74 THE MANURE HEAP AND SEWAGE. 
stored in cemented pits, that will prevent loss by draining, and if 
the excess of the liquid manure is caught in special tanks and 
frequently spread upon the fields before fermentation has progressed 
far enough to cause much ammoniacal fermentation, the greater 
part of the ordinary losses may be prevented. In thus storing the 
manure it should be kept moist by the use of liquid manure, but 
not allowed to become water soaked. It has recently been shown 
that the losses from manure may be greatly reduced by spreading 
fresh manure upon the older manure that has already begun to 
undergo an active fermentation, probably because the carbonic 
dioxid evolved in the fermentation of the older portions combines 
with the ammonia developed from the newer portions, this checking 
its dissipation. The presence of large amounts of hay in manure 
makes it difficult to compact and, moreover, furnishes large amounts 
of fermentable matter that increases nitrogen loss. It is therefore 
usually unwise to allow much hay or straw to be mixed with solid 
manure. 
Thus the best methods of protecting manure from loss are: i. 
The exclusion of air. 2. The regulation of the amount of moisture. 
3. The separation of the excess of liquid manure from the solid and 
its distribution upon the soil at frequent intervals. 4. Prevention 
of loss in liquid manure by leaching. 5. The presence of some 
already fermenting manure to furnish carbonic dioxid to combine 
with the ammonia as it is produced. 6. The use of some kind of 
"litter" to absorb the liquid manure and prevent its loss. 
Constructive Fermentations. In order that the manure may 
become plant food the end-products of decomposition must be built 
up into the form of nitrates by nitrification. Nitrification, however, 
cannot take place in the fresh manure since it contains too large 
quantities of organic products, which, as we have seen, prevent the 
growth of nitrifyers. 
Exactly when it begins is a little uncertain, but it appears to 
start only after the high organic compounds have been almost 
wholly broken up into ammonia, and the ammonia formed has 
either united with the acids to form salts or has been dissipated 
into the air. The oxidation of the ammonia salts into nitrites is 
