FARM MANURES 227 



the liquid portion of the manure, and to the exposure of the 

 manure to rain. 



286. Fermentations of manure. — The mixture of solid 

 and liquid excreta together with litter used as bedding con- 

 stitutes a wonderfully favorable material for the growth of 

 bacteria, the number of which frequently amounts to many 

 billion in a gram of manure. This is many times more 

 than are found in soil. It is then small wonder that fer- 

 mentations proceed at a prodigious rate in a manure heap. 

 These fermentations are produced both by bacteria requiring 

 oxygen for their activity and by those that need little. The 

 fermentations on the outside of the heap are different from 

 those on the inside, where air does not readily penetrate, 

 but as fresh manure is thrown on the pile from day to day, 

 most of the manure first undergoes fermentation in the pres- 

 ence of air and afterwards without air. 



It is through the action of germs on the nitrogenous com- 

 pounds of manure that loss of value through fermentation 

 occurs. In the presence of air ammonia is formed, and this 

 being in a volatile form, is likely to escape. The drier the 

 heap, the more likely the ammonia is to escape. 



The fermentations in the interior of a moist manure heap 

 are, in the main, favorable to the production of readily 

 available plant-food material. It is desirable to keep the 

 heap as compact as possible, and to prevent it from becom- 

 ing dry by the application of water in amounts sufficient to 

 keep the heap moderately moist without leaching it. In 

 the arid and semi-arid parts of the country, this is an im- 

 portant precaution to be taken in the preservation of farm 

 manure. 



287. Leaching of farm manure. — When water is allowed 

 to soak through a manure heap and to drain away from it, 

 there is carried off in solution, and to some extent in sus- 

 pension, more or less of the organic matter and plant-food 



