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Characterization of expandable layer silicates in humic‐ferralic cambisols (umbrept) derived from biotite and hornblende
Author(s) -
Dreher Peter,
Niederbudde ErnstAugust
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(200008)163:4<447::aid-jpln447>3.0.co;2-w
Subject(s) - biotite , cambisol , hornblende , chemistry , clay minerals , soil water , saturation (graph theory) , silt , geology , mineralogy , analytical chemistry (journal) , environmental chemistry , soil science , paleontology , quartz , mathematics , combinatorics
Samples from a paired soil type (humic ferralic cambisol) derived from biotite schist (soil group 1) and amphibolite bedrock (soil group 2) were investigated mineralogically and chemically. Soil smectites and vermiculites were analyzed by using the improved n‐alkylammonium method (Lp correction and curve fitting). The soils of group 1 contain small smectite concentrations. The source mineral is a low charged biotite of the silt fraction (2—6 μm) with a mean layer charge of ξ = 0.58 mol per O 10 (OH) 2 . The soil smectite of the clay fraction (< 2 μm) has a mean layer charge of ξ = 0.48 mol per O 10 (OH) 2 with nearly 100% tetrahedral substitution. The soils of group 2 contain high smectite concentrations. The total charge of these smectites varies between 0.38 and 0.43 mol per O 10 (OH) 2 . The mean value lies between 0.39 and 0.40 mol per O 10 (OH)2; 20% of the total charge originates from octahedral substitution. Thus, the tetrahedral charge amounts to 0.32 mol per O 10 (OH) 2 . These amphibolite derived smectites have low K selectivity (K G values of about 5 (mol/l) —1/2 ) and do not show an illitization tendency. The soils of group 1 have an extremely high K selectivity (K G values ≫ 180 (mol/l) —1/2 ) when the K‐saturation is < 1.5% of CEC. The increase of K saturation up to 8—15% in the system ”natural soil solution versus solid soil” results in a K G decrease to around 10 (mol/l) —1/2 . This trend can be interpreted as illitization of highly charged smectites with 100% tetrahedral substitution developing to K bearing 1.0 nm minerals.