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Re: CEC exchange sites

>Date: Tue, 16 Jun 1998 15:21:16 EDT
>From: IDMiamiBob at aol_com

>1) We add clay (Amano's product line uses peat) to the substrate because it
>has a high CEC, or cation excheange capacity, in molecular locations we like
>to call "exchange sites".  The nutrients attach themselves to these sites, and
>then the plant detaches them by exchanging hydrogen into the site.  Does this
>exchange site become useless once the hydrogen is on it, or do natural forces
>like electronegativity cause the hydrogen to them be replaced by the nutrients
>we are attempting to provide?

Yes - cations can replace the hydrogen ion in a substitution reaction.  I
am thinking that the replacing cation needs to have a charge (partial or
permenant) stronger than the hydrogen charge in order to cause a permenant
change - but in chemistry there is no permenant bond, just bonding,
unbonding, bonding, etc.  The strength of that bond is what keeps the ions
there (boring you, I know).

>And if the latter, how does the plant overcome
>these forces to get the hydrogen back on and the nutrient back off?

The plant has nothing to do in the equation for putting cations back on.
That is a substrate property and not a plant property.

M. Mason
in rainy, wet Ohio.