Kalkmarsch

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The Kalkmarsch is a soil type of the German soil systematics . Kalkmarschen belong to the Jungmarsch and arise from Holocene marine deposits. Kalkmarschen have a high lime content, which makes them a suitable habitat for earthworms. When drained, they bring the highest yields. This soil is characteristic of the marshland areas of the German North Sea coast region. In the soil systematics they are abbreviated with MC and belong to class M (marshes) in the department of semi-terrestrial soils .

The Kalkmarsch was the bottom of the year 2009.

Origin and Distribution

The development of a march follows a time course over several stages. The starting material for soil formation is the result of sedimentation in the tidal flats , which in total outweighs erosion during the twice-daily flooding. If the mudflats grow to a height that is no longer regularly reached by the tidal range , the march begins to form. After the intermediate stage of the raw march , which is still episodically flooded, the young marshes , which are only reached by sea in exceptional cases and are usually diked, follow. The drainage carried out after the embankment, which is necessary to make it usable, leads to subsidence compaction, so that the land surface is usually below the level of the high tide and requires constant, active drainage. The easily soluble salts are quickly washed out by the precipitation, so that a well-developed but not yet decalcified soil is created with structure formation , sulphide oxidation and humus enrichment: the Kalkmarsch. Over time, it develops into the Kleimarsch . The old marshes follow the Jungmarschen over time .

Kalkmarschen have a maximum age of about 300 years before they become the Kleimarsch. It must be noted that this type of soil owes large parts of its area in Germany to the active reclamation of land by the coastal inhabitants in recent centuries. For reasons of cost and nature conservation - the raw marshes with their typical vegetation ( salt marsh ) are under strict nature protection - no dyke construction has been carried out since the 1980s. Since - especially because of the long-term rising sea level - no new young marshes are naturally formed, a decrease in area of ​​this type of soil is to be expected in the next few centuries.

The global areas of the marshland are rather small. One of the largest contiguous areas in Central Europe extends along the North Sea coast from Denmark to Belgium and also on the south-eastern coast of the British Isles .

Horizon sequence

A young march is defined as a Kalkmarsch in the KA5 if free limestone can be detected in the top 40 cm of the soil (cracking noises or the formation of bubbles after the addition of hydrochloric acid). The groundwater influence must also begin in the first 40 cm. Below the topsoil horizon (A horizon) lies a horizon that is only temporarily filled with groundwater (Go), and below that there is a horizon that is permanently influenced by groundwater (Gr horizon).

This results in the typical soil horizon sequence (e) Ah / eGo / (z) eGr. Transitions between Go and Gr are possible (Gor or Gro).

  • The 'e' stands for marly and indicates the amount of lime due to mussel shells, which may have already decreased significantly in the topsoil.
  • The 'z' means salty. Because of the sweetening, salt is restricted to lower horizons. It is only found in marine limestone marshes (see subtypes).
  • Ap or Ah - the topsoil is characterized by a brown-black color. The often fine-sand-silty loam of this horizon has good root penetration , is strongly revitalized and has a medium humosity . It is sweetened, ventilated and has a stable structure. Ah-horizons ('A' - topsoil; 'h' - humos) are rare, since limestone marshes are practically without exception used for agriculture. As a rule, an Ap ('A' - topsoil; 'p' - plowed) can be assumed. The thickness of the horizon is around 30 cm because of the plowing depth.
  • Go - Below the aerated topsoil there is a G horizon influenced by the groundwater, in which, however, oxidation processes predominate ('o' - oxidative). Processes of fermentation take place in it. It has red-brown spots of rust and must start in the top 40 cm.
  • Gr - Up to the Pleistocene subsoil there is another horizon influenced by the groundwater, in which reductive processes ('r') dominate. The dark, almost black color is caused by the iron sulfide still present in large quantities here.

