The storability of grain depends on the grain quality, moisture content, and temperature. Grain moisture content must decrease as grain temperature increases to safely store grain. For example, the allowable storage time of 22 percent moisture corn is about 190 days at 30 degrees, 60 days at 40 degrees, and only 30 days at 50 degrees. Therefore, as stored grain temperature increases the grain moisture content must decrease for safe storage.
Stored grain temperature increases in the spring due to outdoor temperatures increasing and solar heat gain on the bin. There is more than twice as much heat gain from solar energy on the south wall of a bin in early spring as there will be during the summer.
Immature grain and grain with damage to the seed coat is more prone to storage problems, so the grain should be stored at a lower moisture content than normal. Also, stored grain should be monitored more closely to detect any storage problems early. Grain temperature and moisture content should be checked every two weeks during the spring and summer. Grain should also be examined for insect infestations.
Corn needs to be dried to 13% moisture for summer storage to prevent spoilage. Soybeans should be dried to 11%, wheat to 13%, barley to 12% and oil sunflower to 8% for summer storage.
Check the moisture content of stored grain to determine if it needs to be dried. Remember to verify that the moisture content measured by the meter has been adjusted for grain temperature. In addition, remember that moisture measurements of grain at temperatures below about 40 degrees are not accurate. Verify the accuracy of the measurement, by warming the grain sample to room temperature in a sealed plastic bag before measuring the moisture content.
Grain temperature should be kept cool during spring and summer storage. Periodically run aeration fans to keep the grain temperature below 40 degrees during the spring.
Grain storage molds will grow and grain spoilage will occur in grain bags unless the grain is dry. Grain in the bags will be at average outdoor temperatures, so grain will deteriorate rapidly as outdoor temperatures increase, unless it is at recommended summer storage moisture contents.
Corn at moisture contents exceeding 20% should be dried in a high temperature dryer because there is potential for corn field molds to continue to grow at moisture contents exceeding about 20% when grain temperature increases above about 40 degrees. For natural air-drying, assure that the airflow rate supplied by the fan is at least 1.0 cfm/bu. and the initial corn moisture does not exceed 20%. Start drying when outside air temperature averages about 40 degrees. Below that temperature, the moisture holding capacity of the air is so small that very little drying occurs.
An airflow rate of at least 1.0 cfm/bu. is recommended to natural air dry up to 16% moisture soybeans. The expected drying time with this airflow rate will be about 50 days. The allowable storage time for 18% moisture soybeans is only about 40 days at 50 degrees, so a minimum airflow rate of 1.5 cfm/bu. is recommended to natural air dry 18% moisture soybeans.
