Higgs Boson wrote:
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?
Equate no, contrast yes. Yes they are extemes, I said that to illustrate
the difference not to recommend either. They are ends of the spectrum in
particle size but also in minaral composition. Sand is largely silica which
is almost inert with respect to water and minerals. Good soil is neither
extreme but has both (as well as organic matter) avoiding the drainage and
workability problems of too much clay and the poor water and mineral holding
power of too much sand.
Have a look at this:
http://en.wikipedia.org/wiki/Soil_texture
Which shows the situation in three dimensions instead of the two that I
used. It also has some practical tests so you can work out what you have.
It is well worth learning and performing such tests on your soil.
D