To test the pH in soil, place soil into a clean, dry plastic jar or plastic bag. Remove stones and crush any soil clumps. Gather two to three representative samples of each soil sample to verify results.
Gather a standard pH meter, a pH electrode, an ATC probe, a stirrer with stir bar, beaker, deionized water, and buffers. We recommend a Sure-Flow™ electrode because the easy-to-clean junction never clogs.
- Weigh 20 g of soil sample into a 100 mL beaker.
- Add 20 mL of deionized (DI) water and place on a stirrer to mix for 30 minutes.
- Cover and let stand for an hour.
- For the most accurate measurements, allow the buffers and the soil sample both to come to room temperature. (A difference in temperature will add error to your measurement.)
- We recommend a 2-point calibration with a pH 7 and a pH 10 buffer solution. The electrode slope should be between 92 and 102%.
- Rinse electrode and ATC with DI water and blot dry. Place probes in the soil sample and measure pH and record measurement.
- Place soil sample about ¾ full in a sample jar and add distilled water to cover soil.
- Cap jar and shake the soil vigorously a few times.
- Let mixture stand 10 minutes to dissolve the salts in the soil.
- Calibrate the pH tester with a pH 7 and a pH 10 buffer solution.
- Remove the cap and place the pH tester into the wet soil slurry.
- Measure pH and record measurement.
Results: A minor (<±0.5 pH) difference between results of the same soil sample indicates good technique and high confidence in results.
One of the easiest ways to correct the pH of your soil (both acidic and alkaline) is by adding compost. An alternative is to add an alkaline source (such as ground limestone) to acidic soil or an acidic source (such as pine needles or peat moss) to alkaline soil. Consult with authorities from a local agricultural extension office, local growers associations, or university before you apply chemicals to correct soil pH.
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