530 



Basic Slag: Second Interim Eeport. [Sept., 



soluble slags is taken as 100 then the fluorspar basic slags have 

 a value of from 50 to 70. 



2. Rock Phosphates. — The results of all the experiments agree 

 in showing that rock phosphates have a much higher manurial 

 value than has hitherto been admitted. On sour soils and where 

 the rainfall is high there is a certain amount of evidence which 

 suggests that they may even prove superior to the best grades 

 of basic slag. Even under conditions which favour high solu- 

 bility (low rainfall and a sweet soil), as at Horn don, their 

 value as a source of phosphate for the manuring of grass land 

 is very close to that of high soluble basic slag. In every experi- 

 ment they have proved more effective than the open hearth 

 fluorspar slags. 



Of the various types of rock phosphate Gafsa seems to be the 

 most suitable for direct application. There is evidence that on 

 sweet soil, or where the rainfall is low, the more soluble types of 

 North African phosphates, e.g., Gafsa, ^^gyptian, Algerian, and 

 Tunisian, are superior to the richer, less soluble and harder 

 types such as Florida Pebble. 



****** 



BASIC SLAG: 



SECOND INTEEIM EEPOET OF THE PEEMANENT 

 COMMITTEE.* 



The Permanent Committee recently presented to the Minister 

 the following second interim report on their experiments and 

 deliberations during 1921 : — 



The reference given us was to consider the development and 

 improvement of the manufacture of basic slag and the extension 

 of its use. In considering these questions we have been com- 

 pelled to give some attention to other phosphatic manures (viz., 

 raw phosphates) both from the point of view of their being mixed 

 with basic slag so as to supplement supplies of the latter, and also 

 of ascertaining how various grades of basic slag compare with 

 raw phosphates in agTicultural value. 



The basal facts in the situation are as follows : — 



1. Demand for Basic Slag. — The demand for ground basic 

 slag by the farmers of the United Kingdom has increased since 

 the pre-war period (1912) from 290,000 tons to some 400,000 to 

 500,000 tons (with phosphate content of 11,000,000 to 12.500,000 

 units) per annum, and in the view of competent agricultural 



* An abstract of the First Interim Report appeared in the September, 1921, • 

 issue of the Journal, p. 521. 



