Full-season corn products, for a given area, typically have the highest yield potential, which may help offset an increase in drying costs. As planting is delayed, corn product maturities come closer together. Corn generally requires 1.6 growing degree units (GDUs) less each day to reach flowering and 6.8 GDUs less each day to reach physiological maturity (black layer) as planting is delayed beyond about May 11.
Therefore, corn planted in late May compared to an optimum maturity date may actually take 125 to 200 fewer GDUs to reach black layer.
For an example, consider if planting was delayed until the week of May 22 in the Carrington, MN area. In that time, 260 GDUs would have been lost from April 24. If the first killing frost date is October 9, the maximum potential GDUs remaining for Carrington to May 22nd is 2,124 (2384 - 260). A product with a GDU to black layer rating of 2100 GDUs can still be planted because its GDU to black layer rating is below the 2124 potential. Additionally, a product with a GDU to black layer rating of 2100, planted on May 29, should only require 1903 GDUs to black layer [2100-(6.8 x 29)].
The yield for late-planted corn will vary greatly depending on the rest of the growing season. The decision to switch maturity with delayed corn planting is difficult because of variations in growing seasons relative to available GDUs, and the first frost date.