THE HISTORY OF SILOING. 247 



preserved in the uncut form or after it has been run 

 through a cutting box and is packed more or less 

 tightly according to conditions such as those that 

 relate to the variety of the food, its succulence, and 

 the depth of the silo. Soon after the green food has 

 been placed in the silo fermentation begins and the 

 temperature rises. The air within the mass is thus 

 expelled and \vhen it is, chemical change virtually 

 ceases. The product thus preserved may be kept in- 

 definitely, providing air is not allowed to penetrate 

 it. Because of this it is important that the sides and 

 floor of the structure shall be practically air-tight. 

 The air is usually prevented from entering from 

 above to any considerable depth by covering the 

 silage with some less valuable vegetable substance as 

 more fully described in Chapter V. 



The principle in making silage is the same 

 virtually as in canning fruits or in making sauer- 

 kraut. When the temperature in the mass rises un- 

 til it attains 122 degrees Fahrenheit the action of the 

 fermerts is arrested. As soon as the available 

 oxygen is exhausted chemical change ceases and 

 sweet silage is the result. If however from any 

 cause, as for instance an excess of moisture in the 

 plants, the temperature does not reach 122 degrees 

 Fahrenheit, the acid ferments will not be killed and 

 the result will be sour silage. Sour silage is not only 

 less valuable than sweet silage, but there is usually 

 greater waste in making it. 



The terms sweet and sour as applied to silage 

 are only relative terms. There is no line of dis- 

 tinction between them so sharply drawn that it may 

 be said where the one begins and the other ends. 



