Biological Nitrogen Fixation in Dry Bean Cultivars Inoculated with Rhizobia.

Increasing the biological nitrogen fixation (BNF) using Rhizobium inoculation has potential to reduce negative consequences of nitrogen (N) fertilizer application. The incompatibility of common peat-based inoculants to use in air-seeder discourages the farmers to adopt inoculation. Liquid inoculant can be successfully accommodated with the current practice. Field and greenhouse-based studies were conducted to evaluate the responses of dry bean (Phaseolus vulgaris L.) cultivars from four market classes (pinto, navy, black, and kidney) to inoculation. Stable N isotope (¹⁵N) tagged fertilizer was applied to determine BNF using ‘Isotope dilution technique’. Significant variation in the BNF was found among the four dry bean market classes under greenhouse condition; pinto market class fixed highest amount of N₂. In a field study during summer 2016, significant variation in seed yield was found among the market classes and cultivars within market classes, pinto had the highest seed yield. Liquid inoculant was found to have statistically similar response for N₂-fixation and seed yield when compared with the peat-based inoculant, and can be a potential alternative for the peat-based inoculants. Selection of dry bean cultivars should be done to get higher BNF both for cultivation and for breeding purpose.