This harvest season in Iowa, a lot of corn and soybeans have gone into storage at temperatures in the 70 to 80 degree F range and some went in the bin in over the 80-degree range. With grain this warm, moisture migration and spoilage can occur quickly, even with fairly dry grain.
Greg Brenneman, an Iowa State University Extension ag engineering specialist, advises "With the weather forecast for highs in the 50-degree range and with lows in the 30s for this weekend and next week, grain bin fans should be running by the end of this week, beginning on Friday October 5, to get stored grain cooled down as soon as possible."
"While we want stored grain cooled down to the 30 to 35 degree range for winter storage, the sooner we get grain temperatures down, the better," he says. "Every 10 degree drop in grain temperature will nearly double the allowable storage time. Fans might need to be run several times during the fall to get grain down to wintertime storage temperatures."
Important to protect grain in storage by properly cooling it as weather cools off
The time required to completely cool a bin of grain depends on fan size. In general terms, a large drying fan will take 10 to 20 hours to cool a bin of grain. However, a small aeration fan can take a week or more to completely cool a full bin. "In either case, it is best to measure the temperature of the air coming out of the grain to see if cooling is complete," says Brenneman. "It is much better to error on the side of running the fan too long rather than turn it off too soon."
If grain is dried down to the proper moisture content and correctly cooled, it should store very well through the winter. Even so, it is best to check stored grain at least every two weeks during the winter and once a week in warmer weather. For more details, Brenneman suggests you order a copy of "Managing Dry Grain in Storage" AED-20 from Midwest Plan Service or check out more grain storage information online.
Moisture variability is problem this harvest with corn coming out of the same field at wide ranges in moisture content
In addition to warmer-than-normal corn going into bins this harvest, there's another unusual situation in many fields in Iowa. That is a wider than usual range in moisture content of the grain coming out of the same field. That can also increase the risk of potentially difficult storage challenges ahead.
"Many farmers are seeing high- and low-moisture blends of corn going into the combine's grain tank in the same pass through the field," says Charlie Hurburgh, director of the Iowa Grain Quality Initiative at ISU. "Dryers will not equalize such variability. Even after cooling and aeration of the dried corn, there can be four percentage points or more in moisture variation among kernels, which means shorter shelf life and more storage risk."
Thus, properly cooling the warmer-than-normal stored corn is crucial, and more so with the variable moisture content. You need to understand how a cooling cycle works, notes Hurburgh. A cooling cycle moves a cooling front completely through a grain bin when the average outside air temperature is 10 to 15 degrees below the grain temperature. Remember, the time needed depends on the fan's size. With 0.1 cubic foot per minute per bushel of aeration, it takes about 150 hours to complete a cooling cycle. With 1 cfm about 15 hours is needed.
Safe storage means you should be progressively lowering grain temperature in cycles
Safe fall storage means you need to be progressively lowering the grain temperature in cycles. Because the shelf life of grain in a bin is temperature-dependent, it's important to begin these cycles as soon as a 10- to 15-degree temperature drop can be achieved. With higher initial temperatures, at least two additional (beyond normal) cycles will be needed. If the grain has to wait in the bin for a month to be cooled, the shelf life will be reduced and future spoilage is much more likely.
The table below lists the typical storage life expectations for corn. Hurburgh says you should reduce the estimated storage times in the table by at least a third, possibly up to 50%, for corn that's come from drought stressed fields this year.
Farmers put so much work into planning, planting and managing their crop throughout the growing season, and this fall they need to put as much focus on harvest and storage to reap the greatest benefits, he says. If farmers are lucky enough to have a crop to put in the bin this season, it's critical that they manage it properly to take advantage of the record prices available to their operations.