Corn grows in Saunders County, Nebraska, just outside Ashland. These crops, like all plants, sweat out moisture pulled from the ground as a means to keep cooler in the heat. (Aaron Sanderford/Nebraska Examiner)
ASHLAND, Nebraska — Nebraskans like to complain about the humidity this time of year. But some might not realize that the corn and soybeans that help power the state’s economy are part of what’s making farmers and their customers sweat.
All plants release into the air much of the moisture their roots absorb from the ground. But the weather is muggier in these parts in July and August than it otherwise would be because corn and soybeans release more moisture than most crops.
Scientists and farmers call this evapotranspiration. The more common term is “corn sweat.”
Those who monitor the impact of that moisture say corn and soybeans make it more humid here because Nebraska and its neighbors grow a lot of both.
Nebraska farmers produced 1.85 billion bushels of corn in 2021, third most in the nation, according to the Nebraska Department of Agriculture. Farmers here raised 351 million bushels of soybeans, good for fourth in the nation.
Barb Mayes Boustead, an Omaha-area meteorologist, helped spark discussion about “corn sweat” recently by writing a column about it for the Washington Post. She wrote that densely planted acres make summers in the Midwest and Great Plains feel hotter.
Corn releases a lot of “sweat”: One acre of planted corn can release up to 4,000 gallons of water a day, she wrote. Soybeans are no slouch, either, she explained. Evaporated moisture from rivers, ponds, lakes and the Gulf of Mexico make a difference, too.
Evapotranspiration from corn and soybeans aren’t the only factors, Boustead said in an interview Friday.
“But the moisture they release into the air does add in a measurable way to the humidity … of more than just the fields,” Boustead said. “People can feel it in cities like Omaha and Lincoln.”
State Sen. Curt Friesen grows corn and soybeans on his 1,300-acre farm in Henderson, a town of 991 people southwest of York. He said summertime spikes in humidity are just part of life “when you live out here in the middle of corn country.”
He chuckled at Boustead’s finding that an Iowa cornfield can be muggier than Miami Beach. It’s rough this time of year to change a tire on an irrigation center pivot in the middle of a humid cornfield, where no breeze can reach you, he said.
“You just deal with it,” Friesen said. “It’s just the way it’s always been. I always think it’s more stifling in the city when you’re surrounded by concrete, and the buildings block the wind.”
Friesen, who formerly served on both the Nebraska Corn Board and National Corn Growers Association, said his slice of east-central Nebraska was a little less muggy in the 1950s and 1960s, when fewer acres of farmland were irrigated. He said you can feel the difference when the plants let out more moisture.
Al Dutcher, the Nebraska Extension agriculture climatologist, said irrigation plays some role in what’s changing. Federal farm programs and their impact on farmers’ planting choices also have significant influence, he said.
More acres in parts of Kansas, Nebraska and North and South Dakota that used to plant wheat have been shifting toward corn and soybeans. That matters, he said, because wheat reaches its peak point of letting moisture go in the spring and fall.
Because more people are planting corn and soybeans from Texas to central Canada, Dutcher said, the midsection of the United States is seeing more concentrated moisture from crops that release more moisture at the same time of year, in midsummer.
Nationally, 90 million acres have been planted with corn and soybeans. That’s the equivalent, he said, of planting Nebraska border to border 3.7 times with the top two crops contributing moisture into the atmosphere.
“The reason I’m confident we are seeing more moisture is the expansion of the Corn Belt,” Dutcher said. “Some has to do with farm programs, how they’re set up — and individual producers looking at prices and chasing an opportunity.”
Dennis Todey, who directs the U.S. Department of Agriculture’s Midwest Climate Hub in Ames, Iowa, said Iowa and other Midwestern states are used to the humidity spikes of “corn sweats” because they long ago shifted to corn and soybeans.
Great Plains states are feeling more of that shift today, he said. “Corn sweats” and the combined effects of a changing climate are making it feel hotter, boosting dew points and the heat index.
Weather and climate experts say we’re seeing fewer 100-degree days than in the past, combined with warmer nights. That’s because the extra moisture in the air makes it harder for temperatures to swing in either direction — higher or lower.
Higher-than-normal overnight low temperatures affect how much water it takes to grow crops, the livelihood of livestock in cattle ranching states such as Nebraska, and the ability of people to rest well without air conditioning, Todey said.
“It is adding to that effect, where it’s increasing the amount of moisture in the atmosphere,” he said. “Even in cities, though we’re not close to fields, there are enough corn and soybeans out there that it’s influencing what we’re feeling.”
Although evapotranspiration is an issue worth highlighting, Dutcher said, he thinks members of the media are over-using the term “corn sweat.”
Friesen said he understands the fascination over “corn sweat” and chuckled, saying people might be more interested to learn about “corn sex” and the distinctly sweet smell emitted when corn starts to pollinate.
Boustead, who said she wanted to help scientists more easily communicate why some of this month’s summer heat wave feels worse than usual, wrote about “corn sweat” in all its glory.
“If it’s muggy in Mid-America in midsummer,” she wrote, “go ahead and blame the corn. Just don’t forget its friends: soybeans, soil and waterways, just to name a few.”
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