For understanding correlations between the high yield of soybean and the biochemical characteristics of the soils, field experiments were carried out with different fertilizer treatments. In one series of the plots both organic manure and chemical fertilizers were applied, while in the second series only organic manure was used. A third series without fertilizer treatment was taken as control. The biochemical activities of the soil were studied at different growing stages of soybean. Results of present experiments showed that there are definite correlations between the yield of soybean and the biochemical activities of the soil, including enzyme activities, respiration and rate of cellulose decomposition. Good correlations are also found between the yield of soybean and amount of free amino acids present in the soil. The origin of the enzyme activities and the active substances in the soil also show an intimate relationship with the soil microflora. Soil particles possess great absorptive power for the enzymes, other active substances, and soil microorganisms without any inhibition of their activities.