Canola Harvest Timing - Frequently Asked Questions

 
 
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 What is the optimal stage for swathing canola?
Canola should be swathed when the average seed moisture content is 30-35% which corresponds to 30-60% of seeds will have some color change. Swathing decisions should be based on observations of seed color change on the plant’s main stem. At the optimal time for swathing, seed in the middle third of the main stem will have at least some color change, the most mature seed in the bottom third of the stem will have complete color change, and the seed in top pods will be green but firm and not squish when rolled between fingers. Keep in mind that pod color change may be a poor indicator of maturity so it is essential to check for seed color change throughout the field to best estimate harvest staging.

If swathing starts at this optimal stage, won’t the canola be shattering before everything is cut down?
Producers who have a lot of canola acres that are all maturing about the same time will have to balance swathing a little early, and possibly having some shrinkage losses, with late swathing and having shattering losses. In these situations it is probably best to start swathing when seed in the bottom third of plants is just starting to show color change. By starting a little early, hopefully the last fields to be swathed will not have shattering or any losses can be minimized by swathing when the crop is damp.

How much yield is lost by swathing early?
Research indicates that canola swathed with 0-10% seed color change yields about 90% of crops swathed at the optimal stage. Swathing when at least 10% of the seeds have some color change is the earliest that canola can be swathed without significant yield loses.

Is there a problem with swathing in hot weather?
The enzymes that clear the chlorophyll from seed stop functioning at moisture contents of 20% or less. If canola is swathed during hot, windy weather that rapidly dries the immature seed to less than 20% moisture, the green color will not clear. Rainfall and rewetting in the swath may reactivate these enzymes but this cannot be counted on or results may be inconsistent. In hot weather the optimal time to swath may be at 50 – 60% seed color change on the whole plant to minimize the risk of fixing green seed.

With a risk of frost isn’t it best to have canola in the swath?
If green seed is frozen, the green color is fixed since frost permanently deactivates the enzymes that are responsible for clearing chlorophyll from seed. Canola at 30-35% moisture needs to be in the swath for several days of good drying prior to frost to reduce the risk of having green seed. Seed with less color change at swathing will need even more time in the swath to escape frost damage.

Even though swathing prior to frost doesn’t eliminate the potential for damage, in some cases it may reduce the amount of green seed that is fixed. A windrow of canola has insulative properties and can retain some of the radiant energy released from the ground. In mild frost situations, canola on the outside of the windrow may be exposed to lethal frost that fixes green seed, but within the swath the temperature remains at safe levels. In this scenario the harvested canola will still have some greens, but the overall green seed content will be lower than if all the canola had been exposed to lethal temperatures.

For Additional Information
Canola Council Time of Swathing
Canola Harvest Management

Prepared by Ag-Info Centre, Alberta Agriculture and Rural Development

 
 
 
 
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For more information about the content of this document, contact the Ag-Info Centre.
This information published to the web on February 12, 2004.
Last Reviewed/Revised on April 23, 2015.