I I 2 AGRICULTURAL BACTERIOLOGY. 



material is lost from the manure during these changes. The 

 loss includes carbon in large amount, a matter of no signifi- 

 cance, however, as it has simply gone into the air from which 

 it can readily be reclaimed by plants. But the loss includes 

 much nitrogen, and this loss is a misfortune, since it is the ni- 

 trogen that the farmer desires to keep. The ammoniacal fer- 

 mentation results in such large amounts of ammonia that it 

 cannot be held in the manure pile by the small amount of acid 

 formed, and is consequently exhaled into the air. The smell 

 of ammonia tells of this nitrogen loss. The denitrifying bac- 

 teria, of which there are many varieties in the manure, are also 

 vigorously at work reducing any nitrates which may be formed, 

 into nitrites, and, finally, into free nitrogen. As fast as the 

 free nitrogen is loosened from its combinations it disappears 

 from the manure into the air, for it is not able to combine with 

 any substances present. The loss of nitrogen from these 

 sources is very great. From the liquid manure the nitrogen 

 disappears very rapidly, and from the solid manure it goes 

 more slowly, indeed, but far too rapidly for the good of the 

 farm. The total loss of nitrogen by these means is ex- 

 tremely variable and depends upon conditions only partly 

 understood. Sometimes more than half of the whole disap- 

 pears in one of these ways, before the decomposition and deni- 

 trifying processes are finished by the completion of this " ripen- 

 ing" of the manure. 



It is of great importance to the agriculturist to check this 

 nitrogen loss as completely as possible. Various means have 

 been suggested and used for the purpose. One of the most 

 obvious consists in adding to the manure enough of some acid 

 material to combine with all the ammonia as fast as it is 

 formed so as to make non -volatile salts. For this purpose 

 sulphuric acid has been commonly used. Other materials 

 sometimes used appear to have rather the purpose of checking 

 the action of the denitrifying bacteria. Of the various ma- 



