[jaws8]

Hello again,
Can anyone advise on my raised bed growing mix. The bed is only small (4ft x 2ft x 14inch)so was just going to fill it with 100% organic compost because I can buy it far cheaper than topsoil. I am putting good thick cardboard on the base followed by a layer of gravel and then the compost. Does this sound ok.
Many thanks .

[penance]

How good is the existing soil?

If its ok, then I would just mix in the compost and build up like that.

[jaws8]

Thanks for the reply. I am building the whole thing from scratch to sit on top of an old piece of lawn so as such there is no existing topsoil so was just going to use 100% compost instead of a mix.

[penance]

I think a mix is better, compost on its own doesnt have much structure.

[Ropster]

Not sure why your putting Gravel in ? the cardboard should kill the grass with the compost on top

[jaws8]

Maybe I will skip the gravel and just add a percentage of topsoil. Thanks for all the advice,much appreciated.

[woodburner]

Thanks for the reply. I am building the whole thing from scratch to sit on top of an old piece of lawn so as such there is no existing topsoil so was just going to use 100% compost instead of a mix.

I don't follow your reasoning here. Are you implying that the lawn was made of turves placed directly on subsoil?
In my garden there is a least a spits depth of topsoil under the lawn. It was (part of) a field in a previous life though.
I know some recent housing developments only have a skim of topsoil laid over god knows what kinds of builders' rubbish, but if you haven't seen what's under the grass, there's no need to assume the worst.
Someone on here has recently dug up his lawn and has made a very nice veg patch from it. I will try and find the thread.

Edit: Found it here

[jaws8]

Thanks for that Woodburner. I did dig up a test patch to see what the topsoil was like but it was so poor (pure clay and large stones) that it isn't worth using. One of my cricketing buddies has given me a bulk load of organic compost and so was just going to use that but didn't know if I should mix some topsoil in with it.

[Trillium]

It depends where you get your topsoil; some isn't worth the effort to use. I've had some chock full of weed seeds and useless. Just plain good soil (even a newby could tell the difference) is sometimes better than overpriced topsoil. Add lots of other stuff like manure, shredded leaves and/or straw as well as the compost and you'll have fantastic soil to work with. Cardboard alone on the bottom should help kill the grass and weeds.

[richyrich7]

If you've got that compost for free then good for you 

Best thing to mix in with it would be perlite IMHO as recommended by Mel Bartholomew on  http://www.squarefootgardening.com/

[woodburner]

Darn! Whilst clay (eventually) makes the best soil, it takes years so don't try mixing your compost with it!
Strip off the turf with as much topsoil as has formed under it, put it to one side, stacked upside down under black plastic, carpet, tarp or whatever lightproof covering comes most easily to hand. Keep it damp, and after a few months you will have some very good topsoil to add to the compost in the beds.

[jaws8]

Thanks for all the good advice. I'm going have a go mixing with some perlite!