The aim of the pot experiments was study of the influence of the adopted fertilisation (sewage sludge, FYM), soil type and the duration of the experiment on the microbiological and biochemical soil activity. Sediment from a dairy sewage treatment plant with addition of coal ash and FYM was used in the experiment. The experiment was set up in three replications on two types of soil – grey-brown podzolic and brown, with the use of complete randomisation method. The experiment contained the following objects: soil without fertilisation, soil + sewage sludge, soil + FYM, soil + sewage sludge + FYM. In the brown and grey-brown podzolic soil the following doses of dairy sewage sludge were used: 7.3 g kg-1 (22 Mg ha-1), 16.6 g kg-1 (50 Mg ha-1), 33.3 g kg-1 (100 Mg ha-1). Microbiological analysis comprised determination of the following: total number of bacteria, total number of fungi, number of cellulolytic bacteria, number of proteolytic bacteria nad fungi, numbers of ammonifying and nitrifying bacteria.

Biochemical analyses included determinations of the dehydrogenase, protease and urease activity, and ammonification and nitrification intensity.

Microbiological and biochemical analyses were conducted after 7, 14, 30, 60, 90, 120 and 240 days of the experiment. After the experiment end, overall content of organic carbon and nitrogen in the soils was determined.

Conducted research proved that dairy sewage sludge positively influences the microbiological and biochemical soil properties and can be considered as valuable waste in ferilisation aspect. The dairy waste sediment implemented in the soil stimulated microbial population depending on the amount of the waste used in soil, time of interaction, and also the type of soil. Stimulation of the tested microbial groups development was the most evident in the presence of the higher sedi-ment amounts (50 and 100 Mg ha-1). Dairy sewage sludge had, overall, similar to or higher than FYM influence on the amount of bacteria and soil fungi. Conducted research proved that the activity of tested soil enzymes and the intensity of the biochemical processes were stimulated by the sewage sludge intoduced into soil and that the level of the stimulation was similar to that of FYM.

Dairy sewage sludge stimulating influence on the enzymatic activity of soil intensified with in-crease in the amount of waste implemented into soil. Using higher than field dairy sewage sludge amount (50 and 100 Mg) did not cause any unfavourable changes, both in the amount of analysed microbial groups and in the activity of the biochemical processes present in the brown soil. Conducted corelation analysis proved that the microorganisms characterised by high metabolic activity have significant influence on the dynamics of many biochemical processes in soil enriched with dairy sewage sludge. Dairy waste sediment should be used in the vegetal production.