20 Farmyard Manure. 



sition of fresh and rotten dung is exhibited in the relative pro- 

 portions of soluble organic matter. Well-rotten dung, it will be 

 observed, contains rather more than twice as much soluble or- 

 ganic matters as the fresh ; with this increase the amount of 

 nitrogen present in a soluble state rises from *44 per cent, to 

 1*21 per cent. 



7. Not only does the absolute amount of soluble nitrogenised 

 matters increase during the fermentation of dung, but the soluble 

 organic matters relatively get richer in nitrogen also. Thus, 



100 parts of dry organic soluble matter i 6 . M ntof mtr 



from fresh dung contain ) 



parts of dry organic sol 

 from rotten dung contain 



100 parts of dry organic soluble matter ) 



8. Lastly, it will be seen that the proportion of soluble mineral 

 matters in rotten dung is more considerable than in fresh. 



9. On the whole, weight for weight, well-rotten farmyard 

 manure is richer in soluble fertilizing constituents than fresh 

 dung, and contains especially more readily available nitrogen, 

 and therefore produces a more immediate and powerful effect on 

 vegetation. 



Bearing in mind the differences observable in the composition of 

 fresh and rotten dung, we can in a general manner trace the changes 

 which take place in the fermentation of dung. Farmyard manure, 

 like most organic matters, or mixtures in which the latter enter 

 largely, is subject to the process of spontaneous decomposition, 

 which generally is called fermentation, but more appropriately 

 putrefaction. The nature of this process consists in the gradual 

 alteration of the original organic matters, and in the formation of 

 new chemical compounds. All organic matters, separated from 

 the living organism, are affected by putrefaction, some more 

 readily, others more slowly. Those organic substances which, 

 like straw, contain but little nitrogen, on exposure to air and 

 moisture at a somewhat elevated temperature decompose sponta- 

 neously and slowly, without disengaging any noxious smell. On 

 the other hand, the droppings of animals, and especially their 

 urine, which is rich in nitrogenous compounds, rapidly enter 

 into decomposition, producing disagreeable-smelling gases. In a 

 mixture of nitrogenous substances and organic matters free from 

 nitrogen, the former are always first affected by putrefaction ; 

 the putrefying nitrogenised matters then act as a ferment on 

 the other organic substances, which by themselves would resist 

 the process of spontaneous decomposition much longer. Without 

 air, moisture, and a certain amount of heat, organic matters can- 

 not enter into putrefaction. These conditions exist in the drop- 

 pings of cattle and the litter of the stables, hence putrefaction 



