The Heat Is Online

Warming Is Disrupting Corn Pollination

Expert: Climate shift could hurt corn yield by hindering pollination

The Des Moines Register, Sept. 10, 2008


Iowa's farmers may look forward to a longer growing season as the climate warms, but an Iowa State University weather expert warned Tuesday that warmer temperatures could interfere with corn pollination and, ultimately, yields.

"The window of pollination is getting shorter, down to
three to five days from an average of 10 days in past decades," said Jerry Hatfield, laboratory director of the National Tilth Laboratory at ISU and a specialist in agricultural climatology.


Hatfield spoke at the Biobased Industry Outlook Conference at ISU on Tuesday. He said warmer weather stresses the pollination process, which usually begins in July and is the way the corn plant makes the kernels that provide the cash in the crop.

"We're talking about the danger of cobs with fewer kernels, or no kernels at all, if the weather is too warm for pollination," Hatfield said. He noted that "at 104 degrees, the pollen becomes sterile. Temperatures above the mid-90s can kill pollen."


His assessment of the threat goes against conventional wisdom about global warming or climate change: that warmer weather would make a longer and better growing season for Iowa's corn farmers.

"The longer season might not be beneficial if warmer temperatures cut into yields," Hatfield said.

Scientists have predicted a rise in the average temperature in the
Midwest of 2 or 3 degrees during the next half-century. Already, Hatfield said, the traditional Corn Belt has been redefined north into the Dakotas and Minnesota.


But he said the warmer weather would be a mixed blessing to farmers because it will make rainfall in the right place and right amounts even more crucial.

"Corn needs moisture during pollination in any circumstance, but it will need it more with warmer temperatures," Hatfield said. "You can lose 10 to 15 bushels per day in yield if it doesn't rain at the right time."