RELEASE AND FIXATION OF POTASSIUM IN DIFFERENT SIZE FRACTIONS OF SOME CANADIAN SOILS AS RELATED TO THEIR MINERALOGY

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Abstract
The average amount of non-exchangeable potassium removed by H-resin and boiling 1 N HNO3 from the clay in eleven Canadian soils was about twice that in the fine silt, about four times that in the medium silt, and about eleven times that in the coarse silt and sand. Continuous leaching with 0.01 N HCl also removed four times as much potassium from the clay as from the medium silt. The amounts released were usually less from the clay of four Podzols than from the clays of a Brown Chernozemic, a Brown Podzolic, a Brown Forest, and three Dark Grey Gleysolic soils.The percentage of total potassium released from K-bearing minerals by the above procedures was usually in the following order: feldspar < illite < muscovite < biotite.Although fixation of added potassium against extraction with ammonium acetate usually decreased with increasing particle-size, there was considerable fixation in the fine and medium silts. The clays of two Dark Grey Gleysolic and a Brown Forest soil fixed the highest amounts of potassium.Differences in the release and fixation of potassium were not related to the contents of feldspar, illite, vermiculite and mixed-layer minerals in the clays, nor to the amounts of feldspar and mica in the non-clay fractions.
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