Why cec is important

CEC varies according to the type of soil. Humus, the end product of decomposed organic matter, has the highest CEC value because organic matter colloids have large quantities of negative charges. Humus has a CEC two to five times greater than montmorillonite clay and up to 30 times greater than kaolinite clay, so is very important in improving soil fertility.

Clay has a great capacity to attract and hold cations because of its chemical structure. However, CEC varies according to the type of clay. It is highest in montmorillonite clay, found in chocolate soils and black puggy alluvials.

It is lowest in heavily weathered kaolinite clay, found in krasnozem soils, and slightly higher in the less weathered illite clay. Low CEC values can be improved by adding organic matter. Sand has no capacity to exchange cations because it has no electrical charge. Soils and soilless media particles can also have positive charges and this attracts negatively charged particles; these positive sites contribute to the anion exchange capacity of the growing medium.

In comparison, the cation exchange capacity is more significant in a soilless media than the anion exchange capacity. In part two, we will discuss the specific role of CEC in soilless growing medium. Although CEC has value in soilless media, it is not significant when it comes to nutrient exchange and pH management as it is with the soil.

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This article was published by Michigan State University Extension. What is your soil cation exchange capacity? Figure 1. Did you find this article useful? Please tell us why Submit. Check out the Crop and Soil Sciences B.

Learn More. Mornings on the Farm - May Mornings on the Farm - August Evenings in the Garden - Winter Series - March 5. Related Content. Search Search. To improve CEC, the most effective way is to enhance soil organic matter, which can be done by growing cover crops or adding compost.

Another important point is that soil pH decrease due to crop production is faster with lower CEC soils. So sandy soils need to be limed more frequently than clay soils. Remember, it takes 6 to 12 months for the lime to dissolve completely, so fall is a good time to consider adding lime.

I will explain liming in another article. If you have trouble accessing this page because of a disability, please contact Vegetable Crops Hotline at guan40 purdue. Loading Purdue system wide search.

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