522 
Report of Experiments with different Manures 
nitrate of soda alone, the amount of carbon annually removed in 
the crop was increased to something under or over 1300 lbs., 
and bv means of the mixed mineral manure alone to about the 
same amount ; but by the mixtures of both ammonia-salts and. 
mineral manure it was increased to over 2000 lbs. per acre — that 
is, without any supply of carbon in the manure. The addition 
to the latter manures of 2000 lbs. of sawdust, or 2000 lbs. of cut 
wheat-straw, each containing in round numbers about 700 lbs. of 
carbon, gave no increased yield of it in the produce. Nor did 
farmyard-manure, in amount containing at least twice as much 
carbon as the crop yielded by its use, give a produce containing 
more than about three-fourths as much as the mixtures of 
mineral manure and ammonia-salts which supplied none. It 
may be concluded, therefore, that, even admitting that the car- 
bonaceous manures did supply carbon to the growing plants, the 
supply from that source was at any rate unnecessary, provided 
only that mineral or incombustible constituents, and nitrogenous 
manures were liberally supplied. 
As mentioned above, the average amount of mineral or in- 
combustible constituents taken from the land without manure 
was, over the seven years, 167^ lbs., or about 1^ cwts. per acre 
per annum. The amount removed in the crop grown by means 
•of ammonia-salts alone was increased to something under, and 
that by nitrate of soda alone to something over, 2 cwts. ; there 
being, therefore, by such manuring, a further drain upon the 
resources of the soil. 
By means of the mixed mineral .manure alone, the amount of 
incombustible constituents taken away in the crop was raised to 
about 2\ cwts. ; but the manure itself supplied more of almost 
every such constituent, except silica, than the entire produce 
would contain ; so that, excepting in the item of available silica, 
the soil was, compared with the unmanured land, annually accu- 
mulating most of the important mineral constituents. By the 
addition of ammonia-salts to the mixed mineral manure, the 
amount of mineral constituents taken from the land was raised 
from about 2\ to nearly 3£- cwts. when the smaller amount 
(Plot 9), and to nearly 4 cwts. when the larger amount of 
ammonia-salts (Plot 13a) was employed ; and, as the produce 
was in these cases almost entirely Graminaceous, the drain upon 
the available silica of the soil would be very considerable ; though, 
here again, all the other incombustible constituents were supplied 
in far larger quantity than they were taken off in the crops. By 
the addition of nitrate of soda to the mixed mineral manure, 
whether in the smaller amount (Plot 14), or in the larger amount 
