Cation Exchange Capacity (CEC) is the total capacity of a soil to hold exchangeable cations. It is a very important soil property influencing soil structure stability, nutrient availability, soil pH and the soil’s reaction to fertilisers and other ameliorants. Cation Exchange Capacity can also be known as media absorption or anion exchange capacity.
The clay mineral and organic matter components of soil have negatively charged sites on their surfaces which adsorb and hold positively charged ions (cations) by electrostatic force. This electrical charge is critical to the supply of nutrients to plants because many nutrients exist as cations (e.g. magnesium, potassium and calcium).