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College of Food, Agricultural, and Environmental Sciences


Ohio Drought Impacting Potential Corn Yields

July 24, 2007

COLUMBUS, Ohio -- Ohio's moderate drought is taking a toll on the state's corn crop, and some fields are already taking a major yield hit.

Peter Thomison, an Ohio State University Extension agronomist, said that corn is entering the pollination stage, a critical development phase that determines yield. Lack of significant rainfall throughout much of the state, however, is shutting down plants stunted in development, and it's estimated that 25-30 percent yield or more from those fields may already be lost.

"The general overview of the condition of the corn crop is that it's hanging on. Some of the acres don't look too bad, other acres actually look very good, and some corn is basically gone," said Thomison, who also holds a partial research appointment with the Ohio Agricultural Research and Development Center. "That's a scary thing when someone tells you their corn is gone before pollination. That means the drought is so severe that plants have shut down growth, and without any major rainfall they won't recover. At this point, those plants might be best cut for animal feed than harvested for grain."

According to the Ohio Agricultural Statistics Service, corn is 73 percent in fair to excellent condition (compared to 92 percent in 2006). The good news, said Thomison, is that drought impact on cornfields is very localized, and there's hope that much of the crop will generate respectable yields.

"If it wasn't for the mild temperatures we are experiencing right now, yield losses could be even greater," said Thomison.

But rain is desperately needed, and, according to National Weather Service hydrologist Jim Noel, it doesn't look like Ohio will receive significantly widespread rainfall before harvest.

"Long-term precipitation conditions remain in the normal category over the 6-12 month period over most of Ohio. However, short term of 90 days or less is much drier than normal," said Noel, in an OSU Extension report. "Going forward, it will likely not be until the autumn cool season before that pattern changes."

Thomison stressed that what the corn crop needs right now is above-average rainfall to get the corn through the pollination and grain filling processes and produce average to above-average yields.

"Many Ohio corn fields received 1-2 inches of rain last week, which has helped at least temporarily reduce the impact of the current drought. However, more rain is needed to recharge soil moisture and limit drought stress injury during the upcoming weeks until grain fill is complete," said Thomison.

The greatest hit in yield generally occurs during the pollination stage. In cases of severe drought situations during pollination, yield losses can be as high as 40-50 percent in fields under four days or longer of moisture stress.

Grain fill follows pollination, a stage that determines the total number of kernels per ear that a plant can produce. If hot, dry conditions persist during grain fill, another 20-30 percent loss in yields can occur due to kernel abortion. Kernel abortion occurs when the plant cannot produce enough sugars to fill all the kernels of the ear. Kernels that are the last to develop and are generally smaller usually die.

Pierce Paul, an OARDC plant pathologist, said that over 90 percent of the state's corn crop is uneven. Different stages of development means different sensitivities to drought, and plants that are stunted (3 feet or less) will be impacted by the dry conditions more than those plants further along in development.

"The unevenness is the biggest concern," said Paul. "The corn needs water."

Corn is one of Ohio's most valuable field crop commodities, second to soybeans in acreage and economic value. According to the Ohio Department of Agriculture, corn production contributes $836 million to Ohio agriculture. Feed grain serves as a main component of corn production, but the crop is also becoming an integral source for ethanol.

Candace Pollock
Peter Thomison