Umwandlungen von Dreischichtsilikaten unter K‐Abgabe und K‐Aufnahme

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Abstract
Transformation of three‐layer silicates through K‐release and K‐uptake (A review).In soils formed from unconsilidated sediments with illite‐vermiculite‐smectite mixtures in their clay fractions the clay mineral transformation from illite to vermiculite and smectite between pH 5 and 7 cannot be considered so far as proven on the grounds of available analytical data. Studies of soil profiles showed that the formation of illite from expandable three layer silicates predominates over the formation of smectite from illite. Practically all samples of loess and calcareous tills of the areas discussed contain smectites. K loesses between pH 5 and 7 are probably very small, because K released during the formation of vermiculites from micas is immediately fixed by smectitic layers which are converted to illite. In those soils potential K fixation of the clay fraction (« 2 μ) is lower than in the corresponding parent sediments despite of vermiculite formation in the soils. Further analytical data (X‐ray, interlattice‐K, K‐selectivity, specific surface) support the hypothesis of illitization of smectites during soil formation.

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