Soil classification

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A soil classification is a scheme for classification of soils in different soil types . The geological and pedogenetic causes and processes that led to the development of the characteristics do not play a role for the classification, but are the basis for the classification of the soils in a soil systematics . Soil classification describes and differentiates soils or summarizes them according to their characteristics. These features can often be detected in the field, but in some cases they can or must be determined by chemical analyzes or under the microscope .

While soil and geological classifications are mainly dealt with below, there is also a geotechnical soil classification in which the subsoil properties and those of earthworks are in the foreground (see DIN 4022 ). Albert Atterberg , Arthur Casagrande and Karl von Terzaghi made important contributions to soil classification in geotechnical engineering .

Development of soil classification systems

All classification systems are structured hierarchically. Three possible principles of order can be applied:

Factors
z. B. climatic area, vegetation zone, rock or landscape unit
features
z. B. Horizons, color
Processes
z. B. Sound Shift

No classification is based on just one of these ordering principles, but all have chosen a framework that is predominantly applied. The other principles are only used as a supplement.

Common soil classifications

Russia was the first country in the world to develop an applicable classification of its soils in the 19th century. This scientific process met with great interest in all other countries and was initially adopted one-to-one in many. In the course of history, however, the Russian classification has been adapted to the specific circumstances in almost every country and in some cases has been modified considerably. From this initial phase of soil classification, however, terms from Russian have remained everywhere in the worldwide systems (e.g. Podsol , Kastanozem or Solonetz ).

Dozens of soil taxonomies have emerged from the adaptation process to its own soils, so that almost every European country has its own. Numerous classification systems have also been developed worldwide. Floor division is an active process that is by no means complete. This is shown e.g. B. because in the FRG since 1949 five z. Some strongly revised editions of the Soil Science Mapping Instructions have been published. In addition, the systems of the FRG and the GDR have moved slightly apart in just 50 years. Parts of the GDR system (especially in the area of ​​soil substrates) were incorporated into the 4th edition of the all-German classification in 1994.

In general, it must be said that all systems have more or less major weak points. So far, none of them can do 100% justice to all floors worldwide. However, the national classifications are mostly tailored to the country in question.

The German Soil Systematics is well designed for the area of ​​Central Europe and can optimally describe all soils occurring here. However, one should never try to cover salt soils or areas of the tropics and subtropics with this system. The result would be extremely unsatisfactory, since the soils prevailing there z. Sometimes not even mentioned. On the other hand, soils that are very important regionally in Germany, such as the marsh soils or the Plaggenesche, are not mentioned in the international classification (WRB).

The Austrian system is based heavily on the German one, but has developed significant peculiarities. Due to the alpine location, v. A. She treated mountain soils much better and more precisely than the German allows.

The Russian system is factor-oriented v. A. on climatic zones. This makes sense because almost all climatic zones occur in the vast expanses of Russian territory and soils are often tied to them. For Germany, on the other hand, this classification would be nonsensical, since the entire land area is in just one climate zone.

German soil systematics

In national use in Germany, the German Soil Systematics is used, as it is used, for example, in the Soil Science Mapping Guide . The orientation is combined from the three possibilities mentioned above, whereby the processes run through are particularly strongly included. This principle makes them relatively demanding, since soil assignments require a relatively in-depth knowledge of the processes. However, the classification is relatively precise (even in a global comparison).

USDA Soil Taxonomy

After the Second World War, the USA developed a soil classification that was widely used in the English-speaking world from the 1970s onwards. This USDA Soil Taxonomy is strongly oriented towards characteristics (e.g. horizons, color) and in principle is easy to use even for laypeople. In all its depth, however, it is complicated. In Germany it is basically not used. Despite intensive efforts by the USA, it did not prevail against the World Reference Base (WRB) worldwide.

World Reference Base for Soil Resources (WRB)

The classification of the World Reference Base for Soil Resources (WRB), which emerged from the FAO soil classification , is internationally valid . In the area of process orientation, the WRB has also adopted parts of the German Soil Systematics. It is taught in Germany at many universities in addition to the nationally used one and is at least used in international articles. In German literature, the WRB designations can sometimes be found parallel to the German designations. The problem is z. Sometimes a lot of effort is needed to classify soils, as some of them can only be precisely determined using laboratory values ​​such as the grain size composition or the potential cation exchange capacity .

literature

  • Ad Hoc Working Group Soil: Soil Science Mapping Guide . 5th edition. 2005, ISBN 3-510-95920-5 .
  • G. Schwerdtfeger, H. Kuntze, G. Roeschmann: Soil science . 4th edition. 1994, ISBN 3-8252-8076-4 .
  • H.-P. Blume, P. Schad: 90 Years of Soil Classification of the IUSS. In: IUSS Bulletin. 126, 2015, pp. 38–45 ( PDF ).
  • 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).

Web links

Wikiversity: Soil Science Institute  - course materials