Multi-component seed coating boosts faba bean salinity tolerance: Linking laboratory mechanisms with field validation

Soil salinity threatens faba bean production globally, with 20-35% of agricultural lands affected in arid regions. Seed enhancement technologies offer practical solutions for improving crop establishment in salt-affected soils. This study evaluated multi-component seed coating versus hydropriming for enhancing faba bean germination, vigor, stress tolerance, and yield under four salinity levels (320-3000 ppm NaCl) in laboratory and field conditions under Egyptian conditions. Laboratory germination tests followed a completely randomised design, while field pot experiment used a randomised complete block design during 2022/2023 and 2023/2024 winter seasons. Treatments comprised four salinity levels and three seed treatments: untreated, hydropriming, and multi-component coating containing (gum Arabic, humic/fulvic acids, NPK, salicylic acid, and Rhizobium leguminosarum). Salinity reduced germination, seedling vigor, stress tolerance, and membrane stability while increasing electrolyte leakage. Multi-component coating outperformed hydropriming, particularly under stress. Compared to hydropriming, coating enhanced germination (6.1%), reduced mean germination time (13.6%), and increased seedling vigor index (32.2%). Under severe salinity (3000 ppm), coating advantages intensified: 3.9% higher germination and 16.7% improved vigor index over hydropriming. The coating’s relative vigor advantage increased from 39.2% at 320 ppm to 106.8% at 3000 ppm, demonstrating superior stress mitigation. Coating improved stress tolerance indices more effectively than hydropriming by enhancing membrane stability (26%) and reducing electrolyte leakage (25%) compared to untreated seeds. Biochemically, coating reduced malondialdehyde (20.4%) and sodium accumulation (16.3%) while maintaining higher potassium concentrations (26.8%) compared to hydropriming, with 32.1% higher K+/Na+ ratios under severe stress. Pot field experiments over two growing seasons validate lab results: coating seeds improved emergence by 12.5%, pods per plant by 40-45%, seeds per plant by 32-36%, and potential seed yield by 39-42% compared to untreated seeds. Strong laboratory-field correlations (r = 0.86-0.98) confirmed predictive validity. Multi-component seed coating offers a promising strategy for faba bean production in saline soils.