South Coast Sandplain WA – Soils

Description of soils

The landscape in the South Coast Sandplain of WA is dominated by broad undulating plains broken occasionally by incised river and creek systems close to the coast in the western portion of the region and broad flat lake systems in the east.

Soils (Figure 1) are varied however they are broadly identifiable by organically stained sandy top soils overlying leached white and yellow sands over weathered clays. Dominant soil groups are sandy duplex with alkaline subsoil, gravelly sandy duplex, deep sandy duplex with gravel and deep sand (>80cm). These soils are characterized by high sand content (up to 95% in the A horizon) of varying size fractions, low silt and clay content and in some cases lateritic gravels. This has implications for the physical, chemical and biological properties of these soil profiles.

The poor nature of the surface soils are often tempered by the subsoil clays which are often alkaline in nature, with good buffering capacity, subsoil structure, rooting depth, nutrient and moisture retention. This results in often favorable growing conditions for crops where the clays are deep enough to reduce the chance of waterlogging in the top 30cm but are still shallow enough to be utilised by the roots of crops and pastures.

The high rainfall areas of the south coast sand plain are more variable again. There are areas of deep sands and gravelly sand duplexes, however as you move into the >600mm areas there is an increase in gravelly and loamy soils. Pockets of high fertility karri loams are found in the Walpole and Denmark areas.

Several production and environmental issues are associated with soils in the region.  These are described under Environmental Issues and include sub-soil acidity, water repellence, wind erosion, compaction, waterlogging, secondary salinity and phosphate leaching.

A description of suitable pasture species and trends for the South Coast Sandplain is provided under Pastures

Figure 1: Soil types of the south coast
Figure 1: Soil types of the South Coast Sandplain of WA

Regional Information


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