Biology and Fertility of Soils (2007) 44:393-398 EFFECT OF DIFERENTLY POST-TREATED DEWATERED SEWAGE SLUDGE ON β- GLUCOSIDASE ACTIVITY, MICROBIAL BIOMASS CARBON, BASAL RESPIRATION AND CARBOHYDRATES CONTENTS OF SOILS FROM LIMESTONE QUARRIES

This work has evaluated the effects of a thermally dried or composted dewatered sewage sludge on glucosidase activity, total (TCH) and extractable (ECH) carbohydrate content, microbial biomass carbon (MBC) and basal respiration (BR) of soils from limestone quarries under laboratory conditions. Two doses (low, L and high, H) of the dewatered sludge (DS), or of the respective thermally dried (TDS) or composted (CDS), were applied to a clayey (CL) and a sandy (SA) soil, both coming from working quarries. The soil mixtures and the controls (soils with no added sludge) were incubated for nine months at 25oC and 30% of field capacity. The addition of sludge increased all the studied soil parameters, and the increase depended on the amount of sludge. Except in the case of TCH and ECH, the enhancing effect decreased with time but, at the end of incubation, parameters of the treated soils were higher than those of the control. The rank order of the initial stimulating effect was soil-TDS ≥