US3590588A

US3590588A - Process and apparatus for laying a horizontal subterranean film

Info

Publication number: US3590588A
Application number: US741355A
Authority: US
Inventors: Homer L Draper; Duane W Gagle
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1968-07-01
Filing date: 1968-07-01
Publication date: 1971-07-06
Anticipated expiration: 1988-07-06

Abstract

Strips of preformed film are laid underground after passage through a hollow plow. The strips are finally disposed with their major surfaces substantially horizontal, and preferably laid with their edges turned up to act as a trap for water sinking through the ground. The strips can be spaced apart, adjacent or overlapping, and are preferably made of plastic, but may be made of metal foil or of fabric coated previously or coated in place with asphalt. Apparatus to feed the film from a roll through the plow are disclosed, along with tractors to draw the plow, vibrators to vibrate the plow, hydraulic and other means to control the plow depth and position, and means to inject liquid, such as water, asphalt, fertilizer, nematocides or weed killers, on the film as it emerges from the plow.

Description

Phillips Petroleum Company [21 1 Appl. No, [22] Filed [45] Patented [73] Assignee [54] PROCESS AND APPARATUS FOR LAYIlNG A HORIZONTAL SUBTERIRANEAN FILM 3,309,875 3/1967 Niederwemmer 61/726 X 3,339,369 9/1967 Ryan 6l/72.6

3,398,542 8/1968 Hansen ct a1, 1. 61/722 FOREIGN PATENTS 211,745 1960 Austria 61/1 Primary Examiner-Jacob Shapiro Attorney-Young and Quigg ABSTRACT: Strips of preformed film are laid underground after passage through a hollow plow. The strips are finally disposed with their major surfaces substantially horizontal, and preferably laid with their edges turned up to act as a trap for water sinking through the ground. The strips can be spaced apart, adjacent or overlapping, and are preferably made of plastic, but may be made of metal foil or of fabric coated previously or coated in place with asphalt. Apparatus to feed the film from a roll through the plow are disclosed, along with tractors to draw the plow, vibrators to vibrate the plow, hydraulic and other means to control the plow depth and position, and means to inject liquid, such as water, asphalt, fertilizer, nematocides or weed killers, on the film as it emerges from the plow.

PATENTEU JUL6 I97! SHEET 1 BF 5 INVENTORS H L DRAPER BY D. W. GAGLE FIG. 2

A T TORNEVS PATENTEU JUL-6 Ian SHEET 2 BF 5 FIG. 4

FIG. 6

A T TOR/VEVS INVENTORS H. L. DRAPER D W. GAGLE PATENTEU JUL6 x971 SHEET 3 UP 5 FIG. l0

FIG.

FIG. /4

m m 0 N T 0 NEE O E L T VAG T N A A DG & LW 3 Y B 3 7 l m F PATENTEDJUL-$I97I 3,590,588 SHEET '4 OF 5 INVENTORS H. L. DRAPER D. W. GAGLE A T TOR/VE V5 PATENTEU JUL-6871 3,590,588

SHEET 5 BF 5 F/a /& .1; if f;

INVENTORS H. L. DRAPER D. Wv GAGLE A T TO/PNEVS PROCESS AND APPARATUS FOR LAYING A HORIZONTAL SUBTERRANEAN FILM FIELD OF THE INVENTION This invention relates to Class 61, Hydraulic and Earth Engineering, Subclass 1, Water Control, being an improvement over the prior U.S. Pat. No. 3,276,208 of Oct. 4, 1966, to Bolt. Bolt is laying 32-inch wide Strips of liquid asphaltic material, whereas the present invention is laying strips of solid preformed film through a hollow plow. It is submitted that laying a preformed film from a roll of the same is more certain of providing a continuous water-impervious film than the underground injection of liquid asphalt, which cannot be observed and may become discontinuous without warning.

DESCRIPTION OF THE PRIOR ART In addition to the Bolt patent described above, the prior art comprises such U.S. patents as:

Spcrr 2,029,343, Feb. 4, 1936, Class 47, Subclass 9, in which strips of metal screening are used as mulch, but are laid by complete excavation, hand spreading and shoveling the soil back over them.

The same process of excavation and spreading the soil back over the strips is used to bury the perforated plastic foil of Heigl et al. 2,916,854, Dec. 15, 1959, Class 47, Subclass 58.

