Will my corn make it to maturity before a killing frost?

As of Aug. 28, the
Southern Research and Outreach Center in Waseca reports growing degree units (GDUs) since May 1 are 5% less than normal. The Southwest Research and Outreach Center in Lamberton reports GDUs are behind as well, running
5.8% behind the long-term average as of Aug. 26. Corn has generally been at least
1 crop stage behind where we would expect it to be and cooler-than-normal conditions combined with late planting dates contin- ue to make us question if crops will reach maturity before a killing frost.
Grain corn killed by frost before reaching physiological maturity can not only result in lower yields, but grain that is lower in test weight and higher in moisture. Kernel quality can be reduced and harvestability may be a challenge. There is also po- tential for more ear molds, ear drop, stalk rots and/or stalk lodging.
The Midwest Regional
Climate Center website,
which hosts the “Useful to
Useable” Growing De- gree Day Decision tool at https://mrcc.illinois.edu/  U2U/gdd/, uses long-term weather data to make trend projections in crop devel- opment. I ran the tool on Aug. 29 to predict when we might reach physiological maturity (black layer or maximum dry matter ac- cumulation) this fall under various scenarios, using a location in Martin County. You can run the tool for your own location: Re-
sults will vary by location depending on the weather data being used for that location.
At the selected location,
the tool calculated the average first freeze date to be Oct. 13, although dates ranged from Sept.
23 (in 1983) to Nov. 10 (in
2005). 28° F was used as
the killing freeze tempera- ture for corn. Here are six different combinations
of hybrid maturity and planting dates through the tool. The relative maturity, planting date, and estimat- ed black layer date (Est
BL) as predicted by the
tool are listed below:
 
C1) Planted 103 RM hybrid May 15, Est BL = Oct. 20*
C2) Planted 103 RM
hybrid May 25, Est BL =
*/

normally expect.