Soil pH Test
The pH test is a simple indicator test requiring some soil, water, a cup or jar, and a Garden Tutor pH test strip. The Garden Tutor pH test strips cover a pH range of 3.5 to 9.0 in .5 increments. Each pH test strip has four pads that change color depending on the pH of the test material. Each pad on the pH test strip covers a specific segment of the pH range. Having four pads helps with accuracy since a pH range of 3.5-9 is broad and the color changes can be subtle and difficult to determine.
The pH strips have been specifically designed and calibrated for soil testing and cover a pH range that encompasses nearly all garden soils. If you follow the subsequent steps you should be able to determine your soil pH within a .5 increment. If you need pinpoint accuracy, consider sending a soil sample to a professional soil testing laboratory. You can go to the “Toolbox” area of the Garden Tutor site under “Soil Testing” to learn about current options for laboratory soil testing.
You will need a representative sample of your garden soil. Using a garden trowel or spade, dig a small hole (about 6 inches deep) in your site. Slice a sample from the edge of the hole as if you were cutting a thin slice of cake: cut a sliver from top to bottom, using your hand to hold the slice in your trowel or spade. Remove any stones, grass, etc., and put this sample in a bucket or large container. Repeat this process a few times around your garden site. Mix the soil samples thoroughly in the bucket or container and eliminate any foreign debris.
Using a tablespoon put 8 level tablespoons (4 ounces) of the mixed soil into a clean plastic cup or jar and thoroughly mix with 8 level tablespoons (4 ounces) of water for 30 seconds.
Wait 10 seconds for the soil to settle a bit, and then dip one pH test strip into the solution. Hold the strip in the solution for 3 seconds.
Remove the pH test strip and shake it vigorously to remove any dirt on the pads and wait one minute for the soil solution to fully react with the pH test strip. If the pads are still obscured by the dirt after you waited the full minute you can quickly dip the pH strip into a cup of distilled water to rinse off excess dirt. Depending on soil pH some or all the color pads will change color. Match the resulting color(s) with the color chart that accompanied the pH test strips to determine your soil pH. This takes a bit of work and it helps to do this in a well-lit room or by a sunny window to accurately assess the color change against the color chart. Keep in mind, after 5 minutes the pads on the pH test strip will dry out and the colors will fade so the pH test strips will no longer be useful and should be discarded.
Note: If you find that dirt is still making it difficult to see the color pads on the pH test strip you can use a disposable coffee filter to filter your soil/water mixture. Simply place the coffee filter over a small cup and slowly pour your soil/water mixture into the coffee filter. Once enough filtered water has accumulated in the bottom of the cup you can remove the coffee filter and repeat the pH test in this filtered water.
For more consistent results, you can purchase distilled water for the test (it is best to purchase the distilled water just prior to testing as it will have a near neutral pH when unopened). We have included enough indicator strips for 100 tests, so you may want to test various parts of your site individually to see if there are variations within your garden. Spring and fall tests are useful, too.
Using Lime or Sulfur to Adjust Soil pH
Before you can adjust your soil pH you should know your soil type, so perform the jar test first. Your soil type can affect the quantity of pH amendment (lime or sulfur) you use. You should also be aware that it takes a lot of amendments to change pH.
The following charts will give you approximate application rates. If the chart disagrees with the label on the product you buy, always go with the manufacturer guidelines. Adjusting soil pH with lime and sulfur is not permanent so you’ll need to recheck soil pH every year or two and make adjustments as necessary. The degree and duration of the change depends on how finely ground the amendments are (lime and sulfur). The more finely ground (e.g. pulverized) the faster they alter pH but shorter their effects last (generally 1-2 years depending on your climate). Note that pelletized lime is finely ground but aggregated with a binding agent to form easy to spread pellets. It is best to apply lime and sulfur in the fall or early spring, so they can start working on your soil before you plant.