Introduction
This is the measure of the hydrogen ion (H+) concentration of a soil solution, with the amount of hydrogen ions present affecting the level of acidity. Higher concentrations of hydrogen ions result in a more acid soil.
The pH scale ranges from 0 to 14, i.e. from acid to alkaline, with neutral being pH 7.0, with the pH of soils within the UK mainly falling within the range pH 4.0 - 8.0. The pH scale is a logarithmic scale, with, for example, pH 6.0 being 10 times more acidic than pH 7.0, whilst pH 4.5 is 100 times more acidic than pH 6.5.
Some general points about the effects of soil pH
- The maximum amount of essential nutrients are generally available between pH 6.0 - 7.0;
- Most nutrients become 'locked-up', or less available, for plant growth at low (acidic) pH levels;
- The majority of soil micro-organisms prefer a soil pH of 6.0 - 8.0;
- Neutral and alkaline soils usually have higher contents of calcium within the soil and this helps towards soil particles aggregating together (i.e. flocculation), improving soil structure.
Turfgrasses and pH
Turfgrasses vary in their tolerance of pH levels, with different species having different pH preferences. Some examples are given below, however, it should be noted that whilst most turfgrasses will grow outside of their preferred range, it is just that they are not as vigorous in growth and will become more unhealthy as the pH level becomes more unsuitable.
| Turfgrass | Main pH range for suitable growth |
| Browntop bentgrass | 4.0 - 6.0 |
| Creeping bentgrass | 5.5 -7.5 |
| Red fescues * | 5.0 - 7.0 |
| Annual meadow grass | 5.5 - 7.5 |
| Perennial ryegrass | 6.0 - 7.0 |
| Smooth stalked meadow grass | 6.0 - 7.5 |
| Yorkshire fog | 4.5 - 8.0 |
| Hard fescue | 4.0 - 5.5 |
* Some slender creeping red fescues have good tolerance to saline conditions, with consequently higher pH values.
A typical pH for fine turf, such as a bowling green, is 5.5, whilst for perennial ryegrass dominated turf, such as a football pitch, it is 6.5.
Over acidic soils
These can have a detrimental effect on turfgrass growth:
- Slow or weak growth;
- Inability to stand up to much wear;
- A thin sward coverage;
- Poor quality playing conditions;
- Susceptibility to drought;
- An increased build-up of thatch due to low decomposition rates (which is in turn due to reduced micro-organism activity);
- A poor response to fertiliser application;
A rapid increase in soil pH due to liming of an acidic soil will result in an annual meadow grass dominated turf, as well as the encouragement of clover and other turf weeds, earthworms, and fungal disease, particularly take-all patch disease.
This process of applying lime to an acidic rootzone can be very relevant to high sand specification constructions, as they have little buffering capacity, are prone to leaching and are susceptible to a fairly quick acidity build-up if suitable turf management procedures are not followed meticulously.