Cooling Stored Grain

Monday, November 10, 2014

Cooling stored grain prolongs the life and quality of the grain. You can control mold activity and the air currents that can cause moisture migration by cooling grain to 30 to 40 degrees for winter storage. The approaching arctic weather that is moving in to the area provides a great opportunity to cool the grain.

The optimum temperature for insect infestations and mold growth is about 80 degrees. Temperatures below about 70 degrees slow insect reproduction and feeding activity, and insects are dormant below about 50 degrees. The best way to keep stored grain from deteriorating or becoming infested with insects is to cool it. Stored grain should be cooled with an aeration system immediately after harvest. The goal should be to cool it to near or below 70 degrees. As temperatures drop in the fall, stored grain will need to be cooled again, using aeration, whenever outdoor temperatures are 10 to 15 degrees cooler than grain temperatures. The grain temperature eventually should be cooled to about 25 degrees for winter storage in northern climates and 30 to 40 degrees in southern states. Air takes the path of least resistance, so cooling times will vary within a bin or grain storage. Measure grain temperature at several locations to ensure that all the grain has been cooled. Once the grain is cooled, check it weekly for evidence of temperature rise or moldy smell.

Moisture migration can be another issue in stored grain. Moisture migration will increase the grain moisture content near the top center of the stored grain if the grain is about 20 degrees warmer than the average outdoor temperature. That occurs because the air in the grain void spaces near the perimeter of the bin will cool as outdoor temperatures cool. The cool air will settle to the bottom of the bin along the bin perimeter, pushing air in the middle of the bin upward. As this air approaches cooler grain on or near the top surface of the bin, moisture will move from the air to the grain. These convection currents can increase the moisture content of the grain at or near the top surface by several percentage points, leading to grain deterioration. The magnitude of moisture problems due to moisture migration increases with bin size. Cooling the grain as outdoor temperatures cool reduces the convection currents and moisture migration. The allowable storage time, which is related to mold growth, is approximately doubled for each 10 degrees the grain is cooled.