Evaluating Optimum Limited Irrigation Management Strategies for Corn Production in the Ogallala Aquifer Region

Water is the major factor limiting crop production in the Ogallala Aquifer Region of the U.S. Central High Plains. Seasonal precipitation is highly variable, low in amount, and not enough to meet full corn water needs. The Ogallala Aquifer is the major source of irrigation water for commercial agriculture in the region. However, groundwater levels of the aquifer have declined drastically due to water withdrawals for irrigation exceeding mean annual recharge. The purpose of this study was to (1) determine optimum irrigation water allocation and planting dates under various growing season precipitation scenarios for corn using AquaCrop and (2) evaluate the impact of spreading versus concentrating water based on corn yield and crop water productivity in western Kansas. Corn needed on average 450, 300, and 150 mm of irrigation for dry, normal, and wet growing seasons, respectively, assuming initial soil water at planting as 70% of field capacity. There were differences in corn yield among evaluated planting dates. Late planting produced the lowest yield. Yield and biomass were optimumat seasonal evapotranspiration (ET) of 675-703 mm for early, 664-702 mmfor normal, and 623-675 mm for late planting, respectively, in sandy clay loam soils. Similarly, ET values for silt loam soils were 679-709 mm, 662-714 mm, and 625-687 mm, respectively. The highest and lowest ET in the range corresponded to wet and dry growing season precipitation scenarios, respectively. Assuming a limited well capacity of 68.1 m(3)/h, planting 50% of 46.8 ha produced the highest yield and crop water productivity on both sandy clay loam and silt loam soils compared to planting 100% of the area. However, for comprehensive assessments of limited irrigation strategies, further analysis of the different land-water allocation combinations with economic analysis of net income is recommended. The results of this analysis could be useful for other semiarid regions where water for irrigation is limited.