Prosser 3,282,057, Nov. 1, 1966, Class 61, Subclass 72.1, places a vertical plastic film strip in an open trench along with an electric cable 13 and fills the trench, so that the vertical plastic sheet will act as a warning to others excavating at a later date that an electric cable is being approached by their excavation.

Numerous U.S. patents show laying cables through hollow plows, but do not teach how to fold up or pass a ribbon or sheet of film through a hollow plow and then unfold it into a horizontal sheet underground. Examples are Christensen 3,201,944, Aug. 24, l965, Class 61, Subclass 72.5; and Freeman et al. 2,184,912, Dec. 26, 1939, Class 11 l, Subclass 5.

Numerous U.S. patents inject asphalt the ground. Examples are Gagle et al. 3,252,290, May 24, 1966, Class 61, Subclass 36; Miles 2,378,235, June 12, 1945, Class 61, Subclass 38', and Dybalski et al. 3,236,671, Feb. 22, 1966, Class 106, Subclass 277.

Obviously, none of these prior art patents are pertinent to the present invention.

SUMMARY OF THE INVENTION In many places in the world desert conditions prevail, merely because the soil is loose or sandy and the scanty rainfall, which would otherwise be enough to support crops, is lost by sinking deeper into the soil than the roots of plants normally extend, due to a lack of a water table or water barrier at that depth. The present invention, by plowing a horizontally disposed, substantially water-impervious film into the ground at a depth to about which the roots of plants should extend, said film preferably having upturned edges, provides an artifi cial water table or water barrier which retains enough of the rain water in the soil above the film to permit crops to be planted and grow with the scanty normal rainfall. If desired, there can also be irrigation, but it will be much less irrigation than necessary without the artificial water barrier strips. In fact, in many situations vast quantities of water used in irrigation would be lost deep in the loose soil without ever being effective to grow useful plants.

There is a certain expense to laying these plastic films underground, including, of course, the cost of the film which will eventually need replacement, but the value of being able to farm on desert land or grow twice as large a crop as before is much greater than the cost of operation.

As an added feature, asphalt, fertilizer, weed killers, nematocides or water can be added to or above the film or strip as it is being laid, where they will be most effective.

While it is preferred that the plastic film be impervious to water, it need not be completely impervious, as even with some holes or leakage due to porosity, a large degree of value in the practice of the invention is obtained if the film is only substantially impervious.

One object of this invention is to provide a process for forming artificial water tables in loose desert soil.

Another object is to provide processes of farming employing such artificial water tables employing preformed plastic strips laid horizontally underground. These processes may involve the addition of liquid water, asphalt, fertilizer, weed killers or nematocides.

Other objects are to provide suitable apparatus for carrying out the above processes.

Another object is to provide a plow having an elongated shank section and horizontal strip spreading wings, with means to pass a strip down through the shank and spread it out horizontally underground.

Another object is to provide a plow with means to fold up a strip of film, pass the same through the plow, and then unfold and lay it as a horizontal layer, preferably with upturned edges to aid in acting as a water barrier. Means to add liquid to or above the strip may also be provided. Means to vibrate the plow may be provided.

Numerous other objects and advantages will be obvious to those skilled in the art upon reading the present specification, claims and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an elevational view with the earth in cross section ofa plow embodying a first modification of the present invention being drawn by a tractor and laying a horizontally disposed ribbon of film under the ground.

FIG. 2 is an enlarged elevational view of the plow shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2 looking in the direction indicated.

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3 looking in the direction indicated.

FIG. 5 is a rear elevational view ofthe plow of FIG. 3.

FIG. 6 is a bottom view of FIG. 3 showing the film emerging from the hollow plow, with part of the film broken away to show the film guiding shoe in more detail.

FIG. 7 is a schematic view of the roll of film of FIG. 2 with parts broken away and exaggerated to show the way the film is originally folded on the roll and started to be unfolded as it passes into the hollow plow.

FIGS. 8 and 9 are elevational views of the plow of FIG. 1 showing two alternative ways of starting the plow into the ground.

FIG. 10 is a cross-sectional, elevational view of a farm in which a row of plants is growing over each buried strip of film.

FIG. 111 is the same as FIG. 10 except that the strips of film at different elevations overlap horizontally.

FIG. 12 is an elevational view of a knife mounted on a handle, useful to cut the film away from the plow.

