522 The Storage of Farmyard Manure 



The two obvious ways in which nitrogen may be lost from the heap 

 are: 



1. By the washing out of soluble nitrogen compounds. 



2. By the volatilisation of ammonia or other compounds. 

 Washing out is insufficient to account for all the loss because it 



does not operate under cover, and yet loss of nitrogen always occurred 

 here, and was sometimes as great as in the open. 



It is much more difficult to decide whether volatilisation of ammonia 

 accounts for everything else. One or two facts, however, would be 

 difficult to explain on this view. 



Ammonia does not easily volatilise from farmyard manure, even the 

 exposed heaps retaining a good deal of it, not infrequently indeed as 

 much as in the sheltered heaps. Nor is there much volatilisation of 

 water except from the outer crust : usually the moisture only falls by 

 a few per cents, of its total quantity : unless ammonia volatilises more 

 readily and to a greater extent the loss would be insufficient to account 

 for the facts. 



Again, the watered heap (p. 516) showed no more loss of ammonia 

 than the unwatered heap, nor did it accumulate ammonia, yet it lost 

 considerably more nitrogen. 



Thus we are driven to seek for some other cause for the loss of 

 nitrogen. 



It is still more difficult to follow the changes in the complex nitrogen 

 compounds of the heap. Little can be gathered from the analytical 

 data beyond the fact that they disappear. We know, however, that 

 the process is brought about by microorganisms ; our first step is there- 

 fore to summarise the results obtained in the laboratory investigations 

 on the bacterial decomposition of protein, and then to consider another 

 important case of decomposition, — the reactions occurring during 

 sewage purification, — to see what light they throw on the change in 

 the manure heaps. 



The bacterial decomposition of protein under laboratory conditions. 



Considerable work has been done in late years in studying the 

 bacterial decomposition of protein. An extensive literature on this 

 subject has grown up most of which, fortunately, has been summarised 

 in Barger's monograph^; it is, therefore, unnecessary for us to do more 



^ "The Simpler Natural Bases," G. Barger, Longman's Monographs on Biochemistry, 

 1914. 



