"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."