I had the words wrong but the description I gave was fairly close. I didn't
copy the paragraph that talks about too high a CEC that salts build up and
cause their own serious problems. I believe this happened in some Southwestern
farm lands.

Check out http://edis.ifas.ufl.edu/CN004

The essential paragraph.


Cation Exchange Capacity

The ability of a soil or growth medium to retain nutrients against leaching
by irrigation water or rainfall is estimated by measuring the cation exchange
capacity (CEC). Most adsorption sites on growth medium particles are
negatively charged and attract positively-charged ions. Many nutrients required by
plants are positively charged and thus are attracted by these
negatively-charged sites. Sands and other low-surface area materials have low cation exchange
capacities while organic components have a greater ability to retain
cations. Pine bark has a cation exchange capacity in the range of 10 to 13
milliequivalents per 100 cubic centimeters while a CEC of approximately 1 is common
for builders' sand.


Billy on the Florida Space Coast
BSF Annual Convention May 28 - 31, 2004 Radisson Hotel, Cape Canaveral,
Florida
Sponsored by The Bonsai Society of Brevard and the Treasure Coast Bonsai
Society
http://www.bonsaisocietyofbrevard.org/2004/2004.html

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