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College of Food, Agricultural, and Environmental Sciences


Best Time to Harvest Corn a Guessing Game

September 12, 2001

COLUMBUS, Ohio - From too much rain to not enough, to threatening diseases, uneven fields and early season cold injury, the performance of Ohio's corn crop has remained an uncertainty for growers all season.

But one thing that is certain now is that it's harvest time. The big question is when to begin? It seems the time to harvest is just as variable as the weather that has had growers wondering how much of an impact it will have on their crop.

"Right now, one issue is that there's a lot of variability by region as to crop conditions and how this might affect harvest," said Ohio State University agronomist Peter Thomison. "Parts of the state, like the south and southwest, have received average or above average rainfall, while other parts, like the north and northeast, have received next to none."

Thomison speculates that such variation in rainfall will have an impact on when the crop will be harvested. "Corn in some fields in south and southwest Ohio will probably start coming off within the next two to three weeks, while fields in the northern part of the state won't be ready for harvest for much longer than that," he said. "Also, drought stress and nitrogen deficiencies have created conditions favorable for stalk rot which may cause lodging problems. Growers should prioritize harvesting fields by lodging potential."

Between fluctuating rainfall and temperatures and high fuel costs, it is uncertain whether growers will wait as long as possible before harvesting or will attempt to harvest their crop early. "It's going to be interesting to see what growers will do. The recommendation is that they begin harvesting when they've got 25 or 26 percent moisture," said Thomison. "If moisture levels drop too low, you're losing grain, and if moisture levels are too high, then you cause additional injury to the crop."

Recent warm weather has created ideal conditions for drying corn. "Growers naturally will want to take advantage of the recent weather conditions," said Thomison. "Right now, we are probably losing one half to three-quarters of a point of moisture a day, which is very good for drying. We'll see drying rates decrease toward the end of September, and by mid-November we could only have a quarter point of moisture loss a day. As the temperature drops, so does the moisture loss."

When growers do decide to harvest, they may need to take into consideration specific harvest recommendations for corn that has experienced unevenness or shorter overall plant and ear heights due to the weather.

"Dry weather in parts of Ohio plus uneven crop development due to the protracted wet, cold conditions in May and June, have resulted in smaller than normal ears," said Thomison. "In addition, plants are shorter than normal with reduced ear heights. As a result of these conditions, some combine and harvesting adjustments may be necessary."

The U.S. Department of Agriculture is predicting Ohio's corn yield at 138 bushels per acre, down nine bushels from the record high yield of 147 bushels per acre set in 2000. If realized, this yield would result in a total production of 434.7 million bushels, 10 percent below last year, but would still be above the five-year average.

"If August wasn't too stressful, there might be the potential for good yields," said Thomison. "Considering the severe drought we had in 1999, and we still came away with 126 bushels per acre, I'd say the USDA prediction of 138 might be about right."

Candace Pollock
Peter Thomison