THE EFFECTIVENESS OF STRAINS OF THE NODULE ORGANISM WHEN ASSOCIATED WITH DIFFERENT SPECIES OF CLOVER

The effectiveness in nitrogen fixation of fifty-four strains of the clover nodule organism has been tested on red, white and alsike clover in aseptic tube-culture by comparing the nitrogen content of nodulated plants grown on nitrogen-free medium against that of non-nodulated plants grown on media with and without nitrate-nitrogen. The performance of the strains was to a considerable degree consistent on all three hosts. Minor changes were shown but for the most part did not exceed the experimental error. Thus in respect of these three clovers there is no marked host species effect. Seed inoculants or naturally occurring strains effective on one species are likely to be effective on the other species.