4C2 pH of 1:5 soil/1 M potassium chloride extract – following method 4A1 (without stirring during measurement)

This method provides a convenient laboratory procedure when there is a requirement to report soil pH values from both water and 1 M KCl.

Reagent

Potassium Chloride Crystals (KCl; laboratory or analytical grade)

pH Buffer Solutions

pH buffer solutions are as described for Method 4A1.

Procedure

Following the determination of pH in water, add a weighed quantity of KCl to make the suspension equivalent to 1 M KCl (e.g. 7.46 g/100 mL). Immediately restopper and mechanically shake, end-over-end, at 25°C in a closed system for 1 h. Allow around 20–30 min for the soil to settle, then measure pH as described in Method 4B1, completing all measurements within 4–6 h.

Report pH_KCl on an air-dry basis.