CHAPTER X 



COMMERCIAL FERTILIZERS AND THEIR USE 



279. Development of the Commercial Fertilizer Indus- 

 try. The commercial fertilizer industry owes its origin 

 to Leibig's work on plant ash. The first superphos- 

 phate 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 as fer- 

 tilizer 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." 44 



Since 1860 the commercial fertilizer industry in this 

 country has developed rapidly, until now large sums of 

 money are annually expended in purchasing commercial 

 fertilizers and amendments, and nearly all in less than 

 a third of the area of the United States. 



280. Complete Fertilizers and Amendments. - - The 



term ' commercial fertilizer ' is applied to materials made 

 by mixing different substances which contain plant 

 food in concentrated forms. When a commercial fer- 

 tilizer contains nitrogen, phosphoric acid, and potash, 

 it is called a complete fertilizer, because it supplies the 

 three elements which are liable to be most deficient. 



233 



