MUSHROOM GROWING IN THE UNITED STATES 9 



be handled as units during fumigation, and prevent the migration of 

 harmful fungi and insects from old beds to new. The disadvantages 

 are the high initial cost of the house and the high cost of cooling 

 it for the summer crop. 



The principal advantages in using caves or mines for growing 

 mushrooms are : The small initial investment, the low temperatures 

 for growing mushrooms in the summer, and the uniform temperature 

 during the growing period. The disadvantages are : The difficulty 

 of disinfecting and ventilating, often a limiting factor in production 

 in these structures ; the fact that the temperature around the beds is 

 not raised during the final fermentation ; dripping and excessive hu- 

 midity in summer; the fact that bed temperatures can not be con- 

 trolled during the spawn run and that distances from railroad facili- 

 ties, markets, and manure supply are frequently great. 



HOUSE CONSTRUCTION 



Commercial mushroom houses are designed to simplify and facili- 

 tate such operations as filling the beds, spawning, picking, emptying 

 the beds, disinfecting, fermentation in the house, heating soil, heat- 

 ing, and ventilating. Experience has shown that a house constructed 

 along the general lines shown in Figure 8 meets these requirements. 



CONSTRUCTION OF THE BEDS 



In a standard house there are two tiers of beds, 5 to 10 beds high. A space 

 of 6 inches to 1 foot is left beneath the bottom bed to insure a good " heat " 

 (p. 14) during the fermentation of the compost in the bed. A space of 2 feet 

 is allowed between the bottom boards of the beds. (Fig. 7.) These bottom 

 boards are laid in loose in order to facilitate filling and emptying the beds. 

 The side boards (a and b) are also loose and are held in place by the compost 

 in the bed. The side boards have been omitted from the upper beds in the 

 figure to simplify the drawing. The beds are usually 6 to 8 inches deep and 

 6 feet wide (a to &) — sometimes 5 feet — and run the full length of the house, 

 with the exception of the alleys at the ends of the house. The tiers of beds are 

 supported by 2 by 4 inch uprights (c and g) set at 4-foot intervals (c to &). 

 The uprights are joined beneath the bottom boards by iy 2 by 6 inch bed 

 supports (fc). 



ALLEYWAYS 



A space about 30 inches wide is usually provided between the tiers of beds 

 to form a service alleyway which runs the full length of the house. This alley 

 is used in filling and emptying the beds. An elevated runway (level of ;") is 

 built in this alley to make it easier to fill the upper beds. Often the house is 

 built lengthwise into a sidehill with the high ground at the level of the ele- 

 vated runway (;"). An 18-inch alleyway between the outside walls and the 

 tiers of beds is also provided to facilitate picking. 



OUTSIDE DIMENSIONS 



The length of the house is usually determined as the result of a compromise 

 between the ideas of a long house economical to build and a short house 

 convenient and economical to fill. Many successful growers consider 65 feet a 

 suitable length. If the house is constructed as shown in the figure, with two 

 tiers of beds (six beds high, including the floor bed), the width of the house 

 is about 20 feet. Obviously the height depends on the number of beds in a 

 tier ; usually 3 feet is allowed for working space between the top beds and the 

 ceiling. Often several houses are joined together and built alongside each 

 other. When this is done it is customary to make one roof cover four tiers 

 of beds. Two houses joined under one roof in this way are called a double 

 house. 



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