Experiments with different Top-dressinr/s 7ipon JVhcat. 597 
the rain into the subsoil or drainage water; for soils do not 
possess the power of retaining nitrates. Supposing any nitrate 
of soda to have been left in the soil, it is not likely to produce 
any effect on the succeedins; crop. All the more important 
inineral constituents which are required for the growth of wheat 
jnust be furnished by the soil top-dressed with nitrate of soda. 
The amount of available mineral fertilizing matters in the soil, 
therefore, will be less after the removal of the wheat-crop, and 
the soil will be found, I think, in a poorer condition. 
The portions of land top-dressed with guano and wheat- 
manure, on the other hand, were supplied not only with ammo- 
niacal salts and nitrogenized organic matters, but also with 
valuable mineral matters — such as phosphoric acid, sulphuric acid, 
and alkalies. On calculating the proportion of phosphoric acid 
which is removed in the produce of Plot I., I find that the guano 
supplies more phosphoric acid than is removed in the produce of 
corn and straw. After harvest, therefore, the land will actually 
1)6 richer in this important fertilizino: matter than it was before 
the application of guano. Again, I question very much whether 
the total amount of nitrogen in guano and in the wheat-manure 
will be used up in the growth of one wheat-crop. It appears to 
me more likely that some will remain in the soil, ready to 
l)enefit the succeeding crop. However, this point can only be 
decided by direct experiments. Unlike nitrates, ammoniacal 
matters are retained in all soils containing a fair proportion of 
t lay, which circumstance is of course in favour of guano and 
ammoniacal manures in general as top-dressings for wheat. 
Since, then, guano and artificial manures, resembling in com- 
jiosition the wheat-manure used in my experiments, supply the 
wheat-crop with constituents which must be furnished entirely 
by the soil when nitrate of soda alone is employed as a top- 
<lressing; and since an excess of ammoniacal matter will be re- 
tained in the soil, whereas an excess of nitrate is subject to loss ; 
I am inclined to think that the land dressed with guano and 
Proctor's wheat-manure will be left in a better condition than the 
plots manured with nitrate of soda. On the whole, I am of 
opinion that in the recorded experiments the wheat-manure and 
guano have proved to be preferable as top-dressings to nitrate of 
soda. However, nitrate of soda is an excellent material for pro- 
<lucing a rapid improvement in sickly-looking wheat. We have 
used nitrate of soda last season with great advantage on our farm. 
A slight sprinkling with a mixture of nitrate of soda and salt causes 
a marvellous improvement in poor, thin, yellow-looking wheat. 
On the thin brashy soils in our neighbourhood the young wheat 
is apt to turn yellow and sickly in dry springs, especially on the 
brows of hilly fields: nothing can be better in such a case than 
