Increased Selectivity of Naturally Weathered Biotites for Potassium

Abstract

Mica particles from six residual soils were separated from different horizons and separated into three weathering classes. Potassium contents in the centers and in the edges of mica particles were determined by using electron probe microanalysis techniques. The results showed that biotites tended to regain K after an initial loss becoming more resistant to weathering. The regained K concentrated at the edges of weathered biotite particles.

Formation of Trioctahedral Illite from Biotite in a Soil Profile over Granite Gneiss

“…They concluded that trioctahedral illite was reconstituted by reaction of K from decaying plant residues with earlier Copyright 9 1990, The Clay Minerals Society weathering products of biotite, namely, interstratified biotite/vermiculite and vermiculite. Tarzi and Protz (1979) and Ghabru et al (1987) supported this view. Kapoor (1972) described trioctahedral illite as a major component of clays in the lower horizons of many Scandinavian soils.…”

Soil clay mineralogy in relation to fertility management: Effect of soil clay mineral composition on potassium fixation under conditions of upland rice soils

“…Some soil processes such as alternate wetting and drying operative in upland tropical rice soils have been shown to influence K fixation appreciably [11,14,17]. Most documented studies have, however, been conducted either on relatively pure clay mineral aggregates isolated from geological deposits [2,3,6,8,10,16,18,20] with the assumption of identity between them and their counterparts in soils, or on soils with httle or vague mineralogical information or simple clay mineralogies; under often extreme moisture conditions, temperature and nutrient concentrations not prevalent in upland rice soils [1,4,5,7,9,11,12,13,14,15,17,19]. Extrapolation of results from such studies to fertility management of soils in natural environments thus could prove hazardous.…”