Non-hardsetting Sodosols

These soils have a distinct texture contrast between the surface and subsoil horizons. The surface soil is usually non-hardsetting (ie. friable).

Group 12. Non-hardsetting (friable) Mottled Red Sodosols

Group 13. Non-hardsetting (friable) Mottled Yellow Sodosols


Main Characteristics

Soils included in the two groups above have the following characteristics:

• Strong texture contrast between surface (A) horizons and subsoil (B21) horizon.
• The surface soil is soft (non-hardsetting) ie. "friable".
• Commonly, the depth to the clayey subsoil is about 30 cm (range: 10-60 cm). Phases with surface horizons thicker than 100 cm also occur.
• The A2 horizon (subsurface soil) is either:
  Group 12. Present and conspicuously bleached or
  Group 13. Absent .
• Soil pedality is lacking in the surface horizons but is moderate to strong in the subsoils.
• Subsoil structure is typically columnar or prismatic.
• The subsoils are often sodic and contain appreciable amounts of soluble salts.
• The soil reaction trend is neutral (Group 12) or alkaline (Group 13).
• Profiles with alkaline reaction trends, usually contain segregations of CaCO3 (varied amounts) in their subsoils.

Description of Soil Groups

Group 12. Non-hardsetting (friable) Mottled Red Sodosols

These soils have distinct texture contrasts between soft ‘non-hardsetting’ surface horizons and clayey pedal subsoils.

Surface Soil

Commonly, the total thickness of these horizons varies between 30 to 60 cm.

A1 horizon:

This horizon ranges in colour from reddish brown to dark grey-brown and gradually becomes paler with depth. It is sand to light sandy loam; apedal (single grains to weakly coherent); loose to soft (dry and moist), and non-plastic and non-sticky (wet). Clear to gradual boundary to:

A2 horizon:

As above but thick (up to 50 cm) strongly bleached very pale brown to white. Clear to abrupt boundary to:

Subsoil

The upper part of the clayey subsoils (B horizons) is usually strongly mottled reddish brown to yellowish red sandy clay. Subsoil texture gradually changes to heavy clay and the degree of mottling may increase with depth. Soil consistence is usually hard (dry), non-friable (moist), plastic and sticky (wet). Degree of pedality is either moderate or strong and the structural units vary from blocky peds < 5 cm in size or large prisms and columns.

Soil Inclusions

Accumulations of black ferro-manganiferous (soft and/or hard) inclusions may occur, in varied amounts, in the A2 and B horizons.

Soil Reaction (pH)

The soil reaction trend shows a gradual increase in pH value down the profile. The soils are slightly acid at the surface, becoming neutral to alkaline at depth.

In the present survey, this group includes the following soil series:

Ledcourt Series



Group 13. Non-hardsetting (friable) Mottled Yellow Sodosols.

These soils have distinct texture contrasts between soft ‘non-hardsetting’ surface horizons and clayey pedal subsoils.

Surface Soils

About 15 cm thick, (a deep surface, up to 1 meter, phase also occurs). Brown to dark reddish brown loamy sand to sandy clay loam, apedal (single grains to weakly coherent), loose to soft (dry and moist), and non-plastic and non-sticky (wet). A2 horizons are absent. Clear to abrupt boundary to:

Subsoil

The upper part of the B horizon is whole coloured and ranges from reddish brown to grey-brown or yellow-grey sandy clay. The subsoils gradually change to heavy clay and become mottled at depth. Soil consistence is usually hard (dry), non-friable (moist), plastic and sticky (wet). Degree of pedality is either moderate or strong and the structural units commonly prismatic or columnar, parting to blocky peds.

Soil Inclusions

Accumulations of soft and/or hard CaCO3 occur, in varied amounts, in the B horizons.

Soil Reaction (pH)

The soil reaction trend shows a gradual increase in pH value down the profile. Usually the soils range from slightly acid to slightly alkaline at the surface, becoming moderately alkaline at depth.

In the present survey, this group includes the following soil series:

Narrewillock Series