Planosol

Planosol (PL) (from Latin : planus , even) 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 seasonally backwater influenced soils with an abrupt increase in clay content anywhere within 100 cm. Backwater soils without an abrupt increase in clay content belong to the stagnosoles in the WRB .

description

Soil profile of a Planosol

Plano sols have within 100 cm below the ground surface an abrupt soil types difference ( abrupt textural difference ) from a bottom coarser textured horizon to an underlying dense horizon of finer soil on, that is, located within 7.5 cm of the clay content in the soil at least doubled or that it increases by an absolute 20%. Furthermore, stagnic properties (from Latin: stagnare , to flood) are diagnostic. These arise from temporary water saturation of the soil, which leads to reducing conditions . The less clayey horizon often fulfills the criteria of the albic material because the iron was washed out laterally in a reduced form in sloping soils. Marbling usually occurs in the clayey horizon.

Horizons

Typically, a bleached, low-clay E horizon lies above a clay-rich, water-retaining B horizon. The difference in clay content is mostly based on geological stratification, more rarely on lessivation .

distribution

The planosols take up about 130 million hectares worldwide and develop preferentially on flat slopes or in plateau areas above the water table. The largest areas are in the subtropics and temperate climates with regular rainy and dry seasons.

Properties and use

Planosols only have low nutrient reserves (often a lack of N, P, S, K, Mg) and can be prone to aluminum toxicity. Due to the damming horizon, planosols are difficult to penetrate and tend to accumulate water (lack of air) and water stress. As a result, they can hardly be used for arable farming and are mainly used for extensive grazing , grassland or, if the temperatures permit, for wet rice cultivation. The latter requires embankment and fertilization.

Related soil types

Backwater soils without an abrupt difference in soil type belong to the stagnosols in the WRB . In the German soil systematics , the planosols belong to the pseudogleyen or stagnogleyen depending on the intensity of the topsoil bleaching . If the backwater influence only begins at a greater depth, it is a matter of transition subtypes, such as brown earth-pseudogley, parabraunerde-pseudogley, pseudogley- brown earth or pseudogley- parabraunerde .

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 .