Soil pH – What is it and why is it important?

Author: Stefan Palm   Date Posted: 7 February 2018 

pH stands for, “the potential of Hydrogen” which can be measured in a soil to determine whether it is acidic or alkaline. This may sound very sciencey but it’s a very important consideration when setting up your soil to grow lawn

pH can range from 0 (Acidic) to 14 (alkaline) where a neutral soil is 7.  Different plants have adapted to grow in different pH values however when it comes to lawns, the optimal range is 6.5 – 7.

What does it mean?

When a soil becomes overly acidic or alkaline, certain nutrients become locked out and are therefore unavailable to the lawn. For example, if a soil was too acidic (eg had a pH of 4.5), then elements like Nitrogen, Phosphorous and Potassium would be completely locked out which will adversely effect your lawn. You could tip fertiliser on by the truckload but the lawn simply wouldn’t be able to access it. Similarly, if your soil was too alkaline (eg had a pH of 9), then elements like Iron, Manganese, Copper and Zinc would be locked out. It’s only when a soil pH is around 7, that all essential minerals and elements are available to the lawn.

If you find that your lawn simply isn’t responding to being fertilised, the answer could be incorrect pH.  It is important to maintain a soil as close to neutral as possible so that your lawn gets the nutrients it needs to thrive. Imbalances can result in unhealthy and poor looking lawn.
The chart to the left shows which nutrients are effected when a soil becomes acid or alkaline. 

How do you test it?

pH can be tested a number of ways. The most accurate way is to use a pH meter however if you don’t own one of these, the next best option is a barium based soil pH test kit . These will give you more of an indication of pH than an exact read but they are very useful in getting an understanding of your soil pH.  

How do you alter it?

If your soil is too acidic, you can increase the pH by adding agricultural lime at the rate of 40g per square metre. One thing to remember here is that you can generally only alter pH 1 point at a time. For example if you had a pH of 5 (acidic) and you wanted to increase it to 7 (neutral), then you would need 2 applications of lime approximately 4 weeks apart.

Similarly, if your soil is too alkaline, you can reduce the pH by using agricultural sulphur. Sulphur is slow to act so you would need to allow a couple of months between applications. 


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