MUSHROOM CULTIVATION

Introduction to Mushroom Cultivation

Preface

Sufficient food supply is a country's most precious asset. In view of the current energy food crisis it has become most important to make a breakthrough in the technology of food production. Foods richer in minerals, vitamins and energy should be provided in order to supplement the diets that supply only small quantities of nutrients. Mushroom cultivation has a special relevance to India because straw and plant residues are abundantly available and our environment is conducive for its cultivation. Due to its high nutritive value, it is rightly called as vegetarian meat.

I. Introduction

The use of mushroom as human food dates back to time immemorial. Today with the development of better technologies and greater realisation of their nutritive values, mush-rooms have come to occupy an important place in food habits of people in several parts of the world. Commercial cultivation of mushrooms started in Europe at the turn of this century. With all the increasing scientific research in the biology of mushrooms and more improvised techniques for growing them, mushroom cultivation has almost become an industry in several countries like USA, UK, France and Netherlands. With all their historical background and nutritive importance, it is unfortunate that in India mushrooms have not caught the imagination of the people at large to become an important food item. Perhaps the reasons for their not being taken up widely are their non-availability at low prices for the common man and also due to lack of knowledge of their cultivation methods. Hence, it is necessary that a large number of people are made aware of the simple methods required for successful cultivation of edible mushrooms.

II. Mushroom Cultivation in India

Although the methods of mushroom cultivation were known to people in the various countries, its cultivation practices were not well known in our country till recently. Because of its fine characteristics, the mushroom is now being cultivated on a commercial scale in many countries.

Mushrooms grow in every country on all types of soils. They appear in all seasons, chiefly during the rainy weather, where ever organic matter or its decomposition products are available. Plant residues, by suitable treatment, can be converted into substrates for the cultivation of mushrooms. There are two main systems of growing mushrooms. One is shelf-system and the other one of tray system. Both are equally popular. They can be grown in polythene bags also, when the space is restricted. Mushrooms that are cultivated in India are white button mushroom (Agaricus bisporus), paddy straw mushroom (Volvariella volvacea) and oyster mushroom (pleurotus-sajol-caju).

In the north India, the climatic conditions prevailing during different seasons can be exploited for growing mush-rooms throughout the year. For this a year-wise mushroom production schedule has been suggested:

Mid-November to mid-March: white button mushroom

February to mid-September: Paddy straw mushroom

September to November: Oyster mushroom

Commercially mushrooms are grown indoors. It has been observed that the location for growing mushroom is should not be too moist. The best way of mushroom growing should be a place where there is a good and fresh water supply, availability of the fertilizers for making compost and a good market for the disposal of the mushroom.

III. White-button Mushroom

White-button mushroom (Agaricus bisporus) is the most popular and economically sown to grow and is extensively cultivated throughout the world. However, due to its low temperature requirement, its cultivation is restricted to the cool climatic areas and to the winter in the plains of northern India.

It can be grown anywhere if the essential conditions are obtained or controlled. These conditions include-temperature, moisture, ventilation and good spawn. The temperature requirement for the spread of the mycelium or the vegetative growth is 22 to 250 C. For the reproductive stage the temperature requirement is 14 to 180 C. Within the limits prescribed, the temperature should be uniform throughout the growth of the crop. If it is too cold the development of the spawn will be retarded. A high temperature will favour the development of moulds and bacteria, which will soon destroy the spawn or crop.

Moisture is an important factor in the cultivation of the mushroom and needs careful application. The mushroom requires an atmosphere nearly saturated with moisture, get the direct application of water on the beds is more or less harmful to the growing crop. Good aeration is essential for a healthy crop, because ventilation is one of the important factors governing the mushroom production. Good ventilation is responsible for the maintenance of congenial environmental conditions and also for the removal of toxic gas by the introduction of adequate fresh air. Good spawn is also very much essential. Spawn is merely the mycelium from a deleted mushroom grown in some convenient medium and it is the strain of mushroom selected which decides the types of mushroom the spawn will produce.

For the cultivation of white button mushroom (Agaricus bisporus) the toll owing stees should be kept in mind. These include compost and methods of composting, spawn and methods of spawning, casing and harvesting.

