ENHANCING LEGUME N-2 FIXATION THROUGH PLANT AND SOIL-MANAGEMENT

Atmospheric N-2 fixed symbiotically by associations between Rhizobium spp. and legumes represents a renewable source of N for agriculture. C ontribution of legume N-2 fixation to the N-economy of any ecosystem i s mediated by: (i) legume reliance upon N-2 fixation for growth, and ( ii) the total amount of legume-N accumulated. Strategies that change t he numbers of effective rhizobia present in soil, reduce the inhibitor y effects of soil nitrate, or influence legume biomass ail have potent ial to alter net inputs of fixed N. A range of management options can be applied to legumes growing in farming systems to manipulate N-2 fix ation and improve the N benefits to agriculture and agroforestry.