PHOSPHATIC MANURES 125 



experimental evidence goes to show that 

 there is little difference in the effects of the 

 two new substances, preference may on the 

 whole be given to nitrate of lime, which, being 

 a natural plant food, is at once available for 

 the use of crops. 



As regards such a source of nitrogen as 

 Rape Meal or Dried Blood, it may be said 

 that, as a rule, the unit value on the market 

 is much too high ; and, moreover, the 

 nitrogen content (about 5 per cent, in the 

 case of Rape Meal) is so low that the cost 

 of carriage and carting is relatively high. 

 The nitrogen, too, is in the organic form, 

 and slower in its action than any of the 

 four nitrogenous manures mentioned above. 

 The circumstances must be very rare where 

 a farmer would be justified in purchasing 

 rape meal or dried blood as a source of 

 nitrogen. 



CHAPTER VI 



PHOSPHATIC, PHOSPHATIC-NITROGENOUS, AND 

 POTASSIC MANURES 



COMING now to a second group of artificial 

 fertilizers, we may consider the leading forms 



