The aim of the research was to determine the variability of the total numbers of bacteria, actinomycetes and fungi under stress associated with the presence of exogenous organic matter in the soil. Additonaly, the ratio of the total number of bacteria and actinomycetes to the number of fungi was calculated. Another goal of the experiment was to observe the effect of substrates absorbing water and minimizing drought stress on the number of soil microorganisms. Organic waste materials applied to the soil did not significantly affect the number of microorganisms, i.e. bacteria, actinomycetes or the ratio of bacteria and actinomycetes on the one hand to fungi on the other. The results of the research prove the possibility of utilizing organic matter produced by sewage treatment plants, waste treatment plants or mushroom farms as substances enriching the soil of urban green areas.