Sprinkler Irrigation Management for Corn — Southern Great Plains

ABSTRACT IN the Southern Great Plains, sprinkler-irrigated corn (Zea mays L.) yield is often limited by the irrigation water supply capacity. A field experiment conducted in 1987 determined sprinkler-irrigated corn responses which were used to modify and calibrate the CERES-Maize corn growth model. This validated model was then used to simulate corn water use and yield for various levels of irrigation water supply capacity. Effects of management decisions such as allowed soil water profile depletion and net irrigation application amount were studied. The yield, water use, and water use efficiency of fully-irrigated corn were 11.7 Mg/ha, 838 mm, and 1.40 kg/m^, respectively; and all decreased with irrigation deficits. The modified CERES-Maize model accurately simulated evapotranspiration, aerial dry matter yield and grain yield of the corn experiment. A 28-year simulation (1958-1985) at Bushland, TX, indicated that a net sprinkler irrigation supply capacity of 8 mm/d is necessary to avoid irrigation system related yield constraints on the slowly permeable Pullman clay loam soil. During those 28 years, a net irrigation supply capacity of 4 mm/d only reduced the mean yield by 12.5% from 11.15 Mg/ha to 9.75 Mg/ha but more than quadrupled the variance of the corn yield. With adequate net irrigation supply capacity, irrigation application amount (for 1- to 4-day irrigation frequencies) and allowed soil water depletion (up to 50% of the plant extractable soil water) did not greatly affect simulated crop yield but greatly affected the hydrologic efficiency for storage of precipitation and the net irrigation water requirement.