Effects of foliar application of micronutrients on seed yield and oil quality of canola (Brassica napus L. cv. Hyola401) under drought stress conditions

To evaluate the effects of drought stress by withholding of irrigation during reproductive stages and foliar application of micronutrients (Zn, Mn and B) on seed yiled and oil quality, an experiment was carried out as split plot arrangements in randomized complete block design with three replications at Safiabad Agricultural and Natural Resources Research and Education Center, Dezful, Iran, in two growing seasons (2013-2015). Main plots consisted of three irrigation levels: full irrigation (control), withholding of irrigation from flowering stage, and withholding of irrigation from silique stage, and sub plots included 10 levels of foliar application of micronutrients (2, 4, 6‰ zinc, 2, 4, 6‰ manganese, 2, 4, 6‰ boron, and the foliar application of distilled water as control). Foliar applications were made during both budding and initiation of flowering stages. Results showed that withholding of irrigation significantly decreased seed yield and yield components. Withholding of irrigation from flowering and silique stages reduced the silique no. plant-1 by 40% and 8%, respectively. Mean comparison of withholding of irrigation and foliar application showed that the highest seed yield (4301 kg.ha-1) belonged to full irrigation and foliar application of boron (4‰) in both growing seasons. The lowest seed yield (1863 kg.ha-1) obtained in withholding of irrigation from flowering stage and no micronutrient. Withholding of irrigation from flowering stage led to decrease oleic and linoleic acids content. The highest oil content (45.6%) measured in full irrigation and application of zinc (6‰) and boron (6‰). The lowest oil content (40.3%) observed in severe moisture stress conditions and no micronutrients. The results of this experiment showed that withholding of irrigation from flowering stage imposed severe stress on crop and should be avoided. The highest seed yield belonged to application of manganese and boron (4‰) and zinc (6‰) under withholding of irrigation from silique stage. To obtain reasonable seed yield, full irrigation and foliar application of zinc (4‰) and boron (4‰) is possible.