The message
from Janet Baraclough contains these words:

It's a great soil conditioner and if it was made with horse manure
probably contains some remaining nutrients. It also contains chalk, not
good for limehating plants; and has probably been repeatedly sprayed
with insecticide to kill mushroom fly.


Modern mushroom farms don't. They have airlock lobbies between two doors.

Even in ye olden dayes the sheds were only sprayed (with nicotine) while
no mushrooms were growing. Allegedly.

--
Rusty Hinge
horrid·squeak&zetnet·co·uk
http://www.users.zetnet.co.uk/hi-fi/tqt.htm