On 28 Jan 2006 17:37:56 GMT, (Nick Maclaren) wrote:

In article , madgardener wrote:
it sounds like gypsum...........here in Eastern Tennessee where we have red
clay, we're taught in the master gardening classes to apply gypsum to clay
to help break it down. if the product has a website, I'd search the main
ingredients.

And, at 4-6 oz per sq. yard, it is a joke. You can make a serious
difference to clay only by changing the composition of the soil,
which means large quantities of whatever.


Regards,
Nick Maclaren.

As Maddie suggests, many of these so-called clay breakers are gypsum
based, i.e. suppliers of calcium at a relatively low pH (e.g. compared
to lime, another calcium source). The combination of calcium ions and
a low pH is a very effective flocculant for clays in general, and a
little goes a long way. 4-6 oz/sq.yard may be little low, but it's
not way off. I've seen 6-12 oz/sq.yard suggested for improving the
texture of clay soils with gypsum (if my maths is OK; actually stated
as 2000-4000 kg/hectare).
http://www.gypsum.co.nz/pages/product/applying.php

Calcium (whether from gypsum or lime) improves the soil texture by
making the clay particles clump together (flocculate), improving the
crumb structure and allowing better drainage and air movement.

But I doubt you can just sprinkle it on and stand back and bingo,
perfect soil. It'll need working into the clay, along with the other
usual recommendations of grit and humus to get decent texture and
drainage (hence your "large quantities of whatever"?).

The OP can probably get gypsum much cheaper than this stuff. e.g
builders plaster, which is probably best hydrated before use. (IIRC
we've had a discussion before on URG on the merits of builders plaster
as a soil additive, and a slight doubt lingers in my mind....)


--
Chris

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