_ 4 



in 7 silos at the Jlew Jersey Station and one at the Beltsville Research 

 Center of the Department of Agriculture, a-gregatins 12 tests on grass silage 

 and 7 on corn silage. Readings were taken as each 2 or 2-1/2 foot layer of 

 silage was placod in the silos so that the nuiiiber of individual panel_ readings 

 taken during the filling of the various silos ranged from 75 to 150 vdth 

 additional readings heinc taken each morning and evening during filling and 

 each day during the settling period. The panels averaged about 4 square feet 

 in area. Results are quite variable as may be seen from Figure 1, which 

 summarizes the lateral pressures, llaxixaum values for grass silage vary from 

 159 pounds per square foot in a 12-foot dir.meter silo v/ith 64 per cent mois- 

 ture silage at a 25 foot head, to 1189 pounds per square foot in an 18-foot 

 silo, with 77 per cent moisture silage at a 40-foot head. This is a range 

 of from apT^roximatoly one-half to tvro and one-half times the pressures com- 

 monly considered in silo design, v/hich is 12 pounds per square foot per foot 

 of depth. 



Factors that affect the amount of lateral pressure .^n silo walls, in 

 addition to depth, are the moisture content of the silage and its distribution, 

 the oroservativo used, the diameter of the silo, the fineness of cut, speed 

 o^ filling and type of material ensiled. The 12 tests or silo pressures with 

 grass silage that have been run to date show the effect of moisture content 

 and the type of orcsorvf.tivu. Figures 2 and 3 show how the pressures in 12 

 and 14-foot diameter silos increase as the moisture content increases. 

 There are some differences in the typo of preservative used in these silos, 

 but since the moisture content vr.rics in each case »nd there are some dif- 

 ferences in the materials ensiled vrith different preservatives no direct com- 

 parisons on the effect of preservatives can be made for these silos. Figure 

 4 demonstrates the effect of both moisture content and preservative in 18-foot- 

 dirjaeter silos. Curves 2 and 5 show the increase in pressures with molasses 

 silrip-o over the pressures with acid silage given in curves 1 r-.nd 4, Since 

 the silos represented by curves 1 • nd 2, also those represented by curves 4 

 and 5, were filled simultaneously, the effects of diameter, material and 

 moisture content were eliminated and all the differences can be attributed to 

 the prcscrvr.tivo. Smilc.rly the incre-,se in pressure found v;hen comparing 

 curve 1 vn.th 4 and curve 2 mth 3 rnd 5 can be attributed to moisturo content. 

 The fact that the curve 2 crosses curve 3 beti,vcen the 25 and 30 foot levels 

 can be ascribed to the difference in the material ensiled in the t-.TO silos 

 and the fact that the silo represented by curve 2 had the bulk of the low 

 moisture m^.terial in the bottom pr.rt and comparatively high moisture silage 

 on top, while the silo represented by curve 3 was filled with silage of a 

 uniform moisturo content throughout. 



Capacities 



Silo capacity as v:ell as prossuro is influenced by Jioisture, silo 

 size, r.nd fineness of cut. It ho.s bcun observed th^t with average moisture- 

 grass, taken as 65 to 72 per cent, the smaller or average sizes of silos mil 

 hold about the same tonnage of grass as corn. Table I. Those holding a 

 greater total tonnage of grass are about balanced by those holding less. As 

 the moisture content is increased, the total tonnage is increased and vice 

 versa. Silos filled with high moisture grass have hold up to 50 per cent 

 greater tonnage than would be expected with/corn'^silagc. In each case, how- 

 ever, the variation of the dry inattor capacity of the silo is slight. 



