556 SOILS: PROPERTIES AND MANAGEMENT 



merely mixing the various carriers together so that the 

 required percentages of nitrogen, potash, and phosphoric 

 acid are obtained, care being taken that no detrimental 

 reaction shall occur and that a physical condition con- 

 sistent with easy distribution shall be maintained. If 

 the substances used are difficultly soluble, the fertilizer 

 is not so valuable as one composed of easily soluble con- 

 stituents. The general solubility of the various in- 

 gredients should be known by a prospective purchaser. 



The various brands on the market, besides being 

 complete or incomplete, may be designated as high-grade 

 or low-grade. These terms may be used in two ways — 

 high-grade or low-grade as to availability, or high-grade 

 or low-grade as to amount of plant-food constituents 

 carried. A low-grade fertilizer in the percentages of 

 nitrogen, phosphoric acid, and potash is always encum- 

 bered with a large amount of inert material, which adds 

 to the cost of mixing, transportation, and handling. It 

 is thus usually a more expensive fertilizer to a unit of 

 plant-food obtained than one of higher grade. Except 

 for special purposes, a low-grade fertilizer as to avail- 

 ability should be bought sparingly or not at all. 



471. Fertilizer inspection and control.— With the 

 many different materials available for mixing commercial 

 fertilizers, and from the fact that so many opportunities 

 are open for fraud either as to availability or as to guaran- 

 tee, laws have been found necessary for controlling the 

 sale of fertilizers. Most states have such a law, the 

 western laws generally being superior to those in force 

 in eastern states, where the fertilizer sale is heavier. 

 This is because the western regulations are more recent 

 and the legislators have had the advantage of the ex- 

 perience gained where fertilizers have long been used. 



