128 SOILS AND FERTILIZERS 



161. Sodium Nitrate. The nitric nitrogen most 

 frequently met with in commercial forms is sodium 

 nitrate, commonly known as Chili saltpeter. It is a 

 natural deposit found extensively in Chili, Peru, and 

 the United States of Colombia. Various theories have 

 been proposed to account for these deposits, but it is 

 difficult to determine just how they have been formed. 10 

 Their value to agriculture may be estimated from the 

 fact that there are annually used in the United States 

 about 100,000 tons, and in Europe about 700,000 tons. 

 The commercial value of nitrogen in fertilizers is reg- 

 ulated by the price of sodium nitrate which, when 

 pure, contains 16.49 P er cen t- of nitrogen. Commer- 

 cial sodium nitrate is from 95 to 97 per cent. pure. 

 An ordinary sample contains about 16 per cent, of 

 nitrogen and costs from $50 to $60 per ton, making 

 the nitrogen worth from 15 to 18 cents per pound. 

 Sodium nitrate is the most active of all the nitrogenous 

 manures. It is soluble and does not have to undergo 

 the nitrification process before being utilized by crops. 

 On account of its extreme solubility it should be ap- 

 plied sparingly, for it cannot be retained in the soil. 

 As a top dressing on grass, it will respond by impart- 

 ing a rich green color. It may be used at the rate of 

 250 pounds per acre, but a much lighter application 

 will generally be found more economical. Sodium 

 nitrate may contain traces of sodium perch lorate, 

 which is destructive to vegetation if the fertilizer is 

 used in excess. 52 Sodium nitrate, in small amounts, 

 is the fertilizer most frequently resorted to when the 

 forcing of crops is desired as in early market garden- 



