LEPA and spray irrigation for grain crops

Two low energy precision application (LEPA) sprinkler methods (double-ended socks and bubblers) and two spray sprinkler methods (low-elevation spray a pplication and overhead spray) were used to irrigate corn, grain sorghum, a nd winter wheat in the Southern High Plains. For full or 100% irrigation, s ufficient 25-mm applications were applied to maintain soil water at non-yie ld-limiting levels determined in earlier research with the three crops. Def icit-irrigated treatments were irrigated on the same days as the control tr eatment in 25 or 33% increments of the fully irrigated amount. irrigation w ater was applied to or above alternate furrows with a three-span lateral mo ve irrigation system. Corn and sorghum were grown on beds and furrows with all furrows diked, and wheat was flat-planted without basin tillage. Grain yields increased significantly with irrigation amount (p less than or equal to 0.05) for all crops during all years. With full irrigation, grain yield s varied little among the sprinkler methods, and yields averaged 13.5, 8.9, and 4.6 Mg/ha for corn, sorghum, and wheat, respectively. With the 25 and 50% deficit irrigation amounts, sorghum yields with LEPA irrigation were 1. 1 Mg/ha larger than with the two spray methods. For 75% irrigation of sorgh um and for deficit irrigation of the other two crops, there was little yiel d difference between the LEPA and spray sprinkler methods. Grain yields wer e significantly correlated with seasonal water use with regression coeffici ents of 2.89, 1.84, and 0.915 kg/m(3) for corn, sorghum, and wheat, respect ively.