174 THE FIRST BOOK OF FARMING 



leaching through the manure washes out of it nitro- 

 gen and potash, which pass off in the dark brown 

 liquid that oozes from the base of the pile. 



Loss by heating or fermenting. 



When barn manure is thrown into piles it soon 

 heats and throws off more or less steam and gas. 

 This heating of the manure is caused by fermenta- 

 tion or the breaking down of the materials com- 

 posing the manure and the forming of new com- 

 pounds. This fermentation is produced by very 

 small or microscopic plants called bacteria. 



The fermentation of the manure is influenced by 

 the following conditions : 



A certain amount of heat is necessary to start the 

 work of the bacteria. After they have once started 

 they keep up and increase the temperature of the 

 pile until it gets so hot that sometimes a part of the 

 manure is reduced to ashes. The higher the tem- 

 perature the more rapid the fermentation. This can 

 be seen particularly in piles of horse manure. 



The bacteria which produce the most rapid fer- 

 mentation in manure need plenty of air with its 

 oxygen. Therefore fermentation will be more or 

 less rapid according as the manure is piled loosely 

 or in a close compact mass. 



A certain amount of moisture is necessary for the 

 fermentation to take place, but if the manure is 

 made quite wet the temperature is lowered and the 

 fermentation is checked. The water also checks 

 the fermentation by limiting the supply of air that 

 can enter the pile. 



