516 The Storage of Farmyard Manure 



Effect of drying out of the heaf. The effect of drying out of the heap 

 is well seen in the experiment at Woking, where some mixed manure 

 was left in a closed shed protected from wind and weather from November 

 1st, 1913, to May 20th, 1914, during which time its moisture content 

 fell from 76-8 % to 72-6 %. The difference in condition of the manure 

 was more than these figures indicate ; with 76-8 % of water the heap 

 appeared considerably wetter than with 72-6 %. The most characteristic 

 reaction is the formation of nitrates, which, in our experience, only 

 occurs when the moisture content falls below a certain critical amount 

 (see p. 541). In the Woking experiment the nitric nitrogen formed 

 as much as 9 % of the original total nitrogen ; this, however, is quite 

 exceptional : more usually only a small quantity is detected. 



The loss of ammonia amounts to 12 % of the original total nitrogen, 

 and is therefore greater than the nitrate formed: there is also a loss 

 of more complex nitrogen compounds, but not of amide. 



Another instance is furnished by the heap of cow manure also 

 stored under cover, but exposed to wind for the long period, Nov. 29th, 

 1915, to Jan. 26th, 1917, in which the changes on the whole are similar, 

 though the formation of nitrate is less. 



The results are as follows: 



other compounds 76 71 74 63 



' The evaporation of water is naturally accompanied by an evaporation 

 of ammonia, which, therefore, becomes a source of loss of nitrogen. 

 But the amount of water evaporated is not great in proportion to its 

 total quantity, and unless there was relatively more evaporation of 

 ammonia the actual amount lost would only be small. In order to 

 find out whether the continued maintenance of the moisture content of 

 the heap would help to retain the ammonia and the total nitrogen the 

 following experiment was carried out. 



Effect of watering the heap. One of the heaps of cow manure kept 

 loose under cover was periodically watered from a can, sufficient water 



