Effects of Combined Nitrogen on Nodulation and Growth of Phaseolus vulgaris

Abstract

SUMMARYThe effect of Rhizobium strain and low levels of nitrogen on growth and nitrogen fixation was studied on 5 seedlines of Phaseolus vulgaris. All plants responded to irrigation when low levels of nitrogen were supplied throughout each experiment during vegetative growth, but the final seed yield was not significantly affected. All strains induced less nodule tissue and lower nitrogenase activity per plant when nitrogen was applied; some strains were less sensitive than others. The proportion of the plant's nitrogen estimated to be derived from fixation (based on acetylene reduction) and fertilizer was affected by host genetics. Nodulated plants had nitrogenase activities comparable with other grain legumes and responded to combined nitrogen during vegetative growth, but this was not reflected in grain yield.