[She'sinthegarden]

Hi
My new plot hasn't been cultivated for years. It's been under black plastic since May and now I've started digging it. There's just about a spade depth of topsoil and clay underneath.

I understand why it's necessary to fork over the second depth (clay) to improve drainage, but why is it necessary to incorporate organic matter here? I want to save my precious leaf mold/garden compost for the top layer of soil.

I'm missing something obvious, aren't I?

Can anyone tell me, please?

[mumofstig]

It's to increase over time, the depth of the top soil.
But if you put enough of the good stuff on top the worms will do the job for you i think

[woodburner]

I wouldn't bother incorporating organic matter into the subsoil. There's more to making good soil out of subsoil, than adding a bit of manure anyway.
When I double dug my first plot, I did add manure somewhere below the surface, but I wouldn't do more than fork it into the top few inches now. Horses dont 'poo' underground, after all! :blink:    

[Trillium]

True double digging requires incorporation of the lower layer into the first, but it's really hard work with clay. Been there, done that, GROAN!
A better alternative is to simply shove a garden fork into the lower clay area and just loosen it in all possible growing areas. This way root tips can penetrate that layer and take some of the valuable, yes valuable, nutrients from that layer. Keep heaping the good stuff into the upper layer and stirring that about.

[She'sinthegarden]

Thanks all
I'll keep my good stuff for the top layer - especially as I'm going to mound up the beds with a view to making them into raised beds when cash allows.

Another related question, though. I'm going to put in a bed of asparagus crowns. Should I stick a couple of bags of grit into the forked over clay layer to try and improve the drainage?

[Coltar223]

I too suffer from the dreaded clay subsoil. Doesn't matter where I am in the world the basics are the same. There is absolutely nothing wrong with clay based soil, in fact it has better macro and micro elements than so many other soils. Trouble is, it's compact (heavy) does not allow translocation of air and water and lacks friability. So after digging through a decent top soil when we come across this 'nasty clay sub soil' we assume all is lost.

Nothing could be further from the truth. The process will take time ( three to four years) and effort, but with that combination plus good soil tactics you will end up with an outstanding product.

My suggestion is to firstly decide to go down or up. Raised beds or double digging? In my 40+ years of farming and veggie gardening I have come to the conclusion that raised beds for the home gardener are so much easier and by far more productive.

If finances are not a factor then build rasied beds, use your top soil as a base and top off with good soil/manure/compost blend.
Building the soil up is hard work building the sub soil up is horrendous work.

Compost, compost, compost. Use it, it is your best friend and the soils.