Economical and Statistical Based On-Farm Irrigation Scheduling

Most irrigation scheduling techniques are not based upon the statistics of the irrigations or economics of irrigated crop production. Traditional irrigation scheduling is based upon average irrigation depths, calculated crop evapotranspiration (ET), or soil moisture measurements. An irrigation scheduling model for alfalfa was developed that considers; the irrigation water depth distribution and timing, irrigation-yield relationships, price of the crop, and the costs of irrigation and crop production. The model tracks soil moisture and crop ET spatially and temporally to include the effects of the irrigation system's water application uniformity and irrigation timings on crop yields. The model divides the field into elements and a soil moisture budget and corresponding yield is calculated for each element. The model accounts for costs of production and determines the most profitable irrigation schedule, based upon total yield and alfalfa prices. The model was used to determine sensitivity of irrigation and economic conditions on profit and irrigation management. Results from the model show that the most profitable irrigation schedule is influenced by the irrigation uniformity, costs of irrigation and crop production, and prices received for the crop. The number and schedule of irrigations which resulted in the maximum profit varied for differing input variable sets.