Vigilance and grain safety go hand in hand By Bill Casady

Adaptation is good, but unchecked change can lead to chaos, disorder, turmoil and despair, especially when it applies to stored grain. Good grain management is about adapting a grain mass to the environment outside of the bin and at the same time preventing unchecked natural changes from occurring inside the bin. A basic understanding of equilibrium kernel moisture contents, equilibrium relative humidity of the air, and a grain mass in equilibrium with the environment reveals why we aerate as we do and why we trade grain at market moisture contents of 15.5 percent, for example, for corn.

Consider the relationship between the properties of individual kernels and the air in the spaces between kernels. Individual kernels tend to come into equilibrium with the conditions of the intergranular air around them. When we use a fan to aerate grain, the fan causes outside air to replace the intergranular air in the grain mass. When we aerate grain in the fall, the air we introduce to the grain mass is usually cooler and somewhat drier than the air that would normally occupy the intergranular spaces. Hence, the grain becomes cooler and may give up a little more moisture during the cooling process, and both cooler and drier grain lead to better conditions for long-term storage.

The condition of the intergranular air determines the fate of fungi and insects that can cause spoilage in grain. Storage molds or fungi are active only when temperature and moisture conditions support growth. Fungi are essentially inactive in air with less than 70 percent relative humidity. It is no accident that for relatively cool corn, (temperatures at or below 50 degrees F) the market moisture content of 15.5 percent causes the air in the intergranular spaces to fall just below 70 percent. Hence, the key to storing grain for long periods is to keep it both dry and cool and to maintain intergranular humidity below 70 percent.

A lot can happen, however, when a grain mass is left unattended. A small leak in the roof or at the edge of the bin, perhaps a pocket of wetter finnes in the center of the bin, or temperature changes that can move moisture inside the bin, especially at the onset of winter can break this nice little equilibrium. To safely store shelled corn for up to half a year, we recommend drying by another point of moisture (14.5%) and by two points (13.5%) for storage up to a year. Under these drier, safer conditions, small variations in moisture inside the bin are less likely to create an out-of-control situation.

A regular inspection schedule is the surest way to protect your investment. Pick a day of the week and a routine that you can live with and inspect grain on a weekly or bi-weekly basis. Be safe when entering storage bins. Never enter a bin without proper safety education and without a partner on the ground to call for help. When a pocket of grain begins to spoil, carbon dioxide begins to form and can quickly reach concentrations that can kill. Read MU publication G1969, Safe Storage and Handling of Grain, available at http://muextension.missouri.edu/explore/agguides/agengin/g01969.htm for more grain safety tips.

The bottom line is that a vigilant inspection schedule is more likely to prevent grain pests from reaching a critical mass that threatens your own safety as well as the safety of your stored grain investment. Be careful, be vigilant, protect, preserve, and prosper.

Bill Casady, Agricultural Engineering
(573) 884-7307