Re: mimicing mother nature

George wrote:
> [I seem to be getting a little emotional about this thread.  Please
> take the following with a grain of salt.]
In a fresh water tank?? :-) (salt grain taken)
BTW George, thank you for your criticism and insights. 
This is precisely what I'm asking for.

> We need to provide a source of iron in a form easily usable by plants
> (Fe++, not Fe+++) by root uptake AND leaf uptake.
I'm asking what are the chemical processes that provide Fe++ & Fe+++
which the Dupla book mentions being in HIGH solution concentrations
in the Crypt streams in Thailand? I think it's ok to talk about
alternative crazy schemes for trying to duplicate that process.
Perhaps the Dupla method is the only "optimum" (:-) one but its worth
throwing a few ideas out for discussion. My feelings won't be hurt
if someone can help me to understand the mechanisms involved and the
limitations to any particular method.

>  It should be clear
> to everyone here that a lot of plants (especially fast growing stem
> plants like Rotala and Alternanthera sp.) don't really use their roots
> for much nutrient uptake.  Plants that get nutrients through their
> roots need the nurients to be bound to organic substances (chelated)
> The uptake process (adsorption) has the root exchanging H+ ions for 
> nutrient ions (or perhaps something more complicated than that).
> Anyway, the chelated nutrients need to be in intimate contact with the
> roots, not off in a user-conveninent tube somewhere.  
Well, wouldn't chelated iron by a product of humic acids in contact with
mineral Fe compounds? Won't that be in solution where it can be circulated
to the substrate as I described it? I don't know that it would work
but how does it work in nature? What are we missing to duplicate that
process? Quite possibly it's the large volumes of material in the
water table which have slow flow rates but their aggregate flow when
concentrated into the underground water source provides that necessary
concentration. Maybe the size of the reactor chamber required is the
prohibitive factor. Or maybe not. How can we find out?
> > How come you need drops anyhow if you have Laterite?
> The iron in the laterite is being used by the plants and needs to be
> replenished.  Iron also needs to be in solution in the water for
> uptake by the plant leaves. 
So laterite alone is insufficient?? My point is that nobody is putting
drops into the Crypt streams in Thailand. The iron source is undoubtedly
the laterite and other iron minerals underground. Perhaps (or perhaps
not) we could duplicate that.
> Let's keep in mind that there are complex chemical processes taking
> place in the substrate that go far beyond what we understand.  A rusty
> ten-penny nail is not going to get you there. 
So iron oxide cannot be reduced? Can small concentrations of humic acids
in contact with un-oxidized iron such as micronized iron produce 
Fe-EDTA (chelated iron)? Somebody must have done research into
the complex chemical processes in the natural substrate which might
give us insights into useful experiments we could perform.

> It might be useful to reconsider what is happening in natural plant
> environments and try to synthesize ways to mimic that, rather than
> creating some bizarre second derivative by developing cheap
> alternatives of the techniques Dupla uses to mimic nature.
Very excellent point. That was my aim.

> My impression of the direction the discussion is taking is that there
> are three or four things that are recognized as important to a plant
> tank that should (IMHO) be considered dependent on each other, as a
> system.
Hmmm.... what do you mean by this? Yes, circulation near the roots
is something to consider. Mineral Fe compounds in contact with the roots
is something to consider. We're not necessarily excluding that are we?

The question really is: Can we synthesize chelated iron pragmatically
by some home made leaching process? Any and all comments welcome! :-)

 - Steve