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Cation Exchange Capacity (CEC)

The ability of soil to absorb and exchange cations with the soil solution and plant roots.

Soil Colloids

Particles in soil that have both positive and negative charges, affecting the soil's CEC.

Net-negative Charges

The charges in soil that are not neutralized by positive charges, contributing to the soil's CEC.

Units of CEC

Measured in centimol of positive charge per kilogram of soil or milli-equivalents per 100 grams of soil.

Base Saturation

The extent to which the exchange sites in the soil colloids are occupied by basic cations.

Montmorillonitic Clays

A type of clay that generally has higher CEC compared to Kaolinitic clays.

Organic Matter (OM)

Material that increases the CEC value of the soil.

Base Cations

Cations that provide basicity to the soil, essential for plant growth.

Acid Cations

Cations that contribute to acidity in the soil.

Cation Exchange Reactions

Reversible and instantaneous reactions where cations are exchanged between soil colloids and soil solution.

Calculation of CEC

Taking the sum of the centimole positive charges of all cations present in a soil sample.

Influence of Colloids on CEC

Different types of colloids like Montmorillonite, Illite, Kaolinite, and Organic Matter have varying CEC values.

% Base Saturation Formula

Calculated by dividing the sum of cmol positive charge of basic cations by CEC and multiplying by 100.