[dan808]

Hi guys I've got heavy clay soil about a 8inch down I have planned to put raised beds in they are constructed now but before I fill them I want to improve the sub soil slightly and just wondering how much sharp sand should I use per sq metre?

[mumofstig]

according to the RHS add lot n lots 
http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=620

Personally I think you're better to add organic material to improve the soil - manure, home made compost (shop bought isn't as useful, but better than nothing IMO)

[dan808]

I'm lucky enough two have four horse on the allotment next to me and my neighbour is happy for me to take as much as want I seem to be the only one interested :blink:, to help fill the beds I was thinking off ringing a tree surgeon and adding a few bags of wood chipping what are your thoughts on that.

[mumofstig]

wood chippings take the nitrogen from the soil as they rot down, is the theory....

I would use them as a surface mulch in the winter - then they can take the nitrogen from the air, and can be dug in in spring.

IIRC other people dig them straight in but add extra nitrogen feed to compensate.............someone else will be along soon on that, I'm sure 

[fatcat1955]

If you have 8in of topsoil and say a 4in raised bed on top , i would leave things as they are and concentrate on the topsoil you will be filling the bed's with.

[Stree]

I had a garden with heavy clay and I dug up what I could around established plants and shrubs, not too near roots, lifted what I could into nursery beds. I left the clay rough in big lumps and over winter thefrost breaks it down. Then in spring dug it all back in with lots of strawy horsemuck and river sand. Breaking up the clay releases a tremendous amount of nutrients, clay is very rich organically and some plants seek it out and once established on it thrive.