Silage is the term applied to fodder which has been preserved by the process of Ensilage. Ensilage is a French word, tracing through the Spanish, from the Lat. siro, Gr. siros, 'a pit,' whence the Spanish verb ensilar, 'to store grain in a silo or pit.' It was originally employed to denote the preservation of green forage in an air and water tight silo—the contents being tightly pressed down so as to get rid of and permanently exclude the oxygen of the air, and thereby prevent putrefactive fermentation. The practice, since its introduction into the British Isles, has been considerably extended, so that the term silage is now applied to fodder which has been preserved by pressure in stacks as well as to that preserved in silos by pressure. The practice of ensilage is of great antiquity. From time immemorial grain has been stored in underground pits in eastern countries. In the time of Pliny it was, he tells us, pursued with success in Thrace, Cappadocia, Barbary, and Spain. Varro also speaks approvingly of the process, and asserts that by it wheat could be preserved fresh for fifty years and millet for a century. In early times it was probably employed chiefly to hide stores of grain from invaders. It is now used mainly in the preserving of green food for cattle and horses. The converting of green fodder, as distinguished from ripened grain, into silage is believed to have been first practised in Germany. In 1843, in the Transactions of the Highland and Agricultural Society of Scotland, Professor Johnston gave a detailed description of the German system of making 'sour hay.' The practice spread through the Austro-Hungarian empire, where graves or trenches, 4 feet by 6 or 8 feet in breadth and depth, were dug and crammed with green grass or green Indian corn, the whole being covered over with a foot of earth. The distinction of first succeeding in directing general attention to the subject was earned by a Frenchman, M. Goffart, whose book, Manuel de la Culture et de l'Ensilage des Maïs et autres Fourrages verts, published in 1877, was not only widely read in his own country, but was translated into English and published in New York in 1879. The method had already been tried to a small extent in America, and the perusal of M. Goffart's work aroused the deepest interest and led to numerous and extensive experiments. The general results were satisfactory, and soon the system found its way into Great Britain. Although several trials were made earlier, the systematic and extensive adoption of ensilage in the United Kingdom dates from 1882. In that year the successful experience of Vicomte Arthur de Chezelles, who had been pursuing the system upon a large scale in France, was made known through the press to British farmers. A host of experimentalists were instantly at work, and so keenly was public attention aroused that in 1883 the Ensilage Commission, a private but highly influential body, was formed to collect evidence and consider and make known the merits of the practice. A mass of valuable information was collected and was embodied in the official blue-books issued by the government.
The commission reported strongly in favour of the system, concluding as follows: 'After summing up the mass of evidence which has reached us, we can without hesitation affirm that it has been abundantly and conclusively proved to our satisfaction that this system of preserving green fodder crops promises great advantage to the practical farmer, and, if carried out with a reasonable amount of care and efficiency, should not only provide him with the means of insuring himself to a great extent against unfavourable seasons, and of materially improving the quantity and quality of his dairy produce, but should also enable him to increase appreciably the number of live-stock that can be profitably kept upon any given acreage, whether of pasture or arable land, and proportionately the amount of manure available to fertilise it.' From 1883 the progress of the movement in Great Britain was rapid. The British agricultural returns first included statistics as to ensilage in 1884. In that year 610 silos were reported as existing in Great Britain. In the next three years the number increased to 2694. By 1887 it was proved by repeated experiments in England that silage might be made in stacks as well as in silos, and, as would be expected, the discovery of the fact that the advantages of ensilage could be attained without incurring the cost of constructing a silo gave a great stimulus to the movement. It is found in practice that the percentage of loss by the spoiling of the food is rather greater in the stack than in the silo, but the balance of advantages is in favour of the stack, which has therefore gained the lead in popularity. Silos are in almost all conceivable forms, some specially constructed at great expense, others 'converted' from existing buildings at small outlay. The cost of construction has varied so much as from 8s. to 50s. per ton capacity. The methods of pressure employed consist of dead weights or of mechanical appliances. The latter, being more convenient in application, are now most largely used. Many ingenious contrivances have been tried for pressing silage. One of the most popular methods is by jacks, screw, and hydraulic. Several systems of pressure which have been patented are found to work admirably, both in silos and stacks. Two varieties of silage are made, the one 'sweet,' the other 'sour.' Originally all the silage made was of the latter kind. In 1884 Mr George Fry, of Chobham, England, made known the results of experiments by which he proved that 'sweet' or 'sour' silage might be produced at the will of the farmer. Prior to 1884 it was the universal custom to apply pressure as soon as the silo was filled. The product of that method was invariably 'sour' silage. Mr Fry filled his silo without packing the material, and deferred applying pressure for two or three days, until the temperature of the silage rose to about 120° to 140° F., when pressure was applied and the top of the silo covered. The theory advanced and proved by Mr Fry is that this temperature is sufficiently high to kill the bacteria which produce acid fermentation, and that, with the bacteria killed and the silage then weighted and the silo covered, the mass of green fodder will remain sweet and be practically preserved under the same conditions as fruits, vegetables, or meats are preserved when tinned. This process of making 'sweet' silage has been found peculiarly suited for stack ensilage, and, as 'sweet' silage is on the whole preferable to 'sour,' the method originated by Mr Fry has been extensively adopted. Temperature is the principal agent in the making of silage. This is controlled by pressure, and in the mass of silage it is measured by the stack thermometer, which should always be employed in silage-making. It is found a safe practice to allow the temperature of the mass to rise to from 130° to 140° F. before applying pressure if sweet silage is desired. Nearly all kinds of farm crops, except roots, may be preserved by the process of ensilage. The crops most largely converted into silage are meadow-grass, clover, rye-grass, lucerne, sainfoin, vetches, maize, and the cereal crops. In some cases the fodder is cut with the chaff-cutter before being put into the silo or stack, but the rule is, except with maize, to preserve it in its natural length. Nearly all kinds of farm stock eat both 'sour' and 'sweet' silage with relish, and it is the prevailing experience that by the process of ensilage the feeding value of the fodder is as a rule slightly enhanced. In wet climates the system is of great importance, for it practically renders the farmer independent of the weather in saving his fodder crops.
In the United States the subject was discussed by the agricultural journals as early as 1873-74; the French method was fully described in 1875 in the Report of the Agricultural Department; experimental silos were being made about the same date; but the first person who made silos and ensilage on a large scale was Francis Morris in Maryland in 1877. The system rapidly spread, especially in the eastern and middle states.