Testing Soil pH

It’s useful to know the acidity of your soil. The pH influences many of the chemical reactions in the soil, including those that make nutrients available or unavailable. pH can be adjusted by adding various chemicals to your soil. Lime makes the soil more alkaline, and sulfur or a sulfur-bearing chemical makes it more acid.

Soil laboratories test pH routinely. It is one of the most common and least expensive tests they perform. You can also test your pH with a soil test kit, a pH meter, or with nitrazine paper.

Soil test kits usually include a pH test. Some only test pH. These kits usually have you put a soil sample in a test tube, add a liquid, then compare the color of the liquid with a color chart. They are sometimes difficult to interpret.

Meters that measure pH are inexpensive and easy to use. With most meters, you simply poke the meter in moist soil and take a reading. With some, you make a slurry of soil and distilled water and measure that.

Nitrazine paper is used commonly in medicine to test the pH of body fluids. The paper changes color when dipped in a fluid or pressed against wet soil. The color change is compared with a chart to read pH.

Any of these inexpensive tests may be inaccurate, either through impurities in the sample or your lack of experience in interpreting it. You can calibrate a home test by comparing it with a test done by a lab. Save a sample of the soil you send to a lab, and test it by whatever method you prefer. See how close you came when you get the soil test report.