BIOLOGICAL ACTIVITY AND FUNCTIONAL DIVERSITY OF AGRICULTURAL SOIL AMENDED WITH SEWAGE SLUDGE

The biological effects of applying sewage sludge (SS) to agricultural soil (at a low rate of 22.5, LRS, and a high rate of 45 t ha-1 dry basis, HRS) were monitored over a 120-d experimental period. The biological activity was monitored by dehydrogenase, catalase, urease, protease, alkaline phosphatase, arylsulphatase and β-glucosydase activities. Selected characteristics also included soil microbial biomass carbon (MBC) and community level physiological profiling (CLPP), indicating the microbial functional diversity of soil (catabolic potential) and assessed using Richness (R) and Shannon-Weaver (H) indexes. All the enzyme activities were strongly affected by both rates of SS applications. After a rapid increase in the early phases of the experiment, enzyme activities decreased sharply and remained almost stable during the last stages of the trial period. Microbial biomass carbon was also influenced by SS addition, however during the incubation period of 120 days, it remained at high levels only at HRS. The H index increased significantly with the increasing SS applications. Differences in the functional diversity of soil microbial communities were found. For both doses, there was an increase in biodiversity over time, reaching about 9% compared to the control.