Canada
September 27, 2010
Growers will take advantage of a few nice days this week to combine canola. Even with warmer temperatures in the forecast, some of it will come off tough or even damp. All canola should be conditioned after it goes into the bin to ensure safe long-term storage — especially if it goes into the bin warm. For tough and damp canola, the spoilage risk is much higher.
"With warm weather in the forecast for much of the Prairies this week, a lot of canola will go into the bin warm. If it’s also tough, that could be a bad combination," says Derwyn Hammond, Canola Council of Canada senior agronomy specialist for Manitoba.
Canola is considered "tough" at moisture levels between 10% and 12.5%. "Damp" is anything above that. With tough canola, aeration can be enough to dry it to safe storage levels — but only if outside air is warm enough to keep relative humidity (RH) sufficiently low. At RH values above 70%, the equilibrium moisture content will be above 8% to 9% meaning sufficient drying for safe long term storage is difficult to achieve. Drying canola with aeration alone also requires sufficient time for the drying front to move up to the top of the grain mass. Damp canola will require heated air drying and rigorous management to condition it for safe storage.
Drying canola:
Dry canola as soon as possible. While waiting, aerate continuously if possible and move damp canola back and forth between storage facilities to prevent spoilage. The combination of aeration and movement is ideal.
Have the right equipment. Continuous flow or re-circulating batch drying systems are preferable. They reduce the potential for seed damage from heating and allow for slightly higher drying temperatures. For very damp canola, growers may prefer to run the grain through twice at a lower temperature to prevent seed damage and reduce the risk of fires. Also, if the dryer has screens, make sure the screen size is small enough to hold canola.
Watch drying temperatures. Check the maximum safe drying temperature for your system, then reduce it by 11 degrees Celsius when working with damp canola as opposed to tough. As moisture content increases, it gets much easier to "cook" your canola in a heated air drying system.
Over dry canola slightly when using heated air. As grain cools when moved into storage, moisture content tends to rebound slightly. Over drying compensates for this. A general rule is to over dry by 0.1% for every point the grain is dried. For example, if canola is at 14% moisture and your target is 9%, over dry by 0.5 percentage points to 8.5%.
Aerating canola:
Natural air drying can work if warm. Trying to dry tough or damp canola with aeration alone — "natural air drying" — is not usually effective under late fall conditions. Reaching dry equilibrium moisture levels often takes too long to avoid spoilage in many cases. But if growers get some warm or even hot days this week, natural air drying may be able to remove one or two percentage points of moisture.
Adding heat to an aeration system. The general recommendation for this method is to increase air temperature by no more than 10 degrees Celsius. In these late fall conditions, that may be insufficient to provide significant drying, instead contributing to a higher temperature in the bin and greater potential for spoilage.
Can your fan move enough air? When conditioning tough or damp canola, make sure your aeration fan has the horsepower to work effectively. The higher the moisture content of the grain, the more power required to push air through the grain mass. Insufficient air flow can result in a high moisture zone near the top of the bin that can initiate spoilage.
If the fan can’t move enough air, take out some grain. The greater the depth of canola in the bin, the more fan capacity you will need to move air through it effectively. Large diameter bins that provide uniform air flow through a perforated floor may have an advantage when handling damp grain. If you suspect the air flow is insufficient, remove some canola to reduce the depth. This offers two other benefits: It disrupts any high moisture areas that are developing. And it can flatten the cone, making the depth of grain more consistent throughout the bin.
Ventilate the bin. Proper ventilation at the top of the bin to allow for escape of the warm moist air is very important, especially for large bins.
What about blending dry and damp canola? If considering blending in an attempt to bring damp canola down to tough, be very careful. A poor job of mixing may simply put your drier canola at risk for spoilage.
Monitor regularly. This is good advice for all canola. Be extra careful with canola that goes into the bin warm and tough this week.
For more information on safe storage of canola, click here.
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