Soil pH

Definition

Soil pH is a measure of how acidic or alkaline the soil is, on a scale where 7 is neutral, lower values are more acidic and higher values more alkaline. It influences which nutrients are available, how soluble some metals are and which organisms thrive. Low pH can make aluminium and manganese toxic to roots. Home kits give a rough reading and laboratories a more reliable one. See also: Leaching, Cation exchange capacity, and the guide "Soil Contamination and Acidification Explained".