Soil Acidity
Types of Soil Acidity
Soil acidity is composed of two components: active acidity and reserve (exchangeable) acidity. These types of acidity add up to the total acidity of a soil.
Sctive Acidity
The active acidity is the concentration of hydrogen (H⁺) ions in the soil solution. Soil pH is a measure of active acidity, the hydrogen ion concentration in the soil solution. The higher the concentration of hydrogen ions in the soil solution, the lower the pH (i.e., greater acidity). The active acidity is present in the immediate environment of roots and microbes.
Reserve Acidity
Reserve acidity release hydrogen ions into soil solution as conditions change due to moisture changes and concentrations of dissolved ions and salts occur. High concentrations of hydrogen ions in soil solution (low soil pH) may cause the release of soluble aluminum from soil minerals. Soils may have similar measurable pH values (active acidity) but differ dramatically in amounts of reserve acidity.
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