ENGLISH AGRICULTURE. 169 



to answer, for we have plots which are manured not only 

 with ammonia salts, but with sulphate of soda, sulphate of 

 potash, sulphate of magnesia, and superphosphate. Taking 

 the barley experiments, this application gives an average 

 yield of 44J bushels, or only fractionally more than we 

 obtained from the use of ammonia salts and superphosphate. 

 The same result is obtained when the source of nitrogen is 

 changed from ammonia salts to nitrate of soda in even a 

 more marked manner, for while nitrate of soda and super- 

 phosphate have given an average yield of 46f bushels over 

 a period of 34 years, the addition of sulphates of potash, 

 soda, and magnesia have only given a 47 bushel average. 

 The inefficiency of these substances is equally well shown 

 by the fact that while nitrate of soda has given an average 

 yield of 34 bushels per acre, nitrate of soda plus sulphates 

 of potash, soda, and magnesia has only yielded an average of 

 34J bushels. Taking wheat, we see a considerably greater 

 effect. We find 26J bushels from the use of ammonia 

 salts and superphosphate, and 30 and 31 bushels per acre 

 from the use of various mineral substances, including super- 

 phosphate mixed together plus ammonia salts. Still even 

 with the increase in the case of wheat it is evident that the 

 increased yield was rather due to the sulphur or sulphuric 

 acid in combination with the alkalies and magnesia than to 

 the soda, potash, and magnesia. Examination of the tabulated 

 results bear out this idea, because whether sulphate of soda, 

 sulphate of potash, or sulphate of magnesia were used a 

 similar increase is observable, and when all were combined 

 together the effect is not increased at all. It would be 

 difficult to explain the considerable increase from an applica- 

 tion of sulphate of soda on any other ground, and the fact 

 that sulphate of potash produced no greater increase than 

 sulphate of soda also indicates that it was not the potash 

 but the combined sulphur that was needed. 



