The impact of 5, 45, and 75 year agricultural use of a clayey loam Haplic Chernozem on its selected quality indicators was determined. Contents of soil organic matter and microbial biomass carbon were equal to 43.1±2.2 g C kg-1 soil and 480.0± 67.6 mg C kg-1 soil in the fallow land. Soil organic matter content in the agricultural soils ranged from 30.2±1.8 (75 year plot) to 47.5±2.1 g C kg-1 soil (5 year plot), while microbial biomass carbon content varied from 340.2±5.9 (75 year plot) to 371.2±10.2 mg C kg-1 soil (5 year plot). Among the three agricultural treatments, only the 75 year one resulted in a significant decline in total amounts of water-stable aggregates (70.8±8.2%) and clay content (26.9±1.0%), compared to those parameters in the fallow land (90.1±9.4% and 30.5±1.2%, respectively). Distribution of the minimum values of differential entropy of water vapour adsorption in the soil also showed that the 75 year agricultural management unfavourably affected the thermodynamic state of soil solid phase.