January 22, 2016
Check Stored Grain
Warm temperatures this winter will create the potential for grain to go out of condition in bins. When we have warm temperatures, grain nearest the bin walls, especially on the south and west sides of the bin, warms up more than grain in the middle of the bin. This difference in temperatures in the grain mass can cause moisture movement and condensation which leads to grain going out of condition.
You should check the temperature and moisture levels in stored grain now to avoid costly damage. The day that you put grain in the bin is the best condition that grain will ever be. It can not improve in storage, but it can get worse. Keeping stored grain cool is important for several reasons. Insects become dormant below 50oF and many are killed below 32oF. Mold growth also is reduced below 50oF and nearly stops completely below 40oF.
When grain temperature is significantly higher than air temperature, convection currents can occur in the bin. In the fall, a convection current causes air to sink in the cooler grain near bin walls and rise through warmer grain in the bin's center.
When a convection current occurs in a bin, the warm air carries moisture up through the center of the grain mass. When warm air reaches colder grain at the top, some of the moisture can condense and re-wet the grain, resulting in a wet spot in the top center of the bin. Crusted, moldy grain, sometimes with active insect activity, can result if the condition is not discovered and corrected by breaking up the crust and aerating to cool the grain mass.
In winter and spring the opposite conditions occur. Grain warms along the bin walls first causing air to move up along the bin walls and down through the center of the grain mass, causing condensation near the middle of the bin.
To reduce the effect of convection currents, producers should check the temperature in the bin in several locations with a grain probe thermometer. Whenever entering a bin, use a rope or lifeline and have someone with you that stays on the outside of the bin in case of an emergency.
If there is more than a 10oF difference in temperature difference between any of the locations, run the aeration fans to equalize those temperatures. Run the fan long enough to completely move a temperature front through the grain. The goal is to keep the grain at a uniform temperature that is close to the average air temperature.
When the aeration fans aren't running, remember to close roof hatches to prevent rain and snow from getting into the bin. Cover the fan when it's not running to prevent problems caused by the chimney effect that can draw in moist air at the bottom of the bin and up through the grain.
For producers who are unsure whether their grain condition will hold up through the spring, run the fan on a cold day and check the exhaust air for odors or steam. Have someone else turn on the fan after you are situated by the roof hatch. If that first blast of air when the fan is turned on has a musty smell or feels particularly humid, this indicates grain may be going out of condition.
Whenever there are signs of grain heating or going out of condition, run the fan continuously no matter what the season or weather. Also, feed or sell such low quality grain as quickly as possible. Grain quality never improves during storage.
For more information on stored grain management, contact your local Nebraska Extension office.