THE SOURCES OF THE NITROGEN OF 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°6 Ibs., 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 three 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 deans, 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.—Vield of Nitrogen per acre when crops are grown in an actual course of rotation. 
In Boussineavut’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 Rothamsted 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 ncarly 
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. 3P 
