Lixisol

Distribution of Lixisolen

Lixisol (LX) is a reference soil assembly from the World Reference Base for Soil Resources (WRB). Lixisole are base-rich soils characterized by clay shift (lessivization). The clay fraction is dominated by kaolinite . Lixisols occur on ancient land surfaces of the semiarid and subhumid tropics and subtropics. 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 often only low humus contents
• E - clay depletion horizon ( eluvial )
• Bt - clay enrichment horizon ( illuvial ) in the subsoil
• C - parent rock

description

Soil profile of a Lixisol

The prolonged, severe weathering led to the dominance of exchange -poor clay minerals ( low-activity clays ). The dominant clay mineral is kaolinite , but there are also small amounts of 3-layer clay minerals . The potential cation exchange capacity in parts of the Bt horizon is <24 cmol _c / kg clay. The Bt horizons in particular are often colored red, which is due to the formation of the iron oxide hematite . The leaching of silica and the simultaneous accumulation of kaolinite and oxides is called ferrallitization . Lixisols occur in semi-arid and subhumid areas and have a high effective base saturation ≥ 50% in the subsoil , which is associated with relatively high pH values. The low content of clay minerals and oxides in the topsoil offers only few possibilities to stabilize the organic matter against microbial degradation, which is why most Lixisols are relatively poor in humus and have poorly aggregated topsoils that are at risk of erosion.

The low cation exchange capacity and the lack of clay and humus in the topsoil combined with poor aggregation pose considerable problems for agriculture. Added to this are drought and a high risk of erosion. Traditionally, shifting cultivation is practiced. The cultivation of sorghum and millet is widespread. Grazing is common.

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 .