CROPS AND SOIL IMPROVEMENT 



is not to be considered by the farmer, as he uses 

 the bags in which the unmixed materials come to 

 him. 



The Filler. There has been much misleading 

 use of the word " filler," as applied to fertilizers. 

 We have seen that a pure grade of dried blood 

 contains about 13 per cent of nitrogen. The 

 buyer of a ton of dried blood thus gets about 260 

 pounds of plant-food. The remaining 1740 pounds 

 constitute what may be called nature's " filler." 

 The blood is a good fertilizer. We do not buy ni- 

 trogen in a pure state. We buy a ton of material 

 to get the needed 260 pounds of nitrogen. Thus 

 it is with nitrate of soda, sulphate of ammonia, 

 acid phosphate, muriate and sulphate of potash, 

 and all other fertilizer materials. As freight must 

 be paid upon the entire ton, it usually pays best 

 to select materials that run high in percentage 

 of plant-food. It is possible to get very low- 

 grade fertilizers that have not had any foreign 

 material added by the manufacturer. An acid 

 phosphate may be poor in phosphoric acid be- 

 cause low-grade rock was used in its manufacture. 

 Kainit is a low-grade potash because the impuri- 

 ties have not been taken out. Filler may be used, 

 however, for two reasons, and one is legitimate. 



[202] 



