Varying In-Field Moisture Makes Corn Harvest, Drying, Storage Challenge

Due to a challenging spring planting season, corn has varying moisture levels between fields and even within fields. This may be due to replanted portions of fields, with the initial planted acres at about 15% while the replanted acres are still in the upper 20% moisture range.

"One option is to segregate harvest as much as possible," says Ken Hellevang, professor emeritus and retired North Dakota State University Extension agricultural engineer. "Harvest the initial planted acres now, then come back to harvest the replant acres once they've dried down near or below 20% grain moisture."

The NOAA Climate Prediction Center Outlook through the latter part of October is for continued drier- and warmer-than-average conditions. The Iowa State University corn dry-down calculator estimates that 28% moisture corn in Ransom County will dry down to about 20% by the end of October. Typically, little drying occurs during November, so late October is normally when harvest and drying is recommended.

If all the corn is left standing until the replant areas dry down, the corn that is at 15% moisture now is not expected to dry below about 13-14%, due to that being the corn equilibrium moisture content for late October weather conditions. However, there is a risk of preharvest losses due to ear drop or stalk breakdown.

"Scout the corn to check for stalk integrity. Push the plant sideways about 8 to 12 inches at ear level. If the stalk crimps near the base or fails to return to the vertical position, stalk rot is indicated. Also, look for ear drop and ear shank weakness. Most corn hybrids today have good stalk and ear shank strength," Hellevang says.

Corn with a large moisture variation dried in a high temperature dryer will have a large moisture variation after drying. The high moisture corn will dry some and the 15% corn will dry to a very low moisture content. Some of the newer dryers mix the corn in the drying column, which is beneficial. However, a moisture variation will continue in storage. If 20% moisture corn kernels are mixed with 10% moisture kernels, the 20% may come down to 17% and the 10% increase to 13%, but the corn moisture content does not equalize. Extended aeration will help with some moisture equalizing, but it will not reach the average moisture content. Also, kernels segregate as they flow into a grain bin, so if there is a variation in kernel size or density, pockets of wet corn may occur. Even corn harvested with moisture variations of 14% to 20% will have a moisture variation after drying, and aeration for longer than typical is recommended along with more care in storage management. Corn at moisture contents exceeding about 20% cannot be dried using natural air drying.

The two preferred options for large corn moisture content variations in a field are to wait for the high-moisture corn to dry before harvesting the field, or to harvest the dry portion now and wait for the rest to dry. Drying and storage concerns will arise if the corn is dried with large moisture content variations, warns Hellevang.

Corn should be aerated immediately after being placed into storage to ensure the corn has been cooled to below 70 degrees Fahrenheit and cooled as outdoor temperatures cool until it is 20 to 30 degrees for winter storage.

For more information, visit ndsu.ag/dryingcorn.