94 Report of Experiments on the Growth of Barley^ 
It will be observed that most of the above constituents (vvliich, 
in the sense that they are those which are the most likely to 
become deficient in the soil, may be said to be the most important 
constituents of the two crops) occur in nearly equal amounts in 
the total produce of either. The most prominent exceptions are, 
that the total barley crop would remove rather more lime, but 
considerably less silica, than the wheat crop. But looking^ to 
the ^rain alone, the barley is seen to remove considerably more of 
silica, and rather more of each other constituent, than the wheat. 
Therefore, in cases in which the o^rain only is sold, and the straw 
is returned to the land in due course as manure, the eventual 
loss to the soil would be upon the whole greater, especially 
in silica, by the growth of such a crop of barley than of 
such a crop of wheat. In the experiments now to be con- 
sidered, however, both corn and straw are always entirely 
removed from the land. 
In Germany, it has recently been urged against the plan of our 
experiments, that the amounts of the different constituents applied 
as manure, for the different crops, have no direct relation to the 
amounts which are annually removed from the soil in the crops. 
We freely admit that this is the case. We at the same time 
maintain that, with the existing knowledge at the time of the 
arrangement of the experiments — nay, even with present know- 
ledge, or rather ignorance — of the reactions of the different ma- 
nurial substances within the soil, of the consequent distribution 
and state of combination within it of the constituents they supply, 
and of how far, accordingly, they are available for the crop to be 
grown, it would be the merest pedantry to apply only so much of 
each constituent as had been, or was expected to be, removed in 
the crop. We have, indeed, followed the plan supposed by our 
critics, in isolated cases, with the view of testing the validity of 
the assumptions upon which it is founded, and the result has been 
most signal failure, so far as the amount of the resulting crop is 
concerned. 
Both the description, and the amounts, of the manures actually 
employed for the barley, are recorded in full in the folding Table, 
No. XXIV., and in Appendix — Table I., p. 163. They are in many 
respects the same as were adopted in the wheat experiments; and, 
as in those experiments, the most available and convenient forms 
in which the different constituents occur in the market have been 
selected. Thus (omitting from the enumeration those supplied 
in farmyard manure and rape-cake), the different "mineral"* 
or ash-constituents Avere supplied as follows: — 
* With regard to the use of the term " mineral " see vol. xxiv., pp. 506-8 (foot- 
note), and vol, xxv., p. 101 (and context), of this Journal ; also vol. xvi. pp. 447-?, 
and context. 
