Soils of Arid Areas

The exchange capacity of soils in and areas (second group) is filled with calcium, magnesium, and sodium cations and the same cations dominate in the soil solution. Therefore, the electrical parameters show strong relationships with these cations. A strong exponential relationship was obtained between electrical potential, measured on soil surface with the self-potential method and the sum of Ca, Mg, and Na (r = 0.810). For the sodium content alone and electrical potential, the relationship is also exponential with r = 0.599. The Na/(Ca+Mg+Na) ratio is related with the electrical potential by the linear relationship with r = 0.543. Electrical potential decreases with the increase of relative amount of sodium in Aridosols. The same type of linear relationship with r = 0.356 was obtained for Al/(Ca+Mg+Al) ratio and the electrical potential in Alfisols of humid areas. Such ratios are important for soil genesis studies, since they indicate the degree of sodicity in Aridisols, and the degree of eluviation (podzolization) in Alfisols and Spodosols. The obtained relationships can be used to study the soil-forming processes in these soils. Since soil salinity in soils of the second group is the summary characteristics of the available electrical charges, the electrical parameters are strongly related with the total soil salinity. Figure 5 shows the schematic curvilinear relationship between electrical resistivity or potential and soil salinity for the soils of second group.

Figure 5 Schematic relationship between electrical parameters and soil properties showing approximate distribution of data for soils in arid areas.