Forcing In The Field

Forcing asparagus where it is grown in the field has a twofold advantage over removing the roots to a warm place. First, it saves the trouble and expense of transplanting them, which must be done with much care; and, second, it saves the



plants from being ruined by the forcing process. Plants forced in the field where they grow will, if given good care, regain their vigor in a season or two, and may be used again for forcing. By this latter method a better quality and a larger quantity of marketable asparagus is also secured. Various means have been devised to force asparagus in the field, where it is so well established that it continues growth in the summer as though it had not been forced the previous winter. A simple and rather common method of accomplishing this is to place barrels over clumps of asparagus very early in the spring and pile fermenting manure about them, the warmth from the manure forcing the shoots into rapid growth. When the forcing season is over and the danger from frost is past the barrels are removed, and the plants continue growth in the open air. Sometimes asparagus is forced by placing frames, covered with sash, over the plants in the field, the rows of asparagus being set rather close together. This is considered a very profitable method by many market gardeners. Another method of forcing asparagus in the field is to dig ditches between the rows and fill them with fermenting manure. The surface of the bed may also be mulched with manure. The latter plan is extensively practiced by French market gardeners. At the beginning of November the pathways between the beds of asparagus are dug up about two feet in depth and width. The soil coming from the pathway is divided very carefully and put about eight inches thick on the surface of the bed. The trench is filled up with fresh stable manure, not litter, and frames are placed on the bed. The manure should rise as high as the top of the frames and the lights be entirely covered with mats and litter to prevent the heat accumulating in the frame from escaping. In about two or three weeks the asparagus begins to show itself on the surface of the bed. Many market gardeners cover the whole of the bed inside the frames to a thickness of three or four inches with manure, to force the vegetation more quickly; but in this case the manure must be removed when the asparagus begins to shoot. When the shoots are about three inches out of the ground they may be cut. The mats must be taken off in the daytime, but the heat must be well kept up, else the roots and buds will fail to push. The beds are forced every second year only. The gathering of the asparagus may continue for about two months but no longer, or the plantation would be injured. When the gathering is over the frames are taken away, and the soil which was dug up from the alleys is put back again. An ingenious method of forcing asparagus in the field by means of shallow tunnels was devised and successfully carried out by Prof. J. C. Whitten, at the Missouri Experiment Station, who gives the following account in Bulletin No. 43: "The field selected for the experiment was planted to asparagus about ten years ago. The plants were in fair vigor, though of a small variety. The first section forced embraced six rows, four feet apart, and fifty feet long. Fig. 35 shows this section with one tunnel uncovered. Trenches were first made between the rows. This was done by plowing between them, twice in a place, throwing the furrows on the plants so as to cover each row with two furrows of loose earth. These trenches between the rows were then made uniform by means of the spade. When finished they were three or four inches lower than the crowns of asparagus in the adjacent rows. These trenches were then covered with twelve-inch boards, which rested on four-inch blocks, placed at frequent intervals along either side of the trenches. This formed tunnels between the rows for conducting the steam. To guard against the steam's escaping, two or three inches of soil was placed over the boards, and the asparagus patch was then covered with five or six inches of horse manure. This covering was to prevent the heat from escaping from the soil too rapidly. It was then ready for the steam to be turned into the tunnels. "To conduct the steam a one and one-half inch pipe was carried above ground from the boiler to one end of the central tunnel, a distance of one hundred and eighty-five feet. A steam hose long enough to reach each tunnel was attached to this pipe through which to blow steam into the tunnels. It was not the idea to give a constant supply of steam, but to discharge a little into the tunnels each afternoon, or as often as was necessary to maintain sufficient warmth. A piece of tile was inserted into the mouth of each tunnel to prevent the discharging steam from tearing away the earth. "The first steam was turned into the tunnels on November 14th. Steam was discharged into each tunnel, not to exceed five minutes at a time, in order not to heat the earth too hot in any single place. It required about one hour of steaming the first day to bring the bed up to the required temperature of sixty degrees. The distribution of heat throughout the bed was very uniform and satisfactory. The moist steam seemed to permeate the soil equally in all directions. "After the first day very little steaming was necessary until the asparagus began to be produced. On an average the bed was steamed about twice in three days and then only for about five minutes for each tunnel. The soil and horse manure mulch seemed to hold the heat very well, the frequent steamings keeping up fermentation in the mulch. "The first asparagus was cut November 24th, ten days after the first steam was applied. The stems were cut just before they got through the soil and were perfectly bleached. They were as large as those ordinarily produced during the normal period of growth in spring, and were far more crisp and delicious. "Cuttings of asparagus were made almost daily for about a month, when the growth became somewhat weak. The last cutting was made on December 22d. During the month 141 bunches of the ordinary market size, and weighing about one-half pound each, were cut from this bed of 25 x 50 feet. This was equivalent to 300 feet of row or 100 hills of asparagus. "Exhausting steam into the asparagus bed, instead of returning it to the boiler in an inclosed circuit, would at first seem to be a wasteful process of heating. Experiment showed, however, that the circumstances justified this method. Heating a bed of this kind by a circuit of steam-pipes or hot-water pipes is very unsatisfactory. The heat from pipes very soon dries out the soil around the tunnels, destroying its power to conduct heat. In this way the bed becomes too hot and dry adjacent to the tunnels and too cold a short distance from them. It also becomes necessary to maintain heat in the pipes a good part of the time. "By blowing steam directly into the tunnels the soil is kept moist; the steam has a penetrating effect, and permeates all parts of the bed, giving a uniform heat throughout; this moist steam keeps up a continual fermentation of the manure mulch, thus giving heat, and only occasional brief steamings are necessary. "Care must be taken not to use too much steam at one time, or the plants may be ruined by overheating. Our asparagus rows were four feet apart, the tunnels midway between them were only eight inches wide, and yet we found that five minutes at a time was as long as was safe to force steam into a single tunnel. "These experiments have been so successful as to indicate that any one provided with a steam-heating plant could successfully force asparagus for the markets in this manner." Another plan of forcing asparagus in the field, devised by Prof. L. H. Bailey, is thus described in his "Forcing Book": "The Cornell asparagus house--if it may be called a house--is about twenty by fifty feet and the frame is made of steam-pipes. The sides, or walls, are only eighteen inches high, and the frame consists simply of a ridge and three pairs of rafters. The steam-heating pipe or riser is just beneath the ridge, and this feeds two returns upon either side of the house, next the walls. When it is desired to force the asparagus, canvas or muslin is stretched over the frames. No difficulty has been found in starting the asparagus into growth in January and February. The cover is left on and the heat kept up until all danger of frost is past, when the canvas is removed and the plants grow naturally out-of-doors. The secret of this method will no doubt be found to lie in allowing the plantation to become very thoroughly established (at least, three or four years old) before forcing is attempted, in the very best tillage and fertilizing during the summer while the plants are growing, in taking off the cover just as soon as settled weather comes, and in not cutting the plants until after that time."

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