Degree of Base Saturation

Degree of base saturation (V) — the ratio of the sum of exchangeable bases (S) to the cation exchange capacity (T), expressed as a percentage:

Cation exchange capacity (CEC, T) can be expressed as the sum of exchangeable cations (S), such as Ca²⁺, Mg²⁺, K⁺, NH₄⁺ and others, and H⁺, Al³⁺, Fe³⁺, Mn²⁺ cations, which cause hydrolytic acidity (H), in mg-eq/100 g soil:

Then the degree of base saturation can be calculated using the formula:

Degree of soil base saturation — an indicator of the need of soils for liming. The lower it is, the greater the need for lime application.

For example, with equal values of hydrolytic acidity (H) in two soils, e.g., 5 mg-eq/100 g soil, but with different values of cation exchange capacity (T), e.g., 10 mg-eq/100 g for the first and 20 mg-eq/100 g for the second, the degree of base saturation (V) in the first case will be 50%, and in the second 75%. Thus, with equal hydrolytic acidity, the first soil is more acidic, since 50% of the cation exchange capacity is accounted for by acidifying cations, and it is more in need of replacing them with bases.

With equal values of cation exchange capacity, the soil with the higher hydrolytic acidity will need liming first.