CHAPTER X 



COMMERCIAL FERTILIZERS AND THEIR USE 



265. Development of the Commercial Fertilizer 

 Industry. The commercial fertilizer industry owes 

 its origin to L,eibig'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." 44 

 Since 1860 the commercial fertilizer industry in this 

 country has developed rapidly, until now the amount 

 of money expended in purchasing commercial ferti- 

 lizers 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. 



266. Complete Fertilizers and Amendments. The 

 term commercial fertilizer is applied to those materials 

 made by mixing different substances which contain 

 plant food in concentrated forms. When a commer- 

 cial fertilizer contains nitrogen, phosphoric acid, and 

 potash, it is called a complete fertilizer, because it 

 supplies the three elements which are most liable 

 to be deficient. Materials as sodium nitrate which 

 supply only one element are called amendments. 

 It frequently happens that a soil requires only one 

 element in order to produce good crops. In such 



