The cation exchange capacity of a soil is a measurement of its ability to bind or hold exchangeable cations. In other words, it is a measure of the number of negatively charged binding sites in the soil, which can be summed up as the nutrient holding capacity of the soil.

The cation exchange capacity helps characterize the soil type under consideration. For example, because organic matter and clay are a major source of negative electrostatic sites there is a strong correlation between CEC values and the amount of clay and organic matter present in the soil.

Typical CEC values for different soils are follows:

Very low nutrient holding capacity (0-10) indicating sandy soils with little or no clay or organic matter. Nutrients will be easily leached and foliar applied nutrients are strongly recommended.

Slightly low nutrient holding capacity (10-15) indicating a more loamy mineral soil. Leaching may still be a problem and therefore foliar applications should be considered.

Adequate to high nutrient holding capacity (15-40) indicating soils with increasing clay content.

Very high level (+40) normally found in very heavy soils with a high clay content or soils with a high organic matter level. Nutrients can be bound very tightly to the soil particles and availability can be restricted.
Using this information the CEC results can provide advisors with an insight into the type of soil they are dealing with, as well as providing secondary information of use in formulating a fertilizer programme.


Source: Dawson, A. 2001. Cation Exchange Capacity. Phosyn Website [Online]. Available at