Source: Allen Geyer, Rich Minyo, Peter Thomison, OSU
Ohio saw record late corn planting in 2019. According to the Agricultural Statistics Service, only 33% of Ohio’s corn was planted by June 2. The question being asked now is will the June planted corn reach physiological maturity (black layer) before a killing frost? Corn is killed when temperatures are near 32°F for a few hours and when temperatures are near 28°F for a few minutes.
A useful tool is available from the Midwestern Regional Climate Center (the U2U tool, available at: https://mrcc.illinois.edu/U2U/gdd/) that uses current and historical weather data to predict when corn will reach black layer. The user selects the geographic location that they are interested in, actual planting date and the adjusted relative maturity of the planted hybrid.
Previous studies have indicated that the GDD requirement of late planted corn to reach black layer from planting is less than the requirement of corn planted on a “normal” date. Keeping this in mind, Dr. Bob Nielsen from Purdue University has developed an adjustment to the GDD requirements for late planted corn. This calculator can be found at: https://www.agry.purdue.edu/ext/corn/news/timeless/hybridmaturitydelayedplant.html Using this calculator, enter the adjusted GDD value in the U2U tool in the “Black Layer GDDs” line.
We have used the U2U tool to predict whether our corn research will accumulate enough GDDs before a killing frost. Table 1 shows the results of using these tools for the 2019 Ohio Corn Performance Test sites (OCPT) as well as a late planted demo plot that was planted at Hoytville. These results are based on a 109-day (2618 GDD) hybrid. The table indicates the planting date, adjusted GDD requirement for the 109 day hybrid, whether physiological maturity (black layer) will be achieved before frost, the predicted black layer date and the average 32° and 28° frost dates. Because of the adjusted GDD requirements with later planting dates, the predicted GDD accumulations will exceed or just meet the required GDDs before the average frost date for all 10 OCPT sites, including the 5 sites that were planted in June. We hope that these predictions come true! Note that the demo plots at Hoytville that were planted on June 27 will not reach black layer before a killing frost based on the U2U tool.
Table 1. Planting date, Adjusted Hybrid GDD Requirement, Reach BL Before Frost, Predicted Black Layer (BL) Date, and Average Frost Dates for 2019 Ohio Corn Performance Test sites.