FIG. 13 is a schematic perspective view of a way in which the end of a strip of film may be closed to form a complete trough to retain water if desired.

FIG. 14 is an elevational schematic view with the ground in cross section of a second modification of a plow embodying the present invention.

FIG. 15 is a rear view of an upper portion of FIG. 14 taken at an angle of 60 from the horizontal showing folding and feeding the film into the hollow plow.

FIG. 16 is a rear view of the lower portion of the plow of FIG. 14.

FIG. 17 is a rear elevational view with the ground in cross section of a third modification of the plow with a nurse tractor carrying the roll of film.

FIG. 18 is a front view of a fourth modification of a plow embodying the invention with the ground in cross section.

FIG. 19 is a plan view of the plow shown in FIG. 18.

FIG. is a crosssectional, elevational view of the toe portion of the plow of FIG. 19 taken along the line 20-20 looking in the direction indicated.

FIG. 21 is a schematic rear view with the earth in cross section of a portion of a fifth modification of the plow in which means are provided to keep the plow level while plowing the strips into the side of a hill to form a water table in a manner similar to contour plowing.

FIG. 22 is a side elevational view of FIG. 21.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 a hollow plow 21 is being drawn through the ground 22 from left to right by a tractor 23. Details of a first modification of this plow will be given in describing FIGS. 2 to 7 below. The plow may be connected to the tractor by any suitable means known in the prior art for connecting plows to tractors. For example, plow 21 may be connected to the tractor by drawbar 24 pivoted at 26 and adjusted in position in or out of the ground 22 by hydraulic cylinder 27, piston rod 28 and link 29, connected in a conventional manner. Other known linkages allowing more accurate positioning of the plow may be substituted in the practice of this invention, for example, such as shown in FIGS. 21 and 22. In place of tractor 23, horse-drawn vehicles, or the like, may be substituted if desired. As plow 21 is drawn through the ground 22 it lays behind it a horizontal strip of film 31 underground, which film comes from a roll of preformed film 32. If desired, plow 21 may be vibrated as it is pulled through the ground to make it penetrate the ground easier and to feed the film through it easier by a vibrator 33. While an electric motor vibrator with an eccentric flywheel 34 is shown, obviously other vibrators known in the prior art may be substituted, and in loose soil no vibrator is needed.

The strips of

film

31 and 39 and others shown in the drawings may be made of many conventional substances. Preferably they are strips of plastic, made generally by melting pellets of the plastic and extruding the same as film strips. The plastic may be polyethylene, either high-pressure polyethylene or low-pressure polyethylene, preferably the polyethylene of US. patents to Hogan and Banks, 2,825,721 of March 4, I958, and 2,951,816 of Sept. 6, I960, or polypropylene, polyvinylchloride, ethylene-propylene terpolymer of the rubbery type, or saran. These plastic strips can be coated with a thin metal foil. When the strip is to be coated with asphalt or asphalt emulsion, as shown in FIG. 14, the strip may be any fabric, preferably felt, glass fibers, glass wool, burlap or polypropylene fabric, or matted polypropylene fibers. All the above strips may be from 0.003 to 0.2 inch thick, preferably from 0.004 to 0.0625 inch thick. Metal foil by itself in the thinner ranges, employing metals such as aluminum or copper, from 0.001 to 0.02 inch thick, may be used as these underground strips.

FIG. 2 shows the first embodiment of the plow 21 in greater detail. Plow 21 is formed with a penetrating point or toe 36, a generally vertical hollow shaft section 37 disposed with its widest side longitudinally along the axis of movement of the plow and preferably streamlined in cross section, and a lower wedge-shaped, horizontally disposed film distributing blade 38 on each side of shaft section 37.

As shown in FIG. 7, a length of film 39 is folded longitudinally at 41 and is wound up on roll 32, and as the film is drawn off the roll passed down the passageway 42 in plow shank 37 with

edges

43 and 44 passing on opposite sides of a guiding toe 46 of a triangular guide shoe or plate 47 (see FIG. 6). The bottom of shoe 47 is spaced from

downturned edges

48 and 49 of the plow 21, causing the

edges

51 and 52 of the strip 39 to be laid in a turned-upward position as shown in FIG. 5 to form the underground film 31 of FIG. 1.

