50 HOW TO BUILD A SILO. 



of deep silos the loss from spoiled silage on the top is 

 smaller in proportion to the whole amount of silage 

 stored; there is also less surface in . proportion to the 

 silage stored, hence a smaller loss occurs while the silage 

 is being fed out, and since the silage is more closely 

 packed, less air is admitted from the top. As the silage 

 packs better in a deep silo than in a shallow one, the 

 former kind of silos will hold more silage per cubic foot 

 than the latter; this is plainly seen from the figures given 

 in the table on page 53. Silos built during late years have 

 generally been over thirty feet deep, and many are forty 

 feet deep or more. 



3. The silo must have smooth, perpendicular walls, 

 which will allow the mass to settle without forming 

 cavities along the walls. In a deep silo the fodder will 

 settle several feet during the first few days after filling. 

 Any unevenness in the wall will prevent the mass from 

 settling uniformly, and air spaces in the mass thus formed 

 will cause the surrounding silage to spoil. 



4. The walls of the silo must be rigid and very strong, 

 so as not to spring when the siloed fodder settles. The 

 lateral (outward) pressure of cut fodder corn when set- 

 tling at the time of filling is considerable, and increases 

 with the depth of the silage at the rate of about eleven 

 pounds per square foot of depth. At a depth of 20 feet 

 there is, therefore, an outward pressure of 330 pounds, etc. 

 In case of a 16-foot square silo where the sill is 30 feet 

 below the top of the silage the side pressure on the lower 

 foot of the wall would be about 16x330, or 5280 pounds. 



It is because of this great pressure that it is so diffi- 

 cult to make large rectangular silos deep enough to be 

 economical, and it is because the walls of rectangular 

 silos always spring more or less under the pressure of 

 the silage that this seldom keeps as well in them as it does 

 in those whose walls cannot spring. 



As the silage in the lower part of the silo continues 

 to settle, the stronger outward pressure there spreads 

 the wallg more than higher up and the result is the wall 



