6. Sodic and non-sodic, brown and red 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 soils are slightly acidic at the surface becoming neutral to alkaline with depth. Subsoils have strong red mottling.

The surface soil is often a brown sandy loam (silty) to sandy clay loam, which is not structured (massive). It overlies a conspicuously bleached loamy sand to sandy clay loam subsurface horizon which is also massive with few coarse quartz fragments and common ferruginous nodules (buckshot).

There is a clear change to a mottled (red, yellow and brown) brown to yellowish brown, light to medium clay upper subsoil horizon. 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 15-40cm for the subsurface horizon.

Notable features include:

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