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Re: Substrate research

Roger S. Miller wrote:
> We created almost ubiquitous Pb contamination of surface rocks and soils
> through a long history of using leaded gasoline.  I've read that leaded
> fuels are the main source of Pb in many soils.  I noticed that copper and
> zinc are also elevated in your soil.  Copper, zinc and lead are often
> naturally associated in ore deposits, so you can get the three of them
> elevated together by either living near a smelter wher Cu-Pb-Zn ores are
> processed or by living in an area where there are Cu-Pb-Zn deposits
> contributing to the soils.

I believe it is quite common for soils to contain amounts of metals
either participating in relatively inert particles or sometimes in
RELATIVELY soluble forms. As Roger says, these are determined by the
parent bedrock from which the soil was formed locally or as transported
by a glacier a few thousand years ago. Soluble lead compounds can be a
problem in surface soils near roads but should not occur in subsoils in
appreciable amounts particularly where there is sufficient leaching to
carry it away. The lead gets into the subsoil by leaching but it also
gets carried deeper by the same process. 

Lead and other contaminants are worrisome because they can find their
way into agricultural products especially in regions of intensive
farming near the US midwest and northern industrial regions. Southern
Ontario has such a problem as a result of US industrial pollutants
(PCBs). MOST people are UNAWARE that the quality of food has been
STEADILY DECLINING for the last thirty or so years especially the
contamination of MEAT with TOXIC MICROBES that are resistant to
antibiotics!

Natural topsoils are not toxic to terrestrial plants even when the
parent soil contains soluble metals because the soil humus absorbs any
free metals extremely effectively. In an aquarium, topsoils with humus
might contain enough phosphates to be problematic however, you can still
use subsoil together with peat. (subsoil contains little or no humus)
The peat performs the same function of detoxifying free metals. I don't
believe metal toxicity is much of a problem in soils. Its much more
likely that you'd end up with a SHORTAGE of trace nutrients,
particularly iron, because the texture of the mineral component of the
soil is not sufficiently fine; that is to say, it lacks clay. (see
comments below on F-T-E)

I've had my best results using pottery clay, even over my garden soil.
The pottery clay has an EXTREMELY fine texture and this makes iron and
other trace metals MUCH more available to the plant roots. When I
studied the soil and subsoil where my house is, it is composed mostly of
mixed cobbles, sand and silt together with a surface topsoil humus
created primarily from decomposing tree leaves. I live on a hill which
was created by glaciers, probably where a river was running off the
surface of the Fraser valley glacier and depositing its cobble stones
and gravel. There are other areas in the lower mainland around Vancouver
which have significant clay deposits left by the Fraser river. These
clays are also probably of glacial origins. The clay soils would make
far superior substrates in comparison to my rocky subsoil. It seems my
particular garden soil is not very ideal so I need to go a little
further afield. 

Another problem with my particular garden soil may be that the previous
owner was amending it with wood ashes to increase the potash content.
Wood ashes contain all kinds of soluble minerals, while its pretty good
as a potassium supplement for the garden, might not be ideal in the
aquarium. I setup the latest aquarium substrate using subsoil, but I'm
pretty sure that it is quite deficient of trace minerals especially
iron. I'll probably supplement it with clay balls once the Crypts get a
little more established.

The use of F-T-E, a commercial product of fritted trace elements, has
been mentioned on my website. It is difficult to evaluate how effective
it is without a lot more controlled experimentation. I do know that it
can be used without any apparent detrimental effects even at several
times the recommended usage ratios. I just don't know how effective it
is. It is quite easy to supplement trace minerals in the substrate
simply by using soils and in particular, clay, especially very fine
textured pottery clay. Alternatively, it's also very easy to safely
supplement trace minerals by using either a commercial aquarium product
such as TMG or Flourish or by using a home made solution prepared from
the chelated trace nutrient powders which are available for use in
hydroponics. For that reason, I haven't pursued more investigations into
F-T-E although a company in Italy who manufactures fritted materials is
interested in sponsoring such research. Contact me offline if any of you
are interested and I'll put you in touch.

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!!!