Nitrogen level and cultivar effects on nodulation, dinitrogen fixation and yield of grain legumes: I. Cowpea cultivars

Abstract

N fixation was studied by the 15N method in Vigna unguiculata cv. ERI-2, Vita 4 and Machakos 74 grown in a field which had been fallow for 3 years and given 20 or 100 kg N/ha. The higher N rate reduced nodulation in all cv., with effects differing somewhat between cv., and increased DM and N yield/plant and uptake of non-fertilizer soil N, with least and greatest effect in cv. ERI-2 and Machakos 74, resp. The amount of N fixed was 50.5, 73.7 and 60.7 kg/ha at the low N rate and was 69.7, 74.5 and 100% lower at the high N rate in the 3 cv., resp.