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Tips for tough or damp canola

Oct. 29, 2009 -The Canola Council of Canada is sharing some tips for late-harvested canola, acknowledging the impacts of a cold, wet harvest and the effect those will have on storage and other issues.

October 30, 2009  By Canola Council of Canada

October 28, 2009 Harvesting canola this close to Halloween can be a scary proposition, but it is a reality for many producers this year, challenged with wet weather and snow across much of the prairies.

"In most cases harvesting the canola at higher moisture when conditions allow for effective combining is preferable to leaving crop stranded under the snow for the winter, but farmers will need to manage aggressively to prevent spoilage until the crop can be properly dried," say Canola Council of Canada (CCC) senior agronomy specialist Derwyn Hammond.

While it’s difficult to generalize advice because of different weather conditions, grain moisture contents and temperatures, aeration and drier capacities, the CCC does offer some points to consider on storage management this year.


Harvesting in cold weather
Freezing temperatures can be beneficial for late harvesting, allowing a crop that might be too wet otherwise to flow through the combine reasonably well. However, the friction as the crop is processed through the combine will usually thaw the grain (and any layer of ice on the seed), increasing the temperature and moisture of the grain going into the bin. This thawing may also create some issues with icing up sieves, so farmers are advised to monitor regularly and break up or remove the ice as necessary. An accurate assessment of the actual temperature and moisture content of the grain as it goes into storage will be essential for determining the best management strategy.

Damp versus tough canola
Canola is considered damp when moisture content exceeds 12.5 percent, while tough canola ranges from 10 to 12.5 percent. While tough canola can often be stabilized and in some cases even dried down to safe storage levels through natural aeration, damp canola will require heated air drying and rigorous management until that occurs. Farmers who think cool harvest temperatures will protect your grain, remember that mould still grows in a fridge! Cool temperature may help delay issues with heating, but unless the temperature throughout the tough or damp stored canola can be maintained at well below freezing it will spoil eventually.

Regularly moving damp canola back and forth between storage facilities is critical for avoiding spoilage, and may be required even if aeration is available. Physical movement every two to three days may be necessary depending on the level of moisture and temperature of the bulk seed mass. Monitoring continuously is one of the Best Management Practices (BMP) for managing high moisture canola in storage.

When managing damp canola, farmers should consider the following:

  • Use heated air drying to condition the canola as soon as possible. Continuous flow or re-circulating batch drying systems will be preferable, as they reduce the potential for seed damage from heating and allow for slightly higher drying temperatures. However, for very damp canola farmers likely will need to run the grain through twice at a lower temperature to prevent seed damage and reduce the risk of fires. They should also over dry the grain slightly to allow a rebound in moisture as the grain cools when it is moved into storage. A general rule of thumb is to over dry the grain by 0.1 percent for every point it is dried. If using driers with screens, farmers should make sure the screen size is small enough to hold canola, as many driers may have screens originally intended for corn or cereals.
  • Watch drying temperatures. If the canola is mixed during drying, research suggests tough canola can be dried at temperatures as high as 82 degrees Celsius, although the maximum safe drying temperature varies depending on the system. However, it is much easier to "cook" your canola in a heated air drying system as the moisture content increases. Generally the maximum temperature should be lowered by at least 11 degrees Celsius when working with damp canola as opposed to tough. If the canola is to be used for seed, maximum temperatures are substantially lower at around 49 degrees for tough canola and 43 degrees for damp. Check the links below for more details.
  • If you can’t dry the canola right away, aerate it continuously if at all possible. The goal with aeration at this time of year is to keep the temperature of the grain as cool as possible. Natural air drying will likely not be effective under these late fall conditions, as relative humidity of 70 percent or less is needed to achieve equilibrium moisture content of eight to nine percent. Reaching those dry equilibrium moisture levels will likely take too long to avoid spoilage in many cases.
  • Can your fan move enough air? The high bulk density of canola creates a great deal of static pressure, and this is aggravated by higher moisture contents. Air needs to flow continually to move the heat and moisture out the top of the bin, replacing it with cooler air from the outside. Insufficient air flow can result in creation of a high moisture zone near the top of the bin that can initiate spoilage. 
  • Bin style matters. The greater the depth of canola in the bin the higher the static pressure, and the more fan capacity you will need to move air through it effectively. From that standpoint, 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, consider removing some canola to reduce the depth and disrupt any high moisture areas that are developing. Proper ventilation at the top of the bin to allow for escape of the warm moist air is also very important, especially for large bins.
  • Considering adding heat to your natural air system? Keep in mind that it is generally recommended to limit the increase in air temperature to 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.
  • What about blending? 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.
  • The devil is in the details! The best strategy for conditioning your canola will depend to a certain extent on the weather in your area and the strengths and limitations of your storage and drying systems. The links below provide lots of additional information on the proper use of various styles of aeration and drying systems and how all of these are affected by weather conditions. You can also consult with the manufacturer of your specific system to get their input.

The final and most important point regarding storing this year’s canola crop, whether it was harvested dry, tough or damp, is to monitor it regularly! The only constant is change, and catching those changes in temperature or moisture early to avoid spoilage could mean a lot more money in the bank when that canola gets delivered!


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