Cooling Soys & Corn in Bins

The 2008 harvest season has seen lots of sunny, windy weather and some impressive yields. As you drive through the countryside it seems like a race and you're not sure which will finish first - the soybeans or the corn. The soybeans reached maturity but were hard to thresh out of the pods. In mid-October we still had temperatures in the mid 20's - a nice little surprise. Beans that were harvested during those high temperatures need to be cool in the bin.

Beans or any grain put into a storage bin hot will stay hot. Just leaving the hot or warm grain sit in the bin will not cool it down. Individual beans or kernels of grain only make point to point contact with adjacent beans and kernels in the bin. The remainder of the space in the bin is made up of air spaces. The airspaces between the beans or kernels of grain act as insulation, trapping the heat in the grain mass. Because there are many bushels or tonnes of product in the bin there is also a tremendous amount of heat. If these trapped air spaces are not disturbed, the heat will remain trapped between the individual beans or kernels for a long long time, or until spoilage occurs.

Aeration is the only way to remove this 25+ degree field heat. So - if you harvested soybeans and the temperature was near 25°C you better cool down those bins today if you haven't done it already. When the bin contents are much warmer than the outside air temperature, convective air movement will occur. Warm air inside the bin rises picking up moisture from the grain. This moisture will condense on any surface that is at dew point temperature. This could be the bin roof or the grain further down in the bin. The convective air movement then continues down near the edges of the bin. The only way to stop this uncontrolled movement of air is to keep the beans or corn within 5Co of the average outside air temperature. As always you need to be careful with soybeans and run the fan only when outside air is relatively dry. Going into November you should bring your bin temperatures down to 5 to 10°C.

Standing corn fields are also disappearing with combines cleaning up the last fields under near ideal harvest conditions. A lot of people are pleasantly surprised by the low corn moisture content. Obviously, with the corn moisture being lower than normal, drying charges will also be lower. Some farmers with corn coming off at 18% and even 19% moisture content are wondering if they can put the corn in the bin without drying it first. This will depend on the aeration capability of the fan and what you plan to do with the corn.

Minimum Airflow

To affect any change in moisture content of grain in a bin, you need a minimum of a half a CFM per bushel airflow and preferably ¾ CFM / bushel or more. If this nice weather continues you can make drying progress. As the ambient temperatures go down - drying progress will slow. Below freezing, the drying progress is very slow and inefficient using lots of electrical energy for very little drying. Run the fan when outside relative humidity levels are 70% or less. The corn may not dry to your intended target moisture before freeze-up.

Corn Intended Use

If the corn will be used on the farm, putting 17 to 19% moisture content corn into a bin with sufficient aeration is low risk. If the corn is not completely dry it doesn't pose a big problem as we head into the cold winter months. If on the other hand, you plan to market your corn off-farm, the buyer will likely demand 15.5% moisture content. If you plan to ship after April 2009 the corn will likely be dry with routine aeration. If the corn is being picked up in January or February, you might have a problem with corn exceeding 15.5% M.C.