General Information and Agronomic Aspects
Cultivated mushrooms are edible fungi that grow on decaying organic matter, known as a substrate. Unlike vegetables they do not rely on sunlight to grow. Mushrooms start as very small spores (reproductive structures like very, very tiny seeds in fungi). The spores will grow in the substrate to produce a network of fine white filaments called mycelium (portion of the mushroom that grows underground). From the mycelium the mushroom fruit is produced. This is the part that is harvested. Mushrooms have a high nutritional value and are high in protein. They are also a good source of vitamins (B-complex and C), essential amino acids, and carbohydrates but are low in fat and fibre and contain no starch. When fresh they have a very high water content of around 90%. Minerals present include phosphorus, potassium, iron, calcium, zinc and copper. They are an ideal diet for diabetics and weight-watchers. Some species are also grown for their medicinal value.
Mushrooms are a valuable source of food and their cultivation can be a viable small-scale business, but investing in a mushroom growing scheme can be risky so a feasibility study looking at potential markets and supply chains should be done before starting. A general understanding of mushroom growing should be obtained through training or literature to ensure the best chance of success. Some expert assistance will help at this stage. The Agricultural Information Resource Centre (AIRC), Ministry of Agriculture, Kenya (email: agriinfocentre@yahoo.com) has published in 2009 a coloured booklet 'Guide to Growing Mushroom'. Short-term training in mushroom production is conducted by several institutions in Kenya including Juja Community Development Centre (JCDC) and Jomo Kenyatta University of Agriculture and Technology (JKUAT).
As well as individual small-scale production, set up options include cooperatives and community groups that can collaborate in set-up costs, production costs, harvesting and marketing. It does not help to work in isolation, but in joint ventures with regional agro-industries and universities as they can assist with linking to market outlets and training. The most popular mushroom species grown in Kenya are button (Agaricus spp.) and oyster (Pleurotus spp.). Button mushrooms are widely cultivated by large scale farmers as their production requires high input technology. Oyster mushrooms are mostly grown by small scale farmers using simple production techniques.
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| Oyster mushrooms |
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(c) Courtesy of AIRC, Nairobi, Kenya
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| Button mushrooms |
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(c) Courtesy of Wikipedia
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Before starting to grow mushrooms, farmers should consider the following:
1) potential markets and supply chains
2) source(s) of high quality spawn ('seeds' of mushrooms)
3) availability of substrate (material on which mushrooms grow)
4) availability of supplements (additional nutrients to the substrate)
5) production plan to ensure continuous production
1) potential markets and supply chains
2) source(s) of high quality spawn ('seeds' of mushrooms)
3) availability of substrate (material on which mushrooms grow)
4) availability of supplements (additional nutrients to the substrate)
5) production plan to ensure continuous production
Nutritive Value per 100 g of edible Portion
| Raw or Cooked Vegetable | Food Energy (Calories / %Daily Value*) |
Carbohydrates (g / %DV) |
Fat (g / %DV) |
Protein (g / %DV) |
Calcium (g / %DV) |
Phosphorus (mg / %DV) |
Iron (mg / %DV) |
Potassium (mg / %DV) |
Vitamin A (I.U) |
Vitamin C (I.U) |
Vitamin B 6 (I.U) |
Vitamin B 12 (I.U) |
Thiamine (mg / %DV) |
Riboflavin (mg / %DV) |
Ash (g / %DV) |
| Mushroom, oyster raw | 43.0 / 2% | 6.5 / 2% | 0.4 / 1% | 3.3 / 7% | 3.0 / 0% | 120 / 12% | 1.3 / 7% | 420 / 12% | 48 IU / 1% | 0.0 / 0% | 0.1 / 6% | 0.0 / 0% | 0.1 / 8% | 0.3 / 28% | 1.0 |
*Percent Daily Values are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs.
Markets and marketing
When considering producing mushrooms as a business, check on the following:
1) type and amount in demand by market outlets
2) their price and availability
3) current distributors and possibility of business relationship
4) possibility of value addition
1) type and amount in demand by market outlets
2) their price and availability
3) current distributors and possibility of business relationship
4) possibility of value addition
Small scale farmers are, therefore, advised to identify where they can sell their mushrooms, especially to the nearest markets before starting production.
Production plan
Farmers must plan their production in such a way that they produce only the amount they are able to sell. They can divide their production units into four sections such that each section has mushrooms at different growth stages at any one time. This way they will maintain a consistent supply to the market.
