Canola growers will probably have to condition or dry their crops to ensure safe temperatures and acceptable moisture levels, says Canola Council of Canada agronomist David Vanthuyne.
He said bins should be regularly monitored for signs of mould and heat.
Producers should pay particularly close attention to bins if their samples have a high percentage of greenseed.
For safe storage, canola seed should be cooled to below 15 C and be at eight percent moisture. Aeration or turning canola can be an effective way to avoid spoiling, but Vanthuyne said producers should consider heated air drying if moisture levels are 10-12 percent. The original condition of the canola seed is probably the most important factor affecting storage.
Read Also
Stock dogs show off herding skills at Ag in Motion
Stock dogs draw a crowd at Ag in Motion. Border collies and other herding breeds are well known for the work they do on the farm.
Freshly harvested canola can maintain a high respiration rate for up to six weeks before becoming dormant. This process is often referred to as sweating and is an unstable condition for binned canola.
Rapidly respiring seed produces heat and moisture, conditions that favour mould growth in the bin.
Mould growth and respiration produce additional heat and moisture, further increasing temperatures within the seed bulk.
Eventually, the seed may become heat damaged and in severe cases it can ignite, Vanthuyne said.
The temperature of seeds harvested and binned on a hot day is retained within unaerated bins for months due to its insulating effects.
Temperature differences in the seed can result in moisture moving from warmer to colder areas of the bin.
In late fall, cold air sinks in grain at the outside edge of the bin while warm, moister air rises in the centre of the bin.
Condensation may occur when it reaches the cold seeds near the surface. This free moisture near the surface can cause spoiling.
In late spring and summer, moisture can migrate in the opposite direction if the outside temperature is warmer than the seeds. Warming action from the sun on the bin causes air to move up near the outside wall and down through the centre of the bin.
Moisture is reabsorbed by the cooler canola in the centre of the bin.
Removing a portion of the seeds from the centre of the bin by turning it can interrupt the increase in temperature and moisture in the central core.
Spoiling can happen quickly if canola temperature exceeds 10 C, which means seed moisture, temperature or both need to be reduced.
A moisture level of 8.3 percent is too high for long-term, safe storage if the seed is binned at 25 C or if pockets of immature seeds, weed seeds or frozen seed are present.
For storage longer than five months, canola should be binned at no more than eight percent moisture.
Control variables
Conditioning systems, which move air through seed to ensure safe storage, are usually separated into three types: aeration; natural-air drying and heated-air drying.
Aeration is designed to preserve seeds by cooling the bin’s contents and preventing moisture migration. It is used during seed storage, between harvesting and drying and after heated-air drying.
Due to the large amount of air required to change the temperature of the seed, aeration alone is not an effective way to alter moisture levels.
At moisture contents above 11 percent, aeration should not be used alone unless seed temperatures are near or below 0 C.
For best results, fans should be started as soon as the canola covers the perforated areas of the bin floor and should be operated continuously in the fall until either the crop temperature is reduced to 0 C or the crop is dry.
Even under humid or rainy conditions, operate the fan continuously to ensure that the main drying front in the bin will continue moving upward through the bulk despite the risk of slightly rewetting the bottom.
As long as the fan is operated for a few days after the humid period, new moisture will redistribute through the bulk and won’t cause spoiling.
Heated-air drying should be used when natural-air drying fails to adequately condition the canola.
