Optimum Iowa corn planting dates range from mid-April to the end of April in North Central and Northeast Iowa and to the first or second week in May in other parts of Iowa (see Table). If we consider the differences between early-planting and late planting, yields are reduced less early in the planting season than late. That means that planting early during the optimum window is generally a better practice than planting a few days after the optimum window. Yields drop off dramatically in mid-May across Iowa. If possible, plant corn prior to May 15 to avoid this "slippery slope" of rapidly reducing yield potential.
Iowa State University
Elmore, Roger W., "Best Corn Planting Dates for Iowa" (2012). Integrated Crop Management News. 168.
The Iowa State University Digital Repository provides access to Integrated Crop Management News for historical purposes only. Users are hereby notified that the content may be inaccurate, out of date, incomplete and/or may not meet the needs and requirements of the user. Users should make their own assessment of the information and whether it is suitable for their intended purpose. For current information on integrated crop management from Iowa State University Extension and Outreach, please visit https://crops.extension.iastate.edu/.