"Steve Peek" wrote
Ed, your biggest concern should be whether or not the horse's paddock
was sprayed with a broadleaf herbicide. The herbicide will pass
harmlessly through the horse and wipe out you garden. Check with the
source of your manure, it would be heartbreaking to have that happen.

Yes, indeed. Farmyard or stable manure is wonderful stuff if you can get
it, but there's one particular herbicide persisting in manure that has
caused quite serious problems for some allotmenteers and gardeners in
recent years. There's info on the RHS site:
http://www.rhs.org.uk/advice/profile...ler-manure.asp

It can also be quite difficult to actually find out if any particular
load is 'clean', unless the source can be absolutely certain that all
their feed and bedding is clear too, because of buying and selling of
hay and silage feed.

One case I know of locally happened where cattle manure from one farm
where they didn't use this stuff was affected, unbeknownst to the
farmer, due to contaminated feed and hay bought in from elsewhere.
--
Sue