e
years fallow.

6. Including barley without manure three years (eleventh, twelfth, and
thirteenth seasons).

WHEAT EXPERIMENTS.

The first experiments we shall refer to are those on _wheat_, since they
are among the oldest, and their results the most striking of any.

_Unmanured Plots._

Wheat has been continuously grown year after year on three plots for
fifty years, without the application of any manure whatever.

We shall first give the results of the first eight years as illustrating
the effect of season, which accounts for the irregular results obtained.
But for the difference in seasons, we should expect to find a steady
decrease in the amount of produce; and this is shown in taking the
average of groups of years, as we shall do in the next table.

WHEAT GROWN CONTINUOUSLY ON SAME LAND (unmanured).

TABLE II.--(a.) _Remits of first Eight Years (1844 to 1851)._

Year. Bushels. | Year. Bushels.
1844 15 | 1849. 19-1/4
1845 23-1/4 | 1850. 15-7/8
1846 18 | 1851. 15-7/8
1847 16-7/8 | ------
1848 14-3/4 | Average of 8 years 17-3/8
| ------

TABLE III.--(b.) _Results of subsequent Forty Years (1852 to
1891)._

Grain Weight per Straw
(bushels). bushel. (cwts.)
20 years (1852-1871) 14-1/2 57-5/8 13
20 " (1872-1891) 11-1/2 58-3/4 8-5/8
40 " (1852-1891) 13 58-1/4 10-5/8
49th season (1891) 9-3/8 59-1/2 7-1/2

It is interesting to notice the comparatively slight decrease which has
taken place in the yield of wheat during these fifty years. With such
wide variations, due to season, it is extremely difficult, as Sir J.
Henry Gilbert has pointed out, to estimate rate of decline due to
exhaustion. Excluding the very bad seasons, this may be reckoned at from
one-fourth to one-third of a bushel per acre per annum. _The return of
the first year is 15 bushels, while the yield of the forty-ninth season
is 9-3/8 bushels._ The average of the returns obtained during these
fifty years is really in _excess of the average yield of the principal
wheat-producing countries in the world_. This is truly a most astou