Report of Experiments on the Growth of Wheat. 457 
Assuming, as doubtless was the case, that at the commencement 
the 3 plots were practically in very nearly the same condition of 
productiveness, it might be supposed that the mixed mineral 
manure applied each year after ammonia-salts, as on plots 17 or 
18, thus providing the most favourable conditions for the pro- 
ductive effect of the unexhausted nitrogenous residue, would 
give a considerable increase beyond that 1 on plot 5, where the 
mineral manure each year succeeded mineral manure. Table 
XXVI. shows, however, that plots 17 or 18 gave annually only 
about i bushel of corn, and f cwt. of straw more than plot 5. 
Yet the average increase obtained in the years of the application 
of the ammonia-salts on plots 17 or 18, though always succeed- 
ing the mineral manure, would carry off little more than one- 
third of the nitrogen supplied ; whilst, as the next Table 
(XXVII., p. 458) shows, this increase was considerably less 
than when the ammonia-salts were used in conjunction with, 
instead of in succession to, the mixed mineral manure. 
Thus, in the course of 12 years, an annual supply of 400 lbs. 
of ammonia-salts, each year succeeding the mixed mineral 
manure, gave 45 bushels less corn, and 5475 lbs., or nearly 49 
cwts., less straw, than the same amount of ammonia-salts used 
each year in conjunction with the mixed mineral manure — being 
an average annual deficiency of about 3J bushels of corn, and 
rather more than 4 cwts. of straw, where the ammonia-salts were 
used in the year after, instead of with the mineral manure. 
Even adding the average annual increase (over the unmanured 
produce) by the ammonia-salts succeeding the mineral manure, 
to that by the mineral manure succeeding the ammonia- 
salts, the amount scarcely reaches that obtained where the two 
manures were used in conjunction. That is to say, the influ- 
ence of the mineral manure succeeding the ammonia-salts seems 
to have been to render practically available, at any rate no more 
of the unrecovered residue of the supplied nitrogen than brought 
up the increase in two years to that attainable in the one year 
when the two manures were used together, the whole of the 
remainder being still unaccounted for, so far as the immediate 
increase of crop is concerned. 
The facts brought to view in the last five Tables (XXIII. — 
XXVII. ), are of great scientific interest, and of great practical 
importance. 
It has been alleged by Baron Liebig that, in some of our experi- 
ments, there has been so much more nitrogen annually applied 
in manure than taken off in the increase of crop, that after a few 
years the increase obtained on a further addition was not at all 
due to the new supply, but would have been the same without it, 
