Abstract. Numerous studies concerning the use of sludge were done on the nutritional properties of their in order to increasing production, only some studies have been done in our country in terms of ecological impact on soil microbial composition, richness or diversity. The main objective of our research was to assessment the impact of activated sludge on soil microflora and monitoring the presence of pathogenic bacteria with a high risk of contamination for human and animals in case of two cultures of forage crops Dactylis glomerata, and Medicago sativa. For this reason we initiated a field experience in spring of 2012 on Chernozem soil type from SDE Timisoara. The field experience ordered in Latin rectangle model assessed the impact of sludge applied in three doses respectively 15, 20 si 40 tones•ha-1 on. The microbial assays involved estimation of bacteria number, actinomycetes and fungi, and in the second weeks were analyzed the richness of pathogenic bacteria like total number of enterococcus bacteria, coliform bacteria and Escherichia coli. The results show that there are different answers regarding the number of edaphic microorganisms for the treatment administered. So, the larger difference compared with the control was recorded for bacteria number from soil under D. glomerata grass culture for dose of 40 t / ha sludge. In case of fungi the largest number were determined for 15 t ha sludge on soil under D. glomerata grass, and M. sativa culture also. But it was noted that increasing the quantities of sludge applied both to D. glomerata and M. sativa, determine decreases of the number of fungi in soil. After 2 weeks from sludge application did not find any presence of biological contaminants as fecal pollution indicators like Escherichia coli. A higher persistence showed enterococcus bacteria. In conclusion application of wastewater sludge causes temporary changes in the structure and composition of the soil microbial community for a period of time determined by the crop plant and weather. It seems that a drought period installed after applying the sludge has determined a fastest elimination of the pathogenic bacteria.

Keywords: edaphic bacteria, actinomycetes, Escherichia, enterobacteria

Presentation: oral