Hot weather causes stress on farms, Clemson Extension agent says

Published: July 2, 2012

CLEMSON — If you think it’s tough dragging your body around in 100-degree heat, imagine what happens to a 1,500-pound cow.

"This type of weather is hard on plants and animals as well as humans," said Danny Howard, Clemson Extension agent in Greenville County. "Heat stress takes a serious toll on livestock, especially in combination with high humidity. 

"Hot weather can reduce feed intake, milk production, weight gain and even result in livestock death," Howard said. "A rise in temperature from 70 to 95 degrees can double or triple water requirements. All animals need a good supply of fresh water to help survive the heat wave."

A hot spell can cause financial problems for farmers even if their cattle have no physical problems, he said.

"High temperatures cause grazing animals to seek shade in the hottest part of the day. Cattle will stop grazing," Howard said. "If they stop grazing, they do not put on body weight. That translates into a yield reduction to the farmer in lost pounds of beef. "

Livestock farmers at least can provide water, ventilation and shade for cattle, hogs and poultry. But there's no shade for a field crop.

"Plants in general suffer when they face a constant temperature in the high 90s," Howard said. "Pollination needed to produce a high yield is decreased when the temperatures rise above 100 degrees. Also, sun scald on plant tissue is another concern with the extreme temperatures."

Blazing sun and soaring daytime temperatures aren’t the only concern, either.

"When the nighttime temperature remains in the high 70s or low 80s, the plant does not have a resting period, which in turn causes the plant to shut down," Howard said. "We have seen this in the past with the decline of pastures grasses."

Even before this weekend's hot spell, crops and pastures were showing the effects of stress because of heat and lack of rain, according to the USDA Agricultural Statistics Service.

The agency’s most recent crop report listed a third of South Carolina's farms reporting short or very short soil moisture.

"The combination of hot and dry weather is something you worry about at this stage of a crop’s development," Howard said. "So far we are five to six inches behind the normal rainfall for this time of year. As soybeans and corn kernels are growing and filling out, a drop in moisture or serious heat stress can affect their development and hurt crop yield.”

Much of South Carolina already is in or approaching drought conditions, according to the National Drought Mitigation Center at the University of Nebraska. Hardest hit are the counties west of Columbia, especially along the upper Savannah River.

With annual sales of crops and livestock approaching $2.5 billion in South Carolina, a stretch of bad weather could be bad news for the state’s biggest business, Howard said.

"If we get sustained excessive temperatures combined with significant drops in soil moisture, the financial impact could be serious," he said. "A lot of folks will be watching how high the temperatures get, how long they continue and whether crops get the rain they need."

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