Morpho-Physiological Traits, Grain and Oil Yield of Rapeseed (Brassica napus L.) Affected by Drought Stress and Chemical and Bio-Fertilizers

The objective of this research was to evaluate the effect of fertilizer treatments on some morpho-physiological traits, yield and yield components and oil of rapeseed (cv. Delgan) under different levels of water supply.

A field experiments was conducted in two years of 2018 and 2019 as split-plot based on RCB design in three replications. Irrigation intervals as irrigation after 70, 100, 130 and 160 mm evaporation from class A pan were located in main plots and fertilizer treatments as F0: control, F1: chemical fertilizer (nitrogen and phosphorus) , F2: inoculation with plant growth-promoting rhizobacteria (PGPR), F3: vermicompost and F4: combined fertilization (1/3 F1 + 1/3 F3 + inoculation PGPR) were allocated to sub-plots.

Leaf temperature increased under drought stress, but the amount of nitrogen and phosphorus in rapeseed leaves, leaf water content, plant height, stem diameter, number of branches and leaves per plant, length and number of siliques per plant, grains per silique, plant biomass, and subsequently grain yield per plant were decreased. Application of fertilizer treatments, especially the combination of bio-fertilizers and chemical fertilizers (F4), improved all these traits (except stem diameter) and resulted in increased rapeseed plant yield, particularly under moderate (I3) and severe (I4) stresses. Oil percentage was also improved in the treatments inoculated with the growth promoting bacteria.

Increasing oil percentage and grain yield eventually increased oil yield of rapeseed plants. It was concluded that combination of chemical and bio-fertilizers could be an effective method to improve field and economic (oil) performance of rapeseed plants under water stress conditions.