How to Test Soil pH

My Garden Life
March 23, 2022
Table of Contents
Knowing whether your soil is neutral, acidic, or alkaline makes a big difference in your garden. Understanding how to test soil pH is the first step to improving how your food plants produce and how your flowers flourish. Use this DIY soil pH test to get an idea of your soil’s health with simple items from your kitchen.
If your plants are struggling to grow, it pays to balance the soil’s pH so all your plants can thrive.

Here’s how to make a DIY soil pH test at home:

baking soda, vinegar, distilled water, garden trowel, and bowls to be used for DIY soil pH testing

1. Grab two glass bowls, a spoon, distilled water, baking soda and vinegar.

woman with trowel collecting soil samples into two bowls to use for testing soil pH

2. Gather spoonfuls of dirt from your garden and place them in the bowls. You should test each bed separately because each location will probably need its own soil amendments.

hands pouring jug of distilled water into a bowl of soil for pH testing

3. Pour distilled water into one of the bowls and stir until it turns into mud. (Use distilled water rather than tap water because it has a neutral pH.)

hand pouring spoonful of baking soda into a bowl for soil pH testing

4. Add a couple of spoonfuls of baking soda to the mud and stir. If it fizzes or gets foamy, you know you have acidic soil.

hands pouring jug of vinegar into a bowl for soil pH testing

5. Pour a little vinegar into the other bowl and stir until it’s muddy. If it fizzes or gets foamy, you know you have alkaline soil.

two bowls of wet soil showing difference in pH test results between using vinegar or baking soda

6. If neither test produces a reaction, you have neutral soil. In this test, adding baking soda caused some bubbling to occur, indicating that the soil pH is on the acidic side. Adding vinegar did not cause any reaction, so this is more evidence that the soil pH is neutral to acidic, not alkaline.

Adding Compost Can Help Balance Soil pH

person with shovel applying compost to a vegetable garden

Adding compost is the best long-term way to balance your soil, whether you have an acidic or alkaline garden. Add half of an inch of compost to the surface of your garden. It’s best to spread it at the end of the growing season or early in spring before you plant. Of course, you can add compost anytime, but it takes a while to have full effect.
What if you want a quicker fix? Here are some ideas to help your soil get closer to neutral in a shorter amount of time.

Lower the Soil pH – Soil Amendments for Alkaline Gardens

Aluminum Sulfate Can Help Lower Soil pH

scoop of aluminum sulfate granules tilted and spilling out onto a table

Aluminum sulfate or iron sulfate are the recommended amendments for alkaline gardens. Elemental sulfur is also effective but takes longer to make an impact and you should add it in the fall. It’s best to buy this product from the garden center in packaging that provides you with the appropriate directions and application rates for your project.

Pine Needles are a Good Mulch for Acid-Loving Plants

pine needle mulch surrounding a rhododendron shrub

Pine needles, shredded leaves and sawdust are great mulches for plants growing in alkaline soil. These break down gradually through the action of rain or irrigation and change the soil’s pH over time. Don’t overdo it, though, or you may turn your garden acidic.

Coffee Grounds are Good for Compost but not for Adjusting Soil pH

woman carrying a container of coffee grounds applying the grounds to a garden with her hands

Sprinkling used coffee grounds around plants to fix alkaline soil isn’t an effective method. Most of the acid was leached away through brewing, so little is left to balance your soil. However, if you have container gardens or a small area, “watering” with cold, full-strength coffee once a week is helpful to lower the pH of the soil.

Raise the Soil pH – Soil Amendments for Acidic Gardens

Limestone Helps Raise Soil pH

hand with trowel displaying dolomitic limestone that is being applied to a garden bed

Dolomite lime, which you can pick up at any gardening center, is a good investment for acid soils. Ground oyster shells are another healthy soil additive.

Add Crushed Eggshells to Soil to Add Nutrients and Raise Soil pH

gloved hand applying crushed eggshells to a garden bed

If you want to be thrifty and self-sufficient, use your own eggshells to raise the pH, but it will take a while for the shells to break down.
  1. Each time you use an egg, rinse the shell thoroughly and let it air dry completely. (This is to keep your kitchen from becoming smelly and growing nasty bacteria.)
  2. Crush and place in a lidded container.
  3. When you’ve collected enough shells, run them through your food processor or blender until they’re completely broken up.
  4. Then, mix the eggshells into the soil around your plants, trying not to disturb the roots.
Now you have plant food from something you already use.

Wood Ashes Enrich and Help Neutralize Acid Soil

Hand holding trowel applying wood ashes from a bucket to a lettuce garden

Hardwood ashes are another acidic soil amendment, but these should be added in the fall and mixed into the dirt very well to prevent plant burn.
Did you know that you can change the color of bigleaf hydrangea to pink or blue just by altering the soil pH? Learn how in our article, How to Change the Flower Color of Bigleaf Hydrangea.
Bigleaf hydrangea border next to old house with blue and pink flower clusters


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