The beginning of May finds most of the Midwest lagging behind in corn planting as wet weather continues to inundate much of the area. Even though planting is behind our normal progress, it’s important not to panic and make drastic decisions based on emotion. One of the common mistakes that’s made when planting is delayed is changing from a full season variety corn and an early season variety. This change occurs most likely to the worry of not having the corn black layer by the first killing frost.
While a switch in maturity might ultimately be necessary, it should not be warranted this early in the season. Research done by Purdue and Ohio State investigated the effects of delayed planting in corn. This research found that when planting was delayed into May, corn hybrids adjust to this delayed planting. Corn reaches maturity by accumulating a certain amount of heat units called growing degree days (GDD). When the calendar reaches May 1st,GDD’s for corn to reach maturity decreases by 6.8 GDD’s per day. So a corn hybrid requiring 2700 GDD to mature and planted on May 30th would require approximately 2496 GDD’s to reach maturity compared to if planting had taken place on April 30th. With this lower GDD requirement, a full season variety should be able to reach full maturity before the first typical killing freeze even if it’s planted towards the latter part of May in the Midwest. Usually, switching to an earlier maturing hybrid should not take place unless planting is delayed till the very end of May and into June.
It would be wise however to work with your seed supplier in advance and ask about potentially switching maturities before the time comes due to potential shortages in supply. Keep in mind that a full season hybrid can often times have a yield advantage over a shorter season variety. Switching to an earlier maturing hybrid can be risky due to a lack of heat and disease tolerance if its planted outside of its normal area. While planting date is one key to good yielding corn, always remember that timely rains and moderate temperatures in July and August can have an even more dramatic impact on yield. Research has found that corn planting delayed until May 15th can still provide 95% of optimum yield and planting delayed until May 20th provides 91% of optimum yield. So while the weather refuses to cooperate, it’s important to not get discouraged and over react. There is still a lot of hope for the 2019 growing season.