•'^S Journal of Agriculture, Victoria. [10 Jan., 1919. 



multiply these percentages by tJieir unit value, and add together the 

 products. 



Nibrogen . . 3" 16 % x ^Vo = 1*327 % as fine bone 



• . 3-16 % X yVV = 1'833 % as coarse bone 



Phosphoric acid 20-20 % x ^Vo = 8' 484 % as fine bone 



„ 20-20 % X xVo = 11-716 % as coarse bone 



Unit Value per 



Per cent. Value. tou. 



.-. 1-327 X 16/- = £113 



1-833 X 14/- =15 9 



8-484 X 5/- = 2 2 5 



11-716 X 4/3 =299 



Value per ton .. £6 19 2 



From time to time attention has been directed to the difference 

 between a bonedust and a bone fertilizer. As this is a subject of 

 special importance to the user of fertilizers made from bones, and as 

 bone fertilizers have been placed on the market as a substitute for bone- 

 dust, I shall again, briefly, make reference to it. Bonedust is a ferti- 

 lizer made from either steamed or raw bones which have been cru.shed 

 or ground. The value of a bonedust depends largely on its content of 

 fertilizing ingredients, as well as on the relative percentages of fine and 

 coarse bone, and the greater the percentage of fine bone, the quicker 

 will be the disintegration of the bone in the average soil. Bone ferti- 

 lizers are largely mixtures of bones with other materials, such as 

 gypsum, marl, or superphosphate, and ground rock phosphate. They 

 usually show a lower content of fertilizing ingredients than bonedust, 

 while their high percentage of citrate insoluble phosphoric acid places 

 them at a further disadvantage when compared with a bonedust, and it 

 is gratifying to find that the demand for them is declining. Ground 

 rock phosphate contains a large quantity of phosphoric acid, in com- 

 bination with lime, in the least readily available form. Consequently 

 an addition or admixture of rock phosphate or any similar ingredient 

 tends to give any fertilizer a high percentage of citrate insoluble phos- 

 phoric acid. Therefore, before using bone fertilizers, farmers should 

 carefully note from the label accompanying it the percentage of citrate 

 soluble phosphoric acid it contains. 



