25. Sodic, red texture contrast soils/Older alluvial plains: Plains with and without leveed channels

These soils have developed on alluvium of Quaternary unconsolidated material in the Northern Riverine Plains, predominantly on the Wimmera River older alluvial plains (with and without prior streams). Some soils may be gradational and brown in places. The soil is slightly acidic at the surface but becomes alkaline just above or in the subsoil.

The surface soil is usually a dark yellowish brown sandy clay loam, which is weakly structured. This often overlies a bleached subsurface horizon, which is massive and just above the subsoil. There is a clear change to a yellowish red (occasionally brown) medium sodic clay. This is weakly structured (coarse sized peds, sometimes columnar). This grades into lighter textured, mottled lower subsoil often with calcium carbonate soft segregations or nodules, and occasional heavier regolith or buried soils. The profile depth is about 180 cm or more with variable depths of the surface horizons, generally 5 cm for the surface and 15 cm for the subsurface, occasionally deeper.

Notable features include:

• Texture contrast soil, generally low surface friability (generally hardsetting).
• Weak upper soil consistence, but very strong lower subsurface and upper subsoil consistence (strength when dry).
• Mottled subsoil only at depth; slightly restricted soil drainage.
• Soils often sodic at depth, if not sodic in upper subsoil.
• Occasional brown subsoil variants.