engleski

Comparison between methods for determining soil cation exchange capacity of soils with different pH reaction

The aim of this paper was to compare methods for determining cation exchange capacity (CEC) of soils with different pH reaction. Various methods have been proposed for assessing the CEC of soils. Soil testing laboratories do not usually provide a direct measure of CEC. Instead, a pH 7 buffered ammonium acetate (AA) solution and hydrolytic acidity determination are the most widely used methods. The results represents the total extracted calcium, magnesium, potassium, sodium and acid cations (expressed as c mol(+) kg-1 of soil). Ninety five soil samples (grouped in 2 pHKCl classes: <5-5 and >5, 5) were collected in eastern Croatia and used for two methods for determining CEC. The tested methods are the sum of cations displaced with ammonium acetate or barium chloride (exchangeable Ba after saturation with BaCl2 and replacement with MgSO4). Simple linear correlations were carried out to study the relationship between used methods. Analytical results of soil properties ranged as follows: pHKCl from 3, 27 to 7, 91 (average 5, 22) ; organic matter content from 0, 83% to 5, 28 % (average 2, 33 %), carbonate content (pH>5, 5) from 0, 85% to 16, 13% (average 4, 26%) and clay content range from 10, 7% to 58, 8 % (average 25, 43 %). The mean values of CEC was 17, 81 c mol(+) kg-1 (AA) and 21, 23 c mol(+) kg-1 (BaCl2). There was a highly significant correlation between the AA and BaCl2 methods for CEC with a coefficient of determination R2= 0, 82 (n=95). For the noncarbonated soils (pH <5, 5) determination coefficient was R2=0, 94 (n=65) while determination coefficient for carbonated soils (pH>5, 5) was R2=0, 61 (n=30). According to the obtained results, it could be concluded suitability of the method to be used depend on soil pH and soil carbonate content.

soil ; cation exchange capacity ; ammonium acetate ; barium chloride

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