Solo network

Vegetation on a solo net in Podersdorf

Solonetz ( Russian Солоне́ц ; transcription Solonez ; pronunciation: Solon-jetz), often also black alkali soil , is a reference soil group of the World Reference Base for Soil Resources (WRB) and a soil type of the Austrian soil systematics (ÖBS). It is characterized by clay shift as well as high levels of exchangeable sodium and occurs mainly in semi-arid climates.

Soil profile of a solo network

Genesis and characteristics

The high proportion of monovalent sodium in the exchange sites of the clay minerals leads to a widespread dispersion of the clay minerals and to clay shifting (lessivization). The alternately humid climate causes swelling and shrinking in the clay-enriched horizon with a tendency towards a prismatic structure . However, due to the high proportion of sodium, the upper sides of the prisms disintegrate and round off. The resulting structure is called the pillar structure . According to the FAO Guidelines for Soil Description, the typical horizon sequence is:

• A (often low in humus)
• E (clay-depleted eluvial horizon , often significantly lightened)
• Btn (clay-enriched sodium-rich illuvial horizon : the t stands for clay enrichment and the n for high sodium saturation )

The pH value is usually high and can rise to over 9 in Btn. With the clay minerals, some humus is usually also shifted, so that the Btn, at least in its upper area, is relatively dark. In the WRB, the Btn horizon is the diagnostic natric horizon . It has at least 15% sodium saturation or at least more interchangeable sodium and magnesium than calcium. But sodium saturations of 90% can also occur.

The solo networks in Seewinkel, Austria, have a groundwater connection. This is part of the definition in the ÖBS. Typical horizon sequences are: AE – Bh – G; A – AbegBh – G. The G stands for the horizon in the groundwater fluctuation range.

Dissemination and use

The main distribution area of ​​the Solonetz is east of the Caspian Sea and around the Aral Sea, in Canada , Australia and Somalia as well as Argentina . In these countries, the soil type occupies large areas. Only small occurrences of solo nets are known in Europe, for example in Burgenland near Podersdorf or in Hungary and Romania .

When wet, the soils are not very permeable to water and poorly ventilated. When dry, shrinkage cracks and the formation of hard clods often occur . Their suitability for arable farming is therefore only poor. They are often grazed. The lowering of the groundwater around the Aral Sea also favored the formation of solitary nets that could hardly be cultivated.

The Solonetz is to be distinguished from the Solontschak . The Solontschak is defined by the high content of easily soluble salts in the soil solution. This often includes sodium, but sodium saturation does not play a role in the definition of Solontschak. Due to the high salt content, no shifting of clay is possible in Solontschaken. If solo nets show high salt contents, this means that the clay shift has come to a standstill in them. In the WRB key, the Solonetz has priority over the Solontschak.

literature

• IUSS Working Group WRB: World Reference Base for Soil Resources 2014, update 2015. International soil classification system for naming soils and creating legends for soil maps. World Soil Resources Reports 106th FAO, Rome 2015, ISBN 978-92-5-108369-7 ( PDF 2.3 MB).
• O. Nestroy et al .: Systematic classification of soils in Austria. Austrian Soil Systematics 2000 in the revised version from 2011. Announcements of the Austrian Soil Science Society 79. Vienna 2011. ISSN 0029-893-X.
• 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. Springer Spectrum, 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 .

Individual evidence

1. ↑ René Létolle, Monique Mainguet: The Aral Sea. An ecological disaster . Springer-Verlag, Berlin, Heidelberg 1996, ISBN 3-540-58730-6 , pp. 388 ff .

Web links

• Peter Fitze: 7.4 Salt and sodium soils (Solonchak, Solonetz). In: Soil geography. Geographical Institute of the University of Zurich , accessed on November 14, 2009 (script for the lecture). 
• Profile photos (with classification) WRB homepage
• Profile photos (with classification) IUSS World of Soils