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| Spawn in a bottle |
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(c) Courtesy of AIRC, Nairobi, Kenya
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Spawn
It is a planting material equivalent of farmers' seed for starting mushroom cultures. It is made from mycelia (plural of mycelium) of mushroom grown on a carrier such as grains and is produced in specialized laboratories under sterile conditions. The amount of spawn needed is equal to 4-6% of the wet weight of the substrate. For example if the wet weight of the substrate is 50 kg, 2-3 kg of spawn is required. One kg of spawn may cost between Kenya shillings 600 and 800.
In Kenya, there are a number of institutions such as JKUAT producing high quality spawn. Farmers who need spawn or training can contact the university at the following address: Business Manager, JKUAT Enterprises Ltd., P.O. Box 62000-00200, Nairobi. Mobile phone: 0722 728812.
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| Wheat straw |
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(c) Courtesy of AIRC, Nairobi, Kenya
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Substrate
Substrate is an organic-based material on which mushrooms grow. And a good substrate should be rich in nutrients, have good aeration and water holding capacity. Substrates commonly used in mushroom production include agricultural by-products such as cereal straws (wheat, barley, rice, maize), cotton waste, maize cobs, coffee husks and pulp, sawdust, sugar bagasse, water hyacinth among others. 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. However, cereal straws, particularly wheat straw, are usually the best because they are rich in nutrients that mushrooms require and they facilitate quick colonization (the formation of a white mass of mushroom mycelium) of the substrate.
Gypsum is a useful ingredient to be added to the substrate 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. Lime may also be added to the substrate to adjust its pH (level of acidity)
It should be noted that different species of mushrooms will require different substrate mixes. The substrate must not be rotten, mouldy and should be kept dry while in storage.
Supplements
These are materials added on the final mix of substrates to increase nitrogen content in order to improve the yields. Commonly used supplements include urea, bran, cotton seed cake, sunflower seed cake, molasses, broiler chicken manure and horse manure among others. However, it should be noted that heavy supplementation may increase the risk of contamination by other micro-organisms which are likely to benefit from extra nutrients added to the substrate.
Mushroom house
Mushroom house should not be sited near dumping sites and livestock pens to reduce the risk of insect infestation and diseases. It should preferably be under shade. The house can be made from locally available materials that can main cool temperatures and high humidity such as clay or bricks. In a small scale farmer scenario, a grass thatched mud walled house is the most ideal. The house should have air vents or small windows on the upper walls for ventilation and required light during fruiting.
The vents and door should have insect screens and be closed. If the temperature inside the house is high, water can be sprayed on the floor using a knapsack sprayer with fine nozzles and vents and door opened at night. Wooden shelves for holding bags or wooden racks for hanging spawned substrate tubes should be constructed at the height of about 1.5 m from the ground and 1 m apart for ease of working in the growing house.
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| A grass thatched mud mushroom house |
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(c) Courtesy of AIRC, Nairobi, Kenya
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| Wooden shelves holding bags in the house |
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(c) Courtesy of AIRC, Nairobi, Kenya
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Overview on production of mushrooms
A detailed step by step procedure with coloured photos on cultivation of button and oyster mushrooms is given in the AIRC booklet "Guide to growing mushrooms". Farmers intending to start mushroom production as a business are strongly advised to undertake a hands-on training on growing mushrooms. A number of institutions in Kenya such as JCDC and JKUAT conduct short training courses on mushroom production.
Phases of cultivation of button and oyster mushrooms
| Phase | Time span and temperature | Remarks |
| Substrate preparation | 6-8 hours for soaking shredded straw in water for oyster. Pre-wetting of wheat straw for button is done for 3 days | Selection of substrate. Cereal straws are preferred. Wheat straw is ideal for button. In case of oyster it involves shredding, soaking in water to 70% moisture content (1), draining excess water, adding supplements plus lime and packing into polybags. |
| Composting | 18-20 days | Oyster does not require composted substrate. Only applicable to button. Involves pre-wetting of wheat straw to 70% moisture content, adding supplements plus lime and gypsum. Good compost is dark brown, 70% moisture content and pH 8.0 - 8.5 (2) |
| Pasteurization and conditioning | 4-6 hours of steam heating at 60degC for oyster and cool polybags to 20-25degC. For button steam for 8 hours and lower the heat for 4-5 days at 45-50degC then cool to 22-25degC | Steam heating of oyster polybags is done in water drums but it can also be done in hot water at boiling point for 1 hour. Button steaming is done in special chambers (tunnels). Conditioning is to remove ammonia gas which is poisonous for button. Cooling is in preparation for spawning. The moisture content of the substrate then should be 67-70% |
| Spawning and incubation | 5-10 days incubation for oyster; 15 days for button at 23-25degC | Applying spawn to substrate in polybags. The growing room should be kept humid (RH 65-95%) (3) with dim lighting just sufficient to read a newspaper |
| Casing | Sterilize casing soil for 4 hours at 60degC. Casing run (4) is 14-15 days at 25degC | This is not applicable in oyster production. Casing is applying a thin layer of red top soil added with murram and lime on top of fully colonized substrate. Casing soil should be kept wet but not waterlogged. Substrate turns white to grayish due to the colour of mycelium. It is now ready for fruiting. |
| Pinning | Oyster 5-10 days in the growing house at 23-25degC. Button 7-10 days but the growing house temperature will depend on variety (5) | Pinning is when mycelia start fruiting (formation of very young mushroom known as 'pin heads'). It takes 3-4 days for pin heads to develop into mature mushrooms. RH required is 85-95%. |
| Harvesting | Oyster about 30 days, button 30-40 days from spawning to harvesting | Oyster harvesting is done when the mushroom ear is 7.5-10 cm in diameter, turgid and bright in colour. Button is picked at the young stage before opening. Repeated over 7-10 day cycles |
(1) When the substrate is squeezed between the fingers it should give 2 to 3 drops of water. If it gives more drops, continue draining and with fewer drops add more water.
