"Chris Hogg" wrote in message
...
On Sun, 18 May 2008 17:53:09 +0100, "'Mike'"
wrote:



--
"Bob Hobden" wrote in message
...

"Chris" wrote
Just got some pellets called "Claybreaker".
Does anyone know if it works?

I think that's just Gypsum, it's a lot cheaper to use that than the
named
ready made granules if you can get it. However builders plaster is
mainly
gypsum I understand.
Gypsum .
--
Regards
Bob Hobden


Bob interesting statement there, "does break up clay for some years". I
was
under the impression that if you worked clay in the recognised way, grit,
compost, "body" in the form of fibrous 'stuff', it remain workable and NOT
revert back to clay.

Would welcome your comment on this, as would new gardeners trying to get
to
grips with clay

Mike


With many clay soils the fine platy clay particles pack together very
closely rather like sheets of paper or a pile of slates (but on a
microscopic scale). This dense packing restricts the movement of air
and water (and hence nutrients) through the soil and plants don't
flourish. Adding calcium to the soil in the form of lime or gypsum
causes the clay particles to form much more open structures,
reminiscent of a house of cards. The soil structure generally is
improved and can develop a 'crumb' structure, allowing air and water
to move more freely through the soil.

Both gypsum and lime are slightly soluble and can gradually leach out
of the soil, potentially allowing it to return to it's former densely
packed condition.

Using grit, compost etc. breaks up the clay macroscopically, but
doesn't do much on a microscopic scale. Doing both gives you the best
of both worlds. Of course, if the clay already contains plenty of
calcium, in the form of chalk for example, it's unlikely that adding
lime or gypsum will make any difference, and adding grit and compost
is the best you can do.

Be aware that much gypsum these days is the product of flue-gas
desulphurisation processes in coal-fired power stations, and often
contains residual lime, giving it a high pH. Not a problem in general,
especially if you want to lime your soil, but it could be a problem if
you want to grow acid-loving plants such as rhododendrons, camellias
and some heathers. Mined gypsum is mildly acidic and doesn't have this
problem, but where you get it or how you specify it, I don't know.

--

Chris

Gardening in West Cornwall overlooking the sea.
Mild, but very exposed to salt gales

E-mail: christopher[dot]hogg[at]virgin[dot]net


Thanks Chris. I understand now :-)

Mike