PROFITABLE FARMING 13 



contain but little. By placing available phos- 

 phates within the reach of young plants, we are 

 simply acting on a hint given " by Nature, in 

 the care she takes to provide young plants in 

 their earliest periods of existence with a con- 

 stituent which possesses so remarkable an effect 

 in pushing on the young plants." 



The three kinds of phosphates best known 

 in agriculture are : 



Insoluble phosphate, to which class the 

 natural mineral phosphates belong. These 

 are insoluble except in strong acids. 



Citric soluble phosphate, which, though not 

 soluble in water, is more or less available and 

 assimilated by the plants in course of time. 

 Basic slag, precipitated phosphate, steamed 

 bone flour, undissolved bone phosphate are 

 representative of this class. 



Water-soluble phosphate, to which super- 

 phosphate, dissolved or vitriolated bones be- 

 long. 



Phosphates are most advantageously supplied 

 in the form of superphosphate, bones, either 

 ground to powder (bone meal or steamed bone 

 flour) or treated with acid (dissolved or vitrio- 

 lated bones), and basic slag. 



Basic Slag 



Basic Slag is a by-product formed in the manu- 

 facture of steel from low-grade pig iron. The 

 phosphates are in a form which, though insoluble 

 in water, are largely soluble in a standard solu- 



