This post was last updated on October 18th, 2022 at 03:35 am
Is your soil acidic or alkaline? Despite the impact of soil pH, many will not realise the importance of why you should monitor and measure your soil’s pH rate. If you do not know the pH of your soil, stick around and find out why it’s important to monitor your soil pH.
What is Soil PH?
Soil pH is a measurement used to determine whether the soil is acidic or alkaline. Using a logarithmic scale of 0-14 (displaying numerical data across a wide range in a compact scale), a reading can be given to indicate the acidity levels of soil.
A low reading on the pH scale (6 and below) indicates acidic soil. Alkaline soil is measured through a higher reading on the pH scale (8 to 14). A reading of 7 is neutral. Ideally, your soil should be between 6 (slightly acidic) and 8 (slightly alkaline).
When using a pH scale, acidic is presented with the colour red, alkaline is presented in purple, and neutral is green. Your soil pH is determined by the hydrogen ion concentration. Acidic soil has a high hydrogen ion concentration whereas alkaline has a low concentration.
The pH of the soil is affected by several factors, including:
- The rock source from which the soil was formed
- Any weathering processes that act on the soil
- The use of fertilisers
- Soil content (clay soils are more resistant to changes in pH)
- Root respiration
- Decomposition of organic matter
- Acid rain
Some nutrients can be absorbed better in alkaline soil, whereas other nutrients are better absorbed in acidic soil. The graph below outlines what soil pH is best for nutrient absorption.
Why is it Important to Monitor Soil PH?
No matter the size of a garden, or the scale of plant production, it’s important to monitor and measure your soil pH. It’s also important to check your soil pH before planting a new garden (such as fruit and vegetables), if plant foliage starts to yellow, or if plant growth is disappointing.
The all-important question then – why is it important to monitor soil pH? The acidity of the soil is important as it can affect plant growth. If your soil acidity is too high or low, the nutrients in the soil cannot be absorbed by plants.
No matter what efforts you make to fertilise the soil, if the soil pH is not conducive for allowing the plant roots to absorb these nutrients, it won’t make any difference. All plants have an ideal soil acidity level at which they can best absorb nutrients from the soil.
Your garden health is entirely dependent on soil pH. That’s not to say having the wrong pH will kill your plants because it won’t. But the wrong pH does significantly impact growth. That’s why if you have a disappointing show in your garden one year, it may be worth checking your pH level.
Planting flowers in soil that is the wrong pH is often a factor that gets overlooked by many gardeners. Some plants like it acidic while others like it alkaline. Soil acidity can even determine the colour hydrangeas grow. Acidic soil grows blue, alkaline soil grows pink, while neutral grows purple.
How Can I Measure Soil PH?
So, now you know the importance of monitoring your soil pH, it’s time to see how you can easily measure it. Fortunately, there are several easy methods you can use that are quick and effective. Let’s take a look…
It should be noted that if you’ve applied fertiliser or any other solutions to your soil within the last 3 months, this can affect your pH reading.
Soil PH Meter
The first (and easiest) option to measure soil pH is using a soil pH meter. These small devices can provide you with an accurate reading of your soil pH for home use. They can also be used time and time again making them the best way to monitor soil pH over long periods.
These devices are easy to use and only require switching on. You can take the soil pH directly in your garden, without the need of obtaining a small soil sample first. Just stick the probe straight into your garden and switch the device on. No need to obtain a soil sample.
Some meters will also provide you with moisture and light readings. Many meters also don’t require a power supply or battery, so you can use is straight away. Just remember to clean the probes after every use for best results.
These FAQs may answer any questions you have about soil pH meters.
PH Test Kits
Another method for checking your soil pH is using a pH test kit. Unlike the pH meter, these don’t provide you with a precise reading, and they require a little more chemistry too. That’s because pH test kits work by using a testing solution that changes colour.
Inside a test kit, you should find your testing solution, a test tube, and a colour indicator chart. If there’s no tube provided, use a clean small container. You’ll also need to take a representative soil sample from your garden that is free from any debris, such as twigs or stones.
Ideally, a representative soil sample is taken around 6-8 inches below the soil surface. Once you’ve obtained your clean soil sample, mix it with the required amount of testing solution and give it a good shake.
Once the liquid clears, the solution will change colour according to the acidity level of the soil sample. Closely match it to the colour on the chart to find the pH of your soil. It won’t provide you with an exact figure, but will give a rough idea.
Litmus Paper
The other method to measure the pH level of your soil is using litmus paper. The principle is much the same as the testing solution from the test kits. Instead of using a testing solution though, you’ll be using litmus paper.
Litmus paper is specially designed to change colour when exposed to liquid. The colour of the litmus paper will change depending on the acidity levels of the liquid. You’ll need to use a mixture of a clean soil sample (free of debris and from around 6-8 inches below the surface) mixed with water.
Once you’ve mixed the water and soil sample together, dip the litmus paper into the soil and water solution. Then, watch as the paper magically changes colour according to activity. Use the pH scale to get a rough estimation of your pH level.
How Can I Alter my Soil’s PH?
After measuring your soil pH level, you may have uncovered that it’s not the ideal acidity for growing the plants you want. If this is the case, you’ll want to find ways to alter your soil pH. Help is at hand as we look at several ways to do this.
Increasing Soil PH
If you find your soil level is too acidic, you’ll need to use ways to increase the pH. The most popular method for increasing the pH of the soil is using lime or dolomite. Using these solutions will provide you with much more alkaline soil levels, ideal for growing lilacs, lavender, and honeysuckle.
How much lime or dolomite you apply will depend on the type of soil. Clay soils, for example, will need much more lime due to the slow drainage of this soil type. However, if you have rhododendrons or camellias, you’ll need to hold off applying the lime.
You can also use wood ash as a way to increase your soil pH. Not only can wood ash help to add potassium and calcium to your soil, but it also has a similar effect to lime to help increase pH levels. Any leftover ashes from wood fires can be applied to the fallow ground or dug into the soil.
Lowering Soil PH
If you want to be growing blueberries, heathers, lilies, magnolias, or azaleas, you’ll need acidic soil. The most popular option for lowering your soil pH is using sulphur. The finer the sulphur you apply to your soil, the quicker bacteria in the ground can convert it to sulphuric acid.
Using dust solutions of sulphur provides much quicker results compared to chips but is more expensive. Even with sulphur dust, you’ll need to wait at least a few weeks for any effect (longer in the winter). Sulphur is also considered the least likely to cause harm to your plants.
Alternatively, you can use aluminium sulphate or ferrous sulphate. Aluminium sulphate however should be used cautiously as it can lead to a build-up of aluminium that becomes toxic to plants. Ferrous sulphate, when used in large amounts, can interfere with phosphorous availability.
However, both aluminium sulphate and ferrous sulphate have a quicker turnaround for lowering soil pH levels compared to sulphur. The RHS no longer recommends using peat for lowering soil pH.
Now you know the importance of soil pH and how it can affect the growth of plants, it’s time to get to work and find out the soil pH of your garden. So, greenfingers better get gardening!
