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The studies were conducted on the model of a plot experiment of the Chair of Detailed Cultivation of Plants at the University of Agriculture in Lublin. The plot was established in 1999 at the Agricultural Experimental Farm Felin. The following plants were cultivated on the plots: Vicia cassubica of Polish origin, vetch brought from Siberia, chickling vetch, Sida hermaphrodita Rusby, topinambur (Helianthus tuberosus), osier willow and Salix americana. The soil samples were taken for analysis from the sphere where the plant roots were active, while the control consisted of the soil distant from the root system of plants. Microbiological and biochemical analyses were carried out three times in 2001 in different periods of plant vegetation. The studies showed that the examined papilionaceous acidified the soil environment, which was accompanied by stimulation of the development of filament fungi. The other experimental plants inhibited the development of these microorganisms only a little. The studies plants stimulated the total number of bacteria and ammonification bacteria in a small degree at the same time inhibiting the development of cellulolytic bacteria a little. The occurrence of nitrification bacteria was differentiated. Some of the examined plants stimulated their development while others, for example Sida hermaphrodita Rusby and Lathyrus sativus, inhibited it. The greatest quantity of both studied forms of nitrogen was found in the soil under the papilionaceous. All the examined plants only slightly stimulated the amount of exudated CO2. Bacilla, especially isolated from under chickling vetch and both species of osier, proved to be the strongest ammonifiers out of the distinguished strains of bacteria. On the other hand, the strains of caryopses, especially isolated from the soil from under chickling vetch, were the poorest ammonifiers. All the examined plants had a differentiated effect on the number of the analyzed communities of soil microorganisms and their activity. Some of these plants stimulated, and some inhibited the growth of the studied microorganisms.