i6 



For the thirty-two years, 1852 to 1883 inclusive, each of the 

 eight differently manured plots received the same manure each year. I 

 will only call special attention to the average yields over periods of six- 

 teen and thirty-two years. 



Plot 5, treated with mineral manure only, gave, during the first sixteen 

 years, an average yearly yield of 17^ bushels per acre, during the second 

 sixteen years 13^ bushels, and during the whole period of thirty-two 

 years 15^ bushels. 



Plot loa, treated with ammonium-salts only, gave, during the first 

 sixteen years, an average yearly yield of 23^/6 bushels per acre, during 

 the second sixteen years 17^ bushels, and during the thirty-two years 

 an average of 20^ bushels. Thus, ammonium-salts alone produced 

 much more than mineral manure alone. 



On plot lob, previous to 1852, in the years 1844, 1848, and 

 1850, mineral manures had been applied, in the other years previous 

 to 1852 (excepting in 1846, when it was unmanured), and subse- 

 quently, ammonium-salts only. The effect of the residue of the pre- 

 viously applied mineral manures is apparent on comparison with the 

 yields on loa. 



On plot lob we find, during the first period of sixteen years, an 

 average yearly yield of 27^ bushels per acre, against 23^ bushels on 

 loa; during the second period of sixteen years 19^3 bushels, against 

 17^ on ica; and during the thirty-two years, an average yearly yield 

 of 23 1^ bushels, against only 20^ on loa. 



Plot n, with superphosphate but no potash, in addition to the 

 ammonium-salts, gave, during the first sixteen years, an average yearly 

 yield of 293/3 bushels per acre, during the second sixteen years 22^ 

 bushels, and during the thirty-two years 26^ bushels. 



On plot 12, in addition to the ammonium-salts, superphosphate and 

 sulphate of soda were applied ; but potash had been applied prior to 

 1852. The first sixteen years produced an average yearly yield of 34^ 

 bushels per acre, the second sixteen years of 27^ bushels, and the 

 whole thirty-two years of 31 bushels. 



On plot 13, the ammonium-salts, superphosphate, and sulphate of 

 potash were applied, and the average annual produce was, over the 

 first sixteen years 34 bushels, over the second sixteen years 29^, and 

 over the thirty-two years 31^3 bushels. 



On. plot 14, besides the ammonium-salts and superphosphate, sulphate 

 of magnesia was applied, and some potash had been applied prior to 

 1852. The average annual produce was, over the first sixteen years 

 34^ bushels, over the second sixteen years 28^ bushels, and over the 

 thirty-two years 3 1 ^ bushels. 



On plot 7, in addition to the ammonium-salts, superphosphate and 

 the sulphates of potash, soda and magnesia, were applied, and gave, 

 during the first sixteen years, an average yearly yield of 35^ bushels 

 per acre, during the second sixteen years of 29^ bushels, and during the 

 whole thirty-two years of 32^ bushels. 



Thus, not only the effect upon the yield of wheat of a direct supply, 

 but of a residue from long previous applications of potash, is very notice- 

 able. This is rendered more obvious by reference to the following table 

 (VII.), in which the pounds per acre of potash and phosphoric acid 

 removed during two periods of ten years each, in the total produce, 



