Effect of sowing dates and late season water deficit stress on quantitative and qualitative traits of canola cultivars

To investigate the effects of sowing dates and late season water deficit stress on quantitative and qualitative traits of different canola cultivars, a 2-year field experiment was carried out in the 2014–2015 and 2015–2016 growing seasons. The experimental factors consisted of sowing date at two levels (7th and 27th October), irrigation at two levels (full irrigation and irrigation termination at silique formation stage) and four German canola cultivars including Trapper, Makro, Smilla, and Agamax. The results indicated that the main effects of sowing date, irrigation, and cultivar were significant on all studied characteristics except for harvest index. The interaction between sowing date and irrigation was also statistically significant on silique number per plant, oil percentage, linolenic acid, and erucic acid percentage. The results demonstrated that seed yield and its components oil percentage and oil yield, as well as oleic and linoleic acid percentage, decreased when sowing date was delayed until 27th October. Due to irrigation termination, all the studied traits decreased except for linolenic and erucic acid. Seed yield also decreased. The results suggest that to improve seed and oil yield, canola should be sown on 7th October and fully irrigated until physiological maturity stage in the study area