How to test acid value of the soil?

The most frequently used method is 1:5 dilution method for soil pH measurement although there are other methods. Some use a saturated paste extract, others use a 1:5 dilution of soil:water, and then take a pH measurement on the resulting solution with a laboratory pH meter. Others use the 1:5 dilution, but instead of water they use a dilute Calcium Chloride (#CaCl_2#) solution. As a rough guide, the pH in #CaCl_2# is usually 0.8 pH lower than in water, but can be as much as 2.0 pH units lower on grey sands.

Use a clean spoon to weigh out approximately (or preferably exactly) 10 grams of your soil into a clean container. Add 50 mL of distilled water to the sample (soil). Shake the container for nearly 2-3 minutes then allow the soil to settle for 2 minutes. In case your soil has a high clay content and you require an accurate result, it may not be necessary to filter the suspension. If filtering is not required, measure the pH value on the water above the soil in the container. Ensure you get a steady reading on the digital readout. Always clean up your containers washing by tap water then by distilled water out before testing your next sample.