100 SOILS AND MANUEES 



Plot 10. Double ammonia salts alone. 

 11. ,, ,, + superphosphate. 



,,12. ,, ,, + ,, + sulphate of soda. 



,,13. ,, ,, -f ,, + sulphate of potash. 



,,14. ,, ,, -|- ,, -J- sulphate of magnesia. 



It will be noticed that the drainage from the unmanured 

 plot (3) is the most dilute, and that the soluble constituents 

 of the manures are all present in appreciable quantities. 

 Thus, chlorine, sulphuric acid, nitric acid, and even phos- 

 phoric acid, potash, soda and magnesia, are generally found 

 in largest quantity in the drainage from the plots to which 

 these substances were most largely applied in the manures. 



A large amount of lime always occurs in the drainage, 

 even in that from the unmanured plot. The quantity is 

 increased by the application of manures of every kind, but 

 especially by ammonia salts. The fact is closely connected 

 with the general excess of acid radicles over bases other 

 than lime. It is evident that the various salts react with 

 the lime in the soil, producing soluble calcium salts, e.g., 

 the chloride, sulphate and nitrate, which pass into the 

 drainage water, thus : 



(NH 4 ) 2 S0 4 + CaC0 3 = CaS0 4 + (NH 4 ) 2 C0 3 

 Farmyard manure has a similar effect. The carbonic acid 

 evolved by the decomposition of the organic matter con- 

 verts calcium carbonate into the more soluble bicarbonate, 

 which can be washed out. 



Two highly important consequences arise from these 

 changes, viz. : 



1. Loss of lime from the soil ; 



2. Eetention of ammonia and other bases. 



Lawes and Gilbert 1 estimated the loss of lime (calcium 

 carbonate) from unmanured land at about 250 Ibs. per 

 acre annually. When heavy dressings of manure are 



1 J. E. A. S. E., 1882. 



