By preparing compost, you are creating
an ideal medium for mycelial growth. Basic mushroom compost is
made up of wheat straw, horse manure and gypsum (calcium sulfate).
There are a variety of optional ingredients that may be added.
A brief outline of some materials used in making composts follows:
- Straw:
- Serves as a carbon source (carbohydrate) source wheat — considered
the best — contains xylan oat, barley - break down more
rapidly than wheat rye — breaks down slower than wheat also corn cobs,
oak and beech leaves, etc.
- Other Carbohydrate Sources:
- Rice straw, molasses, brewer's grains, cottonseed meal (provides
the fatty acid — linoleic acid — which is reported
to stimulate yields.
- Manures:
- Nitrogen source, provides organisms essential to composting
horse — most commonly used, fresher the better poultry — higher
in nitrogen and phosphorous than horse, not so rich in potash
(provided in wheat straw), faster and hotter than horse, use
dry pig and sheep — must be used before they become
sticky - used partly dry
- Other Nitrogen Sources:
- Blood meal (dried blood), bone meal urea, ammonium sulfate
((NH4)2SO4) Gypsum: calcium sulfate (CaSO4) — essential
to mushroom compost preparation — prevents the compost
from becoming too "greasy" — by forming an equilibrium matrix
with the water, also helps the colloids to flocculate producing
a compost with a more granular structure with increased water
holding capacity: provides Ca++ ions; a mineral essential to
mushroom growth: helps to prevent the loss of nitrogen (from
the breakdown of proteins during the act of composting) by
chelating the ammonia
- Optional Mineral Sources:
- Superphosphate — said to promote vigorous mycelial
growth, but an excess may make the beds too acid too soon which
depreciate the crop. 14 lbs./ton of compost should be added
at the last turn. It should not be used if there are a lot
of droppings 9 fresh) in the compost.
Sulfate of potash — used in synthetic
composts. the ubiquitous calcium carbonate.
Activators — compost "activators" can
be obtained from nursery and garden stores and assures the
presence of the organism essential to composting.
The following recipes create about one half ton of compost.
One half ton of compost will provide enough compost for about
60 square feet of beds (surface area). At least one quart of
grain spawn per 15 square feet of bed surface should be used.
Sample
Compost Recipes:
5 bales wheat straw, half a pickup (half ton) horse manure,
third of a pickup of horse manure, 30 lbs. gypsum, 2 lbs. activator,
70 lbs. chicken manure, 4 lbs. Blood meal and 30 lbs. gypsum.
To prepare compost, the straw must be soaked for several days
until it just about, but not quite, squeezes water out in your
hands. The compost pile is then built by stacking alternating
layers of straw, activator, manure and gypsum until all the materials
are used up. The stack should be 4-6 feet high.
In about 48 hours the heap will begin to generate heat and will
sink somewhat in height. By the fourth to sixth day the temperature
in the interior of the pile should reach 160°F (71°C).
Temperatures of up to 160°F are due to thermophilic organisms.
Temperatures over 170°F are due to chemical bonds being broken
as well as other chemical reactions. Temperatures over 160°F
are undesirable. After the pile reaches a peak temperature the
temp will then begin to fall and the pile should be turned. The
pile is turned by moving the middle half third to the bottom,
the top and sides to the middle, and the bottom to the top. If
any parts appear excessively dry, water should be sprinkled on
those parts at this time. There should be no need to add any
water after the first turn.
The heap will again heat up and be ready for a second turn after
six more days. It should now be turning a rich brown color. With
the second turn, no water should be given unless there are very
dry patches — wet sparingly. One more turn should complete the
mixing but if the temp (peak) is above 130°F a fourth turn
may be necessary, (some authors recommend even another turn).
If on the final turn the compost is too wet or has a greasy appearance,
more gypsum may be added.
When done, the pile should be brown to gold in color, open in
texture, and have a rich humus smell. The straw should break
readily when twisted, and the compost should be just moist enough
to bind together when squeezed in the hand. Initially the compost
will have an alkaline pH. When mature and ready for inoculation
the pH should be between 7.0 and 8.0. The heating of the compost
has pasteurized the compost by the action of the thermophilic
organisms. These organisms will not grow at the lower temperature
at which mycelium grows. With proper composting the resulting
compost will be free from competing organisms. Insects in all
their forms will be absent from the medium and the rapid growth
of the thermophilic composters will have also eliminated bacterial
and fungal competitors.
Inoculating Beds:
The compost is then filled in boxes about 10-12 inches deep.
The temperature should be 80°F or less and there should be
no ammonia fumes present when the boxes or beds are inoculated
(spawned). The compost is inoculated with grain spawn either
by mixing throughout the compost in the bed or box or by sprinkling
a tamped down box with spawn and then covering thin layer of
compost. In either cased the compost and spawn are then tamped
down and covered with moist newspapers or a sheet of plastic
to retain the humidity. The inoculated compost should be allowed
to sit for 2-5 weeks (until the mycelium has taken over the compost).
It may be necessary to moisten the newspapers occasionally during
this time.
When the compost is permeated with mycelium it is then cased
for fruit initiation. A drop in temperature and increase in ventilation
induce fruiting. As the mushroom and mycelium grows there will
be a drop of pH from the excreted metabolites until the pH reaches
5.0-5.5 at which time mushroom production will cease. At this
time, the boxes/beds should be removed and the area thoroughly
cleaned and sanitized.
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