Agriculture in Western Siberia is a dynamically developing sector that has its firm foundation in results of agricultural research. Plowing-up of high-fertility soils led to changes in the direction of soil formation. It reflected in their quality and productivity. Vastly increased anthropogenic burden had negative impact on humus formation and acid-base characteristic of the croplands. To prevent deterioration of quality and develop measures for its reclamation, a complex of multi-year research is necessary. Its goal is monitoring the dynamics of humus state, acidity and composition of arable chernozem cations in Western Siberia. The research was conducted in the Northern Trans-Ural State Agricultural University, at a station located in Tobol-Ishim interstream area of the eastern periphery of the Trans-Uralian Plateau. The multiyear research led to establishing that plowing of leached chernozems leads to increased humus mineralization that has a negative impact on the state of the humus. In 40 years, the loss of soil organics in the 0-20 cm layer amounted to 54 t/ha, of which 9 tonnes migrated deeper into the soil profile. Increased biogenic depletion and leak of calcium and magnesium facilitated acidification of the arable black soil: during the years of the studies, exchangeable acidity increased from 5.5 to 5.0 units, hydrolytic acidity increased from 3.7 to 4.6 mmol/kg. Anthropogenic changes in fertility of arable black soil are seen throughout the humus layer.