Some grain will be stored for many months or even more than a year due to low grain prices, so maintaining grain quality during extended storage will require extra care and management, according to North Dakota State University’s grain storage expert.
“The outer layer of a grain kernel is the pericarp, or seed coat, and provides protection for the kernel. If the pericarp is damaged, the kernel is more susceptible to mold growth and insect infestations. This reduces the expected storage life of the grain,” said NDSU Extension Service agricultural engineer Ken Hellevang.
Broken kernels and foreign material should be removed by cleaning the grain before storing it. Segregation based on size and density occurs as grain flows into storage. Fines accumulate in the middle unless a functioning distributor spreads them throughout the grain. Unloading some grain from the center of the bin will remove some of the fines and help level the grain in the bin.
Also, immature kernels have a much shorter expected storage life. Grain test weight may be an indicator of maturity and storability.
Assure that the storage facility is clean and insects are not living in aeration ducts, under perforated floors, or in handling equipment or debris around the facility. Fumigate the empty bin to kill insects under the floor or in aeration ducts if an infestation occurred during the previous year. Also, consider applying an approved residual bin spray and a grain protectant to repel potential insect infestations if storing grain during warmer portions of the year.
Mold growth requires moist conditions, usually above about 70 percent relative humidity, and warm temperatures. To reduce the potential for mold growth, the grain moisture content should be below the equilibrium moisture content (EMC), at 60 to 65 percent relative humidity.
Grain going into long-term storage should be dried and cooled rapidly after harvest. The allowable storage time (AST) is an estimate of the life of the grain until it has deteriorated enough to affect grain quality. The AST is cumulative, so if one-half of the storage life is used before the grain has been dried and cooled, only about one-half of the life is available for the drier grain.
“Controlling grain temperature is critical for maintaining grain quality,” Hellevang says. “Insect reproduction is reduced below about 70 degrees F, insects are dormant below about 50 degrees F, and insects are killed if grain is below 30 degrees F for a few weeks.”
Moisture migration increases the moisture content at the top of the bin when about a 20-degree F temperature difference occurs between the grain and average outdoor temperature. Therefore, the grain should be cooled with aeration when you have a 10- to 15-degree F difference between grain and average outdoor temperatures.
The bin vents could ice over when the aeration system is operated near or below 32 degrees F. Utilize a sensor to stop the aeration fan if bin roof pressures become excessive, or leave access doors open to serve as pressure relief valves if operating the aeration system near freezing temperatures to reduce the potential for damaging the roof.
Advice for long-term grain storage:
– Check the grain at least every two weeks until it has been cooled for winter storage and every two to four weeks during the winter
– Verify that the moisture content is at the recommended storage level
– Check the grain temperature
– Inspect for insects
– Look for indications of storage problems such as condensation on the roof
“Using temperature cables or sensors to monitor grain temperature is encouraged, but remember that because grain is a good insulator, the temperature can be different just a few feet from the sensor,” Hellevang added.
Source: North Dakota State University
