The Contribution of Clay and Organic Matter to the Base Exchange Capacity of Soils

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Abstract
1. The total exchangeable bases, clay, total carbon and carbon oxidisable by 4 per cent, hydrogen peroxide, have been determined for a number of carbonate soils.2. Assuming soils containing excess of carbonate under natural conditions to be base saturated, equations have been derived connecting exchange capacity with clay and (a) total or (b) “oxidisable” carbon content.3. When the organic matter of these soils was assumed to have a constant base exchange capacity, no correlation was found between the exchange capacity of their clay fractions and either their silica-alumina or their silica-sesquioxide ratios.4. Carbonate soils whose exchangeable base content was appreciably less than the calculated values were found to contain either small amounts of calcium carbonate (< 1 percent.), or the bulk of it was present in coarse form.