Interrelationship between the physical properties and the humus content of chernozems in the south of European Russia

The humus content and the physical properties of soils are interrelated. The humus content correlates with the soil texture and, first of all, with the content and status of the clay fraction. Intensive agricultural use of soils leads to quantitative and qualitative changes in the clay fraction: the portion of aggregated clay increases, and the portion of firmly bonded clay decreases. This is accompanied by the transformation of firmly bonded humus into more active forms.