FARM MANURES 



175 



fertility due to this cause. 60 Many political economists 

 shared the same fear. Since that time the fixation of 

 atmospheric nitrogen through the agency of leguminous 

 crops has been discovered, extensive beds of sodium 

 nitrate, phosphate rock, and Stassfurt salts have been 

 utilized, and larger areas of more fertile soil have been 

 brought under cultivation, so that it is not now so 

 essential to devise means for utilizing human excre- 

 ments as manure. 



THE PRESERVATION OF MANURE 



196. Leaching. Leaching of manure is the greatest 

 source of loss. Experiments by Roberts show that 

 when horse manure is thrown in a loose pile and sub- 

 jected to the joint action of leaching and weathering it 

 may lose in six months nearly 60 per cent of its most 

 valuable fertilizing constituents. The results of these 

 experiments are tabulated as follows : 61 



Cow manure, on account of its more compact nature, 

 does not leach so readily as horse manure. A similar 



