Psamment

InUSDA soil taxonomy,aPsammentis defined as anEntisolwhich consists basically of unconsolidatedsanddeposits,often found in shifting sand dunes but also in areas of very coarse-texturedparent material subject to millions of years of weathering. This latter case is characteristic of theGuiana Highlandsof northern South America. A Psamment has no distinct soil horizons, and must consist entirely of material of loamy sand or coarser in texture. In theWorld Reference Base for Soil Resources(WRB), most Psamments belong to theArenosols.However, Psamments of fluviatile, lacustrine or marine origin belong to theFluvisols.

Psamments cover 3.4% of the global land mass. They occur throughout the world, being especially abundant in the deserts ofAfricaandAustraliaand on the ancient landforms of easternSouth America.Areas dominated by Psamments also occur in other humid regions, notably inFloridaandNebraska(theSand Hills).

Psamments typically have very low water-holding capacities because the sand in the soil is notgradedso that sands of varying coarseness are constantly mixed right through the soil. Because most sands are highly siliceous, Psamments are also extremely low in all essentialnutrients,most especiallyphosphorusand are highlyacidicin all except very arid climates. Psamments formed as a result ofglacialerosion (common innorthern Europe) are typically of rather higher native fertility because of their youth, but are still much less fertile than most soils in the regions they are located in.

The vegetation on Psamments varies enormously owing to the variety of climates, but in many cases is remarkably well-adapted to the climate, as with theFynbosof the Cape region inSouth Africa—famous for its remarkablebiodiversityand the equally species-richKwonganof southwesternWestern Australia.Thecampinasandkerangasare healthy forests typical of Psamments in South America andBorneo.

Few Psamments are farmed, and where they are, the cost is high because of the expense offertilization.They are always much less productive than other soils in the same region even when fertilized, and require careful management because the sand is very easily eroded.

In USDA soil taxonomy, Psamments are divided into:

• Cryopsamments:Psamments that have a cryic soil temperature regime
• Quartzipsamments:other Psamments that have, in the 0.02 to 2.0 mm fraction within the particle-size control section, a total of more than 90 percent (by weighted average) resistant minerals
• Torripsamments:other Psamments that have an aridic (or torric) moisture regime
• Ustipsamments:other Psamments that have anusticmoisture regime
• Xeropsamments:other Psamments that have a xeric moisture regime
• Udipsamments:other Psamments.

See also

• Pedogenesis
• Pedology (soil study)
• Psammosere
• Soil classification
• Soil types

References

• Soil Survey Staff: Keys to Soil Taxonomy. 12th edition. Natural Resources Conservation Service. U.S. Department of Agriculture. Washington D.C., USA, 2014.
• IUSS Working Group WRB: World Reference Base for Soil Resources, fourth edition. International Union of Soil Sciences, Vienna 2022.ISBN979-8-9862451-1-9([1]).

Further reading

• W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the World. Springer, Berlin 2022, Chapter 8.3.1.ISBN978-3-540-30460-9

External links

• profile photos (with classification)WRB homepage
• profile photos (with classification)IUSS World of Soils