Australian Natural Resources Atlas

Natural Resource Topics

Australian Agriculture Assessment 2001

Australian agriculture assessment 2001
National Land and Water Resources Audit, 2001

Appendix 3 - Sodosols

Solosols Map

Sodosols are a specific kind of sodic soil with a clear or abrupt textural B horizon, which is not strongly acid and has an exchangeable sodium percentage (ESP) of 6 or greater in its upper part. The B horizons are usually clayey with restricted hydraulic conductivity caused essentially by the dispersive nature of the sodic clay. An ESP of 6 is the critical limit for the sodicity to have an adverse affect on productivity of the soil.

Red Sodosols

The Red Suborder is the second most common of the colour classes next to the Brown Suborder. The Hypercalcic, Mottled-Hypernatric, Red Sodosol described below has an ESP greater than 25 and has more than 20% soft carbonate in the B horizon and up to 20% hard calcrete fragments/ nodules/ concretions or coated gravel.

Environment

Distribution: Red Sodosols are widely distributed in the arid and semi-arid regions, particularly in Western and South Australia, western New South Wales and Queensland.

Climate: Broad mean annual rainfall range, approximately 250 mm to 1200 mm.

Parent materials or substrate: Most commonly occur on alluvial/ colluvial deposits, also on aeolian accessions and acidic to intermediate igneous, metamorphic and sedimentary rocks.

Landform: Gently undulating plains to some low, hilly areas.

Native vegetation: Depending on rainfall, ranges from arid low open shrublands to mallee shrublands and open woodlands. Open forest is rare.

Land use

Sparse sheep and beef cattle grazing in arid regions. In the Mediterranean climatic zone wheat and barley are grown in conjunction with sheep grazing. Small areas are irrigated for pastures in Victoria and New South Wales.

Common variants

Red Sodosols may vary widely in both morphology and chemistry. A horizons range from sand to clay loam with most soils having bleached A2 horizons. B horizons may be whole coloured and their structure may be blocky rather than columnar or prismatic. Carbonate content can vary in kind and amount and B horizon sodicity can range from ESP 6 to greater than 40.

Nomenclature

Also known as Solodized Solonetz and Solodic soils.

Soil qualities

Water availability: Moderate to very low depending on the thickness of the A horizon.

Drainage: Imperfectly drained. Soil may remain saturated for several weeks. Sandy surface soils are commonly water repellent.

Aeration: Poor aeration in the A2 horizon.

Physical root limitations: Dense clay subsoil may restrict roots.

Erosion hazard: High when exposed by cultivation or over grazing.

Nutrient availability: Low organic matter. Most likely to be deficient in phosphorus, nitrogen, copper and zinc.

Toxicities: Moderate salinity in the lower subsoil horizons and possible boron toxicity.

Workability: Wide variation but good for loose, soft surfaces ranging to poor for hardsetting surfaces.

Acknowledgment

Photo, soil description and laboratory data from Primary Industries and Resources, South Australia. Site MM 035.

Typical profile

Typical profile from Southern Murray Mallee, South Australia.
Southern Murray Mallee, South Australia.

Soil description of a typical profile

Ap 0 – 0.09 m Very dark greyish brown (10YR 3/2) loamy sand; single grain structure; abrupt boundary to:

A1 0.09 – 0.18 m Brown (10YR 4/3) loamy sand; single grain structure; clear boundary to:

A2e 0.18 – 0.23 m Light yellowish brown (10YR 6/4) sand; single grain structure; sharp boundary to:

B1t 0.23 – 0.38 m Yellowish red (5YR 4/8) sandy light clay with yellowish brown (10YR 5/8) mottles; strong columnar structure; gradual boundary to:

B2tk 0.38 – 0.54 m Red (2.5YR 4/6) medium clay with yellowish brown (10YR 5/8) mottles; 5% carbonate; moderate granular structure; gradual boundary to:

B3k 0.54 – 1.34 m Yellowish red (5YR 5/8) sandy clay with brownish yellow (10YR 6/6) mottles; highly calcareous 10 – 20% calcareous nodules; massive structure; diffuse boundary to:

C 1.34 – 1.90 m Red (2.5YR 4/6) heavy clay with pale brown (10YR 6/3) mottles; strong prismatic structure.

Laboratory data for the typical profile
Laboratory data for the typical profile

Grey Sodosols

The Grey Sodosols are one of the most common and widespread of the Suborders. A description of a typical Calcic, Mottled-Mesonatric, Grey Sodosol is given below.

Environment

Distribution: The Grey Sodosols are widely distributed in eastern, southern and south-western Australia.

Climate: Seasonal rainfall ranging from 300 mm to 1200 mm.

Parent materials or substrate: Wide range of rocks (other than more basic forms) and derived alluvial and colluvial deposits.

Landform: Plains, undulating and rolling landscapes and hilly slopes.

Native vegetation: Woodland and open woodland, some mallee shrublands in regions of southern Australia experiencing a Mediterranean climate.

Land use

The largest areas of Grey Sodosols in eastern Australia are used for the grazing of native pastures, mainly by beef cattle. In southern Australia they are used for winter cropping of cereals and some grain legumes.

Common variants

A horizon thickness may range up to 0.25 m and the degree of A2 bleaching may also vary. Some upper B2 horizons may be whole coloured. The degree of sodicity and amount of carbonate may differ in individual profiles.

