EN
The aim of the present study was to determine the effect of soil contamination by insecticides on the counts of soil microorganisms. The experiment was established on brown soil developed from heavy loamy sand with pH 4.9. In some treatments the organic matter content was increased by compost aplication and /or liming (CaO). The counts of soil microbes were estimated on day 10 and 58 of the experiment. Contamination by insecticides disturbed the microbiological equilibrium in soil. Dursban had a positive effect on oligotrophic bacteria, while Nomolt on copiotrophic bacteria. Both insecticides decreased the counts of actinomycetes and Arthrobacter spp. The counts of all bacterial groups analyzed were found to be positively correlated with compost aplication. There was also a positive correlation between the counts of oligotrophic bacteria, copiotrophic bacteria, actinomycetes and fungi and the time of insecticide action.