Buffer area (soil science)
Buffer areas in the soil are chemical buffer systems that regulate the acidity of the soil.
In (Central European) soils, due to the humid climate, there is more precipitation water than it evaporates ( evapotranspiration ). The excess water that is not bound in the soil seeps into the groundwater , is washed out and takes up v. a. basic cations with. In connection with naturally acidic precipitation, i.e. also without anthropogenic influence, one can speak (in Central Europe) of a natural tendency towards soil acidification . For this reason, the buffer functions of the soils are mainly considered in the reduction of acidic inputs.
Buffer in the base are organic and inorganic compounds, the H + - ions can record, and thus an acid reaction or an acidic entry weaken.
The following five buffer areas are defined:
Buffer area | pH values | Buffer capacity | Nutrient ratios | comment |
---|---|---|---|---|
Carbonate buffer area | 6.2 to 8.6; "neutral" | 150 kmol H + per 1% CaO | Ca 2+ , HCO 3 excess, K and trace elements |
Anion excess (phosphate, Fe precipitation) |
Silicate buffer area | 5.0 to 6.2; "Weakly sour" | 25 kmol H + per 1% silicate | little Ca, Mg, K | Cation / anion ratio balanced |
Exchanger buffer area | 4.2 to 5.0; “Moderately acidic” depending on the cation exchange capacity |
7 kmol H + per 1% clay | Leaching of Ca, Mg, K | Cation excess (Al) |
Aluminum buffer area | 3.0 to 4.2; "Very sour" | 150 kmol H + per 1% clay | strong to complete cation washout | Excess of Al 3+ (toxicity) |
Iron buffer area | <3.0; "Extremely angry" | - | extreme nutritional deficiency and Al, Fe toxicity | Fe 3+ and H + predominant |
See also
- Exchange capacity and cation exchange capacity
- Soil pH ("soil reaction")
- Liming
- Chemical soil properties
literature
- Ad-hoc Working Group Soil: Soil Science Mapping Instructions , Ed .: Federal Institute for Geosciences and Raw Materials in cooperation with the State Geological Services, 5th edition, 438 p .; 41 fig., 103 tab., 31 lists, Hanover 2005. ISBN 3-510-95920-5 ( http://www.schweizerbart.de/pubs/isbn/bgr/bodenkundl-3510959205-desc.html )