Sodosols (Australian Soil Classification) are soils that have strong texture contrast between the surface (A) horizons and the clay subsoil (B) horizons. The subsoil is sodic not strongly acid i.e. pH is greater than 5.5 in water.
Sodosols are common on basalt plains and rises throughout much of the region. They are also common on sedimentary plains and rises south of the Princes Highway in lower rainfall areas. The subsoils of Sodosols in the region also often display a strong shrinking and swelling characteristic i.e. vertic, and the subsurface horizons can be ferric i.e. contain significant amounts of ferruginous nodules ‘buckshot’.
The sodic subsoils often disperse and are usually dense and coarsely structured. This results in restricted root and water movement into the subsoil. Waterlogging can be common in wetter periods. In basalt areas, the subsoil horizons can become calcareous at depth.
Sodosols in the Corangamite Region
This broad scale map presents an overview and should only be used as a general indication of the distribution of Sodosols in the Corangamite Region. It shows areas where Sodosols are most likely to occur within the region. Note that other soil types may also occur within these mapped areas.
This map has been developed from work undertaken by Robinson et al. (2003) as part of the Corangamite Land Resource Assessment project. This work utilised existing surveys, remote sensing information and additional field-work to develop an updated 1:100 000 scale soil/landform coverage across the region.
Soils are difficult to map at this broad scale because of their diversity. Even in relatively small areas a number of soils may occur, which relate to differences in topography and landscape position. Variation in some of the major soil profile properties can also occur within these mapped areas. Any agricultural enterprise should be based on a proper on-site assessment of the soil and landscape.
A number of soil surveys have been completed in this region at varying scales and intensity. However, in some areas very little soil survey has taken place. See the Soil and Land Survey Directory for details.
Black Sodosol near Colac with pronounced
coarse prismatic structure in the subsoil.
Sodosol near Colac with very coarse columnar structure in the subsoil.