Biological nitrogen fixation: Investments, expectations and actual contributions to agriculture
- Cite this article as:
- Peoples, M.B. & Craswell, E.T. Plant Soil (1992) 141: 13. doi:10.1007/BF00011308
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Inputs of biologically fixed N into agricultural systems may be derived from symbiotic relationships involving legumes and Rhizobium spp., partnerships between plants and Frankia spp. or cyanobacteria, or from non-symbiotic associations between free-living diazotrophs and plant roots. It is assumed that these N2-fixing systems will satisfy a large portion of their own N requirements from atmospheric N2, and that additional fixed N will be contributed to soil reserves for the benefit of other crops or forage species. This paper reviews the actual levels of N2 fixation attained by legume and non-legume associations and assesses their role as a source of N in tropical and sub-tropical agriculture. We discuss factors influencing N2 fixation and identify possible strategies for improving the amount of N2 fixed.