Keeping Grain in Condition

Management is required to keep grain in good condition once it is placed in storage.  Because of differences in temperature between the grain in the bin and the outside air, air inside the bin migrates.

With cold outside air, the air inside the bin moves downward along the outside wall and then upward toward the center of the bin.  The air that comes up through the center of the bin will carry some moisture as it contacts the cool grain in the center of the bin. Moisture will then condense and cause the grain in this area to go out of condition and crust over.

The crusting will keep air from flowing through the mass of grain and making it impossible to keep the grain in condition. To prevent this problem, grain should be cooled to about 40 degrees F in the fall and warmed to about 60 degrees F in the spring.  This will minimize migration of air through the bin.

Check grain weekly. Use a grain probe and a thermometer to check the temperature by probing below the surface of the grain in several places. Record these temperatures to monitor changes. Moving air through the grain can help in determining grain condition.  If a musty odor is detected, problems may exist not detected by inspecting the grain or checking the temperature. If problems do occur, fans may need to be run to dry the grain. In some cases, grain may need to be removed from the bin.

Covering the fan intake when it is not in use can prevent air from moving through it and minimize insect and rodent problems.

Should air be pushed or pulled through the bin?  There is no right or wrong answer — it depends.   If air is pushed through the grain, moisture is most likely to condense on the cold roof.  This can cause some moisture problems with grain at the top of the bin.  An advantage of pushing the air is if grain spoilage does occur, it will most likely be at the top of the bin and is easier to detect.

When air is pulled through the bin, the moist air coming off the grain can condense on floors and on grain near the floor.  This can block ducts and plug the aeration system.   If air is pulled air through the grain, one should wait until several feet of grain has been placed in the bin to avoid pulling fines into the duct.

Leave the fan on long enough. Anytime a drying or cooling front is started through the grain, make sure the fan runs long enough to move the front completely through the grain. When the temperature of the air coming through the grain is equal to the outside air, drying or cooling is complete.

Source: Kent Shannon, MU Extension Ag Engineering Specialist


What are safe storage moistures?


Maximum Safe Moisture Content (percent)

Shelled Corn or Grain Sorghum


Sold by spring


Stored up to one year


Stored more than one year




Sold by spring


Stored up to one year