206 FARM BUILDINGS IN SOUTH AFRICA 



2. Storage space is saved, i.e. a narrow, deep silo will store a greater 



total weight of silage than can be stored in a wider, shallower 

 one of the same cubic capacity. 



3. Less surface is exposed to the air, while the silage is being used 



layer by layer starting from the top, and there is therefore less 

 chance of loss of surface silage than would be the case in a 

 ■wider silo. " If the silage is fed down at a rate lower than 

 1*2 inches daily, moulding is likely to set in." (King.) 



The height of a tower silo is limited by the power required to elevate 

 the stuff to fill the silo, the higher the silo the greater is the power 

 required for this purpose. A common elevator is that of the pneumatic 

 or blower type worked in conjunction with the ensilage cutter. 



The above remarks apply more to " tower " than to " pit " silos, as, 

 on account of the difficulty of emptying them, the latter cannot con- 

 veniently be made deeper than 8 or 9 feet. Pit silos are not fed down 

 layer by layer starting from the top, as this would expose too much 

 surface. The method adopted is to remove the silage in vertical 

 sections of from 4 to 6 feet wide, across the width of the pit, the 

 superincumbent earth resting on each section having been first set 

 aside, and each section removed to its full depth before starting on a 

 new one. If the silage is unchaffed, a rick-knife will be required for 

 this operation. 



The Pit Silo. — The pit silo is usually made rectangular, and, as 

 already stated, should not exceed 8 or 9 feet in depth. If the soil is 

 stiff, it need not be lined, and it is a good plan to leave a stairway in 

 the natural earth at one corner while excavatiDg in order to facilitate 

 emptying the silo. 



The Tower Silo. — Tower silos are, as a rule, built partially below, 

 but mainly above the ground. They are provided with one filling door 

 in the roof and a number of air-tight emptying doors in a vertical 

 row down one side. The depth of the part of the silo that is below 

 the ground should not exceed that which conveniently allows of the 

 lower silage being thrown out of the lowest emptying door. This 

 limiting depth is about 6 feet from floor of silo to sill of lowest emptying 

 door. By building as much as possible of the silo below ground, we 

 diminish the height to which the silage must be elevated in filling the 

 silo, and gain the advantage of a supporting earth backing to the outside 

 of that part which is below ground. 



