If, after you have tested your soil pH, you find the levels need adjusting, there are substances available to help with this. These are added to the soil to increase or decrease acidity or alkalinity accordingly. You may find it useful to use your pH meter to help in this process, but bear in mind that changes may not happen immediately.
If soil is too acidic…
Lime is added to increase the pH value of soil. Lime is created from the reaction that occurs when heating limestone and adding water.
If soil is too alkaline…
Sulphur or aluminium sulphate is added to decrease the pH value of soil. Sulphur is a naturally occurring chemical element and aluminium sulphate can be created by heating aluminium with sulphuric acid or by combining aluminium hydroxide with sulphuric acid.
When adding a substance to adjust soil pH, there are a few things to consider when deciding how much to use. These include:
What pH you are starting with
What pH you wish to achieve
The type of soil (clay and sand levels)
The type of substance you are using
The area of the ground you are adjusting
As a very rough estimate, the amount of appropriate substance needed to raise or lower pH by one number on the scale is 0.5 kilograms over a square metre of ground.