Effect Of Swathing Date On Yield And Quality

Optimum canola yields are dependent on proper harvest management. Below is some Canola Council research that shows this.

Timing of cutting has a significant impact on yield results with a given variety if not managed properly. In some years this can be particularly evident in field trials.

Field scale trials in western Canada have shown that optimum seed yield and quality were achieved when B. rapa varieties were swathed at 40% seed colour change on the main stem. However, the optimum time for B. napus was between 20 and 40% seed colour change (Table 1.)

Table 1. Effect of Time of Swathing on B. napus Canola Yield, Oil and Protein

% Seed Colour Change	Location Years	Yield (%)	Oil Content (%) @ 8.5% Moisture	Protein Content (%) @ 8.5% Moisture
0 to 10%	25	90	40.8	20.7
10% to 20%	25	96	41.5	21.7
20% to 30%	25	100	42.2	21.6
30% to 40%	25	100	42.8	21.6

The trials found that swathing at 0 to 10% seed colour change on the main stem resulted in reduced yield, oil and protein. Swathing at 10 to 20% or 20 to 30% seed colour change had little effect on yield or protein. The variations in oil content seldom exceeded half a percentage point.

Research at Agriculture and Agri-Food Canada in Saskatoon, SK showed that once canola plants are swathed, the seed does not continue to fill (Figure 2). Seed swathed before accumulating its full complement of oil and protein will not accumulate any more after swathing, resulting in potential yield loss.

Figure 2. Effect of Swathing Date on
Seed Weight after Swathing

Research studies have shown that time of swathing usually has little effect on green seed levels except under abnormal situations.

In all research trials, swathing even prior to seed colour change did not increase the green seed levels. Swathing at a seed moisture content over 45% moisture (0-10% seed colour change on the main stem) reduced average seed size and immature seed turned a reddish colour. Occasionally, reductions in seed size were recorded with swathing at 15 to 20% seed colour change on the main stem. However, under abnormal conditions, swathing too early can occasionally result in green seed when plants are under moisture stress and very hot, windy weather dries out the pods and seed in the swath before chlorophyll has had a chance to clear. As B. napus has a narrower range in development time (due to fewer branches and pods) than B. rapa, it is possible to swath B. napus earlier without yield loss due to immature seed. This range in development time is affected by any factor that influences the number of branches and pods. Since dense or high population stands of canola have fewer branches and a narrower range in development, swath them earlier. Since low population stands tend to branch more profusely and have a wider range in development, swath them at the higher end of the seed colour change range.