92 THE PRINCIPLES OF AGRICULTURE. 



three fourths of the value of these fertilizers may be 

 obtained in the first crop after they are applied. 



In stable manure, only a small proportion of these 

 elements is soluble and available at first. Not more 

 than one fourth of its value is ordinarily obtained the 

 first season. The remainder must wait for chemical 

 action slowly to reduce it to available forms. 



The Care of Manure. The value to be derived from 

 stable manure depends largely upon the care exercised 

 in preserving it. 



Probably nearly one half the value of manure through- 

 out the country is lost. Some loss is, of course, unavoid- 

 able, but it may be largely prevented by proper care. 



There are three general sources of loss : 



1. Fermentation. Fermentation is a process of de- 

 cay, or decomposition, which organic substances un- 

 dergo when brought in contact with moderately warm air. 

 The chemical process consists partly of oxidation, pro- 

 ducing heat. On this account, it is sometimes called 

 heating. 



Some kinds of manure ferment much more readily and 

 rapidly than others. 



Sometimes, if the process is allowed to continue un- 

 checked, it will give to manure the appearance of having 

 been partially burned, leaving only a light, unsubstantial 

 mass behind. It is then said to be " fire-fanged." 



By fermentation the most valuable elements of manure 

 are converted into gases, and tend to escape into the 

 atmosphere. Nitrogen is converted into ammonia, and 

 carbon into carbonic acid gas. The loss of the former is 

 of far greater importance than that of the latter, since 

 carbon, which plants obtain so largely from the atmos- 

 phere, is of less value in manure. 



