Rhizobium-assisted organic-mineral fertilization improves faba bean productivity and soil functioning in marginally saline soil

Marginal salinity limits legume productivity by constraining soil fertility, microbial activity, and plant physiological performance. This study evaluated whether integrating Rhizobium biofertilizer with organic-inorganic fertilization improves soil health and faba bean ( Vicia faba L.) performance under marginally saline field conditions. A two-season field experiment was conducted in Kafr El-Sheikh, Egypt, using five treatments: untreated control, Rhizobium plus P, 50% inorganic N plus 50% organic amendments with P, the same organic-inorganic treatment plus Rhizobium, and conventional inorganic NP. The integrated Rhizobium -organic-inorganic treatment produced the strongest response, increasing the soil fertility index to 0.99, available N to 47.7 mg/kg, available K to 104.4 mg/kg and phosphatase activity to 93.81 µg PNP/g soil/h in the second season. It also enhanced photosynthetic rate to 17.12 µmol CO₂ m⁻² s⁻¹, relative water content to 82.43%, plant N to 13.86 mg/g and grain yield to 4865 kg/ha, while reducing electrolyte leakage to 14.54%. Residual soil fertility also improved, as indicated by greater soybean dry mass and nutrient accumulation. The findings demonstrate that combining Rhizobium with organic-mineral nutrient management can thereby strengthen soil biological functioning and improve faba bean productivity in salt-affected agroecosystems.