By passing the film 39 downward through hollow passage 42 in folded position, as shown, and having its width disposed longitudinally to the direction of motion of plow 21, a minimum of disturbance of the soil 22 is involved, as streamlined shank 21 cuts a narrow slot through the soil 22, which returns to join again as the plow passes, and blades 38 raise the soil 22 a minimum distance and allow it to return as soon as the plow 21 passes with a minimum of disturbance. Thus the film strip 31 is laid underground, disposed horizontally and parallel to the ground surface, or level (ifdesired, as in FIG. 21).

FIG. 3 is a cross section of FIG. 2 taken along the line 33 looking down in the direction indicated. Plow toe 36, horizontal spreader blades 38, passageway 42, film guiding toe 46 and triangular shoe 47 are all visible and can be compared with the same parts in FIGS. 2, 4 and 5 in order to visualize the preferred shape of the parts. The ends of opening 42 can be defined by vertical separating

ribs

53 and 54 ifdesired.

Fig. 4 is a cross section of FIG. 3 taken along the line 4-4 looking in the direction indicated. No further description is necessary. The trailing end of shoe 47 is connected by end closure plate 56 to the plow blades 38. The film is not shown in FIG. 4 so that the construction of shoe 47 is easier to see. Shoe 47 may be bent slightly upward in its central portion to reduce friction on the film 39 if desired.

FIG. 5, being merely a rear view of FIGS. 3 and 6, needs no further description.

FIG. 6, as a bottom view of FIGS. 3 and 6, needs no further description. The right-hand portion of film strip 39 is broken away so that the space 57' is visible between shoe 47 and downwardly depending shoe edge 48 in which the edge of strip 39 turns up automatically as the plow 21 moves forward and strip 39 is laid behind it.

FIG. 7 was described in the sixth paragraph above.

FIG. 8 shows one way of starting off the plow. Some of film strip 31 is shoved into and then pulled by hand out of the plow 21 and may be secured to the ground by a spike or spikes 58, or rocks can be piled on it or someone can stand on it. Tractor 23 then starts pulling plow 21 to the right, and the valves of hydraulic cylinder 27 are manipulated to force plow 21 down into the position below the ground as shown in FIG. 1. By that time there is enough earth on top of sheet 31 behind the plow 21 so that the spike 58 or other holddown means can be removed and sheet 31 will continue to be laid and be held in place by soil friction alone.

FIG. 9 shows another way to start the plow. A hole 59 is dug in the ground 22 and plow 21 is positioned therein with some of strip 31 pulled out of it. Rocks or earth 61 is piled on strip 31 and then the tractor 23 is actuated to pull plow 21 into the soil 22 through the side of hole 59 into the position shown in FIG. 1.

FIG. 10 is a cross section of the ground 22 on a farm where a series of parallel, horizontally disposed strips 31 have been laid. Strips 31 can be laid very close together, but it is preferred to lay them spaced from 2 inches to 2 feet apart. They should be laid l to 4 feet deep, depending on the root structure expected from and needed by plants 62. While plants 62 can be planted anywhere and while plow 21 can be operated to lay strips 31 at one side or under plants 62, it is preferred to lay strips 31 first, and then plant seeds or plants 62 in rows directly over each strip. Strips 31 may be from 6 inches to 6 feed wide, but are preferably about 2 to 4 feet wide.

While it is preferred to lay one strip 31 at a time, it is within the scope of the present invention to lay a plurality of strips 31 at the same time by means of a gang of plows (not shown), each plow being like the single plows shown in the drawings.

FIG. 11 shows a cross section of the ground 22 on another farm, where two levels of strips 31 overlap each other. While it is possible, due to the thinness of shank 37 and the width of spreader blades 38, to lay the upper layer of strips 31 and then lay the lower layer of strips 31 between them, it is recommended that the lower layer of strips be laid first. A vertical spacing of 2 inches to 2 feet and a horizontal overlap of l to 6 inches is recommended, with the depth and other conditions the same for the upper layer of strips 31 as described above for the single layer of the strips in FIG. 10. Plants 62 are preferably planted in rows above each strip 31.

FIG. 12 shows one convenient way to cut the film 31 off at r the end of the row by a knife blade 63 mounted on the end ofa convenient handle 641. Other cutting means known to the prior art of severing plastic sheets may be substituted, such as an electrically heated wire (not shown).

