Effects of Zn enriched sewage sludge on microbial activities and biomass in soil

An incubation study in closed static microcosms was performed to elucidate Zn effects on N mineralisation in relation to other microbial activities and biomass in a sandy soil. Sewage sludge equivalent to 25 t ha−1 was enriched with five different rates of Zn to add concentrations between 50 and 800 μg Zn g−1 soil. All microbial indices were increasingly depressed with increasing Zn concentration of the sewage sludge, but they were affected with different intensity: Zn had especially large effects on CO2 production and qCO2, moderate effects on N mineralisation and relatively small effects on protease activity, biomass C and arginine ammonification.