232 



THE IRRIGATION AGE. 



HOW YOU CAN BUILD YOUR OWN PIT SILO 



By C. LARSEN 



Dairy Husbandman of the South Dakota State College of Agriculture 

 and Mechanics Arts, Brooking;, S. D. 



THE pit or underground silo is useful in the semi- 

 arid sections and on high locations. Where the 

 ground is low, where irrigation is practiced and where 

 the rainfall is great, seepage water will interfere with 

 its usefulness. 



The pit silo can be built with common home labor. 

 The cost is very low. When once properly built a 

 pit silo is long lived, it never rots, it never blows down, 

 and the silage never freezes in it during the winter. 



The pit silo can be filled with an ordinary feed cut- 

 ter costing only about $60. A 6 H. P. engine is large 

 enough for running the cutter. Several neighbors 

 may own such a cutting outfit and co-operate in filling 

 their silos. 



First determine the size of silo to build. This in 

 turn depends on the number of cattle and the length 

 of time they are to be fed. The following table gives 

 some information on this point : 



First locate the silo on a suitable place. It should 

 be handy for feeding. If convenient, locate on the 

 south side of the barn or shed. Do not dig the pit too 

 close to the barn. It should be at least 6 feet away. 



Then locate and drive a peg in the center. With 

 another stake having one end fastened to the center 

 peg, mark out the circumference of the silo as illus- 

 trated. 



Proceed to dig out a trench forming the circum- 

 ference of the silo. Make this trench from 1J4 ft. to 

 3 ft. in depth. The concrete should rest on solid 

 ground, and be about 14 inches wide at the bottom. 

 At the top it need 

 not be over 6 or 8 

 inches wide. This 

 curbing . should be 

 straight on the side 

 next to the silo, and 

 slant in from the 

 bottom on the out- 

 side. 



The circumfer- 

 ence of the curbing 

 of a 12 ft. diameter 

 silo will be about 38 

 ft. If the trench is 

 2 ft. in depth and 

 averages 9 inches c 

 three-fourths of a 



Fig. 1.- 



foot in thickness, then it will hold about 57 cu. ft. 

 of concrete. For this concrete, about 2.1 yards or 

 two good sized loads of clean gravel and about 11 

 sacks of cement, are needed. 



The cement and gravel should be thoroughly 

 mixed before any water is added. 



Use clean gravel and make the concrete in the 

 proportion of 5 of gravel to 1 of cement. Add enough 

 water, and mix until the concrete has a suitable con- 

 sistency, so it will pour. Do not add strong alkali 

 water. It will weaken the concrete. It is better to 

 have the concrete a little too wet than to have it too 

 dry. If the ground or sides of the trench is very dry, 

 then wet the dirt before the concrete is put in. 



Fill the trench with this concrete. Extend the 

 concrete curbing about 6 inches above the surface of 

 the ground, so dirt can be graded around the silo and 

 enable the surface water to drain away. 



Put a few square headed bolts into the concrete to 

 which the sill for the roof can be fastened. If properly 

 put in, this concrete curbing may be used as a founda- 

 tion for a silo to extend above ground, should addi- 

 tional silo room be needed. 



This concrete should be reinforced with a few 

 strands of barb-wire, about six rounds, each about six 

 inches apart. This is not necessary, but it will 

 strengthen the curbing. 



When the concrete curbing has "set," then proceed 

 to dig out the dirt. Dig down 6 ft. and plaster the 

 side. Apply two coats, each about J /2 inch in thickness. 

 If the plastering is done each 6 ft., then no scaffolding 

 is necessary. With a long-handled shovel, a man can 

 throw the dirt out to a depth of 12 ft. When this 

 depth has been reached, it is necessary to have a plank 

 platform on one side of the silo, about 10 feet from 

 the surface of the ground, or to have a windlass or 

 some other simple hoisting device for raising the dirt 

 out of the pit. 



A rough dirt wall will require more concrete, 

 than will a smooth one. For this reason, the man 



who digs the pit 

 should make an ef- 

 fort to have the wall 

 straight and as 

 smooth as is consist- 

 ent with rapid work. 

 An experienced dig- 

 ger, and in the aver- 

 age subsoil, will 

 have no difficulty in 

 digging such a wall 

 without any other 

 guide than the eye. 

 Should it be found 

 necessary, a straight 

 pole may be placed 

 perpendicularly in 



Marking the Circumference of a Pit Silo Before Digging Trench for Concrete 

 Curbing. 



