Many canola growers will face crops at two or more stages of development when it comes time to swath this year.
The most profitable approach is to hold off swathing until sufficient average seed colour change has taken place, said David Vanthuyne, an agronomy specialist with the Canola Council of Canada at Watrous, Sask. But just what is average anyway?
In some fields it may make the most sense to identify representative zones and assess at least five plants per zone for seed colour change. Depending on the distribution of the zones, you may be able to swath them separately in order to capture the most yield and quality, Vanthuyne said in a council release Monday.
In other cases, plant maturity may vary by as much as two to three weeks due to uneven plant establishment and/or delayed maturity as a result of hail. In these situations, focus on the plant stage that represents the bulk of the crop’s yield potential in order to maximize seed yield and quality, he recommends.
The council’s current recommendation to maximize yield and profitability is swathing at up to 60 per cent seed colour change.
“With variable staging in fields this year, it’s more important than ever to look at average seed colour change across the field,” Vanthuyne said. “Staging will be critical because in some fields half the plants may be at 60-70 per cent seed colour change while others may only be at 10-20 per cent.
“The trick will be to capture yield and quality by delaying swathing and allowing as much seed colour change as possible on less mature plants, while still avoiding shattering losses.”
Growers with large acreages may need to start swathing their earliest maturing fields prior to 40 per cent seed colour change to maintain an average seed colour change of 40-60 per cent for the bulk of the crop, he added.
Seeds are sufficiently changed in colour when they have at least small patches of colour or spotting. The main stem will advance about 10 per cent every two to three days under normal conditions. After assessing the main stem, look at seeds from the side branches to ensure they are firm with no translucency, especially in areas with low plant populations where the plants have numerous branches, Vanthuyne said.
Under normal growing conditions, sampling the field every two to three days and averaging the per cent of seed colour change will give an accurate assessment of overall maturity. Plant densities, soil type, topography, variety choice and weather will affect the rate of seed maturation. And don’t be fooled by the change in pod colour, it’s the seed colour that counts, he added.
Swathing late in the day and during the night will reduce shattering and minimize green seed issues by slowing the initial dry down of the swaths.