Segregate structure
The segregate structure (Latin segregare = remove, separate), also segregation structure , describes a form of soil structure . Fine-grained, mineral soil particles form - mainly through shrinkage processes - secretions (segregates) of different sizes. Shrinkage cracks in the pore volume of the soil lead to very large voids between the segregates, while fine pores predominate within the segregates.
description
Changing soil moisture causes the clay minerals in colloid form to shrink and swell, depending on the proportion of swellable three-layer clay minerals . Depending on the cations present (calcium, magnesium, sodium), the clay content and the prevailing pressure conditions, segregates of different orientation and shape are created.
According to their shape, a distinction is made between polyhedral structures, prismatic structures, columnar structures, and plate structures.
- Polyhedral structure
Polyhedral structures are the most common structure in the subsoil of loam and silt soils as well as in the A-horizon of soils with little organic matter and little activity of the soil life . It arises from all-round secretion in connection with calcium ion coating Ca 2+ .
- Fine polyhedra are 1–10 mm in size, they are formed by the effects of frost (frost splinter structure).
- Coarse polyhedra are larger than 10 mm in diameter.
- Price structure
Prismatic structures are sharp-edged pillars that are created by predominantly vertical cracks in soils with a high clay content.
- Pillar structure
are rounded structures with predominantly vertical crack formation in heavy soils with sodium- ion coating Na + and magnesium-ion coating Mg 2+ , e.g. marshy soil .
- Plate structure
Panel structures are created by swelling and shrinking under predominantly horizontal forces, often in the subfloor with load. Forms also when exposed to frost in the sub-floor.
Assessment for land use
Since the secretion structure is not stable with regard to further dispersion , a single grain structure (dust) or - in the case of compaction or silting - a coherent structure from the soil particles can ultimately arise. Both structures are not optimal in terms of air and water flow. A more fertile soil structure with stable aggregates that is favorable for cultivation - i.e. a crumb structure - is only created from soils with a segregate structure by adding organic matter and revitalizing the soil.
See also
- Soil structure
- Bottom cooking
- Frost bake
- Cation exchange capacity
- Lime-clay-humus complex
- Topsoil
- Soil fertility
literature
- Karl Heinrich Hartge: Introduction to Soil Physics. P. 33, Stuttgart 1978, ISBN 3-432-89681-6 .
- D. Schroeder: Soil science in brief. Unterägeri 1984, p. 65, ISBN 3-266-00192-3 .