Extension Ag Update
December 2008
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Corn Drydown Decisions: Some Factors to Consider
Ellen Phillips, Extension Educator, University of Illinois Extension, 708-352-0109,

The rate of corn drydown is affected by many factors such as planting date, fall weather, hybrid, and ear characteristics. Consider the following facts:

  • for field corn the ideal harvest moistures ranges from 15 to 20%.
  •  mature corn will have a “black layer” (at the base of the kernel), indicating the end of dry matter accumulation.
  • After black layer, most moisture loss is from the kernel.
  • Mature corn has about 30% moisture content, requiring 2 to 4 weeks for grain moisture to drop to 15%, under good conditions.
  • Purdue data shows that planting date affects drydown. “Average daily drydown rates will range from about 0.8 percentage point per day for grain that nears maturity in late August  to about 0.4 percentage point per day for grain that nears maturity in mid- to late September”.
  • warm dry weather speeds drying rates, kernels can lose up to 1.0% moisture per day.
  • cool moist weather slows drying rates, kernels may lose as little as 0.3% per day.
  • poor stalk quality become increasingly susceptible to stalk lodging, decreases harvest efficiency with downed corn.
  • hybrids can have different rates of dry down, generally related to maturity date.
  • characteristics of the husk and ear affect dry down. Ears will dry down faster when there are “fewer and thinner husk leaves; ear tips protrude beyond the husks; ears drop from an upright position earlier; or they have thinner or more permeable pericarp”. (Dr. Neilson, Purdue)

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