Alberta research suggests canola producers could benefit by increasing their seeding rates above what has typically been recommended.
Trials carried out during the past three years at Agriculture Canada’s Lacombe, Lethbridge and Beaver Lodge research centres have found advantages in increasing seeding rates of both spring and fall seeded canola by about 25 percent.
“We’re starting to see that it’s going to pay off in most respects,” said Neil Harker, a weed scientist at the Lacombe Research Centre.
Denser stands of canola can reduce the reliance on herbicides, he added.
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However, he is not advocating higher-seeding densities to reduce herbicide use. Instead, he sees higher densities as something that can be used in tandem with herbicides for more effective weed control.
“We think it’s the best form of true biological control,” he said, referring to the advantage canola crops gain over weeds by being planted in higher densities.
The recommendation applies to hybrid and open pollinated varieties.
“Hybrids are more expensive, but we still think it’s worthwhile.”
He said increased lodging was not a problem when seeding rates were increased by 25 percent. However, he cautioned against going overboard, such as doubling the rates.
“If you get carried away you can run into lodging problems, so it is a balance.”
Harker said there are also advantages for crop quality.
Dense canola stands compete for moisture, nutrients and sunlight. Harker and colleagues found that competition led to the crop maturing earlier and more uniformly, which typically meant better quality seed.
Previous research has found that a canola field with only 20 plants per sq. metre can still give acceptable yields. That’s because the plants bush out more and may pod closer to the ground.
That may suggest to producers that they can get away with seeding at lower rates, but Harker offered a word of caution.
“I agree that can be done, but it requires a heavier reliance on herbicides to make that work.”
That’s because a thinner stand of canola offers less competition against weeds, especially earlier in the growing season.
Harker worked with agronomist George Clayton, weed scientist Robert Blackshaw, and cropping systems agronomist John O’Donovan.
John Mayko, a senior agronomist with the Canola Council of Canada, said there are pros and cons to increasing seeding density.
He agreed a higher seeding density can improve weed competition, although that may not be as great a consideration for growers with herbicide tolerant canolas.
And higher seeding densities can offer the advantage of hastening the crop’s maturity by a couple of days, depending on the variety and the crop density.
Density might also influence root maggot pressure.
Root maggots prefer canola plants with thick stems and the stems tend to be thinner in denser stands, he said. There is also what Mayko called the dilution factor. Because there are more stems in a denser stand of canola, the root maggot population gets spread out over more plants.
As for the downsides, Mayko believes lodging would be a problem because of the thinner stems, despite what was seen during the trials in Alberta.
There could also be a higher risk of disease due to the dense canopy, which would reduce air movement and sun penetration, he said.
As well, he said going to a higher seeding rate could backfire in drier areas where plants have to compete more heavily for moisture.
“The plants stifle each other and you get lower yields.”
In terms of the economics, Mayko suspects it would be a “tough sled” convincing canola growers using hybrid seed to increase seeding rates, due to the higher cost of the seed.
