On Sun, 28 Apr 2013 08:09:02 -0400, Gary > wrote:
snip
>
>Most commercial mushrooms these days are grown in manure. Not a bad thing
>to wash them off.
snip
>Gary

from Wiki
Mushroom cultivation substrates
Substrates

Mushroom production converts raw natural ingredients into mushroom
tissue, most notably the carbohydrate chitin.[1]

An ideal substrate will contain enough nitrogen and carbohydrate for
rapid mushroom growth. Common bulk substrates include:[12][14]
Wood chips or sawdust
Mulched straw (usually wheat, but also rice and other straws)
Strawbedded horse or poultry manure
Corncobs
Waste or recycled paper[15]
coffee pulp or grounds[16][17]
Nut and seed hulls
Cottonseed hulls
Cocoa bean hulls
Cottonseed meal
Soybean meal
Brewer's grain
Ammonium nitrate
Urea
(Phases of production)
Phase II composting or pasteurization
7–18 days via composting method, ~2 hours for pasteurization (heat
sterilization)
Reduce number of potentially harmful microbes through further
composting, or apply heat sterilization.
Remove unwanted NH3.

Mushrooms metabolize complex carbohydrates in their substrate into
glucose, which is then transported through the mycelium as needed for
growth and energy. While it is used as a main energy source, its
concentration in the growth medium should not exceed 2%. For ideal
fruiting, closer to 1% is ideal.[1]