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Drying Corn in Late October
The moisture holding capacity of air is directly related to the air temperature. The moisture holding capacity of air at 50F is twice that of the air at 30F. Therefore, it will take twice as long to dry at 30F as it would at 50F. Drying in the field or in the bin will be much slower at cooler temperatures.
Freezing grain does not result in drying. Typically when temperatures are freezing at night, the air is dry during the day. For example at 100% relative humidity at 25F will only have a relative humidity of about 38% when heated to 50F. This low humidity level with a nice breeze dries grain well. This higher humidity level along with the cool air temperatures, results in very slow drying.
Harvested grain can be stored during the fall and winter at fairly high moisture contents if it is kept cool using aeration. The allowable storage time doubles for each 10 degrees that the grain is cooled. Corn at 22% moisture can be stored for 190 days at 30 degrees, but only 60 days at 40 degrees. Aeration fans should be operated to cool the grain to near freezing as quickly as possible. The grain can be cooled later to 20-25F for winter storage.
Natural air drying corn does not work well when outside temperatures are cool. Corn can be dried with an airflow rate of 1.35 cfm/bu from 21% to 15% in about 36 days under normal October conditions of 47F and 65% relative humidity. With normal November conditions of 27F and 73% relative humidity the corn will dry to 18% moisture in 70 days. The long drying time is due to the colder air not being able to hold as much moisture. Warming the air 5 degrees permits drying the corn to about 15% moisture, but it still will take about 52 days. After running the fan and heater for the entire month of November, only about 60% of the bin will be dry. Adding more heat will cause the corn to be dried to a lower moisture content while shortening the drying time by only a couple of days. Drying speed is primarily related to the airflow rate and final moisture content is related to the air relative humidity which is reduced by adding heat. Corn can be cooled to 20-25F for winter storage and dried in the spring. The drying fan should be started in the spring when daily average temperatures are about 40F.
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