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Berlin Environmental Atlas

01.06 Soil-Scientific Characteristic Values (Edition 2002)

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01.06.8 Alkaline Saturation of the Topsoil


Description

The alkaline saturation (Bs) corresponds to the share of alkaline-bound cations in the cation-exchange capacity (KAKpot). These are primarily the basic cations calcium (Ca), magnesium (Mg), potassium (K) and sodium (Na). At a neutral pH value, the soil solution is completely saturated with alkaline cations. At low pH values, acidifying hydrogen (H) and aluminum (Al) ions dominate the soil solution. The alkaline cations serve as important nutrients and as buffers and neutralizers for acidic immissions into the soil; the H-ions have an acidifying effect, while free aluminum ions are toxic for plants. The alkaline saturation of the topsoil is important for plant growth, since this area is the main root zone, except at certain forest and grove locations.

Methodology

The fewer alkaline cations are available, the lower the pH value is. Alkaline saturation can therefore be derived depending on pH value (CaCl2).
Ascertainment is accomplished using the pH value typical of the location of the topsoil, and the alkaline saturation according to Table 1. Then a linear interpolation between these pH stages of this table is carried out.

Table 1: Relationship between Alkaline Saturation (BS) in % and pH (CaCl2) of Mineral Soil Zones in Berlin
pH
(CaCl2)
BS
[%]
3 2
3.1 3
3.2 4
3.3 5
3.4 6
3.5 7
3.6 9
3.7 11
3.8 13
3.9 15
 
pH
(CaCl2)
BS
[%]
4 18
4.1 20
4.2 23
4.3 25
4.4 28
4.5 31
4.6 34
4.7 38
4.8 41
4.9 44
 
pH
(CaCl2)
BS
[%]
5 47
5.1 50
5.2 53
5.3 56
5.4 60
5.5 63
5.6 66
5.7 69
5.8 72
5.9 75
 
pH
(CaCl2)
BS
[%]
6 77
6.1 80
6.2 82
6.3 85
6.4 87
6.5 89
6.6 91
6.7 93
6.8 95
6.9 96
 
pH
(CaCl2)
BS
[%]
7 97
7.1 98
7.2 98
7.3 98
7.4 99
7.5 99
7.6 99
7.7 100
7.8 100
7.9 100
Table 1: Relationship between Alkaline Saturation (Bs) in % and pH (CaCl2) of Mineral Soil Zones in Berlin (Grenzius 1987)

The gradation of alkaline saturation is carried out according to the Soil-Scientific Mapping Directive (1994), using the stages 1 -5 (very alkaline-poor - very alkaline-rich), as in Table 2.

Table 2: Gradation of Alkaline Saturation
BS [%] Stage Designation
<5 1 very alkaline-poor
5 - <20 2 alkaline-poor
20 - <50 3 medium-alkaline
50 - <80 4 alkaline-rich
80 - <100 5 very alkaline-rich
Table 2: Gradation of Alkaline Saturation (Soil-Scientific Mapping Directive 1994)

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