294 Report of Experiments on the Growth of Barley, 
G consecutive years, of 46 or 48 bushels of barley ; or consider- 
ably more than the amount assumed (p. 93) to be a good produce 
under ordinary rotation and cultivation. These amounts are also 
fully one- third more than was obtained by purely mineral 
manure over the same period. 
It was found that these double dressings were too heavy, the 
crops frequently being much laid ; and hence, after the first 6 
years of the experiments, the quantities were reduced to one-half, 
that is, to the same as on plots 1 A and 1 N. For many subse- 
quent years, however, the plots previously receiving the larger 
amounts, whether alone, or with mineral manure (as presently 
to be noticed), continued to yield more produce than the plots 
receiving the smaller quantity from the commencement. But as 
the effects of the unexhausted residue from previous manuring 
upon succeeding crops will be considered separately and in detail 
in Section IV. no more need be said on the point in this place. 
. It would be interesting to compare the effects of purely nitro- 
genous manures on wheat and on barley ; but as the experiments 
with such manures on the two crops are not as parallel as is 
desirable, either as regards the previous history of the plots, the 
quantities applied, or the periods and duration of the experiments, 
the comparison might be misleading unless given with much 
explanation and qualification. The omission is, however, of the 
less consequence, as we shall be enabled to compare the effects on 
the two crops of a mixture of ammonia-salts and mineral manure 
together, which in fact is of much greater practical importance. 
The practice of growing barley for so many years in succession 
on the same land by any means whatever, is not, it is true, 
recommended for adoption in practical agriculture ; and still 
less desirable would it be so to grow it by means of ammonia- 
salts alone, or nitrate of soda alone. But the extraordinary results 
which have been recorded are not the less instructive and im- 
portant, or of less practical value, on that account. 
It is of no little interest to know, that on a soil, consisting of 
a somewhat heavy loam with a clayey subsoil, and of only 
moderate corn-yielding capabilities, purely mineral manures will 
not yield anything like a lair crop of wheat or barley ; but that, 
on the same soil, a comparatively small quantity of purely nitro- 
genous manures has yielded, for twenty years in succession, not 
much less barley than the average crop of the country ; and that a 
larger amount has given, over 6 consecutive seasons, considerably 
more than an average crop. This is knowledge acquired of the 
available mineral resources of such a soil, which analysis would 
not have afforded ; and which supplies, if not examples for exact 
imitation, at any rate a very sound basis for deduction in regard 
to actual practice. 
