482 
Af/ricu It u ra I Chem id 1 1/ . 
the natural yield of the soil and season ; at any i-atc, it will be nscfid to 
renienibcr this as (he amount until I'uturc uxiierinicuts sliall I'urnish further 
information on the isuhject." — Jour. Jloij. A(j. Hoc. Enq., vol. viii., jiart 1, 
p. 24(!. 
" Wo may here observe that the production of straw, as well as that of grain, 
would seem to be intimately connected with the expenditure of nitrogen de- 
rived througli the roots of the plant, and had we time to consider the question 
more full}' on this occasion, we should not have dwelt so exclusively on 
the production of corn alone as we liave done, ^^'e may, however, remark, 
that the production of a heavy crop of straw in a wet season is iirobably, from 
the cause alluded to, a very dearly-purchased produce." — A^ol. xii., part 1, 
p. 27. 
" Jn our paper upon the growth of wheat, published in the Journal of the 
Eoyal Agricultural Society in 1847, we have attempted an estimate of the 
probable amount of niti'ogen required to obtain a given amoxmt of it in the 
increased produce. We there provisionally assumed that 5 lbs. of ammonia 
were required to jiroduce an increase of one bushel of corn and its equivalent 
of straw. We do not intend to enter I'ully into the question of the accuracy of 
this estimate on the jircsent occasion, Viut we may observe in passing, that 
among the ]ilots the history of which we have given in the ibregoing pages 
down to the last harvest, there is not one, even under the best conditions as to 
artificial mineral supply, where the ammonia, on the average of seasons, has 
given an increase equal to that supposed in our estimate 
" Without further inquiring then, into the correctness of our estimate, it would 
seem that a loss of this kind during the growth of the plant is a fact which is 
sufficiently substantiated, at once by the ]iractical experience of the fanner, and 
by experiments of an independent kind relating to it. And, let it once be recog- 
nised, in agricultural science, that there is a definite expenditure or consumption 
of the nitrogenous bodies derived through the roots, connected with the fixation 
and elaboration of certain constituents of plants, and that this is greater or less 
according to tlie sources or the exact composition or state of elaboration of the 
jiroducts, and an important step will be gained towards a clearer conception of 
the principles involved in the alternation in a coiu-se of crop])ing, of plants of 
varying products and habits of growth." — Vol. xii., part 1, pp. 31, 32. 
We will next show, whether or not that which we liave assumed 
regarding the excess of nitrogen required in manure over that 
obtained in the increase of the cereals grown by it, was " a mere 
stroke of fanry," or whether it was " ascertained by a series of 
observations." On this subject we will bring one quotation 
from our former papers, and we will then adduce a summary of 
an immense mass of experimental evidence on the point in ques- 
tion. We say : — 
" Thus, among from turn to three hundred exjjcriments with ammoniacal 
manures, we have in no single instance recovered in the increase the amount 
of nitrogen provided in tlie manure; and this fact is perfectly consistent with 
the amounts of produce found, in the experience of the farmer, to be obtained 
by the use of Peruvian guano and flther nitrogenous manures." — Jour. Boy. 
A(jr. Sac. Eng., vol. xii., part 1, p. 29. 
In the following Table (VII.) is given a summary of the 
amount of nitrogen recovered in the increased produce, for every 
hundred parts of it supplied in manure, in the cases both of 
barley and of wheat. It will be seen, tliat we have here the 
