WO2008132749A1

WO2008132749A1 - Improved underground irrigation system

Info

Publication number: WO2008132749A1
Application number: PCT/IL2008/000592
Authority: WO
Inventors: Shahar Harari; Avihai Simner
Original assignee: Shahar Harari; Avihai Simner
Priority date: 2007-05-01
Filing date: 2008-05-01
Publication date: 2008-11-06
Also published as: WO2008132749A4

Abstract

A conduit for dispersion of a fluid underground, the conduit comprising a sleeve; the sleeve comprising a base structure and an upper structure thereover and coupled thereto, thereby defining a chamber between said base structure and said upper structure; the base structure comprising an impermeable material and having a cross-section with a substantial flat or raised center on its upper surface to encourage liquid thereon to flow towards outer edges thereof, and the upper structure comprising a permeable material to allow fluid flow therethrough. The conduit may further include one of more intermittently perforated fluid pipes to drip liquid or aerate the conduit and thereby irrigate and / or aerate soil therearound.

Description

IMPROVED UlNfDERGROUND IRRIGATION SYSTEM

FIELD OF THE INVENTION

The present invention relates to underground irrigation systems. In particular the invention relates to underground irrigation systems with high uniformity of watering and / or aeration. BACKGROUND

Sub surface irrigation systems are known. Sub surface irrigation has several advantages compared to watering from above. These include reduced water loss through evaporation, relative immunity to tampering, reduced weed germination, amenability to use of 'gray' water for irrigation, and avoidance of wetting of the culm (ground plant matter), which minimizes mildew and the like.

Companies such as Netafim™, Plastro™, and others have developed and supply irrigation systems based on drip irrigation pipes. Such pipes may be arranged in a branched network that is connected to a mains water supply, generally via appropriate filters, controllers, valves, etc.

Underground irrigation systems are usually based on periodically spaced drippers and thus tend to provide non-uniform irrigation, as the ground adjacent to the drippers tends to be over-watered, whereas the ground between the drippers tends to be under-watered. In order to overcome this problem, more irrigation water is applied so that the ground between the drippers becomes sufficiently irrigated, leading to over watering closer to the drippers. Furthermore, a significant proportion of the water is wastefully distributed to below the root zone.

The flow of water out of drippers in long pipes and in pipes laid in a sloping manner tends to decrease along the pipe. A more uniform pressure may be achieved by connecting the pipe at both ends to pressurized water sources. Even so, the flow out of drippers tends to vary along the dripper pipe and may be affected by blockages.

Companies, such as KISSS™ and Leaky Pipe Systems™, provide irrigation systems having a more uniform distribution of the irrigation water, by providing irrigation pipes made of porous material or by covering or wrapping the dripper pipe with a fabric sheath or other means.

Maintenance of such systems is difficult, requiring tedious digging to locate and access problem sections. International Application No. WO2006061132 to Herbert and Gisbert, titled" Tube System for Supplying a Fluid, Preferably for Subsoil Irrigation", relates to a subsoil irrigation system consisting of inner and outer tubes. Water within the inner tube is ejected into chambers between the tubes, and diffuses through the outer tube into the soil. The resulting irrigation tends to be nonuniform in the soil along the outer tube. Being pressured, the outer tube is susceptible to punctures and to blocking of the porous wall, and requires the ends of the tubes to be pressured sealed, which makes the system expensive and susceptible to leaks. US patent No. 3,874,598 to The Dow Chemical Company, titled

"Irrigation tube", describes an irrigation system which has an inner tube and an outer tube, both of which have periodic apertures therealong, with the openings in the outer tube being larger than those of the inner tube.

The outer tube and inner tube thereof are sealed together. This results in non-uniform irrigation. Furthermore, it is difficult to perform maintenance on the system in case of puncture or blockage. The system is also very sensitive to elevation differences which result in the flow in lower portions along the tube being greater than in the higher portions.

