The term "duplex" is used in Australia for soils with contrasting texture between

soil horizons A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

, although such soils are found in other parts of the world. Duplex soils are also termed "texture contrast soils". With the term "duplex soil", Northcote defined a primary profile in his ''Factual Key'' classification.Northcote, K. H., and CSIRO. 1979. A factual key for the recognition of Australian soils / by K.H. Northcote. 4th ed. Adelaide, S. Aust: Rellim Technical Publications. He described a group of texture contrast soils where the

B horizon A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

is dominated by a texture class one and a half (or more) finer than the

A horizon A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

. In addition, the clear to sharp change between the two horizons must occur within 0.1 m.

Texture Texture may refer to: Science and technology * Image texture, the spatial arrangement of color or intensities in an image * Surface texture, the smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface c ...

in duplex soils is highly variable, with the top-soils ranging from coarse sand to clay loam and the subsoils from

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

to heavy

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

.Tennant, D, G Scholz, J Dixon, and B Purdie. 1992. Physical and chemical characteristics of duplex soils and their distribution in the south-west of Western Australia. Australian Journal of Experimental Agriculture 32 (7):827-843.Gardner, WK, RG Fawcett, GR Steed, JE Pratley, DM Whitfield, Hvan Rees, and Rees H Van. 1992. Crop production on duplex soils in south-eastern Australia. Australian Journal of Experimental Agriculture 32 (7):915-927 Some duplex soils are distinguished by the presence of an A2 bleached horizon, a character also used as a diagnostic key for the distinction between these types of

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

s. The diagnostic properties used by Northcote for the definition of duplex soils consider only the

soil texture Soil texture is a soil classification, classification instrument used both in the field and laboratory to determine soil classes based on their physical texture. Soil texture can be determined using qualitative methods such as texture by feel, and ...

(texture contrast and type of boundary between horizons A and B) and the colour is used for their differentiation (i.e. brown, red and yellow duplex soils). Under the Australian Soil Classification Isbell, Raymond, and Ebooks Corporation. 2002. The Australian Soil Classification : Revised Edition. In Australian Soil and Land Survey Handbooks, 4. 153 p. Melbourne: CSIRO PUBLISHING. they can be included in different orders such as Podosols, Sodosol, Chromosols or Kurosols.

References

{{soil type Soil science Types of soil