The right pH level can mean the difference between a thriving garden or stunted plants failing to grow.
If you’re planning to start a new garden bed or lawn, or your plants are struggling to grow with discoloured leaves, testing your soil pH will help you know how to fix it.
What is soil pH, and why is it important?
Soil pH is how acid or alkaline your soil is. pH actually measures the amount of hydrogen ions in the soil, with more hydrogen ions meaning the soil is more acidic.
It’s measured logarithmically in pH units from 0 to 14, where 0 – 7 is more acidic, 7 is neutral, and 7 – 14 is more alkaline.
The logarithmic part means that a pH of 5 is 10 TIMES more acidic than a pH of 6. pH 5 is 100 TIMES more acidic than pH 7.
So what does this mean for your garden?
The pH level affects a plant’s ability to absorb nutrients. Plants absorb the 14 essential plant nutrients most efficiently at different pH levels.
Some become more available to a plant when the pH is more acidic, and some when it’s more alkaline.
For example, phosphorus is most accessible when the pH level is 6.5. If the pH level is too far off, your plants won’t be able to absorb enough nutrients to thrive or even survive.
But you don’t always want the maximum efficiency. When the soil is too acidic (pH 4 – 5), most plants absorb toxic amounts of soluble aluminum, iron, and manganese. Acid-loving plants, however, have adapted to those levels of nutrients.
Soil pH also affects the beneficial microorganisms that live in the soil and decompose organic matter into nutrients for plants to absorb. Too acidic soil hinders their ability to do this.
The best soil pH depends on the plant. Most plants do well in slightly acidic soil between pH 6 and 7, or even do fine in slightly alkaline soils up to 7.5.
Acid-loving plants like blueberries and rhododendrons do better with higher acidic levels, from 4.5 to 6.0.
You can add amendments to change the pH to something more suitable, or you can choose to grow plants that do well in your existing soil.
What impacts soil pH?
The soil pH level depends on the mineral composition of the soil, climate, and weather.
Your soil probably has the same pH as your neighbour’s, unless it’s been altered by amendments or fertilizers.
Causes of acidic soil
- Rainfall (rain has a pH of 5.6)
- Acid rain
- Root respiration and plant growth
- Synthetic fertilisers (especially those containing ammonium)
- Oxidative weathering (when compounds in rock are exposed to oxygen)
Common myths state that coffee grounds and pine needles make soil more acidic, but they only affect the pH level a tiny bit, if at all.
Causes of alkaline soil
- Weathering or addition of silicate, aluminosilicate, and carbonate minerals
- Water containing dissolved bicarbonates (like baking soda)
- Arid conditions and poor internal soil drainage (soluble salts can’t leach away)
Testing your soil pH is vital to avoid nutrient lockout and other growing issues. It’s not hard to do and the test is quite cheap. So get it done!
Is it necessary to know my soil pH?
A lot of gardening books and blogs advise that knowing the soil pH is essential. But really, it depends on what you’re going to do with the information.
For most gardeners, if everything is growing just fine, then it doesn’t matter knowing the exact pH. Most plants will happily grow in a pH range of 6 to 7.5, after all.
However, if you want or need to adjust your soil pH level, then you should definitely get a pH test done first.
You need to know exactly how much to change the pH level so you don’t overdo it and cause too acidic or too alkaline soil.
Other than that, you can decide if you want to know your soil’s pH level.
When should I do a soil pH test?
You should do a pH test:
Before trying to change your soil’s pH level.
The concentrations/amounts of amendments to add can be tricky, so knowing what exactly your soil’s existing pH level is will help you get to the right pH level and not overdo it, causing new problems.
Before planting a new garden or lawn.
If you’ve decided to dig up that abandoned corner of the yard for a vegetable garden or replanting an ornamental garden with acid-loving rhododendrons, a pH test will help you determine which plants can grow there and which plants can’t.
If you know that your soil is too alkaline for rhododendrons, you’ll save yourself time, money, and failure.
If your plants have stunted growth and severe discoloration from nutrient deficiency
Before applying more fertilizer or compost, get a soil test done to see if it’s the pH level or a severe deficiency in one or more nutrients.
In today’s video this guy shows you everything you need to test your soil pH levels:
How can I test my soil’s pH?
To test your soil pH level, you can either get a home test or a lab test from your local university extension office.
Should I use a test kit or DIY solution?
The most accurate tests are:
- Test kit from your local university extension office (most accurate)
- Lab-grade pH strips
- Electronic pH meter
If you’re just mildly curious and/or would like to have a little fun with the kids, then do one of the DIY alternatives.
