142 Report of Experiments on the Growth of Wheat. 
On the other hand, it has been seen that those seasons which 
were the most favourable for the unmanured, or for the merely 
mineral-manured plots, were not at all the most favourable for 
those manured highly with nitrogenous manures — that is, for 
those conditions under which alone large crops could be obtained. 
Hence, the best season for land in low condition is not the best 
for land in high condition. 
But, by comparing the increasing or diminishing amount of 
produce from year to year, under very different conditions of 
manuring, a very fair judgment of the relative character of the 
earlier and the later seasons can be formed. To this end there are 
given at one view in Table XXII. (opposite) the average annual 
produce without manure, with ammonia-salts alone, and with 
farmyard manure, respectively over the first half, the second half, 
and the total period of the experiments ; and also the average 
annual produce without manure, with mixed mineral manure 
alone, with ammonia-salts alone, with ammonia-salts and mixed 
mineral manure, and with farmyard manure, over the first six, 
the last six, and the total of the last twelve years of the 
experiments. 
Taking first the whole period of the experiments (twenty years 
without manure and with farmyard manure, and nineteen with 
ammonia-salts alone), there is, without manure a slightly, though 
very slightly, increased annual produce of corn and total pro- 
duce (though not of straw) over the last half as compared with 
the first half of the period ; with ammonia-salts alone there is 
a decreased, and with farmyard manure a very much increased, 
rate of produce in the later years. 
Thus, where the crop was simply dependent on the soil and 
season, the produce was somewhat higher in the later years ; 
where the resources of the soil were overtaxed by the use of a 
large amount of ammonia-salts every year, the produce dimi- 
nished ; but where an excess of every constituent was annually 
applied, the crop enormously increased as the experiment pro- 
ceeded. 
Referring to the results obtained over the last twelve years 
only, the latter half of that period gives, without manure, as much 
corn, but scarcely as much straw as the former half; with 
mixed mineral-manure alone (the condition nearest allied to the 
unmanured) there is a diminution, more particularly in the 
produce of straw, in the later years ; with ammonia-salts alone 
there is also a diminution, both of corn and straw, but in a some- 
what less degree than when the whole period of twenty years is 
taken into the calculation. With ammonia-salts and mixed mine- 
ral manure together, there is a considerable increase of corn, and, 
