Cation-Exchange Capacity Indicates soil’s Ability to Retain Nutrients.
Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces.
CEC affects many aspects of soil chemistry, and is used as a measure of soil fertility, as it indicates the capacity of the soil to retain several nutrients (e.g. K+, NH4+, Ca2+) in plant-available form.
Cations are held by negatively charged particles of clay and humus called colloids. Colloids consist of thin, flat plates, and for their size have a large surface area. For this reason they are capable of holding huge quantities of cations. They act as a storehouse of nutrients for plant roots.
You can improve CEC by applying lime and increasing the pH. However, increasing organic matter is the most efficient way of improving cation-exchange capacity.