How to collect soil samples for testing
Regardless of the method, to get the most accurate pH level, follow these sampling guidelines.
You will need:
- A plastic container with each area you plan to sample
- A trowel
- Divide up your land into sections based on what grows there (your lawn, vegetable garden, wooded areas, low-lying areas, or areas with particular trouble).
- Decide which ones you want to test. Keep soil samples from different areas in different plastic containers.
- Label the plastic container clearly with the area you are testing.
- Walk in a zigzag pattern through the area, collecting 8 to 10 samples for each area in one plastic container. (For trees and shrubs, take 6 to 8 samples around drip lines.)
- To collect the samples, dig down to a depth of 4 inches for lawns or 6 inches for gardens, ornamentals, mixed fruit trees, and wildlife plots, and put a bit of soil in the container. Keep going until you have 8 to 10 samples in one plastic container (at least one 1 cup worth of soil).
- Remove any rocks, debris and plant parts from the samples.
- Mix the soil samples in the container.
- Continue with the next area and a new container.
How to test soil pH with a test kit
For $10 – $15, you can get a soil test from your local university extension office.
Your local extension office is a tremendous source of local knowledge, advice and expertise, up-to-date gardening information, and inexpensive but accurate soil testing.
They’ll send you a test kit with instructions through the mail, and when you mail back the samples, they’ll give you a thorough report of nutrient availability and soil pH along with advice on what to do about it.
If your local extension office doesn’t provide testing, then you can also buy a commercial soil sample test.
The test kit will come with instructions on the proper procedure for collecting and submitting samples. Follow the included instructions over anything you find on the Internet as testing methods may differ.
The general procedure is:
- Follow the instructions above for collecting samples.
- Let the soil samples dry in the container.
- Fill out the soil testing form.
- Mail the completed form and soil samples with payment to the testing office.
How to test soil pH with pH strips
pH strips are strips of paper that turn different colors based on the pH level.
After dipping the strip into the soil solution, you compare the color you get to the color guide to figure out the pH level.
pH strips sold to gardeners are not accurate enough to make decisions. It’ll tell you if it’s 6.0 or 7.0, but that’s a vast range. Instead, pick up lab grade pH strips which will give a more precise pH level, although some numbers/colours will still blur together.
For more accuracy, use a test kit or the electronic meter.
You will need:
- Lab-grade pH strips
- Soil sample
- Container with a lid
- Distilled water (pH neutral)
To use the pH strips:
- Collect samples using the steps above.
- Place 1 cup of soil (from the mixed plastic container) and 1 cup of distilled water into a lidded container.
- Cover the container and shake well.
- Let the container sit for 30 minutes to allow the soil sediment to settle.
- Take a 1-inch strip of the pH test paper and touch the tip to the soil solution.
- Keep the test strip on the surface of the water until the paper draws up ½ inch of water.
- Match the colour that appears to the colour guide.
How to test soil pH with an electronic pH meter
An electronic pH meter provides a precise readout on a digital screen that tells you exactly what pH the soil is. A more expensive meter where you insert the probe into a soil solution will give you more accurate results than the cheap meters you stick directly into the ground.
To use the electronic pH meter:
- Collect samples using the above guide.
- Calibrate your electronic pH meter following the manufacturer’s instructions.
- Mix 1 cup of soil with 2.5 cup of distilled water in a lidded container.
- Cover the container and shake well.
- Allow the mixture to sit for 30 minutes for the sediment to settle.
- Stir just before immersing the meter’s probe into the solution.
- Read the pH level and write it down for reference.
How to test soil pH without a test kit?
This method is more for fun (and an interesting experiment with young kids!) than to figure out the pH level of your soil.
This test will only give you a vague idea of how acidic or alkaline your soil is, not give you a precise number that you can make decisions with.
You will need:
- Soil sample in plastic container
- Red cabbage
- Distilled water (pH neutral)
- A knife
- A pot
- A strainer
- A stove
- A clear container
To test the pH level with red cabbage:
- Collect the soil sample.
- Chop the red cabbage into small pieces.
- Boil the red cabbage in distilled water.
- When the boiling water turns violet (this takes about 10 minutes), remove the pot from the stove and strain out the cabbage.
- Pour some violet water into a clear container.
- Add a spoonful of soil to the violet water. The colour will change. Pink means the soil is acidic. Blue-green means alkaline. Unchanged violet means neutral. The deeper the colour, the more acidic or alkaline it is.
Conclusion
Knowing your soil pH level can help you figure out why plants are stunted or help you start a new garden bed or lawn off right. Spending the money and time to get an accurate pH test done will save you heartache in the long run.
