nding
result.

The next experiments we shall describe are those on the influence of
farmyard manure on the wheat crop when grown continuously.

TABLE IV.--WHEAT GROWN CONTINUOUSLY WITH FARMYARD MANURE (14
tons per annum).

Weight per
Bushels. bushel Straw
(lb.) (cwts.)
8 years (1844-1852) 28 - -
20 " (1852-1871) 35-7/8 60 33-7/8
20 " (1872-1891) 33-1/2 60-3/8 31-3/8
40 " (1852-1891) 34-7/8 60-1/4 32-5/8

It will be seen from the above results, which contain merely a selection
from a very much greater number of experiments, that farmyard manure
gives as good an average over the forty years as most of the artificial
mixtures do. That this is due to the nitrogen it contains, is strikingly
illustrated by the fact that mixed mineral manures alone give less than
half the return, and also by the fact that ammonia salts alone give a
return twice as great as mineral mixtures; while, lastly, the mixture of
mineral manures and ammonia salts gives but a slight increase over that
obtained with ammonia salts alone.

The remaining results, selected from a much larger number, need no
comment, and we shall give them in tabular form.

Table V.--WHEAT GROWN CONTINUOUSLY WITH ARTIFICIAL MANURES, FARMYARD
MANURE, AND UNMANURED.

_Average of Forty Years (1852-91)._

-------------------------------------+--------------------------------------+
| PRODUCE PER ACRE--AVERAGE PER ANNUM. |
+--------------------------------------+
| Dressed grain. |
MANURES PER ACRE PER ANNUM. +--------------------------------------+
| Quantity. |
+------------+------------+------------+
| 20 years, | 20 years, | 40 years, |
| 1852-71. | 1872-91. | 1852-91. |
-------------------------------------+------------+------------+------------+
| bush. | bush. | bush. |
Farmyard manure, 14 tons per annum | | | |
since 1843