YIELD AND BIOLOGICAL NITROGEN-FIXATION OF COMMON BEAN (PHASEOLUS-VULGARIS L) IN PERU

Two field experiments were performed to evaluate the nitrogen fixation potential of twenty common bean cultivars and breeding lines during s ummer and winter seasons of 1986 and 1988, respectively. The N-15 isot ope dilution method was used to quantify N2 fixation. The cultivars an d breeding lines were variable in terms of their N2 fixation. The cv. Caballero was very efficient, with more than 50% N derived from the at mosphere and 60-80 kg N ha-1 fixed in both seasons. Other cultivars we re less efficient, since the poorest ones derived less than 30% of the ir nitrogen from the atmosphere and fixed less than 20 kg N ha-1. Afte r additional testing the best cultivars may be used directly by the fa rmers for cultivation. The experiments have provided information about which genotypes may be used to breed for enhanced fixation in common bean.