HOME MIXING 201 



manufacturer makes use of various compounds of nitrogen, 

 phosphoric acid, and potash in forms that are immediately 

 soluble, or will become soluble very quickly. The farmer 

 wants quick returns from his fertilizer and hence the various 

 ingredients must be readily available. Chapters IX, X, 

 and XI give the various sources of the individual elements. 

 An almost infinite number of combinations of the different 

 constituents can be made and the manufacturer uses many 

 of them, with phosphoric acid, however, predominating 

 in most of the fertilizers. In making the so-called high 

 grade fertilizers only compounds containing the maximum 

 amount of nitrogen, phosphoric acid, and potash are used, but 

 even here it is not possible to manufacture a product contain- 

 ing very much of the essential elements. Few nitrogenous 

 materials contain more than 15 per cent, nitrogen, or phos- 

 phate substances more than 16 to IS per cent, available 

 phosphoric acid, or potash compounds more than 50 per cent, 

 potash. The rest of the product is worthless as a fertilizer, 

 but its presence can not be helped, for it is obviously impos- 

 sible to use elemental nitrogen, or phosphorus pentoxide, or 

 potassium oxide in a fertilizer (cf . Section 209) . In making 

 low grade fertilizers, however, various diluents are used to 

 reduce the percentage composition; diluents, however, 

 which are harmless in themselves, although of course value- 

 less as fertilizers. These substances are gypsum, fine, dry 

 soil, peat (which does contain a small amount of nitrogen, 

 although not very available), sawdust, and other dry, cheap 

 substances. Sometimes it is necessary to add these materials 

 to a complete fertilizer to serve as driers, for some single 

 fertilizer ingredients, like sodium nitrate and calcium 

 nitrate, absorb water and make the mass sticky, or cause it 

 to cake in hard lumps and hence render it unfit for drilling- 

 purposes. 



152. Incomplete Fertilizers. — An incomplete fertilizer is 

 one which contains only one or two of the above named 

 three elements. Those containing only one are frequently 

 referred to as .single fertilizers. 



153. Home Mixing. — It is not necessary for the farmer 

 to purchase ready mixed goods. He may buy single ferti- 



