Knowing how to test soil pH is important for proper plant growth. Most plants have a preference for the degree of acidity or alkalinity in the soil, which is measured by a pH scale that ranges from 0 (extremely acidic) to 14 (extremely alkaline). It's possible to have your soil pH tested by taking a sample and sending it away to a lab for analysis (usually for a fee). You also can test your soil pH yourself at home with test strips.
If you don't want to purchase test strips, you can test your soil with baking soda and vinegar. Using these common household items for a DIY soil test will give you immediate results, and the test is easy to conduct. The results won't be as precise as a lab test, but they will give you a ballpark idea of whether your soil is acidic or alkaline. An extreme reaction in either direction will let you know whether you need to amend your soil either to raise or lower the pH.
When to Test Soil pH
You won't know if your soil pH is too low or too high unless you test it. You don't want to wait until your plants start to struggle with an incorrect pH, and even then it can be difficult to pinpoint a problem with the pH unless you run a test. Thus, it's a good idea to test soil pH whenever you are planting a new garden bed, you move to a new location, or you are growing a new plant variety that has very specific pH needs.
Some experts recommend that gardeners test the soil every few years, especially when you have needed to amend the soil in the past. The materials used to adjust soil pH, such as elemental sulfur (used to lower soil pH) or lime (used to raise soil pH), break down over time and might need to be reapplied to keep the pH level at optimal levels.
Equipment / Tools
Vinegar and Baking Soda
- 2 small containers
- Measuring cup
- 2 small containers
Vinegar and Baking Soda
- 1 cup distilled water
- 1/2 cup white vinegar
- 1/2 cup baking soda
- Soil amendments (if needed)
- Distilled water
- Coffee filter
- Soil pH test strip
Soil pH Test With Baking Soda and Vinegar
Collect 2 Soil Samples
To test your soil pH at home, first scoop some soil from the planting area into two clean containers with your trowel. Take soil from a few inches below the ground surface. You'll need approximately 1 cup of soil in each container. Break up any clumps, and remove any rocks, sticks, or other debris.
For best results take a blended soil sample. For example, if you're planting a single garden bed, take a few samples from just that area and mix them together. If you're planting a large area, such as an entire lawn, take samples from many areas of the yard and blend them together for testing.
Testing a blended soil sample will give you the most accurate results because a single garden spot might be atypical of the rest of the soil. For example, a sample taken from an area near a pine shrub might be extra acidic because pine needles tend to add acidity.
Test for Alkalinity
Add 1/2 cup of distilled water to one soil sample container, and mix it up with a spoon. Then, add 1/2 cup of white vinegar. If the soil shows a visible bubbling or fizzing action, then it has an alkaline pH.
The chemical reaction that you're seeing occurs when an acid (vinegar) comes in contact with something alkaline (soil). The more pronounced the fizzing action, the higher the soil pH is. Because most soils are naturally slightly acidic, any reaction at all with this test usually indicates that you have alkaline soil.
Test for Acidity
Now, add 1/2 cup of distilled water to your second soil container, and mix it up. Then, add 1/2 cup of baking soda. If the soil bubbles or fizzes, that means it's acidic.
The reaction you're seeing is the result of acidic soil coming in contact with an alkaline substance (baking soda). Again, the vigor of the action indicates how acidic the soil is. A very small amount of fizzing is natural because most soils are slightly acidic to begin with. But a forceful reaction might indicate that you have very acidic soil.
Amend the Soil if Necessary
If your tests show your soil pH is too alkaline or acidic for your needs, you can blend in amendments to bring the pH into a suitable range. Agricultural lime is commonly used to help raise soil pH. But you can also raise the pH of soil without lime by using wood ashes. To lower soil pH and make it more acidic, pine needles and elemental sulfur are traditional amendments used.
It can be difficult to gauge how much amendment is needed. You can start by amending with small amounts and then repeating your soil pH test at home to gauge where you're at. But if you want to lower or raise the pH of your soil fast, it's often best to invest in a laboratory test to determine exactly the type and quantity of amendment needed. University extension offices usually offer soil pH testing services, and the report you get will give you lots of detail on how to do it.
Soil pH Test With Strips
Dig for a Sample
Take a blended soil sample from different parts of your planting area. Dig for it with your trowel a few inches below the soil line, and put the soil in your clean container. You'll need about a half cup to a cup of soil; it doesn't have to be exact. Break up clumps, and remove any debris from the soil.
Pour in Distilled Water
Pour distilled water into your container up to the same level as the soil. Vigorously stir the mixture, and then let it sit for around 30 minutes.
Drain the Sample
Pour the soil sample through a coffee filter and into another clean container. Make sure you are capturing the solids and allowing the liquid to pass through.
Use the pH Test Strip
Dip the soil pH test strip into the liquid. Pay close attention to the instructions that came with the test for how long to leave the strip in the liquid. When the strip turns a color, compare the color to the chart on the test strip packaging to determine the pH.
Soil Testing Tips
- You might have different types of soil in different parts of your yard, so consider testing each of your garden beds.
- The DIY soil pH test with vinegar and baking soda will be your cheapest option but also the least specific. Purchasing a test strip kit will be slightly more expensive but more definitive. And a laboratory test will be the most expensive, but it also will give you precise information about your soil.
- If you test your soil pH at home using vinegar and baking soda and neither produces much of an effect, your soil is probably in the neutral range.
- Continue to test and tweak your soil over time. Maintaining healthy soil is an ongoing task.