Soil pH and its Influence on Plant Growth

The main influence that soil pH has on plant growth is that of limiting the ability of plants to grow and develop within a range of pH values, depending on how well adapted they are to certain levels of acidity, or concentrated of hydrogen ions within a soil. In addition, micro-organisms (especially soil bacteria) which help decompose organic matter, thereby releasing stored nutrients, are affected by soil acidity, being less active and present, in general, the acidic the soil.

The second major factor is that the extent of acidity influences the availability of nutrients within a soil, whether some nutrients, for example manganese, become toxic due to excessive availability, or very limited as they become ‘locked-up’ by excess acidity, for example calcium, resulting in nutrient deficiencies within a soil, as well as how nutrients interact with each other, for example with phosphate becoming more fixed and unavailable with iron in highly acidic soils.

For the majority of plants, a soil pH of 6.5 ±0.5 is probably an optimum value, although specific species can vary significantly from this.