4. CIRCULAR 609, U. S. DEPARTMENT OF AGRICULTURE 
relative amount of heat generated from day to day as the composting 
proceeds, and indirectly an index of the amount of easily decomposed 
carbonaceous material remaining in the compost. Figure 3 shows 
this difference diagrammatically and also indicates the approximate 
control of air temperature necessary to maintain a manure tempera- 
ture of 135° F. During the first 3 days of composting the manure 
goes through a violent fermentation that generates sufficient heat to 
maintain the temperature inside the manure from 30° to 40° F. 
higher than in the air surrounding the bed. The amount of heat 
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TEMPERATURE (°F) 
Air heated with live steam 
eee ey yc CeO le ie es SE 
COMPOSTING PERIOD (DAYS) 
Figure 3.—Diagram showing the relation of the temperature of the manure in 
the beds to the temperature of the air surrounding the beds throughout the 
composting period. Manure mixed and moistened on the 10th day of com- 
posting; beds cooled and spawned on the 15th day. 
evenerated decreases from day to day until after 5 or 6 days it is about 
equivalent to that produced by manure during a normal sweating out 
following outdoor composting. 
In the experiments at the Arlington Experiment Farm, Arlington, 
Va., the excess heat generated during the second and third days of 
composting was controlled by opening the door of the growing room 
and directing the flow of air from a 16-inch fan, thermostatically con- 
trolled, into the doorway. Usually after 3 or 4 days the amount of 
heat generated by the manure had receded so that some auxiliary heat 
was needed. In some cases the manure temperature was kept at a 
proper composting level by raising the air temperature from day to 
day with steam, thermostatically controlled. In others the manure 
temperature was allowed to drop slowly, and auxiliary steam heat was 
delayed until the last 2 or 3 days of composting. Temperature 
stratification of the air was prevented in the usual manner during the 
entire composting process by means of fans set vertically in the aisle 
of the growing room. 
As with the customary sweating out process, crop failure will 
result from improperly controlled temperatures. If the manure 
temperature is allowed to go above 140° F. for several hours the 
