CIRCULAR No. 436 



Issued June 1937 



Slightly revised February 1940 



UNITED STATES DEPARTMENT OF AGRICULTURE 

 WASHINGTON. D. C. 



PRODUCTION AND AGRICULTURAL USE OF 

 SODIUM NITRATE 



By Albert R. Merz, chemist, Fertilizer Research Division, Bureau of Agricultural 

 Chemistry and Engineering, and C. C. Fletcher, associate chemist, Division of 

 Soil Fertility Investigations, Bureau of Plant Industry 



CONTENTS 



Page 



Natural sodium nitrate. 1 



Synthetic sodium nitrate 2 



Composition .. ._ 3 



Cost of nitrogen in nitrogenous fertilizer mate- 

 rials 5 



Sodium nitrate in relation to crop production... 5 



Nitrogen an essential plant-food element 5 



Properties of sodium nitrate in relation to the 



soil 6 



Residual effect. 7 



Agricultural uses of sodium nitrate 7 



Application to soil 7 



Page 

 Sodium nitrate in relation to crop production— 

 Contd. 



Special uses 8 



Soil bacteria- - 8 



Nitrate in mixtures 8 



Complete fertilizers 8 



Home mixing 8 



Use on individual crops. 10 



Quality of crops 10 



Proper use of sodium nitrate 11 



Use in small gardens. 11 



Methods of applying - 11 



NATURAL SODIUM NITRATE 



All fertile soils contain small quantities of nitrates, mainly as a 

 result of bacterial nitrification processes. More or less concentrated 

 accumulations of nitrates have been found in various parts of the 

 world, but, with one exception, none of these have been of such size 

 and richness as to allow continued working for fertilizer use. In 

 Tarapaca, Atacama, and Antofagasta, northern Provinces of Chile, 

 however, are located large deposits of sodium nitrate, along with 

 other salts, the exploitation of which commenced before Liebig's 

 invention of superphosphate in 1840. Exportation of sodium nitrate 

 from these deposits to Europe began in 1830, and they have continued 

 to supply sodium nitrate for agricultural use to the present. Sodium 

 nitrate, or nitrate of soda, also known as Chilean nitrate and Chile 

 saltpeter, is, therefore, the oldest of the inorganic commercial fertilizer 

 materials. Although the early development of the Chilean nitrate 

 industry was slow, growth became rapid after about 1880, and Chile 

 soon enjoyed a monopoly of the world's fixed-nitrogen supply, the 

 price of which was controlled by the Chilean producers. This control 

 was destined to last until modern processes for fixing atmospheric 

 nitrogen were established on a commercial basis. 



The Chilean deposits lie in the desert region between the Andes 

 and the coastal range along the Pacific Ocean and occur mainly on the 

 eastern slopes of the latter mountains, the deposits actually worked 

 lying at elevations between 4,000 and 7,500 feet above sea level. They 



199990°— 40 1 



