Effect of seed treatment with salicylic acid, humic acid and zinc on the growth rate of broad bean seedlings (Vicia faba L.)

Seed germination and early seedling growth are critical stages that determine successful crop establishment and productivity in grain legumes. However, limited information is available regarding the comparative physiological effects of individual seed treatments with salicylic acid (SA), humic acid (HA) and zinc (Zn) on faba bean seedlings. This study aimed to evaluate the physiological effects of individual seed treatments with SA, HA and Zn on the germination performance and growth of faba bean (Barcino cultivar) seedlings. Seeds were sterilized and soaked in different concentrations of each treatment (SA at 0, 50, 150, 200 mg/L; HA at 0, 100, 200, 300 mg/L; Zn at 0, 200, 300, 400 mg/L). Germination and seedling vigour were assessed using standard indices. The results showed significant superiority of all treatments compared to the control. Salicylic acid at 150 mg/L was the most effective treatment, recording the highest values for the final germination percentage (98.21 %), the lowest average germination time (3.4 days) and the highest germination index (37.21), in addition to its superiority in all vegetative growth traits and vitality indicators. Humic acid followed in performance at 300 mg/L, followed by Zn at 300 mg/L. This study concludes that seed pre-treatment with 150 mg/L SA is a promising approach enhancing germination and early seedling growth in faba bean. The findings highlight the importance of determining the optimal concentration for each biostimulant to avoid potential inhibitory effects at higher doses.