14 Experiments with different Top-dressings upon Wheat. 



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 succeeding crop. All the more important 

 mineral constituents which are required for the growth of wheat 

 must 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 

 be richer in this important fertilizing 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 

 benefit 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 

 clay, 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- 

 position 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- 

 dressing ; 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- 

 ducing 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 



