Researchers found no difference in emergence, yield or quality between the sizes of 3.96 and 5.7 grams per 1,000 seeds
Agriculture Canada researchers have found that canola seed size many not affect emergence and yield above a certain threshold.
They conducted trials at nine prairie sites in 2013 evaluated the performance of canola seed ranging from 3.96 to 5.7 grams per 1,000 seeds.
The scientists found no significant difference in canola emergence, yield or seed quality.
“It is noteworthy that seed size did not influence canola emergence. One might assume enhanced recruitment with larger seed given greater resources to reach and penetrate the soil surface.
“However, the lack of a seed size effect on canola emergence is consistent with other studies,” the authors wrote in the paper, which was published in the Canadian Journal of Plant Science this winter.
“It is possible that there is a threshold canola seed size that optimizes canola emergence and yield…. If such a threshold exists, canola emergence and yield benefits from seeds with weights (sizes) above the threshold would be unlikely.”
Neil Harker, an Agriculture Canada research scientist in Lacombe, Alta., and lead author of the study, said larger seeds do provide an advantage but only when compared to tiny canola seeds.
“When you had really small seeds, around three grams per 1,000 (seeds) and that size, then you might get some emergence differences that others have talked about in the past,” he said.
“In recent times (with relatively larger seed size), emergence (has) already reached a stage where it’s not going to change (improve).”
The scientists evaluated four canola seed sizes — 3.96, 4.6, 4.8 and 5.7 grams per 1,000 seeds — at two sites in Saskatoon, Scott, Sask., Melfort, Sask., Lacombe, Fahler, Alta, Beaverlodge, Alta., Carman, Man., and Brandon.
The researchers detected no correlation between larger seed size and increased yield, with the exception of Scott.
“Given these data, we reject our hypothesis that canola seed size would influence yield,” they wrote in the paper.
Harker and his colleagues didn’t provide a threshold seed size where emergence and yield benefits plateau for canola, but they did find other benefits from larger canola seeds, such as more biomass at the six-leaf stage.
“Which suggests the plants might be growing a little faster with the larger seed,” Harker said.
“It looks like days to flowering happens more quickly with the larger seed, and it finishes flowering more quickly. Both of which are positive because … the longer flower happens the more risk you have of high temperatures.”
The difference in days to flowering was relatively small:
The 3.96 grams per 1,000 kernel seed took slightly less than 63 days to reach flowering.
The 5.7 grams per 1,000 kernel seed took less than 62 days to reach the flowering stage.
“But every day that canola growers can avoid high temperatures during the flowering period is important,” the authors said.
Harker said the larger canola seeds do have disadvantages.
For example, growers who plant seeds that weigh 5.7 grams per 1,000 seeds might not put a sufficient number of seeds in the ground.
“We’ve had this old (rule) of five pounds per acre forever,” he said.
“As the seed gets larger and larger, it’s pretty hard to get the right plant population if the seed size is increasing and you’re putting on the same weight of seed.”
For example, if one grower receives seed that is six grams per 1,000 kernels and a second farmer has canola seeds weighing four grams per 1,000 kernels, the second grower will have 50 percent more seeds.
Murray Hartman, an Alberta Agriculture oilseed specialist, said canola hybrids typically range from four to five grams per 1,000 kernels, but weights higher than six grams are possible.
“It often comes on the bag, but when you’re ordering the seed, you don’t know what the 1,000 kernel weight is till you get it,” he said.
Harker and his fellow researchers said farmers who plant larger canola seed should increase seeding rates to ensure that a sufficient number of seeds get in the ground.
“As seed costs increase, growers are pressured to reduce seeding rates,” they said.
“A failure to consider seed numbers for a given weight of seed may threaten canola yield potential.”
The Agriculture Canada researchers also studied the relationship between seeding rates and canola yield by looking at two rates: 75 seeds per sq. metre and 150 seeds per sq. metre.
They found that the higher seeding rate didn’t increase canola yield.
“There is some (research) that suggests (higher yields with higher rates),” Harker said.
“(But) the seeding rate doesn’t give you a yield advantage unless you’re comparing too low to normal.”
Harker said ideal growing conditions in 2013 might have skewed the seeding rate results because germination rates were unusually high.
“We happened to do this experiment in 2013 … where we had plenty of moisture all the way across the Prairies,” he said.
“If you want to say what the No. 1 determinant of getting seeds out of the ground, it’s moisture, and No. 2 is moisture and No. 3 is moisture.”