Re: CULT: clay...the end?

Linda, and others fascinated by dirt details, I am not having any luck
finding information about where different kinds of clays are found other
than some vague generalities.

Allophane clay, contributing to light fluffy soil, rich in nutrients,
and high in organic matter, is mostly found in the continental USA in
parts of California and Oregon. This type of clay is only found in soils
classified as belonging to the Andisol soil order.  There is a USDA-NRCS
map of soil orders - I can dig up the link if anybody is interested.

The only other generalization I can make is that vermiculite and
smectites (including Montmorillonite) are generally found in subsoils of
highly weather, ancient soils (i.e., southeastern US).  And I'm not even
completely positive about that.  I will keep looking if anybody is
interested.

The important thing about managing any kind of clay garden soil is
getting the clay bound together with humus (highly decomposed organic
matter) into larger aggregates.  In some types of clay, adding calcium
(i.e., lime or gypsum) helps stick these aggregates together, but in
others it won't change anything because of the physical and  chemical
properties of the clay.  Bacteria, fungi, and earthworms are essential
for making soil aggregates.

So, the bottom line for all types of clay (except those lovely allophane
clay soils) is add lots of well-decomposed organic matter, check with
your local soil conservation service folks about whether or not to add
lime/gypsum, and add worms.

Only about 2% of fresh organic matter added to soil is still there after
one year, and most of that is gone within another few years.  The more
you till, the faster the organic matter breaks down and goes away.  On
the other hand,TB iris <really> like loose soil for their roots.

I hope that's more than enough about clay?

--
Linda Mann east Tennessee USA zone 7/8
Updates on migrant whooping cranes:
http://www.savingcranes.org/whatsnew/Class2002FloridaMain.asp
American Iris Society web site <http://www.irises.org>
iris-talk/Mallorn archives: <http://www.hort.net/lists/iris-talk/>
iris-photos/Mallorn archives: <http://www.hort.net/lists/iris-photos/>
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