Food for that when exported the commercial article contains from So 

 Plants ^Q 3^. pgj. ^gj^,- Q|-' p^j-e muriate of potash, or 50 to 52 per 

 ^ cent of actual potash. This is the cheapest form in which 

 potash can now be bought. 



It is claimed that a few plants, of which tobacco is the 

 most important, are injured by the chlorine contained in 

 the muriate of potash ; sulphate of potash is therefore used 

 for these crops. 



Nitrosen is the most expensive, impor- 

 " ' ^ ^^^' tant and effective element of plant tood, 



and at the same time is the one that is generally deficient 

 in the soil. 



There are a great many sources of Nitrogen, such as 

 sulphate of ammonia, which is obtained during the process 

 of making gas, drv ground fish, cotton-seed meal, dried 

 blood, lea'ther scraps, etc. But none of these furnish Nitro- 

 gen in the form in which it is taken up by plants. This 

 can onlv be furnished to plants in the form of Nitrates. 

 Nitrogen applied in any other form has to be converted 

 into Nitrate before it can be taken up by the plants. 



A Nitrate is the result of a union between nitric acid 

 and an element called a "base." Nitric acid contains the 

 Nitrogen that is necessary for the growth ot plants. It 

 unites with manv different elements, and forms a number ot 

 salts that are useful for many purposes. For instance, when 

 united with potash it forms Nitrate of potash, or what is 

 commonly called "nitre'' or "saltpetre;" when united with 

 soda it forms Nitrate of Soda, which is the best form in 

 which to furnish Nitrogen to plants. When we say the 

 best form we mean the best practical form. Nitrate ot 

 potash I saltpetre I would be just as good, but is much too 

 expensive. Nitrate of Soda not only furnishes Nitrogen in 

 its most available form, but it furnishes it at a lower price 

 than almost anv other source. The exceptions are a tew 

 organic substances in which Nitrogen exists in an insoluble 



form. 



„ J, Nitrate of Soda is found in vast quanti- 



^'^'^^^ ot boda. ^.^^ .^ ^^^ ^^^^^ ^^ ^^^y^^ 5^^^^ America. 



The beds of Nitrate, or "caliche," as it is called in Chile 

 before it is refined, are several thousand feet above the sea, 

 on a desert plain extending for seventv-live miles north and 

 south, and about twentv miles wide, in a rainless region. 



