It is known that legumes generally respond to existing N in the soil. When soil N is relatively high, legumes prefer to use soil N rather than to engage in symbiosis with rhizobia. However, the ecophysiological responses of legumes to existing soil-N level and the changing climate - including temperature changes and precipitation dynamics impact rhizobia nodulation - have not been studied in actual field conditions. This study seeks to understand these responses in order to improve N management, maximize the benefits of legumes, reduce off-farm inputs, and enhance soil health. Moreover, growth and N accumulation of legumes is heavily dependent upon the nitrogen-fixing performance of the microbial partner recruited by the host legume. Native rhizobia strains in the Northeast that associate with faba bean (Vicia faba) and sunn hemp (Crotalaria juncea), two multipurpose legumes newly introduced by the current project team to the area, have not been identified. In this project, native strains will be recovered from nodules, genetically sequenced, and their performance will be compared with elite strains maintained at USDA.
