CHAPTEK VIII 



PHOSPHATIC MANURES 



PHOSPHATES are by far the most popular and most 

 extensively used of all the special or so-called artificial 

 manures. The history of their introduction dates hack 

 to the time towards the latter end of the 18th century 

 when bones were first used in this country. The manurial 

 value of bones was soon recognised, and in 1840 Liebig 

 proposed to hasten their action by treating them with 

 sulphuric acid. A couple of years later, Lawes applied 

 the same process to coprolites and mineral phosphates, 

 and took out a patent for the manufacture of what are 

 now called superphosphates. Since that time the use of 

 phosphatic manures has steadily increased, and enormous 

 quantities are now consumed annually. It is scarcely 

 too much to say that, in this country at least, phosphatic 

 manures have come to be regarded as practically indis- 

 pensable in modern farming, and that their use is con- 

 sidered almost as natural as that of farmyard manure 

 itself. 



NATIVE PHOSPHATES. 



Use of Native Phosphates as Manure. The native 

 phosphates have been used to some extent, directly, as 

 manures and it has been demonstrated that, when finely 

 ground, they may have a distinctly favourable effect on 

 the growth of crops. Owing to their comparative in- 

 solubility, however, their action is necessarily slow, 

 though it may be more rapid than was at one time 



