Report of Experiments on the Growth of Wheat. 
97 
small scale, at Rothamsted, on the effects of various mineral and 
other substances when applied as manure to a variety of agricul- 
tural plants. The most marked result observed in these early 
trials was the very striking increase in the rapidity of growth 
of certain plants when earthy phosphates decomposed by sul- 
phuric acid were employed. 
In 1843, it was decided to make experiments at once more 
systematic and on a larger scale, on some of the most important 
crops of our rotations, to determine, as far as possible, the relative 
or characteristic dependence of each, on the soil, the atmosphere, 
and manure. Boussingault's researches had been designed to 
ascertain what constituents were furnished, respectively by the 
soil, the atmosphere, and manure, to the aggregate of crops forming 
a rotation, rather than to each description of plant individually ; 
and he himself says that his plan and results were silent on the 
latter point, though there is no doubt they did, at the same time, 
afford some very trustworthy indications in relation to it. 
Of the new series of experiments made at Rothamsted, the 
first commenced was on turnips ; and in accordance with the 
results previously obtained on a small scale, and apparently quite 
consistently with the views put forth by Liebig as to the relative 
importance of supplying the mineral constituents, the effects of 
the phosphatic manures were most striking, especially in the 
early stages of growth ; though, when the experiments of the 
first year were concluded, it was found that certain organic 
manures had very materially influenced the final amount of 
produce. 
For the experiments upon wheat, a field of 14 acres was 
selected, which had grown turnips, barley, peas, wheat, and oats, 
since the application of manure, and would, therefore, according 
to the ordinary rules of practice, be considered so far exhausted 
as to require to be re-manured before growing another crop. 
It was thought that a field in such a condition was peculiarly 
fitted to show in which of the constituents of the crop to be 
grown the soil had become practically the most deficient by the 
removal of the five preceding crops ; and that, if, on some plots 
of the land, in this agricultural sense exhausted, certain con- 
stituents of farmyard manure were supplied separately, on others 
in combination, and if, on others by their side, the crop were 
grown respectively without manure, and with farmyard manure 
itself, the comparative results obtained would far more satis- 
factorily indicate what constituents were the most exhausted, so 
far as their available supply for the crop to be grown was con- 
cerned, than any analysis of the soil could do. 
This view has been fully confirmed, not only by the results 
obtained on the plan adopted, but by those obtained by others 
VOL. XXV. II 