(2) pH is a measure of acidity. A pH value of 7 is neutral, lower than 7 is acidic and above 7 is alkaline. It can be determined using a pH meter. pH meters are readily available in shops selling laboratory equipment for schools in urban areas of Kenya.
(3) Relative humidity (RH) is the percentage of moisture in the air compared to the maximal amount that the air can hold at that temperature and pressure. It can be monitored by using a hydrometer which can be bought in shops selling laboratory equipment. If the RH is low, spray clean water on the floor or place pots with water in the room. If the RH is above the required, open windows or vents of the room.
(4) Casing run is the period in which the mycelia is left to grow on the casing soil.
(5) There are varieties grown: white mushroom or 'champignon') (Agaricus bisporus) and tropical mushroom (Agaricus bitorquis). During pinning the temperature in the growing house should be reduced from 25 to 20-22degC for tropical mushroom, and for white mushroom to 12-18degC.
Yield
An average of 33 kg of fresh button mushrooms per square metre of substrate can be obtained. In case of oyster mushrooms yield depends on the type of substrate used. For example wheat straw would convert at 75 to 100% (75-100 kg fresh mushrooms are expected from 75-100 kg of dried wheat straw).
Post-harvest handling
Mushrooms are highly perishable and if possible should be sold the same day of harvest. Under cool conditions their shelf-life is 1-3 days. The shelf-life can be extended to up to 7 days under refrigeration at 10degC. Surplus can be preserved by drying, canning, pickling and grinding dry mushroom into powder for soups.
General Information on Pests and Diseases
There are a whole range of pests and diseases that can attack mushrooms. The longer mushrooms are grown in one location the greater the chance of having pest and disease problems. Therefore, it is very important to strictly maintain sanitation and hygiene in the farm (e.g. by sterilizing growing houses, proper disposal of spent substrate etc). Even with care there will be times when a pest or disease problem may occur, so it is useful to be able to identify the particular problem in order that appropriate action can be taken. Record keeping is important to identify where problems arise. Information required includes dates of all phases of production and particularly their parameters (temperatures, moisture levels, pasteurization times etc).
Mushroom abnormalities
Formation of scales or "crocodile skin"
Causes:
- Very dry air
- Strong air movement with low relative humidity
- Shortcomings in the air supply and distribution system
- Tendency of the strain to form scales
- Damage done by pesticides
Formation of stroma (dense layer of mycelium without fruiting on casing soil)
Causes:
- Low-quality degenerating mushroom strain
- Mycelial growth in a poorly ventilated casing layer, with a high concentration of carbon dioxide, high temperature and low humidity, and a high volume of evaporation
- Overly long period of mycelial growth in the casing layer
- Petroleum-based fumes or chemicals
Rosecomb (misshapen cap with gills on the cap)
Causes:
- Casing layer contaminated by mineral oils
- Contamination by petroleum-based materials
Outgrowths on mushroom caps - "cock's comb"
Causes:
- An overdose of pesticides
- Casing layer contaminated with chemicals
- Effect of exhaust gases, heating appliances, diesel oil, formalin vapors, dissolvers, paint
Thick stipes, small caps
Cause:
- Excessively high carbon dioxide level on the initial stage of growth
A small cap on a normal stipe
Causes:
- Improper climatic conditions for specific strains
- Susceptibility of some strains