Impact of Planting Date and Maturity Group on Irrigation Water Use Efficiency in Mid-South Soybean Production.

The Mississippi Alluvial River Valley aquifer is being depleted at distressing rates due to irrigation withdrawal for cotton, corn, soybeans and rice. Current soybean production strategies consist of planting a majority of acres with maturity group IV and V soybean varieties. However, it is believed that transitioning more planted acres to maturity group III or IV soybean varieties could allow for an earlier harvest and the potential for less irrigation events when compared to maturity group V soybean varieties. An experiment was conducted at the Delta Research and Extension Center located in Stoneville, Mississippi in 2015 and 2016 to determine the impact that planting date and soybean maturity group has on yield, irrigation water use efficiency and harvest date. Maturity group III, IV, and V soybean varieties were planted within three separate planting dates, which ranged from 20-April to 2-June. Irrometer Watermark moisture sensors were used to determine when irrigation events would be initiated. Each individual maturity group within a planting date was irrigated based upon the water use needs of the plants within the plot. For planting dates ranging from 15-April to 20-May, maturity group IV soybean varieties were found to be the optimum choice for producers due to yield and irrigation water use efficiency. For planting dates past 20-May, both maturity group III and IV soybean varieties had similar yield and irrigation water use efficiency, meaning either would be a good option for producers. These results provide producers with knowledge on maturity group selection by planting date, and water management strategies for Mid-South soybean production.