Scheduling of Furrow Irrigation Initiation on Soybean Yield and Net Returns

Core Ideas Irrigation delays reduced yield and profit for indeterminate soybean on loamy soils. Irrigation delays did not affect a determinate cultivar on a loamy soil. A 2‐week irrigation initiation delay can reduce yield on a cracking clay soil. Delays in irrigation initiation will reduce plant heights and canopy cover.The majority of soybeans ( Glycine max L. Merr.) grown in alluvial soils of the Mid‐South USA are irrigated. The impact of delayed irrigation initiation of 0, 5, 10, and 15 days on soybean growth, yield, and economic returns was investigated for three seasons on two contrasting soils located 1,000‐ft distance apart: silt loam and silty clay. Scheduling was determined using the Arkansas Scheduler, a deficit‐driven program. On the silt loam soil, cultivars representing maturity groups (MG) 3, 4, and 5 were planted in 2007, 2009, and 2010. In 2007, delays of 15 days were omitted on the silt loam soil due to rain. On the silty clay, MG 4 was planted in 2008 and MG 5 in 2009 and 2010. Delays of 15 days reduced seed yields and net returns in 2 of 3 years on the silt loam for MG 3 and 4 cultivars but not for MG 5. On the silty clay, a 15‐day delay reduced yields in all three seasons but had no effect on net returns. Irrigation initiation delays reduced plant heights and canopy cover at both sites and all seasons, especially for 15‐day delays. Delays in irrigation initiation of 15 days increased risk for early maturing indeterminate cultivars more than later‐maturing determinate cultivars in the silt loam soil and for all cultivars in the silty clay. However, delaying irrigation initiation by as much as 10 days for determinate cultivars can potentially reduce irrigation costs without sacrificing yield and net returns.