490 Report of Experiments on the Growth of Wheat. 
ammonia-salts were also used, the amount reckoned as increase 
due to the ammonia was by so much the greater in 1853, and 
hence the better result for a given amount of ammonia in that 
year than in 1852. 
To conclude on this point : Great as is the difference of effect 
of a given quantity of ammonia, according to the amount applied 
per acre, to the mineral condition of the soil, and to the season, 
still, when only moderate quantities were used, when there was 
a sufficient supply of mineral constituents, and taking the average 
of many seasons — that is, under the conditions the most com- 
parable with those of the average of common practice — the result 
was, in marked accordance with our early estimate, that almost 
exactly 5 lbs. of ammonia were required to be expended to 
obtain an increase of 1 bushel of wheat grain, and its proportion 
of straw. 
V. Concluding Observations; showing the Pkactical 
Bearings of the Kesults. 
Referring the reader to the fuller summaries already given, of 
the conclusions arrived at in reference to each separate branch 
of the subject, it only remains, in bringing this paper to a close, 
very briefly to recapitulate a few of the most prominent facts 
elicited, and to show their connexion with, and bearing upon, 
the ordinary farm practice of this country. 
1. On a soil of not more than average wheat-producing 
quality, and taken for experiment after a course of 5 crops since 
the application of manure, wheat has been grown successfully, 
without manure, and with different descriptions of manure, for 
20 years in succession. 
2. Without manure, the produce of dressed corn was, in the 
first year, 15 bushels per acre; in the last, 17J bushels; and, 
taking the average of the 20 years, 16^ bushels. 
3. With farmyard manure, applied every year, the produce 
was, in the first year, 20^ bushels ; in the last, 44 bushels ; and, 
on the average of the 20 years, 32^ bushels. 
4. With artificial manures, the highest produce was, in the 
first year, 24^ bushels ; in the last, 56^ bushels ; and, taking the 
average of the 20 years, 35 J bushels, or considerably more than 
the average produce of Great Britain when wheat is grown in 
the ordinary course of agriculture in rotation ; and also con- 
siderably more than was obtained in the same field by an annual 
application of farmyard manure. 
5. Mineral manures alone, though applied in the soluble form, 
increased the produce scarcely at all ; that is, they did not enable 
the plant in any material degree to assimilate more nitrogen and 
