This study reports the interaction of rhizobium strains and varieties on yield and yield components of faba bean, and economic feasibility of the inoculant use in faba bean production. The two years field experiments used a split-plot design that involved six elite rhizobium strains as main plot and three faba bean varieties as sub-plot treatments. Non-inoculated plants with N fertilizer and without fertilizer were included as +N (46 kg ha-1) and -N controls, respectively. Nitrogen fertilizer was applied two times in equal split doses at planting and six weeks after sowing. Phosphorus (P) was applied as triple super-phosphate at the time of sowing. Data on yield and yield components were collected and statistically analyzed. Partial budget, dominance and marginal rate of return analyses were conducted to identify profitable rhizobial strain-variety combinations for each study location. Rhizobium strains NSFBR-15, TAL_1035 and NSFBR-12 increased grain and haulm yield of faba bean more than N fertilizer across the study locations. Increased haulm yield due to Rhizobium inoculation was the most important contributor to grain yield of faba bean. Location, Rhizobium strain and variety interaction influenced yield and yield components of faba bean. Economic analyses document that Rhizobium inoculation for symbiotic N fixation is more profitable for supplying N to faba bean than N fertilizer application. Rhizobium strains NSFBR-15, TAL_1035 and NSFBR-12 with all faba bean varieties resulted in the highest revenue with higher marginal rate of return at all study locations.

Keywords: Faba bean, inoculation, nitrogen, strain, yield