af contributor |lethbridge
Just because it’s in the bin, doesn’t mean your canola is safe. Agronomists have seen a lot of heated canola this winter – in some cases whole bins – and more trouble may be on the way.
“It’s hard to hear of a whole bin of canola spoiling, especially at this year’s prices,” says Troy Prosofsky, Canola Council of Canada’s agronomist for southern Alberta.
“You really have to check it often, as long as it’s in your bin. If you had $75,000 worth of $100 bills, you’d check it every week. You need to check your canola just as often, pulling out a few loads and keeping them on trucks for a day or two. Make sure what you’ve sold is what you really have. If you have any spoilage, you need to talk to your buyer. Shipping heated product could be extremely costly.”
Spring is an especially risky time for canola, says Jim Bessel, the council’s senior agronomist.
“Air currents inside the bin change with the start of spring weather,” he says. “That’s when you get heating situations. As soon as you feel some strength in the sun, the sides of your bins are getting warm and it’s time to move canola. That’s the best protection. A good rule of thumb is to move about a third of the seed in a bin to break any moisture fronts that have developed at harvest time.”
Spring and summer temperatures can lead to moisture migration in the opposite direction. The sun warming the side of the bin causes air to move up near the outside of the seed bulk and down through the centre. Moisture is reabsorbed by the cooler canola in the centre of the bin. Removing grain from the centre of the bin interrupts this process, which can be significant even at eight per cent moisture.
Probing and sensors help in monitoring conditions, says Bessel, but even sensors only give you an idea of conditions at their locations in the bin. They can miss small clumps of green material or insect debris where a little hot spot can develop. Aeration could help too, but it’s not foolproof, says Bessel.
“If I was working with $12 or $13 canola, I wouldn’t depend on aeration,” he says. “Especially if it’s not as stable as it should be after last year’s harvest.”
Low temperature and moisture are key to safe canola storage. If either is too high, moulds can develop from spores spread through the seed at harvest. As mould grows, it produces moisture, causing seed clumping and further mould development.
Last year, some canola was hit by frost, so immature seeds went into the bin and may not have cured properly. When spring sun puts some heat on the side of the bin, pockets of immature seed or dockage can start hot spots.
“As you fill a bin, you do it one truckload at a time,” says Bessel. “Different bulk densities develop as each load falls a different distance. Each load makes a layer with the dockage floating to the top and sliding to the edges. Deflectors on augers may help a little, but you still get dockage – pods, insect parts, whatever – sliding out to the side of the bin. Moisture levels in dockage can be three or four per cent higher than the canola seed.”
In Bessel’s opinion, newer canola varieties with their higher oil content have thinner hulls that make them more susceptible to compaction damage. A little oil lost when a seed is squashed can provide a food source for moulds to grow and produce moisture.
Good conditioning sets up canola for long-term storage. Freshly harvested canola can have a high respiration rate, or “sweat,” for up to six weeks, producing heat and moisture that favour growth of storage moulds and leading to further heating. This cascade of events is the reason canola can spoil so fast.
“IfIwasworkingwith $12or$13canola,I wouldn’tdependon aeration.Especially ifit’snotasstableas itshouldbeafterlast year’sharvest.”