180 



THE ROTHAMSTED EXPERIMENTS. 



Effect of 

 nitrogen 

 with differ- 

 ent mineral 

 manures. 



Mineral 

 manure. 



Ammon- 

 ium-salts. 



Residue of 

 mineral 



Potash 

 omitted. 



Sulphate 

 of soda. 



quantities as farmyard or other organic manure, there may be 

 considerable loss by evolution as free nitrogen. 



The next point to consider is the differences in the 

 amount of crop with equal nitrogen, but different mineral 

 supply. This is illustrated by the results in Table 51, 

 which shows the produce by mineral manures alone, by 

 ammonium-salts alone, and by ammonium-salts with different 

 mineral manures. 



Over the 40 years, 1852-91 inclusive, each of the eight dif- 

 ferently manured plots received, respectively, the same manure 

 each year. Leaving the details for careful examination and 

 study, it will be well to call special attention to the average 

 yields over the first 20, the second 20, and the 40 years. 



Plot 5, which received mixed mineral manure alone each 

 year, gave, over the first 20 years, an average annual yield 

 of 17 bushels per acre, over the second 20, 12$ bushels, and 

 over the whole period of 40 years, 15 bushels. 



Plot 10a, with ammonium-salts alone, each year gave, over 

 the first 20 years an average of 22i bushels per acre per 

 annum, over the second 20, 17f bushels, and over the 40 

 years 20| bushels. Thus, ammonium -salts alone produced 

 much more than mineral manure alone. 



To plot 105, 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 each year subsequently, ammonium -salts alone were 

 applied, and the effect of the residue of the mineral manures 

 applied in the early years is apparent on comparison with 

 the yields on 10a. 



Thus, on plot 105, over the first period of 20 years, there 

 was an average annual yield of 25| bushels per acre, against 

 only 22 J bushels on 10a; over the second 20 years 19 bushels, 

 against l7f on 10a ; and over the 40 years an average of 22£ 

 bushels, against only 20| on 10a. For further comparison 

 of plots 10a and 105, especially in regard to the manuring 

 during the first 8 years, see the last two columns of Table 47 

 (p. 168), as well as Table 51. 



Plot 11, with the ammonium -salts and superphosphate 

 (but no potash), gave, over the first 20 years, an average 

 of 28 bushels per acre, over the second 20, 22£ bushels, and 

 over the 40 years 25| bushels. 



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

 phosphate, sulphate of soda was applied ; but the plot had 

 received potash prior to 1852. The first 20 years after 1852 

 produced an average of 33$ bushels per acre, the second 20 

 of 27| bushels, and the whole 40 years of 30f bushels. 



