Farm Progress

Heat stresses crops: Mississippi

Bonnie Coblentz

August 13, 2010

4 Min Read

Record-breaking heat is forcing Mississippi producers to manage crops more carefully than normal to bring what looks like successful yields to harvest.

Temperatures in the Delta, home to the majority of the state’s row crops, have set as many as five record highs during the first week of August.

Nancy Lopez with the U.S. Department of Agriculture in Stoneville, Miss., said some daily records from Greenville, Miss., to Vicksburg, Miss., were broken consecutively in August. July also was unusually hot across most of the state.

During the last week of July, Rolling Fork, Batesville and Verona, Miss., were 3 degrees warmer than normal, while much of the rest of the state was 2 degrees warmer than average. Waynesboro, Miss., had the record, posting temperatures 6 degrees warmer than normal for the week.

Along with the heat has been drought, with only scattered rains since July.

“There is wider rain coverage in the southern part of the state, which has received heavier cumulative rainfall than in the north since Aug. 1,” Lopez said. “By Aug. 10, the state average for the month was just .79 inch of rain.”


It is hard to categorize the state’s soybean crop because a wide planting window has resulted in some fields nearly ready to harvest, while others are just getting started. Trey Koger, Extension soybean specialist, said the crop rates range from fair to excellent, and how a field handles the heat and drought depends largely on when it was planted.

“For soybeans planted in May and later, the peak water demand coincides with the hot, dry weather,” Koger said.

Soybeans can tolerate extremely hot temperatures, such as those this summer has brought, but high temperatures are tough on pollination. This is especially true when nighttime temperatures stay in the upper 70s to low 80s.

“When the temperatures get above 90 degrees and the nighttime temperatures don’t get down in the lower 70s, then the viability of the pollen starts to decline, resulting in poor pollination and excessive flower and pod abortion,” Koger said. “Temperatures in the upper 90s also result in a plant that struggles to stay cool, especially in non-irrigated environments.”

About 65 percent of the state’s soybean crop is irrigated.

“Early-planted, non-irrigated soybeans have fared pretty well, yielding harvests of 40 to 50 bushels an acre,” Koger said. “Later-planted, non-irrigated beans have a ways to go and are going to need rainfall to make a good crop.”


Darrin Dodds, Extension cotton specialist, said USDA estimates 55 percent of the state’s cotton crop is in good to excellent condition.

“Extended periods of drought and high temperatures have been detrimental to a portion of this crop,” Dodds said. “Irrigated cotton constitutes the majority of the good to excellent cotton in the state. However, dryland fields are variable, depending on the variety planted and the level of rainfall received.”

August heat caused high levels of fruit shed in upper portions of the plants in many fields. Some of the retained fruit may develop into malformed bolls.

“Excessive heat reduces pollen viability, which can lead to poor pollination,” Dodds said.


USDA estimates 76 percent of the state’s rice crop in good to excellent condition.

“This has been a good year for rice production,” said Nathan Buehring, Extension rice specialist. “There has been some concern about the small percentage of late-planted rice that was heading during the recent high heat. Most of the earlier-planted rice had finished pollination before the 100-plus degree temperatures arrived.”

Buehring said he expects heat to have a minimal impact on Mississippi’s state average rice yields this year.

“Looking back at history, our highest yields come from hot and dry summers,” he said.


Erick Larson, grain crops agronomist with the Mississippi State University Extension Service, said corn has not suffered in recent hot and dry conditions.

“The heat of the first 10 days of August didn’t hurt much of the corn crop,” Larson said. “Most of the corn in the state has reached physiological maturity, so the hot, dry conditions are actually enhancing the dry down of the crop.”

Heat stresses corn when it comes in June, the middle of the growing season. About half of the state’s corn acres are irrigated. Fields in the south Delta experienced the most drought, and Larson said dryland yields there will likely be poor.

“The irrigated crop is going to be very good this year, but that’s going to depend on growers’ ability to irrigate individual fields,” Larson said.

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