Wild legumes (herbs, shrubs or trees) play a critical role in natural ecosystems, agriculture, and agroforestry, where their ability to fix nitrogen makes them excellent colonizers of low-N environments, and hence an economic and environmentally friendly species. The field natural nodulation of the Tunisian Sulla crnosa, its symbiotic-efficiency and feed production potentiality in its saline biotope (sebkha d'El kelbia) were investigated in this study. A greenhouse experiment was conducted on plants transferred from sebkha with their soil in pots to explore the maximum potentialities of biomass production and nitrogen fixation of this legume when water is not a limiting factor (natural soil salinity was maintained in greenhouse). Obtained field and greenhouse study demonstrated that Sulla carnosa can be a good candidate for saline agriculture regarding its important ability to grow, produce biomass and fix nitrogen under high level of salinity (about 150 mM NaCl). This legume protects its photosynthetic and symbiotic organs against their overload with sodium by an important uptake of potassium and accumulation of Na in the roots. Sulla carnosa can play a goal role in the sustainable development in a region traditionally considered marginal.