The effect of green fertilizer, vermicompost, and chemical fertilizer on grain yield, oil content, and composition of rapeseed (Brassica napus L.)

A field experiment was carried out based on a randomized complete block design (RCBD) with 8 treatments and three replications in two successive stages in the Miandoab city, Iran during 2019 and 2020. The results showed all studied traits except harvest index were significantly affected by different fertilizer sources. The highest number of grain per pod, 1000 grain weight, seed, and biological yield of rapeseed were obtained with the application of chemical fertilizer without significant difference with a green manure of 50% P+ 50% B. In addition, the maximum oil content and yield were obtained in green manure of 50% P+ 50% B followed by 75% P+ 25% B. Chemical analysis of the rapeseed oil demonstrated that in all treatments, oleic acid, linoleic acid, and palmitic acid were the main dominant components. So that, the highest (92.43%) and lowest (83.37%) of oleic acid were achieved in 50% P+ 50% B and control treatments, respectively. Also, the highest of (6.07%) linoleic acid was observed in vermicompost treatment. While the highest percentage of palmitic acid (92.43%) has belonged to green manure treatment of 25% P+ 75% B. Generally, the maximum (92.61%) and minimum (88%) of unsaturated fatty acids were achieved in 50% P+ 50% B and 25% P+ 75% B green manure treatments, respectively. Considering that the greatest amount of soil nitrogen, phosphorus and potassium were obtained by application of 50% P+ 50% B green manure.