Illinois corn crops seeing biggest yield variability in at least 30 years, crop scientist says; extreme July heat, dearth of rain among likely culprits

BLOOMINGTON, Illinois , August 25, 2011 () – Emerson Nafziger is used to seeing yield differences between corn fields, but says this year's crops are showing more variability than any he has seen in 30 years as a University of Illinois crop scientist.

"In driving through quite a bit of the state this past two weeks, the variability is not only region to region and field to field, but sometimes row to row and plant to plant," said Nafziger, of Urbana.

"We see this in years that are dry, but even in areas that aren't dry, we are seeing a lot more of it (variability)," he added.

While not entirely sure of the cause, he feels a combination of extreme July heat, a lack of rain and planting on wet fields in May combined to produce widely varying yield estimates.

The dry conditions are reflected in the most recent U.S. Department of Agriculture crop progress update, which rates 42 percent of the state corn crop in excellent or good condition, down from 50 percent a week earlier.

The wide range of estimates is also shown in analysis of area test plots. In Heartland Bank and Trust Co.'s 100 plots in six counties, the expected yields range from 112 to 210 bushels per acre.

Statewide, the range is even higher, said Nafziger. "I've seen fields with only 50 bushels an acre, and some over 200. You always see that range, but often have to look for it a little closer," he said.

McLean County has received some timely rain over the past month, including 0.87 of an inch Tuesday, but some counties to the south have not been as fortunate.

"It rained here for about two minutes (Tuesday)," said Ken Bjelland, manager of the DeWitt County Farm Bureau in Clinton, He was not sure how yields were holding, but said some farmers were expecting yields close to or above the 178-bushel per acre county average, while others may be 50 to 60 bushels an acre below that.

Eric Mennenga, who farms near LeRoy, is one of the recipients of adequate rainfall this year and is "pretty optimistic" about his corn. But he knows it is the luck of the draw.

"It's mile by mile. Three miles south of me, they did not have a drop of rain when I had 1.5 inches one day in July," he said.

Crop experts have hope for at least average soybean yields. Fifty-three percent of the Illinois crop is rated in excellent or good condition, according to the latest update, compared to 57 percent a week earlier.

"The number of pods is pretty much set, but how full and fat and heavy they get is to be determined," said Dennis Bowman, a crop systems educator at the University of Illinois Cooperative Extension in Urbana. He said the later-planted beans are more forgiving in August, and "have the ability to add yield at the last minute more than corn."

Jason Lay, a Hudson-area farmer, also hopes his beans will reach the 50-plus bushel an acre point, but said it will take some significant cooperation from Mother Nature.

"We need more favorable weather conditions, and cooler temperatures. That would extend the growing season" and give soybeans a chance to add weight, said Lay.

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