Nomenclature

Commonly known as Solodized Solonetz and Solodic Soils.

Soil qualities

Water availability: Low to very low (< 50 mm) and controlled primarily by the depth of the A horizon.

Drainage: Poorly drained, slowly permeable. Shallow, saline watertables may develop.

Aeration: Restricted aeration in the A2 and B horizons.

Physical root limitations: Dense, sodic clay subsoils may inhibit root development.

Erosion hazard: Sandy surface soils are subject to wind erosion and dispersive subsoils are prone to gully erosion.

Nutrient availability: Poor due to shallow, sandy surface soil.

Toxicities: Surface soil may develop strong acidity.

Workability: Good, providing clay subsoil is below the depth of cultivation.

Acknowledgment

Photo and soil description from Agriculture Western Australia. Laboratory data from McArthur (1991), p. 173.

Typical profile

Typical profile from Narrogin district, south-west Western Australia.
Narrogin district, south-west Western Australia.

Soil description of a typical profile

A1 0 – 0.03 m Dark greyish brown (10YR 4/2) sand; single grain; dry, soft consistence; abrupt boundary to:

A2e 0.03 – 0.05 m Light brownish grey (10YR 6/2) clayey sand; massive structure; dry, soft consistence; sharp boundary to:

B21 0.05 – 0.30 m Light brownish grey (10YR 6/2) sandy light clay with many distinct brown mottles; columnar structure coated with white, bleached, clayey sand; moist, very hard consistence; gradual boundary to:

B22 0.30 – 0.60 m Light grey (10YR 6/1) sandy light clay; moist, firm consistence; gradual boundary to:

B23 0.60 – 0.90 m Yellow light medium clay with (20 – 50%) distinct grey mottles; (2 – 10%) carbonate nodules; clear boundary to:

BC 0.90 – 1.25 m Yellowish brown light medium clay with common grey mottles.

Laboratory data for the typical profile
Laboratory data for the typical profile

Black Sodosols

The Black Suborder is less common than most of the other colour classes. The Vertic (and Calcic), Mottled-Mesonatric, Black Sodosol described below has an ESP between 15 and 25, displays vertic properties and has a calcareous lower B horizon.

Environment

Distribution: Mainly occurring in the subhumid to semi-arid regions of eastern Australia, often associated with Vertosols.

Climate: Mean annual rainfall ranges from 400 mm to 800 mm, is summer dominant in Queensland and winter dominant in the south.

Parent materials or substrate: Most commonly occur on alluvial clayey deposits on flood plains, also on intermediate igneous, metamorphic and sedimentary rocks.

Landform: Plains and undulating or rolling landscapes but may also occur on hilly slopes up to 30%.

Native vegetation: Mainly eucalypt woodlands and some Acacia open forests.

Land use

The eastern Australian Black Sodosols are used for both summer and winter cereals with small areas of irrigated pastures and cotton. Elsewhere they are used mainly for beef cattle grazing of native pastures.

Common variants

A bleached A2 horizon is present in many Black Sodosols. B horizons are often whole coloured and columnar or prismatic structure is common. High amounts of carbonate are uncommon but B horizon sodicity is often high (ESP >25).

Nomenclature

Also known as Solodized Solonetz and Solodic soils.

Soil qualities

Water availability: Low to very low depending on A horizon thickness.

Drainage: Moderately to imperfectly drained.

Aeration: Restricted aeration in the A2 and B horizons.

Physical root limitations: Effective rooting depth approximately 0.50 m, restricted by the strongly sodic and dispersive subsoil.

Erosion hazard: Low, provided vegetation cover is adequate.

Nutrient availability: Molybdenum, calcium, magnesium and potassium deficiencies in strongly acid surface horizons.

Toxicities: Aluminium problems may occur in the strongly acid surface soils.

Workability: Excessive cultivation may lead to surface sealing and hardsetting.

Acknowledgment

Photo, soil description and laboratory data from Department of Natural Resources and Environment, Victoria. Site LP 65.

Typical profile

Typical profile from Lexton distric, south-west Victoria.
Lexton distric, south-west Victoria.

Soil description of a typical profile

A11 0 – 0.25 m Dark brown (10YR 3/3) fine sandy clay loam; hard setting surface; weakly structured; 5% ferromanganiferous nodules; rusty root channel mottling; dry, firm consistence; abrupt and wavy boundary to:

A2 0.25 – 0.30 m Brown (10YR 4/3) fine sandy clay loam; weakly structured; 5% ferromanganiferous nodules; rusty root channel mottling; moist, firm consistence; sharp boundary to:

B21 0.30 – 0.55 m Dark grey (10YR 3/1) heavy clay with yellowish brown (10YR 5/8) mottles; moderate coarse blocky structure; moist, firm consistence; clear boundary to:

B22 0.55 – 0.80 m Greyish brown (10YR 5/2) medium heavy clay with a yellowish (10YR 7/6) diffuse mottle; moist, very hard consistence; clear boundary to:

B23k 0.80 – 1.00 m Greyish brown (10YR 5/2) medium heavy clay; 2 – 5% soft carbonate and trace (2%) hard carbonate; slickensides below 0.70 m; moist, very hard consistence; abrupt boundary to:

BC 1.00 m+ Dark greyish brown (10YR 4/2) sandy clay loam; moist, very hard consistence; 5% manganese flecks.

Laboratory data for the typical profile
Laboratory data for the typical profile

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