CFAES Give Today
News Releases Archive (Prior to 2011)

College of Food, Agricultural, and Environmental Sciences


Stressed Crops Tapping Hidden Soil Moisture, But Rain Still Needed

June 26, 2007

COLUMBUS, Ohio -- Despite some recent showers, drought-like conditions continue across Ohio and field crops are beginning to exhibit signs of stress. At the moment, however, enough soil moisture is still available for the crops to get by.


According to the Ohio Agricultural Statistics Service, soybeans and corn remain over 70 percent in fair to good condition, despite the fact that topsoil moisture is nearly 80 percent short to very short. But the stresses from the lack of prolonged, adequate moisture are beginning to take a toll on the state's major crops, especially corn.

Peter Thomison, an Ohio State University Extension agronomist, said that corn in areas of the state is beginning to roll, an early symptom of drought stress. The plant rolls its leaves during mid-day as a defensive mechanism to reduce photosynthesis and conserve water.

"Corn plants with leaf rolling during early-to-mid vegetative development may look severely stressed, but it's usually cosmetic and has no long-term impact on yields," said Thomison, who also holds a research appointment with the Ohio Agricultural Research and Development Center. "Yield losses to moisture stress are directly related to the number of days that the crop shows stress symptoms during different growth periods."

He indicated that drought stress during early vegetative growth usually has a negligible impact on yield, but as the corn develops and begins to form ears, drought conditions will have more of an impact on the plant.

"The number of kernels per row on an ear will be affected more by stress than the number of rows on an ear," said Thomison. During the late vegetative stages, drought stress can reduce yields 5 percent to 10 percent. However, severe water stress during tassel emergence can reduce yields up to 25 percent, and during pollination it can reduce yields up to 50 percent."

A current condition of corn that can have a direct impact on yields is uneven plant emergence. Thomison said that corn some fields are exhibiting extreme height variations -- for example corn that is 5 inches tall growing next to corn that is 20 inches tall.

"As much as 30 percent or more of the corn crop is experiencing some level of unevenness," said Thomison. "This situation could have an impact on yields later in the season because late developing plants can't compete with those more developed. Later developing plants don't have a well-established root system to combat the stresses later in the season, and they are also more susceptible to insects and diseases."

Despite the potential troubles facing the corn crop, soil moisture is keeping it going -- for now.

"We've got good soil moisture 4 to 7 inches deep in the soil. If the roots can reach that far, the crop for right now is still doing OK, based on observations of the crop in my region," said Harold Watters, an OSU Extension educator from Champaign County. "Any lack of significant rainfall after the 4th of July holiday may place the crop in critical condition. But we've had instances in the past where we haven't seen any good rainfall until August 1, and we still made some recovery."

Watters said that the soybean crop is "struggling along," but may not experience any significant impacts from lack of rainfall until August.

"Ideally, we'd like to get an inch of rain a week throughout the state between now and harvest," said Watters.

In case that doesn't happen, growers can help their drought-stressed crops by keeping weeds under control, as they steal nutrients and moisture; applying the right amount of nitrogen for corn yields; and following proper management practices during the growing season.

According to the National Drought Mitigation Center, Ohio is currently experiencing abnormally dry to moderate drought conditions.


Candace Pollock
Harold Watters, Peter Thomison