As outdoor temperatures increase, stored grain requires attention to prevent losses, says Ken Hellevang, North Dakota State University Extension agricultural engineer and grain-drying expert.
The stored grain temperature increases in the spring not only due to an increase in outdoor temperatures but also due to solar heat gain on the bin. Solar energy produces more than twice as much heat gain on the south wall of a bin in early spring as it does during the summer.
Hellevang recommends periodically running aeration fans to keep the grain temperature near or below -1 C until the grain is dried if it exceeds recommended storage moisture contents, and below 4.4 C as long as possible during spring and early summer if it is dry. Soybean oil quality may be affected in less than four months if even 12 per cent moisture soybeans are stored at 21 C.
Cover the fan when it is not operating to prevent warm air from blowing into the bin and heating the stored grain. He also recommends ventilating the top of the bin to remove the solar heat gain that warms the grain. Provide air inlets near the eaves and exhausts near the peak or use a roof exhaust fan.
Bin vents can become blocked with frost and ice when the fan is operated at temperatures near or below freezing, which may lead to damage to the roof. Leave the fill and access door open as a pressure relief valve when operating the fan at temperatures near or below freezing.
Monitor moisture, temperature
Stored grain should be monitored closely to detect any problems early, Hellevang advises. Grain temperature should be checked every two weeks during the spring and summer. Grain also should be examined for insect infestations.
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 4.4 C may not be 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.
Corn needs to be dried to 13 to 14 per cent moisture for summer storage to prevent spoilage. Soybeans should be dried to 11 per cent, wheat to 13 per cent, barley to 12 per cent and oil sunflowers to eight per cent. The allowable storage time for 13 per cent moisture soybeans is less than 100 days at 21 C.
Corn at moisture contents exceeding 21 per cent should be dried in a high-temperature dryer because deterioration is rapid at warmer temperatures. For example, the allowable storage time of 22 per cent moisture corn is about 190 days at -1 C but only 30 days at 10 C.
- Corn: For natural air-drying, assure that the fan’s airflow rate is at least one cubic foot per minute per bushel (cfm/bu.) and the initial corn moisture does not exceed 21 per cent. Start the fan when the outdoor temperature averages about 4.4 C.
- Soybeans: Use an airflow rate of at least one cfm/bu. to natural air-dry up to 15 to 16 per cent moisture soybeans. Start the fan when the outdoor temperature averages about 4.4 C. Follow the manufacturer’s recommendation for high-temperature drying soybeans. Monitor the soybean quality and reduce the drying temperature if excessive cracking or splitting occurs. Reduce the fire hazard by keeping the soybeans flowing in the dryer. Pods and trash can become lodged and combustible. Frequently clean the dryer to remove anything that may impede flow. Constantly monitor the dryer when drying soybeans.
- Sunflowers: Natural air-drying for oil sunflowers requires an airflow rate of 0.75 cfm/bu. for up to 15 per cent moisture. The drying should start when outdoor temperatures average about 4.4 C.
- Wheat: Use an airflow rate of at least 0.75 cfm/bu. to natural air-dry up to 17 per cent moisture wheat. Start drying when the outside air temperature averages about 10 C.
- Barley: Use an airflow rate of at least 0.75 cfm/bu. to natural air-dry up to 16 per cent moisture barley.
Watch grain bags
Grain storage moulds 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.
Grain bags that run east-west will have solar heating on the south side, which creates a temperature variation across the bag that will move moisture to the north side of the bag. Continue to monitor grain stored in bags frequently.
“Also, everyone needs to become aware of safety hazards associated with handling grain and to apply recommended safety practices,” Hellevang stresses.