A. Composting

Compost is the substrate on which mushroom grows. The biochemical activities of a number of micro-organisms make the substrate selective for the growth of mushroom, Agaricus bisporuc (white button mushroom). The process of compost making is known as composting. Composting is defined as indefinite microbial degradation of organic wastes. The process of composting involves microbial decomposition of the organic materials, synthesis of microbial proteins and conditioning of the fibrous material to absorb and retain moisture.

By composting we kill all the harmful organisms present in the manure and transform the medium being used into one which would be more suitable for mushroom growth. Compost is prepared by mixing wheat straw or paddy straw with a number of organic or inorganic fertilisers in fixed proportions. Horse manure and chicken manure can also be used besides wheat straw and paddy straw. Composting yard should be large enough to spread compost heap. Constant turnings should be given in order to allow uniform fermentation. While turning is going on watering should be done to make the pile moist in an even manner.

A good compost should be brown with a distinct but inoffensive smell. There should be no smell of ammonia. When squeezed in the hand no water should trickle down, yet it should be moist. When rubbed between the fingers there should be no feel of greasiness. The entire compost will be placed in controlled environment. By raising the temperature of this environment to 54.4°Cby peak heating for one week in order to kill all insect pests and fungal parasites is called pasteurization which may not be possible under normal environmental conditions. This is the second phase of composting. After composting, the spawn will be introduced into the compost and the process is called spawning.

B. Spawning

Spawn is the mushroom seed, comparable to the vegetative seed in crop plants. It is merely the vegetative mycelium from a selected mushroom grown in a convenient medium and the particular strain of mushroom the spawn would produce. The success of mushroom cultivation and its yield depend to a large extent on the purity and quality of the spawn used. The amount of spawn should be sufficient to help rapid and vigorous coverage of the beds with the organism. It must be sufficient to fight successfully against any other organism that are always present in manure and to overcome any slightly adverse conditions of moisture or consistency that are present. When conditions are ideal in the beds, less spawn is needed.

C. Casing

Casing means covering the compost with a thin layer of soil or soil-like material after the spawn has spread in the compost. Casing is done due to some reasons like, it helps to give support to the mushroom. Casing soil provides humidity as it can hold water for a longer period. Casing prevents quick drying of the spawned compost and, therefore, it helps better spawn growth. Casing helps to regulate the temperature. Sudden reduction of temperature also encourages fruiting, soil loses moisture by evaporation and after each watering a cool layer is provided.

A good and ideal casing material should have good water holding capacity, otherwise the water will go straight to the compost and the surface of the compost will become water logged and will cause damage to the spawn. It should absorb water quickly and should release it slowly. It should have good aeration capacity, that is, it should be quite porous so that exchange of gases can take place easily. The texture of the casing material should be such that it should not be altered by watering. It should be free from disease organisms, insects and undecomposed vegetable matter.

Soil has been recognized as the universal casing material. Soil contains many micro-organisms. To use it as a casing material it should be sterilized in such a way that harmful micro-organisms are killed and the useful ones remain. Sterilization of the casing materials done either by chemicals or by heating. Sterilization under pressure is not advisable as the beneficial micro-organisms are also killed and leave the soil more susceptible to re-infection.

D. Cropping and harvesting

Excessive humidity during the cropping will result in heavy concentration of carbon-di-oxide. The more the volume of mushrooms grown in a room the more will be the need of  fresh air, a more carbon-di-oxide will be formed. The greater the humidity and higher the temperature, the more are the changes of pests and diseases. It is; therefore, essential to keep the temperature low. Apart from regular spraying of insecticides, efforts should be made to keep the circulation of fresh air around the beds Mushrooms mostly appear in "flushes" and at temperature of 68^o F, it generally takes 7 to 8 days to come to the button stage from the first appearance of the formation of a pin head. The humidity of the mushroom house will determine whether there is any need of watering the bed. If the atmosphere is dry then frequent watering is essential. While watering, gentle spraying is essential, otherwise the casing soil will get disturbed. The duration of cropping varies with the circumstances.

