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Straight cutting canola

To swath or not to swath? That’s the question more and more farmers are asking every year as straight cut canola becomes more common across the Prairies. For Kevin Bender, who farms in the Sylvan Lake/Bentley area of central Alberta, the question was answered a long time ago. He started straight combining Polish canola back in the early 1990s but swathed his Argentine canola until 2003.

“In 2003 about one-half of our canola acres became too ripe. One of the fields was really ripe and we didn’t want to swath it, so we went ahead and straight cut it. We had no choice,” says Bender. “It worked so well that it was the last year we swathed canola on our farm.”

Over the years, Bender has seen several risks and rewards of straight cutting.  On the benefits side, he believes he achieves slightly better yield with reduced harvest losses, bigger seed, one less piece of equipment and one less field pass.  On the downside, he’s seen challenges with green material plugging combines, uneven uniformity causing timing problems, and green weeds and plant material in the sample causing heating concerns in storage.

Those risks and rewards are typical of straight cut canola, says Angela Brackenreed, agronomy specialist with the Canola Council of Canada at Minnedosa, Man. However, she says that growers looking for higher yield and better quality should temper those expectations.

“I caution that yield and quality are not the main reasons to move to straight cutting. The biggest benefit is that it helps manage the narrow window that is present for swathing,” explains Brackenreed. “When canola is swathed at 60 to 70 per cent seed colour change, yield and quality is usually pretty similar to straight cut canola. The difficulty is that many producers have to start swathing earlier in order to get all their canola swathed before it gets too ripe, and that can reduce yield and quality.”

Chris Holzapfel, research manager at the Indian Head Agricultural Research Foundation, has conducted several research projects on straight cut canola over the past 10 years. He says in addition to time management issues, swathing also has other risks. Many farmers will remember the fall of 2012 when high winds devastated swathed canola with losses greater than 50 per cent in some cases.  The risks of environmental and header losses increase with the time the canola remains in the swath.  

Yield and quality are similar
Holzapfel cites several research studies that show yield is similar.  A University of Saskatchewan project on commercial farms found that total seed losses (environmental + header + threshing) for swathed and straight-combined canola were equal and approximately 10 per cent on average (Haile et al. 2014. Can. J. Plant Sci. 94:785-789).

An AgriARM project at Indian Head, Melfort and Swift Current, Sask., in 2009 and 2010, found no significant difference between swathing at 60 to 70 per cent seed colour change and straight combining. However, there were some year-to-year and site-to-site variations with swathing sometimes better and straight combining sometimes better.  

Average seed size is frequently larger with straight cut canola. An Indian Head ADOPT canola harvest demonstration found that thousand kernel weight was significantly larger for straight cut canola compared to canola swathed at 15 to 20 per cent seed colour change or 40 to 50 per cent seed colour change. An eight site-year AgriARM project found similar increases in seed size with straight cut canola (approximately five per cent) when averaged across sites. When higher yields are observed with straight-combing relative to swathing, this is primarily a result of larger seeds but is also a function of the time of swathing.

“This is consistent with other research, and because many farmers have to start swathing before the recommended 60 to 70 per cent seed colour change, this can be a real benefit. It’s not hype,” says Brackenreed.

Lower green seed count has also been promoted as a benefit of straight cut canola. Brackenreed says the research has found that the relationship of green seed to harvest method is inconsistent and is most heavily influenced by relative timing of harvest, crop uniformity, weather leading up to harvest, and frost.  

“You can’t count on straight cutting to lower green seed. It is mostly related to how long the seed is left to mature prior to harvest,” says Brackenreed.

Which fields are suitable?
Brackenreed’s experience of straight cut canola is that the decision to straight cut should be assessed just before swath timing. A field that is a good candidate for straight cutting would have a thick, heavy stand that is slightly lodged, uniformly mature, well knit together, and with little disease or insect damage to the pods. These conditions help the crop resist wind damage that could cause pod shatter or pod drop. Straight cut might also be the best option for short, severely lodged or excessively branched canola that would be hard to swath and have little stubble to anchor the swath.

“I used to say you couldn’t decide which field you would straight cut at seeding, but this may be changing with the new shatter resistant varieties,” Brackenreed says.  

Potentially bad options are fields with really high plant counts with little branching to knit the crop together, highly variable maturity, and a late crop with a risk of frost.

Varieties, pod sealants and glyphosate
Holzapfel has looked at variety suitability for straight cutting, pod sealants and interactions with glyphosate. In 2011, researchers initiated a four-year multiple location study at Indian Head, Scott, Swift Current and Melfort to provide a broader understanding of the frequency and magnitude of environmental seed losses that can occur under field conditions when B. napus hybrids are left to mature while standing. Over the four-year period, a total of 15 canola hybrids were evaluated, with updated canola hybrids added during the project.

