466 Report of Experiments on the Growth of Wheat. 
conditions and results of the different experiments will be suffi- 
ciently understood from the following few comments. 
It is seen, as shown in another form in Table XXVI., that 
plots 5, and 17 or 18, give almost identical amounts of average 
annual produce, and therefore of average annual increase over 
plot 3, during the 12 years in question — the one (plot 5) having 
mixed mineral manure alone every year, but succeeding heavy 
dressings of mineral manure and ammonia-salts in preceding 
years, and the others having the same mixed mineral manure 
each year succeeding an excess of ammonia-salts in the pre- 
ceding year, and succeeding also, as on plot 5, mixed mineral 
manure and ammonia-salts in the eai-lier years. 
But the point which it is the chief object of Diagram II. 
to illustrate is, the very different effect of a given amount of 
ammonia-salts according to the supply of available mineral con- 
stituents within the soil. 
During each of the 12 years, plots lOer, 10b, 17 or 18, and 7, 
each received exactly the same amount of ammonia-salts ; and, 
taking the results of each year separately, the qrder as to amount 
of produce is, invariably — plot 7 (highest), 17 or 18, 10Z>, and 10a 
(lowest) ; that is, the lowest where the mineral constituents were 
the most exhausted, and the highest where their supply was most 
liberal. 
The point is also well illustrated by reference to the average 
annual results over the 12 years. Thus, the average annual 
increase (over the unmanured produce) was : — on 10a, with 
ammonia-salts alone (not only each year of the 12, but for seven 
years previously), 7-J- bushels of dressed corn, and nearly 8J cwts. 
of straw ; on lOj, also with ammonia-salts alone every year of the 
12, and for some years previously, but with mineral manure in two 
of the seven preceding years, nearly \\\ bushels of dressed corn, 
and V&\ cwts. of straw ; on 17 or 18, where ammonia-salts each 
year succeeded mineral manure, 17-^ bushels of dressed corn, and 
nearly 18f cwts. of straw ; and, lastly, on plot 7, with the ammonia- 
salts and mixed mineral manure used each year together, 
ncarlv 21 bushels of dressed corn, and 22f cwts. of straw. 
With the same amounts of ammonia-salts, therefore, there was 
a difference in the amount of increase of produce annually ob- 
tained of from 7i bushels of dressed corn and nearly 8-J cwts. of 
straw, to 20£ bushels of corn and 22f cwts. of straw, according 
to the supply of available mineral constituents within the soil. 
There was a difference of from 7^ bushels of corn and nearly 8^- 
cwts. of straw, to nearly 11J bushels of corn and 12£ cwts. of 
straw, due to the application of mineral manure twice in the 
earlier years of the experiments (10b) ; and there was a difference 
