Cation Exchange Capacity or CEC of a soil is basically the soils ability to hold onto nutrients and make them available (or unavailable) to plant roots. Clay particles (and organic matter) have a high CEC number and will hold onto nutrients like phosphorus, and potassium very tightly. Sand on the other extreme has a very low CEC and holds little chemical attraction for these nutrients. Therefore, they will easily move through a sandy soil and be lost to the plants.

According to the following chart, a soil with a CEC of 6 would be a sandy soil while one with a CEC of over 40 has mostly clay in its makeup.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.


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