Buffer area (soil science)

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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