Agricultural Cliemistri/. 
435 
tables of detail. Leaving-, then, entirely out of the question, on 
this occasion, all detail or discussion as to the amount and 
specific description of the different manures, and also as to the 
varying proportions of corn and straw respectively, which make 
up the sum of the total produce, let us see what are the broad 
and main features brought out by this immense mass of experi- 
mental evidence. 
The average annual total produce (corn and straw) per acre un- 
manured, including the results of eleven years, and extending in 
all to 27 cases, is 2864 lbs. The average annual increase over this 
amount, obtained by various purely mineral manures, in 40 cases, 
distributed over eight different years, is only 154 lbs. The increase 
by farm-yard manure on the other hand, taking the average of 
eleven years, is 2172 lbs. It is clear, therefore, that tliere are 
here 2000 lbs. of increased produce, beyond that which the 
mineral manures were adequate to yield. Again, it is seen (in 
Series 4), that the average of 36 cases of purely ammonlacal 
manure, gave an average increase over the unmanured plots of 
1993 lbs. ; whilst nitrate of soda, another manure whose efficacy 
is due to the nitrogen it supplies, and which was applied in 
quantity as nearly as possible equal in nitrogen to that of the 
ammonia-salts, has given a mean average increase of 2043 lbs. 
In the next series (6), we have 117 cases, distributed over nine 
years, in which ammonia-salts were employed, in quantity equal 
in their contents of nitrogen to the ammonia-salts of Series 4, 
and the nitrate of soda of Series 5 ; but Ave have here (in Series 6), 
the addition to the nitrogenous manure, of various purely mineral 
manures ; and the increase becomes 2667 lbs. instead of only 
about 2000 lbs. with nitrogenous manure alone ; so that, with 
this combined mineral and nitrogenous manure, the produce 
considerably exceeds that by farm-yard manure. Whilst, then, 
an excessive supply of nitrogenous manure alone has produced 
an average increase of about 2000 lbs., the further addition of 
minerals has, when there was at the same time a large amount 
of nitrogen artificially ■provided within the soil, given a further 
average increase of 674 lbs. ; though, when these minerals were 
added without an excess of nitrogen in the soil, the average in- 
crease they yielded was only 154 lbs. 
It is seen then, that mineral manures alone, increased the pro- 
duce of this agriculturally exhausted field in no practical degree ; 
that pure nitrogenous manures increased it nearly as much as 
the ordinary manure of the farm ; and that nitrogen together with 
minerals gave a produce nearly double that of the unmanured 
land, and considerably exceeded that by farm-j^ard manure. " That 
the mineral constituents of wheat cannot by themselves increase the 
fertility of land ^' — and that the produce in grain and straic is 
