Will Your Corn Beat The Frost?

Iowa Farm Scene

August heat advanced crop maturity, but Iowa fields still need more time before Jack Frost arrives.

Published on: September 3, 2013

Hotter than normal weather the last half of August added heat units to Iowa's late-planted, slow-growing 2013 corn crop. The crop had been lagging in development all summer. The recent blast of heat helped speed up crop maturity somewhat. But many Iowa fields still need more time to develop the crop. Iowa needs a later-than-normal frost this fall.

In a nutshell, that's what Iowa State University Extension corn agronomist Roger Elmore told the crowd attending a field day August 30 at the ISU Agronomy Farm near Boone, just west of Ames. It was 104 degrees in central Iowa, a good day to talk about the effects of hot, dry weather on growth and development of this year's crop.

TRACKING CORN MATURITY: Barb Halbur, a Carroll County farmer, looks at the milk line on corn kernels developing on an ear. The milk line moves from the top of the kernel toward the cob as kernels mature. When the milk line reaches the kernel tip, a black layer forms in the tip. The black layer is the first visible sign that physiological maturity has occurred and the corn is safe from frost.
TRACKING CORN MATURITY: Barb Halbur, a Carroll County farmer, looks at the milk line on corn kernels developing on an ear. The milk line moves from the top of the kernel toward the cob as kernels mature. When the milk line reaches the kernel tip, a black layer forms in the tip. The black layer is the first visible sign that physiological maturity has occurred and the corn is safe from frost.

Elmore also has recently spoken at other ISU field days, fielding questions from farmers wondering: Will my corn reach maturity before first killing frost hits this fall? Are we headed for a late harvest this year or not? We had a cool growing season, and then it turned hot. What are the effects of the continued dryness in this 2013 growing season—what kind of yield can I expect?

Is Iowa headed for a late harvest this year or not?

Will Iowa have a later than normal harvest? Yes, says Elmore. Harvest is likely to be a stop-and-go affair for a number of farmers this fall due to a wide range of planting dates and variable growing conditions. "Despite the blast of heat units that came during the last two weeks of August, which sped up crop development somewhat, many corn fields in Iowa were planted so late that they need a later-than-normal frost this fall to be safe from damage," he explains.

Because of the wet spring only about half of Iowa's 2013 corn was planted before May 16-17. So half of the crop was planted in the last half of May or sometime in June—a very late start. Some corn was planted in mid-June. Then it quit raining. But the weather was cooler than normal so that helped conserve moisture. On the other hand, with the lack of heat units the crop continued to lag in development.