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[APD] Red Clay composition.

> On another topic I live near the Red River, at the Tex/Okla
> border has anyone ever checked to see what the content of
> the "red clay" soil here is or if it is of any use as a
> substrate?


If you really wanted to do some detective work, you may be able to find out
the composition of the red clay, but it would certainly take some effort.  I
have a list of Texas counties that each have a book called a Soil Survey
which describes some of the properties of the soils in the county. The books
are put out by the USDA Soil Conservation Service. If you give me a list of
the Texas counties that border the area of concern,  I'll see if there is a
soil book for one of those counties. If you can then locate the desired soil
in that county, you can give the location to someone at a local university
who can look up the characteristics of the soil including its name.  The
books have a bunch of aerial maps with notations on the composition of the
soil in each area.

Although each county's Soil Survey book is different, I have listed the
characteristics of a "Victoria" clay as an example, which is very prevalent
in Corpus Christi, TX, (Nueces County) where I live.  (I happen to have the
Nueces County soil survey book)

Series Name:    Victoria
Type:            Clay
Reaction (1:1 ratio), ph    7.9
Organic carbon                1.18
Nitrogen                        .086 %
carbon-nitrogen ratio        13.7
salt content                .2 %
electrical conductivity (ecx103)(Mmhos/cm)    1.1
calcium carbonate equivalent            5%
cation exchange capability (Meq/100/gm)        37.1
extractable cations (Meq/1000/gm)
                                            Ca    20.1
                                            Mg    4.9
                                            Na    1.5
                                            K        1.8
exchangeable sodium %            3.0

Note that they do not mention anything about iron.  But there is a soils
engineer assigned to each county who will answer questions, and the county
agricultural agent may have some info on iron, since the purpose of these
books is to help farmers grow crops.  I have heard that some soils are red
due to Aluminum and these soils should be avoided.  I think their policy is
that if you just need one book the USDA will send the book to you free.

We don't really have top soil down here so I have been a bit frustrated
finding a local soil to use in a lo tech tank.  I've tried the 10% Victoria
clay/90% sand mixes and they were too active. (yellow water and lots of
algae).  What I found interesting was the data on C.E.C.  Perhaps someone on
the list could interpret all this info.

Yes it is a lot of work.  As an alternative, I suggest you get a small tank
(like 5 gallons) set up a soil substrate with the red clay covered with
gravel and add plants and fish you wouldn't mind losing.  You can observe
how the plants and fish do, and take some iron measurements of the water.
The experimental way is sometimes a lot easier.  Also, have you noticed any
plants living in the wet red clay near the river?  Bring these plants home
and put them in the tank.  Since they grow in nature in the red clay, they
should do well in your tank.  And the bonus will be that you will be well on
your way to completing your "Red River" biotope.

I'm betting that, in general, if you ever find emersed/submerged aquatic
plants growing well in nature, the soil they are in would probably work well
in your tank, but may have to be cut with sand if it is too active.

Steve Pituch

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