E. Diseases

Mushrooms are subject to many fungal, bacterial and viral diseases. Even a little carelessness in the different steps during cultivation can play a disturbing role in the mushroom growth. Improper pasturisation of compost and casing soil can be the major source of diseases. Once the disease is introduced in the farm the secondary infections can be carried out by different agencies such as air water, meachines and workers. The Important fungal, bacterial and viral diseases with symptoms, causal organisms and control should be well understood. The important diseases are soft mildew or cob- web, brown plaster; mould, white plaster mould, olive green mould, inky cap, green mould, truffle disease, bubble disease, brown spot disease, bacterial blotch, and viral diseases. The important insect pests are sciarids, phorids, spring tails, cecid, mites and nematodes.

F. Preservation

Mushrooms, like fruits and vegetables are highly perishable. The demand for mushrooms never coincides with the supply, the day when there is good production the demand may be low and vice-versa. To prevent such a glut in the fresh market it is necessary to preserve them. Mushrooms require a great deal of attention during storage, marketing and processing at the post harvest stage. Discolouration, weight and flavour loss are some of the problems. Mushrooms stored at 21^o C remained whiter than those stored at 1⁰ C or 11⁰ C, but they mature at a much faster rate. The loss of whiteness during storage is a complex process. It was found that the mushrooms stored at 21⁰ C hardened at a faster rate than mushrooms stored at 11⁰ Cor 1⁰ centigrade. Chemical action plays a great role in the toughening process. Toughening arid the degree of maturity were greatest at 21⁰ centigrade. Different methods are given here to increase the shelf-life of white button mushrooms.

1. Storage in fresh conditions

Mushrooms have a high rate of respiration and hence proper attention should be given during storage. Vacuum cooling also helps in increasing the shelf life. In this case mushrooms are packed in a film which is punctured to allow evaporation from the mushrooms. The punctured hole is covered with a small piece of sticking tape after vacuum cooling, to stop the gas flow and to allow the over-wrap to function properly. In South India fresh mushrooms are sent to other places by packing in polythene bags and these are kept in paper lined bamboo baskets or in corrugated cardboard.

2. Controlled atmosphere

Shelf-life of fresh mushrooms in increased in a controlled atmosphere consisting of 9 percent oxygen and 25 per cent carbon-ill-oxide. Partial evacuation followed by flushing with carbon monoxide and storage at low temperature, can also extend the storage life up to 20 days.

3. Gamma radiation

Shelf-life of mushroom can be increased up to 10 days by giving gamma radiation and storing mushroom at 150 centigrade.

4. Freeze drying

Freeze drying is done by immersing the sliced mushroom in a solution of 0.05% sodium meta-bisulphite and 2 percent salt for about 30 minutes. These are then blanched in boiling water for 2 minutes, followed b) cooling. The product is frozen at -22⁰ F for one minute. The frozen mushrooms are dried to a moisture content of 3 per cent in freeze drier and packed in cans under vacuum.

5. Steeping

Edible mushrooms have been steeped in a solution of 2.5% salt, 02% citric acid, 0.1 % ascorbic acid, sodium bicarbonate, potassium metabisulphite, which can preserve the mushrooms up to ten days without any microbial spoilage.

6. Dehydration

For dehydration purpose, mushrooms are harvested at a mature stage. These can be dried in the sun or in mechanical dehydrator at 60- 70°C. Dried mushrooms can be stored for 6- 7 months and better reconstituted by immersing in a solution of sugar and ascorbic acid.

7. Canning

Canners prefer mushrooms to be picked up at an early stage. Fresh mushrooms are dipped in boiling water for two to three minutes and put in cold water. Blanching is necessary to control discolouration. Blanched and cooled mushrooms are filled in cans. Brine solutions (2% common salt + 2% sugar + 0.3% citric acid) is boiled and filtered and added into the cans. The cans are sterilized with boiling water at 85°C and later they are wiped dry and kept in cool dry place.

IV. Paddy Straw Mushroom

Paddy straw mushroom (Volvariella species) is cultivated in the tropical climates of India. 'Even then it is less attractive commercially owing to very low yield per unit weight ,of the substrate and an extremely short shelf life. But, as a kitchen  garden crop it is preferred because it is very delicious and also very nutritious.

