Many factors affect how quickly corn dries in fields
August 26, 2019
After a tough planting season, field drying is going to be slow this year and farmers are going to have some high-moisture corn.
First, we need corn to reach the black layer stage. Then we need a warm October and a very late frost.
Corn reaches black layer, which is considered physiological maturity, at about 32 percent grain moisture in most hybrids. Ideal moisture for grain harvest is 15-20 percent. Highest yields are usually at 28 percent moisture. After that point, yields starts dropping due to field losses caused by stalk lodging, ear droppage, insects and ear rots.
Field drying
In a typical season, grain drying in the field ranges from 0.5-0.8 percent moisture loss per day for corn, which occurs mostly by evaporation. Even if hybrids have similar relative maturity ratings, some hybrids drydown faster than others.
Disease tolerance of hybrids may be different as well. Hybrids that have good stay-green power live longer and have a higher yield potential, but dry-down slower because they die more slowly and the grain carries higher moisture into fall.
Corn breeders must constantly compromise to find hybrids with the right combinations of agronomic and genetic traits that will produce the highest income for growers.
Management decisions such as planting date, plant population, amount of nitrogen applied and use of foliar fungicides also affect dry-down rate and grain moisture at harvest.
Moisture loss
As corn matures, moisture is lost through cob and ear shanks, exposed ear tips and husks. Hybrids with thinner cobs tend to lose moisture faster. Upright ears tend to capture moisture in the husks, slowing down the drying process. All other things being equal, droopy ears lose moisture faster than upright ears.
Grain with thicker “skin,” technically called the “pericarp,” and higher test weight dries slower. Chaffy and light-weight grain dries faster. Husk cover, number, thickness and tightness can affect rate of drydown. Cob thickness and kernel depth also influence how fast grain will dry. Since hybrids differ in these agronomic traits, they also differ in rate of drydown.
Weather has a major effect on grain moisture at harvest. Temperature, rainfall and amount of sunshine influence grain drying. Weather conditions after grain fill is over have a major effect on how fast grain will dry. On average, 20 to 25 growing degree days are needed to dry grain in the field by one point.