Rising outdoor temperatures and solar radiation can warm stored corn, creating an environment for grain storage problems.

Grain spoilage could be a problem especially this winter because corn matured late in the 2008 growing season in parts of North Dakota and many producers were forced to store corn at wetter-than-normal levels last fall.

“Keep corn temperatures near or below 30 degrees by aerating the corn periodically when outdoor temperatures are below 30 degrees to enhance storability,” advises North Dakota State University Extension Service agricultural engineer Ken Hellevang. “However, there is no benefit to cooling corn below about 20 degrees.”

He also urges producers not to rely on air temperatures to determine when to aerate corn. For example, the average maximum daily temperature on Feb. 1 is 15 degrees, on March 1 is 27 degrees and on April 1 is 45 degrees, while the daily total solar energy heating the south side of a grain bin on Feb. 21 is more than twice as much as on June 21. Also, the amount of solar energy heating the bin roof is about equal. Therefore, corn next to the bin wall may be much warmer than the outdoor air temperature.

Keeping corn cool is vital because the estimated allowable storage time, or AST, decreases rapidly at warmer grain temperatures. For 26 percent moisture corn, the AST is about 90 days at 30 degrees, 35 days at 40 degrees and only 12 days at 50 degrees. For 22 percent moisture corn, the AST is about 190 days at 30 degrees, 60 days at 40 degrees and only 30 days at 50 degrees. For 20 percent moisture corn, the AST is very long at 30 degrees, about 90 days at 40 degrees and 50 days at 50 degrees.

“Immature, cracked and broken corn kernels are more prone to deterioration than good-quality corn, so corn this year may be more prone to storage problems,” Hellevang says.

Warming of the grain normally will be limited to a couple of feet near the bin wall and a few feet at the top of the bin. Hellevang recommends monitoring grain temperature in these locations to determine when to operate the aeration fan. Bin temperature cables help monitor grain temperature but only detect the temperature of the grain next to the cable. Grain has an insulation value of about R-1 per inch, so grain insulates the cable from hot spots just a few feet from the cable.

Here is some other advice on aerating corn:

• Do not operate the fan during rain, fog or snow to minimize blowing moisture into the bin.
• Bin vents may frost or ice over at temperatures near or below freezing, so leave the fill hole or manhole open or unlatched while operating the fan to prevent damage to the bin roof.
• Cover aeration fans when they are not operating to prevent wind from warming the corn. Wind blowing into an uncovered aeration fan or duct will aerate the corn, warming it to temperatures near the daily maximum. This occurs because more wind tends to blow during daylight hours than at night.
• Corn at moisture levels exceeding 21 percent should be dried in a high-temperature dryer during February or early March to minimize the potential for grain deterioration. Natural air drying is not efficient until the average outdoor temperature reaches about 40 degrees, which normally occurs in early April. The moisture-holding capacity, and therefore the drying capacity, of colder air is so limited that drying at colder temperatures is extremely slow.

For more information about corn drying and storage, do an Internet search for NDSU corn drying or go to the NDSU Web site http://www.ag.ndsu.nodak.edu/abeng/postharvest.htm.

NDSU Agriculture Communication