By Joe Lauer, University of Wisconsin Corn Agronomist

The recent high pressure ridge that has settled over Wisconsin has meant millions of dollars to farmers in reduced drying costs. The favorable weather of sunny, warm days with little rain has allowed the 2015 corn crop to dry faster than normal. Last week, farmers in northern Wisconsin had corn below 25% moisture.

There is a trade-off though. With high fuel prices and/or low grain prices, it is important to let corn grain dry in the field as much as possible, yet hold harvest losses at a reasonable level. Most corn hybrids mature when the grain has about 30% moisture. 

Ideally harvest should begin around 25% kernel moisture and be complete by the time grain reaches 20%. Corn ears that are too dry can break from the plant and drop to the ground. Also, kernels can shatter off the ear as they are stripped from the plant by the combine head.

Kernel Moisture Ranges (%) for Harvesting Corn for Various Uses
33-40% Kernel moisture = Silage harvest
29-32% Kernel moisture = High Moisture Corn (ensiled)
25-26% Kernel moisture = Ideal for combining
20-23% Kernel moisture = Ideal for picking
<20% Kernel moisture = Field losses increase, but cost of drying shell corn is reduced

Once the kernel is mature (black layered) the dry-down of corn grain is a simple drying process subject to weather conditions and most consistently associated with degree-days. 

Factors that have been shown to speed the rate of drying include premature death, physical structure of the seed coat or pericarp, a low number off loose, short husks, and ear angle and date of husk death. Factors not associated with faster dry-down were husk and shank characteristics and the shape or size of ears.

This year it will be even more important because of high yields and the potential for lodging, especially for growers with a long harvest season due to acreage demands. In years past, European corn borer caused increased lodging and ear drop. All are reasons to pay attention to corn harvesting. 

As harvest is delayed from October to December, losses can increase 5-18%. Of course, there is always a risk of 100% loss due to a storm or some other bad weather event.

Harvest decisions are affected by the kind of drying and storage facilities available and depends upon the use of the grain. Grain stored for a long period of time (more than 1 year) must be dried to less than 14%, which is not likely in a field situation, so some artificial drying must occur. 

Corn stored above 15% moisture is subject to heating from the natural respiration of the grain and molds present. As temperatures rise, so does humidity, which causes molds, insects and bacteria to grow, and decreasing the amount of time that the grain can be stored before it goes out of condition. Regardless of the moisture in stored grain, aeration is needed to control moisture migration.