Sowing larger canola seed can lead to better crop establishment, increased seedling vigour and early plant growth. These benefits have been demonstrated in replicated trials and observed in farmer demonstrations, often leading to increased crop yield.
The size of canola seed varies with variety and in response to management and seasonal conditions. It would be ideal to only sow canola seed that is greater than 2mm in diameter, but given the seasonal variation, it may not be practical to grade to the same size each year.
Anecdotal reports regarding 2014 retained seed, suggest that the following seed yields were achieved when grading canola seed.
The cost to clean and treat seed is approximately $2.50 to $3.00/kg. Sizing seed can incur an additional cost of $0.50 to $1.00/kg. This seems like a minimal cost given the likely benefits.
Taking into account the variation in seed size from year to year, plus the logistical difficulties of grading out 2mm or larger seed, it is difficult to develop a rule of thumb for canola seed size. Rather, growers should be aware that there are benefits from sowing larger seed and that the time and effort required to size canola seed to the largest practical diameter is likely to be rewarded.