THE SOURCES OF THE NITROGEN OP VEGETATION, ETC. 439 



cases, — namely, 234 lbs. in the ten crops of wheat grown consecutively, and 219-3 lbs. 

 in the five crops of wheat alternated with fallow. 



Again, five crops of wheat alternated with beans gave 45 - 2 lbs. of Nitrogen per acre, 

 per annum, over the five years — equal half that amount, or 22 - G lbs., averaged over the 

 ten years. The total amount of Nitrogen obtained during the ten years was, in the 

 ten crops of wheat grown consecutively, 234 lbs., in the five crops of wheat alternated 

 with fallow, 219-3 lbs., and in the five crops of wheat alternated with beans, 225*8 lbs. 

 — or not very materially different in the tbree cases. But, notwithstanding that the 

 land has thus yielded in wheat, over ten years, almost as much total Nitrogen in five 

 crops alternated with beans, as in ten crops grown consecutively, and rather more than in 

 five crops alternated with fallow, the five intermediate crops of beans have, in addition 

 to this, themselves carried off more than the same amount of Nitrogen as the wheat — 

 namely, 244 - 5 lbs. 



The general result is. then, that pretty nearly the same amount of Nitrogen was taken 

 from a given area of land in wheat, in ten years, whether ten crops were grown con- 

 secutively, five crops in alternation with fallow, or five crops in alternation with beans. 

 In fact, the crop of wheat was increased fully as much when it succeeded leans, which 

 carried off a large amount of Nitrogen, and of mineral matters also, as when it succeeded 

 fallow, which conserved the stores both of Nitrogen and of mineral matter. 



It will be seen, by the illustrations given in the next sub-section (C), that the experi- 

 mental results thus far adduced are perfectly consistent in character with those obtained 

 under circumstances more nearly allied to those of ordinary farm practice. 



C. — Yield of Nitrogen per acre when crops are grown in an actual course of rotation. 



In Boussingault's experiments, he obtained, taking the results of six separate courses 

 of rotation, an average of between one-third and one-half more Nitrogen in the produce 

 than had been supplied in the manure. He found, moreover, that the largest yields of 

 Nitrogen were in the Leguminous crops, and, further, that the Cereal crops were the 

 larger when they next succeeded upon the removal of the highly nitrogenized Legumi- 

 nous crops. 



For our own experiments at Bothamsted upon an actual course of rotation, a piece 

 of land was selected which was, in an agricultural sense, exhausted ; that is to say, it 

 had grown a course of crops since the application of manure, and would, under ordinary 

 practice, have received a new supply before growing another crop. On this land the 

 four-course rotation of Turnips, Barley, Leguminous crop (or Fallow), and Wheat, in 

 the order of succession here enumerated, and without manure, has now been followed 

 for twelve years- — that is, through three separate courses. The yield of Nitrogen during 

 these twelve years, or three courses, has been determined ; and the result shows an 

 average annual amount, per acre, of 42-6 lbs. This, it will be remembered, is nearly 

 twice as much as was obtained in either wheat or barley when these crops were, respect- 

 ively, grown year after year on the same land. The greatest yield of Nitrogen obtained 



MDCCCLXI. 3 p 



