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[APD] Driftwood, tannins and calcium deficiency
Question: Does the leached tannins chelate Ca/Mg
rendering it useless to the plants but still can be
measured by GH and Ca-tests?
No. Chelating agents hold a chemical in a particular oxidation state.
For example, the iron in our trace additives is Fe2+. When exposed to
oxygen (in water or air), iron is stripped of electrons and converted to
Fe3+, usually in the form of rust, Fe2O3. The Fe2+ is higher in energy
and what our plants prefer. The cleating agent encapsulates the iron
molecule and prevents oxygen from attacking it, holding it in a form
useful to plants.
Calcium is a group IIA chemical which is only stable in a +2 oxidation
state, so it does not need the protection a chelate can offer. Chelates
are by definition weak associations that can be broken fairly easily --
I would not expect a tannic - metal complex to ever be strong enough a
plant could not break it. The type of reaction you need to worry about
are precipitation reactions, such as the Fe + phosphate reaction. These
strongly bound salts would be fairly inaccessible to plants.
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