PRIMGHAR, Iowa — In the past couple of weeks, high temperatures have been well above average with dew point temperatures above grain temperatures. This can cause grain bins to act like solar collectors on the south side, causing currents to move inside bins. The southwest side heats up, causing the air to rise and dry the grain. This warm, dry air falls onto cold grain on the northeast surface grain, producing moisture because it is colder than the dew point temperature. Optimal grain temperature in spring should be above 40 degrees Fahrenheit, but below 50 degrees Fahrenheit, which is where bugs and molds can grow, even with fairly dry grain.
With average daily temperatures expected in the low to mid 40s, grain should be warmed up as soon as possible. Stored grain should be warmed to 40-45 degrees Fahrenheit for summer storage. Early very warm temperatures, when the sun is still low in the sky, cause greater problems, especially if the grain temperature is below zero.
The time required to completely cool a bin of grain depends on fan size. In general terms, a large drying fan will take 10-20 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 important to measure the temperature of the air coming out of the grain to see if cooling is complete. It is also much better to err on the side of running the fan too long rather than turning it off too soon. During spring warm up, never shut down the fan unless it is snowing because the grain in the warming weather front will condense when the grain is below the dew point until the temperature front passes.
Now is also a good time to sell a load from all of the bins to remove any of the grain that has been exposed to the moisture migration from the warm February temperatures. Most grain storage issues occur near the top of bins. Walking the bin and regular moving of this grain helps reduce major problems. All of the big problems I have dealt with have been the result of improper temperature control rather than drying.
If grain is dried down to recommended moisture content and properly warmed in the spring, it should store very well through the season. Even so, it is best to check stored grain at least weekly during the spring and summer. To do a good job checking grain, inspect and probe the grain for crusting, damp grain, and warm spots. In addition, run the fan for just a few minutes and smell the exhaust air for any off odors. For more details, order a copy of “Managing Dry Grain in Storage” AED-20 from Midwest Plan Service at https://www-mwps.sws.iastate.edu/catalog/grain-handling-storage or check out more grain drying and storage information at https://www.ag.ndsu.edu/graindrying.
— Kris Kohl, Ph.D., P.E., Agricultural Engineer, Iowa State University Extension and Outreach
For more news from Iowa, click here.