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Methods for the assessment of total soil nutrient potential with special regard to soil skeleton and its integration into the German Soil-state survey in forests (“BZE II”)


For nutrient potential assessment in forest ecosystem research, the soil skeleton (fraction > 2 mm) is regarded as chemically inert in short or medium time considerations. Only a long term effect is attributed by means of weathering / alteration.
However, recent research has shown that the soil skeleton may have a substantial exchange capacity and therefore needs to be considered in any assessment of short and medium time available element supplies in soil. So far known methods for direct measurement of available nutrient potentials from weathering of the soil skeleton are time consuming and costly and therefore not applicable as routine methods for soil monitoring.
Thus, the aim of this project is the development and validation of easily applicable methods for the assessment or estimation of nutrient potentials of the soil skeleton.

In previous studies, two approaches have shown good prospects:
Elaboration of pedo-transfer functions
Easily measurable soil parameters are to be tested as predictors of the soil skeleton exchange potential. For the crystalline bedrocks of the Southern Black Forest region, adequate predictors have already been identified and transfer functions have been established, explaining 30 to 50 % of variation in effective cation exchange capacity (CECe) and nutrient supply in soil skeleton (HEISNER et. al. 2004).
Direct determination of soil skeleton Exchange capacity
A method for direct determination of CECe of the soil skeleton is to be developed in analogy to routine methods for determination of CECe of fine earth. Preliminary work has shown that in principle an already existing method can be applied.
Furthermore, with only marginal additional work and expense, an estimation of the methodological error caused by sieving and homogenizing the fine earth before measurement of CECe can be accomplished.
Results of all these surveys shall contribute to an area-based assessment of nutrient supplies in soil monitoring, especially in the second edition of the German Soil-state survey in forests (“BZE II”).

First results can be found here:



duration: 15.11.2004 - 31.05.2006