462 Report of Experiments on the Growth of Wlicat. 
salts alone, evidence of considerable relative deficiency of avail- 
able mineral constituents, notwithstanding the application in the 
1st year of silicate of potass and superphosphate of lime. Nor is 
this to be wondered at when it is considered that, in the 4 crops 
grown by ammonia-salts alone, there would probably be more than 
five times as much potass, about three times as much phosphoric 
acid, and more than thirty times as much silica removed from 
the land, as would be lost to it in a whole course of rotation of 
turnips, barley, clover, and wheat — supposing only the corn and 
. meat to be sold, and the manure produced from the straw, and 
the consumption of the roots and clover, to be returned to the 
land. 
In the 6th year (1848-9) both plots were again equally manured 
with ammOnia-salts alone, and they gave almost identical quan- 
tities of dressed corn, amounting to about 13 J bushels more than 
that on the unmanured plot ; whilst, of straw, 10a gave an 
increase of about 11 cwts., and the much less exhausted plot 
10Z» only about 1 cwt. more. 
In the 7th year (1849-50), 10a again received ammonia-salts 
alone, and gave nearly 27 bushels of dressed corn and 27^ cwts. 
of straw, which was equal to an increase over the unmanured 
produce of nearly 11 bushels of corn and about 12J cwts. of 
straw. 105, on the other hand, had a manure supplying libe- 
rally every mineral constituent at all likely to be wanting, 
except silica, but containing no ammonia, and the result was, 
an increase over the unmanured plot of little over 2 instead 
of 11 bushels of dressed corn, and of only about 2 instead 
of \1\ cwts. of straw. Thus, even in the 6th year of their 
application, ammonia-salts alone gave 9 bushels more dressed 
corn and nearly 10:j: cwts. more straw, than the mixed mineral 
manure alone, notwithstanding that a relative deficiency of 
mineral constituents had shown itself 2 years previously, and 
that even on 10Z», where so much less ammonia-salts had been 
applied in previous years, there had still been considerably more 
than twice as much nitrogen supplied as had been recovered 
as increased yield in the crop. The defective result on 105, by 
the mineral manure alone, could not be due to the want of avail- 
. able silica, since the exhaustion of it was very much less than 
on 10a, which, nevertheless, gave so much more produce. It 
is, moreover, clear that, although the available supply of mineral 
constituents had become defective in relation to the amount of 
ammonia artificially supplied, it was still in excess relatively to 
the annually available supply of nitrogen from natural sources. 
From this time forward, for 13 consecutive years, plots 10a 
and lOi received exactly the same amount of ammonia-salts 
annually (200 lbs. sulphate and 200 lbs. muriate), and neither of 
