23. Cracking clay soils/Older alluvial plains: Plains with and without leveed channels and Alluvial fans and aprons

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). This soil is alkaline throughout.

The surface soil is usually a light to medium clay, usually structured (occasionally massive). These soils have strong consistence (strength) depending on moisture condition. There is a clear change to a dark grey (occasionally grey) heavy clay. This has moderate structure (with coarse size peds), subplastic often with few calcium carbonate nodules throughout the profile. The subsoil has slickensides indicating high shrink-swell characterisitics. This often grades into lighter textured alluvial material at depth. The profile depth is about 160 cm or more with variable depths of the surface horizons, generally 5 cm for the surface.

Notable features include:

• Cracking clay soil, variable surface friability (may be massive or slightly self-mulching).
• Strong consistence (strength) when dry.
• The surface soil is subplastic and the subsoil is sodic, strongly at depth and has vertic properties.
• The paler, yellower hued subsoil has restricted soil drainage.