As harvest winds down and bins fill up, many farmers are likely breathing easier. But a university researcher warns that stored grain will spoil if conditions aren’t right.
“Grain storage is part of farming. Before the money is inside your pocket, you can’t say it’s safe,” says Dr. Fuji Jian, grain storage specialist with the University of Manitoba.
Keeping grain dry and a consistent temperature is vital to preventing spoilage. Aeration cools grain in the fall, while natural air drying dries tough or damp grain. The basic difference between the two processes lies in the air flow rate.
“When your air flow rate is low, basically you could not dry your grain,” Jian says. Aeration uses low air flow rates to cool grain and keep temperatures uniform. Grain can dry by up to one per cent if grain temperatures start out very high and cool substantially, but aeration is not a grain drying system.
Natural air drying requires higher air flow rates and warm, dry weather. Air is forced into a perforated floor in the bin bottom, pushed up through the bin, and out roof vents. The right weather conditions are needed for natural air drying. If the air outside is hot and humid, the grain will heat up and become wet.
Many bin systems are designed for aeration rather than natural air drying. Jian says that a system’s air flow rate depends on fan power, but farmers can also boost air flow rates by loading bins strategically.
“If your silo is six metres high, than you can do aeration. But if you load your grain only half, then in that case air flow rates will be much higher and then you can do natural air drying,” Jian says.
Volume isn’t the only consideration. Jian recommends coring the bin to level the peak, increase airflow, help with moisture migration and remove fines. The grain pile should be level or even concave to maximize air flow rates.
Narrow bins are ideal for low moisture grain. Jian doesn’t recommend putting wet grain in bins with diameters less than four meters as it’s hard to boost air flow rates in tall, narrow bins. Bins less than six metres in diameter don’t hold enough grain to insulate hotspots so aeration isn’t necessary during cold winter months. Bins with a diameter greater than six meters will develop hotspots in the winter, making aeration necessary.
Drying wet canola, flax, and mustard using natural air drying is often impossible because the small seeds are densely packed, cutting airflow rates. The Canola Council of Canada recommends making sure there is enough fan power to keep air flow rates high, ventilating the bin, and removing some canola if necessary. If the outside air temperature isn’t high enough, or the canola is too damp, farmers will have to look at other strategies such as adding heat, batch drying or moving damp canola back and forth to prevent spoilage.
Silo bags (grain bags) are a popular storage method with some farmers, but Jian warns they aren’t a good option for every situation.
“Even for short term storage, you couldn’t put a high moisture grain inside because for high moisture grain in a silo bag, you have no ability to do monitoring. You have no ability to do aeration. Of course you can’t do any drying. And then if your silo bag is in the field in the winter time… you couldn’t access it because it’s snowing.”
Canola sitting at 12 per cent moisture should only be stored in a silo bag for six to eight months maximum, Jian adds. Storing such canola for a year leads to large losses. Canola at less than 10 per cent moisture can be stored for up to a year.
Silo bags should be placed on high ground to keep them dry, and surrounding grass should be knocked down to discourage mice from raiding the bags.
New storage technology
The ethanol industry is using probes to monitor insects in bins. The Insector, manufactured by OPI Systems, integrates with software to report what kind and how many insects are in the bin, Jian explains. It can also be used as one component in a system that may include aeration and natural air drying. However, cost can be a barrier for farmer hoping to adopt the technology. A large bin requires several probes, and each probe currently sells for over $200, plus the other system components.
Farmers can buy perforated tubes that take advantage of natural convection to cool and dry stored grain. Heat from within the grain travels up the tube and escapes out the bin’s top, preventing large hot spots from forming. Gatco, Grain Air Tube manufacturer, states the tubes can cut moisture by one to two per cent. No power is needed to operate the tubes.
Jian says the tubes are a good idea, though he adds farmers must make sure snow and rain doesn’t get in the bin while the heat is venting out the top. He also says farmers need to make sure their grain doesn’t get too cold in the winter.
Farmers could also use sealed tubes filled with refrigerator coolant or another cooling chemical. The tubes would stick out the bin top. When the grain temperature broke 20 C, the liquid would turn to steam and rise to the top.
“It would always move heat from inside the grain to the outside,” says Jian. The cooler conditions outside would chill the chemical, which would travel back down the tube and cool the grain.
Jian warns against looking for a simple solution to what may be a complex grain storage problem.
“Look for more deep insight into what’s going on and understand it.” †