160 SOILS AND FERTILIZERS 



207. Composition of sulfate of ammonia. — There is more 

 nitrogen in a ton of this fertilizer than in any other. The 

 commercial material usually contains about 20 percent of 

 nitrogen, which is from eighty to one hundred pounds more 

 than is contained in a ton of nitrate of soda. It is easily 

 soluble in water, but when applied to soils the ammonia is 

 absorbed, and probably very little of it is taken up directly 

 by plants. On the other hand, the absorbed ammonia 

 nitrifies readily, especially if there is plenty of lime in the 

 soil, and the nitrates thus formed may readily be used by 

 plants. 



208. Action when applied to soils. — A pound of nitrogen 

 in the form of sulfate of ammonia has slightly less value than 

 the same quantity in the form of nitrate. If the soil to which 

 it is applied is in need of lime, the value of the fertilizer will 

 be less than if sufficient lime be present. It also tends to 

 make a soil acid when used in large quantities for a long 

 period. These two facts make it apparent that lime should 

 be abundantly supplied to soils on which this fertilizer is 

 used. Lime, whether it is applied to the soil or is naturally 

 present, serves to neutralize/ the acid formed when the am- 

 monia is converted into niwic acid by soil bacteria, which is 

 the process by which nitrates are formed, and also to neutral- 

 ize the sulfuric acid left in the soil when the ammonia is 

 changed by this process. 



The nitrates resulting from the fermentation of sulfate of 

 ammonia are quickly leached out of the soil when no plants 

 are growing on it ; therefore sulfate of ammonia should not 

 be applied at that time. In England the following losses 

 of nitrogen occurred from plats on which nitrate and am- 

 monium salts were used, and on which crops were grown. 

 The term " minerals " is here used to mean phosphoric acid 

 and potash fertilizers. 



