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ear of corn
GENETIC FACTORS: Even such things as diameter of the cob can affect drydown rate. Corn breeders can control some things, but weather is often the overriding factor.

How will corn dry down this year?

Breeder’s Journal: A whole host of factors can affect how quickly corn dries in the field.

After a tough planting season, I’m hoping for a late killing frost. We need a break from Mother Nature this fall. 

We’re having extremes of weather, and some scientists are saying “climate change” is already here, whether we like it or not. I’m afraid we’re going to have some high-moisture corn and field drying is going to be slow this year.

First, we need corn to reach the black layer stage. Then we need a warm October and a very late killing frost.

Corn reaches black layer, which is considered physiological maturity, at about 32% grain moisture in most hybrids. Ideal moisture for grain harvest is 15% to 20%. Highest yield is usually at 28% moisture. After that point, yield starts going down 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% to 0.8% moisture loss per day for corn, which occurs mostly by evaporation. Even if hybrids have similar relative maturity ratings, some hybrids dry down 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 more slowly 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 drydown 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, we need 20 to 25 growing degree days to dry grain in the field by 1 point.

So, there are lots of factors that can influence moisture at harvest. First and foremost, let’s hope for a warmer fall season so our late-planted crops can fully mature.

Nanda is director of genetics for Seed Genetics-Direct, Jeffersonville, Ohio. Email him at dave.nanda@gmail.com or call 317-910-9876.

TAGS: Harvest
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