Submitted to: Journal of Irrigation and Drainage Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 19, 1999
Publication Date: N/A
Interpretive Summary: Do I equip my center pivot irrigation system with spray heads, or do I invest more money and management time to achieve higher efficiencies with LEPA (Low Energy Precision Application) application devices? This question is asked by the owners of tens of thousands of center pivot irrigation systems both in the United States and worldwide. To help growers answer this question, spray heads and LEPA devices were compared for irrigation o corn, grain sorghum and wheat at the Conservation and Production Research Laboratory at Bushland, Texas. Each of the three crops received 100% irrigation for maximum production and lesser percentages of irrigation to measure the response to deficit or partial irrigation. Tillage, fertility, cultural practices and weed and insect control were similar to those used for high-yield, on-farm crop production in the Southern High Plains. Two year average grain yields with the LEPA and spray sprinkler methods were, respectively, 209 and 221 bu/ac for corn, 7900 and 8150 lb/ac for grain sorghum and 67 and 72 bu/ac for wheat. Deficit or partial irrigation was highly efficient for grain sorghum, a drought tolerant crop. For example, with half of the irrigation applied for maximum production, the yield with the LEPA method was 1000 lb/ac larger than with the spray method. For corn and wheat, deficit irrigated yields were similar, however. The three studies summarized in this paper show that the LEPA sprinkler method was highly efficient for deficit irrigation of grain sorghum. But, for 100% irrigation of corn, grain sorghum and wheat or deficit irrigation of corn and wheat, the two sprinkler methods were equally efficient.
Technical Abstract: Two LEPA sprinkler methods, double-ended socks and bubblers, and two spray sprinkler methods, low-elevation spray application (LESA) and overhead spray, were used to irrigate corn, grain sorghum and winter wheat in the Southern Great Plains. For full or 100% irrigation, sufficient 25-mm applications were applied to maintain soil water at non-yield-limiting levels determined in earlier research with the three crops. Irrigation amount was verified with neutron soil water measurements. Deficit irrigated treatments were irrigated on the same days as the control treatment but in 25 or 33% increments up to the fully-irrigated amount. Irrigation water was applied to or above alternate furrows with a 3-span lateral move irrigation system. Corn and sorghum were grown on beds and furrows with all furrows diked, and wheat was flat planted without basin tillage. Cultural practices were similar to those used for high-yield, on-farm grain production in the area. With full irrigation, grain yields 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 , grain sorghum yields with LEPA irrigation were 1.1 Mg/ha larger than with the two spray methods. For larger amounts of deficit irrigation of sorghum and for deficit irrigation of the other two crops, there was little yield difference between the LEPA and spray sprinkler methods. For fully-irrigated grain production in the Southern Great Plains, grain yields with the LEPA and spray sprinkler methods were essentially equal. For deficit irrigation, sorghum yields only were larger with the LEPA sprinkler method than with the spray sprinkler method.