Numbers of selected microbial groups in a podzolic soil under willow culture (Salix viminalis L.), amended with sewage sludge, in the third year of its effect

Abstract

The paper presents the results of studies conducted on a podzolic soil under willow culture (Salix viminalis L.), amended with various doses of industrial-municipal sewage sludge i.e. 30 Mg·ha^-1 (1%), 75 Mg·ha^-1 (2,5%), 150 Mg·ha^-1 (5%), 300 Mg·ha^-1 (10%) and 600 Mg·ha^-1 (20%). The analyses were made in the third year of the experiment, in order to determine the effect of the applied sludge on the growth of selected microbial groups in the soil. The results obtained for the soil from the Ap horizon showed continued stimulating effect of the sludge on the numbers of all the groups under analysis. Stimulation of the of oligo- and macrotrophic bacteria was observable in almost all, and of filamentous fungi in all the objects of the experiment, and increased with increases doses of the sludge. Also in the case of cellulolytic and „ proteolytic” bacteria and
fungi the stimulation increased with increasing dosage of the sludge, and was the most pronounced in objects with the highest levels of the sludge content (5, 10 and 20%). In deeper layers of the soil, the effect of the sludge was notably weaker than in the Ap horizon. There was a certain slight stimulation of the growth of oligotrophic bacteria and cellulolytic fungi, and a more pronounced growth in the number of filamentous fungi, but only in objects with higher concentrations of the sludge. Moreover, positive correlations were noted between the numbers of all the microbial groups under analysis.