US 3,946,762 to Green, titled "Underground irrigation system", describes a fabric material enclosing apertures along an underground pipe. As with the system described in US 3,874,598, the external layer is glued directly to the pipe. Water pressure in the pipe drives irrigation water through the fabric opposite the aperture and the resultant irrigation is non-uniform. Additionally, the fabric acts like a filter, trapping small particles previously suspended in the water, resulting in blockades. Furthermore, it is impossible to replace the pipe without replacing the fabric. Additionally, if the pipe is installed in a sloping manner, more water tends to be emitted from the lower part of the pipe than from the upper part, due to water pressure differences, causing uneven irrigation.

US 4,904,112 to McDonald, titled "Underground irrigation system", describes an inner pipe having a plurality of apertures on a top surface thereof, connected to a pressurized water source. The inner pipe is located within a slightly larger outer pipe and rests on a bottom inner surface of the outer pipe. The outer pipe is designed to be buried just below the plant root line. A series of longitudinal slots on a bottom portion of the outer pipe permits water flowing from the inner pipe to the outer pipe to trickle unimpeded into the surrounding soil. Since the water tends to percolate under gravity to below the outer pipe, the resulting irrigation is wasteful.

British patent GB2006591 to JUFORS BO titled "Irrigation Systems" presents a system for the irrigation of plants, the system having a spaced plurality of tubular clay pipes buried underground and communicating at the respective upstream ends thereof with a conduit for water supply. The tubular pipes have sufficiently porous side walls so that capillary forces in the ambient soil draw water from the tubular pipes through the walls to replace water taken up by plants growing in the soil.

When the pipe is installed in a sloping manner, water pressure differences may result in uneven irrigation and over wetting of the soil. In addition, the structure of the system makes it impossible to replace the inner tube in case of puncture or blocking without digging in the ground to expose the pipe. US 5,839,659 to Grain Security Foundation Ltd., entitled "Capillary root zone irrigation system" depicts a system that uses one or more conduits having spaced apart perforations therealong, with the conduits being held in pockets. The pockets are formed by an upper layer of capillary cloth and a lower layer of capillary cloth and/or a water impermeable material. The upper layer of capillary cloth is moistened by the flow out of the perforations and in turn distributes water to the root area of plants.

The structure of the system makes it impossible to replace the inner tube in case of puncture or blocking without digging in the ground and exposing the pipe. The system is not suitable for even distribution of fluids along the system, since the irrigation pipe is tightly sandwiched between two layers of cloth, and the fluid goes directly from drippers along the pipe to the cloth. Furthermore, the system does not compensate for non uniform flow of air and/or gas from the drippers due to pressure difference along the pipe; the pressure tending to drop with distance from the fluid source, blocked drippers etc. Systems having similar structures and associated problems are described in

US 5,938,372, FR 2473262, FR 2331953, US 3,946,762 and in the Internet pages, http://www.kisssusa.com/agriculture/bff/index.htm, http://www.kisss.net.au/below flow safety flow/wrap or flat. US 5,816,742 describes integral hollow conduits to disburse fluids along their length. The conduit has longitudinal openings that vary in width along its length and are fabricated out of two materials: a profile of thermoplastic material with a lengthwise slit wall and a layer of fabric imbedded and sandwiched on its sides in the thermoplastic walls, lengthwise along both sides of the slit. The fabric is purported to control emission of fluid. However, underground irrigation with such a conduit requires filling the conduit with the liquid, which tends to cause over-irrigation. When the conduit is laid in a sloping manner, the liquid quickly concentrates at the lower sections whereas the upper sections of the conduit remain dry unless the entire conduit is completely and continuously filled with liquid. Particulate material in the irrigation liquid may block the fabric, requiring digging up and replacing the entire conduit. Water can only reach the fabric by evaporating from the trough like receptacle formed by the section of the pipe thereunder or by piping the liquid through the pipe under pressure, which is difficult to do since large sections of the periphery are fabric covered slits or spaces and very large pressures are required to reach the end of the pipe, whereas such large pressures will cause water to spurt out at the upstream ends of the pipe. The large damp fabric covered openings are also attractive to thirsty animals and such systems may be susceptible to rodent damage. Where sub-surface irrigation systems have been used for soil aeration purposes, air is typically pumped through the dripper pipe instead of water, or bubbles are added to the water, for example via a Venturi injector as described in http://www.mazzei.net/applications/airjection_ag.htm, for example. It will be appreciated that when pressurized gaseous species exit a dripper they tend to break out of the soil via the path of least resistance, rather than to diffuse throughout the soil.

