THE FERMENTATIONS OF MANURE. 73 
loss. Some manure heats more rapidly than others, that from the 
horse being especially subject to this destructive fermentation; a 
fact due partly to the large amount of hay that it contains and partly 
to its loose and porous nature, which allows a free access of air. It 
suffers more loss for this reason than most other types of manure a 
loss that may be lessened by mixing with it some of the moister, 
denser cow manure. Liquid manure also is subject to heavy losses, 
because it so rapidly undergoes the ammonical fermentation. 
There are two general methods of controling and reducing these 
losses. The first is by chemical means. Since the ammonia is 
volatile and a strong base, the addition to the manure of some 
chemical to conbine with it will produce salts that will be more 
likely to be retained in the manure. For this purpose quite a list 
of substances has been recommended. Among them are, gypsum, 
burned lime, shell lime, lime-stone, kainit, superphosphates and sul- 
phuric acid. Each of these has a value when properly used, but 
none of them will wholly prevent nitrogen loss and all are some- 
what costly. The losses due to ammonia vaporization may be pre- 
vented by these chemicals; but the losses caused by the liberation 
of free nitrogen cannot be checked by any means short of stopping 
bacterial growth, and this would check the beneficient as well as the 
injurious fermentations. On the whole, the result of experience 
seems at present to be against the use of chemical means of 
preserving manure. 
The second method is mechanical and is more efficient. It is 
based upon the facts already emphasized, viz., that the destructive 
fermentations take place most vigorously in the presence of a large 
supply of oxygen and that the volitilization is much more rapid 
from a partly dry than from a wet mass. Hence manure that is 
loosely piled loses much more nitrogen than that which is firmly 
compacted. The practice of firmly compacting manure into conical 
heaps with smooth sides is best calculated to reduce the losses to a 
minimum. Experiment has shown that a lot of manure firmly 
compacted may lose 15 per cent, of its nitrogen during storage, 
while a similar lot loosely stored loses 35 per cent.; a very striking 
testimony to the value of compacting. If, further, the manure be 
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