Ike Hammers Corn, Hinders Harvest
Chad Lee and Jim Herbek, Extension Agronomists, Plant and Soil Sciences

September 15, 2008

Remnants of Hurricane Ike passed quickly through western Kentucky knocking down corn as it went. Corn was in various stages of kernel fill and dry down. (See the end of this article for more on growth stages.) If corn kernels had not reached black layer prior to the storm, then those kernels would prematurely reach black layer and they will be lightweight. Grain moisture in these fields will be above 35% which normally requires time in the field for dry down.

The challenge is that corn kernels laying near or on the ground will not dry down as quickly as kernels on upright plants with exposure to more air movement. More than likely, these kernels will have to be harvested wet and then dried down in a grain bin.

Downed corn ears run a greater risk of getting ear molds. Many of the fields are dry, possibly giving us a little bit of a break from moldy conditions. Forecasts do not call for rain until Sept. 20, 2008, allowing for more of chance for grain to dry down, and for more of a chance for you to harvest these fields.

This may be a time when you segregate harvest loads if possible, keeping the downed corn away from the rest of your crop. Up to 5% damaged kernels are allowed for U.S. no. 2 corn. Grain harvested from downed corn is more than likely going to be above that threshold and you do not want to penalize your grain from good fields with grain from the damaged ones.

Keeping harvest losses to a minimum is difficult for downed corn. Your combine operator’s manual will be your best guide for combine adjustments. Most of the harvest losses will come from the head of the combine. Adjust stripper plates and snapping bars to prevent ears from falling through. You will run more trash through the combine, but you will lose less grain. Use very slow ground speeds to harvest. You may need to harvest the field based on the pattern of lodged plants rather than the rows of corn. Harvesting lodged corn with the tassels facing the combine usually works well for picking up the ears.

Several farmers have used add-on reels to help pick up lodged corn. Talk with your neighbors about which reels work best for them. If corn stalks are severely damaged and/or the corn roots are out of the ground, then a soybean head may work better than a corn head.

Finally, be patient. Corn harvest is always a nerve-racking time. Delays, especially with downed corn, will only add to harvest season frustration. Driving too fast will only add to those problems.

Kernel Development
R5, dent stage. Normally occurs at 35 to 42 days after silking. Kernels dented at the top are drying down. Kernels have 55% moisture concentration at the beginning of R5. A line separating yellow from light yellow to white occurs on the kernel. This lines moves from the top of the kernel downward to the base. Stress will hurt yields by hindering dry matter accumulation. A storm like Ike qualifies as stress that will hinder dry matter accumulation.

R6, physiological maturity (black layer). Normally occurs about 55 to 65 days after silking. Kernel moisture is at 30 to 35% concentration at the start of R6, depending on hybrid and the environment. The starch has hardened from the top of the kernel all the way to the base. A black or brown layer is visible at the base of each kernel. (Usually, you can use a thumb nail to remove a bit of the base to expose the black layer.) Dry matter accumulation is complete. Stress at this point can only hinder harvest. Lodged corn qualifies as a stress that hinders harvest.

Sources:
Abendroth. L. 2006. Corn development from R1 to R6. Iowa State Extension. http://www.agronext.iastate.edu/corn/production/management/growth/yield.html

Nicolai, D. and D. Hicks. 2006. Corn development and maturity as affected by wind storm damage. Minnesota Crop eNews. Sept. 1. http://www.extension.umn.edu/cropenews/2006/06MNCN53.htm


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