Matinum

Taking Charge of Your Health


(Peter Cundall) In
the final analysis everything wonderful
comes from healthy soil. That’s why it’s probably
our most precious resource and Kevin Handreck, look he’s
been an inspiration to gardeners everywhere because of his deep
knowledge and understanding of soil. That’s why we at
Gardening Australia are so delighted to be
associated with this project. Here is a video cassette that’s
crammed with information. It’ll be used again and again and every time you see it
you’ll learn something new. [Music plays] (Kevin Handreck) We spend a
very large amount of effort in very carefully
selecting plants for our new garden, but most of us
don’t take much notice of the soil that they’re going
to be growing in. If that soil is lousy then
we’re going to have a great deal of difficulty in getting
a good garden established. On this site here we’ve got a
quagmire down the bottom here and up the slope here
we’ve got massive runoff of water that’s taken
the soil and the clay subsoil down to that lower area. This is about the worst possible
start to a garden you can have. The builder has just bulldozed
up the subsoil to the side. He’s taken away the surface
soil and put it somewhere else. Perhaps he’s going to
even sell it back to us. But what they’re actually trying to
do here now is to put a little bit of well, I suppose it’s topsoil. Yeah, it’s not too bad but
it’s still a bit clayey. They’ve put a thin veneer of
that over this crud underneath and now they’re putting some
instant lawn over the top of that. Now that’s a recipe
for disaster. I’ll show you just over
here what’s happened. This lawn doesn’t look too bad.
It’s fairly lush but you can see that I’m really
staggering around in it. It feels like quicksand
underneath me here or perhaps it’s quick clay because
that’s really what it is. It’s just soft clay under here. You can see that there’s water
lying all over this site here. There’s no drainage
system here at all. The water isn’t getting
away from this site and we might as well just
have a lake here in fact. But if we do want to have a garden
here what we need to do is put a drainage system in to take the
water away but more importantly, the soil itself has
to be improved. All of the houses in this
area are built on much the same sort of heavy clay subsoil.
This site here you can see that there hasn’t
been any landscaping done yet so I can show you just what should
be done to improve this soil, get it ready for planting.
The subsoil surface here has all compacted. The machinery’s
run over it and the rain has beaten down on it. It’s very
hard for water to get through that sort of compacted surface and
of course if water can’t get through plant roots have a great deal of
difficulty in getting through too. The first thing to do in this
sort of site is actually to relieve that compaction, to
start digging into it like this and you can see it’s pretty hard.
I’m going to be here all day and probably all weekend before
I can do anything with that so I’m really going to have
to get some machinery in. OK well, look once we’ve
relieved the compaction we can add several different
things to this soil, one or several of them anyway.
We could add sand. Now there’s some caution here. If you
want to add sand just be very careful. Just adding a little bit is not going
to make much difference at all to the properties of this
soil down here. If you really want to add sand use two
or three times the volume of soil that you’re
incorporating it into. That will then make a sort
of a loam out of the clay. The other things that you can
do are to put on some gypsum, something like one to two kilos of
gypsum per square metre of soil. That will allow the clay
particles to aggregate together and so allow water to infiltrate
between them and of course the roots can then go down and
get the water down there. The other thing that you can do is
to incorporate some organic matter, some compost. You can buy it in.
There’s plenty available these days. Just a caution about mushroom
compost, it’s very alkaline and you may increase the
pH of your soil too much if you use a lot of mushroom compost
so just check that. Check the pH. Now the final thing that you need
to do after incorporating all those things into the subsoil is to put
some topsoil over the whole lot. It may have been
stockpiled on your block and then you can just bring it back
over or you might have to buy it in. We’ve got some here that’s
rather a nice sort of mixture of some soil and some organic matter.
That’s good, so you spread that over and then
you’re ready to do your planting.

6 thoughts on “Down to Earth — Episode 1: Treating clay soil (1990)

  1. I live in southern california and your soil sounds and looks exactly like mine. I have been digging out all the compacted clay and tons of rocks and plan to replace it with yards of good soil which is sand and compost and wood shaving mix. One place sells a mixture with that mushroom compost for more money but I didnt know if it was worth it or not. Also I tried rototilling and it didnt get into the ground more than an inch or so. What kind of tool or equipment do you use to turn over the soil and do you remove rocks if the soil is mostly all rocks and clay? Would gypsum soften the soil fast enough to plant right away without amending the soil around the plant or is it best to spend the time and money to amend the entire area especially if you want the ground cover flowering sedum to be able to spread? Thx

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