52 CROP GROWING AND CROP 



and transforms the nitrite into a nitrate, which is the form in which green 

 leaved plants use nitrogen. Ammonia is manufactured as a by product in the 

 making of illuminating gas, and also in the manufacture of bone charcoal 

 for the sugar refiners. This is the source of the article in commerce known 

 as the sulphate of ammonia. Large quantities are now made also in the 

 manufacture of coke for the iron furnaces. In the sulphate the ammonia is 

 in a very concentrated form, and will probably be*come more largely used 

 as the price is reduced ; though with many plants is seems at times to exert a 

 poisonous influence. It is common to say that cotton seed meal and other 

 organic matters have a certain percentage of ammonia, but there is really no 

 ammonia there until the organic matter has decayed and the combination of 

 the nitrogen has been made with the hydrogen. The more correct way would 

 be to give the percentage of nitrogen in the matter which forms ammonia 

 in decaying. But, as we have said, the figures for ammonia look larger, and 

 hence manufacturers like to put it as ammonia in their claims. Pure sul- 

 phate of ammonia contains 21.2 per cent, of nitrogen. 



In recent years there have been large discoveries of nitrogen in the form 

 of a nitrate of soda, which is formed .in large masses in certain parts of the 

 western coast of South America where no rain falls. This is now probably 

 the cheapest source of nitrogen for fertilizing purposes. We have seen that 

 green leaved plants use nitrogen in the form of a nitrate, and that the organic 

 nitrogen must be changed into this form in the soil before they use it. The 

 nitrate of soda being already in the nitrate form is at once available for plant 

 food. As it rapidly leaches from the soil in the rainfall this form should 

 only be used while plants are in active growth. If applied during the 

 dormant season much if not all of it will be lost by leaching. In making a 

 complete fertilizer mixture, if nitrate of soda is used, it should always be ac- 

 companied by a due proportion of organic nitrogen to continue the supply 

 after the nitrate is used up. 



The nitrate is useful in the first growth of the plant while the nitrifica- 

 tion of the organic matter is going on, as it is immediately soluble and quite 

 concentrated. It is often sold under the name of Chili saltpetre, (ordinary 

 saltpetre being the nitrate of potash) and contains from 15 to IK per cent, 

 of nitrogen. Professor Voorhees, in his book on fertilizers, wet! says that 

 "The practical point, and the one of prime importance to the farmer, is, then, 

 to know how to estimate the relative value or usefulness of these different 

 products, what is the rate of availability as compared with the nitrate, and 

 thus the relative advantage of purchasing the one or the other, at the ruling 

 market prices. Relative values, however, cannot be assigned as yet, though 

 careful studies of the problem have been made, chiefly by what are known as 



