The effect of system mineral and organic-mineral fertilization on the humus content and humus fractions in mollic fluvisols in condition of long-term fi eld experiment was studied. Forty years period of organic-mineral fertilization (N420P260K380 + 27 t/dka manure) have had stabilizing effect on humus content in the soil. The system mineral fertilization led to a slight decrease of soil humus. The humus type was not infl uenced from the fertilization.
