I'm in the process of taking up an old path and converting the area
into a flower bed. Beneath the concrete slabs (and beneath the
underlying sand and beneath the polythene sacks below that) there's a
2-inch thick layer of consolidated cinders or boiler ash or whatever
(a previous owner of the property is said to have had a Rayburn). It
comes out in largish chunks, but inevitably some of it crumbles and
gets into the soil. I suspect it was the original path surface, and
it's probably been there for several tens of years.

My query is this: is it likely to have poisoned the soil in any way
(leached chemicals, pH change, etc) and should I dig it out, or is it
a reasonable bet that it's now pretty inert and can just be broken up
and dug in deep to assist the drainage (bear in mind I'm not proposing
to grow vegetables on the area)?. The soil below it is a good dark
brown to black and looks/smells good, but there's not much worm
activity visible, which may not be surprising under a path.


--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net