Correlation among microbial biomass S, soil properties, and other biomass nutrients

The soil physicochemical characteristics and amounts of microbial biomass C , N, and S in 19 soils (10 grassland, 2 forest, and 7 arable soils) were in vestigated to clarify the S status in granitic regosols in Japan, in order to determine the relationships between biomass S and other soil characteris tics and to estimate approximately the annual S and N flux through the micr obial biomass. Across the sites, the amount of biomass C ranged from 46 to 1,054, biomass N from 6 to 158, and biomass S from 0.81 to 13.44 mg kg(-1) soil with mean values of 438.8, 85.8, and 6.15 mg kg(-1) soil, respectively . Microbial biomass N and S accounted for 3.4-7.7% and 1.1-4.0% of soil tot al N and S, respectively. The biomass C:N, C:S, and N:S ratios varied consi derably across the sites and ranged from 3.0-10.4, 32.5-87.7, and 5.0-18.8, respectively. Microbial biomass S was linearly related to biomass C and bi omass N. The regression accounted for 96.6% for biomass C and 92.9% for bio mass N of the variance in the data. The amounts of biomass C, N, and S were positively correlated with a number of soil properties, particularly with the contents of organic C, total N, SO4-S, and electrical conductivity and among themselves. The soil properties, in various linear combinations showe d a variability of 84-97% in the biomass nutrients. Stepwise multiple regre ssion indicated that biomass C, N, and S were also dependent on SO4-S as a second factor of significance which could limit microbial growth under the conditions prevailing at the study sites. Annual flux of N and S was estima ted through the biomass using the turnover rates of 0.67 for N and 0.70 for S to be approximately 129 kg N and 9.7 kg S ha(-1) y(-1), respectively, an d was almost two times higher in grassland than arable soils.