Yield and quality of canola seed as affected by stage of maturity at swathing

Swathing is an important canola (Brassica napus L.) harvest operation in western Canada. The determination of the optimum timing for this operation is worth considering, as premature swathing may lead to reduced seed yield and quality. Seed yield and quality of three canola cultivars (44A89, AC Excel and Ebony), as affected by two seeding dates and several harvest times (six or eight swathing times and one direct combined treatment) was investigated on a Black Chernozem silty loam soil at Melfort, Saskatchewan, Canada, during 1998, 2000 and 2001. Seed yield, weight, protein content (oil-free meal basis) and oil content generally increased with seed development and swathing time. Early seeding was more conducive to achieving higher seed yield, especially in good growing conditions, and resulted in heavier mature seeds with higher oil content. Seed oil composition also changed during seed development. The proportion of oleic (C18:1) and linolenic (C18:3) acids increased, while that of myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), linoleic (C18:2) and arachidic (C20:0) acids decreased. The levels of the long chain fatty acids eicosenoic (C20:1) and erucic (C22:1) acids were unaffected. However, the overall amount of fatty acids synthesized (mg 100 seeds(-1)) increased as seeds matured. Swathing was advantageous over direct combining in preventing weather-induced shattering.