Experiments on the Givwth of Wheat. 
crop to bo grown ; and it would supply a large amount of avail- 
able silica, and a large amount of carbonaceous matter beyond 
that of any of tlie other manures. Notwithstanding this, it gave, 
over the lour years of its application, an average annual produce 
of about 3 bushels less dressed corn and about 11 J cwts. less 
straw than the mixed mineral manure and ammonia-salts ; and 
about 2^ bushels less corn and about 8J cwts. less straw 
than the guano — neither of which would supply either silica or 
carbonaceous matter. This result is also perfectly consistent 
with that obtained at Rothamsted and elsewhere. It is not to be 
concluded from this, however, that the farmer may with impunity 
grow large white-straw crops by means of artificial manures 
without a due supply of farmyard manure to the land at some 
period of the rotation. 
Thus, the results obtained during the four yeais that the 
manures were applied, showed that mineral manures increased the 
wheat-crop but little, ammonia-salts much more, mineral manures 
and ammonia-salts used together more than either, or both, 
used separately ; that Peruvian guano, containing both mineral 
and nitrogenous constituents, gave a considerable amount of 
increase ; but that carbonaceous manures had no perceptible 
effect. They further showed that the condition of the land was 
higher than was desirable for the purposes of the experiments, 
the result of which was, not only that the seasons set a limit to» 
the amount of crop, and therefore to that of the increase produced, 
below that which- the manures might otherwise have yielded, but 
that the increase consisted of a ^ ery undue proportion of straw. 
The first season after the cessation of the manuring (1859-60) 
was a very unfavourable one, and the produce on the permanently 
unmanured plot was only 7^ bushels of dressed corn, and about 
14-| cwts. of straw. The next season (1860-61) was not very 
much better, and yielded, on the same plot, only 15^ bushels of 
dressed corn, and about 16| cwts. of straw. But the whole of 
this decline of crop is not to be attributed either to gradual 
reduction of the condition of the land, or to the badness of the 
seasons ; for, as already noticed, the land, which had for the 
first few years been very clean, had, by this time, become some- 
what foul by the continuous cropping. 
Although the produce of the continuously unmanured plot, 
which supplied the standard by which to compare that of the 
others, was so much less during these two concluding years of the 
experiments, the average increase of dressed corn on the other 
plots, due to the residue of ihe manures previously applied, was, 
in every case excepting that of the rape-cake, even somewhat 
greater than during the seasons of the application. The increase 
