Effect of Winter Planting Date on Oil Yield and Fatty Acids of New Spring Canola (Brassica napus L.) Cultivars Under Foliar Zinc Spray

Canola (Brassica napus L.) oil yield and fatty acid composition are the function of genotype, climate conditions, morphology, and physiology as well as crop management. In this study, the reaction of different canola cultivars—in terms of seed oil content and fatty acids—to different planting dates and foliar zinc application during two experimental years (2016–2017) was investigated in the field in arid and semi-arid regions of Karaj, Iran. The experiment was performed as a factorial split plot in a randomized complete-block design with three replications. Three sowing dates (February 9, 19, 29) and two foliar zinc applications (non-application as control and zinc application; spraying in the stem elongation stage) were factorially randomized to main plots, and canola cultivars (Sarigol, Dalgan, Salsa, and Solar) were allocated to sub-plots. The results indicated that the effect of year, planting date, zinc application, cultivar, and the interaction effect of planting date and cultivar on quality traits (glucosinolate and fatty acids) and seed yield were significant (p < 0.01). The delay in winter planting of spring canola cultivars caused a significant reduction in seed yield, oil yield, and the content of oleic, linoleic, and palmitic fatty acids and increased the content of linolenic, erucic, stearic, arachidic, and behenic fatty acids and glucosinolate. The highest seed yield (4732.2 kg/ha), oil yield (2066 kg/ha), and oleic acid content (66.52%) were observed in the Dalgan cultivar in the zinc application treatment with normal planting date (February 9). The Salsa cultivar had the highest content of erucic acid (0.46%) and glucosinolate (17.3 μmol/g meal) in the control treatment with the last planting date. Because the quality of edible canola oil depends on the increase in unsaturated fatty acids, particularly oleic and linoleic acids, and the reduction of erucic acid and glucosinolate, planting Dalgan cultivar with zinc application at the normal planting date is recommended for the study area and similar areas.