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Show 102 Utah Academy of Sciences, Arts and Letters Eight crops were grown and analyzed during the first eight years, and eight during the second eight years. The results re ported are for the averages for each of the two eight year periods. ... ... EXPERIMENTAL RESULTS The data for the in table 1. variously treated alfalfa plots are given Nodules were found on both the inoculated and the unin oculated plants even in the early stages of the experiment, but were more numerous on the inoculated. It is evident that during the first eight years there was no difference between the pro -tein content of the inoculated and the uninoculated alfalfa. How ever, during the second eight years there was a highly siqnifi cant difference in favor of the inoculated alfalfa. Probably dur ... ... ... ... ... ing the first eight years the nitrogen content of the soil Was suf ... ficient so that the young alfalfa plants got a good start and resisted the invasion of the Rhizobium, whereas during the se cond eight years the lower nitrogen content of the soil weakened the young plants so that the Rhizobium invaded the host plant early in its growth. This supposition is borne out by the data obtained on the plants grown with green manure. During the first eight years when the legumes were developing, soil sapro phytic bacteria were rapidly decomposing the plant tissues, hence were competing with the growing legume for the limited supply of soil nitrogen. During the second eight years considerable of the- nitrogen added in the green manure became available to the growing plant and manifest itself by an increase in the percent age of protein of the alfalfa grown on the soil which had re ceived the green manur. ... ... ... ... The results for the crimson clover are given in table 2. The inoculation was without effect on the crimson clover throughout the life of the experiment. However, green manure during the first period depressed the nitrogen content of the plant, but was without effect during the second period. The data for the cow peas are presented in table 3. Inoculation was without effect upon cow peas, whereas the protein content of the peas raised with green manure was lowest during the first period, and highest during the second eight period. The differences closely approached the 5 percent level of significance. This reversibility may have been due. to competition between the plant and microorganisms during the first period of the experiment, whereas sufficient nitrogen may ... year have been available for both during the second period. |
