Mushroom growing
Practical Action
What to grow your mushrooms in - Substrates
Mushrooms can be cultivated on a wide variety of substrate. The quality of the substrate is
the main factor in the success of growing mushrooms as it provides all the energy and
nutrients that the mushrooms will use while growing. Different strains of mushroom will
require different substrate mixes. The substrate must not be rotten, mouldy and should be
kept dry while in storage.
Agricultural wastes are often used as a source of material for the substrate including; cassava
stalks, cocoa pods, coffee bean husks, coffee pulp, corn cobs, corn stubble, cotton seed cake,
pulse husks, rice hulls, sawdust, sugarcane bagasse, tealeaves, tobacco stalks, wheat straw
and water hyacinth.
In many parts of Zimbabwe wheat straw, bush grass and horse manure are commonly used
with the addition of chicken manure, cotton seed meal, ammonium nitrate or urea, gypsum
(calcium carbonate).
Growing mushrooms on a substrate of water hyacinth was first promoted by the Chinese
University of Hong Kong, and has been taken up by the African University of Mutare in
Zimbabwe. The advantage of using water hyacinth, which is an unwanted weed that clogs up
many waterways in Africa, is that the costs of preparing the substrate can be kept down.
When making the substrate the objective is to provide a uniform material that will provide all
the requirements of the mushrooms. Nitrogen content is important. Analytical laboratories
can measure the nitrogen content of the substrate to ensure it is sufficient.
The ratio of carbon to nitrogen is also important. The approximate requirement at the time of
filling the bags or trays is 20:1. Carbon component is obtained from materials such as straw
while the nitrogen comes from manure. Cotton seed meal and castor bean meal contain both
elements.
Gypsum is a useful ingredient as it provides calcium to the growing mushrooms, regulates the
acidity level of the substrate, counters potassium, magnesium and phosphorus concentration
and increases water holding capacity thus decreasing the risk of over wetting. It also improves
the physical structure of the substrate.
For some varieties wood logs can be used if available. These should be freshly cut. Shiitake,
oyster and tremella are suitable for growing on wood. Shiitake can take 6 to 18 months to
sprout and are therefore more expensive to produce. Logs can be difficult to obtain, especially
in areas where there is a demand for fuelwood.
Preparation process
A suitable area needs to be set aside for preparing the substrate. For best results it should
consist of a large concrete floor which has a slope, so that run-off can be collected and
reused. A storage area is needed for the straw, chicken manure etc used to make the
substrate, but the longer any manure is stored the more nitrogen will be lost. Another smaller
area is required for filling the substrate into its growing bags or trays. This is usually roofed
and walled. Lime, gypsum, small tools and chemicals for pest and disease control should be
stored separately is a secure area.
The preparation to make a substrate for Pleurotus involves mixing with water. This can be
done by
Spraying the heap of material with a hose
Making a flat pile and using a sprinkler
Soaking in a tank of water.
Soaking requires a suitable container for mixing the water and the substrate materials
together to allow the straw etc to soak up water. Alternatively a pit can be dug. The size of the
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