Methodological Problems of Assessing the Salinatization of Arid Soils by the Electrical Conductivity of the Liquid Phase

Rapid assessment of salinity based on the electrical conductivity of the liquid phase of the soil is widely used throughout the world. However, the results of such an assessment strongly depend on the soil–water relationship, while the known salinity standards based on electrical conductivity are proposed for a soil solution in the state of soil water saturation (full moisture capacity). Thus, a serious underestimation of the degree of salinity may occur when studying water extracts (suspensions) with an obviously higher soil–water ratio compared to the state of full moisture capacity. In this regard, the purpose of the study was to compare the GOST methodology in Russia with a soil–water ratio of 1 : 5 and the classical Richards method with the assessment of the electrical conductivity of the soil solution in a water-saturated state using the example of arid soils of different genesis and dispersion of the Republic of Uzbekistan. In contrast to well-known works on the empirical assessment of the influence of the soil–water relationship on the conductometric assessment of salinity, we applied the fundamental theory of dilution to justify the reduction of the results to a standard state of water saturation and the possibility of using the international classification of soils according to the degree of salinity. The results showed satisfactory agreement between the experimental data and the theory of solution dilution in the range of electrical conductivity values up to 30–35 dS/m, that is, up to a gradation of a very strong degree of salinity according to the international classification. Deviations from the theory can be explained by the nonlinearity of the dependence of electrical conductivity on the concentration of electrolytes and the immobilization of ions by the solid phase and thin pores, as well as a higher yield of electrolytes into solution at high dilution compared to the standard state of water saturation.