With so much rain this fall, more than a few farmers are likely going turn their combines loose in some tough grain just to get harvest finished. Grain dryers will be logging a lot of overtime to keep up. But the odds are at least some damp grain will have to be put into storage to wait until it can be dried properly. Aeration bins can help keep that damp grain cool and safely stored, at least temporarily.
“I think we’ll see (aeration storage) being a relatively common practice this year,” says John Ippolito, a regional crop specialist for the Saskatchewan Ministry of Agriculture. “Because there is that temperature and moisture relationship, (grain) is safe for storage as long as we’ve got it down to a cooler temperature. We recommend using those aeration systems to bring the grain temperature down in stages. Move it down to within about five degrees of the outside air temperature (each time).”
That means as the average daily air temperature continues to drop throughout autumn, farmers should consider repeating the aeration process two or three times to keep grain close to the outside air temperature. “You may need to (run the fans) a second time when the temperature goes below zero,” adds Ippolito, “But we don’t recommend taking the grain mass to below zero, especially if it’s tough grain. But there is merit in getting the entire grain mass down close to zero.”
KEEP THE FANS ON
If the weather turns damp again, though, should fans be turned off to avoid forcing ambient air with high humidity into an already damp grain pile?
Not according to the Grain Aeration Fact Sheet published by the Ontario Ministry of Agriculture and Rural Affairs (OMAFRA). “Once aeration is started, it should continue (even through high humidity periods) until the aeration front has moved completely through the grain mass,” it reads. However, once the front is through, the grain will be relatively uniform and continued aeration especially during high humidity periods will cause a new front.
Ippolito agrees. “Once we’ve started the fans and are moving some of that moisture through the grain, there ends up being a layer that is actually wetter than the grain was when it was put in,” he says. “So we really can’t stop moving air through there, because there’s a chance we could have spoilage in that area. We want to move that front all the way through the bin before we shut the fans off.”
The front is a moving transition point between lower-temperature, aerated grain and warmer and damper grain that has yet to be affected by the air flow. Aeration cools warm grain similar to the way a bin dryer dries grain through a “drying front,” continues the OMAFRA paper. Essentially, a similar front, sometimes called an “aeration front,”moves up or down (depending on the direction of airflow) through the grain mass.
UP OR DOWN?
Because many aeration fans can either push or pull air, producers can set up bins to move the aeration front up or down through the grain mass. There are advantages and disadvantages to each method, according to OMAFRA. If air moves up, it can pick up heat from the fan as it is forced into the bin. The warmer air then picks up moisture from the grain and the resulting warm, moist air can condense on the cold metal roof inside the bin and drip water onto the top of the pile.
Pulling air down and out through the fan, on the other hand, eliminates that problem. Any heat from the fan is immediately exhausted outside the bin. But because the last point reached by the front is the bottom of the pile, farmers need to monitor the aeration progress which is more difficult to do at the bottom of a bin, unless the bin is equipped with a permanent monitoring system.
When pushing air up, the top of the pile needs to be monitored. Barring gadgetry, you can monitor the temperature simply by inserting a metal rod about one metre into the top of the grain mass, leave it in for about 30 minutes, then pull it out feel for heat with your bare hand. If the aeration front has passed completely through, the temperature at the top will have dropped.
Whatever method you choose, Ippolito says fans should be started even before the bin is full. Waiting until the top hatch is closed and the auger moved to the next granary may be too late to prevent damage. “As soon as the tubes or the screens are covered, start the fans. If it takes an extended period to get the bin full, especially with tough or very hot grain, we might have spoilage already. It’s about making sure we start to condition that grain right away.”
And avoid filling the bin much higher than the sidewalls. Grain coned too near the top will restrict the air flow. The higher the volume of air flowing through the bin, the faster the front will progress through the pile and keep temperatures down.