290 Report of Experiments on the Growth of Barley, 
having nitrate received, in the first year of the twenty, 3J cwts. 
of superphosphate of lime, and 300 lbs. of sulphate of potass, per 
acre. These mineral manures gave no increase whatever in the 
year of their application; but, under the exhausting process of 
afterwards using nitrogenous manures alone for so many years 
in succession, they have doubtless had considerable effect on the 
succeeding crops. Hence, unfortunately, the two experiments, 
the one with a given amount of nitrogen as ammonia-salts for 20 
years, and the other with the same amount as nitrate of soda for 
the last 19 of the 20 years, are not strictly comparable. (Table 
XXXI. next page.) 
In the first place, notwithstanding the great demand made on 
the mineral resources of the soil, by applying ammonia-salts alone 
year after year, there is considerably less falling off in the produce 
over the second as compared with the first ten years, under such 
treatment, than by the application of mixed mineral manure alone 
every year. And not only so : whilst, over the twenty years, the 
average annual produce was, by the mixed mineral manure only 
27 J bushels of corn and 14^^ cwts. of straw, that by the 200 lbs. 
of ammonia-salts alone was 32^ bushels of corn, and 18^^ cwts. 
of straw. In other words, whilst the increase of produce by the 
mixed mineral manure alone averaged, over twenty years, only 6J 
bushels of corn and 2f cwts. of straw, per acre per annum, that 
by this comparatively small quantity of ammonia-salts alone ave- 
raged, over the same period, 11^ bushels of corn, and 6f cwts. 
of straw. 
Comparing the result by ammonia-salts for 20 years, with that 
by the same quantity of nitrogen as nitrate of soda for 19 years, 
the average annual produce and increase are b\ bushels of corn, 
and 44 cwts. of straw, more by the nitrate than by the ammonia- 
salts. 
It is obvious that, owing to the greater solubility, and more 
rapid distribution in the soil and subsoil, of the nitrate or its 
products of decomposition, it will be the more liable to loss by 
drainage when there is an excess of rain. On the other hand, as 
already referred to (p. 140), the subsoil in its case becomes more 
disintegrated, therefore more porous, more retentive of moisture 
in a favourable condition, and more permeable by the roots. It 
is, probably, in part due to this action that the effects of a 
given amount of nitrogen as nitrate of soda increase from year to 
year compared with those of an equivalent application as am- 
monia-salts. How much of the greater effect of the nitrate in 
the experiment in question may be due to this action, and how 
much to the supply of mineral manure to the nitrated plot in the 
first year, it is impossible to determine. 
On the latter point it may be mentioned, that the amounts of 
