Six strains and a commercial inoculant of Bradyrhizobium japonicum were evaluated in association with Glycine
max (L.) cultivar Clark. Inoculated and uninoculated plants were grown in pot and field experiments. Nodules were
counted and weighed and roots and shoots were separated and analysed for total nitrogen. In pot experiments,
two of six bacterial strains were superior to the other four, and to the commercial inoculant (Nitragin) in promoting
greater root and top growth and plant nitrogen accumulation. In the field experiment, there were indications that
environmental conditions may have affected nodulation by the bacteria. The strains could be divided into three
groups according to nodule efficiencies, accumulation of plant dry matter, and total nitrogen content. The greater
variations in nodule efficiencies of the tested strains could be attributed to the quantities of bacteroid, cytosol
protein and leghaemoglobin in the nodules.