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How to Test Soil pH

Four Methods:Testing Soil pH with a Commercial Test ProbeTesting Soil pH Using Red CabbageTesting Soil pH Using Vinegar and Baking SodaChanging Your Soil pH

Do you want to plant a garden? Then it is important to know about the pH of your soil. The pH is a measure of the soil's acidity or alkalinity. Different plants require different pH levels, so once you know your soil's pH, you can plant plants that will thrive in that soil, or you can amend the soil to expand the range of plants you can use. Getting a measurement is easy, and there are a number of different ways to do it.

Method 1
Testing Soil pH with a Commercial Test Probe

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    Dig a small hole in the soil. Use a trowel or spade to dig a hole 2–4 inches (5.1–10.2 cm) deep. Break up the soil within the hole and remove any twigs or foreign debris.
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    Fill the hole with water. Use distilled (not spring) water. You can find this in your local pharmacy. Rainwater is slightly acidic, and bottled or tap water tends to be slightly alkaline. Fill the hole until you have a muddy pool at the bottom.
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    Insert the test probe into the mud. Make sure your tester is clean and calibrated (for a more exact measurement). Wipe the probe with a tissue or clean cloth, and insert it into the mud.
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    Hold it there for 60 seconds and take a reading. pH is usually measured on a scale of 1-14, though the tester may not include this entire range.
    • A pH of 7 indicates neutral soil.
    • A pH above 7 indicates alkaline soil.
    • A pH below 7 indicates acidic soil.
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    Take several measurements in different spots in the garden. A single reading may be an anomaly, so it's good to get an idea of the average pH in a plot. If they're all around the same, take the average and amend the soil accordingly. If one spot is very different than the rest, however, you may need to "spot treat" it.

Method 2
Testing Soil pH Using Red Cabbage

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    Take a head of red cabbage and finely chop it using a knife or food processor. The solution created from the cabbage juice will change color depending on the pH of what it comes in contact with.
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    Heat distilled water until boiling. Using pure distilled water will give an accurate pH test result.
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    Add the chopped red cabbage to the boiling distilled water. Allow it to soak for about about ten minutes and then drain the solid pieces out, leaving a violet hued juice. This juice should have a neutral pH of about 7.
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    Test the cabbage juice. Pour a small amount into two separate cups, and add vinegar to one cup and baking soda to the other. Vinegar is acidic, and should turn the solution hot pink. The baking soda solution is alkaline and will turn blue or green.
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    Test your soil. Pour a few inches of the cabbage juice into a clean cup and add one to two spoonfuls of soil. Wait thirty minutes, and check the color of the solution.
    • Purple or violet is a pH near 7, neutral.
    • Pink means the soil is acidic with a pH between 1 and 7. The more acidic the soil is, the brighter the pink will be.
    • Blue or green is a pH between 8 and 14, alkaline. The brighter green the juice is, the more alkaline it is.

Method 3
Testing Soil pH Using Vinegar and Baking Soda

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    Take a cup of soil from your garden. Put a few spoonfuls of it into two separate containers.
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    Add vinegar to one container. If it fizzes, it means your soil is alkaline. In that case, you do not need to proceed to the next step.
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    Add water to the other container of soil. You want enough that it becomes very wet and muddy. Pour baking soda into this cup; if it fizzes, it means your soil is acidic.
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    Check both soil samples again. If neither sample began fizzing, it means you probably have a neutral pH of 7. This is good, as this is the pH most plants need to grow in.

Method 4
Changing Your Soil pH

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    Make your soil less acidic. If your soil pH tested below 7, add dolomite or quick lime to the soil. Wood ash in moderation helps as well. Both are available at local gardening centers.
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    Make your soil less alkaline. If your soil pH tested above 7, add organic matter such as pine needles, peat moss, decomposed tree leaves. Sulfur is very effective as well.
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    Change your soil pH to suit specific plants. For example, add sulfur to a certain area of your garden to encourage beautiful blue blooms on your hydrangeas, which prefer more acidic soils. The pH of your soil does not need to be uniform your entire garden over; feel free to alter it to support different plants.


  • Record your results. You may need to reference your test results at a later date, as they may change over time.
  • Prevent contamination (and incorrect readings) by making sure your pH tester probe and your spade are clean. Do not handle soil with your bare hands.
  • Take multiple soil readings with each test. A minimum of six samples from different parts of your garden is a safe amount.
  • Some testers present the approximate pH as a color, rather than as a number. In this case, green usually indicates neutral soil; yellow or orange indicates acidic soil; and dark green indicates alkaline soil.
  • Contact your local agricultural department or extension service office for more information about soil testing or for professional assistance testing your soil.
  • Make sure the tester is properly calibrated before taking a reading (if you want a more accurate measurement).
  • pH changes the availability of nutrients for plants. Optimum pH is generally between 5.5 and 7.


  • As noted above, the water you pour into the hole can affect your reading if the pH of the water is not neutral. Use distilled water for all testing.
  • Some testers will function differently than that described in this article. Always make sure to read the manufacturer's instructions carefully to ensure accurate readings.

Things You'll Need

  • pH tester
  • Small garden shovel (often called a "spade" or "trowel")
  • Water with pH of 7 or distilled water
  • Red cabbage
  • Knife
  • Stove (or other means of boiling water)
  • Multiple cups
  • Vinegar
  • Baking soda

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