As little as 2% green seed in a canola sample can cause the loss of a No. 1 grade in Canada, traditionally equating to roughly $10-15/tonne.
Immature canola seed naturally contains chlorophyll, a green pigment essential for photosynthesis. As canola seeds mature, enzymes remove the chlorophyll, a process thought to improve seed longevity. The enzymes responsible, however, are relatively picky, agreeing only to work when temperatures are above 5ºC and at seed moisture contents above 20 per cent. If this environment is altered, the enzymes might take some time off, or may quit entirely.
In the case of frost, enzymes may be denatured or destroyed and the chlorophyll will remain in the seeds, regardless of moisture and temperature conditions. Though extreme wind or heat during harvest may result in the same levels of green seed, it is not because the enzymes have been destroyed, but because the plant has dried too quickly. In the latter case, it’s possible to see levels of green seed decreasing, in the event of supportive environmental conditions.
As we reach the middle of October, it’s likely most high-green canola has already been harvested. For those still waiting with swaths in-field, Shawn Senko, agronomy specialist with the Canola Council of Canada suggests it may be time to take it off, particularly in the case of frost where any change in green seed levels is rare.
In the following Canola School, Senko expands on why green seed poses such a risk to grade, some of the factors that exacerbate its presence and how to deal with high-green canola once it’s in the bin.