60 



EXPEULMEXT STATION. 



[Jan. 



There were a few brauds showiug rather serious deficiencies 

 in some element of plant food, but which did not suffer a com- 

 mercial shortage on account of an overrun of some other ingre- 

 dient. Such brands, of course, may be seriously out of balance, 

 and while not excusable, the manufacturer evidently had no 

 intention to defraud. 



Quality of Plant Food. 



As a general rule the ])()tasli and phosphoric acid were fur- 

 nished in the forms guaranteed. 



It is hoped that methods of analysis may soon be perfected 

 so that it will be possible to indicate the relative availability 

 of the organic nitrogen in mixed fertilizers. The importance 

 of this may, in a measure, be realized when it is remembered 

 that nearly 45 per cent, of the nitrogen used in the complete 

 fertilizers this year was derived from organic sources. 



Grades of Fertilizer. 

 The following table shows the average comparative commer- 

 cial values, the retail cash prices and the percentages of 

 difference of the licensed complete fertilizers analyzed in 

 Massachusetts during the season of 1909 and 1910, grouped ac- 

 cording to commercial valuation. Those having a valuation of 

 $18 or less per ton are called low grade; those having a valua- 

 tion of between $18 and $24 are called medium grade; and those 

 having a valuation of over $24 are called high grade. 



The percentage of difference column becomes a convenient 

 method of comparing the commercial worth of fertilizers of the 

 same grade and cost, and usually indicates fairly the most eco- 



