Testing Garden Soil pH | Gardening In Canada

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Ashley is a soil scientist who has had a passion for plants since she was a small child. In the long summers as a child, she would garden alongside her grandmother and it was then that she realized her love for greenery. With years of great studying, Ashley had begun her post-secondary education at the University of Saskatchewan. After years of working in agriculture R&D she has decided to take on teaching gardeners using science.

Why is pH important?

Soil pH is important because it influences several soil factors affecting plant growth. This includes soil bacteria involved in cycling nutrients, reducing nutrient leaching with water, nutrient availability, and absorption of toxic elements into plants and soil structure. The bacterial activity involved in nutrient cycles such as nitrogen, phosphorus and potassium perform best in pH range 5-7.5. Bioavailable plant nutrients are leached out of soils with a pH below 5.0 relatively rapidly. This means it is not accessible to plants and can end up in waterways or simply out of range for the plant roots.

Toxic Nutrient Release

Toxic elements such as aluminum can become toxic to plant growth when the pH is below 5 due to it becoming released from the soil solution. This release results in nutrients suddenly being available to the plant due to weakened bonds. Clay soil when outside the pH of 5.5 – 7.0 can become sticky or compact making it difficult to cultivate and work with. Testing your soil pH will tell whether your soil will need to be amended or not.

Acidic Loving Plants

Keep in mind some plants enjoy pH outside of the normal range of 5.5 to 6.5. The pH is not an indication of nutrients, but it does affect the bioavailability of fertilizer nutrients both in the soil and being added in the future. Soil may contain adequate nutrients, yet growth may be limited for plant usage due to the pH.

Scientific Literature Says

According to scientific literature, plants have a specific pH range in which they grow optimally. For example, many vegetable crops, such as tomatoes and peppers, prefer a slightly acidic soil with a pH between 6.0 and 7.0. On the other hand, plants such as blueberries and azaleas require a more acidic soil with a pH between 4.5 and 5.5.

An article published in the journal “Agronomy for Sustainable Development” states that “pH is one of the most important soil properties for plant growth and nutrient availability, and its management is essential for sustainable crop production.”

Another study published in the “Journal of Plant Nutrition” states that “pH directly affects the solubility and availability of nutrients in the soil. At low pH, aluminum and manganese can become toxic to plants, while at high pH, iron, zinc, and manganese can become less available.”

Microbe Health Depends Soil Ph It

The variety and activity of the soil’s microorganisms can be greatly influenced by the pH of the garden soil. Various kinds of microorganisms, such as bacteria, fungus, and actinomycetes, can grow and survive depending on the pH level of the soil, according to scientific literature.

According to a study that appeared in the journal “Soil Biology and Biochemistry,” soil pH has a significant impact on the variety of bacterial populations in soil. The study discovered that as soil pH rose, the diversity of bacterial species shrank.

Another study discovered that soil pH can impact the activity of soil enzymes, which are crucial to nutrient cycling. This study was also published in “Frontiers in Microbiology.” According to the study, soils with a pH of neutral had the maximum activity of the enzymes involved in the cycling of carbon and nitrogen (6.5-7.5)

According to a study in “Microbiology,” the growth of helpful microbes like mycorrhizal fungi, which are crucial for plant nutrient uptake and disease prevention, might be inhibited by soil acidity.

How to Correct an Alkaline Garden Soil pH

There are numerous ways to fix alkaline garden soil (pH above 7.0):

Sulfur can be added to the soil in order to reduce pH. It is available in a number of forms, such as sulphur coated urea, sulphur powder, and elemental sulphur. It’s crucial to adhere to the product’s recommendations and refrain from overapplying.
Reduce the pH of the soil by using acidic fertilisers, such as ammonium sulphate or ammonium nitrate. The nitrogen and sulphur that are released into the soil by these fertilisers over time may cause the pH to decrease.
Peat moss, pine needles, or coffee grinds are examples of organic materials that you can add to your garden to help lower the pH of the soil. As organic matter breaks down, the pH of the soil will steadily decrease since it is naturally acidic.
Watering your plants with acidified water: Watering your plants with water that has had the pH of the soil lowered by adding vinegar or citric acid to it will assist. However, as it is simple to over-acidify the soil, this approach should only be used sparingly and with care.

