How Accurate Are Home Soil pH Testers?

Expert advice on the accuracy and importance of testing your soil’s pH.

| Spring 2018

Q: I want to test my soil in preparation for spring planting without sending samples off to a lab. How accurate are the results from home test kits?

A: There are three types of home soil pH testers, each with a different degree of accuracy. A soil-water mixture gives the best results from each.

The first type requires you to combine chemical colored dyes with a soil-water mixture, and then compare the resulting color to the kit’s chart to determine soil pH. This type of test is very easy to use, but often produces inaccurate results.

Indicator test strips, which are advanced versions of litmus paper, are another type. Look for kits with several color spots on each test strip and a pH range of 5.0 to 8.0 (the important range for soil).

Finally, you can use an electronic pH meter. Insert the probe into the soil-water mixture and read the pH directly from the display. Cheap models often suggest that you insert the probe directly into the soil; this is more convenient, but incredibly inaccurate.

The pH scale measures acidity on a logarithmic scale from 0.0 to 14.0. Each whole number on the scale is 10 times more acidic than the next highest number: 5.0 is 10 times more acidic than 6.0, for example. For this reason, gardeners need to measure pH to one decimal place for any real value — but none of the above pH testers provide such accuracy.

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