Classification of Salt-Affected Soils

Both EC_e and SAR are commonly used to classify salt-affected soils (Table 6). Saline soils (resulting from salinity hazard) normally have a pH value below 8.5, are relatively low in sodium and contain principally sodium, calcium, and magnesium chlorides and sulfates. These compounds cause the white crust which forms on the surface and the salt streaks along the furrows. The compounds which cause saline soils are very soluble in water; therefore, leaching is usually quite effective in reclaiming these soils.

Sodic soils (resulting form sodium hazard) generally have a pH value between 8.5 and 10. These soils are called "black alkali soils" due to their darkened appearance and smooth, slick looking areas caused by the dispersed condition. In sodic soils, sodium has destroyed the permanent structure which tends to make the soil impervious to water. Thus, leaching alone will not be effective unless the high salt dilution method or amendments are used.

Table 6. Classification of salt-affected soils based on analysis of saturation extracts. (Adapted from James et. Al., 1982)