Proper Spring Grain Drying and Storage Critical

The warmer winter and early spring have increased the potential for grain storage problems and the need for grain monitoring and management, says Ken Hellevang, North Dakota State University Extension agricultural engineer and grain drying expert. Stored grain temperature increases in parts of a bin in the spring, which is 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 spring as it does during the summer. That, in addition to the solar heat gain on a bin roof, can create an environment conducive to grain spoilage. A ten degree increase in temperature reduces the allowable storage time of grain by about one-half. For example, the allowable storage time of corn at 17% moisture is reduced from about 130 days at 50 degrees Fahrenheit to about 75 days at 60 degrees and 45 days at 70 degrees.

Hellevang recommends periodically running aeration fans during the spring to keep the grain temperature near or below 30 degrees if it exceeds recommended storage moisture contents and below 40 degrees as long as possible during spring and early summer if the grain is dry. In northern states, night air temperatures are normally near or below 30 degrees in April and 40 degrees in May.

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.

Cover the fan when it is not operating to prevent warm air from blowing into the bin and heating the stored grain. Warm grain is more prone to spoilage and insect infestations. Hellevang 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 so the top of the bin can ventilate due to warm air rising, similar to what occurs in an attic, or use a roof exhaust fan.

Stored grain should be monitored closely to detect any storage problems early, Hellevang advises. Grain temperature should be checked every two weeks during the spring and summer. A temperature increase may indicate a storage problem. The goal is to keep the grain cool. 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 40 degrees 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.

Some in-bin cables measure grain moisture content by measuring the temperature and air relative humidity then calculating the grain moisture content based on grain equilibrium moisture content equations. The measured moisture may be 1.0 to 1.5 percentage point different than the true moisture content, so it is a tool that should be verified with another moisture content measurement method.

Corn needs to be dried to 13% to 14% moisture for summer storage to prevent spoilage. Soybeans should be dried to 11% to 12%, wheat to 13%, barley to 12% and oil sunflowers to 8%. The allowable storage time for 13% moisture soybeans is less than 100 days at 70 degrees.

Corn at moisture contents exceeding 21% and soybeans exceeding 15% should be dried in a high-temperature dryer because deterioration is rapid at warmer temperatures. For example, the allowable storage time of 22% moisture corn is about 190 days at 30 degrees but only 8 days at 70 degrees. 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.

Recommended Airflow Rates and Maximum Air-Drying Moisture Contents

• Corn – For natural air-drying, assure that the fan’s airflow rate is at least 1 cubic foot per minute per bushel (cfm/bu) and the initial corn moisture does not exceed 21%. Start the fan when the outdoor temperature averages about 40 degrees. The grain will reach a moisture content based the average air temperature and relative humidity during the fan operation. Nighttime higher humidity air is generally needed to balance the lower daytime relative humidities.
• Soybeans – Use an airflow rate of at least 1 cfm/bu to natural air-dry up to 15% to 16% moisture soybeans. Start the fan when the outdoor temperature averages about 40 degrees.
• Sunflowers – Natural air-drying for oil sunflowers requires an airflow rate of 0.75 cfm/bu for up to 15% moisture. The drying should start when outdoor temperatures average about 40 degrees.
• Wheat – Use an airflow rate of at least 0.75 cfm/bu to natural air-dry up to 17% moisture wheat. Start drying when the outside air temperature averages about 50 degrees.
• Barley – Use an airflow rate of at least 0.75 cfm/bu to natural air-dry up to 16% moisture barley.

“Remember that some of the allowable storage life was used during the fall before the grain was cooled to near or below freezing, so there is less time for spring drying before deterioration occurs,” Hellevang says. “This is particularly important for malting barley, where germination can be lost, so using a higher airflow rate to reduce the drying time is encouraged.”

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.

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. “More grain deaths occur during years with challenging conditions when there is more potential for chunks of grain to block unloading sumps or when grain columns occur.”