54 



EXPERIMENTS UPON WHEAT 



as dung during the whole period, only about 2600 lb. have 

 been recovered in the crop, or about 26 per cent., and that 

 although the nitrogen present in the soil at the end of the 



Table XVI II. 



period has been doubled, the excess over the manured plot is 

 only 2580 lb. per acre ; so that there is still 5670 lb. which 

 has been supplied in the manure, but is unaccounted for either 

 in the crop removed or in the accumulation in the soil. Some 

 of this has no doubt been washed away as nitrate into the 

 drains and the subsoil water, some has been removed in the 

 weeds, but much must have been lost by the conversion, 

 through bacterial action, of nitrogenous compounds in the 

 manure into free nitrogen gas. 



Phosphoric acid and potash, however, behave very differ- 

 ently from nitrogen ; but little of these substances are ever found 

 in the drainage waters, and Dr Dyer's analyses show that the 

 greater part of the excess of phosphoric acid supplied over that 

 removed in the crop is still to be found in the top 9 inches of 

 soil, where it remains in a condition readily available for the 

 plant. The potash is not quite so completely retained as the 

 phosphoric acid, and descends further below the surface. There 

 is still, however, no practical loss to be feared when potash is 

 applied to the land before there is any crop immediately able 

 to utilise it. 



E. Character of the Crop as affected by Manuring and Season. 



Table XIX. gives certain particulars regarding the quality of 

 crops grown during the last fourteen years, covering the years 



