ENVIRONMENTAL CONSEQUENCES OF SOIL SODICITY

Australia has the highest ratio of salt-affected soils in relation to total surface area of any continent in the world, with approximately o ne third of the land mass being covered by sodic soils and 5% affected by soil salinity. Sodicity often coincides with the distribution of d uplex soil profiles. In many areas these duplex soils are under agricu lture. Sodicity substantially limits agricultural productivity. Althou gh sodicity is considered to be an intrinsic property of the clay frac tion of an affected profile, its full impact may be revealed through i nteractions with hydrological processes, resulting in various forms of both on-site and off-site environmental degradation. Some of the conc epts, criteria and properties used to diagnose and classify sodic soil s are discussed as a prelude to reviewing the nature and causes of the complex interactions which exist between related environmental proble ms such as dryland salinity, water erosion, waterlogging and water qua lity. There is a need for detailed studies to evaluate more thoroughly pertinent soil variables which link sodicity to both current and futu re environmental hazards, so that appropriate management strategies ca n be formulated.