With cooler temperatures soon heading our way, farmers and stored grain managers holding corn, wheat, or soybeans are reminded to keep an eye on the weather and run their fans in the next few weeks when cooler temperatures are available.

Right now, the temperature of most stored grain that has not been aerated is between 70 and 80 degrees Fahrenheit. This is warm enough to promote abundant growth of damaging insects and storage fungi/molds, said Sam McNeill, an agricultural engineer with the University of Kentucky Cooperative Extension Service.

“We want to be sure and start a cooling cycle in October when Mother Nature gives us the opportunity to lower the temperature of grain to a level that’s near the monthly average temperature — in Kentucky that’s 60 degrees,” he said.

Anyone who’s planning to hold grain into the winter should run their fans about once a month during the fall to continue cooling grain in increments of 10 degrees each until a target temperature range between 35 and 40 degrees is reached, McNeill said. This usually occurs by mid-December when more stable conditions are reached.

Farmers and stored grain managers should keep in mind that it can take anywhere from 15 hours to 150 hours to move a cooling front through grain. The time required depends on the size of the fan relative to the bin. For example, a 10 horsepower fan on a 10,000 bushel bin (or 1 hp per 1,000 bushels) can move a cooling front through a bin in close to 15 hours. In contrast, a 1 hp fan on a 10,000-bushel bin, a 10-fold decrease, will take 150 hours to cool all the grain in the bin.

“To give folks a little perspective on the amount of time that’s been available recently, I’ve looked at some hourly temperature data for the past seven weeks for Princeton,” McNeill said. “I discovered that since Aug. 7, we’ve actually had 152 hours when temperatures were below 65 degrees; 66 hours below 60 degrees; and 21 hours below 55 degrees. Obviously then, we’ve already had opportunities to cool grain below 75 degrees, which is highly desirable to improve grain storability.”

More opportunities to cool grain will come as average daily temperatures fall from 64 to 53 degrees during October. Operators should run their fans when the air temperature is 10 degrees below the grain temperature. They can track the progress of a cooling front by measuring grain temperatures in the top of the bin if pushing air up through the grain; or by measuring the temperature of the air coming out of the fan if pulling air down through the grain, he said. Fans can be turned off after the cooling front has moved completely through the grain.

“When you consider the economics of cooling grain, aeration is an inexpensive way to maintain grain quality,” McNeill said.

With an electrical cost of 7 cents per kilowatt-hour, it usually will cost less than half a cent per bushel to move three cooling cycles through grain this fall. Considering that other (chemical) options for insect control can cost up to a nickel per bushel, aeration is definitely a bargain, he said.

Anyone seeking more information on aeration requirements for stored grain should contact their local UK Cooperative Extension Service, or access publications from the UK Biosystems and Agricultural Engineering Department at www.bae.uky.edu.