COLUMBUS, Ohio - As days with extreme heat coupled with drought conditions have dominated the weather statewide in recent weeks, growers have begun to ask themselves just how hot is too hot for corn and soybeans?
While corn originated as a tropical grass and can tolerate exposures to temperature extremes as high as 112 degrees for brief periods, the optimal daytime temperatures for corn typically range between 77 degrees and 91 degrees, said Peter Thomison, an Ohio State University Extension agronomist.
When temperatures rise above 95 degrees, corn growth decreases, he said.
"When temperatures hit between 93 degrees to 98 degrees for four days or more, you could start to experience yield losses in corn, but it also depends on the amount of moisture in the soil," Thomison said. "It's hard to separate high temperature effects on corn from effects of drought on corn because the two usually go hand in hand.
"It's really hit or miss right now because of very localized drought conditions, where you have a lot of people who are suffering while others may not be experiencing conditions that are as bad. This is a very critical period for corn."
Growers are extremely watchful of the weather now, considering that the majority of Ohio except for small portions of some counties near the Kentucky, West Virginia and Pennsylvania borders is experiencing moderate drought, with areas near the Indiana and Michigan borders experiencing severe drought as of July 31, according to the most recent U.S. Drought Monitor.
And the weather outlook for the first couple of weeks of August call for above-normal temperatures, with periods of high heat throughout the state and below-normal rainfall in some places, and the potential for near-normal amounts of rainfall in other areas, according to Jim Noel of the National Weather Service.
Noel, whose weather updates are featured in the OSU Agronomics Crop Team's weekly C.O.R.N. (Crop Observation and Recommendation Network) Newsletter, said rainfall will average 0.25 to 1.00 inches through Aug. 5, with the normal range for the period at 0.75 to 1.00 inches.
The outlook for Aug. 6 to Aug. 12 calls for temperatures mostly between 85 to 95 degrees, with lows ranging from 65 to 72 degrees, he said. Rainfall will average 0.25 to 0.50 inches, which is below normal for the period, Noel said.
Soybeans, on the other hand, are a more temperate leguminous plant with an ideal daytime temperature of 85 degrees, said Laura Lindsey, an assistant professor of horticulture and crop science at Ohio State. When air temperatures exceed 85 degrees, soybeans can experience heat stress regardless of reproductive stage, she said.