Methods of pH determination in calcareous soils of Oman: The effect of electrolyte and soil/solution ratio

Determination of pH assists in understanding many reactions that occur in soil. Soil pH values are highly sensitive to the procedure used for determination. In this study, pH was measured in different electrolytes [distilled water (pH w ), 0.01MCaCl2 (pH c a ), 1MKCl (pH k ), and 0.01MBaC12 (pH b a )] with different soil:electrolyte ratios (i.e. 1:1, 1:2.5, and 1:5). The objective was to determine the effect of each electrolyte and dilution ratio on pH of saline and non-saline soils from Oman. It was found that pH values varied significantly between electrolytes and with different dilution ratios. Linear regression equations were generated between electrolytes, dilution ratios and were mostly significant. Soil pH values determined in different electrolytes were significantly interrelated. Water appeared as a highly suitable solvent for soil pH measurements because it is simple and values are familiar to soil users. However, alkaline errors and electrode instabilities, due to liquid junction and soluble salt effects, affected soil pH measurements in water. Soil salinity affected pH measurements, especially in water, and resulted in alkaline errors during pH measurements. Errors were minimized when pH was measured in electrolytes rather than in water.