98 Concrete Silos 



While silage will keep very well in a pit silo if the 

 silo is made moisture proof, there is one insurmountable 

 objection to this form of silo as above suggested, and 

 that is the difficulty of getting the silage out. The 

 advocate of this form of construction will say that this 

 is offset in a measure by 'the ease with which the pit 

 silo is filled; but when it is considered that the filling 

 is done in favorable weather, while the silage is re- 

 moved during the winter, this does not constitute as 

 great an offset as might at first appear. Furthermore, 

 there is a tendency in constructing the pit silo to rely 

 entirely too much on the stability of the ground, simply 

 giving a plaster coat to form a smooth interior wall. 

 This plaster will crack sooner or later, depending on 

 the condition of the soil; while, if the builder goes to 

 to the trouble of preparing an inner form and pouring 

 a substantial monolithic wall, this expense, added to 

 the cost of excavation, will show little gain over an 

 above-ground silo. 



In the case of pit silos it must also be remembered 

 that there is a possibility of carbon dioxide gas collect- 

 ing in the bottom and making it dangerous for persons 

 to enter. This gas is apt to form in larger quantities 

 within a day or two after the filling begins, so that if 

 it is necessary to partially fill the silo and then let it 

 stand for a time, a lighted lantern should be lowered 

 into the pit before entering it. If it is found to contain 

 gas, running the cutter for a few minutes and empty- 

 ing its contents into the silo will usually set up a suffi- 

 cient current of air to carry the gas away. 



There are three types of pit silos: Plain holes in 

 the ground, where the walls are plastered and the silage 

 is cropped in and lifted out at the top; holes in the 

 ground, but with the silo extended above the ground 



