SOIL TYPES

Classification and characteristics

Wendy Jansenwww.copleysociety.org

CONTENTS

Soil Types Australian Soil Classification Great Soil Groups Ferrosols Sodosols Gypsum Dispersion test

Parent material Climate Topography Organic activity Age

Several factors influence the distribution of soil types

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SOIL TAXONOMY - AUSTRALIAN CLASSIFICATION

Order 14 soil

orders Each order is

identified by a word

ending in 'sol.'

Suborder

Each order is divided and is important to plant growth

Great Group Each

suborder is divided into great groups on the basis

of similarities in horizons,

soil moisture or

temperature

Subgroup Each great group has a

typical subgroup which is basically

defined by the Great

Group.

Family Families are established

within a subgroup on the basis of physical and

chemical properties along with

other characteristics that affect

management.

GREAT SOIL GROUPS

AUSTRALIAN SOIL CLASSIFICATION

14 soil orders.

Each one describes key attributes of that soil including colour, texture, and structure.

http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/

Name of order Derivation Connotation Types

Anthroposols Gr.anthropos, man 'human-made' soils

Calcarosols L. calcis, lime calcareous Brown, grey and red soil.

Chromosols Gr. chroma, colour often bright coloured Brown/red earth

Dermosols L. dermis, skin clay skins on ped faces Red and yellow

Ferrosols L. ferrum, iron high iron content Krasnozem

Hydrosols Gr. hydor, water wet soils Humic grey

Kandosols Kandite clay minerals Lack clear horizons Red, yellow, grey

Kurosols - pertaining to clay increase Podzolic

Organosols - organic materials Neutral pH

Podosols Rus. pod, under; zola, ash podzols Humic peats

Rudosols a beginning rudimentary soil Siliceous sands

Sodosols - influenced by sodium Red, brown, desert loams

Tenosols L. tenuis, weak, slight weak soil development Sands, alluvial

Vertosols L. vertere, to turn shrink-swell clays Clays

FERROSOL

Their B2 horizon has high free iron oxide (Fe >5%).

These soils are only found in well-drained sites with

rainfall between 700mm and 1450mm.

High agricultural potential because of their good structure and water-holding capacity.

Krasnozems may suffer from acidification and nutrient leaching.

They also have potential for structural decline.

www.soil.org.au/

FERROSOL (IRON SOIL) THE RED SOIL

Ferrosol is formed from Tertiary Basalt and is of volcanic origin.

The red colour is due to oxides of iron. Oxides are an indication of well-aerated and therefore free-draining soil.

Soil depths can be 6m+ and well-structured throughout.

DISTRIBUTION OF FERROSOLS IN AUSTRALIA

www.soil.org.au/

SODOSOL

Highly sodic B horizon Found in poorly drained

sites with rainfall between 50mm and 1100mm.

Low agricultural potential with high sodicity leading to high erodibility,

Poor structure and low permeability.

www.soil.org.au/

SODIC SOILS Sodic soils are those soils with a high proportion of sodium

ions relative to other cations in the soil or water.

There are large areas of soils in Australia which have developed on sedimentary parent rock.

Soils containing high amounts of sodium.

Sodic soils are traditionally defined as having an exchangeable sodium percentage (ESP) of greater than 6%,

Sodicity promotes swelling and dispersion in clay soils. Salinity

has the opposite effect.

Saline soils are those with an high concentration of any kind of salt,

GYPSUM Calcium sulphate is

known as the clay breaking chemical.

Gypsum has been widely used as a calcium source to replace sodium.

Often misused. Only improves soil

structure of sodic clays. When gypsum is

applied it dissolves in water and stops clay dispersing.

.

Operating face in a cross-bedded gypsarenite dune, Cooke Plains S.A www.pir.sa.gov.au/minerals/geological

HOW TO TEST FOR SODICITY

Dispersion test 100ml of rainwater Add 4mm

aggregates Wait 2 hours Cloudy = Sodic The clay has

dispersed.

www.vro.dpi.vic.gov.au/dpi/Simulating cultivation

Dry aggregates

References

Australian Soil Club http: www.soil.org.au/accessed 09/10/10Isbell, R.F 2002. The Australian Soil Classification. CSIRO. ACT.Lines –Kelly, R. 1994. Soil Sense. NSW Agriculture. Wollongbar.Morand,D.T. 1996 Soil Landscape Murwillumbah – Tweed. Land and Water Conservation.Sydney.Steven R Raine1 and Rob J Loch2 What is Sodic Soil? National Centre for Engineering in Agriculture, University of Southern Queensland.Young A and R, 2001 Soils in the Australian Landscape. Oxford University Press. Victorian Government http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/gloss_DG#dispersion accessed 05/10/12