The salts are white, chemically neutral and include the chlorides, sulfates and sometimes nitrates of calcium, magnesium, sodium, and potassium. Sodic soils are high in exchangeable sodium. Desirable cations in the soil include calcium, magnesium, potassium and ammonium. These cations readily interchange with one another. However, sodium also can occur in soils and replace desirable cations.
Sodic soils are hard and cloddy when dry and tend to crust.
Water intake usually is poor, especially in soils high in silt and clay. Saline-sodic soils contain large amounts of salts as well as high exchangeable sodium. If excessive salts are present as well as excessive sodium, the physical condition of the soil and water intake may be satisfactory, but plant growth may be restricted. Salinity and Sodium Determination Salinity is measured by conducting an electrical current through a soil solution made from a soil sample. An SAR value below 13 is desirable.