Application of Silicon for Improving Some Physiological Characteristics, Seed Yield, and Oil Quality of Rapeseed Genotypes Under Late-Season Drought Stress

Drought stress is one of the most important factors in reducing yield and seed quality of rapeseed. Therefore, in this study, several new rapeseed genotypes were evaluated to provide practical solutions to reduce the effects of drought stress or improve canola yield. Seed and oil yield, fatty acids, physiological features, and the activity of antioxidant enzymes were assessed in late-season drought stress conditions with the foliar application of silicon. A factorial split-plot experiment was performed in a randomized complete block design with three replications in two cropping years, 2016–2018. Treatments included irrigation at two levels (normal irrigation (control) and limited irrigation from the silique formation stage onwards) and foliar application at two levels (0 and 4 g L−1 of silicon), as factorial in the main plots, and spring rapeseed genotypes (Dalgan, RGS003, RGS × OKAPI, RGS × SLM, and OG × AL) as subplots. The results showed the highest seed yield (5620 kg ha−1), oil yield (2601 kg ha−1), oleic acid (68.16%), and linoleic acid (18.68%) was obtained in normal irrigation conditions along with the foliar application of silicon in OG × AL. Drought stress increased the activity of superoxide dismutase, catalase, and peroxidase enzymes in all genotypes. Among the genotypes, both RGS × SLM and Dalgan were the best (with high seed yield and oil quality) in late-season drought conditions when silicon was applied. In arid and semi-arid locations, introducing and diversifying rapeseed genotypes are one of the management techniques for achieving satisfactory yield. The quality of rapeseed oil diminishes as a result of environmental challenges. However, the foliar application of nutrients can help mitigate the impacts of drought stress. As a result, the current study’s findings revealed that silicon positively improved rapeseed drought tolerance during the late growing season.