454 
Afjricultural Chemistry. 
If ammonia-salts do give ina-case, they hut exhaust the land ! 
Their action is only a gain of time ! 
And lastly, their observed effect in our own experiments is only 
exceptional, so that no deductions whatever can be formed there- 
from, in regai'd to corn-exhaustion in any other case ! 
The point which we propose next to illustrate, by reference to 
a very condensed tabular statement of a large number of experi- 
ments is, that the provision of available nitrogen within the soil, has 
a very marked effect upon the increased growth of barley also — 
the second in importance of the cereal grains in our own country 
and climate. 
In Table II., given below, we have the results of experiments 
on the growth of barley in the year 1854, in two separate fields 
of widely differing previous history. The portion of " Barn- 
field,^'' the produce of which is given in the upper part of the 
Table, had grown turnips experimentally for ten successive years, 
without being manured with any nitrogenous or carbonaceous 
substance. It had, however, l)een exceedingly liberally supplied 
every year, with various mineral manures ; which in some 
cases included in very large excess every constituent which the 
ashes of the crop would contain. The condition of these plots, 
indeed, would be that of such exhaustion of organic substance, 
and, on the other hand, of such a repletion of mineral consti- 
tuents, as could not occur in the oi'dinary course of farming. 
Strange to say, however — that is, for the credit of the " mineral 
tlieory^^ — this exceedingly mineral-enriched, and nitrogen-impo- 
verished land, gave for the season in question an excessively 
meagre crop. In fact, its total pr'oduce (corn and straw) was only 
two-thirds that of our continuously unmanured wheat-plot, and 
little more than half as much as that grown without manure or 
by mineral manure alone, in our other experimental barley-field ; 
although the crop in the latter, some of the results of which are 
also given in the Table, was the fourth of barley, and the third 
without nitrogenous manure. Previous to the first experimental 
crop, however, the latter field had not been submitted to more than 
an ordinary course of exhaustive cropping. We have here, then, 
a remarkable instance of the utter incapability of a very liberal 
supply of mineral constituents, on a soil exhausted of organic food, 
to enable the plant to obtain sufficient nitrogen from atmospheric 
sources, for the growth of the barley-crop in adequate agricul- 
tural quantity. Nor was there in this " Barn-fiekV^ a difierence 
of more than a bushel or two, between the produce of those plots 
w liich had previously received large amounts of alkalies as well 
as phosphates, and those which had only been manured with the 
latter. 
