Button Mushroom Production

In General, button mushrooms are grown seasonally and in environment controlled cropping houses. White button mushroom requires 20-28 ^o C for vegetative growth (spawn run) and 12-18^o C for reproductive growth. Besides that it requires relative humidity of 80-90% and enough ventilation during cropping. Seasonally, it is grown during the winter months in the north-west plains and for 8-10 months in a year on the hills. However, with the advent of modern cultivation technology of button mushroom it is now possible to cultivate this mushroom anywhere.

The growers can take on average 3-4 crops of white button mushrooms in a year depending upon the type and varieties cultivated. Factors affecting the yield of the crop both in terms of quality and quantity are incidence of pests/pathogens and non-availability of pure quality of spawn.

The whole process of mushroom production can be divided into the following steps:

• Spawn production
• Compost preparation
• Spawning
• Spawn running
• Casing
• Fruiting

Spawn is produced from fruiting culture / stocks of selected strains of mushrooms under sterile conditions. Stock culture may be produced in the lab or may be obtained from other reputed sources. Fruiting culture is mainly imported from various places including foreign sources which give higher yield than General strains and the spawn is produced in the lab. The spawn should be of good quality in terms of flavour, texture and size apart from having potential for high yield and longer shelf life.

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

The process of mixing spawn with compost is called spawning. The different methods followed for spawning are given below:

1. Spot Spawning: Lumps of spawn are planted in 5 cm. deep holes made in the compost at a distance of 20-25 cm. The holes are later covered with compost.
2. Surface Spawning: The spawn is evenly spread in the top layer of the compost and then mixed to a depth of 3-5 cm. The top portion is covered with a thin layer of compost.
3. Layer Spawning: About 3-4 layers of spawn mixed with compost are prepared which is again covered with a thin layer of compost like in surface spawning.
4. The spawn is mixed through the whole mass of compost at the rate of 7.5 ml./ kg. Compost or 500 to 750 g./ 100 kg. compost (0.5 to 0.75%).

After the spawning process is over, the compost is filled in polythene bags(90x90 cm., 150 gauge thick having a capacity of 20-25 kg. per bag)/ trays(mostly wooden trays 1x1/2 m. accommodating 20-30 kg. compost) / shelves which are either covered with a newspaper sheet or polythene. The fungal bodies grow out from the spawn and take about two weeks (12-14 days) to colonise. The temperature maintained in cropping room is 23 ± 20 C. Higher temperature is detrimental for growth of the spawn and any temperature below than that specified for the purpose would result in slower spawn run. The relative humidity should be around 90% and a higher than normal CO2 concentration would be beneficial.

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 General, 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 CO2 concentration is favourable for reproductive growth at this stage.

Under favourable environmental conditions viz. temperature (initially 23 ± 20 C for about a week and then 16 ± 20 C ), moisture (2-3 light sprays per day for moistening the casing layer), humidity( above 85%), proper ventilation and CO2 concentration (0.08-0.15 %) the fruit body initials which appear in the form of pin heads start growing and gradually develop into button stage.