Extra-cool corn this fall
With a lot of corn being harvested and dried this year with high outside temperatures, corn bins are, in turn, at much higher temperatures than normal. And early harvest corn will require at least two additional cooling cycles to reach the desired eventual temperature of 40 degrees or below, according to Charles R. Hurburgh, professor in the Department of Ag and Biosystems Engineering at Iowa State University.
"A cooling cycle is moving a cooling front completely through a bin and is done when the average outside temperatures are 10-15 degrees below the grain temperature," he says. "Fall storage means progressively lowering the grain temperature in cycles. Because the shelf life of the grain is temperature dependent, it is important to begin these cycles as soon as a 10-15 degree temperature drop can be achieved. With higher initial temperatures, at least two additional (beyond normal) cycles will be needed. If the grain waits for a month to be cooled, the shelf life will be reduced and future spoilage is much more likely."
"Lots of the grain will be at a 75-degree ambient temperature," adds Dean Dodd with Sukup Manufacturing. "There are lots of fall seasons that don't take so long due to a low ambient temperature, but this year it may take three weeks." And don't be tempted to cool it all down at once, which can cause moisture troubles. "With the equipment we have today and the current price of grain, there's no sense in not taking the time to do it right."
Grain quality varies
Quality is going to vary widely, even in the same field, Hurburgh says. "Expect high and low moisture blends in the same pass. Dryers will not equalize variability; even after cooling and aeration, there can be four percentage points or more variation among kernels. Moisture variation means shorter shelf life and more storage risk."
Test weight, which is typically the best indicator of storability, will also vary, experts say. Overall test weights are somewhat below average, in the 54-55 lb/bu range, which is what experts expected from drought-stressed corn. In severe cases, which can include parts of the same field, 46-50 lb/bu test weights are likely. The combination of generally lower average test weight and highly variable moisture means we should reduce the typical estimates of storage time before loss. Hurburgh advises to reduce these by at least a third, possibly up to 50 percent for corn from drought-stressed areas.
Aflatoxin incidents persist
Aflatoxin continues to be an issue for grain. Though the recent cooler temperatures have been helpful in controlling increases, Iowa is seeing scattered incidents, more frequently in the southern part of the state. "It is very important to contact your crop insurance carrier if you suspect aflatoxin, because there is no coverage once the grain is harvested," advises Hurburgh.