10 May, 1916. 



Results of Experiments, 1915. 



289 



Why, it may be asked, need we manufacture at considerable cost 

 superphosphate from insoluble phosphates if this process of reversion 

 takes place sO' quickly in our wheat lauds. The explanation is probably 

 as follows : — 



Before the superphosphate reverts the soluble phosphate, which is its 

 essential constituent, becomes dissolved in the soil water, and assumes 

 a form infinitely nioi-e minute than can ever be attained by mechanical 

 grinding. In this minute form it gets distributed evenly throughout the 

 surface soil. Its superiority is due to its fineness of subdivision and its 

 intimate diffusion through the soil. 



Reversion of the water soluble phosphate takes place shortly after 

 application of the super, to the soil; but wherever the root hairs of tlip 

 plant may penetrate small quantities of citrate soluble phosphate in the 

 most minutely subdivided form are everywhere awaiting absorption. 



For the past three years tests have been conducted at the State 

 Farms with the object of finding out the most profitable rate at which 

 superphosphate could be applied per acre, and the results are sum- 

 marized in the following tables. 



The results are interesting inasmuch as they show the gross returns 

 and net profits per acre (1) in wet seasons and (2) over an average of 

 years. 



The results in the case of Rutherglen are on an average of four 

 years, and those of Werribee and Longerenong for three years. 



Returns from Plots treated wiih Light and Hsavy Dressings oi Superphosphate, 



Season 1915. 



No raaiiuro 

 i cwt. Supcir. 



1 cwt. Supor. 



2 cwt. Super. 



H\itlirr^U>n. 



6-0 

 10-8 

 15-6 

 12-0 



20-0 

 27-5 



28-75 

 28-0 



Lon^crenons;. 



37-5 

 49-4 

 51-3 

 54-7 



Avprajjc Returns 



from 



Thrc- Cciitrt'S. 



21-0 

 29-2 

 .SI -9 

 3r() 



II. 



Average Yields for three seasons (1913 15) from Light and Heavy Dressings 

 of Superphospiiaie. 



