HUTCHINSON -- Stored grain must be monitored so that insect infestations or grain spoilage can be detected before serious losses occur. It is recommended that growers check stored grain bi-weekly during the critical fall and spring months when outside air temperatures are changing rapidly and during the summer.
After the grain has been cooled for winter storage, and after a storage history without problems, check the grain at least monthly during winter months. Check and record that grain temperature and temperatures are below 40 at several locations in the storage facility. The temperature history can be used to detect grain warming, which may indicate storage problems.
Temperature plays an important role in grain storage. The optimum temperature for insects is between 70 F and 90 F. Therefore, grain should not be stored at this temperature. Cooling below 70 F reduces insect reproduction and feeding activity, and cooling below 50 F causes the insects to become dormant. The optimum temperature for mold growth is also about 80 F. Mold growth is extremely slow below 30 to 40 F. The expected grain allowable storage time is approximately doubled for each 10 degrees that the grain is cooled.
Aeration should be used to cool the grain whenever outdoor temperatures are cooler than the grain. It should be cooled to a temperature within 10-15 degrees of average winter temperatures or to about 20-30 degrees in northern states for winter storage.
The time required to cool grain weighing 56 to 60 pounds per bushel using aeration can be estimated by dividing 15 by the airflow rate. For example, the grain will cool in about 75 hours using an airflow rate of 0.2 cubic feet per minute per bushel. Air takes the path of least resistance, so cooling times will vary in the storage. Measure grain temperature at several locations to assure that all the grain has been cooled.
It is important to look for indications of problems such as condensation on the roof or crusting of the grain surface. Probe to examine grain below the surface. Bring a grain sample indoors if the grain temperature is below 50 degrees; allow it to warm to room temperature, then place the grain on a white surface, and examine for any insect activity. It is not recommended to fumigate at grain temperatures below 60 degrees. Remember that most storage problems can be controlled during the winter by cooling the grain.
For more information about allowable storage times based on grain moisture and other information, please consult the University of Minnesota publication "Grain Storage Tips, Factors and Formulas for Crop Drying, Storage and Handling" available on the internet at http://www.extension.umn.edu/distribution/cropsystems/M1080-FS.pdf
David Nicolai is a crops educator with the University of Minnesota Extension Service Regional Center, Hutchinson.