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Effects of silicate weathering and lessivage on K‐content in forest soils derived from Pleistocene sediments
Author(s) -
Dultz Stefan
Publication year - 2000
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200006)163:3<299::aid-jpln299>3.0.co;2-f
Subject(s) - illite , silt , weathering , loess , geology , soil water , calcareous , mineralogy , soil science , clay minerals , glacial period , geochemistry , geomorphology , paleontology
The potassium (K) content of soils developed from Pleistocene calcareous till, glacial sand and loess in NW Germany was investigated in order to characterize stores of K in feldspars (K feldspar ) and mica/illite (K mica/illite ) as well as changes as a function of soil depth. From each horizon, up to seven sand, six silt and three clay fractions were separated. K feldspar and K mica/illite were quantified by means of chemical composition and estimation by IR‐spectroscopy. On account of distinct differences in mineralogical composition between different particle size fractions, K‐content of the bulk soil < 2000 μm and the proportion of K mica/illite and K feldspar are clearly related to grain size distribution of the sample. Generally, the K‐content of particle size fractions of a soil derived from calcareous till is significantly higher than that of a soil from glacial sands. K mica/illite of clay and silt fractions increases with depth, reflecting greater mica/illite weathering at the soil surface, whereas K feldspar shows no noticeable change. Illite accumulates by lessivage in Bt horizons. On a whole‐soil basis, the Bt horizons of Luvisols derived from loess and calcareous till contain more K mica/illite than either the A or the C horizons. By comparing the K‐content in the different particle size fractions with soil depth, the highest rate of change is found for soils derived from glacial sand. Gains in K in the silt fractions of soils from calcareous till and glacial sand result from weathering of feldspar sand grains. Additionally, decomposition of feldspar‐containing rock fragments of gravel size, and aeolian sedimentation, may also have contributed to these gains.