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Corn Illustrated: Learn how corn dries down in the field and what factors influence the process.

Dave Nanda

July 31, 2018

3 Min Read
STAY-GREEN FACTOR: Disease and natural processes are causing this corn to die. These factors may result in faster drydown than in plants with more stay-green power. However, yield could be a different story.

The spring of 2018 gave us the fastest early growth of corn I’ve seen in more than 50 years. After corn reaches physiologic maturity, or black layer, what factors will affect its drydown? Black layer indicates the end of dry matter accumulation in the kernels. Grain moisture varies from 32% to 35% at this point, depending on the hybrid.

Ideal moisture for grain harvest is 15% to 20%. Highest yield usually occurs at 28% moisture. After that point, yield starts dropping because of field losses due to stalk breakage, ear droppage and damage caused by ear rots and insects. What happens next, and how does corn dry down to harvestable moisture?

How corn dries
In a typical season, grain drying in the field loses moisture at a rate ranging from 0.5% to 0.8% per day. This occurs mostly by evaporation.

Even if hybrids have similar maturity ratings, some hybrids dry down faster than others. Disease tolerance of hybrids can differ. Hybrids that have good stay-green power live longer and may have a higher yield potential, but they dry down more slowly because they die at a slower rate. Therefore, kernels carry a higher moisture content.

Hybrids that live longer aren’t going to die early and dry fast. Management decisions such as planting date, population, amount of nitrogen used and use of foliar fungicides all affect rate of drydown and grain moisture at harvest.

As corn matures, moisture is lost through the cob and ear shank, exposed ear tips, and husks. Hybrids with thinner cobs tend to lose moisture faster.

I was a corn breeder for a long time, and in our hybrid selection process, we constantly compromised to find hybrids with the right combinations that would produce the highest income for corn growers.

Factors affect drying
What are the agronomic and genetic characteristics of corn hybrids that affect the rate of drydown? Hybrid relative maturity, pericarp or kernel skin, and ear angle after maturity can all affect drydown rate.

Upright ears tend to capture moisture in the husks and slow down the drying process. Droopy ears lose moisture faster. Grain with thicker skin and higher test weight dries more slowly compared to chaffy and light-weight grain. Husk cover, number, thickness and tightness also affect rate of drydown. Cob thickness and kernel depth influence how fast grain will dry, as well.

We all know that weather has a major effect on grain moisture at harvest. Temperature, rainfall and amount of sunshine influence grain drying. Weather conditions after the grain fill period ends have a major impact on how fast grain dries in the field. You need 20 to 25 heat units to dry grain in the field by 1 point. So, there are lots of factors that can influence moisture at harvest.

Let’s hope for a warmer fall season so our crops can mature and dry down for a bumper crop. No trade wars and higher prices for our grains!

Nanda is president of Agronomic Crops Consultants LLC. Email him at [email protected] or call 317-910-9876.

About the Author(s)

Dave Nanda

Dave Nanda is director of genetics for Seed Genetics Direct, Jeffersonville, Ohio. Email [email protected] or call 317-910-9876. Please leave a message.

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