Alisol
Alisol (AL) is a reference soil assembly from the World Reference Base for Soil Resources (WRB). Alisols are acidic soils that are characterized by shifting clay (lessivization). The clay fraction is dominated by three-layer clay minerals . Alisols occur in humid climates on young land surfaces. The diagnostic horizon is the argic horizon (Bt) characterized by tone enrichment .
The typical horizon sequence according to the FAO Guidelines for Soil Description is:
- A - topsoil with mostly medium to high humus contents
- E - clay depletion horizon ( eluvial )
- Bt - clay enrichment horizon ( illuvial ) in the subsoil
- C - parent rock
description
The still little advanced weathering is characterized by highly exchangeable three-layer clay minerals ( high-activity clays ) such as vermiculite , smectite and illite . The potential cation exchange capacity in the Bt horizon is ≥ 24 cmol c / kg clay. The Bt horizons are often intensely colored, which is due to the formation and accumulation of iron oxides . Alisols show intensive leaching of base cations and are characterized in the subsoil by a low effective base saturation <50%, which is associated with low pH values. The topsoils have medium to higher humus contents.
Alisols are widely used in forestry. Grazing is also common. If you want to achieve higher yields in arable farming, the soils must be limed and intensively fertilized. Long-term liming can, however, increase the base saturation to such an extent that the Alisols are converted into Luvisols . The clay-rich subsoil can have a water-retaining effect, and over time, alisols can turn into stagnosols . The topsoils of the Alisole are often rich in silt and at risk of erosion.
Related soil types
The WRB knows five reference soil groups with an obligatory argic horizon . Only the retisols have additional retic properties. The other four do not have any and are differentiated according to potential cation exchange capacity per kg clay (KAK / kg clay) in the argic horizon and effective base saturation (BSeff) in the subsoil. With the Luvisoles , both are high. In the case of the alisols, the KAK is high and the BS is low. The KAK is low and the BS high for the Lixisols , and both are low for the Acrisols .
Web links
- Profile photos (with classification) WRB homepage
- Profile photos (with classification) IUSS World of Soils
literature
- 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 .
- FAO: Guidelines for Soil Description. Prepared by R. Jahn, V. Asio, H.-P. Blume , O. Spaargaren and P. Schad. Rome 2006. ISBN 92-5-105521-1 .