Producers attempt to plant corn earlier every year. For example, in 2006, 50 percent of the statewide crop was planted by approximately April 25. Earlier planting dates are attributed to several causes: larger acreage per producer, less spring tillage, advancements in hybrids, and seed treatments. However, in contrast to this, Iowa producers in 2008 did not have half of Iowa’s corn acreage planted until May 13 due to weather; this is 18 days later than 2006. Planting the crop during the optimum window is one management practice that is generally important in achieving high yields.
Iowa State University
Abendroth, Lori; Elmore, Roger W.; and Marlay, Stephanie, "Corn Planting Date" (2009). Iowa State Research Farm Progress Reports. 527.