Subtypes

The water that fluctuates in the ground can be salt , fresh or brackish water . The latter is often the case in estuaries . In the German soil system, three sub-types are distinguished:

  • Normkalkmarsch: tm (e) Ah… 'tm' stands for tidal-marin. The sediments are deposited in the tidal area of ​​the sea ( typical Kalkmarsch ; sea march ).
  • Brackish lime march: tb (e) Ah ... 'tb' stands for tidal-brackish. The sediments are deposited in those affected by salt water at high tide and freshwater at low tide.
  • River Limestone March: tp (e) Ah… 'tp' stands for perimarin (tidal-fluviatil). The sediments come from the water of a river that has accumulated at high tide.

In the international soil classification World Reference Base for Soil Resources (WRB), marshes are not listed as a separate group. There they belong to other water-affected soil groups. The Kalkmarschen mainly belong to the Gleysolen and are characterized by the Principal Qualifier Calcaric.

properties

Basically, the littoral sediments washed up by the sea are decisive for the characteristic properties of the Kalkmarsch. The sediment packages from silt reach down to the Pleistocene subsoil at a depth of many meters. After the dyke has been dyed, it quickly comes to the stage of the Kalkmarsch. The once high salt loads are washed out by precipitation (sweetening). Due to the proximity to the coast, however, there is a continuous, low salt supply (approx. 200 kg / ha a) via spray and sea wind.

The soil-forming processes created a loose, stable crumb structure that is easy to work with. The soil types are more or less rich in silt. An essential legacy of the sea is the high lime content from grated mussel shells. This is why the soil has relatively high pH values in the slightly acidic to neutral range. As humus easily formed at these conditions degradable Mull (humus form) .

The entire body of the soil contains large amounts of easily decomposable organic matter from the former tidal currents. This substrate represents an optimal habitat for soil organisms such as deep-burrowing earthworms (e.g. Lumbricus terrestris ). The soils of the limestone marshes are strongly animated and subject to a high degree of biological mixing ( bioturbation ). The soil body is still traversed by fine storm surge layers, which, however, are increasingly unrecognizable due to the bioturbation.

As a result of the ventilation as a result of the drainage, the previously very thin oxygen-containing oxidation area (Go) increases to the extent that the permanently wet reduction area (Gr) decreases. The black iron sulphides formed in large quantities in the mud flats are rapidly oxidized under the influence of oxygen. They are therefore no longer detectable in the A and Go horizon. Due to the oxidation of the sulfur compounds, however, the pH value drops, so that intensive lime dissolution and calcium ion leaching occur ( sulfur dynamics of the marshes ).

In summary, the high fertility of the Kalkmarschen is based on the following parameters:

use

The Jungmarsch is still used as pastureland in the Kögen , which was only briefly diked . In the past, however, this condition was changed as quickly as possible through drainage and embankment due to the extremely high soil fertility. Drainage can take place through trenches, today pipe drainage is used. As soon as the soil is drained sufficiently, the usability is increased. Whenever possible, Kalkmarschen are used intensively for agriculture. The yields of the Kalkmarsch are very good, as the vegetation can take root well and the conversion of the organic material in the soil supplies the plants with nutrients. This is the reason for the historical wealth of the march farmers . Forest does not settle there because common tree species are sensitive to salt. The limestone marshes on the North Sea coast have the highest soil values ​​of over 100, similar to that of the black earths in the bordering landscapes . The average rating is around 85 ground points. Typical crops are wheat or cabbage ( Dithmarschen ).

literature

  • Ad hoc working group Soil: Soil-Scientific Mapping Instructions . Ed .: Federal Institute for Geosciences and Raw Materials in cooperation with the State Geological Services of the Federal Republic of Germany. 5. revised u. exp. Edition. Hannover 2005, ISBN 3-510-95920-5 , pp. 438 .
  • Gerd Hintermaier-Erhard and Wolfgang Zech: Dictionary of soil science . Enke Verlag, Stuttgart 1997, ISBN 978-3-432-29971-6 .

Web links

Individual evidence

  1. ↑ 2009 - Kalkmarsch
  2. ↑ a b c see Schlichting 1986, pp. 90–92.
  3. ↑ a b c d see Mückenhausen 1993, p. 470 f.
  4. ↑ a b c d see Scheffer / Schachtschabel 2002, pp. 511–514.
  5. ↑ a b c see Mückenhausen 1993, Appendix, Table 21