In the paper we examined microbial activity of rhizospheric soil in the poplar nurseries and plantations. Investigations were conducted on two systematic units of soils fluvisol form sandy clay and swampy gleys soil. Analyses were conducted in 2010 in the middle (July) and the end of vegetation (October). Investigated total number of bacteria, actinomycetes, fungi, aminoheterotrophs, azotobacters and as well as physical and chemical properties of soils. Total number of bacteria, number of actinomycetes and fungi was higher in the soils of poplar plantations. The number of azotobacters and aminoheterotrophs was higher in the soils of poplar nurseries. On the number of the microorganisms influenced the growing season. In the middle growing season were more numerous aminoheterotrophs and total number of bacteria and at the end of the vegetation azotobacters, actinomycetes and fungi.