North Dakota Ag Connection - Long-term Grain Storage Requires Good Management

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Long-term Grain Storage Requires Good Management
North Dakota Ag Connection - 08/29/2016

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.

"Grain that will be stored for an extended time needs to be good-quality grain," says NDSU Extension Service agricultural engineer Ken Hellevang. "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."

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.

The EMC of corn at 70 degrees and 65 percent relative humidity is about 13.5 percent, and at 50 degrees, the EMC is about 15 percent. If you can keep stored corn below 50 degrees, you can store it at 15 percent moisture. But if the temperature will be warmer, then the recommended storage moisture content is about 13.5 percent. Equilibrium moisture content charts for various types of grain are available on the internet.

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. Grain AST charts, such as those in the publications section of the NDSU grain drying and storage website, are available online.

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. For example, corn stored at 20 percent moisture and 50 degrees has an AST of about 50 days. If it is dried to 15 percent after 25 days and cooled for winter storage but warms to 70 degrees next summer, the AST at 15 percent and 70 degrees is only about 60 days, rather than the 125 days shown in an allowable storage time chart.

"Controlling grain temperature is critical for maintaining grain quality," Hellevang says. "Insect reproduction is reduced below about 70 degrees, insects are dormant below about 50 degrees, and insects are killed if grain is below 30 degrees for a few weeks."

Moisture migration increases the moisture content at the top of the bin when about a 20-degree 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 difference between grain and average outdoor temperatures. Cool the grain to 25 to 30 degrees in northern states and 40 degrees or cooler in southern states for winter storage.

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