Cultivation technology of button mushroom

Mushroom cultivation is increasingly becoming popular because it not only meets the dietry requirements but also adds to the income, especially of growers with insufficient land. It is considered to be a very rewarding and fascinating hobby for the retired persons as well as house-wives who can grow mushrooms in small boxes

or other containers while attending to household chores. Today, mushroom cultivation faces less difficulties provided the grower will follow simple rules of growing.

It is really amazing that a small quantity of spawn when planted in suitable growing medium can, within almost six weeks, grow into a highly profitable crop inside a room, where no other crop would grow. Moreover, mushrooms have more uses in modern culinary cuisine than any other food crop. Mushroom cultivation is carried out indoor in any room, shed, basement, garage, etc. which should be well ventilated. However, paddy straw mushroom can be grown outside in shady places also. 

Of the many mushrooms only three kinds namely button mushroom (Agaricus bisporus), straw mushroom (Voluariella uoluacea) and oyster mushroom (Pleurotus sajor-caju) are suitable for cultivation in India.

Cultivation of button mushroom:

Button Mushroom  is the most popular mushroom variety grown and consumed the world over. In India, its production earlier was limited to the winter season, but with technology development, these are produced almost throughout the year in small, medium and large farms, adopting different levels of technology. The species being grown in most farms is the white button mushroom  belonging to Class Basidiomycetes and Family Agaricaceae.

Compost Preparation:

The substrate on which button mushroom grows is mainly prepared from a mixture of plant wastes (cereal straw/ sugarcane bagasse etc.), salts (urea , superphosphate / gypsum etc), supplements (rice bran/ wheat bran) and water. In order to produce 1 kg.of mushroom, 220 g. of dry substrate materials are required. It is recommended that each ton of compost should contain 6.6 kg. nitrogen, 2.0 kg. phosphate and 5.0 kg. of potassium (N:P:K- 33: 10:25) which would get converted into 1.98% N, 0.62% P and 1.5% K on a dry weight basis. The ratio of C: N in a good substrate should be 25-30 : 1 at the time of staking and 16-17 : 1 in the case of final compost.

Short Method of composting:

During the first phase of compost preparation, paddy straw is placed in layers and sufficient water is added to the stack along with fertilizers, wheat bran, molasses etc. The whole thing is mixed thoroughly with the straw and made into a stack (almost 5feet high,5 feet wide and of any length can be made with the help of wooden boards). The stack is turned and again watered on the second day. On the fourth day the stack is again turned for the second time by adding gypsum and watered. The third and final turning is given on the twelveth day when the colour of the compost changes into dark brown and it starts emitting a strong smell of ammonia.

The second phase is the pasteurization phase .The compost prepared as a result of microbe mediated fermentation process needs to be pasteurized in order to kill undesirable microbes and competitors and to convert ammonia into microbial protein.The whole process is carried out inside a steaming room where an air temperature of 60⁰ C is maintained for 4 hours. The compost finally obtained should be granular in structure with 70% moisture content and pH 7.5. It should have a dark brown colour, sweet unobnoxious smell and free from ammonia, insects and nematodes. After the process is complete, the substrate is cooled down to 25⁰ C.

Long Method of composting:

The long method of composting is usually practiced in areas where facilities for steam pasteurization is not available. In this method, the first turning is given about six days after preparation of the substrate for composting. The second turning is given on the tenth day followed by third one on the thirteenth day when gypsum is added. The fourth, fifth and sixth turnings are given on the sixteenth, nineteenth and twenty-second day. On the twenty-fifth day the seventh turning is given by adding 10% BHC (125 g.) and the eighth turning is given on the twenty-eighth day after which it is checked whether there is any smell of ammonia present in the compost. The compost is ready for spawning only if it doesn’t have any smell of ammonia; otherwise a few more turnings are given at an interval of three days till there is no smell of ammonia. 

Spawning:

For spawn run air temperature of 23° ± 1C is maintained in the room, with corresponding bed temperature of 24-25°C (1-2°C higher than air temperature). The fresh air valve is closed and entire air is re-circulated, allowing the carbon dioxide to accumulate to the level of 15000 ppm, desirable for quick spawn run. Higher concentration of CO₂ accelerates the spawn run/vegetative growth of the mushroom fungus. During spawn run above temperature has to be maintained, till entire compost is impregnated with the mushroom mycelium, alongwith other parameters like high CO₂ concentration, high RH (will be discussed later). Increase or decrease in temperature effects the CO₂ production of the compost and the RH of the room. With increase in temperature, RH will tend to fall, and with decrease in tempt. RH will increase. The properly insulated room will ensure uniform temperature in the cropping room at every stage of crop growth. The air will go into the room at the will of the grower and as per requirement inside, suiting the crop stage. The heat from the cropping room is removed via cooling coils in the AHU.

Casing:

The compost beds after complete spawn run should be covered with a layer of soil (casing) about 3-4 cm. thick to induce fruiting. The casing material should be having high porosity, water holding capacity and the pH should range between 7-7.5. Peat moss which is considered to be the best casing material is not available in India, as such the mixtures like garden loam soil and sand (4:1); decomposed cowdung and loam soil (1:1) and spent compost (2-3 years old); sand and lime are commonly used.

The casing soil before application should be either pasteurized (at 66-70⁰ C for 7-8 hours), treated with formaldehyde (2%), formaldehyde (2%) and bavistin (75 ppm.) or steam sterilized. The treatment needs to be done at least 15 days before the material is used for casing. After casing is done the temperature of the room is again maintained at 23-28⁰ C and relative humidity of 85-90% for another 8-10 days. Low CO₂concentration is favourable for reproductive growth at this stage.

Crop Management:

After completion of case run, the cooling of the room is enhanced to bring the air tempt down to 15-17°C in the room within 2-3 days time. Simultaneously, the fresh air vent is opened to 30% and rest of the air is re-circulated (70%). This brings down the CO₂ conc. in the room to 300 ppm to 1000 ppm, desired for pinhead formation. Likewise, the RH is also reduced to 85% from 95%. This facilitates pinhead formation on the casing within a week’s time. The pinheads grow into full button sized mushrooms in another 3-4 days. The environment parameters are maintained as above during entire period of cropping. Temperature has influence on RH and CO₂ conc. and hence should be maintained/manipulated, keeping in mind its effect on other two factors. All the three parameters work in synergy with each other to induce pinning on casing surface.

Harvesting:

Mushrooms are harvested by gently holding a mushroom body and twisting it. Washing becomes necessary to remove soil particles if non-peat casing soil is used but washed mushrooms generally deteriorate rapidly than mushrooms packed dry, due to the increased water content that results in greater growth rate of spoilage by bacteria. Small growers wash in solution of reducing agents to retard the browning caused by polyphenoloxidase.

Processing

Sun-drying of mushrooms is one of the simplest and oldest methods followed by the growers from the time immemorial. Due to the difficulties in drying of some of the mushrooms, new preservation technologies like cabinet drying, canning, pickling, freeze-drying and irradiation treatment of mushrooms have developed to improve the shelf life and consumption of mushrooms. A variety of products are being prepared from mushrooms. These are mushroom pickle, mushroom powder for preparing mushroom soup, mushroom sauce, mushroom candy etc. Farmers can prepare these products when there is surplus.