Duplex soil

With the term “duplex soil”, Northcote defined a primary profile in his Factual Key classification.^[1] He described a group of texture contrast soils where the B horizon is dominated by a texture class one and a half (or more) finer than the A horizon. In addition, the clear to sharp change between the two horizons must occur within 0.1 m.^[1][2]

Texture in duplex soils is highly variable, with the top-soils ranging from coarse sand to clay loam and the subsoils from light to heavy clay.^[2][3] 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 type of soils.^[1]

The diagnostic properties used by Northcote for the definition of duplex soils consider only the soil texture (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 ^[4] they can be included in different orders such as Podosols, Sodosol, Chromosols or Kurosols.

References

1. ^ ^{a b c} 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.
2. ^ ^{a b} 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.
3. ^ 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
4. ^ 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.