The cultivation of this mushroom was first tried at Coimbatore and since then its cultivation has been taken over at other places also. It grows at high temperature between 30 and 45° C. It can therefore, also be cultivated during the summer months. A variety of materials have been tried for cultivation, for example, cotton waste, paddy straw etc. In India, three species of Volvariella are grown, namely V:diplasia, v: volvacea and V:esculenta. Volvariella volvacea is the most commonly grown mushroom out of this species.

A. Cultivation

Paddy straw (Volvariella species) which is to be used should be uncrumpled, not very leafy, not more than one year old and preferably should be hand threshed. It should be stored at a proper place so that it does not get wet during rain. Paddy straw is made into bundles. The bundles are soaked in water for 18 to 24 hours. Soaking can be done in small tanks and the bundles should be completely immersed in water. The bundles are taken out and excess water drained off. The bundles are arranged such that they make one layer on which small bits of spawn are placed 3 to 4 inches inside the margin, leaving a space of 5 to 5.5 cm from each other. A small quantity of arhar or gram dal powder is sprinkled over the spawn bits. Each layer is spawned in the same way. Finally the last layer is spawned allover and covered with a thin layer of loose straw and the bed is pressed down. The bed is covered with a polythene sheet. Watering depends upon the humidity of the air. Mostly no watering is required for the first 3 or 4 days. Watering of the beds and temperature within the beds are very important factors for the yield of paddy straw mush- room.

The bed temperature should remain between 30 and 350 C after spawning. The temperature should not go below 30°C during the growing period. Small buttons start appearing 7 to 10 days after spawning. At that time the polythene sheet should be removed from the bed. They remain in the button stage for 4 to 5 days and then grow into full size. Picking is done by gently twisting the fruiting bodies. Different methods are used for cultivation by different workers. Spawning the different layers of the bed is an influencing factor in straw  mushroom production. Spacing between the spawn bits also influences the yield. Smaller spacing (5 cm) between small spawn bits (10 mm) and larger spacing (10 cm) between large spawn bits (100 mm) gives better yield.

Volvariella species can also be grown in winter. The only care taken is to maintain the temperature of the bed. As the atmospheric temperature is low, the bed temperature will also be low. Hence, bed temperature is increased by incorporating the leaf materials which can be used fresh or partially dried. The bed is compacted and covered with transparent polythene sheet.

B. Preservation

Paddy straw mushroom has very little shelf life. It is consumed fresh but it can be preserved either by dehydration or by canning. Fresh mushroom must be consumed immediately after harvest. It if is preserved at a low temperature (10 to 15^o C) it can be kept well for about 48 hours. If the mushrooms are immersed in 10 percent brine solution followed by drying in the air they can be preserved for one week. Drying is done either in the sun or at a temperature ot 55 to 60^o C. Fresh mushrooms are reduced to one eighth their original weight after dehydration. Dried mushrooms can absorb water from the atmosphere, so they should be packed either in aluminium foil or in polythene bags. If they are not dried properly they give a fowl smell, which however, goes off during cooking.

V. Oyster Mushroom

The oyster mushroom (Pleurotus species) needs moderate, ate temperatures of 22-28°C for its growth. It grows under natural conditions on trees or dead woody branches of trees. This mushroom is also known as "wood fungus" and in India it is commonly known as "Dhingri". It is used in the preparation of many delicious dishes. In India, the following species of Pleurotus genus have been cultivated so far Pleurotus ostreatus, Pleurotus flabettatus, Pleurotus sajor caju, Plellrotus cryrgil, Pleurotus sapidus, Pleurotus cornucopiae. The cultivation of Pleurotus flabellatus has been tried on wheat, ragi and rice straw. The highest yield was obtained on rice straw.

