Management of Irrigated Soybean.

Though irrigated soybean only make up a small portion of total U.S. soybean production, interest has been generated due to the potential for high yields and production.  In 2012 and 2013, we examined the effect of supplemental irrigation on soybean grown in productive silt loam and silty clay loam soils, and also looked at how irrigation might interact with other management factors.  Rainfall in July and August totaled 157 and 99 mm in 2012 and 2013, respectively; we applied 242 and 176 mm of water to irrigated soybean in these two years. Irrigation increased yield in both years, by an average of 696 kg/ha (15.4%).  In 2013, the seeding rate of 420 000 seeds/ha produced 134 kg/ha (2.9%) more yield than did rates of 296 000 and 346 000 seeds/ha, and a combination of foliar fungicide and insecticide increased yield by 231 kg/ha (5.1%) over the control.  Neither of these management responses interacted with irrigation, however.  While these results confirm that irrigation can increase soybean yield modestly in soils with high water-holding capacity, we did not find that water availability affected the response to other management factors.