Knickmarsch

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The Knickmarsch is a brackish marshland that occurs mainly in the Altmarschen . A characteristic feature of this soil is the so-called kink , a clay-rich , compacted soil horizon that arose in the course of pedogenesis . In the more recent German soil classification , this soil type is assigned to the division of semiterrestrial soils of class M (marshes). Its abbreviation is MK. In the older literature the Knickmarsch was called Brackmarsch (BM3) or Knickige Brackmarsch (BM4).

Origin and Distribution

The starting substrate for the formation of the kink march is a brackish- tidal (the sediments come from the tidal range of the brackish water zones ) or fluviatile- tidal (the sediments come from the tidal range of a river), clayey silt or clay . Articulated marsh soils are widespread on the German North Sea coast , especially in old marsh areas far from the North Sea . In Dithmarschen these soils are only widespread east of the 1000-year-old dike. The Knickmarschen occupy over 40% of the marshland in Lower Saxony .

genesis

Knick marshes have been formed in several phases from marinogenic clays of the silt in mud flats . The formation of the marshes in the coastal areas of the North Sea began 7500 years ago, in the late boreal . The soil formation process was initially characterized by pronounced humus formation and oxidation of the organic matter. The salt marsh formed in this way developed into a lime marsh as a result of the sweetening . In the further ripening process, the soil was thoroughly decalcified ( Kleimarsch ). The process of the formation of the kink horizon, which shapes the soil profile, is accompanied by a shift of clay minerals as a result of the sweetening, decalcification and incipient soil acidification . The kink horizon is characterized by seasonal structural changes - swelling in the wet state and shrinkage with vertical cracks in the dry state. The Knickmarschen thus represent the stage of maturity of the soil development of clayey tidal sediments.

Leveling

The Knickmarsch is characterized by a characteristic Ah / Sw / Sq / (Gro) / Gr - ground leveling. The first horizon is formed by younger sediments deposited on the older surface.

A-horizon: Mineral topsoil with an accumulation of a maximum of 30% organic matter, which gradually decreases towards the bottom.

  • Ah: The topsoil ('A') is humic ('h') and therefore brown to black in color. It consists of humus, silty loam .

S-Horizont: Mineral subsoil with backwater influence , which is temporarily wet or drained.

  • Sw: Due to the damming effect of the underlying kinked horizon ('Sq'), the area immediately above the third horizon is influenced by dammed water ('S'). However, this section of the ground is still ventilated, so the horizon is water-conducting ('w') to some extent. The Sw horizon shows signs of pseudo-gleying and is usually formed from slightly rust-stained, silty loam.
  • Sq: The Sq horizon ( kink ) is formed from a silty clay. The horizon acts as a water reservoir and is usually only slightly ventilated. Due to the mineralogical composition, this horizon is exposed to seasonal swelling and shrinking.

Below these horizons follows the mineral soil, formed from older sediments overlaid in the Holocene .

G horizon: Mineral soil horizon with groundwater influence Sometimes the G horizon can be subdivided into a mineral soil horizon with temporary and permanent influence on groundwater .

  • Go: The upper horizon of silty clay, influenced by groundwater, is predominantly characterized by oxidizing conditions. It does not necessarily have to be designed in the Knickmarsch profile.
  • Gr: Up to the Pleistocene approach, there is another groundwater-influenced soil horizon ('G') made of silty clay, in which reductive processes ('r') dominate almost all year round (more than 300 days) . The dark gray to black color is due to the reduction of iron minerals such as pyrite and marcasite . Partly there are rust-stained areas.

In the international soil systematic World Reference Base for Soil Resources (WRB), the knick marshes are predominantly stagnant .

Properties, use and risk

Due to the high clay content, which makes soil cultivation difficult, and due to the predominantly acidic soil reaction, soils are mostly only suitable for grassland use. The land value number of the soil estimate of the Knickmarschen lies between 62 and 70 (arable land) and 55 and 64 (grassland). Articulated soils belong to the so-called minute soils , which means that these soils can only be worked at very specific times with a defined soil moisture. Wet floors of this type tend while processing heavy agricultural device for soil compaction .

Individual evidence

  1. ^ E. Gehren, H. Sponagel & I. Benne: The marshes in Lower Saxony - soil forms, distribution and area proportions, Oldenburg 2008, available online: http://eprints.dbges.de/64/1/Gehre.pdf , 4 pp .
  2. ↑ State Office for Agriculture, Environment and Rural Areas (Ed.): The soils of Schleswig-Holstein: Origin, Distribution, Use, Properties and Endangerment , 4th edition, Flintbek 2012, ISBN 978-3-937937-03-8 , p 49
  3. ^ E. Gehren, H. Sponagel & I. Benne: The marshes in Lower Saxony - soil forms, distribution and area proportions , Oldenburg 2008, available online: http://eprints.dbges.de/64/1/Gehre.pdf , 4 pp .
  4. ↑ State Office for Agriculture, Environment and Rural Areas (Ed.): The soils of Schleswig-Holstein: Origin, Distribution, Use, Properties and Endangerment , 4th edition, Flintbek 2012, ISBN 978-3-937937-03-8 , p 49
  5. ↑ State Office for Agriculture, Environment and Rural Areas (Ed.): The soils of Schleswig-Holstein: Origin, Distribution, Use, Properties and Endangerment , 4th edition, Flintbek 2012, ISBN 978-3-937937-03-8 , p 48
  6. ↑ Ad-hoc working group soil in the Federal Institute for Geosciences and Raw Materials in cooperation with the State Geological Services of the Federal Republic of Germany (Ed.): Soil-scientific mapping guide . 5. revised u. exp. Edition. Hannover 2005, ISBN 3-510-95920-5 , pp. 317-320

literature

  • Ad hoc working group Soil in the Federal Institute for Geosciences and Raw Materials in cooperation with the State Geological Services of the Federal Republic of Germany (Ed.): Soil science mapping guide . 5. revised u. exp. Edition. Hanover 2005, ISBN 3-510-95920-5 .
  • 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 .
  • H. Streif: The East Frisian coastal area - North Sea, islands, mud flats and marshes . Geological Guide Collection 57, 2nd completely revised edition, Gebrüder Borntraeger, Berlin, Stuttgart 1990, ISBN 978-3443150518 .
  • H. Kuntze, G. Roeschmann, G. Schwertfeger: Soil science . Eugen Ulmer, Stuttgart 1994, ISBN 3-8252-8076-4 .