COMPARISON OF SDI, LEPA, AND SPRAY IRRIGATION PERFORMANCE FOR GRAIN SORGHUM

Abstract

Subsurface drip irrigation (SDI), low-energy precision application (LEPA), and spray irrigation can be veryefficient by minimizing water losses, but relative performance may vary for different irrigation system capacities, soils, crops,and climates. A three-year study was conducted at Bushland, Texas, in the Southern High Plains to compare SDI, LEPA, andspray irrigation for grain sorghum on a slowly permeable Pullman clay loam soil. Performance measures were grain yield,seed mass, soil water depletion, seasonal water use, water use efficiency (WUE), and irrigation water use efficiency (IWUE).Each irrigation method was compared at five irrigation levels: 0%, 25%, 50%, 75%, and 100% of crop evapotranspiration.The irrigation levels simulated varying well capacities typically found in the region and dryland conditions. In all three years,SDI had greater yield, WUE, and IWUE than other irrigation methods at the 50% irrigation level and especially at the 25%level, whereas spray outperformed SDI and LEPA at the 75% and 100% levels. Differences in seed mass, soil water depletion,and seasonal water use were usually insignificant at the 25% and 50% levels and inconsistent at the 75% and 100% levels.Performance was most sensitive to irrigation level, then year, and then irrigation method, although relative rankings ofperformance for each irrigation method within an irrigation level were consistent across years. For this climate and soil, SDIoffers the greatest potential yield, WUE, and IWUE for grain sorghum when irrigation capacities are very low.