By Dave Nanda, Director of Genetics & Technology for Seed Consultants, Inc.
Can the corn crop planted in June catch up and mature? Maturity is a function of Heat Units or Growing Degree Days, also known as GDDs. It is a measure of the heat units accumulated each day and is based on a simple formula:
GDDs = Average daily temperature – 50. For example, if the high temperature of a day is 84 degrees F and low 68 degrees F, add the two to get 152. Now divide it by 2 to get the average temperature of 76 for that day. Subtracting 50 from 76 will give you 26. This number is the GDDs for that day. The stipulation in the formula is that we don’t count numbers above 86 and below 50.
Most of the corn hybrids planted in Indiana and Ohio require 2,400 to 2,800 GDDs to reach physiological maturity (about 32% kernel moisture) when planted in late April to middle of May. After reaching this point, no additional dry matter is added to the grain. However, the late planted corn needs about 200 fewer growing degrees to mature than normal as shown by studies conducted by Dr. Nielsen at Purdue and Dr. Thompson at Ohio State University. If we continue having hot temperatures in the next couple of weeks like the first two weeks of July, there is a good chance the corn crop will catch up, but we will need a late killing frost to have dry corn.