COMMERCIAL FERTILIZERS 499 



The continued and abundant use of sodium nitrate 

 on the soil may result, through its deflocculating action, 

 in breaking down aggregates of soil particles, thus com- 

 pacting and injuring the structure. This effect is attrib- 

 uted to the accumulation of sodium salts, particularly 

 the carbonate, as the sodium is not utilized by the plant 

 to the same extent as is the nitrogen. 



421. Ammonium sulfate. When coal is distilled, a 

 portion of the nitrogen is liberated as ammonia and is 

 collected by passing the products of distillation through 

 water in which the ammonia is soluble, forming the am- 

 moniacal liquor. The ammonia thus held is distilled into 

 sulfuric acid, with the formation of ammonium sulfate 

 and the removal of impure gases. 



Commercial ammonium sulfate contains about twenty 

 per cent of nitrogen. It is the most concentrated form in 

 which nitrogen can be purchased as a fertilizer, having 

 from sixty to eighty pounds more of nitrogen to a ton 

 than sodium nitrate. It is therefore economical to 

 handle. Its effect on crops is not so rapid as that of sodium 

 nitrate, but it is not so quickly carried from the soil by 

 drainage water, as the ammonium salts are readily ab- 

 sorbed by the soil. A pound of nitrogen in the form of 

 ammonium sulfate has about the same agricultural value 

 as the same amount in the form of nitrate if the soil on 

 which it is used is abundantly supplied with lime; but 

 on an acid soil ammonium sulfate has less value. 



The long and extensive use of ammonium sulfate on a 

 soil has a tendency to produce an acid condition, through 

 the accumulation of sulfates which are not largely taken 

 up by plants. 



Ammonium sulfate, like sodium nitrate, should not be 

 applied in autumn, as the ammonia is converted into 



