78 Report of the Acting Director and Chemist of the 



mences very soou to ferment or undergo decomposition. In this 

 process the vegetable matter used as litter and the excrements pass 

 through several changes. The fermentation is caused by minute 

 living organisms, and varies according to the kind of organisms at 

 work. Some will flourish only in the presence of an abundant 

 supply of air, others will thrive only away from air ; some require 

 much moisture, others little, etc. According to circumstances, then^ 

 one kind or another will flourish, and the fermentation taking place 

 will vary according as it is caused by the action of one kind of or- 

 ganism or another. 



Conditions. — The more important conditions influencing the 

 character of fermentation in manure are the following : (1) tem- 

 perature, (2) moisture, (3) the amount of air supplied as regulated by 

 looseness or compactness of manure heap, (4) the composition of the 

 manure, and (5) the kind of preservatives added. 



Manure ferments more quickly at higher temperatures. Where 

 air is supplied freely, as on the outside of the heap, the temperature 

 may rise as high as 150° F. or even higher. The most favorable 

 temperature seems to be about 130° F. On the inside of the heap^ 

 whei'e the supply of air is very limited, a slower form of fermenta- 

 tion occurs and the temperature rarely goes above 95° F. 



If a manure heap is too loose, the fermentation is too rapid. The 

 result is that the humus forming material is destroyed and large 

 proportions of nitrogen escape as ammonia. If, however, the ma- 

 nure is too compact, the fermentation may be so slow as not to de- 

 compose the manure enough for its most efEective use in the soil. 



The amount of moisture in manure is an important factor in con- 

 trolling the rapidity of fermentation. The addition of water causes 

 reduction of temperature and a corresponding slowless of fermenta- 

 tion. Water, when added in sufficient quantities, also fills up the 

 pores of the heap and serves to exclude air, thus retarding the most, 

 active form of fermentation. 



Manures which are rich in soluble nitrogen decompose more read- 

 ily tlian others which contain less soluble nitrogen. Thus urine de- 

 composes much more rapidly than solid excrement. 



Changes Produced hy Fertnentation. — The principal changes 

 that take place in the more common methods of fermentation or 

 " rotting " of manure may be briefly outlined as follows : (1) The 

 carbon of the manure combines, to a greater or less extent, with the 

 oxygen of the air, forming carbon dioxide (carbonic acid gas), which 



