444 
Agricultural Chemistry. 
3701 lbs. ; l)ut 10Z>, with minerals and ammonia, gave 4530 lbs. 
Here, then, after growing wheat successively year after year by 
meajis of very large amounts of ammonia-salts, vpOn land pre- 
viously exhausted by a Jieavy course of cropping, we find a distinct 
effect from tlie admixture of minerals with a further dressing of 
ammonia. But is this action of minerals in rendering efficient 
an excessive supply of ammonia in the soil, after such a course of 
mineral exhaustion as never happens in the ordinary course of 
farming with rotation — is this the action still insisted upon by 
Baron Lieljig, namely, that of enabling the surface of the land, 
" by the plants growing on it, to absorb from the air " a larger 
amount of carbonic acid and ammonia ? 
In 1849, both plots (lOrt and lOZ*) were again supplied with 
equal quantities of ammonia-salts alone, and both gave more than 
2000 lbs. increase over the unmanured plot ; whilst \0b, with its 
liberal supply of minerals the year before, only gave 125 lbs. 
more than \0a. 
In 1850, ammonia salts alone on 10a again gave more than 
2000 lbs. of increase ; but lOi, to which minerals were added 
— this time without ammonia — gave only 399 lbs. of additional 
produce, this slight amount being chiefly due to a small residue 
of ammonia remaining in the soil from the high ammoniacal 
manuring of the previous years. 
That the minerals employed in 10^, though yielding only 
399 lbs. of increase, still practically exhausted the soil of its im- 
mediately available supplied ammonia, is obvious from the results 
of the next two years (1851-2). Thus, with a large and equal 
supply of ammonia-salts only to both plots (10a and 10^) in these 
two years, we have almost identically the same amount of produce 
on the former as on the latter ; although 10b had not only 
twice received a liberal supply of minerals, which had been 
withheld from 10a, but had also given a less gross total produce, 
reckoning from the commencement of the experiment. 
From this time — although the continued application of am- 
monia-salts only on 10a gave in the ninth year an increase of 
919 lbs.; in the tenth, of 2312 lbs.; and in the eleventh, of 
937 lbs. of corn and straw — the employment (on lOi) of minerals, 
in addition to the excessive amount of ammonia, produced a still 
further increase. 
What, then, is the general result of these experiments ? 
Excluding the first year, in which the plots 10a and lOi both 
received mineral manure without yielding any practical amount 
of increase, it is as follows: — On the average of eleven years of 
the continuous growth of wheat, the unmanured plot gave a total 
annual produce (corn and straw) of 2856 lbs. ; plot 10a, with 
eleven years of am.moniacal salts alone, gave 4534 lbs., being 
