Allotments 4 All

nice soil there, robert  ;D

Like Robert said, it will rot down.
When I was clearing my plot I started by trying to pick every little bit out, but I could see that I would be there forever, so in the end I shook as much soil off as possible and stacked it grass to grass in a line along the edge of the plot about 2 to 3 ft deep.

Eighteen months later there was grass growing on the top and sides as I didn't cover it,  but underneath was some lovely soil. I just picked out the obvious roots and put the remainder into a dalek to compost down further.
The spread out soil grew some lovely dahlias and cosmos, and there was no sign of couch.
I must say I was surprised though, but I'd never have cleared my plot if I hadn't done as I did, and there was just too much to take away and bin it.

I also tried putting sods of couch around the remains of a bonfire in a sort of igloo, building it up until there is just a small hole at the top. This keeps the embers going and is supposed to kill off the roots. It does dry out the soil so that roots can be separated, but I'm not sure how well it works. Worth a try.

My guess is that it will work well as long as the sods don't just catch fire; I remember my father just sticking them on the bonfire, and they always burnt. Roots under and around a fire always seem to be killed.