The use ofMucuna pruriensas source of N for the succeeding poor N-fixing soyabean genotypes was tested during the 1991/92 rainy season at the IDR site. Field studies revealed thatM. pruriensproduced 31 nodules plant−1with a nodule mass of 306 mg plant−1and a crop N yield of 340 kg ha−1. This high nodulation was attributed to a wide range of indigenous rhizobia identified as strains ofBradyrhizobiaisolated from nodules ofStylosanthes gracilis(two isolates G7, G71),Crotalaria juncea(two isolates C4, C41),M. pruriens(two isolates II, 13),Mimosa pudica(three isolates W3, W31, W32) andPhaseolus vulgaris(one isolate H51), which formed nodules with dark red interiors onM. pruriensas revealed by the plant-infection test. The antibiotic resistance profile differed among the various isolates, and among isolates of the same plant of origin. Consequently, the use ofMucunaas green manure for the succeeding soyabean crops is quantified as a fertilizer-N equivalent of as much as 95 and 80 kg N ha−1for genotypes cv. FN3 and cv. IRAT 274 respectively. Our findings illustrate the high agronomic efficiency ofM. pruriensfor soyabean.