Podzol

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Spodosol
)
Podzol
Podsol, Podosol, Spodosol, Espodossolo
illuviation

C: common

In soil science, podzols are the typical soils of coniferous or boreal forests and also the typical soils of eucalypt forests and heathlands in southern Australia. In Western Europe, podzols develop on heathland, which is often a construct of human interference through grazing and burning. In some British moorlands with podzolic soils, cambisols are preserved under Bronze Age barrows.[2]

Term

Podzol means "under-ash" and is derived from the Russian под (pod) + зола́ (zola); the full form is подзо́листая по́чва (podzolistaya pochva), meaning "under-ashed soil". The term was first given in mid-1875 by Vasily Dokuchaev.[3][4] It refers to the common experience of Russian peasants of plowing up an apparent under-layer of ash (leached or E horizon) during first plowing of a virgin soil of that type.[5]

Characteristics

Podzols can occur on almost any parent material but generally derive from either quartz-rich sands and sandstone or sedimentary debris from magmatic rocks, provided there is high precipitation.[6] Most Podzols are poor soils for agriculture due to the sandy portion, resulting in a low level of moisture and nutrients. Some are sandy and excessively drained. Others have shallow rooting zones and poor drainage due to subsoil cementation. A low pH further compounds issues, along with phosphate deficiencies and aluminum toxicity. The best agricultural use of Podzols is for grazing, although well-drained loamy types can be very productive for crops if lime and fertilizer are used.

The E horizon (or Ae in Canadian soil classification system), which is usually 4 to 8 centimetres (1.6 to 3.1 in) thick, is low in Fe and Al oxides and humus. It is formed under moist, cool and acidic conditions, especially where the parent material, such as

soil profiles are designated by the letters A (topsoil), E (eluviated soil), B (subsoil) and C (parent material
).

In some Podzols, the E horizon is absent—either masked by biological activity or obliterated by disturbance. Podzols with little or no E horizon development are often classified as brown Podzolic soils, also called

Umbrepts
.

Geographic distribution

Distribution of Podzol soils according to the World Reference Base for Soil Resources classification:
  Dominant (more than 50% of soil cover)
  Codominant (25-50%)
  Associated (5-25%)

Podzols cover about 4,850,000 square kilometres (1,870,000 sq mi) worldwide and are usually found under sclerophyllous woody vegetation. By extent Podzols are most common in temperate and boreal zones of the Northern Hemisphere but they can also be found in other settings including both temperate rainforests and tropical areas.[7]

In South America Podzols occur beneath Nothofagus betuloides forests in Tierra del Fuego.[8]

Podzolization

A Podzol with a characteristic eluvial (bleached, ash-colored) horizon and intensely coloured illuvial horizons. The photo was taken in the Feldberg area, Southern Black Forest, Germany.

Podzolization (or Podsolization

illuviated horizons which are commonly coloured brown, red or black as they accumulate and consist of cemented sesquioxides and/or organic compounds. The podzolization is a typical soil formation process in Podzols.[9][10]

Preconditions

Podzolization usually occurs under

soil microbes in the topsoil. Overall, podzolization happens where the decomposition of organic matter is inhibited and as a result, acidic organic surface (mor) layers build up. Under these typically acidic conditions, nutrient deficiency further hampers the microbial degradation of organic complexing agents.[10][11] Medium to coarse textured soils with base-poor parent material (usually rich in quartz) also promote podzolization, as they encourage percolating water flow.[11][12]

Key steps

The soil-forming process of podzolization can be broken down into two main steps:

  1. Mobilization and translocation of organic matter, Fe and Al from the surface horizon, and
  2. Immobilization and stabilization of organic matter, Fe and Al into the subsoil.[11][13][14]
    Podzol A layers

In the topsoil of acidic soils, organic matter (mostly from

B horizon. As a result of this, the E horizon (or Ae horizon in the Canadian system of soil classification) is left bleached and ash-grey in colour, while the B horizon becomes enriched with relocated organo-mineral complexes. The colour of B horizon is consequently red, brown or black, depending on the dominance of metal ions or organic matter. Usually, the boundary between the B and eluvial Ae (or E) horizon is very distinct, and sometimes a hardpan (or Ortstein[12]) can form, as the relocated Fe and Al and organic matter increase mineral particles, cementing them into this compacted layer.[10][11][12]

