BIOLOGICAL NITROGEN FIXATION BY Adesmia bicolor AND A. macrostachya, POTENTIAL FORAGE SPECIES FOR ARID AND SEMI-ARID ENVIRONMENTS

In South American arid regions cattle feed lacks during winter Adesmia bicolor and A. macrostachya are promising forage species because of their growth habit anti adaptability to dry winters and N poor soils. Information about their biological nitrogen fixation (BNF) efficiencies is needed. The aim of this work is to determine their BNF efficiencies, nodule morpho-anatomy and spatio-temporal distribution, in symbiosis with rhizobia. In a greenhouse, both species were, seeded and irrigated with nittritive solution: "Without N"; "With N"; and "Inoculated seeds with nutritive solution without N". Nodules morpho-anatomy and spatio-temporal distribution; shoot-leaf root, and nodule dry matter and N content were analyzed. The studied species showed a mean BNF efficiency of similar to 60%, which is a relatively high efficiency considering that alfalfa shows a 61% efficiency when grown in central Argentina. This attribute is desirable in wild species with forage potential in arid environments.