ИСТИНА

Rheological properties of undisturbed monoliths of Typical Chernozem of Kursk region (Russia) and Vertic Solonetz of Voronezh region (Russia) have been investigated. The rheological properties were determined by the amplitude sweep test on the rheometer MCR-302 (Anton Paar, Austria). Measurements were carried out at a moisture content of 3-day capillary humidification. It has been shown the linear viscoelastic range of Vertic Solonetz significantly exceeds the value of LVE-range of Typical Chernozem. This fact is probably related to the more heavy texture of Vertic Solonetz. At the same time, the storage modulus in the linear viscoelastic range of Vertic Solonetz`s sample is much weaker than of Typical Chernozem`s sample. Perhaps, this fact is due to a higher content the silt fraction (>40-55 %) and the predominance of smectite minerals in them, which leads to the formation of weak interparticle bonds due to the expanding crystal lattice, and the greater amount of absorbed moisture. The value of the intersection of storage modulus and loss modulus (crossover, yield point) of Vertic Solonetz`s sample is considerably smaller than of Typical Chernozem`s sample. This is evidence that Vertic Solonetz has faster transition to a viscous state with increasing of stress than Typical Chernozem. The structural properties of Vertic Solonetz, its stability to mechanical stresses is much less than that of Typical Chernozem. The combination heavy texture, smectite mineralogy, high alkalinity, exchangeable sodium percentage and low total salt concentration in soil solution leads to the degradation of the soil structure and reduces the resistance to mechanical loads.