On tlic Composition of Waters of Land-Drainarje. 1()5 



'Considerable when nitrate of soda is applied to the land as a 

 top-dressing for wheat. 



13. The drainage from the unmanured parts of the Experi- 

 jnental Wheat Fields, as well as the manured plots, contained 

 appreciable quantities of nitrogen in the shape of nitrates, 

 riiere is, consequently, a loss of nitrogen by drainage, whether 

 nitrogenous manures, ammonia-salts, nitrate of soda, or no 

 manure at all is applied to the land. 



14. The fertility of land is more readily impaired l)y the loss 

 /)f nitrogen by drainage, than by the removal in that manner of 

 those mineral matters which are food to plants. 



15. Inasmuch as a considerable proportion of the nitrogen 

 .supplied by manure is wasted by drainage, much more nitro- 

 genous food must be applied to the land than would appear 

 necessary on theoretical grounds to produce a given increase in 

 the crop. 



1(5. Nitrates are invariably found at all times of the year in 

 the watery liquid which circulates in the land, whereas ammonia- 

 salts are never found in any appreciable quantity in that liquid. 

 It may, therefore, be assumed that it is chiefly, if not solely, 

 from nitrates that our crops build up their nitrogenous organic 

 -constituents. 



17. It follows from the preceding paragraph that farmyard- 

 manure fresh from the stables, or cattle sheds, as pointed out by 

 practical experience, is best applied in autumn or winter. The 

 manure will then have time to become rotten, and, by degrees, 

 the nitrogenous constituents of the manure will become trans- 

 formed into nitrates, of which there will be a ready supply in 

 spring when vegetation makes a fresh start. 



18. Ammonia-salts and other ammoniacal manures, as a rule, 

 should not be applied to the land in autumn, but they may be put 

 upon the land earlier in spring than nitrate of soda, with less 

 risk of being washed into the drains. Probably the end of 

 February, or beginning of March, is the best time for the appli- 

 cation of ammoniacal dressings. 



19. Nitrate of soda should be applied later in spring, and, 

 generally speaking, the middle, or end of March, appears to be 

 the best time in average seasons for the application of nitrate of 

 soda as a top-dressing for cereal crops. 



Lahoratory, 11, Sallshiiry-square, Fleet-street, London, E.C., 

 Febriuiry, 1874. 



