Cation Exchange Capacity (CEC)

Cation exchange capacity (CEC) is the total of its negatively charged (mineral and organic) sites, which are able to hold cations. CEC is measured as meq/100 g (milli equivalents per 100 gm soil). Soils rich in clay and organic matter exhibit maximum CEC. Moderate to high CEC soils are desired since they hold more cations and minimize leaching. The cation exchange is governed by the charge, reactivity and concentration. e.g. Al+++ > Ca++ > Mg++ > K+ = NH4+ > H+ > Na+. CEC increases with increase in soil pH.