Overall, the study showed that environmental conditions had a large effect on the magnitude of yield losses and were generally of greater importance than hybrid differences within any given site. When harvest was completed early, environmental yield losses were below five per cent at 93 per cent of the 13 sites. Losses generally increased when harvest was delayed by three to four weeks; however, total losses were still less than or equal to five per cent (averaged across hybrids) at 53 per cent of the sites and 10 per cent or lower at 77 per cent of the 13 site-years.

Holzapfel says the results suggest that environmental yield losses with straight-combined canola are unlikely to exceed 10 per cent, even with minor delays in harvest. Those losses are consistent with the University of Saskatchewan study cited earlier.

“Environment is important. The differences between varieties weren’t consistent,” Holzapfel says. He says newer shatter-tolerant hybrids such as L140P showed excellent potential for further reducing the risks of yield loss with straight combining. However, factors such as overall yield potential, maturity and herbicide system continue to be important when choosing a canola hybrid, regardless of harvest method.

Bender hasn’t tried pod sealants or shatter-resistant varieties. On one occasion, shatter losses were high in his standing canola. About 10 years ago he had one field that was dead ripe, standing straight up and more prone to shattering that other varieties. The field was hit with 100 kilometres-per-hour winds.  

“We probably lost 20 to 30 per cent of the crop, but there was also a lot of damage to swathed canola, too,” Bender says.

Holzapfel looked at glyphosate and pod sealants to see if harvest losses could be reduced in a two-year study at Indian Head. Field trials were conducted in 2010 and 2011 near Indian Head on large field plots, each approximately two acres in size. Commercial equipment was used for all field operations. A canola cultivar that was relatively prone to shattering was purposely chosen for this study to assist researchers in detecting any potential benefits of the pod sealant or other foliar treatments. The treatments included two harvest methods (swathed or straight-combined) and four pre-harvest treatments (untreated, pod sealant, glyphosate or pod sealant plus glyphosate).

Consistent with the findings of the small plot studies, pod sealants did not provide a yield benefit over untreated canola regardless of harvest treatment, but a slight benefit was observed in the visual shattering ratings of the straight-combined canola.

The research also showed that the effect of glyphosate was not consistent from one year to the next, with lower yields observed in 2010 and a tendency for higher yields with glyphosate in 2011. These differences were most evident in the straight-combined treatments as all swathed treatments tended to have similar yields regardless of the foliar treatment.

Holzapfel says even though he did not necessarily expect a yield benefit with pre-harvest glyphosate for straight-combined canola, glyphosate can accelerate and even out maturity while also providing weed control benefits for the following crop. This would only be the case in conventional and Liberty Link canola.

Brackenreed agrees that glyphosate can help manage harvest in non-Roundup Ready crops, but isn’t absolutely necessary. Timing would be at around 40 per cent or more seed colour change.  

Desiccation with Reglone or Heat can also be used to help manage harvest by drying down green straw and weeds. Unlike glyphosate, which translocates and allows the crop to mature, a desiccant shuts the crop down and stops it from maturing. Brackenreed says Reglone timing is 80 to 90 per cent seed colour change, and Heat timing is 60 to 75 per cent seed colour change.

“Timing is critical with Reglone and Heat although Heat acts slightly differently. They are contact herbicides and quickly dry out the crop, so the seeds should be relatively mature,” Brackenreed says.

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Header selection
Over the years, Bender has tried several styles of straight cut headers. He’s used 20- and 25-foot John Deere rigid draper headers, 25-foot Honey Bee and John Deere draper headers, a 30-foot Mac Don draper header, and 35- and 40-foot flex draper headers.  

“I would say they all worked reasonably well, some better under certain conditions,” says Bender.

Earlier research by the Wheatland Conservation Area AgriARM site found that the BISO header was superior to the rigid and draper headers in the evaluation. That research found that the BISO with an extended knife had 10 per cent higher yield.  

More recently, a three-year research project was initiated by PAMI in 2014 at Swift Current, Indian Head and Humboldt. It includes L140 “shatter resistant” and L130 “standard” hybrids and added in 74-44 and 75-65 hybrids in 2015. A New Holland 35 foot Varifeed header with a knife that extends forward 23 inches, the 35-foot Varifeed with knife retracted, and a Honey Bee 35-foot draper header were compared to a swath and pickup header.  

“Looking at the preliminary results, overall there were very small differences in losses with maybe a trend to slightly lower losses with the extended knife. However, the overall losses were low, in the 1.5- to 2.5-bushel-per-acre range,” says Brackenreed. “The combine operators felt in the first two years of the study that the Varifeed was the most comfortable and forgiving header to operate.”

Bender typically harvests wheat and barley first, and then moves into canola.  He cautions that growers considering straight cut canola should be set up for aeration and be ready to monitor bins. Bender typically harvests a bit on the tough side, and green weed seed and green chaff can create hot spots.  

His final advice is that you need to be flexible and prepare for the unexpected. “If you’re high stress and have low patience, then I don’t think straight cut canola is for you.”


September 7, 2016
By Bruce Barker

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