96 



NITROGENOUS MANURES 



[chap. 



were of service to the succeeding crop, while little 

 benefit was derived from the preceding year's application 

 of nitrate of soda. With barley the residues from both 

 manures were more pronounced. 



Table XXVIII.— Effect of Nitrate of Soda and Ammonium 

 Salts applied in the Previous Year. Woburn (1882-1886). 



Plot. 



4 

 ia 



93 



Maunring. 



Wheat. 



Minerals only . 



Minerals + Residue of Ammonium 



Salts ...... 



Minerals + Ammonium Salts . 

 Minerals + Residue of Nitrate of 



Soda 



Minerals + Nitrate of Soda 



Bushels. 

 18.3 



20-4 



42.8 

 I7.I 



40-9 



Barley. 



Bushels. 

 24-6 



37-0 

 55-5 



34-5 

 59-9 



This essential difference in the results at Rotham- 

 sted and Woburn arises from two causes ; in the first 

 place, the soil at Woburn is very deficient in carbonate 

 of lime, indeed at a later date than the period from 

 which the figures in the table are quoted the soil of the 

 barley plots had become so acid that the crop would no 

 longer grow. Under these conditions nitrification will 

 be very slow and some of the ammonium salts will be 

 retained unchanged in the soil until the following season, 

 instead of nitrifying and so getting into a form that 

 will wash through the soil. Thus the ammonium salts 

 will leave a much greater residue than the nitrate ; 

 that the latter has any effect in the following season 

 must be set down to the texture of the fine sandy 

 loam at Woburn, which admits of a much greater capil- 

 lary rise of the soil water than is possible in the close 

 Rothamsted soil, with the result that some of the 

 nitrates which have been washed down during the 

 winter are brought back to the surface. 



