Raising clay soil by 3-4 inches, what to add?

Jennifer243

We have clay soil, which judging from what I've read is not as bad as some people have.  But it is dense and with woodland nearby it can get mossy.  Following an extension project our front garden was trashed but we have now sorted out the hard landscaping.  Now I have a path that is between 3-4 inches above the current soil level (a consequence of something the builders did, not the landscapers).  So I have an opportunity to improve the soil but with approx 63m2 of garden to raise I'm worried I mess up.  I reckon we need in the region of 6 bulk bags - i'm happy to leave path slightly proud as i'm not putting grass down.  I want my front garden to be where I get to play with my gardening ambitions so the plan is a lot of planting.  I'm not looking to completely transform the soil, just improve it, I'm kind of used to the clay.  So after that LENGTHY introduction, could anyone give me advice on what might be best to add? And does it really matter what it is?  Thanks for any advice you can give!  

Please forgive any forum etiquette fails, this is my first post!

Fairygirl

Hi Jennifer - I think you'd need considerably more than 6 bulk bags of soil if you have that size of area to improve. It always seems like enough, but rarely is!
Lots of well rotted manure, compost and grit all mixed in will improve the structure, and help bulk it out, but it will tend to settle down with weather etc. As you plant and create borders and beds, the level will settle and you can add to it as you put plants in. It's one of those ongoing things, and most people find that soil levels settle over time.
Clay is brilliant, and will allow lots of scope for planting. 

Jennifer243

Fairygirl said:

Hi Jennifer - I think you'd need considerably more than 6 bulk bags of soil if you have that size of area to improve. It always seems like enough, but rarely is!
Lots of well rotted manure, compost and grit all mixed in will improve the structure, and help bulk it out, but it will tend to settle down with weather etc. As you plant and create borders and beds, the level will settle and you can add to it as you put plants in. It's one of those ongoing things, and most people find that soil levels settle over time.
Clay is brilliant, and will allow lots of scope for planting. 

Thank you Fairygirl.  No topsoil in the mix?  RE 6 bags - I'm prone to optimism :-)

Pete.8

I had the end of my slopey garden landscaped a couple of years ago and had to raise the soil level by as much as 2ft on one side of the garden. I'm in Essex so it's mostly clay.
I got 25 ton of excellent topsoil from Silverton Aggregates and over the last 2 years I've dug in about 8 ton of well rotted farmyard manure from CPA Horticulture.
It's very fertile now, but I feel still needs more organic matter, so more manure digging in this autumn.

PS - I did find that when the topsoil was first put down it was at the right level. A few months later it had settled and sunk a bit - so I did get another 2 ton to correct that and I feel this year I'll probably need another ton.. so as Fg says above best to get a bit more than you think you need.

Jennifer243

Thanks Pete8, that's helpful.  I can see a future of regular topping up!  I'm in Edinburgh so I'll have to check out suppliers.

Fairygirl, I've read yours again and think you meant that the manure, grit and compost is in addition to soil.  Thank you.

Nollie

I used about 20 big builders bags in total of acid compost (my tough clay is very alkaline) and manure on an area about half your size and it wasn’t nearly enough, plus endless grit bought in 25L sacs to try make my soil more workable, plus 70L bags of compost bought locally and added every time I plant. It’s getting there but I reckon another big delivery plus my homemade compost should just about do it. It is amazing where it all disappears to Jennifer!

The main thing to watch out for is never add fine/builders sand as this turns it to concerete. 

The compost, manure and grit mix will give you a better structure (as per fairygirls advice) than using topsoil which may not necessarily improve the workability of your clay, but if it’s a lot cheaper there would be no harm in adding some to the mix.

Jennifer243

Thanks Nollie, it looks like I'm going to have raid savings!! Maybe i'll start with one side of the path to get going!  Thanks for clarity around topsoil.  

I've found a local company that does reshredded mushroom compost bulk bags which they say is the best thing for clay soil. Mushroom is £76 for 1000L and their horse manure bulk bag is £105.  Any thoughts on mushroom compost? Plus another company does a soil improver 850L for £35 that comes from the processing of Council collected garden waste. Maybe I could try manure on one side of the path and mushroom on the other side, along with compost and grit :-) 

I can feel my muscles starting to ache!

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Buttercupdays

Mushroom compost is also alkaline, so it depends on what your soil pH is now and what you want to grow eventually.

Fairygirl

Yes - I meant in addition to the soil Jennifer 
I'm  not sure why you say grit isn't good for plants, F's Dad. Obviously - it has to be the right kind, but on heavy clay soil [which I've always gardened on ] it benefits most plants as it improves drainage. I often add pea gravel, and I can't say it's ever been an issue with anything I've grown. 
As B'cupdays says - you need to know your soil pH re the mushroom compost  

fidgetbones

Try a local farmer or stables. I get a tipper load of well rotted manure, tipped  on to a hard standing, for £40. It is probably about 20 cubic metres.  When we took over next door, the clay soil had never had any improvement. I put six inch of FYM on it over the winter and let the worms pull it down. When it came to digging in the spring, it was much improved.