Degree Days - Entering the Stretch, Aiming for the Finish Line

August 25, 2009

By Rich Pope, Department of Plant Pathology

Another week of cool but not too cold weather has positioned the Iowa grain crop well for the final run to harvest.  During the week of August 17 we lost a net 50 to 60 degree days to average, but favorable night temperatures allowed for crop condition to improve slightly. The August 24 USDA crop condition report assesses Iowa corn and soybean both at 79 percent good to excellent. Another two or three weeks of good weather and we will begin the final dry-down push to harvest.

Degree day accumulations through August 23, 2009

Most soybeans have now reached growth stage R5 to R6 and corn is at R3 to R5. We are near the peak of whole plant dry matter accumulation, and the last phase of grain fill is the mobilization of carbohydrates into the developing seed.  See the ICM article that compares the 2009 growing season with selected previous crop years.


Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted at or by calling (515) 294-5899.

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