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Berlin Environmental Atlas

01.06 Soil-Scientific Characteristic Values (Edition 2002)

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01.06.6 Mean pH Values as an Average of Topsoil and Subsoil


The pH value (soil reaction) influences the chemical, physical and biological qualities of the soil. It affects the availability of nutrients and pollutants, and provides information about the ability of the soil to neutralize acids or bases. It is important for the filtration and buffering capacities of soils. Thus, at low pH values, no acids can be neutralized in the soil, the heavy-metal connections increasingly dissolve and the available nutrients are largely washed out.


The pH values were derived from existing documents for the soil associations, taking land use into account. The data were essentially taken from the profile sections in Grenzius (1987). Some values have been supplemented by expert assessments, in most cases using a great variety of different soil-scientific reports. If there were no measurements, the values were assessed using data of comparable uses or comparable soil associations. In addition to the representative values (typical pH values) for the topsoil and subsoil, the respective maximum and minimum values were also determined.

However, since only one characteristic pH value per lot can be processed for generalized soil function assessments, but pH values are stated separately for the topsoil and the subsoil, it was necessary to combine these two values. The arithmetic average was thus calculated from the typical pH values for the topsoil and subsoil. This simplification permits general statements regarding the soil reaction of the locations, e.g. whether a location is more alkaline or more acidic. However, for soils with very different pH values in the topsoil and subsoil, this averaging often yield values which do not always accurately represent the ecological qualities at the location.

The gradation of the mean pH values, as averages of the topsoil and subsoil values, has been carried out according to the Soil-Scientific Mapping Directive (Bodenkundliche Kartieranleitung) (1994) in the stages 1 - 13, from extremely alkaline to extremely acidic (cf. Tab. 1). This gradation permits the soil reaction to be differentiated according to its alkalinity or acidity.

Table 1: pH Stages, changed
pH value pH stage Designation
≥11 1 extremely alkaline
10 - <11 2 very strongly alkaline
9 - <10 3 strongly alkaline
8 - <9 4 medium alkaline
7.5 - <8 5 weakly alkaline
7 - <7.5 6 very weakly alkaline
6.5 - <7 7 very weakly acidic
6 - <6.5 8 weakly acidic
5 - <6 9 medium acidic
4 - <5 10 strongly acidic
3 - <4 11 very strongly acidic
<3 12 extremely acidic
Table 1: pH Stages (Soil-Scientific Mapping Directive, 1994) changed

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