Effects of Electrolytes and Soil-to-suspension Ratios on pH in Acidic-coarse Textured Soil

Background: Soil pH is determined using a variety of methods. The key differences among them are the electrolytes and soil-to-suspension ratios. However, an optimal procedure tailored to a particular soil is required. This study, therefore, aimed to evaluate the effects of electrolytes and soil-to-suspension ratios on soil pH and to optimise pH measurement methods for acidic-coarsely textured soil. Methods: Varied standard electrolytes (water, 0.01 M CaCl2 and 1 M KCl) and soil-to-suspension ratios (1:1, 1:2.5 and 1:5 w/v) were used to measure the pH of thirty samples of acidic-coarsest textured soil. Result: Soil pH values were observed in the following order: water greater than 0.01 M CaCl2 greater than 1 M KCI. Higher soil pHs were a result of higher suspension volumes. The most optimal pH measurement method for an acidic-coarsely textured soil was obtained from the 1:2.5 soil-to-suspension ratio of 1 M KCl, which held the highest R2 (0.850), as well as the lowest root mean square error (RMSE) (0.010), indicating the most precise method. An alternative method suitable for a cost-saving laboratory was the 1:1 soil-to-suspension ratio of 0.01 M CaCl2, which owned R2 of 0.766 and RMSE of 0.013, as its pH measurement was similar to those under the most optimal method.