How do mushrooms grow? Thuis zelf champignons en paddenstoelen kweken, paddestoel thuiskweekset, grow mushrooms, Champignons anbauen, cultiver de champignons

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How do mushrooms grow?

Compost preparation

Cultivated mushrooms grow on compost. In the Netherlands, this culture medium is made with the following ingredients: straw, poultry and horse manure, gypsum and a lot of water. For the rest, no chemicals are used. After these ingredients have been mixed, a fermentation process begins. The product at the end of this process is called “mushroom compost”.

Incubation and inoculation

The mushroom propagates by releasing spores. One single fungus produces billions of spores. The compost, however, is not inoculated with spores because then the cultivation would be too time-consuming. That is why it is inoculated with the so-called spawn. Spawn is a substance that consists of sterile compost or corn grains and is fully colonised with the mushroom mycelium. The mushroom compost is inoculated with this spawn. Once inoculated, it takes approximately 2 weeks before the compost is fully colonised with the mycelium.

Covering with casing soil

Mushrooms will not grow in colonised compost alone. That is why the compost has to be covered with a so-called top layer made up of a mixture of different types of peat and lime residue (a by-product from the sugar industry). This top layer is called casing soil. The casing soil is critical and must be free of pathogenic bacteria, have the correct structure, an acidity degree of pH 7.5, and be capable of retaining a lot of water. The bacteria that live in the casing soil stimulate the mycelium to produce the mushrooms. Without these bacteria, no mushrooms would grow, therefore good casing soil is imperative to mushroom cultivation.

The growth during the cultivation

  • Ingrowth in casing soil: when the colonised compost has been covered with the casing soil, the casing soil is kept well moistened by spraying it with water and the air humidity and CO2 content is kept in a closed area as high as possible. The temperature of the air is kept at approximately 22–23°C and the core temperature of the compost is between 25-27°C. This way, the casing soil is quickly penetrated and well colonised with the mycelium.  
  • Fruiting: after this colonisation, the cultivation area is intensively ventilated. The air temperature then drops to 17-18°C, the core temperature of the compost drops to 20°C and the CO2 content drops to 1,200 ppm. This stimulates the mycelium in the casing soil to form fruiting bodies, which at first, are visible in the form of tiny pinheads.  
  • Button outgrowth: after the fruiting, the quantity of buttons can be determined by means of the air temperature and humidity. By working faster with low air temperature and air humidity, more buttons will appear, and therefore, smaller mushrooms. A higher air temperature and air humidity will yield fewer buttons, which means that they can grow bigger. The small buttons will grow into ready to harvest mushrooms in approximately 5 days. The entire process from covering the compost with casing soil to harvesting the first mushrooms takes approximately 3 weeks.

The harvest

The mushrooms do not grow continuously, but appear in weekly “flushes". Such a "flush" can be defined as a harvesting period. After three to four harvest weeks, a culture terminates. There is a substantial decline in the harvest and a considerable increase in the likelihood of disease. Mushroom harvesting can be divided into 2 categories:
  • The manual harvesting: this is very labour-intensive. Approximately 15-18kg of mushrooms can be harvested per hour by hand. All mushrooms for fresh consumption are harvested in this manner, in other words, all fresh mushrooms that we, as consumers, buy in the shops.
  • Mechanical harvesting: using machines, approximately 100–120kg can be harvested per hour. The mechanically harvested mushrooms are almost only processed by the canning/preserved foods industry (soups, tins, jars, etc.).

What is left is ‘champost’ (mushroom compost)

After the last flush, the bed is steamed. The bed is steamed in order to kill off all moulds present in the bed so that no diseases from the old bed will be left over in the new cycle. When steaming, the bed is kept at 70°C for eight hours. Once destruction by steaming is complete, the bed is emptied. The residual product of the combined compost and casing soil is called ‘champost, an extremely clean and high quality compost that is widely used in greenhouse cultivation, bulb growing and at home in the garden.

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How do mushrooms grow? Thuis zelf champignons en paddenstoelen kweken, paddestoel thuiskweekset, grow mushrooms, Champignons anbauen, cultiver de champignons