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College of Food, Agricultural, and Environmental Sciences


Rains Arrive Too Late To Help Corn Crop

October 1, 2002

COLUMBUS, Ohio - Recent scattered rainfall and saturated conditions generated from the remnants of Tropical Storm Isidore have arrived too late to pull Ohio's corn out its drought-stressed state, and may even prove detrimental for farmers trying to harvest their crop.

Peter Thomison, an Ohio State University Extension agronomist, said that because of the long-term drought conditions, corn is drying down more quickly than farmers may expect. And the late-season rainfall may delay harvest, potentially contributing to yield losses.

"The corn crop has been drying down very quickly because of the very warm weather we've had until recently. Because it was a late planting season and, in some cases, the corn is still somewhat green, growers might think the corn isn't as dry as it is," said Thomison.

Some Ohio State field plots in South Charleston, Ohio varied in moisture content. One hundred and fourteen-day hybrids planted in mid-May were down to 22 percent moisture; 108-day hybrids were at 18 percent moisture; and hybrids planted in late April well before Ohio was plagued with wet weather were at 11 percent moisture.

"When it gets down to that level, you are looking at some potential corn losses because the grain is less harvestable during the combine operation," said Thomison. "The optimum level to harvest is around 24 percent and when it gets between 15 and 20 percent, farmers need to get in their fields to minimize harvest losses. But the recent rains may delay that." The potential harvest delays just compound the list of problems corn growers have been facing all season due to the unusual weather conditions. A cool, wet spring followed by a hot, dry summer has created stalk lodging, or fallen stalks, in some corn hybrids - another reason why farmers need to harvest as soon as possible.

"With the heavy storms we've had, some corn did go down and they are going down with ears on them," said Thomison.

In addition to stalk lodging issues, recent rainfall has facilitated a rapid deterioration of the grain on some plants, which may also impact yields if farmers are unable to harvest their fields on time.

"The one thing that has surprised me is that the quality of the grain that's on the plants is deteriorating. It's only late September and we're seeing corn ears that look like they've been out in the field for four or five weeks," said Thomison. "The husks have opened up and facilitated dry down, which is good, but the downside is they've got to get harvested. The ear tips are exposed promoting grain deterioration." The occurrence of European corn borer late in the growing season may also impact corn harvest.

"There are corn borers in the stalks, which will contribute to the lodging problem," said Thomison. "Even worse, the corn borers are located around the shank of the ear and, if there are any extended harvest days, will cause a lot of ears to fall off the plants prematurely. Any ears on the ground is basically lost yield." Once farmers get the opportunity to harvest, they may run into actual harvesting problems due to the crop stresses. Drought conditions have resulted in smaller than normal ears and shorter than normal plants with reduced ear heights.

As a result of these conditions, some combine and harvesting adjustments may be necessary, said Thomison.

"Small ears or ears with a limited number of kernel set may not make it through the combine," he said. The loss of one "normal" sized ear per 100 feet of row translates into a loss of more than one bushel per acre. An average harvest loss of two kernels per square foot is about one bushel per acre.

Growers may find the following suggestions helpful when harvesting drought-stressed corn: * Review the operator's manual for suggestions on harvesting a "light crop".

* With short or lodged corn, run the gathering snouts and chains low. Watch for stones, and be sure stone protective devices are working.

* Drive carefully and at normal speeds to avoid excessive harvest loss and machine damage from stones.

* For small ears, set stalk rolls and snapping plates closer than normal to snap off a higher percentage of ears. Do not attempt to snap off barren cobs.

* If clean shelling is a problem, increase cylinder speed slightly, and if necessary, decrease concave clearance. With a rotary machine, check rotary concave clearance. Avoid excessive damage to kernels from good ears.

* If cleaning losses are high, open the chaffer and chaffer extension slightly.

* Initially decrease the amount of air from the cleaning fan. If cleaning becomes a problem, increase the fan blast, and close the lower sieve slightly.

According to the Ohio Agricultural Statistics Service, Ohio's corn crop was rated 60 percent in poor to very poor condition as of the week of September 30 - little change from the previous three weeks. As of the September crop production report, the U.S. Department of Agriculture has projected average corn yields in Ohio at 110 bushels per acre, down from 112 bushels per acre the month earlier. Yield projections are likely to continue to decrease. Ohio averaged 138 bushels per acre in 2001.

"With the problems we've had with corn this year, I think it would behoove growers to get out and harvest corn as quickly as possible," said Thomison. "With the way corn prices are this year and as dry as it's been, there's no reason to be leaving that corn out in the field."

Candace Pollock
Peter Thomison