An overview of acid-sodic soils in two regions of New South Wales, Australia

Acid-sodic soils are relatively common throughout eastern New South Wales. Such profiles are thought to be less erodible than the alkaline sodic soils due to the abundance of aluminium and its role in suppressing dispersion. Few studies appear to have been carried out on these soils, although field evidence suggests that they are highly erodible and susceptible to degradation. This paper examines the properties of some acid-sodic soils from two regions of New South Wales - the Northern Rivers region of the far north coast and the Southern Tablelands. The soils examined in the Northern Rivers are generally Grey Kurosols with natric, natric-magnesic or magnesic great groups, and/or sodic subgroups. Soils examined in the Southern Tablelands are generally Yellow Kurosols with natric, natric-magnesic or magnesic great groups or sodic subgroups. Relationships between ESP, dispersion, CEC and aluminium in these profiles were complex and generally no trends were discernible. Exchangeable aluminium and magnesium levels were large. Exchangeable sodium percentage (ESP) was found to be a poor indicator of soil sodicity and dispersive behaviour. Landscape relationships were generally consistent, with most acidsodic soils occurring in lower slope and depositional positions. The role of parent material (geology), clay mineralogy, landform evolution and climate should be investigated to help further understand the origins and behaviour of these soil types.