Armstrong Research and Demonstration Farm
Producers continue to plant corn earlier each year. In 2006, 50% of the statewide crop was planted by approximately April 25. Earlier planting dates are contributed to several reasons: larger acreage per producer, less spring tillage, advancements in hybrids, and seed treatments. Planting the crop during the optimum window is important to achieving high yields.
Iowa State University
Abendroth, Lori and Elmore, Roger W., "Corn Planting Date" (2007). Iowa State Research Farm Progress Reports. 827.