5. Sodic and non-sodic, yellow and brown texture contrast soils/Dissected Uplands: Low plateaux on Cainozoic sediments

This soil has developed on mainly Cainozoic (generally gravels and associated unconsolidated material) in the Western Uplands. There are associated minor gradational soils (Kandosols). The soil is slightly acidic at the surface becoming neutral to alkaline with depth.

The surface soil is usually a brown sandy loam, silty to sandy clay loam, with no structure (massive). It overlies a conspicuously bleached loamy sand to sandy clay loam subsurface horizon with no structure (massive) and contains variable amounts of coarse quartz fragments.

There is a clear change to a mottled (pale, yellow and red) yellowish brown to brownish yellow, light to medium clay. This is moderately structured (with coarse to medium sized peds) and grades into lighter textured weathered material. The profile depth is about 140 cm or more with variable depths of the surface horizons, generally 10 cm for the surface and 15-40 cm for the subsurface horizon.

Notable features include:

• Texture contrast and associated structure differences between the surface horizons and subsoil.
• The occasionally strongly sodic subsoil.
• Coarse fraction component of the soil and subsurface horizon with low nutrient capacity and low water holding capacity and the densipan above the subsoil.
• These features make these soils vulnerable to sheet and rill erosion particularly on sloping terrain given poor drainage characteristics and lighter surface materials and compaction of the subsurface and upper subsoil horizons.