CONFORMITY TO GUARANTEE 



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

 adopted by the Association of Official Ag-ricultural Chemists. 



Number of brands analyzed 112 



Equalling or exceeding all guarantees 65 



Deficient in nitrogen only 19 



Deficient in available phosphoric acid only 5 



Deficient in potash only 3 



Deficient in nitrogen and phosphoric acid 7 



Deficient in nitrogen and potash 6 



Deficient in phosphoric acid and potash 3 



Deficient in nitrogen, phosphoric acid, and potash 4 



Five brands w^ere guaranteed to contain magnesium oxide. None failed 

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

 the deficiencies w^hen 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, phophoric 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 manufacturer. 



In the tabulation of the analyses in the following pages deficiencies of one- 

 half per cent or more are shown in red type. The names of the manufacturers are 

 arranged alphabetically. The brand names are listed alphabetically, or nu- 

 merically by formula, under the manufacturer. 



