ALERT: What to do with high moisture canola?

October 21, 2016

Canola Watch Alert

Weather is finally allowing for some harvest to resume across the Prairies, but the concern now is how to handle canola that will undoubtedly come off very tough, or damp.

Try to make a plan prior to taking it off the field, as even at low temperatures the bulk will likely be quite volatile. Spoilage can occur rapidly.

These steps will help improve conditioning results and reduce risk:

  1. If possible, under-fill available bin space. The less depth to aerate, the better, because it is possible that spoilage could occur before the aeration front even reaches the peak of the bin.
  2. Keep aeration fans on. Even if the air doesn’t have capacity to dry at this point, aerate to cool and create uniform temperature conditions in the bin.
  3. Use supplemental heat, if possible. Air that is less than 10°C has very limited drying potential. Adding heat to cool air will increase its water holding capacity, and therefore capacity to dry. (See below for more points on this.)
  4. Turn the bulk frequently. Turning the bulk can break up potential hot spots that have started to form, and will also help to even out the conditions in the bin.
  5. Monitor diligently.

USE OF SUPPLEMENTAL HEAT

Adding heat to cold air will greatly increase that air’s capacity to dry, even if the relative humidity (RH) of the cool air is high. Here are some key tips for that process:

  1. Air needs to be heated to more than 10°C to have good drying potential.
  2. Only heat the air up to 15-20°C. With relatively low air-flow rates of aeration systems, it is important to only use warm air, not hot, to avoid “baking” seeds closest to the fan.
  3. Airflow of at least 0.75 cubic feet per minute per bushel is recommended for natural air drying with supplemental heat.
  4. To estimate the required heater capacity for supplemental heating, multiply the desired temperature rise in degrees Fahrenheit by the air-flow rate provided by the fan in cfm. Then multiply by 0.8. The result will be the heater capacity in btu/hr. For example, for a target temperature rise of 10°C (18°F) and an airflow of 5,000 cfm, the required heater capacity is 18 x 5,000 x 0.8 = 72,000 btu/hr.

Although it is potentially possible to stabilize a bulk if the temperature is uniformly dropped to less than 5°C, drying canola now is better than waiting. Otherwise the bin will be unstable as soon as temperatures warm up, whether next spring or sometime this fall, and will need to be dried immediately. More: Tips for drying tough and damp canola

What if you have a plan for drying, but it means holding onto the grain in the meantime? The graph below is often referenced when trying to determine the number of “safe days” producers have before spoilage begins. Be very cautious using these charts. This work was performed in small tubes, where the temperature and moisture conditions were uniform. Realistically, conditions are never totally uniform in a bin, and this is what precipitates the spoilage process.

These charts should only act as a very rough guide. Assume much fewer safe days in the “real world.”

Use these numbers with caution. They are based on test tube experiments (Burrell et al., 1980) without the variability found in most bins.

Use these numbers with caution. They are based on test tube experiments (Burrell et al., 1980) without the variability found in most bins.


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