At present, the development of agriculture is impossible without the use of fertilizers which provide increased soil fertility and yields as well as improve the quality of agricultural products. However, it can lead to signifcant changes in the composition, properties and formation of arable soil regimes. First of all, the negative influence of fertilizer materials on the environment is related to their chemical composition and presence of ballast substances. The maximum permissible concentrations of chemical elements in the soil must be taken into account under applying fertilizer materials for each crop. The research was conducted under the conditions of a long stationary feld experiment using different levels of mineral fertilizers of N 45P45K45, N90P90K90 and N135P135K135. . The research results reveal that different doses of mineral fertilizers have an effect on the change of the specifc activity of radioactive isotopes in the soil (226Ra, 232Th, 40K, 137Cs, 90Sr) in their long-running application (50 years). The specifc activity of radionuclides in podzolized chernozem and in winter wheat grain was established. Winter wheat plants accumulated 232Th most of all but the use of fertilizers reduced it due to biological dilution in larger mass of the crop. The absorption of radioactive nuclides by winter wheat grain after cultivation after peas and silage corn depended on fertilization varied similar to that of the clover predecessor. According to the specifc activity of radioactive nuclides in the soil and winter wheat grain, the coefcient of their biological absorption is calculated. Absorption of radionuclides by soil prevents them from moving through the profle and further penetration into groundwater. Thus, their specifc activity was two times lower at the depth of 40–60 cm than in the soil layer of 0–20 cm. This indicates that radioisotopes are fxed in the upper layers of the soil which in turn increases their entry into crop production.

Key words: radioactive isotopes, radium, thorium, potassium, cesium, strontium, specifc activity of radioactive nuclides.