Management of saline and sodic soils

Abstract

Saline and sodic (alkali) soils can significantly reduce the value and productivity of affected land. Soil salinity and related problems generally occur in arid or semiarid climates where rainfall is insufficient to leach soluble salts from the soil or where surface or internal soil drainage is restricted. Salinity problems can also occur on irrigated land, particularly when irrigation water quality is marginal or worse. It has been estimated that slightly more than one-fourth of irrigated farmland in the United States is affected by soil salinity. In humid regions salt problems are less likely because rainfall is sufficient to leach soluble salts from the soil, but even in higher rainfall areas, salinity problems occur. In some areas with high water tables, problems may occur with surface evaporation leaving salts to accumulate. In Kansas, salt-affected soils and related problems occur statewide but often on small areas. Field-wide problems often are due to poor quality irrigation water and/or excessive manure applications. Drilling activity causing high-salt water to escape to the soil surface, spills, or natural causes may result in spotty problems. Some areas of the state where salt mining occurs, particularly south central Kansas, have soils naturally high in sodium and soluble salts. Ions most commonly associated with soil salinity include the anions chloride (Cl-), sulfate (SO4), carbonate (HCO3), and sometimes nitrate (NO3) and the cations sodium (Na+), calcium (Ca++), magnesium (Mg++), and sometimes potassium (K+). Salts of these ions occur in highly variable concentrations and proportions. Saltaffected soils have been called white alkali, black alkali, gumbo, slick spots and other descriptive names. These names are associated with soil appearances caused by salt accumulation. The term alkali often refers to soils light in color and prone to surface crusting and implies that affected soils are high in exchangeable sodium. Salt-affected soils differ considerably in use suitability, productivity, ease of reclamation, and management.