Stagnosol

Stagnosol (ST) (from Latin : stagnare , to flood) is a soil science term and names one of the 32 reference soil groups of the World Reference Base for Soil Resources (WRB). The group includes soils that are seasonally affected by backwater. The water accumulation is triggered by a temporary lack of coarse pores in the subsoil. This can be caused by higher clay content , but there is no sudden increase in the clay content as in planosols .

description

Stagnosols show stagnic properties, i.e. the accumulation of intensely colored iron oxides and mostly also black manganese oxides inside the aggregates . The aggregate surfaces are depleted of iron and manganese and thus bleached. The pale colors can dominate in the topsoil if iron and manganese are removed laterally in a reduced form in sloping floors. Smaller oxide accumulations inside the aggregate are called concretions. Larger spots and the bleaching zones that alternate with them are called marbling. The stagnic properties arise from reducing conditions , which are triggered by water stagnation . The water accumulation dominates after the snowmelt in spring and mostly disappears in the course of summer as evapotranspiration increases . In the profile of a stagnosol, the areas with oxidation and reduction colors occupy a weighted average of at least 50% over a depth range of 50 cm - the original colors that have not been changed by redox processes therefore remain below 50%. This depth range begins at the latest 25 cm below the soil surface.

distribution

Stagnosols are common in all humid climates that alternate between humid and slightly drier seasons. They are most common in the humid middle latitudes and the boreal zone . Usually they do not take up large areas. They can be found in plateau and hillside locations and are rather untypical for lowlands.

Properties and use

Plants on stagnosols often suffer from a lack of iron and manganese, which are defined as oxides inside the aggregate that are not available to plants. Phosphorus is bound to the oxides inside the aggregate and is also a deficiency element. The backwater is detrimental to arable crops (with the exception of rice). Therefore, pastures and forests dominate, with the choice of tree species being restricted by the backwater. Drainage is difficult with higher clay contents.

Related soil types

Backwater soils with an abrupt increase in the clay content belong to the planosols in the WRB . In the German soil systematics , the stagnosols belong predominantly to the pseudogleyen , but also to the stagnogleyen when the topsoil is heavily bleached . Stagnosols with a predominance of silt or fine sand and largely the same type of soil in the entire profile belong to the sticky pseudogleyen .

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 .