Effect of seaweed extract application on reducing chromium toxicity in cowpea (Vigna unguiculata L.)

In order to investigate the effect of seaweed extract application on the reduction of toxicity due to heavy metal chromium (Cr) stress in cowpea (cv. Kamran), a pot experiment was conducted in Shahre rey region in summer 2019. The research was a factorial experiment at the basis of completely randomized design with 8 treatments and 3 replications. In this experiment, the first factor was Cr stress at two levels including concentrations of 0 and 50 mg/kg of Cr from potassium dichromate source (K2Cr2O7) and the second factor was the application of seaweed extract (Ascophyllum nodosum) at four levels including no application, pre-treatment for 12 hours, two and three stages foliar application at the concentration of 7 mL/L. According to the results of this study, Cr stress (50 mg/kg) reduced number of pods per plant, number of seeds per pod, 100 seed weight, grain yield, biomass and harvest index. On the other hand, application of seaweed extract improved the above traits under Cr stress. In this study, the highest seed yield per plant (38.58 g) was obtained from control treatment with three-stage foliar application of seaweed extract and the lowest grain yield per plant (7.64 g) was recorded in Cr stress conditions with no application of seaweed extract. In other words, three-stage foliar application of seaweed extract increased grain yield by 90 and 94% in both non-stress and Cr stress conditions, respectively. Therefore, based on these findings, three-stage foliar application of seaweed extract can be used to improve growth and yield of cowpea under non-stress and Cr stress conditions.