A. Cultivation

There are several methods of cultivation of Pleurotus species with only little difference or modification. Dried paddy straw was chopped into 1 to 2 cm long bits and soaked in water overnight. Excess water is drained off and horse gram powder and spawn were added and mixed with the wet straw. Polyethylene bags with holes were then filled with the foregoing mix (substrate) and kept in a room at 21 to 31^o C with sufficient light and ventilation. The mycelium took 11 to 14 days to permeate the substrate in the bags. During the period the temperature of the substrate varied between 32 and 36^o C and later became almost constant at 25 to 28^o C with the appearance of mushroom pins on the upper side. The polythene bags were cut open on the sides without disturbing the bed, which had become quite compact by them. Water should be sprayed over it twice in a day. In 3 to 4 days, the crop started coming up. The beds, in bags as well as on the circular stands, were placed in a well-ventilated room with normal conditions of temperatures, relative humidity and light. The temperature range is 20 to 32⁰ C with relative humidity 35 to 75 percent. The mushrooms are harvested from the 4th day onwards. Supplementation of mushroom beds with cotton seed powder after the spawn seen, increases the yield by 85 percent. This also improves the texture and flavour of the mushrooms.

Oyster mushroom is grown on paddy straw and some , other agro-residues. It can be grown in a thatched hut, polyethylene bag find a mud/pucca house.

VI. Edulis Mushroom

Agaricus bitorquis is a new species of mushrooms also known as "Edulis" and grown at a higher temperature and higher carbon-ill-oxide concentration. It has a better shelf life r as compared to Agaricus bisporus. The difference with Agaricus bisporus is that the first flush in Agaricus bitorquis .( comes a little later and also the intervals between the flushes are more. The first flush generally appears between 22 to 26 days after casing and the second flush comes in the interval of 10 to 12 days. The compost which is used for the cultivation of Agaricus bisporus can be used for the cultivation of Agaricus buorquls.

A. Spawning ..

The rate and method of spawning is the same as that of A. bisporus. The mycelium of Agaricus bisporus grows at a higher temperature. The average bed temperature during mycelium growth should be about 30°C. and the growing ( room should be ventilated as little as possible. The mycelium of Agaricus bitorquis dies off after prolonged exposure to temperature above 34^o C. After 12 to 14 days of spawning the casing can be done. As the mycelium of Agaricus bitorquis is finer the compost at casing time will look less white than that of Agaricus bisporus. A few weeks after casing the compost turns extremely white. The same sterilised casing material as that of Agaricus bisporus can be used for Agaricus bitorquis. After 10 to 12 days when the mycelium has reached. The casing soil, the temperature should be lowered. By starting the ventilation, the temperature can be brought down to 25^o C. It is believed that the requirement of fresh air for Agaricus bitorquis is less than that of Agaricus bisporus. During growth, due to less ventilation, evaporation may be less. For this the moisture of casing layers should be regularly checked as high temperature and high humidity may be conducive to many diseases such as bacterial spot and blotches which may cause heavy damage. If the cut surface of the stem turns brown and if many pin heads die it shows that the casing layer is too wet.

B. Harvesting

As the time period between the button and open stage is quite short, it is advisable to pick the mushroom at the proper time. As the mushroom requires high concentration of carbon dioxide and high temperature for its growth, one feels inconvenient at the harvesting time, so before and during picking, ventilation and circulation be temporarily raised. Hence, we see that the temperature requirement of Agaricus bitorquis is high.

In general, it can be said that stagnation, damp air, with temperature above 15°C to 16^o C encourage the infection, so the growers are mostly in a fix, as increasing the ventilation will cause scaling and a higher humidity will promote the bacterial infection.

VII. Conclusion

Increase in population is creating an alarming situation in the food problem in India. Malnutrition in terms of "protein" deficiency is becoming. Major health hazard in the developing countries. It is unfortunate to realise that mushrooms rooms did not receive universal acceptance over the years since a number of naturally growing mushrooms are poisonous. Today the concept has changed because the cultivated edible species of mushrooms are totally safe tor human consumption. Mushroom farming is becoming successful because of its very low inputs. In India, mushroom growing can  be highly rewarding because of a variable climate. The technology can be profitably considered in areas where land is a limiting factor and agricultural residues are abundantly available able. The cultivation of three types of mushrooms, white r button "(Agaricus bisporus), paddy straw (Volvariella spp) I and dhingri (Pleurotus spp.) which can be grown at different temperature in different seasons, should be intensified, thus making mushroom a year round crop.