Canola’s seed kernel size can vary greatly from year to year, ranging from three to 7.5 grams per 1,000 kernels. While some growers believe larger seeds have a better chance of survival and can be seeded at lighter rates, others say there isn’t enough evidence to assume that larger seeds will always have higher survivability.
Shaun Vey, Syngenta’s seed product lead for canola and cereals at Saskatoon, said “there is no definitive answer.”
Asked if growers can assume they’ll have higher survivability and lower their seeding rates when planting larger seeds, Vey said “I don’t recommend that.”
Under normal conditions, he said, “It’s inconclusive at this point and tough to give an answer.”
Bigger seeds, he said, “can, in my opinion, give some advantages under certain conditions. In a cool, wet spring, larger seeds may be more vigorous early on.”
For varieties coming in at less than four grams per 1,000 kernels, he said, “I would seed it heavier,” to compensate for a potential lower survival rate.
The Canola Council of Canada’s online growers’ manual says the research is contradictory, adding that “in some cases larger seed produced more vigorous seedlings, but this advantage wasn’t carried through to seed yield.”
This year, Vey said, Syngenta’s two canola varieties weight between 4.7 and five grams per 1,000 kernels. “We feel that’s a pretty good size. Kind of a sweet spot.”
Wilt Billing, an agronomist with DuPont Pioneer at Morden, Man., said the average Pioneer canola seed 1,000-kernel weight this year is “just below four to 5.5 or 5.75.”
When asked if growers should expect better survivability from larger seeds, he said “there are a bunch of factors to consider.”
Researchers are re-evaluating previous studies, he said, and he’s looking forward to having better information in the future. For now, he added, “the environment will influence survivability more than your seed size.”
Under optimal conditions, Billings said, different-sized seed should yield the same in the end.
For growers calculating seeding rates with 1,000-kernel weights, seed size can have a big impact on costs.
A 50-pound bag of seed weighing four grams per 1,000 kernels holds 5.6 million seeds. Growers targeting eight plants per square foot and expecting 50 per cent survivability need to seed 4.6 pounds per acre. One 50-lb. bag will cover a little over eight acres.
Assuming growers with larger seed want the same number of plants per foot and still expect 50 per cent seed survival, seeding rates will need to be heavier. Using the same formula, seed weighing 7.5 grams per 1,000 kernels should be seeded at 11.5 pounds per acre. At this rate, one 50-lb. bag only holds enough seed for 4.3 acres.
To calculate canola seeding rates, multiply 9.6 by the number of desired plants per square foot by the 1,000-kernel weight (in grams). Then, divide that amount by the estimated seed survival rate (for example, use “50” for an expected 50 per cent survival rate).
With this year’s cool spring, farmers with bags of large-sized seed may prove to have an advantage. However, growers with smaller-size seed are also winners. Vey points out, “You’re getting more seeds in the bag.”
— Leeann Minogue is the editor of Grainews at Griffin, Sask.