Pkoc. Rot. Soc. Victoria, 2 8 (X.S.i. Part II., 19K 



Art. XIII. — Phosphate Fertilisers. 

 Bv BRENDA SUTHERLAND, B.s«. 



Bead Oth September, 1915]. 



The most important artificial manures used in Australia are- 

 those supplying phosphorus. Potassium and nitrogen applications 

 are of occasional value only, but even small quantities of super- 

 phosphate may double or treble the yield. Experiments have shown 

 superphosphate to be more effective than either bone dust or basic 

 slap:, but it remains to be seen if superphosphate is the best obtain- 

 able fertiliser. It. of course, precipitates as normal calcium phos- 

 phate in the presence of soil lime, and always tends to sour the 

 soil. A neutral fertiliser in which this precipitation did not occur 

 might be less deleterious and more effective, because more readily 

 available. 



Metaphosphates and pyrophosphates were the most obvious com- 

 pounds to try. as the results obtained from them by previous 

 investigators seemed indecisive. FL r L r ertz and Nilson (Bied. Cent.. 

 1893) gives potassium metaphosphate as being two per cent, less 

 effective than potassium dihydrogen phosphate. Nilson (Bied. 

 Cent., 1894) gives potassium metaphosphate and potassium ortho- 

 phosphate as equally effective, and Marcker (Bied. Cent.. 189E 

 records that potassium metaphosphate gave good results with barley. 

 original papers were not available, but-, judging from the 

 abstracts, the authors do not state which polymer of potassium 

 metaphosphate was used. There are six polymers known, and 

 among them trimetaphosphate (which is difficult to obtain and there- 

 fore not likely to have been used), is sharply marked off by the 

 solubility of all its salts. So while all the other metaphosphates 

 would, by double decomposition with the calcium carbonate of the 

 soil, produce insoluble calcium salts, calcium trimetaphosphate 

 would remain in solution, and so be immediately available. 



Field experiments were therefore run. in which sodium ortho- 

 phosphate, sodium pyrophosphate, and sodium trimetaphosphate 

 • ciupaied with one another, and with ordinary superphos- 

 phate. For the management of the plots I have to thank Mr. 

 Whelan, Field Officer, and Mr. Adcock. Principal of the Ruther- 



