To keep your garden or yard green and full of life, test your soil’s pH value to ensure it will meet your plants’ needs.
The pH value affects how easily plants can absorb nutrients and chemicals in the soil’s water. Some nutrients are more available under acidic conditions; others require more alkaline.
You should test a soil sample at least once every three years or when you want to change your landscaping.
You can buy a soil test kit at the home center, or check your soil’s condition with this basic DIY test.
Simple Soil pH Test
For this simple soil pH test, all you need is baking soda, vinegar, water, a container, a measuring cup and, of course, a sample of your soil!
Testing for Alkalinity
- Place a handful of soil into a clean container.
- Add ½ cup of white vinegar.
- If the soil starts to fizz, it’s likely high in alkaline.
- If the test proves the soil’s alkalinity, amend the soil with sulfur or pine needles.
Testing for Acidity
- If there is no reaction in the vinegar test, take a second container and add fresh soil.
- Pour ½ cup of water into the container, mix well, and add ½ cup of baking soda.
- If the soil begins fizzing, the soil is likely acidic.
- If there’s no reaction to either test, the soil has a neutral pH and it’s fine.
- If the soil is acidic, amend it with pulverized lime or wood ash.
How to Make Acidic Soil More Alkaline
Acidic soil has a lower pH value. If you need to increase the soil pH, add lime in the form of calcium carbonate or dolomite (calcium and magnesium carbonate), according to the Mississippi State University Extension.
Some homeowners prefer the pellet form of lime over agricultural limestone because it is easier to apply with broadcast spreaders. It’s also not dusty and can be evenly distributed without wind affecting it.
Apply lime before planting so you can thoroughly incorporate it and have time — several months — to increase the soil pH.
MSU does not recommend using hydrated lime because it can easily burn plants. Applying too much lime can reduce nutrient availability, especially micronutrients like iron, manganese and zinc.
How to Make Alkaline Soil More Acidic
Alkaline soil has a higher pH value. If you need to decrease the soil pH, add elemental sulfur several months before planting, according to MUS’s Extension. It’s slow-acting but effective.
If you add elemental sulfur to established plants, water the soil immediately to avoid burning shallow roots. Once the correct pH is established, the sulfur remains effective for years.
Here’s what else you should know, according to MSU’s Extension:
- Iron sulfate decreases soil pH and is faster-acting than elemental sulfur. But you need more iron sulfate than elemental sulfur to achieve the same pH change. Follow the label instructions carefully because too much iron sulfate can burn shallow plant roots.
- You can also use ammonium sulfate to decrease soil pH, and it is less likely to burn shallow plant roots.
- If you want to produce blue blossoms on your mophead hydrangeas, use aluminum sulfate to lower the pH while adding aluminum. Aluminum, together with a low pH, produces a blue color.
- Except for blue hydrangea, don’t use aluminum sulfate as a soil acidifying amendment because of the potential for aluminum toxicity to plant roots.
Read MSU Extension’s full guide, Soil pH for Landscape Plants, for more information.