Effect of Various Techniques of Measurement on the PH Determination of the Acidic Soil

An experiment was conducted at Soil Science Lab., Sylhet Agricultural University, from November 2020 to February 2021 to observe the effects of different matrix, their mixing ratios, and time lapse of reading on pH of surface and sub-surface acidic soil and the relationship of different soil properties with pH. The study was conducted using two factorial complete randomized design with six replications, Factor A: mixing ratios of soil and matrix i.e. 1:1.0, 1:2.5, and 1:5.0 and Factor B: time of reading after mixing/stirring of soil and matrix i.e. Reading after 30 minutes (RA30MM), after 90 minutes (RA90MM) and after 150 minutes (RA150MM). Soil samples collected from distinct locations served as the six replications and a total of 12 soil samples - comprising six surface and six sub-surface samples - were examined for pH levels using three different matrixes: distilled water, CaCl ₂ , and KCl. The average pH values of the acidic soil analyzed in distilled water, CaCl ₂ , and KCl exhibited a clear declining trend (pHDW > pHCaCl ₂  > pHKCl). As the dilution of the soil and matrix ratio increased, there was a corresponding rise in the pH value, demonstrated by the order pH1:1.0 < pH1:2.5 < pH1:5.0. The duration after mixing/stirring also influenced the pH values, with RA90MM generally showing higher pH readings compared to both RA30MM and RA150MM. Furthermore, the interaction between the soil-matrix ratio and the duration significantly impacted the soil pH in acidic soils. The variations in the relationship between soil pH and other soil characteristics were minimal.