A regional approach to improving soybean irrigation management in the Southeastern United States

Soybean irrigation in the Southeastern United States presents significant challenges due to unpredictable periods of excess rainfall or drought, a wide range of planting dates/maturity groups, and extreme soil textural differences combined with varying degrees of drainage. The Universities of Kentucky, Georgia, Tennessee and Auburn received supplemental funds from the Southern Soybean Research Project in 2015 through 2018 to conduct a regional project that shared research results with the goal of improving irrigation management tools for producers. The best irrigation treatments in sandy soil increased yield from 15 to 100% with irrigation amounts ranging from 8.3 to 17 cm that resulted in irrigation water use efficiencies from 53 to 86 kg ha^-1cm^-1. The best irrigation treatments in higher water-holding capacity soils increased yield from 15 to 27% with irrigation amounts ranging from 4.6 to 11.9 cm that resulted in irrigation water use efficiencies from 15 to 146 kg ha^-1cm^-1. Irrigation beyond these optimum amounts sometimes resulted in yield reductions of up to 7%. Sandy soils required more irrigation and had a bigger impact on yield than soybean irrigation in higher water-holding capacity soils but soybean irrigation in the southeast is supplemental with the greater portion of the crop's water needs being meet via rainfall. The wide range of soybean response to irrigation is due to the year-to-year variability in rainfall and growing conditions. As a result of this project, a new generation of irrigation scheduling tools and extension materials were developed that benefited from the larger sphere of knowledge provided by a regional approach.