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Geosciences LibreTexts

7.4: Activity 3 - Soil Charge Calculations

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    1. A prairie soil contains 30% clay. This clay-sized fraction is dominantly montmorillonite. The soil also contains 5% humus (organic matter).

    a. Using the mineralogy method, what is the cation exchange capacity (CEC) contributed by the clay?

    b. What is the estimated cation exchange capacity (CEC) contributed by the humus?

    c. What is the total estimated CEC of this soil?

    The following is actual laboratory data for the soil in the example:

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    d. Calculate the CEC from the data in the table using the sum of cations method.

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