What you need to know about your soil’s pH levels
If you’re wondering why, despite following instructions to the letter, your plants still aren’t thriving, the problem might be in your soil’s pH. All plants have a preferred range of soil acidity and if the pH level is not conducive to your plants, a host of problems often follow. Here’s what you should know.
What is pH?
In a scale running from zero to 14, pH units measure the acidity or alkalinity of a substance. A pH level of seven is neutral and as numbers decrease from seven, the acidity rises, whereas when numbers increase from seven, the higher the alkalinity. Generally, soil ranges from an extremely acidic pH of three to a very alkaline pH of 10. The pH level is affected by many different factors like rainfall, temperature and vegetation type. Most plants enjoy slightly acidic conditions with a pH level of six-and-a-half but common exceptions include blueberries, potatoes, azaleas, and rhododendrons, which like moderately acid soil.
What does pH do?
Soil pH indirectly but importantly influence how easily plants can take up nutrients from the soil. Plant roots absorb nutrients such as nitrogen and iron when dissolved in water. If the mixture of water and nutrients in the soil is too acid or alkaline, some nutrients won’t dissolve and so will not be absorbed by the roots. Most plants thrive in slightly acidic soil that range from six to seven-and-a-half but once pH level is below six, nutrients such as nitrogen, phosphorus, and potassium, are less available. If the pH rises above seven-and-a-half, iron, manganese, and phosphorus are less available.
How do you adjust your pH levels?
Firstly, you need to know what the current pH level is so you can determine if you need to raise or lower the acidity. A simple soil test can be done at home with a pH kit purchased from most nurseries and garden centres.
If your soil is too acid, add an alkaline material to correct the soil. The most common material is ground limestone, which is available in two types: calcitic limestone (calcium carbonate) and dolomitic limestone (calcium-magnesium carbonate). If soil is too alkaline, the most common material to add is sulphur. Both are available in powdered and pelletised form, but pellets are easier to spread uniformly. Mix materials with top soil if quick action is needed, otherwise just lay pellets or powder on top of ground and let it work its way down.
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