On Aug 11, 7:49*pm, "David Hare-Scott" wrote:
Higgs Boson wrote:
On Aug 11, 3:54 am, Jeff Layman wrote:
On 11/08/2012 00:12, David Hare-Scott wrote:

Jeff Layman wrote:
On 10/08/2012 00:27, David Hare-Scott wrote:
Kay Lancaster wrote:
Treat clay soils with respect... they're difficult to grow on.

yes indeed.

D

A commonly held and vastly mistaken view, IMHO. Difficult to work
maybe. But they are not difficult to grow on at all, if you keep
to a couple of simple rules. Firstly, never try to plant anything
when they are soaking wet. Secondly, never try to plant anything
when they are bone dry. Clay is far more suited to growing many
plants than sandy soil; even those naturally found in sandy
environments will often more than just tolerate clay. I have grown
heathers without problem, and grown and fruited blueberries on
clay (pH 6 -
6.5). I have even been able to move plants which are said to really
dislike being moved because a great lump of clay sticks to the
roots, and, to all intents and purposes, the roots really haven't
been disturbed at all. Try that with sandy or even "highly
desirable" loamy soil. The one plant I have given up with on clay
soil is grass. Where it is constantly wet, a lawn simply ends up a
mess, often with more moss than grass. The previous owner of the
house I moved in to had so much trouble he installed land drains,
but even those couldn't make a meaningful difference and in the
end I had the lawn removed (no great loss as I can't stand lawns
anyway).
I live in the Sussex weald, and have been gardening on clay for
over 25 years. And, believe me, Sussex clay is real clay. I have
about 10 inches of claggy "soil" over a solid clay subsoil (solid
with ironstone lumps, that is. Even a pickaxe fails to penetrate
some parts. and I have to resort to a hammer drill if I want a
deep hole). The most difficult thing about gardening on clay is
digging the damn stuff; it is /very/ hard work. It even sticks to
stainless steel spades with a vengeance. And when dry, don't even
bother with a hammer drill - it's not worth the effort. Wait until
it's workable again.
But when it grows stuff, it is brilliant. It holds moisture; it
holds nutrients; it anchors. It tends to help withstand frosts
much better than lighter soils.

My situation is similar to yours, a layer of topsoil over plastic
clay, though I suspect my topsoil is naturally better. I agree that
clay soil holds water and nutrients well and can produce great
crops. Every time the region goes into drought I thank my stars for
the clay underneath that acts like a big sponge and keeps my
pasture growing for months without rain. Having had very sandy soil
(that I was always trying to build up) and very clayey soil that I
have to break down I will take the clay.

BUT You have to have (or to make) actual soil. Clay by itself ( I
mean the plastic stuff you can mould into complex shapes) is
hopeless. The process of amending it takes years of effort and some
skill. The choice of plants has to be considered carefully as many
will die in a wet spell due to lack of drainage and it is
impractical (for me anyway) to landscape the whole garden for
drainage and to amend all its soil to prevent the problem. As it is
all my fruit trees grow in mounds and my vege garden has raised
beds with drain paths running down-slope: at considerable effort
and cost.

Clay is not for people who just want to plop something in the
ground and see it grow. I thought it interesting that in response
to "Treat clay soils with respect... they're difficult to grow on."
you first deny that it is so and then go on to explain all the
difficulties that have. :-)

Did I? Read my post again.

You are confusing "growing" with the act of digging or cultivating.
For the latter, good loam or even sandy soil wins every time, as the
job is easy. But once in, plants grow much better in clay without a
lot of additional help such as watering and use of fertilisers.

--

Jeff

Cites, please? *I am interested in following this up.

TIA

The reason is that clay contains a lot of colloidal (ie very very small)
particles that have a high surface area and a surface charge. *This has two
consequences.

One that they bind water, this accounts for behaviour of clay soils in that
they swell when wet and shrink when dry. *So a soil with a modest amount of
clay will hold water much better than just sand or pebbles whose surface
area is much smaller and don't bind water. *If you have a reasonable amount
of clay this is advantageous to growing, especially active annuals like
cucurbits that wilt on hot days if the soil doesn't supply enough water. *In
my case I have another benefit that the solid clay sub-strata acts a
reservoir evening out the erratic rainfall of the region. *It takes up water
during wet spells and gives it back in dry.

Two that clay binds minerals. *The cation exchange capacity and total
exchange capacity is much higher than sand. *So clay soils don't leach
minerals nearly so easily and stay more fertile for the application of a
given amount of fertiliser than sand. *The disadvantage is that if you have
undesirable minerals such as sodium ions these will bind and displace
desireable ions like calcium, magnesium etc. *This sodised soil is unfertile
and very hard to remedy.

Provided you take care not to work it when too wet or too dry and deal with
drainage issues soil with a reasonable amount of clay will be more
productive than that with very little or none. *I think Billy has some
tables of the desireable amount of clay in garden soil.

David

(Awed) I sit at your feet!

Question: Why equate clay to sand? Isn't that going to extremes? My
soil is, AFAIK, a good loam (I see that term is still used). The clay-
ey (adobe) soil characteristic of this area has been greatly modified
by application of various Good Things over time. I inherited pretty
good dirt from the sellers [censored] years ago, and have continued to
apply compost and worm castings, as well as small amounts of Other
Stuff, so it's nice and friable.