Coarse soil
As a rough ground or soil skeleton those components are of a soil called, the particles have an equivalent diameter have greater than 2 mm. It is differentiated from fine soil with a grain size of less than 2 mm.
Determination of the skeletal proportion
When working in the field, the skeletal proportion of the total soil is usually estimated and only rarely determined by a coarse screening on site.
The proportion of skeleton is normally given in percent by weight and is determined when it is absolutely dry.
If the proportion is below 75%, the type and proportion of coarse soil are given as additional information on fine soil when determining the soil type ; If the proportion exceeds 75%, the dominant fraction of coarse soil takes the place of fine soil, giving it its name. Soils that consist of more than 75% coarse soil are referred to in the soil systematics as skeletal or rubble soils .
In order to sort out or to determine the skeletal part during the examination in the laboratory, the soil sample is first dried for four days in a drying cabinet at around 40 degrees. The soil sample filled in a bag is crushed with a hammer and then sieved with a sieve with a mesh size of 2 mm. If necessary, the dried soil sample is filled into a plastic bag and pre-crushed using a hammer. The part of the skeleton retained in this way is, depending on the task, discarded or stored separately from the sieved soil for later investigations.
Grain fractions of the coarse soil
When determining the coarse soil, a distinction is made between size on the one hand and rounded and angular shapes on the other hand, according to the following table
Subdivision and grain fractions of the coarse soil
| angular coarse soil fractions | rounded coarse soil fractions | diameter | ||
|---|---|---|---|---|
| designation | Abbreviation | designation | Abbreviation | in mm |
| Grus | Size | gravel | G | 2 to <63 |
| Fine gravel | fGr | Fine gravel | fG | 2 to <6.3 |
| Mittelgrus | mGr | Medium gravel | mG | 6.3 to <20 |
| Grossgrus | gGr | Coarse gravel | gG | 20 to <63 |
| angular stones and blocks | X | rounded stones and blocks | O | ≥ 63 |
| angular stones | fX | rounded stones | fO | 63 to <200 |
| angular blocks | mX | rounded blocks | mO | 200 to <630 |
| large angular blocks | gX | rounded large blocks | gO | ≥ 630 |
Importance of the soil skeleton for the soil
For a given body of soil, the increasing proportion of coarse soil initially reduces the water storage capacity ( usable field capacity and field capacity ); this applies as long as the soil skeleton virtually floats in the fine soil material . If the coarse soil proportions become so large that the particles support each other, this effect decreases and the soil skeleton forms a stable matrix for coarse pores ; so the air capacity increases . In addition, floors in which the coarse particles support each other are significantly less sensitive to the load from machines; so they are less subject to mechanical soil compaction . The skeletal part also acts as a (slowly flowing) base reservoir. In the course of weathering , nutrients are converted into forms available to plants.
literature
- Herwig Finnern (Red.): Soil science mapping instructions . 4th edition. Verlag, Schweizerbart, Hannover 1994, ISBN 3-510-95804-7 , p. OA
- Fritz Scheffer , Paul Schachtschabel: Textbook of soil science . 14th edition. Verlag Enke, Stuttgart 1998, ISBN 3-432-84774-2 , p. OA
- Ute Heisner: The role of the soil skeleton in the sustainable securing of storage and control functions of the forest soils in the southern Black Forest (on freidok.uni-freiburg.de).
Individual evidence
- ↑ Hans Joachim Fiedler : Soils and soil functions in ecosystems, landscapes and urban areas. P. 183.
- ^ W. Durner: Geo-ecological field methods: location approach. (PDF; 519 kB) (No longer available online.) TU Braunschweig Institute for Geoecology, Dept. Soil Science and Soil Physics, archived from the original on November 3, 2013 ; Retrieved November 1, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Ad-hoc AG Soil 2005: Soil Science Mapping Instructions. 5th edition, 438 pp. Stuttgart: Swiss beard
- ↑ Freiburg Soil Science Treatises, Significance of the Skeleton Part
- ↑ Preparation of soil samples ( Memento of the original dated November 4, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Grain fractions of the coarse soil
- ↑ Roland Irslinger: Soil Ecology - Manuscript for the lecture and the field exercises. (PDF; 446 kB) (No longer available online.) Archived from the original on November 2, 2013 ; Retrieved November 1, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
