Effect of sewage sludge on decomposition processes in soils

The effects of sludge amendment and addition of the earthworm, Eisenia foetida , to an old field soil and two forest soils was studied in central New York. Experimental plots were established in the old field, a mixed hardwood forest, and a spruce plantation. In each site, municipal wastewater sludge was added to two plots and E. foetida were placed in two plots, including one sludge-treated plot. Redox potential (Eh), moisture content, nematode and enchytraeid densities, and fluxes of oxygen and carbon dioxide were monitored in the plots. Addition of E. foetida produced limited effects on Eh, moisture content, and densities of invertebrates since these earthworms dispersed after innoculation. Worms which were added to glass cylinders used for gas flux measurements could not disperse. Containment of E. foetida produced localized and relatively intense burrowing and egestion, which resulted in stimulation of microbial respiration and increased fluxes of O sub(2) and CO sub(2). Sludge addition to soil-caused reduced Eh, and increased moisture content, invertebrate densities, and rates of decomposition.