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."