CHAPTER X 



COMMERCIAL FERTILIZERS AND THEIR USE 



262. Development of the Commercial Fertilizer 

 Industry. — The commercial fertilizer industry owes 

 its origin to Liebig's work on plant ash. The first 

 superphosphate was made by Sir J. B. Lawes, about 

 1840, from spent bone-black and sulphuric acid. His 

 interest had previously been attracted to the use of 

 bones by a gentleman who farmed near him, " who 

 pointed out that on one farm bone was invaluable for 

 the turnip crop, and on another farm it was useless." 43 

 Since i860 the commercial fertilizer industry in this 

 country has developed rapidly, until now the amount 

 of money expended in purchasing commercial fer- 

 tilizers and amendments is estimated at $60,000,000 

 annually. Nearly all of this sum is expended in less 

 than a quarter of the area of the United States. 



263. Complete Fertilizers and Amendments. — The 



term commercial fertilizer is applied to those materials 

 which are made by the mixing of different substances 

 which contain plant food in concentrated forms. 

 When a commercial fertilizer contains nitrogen, phos- 

 phoric acid, and potash, it is called a complete fer- 

 tilizer, because it supplies the three elements which are 

 liable to be most deficient. Materials as sodium nitrate 



