702 Journal of AgricuUurc , Victoria. [[i Nov., 1912. 



made available. Ilenee, in the preparation of bonedast, the fat is 

 first removed from the bones by steaming or by treatment with benzine, 

 and the treated bone ground to fine. meal. 



The value of a bonedust will depend on its composition and its 

 fineness of subdivision. The purchaser should always insist on a 

 guaranteed analysis for b(medust. for there is no fertilizer on the 

 market so liabh^ to vary in composition like the so-called bone 

 fertilizers. 



The phosphoric acid in bonedust is in a most insoluble condition. 

 It is only very slowly made available in the soil, and therefore it has 

 a very limited use in most of the wheat areas. It gives best results 

 on soils rich in organic matter, for with these there is a possibility 

 of the insoluble phosphate being slowly made available. On limestone 

 soils in the drier districts, however, it has been proved of little value, 

 because it takes so long for the tricalcie phosphate to be rendered 

 available. 



Other sources of phosphoric acid are the phosphatic guanos and raw 

 ground i)iiosphate rock. In both these substances the phosphoric acid 

 is insoluble, and they are of very little value in the majority of our 

 Avheat areas. 



Potash Manures. ~ 



Potassic manures do not figure very largely in Australian manu- 

 rial practice. ^lost of the strong soils characteristic of the wheat areas 

 are well suj)plied with potash, and further supplies in the form of 

 artificial manures are generally unnecessary. There are some soils, 

 however, on which potash may possibly be of considerable benefit. 

 These are the light, sandy loams, and possibly heavy, j)eaty soils. 

 Dressings of potash are fre([uently necessary to secure a full crop from 

 these soils, more especially with root crops such as potatoes, onions, 

 beets, &e. On the clay loams and stiff clay soils of the wheat areas, the 

 application of potassic manures is generally unnecessary and unprofit- 

 able. This may be gathered from the results of many field experiments 

 conducted by the Department some ten years ago. The addition of 

 potassic manures to phosphates did not materially increase the yield. 

 In fact, in many cases the effect of the application was to depress the 

 yield, and resulted in actual loss. 



The principal potassic manures are Sulphate and JMuriate of 

 potash and kainite. These are obtained from the Stassfurt potash 

 mines which form the principal source of the world's potash. 



Sulphate of potash contains from 50 to 52 per cent, of potash, and 

 costs from £13 to £14 per ton. 



Muriate of potash contains an equivalent of 60-62 per cent, of 

 potash, and is quoted from £14 to £14 10s. per ton. 



Kainite is (me of the crude potash minerals of the Stassfurt mines. 

 Its composition varies considerably, but it generally contains from 

 12-13 per cent, of potash, most of which is in the form of sulphate, 

 whilst a lesser quantity is present as chloride. It is quoted at £5 per 

 ton. 



Potash is required in, fairly large c^uantities by leguminous plants, 

 such as clover and lucerne, but the drain on the soil reserves of potash 