Products for Amending Alkaline Soil:

How to Correct an Acid Garden Soil pH

There are numerous ways to fix acidic garden soil (pH < 7.0):

The pH of acidic soils can be raised by adding lime, a popular soil supplement. Limestone that has been pulverised into it has a lot of calcium and magnesium. Dolomitic lime or agricultural lime can be used to amend the soil.
Utilize wood ash: Produced by burning wood, wood ash is rich in potassium and calcium. To increase the pH of the soil, it can be added. It’s crucial to remember that wood ash should only be used sparingly because it can significantly elevate the pH.
Include bone meal: Bone meal is an organic calcium and phosphorus source. To increase the pH of the soil, it can be added.
Use hydrated lime: When put to soil, hydrated lime raises pH quickly because it is a dry powder. It should be handled carefully and with protective equipment because it can irritate the skin and the eyes. Hydrated lime will cause burn so avoid this.

Products for Amending Acidic Soil

This Takes Time…

It is crucial to remember that adjusting the pH of soil requires time and may call for several applications to reach the desired pH level. Following corrections, it’s crucial to check the pH level and make any necessary modifications.

I have a video on this topic, but lime or dolomite are used to increase the pH of the soil. Lime contains mainly calcium carbonate and dolomite contains both calcium carbonate and magnesium carbonate. Use caution with hydrated lime because this can cause root “burn”. The amount needed to change the pH will be higher for soils with large amounts of organic matter or clay in the soil. Start with a little bit and work your way up to testing every step of the way.

It’s crucial to remember that adjusting the pH of soil takes time and may call for several applications to reach the ideal pH level. Following corrections, it’s crucial to check the pH level and make any necessary modifications.

There are several at-home pH soil test methods that you can use to test the pH of your garden soil:

Liquid pH test kit: These kits typically include a dropper, test solution, and a color chart to compare the results to. Simply mix a small amount of soil with water in a container, add a few drops of the test solution, and compare the resulting color to the chart to determine the pH level.
pH indicator paper: This paper changes color when it comes into contact with a solution of a certain pH. Simply mix a small amount of soil with water in a container, dip the indicator paper in the mixture and compare the color to the chart to determine the pH level.
Baking soda test: Mix a small amount of soil with water in a container, add a teaspoon of baking soda and stir. If the mixture fizzes, the soil is likely acidic. If it doesn’t fizz, the soil is likely alkaline.
Vinegar test: Mix a small amount of soil with water in a container, add a tablespoon of white vinegar and stir. If the mixture fizzes, the soil is likely alkaline. If it doesn’t fizz, the soil is likely acidic.
Red Cabbage Test: See Below
pH meter: A pH meter is a handheld device that measures the pH of a solution. It can be used to measure the pH of soil mixed with water. (not my favourite)
pH indicator paper: This paper changes color when it comes into contact with a solution of a certain pH. It can be used to test the pH of soil mixed with water.
Soil test: A soil test is a laboratory analysis of soil samples to determine pH, nutrient content, and other properties. Soil test kits can be purchased or collected by samples from a local extension office. This tends to be the MOST expensive option.

Test Your Soil pH Using the Red Cabbage Method

You can even use this test on your tap water or rainwater to see what your baseline is.

Step 1. Measure 2 cups of distilled water into a pot.
Step 2. Dice up and add 6 red cabbage leaves. It must be red cabbage.
Step 3. Simmer for 10 minutes. Remove from heat and allow it to sit for up to 30 minutes. Ensure is cooled down enough to work with.
Step 4. Strain off the coloured liquid. This will have a neutral pH of 7.
Step 5. Add 2 teaspoons of soil from the selected horizon to a mason jar and a few inches of cabbage water. Stir and wait for 20-30 minutes.
Step 6. Check the colour. If it turns red/pink, your soil is acidic. If it is blue/ yellow-green, your soil is alkaline. Neutral soil will stay close to the original colour of purplish/blue.
If you add too much soil and the water turns brown or grey, you will need to redo the test.

References:

Soil Biology and Biochemistry, “The effect of soil pH on bacterial community structure and diversity”
Frontiers in Microbiology, “Soil pH effects on enzyme activities and microbial community structure”
Microbiology, “Acid soils and acid rain: do they have an impact on the diversity and function of mycorrhizal fungi?”
Agronomy for Sustainable Development, “pH management: an essential component of sustainable soil fertility”
Journal of Plant Nutrition, “Soil acidity and plant nutrition”