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

Since K fixation in soils is largely a function of clay mineralogy, an effort was made to elucidate the influence of mineralogical variations in soil clays on K fixation, under the moisture-temperature regimes usually prevalent in tropical upland rice soils. Beidellitic clay turned out to be the most severe fixer of addedK (80%), followed by vermiculitic (69%) clays. Fixation is not appreciable (< 15%) in clays consisting of montmorillonite, x-ray amorphous material, chlorite, hydrous mica, kaolinite and halloysite. Fixation by beidellite and vermiculite clays is reduced by the simultaneous occurrence of other mineral species.