Soybean Yield and Yield Component Response to Limited Capacity Sprinkler Irrigation Systems

Abstract

The rapid increase in soybean [Glycine max (L.) Merr.] production under sprinkler irrigation systems in the semi-arid Great Plains necessitates more research on minimum-capacity center pivot irrigation systems. A three-year field study was conducted to evaluate yield and yield component responses to sprinkler irrigation scheduling strategies. Irrigation treatments (main plots) were nonirrigated (NI), irrigation commencing at R2 (FL), irrigation commencing at R3–R4 (POD), and irrigation scheduling based on 50% available soil moisture depletion (SCH). A solid-set sprinkler irrigation system was used to simulate a minimum-capacity center pivot system for central Nebraska on silt loam soils (1.5 in. water/wk). Water applied was greatest for SCH, intermediate for FL, and least for POD. Row widths of 30 and 10 in., were subplots, and three cultivars were evaluated as sub-subplots. In two low rainfall years, POD yielded 5 bu/acre less than FL and SCH. In a year with adequate rainfall, POD yielded 3 bu/acre more than FL and SCH due to greater lodging of two cultivars in FL and SCH. Irrigation treatments had no major effect on soybean responses to row widths. Irrigated soybeans had 16% less flower and pod abscission than nonirrigated. With a minimum-capacity irrigation system and the concomitant differences in water application of our irrigation treatments, delaying irrigation until R3–R4 in low-rainfall years will likely result in reduced yields relative to irrigation commencing at R2 or irrigation timed according to a soil moisture based irrigation scheduling system.