Hot Night Theory Reflected in September Crop Report

USDA drops corn estimate by slightly more than expected.

Published on: Sep 13, 2010
Those who study corn development and have reviewed the weather statistics across the Corn Belt for the heart of the growing season weren't surprised that USDA dropped it's estimate of national corn production in its September Crop Report issues last Friday. USDA lowered the national estimate by about 2.5 bushels per acre, notes Arlan Suderman, a marketing analyst for Farm Progress Companies.

States like Indiana contributed to the trend. High nighttime temperatures impact corn in various ways, Suderman says. In those late days of July and early days of August when temperatures bottomed out at 80 to 83 degrees for the low in central Indiana, corn was burning up energy it didn't need to lose because respiration continued well into the night.

The grain trade expected USDA would drop its estimate. However, the trade guess was 2 bushels per acre, Suderman says. USDA went a bit deeper, going to 2.5 bushels per acre. On a national basis, a one-half bushel cut amounts to a sizable number of bushels of corn that USDA now thinks won't appear and ever get into the bin.

"Nationwide, the lowering of estimated yield from the August report took off about 200 million bushels," Suderman says. He expected USDA's estimate to be lower, because he ahs long believed in the concept that if it's too hot at night, it's tougher to obtain the very top yields in corn most producers like to see.

Suderman learned this first while working as an Extension agent in Kansas. He discovered after spending time in southwest Kansas, then Wichita, further east, that warm nights were much more prevalent in eastern Kansas. The air is drier in southwest Kansas and temperatures tend to bottom out lower. Under irrigation, farmers there were besting farmers with irrigation near Wichita by 30 bushels per acre, and it wasn't because soils were any better, Suderman notes.

With the help of Kansas State agronomists, he finally identified that the difference was what happened to plants when they couldn't cool off at night. Two commodity groups just this summer reviewed weather records going back 60 years, and agree that Suderman's conclusions are likely valid.

Learn more about what Suderman has to say in the next issue of Indiana Prairie Farmer. Corn Illustrated consultant Dave Nanda also gets down to the heart of the theory as to why hot nights are not good for corn in the same issue.