FERTILIZERS. 11 



product is then ground to a coarse consistency. It is sold as fertilizer when it has 

 served its usefulness in the process of clarifying syrups. 



Bone-ash that is sold as a fertilizer consists of burnt bones. 



Bone-tankage consists of refuse from slaughter-houses. 



Basic slag, a by-product of iron-smelters, is known by several names, as iron 

 phosphate, Thomas phosphate, odourless phosphate, and phosphatic slag. The 

 phosphoric acid in basic slag is often rated as valuable as the phosphoric acid in 

 bone-meal. The composition is variable, depending upon the composition of the iron 

 ore. The lime content of this material adds to the value on acid soils. 



The phosphoric acid in ground rock phosphate is the least available of the raw 

 phosphates. (Section (a) of the above table.) The composition and the fineness 

 of the material determines its value. 



Availability of the Raw Phosphates. The raw phosphates are slowly available 

 as plant-food and practically insoluble in water. The phosphoric acid is not entirely 

 used the first year, so the maximum returns cannot be expected immediately. For 

 quick-growing crops the raw phosphates are not always desirable. 



SUPERPHOSPHATES. 



Many of the raw phosphates are treated with sulphuric acid to render the 

 phosphoric acid more available. The commonest of these is the acid phosphate or 

 superphosphate of lime. The composition is variable, depending upon the phosphate 

 ore from which it is manufactured and upon the process of manufacture. 



There seems to be a great deal of confusion among farmers as to what con- 

 tributes available phosphoric acid. Chemists usually class the phosphoric acid 

 soluble in water as "soluble," and the phosphoric acid soluble in citrate acid as 

 " reverted." The sum of the two is the " available phosphoric acid." For all 

 practical purposes the farmer in purchasing superphosphate need only to consider 

 the percentage of available phosphoric acid. 



Dissolved bone-black is manufactured by treating bone-black with sulphuric acid. 



The double superphosphates are not frequently found in the market in this 

 country. It is manufactured by treating high-grade phosphate rich with sulphuric 

 and phosphoric acid in solution. 



The phosphatic manures as a whole are very variable in composition. Their 

 value should be based on a guaranteed analysis. Owing to the acid nature of the 

 superphosphates they should not be applied to sour soils. Liming should precede 

 an application of superphosphate. When immediate returns are expected the super- 

 phosphates are superior to the raw phosphates. 



POTASH MANURES. 



Until the discovery of the potash-mines in Germany in I860 wood-ash was the 

 chief source of this constituent as a fertilizer. Until the recent European conflict 

 practically all the potash salts used as fertilizers throughout the world came from 

 the German mines. The war stimulated the development of other supplies. It 

 would be difficult to say whether the supplies from the newly developed sources are 

 to become permanent. 



The following table includes the principal potash fertilizers : 



Actual Potash. 

 iv r Cent. 



1. Kainit 12.5 



2. Sylvinit 32-15 



3. Muriate of potash 50 



4. Sulphate of potash 50 



5. Double sulphate of potash and magnesium 2G 



6. Potassium magnesium carbonate 20-25 



7. Wood-ashes 5-6 



' 8. Kelp or seaweed (dried sample) 12 



(ash) 20-30 



