As air temperatures go above 40° F in the coming weeks, it’s important to monitor grain stored in on-farm bins. While a colder-than-normal winter likely kept mold and insect development from happening, warmer temps will call for increased bin monitoring to manage moisture.
Ken Hellevang, Extension engineer at North Dakota State University, offers tips for monitoring corn and soybeans in grain bins.
1. Solar radiation can warm stored grain, creating an environment for grain storage problems. The daily total solar energy heating the south side of a grain bin on Feb. 21 is more than twice the amount as on June 21. Therefore, grain next to the bin wall may be warmer than the average outdoor air temperature.
Grain warming normally will be limited to a couple of feet near the bin wall and a few feet at the top of the bin. Monitor grain temperature at least in these locations to determine when to operate the aeration fan. Bin temperature cables help monitor grain temperature but only detect the temperature of the grain next to the cable. Grain has an insulation value of about R=1 per inch, so grain insulates the cable from hot spots just a few feet from the cable.
2. Do not operate the fan during rain, fog, or snow to minimize blowing moisture into the bin. Bin vents may frost or ice over if fans are operated when the outdoor air temperature is near or below freezing, which may damage the bin roof. Open or unlatch the fill or access cover during fan operation to serve as a pressure relief valve. Cover the aeration fan when the fan is not operating to prevent pests and moisture from entering the bin and warm wind from heating the grain.
3. Collect some grain samples and check the moisture content to ensure it is at the desired level. However, many grain moisture meters are not accurate at grain temperatures below about 40° F. When the grain is cold, it should be placed in a sealed container, such as a plastic bag, and warmed to room temperature before checking the moisture content.
At temperatures above 40°F the meter reading must be adjusted based on the grain temperature unless the meter measures the grain temperature and automatically adjusts the reading. Check the operator's manual for the meter to determine correct procedures to obtain an accurate value.
4. Natural air drying is not efficient until the average outdoor temperature reaches about 40°F. The moisture-holding capacity and, therefore the drying capacity, of colder air is so limited that drying at colder temperatures is extremely slow and expensive. When natural air drying, adding supplemental heat primarily reduces the final moisture content of the grain and only slightly reduces drying time. Regardless, try to keep the temperature of the grain within 10° of the average outside air temperature to limit condensation in the bin.