Certain other substances also tend to render potash available as 

 lime, salt and plaster. 



13. If potash is to be applied to the soil, it may be had in three 

 forms : as the sulfate of potash, mandate of potash, and carbonate of 

 potash. The last occurs in wood ashes. 



Potash is represented by two letters, K and O, to indicate that 

 it, like phosphoric acid, is composed of two elements, i. e., potas- 

 sium K* and oxygen O, and the figure 2 in K^O denotes that it 

 contains two parts of K and one of O. 



When potash is combined with sulfuric acid, or oil of vitrol, it 

 forms sulfate of potash. 



When combined with muriatic acid it forms muriate of potash. 

 In wood ashes the potash is united with carbonic acid to make 

 the carbonate of potash. Muriate of potash, KCl, comes from 

 Germany, where deposits are found, about like our own deposits 

 of common salt. 



The sulfate is made from the muriate, by substituting sulfuric 

 acid in the place of muriatic acid. 



14. Nitrogen is an essential fertilizing element. — Nitrogen is the 

 most expensive and consequently the most important, commer- 

 cially, of the plant-foods. It exists in that part of the soil com- 

 posed of organic material, i. e., that arising from the decay of 

 vegetable or animal matter. 



There is no nitrogen in common rocks. By burning from a 

 handful of soil all the organic part, the nitrogen will be lost. The 

 nitrogen originally all came from the atmosphere. Four-fifths 

 of the air is nitrogen. In the pure state it is a gas, but in the 

 soil it is a constituent of the organic materials. 



1 5 . Nitrogeii jnust be iri combinations to be available. — The nitro- 

 gen that exists as a constituent of any organic material is called 

 organic nitrogen. This combination is found in manures, green- 

 crops and in fact in all vegetable material ; also in dried blood and 

 tankage. 



Nitrogen is a constituent also of ammonia or hartshorn (N H^) . 

 By weight, fourteen of every seventeen parts of ammonia is ni- 

 trogen. Hence when the odor of ammonia escaping from manure 



*This letter is used to denote potassium to avoid confusion with phos- 

 phorus, and because K is the first letter of kalium, I^atin for potassium. 



