CONFORMITY TO GUARANTEE 



The chemical analyses reported in this bulletin were made by the methods 

 adopted by the Association of Official Agricultural Chemists. 



Number of brands analyzed 114 



Equalling or exceeding all guarantees 64 



Deficient in nitrogen only 17 



Deficient in available phosphoric acid only 14 



Deficient in potash only 10 



Deficient in nitrogen and phosphoric acid 2 



Deficient in nitrogen and potash 4 



Deficient in phosphoric acid and potash 2 



Deficient in nitrogen, phosphoric acid, and potash .... 1 



Thirteen brands were guaranteed to contain magnesium oxide. None failed 

 to meet the guarantee. In general, the overrun in plant food guarantees exceeds 

 the deficiencies when all brands of a manufacturer are included. 



Fertilizers are largely mixtures of highly purified chemicals. Segregation 

 of these materials in the bag may be expected. To obtain a truly representative 

 sample of a fertilizer mixture requires careful work. The chemist can accurately 

 determine the nitrogen, phosphoric acid, and potash content of the sample sent 

 to the laboratory. If this sample does not correctly represent the larger lot, the 

 analytical work is of no use. The obligation of the fertilizer control program is 

 to see that the manufacturer is supplying the guaranteed amount of plant food 

 to the consumer. For this reason the sample- must be drawn and analyzed very 

 carefully so that injustice will not be done to either the consumer or manu- 

 facturer. 



In the tabulation of the analyses in the following pages, deficiencies of 

 one-half of one per cent or more are shown in red ink. The names of the 

 manufacturers are arranged alphabetically. The brand names are listed 

 alphabetically, or numerically by formula, under the manufacturer. 



