By Brian Hall, OMAF/MRA, Stratford
Many 2014 canola crops had a markedly varied emergence. Variable soil moisture conditions, lack of rain, uneven seeding depth and/or deep seeding were all were major factors in when canola emerged this year. For growers this could mean maturity variations and challenges at harvest.
When managing these fields, harvest management either by swathing or direct harvest becomes critical to achieve the highest yield and minimize green seed. As canola nears maturity it ripens very quickly and being ready to harvest will reduce the risk of loss due to pod shatter. Pod shatter from windy conditions or heavy rains can cause significant yield loss.
Key Points for Harvest
- A heavy crop canopy that is well knit together is the best candidate field for direct harvest.
- Thin canopy canola crops will be more prone to shatter loss from wind, so timely harvest will be critical.
- Swathing allows earlier harvest (8 to 10 days) and more uniform seed maturity, which is more important where maturity is uneven.
- Be patient when swathing – the optimum stage to swath is up to 60% seed colour change (SCC). Research shows 8 to 10% yield advantage to swathing at 50-60% SCC versus 30 to 40% SCC.
- Uneven crop – determine where the bulk of yield will come from and make the decision based on those plants.
- Thin stands branch more profusely and more yield will come from secondary branches. Base harvest timing on whole plant and not just main stem.
- Avoid swathing on hot days (30º C+) by swathing in evening. Hot weather can cause excessive seed shrinkage, increased shatter and lack of curing from premature dry down. Rapid dry down due to hot dry weather does not give enough time for degreening enzymes to work, resulting in locking the green colour in the seed.
- Desiccants (for example: Reglone) provide rapid dry down and glyphosate provides perennial weed control, but neither will speed maturity.
- Green seed is the most common downgrade factor. Use crush strip before combining to determine green/brown seed. Canada grade number 1 canola allows 2.0% distinctly green seed.
- Assess combine harvest loss using a drop pan. In direct harvest canola a loss of 2 seeds/ft2 behind the combine equates to loss of 1 lb/ac. A loss of 50 to 100 lb/ac is considered ‘normal’.
- Once mature, seed moisture loss can quickly change by 1 to 3% per day. Seed colour change advances by 10% on average every 2 to 3 days.
- If swathing, begin checking fields about 10 to 14 days after flowering ends.
Canola pods mature from the bottom upwards and from the middle outwards. If plant population is good and the canola canopy is well knit together (often on a slight lean) then maturity for swathing or pre-harvest timing can be based on seed colour change on main stem. Check individual plants in a number of areas of the field to evaluate maturity and estimate which growth stage represents the greatest majority of the yield.
Thin Stands (easy to walk through)
Thin stands where plants are not knit together and move easily in the wind will be highly prone to shattering loss as the crop dries down. In thin stands it is not advisable to judge maturity on only the main stem, because of the added branching resulting in more pods lower in the canopy. In thin stands, more yield comes from side branches so it will be important to assess pod colour change of the whole plant and not just on the main stem in deciding when to swath or time any desiccant application. When swathing, any seed that is translucent to light green will likely shrivel and be lost at harvest. A thin crop can result in more header losses, because there may not be the crop volume to feed into the combine. If someone else is combining your canola, discuss with them the best option for harvesting – swathing or direct harvest.
Swede Midge Damaged Canola
Canola stands damaged by swede midge will be the biggest challenge to time for harvest because of tremendous variability in stage of plants. These stands will also have a very thin canopy, so shattering could become an issue if harvest is delayed. Swathing may be the best option for some stands to allow time for immature plants to ripen while in the swath. Using a pre-harvest herbicide and direct harvest may not be the best option. Pre-harvest desiccants speed the dry down of canola plants and weeds, but will not advance maturity. Applying these products too soon can reduce both yield and quality.
The Canola Council of Canada has an excellent video to assess time of swathing. To access their swathing and harvest information go to: www.canolawatch.org and look for Tips to Time Swathing, which includes the link for swathing guide and video on assessing swathing timing.