1908.] 



Farmyard Manure. 



163 



however, was three times as much in the cake-fed as in the 

 other manure. These differences in composition are clearly 

 reflected in the crops grown with equal quantities of the two 

 manures, the weights of which are summarised and reduced 

 to a common standard (the yield of the unmanured plots 

 being taken as 100) in Table VI Ia. The crops grown in these 

 experiments were swedes, barley, mangolds and wheat in 

 rotation, and after the two kinds of dung had been applied 

 in a given year no other manure was used on those plots for the 

 next three years. In the first year the increase in yield pro- 

 duced by the cake-fed dung was 83 per cent, as compared 

 with an increase of 32 per cent, produced by the root and hay 

 dung ; in the following year the residue left by the cake-fed 

 dung produced an increase of 40 per cent, as against 36 per 

 cent, from the residue of the other manure ; in the third 

 year the increases produced by the residues still remaining 

 were 21 and 17 per cent, respectively. The great difference 

 in the value of the two manures comes in the first year, for 

 though the superiority of the cake-fed dung may still be seen 

 in the second and third year, it is almost covered by the experi- 

 mental error. 



The analyses in Table VIII show the change in composition 

 which result from the storage of farmyard manure ; it will 

 be seen that old short dung contains a higher proportion of 

 fertilising constituents (i.e., when reckoned in the dry matter, 

 because the amount of water present at any time is a matter 

 of accident) than fresh dung, if it has been at all properly 

 managed. We have already seen that though considerable 

 losses of nitrogen take place during the rotting down of the 

 manure, the losses of the non-nitrogenous organic matter are 

 the greater, so that the manure becomes concentrated in 

 nitrogen and still more so in phosphoric acid and potash. 

 The active compounds of nitrogen, however, such as ammonium 

 carbonate, grow less as the manure ages, since they are con- 

 stantly being converted into insoluble protein-like bodies 

 making up the bacteria themselves. These, of course, die and 

 decay, giving rise again to soluble nitrogenous compounds, 

 but the tendency is on the whole in the other direction, so 

 that the older the manure the poorer it becomes in ammonia 

 and kindred bodies. Hence old short dung is both slower in 



