TEST METHOD: pH of soils

Revised: 3 June 2002

OVERVIEW

pH is an important indicator of soil conditions.

TASK SAFETY REQUIREMENTS

Safety boots are mandatory. Use appropriate PPE.

SPECIFIC JOB STEPS HAZARDS WITHIN THIS STEP HAZARD CONTROL
This method uses the 1:5 soil/water extract, as considerable Australian data exists for this method.    
Weigh 20 g of air-dried soil and place in a stirring jar. Add 100 mL of deionised water. Shake, stir or roll for one hour, then leave for 20-30 mins to settle. A mechanical stirring device is not available. Shake vigorously for 2 mins every 15 mins for two hours.
Decant the supernatant and test the pH as follows:    
Calibrate the meter following the directions in the pH meter manufacturer's manual. Out of date calibration solution. Date calibration solution containers when opened and replace after the specified time (see label for details).
Insert the pH probe and temperature probe (if separate) into the water sample and stir gently.    
Wait until the reading stabilises and record reading in the laboratory daybook. Report as: pH (1:5 soil water) on an air-dry basis.    

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