Project list
Sign in to your account
With project lists you can...
Please sign in or create an account to use Project Lists
Understanding soil pH is essential for maintaining a healthy lawn. Soil pH directly influences nutrient availability. If the pH levels are too high or too low, certain nutrients become less accessible to the lawn, leading to issues with yellowing, stunted growth and increased susceptibility to pests and diseases. Here’s how to measure the pH of soil and maintain the best pH number for a lush and healthy lawn.
Safety tip: Always wear the appropriate safety equipment (safety glasses, gloves, ear muffs and a mask, for example) and always follow the instructions for the product or equipment.
In technical terms, pH (which stands for the ‘potential of hydrogen’) is a logarithmic scale that measures the concentration of hydrogen ions in a solution. “Put simply, it is a measure of how acidic or alkaline your soil is [by] a number on a scale [from 0-14], with seven being neutral,” explains Steve Jackson, Munns lawn expert.
If the soil pH value is less than 6.5, it is considered to be acidic; if it’s more than 7.5, it is considered to be alkaline.
The soil’s pH levels influence its chemical and biological properties, impacting microbial activity, soil structure and nutrient availability. All of these have a direct effect on overall lawn health.
“For the lawn, you want a pH between 5.5 and 7.5,” advises Steve. Outside of this range, you run the risk of acidic soil or one that has higher alkalinity, which means macronutrients (like nitrogen, phosphorus, potassium and calcium) and micronutrients (like iron, manganese and zinc) become unavailable to plants.
“When your soil starts to move away from this balance point, the nutrients in your soil become unavailable to your plants,” Steve says. “So, if you notice your plants looking yellow or the veins are discolouring despite you fertilising properly, check your pH because the nutrients could be there, but your plants are just not able to access them.”
Maintaining optimal pH levels ensures nutrients are readily available for uptake and promotes a healthy environment for robust root development, lush greenery and overall resilience of your grass.
Several factors affect soil pH, including the parent material, or the geological origin of the soil, which plays a big part. “Soil is composed of a mixture of minerals, organic matter and microorganisms, and minerals in the soil can contribute to alkalinity or acidity,” Steve says.
For instance, a soil derived from limestone will naturally have a higher pH, while those formed on granite will have a lower pH, and therefore be more acidic. “It can be challenging to completely change the pH with soils derived from these rocks, but you can manage with the regular addition of soil amendments,” adds Steve.
Soil pH is also influenced by factors such as the application of fertilisers (which can contribute to soil acidification over time), the decomposition of organic matter, soil biological processes and debris of builders’ or construction materials. “If you’ve been building or there’s run-off from adjacent work sites, this can contaminate the soil and disrupt the pH balance,” says Steve.
If you suspect an issue, test your soil’s pH levels and check the figures against a pH level chart. “Look for soil pH meters or pH test kits at your local Bunnings store,” advises Ash Makin, Bunnings garden care buyer. “It’s a good idea to test multiple areas as soil pH can vary.”
This will give you a better understanding of the area and what’s required to address it.
Tip: Test your soil’s pH levels prior to installing a new lawn to ensure the grass gets a good start.
Once you’ve completed your soil’s pH test, the two best amendments to alter soil pH are lime and sulfur. “Garden lime will raise the pH, increasing alkalinity, while sulfur will lower the pH, increasing acidity,” Steve says. “Always read the instructions to understand how much is required for your lawn area.”
Tip: Multiple applications may be required to achieve the desired pH levels.
“Over time, fertilising and some biological processes decrease the soil pH,” says Steve. “This is normal, so a handful of lime every now and then will help keep your soil pH in balance.”
Alternatively, use a pH soil tester periodically, or more frequently if issues are suspected. Regular soil testing and applying appropriate amendments based on the results are essential practices for promoting healthy turf growth.
Check out our guide to the 10 must-have products every lawn fan should own.
Photo Credit: eg. Cath Muscat, Getty Images
Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. 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.
When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.
