id 
INDOOR COMPOSTING FOR MUSHROOM CULTURE 9) 
chances of a maximum crop are greatly reduced, and if the aic tem- 
perature in all parts of the house does not at some time reach 130° 
insect control will not be satisfactory. The use of auxiliary heat 
during the last 2 or 3 days of the composting is considered by the 
writer as an essential part of the composting process for reasons that 
will be explained in the discussion of the control of fungus diseases and 
insect pests (see p. 7). In the experiments at Arlington Farm, low 
pressure steam, liberated into the air by means of perforated pipes, 
has been used as an auxiliary source of heat during sweating out for 
more than 10 years and there has been no difficulty from steam 
overwetting the manure, provided it is not liberated directly over a 
bed and the beds are protected from the dripping of water condensed 
on the ceiling of the growing room. As stated before, the temperature 
of the manure in the center of the bed should not be allowed to go 
above 140° at any time during the composting process. To prevent 
the steam from carrying the temperature too high a thermostatic 
control was used, which was arranged so that the bulb actuating the 
control was suspended in the air near one of the beds. With this 
arrangement uncontrolled fluctuations in the air temperature were 
-never more than 3°, and there was less than 1° fluctuation in the 
manure temperature. 
This should not be taken to mean that all parts of the bed were 
uniform in temperature. As a matter of fact the temperature of the 
manure was always greater in the center of the bed than in the outer 
layers nearer the cooler air surrounding the beds. During the early 
part of the composting period this difference might be as much as 10° 
F., whereas during the last few days, when the fermentation had 
slowed down, the difference would be less than 5°. 
With thermostatic control it is possible to regulate the composting 
temperature so that most of the manure is within a 10° range, but the 
optimum 10° or 15° range within the suggested limits of 120° up to 
140° F. has not yet been determined. 
MOISTURE CONTROL 
In all of the experiments there was a tendency for the manure to 
lose water into the atmosphere. The beds as a whole dried out most 
rapidly during the first few days when the temperature gradient was 
ereatest between manure inside the bed and the air surrounding the 
beds. This appears to be due to the tendency for water to move along 
the decreasing vapor-pressure gradient, which exists between the 
comparatively warm air within the beds and the cooler air surrounding 
them even though the air surrounding the beds might have a higher 
relative humidity than the air inside the compost. 
The relatively large moisture content supplied at the time of chop- 
ping takes care of most of the loss during fermentation. In the 
experiments at Arlington Farm, however, it was found desirable to 
add water to the beds on the third and fifth days and again to mix the 
manure and water it to a desired moisture content (about 180 to 
200 percent) after 8 or 10 days of composting. In order to accom- 
plish the final mixing in comfort the rooms were opened up and cooled 
off overnight before watering and later brought back with steam 
to at least 120° F. for a day or two to obtain an even distribution of 
