EN
In order to compare the effect of organic and mineral fertilization of various soil types, long-term fertilization experiments frequently use indices, being a function of various parameters considered simultaneously; the content of organic carbon, microbiological parameters and soil enzymatic activity. The aim of the present research was to define soil fertility based on the values of Biochemical Soil Fertility Index (B). The index has been formulated based on the research results obtained: enzymatic activity, content of organic carbon and total nitrogen. The research material was sampled from topsoil of a many-year experiment which included varied organic and mineral fertilization, established on typical lessive soil. Soil samples were collected in 1998 from winter wheat stand, four times over the vegetation period. The following enzymes were determined: dehydrogenases, alkaline phosphatases, proteases and amylases. Additionally Corg and Ntotal and pH in 1 M KC.