There are several reasons why these organo-mineral complexes immobilize in the B horizon: If during the eluviation process more Al- or Fe-ions bind to the organic compounds, the complex can flocculate as the solubility of it decreases with increasing metal to carbon ratio. Apart from that, a higher

B horizon can act as a filter, as they adsorb the traveling complexes from the upper soil horizons. A decreased water conductivity due to higher clay content can also result in the early flocculation of organo-mineral complexes.[10][11]

The relocated substances can sometimes separate in the illuvial horizons. Then, organic substances are mostly enriched in the uppermost part of the illuvial horizon, whereas Fe- and Al-oxides are mostly found in the lower parts of the illuvial horizon.[10]

Podzolization also promotes the relocation of some nutrients (Cu, Fe, Mn, Mo and P) that sometimes brings them closer to plant roots.[10]

In different soil classification systems

The definitions in different soil classification systems are quite different. Especially soils that show pronounced other soil-forming processes in addition to podzolization are handled in different ways. The following correlations refer to soils, which have undergone advanced podzolization but lack prominent other soil-forming processes.

The term Podzols is used in the World Reference Base for Soil Resources[15] (WRB) and in many national soil classification systems (in some of them, spelled Podsols).

See also

References

  1. ^ Podzols by Otto Spaargaren in Encyclopedia of Soil Science, pp. 580-582
  2. OCLC 3814746.[page needed
    ]
  3. ^ Докучаев В. В. О подзоле Смоленской губернии // Труды Санкт-Петербургского общества естествоиспытателей. 1875. T. 6. Отд. минерал. и геол. Протоколы. С. XXI—XXII.
  4. ^ Докучаев В. В. О подзоле // Труды Императорского Вольного экономического общества. 1880. T. 1. Вып. 2. С. 142—150.
  5. ^ Rode A. A. To the problem of the degree of podzolization of soils // Studies in the genesis and geography of soils. M.: Acad. Sci. USSR, 1935. P. 55-70.
  6. ^ Chesworth, W. (Eds.), 2008. Encyclopedia of soil science, The Netherlands.
  7. ^ Spaargaren, Otto. Podzols. Encyclopedia of Soil Science, pp. 580–581.
  8. doi:10.4067/S0716-078X2002000400015
  9. ^
    OCLC 970401188.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  10. ^
    OCLC 506415938
    .
  11. ^
    ISSN 0016-7061
    .
  12. ^
    ISSN 0008-4271
    .
  13. ISSN 0016-7061
    .
  14. ISSN 0016-7061
    .
  15. ^ IUSS Working Group WRB (2022). "World Reference Base for Soil Resources, fourth edition" (PDF). International Union of Soil Sciences, Vienna. Retrieved 2023-08-18.
  16. ^ "Keys to Soil Taxonomy 2014". Archived from the original on 2018-11-28. Retrieved 2018-11-27.
  17. ^ Institute of Soil Science, Chinese Academy of Sciences (2001). Chinese Soil Taxonomy. Science Press, Beijing, New York.
  18. ^ "Spodosols". geo.msu.edu. Archived from the original on 2018-03-30. Retrieved 2018-05-04.
  19. ^ "Podzolic - Soils of Canada". www.soilsofcanada.ca. Archived from the original on 2018-04-22. Retrieved 2018-05-07.
  20. OCLC 44961488
    .
  21. ^ R.F. Isbell and the National Committee on Soil and Terrain (2016). "Australian Soil Classification, second edition (as Online Interactive Key)". CSIRO. Archived from the original on 29 February 2016. Retrieved 11 February 2016.
  22. ^ dos Santos, Humberto Gonçalves; et al. (2018). Sistema Brasileira de Classificação de Solos, quinta edição. Embrapa, Brasilia.

Further reading

  • W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the World. Springer, Berlin 2022, Chapter 3.3.3.
    ISBN 978-3-540-30460-9

External links

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