Phaeozem

The Phaeozem (from Greek : phaios = dark and Russian : semlja = soil ) is a reference soil group of the international soil classification World Reference Base for Soil Resources (WRB), which belongs to the group of humus accumulation soils . It is the zonal soil of the semi-humid transition area between steppe and forest .

Occurrence

Phaeozemes occur in many parts of the world. An important distribution area is in the transition area between steppe and forest. The climate there is semi-humid (to humid), so that not only grasses but also woody plants can grow. In addition, phaeozemes are also found in the semi-humid, cooler tropical highlands.

The largest areas are in North America (eastern Great Plains and Midwest ) and the South American pampas ( Uruguay and Argentina ). In addition, there are significant areas in northeast China and central Russia . Phaeozemes also occur in the steppes of Hungary or Bulgaria .

Main features

Soil profile of a Luvic Phaeozem

It is named after the dark color , which results from the high humus content . The humus is worked in deeply by soil diggers ( bioturbation ). The dark, humus-rich mineral topsoil horizon is called mollic horizon in the WRB . Because of the relatively high precipitation, secondary lime does not form , unless at a greater depth. In spite of greater leaching compared to the closely related chernozemes , the base saturation is still consistently high.

The soils have a very rich soil life, optimal water retention capacity , favorable pH values and high nutrient contents .

use

Phaeozemes are very fertile. Because they are located in areas with relatively secure rainfall, they are among the best locations for agriculture in the world. They produce crops with high demands such as wheat , soy and cotton , but also barley , sugar beet (especially Europe ) and maize . In large areas (South American pampas , North American prairies ) grazing ( cattle ) is practiced.

The humus accumulation soils in Germany ( Hildesheimer Börde , Magdeburger Börde and more to the east) are insignificant worldwide, but are of great national importance. In Germany, the maximum possible productivity of a soil is defined on the basis of the yields of the soils in the Magdeburg Börde. In the WRB, depending on the presence of secondary lime, these belong partly to the Chernozemes and partly to the Phaeozemes.

The problem is the high susceptibility to erosion from rain and wind when the natural vegetation has been cleared. The soils also have an unstable structure , which can result in severe soil damage during cultivation ( soil compaction , structural destruction).

Related soil types

With decreasing rainfall, the Chernozem borders the Phaeozeme zone as the zonal soil of the long-grass steppe. It is similar in its properties to the Phaeozem, but always has secondary lime, is less washed out and even darker in color. If you get to even drier areas, the Kastanozem , the humus accumulation soil of the semi-arid short-grass steppes, dominates .

On the moist side the phaeozemes go e.g. B. in Luvisole and Cambisole , but also in the related Umbrisole .

According to the German Soil Systematics, most of the phaeozemes with thick Axh horizons belong to the Chernosem type in the class of black earths, and with less powerful A horizons belong to various other types. Phaeozemes with a dominant Bt horizon (such as the Luvic Phaeozem shown here) belong to the parabrown earths . Also alluvial soils can be among the Phaeozemen.

See also

• Black earth

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 .