MUSHROOM GROWING IN THE UNITED STATES 



21 



develop, and the first mushrooms to come up will have a tendency 

 to form beneath the soil layer rather than on the upper surface. 



After the mushrooms begin to appear they usually develop in sud- 

 den outbreaks at intervals of about a week. These outbreaks are 

 called " flushes " or " breaks " and are followed by periods during 

 which there are only a few mushrooms on the beds. (Fig. 12.) 

 There are several systems of watering in relation to these breaks. 

 Some growers water only between breaks so as to avoid wetting the 

 mushrooms. Others water lightly two or three times a week regard- 

 less of the breaks. Many follow a compromise system of watering 

 regardless of the breaks during the first three breaks. During this* 

 period spotting is not serious because the fresh mycelium is vigorous 

 and harmful fungi and bacteria in the soil are comparatively scarce. 

 Thereafter, watering is done only between breaks. In any case, when 

 water is applied to the beds while mushrooms are growing a gentle 





















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111 



fin n 



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Figure 12. — Graph showing the daily yield of mushrooms from a test bed (10 square 

 feet) at Arlington Experiment Farm, Rosslyn, Va. Note cycles of growth 

 referred to by growers as " flushes " or " breaks " 



shower is used to avoid spattering soil on to the caps of the mush- 

 rooms, and ventilation is increased after watering until the droplets 

 on the mushroom caps are evaporated. 



VENTILATION 



Considerable ventilation is necessary in growing a good crop of 

 mushrooms, and it is advisable to give as much ventilation as possible 

 without interfering with temperature and humidity control or caus- 

 ing excessive evaporation from the beds by cross drafts. Usually 

 it is easier to ventilate, without interfering with these factors, in the 

 spring and fall months. When the temperature outside the mush- 

 room house is higher than that inside, the fresh air will become 

 damp upon entering the house. Conversely, cold air brought into a 

 warm mushroom house absorbs moisture and will have a tendency 

 to lower the relative humidity inside the house. 



