Fluctuating temperatures, from record setting warmth to more typical late winter cold, seems to be our weather pattern of late. With the approach of spring, temperatures normally tend to fluctuate, along with a warming trend. From a stored grain management perspective, fluctuating temperatures present challenges to maintaining grain quality. Given the grain prices and markets that producers are working with, there is a considerable amount of grain in storage waiting for an improvement in prices. I’m going to rely on Ken Hellevang, a North Dakota University Extension grain storage specialist to provide some stored grain management advice as we move into spring.
The first thing to be aware of is that grain bins act as a solar collector as daytime temperatures rise. More heating occurs on the south wall of a grain bin on March 1 than during the middle of the summer. According to Hellevang, the result is that the grain next to the bin wall is heated to temperatures exceeding average outside temperatures. If grain was put into storage last fall at above recommended storage moisture content then this heating is a concern. Remember that the maximum moisture content for warm-season storage is 13 to 14 percent for corn, 11 percent for soybeans, and 13.5 percent for wheat.
Hellevang recommends producers run the aeration fans periodically during the spring to keep the grain temperature cool, preferably near 30 F in the northern part of the country during March and April, and below 40 F in southern regions. Nighttime temperatures typically are near or below 30 F in March and below 40 F in April across the north-central region of the U.S. Cover aeration fans or ducts when not operating. The wind and a natural chimney effect will push warm, moist spring air through the grain. If the wind blows primarily during the daytime, the grain will be warmed to the daily maximum temperature. Typical maximum temperatures, even in northern states in late March, are in the mid-40s and increase in late April to around 60 F. Additionally, grain moisture will increase as the grain is warmed.
The goal for grain storage through the summer months is to keep the grain as cool as possible to limit insect activity that damages stored grain. Maintaining grain temperature below 60 degrees F reduces insect multiplication. Other management practices that can help to keep grain cool is to provide an air inlet near the bin roof eave and an outlet near the peak to reduce the hot air in the top of the bin. A ventilation fan to exhaust the hot air is another option. Hot air under the bin roof will heat several feet of grain at the top of the bin to temperatures conducive for insect infestations. If necessary, running the aeration fan for a few hours to push air up through the cool stored grain will cool grain near the top. Pick a cool morning every two to three weeks during the summer to run the aeration fan, and only run the fan a few hours to minimize heating grain at the bottom of the bin. Cover the fan when it is not operating to prevent additional heating of the grain.
Hellevang suggests checking the stored grain at least every two weeks. While checking on the grain, measure and record the grain temperature and moisture content. Rising grain temperature may indicate insect or mold problems. Insect infestations can increase from being barely noticeable to major infestations in three to four weeks when the grain is warm.