Cation exchange capacity

Definition

Cation exchange capacity is a measure of how many positively charged nutrient ions, such as calcium, magnesium and potassium, a soil can hold on its clay and organic matter surfaces. Soils with a higher capacity generally store nutrients better and lose fewer to leaching, while sandy soils low in organic matter hold fewer. Laboratories report it as a number on a soil test, and it helps explain why two soils with the same nutrient levels behave differently. See also: Soil organic matter, Soil texture, Leaching, and the guide "Nutrient Depletion, Organic Matter Loss and the Decline of Soil Life".