Dry grain or keep it cool to prevent mold growth during winter storage.
Warm weather the first half of this winter has increased the potential for problems in stored grain.
“Grain needs to be either dried or stored at a cool temperature to prevent mold growth,” says North Dakota State University Extension Service grain drying expert Ken Hellevang. “If the stored grain is dry, the warm winter temperatures will not cause storage problems. But if the grain is not dry, the warm temperatures may be a concern. The potential for insect problems also increases at warmer temperatures.”
For example, cereal grain at 18% moisture content can be stored for up to about 200 days at 40 degrees and 90 days at 50 degrees, but only about 15 days at 80 degrees. For each 10-degree increase in grain temperature, the allowable storage time is reduced by about one-half.
The allowable storage time increases at lower grain moisture contents. At 70 degrees, the allowable storage time increases from about 30 days for cereal grain at 18% moisture to 45 days at 17% moisture, 70 days at 16% moisture and 200 days at 14% moisture.
Insects are dormant below about 50 degrees, so keeping the grain temperature below 50 degrees if possible is important, Hellevang says. If the grain temperature is kept below freezing during winter storage, insects can be killed.
The grain temperature near the bin wall and on the top surface depends both on the outdoor temperature and solar radiation. The amount of solar energy on the south wall of the bin will be two to three times as much on Feb. 21 as on June 21 due to the low solar angle. The amount of solar radiation on the bin roof is about three-fourth as much as during the summer.
“Monitor the grain temperature, particularly near the south wall and near the grain surface, and periodically run the aeration system to keep the grain cool,” Hellevang advises. “The goal in northern states should be to keep the grain temperature at 20 to 30 degrees during the winter and in southern states to keep the grain temperature below 40 degrees or as cool as possible.”
Check dry grain at least every two to three weeks as long as the grain is at winter storage temperature and at least every couple of weeks if it is warmer. Measure and record the grain temperature, watching for trends that indicate problems. Check the grain moisture content and examine the grain in several locations. Search for small changes that are indicators of potential problems. Collect a sample, warm it to room temperature and place the grain on a light-colored or white surface to look for insects.
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.
Bin vent screens have the potential to become iced over when fans are operating in temperatures near or below freezing. Hellevang recommends leaving a bin fill-hole or manhole unlatched as a pressure relief valve if the air is being pushed up through the grain. If humid air is being pulled in through bin vents at temperatures near freezing, provide an unscreened opening, such as the manhole, for the airflow.
“Always remember safety when working around grain bins,” Hellevang says. “Grain suffocation is likely if entering a bin while unloading. It only takes seconds to be engulfed in the grain. Never enter a grain bin without stopping the auger and using the ‘lock-out/tag-out’ procedures to secure it.
“Also, a person can be instantly buried if bridging has occurred or a column of grain attached to the bin wall collapses,” he warns.