Evaluation of the N2-fixing Ability of Rhizobia Strains in Common Bean Cultivated Region of Qazvin

This study was conducted to evaluate N2-fixing ability of rhizobia strains inoculated with common bean. The experiment was carried out in a randomized complete block design (RCBD) with 13 treatments including 10 Rhizobium isolates، two nitrogen fertilizer levels (200 and 400 kg urea per ha) and one control (without Nitrogen and rhizobium) in four replications at Esmaeel Abad research station of Qazvin. Plant sampling was done in two growth stages and nodule number and dry weight، shoot dry weight and total N-uptake and seed yield were evaluated. Results of two years field experiment showed that isolate L-75 showed the superior N2-fixing performance and had the highest positive effect on growth factors and could be recommended to use as inoculants strain in Qazvin region. This isolate، produced highest nodule number and dry weight in both years of study. Seed yield production was promoted by 26 and 40% more than control by application of isolate L-75 in the first and second year، respectively. This study showed that inoculation of common bean with effective rhizobia strains resulted in promoting of plant growth and seed yield production and have the benefit to reduce nitrogen fertilizer application in bean cropping.