Sponsored By
indiana Prairie Farmer Logo

Did wildfire smoke cause corn to mature late?Did wildfire smoke cause corn to mature late?

Corn Illustrated: Smoke from Canadian wildfires affecting the crop is a popular rumor spreading across farm country, but there is a better explanation.

Tom J. Bechman

November 14, 2023

2 Min Read
A cornfield with young plants
COOL, HAZY DAY: Purdue Extension’s Weed Science Field Day on June 27 was a damp, cool, dreary day, hemmed in foggy, cloudy conditions from wildfire smoke. Experts say cool weather, not smoke, is more likely directly linked to the unusually slow corn drydown this fall. Tom J. Bechman

The 2023 corn harvest will likely be remembered for three things. First, yields in many areas that caught timely rains around pollination were good to excellent. Second, in those same areas, corn tended to reach black layer later than normal and dried down in the field slower than expected. Third, the leading explanation by far in elevator truck lines and coffee shops for so much wet corn so late in the season was wildfire smoke that blanketed some areas on several occasions in June and again in late July.

The first two observations are true, notes Bob Nielsen, retired Extension corn specialist with Purdue. However, Nielsen doesn’t believe wildfire smoke was a direct cause of the slow grind to black layer and subsequent delay in grain drydown.

“It may have indirectly played into it if it resulted in some cooler days,” Nielsen says. “But there were plenty of cool days where there wasn’t wildfire smoke.

“The better explanation is that cooler weather in June and again in early to mid-August slowed accumulation of growing degree days, and that slowed corn maturity. The cooler the temperatures, the slower GDDs accumulate. Corn hybrids need a certain level of GDDs to mature.”

Nielsen adds that when corn matures later into the fall, drydown is usually slower. That’s partly because some of the best weather for drying typically occurs in September.

Mapping trends

Nielsen turns to the GDD Corn Tool developed by the Useful to Usable USDA-funded project to illustrate how the 2023 season compares to previous years for temperature. The tool allows the user to select from many, though not all, counties in several Midwestern states, and view actual vs. historical temperature data. It is maintained during the growing season.

To create the chart shown below, Nielsen chose Blackford County, Ind., a 109-day hybrid maturity, and a May 19 planting date.

“That represented one of our on-farm sulfur trials where corn was still running about 30% grain moisture at the end of October,” he explains.

Corn GDD Tool chart

The purple line represents normal GDD accumulations for that location, and the black line represents GDD accumulations this year.

“The GDD tool estimated that black layer did not occur until Oct. 4, which was exactly what our cooperator told us happened,” Nielsen says. “More importantly, the chart illustrates the deviation from normal GDD accumulations for this location throughout the season. Cooler temperatures in mid-June put us behind normal early. Then around mid-August, cooler-than-normal temperatures again expanded that deviation further. Continued cooler-than-normal weather since black layer further slowed in-field drying.”

Weather records like this one are useful because they document what happened vs. what you think happened, Nieslen says. “Yes, there was an extremely hot week at the end of August, but GDDs top out at 86 degrees F in the formula,” he says. “One very hot week doesn’t offset several weeks of cooler weather at key times.”

Read more about:

Dry Down

About the Author(s)

Tom J. Bechman

Editor, Indiana Prairie Farmer, Farm Progress

Tom J. Bechman is editor of Indiana Prairie Farmer. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like