Unlike the past several years, Mother Nature gave us a bit of a break this year. Harvest progressed quickly and grain, for the most part, was dry when it was harvested and put in grain bins. However, just because the grain was dry and in good condition when it went into the bin doesn’t mean you can ignore it until spring and not have any quality issues. Bins still need to have the centers cored, and they need to be monitored to make sure problems do not arise.

Corn in bins that are aerated and monitored to stay below 30 degrees will generally stay in good condition, if the center cores were removed during the winter months. Un-aerated bins and temporary grain piles can quickly loose quality once the temperature starts to climb.

According to North Dakota State University extension agricultural engineer Ken Hellevang, the estimated allowable storage time (AST) decreases rapidly at warmer grain temperatures. 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 about 90 days at 40 degrees and 50 days at 50 degrees.

Charles Ellis, University of Missouri extension ag engineer, warns that temperature differences in a bin of stored grain can cause moisture to migrate from warmer to colder areas.

Warm air rising in the center of the bin cools when it reaches the cold grain near the surface. Ellis says this results in moisture condensation near the surface and leads to rapid spoilage when the weather turns warm.

Hellevang advised, “Warming of the grain will normally be limited to a couple feet near the bin wall and a few feet at the top of the bin. Monitor grain temperatures in these locations to determine when to operate the aeration fan. Bin temperature cables help monitor grain temperatures, but they only detect the temperature of the grain next to the cable. Grain has an insulation value of about R1 per inch, so grain insulates the cable from hot spots just a few feet from the cable.”
He urges producers not to rely on air temperatures to determine when to aerate corn.

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.

Bottom line: check your bins and take temperature readings on a regular basis.
Here are some tips on aerating corn by North Dakota State University:
•    Do not operate the fans 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. The moisture-holding capacity, and therefore the drying capacity, of colder air is so limited that drying at colder temperatures is extremely slow.

The active period for grain spoilage begins in mid to late February.
Use every opportunity to keep the grain cold. Core storage bins by taking some grain out in the near future. Coring bins will indicate if there are problems starting, such as wet corn bridging over the unloading slide. Once the grain temperature cannot be maintained below 30 degrees, wet corn over 17 percent will have to be dried or sold to prevent spoilage. Natural air will work if the bin has 0.5 cfm per bushel or more of airflow and the moisture is less than 20 percent, according to Ken Hellevang. Moisture over 20 percent will require heated air.
Diana DeHart is Grain Coordinator for West Central AGRIServices, a division of MFA Enterprises.