All canola should be conditioned immediately after combining to cool it down, even out the temperature throughout the bin and remove any moisture released through natural seed respiration that occurs in the first hours to weeks after harvest.
In some cases, canola will need some extra care to make it safe for long-term storage. A Canola Watch Twitter poll in mid-September asked farmers, “Which risk are you most concerned about for your binned (or soon to be binned) canola?” Some 45% of respondents chose “Nothing major so far,” which is good, but 38% said moisture, 10% said green seed and 7% said dockage.
This article describes each of these risks.
Moisture. The ideal moisture is eight per cent, but growers should consider moisture and temperature together. For example, eight per cent moisture is still too high if the grain temperature is 25°C or more, and 10% is probably low enough if the grain temperature is cooled to 5°C degrees or less.
Moisture creates a more hospitable environment for moulds that trigger heating. Clumping is a sign of mould growth. This can occur fairly quickly. Lab-based research found that canola seeds at 25°C and 10.6% moisture clumped together after 11 days and visible mould colonies appeared after 21 days. With variable conditions in most bins, clumping may occur more quickly in an on-farm situation.
Green canola. Green canola seeds can increase the storage risk, even if canola is dry and cool. Monitor closely. Small shriveled canola seed, which often comes with high green seed, can mean smaller air pockets between seeds in the bin. Smaller particles will increase the resistance to air flow. This makes it even more important to leave the fan on as it will need to work longer to cool the entire bulk.
Dockage – weed seeds. Weed seeds tend to contain more moisture than canola seeds, especially if they are green or immature. These high-moisture seeds may not be enough to elevate overall grain moisture tests, but if they congregate in pockets in the bin they can create a localized hot spot for spoilage to begin. Bits of green plant material in the sample similarly increase the risk.
Dockage – chaff. Without a spreader in the bin, chaff tends to concentrate closer to the walls of the bin and fines closer to the centre of the bin. This distribution exaggerates airflow problems, with more air taking the path of least resistance up along the walls of the bin and less pushing through the central core. Chaff can also have higher moisture than seed, adding to the risk. That is why concentrated areas of chaff could be a start point for spoilage, even in a bin where the seeds test dry.
Dockage – insects. In some years, the canola harvest sample can include a lot of grasshoppers, crickets, cabbage seedpod weevils and even flea beetles. Vincent Hervet, stored product entomologist with Agriculture and Agri-Food Canada, says insect species that come from the field are not a problem with regard to feeding on canola in the bin. However, he says that if the grain has a lot of dead insects coming from the field, the grain should be conditioned (even dried, if necessary) to prevent the development of mould.
Hervet adds that canola is not a hospitable environment for most storage insects. Often insects found in canola storage are those that were in the bin prior to loading from previous cereals or other decaying material, but they generally are unable to survive in a canola bin. If bins are treated this fall with malathion to remove any previously existing storage insects, note that those bins cannot be used for canola.
Hot canola. Canola binned hot, even if it has low moisture, low dockage and low green, should be put on aeration to cool it down. This will even out the temperature throughout the bin, and help remove some of the moisture from respiring seed. Even at low moisture, air movements within the bin could concentrate this moisture. Try to get canola down to below 15°C at harvest time, then turn that fans on again in the early winter to bring it down even lower. Don’t be afraid to freeze a bulk during periods of cold winter weather.