Do It Yourself Soil pH Test

DIY Soil Test for pH
The soil on the left, with baking soda, remained mud. The soil on the right, with vinegar added, has started to bubble. This soil is on the alkaline side. Photo: © Marie Iannotti

We're always told to test for our soil pH. It's not one of the more fun or interesting tasks of tending a garden, but it really is crucial. Plants can only access nutrients from the soil if the soil pH is within a certain range. If it is not, you can add all the fertilizer you want and it will never make it into your plants.

So What is pH Anyway?

Technically, pH means "potential hydrogen" and is a measure of how many hydrogen ions are in a substance.

For a gardener's purpose, it is a measure of how acidic (sour) or alkaline (sweet) something is. We generally use it to test our soil, but the pH of the water you use on your garden also affects their growth.

The pH measurement is a logarithmic scale that goes from 1 to 14 with anything less than 7 being acidic, 7 neutral, and anything higher than 7 being alkaline. Because it is a logarithmic scale, each value increases by 10 times. For example: 8 is 10 times more alkaline than 7. 3 is 10 times more acidic than 4.

Pure water would measure a neutral 7. Cow's milk is slightly acidic at 6.5. Both tomatoes and beer measure 4.5. Lemons are very acidic at 2.5 and stomach acid is 2.0;

On the alkaline end, sodium bicarbonate measures 8.4, ammonia is about 11.1 and lime comes in at 12
        
So being acidic or alkaline isn't necessarily bad. It all depends on what the substance is interacting with.

While most plants can adapt to any soil pH in the neutral range of 6.0 to 7.5, some have distinct preferences. Your weeds can even give you a clue about your soil pH. Dandelions, wild strawberries and plantain will proliferate in acidic soil. Chickweed, Queen Anne's Lace, and chicory favor alkaline soil.

In the garden, there are times when you want a slightly off kilter soil pH. Lilacs love alkaline soil and blueberries absolutely need some acidity. You need to know what you will be growing, before making changes to your soil. Then you need to know your soil pH.Here's a simple home test to give you a general idea.

Do It Yourself Soil pH Test

Testing for Alkalinity

1. Take a soil sample from 4 - 6 inches below the surface of your garden. If you have a small garden, you can mix soil for 3 - 4 different spots. If you have a large or spread out garden, it would be better to test several samples separately.

2. Remove any stones, sticks, or other foreign debris and break up any large clumps.

3. Put about 1 cup of soil into a clean, glass container.

4. Add enough water to turn the soil to mud.

5. Add a 1/2 cup of vinegar and stir slightly.

If the soil fizzes, foams, or bubbles, your soil is alkaline. If not, test it for acidity.
 

Testing for Acidity

1. Take a soil sample from 4 - 6 inches below the surface of your garden. Do not try this second test on the soil you poured vinegar on.

2. Remove any stones, sticks, or other foreign debris and break up any large clumps.

3. Put about 1 cup of soil into a clean, glass container.

4. Add enough water to turn the soil to mud.

5. Add a 1/2 cup of baking soda and stir.

If the soil fizzes, foams, or bubbles, your soil  is acidic. If neither test produced much of an effect, your soil is probably in the neutral range.
 

This test can tell you toward which end of the soil ph scale your soil is leaning, but for an exact measurement, you will need to get a pH soil testing kit or send a soil sample out to a lab for testing. You can purchase home testing kits at most garden centers and your local cooperative extension service often sells them, too. They can also test your soil for you.

In general, acidic soil is made neutral by adding lime and alkaline soil is corrected with sulfur. How much to add depends on the actual correction needed, so the more accurate the test the better.