Unusual growing conditions and a challenging harvest raise risks of deteriorating quality of stored grain.
University of Wisconsin Extension specialists Brian Holmes and Cheryl Skjolaas note that the quality of the 2009 corn crop could slip further while in storage.
Cool, wet conditions during the growing season resulted in mold infestation of the crop before it was mature. These molds remain viable in storage and, if the right conditions develop, could flare up. Corn that was frosted before maturity is more susceptible to infestation by molds than is mature grain, they note.
“Molds and fines are at the core of the situation,” Holmes explains. Cool growing conditions and a delayed harvest meant much of the grain was harvested wetter than usual. Harvesting wet grain increased kernel damage, which increases susceptibility to mold infestation.
“The fines resulting from the damage should have been removed before storage,” Holmes explains. “If all or some of these fines remained in the storage, they are susceptible to mold infestation and interfere with aeration of the stored grain.”
Exacerbating the problem, producers may have operated their dryers at high temperatures to increase the drying rate. Hot grain cooled quickly in the dryer can cause stress cracking, which increases the likelihood of kernel breakage. Cracking increases the fines in storage.
Generally, corn should be dried to 15% moisture if stored for six months, 14% if stored up to 12 months. Corn with a higher risk of mold infestation should be dried down an additional percentage point, Holmes says. In the haste to move corn through the drying process as quickly as possible, some corn may not have been dried to these recommended values.
“Bottom line is the current crop in storage needs extra management to reduce further quality loss. Inspection is the key to helping preserve the quality of your stored crop,” he continues.
Inspect with Caution
When inspecting stored grain, look for accumulations of fines, signs of molds and “hot spots,” Skjolaas says. Inspection requires a person to enter the bin, so take precautions:
Lock out and tag out the removal auger system to ensure it is not turned on while a person inspects the grain.
Turn on the aeration fan to clear accumulated gases from the head space above the grain. If molds are present, carbon dioxide levels may be elevated, creating an oxygen-deficient atmosphere.
Use an approved respirator to filter out molds and spores that may enter your respiratory tract.
Safe entry requires using a harness with two ropes and two assistants outside the bin. This may seem excessive, but the forces of grain are significant if a person becomes engulfed.
Before entering a bin, check grain levels by looking through the hatch. If grain has been removed from the bin, look to see if a cone on the surface of the grain has formed. If there is no cone present, there is a high likelihood of a cavity below the crusted surface. Always probe the crusted grain with a long pole. If a cavity exists, use the pole to break up the crust before entering the bin.
Checking for Mold
Once in the bin, move around the grain surface and smell for zones of mold odor. Make a note of the location. Using a temperature probe, check various depths and locations for elevated temperature, taking special care to check the zones where mold smell was noted.
If the center core of grain has not been removed from the bin, exit the bin and remove the core, Skjolaas recommends. The core is a common location for fines to accumulate, increasing the chances of molds in that area.
Inspect the grain taken from the core for molds and crusted grain. If a problem is noted during inspection and the grain appears to be going out of condition, turn on the aeration fan to cool down any “hot spots.”
Even if no problems are found, repeat the inspection process at two-week intervals throughout the winter. In the spring, increase inspections to once weekly.
If increasing aeration does not control grain temperature, the grain will have to be removed from the bin and marketed or moved to another bin. If grain is moved to another bin, be sure to screen the grain to remove fines, Holmes advises.