Our study was conducted on a podzolic soil from a field experiment in which, 9 years earlier, municipal- industrial sewage sludge was introduced at doses of 30, 75, 150, 300, and 600 Mg·ha^-1. Following the application of the sludge, the soil was planted with basket willow (Salix viminalis L.). Soil samples for the analyses were taken twice (at the beginning and at the end of the vegetation season of the 9^th year) from depths of 0-20 cm and 20-40 cm. The soil material was used for determinations of the total numbers of bacteria with low and high nutrition requirements, the numbers of filamentous fungi, proteolytic bacteria and fungi, respiratory activity, rate of cellulose mineralization, rate of ammonification and nitrification, and of dehydrogenase and protease activity.
The results obtained demonstrated that in the 9^th year from the application of the sludge there was continued effect of its application on most of the microbiological properties (exception – proteolytic bacteria) and on all of the biochemical parameters. There was notable stimulation of the growth of cellulolytic bacteria and of the fungal groups under analysis. Increased activity was also displayed by almost all biochemical parameters, with the exception of ammonification (in both layers of the soil) and nitrification (in the deeper horizon of the soil), in which case significant inhibition was observed.