Mike Lyle wrote:
[H]omer wrote:

I finally took the plunge and started digging to discover the cause
of my drainage problems. Surprise, surprise - it's heavily compacted
soil on top of solid clay ... lots of clay.

I've decided to start from scratch and just excavate the whole site.

What I need to know is this:

1) ... What depth should I dig to? (I have a digger).
2) ... What type of aggregate and organic materials do I need?
3) ... What depths should each material be, and in what order?

my experience of hardening up a west Wales clay patch about 80' x 35'
suggests a foot of 4" to 1" limestone with what little soil and compost
I could spare on top (varying in depth from 6" to 1/2"

So you reckon 12" of chips followed by 6" of organic material?

6" doesn't sound very deep. I was planning on planting trees as well.

Is that really all I need?

It sounds as though you may have a bit more money than I did, so you
can do a more refined job.

Well I can pretty much afford to do anything I like with this garden, so
yes, I want to do the best job possible.

Thanks for the info.

-
[H]omer

In article , [H]omer wrote:

So you reckon 12" of chips followed by 6" of organic material?

6" doesn't sound very deep. I was planning on planting trees as well.

Is that really all I need?

Most clays are very fertile - all they need is to be opened up
so that water can drain and air reach the roots. So you don't
want to remove the clay so much as dilute it in the soil with
coarse material. This needs to be done fairly deeply, for the
drainage.

6" of organic matter is far more than most soils have. My loam
has 12-18" of topsoil, of which only a small proportion is actually
organic material, and it is nearly as fertile as soils get.


Regards,
Nick Maclaren.

Nick Maclaren wrote:
In article , [H]omer wrote:

So you reckon 12" of chips followed by 6" of organic material?

6" doesn't sound very deep. I was planning on planting trees as well.

Is that really all I need?

Most clays are very fertile - all they need is to be opened up
so that water can drain and air reach the roots. So you don't
want to remove the clay so much as dilute it in the soil with
coarse material. This needs to be done fairly deeply, for the
drainage.

6" of organic matter is far more than most soils have. My loam
has 12-18" of topsoil, of which only a small proportion is actually
organic material, and it is nearly as fertile as soils get.

I didn't make it clear before, but my current 'soil' is about 1/2" of
what looks like mainly sand (think the kind of soil you get at the
inland edge of a beach), followed by ???" of clay (I haven't struck rock
yet!!!). Therefore, for all intents and purposes, there is no real soil
on site; I'll have to buy some in.

/me gets his calculator out

Is this about right then? ...

I excavate 24", and keep the clay.
I mix the clay with aggregate, and backfill 12".
I buy in a skip of topsoil, and backfill 6"
I buy in a skip of GP compost, and backfill the remaining 6"

Does that look OK?

Thanks,

-
[H]omer

[H]omer wrote:
Nick Maclaren wrote:
In article , [H]omer
wrote:

So you reckon 12" of chips followed by 6" of organic material?

6" doesn't sound very deep. I was planning on planting trees as
well.

Is that really all I need?

Most clays are very fertile - all they need is to be opened up
so that water can drain and air reach the roots. So you don't
want to remove the clay so much as dilute it in the soil with
coarse material. This needs to be done fairly deeply, for the
drainage.

6" of organic matter is far more than most soils have. My loam
has 12-18" of topsoil, of which only a small proportion is
actually
organic material, and it is nearly as fertile as soils get.

I didn't make it clear before, but my current 'soil' is about 1/2"
of
what looks like mainly sand (think the kind of soil you get at the
inland edge of a beach), followed by ???" of clay (I haven't struck
rock yet!!!). Therefore, for all intents and purposes, there is no
real soil on site; I'll have to buy some in.

/me gets his calculator out

Is this about right then? ...

I excavate 24", and keep the clay.
I mix the clay with aggregate, and backfill 12".
I buy in a skip of topsoil, and backfill 6"
I buy in a skip of GP compost, and backfill the remaining 6"

Does that look OK?

I wouldn't bother buying in the compost: the topsoil you buy probably
won't be brilliant, but it'll do perfectly well; and compost alone
won't provide enough physical support for plants (remember it's used
in pots and other containers, not the open ground). I reckon the
stone underneath should give you reasonable drainage, as long as the
water's got somewhere to _go_. If there's no way out, all your
operations won't have any long-term effect. So if you're going to dig
out, it would be worth putting in some plastic land drains (local
farmer's merchants or Jewson-type place). But of course, they'll
still have to lead somewhere.

I think I'd let it all settle for a year before putting in trees: it
won't be very stable. (I have to say it's amazing what will survive
in almost pure clay; and of course growing things will improve the
soil in itself.)

--
Mike.

In article , [H]omer wrote:

I didn't make it clear before, but my current 'soil' is about 1/2" of
what looks like mainly sand (think the kind of soil you get at the
inland edge of a beach), followed by ???" of clay (I haven't struck rock
yet!!!). Therefore, for all intents and purposes, there is no real soil
on site; I'll have to buy some in.

That smells wrong. I strongly advise analysing it first - your clay
may not be entirely clay. My soil is 60% sand, 18% silt and 22% clay,
and you should likke at various loams - if you have basically clay,
you WANT the sand.

To analyse clay at home, half fill a clear glass wine bottle with
soild from a particular horizon, put a spoonful of washing powder
(the corrosive type) into it, fill up with water and shake until
it is an emulsion. The sand will drop out almost immediately
(20 seconds?), the silt fairly quickly (30 minutes?) and the clay
over a period of days to weeks. Somwhere on the net is the actual
description of the method and times.

Again, you can find it on the net, but look up what a good loam is.
If I recall, equal parts of sand and clay is heavy, but good. Mine
is a fairly sandy loam. If your clay contains a fair amount of
sand, you may want to add a bit more sharp sand or fine gravel (or
small aggregate), but the key is to loosen it. This will be tricky
as diggers compact the soil - so you may need to reverse carefully.

Anyway, while I am no expert, that is roughly right.


Regards,
Nick Maclaren.

Nick Maclaren wrote:
In article , [H]omer wrote:

I didn't make it clear before, but my current 'soil' is about 1/2" of
what looks like mainly sand (think the kind of soil you get at the
inland edge of a beach), followed by ???" of clay (I haven't struck rock
yet!!!). Therefore, for all intents and purposes, there is no real soil
on site; I'll have to buy some in.

That smells wrong. I strongly advise analysing it first - your clay
may not be entirely clay. My soil is 60% sand, 18% silt and 22% clay,
and you should likke at various loams - if you have basically clay,
you WANT the sand.

To analyse clay at home, half fill a clear glass wine bottle

Hi Nick,

Yeah I remember doing the soil-test-in-a-jar experiment way back in my
school days.

Let me put it this way, the clay under my garden has the consistency of
putty, i.e. it is nearly pure, terracotta-red, potter's clay. It's so
'good' in fact that I am actually going to be selling it to a local arts
and crafts club.

It would seem that I'm sitting on top of a clay pit. Oh lucky me.

I am brassed off that the property developers slapped lawns directly on
top of wet-clay with zero drainage.

I understand that clay is not intrinsically the evil entity that some
people think it is; it is rich in nutrients after all, but it's also a
pain WRT drainage.

I think my garden may actually be one of those that really does need
field drainage pipes.

I'm going to be calling in a guy who's a tree surgeon and landscaper, to
help me with a tree that's been blown partly over by the horrendous wind
we get round here, so I'll ask for his expert opinion about drainage on
site as well.

Thanks again,

-
[H]omer