College of Engineering News • Iowa State University

Brenneman on grain storage: core it, cool it, store it

Originally posted on the Pork Network.

Grain is quickly coming out of the fields this fall, with 92 percent of soybeans and 73 percent of corn harvested in Iowa as of Oct. 26, according to the United States Department of Agriculture.

Since much of it has been harvested and put into the bin at 60 degrees and warmer, proper grain drying and cooling is essential for storage life and grain quality. For safe grain storage during warmer conditions, Greg Brenneman, agricultural and biosystems engineering specialist with Iowa State University Extension and Outreach says you need to core it, cool it and check it.

“With grain this warm, moisture migration within the grain mass and spoilage can occur very quickly, even with fairly dry grain,” said Brenneman.

Core it
Fines and broken grain tend to accumulate near the center of the bin and often cause aeration and storage problems. Brenneman recommends removing a few loads of grain from the center, so the unloading sump will “core” the bin and remove most of those fines. Then, remove grain until approximately half of that center peak is gone.

After coring, the top of the grain should be visually inspected to ensure an inverted cone has been created. If no cone is created, bridging of the grain has taken place and a very unsafe condition has been created. No one should enter the bin until situation has been safely corrected.

Cool it
This week’s forecast shows cooler temperatures for Iowa, providing an ideal time to get stored grain cooled down. However, farmers may still need to run fans later this fall to lower temperatures further.

“The sooner you can lower grain temperatures, the better,” said Brenneman. “Grain should be stored at 30 to 40 degrees for winter storage, so you may still need to run fans a couple times during the fall to get grain down to wintertime storage temperatures.”

The time required to completely cool a bin of grain depends on fan size. In general terms, a large drying fan will take 10-20 hours to cool a bin of grain. However, a small aeration fan can take a week or more to completely cool a full bin.

In either case, it is best to measure the temperature of the air coming out of the grain to see if cooling is complete. It is also much better to err on the side of running the fan too long rather than turning it off too soon.

Check it
If grain is dried down to the proper moisture and correctly cooled, it should store very well through the winter. Even so, it is best to check stored grain at least every two weeks during the winter and once a week in warmer weather.

To do a good job checking grain, inspect and probe the grain for crusting, damp grain and warm spots. Also, run the fan for just a few minutes and smell the exhaust air for any off odors.

For more details, order a copy of “Managing Dry Grain in Storage” AED-20 from Midwest Plan Service at, or check out more grain drying and storage information at