Ammonia-salts versus Nitrate of Soda. 45 



the large amount of nitrogen supplied in the manure, and 

 not accounted for in the crop. Hence, when ammonia-salts 

 are applied to grow wheat, it is not safe to calculate upon 

 any of the unexhausted residue being available for the 

 purpose of growing a second corn crop. The evidence also 

 indicates that the exhausting character which farmers attri- 

 bute to corn crops is quite as much due to the nitrogen 

 which they do not assimilate being washed out of the soil, as 

 it is to the amount of that substance which is removed in the 

 produce. 



COMPARISON BETWEEN AMMONIA-SALTS AND 

 NITRATE OF SODA AS SOURCES OF NITROGEN. 



One other series of experiments with artificial manures 

 remains to be discussed. The results already considered are 

 those of experiments in which mixed minerals alone, or salts 

 of ammonia alone, are employed. It is necessary now 

 to notice those in which one uniform quantity of mixed 

 minerals is used in each case, but with different amounts of 

 nitrogen in the form of ammonia- salts, and also as nitrate of 

 soda. The nitrogenous applications were as follows : Plots 

 6a and 6fc, 2001b. of sulphate and muriate of ammonia, con- 

 taining 431b. of nitrogen ; plots 7a and 76, 4001b. of the same 

 salts, containing 861b. of nitrogen ; and plots 8a and 86, 6001b. 

 of the same salts, containing 1291b. of nitrogen; whilst 

 plot 9a received 861b. of nitrogen as nitrate of soda, instead 

 of as ammonia-salts. Table VIII. is drawn up on the same 

 principle as the preceding tables, and similarly records the 

 result in four periods of eight years each. 



It is apparent that in the separate periods of eight years 

 each, and also in the whole period of thirty-two years, the 

 increase of wheat obtained by adding 431b. of nitrogen 

 (plot 6) to the minerals varies from 8 to 11 bushels per acre, 

 the total increase over the whole period being not quite 



