The recommendation when it comes to choosing a canola seeding rate is to start at 5 lb./ac., and then tweak from there to achieve a plant population of 7 to 10 plants per square foot.
This plant stand allows for some plant mortality during the year to still achieve a minimum five plants per square foot at harvest. Five plants per square foot is the minimum required for a crop to reach its yield potential, based on a SaskCanola-funded meta-analysis by Steve Shirtliffe from the University of Saskatchewan,
However, achieving 7 to 10 plants per square foot can mean some high seeding rates for seed with large thousand seed weights (TSW). Therefore, going much above 6 lb./ac. is not generally recommended — regardless of TSW. The better agronomic strategy is to put effort into increasing seed survival rather than invest in a higher seeding rate.
Shirtliffe’s concluding paragraph in his full length report states:
“In summary, canola seeded at below recommended seeding rates will on average have lower seed yield. On average, canola seeded at 5 lb./ac. yielded 4% greater than canola seeded at 3 lb./ac. However reducing seeding rates can result in much greater yield losses. In years where plant emergence is below 50 per square metre (5 plants per square foot) yield losses were much higher.”
This is the basis for the current seeding rate recommendation. The paragraph continues with:
“Economic analysis reveals that in years with low yield potential and low canola selling price, the extra yield from seeding at the recommended rate was not enough to cover the additional cost of hybrid seed. …. Hybrid canola can maintain a high yield potential even when plant populations are very low. On average, the yield at 1 plant per square foot is only 30% lower than the yield at 5 plants per square foot. Canola farmers seeking to maximize returns should target populations greater than 50 plants square meter (5 per square foot).”
This suggests that some consideration for the cost of seed and selling price for canola is warranted when settling on a rate. While plant populations below 5 per square foot are not ideal, with lower canola prices and high seed costs the economic sweet spot some years may be achieved with populations slightly below this level.