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 gradually 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 making 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 structures, 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

ciently heavy to largely exclude the air in the siloed fodder and
thus secure a good quality of silage. In case of deep silos the loss
from spoiled silage on the top is smaller in proportion to the amount
of silage stored, and a smaller loss occurs while the silage is being
fed out. 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 (Fig. 28).

3. The silo must have
smooth, perpendicular walls,
which will allow the fodder 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 thus formed will
cause the surrounding silage
to spoil.

The walls of the silo must be made rigid and very strong, so as not to spring when the siloed mass settles. The lateral (outward) pressure of cut corn when settling at the time of filling is considerable, and increases with the depth of the

silage, at the rate of about Fig. 28.-A good concrete silo costs more than a wooden silo, but will last indefinitely eleven pounds per square foot when properly cared for, and needs no attention beyond an application of a coat of pure

for every foot in depth of silcement wash every two or three years. (Wisconsin Station.)

age. At a depth of 20 feet

there is, therefore, an outward pressure of 220 pounds per square foot; at 30 feet, a pressure of 330 pounds. It is because of this great pressure that it was difficult to make large, rectangular silos deep enough to be economical, since the walls of such silos always spring more or less under the pressure of the silage, and this seldom keeps as well in them as it does in those whose walls cannot spring. In the round wooden silos every board acts as a hoop, and, as the wood does not stretch much lengthwise, there is but little danger of spreading of such walls; it

is on account of this fact and because of the economy of construction that only round silos are now built.

After the silage has settled there is no lateral pressure in the silo; cases are on record where a filled silo has burned down to the ground with the silage remaining practically intact as a tall stack.

Silo Structures. It does not lie within the scope of this book to discuss different methods of silo construction; suffice it to say that there are four or five different kinds of materials now used in the building of silos: Wooden silos (either stave, so-called re-saw, or plastered), cement (solid or block), brick, stone, glazed tile, and steel. A satisfactory and more or less permanent silo can be built of any one of these materials, provided due care is taken in the construction. The cost of different kinds of silos will vary greatly

Fig. 29.-A California dairy barn, with concrete silos, each 15 ft. diameter by 30 ft. high;

capacity, 100 tons. in different sections, according to the relative price of lumber, cement, brick, etc. Pit or bank silos are satisfactory and cheap structures sometimes met with in the dry regions of Western and Southwestern States. They are rarely over 12 to 18 feet deep or over 50 tons capacity.

A number of different experiment stations have published bulletins on silo construction which describe the silo materials best adapted to the conditions in the respective States, and these may profitably be consulted before a silo is built. Silos built by farmers living in the same localities may also be examined, and advantage thus taken of the experience of others (Fig. 29).

Advantages of Silos.—There are several reasons for the rapid increase of silos on American farms during the past few decades; the most important ones are given below.

1. Generally speaking, the silo enables the farmer to secure the largest possible amount of feed materials in the corn crop for feeding farm animals in the most convenient and cheapest manner.

2. Corn silage furnishes a uniform succulent feed during the winter and spring, which is greatly relished by all classes of farm animals and especially adapted for feeding dairy cows and beef cattle.

3. The silo will preserve feeds like corn, sorghum, clover, alfalfa, pea vines, etc., in a succulent condition for feeding any time during the year, and thus furnishes valuable supplementary feeds for late summer and early fall feeding when pastures are likely to be short, as well as for winter feeding when other succulent feed is either lacking or scarce.

4. The silo makes the farmer more independent of weather conditions than when hay is made, and enables him to get along with smaller barns than otherwise, since less room is required for storing feed in a silo than in the form of hay in a barn.?

a

Fig. 30.—A “re-saw" silo being filled with alfalfa. These silos are well adapted to mild

climates, as that of Caliiornia and the southern States. (Pacific Rural Press.)

The value of the silo on American stock farms, and especially to dairy farmers and cattle men, has been fully established during the past few decades by numerous carefully-conducted feeding experiments with different classes of farm animals, as well as by practical feeding experience. The present general distribution of the silo in this country has been the most important factor in the

2 The advantages of silos are discussed more fully in the author's " Book on Silage" (Chicago, 1900; now out of print) and in “Modern Silage Methods," published by Silver Manufacturing Company, Salem, Ohio, both of which books have been freely used in the preparation of this chapter,

development of our livestock industry that has come since the introduction of modern agricultural machinery (Figs. 30 and 31). The silo is most economical where the number of stock kept is sufficiently large to consume at least 100 tons of silage during the season. The investment in a silo and necessary machinery is relatively high for smaller silos, and the cost of storing and loss of silage through spoiling relatively larger than with large silos. The silo belongs with intensive farming, where the greatest profit results from keeping as large a number of livestock as possible on a given acreage. For small herds of, say, 12 head of cattle or less, the growing of roots where the land is suited to these crops may prove a more economical practice for supplying succulence in the rations fed than making silage.

3

FIG. 31. Battery of four cement silos on a California cattle ranch. Dimensions 20 feet in

diameter, and 60 feet high, capacity about 400 tons each. (Pacific Rural Press)

SILAGE CROPS.-Indian corn is preëminently the great American silage crop and is, in general, better adapted for siloing purposes than any other agricultural crop. The reason for this is easily seen : The thick stems and broad leaves of the corn plant, when cut, pack well in the silo; corn is rich in starch and other non-saccharine carbohydrates, which insures silage of a moderate acidity, and it is relatively low in protein substances, so that the danger of undesirable fermentations in the silo is removed. The acids normally present in corn silage are lactic and acetic. Lactic acid is non-volatile and makes up about two-thirds of the acidity of silage made from nearly matured corn, or about 1 per cent on the average, while acetic acid is present in from 0.2 to 0.5 per cent on