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A.P. Environmental Science - Soil Quality

Terms in this set (47)

Cation Exchange - the ability of the soil to hold onto nutrients and prevent them from leaching beyond the roots.
Cations are "+ "charged ions = Ca++, Mg++, K+, NH4+(ammonium),
The more cation exchange a soil has the more likely the soil will have a higher fertility level.
The Cation Exchange Capacity (CEC) in laymen's terms is basically a rating of the soil's ability to hold nutrients or a fertility-holding capacity. The CEC number represents milliequivalents (ME) and can be thought of as a storage battery holding volts of electricity. The higher the number, the more storage capacity or milliequivalents the soil can hold.

High CEC soils hold nutrients longer, prevent leaching, maintain high microbial activity and help hold moisture in the root zone area. The only practical way to increase the CEC rating of a soil would be to increase humus levels. This can be achieved by adding organic matter such as compost, returning harvest residues, growing permanent cover crops or applying carbon based fertilizers. Fertile soils should have an organic content of 2 to 5 percent.

It should be noted that most fertilizer chemicals can rapidly destroy soil humus. Examples are sulfuric acid, anhydrous ammonia, and salt-based fertilizers. Many pesticides may effect the same destruction.

A high CEC value (>25) is a good indicator that a soil has a high clay and/organic matter content and can hold a lot of cations.
Soil with a low CEC value (<5) is a good indication that a soil is sandy with little or no organic matter that cannot hold many cations.