Re: Vermiculite

>To: Aquatic-Plants at actwin_com 
>Subject: Vermiculite 
>From: Stephen.Pushak at hcsd_hac.com (Stephen Pushak) 
>Date: Mon, 29 May 95 11:21:40 PDT 
>Does vermiculite have any useful properties for plant substrates?
>Has anybody analyzed it's properties? Why do we put it in our
>house plant pots?

Jim Kelly posted an article on sci.aquaria a while ago, with the title
"Build a Better Substrate". It is about 500 lines long, so I will not
quote it here. I believe Erik has archived it on the Krib.  If you
can't find it, let me know, and I'll email it to you.

Jim's article pointed out that the Cation Exchange Capacity (CEC) of
Vermiculite was quite high.  This means that Vermiculite is very good
at making metal ions and NH4+ available for uptake by plants.  The
problem of course, is that it is hard to make Vermiculite sink.

The article also listed humus as having a high CEC, but humus is high
in organics, which is often a disadvantage in aquaria. Jim also
pointed out that laterite clays have a relatively low CEC.

Shaji Bhaskar                                              bhaskar at bnr_ca
BNR, 35 Davis Dr., RTP, NC 27709, USA                      (919) 991 7125