Planting dates are earlier today than ever before, with 50 percent of the crop planted by April 25 last season. In general, research has shown a small yield loss with very early planting dates and a larger yield loss with later planting dates. Research conducted during 1998-2000 showed that planting approximately between April 20 and May 20 resulted in 100 percent yield (see Iowa State University Extension's Planting Guide). Based on newer research (2003-2006), we believe that this window is actually earlier; corn can be planted prior to April 20 and reach 100 percent yield.
Iowa State University
Abendroth, Lori and Elmore, Roger W., "How to plant all the acres" (2007). Integrated Crop Management News. 1152.
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