304: EGYPTIAN AGRICULTURE. 



an analysis, which should also indicate the fineness of 

 grinding. /.This ought always to be such that at least 

 80% of the sample passes through a sieve of 10,000 meshes 

 to the square inch, i. e. about 1500 meshes per square 

 centimetre, as the availability of the manure is greatly 

 influenced by its state of division. 



Tetracalcic phosphate is a more soluble substance than 

 tricalcic phosphate for, although both are practically insol- 

 uble in pure water, the former readily dissolves in certain 

 solutions in which the latter does not, e.g. in solutions of 

 ammonium citrate and to a less degree in carbon dioxide 

 solutions. Basic slag is therefore a more rapid manure 

 than ground mineral phosphate, both being applied in 

 the same degree of fineness. 



On account of its basic character it is best suited for 

 land high in organic matter and low in lime. When applied 

 with soluble nitrogen this latter should be in the form of 

 nitrate as the free lime of slag rapidly drives off ammonia 

 from ammonium sulphate. This free lime and also the 

 oxide of iron present have also the effect of causing a large 

 reversion of soluble phosphate if by any chance the powder 

 is mixed with super. From its nature, basic slag is a 

 manure the effect of which extends over several years, 

 Applications run from one hundred and fifty to three 

 hundred kilograms per feddan. 



Basic slag has till now been used only to a limited 

 extent in Egypt. It costs from 250 P.T. to 300 P.T. 

 per ton according to quality. 



