76 



THE EOTHAMSTED EXPERIMENTS. 



Plan of ex- 

 periments. 



Nitrogen 

 supplied. 



Influence 

 of seasons. 



manures, of various nitrogenous manures, and of combinations 

 of the two. 



Eesults are given for sixteen plots, arranged in four series 

 of four plots each, and for each plot the produce — dressed 

 grain per acre — is given for forty-three years in succession. 



Series 1 comprises four plots, without any nitrogenous 

 manure, namely — 



Plot 1. Without manure, 

 it 2. Superphosphate alone. 



ti 3. Potassium, sodium, and magnesium sulphates. 

 .1 4. Superphosphate, and potassium, sodium, and mag- 

 nesium sulphates. 



Series 2 comprises four plots, with the same four conditions 

 as to mineral manures as to Series 1, with ammonium-salts, 

 supplying 43 lb. of nitrogen per acre per annum, in addition, 

 in each case. 



Series 3, the same four conditions as to mineral manure; 

 with, in each case, for six years 86 lb., and for ten years 43 

 lb., of nitrogen per acre per annum, as ammonium-salts, and 

 for the last twenty-seven years 43 lb. as sodium nitrate. 



Series 4, the same four conditions as to mineral manure ; 

 with, in each case, 2000 lb. rape-cake per acre per annum in 

 the first six years, and 1000 lb. each year since. 



It may be mentioned that 1000 lb. rape-cake will, on the 

 average, contain 48 to 50 lb. of nitrogen, or rather more than 

 in the amounts of ammonium-salts or nitrate used, though 

 probably not more is rendered available within the years of 

 application ; but there will obviously be accumulation, and 

 some cumulative action, from year to year. 



Space will not allow us to call attention in any detail to 

 the produce of individual years, but it will be observed that 

 under all conditions of manuring, whether without nitrogen- 

 ous supply as in Series 1, or with it, in the different forms and 

 combinations, as in the other series, there is great fluctuation 

 from year to year according to season. Thus, without manure, 

 the produce ranges from 35 bushels in 1854 to only 6| bushels 

 in 1879; with a full mineral manure (Series 1, plot 4) from 

 42 bushels in 1854 to 7J bushels in 1879 ; with the full 

 mineral manure and ammonium-salts (Series 2, plot 4) = 43 lb. 

 nitrogen, from 60f bushels in 1854 to 22| in 1887. 



As in the cases of Series 3 and 4 more nitrogen was applied 

 during the first six years than afterwards, the comparison of 

 the produce in individual years at the beginning and at the 

 end of the period have not quite equal significance ; but it may 

 be observed that, with the full mineral manure and ammonium- 

 salts at first, and sodium nitrate afterwards (Series 3, plot 

 4), the produce varied from nearly-65 bushels in 1857 to 25| 

 bushels in 1879 and 1887 ; and lastly, with the full mineral 



