Effective infection of soybean root by rhizobia bacteria is critical for nitrogen fixation and high yields of soybeans with addition of nitrogen fertilizer. Extension recommendations are to apply commercial inoculants at planting time if fields have not been recently in soybeans, or if the grower suspects that environment conditions may have harmed the soil rhizobia population. Several new rhizobia inoculants have been introduced into the market place in recent years, along with claims that they are more effective than existing strains or surviving native soil rhizobia. The unknown of whether native rhizobia are providing needed nitrogen levels for maximizing soybean yields is the reason...