How to test and adjust your soil pH level

Knowing your soil pH level is essential to growing healthy plants in your garden. Here’s how to make sure you get it right.

Why it is important to know your soil's pH level

The pH level is a measure of acidity that is represented by a value between 0 and 14. Acidic soil has a pH value below 7.0 and alkaline soil has a value above 7.0. Different plants thrive in different soil conditions, and because soil provides many of the nutrients and minerals that plants need, getting the right pH level is important. The wrong pH level will mean that your plants may become nutrient deficient and struggle to grow.

When to test your soil

It’s a good idea to test the pH level of your soil before designing or planting a new garden, creating a vegetable plot or planting varieties of fruit. You should also test when you are disappointed in the growth of your garden or some foliage is starting to show evidence of yellowing. You may even want to consider testing your soil in a few different parts of your garden. You’d be surprised how much the pH levels can vary.

Another thing to note is that if you’ve already added lime, fertiliser or organic matter to your soil recently, you’ll need to wait three months before you get an accurate reading.

How to test for soil pH

To test your soil pH level, a simple and effective way is to use a home testing kit. A good tip when taking soil samples from your soil is to get a sample from just below the surface for an accurate reading.

Another way to test for the pH level is by using an electronic pH meter. They come with a probe that is inserted into the soil that quickly gives you an accurate reading.

Adjusting and balancing alkaline soil pH

After testing your soil, if you have a pH value over 7.0, it indicates you have alkaline soil. This will mean that your soil is low on nutrients like phosphorus, iron and manganese.

To increase the acidity in your soil, you can add things like compost and manure, leaf matter or clippings from your garden or mulch. However, make sure you avoid using mushroom compost and poultry manures as these will drastically increase the alkalinity. A powdered sulphur may be needed to help if the pH reading is excessively high.

Some vegetables like a slightly alkaline soil with a value between 7.0 and 8.0. These include asparagus, Brussels sprouts, cabbage, grapevines, leeks and turnips.

Adjusting and balancing acidic soil pH

If your soil has a pH value below 7.0, it is acidic, which is the case with most Australian soils. This may be a problem as many soil nutrients become more soluble under these conditions and can be easily washed away by rain or watering. Nutrients you may lose include calcium, potassium, magnesium and copper. Another thing to note is that in very acidic soil, bacteria can rot organic matter resulting in plant damage. The easiest way to balance acidic soil is to add lime, dolomite or poultry manure.

There are many vegetables and fruits that will thrive in acidic soil with a pH value below 7.0. These include blueberries, beans, broccoli, beets, garlic, kale, lettuce, peas, potatoes, onions and spinach.

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Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.
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