Studies were performed on a model of plot experiment (Department of Detailed Plant Cultivation, University of Agriculture in Lublin) set on brown soil developed from loess-like dusts at the Experimental Station in Felin. The following plants were cultivated: kaszubska vetch (Polish origin), Siberian vetch, chickling vetch, Sida hermaphrodita, Helianthus tuberosus, konopianka osier and American osier. Soil samples for analyses were taken three times at different developmental stages of plants from their rhizosphere zone. It was found, that in general, plants used in the experiment favored the development of proteolytic and nitrifying bacteria but reduced the growth of ammonifying ones. Papilionaceous plants enriched the soil environment in nitrogen with strong acidification. It made perfect conditions for hypha fungi development. The highest amounts of nitrates were found under papilionaceous plants. Ammonium nitrogen occurred in larger quantities under konopianka osier. The highest levels of both nitrogen forms were recorded under chickling vetch and in control soil, the lowest – under Sida hermaphrodita and Helianthus tuberosus. Thus, the studied plants exerted variable influence on bacteria entering nitrogen transformations.