile, available water holding capacity of the top 1.0‐m profile, allowable soil moisture depletion, water table contribution, and rainfall. Estimated evapotranspiration is calculated from the daily maximum and minimum air temperature, solar radiation, and a crop coefficient. The technique shows the need for one or two irrigations for optimum yield of wheat in soils with a water table between 0.5 m and 1.5 m deep. Verification of the technique on farmers' fields also shows a net savings of two to four irrigations, relative to the conventional practice of five irrigations. The soils irrigated include clay loam, silty clay loam, loam, and sandy loam. The technique has the potential to optimize the use of available water resources and reduce one‐time pressure on the water supply system.