In normal years in the upper Midwest, corn producers who have natural-air dryers (no heat) can expect to accomplish a significant amount of corn drying during the month of November. In 1996, however, November was colder and wetter than normal, and consequently, drying progress was limited. In many cases, the drying front probably did not move all the way through the bin before winter weather arrived.
It would be a good idea for managers of natural-air grain dryers to probe their bins this winter to find the drying front. Corn below the drying front should be at a moisture content that is in equilibrium with the drying air that last moved through the bin. If the fan was operated very much during November, corn below the drying front will probably be in the 15% to 17% moisture range. Corn above the drying front will still be at harvest moisture.
The best way to find the drying front is to pull grain samples from various depths and actually measure the moisture. An alternative is to simply push a long slender rod down into the corn. If there is very much difference in moisture between the corn below the front and that above the front, the rod will suddenly start to move more easily when it reaches the drier corn. (Watch for overhead powerlines when handling long metal rods at the top of grain bins!)
If the drying front has progressed at least half way through the bin and corn at the top of the bin is not wetter than 22% moisture, you should be able to hold corn without spoilage during winter and finish drying in spring. Just aerate as needed to keep the corn cold through the winter (20°F to 30°F) and then resume drying some time after mid-March. The wetter the corn is, the earlier you need to start spring drying.
If the drying front has not moved at least half way through the bin, or if there is corn in the bin that is wetter than 22% moisture, holding corn for spring natural-air drying is pretty risky. It would be better to feed or sell this corn during the winter, or pull it out of the bin and dry it in a faster type of dryer.
For more information, get a copy of Natural-Air Corn Drying in the Upper Midwest, BU-6577, from the University of Minnesota Extension Service Distribution Center (call (612) 625-8173, or (800) 876-8636 for credit card orders.)
This page is part of the Biosystems and Agricultural Engineering Department web at http://www.bae.umn.edu/