FIG. 13 shows one convenient way to finish the end ofa row by cutting off strip 31 with knife 63 and then cutting slots at 66 and 67 between the floor 39 and

walls

51 and 52. The end of 39 can then be bent up as shown, and the ends of 51 and 52 bent around as at 67-and secured to the end of 39 by suitably adhesives or heat welded, or any means known for the specific film in the prior art. However, good results are obtained without closing the ends of the strips or channels 31, especially if the ends are left coming up out of the ground as in FIG. 8.

FIG. 14 shows a second modification of a plow 68 having a hollow shank 21A, is drawbar 241A, a.plow toe 36A and a horizontal spreader blade 38A, which are substantially identical to corresponding parts 21, 2 1, E16 and 39 described above. However, either an imperviousfilm or a woven or nonwoven fabric from roll 71 with its axis transverse to the direction of plowing is passed over idler roll 72 in unfolded condition and is then folded and passed down through shank 21A where it emerges a film 73, which may have turned up edges or may be flat, and which may be coated under the overhanging edge with asphalt emulsion, or hot asphalt, or liquid such as water, weed killer, nematocides or fertilizer from spray head 76 fed by pipe 77 controlled by valve 78 from tank 79, which may be heated by heater 81. This widens the invention to include laying porous or perforated strips 73 of fabric and also, if desired, coating the strips 1 3 with asphalt emulsion or hot asphalt'or tar and/or impreg ating or coating the strips 73 with various liquids.

FIG. is merely a view ofa portion of FIG. 11- taken at an angle of 60 from the horizontal to show how strip 69 folds into 21A.

FIG. 16 is merely a rear view of a portion of plow 69 of FIG. 14 and needs no further description.

FIG. 17 is a third modification of the invention in which a plow 92 mounted on a tractor 23B has a hollow shank 37B and upwardly and outwardly disposed spreader arms 398 so that the film 398 being laid is laid as a V-shapcd trough. The roll 32B is carried by a nurse vehicle 83 alongside tractor 23B, being either pulled by tractor 238 or as shown with its own means of locomotion, moving tracks 94. The film 39 is folded with a fold at edge 11 and a double layer of film at 13 and 4 3, which passes over roller 86 and down through hollow shank 378 to be spread into V-shaped cross section sheet 398 under the surface of soil 22. Obviously, other configurations than a V-shape can be used, such as a semicircular, upwardly concave strip (not shown). The upper edges of the V or other upwardly concave shape can be laid to extend up close to the surface, or even above the surface, of the ground (not shown) so the strip can act as a sand-filled irrigation ditch, if desired.

FIG. 19 is a front view of a fourth modification of a plow 87, also shown in a plan view in FIG. 19 and as a cross-sectional view in FIG. 20. Plow 97 comprises an underground cutting blade having a cutting toe or edge 89 lying at about 45 to its line of travel in FIG. 19, two vertical shanks 99 and 91, and a top frame member 92, all rigidly connected together to form a rectangular cutting frame which is pulled to the right in FIG. 19 and pulled directly out of the picture plane in FIG. 18 with the lower ends of vertical frame members 99 and 91 and lower horizontal blade 89 submerged under the soil 22. A roll 93 of a single strip of film 94 is mounted on the frame 92 and film 94 passes vertically down behind vertical cutting bar 91, under roller 96 mounted on

frame members

91 and 92, across behind horizontal cutter bar 87, under roller 97 mounted between

members

91 and 92 behind cutter 87, up over roller 97 and back to the left in FIGS. 19 and as a film layer 941 laid under the surface of soil 22.

FIGS. 21 and 22 are rear and side views, respectively, of a fifth modification of the invention in which the plow parts 21,

317 and 311 are the same as in FIGS. 5 and 1, respectively, but are mounted differently on tractor 99 so that plow 21 can pivot at 1111 to a level position and can lay film strips 31 as a series of level strips under the sloping surface 102 of the ground 22. Any suitable means for tilting and for raising and lowering plow 21 in the ground may be employed, such as hydraulic cylinder 1911, piston rod 19:1, link 106 and arm 107 all mounted together as shown to allow rotation of plow-holding means 111%. Drawbar 109 can be supported at any desired elevation from plow support bar 11]. mounted on tractor 98 by mean of rightand left-handed

screws

112 and 113 which are rigidly secured to meshing

gears

114 and 116, gear 116 being driven by reversible motor 117 mounted by arm 118 on support bar 111.

