The mineral fertilization of arable land positively affects an increase of the biological productivity of various ecosystems as well as the microbial activity in soil. From the three elements N, P, K used for fertilization ± nitrogen is one of the most important factors affecting soil fertility and productivity as well as the growth and development of cultivated plants. The chemical studies show that high N rates of fertilization result in the formation of carcinogenic nitrosamines in soil environments. The use of mineral N resulted in significant changes in microbiocenoses under investigated ecological condition. The decline of some beneficial microorganisms, as well as the occurrence of carcinogenic nitrosamines in soil, were the symptoms of changes in the environment.