Fourteen 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 manufacturer. 



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 manu- 

 facturers are arranged alphabetically. The brand names are listed alphabetically, 

 or numerically by formula, under the manufacturer. 



