RELATIONSHIP BETWEEN MICROBIAL BIOMASS AND ELEMENTAL SULFUR OXIDATION IN AGRICULTURAL SOILS

Elemental sulfur oxidation in 28 agricultural soils was correlated with the size and activity of the microbial biomass. Sulfur oxidation increased linearly with microbial biomass C (r equals 0. 68, P less than 0. 01) and soil respiration rate (r equals 0. 88, P less than 0. 01). Canonical analyses of the same data set further emphasized the strong interrelationship of sulfur oxidation, microbial biomass C, and respiration. These results indicated that the size and activity of the microbial biomass determined the rate of elemental S oxidation in agricultural soils. Increasing the heterotrophic biomass by glucose additions caused an increase in sulfur oxidation that was proportional to the increase in biomass C. These results and the absence of detectable populations of elemental S oxidizing autotrophs indicated that S oxidation in these soils was primarily a heterotrophic process.