The invention is not limited to the above description of five illustrative embodiments thereof, as it will be evident to those skilled in the art that various further modifications may be made without departing from the spirit or scope thereof.

Having described our invention, we claim:

1. Apparatus for laying a horizontally disposed strip of preformed film under the surface of the ground comprising in combination a hollow plow, a roll of film, means for unrolling the film, means to pass the film through the hollow plow, and means to spread out the film in a horizontally disposed position behind the plow as the plow is moved wherein the roll of film is mounted with its axis in a plane passing vertically through a line in the direction of travel of the plow and there is means to pass the film folded along its longitudinal axis from the roll down through a hollow shank of the plow disposed with the longitudinal axis of the shank lying in the direction of movement of the plow, and the means to spread out the film comprises a triangular shoe on the bottom of the hollow plow disposed to unfold the film into a flat, horizontally disposed strip underground.

2. The apparatus of claim 1 wherein the means to spread out the film includes means to fold the edges of the film upwardly in the ground.

3. Apparatus for laying a horizontally disposed strip of preformed film under the surface of the ground comprising in combination a hollow plow, a roll of film, means for unrolling the film, means to pass the film through the hollow plow, and means to spread out the film in a horizontally disposed position behind the plow as the plow is moved wherein the means for unrolling the film and means for passing the film through the hollow plow includes means to dispose the film vertically with its transverse axis in the direction of travel of the plow, and the means to spread out the film in a horizontally disposed position comprises means to turn the :film horizontally in the plow and then to turn the longitudinal axis of the film in the direction the plow is moved.

1. The apparatus of claim 3 wherein the means to spread out the film includes means to fold the edges of the film upwardly in the ground.

5. Apparatus for laying a horizontally disposed strip of preformed film under the surface of the ground comprising in combination a hollow plow, a roll of film, means for unrolling the film, means to pass the film through the hollow plow, and means to spread out the film in a horizontally disposed position behind the plow as the plow is moved wherein the roll of film is supported on one vehicle and the plow is supported on a separate vehicle.

6. Apparatus for laying a horizontally disposed strip of preformed film under the surface of the ground comprising in combination a hollow plow, a roll of film, means for unrolling the film, means to pass the film through the hollow plow, and means to spread out the film in a horizontally disposed position behind the plow as the plow is moved wherein a spray pipe is provided on the plow with means to spray liquid through the pipe on the film in place in the ground.

7. The process of laying a horizontally disposed strip of preformed film below the surface of the ground, comprising the steps of plowing the ground with a hollow plow, feeding the film down inside the plow, and moving the film out into a horizontally disposed position underground behind the plow wherein the strip of film is folded longitudinally and would in longitudinally folded form on a roll which has its axis in a plane passing vertically through a line in the direction of travel derground.

8. The process of claim 7 including the step of simultaneously turning the edges of the strip upwardly to increase its ability to retain water while moving the film out into its or the plow and the film is fed from the roll through the plow horizontally disposed Positionand unfolded into a horizontally disposed position un-

Claims

3. Apparatus for laying a horizontally disposed strip of preformed film under the surface of the ground comprising in combination a hollow plow, a roll of film, means for unrolling the film, means to pass the film through the hollow plow, and means to spread out the film in a horizontally disposed position behind the plow as the plow is moved wherein the means for unrolling the film and means for passing the film through the hollow plow includes means to dispose the film vertically with its transverse axis in the direction of travel of the plow, and the means to spread out the film in a horizontally disposed position comprises means to turn the film horizontally in the plow and then to turn the longitudinal axis of the film in the direction the plow is moved.

4. The apparatus of claim 3 wherein the means to spread out the film includes means to fold the edges of the film upwardly in the ground.

7. The process of laying a horizontally disposed strip of preformed film below the surface of the ground, comprising the steps of plowing the ground with a hollow plow, feeding the film down inside the plow, and moving the film out into a horizontally disposed position underground behind the plow wherein the strip of film is folded longitudinally and would in longitudinally folded form on a roll which has its axis in a plane passing vertically through a line in the direction of travel of the plow and the film is fed from the roll through the plow and unfolded into a horizontally disposed position underground.

8. The process of claim 7 including the step of simultaneously turning the edges of the strip upwardly to increase its ability to retain water while moving the film out into its horizontally disposed position.