Measurement of pH in soil samples from a cutover peatland in Sweden: The effect of electrolyte and solution/soil ratio

Abstract

Abstract Ninety‐seven organic soil samples were collected from a cutover peatland in west‐central Sweden and soil pH (12.5:1 v/w solution/soil) was measured in water (pHw), 0.01M CaCl2 (pHca) and 1M KC1 (pHK). The pH values obtained by these three methods were found to be highly correlated over the pHw range 3.95 to 5.91. Base saturation and pHK were shown to influence the difference pHw‐pHK, while electrical conductivity and CEC also influenced the difference pHw‐pHca. Increasing the solution/soil ratio from 5 to 80 (v/w) or 1 to 10 (v/v) increased pHw significantly, while there was no significant effect on pHK and pHCa. The difference between pHw values at different solution/soil ratios increased with increasing pH, carbon (C) content, titratable acidity (pH 7.0) and base saturation and decreased with increasing CEC. Our study showed that on organic soil samples the water/soil ratio should be ≥ 10 for v/w ratios or ≥ 2 for v/v ratios to attain stable and reliable pHw values.