Drought stress is the main factor limiting the growth and crop yield in most regions; thus, reducing the effects of drought stress is a research priority worldwide. The aim of this experiment was to evaluate the effect of sodium nitroprusside (SNP) on physiological traits and grain yield of oilseed rape under drought stress. Two field experiments with three irrigation levels (I1: full irrigation (control), I2: irrigation cut-off at the beginning of pod development, and I3: irrigation cut-off at the beginning of grain filling) and SNP foliar applications with four levels (0, 100, 200 and 300μM) were conducted during the 2015–2017 growing seasons. The results indicated that applying 200 and 300μM of SNP significantly increased antioxidant enzymes, total chlorophyll, and proline at all levels of drought stress in comparison with applying zero and 100μM of SNP. Moreover, applying SNP increased grain yield via improving the biochemical traits of the plant under stress and non-stress conditions. Comparison results of the average test of two years showed that the application of 200 and 300μM SNP increased grain yield to 11.2 and 15.1% in control conditions, 33.6 and 36.7% in I2 and 20.9 and 40.6% in I1 compared to the control. Generally, the results indicated that applying SNP reduced the effects of water-deficit stress on oilseed rape.
