Drainage water management effect on corn planting date in southeast Iowa

In Iowa, producers achieve an adequate growing season for high yielding corn (Zea mays L.) by beginning field activities in a timely fashion. Subsurface drainage allows for early field activities by improving trafficability and decreasing excess water stress to crops on poorly drained soils. Drainage water management practices reduce drainage volumes and nitrate (NO3) loss by maintaining the water table closer to the ground surface when compared to conventional drainage systems. The objective of this study was to determine the effect of shallow, controlled, conventional, and no drainage on depth to water table, volumetric water content, and soil temperature during a 51-day period, from mid-April through May, to evaluate if drainage water management practices delay planting. At the Iowa State University Southeast Research Farm near Crawfordsville, Iowa, we evaluated eight large-scale research plots with two replicates for each of the four drainage treatments over the 51-day planting period during 2012 to 2015. Each plot was planted half to soybeans (Glycine max [L.] Merr.) and the other half to corn, and the halves rotated every year in accordance with a typical corn–soybean rotation. Conventional and controlled drainage significantly lowered (p