Deficit Irrigation, Planting Date, and Hybrid Selection Impacts on a Mid‐South Corn Production System

Core Ideas Early planting reduced irrigation water use by 52% and improved WUE by 29%. Deficit irrigation reduced irrigation water use and net returns by 91% and $53 acre, respectively. Conventional full‐season hybrids planted early generated the highest net returns. The Mississippi River Valley Alluvial Aquifer (MRVAA) is the primary irrigation source for the mid‐southern USA, but the current withdrawal rate from the aquifer is unsustainable. This research was conducted to determine if interactions among factors that have an effect on the water use efficiency (WUE) of corn could be manipulated to decrease irrigation requirements while maintaining or improving yield and net returns relative to current practices in this region. The effects of deficit irrigation utilizing soil water tension (−50 cbar vs. –125 cbar), planting date (late March vs. late April), and hybrid selection (conventional short season, drought‐tolerant full season, or conventional full season) on corn grain yield, WUE, and net returns above seed and irrigation costs were investigated on a Marietta fine sandy loam and a Leeper silty clay near Starkville and Verona, MS, respectively. Yield, WUE, and net returns above seed and irrigation costs for conventional full‐season hybrids were at least 18% greater when planted in March rather than April and, regardless of planting date, at least 6% greater than that of conventional short‐season and drought‐tolerant full‐season hybrids. Relative to full irrigation, deficit irrigation increased WUE up to twofold in three out of four planting dates, had no adverse effect on yield or net returns in wet years, but reduced yield and net returns up to 11% in dry years. Our data indicate that the best option to reduce aquifer withdrawal without having an adverse effect on net returns above seed or irrigation costs is to plant conventional full‐season hybrids on the early side of the recommended planting window and meet the evapotranspiration demand fully with supplemental irrigation.