Studies of the effects of the level of sewage sludge crumbling on microbial and biochemical activities of soils

The influence of crumbled sewage sludge on the biological properties of podzolic soil was studied under laboratory conditions during a five-month period. It was found that when compared to only slightly crumbled sludge, soil mixed with two different concentrations of crumbled sludge (1% and 10%) of a 0.5-mm particle diameter exhibited an increase in the numbers of all tested bacteria groups (total, lipolytic, cellulolytic, proteolytic). The stimulation of development of some fungi groups (cellulolytic, proteolytic) was also observed in soil with higher contents of crumbled sludge. Finally, strongly crumbled sludge stimulated most of the biochemical activities of the soil (ammonification, nitrification, dehydrogenases, lipase, protease). Such an effect was most evident in the cases of dehydrogenases and protease.