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Cation Exchange Capacity (CEC)

  • Soil Health

  • Chemical


Soil Cation Exchange Capacity (CEC) is a measure of the soil’s capability to retain and exchange positively charged ions (cations) within its structure. CEC plays a pivotal role in influencing nutrient availability, soil fertility, and water quality (Cation Exchange Capacity, UK Soil Observatory; Arias et al., 2005; Lehmann et al., 2020). The principal cations involved in this exchange include calcium (Ca2+), magnesium (Mg2+), potassium (K+), and ammonium (NH4+) (Cation Exchange Capacity, UK Soil Observatory).

Soils with a higher clay content typically exhibit higher CEC due to the characteristics of clay particles, enabling them to effectively retain and exchange cations. This property endows these soils with the ability to retain more nutrients, mitigating the risk of nutrient runoff, and consequently, playing a crucial role in maintaining water quality (Soil Texture and Cation Exchange Capacity, AHDB).

Methodology summary

Different testing facilities employ diverse techniques to assess Cation Exchange Capacity (CEC), and outcomes may vary based on the specific soil fraction subjected to measurement. CEC is conventionally expressed in meq/100 g.

The determination of cation exchange capacity (CEC) and exchangeable bases (calcium, magnesium, potassium and sodium) in soil using 1N ammonium acetate at pH 7 is used as the standard methodology by FAO, although different methods can be used depending on the different soil types. For detailed instructions read the pdf.

To collect samples for sending to a laboratory, detailed information on soil sampling such as where to take the samples from, how many, the best time to sample, and depth of sampling, can be found at the Farm Carbon Toolkit.

Metric threshold or direction of change

Typical CEC valuesCEC (meq/100g)
Very low: 0-10
Slightly low: 11-15
Normal range: 16-40
High > 40

Very low nutrient holding capacity 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 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 indicating soils with increasing clay content.

Very high level 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.


  • Agricultural
  • Forest
  • Grassland
  • Peatland
  • Saltmarsh
  • Wetland


  • Community


  • High


  • Tier 2

Technical expertise

  • High

Standardised methodology

  • Partial