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Don’t cut canola too soon

Swathing at 30 per cent seed colour change is so 1980s. Recent surveys show it’s better to wait until 60 per cent — or later

Thirty was OK when canola plant populations were higher than 10 plants per square foot, and basically all the yield came from the main stem. Stands are half that now, and more yield comes from side branches.

In late 2020, the Canola Council of Canada surveyed 1,000 canola farmers from Manitoba, Saskatchewan and Alberta to check in on common practices. One notable finding is that 10 per cent of respondents still target 30 per cent seed colour change on the main stem when swathing canola. Another 26 per cent target 31-50 per cent. This is despite pretty strong evidence that yields get better with later swathing, and that 60 per cent seed colour change — or later — is a much better target.

This could be a case of old habits dying hard. The recommendation used to be 30 per cent seed colour change, and perhaps some farmers who came of age in that era are still locked in. The situation has changed considerably in the past 20 years. Thirty was OK when canola plant populations were higher than 10 plants per square foot, and basically all the yield came from the main stem. Stands are half that now, and more yield comes from side branches. You want to capture that yield? You have to cut later.

John Mayko had a front-row seat when the canola swath timing recommendation increased to 60 per cent seed colour change. The farmer from Mundare, Alberta was a Canola Council of Canada agronomy specialist from 1987 to 2010. He was there when the CCC ran a research program called Canola Production Centres (CPC), and for 2000-02, the program included swath timing trials.

CPC reports outlined the issue on swath timing: “Traditionally, the recommended stage of swathing is at 30 to 40 per cent SCC (seed colour change) on the main stem to maximize yield and quality and minimize green seed and shattering. The introduction of hybrids, with associated lower seeding rates and lower plant densities, can result in extra secondary branching. The secondary branching causes a wider range of seed development and maturation as compared to traditional seeding rates. Therefore, the normal time of swathing may need to be delayed to a later stage.”

In 2000, the trial compared yields for InVigor 2573 swathed at four stages — 30-40 per cent, 40-50 per cent, 50-60 per cent and 60-70 per cent seed colour change on the main stem. Trials were repeated at four locations across the Prairies. Trials in 2001 compared swath timing for Hyola 401 at six locations, and in 2002 compared Prairie 499 RR at six locations.

Results showed a yield benefit of eight per cent by waiting until 50-60 per cent SCC and 11 per cent by waiting until 60-70 per cent SCC. This led to an update in swathing timing recommendations for the 2003 rewrite of the Canola Growers Manual (which was subsequently updated and posted online at canolaencyclopedia.ca). The 2003 update said <Brassica napus> achieves optimum seed yield and quality when swathed at 60 to 70 per cent seed colour change.

Results confirmed

Subsequent research confirmed these results. In 2013, Indian Head Agricultural Research Foundation (IHARF) included two swath timings — 20-30 per cent SCC and 50-60 per cent SCC — in a study on straight combining canola. The variety was InVigor 5440. The study reported early swathing yield of 3,355 kg/ha (around 59 bu./ac.) and later swathing yield of 3,644 kg/ha (around 64 bu./ac.), with the gain entirely due to increased seed fill. Average seed weight for early-swathed canola was 3.14 grams per 1,000 and for late-swathed was 3.47.

This graph shows results for the two six-location years of the Canola Production Centre swath timing trials. Average results from across the Prairies show that canola yields increased eight per cent when swathed at 50-60 per cent seed colour change compared to 30-40 per cent seed colour change, and 11 per cent when swathed at 60-70 per cent instead of 30-40 per cent. Note: A seed with any degree of mottling or speckling is considered “colour changed.” It doesn’t have to be full brown or black. photo: CCC

The IHARF report concluded that “Swathing at 20-30 per cent SCC resulted in the lowest seed yield, and postponing the operation by less than a week during this critical period increased canola yields by nearly nine per cent.”

More recently, BASF has used harvest timing trials to demonstrate the benefit of its pod-shatter trait, which reduces shatter losses for canola swathed very late or straight combining. BASF compared hybrid with the pod-shatter trait and without the trait, using three treatments — swathing at 60 per cent seed colour change, which it calls “normal” swathing timing, swathing at 80 per cent, and straight combining.

“We don’t even think of cutting before 60,” says Russell Trischuk, regional technical services manager for InVigor Canola. “Even between 50 and 60 seed colour change, growers will notice a yield difference. Sixty is the sweet spot.”

Well, 60 is the sweet spot for hybrids without pod-shatter tolerance. BASF research shows that for hybrids with the pod-shatter trait, yield continues to climb if canola is swathed at 80 per cent and are highest if straight combined. That’s because the trait protects those earliest pods from shattering while waiting for all seeds to reach full size and weight.

Why do some still cut early?

As noted earlier, it could be an age thing. The CCC 2020 Canola Grower survey bears this out, showing that farmers who swath early also tend to be older. The survey found that 57 per cent of farmers 18 to 34 years of age target a seed colour change of 60 per cent or higher, while only 43 per cent of farmers 55 or older target that higher range.

This image shows what seeds at the bottom, middle and top of the main stem will look like at around 60 per cent seed colour change. Note: A seed with any degree of mottling or speckling is considered “colour changed”. It doesn’t have to be full brown or black. photo: CCC

The other factor is perceived risk. “Delaying until 60 per cent is the best under normal circumstances,” says Mayko, “but when you're faced with conditions like we had in 2018, when crop development was delayed and weather was cool, the bigger concern was to get the crop dried down before we had a killing frost.”

That was the year of heavy forest fire smoke in Alberta. “Crops wouldn’t turn for a month,” Mayko says. “Personally, I cut one field that year that was lucky to be 20 per cent changed. It was the third week of September and I had to put it down.”

Earlier swathing does mean earlier combining, although swathing a week earlier doesn’t mean you’re combining a week earlier. “That gaps narrows to perhaps three or four days,” Trischuk says.

Whatever delays may show up at harvest, the key word for a farm’s swath timing strategy is “target” — which was the word used in the survey question. The target is when the farm plans to swath. Though Mayko will swath earlier if he has to based on harvest circumstances, his target is 60 per cent SCC. When asked if the CPC research results caused him to update his approach to swath timing, he says, “Definitely.”

More on canola harvest

The Harvest Management chapter at canolaencyclopedia.ca has more detail on seed colour change and harvest timing, including straight combining. The Canola Research Hub at canolaresearch.ca has annual reports for the Canola Production Centre program, including yield results for each location.

About the author

Contributor

Jay Whetter is communications manager for the Canola Council of Canada.

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