Cation Exchange Capacity

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Cation Exchange Capacity
CEC is a measure of readily exchangeable cations
neutralising negative charge in
soil. Exchangeable cations are those that can
be exchange by a cation of a salt solution when
added to soil. The exchangeable cations that
commonly occur in soils are Ca2, Mg2, K and
Na, often called exchangeable bases)
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CEC may be used as an indication of the soils
potential to hold cations such as plant
nutrients. The electrical charges in soils
constituents can be derived from clay minerals,
organic matter and free oxides. This can be
critically influenced by ionic strength and pH
value. The amount of positively charged cations
a soil can hold is expressed in centimoles
positive charge per kilogram (cmol/kg),
numerically equal to the formerly used unit of
milliequivalents per 100 grams (meq/100g) of
soil.
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Values of CEC according to different soil
textures