Irrigation - Australian Agriculture Assessment 2001 - Appendix 3 - Kurosols
KUROSOLS
Kurosols are distinguished by a clear or abrupt texture contrast between the A and B horizons. The upper part of the B horizon is strongly acid. Many of these soils have unusual subsoil chemical features such as high exchangeable magnesium, sodium and aluminium and very low calcium.
Red Kurosols
The Red and Brown Suborders are the most widespread Kurosols in Australia but are not extensive. The Bleached-Mottled, Natric, Red Kurosol described below is a typical example of a Kurosol with a sodic clay B horizon.
Environment
Distribution: Eastern coastal and subcoastal regions of southern Queensland, New South Wales, southern Victoria and Tasmania. Mt Lofty and Eyre Peninsula regions of South Australia and the south-west of Western Australia.
Climate: Mean annual rainfall ranges from 600 mm to 1200 mm.
Parent materials or substrate: Parent materials are mostly siliceous, in particular sandstones, metasediments and granitic rocks are common.
Landform: Occurs on a very wide range of landforms.
Native vegetation: Largely dependent on rainfall and ranging from eucalypt woodland to open forest.
Land use
Improved perennial pastures and grazing of native pastures. Native hardwood forests.
Common variants
The Red Kurosols vary widely in morphology and subsoil chemistry. The soils may have unbleached A2 horizons, B horizons may be whole coloured and lack columnar structure. They may be non-sodic, have high exchangeable magnesium, very low calcium and high extractable aluminium.
Nomenclature
Also known as Red Podzolic soils and Soloths.
Soil qualities
Water availability: Moderate water holding capacity in the root zone, depending on the depth of surface horizons. Storage capacity of the B horizon may vary greatly.
Drainage: Moderate. Surface soil may be water repellent.
Aeration: May be restricted by impermeable B horizons.
Physical root limitations: Tough clay subsoil.
Erosion hazard: Moderate to high wind and water erosion potential due to deep, loose, sandy surface.
Nutrient availability: Low nutrient retention. Phosphorus and organic matter deficient.
Toxicities: Acidity may limit root growth.
Workability: Good.
Acknowledgment
Photo, soil description and laboratory data from Primary Industries and Resources, South Australia. Site CH006.
Typical profile
Torrens Vale area, South Australia. |
Soil description of a typical profileA11 0 – 0.10 m Very dark greyish brown (10YR 3/2) sand; single grain structure; dry, very soft consistence; clear boundary to: A12 0.10 – 0.22 m Brown (10YR 4/3) loamy sand; single grain structure; dry, very soft consistence; gradual boundary to: A2e 0.22 – 0.75 m Light yellowish brown (10YR 6/4) sand; single grain structure; dry, very soft consistence; sharp boundary to: B21 0.75 – 0.85 m Red (2.5YR 4/6) medium heavy clay with yellowish red mottling; strong columnar structure; moderately moist, very hard consistence; gradual boundary to: B22 0.85 – 1.30 m Greyish brown (2.5Y 5/2) medium heavy clay with yellow and red mottling; weak prismatic structure; moderately moist, very hard consistence; diffuse boundary to: B3 1.30 – 1.70 m Light yellowish brown (2.5Y 6/4) sandy medium clay with yellow and red mottling; massive structure; moderately moist, very hard consistence; gradual boundary to: B3/C 1.70 – 2.00 m Pale yellow (2.5Y 7/4) sandy light clay with yellow mottling; massive structure; moderately moist, firm consistence. |
Laboratory data for the typical profile
Brown Kurosols
The Red and Brown Suborders are the most widespread in Australia but are not extensive. The clay subsoil of the Bleached-Vertic, Eutrophic, Brown Kurosol described below may shrink and swell on wetting and drying. The clay subsoil is non-sodic but high in exchangeable magnesium.
Environment
Distribution: Eastern coastal and subcoastal regions of southern Queensland and New South Wales, southern Victoria and Tasmania, Mt Lofty and Eyre Peninsula regions of South Australia and the south-west of Western Australia.
Climate: Mean annual rainfall range approximately 600 mm to 1200 mm.
Parent materials or substrate: Mostly siliceous rocks and sediments.
Landform: The soils occur on a very wide range of landforms.
Native vegetation: Eucalypt woodland and open forest are most common.
Land use
Improved pasture grazing for dairying, fat lambs and beef cattle. Otherwise beef cattle grazing of native pastures and timber from native hardwood forests.
Common variants
The Brown Kurosols may vary in both morphology and subsoil chemistry. A2 horizons may be absent and the B2 horizon may be whole coloured. The latter may also be sodic and have high exchangeable magnesium and very low calcium, but is not likely to disperse due to strong acidity.
Nomenclature
Also known as Soloths and Grey-brown Podzolic soils.
Soil qualities
Water availability: Moderate unless restricted by impenetrable B horizons.
Drainage: Often imperfectly drained due to restrictive heavy clay subsoils.
Aeration: Saturation may occur above the B horizon.
Physical root limitations: The dense clay subsoil may restrict rooting depth.
Erosion hazard: Moderate to low erosion risk.
Nutrient availability: Phosphorus deficient.
Toxicities: High extractable aluminium levels may affect sensitive species.
Workability: Good.
Acknowledgment
Photo, soil description and laboratory data from Department of Natural Resources and Environment, Victoria. Site 2 SW Gippsland.
Typical profile
South-west Gippsland, Victoria. |
Soil description of a typical profileSouth-west Gippsland, Victoria. Soil description of a typical profileA1 0 – 0.15 m Dark greyish brown (10YR 4/2) fine sandy clay loam; hardsetting surface condition; strong polyhedral structure; dry, very hard consistence; abrupt wavy boundary to: A2e 0.15 – 0.45 m Light brownish grey (10YR 6/2) fine sandy clay loam; root channel mottling; dry, firm consistence; clear wavy boundary to: B21 0.45 – 0.70 m Brown (10YR 5/3) medium heavy clay with brownish yellow (10YR 6/8) mottling; strong coarse prismatic parting to strong coarse blocky structure; dry, very hard consistence; gradual boundary to: B22 0.70 m+ Light brownish grey (10YR 6/2) medium clay with brownish yellow (10YR 6/8) mottles; strong coarse prismatic parting to strong coarse blocky structure; moist, firm consistence; slickensides present. |
Laboratory data for the typical profile
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