SILOS AND SILAGE 151 
The figures for the capacity of silos given in the table refer to 
Indian corn cut when nearly mature. Somewhat larger quantities 
can be put in of immature corn or sorghum, and less of dry corn, 
alfalfa, grain sorghums, and similar crops that do not pack well. 
If cut when nearly ripe, the grain sorghums will occupy at least 
one-third more space than Indian corn cut at the usual time, and the 
capacity of a silo for these crops would then be decreased’ in this 
ratio from the figures given in the table. 
Important Points in Building Silos.—The following points 
should be kept in mind in building silos: 
1. The silo,must be air-tight. The process of silage making is 
largely a series of fermentation processes. Bacteria pass into the 
silo with the green fodder and after a short time begin to multiply 
there, favored by the presence of air and an abundance of feed 
materials:in the fodder, especially soluble carbohydrates. As a 
result of this action, as well as of the respiration of the plant cells, 
carbon-dioxide and heat are evolved. The more air at the disposal 
of the bacteria, the further the fermentations will progress, and the 
greater will be the losses of feed materials. If a supply of air is 
admitted to the silo from the outside, the bacteria will have a 
chance to continue to grow, and more fodder will, therefore, be 
wasted. If no further supply of air is at hand, except what remains 
in the air spaces between the siloed fodder, the bacteria will gradu- 
ally die out, or only such forms will survive as are able to grow in 
the absence of air. The changes occurring in siloed fodder are also 
due in part to intramolecular respiration in the plant tissues, which 
continues until the cells are killed. When there is available oxygen 
in contact with the plant cells, these will live longer and the loss of 
plant materials will be greater than when only a smaller supply of 
air (oxygen) remains in the air spaces in the siloed mass. 
2. The silo must be deep. Depth in the silo is essential in mak- 
ing silage so as to have the siloed mass under great pressure; this 
will cause it to pack well and will leave as little air as possible in 
the interstices between the cut fodder, thus reducing the loss of feed 
materials to a minimum. 
The early silos built in this country or abroad were shallow struct- 
ures, often not over 12 to 15 feet deep, and were longer than they 
were deep. Experience showed that it was necessary to weight heavily 
the fodder placed in these silos in order to avoid a large amount of 
moldy silage. In modern silos no weighting is necessary, since the 
material placed in the silo, on account of the great depth, is suffi- 
