Windrow and direct-harvest canola losses similar

Swathed and direct-harvested canola suffered the same harvest seed losses, at 10.2% of total seed yield, and canola losses added to the seedbank averaged 830 viable seeds/ft2 (8300 viable seeds/m2).

Before the development of shatter-resistant Brassica napus canola, seed shatter was a concern for canola growers who were experimenting with direct-harvesting canola. This field trial was conducted from 2010 to 2012, and the results highlight that direct-harvested canola is a viable option, perhaps even more so with today’s shatter-resistant canola.

The objective of this study was to compare canola seed loss and seedbank addition from windrowed and direct-harvested operations on commercial farms in western Canada. It was conducted on 16 direct-harvested and 19 windrowed canola fields in central and southern Saskatchewan from 2010 to 2012, which were managed by 6 different canola growers.

A questionnaire captured data from each field including seed yield, canola variety grown, area sampled and year of last canola crop. Fields were selected that had at least a 2 year break from canola to reduce the chance of collecting canola seed from previous years’ seedbank.

Canola loss was estimated by collecting remaining crop residue and shattered seeds with an industrial vacuum cleaner within 3 weeks after harvest. Samples were collected from 3 random transects in each field.

Six to 7 quadrants 2.7 ft2 (0.25 m2) in size were sampled along transects at 40 inch (1 m) intervals. In windrowed fields, the transects ran from the center the area where one windrow had laid to the center the area where the adjacent windrow had laid before combining. In the direct-harvested fields, transects ran from the center of one combine pass to the center of the adjacent combine pass.

Canola variety harvested varied by producer and included InVigor 5440, InVigor 5770, InVigor L150, YN-429, and 45H28.

No difference between windrowed- and direct-harvested management

There was no significant difference between the two management systems. Direct-harvested canola averaged slightly higher yield at 47 bu/ac (2625 kg/ha), but was statistically similar to windrowed at 45.5 bu/ac (2556 kg/ha).

Seed of the direct-harvested canola was statistically larger at 3.1 Thousand Kernel Weight (g) compared to 2.8 g TKW for windrowed canola.

Over the three years, the total seed loss averaged 4.6 bu/ac (260 kg/ha), or 10.2% of total seed yield. There was a 94% average viability of theses seeds collected, resulting in a seedbank addition of approximately 830 viable seeds/ft2 (8300 viable seeds/m2). This seedbank addition can result in volunteer weed pressure for subsequent crops. Although previous research has shown that 0.2% of canola seeds survive after 3 winters in western Canada, substantial volunteer weed pressure can still occur in the two years after harvest.

These results found that direct-harvested canola was a viable option, even prior to the development of shatter-resistant canola. However, the decision to direct-harvest comes down to risk assessments for both windrowed and direct-harvested crops.  Windrowed canola can suffer large losses from windstorms that blow swaths across the field. On the other hand, canola left standing for direct-harvesting can also suffer losses from wind, snow and lodging.

The Canola Council of Canada indicates that some factors can contribute to a successful direct-harvested crop, including:

  • slight lodging to protect from wind events,
  • plants are well knit together,
  • good pod integrity due to limited disease (e.g. alternaria or sclerotinia), hail, or insect damage,
  • evenly matured,
  • relatively even field topography.

The authors acknowledge the Canola Council of Canada and the Growing Forward Science Cluster for funding this research.

Haile, T. A., Gulden, R. H. and Shirtliffe, S. J. 2014. On-farm seed loss does not differ between windrowed and direct- harvested canola. Can. J. Plant Sci. 94: 785789.


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