Written by Bob Fanning, former SDSU Extension Plant Pathology Field Specialist.
Many upper Midwest states are facing grain storage capacity concerns, and Ken Hellevang, Extension Engineer at North Dakota State University, recently shared valuable information with Extension staff across the region. As Ken states, grain can be stored in many types of facilities, but all storage options should keep the grain dry and provide adequate aeration to control grain temperature.
Figure 1. Temporary grain storage
Grain must be dry and cool when placed into alternative storage. Aeration to control grain temperature is a critical part of any storage method, but it is not feasible to provide adequate airflow quantity and uniformity to dry grain in alternative storage. If grain needs to be dried, it should be cooled to near average outdoor temperature before putting in alternative storage. It is generally not feasible to provide enough uniform airflow to cool grain in these facilities.
Buildings that are not designed for grain storage can incur significant damage if grain is allowed to build up against the walls. Ensuring that a building can withstand the forces of grain is a complex engineering problem. Building failure can result in both a damaged building and grain that is exposed to the elements and subject to going out of condition.
Poly bags are a good storage option, but current knowledge says they do not prevent mold growth in damp grain or insect infestations. Grain should be placed in the bag at recommended storage moisture contents based on grain type and outdoor temperatures. Heating will occur if the grain exceeds safe storage moisture content. Because the grain cannot be aerated to control heating of damp grain, bagging damp grain is discouraged. The average temperature of dry grain will follow the average outdoor temperature.
Select an elevated, well-drained location for the storage bags, and run the bags north and south so solar heating is similar on both sides. Sunshine on just one side of the bag heats that side and can lead to moisture accumulation in the grain on the cool side of the bag. Wildlife can puncture the bags, creating an entrance for moisture and releasing the grain smell, which attracts more wildlife. Monitor the grain temperature at several locations in the bags.
Short-term storage is frequently in outdoor piles. Precipitation is a severe problem for uncovered grain. Grain has a void percentage of about 43%, so the grain is very porous. A one-inch rain will increase the moisture content of a one-foot layer of corn by 9 percentage points.
Grain covers can reduce damage from precipitation, but they need to be held in place, typically by a combination of restraining straps and suction from an aeration system. The aeration system should be designed and sized to adequately cool the grain as the outside air temperature drops, and provide suction to help hold down the grain cover. For suction to develop, adequate to hold the grain cover down, the amount of open area for intake air would need to be limited.
Cooling grain as outdoor temperatures cool will reduce moisture migration, the potential for condensation near the top of the grain pile, the rate of mold growth and insect activity. Grain deterioration is affected by both the grain moisture content and temperature. The allowable storage time is approximately doubled with each ten-degree reduction in grain temperature.
Drainage is of critical importance to the success of any grain storage, but particularly when grain is piled on the ground. The ground surface of an outdoor pile needs to be prepared to prevent moisture from reaching the grain. The ground surface where the grain will be piled should be crowned so any moisture that does get into the pile drains to the exterior rather than creating a wet pocket that leads to grain deterioration. The ground surface needs to be a prepared surface including a low permeability surface. This may include using lime, fly ash, cement, or asphalt to make the surface.
Grain drying and storage is a complex subject and there is a great deal at stake. Additional information is available on the NDSU Extension Service website.