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Agronomist: The longer corn sits in fields, the greater the yield losses

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Written Thursday, November 26, 2009  

Ohio growers waiting to harvest their corn likely won’t see a significant decrease in grain moisture, but the longer corn sits in the fields, the greater the risk of increased stalk lodging, moldy ears and yield losses.

Peter Thomison, an Ohio State University Extension corn agronomist, said unfavorable weather might be keeping growers out of the fields, but corn should be harvested as soon as possible.

“We have a fantastic crop out there with yields averaging above 200 bushels per acre in many fields,” Thomison said. “Why let that crop go down the tube waiting on grain to dry down, which is questionable at this late date? Right now, in many areas we have a crop that is standing well, exhibiting good plant integrity with stalks and intact ear shanks. But there’s only one direction that plant health is going to go and that’s down.”

Thomison pointed to research he conducted a few years ago, that evaluated the state of corn hybrids the longer they stayed in the field. What he and his fellow researchers found was the longer corn was left in the field, the higher the rate of yield loss – an average of 11 percent between mid-November and mid-December.

“The results of the research suggest that corn can tolerate a harvest delay until mid-November without major yield losses, but after that things start falling apart,” Thomison said. “After mid-November harvest delays begin to exact a toll on corn left standing in the field. In some years, our data shows yield losses as low as 5 percent, but in other cases it was as high as 24 percent.“

Thomison said yield losses are closely associated with stalk lodging, especially with hybrids that are sensitive to stalk rots. Another major concern is grain quality. Ears subjected to prolonged wet conditions can turn moldy, potentially contaminating grain with mycotoxins that are harmful to livestock.

“In extreme situations, kernels can start sprouting, which adversely affects marketability of the grain,” Thomison said.

According to the Ohio Agricultural Statistics Service, 76 percent of Ohio’s corn crop has been harvested, behind last year and the five-year average. Thomison said that farmers either can’t harvest their corn because of unfavorable field conditions or are waiting for the corn to dry down further.

“Perhaps the most striking finding about the research is that we didn’t see a significant decrease in grain moisture after mid-November. We saw grain moisture decrease 6.3 percent between mid-October and mid-December, but only 0.5 percent of that dry-down occurred after mid-November,” Thomison said. “If a grower is expecting to see a big jump in grain moisture change between now and mid-December, studies suggest otherwise. We even left corn in the field as late as March and didn’t see a drastic decrease in grain moisture.”

Thomison said that in recent years farmers have experienced good growing conditions that have allowed them to leave corn in the field longer than they probably should. However, he said this probably isn’t the year to do that.

The last time growers faced delayed harvest issues on this scale was in 1992, when cool, wet fall conditions kept some growers out of the fields until winter.

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