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Re: Laterite and the meaning of life

Hello everyone,

> Subject: laterite, aluminum, silicates and plants
> >     My suspicion is that one of the reasons for using 
> >     laterite is that it won't greatly affect the water hardness and pH.
> One point of interest here.  Not all "laterite" products are created
> equally.  I recently saw a soil analysis of several substances done by
> Neil.  The pH  of Duplarit was 7, while the pH of Tetra's Hilena
> additive (can't remember the exact name) was 3!
> Karen Randall
> Aquatic Gardeners Association

Excuse me Karen, for jumping in here, but Tetra makes no claim that their
Hilena substrate additive is laterite. 

We are getting into unsafe ground here, in using words that mean one thing
to us as aquarists while having a possibly different meaning to a chemist
or a geologist. (Please don't jump on me Craig!) 

Dupla was the first company (I believe) to popularize the use of "laterite"
as a soil additive. Like a lot of Dupla's research, the actual mechanism
that caused the reported results may have been misreported in "The Optimum
Aquarium".  Think back to the arguments over substrate heating. Dupla gave
a reason WHY they thought it worked, although they certainly didn't qualify
their reasoning as I am doing here.

George Booth (and others) followed Dupla's recommendations to varying
degrees in a number of tanks and reported their results both here and in
print. Again, reasons WHY the techniques worked were put forward, and at
least in George's case were prefaced by the statement that they were only
possible reasons why some things (such as substrate heating and laterite)
worked better than others. Both Dupla and George agree that substrate heat
and laterite work, but they postulate rather different reasons as to
exactly WHY they work. Personally, my money's on George.

In the substrate heating debate, it now looks like Dupla was WRONG, or at
least INCOMPLETE in their explanation as to why it works. The very same
case might be true with regards to the use of "laterite". Is it a source of
iron or a sink and storehouse for micronutrients which are attracted to the
particles in the substrate by the electrical charge of the minerals and
thus bonded to it awaiting uptake by the plant roots?

The short answer in both cases is that NOBODY KNOWS. We can theorize and
speculate all we like, but until someone undertakes scientific controlled
experiments of various substrates we will NEVER know for sure.

Plants can be grown successefully in a variety of substrates. Some people
swear by peat, others swear at it. The same could be said about topsoil,
subsoil, earthworm castings, clay, vermiculite, laterite, fish poop, kitty
litter,  etc., etc., etc. For some people, results are what counts, others
like to know WHY something works (or doesn't work), or at least they like
to THINK that they know.

As I write this, I'm looking at a blooming waterlily in a rather neglected
tank in my study - the darned thing is flowering AGAIN, in spite of the
fact that I haven't paid it any attention at all for at least four months.
I used to think that I had a green thumb - but if my plants bloom and my
fish breed while I am incapable of lavishing all of my attention on them,
where's my green thumb? (Don't go there....)

Recent posts have cast a pall (for me at least) over our use of the term
"laterite". I was always under the impression that it was a form of clay
which had had most things leached out of it except for iron and aluminium.
Recently I have read that it isn't clay at all. Just goes to show you all
how little I know!

I have started feeding Steve's appetite for information by sending him
references I have found through the Web on "laterite". Perhaps he will be
able to put something together which will lead us out of this darkness.

James Purchase
jpp at inforamp_net