The value of supplementary bacteria for legumes

Experiments have been conducted to determine the value of supplementing the legume bacteria which the soil naturally supports with an artificial culture for alfalfa, red clover, beans, and peas. Limed and unlimed field plats, representing only one type of soil, have been used. Yields from one season only are presented. A few points may be emphasized. Alfalfa which was grown on limed soil produced about 11% more dry weight when supplementary bacteria were applied at seedtime, although roots 46 days old failed to indicate any value of the extra bacteria as measured by the number of nodules. Supplementing the legume bacteria on the unlimed soil which had a pH of 5.3 produced an increase over the plats not receiving such a treatment not only in the number of nodules and in the dry weight of the crop, the latter being equal to 18%, but also in the number of plants that survived throughout the season, this being equal to several hundred thousand plants per acre. Red clover which was grown on limed and unlimed soils produced 39.9% and 32.2% more dry weight, respectively, when supplementary bacteria were applied at seedtime. Red kidney beans which were grown on the limed plats showed an increase of 12.8% in oven-dry crop and 9.2% in shelled beans per acre in favor of supplementary legume bacteria. On the acid plats there was a slight gain of total dry crop and a slight decrease in shelled beans where the artificial culture was used. An average of both total crop and of shelled beans from the six plats receiving the supplementary bacteria compared with that from the six not receiving such treatment shows an increase of only 9.2% in total crop and 4.98% in shelled beans in favor of supplementary bacteria. Peas which were grown on both limed and unlimed plats had a larger quantity of nodules on their roots than plants from similar plats which did not receive supplementary bacteria. The total crop and the dried peas from these plats were also considerably larger, being 15.1% and 35.8% greater in total crop and 14% and 25.7% greater in dried peas, respectively, than those from similar plats not receiving supplementary bacteria. The total yield from the six plats which received supplementary bacteria was 14.3% larger than the total yields from the six plats not so treated. In dried peas it was 29.3% in favor of supplementary bacteria.