Buffer Capacity

The ability of a soil to resist changes to its soil pH. It is measured by determining the amount of acidic material (such as sulphur) required to raise the pH of a soil, or the amount of base or alkaline material, such as lime (calcium carbonate) to lower the pH of a soil. The unit amount is usually given as one kg, so for example, to lower a soil with a pH of 7.0 to a pH of 6.2 might require the addition and incorporation of x kg of sulphur.

Sandy soils have a lower buffering capacity than a clay loam soil. The main reason being that pH measures the concentration of hydrogen ions within a soil and the more organic and clay particles present means that more hydrogen ions can be retained and used to offset any potential change (decrease or increase) in soil pH through the addition of an acid or base material.

A soil with a high buffering capacity will also be able to retain more nutrients available for plant growth, whilst a soil with low buffering capacity will retain few plant nutrients and be more prone to leaching. Slightly different approaches to turf nutrition are required for soils of different buffering capacities.