Effect of plant density and foliar application of salicylic acid on agronomic traits and seed yield of rapeseed (Brassica napus L.) genotypes

To investigate the effect of plant density on agronomic traits of winter rapeseed (Brassica napus L.) cultivars under foliar application of salicylic acid a factorial split-plot arrangement in randomozide complet block design with three replications was carried out in Karaj, Iran, in two cropping seasons (2015-2017). Plant density at three levels of 40, 50 and 60 plants.m-2 and salicylic acid at two levels of 0 (non-application) and application with a concentration of 1‰ in two stages of 6 leaf and stem elongation were assigned in main plots and rapeseed genotypes; HW118, WPN6, HL3721, L14, Tassilo and Natali were randomized in sub-plots. The Plant density × salicylic acid × genotype interaction effect was significant (P≤0.01) on plant hight, number of silique on the main stem and branches, seed number of silique on the main and branches, 1000-seed weight, seed yield, oil yield, biological yield and total chlorophyll content. This interaction effect was also significant (P≤0.05) on seed oil content. All rapeseed genotypes showed positive responses to foliar  application of salicylic acid at different plant densities, and L14 and Natali genotypes in 40 plants.m-2 and application of salicylic acid had the highest seed yield (5629 and 5448 kg.ha-1), oil yield (2444 and 2352 kg.ha-1) and 1000 seed weight (5.3 and 5.1 g), respectively. Therefore, for rapeseed production, especially in low densities (40 plants.m-2), foliar application of salicylic acid is suitable for increasing seed yield.