EFFECT OF FERTILIZERS AND BLACK FALLOW ON SMALL-PARTICLE FRACTION OF CHERNOZEM SOILS

The heterogeneous system of the soil and its mineral components are al tered by prolonged application of mineral and organic fertilizers and by constant black fallow condition. These procedures result in a decre ase in the strength of bonding between mineral components of micron si ze, the breakup of mica-smectite structures with a high percentage of smectite packets, and accelerated disintegration of clastic minerals. Application of manure prevents mobilization of the clay fraction and t he breakup of the smectite component. Increased yields after black fal low result from accelerated weathering of minerals, especially the lay ered clay minerals.