Mushrooms are a unique biota which assembles their food by secreting degrading enzymes and decompose the complex food materials present in the biomass where they grow, to generate simpler compounds, which they then absorb, and transform into their own peculiar tissues.
If a section of the gills is cut and examined under the microscope, spores will be observed on their surface. The spores will start to fall as the cap fully expands, indicating maturity of the mushroom. The spores are so minute that they float in the air and eventually, they fall to the ground. If conditions are favourable (optimum temperature and moisture), the spores will germinate to form a mass of mycelium
This is the start of the vegetative phase of the mushroom. Given an unrestricted amount of nutrients and favourable growing conditions, it is capable of unlimited growth. The mycelium developing from the germinating spore is the so-called primary mycelium and is usually uninucleate and haploid. This stage is short-lived because mycelia from different spores tend to ramify and fuse to form the secondary mycelium with two compatible nuclei, which continues to grow vegetatively and is able to form fruiting bodies.
The cultivation of mushrooms can be both a relatively primitive farming activity, and a high
technology industry. In each case, however, continuous production of successful crops requires both practical experience and scientific knowledge.
Mushroom cultivation technology is friendly to the environment. The production of edible and medicinal mushrooms utilising, for example,: straw, cotton wastes, coffee waste, water hyacinth, tree saw dust, sugar cane bagasse, wild grasses and various categories of refuse and lignocellulosic wastes, could readily be adopted in Asian and Pacific communities in sophisticated, but low technology approaches.
Mushroom growth dynamics involve some technological elements, which are in consonance with those exhibited by our common agricultural crop plants. For example, there is a vegetative growth phase, when the mycelia grow profusely; and a reproductive (fruiting) growth phase, when the umbrella-like body that we call mushroom develops. In the agricultural plants, e.g., sunflowers, when the plants switch from the vegetative growth to the reproductive growths, retarded tips for further growth (elongation) is an obvious phenomenon of mature. It is the same principle in mushroom production. After the vegetative (mycelial) phase has reached maturity, what the mushroom farmer needs next is the induction of fruiting. This is the time the mycelial growth tips should be retarded by regulating the environmental factors. These factors generally called “triggers” or “environmental shocks”, such as, switching on the light, providing fresh air, and lowering temperatures, can trigger fruiting.
Major Phases of Mushroom Cultivation
Mushroom farming is a complex business, which requires precision. Indeed, it calls for adherence to precise procedures. The major practical steps/segments of mushroom cultivation are:
• selection of an acceptable mushroom species;
• secreting a good quality fruiting culture;
• development of robust spawn;
• preparation of selective substrate/compost;
• care of mycelial (spawn) running;
• management of fruiting/ mushroom development; and
• harvesting mushrooms carefully (Chang and Chiu, 1992, Chang 1998).
If you ignore one critical step/segment, you are inviting trouble, which could lead to a substantially reduced mushroom crop yield and mushroom marketing value
It is important to note that different species of mushrooms require different growth requirements and these should be researched and integrated into your cultivation processes and plans. Two basic ref¬erences are The Mushroom Cultivator, by Stamets and Chilton, and the aforementioned Growing Gourmet and Medicinal Mushrooms, by Stamets.
Growing mushrooms outdoors as a part of a market garden involves little effort after you have inoculated the logs or other substrate with the mushroom spawn. Your duties are mainly to maintain humidity and monitor for fruiting. When mushrooms appear, you add them to your other garden products and sell them.
Most available markets, however, require more mushrooms than occasional fruiting provides. Indoor production can fill the gaps when outside fruiting lags. The entire operation can also be conducted inside. However, indoor mushroom production demands a much higher level of knowledge, continuous monitoring, and timely manipulation of environmental conditions.
While the mycelium is growing, and until it fully occupies the substrate, the mushroom farmer typically manipulates the growing environment to favor mycelial growth. The atmospheric conditions are then changed to initiate “pinheads,” and then to complete fruiting. For example, in oyster mushroom production under closely controlled conditions, the grower lowers the temperature and the CO2 in the grow room to initiate fruiting. Each species has specific requirements for its stages of development.
When you can cut the time between harvests, annual production increases. Short cycles are what large-scale commercial producers aim for, constantly looking for ways to increase efficiency. This is the competition you face if you plan to sell your product on the wholesale market.
Under suitable environmental conditions, which may differ from those adopted for spawn running, primordial formation occurs and then followed by the production of fruiting bodies.
The appearance of mushrooms normally occurs in rhythmic cycles called “flushes”. Different genus’s have different number of flushes – generally 2 – 3. Decisions need to be made on the commercial viability of second and third flushes in terms of time, room occupancy and yield.
The temperature for growth of mycelium is 10-35 degrees C. The optimum growing temperature of the mycelium is 23-28 degrees C.
The optimum developmental temperature of the fruiting body is 18-24 degrees C.
The optimum pH of the substrate used in making the mushroom bag/bed is 6.8-8.0.
The C:N ratio in the substrate is in the range of 30-60:
A large circulation of air and reasonable light are required for the development of the fruiting bodies.
Examples of spawn substrates:
(i) Wheat grain + 1.5% gypsum or lime.
(ii) Cotton seed hull 88%, wheat bran 10%, sugar 1% and gypsum 1%.
(iii) Sawdust 78%, wheat bran 20%, sugar 1% and gypsum 1%.
(vi) Sawdust 58%, spent coffee grounds/spent tea leaves 20%, water
hyacinth/cereal straw 20%, sugar 1% and gypsum 1%.
Examples of cultivation substrates:
(i) Cotton seed hull 95%, gypsum 2%, lime 1% and Calcium superphosphate 2%.
(ii) Rice straw 80%, cotton waste 18%, gypsum 1% and lime 1%.
(iii) Water hyacinth 80%, cereal straw 17%, gypsum 2% and lime 1 %.
(see ‘Facility’ tab for the Barefoot and Tiptoe infrastructure for Mushroom cultivation)