"B & J" wrote in message
...
A friend called this afternoon asking if I had an idea what salt used
mushroom growing medium contained that made it too "hot" to be used around
plants prior to composting for six months to a year. She had done searches
prior to calling and told me she could find nothing specifying the "salt"
involved. I speculated that it probably was a nitrate, but....

Any help would be appreciate. BTW, I mentioned this group had a number of
knowledgeable people who probably could help. Last week she was
particularly
impressed with paghat's description about the echinacea problem, including
its vectors, that I forwarded to her after she had experienced a similar
problem. Personally, I really enjoy paghat's political observations.

John

Actually it's 'salts' in the plural, in particular soluble salts, primarily
as a result of too high levels of potassium and ammonia in fresh mushroom
compost, much the same as one would encounter with fresh chicken manure
(which is often a primary ingredient of the mushroom growing medium). The
potassium is very soluble and will leach out rather rapidly and the ammonia
will undergo a process of nitrification which will convert it into a usable
(and non-burning) form of nitrate but the speed with which this is
accomplished is determined by temperature and pH. Best to age it well if the
mushroom compost is fresh.

Most bagged mushroom compost has been properly aged, but I would avoid using
it on seedlings or with any seed starting medium as young plants and seed
germination are particularly sensitive to soluble salts.

pam - gardengal