Pennsylvania: Stored Grains – Prevent Mold with Proper Temp. Management

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I once read a statement; “Grain quality can never be improved during storage.”

I cannot recall where I read it but the change to very cold temperatures serves as a reminder that if grain stored in bins has not already been cooled it should be aerated to adjust its temperature to be close to the outside air temperature.

Otherwise the difference in temperature will cause movement of the warm air in the center to the top where it can condense as it approaches the cooler air. This causes moisture pockets, which can allow mold to start and attract insects.

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Aeration should begin when the average daily temperature (high + low / 2) is 10-15°F cooler than the grain. Be sure to keep aerating until the cool air front has moved through the entire bin. The time needed depends on the airflow rate of the fan used. See the accompanying table.

Airflow rate, cf/bu Cooling time, hours
1/20 400
1/10 200
1/4 80
1/2 40
3/4 27
1 20
1.5 13

If air is pushed up through the grain, the grain temperature should be checked about 1 ft down in several locations to confirm this. If it is pulled down, check the air temperature in the duct before it is exhausted by the fan.

Be sure to have the grain level, not peaked, in the bin before aeration. Otherwise airflow my not be uniform. Also, if a moisture pocket has already formed at the top of the bin and caused the grain to crust from mold, or freeze from contact with cold air above the level of the grain, aeration flow will not be uniform.

After completion of the cooling cycle, aeration fans should be covered to prevent air from being drawn into the bin that can cause moisture migration.

One other note, that comes from an article by Dr. Ken Hellevang, grain drying and storage expert and extension engineer at North Dakota State University, is that there is no advantage to cooling the grain below 25 degrees F. If it is extremely cold, it is best to not run the fan and wait for an appropriate air temperature.

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