NITROGEN. 



Nitrogen is a costly element of plant food, its use should 

 be well looked to, when we remember that every pound of ni- 

 trogen will cost us not far from twenty cents, while a pound of 

 phosphoric acid (PgO^) costs less than eight, and of potash 

 (KgO) about five cents, it is evident that we cannot afford to be 

 so thoughtless about the nitrogen as we often are about the 

 other two. 



As has been already said nitrate of potash was one of the 

 earliest fertilizers used, it contains about thirteen per cent, of 

 actual nitrogen. The high value of nitrate of potash as a con- 

 stituent in the manufacture of gunpowder prevents the use of 

 this source of nitrogen in agriculture, but about 1820 a substi- 

 tute was found in the so-called Chili Saltpetre, or nitrate of 

 soda. This source of nitrogen was not at first popular, the 

 first ship load going begging for a customer in England, was 

 sent off to this country, at present, however, Chili Saltpetre is 

 regarded as a valuable source of nitrogen. It is dug from the 

 ground in South American, where it has accumulated in past 

 ages. 



In 1836 "Gas Liquor" was first used in England. This is 

 the water in which illuminating gas is washed, and is found tp 

 contain ammonia gas (commonly called hartshorn), ammonia 

 gas is made up nitrogen and hydrogen, fourteen parts of the 

 former to three parts of the latter, the results from the use of 

 this liquor compared favorably with those from saltpetre, but 

 the bulk was too great. Later, by the use of sulphuric acid the 

 ammonia gas was saved !n the form of Sulphate of Ammonia^ 

 which to. day forms one of the best sources of nitrogen. 



English farmers long ago learned the value of dried bloody 

 and for a time English speculators bought both dried blood and 

 bones in this country and shipped them to be used on English 

 fields, but as the demand for plant food became greater at home, 

 this trade ceased, and to-day this valuable form of nitrogenous 

 fertilizer is extensively used. Meat 'and fish scrap are also 

 largely used. 



These are among the principal sources of the three sub- 

 stances, which I have classed as deficient plant food^ and in the 

 following table is given the average per cent, of plant food which 

 they contain. 



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