Production and Biological Nitrogen Fixation of Tropical Legumes -- Nitrogen Fixation by Soybean in North America -- The Importance of Nitrogen Fixation to Soybean Cropping in South America -- Production, Regional Distribution of Cultivars, and Agricultural Aspects of Soybean in India -- Soybean Cultivation and BBF in China -- Soil Stress Factors Influencing Symbiotic Nitrogen Fixation -- Nodula…