332 Bacteria in Relation to Country Life 



Nitrogen may, therefore, be lost from fermenting 

 manure as ammonia (and, to a slight extent, in the form 

 of other gaseous compounds of nitrogen), or as free 

 nitrogen gas. The latter, in its turn, may be produced 

 by the destruction of nitrates by denitrifying bacteria, 

 or by the oxidation of ammonia by another class of 

 bacteria, at present but imperfectly known. 



Since the numbers and kinds of bacteria are affected 

 by the composition of the manure and the conditions 

 under which it is kept, the transformation and losses 

 of nitrogen are, of necessity, variable. No better proof 

 of this is required than the conflicting results secured 

 by different investigators, some of whom claim that 

 the losses of nitrogen from manure are slight; others, 

 that they are large. 



Again, some investigators assert that the losses that 

 occur are due almost entirely to the volatilization of 

 ammonia. Others assert that they are due to the escape 

 of free nitrogen gas produced in the processes of denitri- 

 fication, or in the oxidation of ammonia. Wagner found, 

 for instance, that in some of his experiments only 1 per 

 cent of nitrogen was lost in four months when the 

 manure was kept compacted, and 2 to 6 per cent when 

 the manure was kept loose and frequently stirred. On 

 the other hand, some of the experiments by Pfeiffer and 

 his associates show losses of more than 42 per cent of 

 nitrogen in ten months. Small amounts of ammonia 

 escaped from the manure. The loss must be attributed 

 to the evolution of nitrogen gas. It seems, also, that 

 vigorous aeration of the material intensified the loss of 

 nitrogen. 



