Aggregate structure

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The structure of a soil (the structure) can be divided into three groups according to the cohesion of the soil particles - with transitional forms. In addition to the single grain structure or elementary structure of independent soil particles (typically sand) and the coherent structure - a bonded mass (typically clay sediment ) - exists as a third group, the aggregate structure (Latin aggregare: pile) - including building structure or crumb structure of rich topsoils with strong biological Activity.

By dividing forces in the event of shrinkage, cracking, and the effects of frost, fine-grain mineral soil particles continue to form so-called segregate structures , for example polyhedron structures in clay soils with inhibited biological activity.

Assembled soil particles (aggregates) are:

  • 'Crumbs' with a diameter of 1 to 10 mm, they are rounded, humic and very porous.
  • 'Crumbles' are like crumbs, but larger than 10 mm in diameter.

This heterogeneous aggregate structure arises in the case of advanced soil development in the A h horizon due to the effects of frost (frost bake), mixing processes ( turbation ), soil organisms and as a result of suitable soil cultivation in cultivated soils.

Adhered soil particles, humus particles and single grains form more or less stable crumbs, which are coupled together as lime-clay-humus complexes through mixed coagulation ( cement structure ). The bond takes place via polyvalent cations, mainly Ca ++ and Mg ++ , as well as water and organic dipoles with OH bridges.

Aggregate structures are isolated, have different causes and different shapes. A distinction is made on the basis of the following under ab and c. mentioned mark:

  • A. 'Structure' created by biological activity
    • 1. worming structure
      • a. high stability
      • b. Formation of clay-humus complexes (THK)
      • c. Live shoring by the earthworm
    • 2. Crumb structure
      • a. very porous
      • b. high stability (THK, living shoring)
      • c. Technically optimal
  • For example, by shrinkage resulting isolation structure
    • 1. Polyhedral structure
      • a. sharp edges
      • b. poor stability
    • 2. Plate structure
      • a. stored horizontally
      • b. Plow or milling base
      • c. Paths, lanes (compaction)
  • C. resulting from tillage fragment structure
    • 1. Crumble
      • a. Tillage in optimal condition
    • 2. Lump
      • a. Cultivation of the soil when the condition is too wet or too dry

See also

literature