G R O W I N G O Y S T E R M U S H R O O M S
Mushroom are a nutritious vegetarian delicacy and have many varieties. They are also easily digested and are a good substitute for meat and eggs. Fresh mushrooms can be sold in the market. There is also a growing market for processed – dried and packed – mushrooms as their shelf life is longer.
Mushroom production in Africa is growing as consumption rises due to their nice aroma, subtle flavor, nutritious values and special taste. There are two main varieties of mushrooms grown, the button and the oyster mushroom. Of the two, the button mushrooms are the most popular which many people are familiar with. The oyster mushroom may require some lobbying to persuade people to buy it.
Characteristics of a button mushroom: a smooth rounded cap, the mushroom is pinkish brown at first and later turns dark brown to blackish when mature. Its stem is thick, sturdy, smooth. Its flesh is white and firm. Its flavor is mild when raw and more fragrant and meaty when cooked.
Characteristics of an oyster mushroom: an oyster/fan shaped cap, the cap is smooth. It is usually white to light brown with firm white flesh. They may or may not have a stem, but if the stem is there, it will often be stubby and off the center if the mushroom is growing on the side of a log.
Growing Oyster mushrooms:
Advantage of oyster mushrooms is that they are easy to cultivate and process and do not require huge investment.
Fresh mushrooms have very limited shelf life but dried and packed mushrooms have considerable shelf life.
For successful cultivation of mushrooms, careful attention has to be paid to three aspects:
- good compost,
- reliable spawn
- and right temperature during growing period or else partial or complete failure of the crop may result.
(i) Compost Preparation:
This is prepared to provide the crops with a place to grow. The compost must be made up of nutrients suitable for the growth of the mushrooms. Natural compost is prepared from materials such as wheat straws because they are locally available. An example of the measurements of ingredients for the compost:
- 250kg wheat straw (chopped 8-20cm long),
- 3kg of ammonium sulphate/calcium ammonium nitrate,
- 3kg of urea
- and 20kg gypsum.
Gypsum reduces greasiness that the straws would otherwise have and is a conditioning agent. Cotton seed meal supplements nitrogen while ammonium nitrate and urea are added at the beginning to provide a ready source of nitrogen. These ingredients are mixed well and water is added.
The compost is then piled into stacks measuring about 1.5 by 1.5m and regularly turned to allow for aeration and proper watering. The by-products of composting is ammonia and heat, so you should expect the temperatures to rise.
The compost is ready when the straws become easy to bend, have a high water-holding capacity, the color changes and becomes darker, and has a strong smell of ammonia.
The compost should then be packed into clear bags to enable the farmer to see the changes going on and to identify diseases and infections easily. The bags should then be taken to the mushroom house/building and placed on “shelves’’.
(ii) Spawning: The process of planting the mushroom
The spawn is spread on the surface of the compost, but it slightly penetrates the surface. This is done by making a small hole using a finger and planting the spawn, which is then covered with a thin layer of compost.
The temperature of the room should be maintained at around 25 degrees Celsius.
A humidifier is used to make the room humid, but if the gadget is not available, water can be manually sprayed on the walls and floor of the room. Also old newspaper sheets sprayed with water can be placed on top to provide humidity.
At a temperature of around 24 – 25 degrees Celsius white cottony mycelium spreads and permeate through the compost(at this stage the spawn has attached to the wheat straws and looks like a white substance). It takes around 12 to 15 days for the complete spawn running.
The surface of the compost is then covered with half to one inch level of casing soil, forest soil is preferred. This soil is sterilized to kill insects, nematodes and molds.
The casing soil is spread over plastic sheets and treated with formalin and stirred frequently for a week to remove formation fumes. After casing, the temperature has to be maintained at 24-25 degrees Celsius for 3 days after which it must be lowered to 18 degrees Celsius.
(iv) Growth and Harvesting
The mushroom can be harvested several times throughout its lifetime. What are harvested are called flushes. The first flush comes 15-20 days after soil casing and 35-40 days after spawning.
Mushrooms should be harvested at the right size, otherwise they will become too big and rapture.
Each bag should produce at least a kilo throughout its lifetime. The harvests can go up to the fifth flush. It takes approximately 15 weeks from composting to end of harvesting.
A mushroom house should not be close to a cattle shed because the flies from the cattle can contaminate the mushrooms.
One of the biggest challenges in mushroom production is getting quality spawn. Quality spawn can be obtained from private farms.
Fresh mushrooms have very limited life and hence processing is recommended to enhance their shelf-life.
Initially, fresh mushrooms are washed in cold water and then blanched in boiling water for about 3-4 minutes. Then they are dehydrated in a drier and packed.
It is advisable to pre-treat fresh mushrooms in a solution containing brine to prevent discoloration. Packing is very critical as formation of moisture contaminates mushrooms very quickly.