Now is the Time for Farmers to Turn on Fans

October 26, 2017 3:40 PM
Blog Post

Up to this point in the harvest season we have been short on grain dry down and cooling weather. Corn moisture percentages have been hanging in the 20’s, sometimes in the upper 20’s. This past week eliminated much of the moisture, but favorable field dry down weather rarely continues into November. Farmers should now focus their attention on cooling, both of wet corn in holding or air dry situations, and of dried corn being removed from dryers. Inadequate or delayed cooling is very costly to future storage properties. Remember, a significant portion of the 2017 crop will be held over for more than one year, as carryovers expand.

Starting Friday morning, great conditions arise to get grain cooled down from this Fall’s harvest. With the average daily temperatures predicted to be in the mid- 30s to low- 40s for Friday well into next week, this will be a perfect time to get recently harvested corn and soybeans cooled to a temperature required for winter storage. Allowable storage time for grain roughly doubles for every 10 degree drop in temperature. So, getting grain cooled down soon after harvest will significantly improve chances of keeping it in good condition while in storage.

In order to determine the length of time it will take to cool a bin of grain, first determine how much fan horsepower you have per 1,000 bushels. For example, if you have a 5 hp fan on a 20,000-bushel bin, you have 0.25 hp/1,000 bu. Divide this number into 15 and you get an estimate of the hours it will take to cool the full bin.  In this example, 15 / 0.25 = 60 hours.

Air dew point is a rough measure of how low grain temperature can be reduced. For example, right now the temperature is 63°F and the dew point is 44°F. A 20- degree difference is good; the larger the difference, the greater chance that air will dry corn, and 44°F is approaching the below 40°F temperatures required for storage.

There will be a lot of long term storage this year, so cool rapidly now to prevent mold and insect damage next Spring and Summer.


Charles Hurburgh Professor, Agricultural and Biosystems Engineering

Dr. Charles R. Hurburgh, Charlie to most everyone, is a native Iowan from Rockwell City (Iowa, USA). He continues to operate the family farm, and is a professor of Agricultural and Biosystems Engineering at Iowa State University. He has a bachelor's degree, master's degree, and doctoral degree fr...