MICROBIAL ACTIVITY AND BIOMASS IN MIXTURE TREATMENTS OF SOIL AND BIOGENIC MUNICIPAL REFUSE COMPOST

An incubation experiment was performed to determine how the mixing of soil with municipal organic refuse compost affects C mineralization, g rowth of the microbial biomass, and changes in organic components, esp ecially in the fractions of amino acids and amino sugars. Compost and soil differed in almost every parameter measured, with the organic C c ontent of the compost representing only 10.8% of the dry weight. The f ractions of K2SO4-extractable organic C and of non-hydrolyzable C were larger in the compost (1.24 and 62.9% of organic C, respectively) tha n in the soil (0.56 and 41.6% of organic C). These two fractions incre ased in proportion to the addition of compost, in contrast to amino su gar and amino acid C which were identified overproportionately in the mixture treatments, especially in the 30% compost treatment. Overpropo rtionate increases in the microbial biomass C content and CO2 evolutio n rate were also measured in this treatment. The adsorption of compost colloids on the surface of regular soil silicates increased both the availability for microbial enzymes and the detectability for chemical analysis.