Spring is in the air—and the first significant warmup of the year is a reminder to check stored grain frequently. If good practices were followed through the fall and winter seasons, grain temperatures should be in the 30 to 40 degree Fahrenheit range or below. Grain moistures at harvest last fall were above average, and there are many bins with corn moistures this spring in the range of 16% to 20%. This wetter grain will spoil quickly if grain temperatures rise, warns Charlie Hurburgh, professor of ag and biosystems engineering at Iowa State University. An expert on grain quality and stored grain management, he is director of the Iowa Grain Quality Initiative.
In the bin, headspace warms first which can lead to condensation, Hurburgh explains. To reduce this problem, he recommends that you ventilate the headspace by running the roof fans, if the bin has them. This will take out moisture without having to warm the grain mass.
Check temperature of stored grain, the air coming out of fans
"If there is a temperature rise in the grain, it means mold activity is starting and the aeration or drying fan should be operated," says Hurburgh. "If the bin doesn't have temperature monitoring capability, then it will be necessary to run the fans periodically whether there is a need or not."
It is possible to preserve cold temperatures even if the fans have to be operated, he points out. "Pay attention to the dew point of the air; recent dew points have been in the 30s and 40s with 60 to 70 degree outside temperatures. Evaporative cooling, especially from wetter grain, will keep the grain slightly above the dew point. Low humidity days will not warm the grain as much as high humidity days that are at the same temperature."
For bins with wet corn, it's important to not hold onto the moisture much longer. "Low humidity, moderate-temperature days are good for air drying. Humidity typically goes up in May and June, so it will be best to have the grain dry by then," says Hurburgh.
As outdoor air temperature warms up, run the aeration fans
As outdoor temperatures change, it is important to transition grain temperature as well, he adds. For a drying fan of 1 cubic foot per minute per bushel flow rate, this will take about 15 hours; for an aeration fan of 0.1 cfm/bu it will take about 150 hours. As a reminder, low humidity days have an advantage because the grain temperature may not change much due to evaporative cooling.
"Plan to sell or use the wetter corn first since much of the storage life has been used up, even at cold temperatures," says Hurburgh. "The likelihood of spoilage later in the summer, when even dry corn is at risk, is much higher." Based on USDA estimates, a considerable amount of 2014 crop corn will have to be kept in condition over a year in storage, based on supply/demand and price projections for the 2015 marketing year.
"Spring is the time to pay close attention to stored grain," he sums up. "This year, there is more wet corn in storage, and there has been a rapid weather switch from cold to warm. Check now and often to prevent future problems."
For information on managing stored grain, check these sources
* Iowa Grain Quality Initiative website is www.iowagrain.org
* ISU has online training modules which cover these three topics: Aeration and Dry Grain Storage, Fan Performance, and Dryeration. Visit www.iowagrain.org and select the 'grain storage training' tab.* Mycotoxin training modules are also available. There's the Mycotoxin Development module at http://cai.iastate.edu/extension/mycotoxinsone/index.html and the Mycotoxin Management module.