Sub soil / bad soil spread on top, how to fix it?

noah1234

Hi,
I did a diy room in the garden last year. We excavated too much earth and reached I think the sub soil layer (pale orange color) and I think we hit the water table, don't ask me why, it was just a mistake!

When time came to dispose of the soil from excavation (few months later), someone suggested that I spread some of the soil mix all over the garden to save money and we did.

The mix had different types of soil. Not sure if clay or sand were mixed with the soil, or both.

We spread that mixed soil in October/November. Afterwards, the soil became very very m (Almost liquid) with puddles everywhere and stayed like that until March.

Now the top layer of the soil is really dry and hard. When I dig it, it breaks into big pieces. I tried to crumble it by hand, but the texture never returns to normal top soil texture.

Now I want to lay paving blocks on half and plant vegetables and other plants on the other half.

My questions are,
Can I plant in this hard and mixed soil?
If not, can I make a raised bed on top of this bad soil and fill it with top soil only, will that work? Or will the water be clogged once it reaches the bad soil?

Will it become very muddy again next winter?

Will I be able to lay paving blocks on it obviously after putting hard core and sand? Will that soil affect the permeability of the paved area?

I hope I can fix this mess 😅

Thank you.

Grenage

It takes years for subsoil to become topsoil, but you can speed the process up by adding lots of organic matter.  If you've pulled up a load of clay then that's not going anywhere on its own.

I would either raise the vegetable area with some decent top soil or dispose of the top layer and redress. The former will be cheaper and less effort.

I'd not worry too much about the area you plan to pave.

-taff

The texture won't return to top soil texture because top soil has lots more stuff in it,air, fungi, rotted matter, worm casts [ and worms!], roots etc. Just spreading that on top of your original soil won't turn it into topsoil. It's just soil that's on top.

It's going hard and cracking because it's clay, there's no air in between the soil particles so it dries like clay would, hence the cracks you see.

You can make a raised bed and fill with compost/soil mix that you buy in. It shouldn't make too much difference to the part you're going to slab, it won't go muddy if there's stuff on top of it.

You could also, if you felt like spending money and didn't want to go down the raised bed route, get someone in with a mini digger, scrape off the rubbish you put on top, skip it, and you'll have your original soil back again to do with what you wished.

twopenny

If you do make a raised bed I would add some horticultural sand and cheap potting compost to the soil beneath where you place the raised bed. Just a layer mixed in as well as you can. It may help the top soil in the raised bed to start to be mixed in and improve it.

When you buy topsoil for the raised bed check that it has been sterilised. Costs a bit more but will save you heartache of any fungal diseases that may be lurking. Nurserys and Garden Centres should have good top soil, builders merchants often don't so you'd be potentially going for a lottery of the whole thing happening again.