PRESERVATION OF MANURE 1 57 



through the agency of leguminous crops, the exten- 

 sive beds of sodium nitrate, phosphate rock, and Stas- 

 furt salts, have been discovered, and larger areas of 

 more fertile soil have been brought under cultivation, 

 so that it is not now considered so essential to devise 

 means for utilizing human excrements as manure. 



THE PRESERVATION OF MANURE 



189. Leaching. — Leaching of manure is the great- 

 est source of loss. Experiments by Roberts have 

 shown that when horse manure is thrown in a loose 

 pile and subjected to the joint action of leaching and 

 weathering it may lose nearly 60 per cent, of its most 

 valuable fertilizing constituents in six months. The 

 tabular results are as follows : 15 



April 25. Sept. 28. Loss. 



Lbs. Lbs. Per cent. 



Gross weight 4,000 1,730 57 



Nitrogen 19.60 7.79 60 



Phosphoric acid .. 14.80 7.79 47 



Potash 36.0 8.65 76 



Value per ton $2. So $1.06 



Cow manure, on account of its more compact nature, 

 does not leach so readily as horse manure. A similar 

 experiment with cow manure, conducted at the same 

 time, showed the following losses : 



April 25. Sept. 28. Loss. 



Lbs. Lbs. Per cent. 



Gross weight 10,000 5,125 49 



Nitrogen 47 28 41 



Phosphoric acid 32 26 19 



Potash 48 44 8 



Value per ton $2.29 $1.60 



