By Greg Brenneman, ISU Extension and Outreach
So far this harvest, a lot of corn and soybeans have gone into storage at temperatures in the 70s and some 80s. With grain this warm, moisture migration and spoilage can occur quickly, even with fairly dry grain. With forecast highs in the 50s with lows in the 30s for this weekend and next week, grain bin fans should be running by the end of the week to get stored grain cooled down as soon as possible.
While we want stored grain cooled to 30 to 35 degrees for winter storage, the sooner we get grain temperatures down, the better. Every 10 degree drop in grain temperature will nearly double the allowable storage time. Fans might need to be run several 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 to 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 much better to err on the side of running the fan too long rather than turn it off too soon.
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. For more details, order a copy of Managing Dry Grain in Storage, AED-20, from Midwest Plan Service at or check out more information on grain drying and storage information.
Greg Brenneman is an agricultural engineering specialist with Iowa State University Extension and Outreach. He can be reached at (319) 337-2145 or e-mail gregb@iastate.edu.
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