ii8 



Journal of Agriculture. 



[lo Feb., 1910. 



The Purchase of Superphosphate. 



Memorandum by the Hon. George GraJiam, M.L.A. 



The Department of Agriculture numbers among its manv functions, 

 that of guide and protector of the farmers' interests, especially in regard 

 to matters involving a complicated estimation of commercial worth. In 

 the use of artificial manures, the Department has done much ser\ice in 

 educating the farmer by means of lectures, demonstrations, and Journal 

 articles, to understand that the value of such materials depend entirely 

 upon their solubility and consequent availability to the crops to which thev 

 are applied. 



INIanures, nowaday.^, are looked upon as an absolutely essential item 

 in the cost of crop production, and any falling off in the quality must be 

 regarded with apprehension unless there is an equivalent reduction in the 

 price of the material. It has been frequently pointed out that the agri- 

 cultural value of a manure may differ widely from its commercial value, 

 for the reason that the former is regulated by soil and climatic conditions 

 over which the farmer has little control, whereas the latter is measured by 

 the trade values of the i)lant foods present according to their degree of 

 availability. 



The farmer is more concerned with the commercial value of suferphos- 

 fhate than most other forms of artificial manure and the purpose of this 

 article is to draw attention to the rise in value of the insoluble phosphoric 

 acid as compared with that in previous years. As has been stated, the value 

 of a manure depends upon its solubility and consequently thorough distri- 

 bution throughout the soil, as well as its easy availability by the plant. 

 The term "insoluble" implies a material of little service to the crop to 

 which the manure is applied, and hence should only have a low commercial 

 value. It has been the policy of the Department to discourage any more 

 than a very small amount of insoluble phosphoric acid in superphosphates 

 by the giving of only a nominal value per unit. 



The unit values under the Artificial Manures Act have been calculated 

 from the average qualities of the samples forwarded by vendors for 

 analvsis under the terms of the Act. 



The effect of the increa.se of value for insoluble phosphoric acid in super- 

 phosphates is likely to have an appreciable influence upon the qualitv of 

 superphosphates sold in the future, for the reason that it opens up the 

 way for a reduction of the water soluble phosphoric acid and the increase 

 of the insoluble phosphoric acid, without altering the total quantity con- 

 tained in the manure. 



It is admitted by all competent authorities that it is the water soluble 

 phosphoric acid which gives value to superphosphate. The acid is made 

 in a quickly soluble form in order that it mav become thoroughly and 

 rapidly distributed throughout the soil. If there is any fairly large amount 

 of insoluble phosphoric acid it stands to reason that this portion cannot 

 readily come in contact with the .soil particles and hence is of practically 

 no service to the crop to which the manure is applied. 



