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Mushroom growing cycle

A grower will fill each house 4-5 times each year.

One Week

Filling

  • Growers receive compost in 18-20 tonne loads in 900-1000 bags each 20 KG
  • Compost-filled bags are set out in rows in mushroom growing tunnels.

Running

  • Temperature is maintained at 25°C, relative humidity 84-86 percent and CO2 levels raised to 5000 ppm + to allow mycelium (mushroom fungus) to grow within the compost

Two Weeks

Casing

  • After 14-21 days the casing layer (a mixture of lime and peat) is added to a depth of 2 inches to the top of the bags.
  • Mycelium grows through the casing in 10 days

Breaking

  • Three to four weeks after receiving compost, breaking occurs (ie-cool fresh air replaces the humid warm air) and growth changes from vegetative to fruiting.
  • Pin initiation occurs – ie the small mushrooms of the first flush (see below)

Three Weeks

Mushroom Harvesting

  • The first flush is harvested one week later over a period of 3-4 days.
  • Bags are watered, the environment in the growing tunnel is set for re-pinning and a second flush appears and is harvested. Flushes appear at approximately 7 days intervals until 4 flushes are harvested.

Four Weeks

Empty

  • The growing tunnel is emptied and the spent mushroom compost removed.
  • House is cleaned and disinfected for a new crop.
  • Each growing tunnel is cropped 4 times per year producing approximately 9

    ,

    000 lb mushrooms from 1000 bags per crop. Yield is approx. 500 lb mushrooms per tonne of compost.

TERMINOLOGY

Composting

is the incomplete artificially accelerated decomposition of organic matter by a mixed microbial population in a moist warm aerobic environment.The aim of composting is to produce a medium which is selective for Agaricus bisporus growth. Composting is a compromise of producing a nutritional base for mushrooms and yet at the same time a substrate which will not support other fungal competitors.
The basic ingredients of compost are: straw, which supplies cellulose, hemicellulose and lignin and poultry litter, which supplies nitrogen, essential elements, vitamins and carbohydrates.
There are two phases in compost production

Phase 1

.
The raw materials - wheat straw, poultry litter, gypsum and water are mixed and blended together and put into windrows. The windrows are turned every 2-4 days to ensure thorough mixing and to achieve an aerobic environment in the compost, these windows are maintained for 7-14 days and temperatures can reach 75°C. During this time the mix begins to decompose the complex fractions are converted into elements the fungi will eventually use.

Phase 2

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The compost is moved into controlled environmental chambers for the pasteurisation stage, there is no turning during this phase. The phase can be split into two sections:
Peak heating and conditioning of compost
Peak heating and conditioning are vital for disease control
Peak heating . Temperatures are run at 60°C for 8 hours to kill off harmful organisms. Nematodes are killed off at 60°C for 3 hours.

Conditioning

:
Temperatures are reduced to 48°C for 5 days. Here ammonia is converted to ammonium and free carbohydrates are used up On emptying, the peak heat room the compost is at 20°C and is inoculated with Agaricus mycelium then bagged into 20 kg lots then sent to the grower.
The compost undergoes major chemical and structural changes during composting, spawn running and cropping. These are evident in the texture, colour and smell of the compost.

Agaricus bisporus

is a hetertropic organism as are all fungi growth requirements are met by four classes of chemical compounds - carbon, nitrogen, essential elements (iron, potassium etc) and vitamins.

Spawn run

lasts between 14-21 days. In this time the mycelium grows through the compost fully colonising it. Temperatures in the compost are maintained in the region of 25°C. This is optimum for Agaricus, 28°C+ favours competitor fungi ie Trichoderma, Truffle.

Casing

This is a 2 inch depth of peat and lime mixture put over compost after spawn running This ideally has a pH of approximately 7.5 and is free from pests e.g. fly larvae and nematodes.

Breaking

After the 10 days taken for the case run the mycelium should be just below the surface of the bag. and we are now ready to break the crop This is a process of altering the environmental conditions in the house to change the mycelium growth from vegetative to fruiting growth.

Cropping

After 3 days the environment is reset for the mushroom production phase. Within 10 days picking will commence. Bed temperatures are maintained about 20°C, CO2 around 1100 ppm and RH 85-88%.

Flush

Mushrooms appear in flushes ie a flush of mushrooms will appear and be picked in 3-5 days, then a gap of 5 days will lapse before the next flush appears. Growers generally take between 3-5 flushes from each crop before the crop finishes and the house is emptied.
A grower will fill each house 4-5 times each year.