CULT: clay, CEC - shorter & easier
- Subject: [iris] CULT: clay, CEC - shorter & easier
- From: Linda Mann l*@volfirst.net
- Date: Tue, 04 Mar 2003 10:05:14 -0500
- List-archive: <http://www.hort.net/lists/iris/> (Web Archive)
Briefly reviewing, CEC (cation exchange capacity) indicates the ability
of soil to hold and provide nutrients to plants.
I found this nice summary on the web, by Jim Kelly
<jkelly@landau.ucdavis.edu>
It includes humus (decomposed organic matter) for comparison with the
most common types of clay found in garden soil.
Soil Component approximate average CEC (cmol/kg) (~pH 7)
-------------- -------------
humus 200
allophane ?
vermiculite 150 [shrink/swell type of clay]
smectites 100 [shrink/swell type of clay]
illite 30
chlorite 30
kaolinite 8
Fe, Al oxides 4
I haven't been able to find estimated CEC for allophane, which is the
predominant clay mineral that forms in material of volcanic origin. It
has a high CEC value, but is amorphous (i.e., not layered, & definitely
not a shrink/swell type of clay), and can be highly productive.
--
Linda Mann east Tennessee USA zone 7/8
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