You may be in the thick of harvest, but don’t forget to cool stored grain. With forecast average day/night temperatures of 34 to 13 in the coming seven days, the time is right to cool any grain that went into the bin at higher temperatures. This article will review some tips and rules of thumb for cooling and storing grain through the winter.

Tips for cooling grain

A good rule of thumb is to cool grain any time the average air temperature is around 20 degrees F cooler than the grain temperature. Repeat this cooling cycle until the grain temperature is 30-40 degrees F for winter storage. This storage temperature minimizes insect activity and mold growth in the stored grain. Cooling grain below 30 degrees F has little added benefit and can cause ice to form in the grain. Air humidity makes little difference when cooling grain.

When cooling, the cooling front moves through the bin in a wave, so the grain temperature where the air exits will stay fairly steady until the cooling front gets there. The hours required for cooling the whole bin can be estimated as 15 divided by the cubic feet per minute of airflow per bushel of grain in the bin (cfm/bu). If you don’t know how much airflow per bushel your fan provides, you can estimate it using the calculator on the U of M fan selection for grain bins webpage (bbefans.cfans.umn.edu). Select the crop stored, choose fan(s), and enter bin parameters, then find cfm/bu for the grain depth that you have stored in the bin. For bins set up for drying, a cooling front may pass through the bin in less than one day. Bins with only small aeration fans may require a week or more. For example, if the fan(s) provide 0.15 cfm/bu, then the time for cooling the bin would be 15/0.15 = 100 hours, or about 4 days.

“Core” the bin

It is always a good idea to “core” the grain bin just after filling the bin by removing about half the peak height. Leveling the top of the grain and removing the fines accumulated in the center of the bin will improve aeration and storage quality. If the top of the grain does not show signs of an inverted cone after coring, beware of grain bridging and do not enter the bin until the bridging has been corrected. Find more information on grain bridging and other grain storage hazards in the NDSU article, Caught in the Grain (tinyurl.com/y88oqhpn).

Final thoughts

After the final cooling cycle in the fall, remember to cover the fans to prevent warm air, rain, or snow from entering the bottom of the bin. While properly dried and cooled grain should store well through the winter, be sure to check stored grain weekly through the winter and spring.

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