CHAPTER XVI 



SILAGE— SOILAGE 



I. Silage and the Silo 



The preservation of green forage by placing it in pits or heaps and 

 covering with earth has long been practiced in Europe. However, 

 silos — special structures built mainly above ground to contain such 

 material — have been in use only during the past 40 years. From 

 1879, when the first silo was built in this country, the use of silage has 

 increased rapidly, until now it is a factor of vast importance in Amer- 

 ican agriculture. 



How ensiling preserves forage. — When green forage is packed 

 firmly in a chamber with air-tight walls, such as a silo, fermentations 

 take place, caused both by the enzymes contained in the plant cells and 

 by bacteria and yeasts carried into the silo on the forage. During these 

 fermentations much of the sugar in the forage is broken down into 

 organic acids, chiefly lactic acid (the acid in sour milk) and acetic acid 

 (the acid in vinegar). In these changes oxygen is taken up and car- 

 bon dioxid (carbonic acid gas) given off. At first the oxygen in the 

 air -which has been entrapped in the ensiled mass is used up, but if 

 the forage has been well packed, this is soon exhausted. The enzymes 

 and bacteria then obtain the oxygen for these decompositions from the 

 oxygen-containing compounds in the forage — chiefly the sugars. 

 When the sugar in the forage has been changed into acids the fermen- 

 tation is checked, for the other carbohydrates are attacked to only a 

 small extent. It is due to this that corn or sorghum makes less acid 

 silage when well matured than if ensiled when the plants contain 

 more sugar. Even tho much sugar is present, the fermentation fi- 

 nally comes to an end, for sufficient acid is produced to prevent both 

 the further growth of the bacteria and yeasts and the action of the 

 plant enzymes. During the fermentation the temperature rises some- 

 what, but rarely reaches 100° P. if the mass has been well tramped to 

 exhaust the air. 



The acid in silage prevents the growth of undesirable putrefying 

 bacteria, such as cause the decaying of meat. The foul-smelling silage 

 often obtained from alfalfa, clover, and other legumes is largely due 

 to the fact that not enough sugar is present in such plants to form 

 sufficient acid to check the growth of these putrefying bacteria. 



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