How To Test And Adjust Soil pH

When establishing new garden beds, planting a new lawn, or just adding some new plants to your garden, it’s useful to know the pH of your soil.

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Different plants require different soil conditions and the pH level of your soil is one important consideration.

Let’s discuss how to test the pH level of your soil and also how to adjust it if necessary.

Why test soil pH?

Different plants respond to different levels of soil pH. Some plants will thrive in acidic soils with a pH level below 7.0, while others do better in alkaline soils that have a pH level above 7.0. 

Soils that have extremes either way, such as very acidic soil, are not always good for premium plant growth.

This is because it can mean that your plants are not able to absorb the nutrients in the soil. Hence, their growth will be stunted.

How to test soil pH with strips

Easy-to-use pH test strips are available at various outlets around Australia. These Litmus paper strips will accurately test the pH level of your soil.

Just make sure that you purchase soil pH test strips that cover the full pH range from 0 to 14. 

How to test soil pH

Time required: 1 hour

  1. Take a soil sample

    Take 2 or 3 teaspoons of soil and place them in a plastic bag or small glass jar.

  2. Add water

    Cover the soil with distilled water. Only add enough water to just cover the soil.

  3. Combine

    Shake the soil and water so that they’re fully combined. Let the soil and water sample rest for around 30 minutes.

  4. Strain

    Strain the liquid from the soil into another jar. You can use a paper coffee filter or even a piece of cheesecloth.

  5. Dip pH strip

    Dip the pH strip into the strained liquid and wait for it to change colour.

  6. Interpret results

    Using the chart provided with the strips, compare the colour to determine your soil pH.

The test result should give you a fairly accurate indication of your soil’s pH level. You might want to test different soil samples from separate areas in your garden because the pH can vary from one area to another.

How to test soil pH without a test kit 

You can also do a simple pH test by using vinegar and baking soda. This won’t give you the exact pH level of your soil but it will let you identify whether your soil is acidic or alkaline.

Testing alkalinity with vinegar

  • Take a small soil sample and add some distilled water to turn it into mud.
  • Pour white vinegar over the top.
  • If the mixture starts to fizz, your soil is alkaline.

Testing acidity with baking soda

  • Mix a small sample of soil with distilled water.
  • Sprinkle some baking soda over the mud.
  • If the mixture starts to bubble, then your soil is acidic.

How to lower pH in soil

If you find that your soil is alkaline (pH 7 to 14), you can easily lower the pH level in your soil by incorporating some compost into it.

You can also add cow or horse manure, leaf mulch, or even aged grass clippings. All of these products will help to increase the acidity in your soil.

Avoid adding things like poultry manure and mushroom compost as these products will increase the alkalinity in your soil.

A soil that is alkaline is often low in important nutrients such as iron, phosphorus, and manganese.

However, there are certain vegetable crops that prefer slightly alkaline soil with a pH level of between 7 and 8. Among these are cabbage, leeks, turnips, asparagus, Brussels sprouts, and grapevines.

How to increase pH in soil

Most native Australian soils are acidic. That is they have a pH level below 7.

In acidic soils, nutrients will become more soluble. Therefore, they can easily be washed away and end up in local waterways. This includes nutrients such as potassium, calcium, copper, and magnesium.

The best way to raise the pH level of your soil is to make a soil amendment with agricultural lime, dolomite, or even poultry manure.

A large variety of vegetables and flowering plants prefer slightly acidic soil. Among these are onions, beans, peas, broccoli, garlic, beetroot, lettuce, potatoes, spinach, kale, and blueberries.

It’s also interesting to note that most Australian native plants prefer acidic soil of around 5 to 5.5.

Frequently asked questions

Is clay soil acidic or alkaline?

Most clay soils will be alkaline with a pH range between 8 and 10. This is primarily because clay soils often lack organic matter. The clay particles tend to bind together tightly and thus, important nutrients such as phosphorus, iron, and manganese are not available to plants.

Should I use lime or gypsum?

Lime should be used to raise the pH level of your soil. Gypsum, on the other hand, is often used to break up heavy clay soils and will add important nutrients such as sulphur and calcium. However, adding Gypsum will not affect the pH level of your soil.

Does sand make soil acidic?

Generally speaking, sandy soil is likely to be more acidic than clay soil. This is because water can move through the sand much quicker and leach out the nutrients. Nutrients such as potassium, calcium, and magnesium tend to keep soil pH slightly more alkaline. Therefore, when these nutrients are constantly being leached out, the pH level of the soil will drop.

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Annette Hird

Annette Hird has an Associate Diploma of Applied Science in Horticulture. She has worked in a variety of production nurseries, primarily as a propagator. She also had the responsibility of a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.