Vertisol

Soil regions with vertisoles.

Vertisol with the typical shrinkage cracks caused by peloturbation

As Vertisol refers soils with high contents of highly swellable clay minerals . They are an order of the USDA Soil Taxonomy and a reference soil group of the World Reference Base for Soil Resources (WRB). They are found worldwide in regions with strong seasonal fluctuations in rainfall, such as in eastern Australia , the Sudan and Ethiopia (here as English black cotton soil known), Texas or the Indian Deccan -Plateau.

Depending on the moisture content, vertisoles expand or contract. During dry periods, the contracting of the clay minerals can cause vertical gaps in the floor to form meters deep. This special property is due to the high amounts of swellable clay minerals, often montmorillonite .

In addition, wedge-shaped aggregates are formed in the sub-floor and are inclined 10 to 60 degrees to the horizontal. Shiny shear surfaces with individual grooves appear on many aggregate surfaces. Such aggregate surfaces are called slickensides . A horizon with these properties is defined in the WRB as a diagnostic vertic horizon .

Vertisols are formed directly from very clayey rocks by hydroturbation , are mostly neutral or slightly acidic and are often quite thick.

The natural vegetation of vertisoles consists of grass or forest.

Worldwide, around 3.2 million square kilometers, or just under 2.5 percent of the ice-free land area, are covered by vertisoles.

classification

The Soil Taxonomy distinguishes six sub- orders for vertisoles:

• Aquert
• Cryert
• Xerert
• Torrert
• Ustert
• Udert

Web links

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

literature

• Soil Survey Staff: Keys to Soil Taxonomy. 12th edition. Natural Resources Conservation Service. US Department of Agriculture. Washington DC, USA, 2014.
• IUSS Working Group WRB: World Reference Base for Soil Resources 2014, Update 2015. World Soil Resources Reports 106, FAO, Rome 2015. ISBN 978-92-5-108369-7 ( PDF 2.3 MB).
• W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the world. 2nd Edition. Springer Spectrum, Heidelberg 2014. ISBN 978-3-642-36574-4 .
• W. Amelung, H.-P. Blume , H. Fleige, R. Horn, E. Kandeler , I. Kögel-Knabner , R. Kretschmar, K. Stahr , B.-M. Wilke: Scheffer / Schachtschabel textbook of soil science. 17th edition. Heidelberg 2018. ISBN 978-3-662-55870-6 .