13 ^ 



tains is vaporized in the form of ammonia. Ammonia is also got in the same 

 way from coke ovens, and to some extent in the preparation of producer gas 

 and water gas. The ammonia thus secured is passed into sulphuric acid and 

 ammonium sulphate is formed. This crude material is then more or less purified 

 and sold under the name of "Ammonium Sulphate." In the form in which it 

 is used as a fertilizer it usually contains about 30 per cent, of nitrogen. 



Ammonium sulphate is not so quick in its action as nitrate of soda, because 

 it has to undergo nitrification, or change into nitrates, before it can be absorbed 

 The presence of calcium carbonate is essential for this change, consequently, i^ 

 should not be applied to soils deficient in lim:e, and furthermore, its use i^ 

 always associated with a rapid depletion of the soil in lime. Nitrate of sods 

 is best applied in several small dressings during the growth of the plant, whereas, 

 ammonium sulphate may be applied at once, even before the crop is sown, without 

 fear of loss, because in various ways it is retained by the soil. The asual quanti- 

 ties of either of these materials applied is from 100 to 200 pounds to the acre, 

 but with such crops as mangels and potatoes and many garden crops large? 

 quantities may be used. 



Calcium Cyanamid. 



Calcium cyanamid is one of the newer forms of nitrogenous manures. Ii 

 is prepared by heating calcium carbide to a very high temperature by electricitr 

 and passing the nitrogen of the air over it. The resulting compound is some- 

 what bluish black in color and contains about 15 per cent, of nitrogen. It alsc 

 contains calcium equivalent to 70 per cent, of slaked lime. Many of its forme? 

 disadvantages are being overcome and it will doubtless become one of the most 

 valuable of our nitrogenous manures. At present it is used principally as & 

 constituent of mixed fertilizers. 



Calcium Niteate. 



Calcium nitrate is another of the newer products in which the nitrogen 

 of the atmosphere is put into a commercial form. Little or none of this com- 

 pound has been used in this country, although it is becoming a somewhat commoE 

 product of commerce in some parts of Europe. 



Nitrogen in the Organic Form. 



Considerable difference of opinion exists as to the value of organic nitrogen. 

 From a purely plant food standpoint, organic nitrogen has no higher value thai 

 the available nitrate nitrogen, since it must be changed into the nitrate conditioE 

 before it can be assimilated by the plant. The value of organic nitrogen as a 

 plant food compared with quickly available forms lies in the fact that as it 

 gradually decomposes, it fonns a gradual supply of available nitrogen to the grow- 

 ing plant over a long period. It should be remembered, however, that many organi( 

 nitrogenous manures are so complex that their decomposition is extremely difficul: 

 and they are of little service to increase the crop yield. Among these slowlv 

 available nitrogenous substances may be mentioned rags, hair, skin, horn, crushed 

 hoofs and leather. Of the more valuable and easily rendered available forms of 

 organic nitrogen may be mentioned feeding cake refuse such as rape cake, dried 



