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Deciding when to swath canola

Agronomist Doug Moisey says if you really want to know whether or not your canola crop is ready, you’ll have to get out of your truck

To gauge harvest readiness of canola crops, farmers need to get into the field and pop open seed pods, according to an agronomist.

“Seed colour change is the only true measure of maturity. Pod colour, plant colour (aren’t reliable). There are varieties out there that will turn a lighter shade of green, get to almost a yellowish appearance, and the seed inside can be green,” says Doug Moisey, senior agronomist with the Canola Council of Canada. He adds that other varieties will have stems and pods that will be green even when they’ve reached 50 per cent seed colour change.

Farmers can start checking for seed colour change 10 to 15 days after the crop flowers. Under normal conditions, the seed colour changes about 10 per cent every three days, so Moisey recommends checking crops regularly. Farmers can scout for late-season insects like bertha armyworms, lygus bugs and diamondback moths while checking seed colour.

Moisey says farmers can start swathing as late as 60 per cent seed colour change, and warns against swathing too early. “At the end of the day, you may have to start on the early side, but when we’re talking early, it may be at 30 to 40 per cent seed colour change. But a lot of guys with a lot of acres sometimes will start at 10 or 20. And that can become a concern… Our research showed us that if we went in that earlier side, below 20 per cent seed colour change, we typically lost yield and had quality issues. What can happen, if you’ve got hot, dry conditions happening, you can typically lock in some green seed.”

Checking your field

Moisey suggests hopping on a quad and choosing 10 to 20 sites within the field, depending on the topography. Farmers should figure out where the yield is, and concentrate on those areas. “Is it the lowlands, is it the side slope, or is it the top of hills, depending on what your weather and moisture’s been like. As well, concentrate in the sample areas on what stage the majority of plants are at and what is the contribution to yield.”

If topography isn’t an issue, Moisey likes to stand in the back of a truck box and scan the crop for straw coloured shading. Though shading isn’t a reliable sign of maturity, Moisey pulls plants from different shaded areas. Sunlight can affect shading, so Moisey will look at a field from the east and west. Farmers can also set up a diagonal quad line across the field, picking out sites close to the line.

Colour indicators

Farmers should check eight to 10 plants from each location in the field, making sure they are picking plants representative of the surrounding area. Because the main stem is the first part to mature, Moisey starts with the middle pod on the main stem. He looks for black dots or mottling on the seeds. He then looks at pods further down the main stem. If there’s colour from the middle of the main stem down, Moisey estimates the plant is at 40 to 50 per cent seed colour change.

Banding around the middle of the seed is a precursor to seed colour change, and is often visible in early or mid-August. Though banded seeds aren’t mature, colour change isn’t far off.

After checking the main stem, Moisey pulls pods from the side branches and rolls the seeds between the thumb and finger. The seeds don’t need to be changing colour, but if they are firm, the area is likely ready to swath. If the seeds are watery or mushy, the plant isn’t ready.

Thinner plant stands lead to more branching, which will affect how to gauge maturity. “And so the 60 per cent seed colour change on the main stem can be an indicator but you have to determine also where your yield’s at. Is it on the main stem or is it on the side branches? And that’s how you form your plan of attack,” says Moisey.

Moisey stresses that farmers can’t rely on seeding date or pod colour change when deciding when to swath.

“The whole bottom line is, you have to get out of your truck,” Moisey says.

The Canola Council has more information on harvesting, including a video on assessing seed colour change, at http://www.canolawatch.org/tag/harvest/. †

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.

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