158 SOILS AND FERTILIZERS 



When mixed cow and horse manure was compacted 

 and "placed in a galvanized iron pan with a perfo- 

 rated bottom" for six months, the losses were as fol- 

 lows : 



March 29. Sept. 30. Loss. 



Lbs. Lbs. Percent. 



Gross weight 226 222 



Nitrogen 1.04 1.01 3.2 



Phosphoric acid • • 0.61 0.58 4.7 



Potash 1.20 0.43 35.0 



Value per ton $2.38 $2.16 



190. Losses by Fermentation. — When rapid fer- 

 mentation takes place in manure, appreciable losses of 

 nitrogen may occur. When the manure is well com- 

 pacted and the pile is so constructed as to prevent the 

 rapid circulation of air through the pile, the losses are 

 reduced to the minimum. Experiments have shown 

 that when leaching is prevented, the losses of nitrogen 

 by the fermentation of mixed manure are very 

 small. Under unfavorable conditions the losses 

 by fermentation may exceed 15 per cent. Hen ma- 

 nure, sheep manure, and horse manure suffer the 

 greatest losses by rapid fermentation. When extreme 

 conditions follow each other in succession, as exces- 

 sive moisture, drought, and high temperature, then 

 the greatest losses occur. 



191. Different Kinds of Fermentation. — The large 

 number of organisms present in manure all belong to 

 one of two classes : (1) aerobic, or (2) anaerobic. 

 The aerobic ferments require an abundant supply of 



