460 Report of Experiments on (he Grow'li of Wheat. 
is but very slowly, if ever fully, recovered in succeeding 
crops. 
The next question to consider is, the degree, or limit, of effect on 
succeeding crops, of the unexhausted residue of mineral manures. 
This point is illustrated in a very interesting manner in the 
coloured diagrams (I. and II.) facing p. 461. 
The results obtained on plots 3, 10a, and 10b, to which dia- 
gram I. relates, will be first noticed. The diagram, which will 
be easily understood on inspection, shows at one view the general 
character of the manuring, and the bushels of corn obtained per 
acre, on each of the plots, in each of the 20 years of the experi- 
ments (harvests 1 844-1 8G3 inclusive) ; and the following is a 
more detailed description of the experiments and their results : — 
Plot 3 Was unmanured throughout the 20 years, and during 
several previous seasons. 
Plots 10a and 10b had the same mineral manure in the first 
year (1843-4). 10a had ammonia-salts in each of the 19 succeed- 
ing years. 10Z> had the same amounts of ammonia-salts in 17 
out of the 19 years ; in the 3rd year of the experiments (184(3) it 
was left unmanured, in the 5th (1848) it had mixed mineral 
manure with the ammonia-salts, and in the 7th (1850) mixed 
mineral manure alone. , 
The following Table shows the total amounts of the different 
manures applied per acre on each of the two plots (10a and 10b) 
during the 19 years, 1845-1863 inclusive: — 
Tablk XXVIII. 
Plot 10a. 
riot 105. 
10a 
over or under 
106. 
lbs. 
lbs. 
Ib-s. 
.•3092 
3268 
+ 424 
3468 
3268 
+ 200 
.. 
400 
-400 
.. 
300 
-300 
600. 
-600 
400 
-400 
200 
-200 
In the 1st year (1843-4), although the land was in that state 
of practical exhaustion consequent on the removal of turnips, 
barley, peas, wheat, and oats since the last application of farmyard- 
manure, plots 10a and 10b, manured with silicate of potass and 
superphosphate of lime, gave less than half a bushel of dressed 
corn, and only 77 lbs. of total produce more, per acre, than the 
unmanured plot (3). 
