Phenology, Physiology, and Fatty Acid Profile of Canola (Brassica napus L.) under Agronomic Management Practices (Direct Seeding and Transplanting) and Zinc Foliar Application

Canola production is undergoing a shift from direct seeding to transplanting. There are also serious global challenges caused by zinc (Zn) deficiency in most crops. The aim of this study was to evaluate the crop establishment methods (direct seeding and transplanting) along with foliar application of Zn on phenology, physiology, and fatty acid (FA) profile of canola under semiarid conditions. The treatments were crop establishment methods at three levels (direct sedding, 2-leaf transplanting, 4-leaf transplanting) and foliar application of Zn in two levels (control and 5 g L-1 ZnSO4) during 2017-2018 and 2018-2019 growing seasons. Transplanting reached the stem elongation and flowering stages in a short period compared to direct seeding. The 4-leaf transplanting practice represented the increased plant height, number of silique per plant, and seed yield compared to 2-leaf transplanting and direct seeding. The significant effect of Zn was only observed in 4-leaf transplanting with respect to the increase of plant height, number of silique per plant, seed yield, and decline of photosynthetically active radiation (PAR). The maximum total soluble sugar (TSS) and seed oil content were observed under the 4-leaf transplanting practice. The main FA profile was oleic acid (65.07-67.13%) followed by linoleic acid (16.37-18%), linolenic acids (6.63-7.92%), palmitic acid (4.10-4.52%), steric acid (1.77-2.22%), and erucic acid (0.21-0.25%). Heat map analysis showed the highest variation of branch number, silique number, PAR, and TSS under different copying systems. We suggest 4-leaf transplanting with Zn application to meet the optimum productivity of canola under semiarid conditions.