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Northern Illinois Agriculture

University of Illinois Extension
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Corn yields, revisited

Last week we touched on the subject of corn that had died prematurely due to dry weather and warm temperatures and its effect on grain fill and final yield. (Not an issue at the NIARC, we picked up .79 inches on Sunday)

It was shared that corn just entering the dent stage (R5) still has about 40% of its potential yield to assimilate. To ground truth this assumption Dr. Emerson Nafziger, University of Illinois agronomist, oven dried and weighed kernels from a trial at the University of Illinois campus. The kernels were collected at beginning R5 (full dent) and 10 filling days (about 250 GDD) later. In his summary of the kernels collected on the second date Dr. Nafziger shared "The milkline – the separation between hard and soft starch – was about halfway down the kernel. According to the Iowa State University publication "Corn Growth and Development" (PMR 1009), kernels at ½  milkline have accumulated about 90% of their maximum dry weight, are at about 40% moisture, and have about 200 GDD left to go before maturity. These kernels weighed 306 mg, or about 83,000 kernels per bushel, and they were at 31% moisture, which is considered typical for grain at physiological maturity. Thus it's likely that these kernels were at or very close to their final weight."

While this was a singular evaluation, it is a good news scenario as it suggests that the hybrid was able to reach near maximum kernel weight in a shortened time frame in this year's conditions. Emerson's article in its entirety can be accessed at

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