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Re: Laterite

I've been slowly catching up on the old APD issues I haven't had a
chance to read since my move and couldn't resist tweaking James on this

> Date: Fri, 5 Feb 1999 10:59:14 -0500
> From: "James Purchase" <jpurch at interlog_com>
> Subject: RE: Laterite
> Richard Sexton is wondering about laterite -
> >Ok, so whats the deal with this stuff? Is red potters clay good enough ?
> >is kitty litter as good ? Does the brand of laterite make any difference ?
> >The Dupla stuff was supposed to be from Malaysia as far as I know, will
> >laterite from other countrues work ?
> For a discussion of exactly _what_ laterite is, try this URL -
> http://www.dupla.com/e037.htm. It is an article by Kaspar Horst (Dupla
> co-founder), which appeared in the German language magazine Aquarium Heute.
> There is also a lot of information in the archives of the APD on laterite
> (thank's to the Geologist's on the list).
> Red potters clay (Red Art Clay is the brand I'm most familiar with) is not
> laterite. It has _some_ properties which are desirable for our purposes
> (high iron content, high CEC) but others which we don't (it can form an
> almost colloidial solution due to how finely it is ground).

Laterite can also create red, cloudy water if improperly used. I presume
this is what you mean by _colloidal_  solution. Some but not all
lateritic soils are claylike in texture. The term laterite refers to
composition, the term clay refers to texture. So your statement is like
saying not all round things are red!! so?

> Kitty litter is not laterite (not even _close_).

Thank heavens! Hellishly expensive to be using for the cat to pooh in!
(Oops, sorry, another scatalogical reference about cats!)

> Laterite is:
>  1.)a type of clay
>  2.)high iron content
>  3.)has suffered heavy leaching
>  5.)under tropical conditions
>  6.)over geological time.
> There are many types of clay - the term clay only really refers to the
> particle size of the material. A number of clays are available which have
> high iron content - the red colour in some "pottery clay" is generally due
> to the presence of iron oxides. The unique properties of laterite which made
> Dupla (and several other companies) sit up and take notice are due to the
> last three points - highly leached, formed under tropical conditions over
> geological time.

Here I have to ask my question. Why is being highly leached important?
Why is being highly leached under tropical conditions over geological
time important? Surely this will cause the LOSS of almost all the
nutrient value of the soil! Perhaps the only important thing about the
laterite leaching is thus, the LOW concentration of phosphates and
nitrates??? Why even pottery clay and kitty litter have this quality.
Surely the leaching for thousands of years is not critical to this

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!