8 Feb., 1907.] Artificial Manures Acts. 109 



Table II. 



UNIT VALUES OF FERTILIZING INGREDIENTS IN MANURES FOR CALIFORNIA 

 AND MASSACHUSETTS, CONNECTICUT, RHODE ISLAND, MAINE, VERMONT, 

 AND NEW JERSEY STATIONS. 



Other States 



The practical utility of the unit value system is that it enables a farmer 

 to readily ascertain if the price asked for a manure is its reasonable com- 

 mercial value. The term used the "commercial value" must not be 

 confused with the " agricultural value " of a manure. They are quite 

 distinct. The commercial value represents the value of a manure according 

 to its composition. The agricultural value of a, manure is measured 

 by the extent of the increase in quantity and quality produced bv it in 

 a particular crop grown in a particular soil, under certain conditions. 

 The agricultural value of a manure may vary quite extensively. A parti- 

 cular soil, for instance, may not give an increased crop return after applica- 

 tion of nitrogenous manures commensurate with the cost of the fertilizer. 

 On another soil an application of superphosphate may not increase the 

 yield. In both instances the manures would have no positive agricultural 

 value. A practical illustration of this point is afforded by the effects 

 of ordinary applications of nitrogenous manure in wheat-growing in the 

 northern areas. Such applications are generally unremunerative. 



The "commercial value" of a manure is determined bv the percentage 

 of certain constituents in its possessing fertilizing properties and their unit 

 value. The assumption is made that the manures are all prepared from 

 materials of the same quality and value, but this is not strictly in accord 

 with practice as each manufacturer has his own source of supply of 

 materials. In the table of unit values it will be seen that that the value for 

 citrate soluble phosphoric acid is quoted as 6d. less per unit than the 

 water soluble. The general result of Victorian experiments shows that 

 water so'luble phosphoric acid has a higher agricultural value in wheat grow- 

 ing that citratle soluble phosphoric acid, and it is generalK' assumed that its 

 solubilitv enables it to come more easily within range of plant roots. In 

 any case, after application to the soil, the water .soluble phosphoric acid 



