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close this bookBioconversion of Organic Residues for Rural Communities (UNU, 1979)
close this folderMushroom production technology for rural development
View the document(introduction...)
View the documentMaterials and methods for growing mushrooms under natural or field conditions
View the documentGrowing mushrooms under semicontrolled conditions
View the documentResults and discussion
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View the documentDiscussion summary

Growing mushrooms under semicontrolled conditions

One possible approach towards establishing a mushroom industry in the countryside is the so-called community level scheme of production. This involves most of the people from all strata in the rural areas, thereby providing an additional source of income to a greater number of persons.

Recently, it has been shown that it is feasible in the Philippines to grow Volvariella mushrooms on a commercial scale in boxes placed in special growing houses. Compared with the ordinary open-bed method, the percentage of yield conversion of box-grown mushrooms was improved from 10.5 to 25 per cent based on the weight of dry straw. There is greater assurance of consistent production because pests and diseases are more easily controlled under these more protected growing conditions. The only possible drawback is the higher initial cost of constructing the growing houses and boxes.

Materials and Methods

Growing houses

The growing houses consist of a concrete floor set on a gravel base, four layers of hollow blocks set on the floor, wooden frames, plastic walls (gauge 6), plain galvanized sheets for roofing, and a plastic screen for ventilators (Figure 2).

Figure. 2 Mushroom-Growing House Plan in Series

The roof is convex for better air circulation - about 2.4 m high from the floor to the rafter. There are two ventilators with hinged covers, properly screened to keep out insects. The length of the house is 7.5 m and it is 4.5 m wide. There are five rows of one-foot high cement blocks spaced 60 cm apart where 150 mushroom boxes can be accommodated. This type of growing house can be constructed singly or in a series of five or more units.

Making and filling the box

The box is made of 2.5 cm x 5 cm wood, The wooden frame is 60 cm long, 45 cm wide, and 20 cm thick (Figure 3).

Figure. 3. Mushroom Box, and Planting of Tropical Mushrooms

The bedding materials (rice straw or dried banana leaves) are cut to a uniform length of 20 cm. The box is tightly filled to the brim in anticipation of loosening when the pack is soaked in water, Any protruding or dangling bedding materials are trimmed to avoid obstruction during watering. The bedding materials in the boxes are soaked for at least three hours in water, or until the straw becomes dark-brown or the banana leaves exhibit a certain degree of transparency. The boxes are then removed from the soaking tank and drained of excess water immediately prior to planting of the spawn.

Planting the spawn

Young (10-14-day-old) spawn are used Thumb-sized pieces are removed from the bottle and distributed on the surface of the bedding material. Starting on one side of the box, four pieces are equally distributed along the width, and five pieces are placed along the length at a distance of 5 cm from the side of the box. The spawn are then buried 5 cm deep in the bedding material, after which the surface is massaged to close the open spaces resulting from spawn insertion. The same procedure is carried out on the other side of the box.

Incubation of the boxes

The boxes are placed in a specially built incubation room (similar to the growing house, only smaller and without ventilation), where the temperature is maintained at 35 - 38 C, with high relative humidity (85 C +). In lieu of an incubation room, the boxes can be covered with plastic sheets. The boxes are removed from the incubation room after three days, or once a good spawn run has been obtained. When the box is merely covered with plastic, it takes five days to attain good mycelial growth.

Care of the boxes

Incubated boxes should be exposed to conditions not too different from those in the growing house to minimize serious stress on mushroom mycelial growth. Twenty-four hours after removing the boxes from the incubation room, the temperature should be lowered gradually by opening the ventilator(s) or by allowing fresh air to circulate in the growing room The temperature should be maintained at 26 - 28 C with a relative humidity of 75 85 per cent.

Aerial spraying with superfine mist will maintain the desired relative humidity, and the proper temperature can be assured by manipulating the ambient air through aeration or closing the ventilators, whichever is called for. The bedding material must be watered with fine mist to avoid destroying the delicate mycelial threads of growing mushroom molds.