Tom J Bechman NO YIELD DIFFERENCE: These replicated plots were harvested at three different dates in 2020. There was no yield difference based on date of harvest for any of the three hybrids in the trial. Corn Illustrated: Second-year trial confirmed 2019 results. The decision on when to begin harvesting corn this fall may seem a long way off. Yet when the time arrives, findings from a 2020 study that compared harvest dates may guide your decision. For the second straight year, Indiana Prairie Farmer , Purdue University and the Purdue Throckmorton Ag Center compared three harvest dates on corn. In 2019, a late season, harvest dates were late October, late November and early December, with a windstorm causing major lodging before the final harvest. In 2020, corn was harvested on Sept. 30, Oct. 30 and Nov. 20, with virtually no lodging issues.