Minerals Recovered, and not Recovered, in Hay Crop. 203 



unrecovered residue becomes so locked up (or distributed) as 

 to be but slowly available to succeeding crops. 



Of soda, there was, in the presence of an abundant supply 

 of potash, even less taken up in the manured than in the 

 unmanured crop during the years of the application. In later 

 years there was some, but comparatively little, increase in the 

 amount compared with that in the unmanured crop. 



Of phosphoric acid, in the twenty years about 57 per cent. 

 of the quantity estimated to be supplied was contained in the 

 total produce, whilst the increased yield represented 33 per 

 cent. The residue of the phosphoric acid, like that of the 

 potash, is very little subject to loss by drainage. 



Of sulphuric acid there is proportionately a much less 

 increased amount than of phosphoric acid. 



Of chlorine, the increased amount found in the produce is, 

 during the years of application of the manure, greater in 

 proportion to the estimated supply than that of any other 

 constituent. Both chlorine and sulphuric acid are very subject 

 to loss by drainage. 



Lastly, of silica, the produce of the twenty years contained 

 about 41J per cent, as much as there was estimated to be 

 supplied of soluble silica in the manure, and the increased 

 yield of it represented about 22 per cent. 



The general results may now be summarised. Of the three 

 more important constituents of manure nitrogen, potash, 

 and phosphoric acid, when these are supplied in farmyard 

 manure, the nitrogen is recovered in the least proportion in 

 the increase of the crop for which it is supplied. It leaves 

 a large determinable residue within the soil, which, however, 

 is very slowly available to succeeding crops ; and, finally, it 

 is subject to serious loss by drainage, and probably by evolu- 

 tion into the atmosphere also. The potash so supplied is 

 recovered in increase in much greater proportion during the 

 years of the application, in much greater, though still rapidly 

 decreasing proportion, in subsequent years, and is very little 

 subject to loss by drainage. The phosphoric acid again, is 



