The rheological properties of undisturbed samples of Typical Chernozem and Vertic Solonetz

The rheological properties of undisturbed monoliths of the Typical Chernozem of Kursk Oblast (Russia) and the Vertic Solonetz of Voronezh Oblast (Russia) are presented in this article. The rheological properties were determined by the amplitude sweep test on the rheometer MCR–302 (Anton Paar, Austria). It has been shown that the linear viscoelastic range (LVE-range) of the Vertic Solonetz significantly exceeds the LVE-range of the Typical Chernozem, which is probably related to the more heavy texture of the Vertic Solonetz. The storage modulus G` in the LVE-range of the Vertic Solonetz is much lower than Typical Chernozem. Perhaps, this fact is due to the higher silt fraction content (> 40–55%) and predominance of smectite minerals in them. Also, the weakening of inter-particle bonds in the Vertic Solonetz is related to the high alkalinity (pHH2O 8.5–9.3) and high content of exchangeable sodium (> 30%). Yield point of the Vertic Solonetz is considerably smaller than Typical Chernozem. The stability of the Vertic Solonetz to mechanical stresses is much less than the Typical Chernozem. The combination of heavy texture, smectite mineralogy, high alkalinity, exchangeable sodium percentage in soil leads to the degradation of the soil structure and reduces its resistance to mechanical loads.