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 one third of the land mass being covered by sodic soils and 5% affected by soil salinity. Sodicity often coincides with the distribution of duplex soil profiles. In many areas these duplex soils are under agriculture. Sodicity substantially limits agricultural productivity. Although sodicity is considered to be an intrinsic property of the clay fraction of an affected profile, its full impact may be revealed through interactions with hydrological processes, resulting in various forms of both on-site and off-site environmental degradation. Some of the concepts, criteria and properties used to diagnose and classify sodic soils are discussed as a prelude to reviewing the nature and causes of the complex interactions which exist between related environmental problems such as dryland salinity, water erosion, waterlogging and water quality. There is a need for detailed studies to evaluate more thoroughly pertinent soil variables which link sodicity to both current and future environmental hazards, so that appropriate management strategies can be formulated.