49 



Taiu-e XVT. 



NUror/en as Nitric Acid. 



Complex Mineral Manure 



and 



Ammonium 



Salts. 



and 

 Sodium 

 Nitrate. 



Sodium 



Kitrate 



alone. 



Unmanured 

 continuously. 



Per Million Dry Soil. 



Per Acre. 



Thus, in these 1881 samples, collected, like those in 18G5, about 

 two months after the removal of the crops, the amounts of nitric acid 

 found to the depth of 27 inches only, represented — in the soil of the 

 plot receiving mixed mineral manure and ammonium salts, 39"9 

 pounds of nitrogen per acre to that depth ; in that of the plot receiving 

 the same mineral manure and sodium nitmte, 38 pounds ; in that of 

 the plot to which nitrate of soda alone is annually applied, 54-4 pounds; 

 and in the soil of the continuously unmanured plot, 177 pounds. 



As in the case of the white clover land, in all cases (except with the 

 nitrate alone), the amount decreased from the first to the third 9 inches 

 of depth from the surface ; and if, as in that case, it increased in the 

 lower depths, and in anything like the same degree, we have evidence 

 of a considerable store of nitric acid available for such plants as, by 

 virtue of their habit of growth, are able to gather up the residue 

 accumulated within the subsoil. 



Determinations made in samples collected in the experimental rots,- 

 tion field, in September 1878, showed the following amounts of 

 nitrogen as nitric acid per acre to the depth of 18 inches - 



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