Organic march

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The Organomarsch is a marching ground , which especially in the former lagoons and reed beds of soil large landscape march and Moore under Tideeinflussbereich occurs. A characteristic feature of this soil is the widespread presence of the iron minerals jarosite and sword mannite (Maibolt). 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 MO. In the older literature, the organic march was also referred to as the humus march.

Origin and Distribution

The starting substrate for the development of the organic marsh is a humus, brackish- tidal or fluviatil -tidal, partially lithogenic clay silt or clay . Peat and mud deposits can often be observed. The humus clays were deposited in still water areas and lagoons on the Geestrand and are often found in the area of spits and their hinterland as well as in tidal river plains, e.g. B. from Ems , Weser , Elbe and Eider . In the course of soil formation, the organic matter present in the initial sediment was degraded, accompanied by strong acidification of the soil and the formation of the iron minerals jarosite (Maibolt), which is characteristic of this soil type .

Organ Omar's are common with Dwog- and bend marshes as well as fens socialized. The organic marshes only take up 1% of the marshland in Lower Saxony .

Division and subtypes

Organic marshland can be subdivided into "Rohorganomarsch" (OM1), the "immature organic march" (OM2), the "normal organic march" (OM3), the "sulfur-rich organic march" (OM4) and the "iron-rich organic march" (OM5). In addition to the typical organic march, the "flat organic march", for example over low moor or the "flat organic march" over fossil soils, such as Podzol (Geestmarsch), are subtypes of these soils .

In the international soil classification World Reference Base for Soil Resources (WRB), organic marshes belong predominantly to the Gleysols . The high content of organic matter is expressed by the Supplementary Qualifer Hyperhumic.

Leveling

The Organomarsch is characterized by a characteristic oAh / oGo / oGr - soil leveling . The first horizon is formed by younger sediments deposited on the older surface.

A horizon: The very humus-rich, mineral topsoil horizon is characterized by the accumulation of organic matter, which gradually decreases towards the bottom.

  • oAh: The organic ('o') topsoil ('A') is humic ('h') and therefore dark brown to black in color. It consists of very humic, silty loam .

Below this horizon follows the groundwater-influenced mineral soil (G horizon: mineral soil horizon with groundwater influence).

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

  • oGo: The upper horizon, which is influenced by the groundwater and consists of slightly humic, silty clay, is predominantly characterized by oxidizing conditions and a small proportion of sedimentary organic matter. This horizon is partially rusty and characterized by the precipitation of potassium iron sulfate minerals (Maibolt, Jarosite), which can sometimes form concretions .
  • oGr: Up to the upcoming, another groundwater-influenced, mostly water-filled soil horizon ('G') of humus, clayey silt follows, in which reductive processes ('r') dominate almost all year round (more than 300 days) . This soil horizon is characterized by the appearance of small proportions of sedimentary organic matter with reed remains .

Properties, use and risk

The very humus-rich organic marshes are extremely acidic soils ( pH value around 2-3) and, in addition, due to the structure of the soil, they are hardly sustainable or resilient. The soils are characterized by a high supply of nutrients and a high pollutant binding capacity, but are usually only slightly rooted. In principle, they are not suitable for arable farming , but extensive grassland management is possible. The soil value number of the soil estimate of the organic marshes is usually between 55 and 64. Such soils are generally not suitable as building ground . The soils cannot be driven on and worked on with heavy equipment, as this can lead to irreversible soil compaction .

By lowering the groundwater level , organic marshes are potentially endangered in the stock, as the loose storage of the soil can lead to subsidence and relative lowering of the terrain level as well as decomposition of the humus due to increased oxygen supply.

Individual evidence

  1. ↑ 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. 253f.
  2. ↑ L. Giani, E. Gehre and H. Sponagel: Excursion Guide: Soils of the Lower Saxon Marsch (contribution to the conference "Soils of the coast and their genesis in the field of tension between land use and climate change" at the C.-v.-O. University Oldenburg, September 3-5, 2008 ), p. 19
  3. ↑ 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 53
  4. ^ 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 .
  5. ^ 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 .
  6. ↑ H. Kuntze, G. Roeschmann, G. Schwertfeger: Bodenkunde . Eugen Ulmer, Stuttgart 1994, ISBN 3-8252-8076-4 , p. 287
  7. ↑ 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

Web link

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 .