Аннотация:Soils of unmanaged fallow lands differ from soils of conventionally background areas. The soils ofpostagrogenic (fallowed, abandoned) areas are characterized by the preservation of agrohumus horizons, the absence of forest litter, and the less pronounced podzolic horizon in comparison with soils of conventionally background areas. Agricultural development of soils and their further removal from agriculture lead to significant changes in the composition of soil organic matter. In the upper mineral horizons of postagrogenic soils, the total carbon content increases mainly due to an increase in the content of organic matter firmly bound with the mineral soil matrix.