An inherent problem of underground irrigation systems is their sensitivity to blocking. Although filters are typically installed along the main water line, and the pipes may be periodically flushed to dislodge blockages, soil may nevertheless get sucked into underground drippers due to the pressure reversal created when the water flow is halted. In addition, deposits such as minerals from hard water, rust and non-dissolved fertilizer particles tend to build up within the pipe over time, particularly next to or on the drippers themselves, inhibiting the functioning thereof. Furthermore, the water exiting the drippers may attract roots which may block the drippers. To overcome this effect, one known solution is to use an herbicide such as Treflan^® in the irrigation water; however, such herbicides are harmful to the environment and irrigation with herbicides may be detrimental to the crop being cultivated. In contrast with irrigation systems where the pipe is positioned above the ground, and identification and replacement of blocked drippers or pipe sections is fairly straightforward, in sub-surface irrigation systems, maintenance is much more difficult since it is more difficult to identify blockages or leaks, until the plants thereabove are adversely affected thereby. Additionally, maintenance typically involves digging to access the pipe, which is generally costly, time- consuming and may damage the plants thereabove.

Underground irrigation systems, are often susceptible to rodent damage. There is a need for underground irrigation systems that are easily serviceable, that provides uniform irrigation and/or aeration, that are less susceptible to damage by rodents, and that are robust to blockages. Embodiments of the present invention address this need.

SUMMARY OF THE INVENTION

It is an aim of the invention to provide an irrigation conduit for installing below the topsoil.

It is a further aim of preferred embodiments to provide conduits capable of aerating the soil therearound.

One aspect of the invention is directed to providing a conduit for dispersion of a fluid underground, the conduit comprising a sleeve; the sleeve comprising a base structure and an upper structure thereover and coupled thereto, thereby defining a chamber between said base structure and said upper structure; the base structure comprising an impermeable material and having a cross-section with a substantial flat or raised center on its upper surface to encourage liquid thereon to flow towards outer edges thereof, and the upper structure comprising a permeable material to allow fluid flow therethrough.

Optionally, the upper structure comprises walls and a roof. Alternatively, the upper structure is arched.

In some embodiments of the invention, the permeable layer is permeable to liquid and to gas and is selected from the group comprising woven fabrics, non- woven fabrics, sponges and geo-textiles.

Preferably, the permeable layer is a non-woven fabric devoid of biodegradable fibers.

In other embodiments of the invention, the upper structure further comprises a support framework for supporting the permeable layer.

Preferably, the framework is rodent proof.

The framework may comprise a material selected from the group of plastics, metals and alloys.

In some embodiments of the invention, the conduit has a coupling of the upper structure to the base structure comprising at least one of the group comprising stitches, mechanical coupling, plastic welding and adhesives.

In other embodiments of the invention, the permeable layer is impregnated with at least one active ingredient selected from the group comprising rodent repellent, root growth inhibitors and fertilizers.

According to yet other embodiments of the invention, the conduit further comprises at least one intermittently perforated pipe therealong for leaking a fluid into the chamber for subsequent dispersion of the fluid through the permeable layer.

Optionally, the conduit further comprises an intermittently perforated liquid pipe running freely through the chamber for leakingly piping a liquid along the sleeve such that the intermittently perforated pipe leakingly dispenses said liquid onto the base structure and the liquid wicks through the permeable layer.

Alternatively, the conduit further comprises a liquid pipe running through the base for piping liquid along the base of the sleeve, the liquid pipe having perforations on an upper surface thereof for leaking liquid onto the base. Preferably, the liquid comprises water and dissolved fertilizer.

According to other embodiments of the invention, the conduit further comprises an intermittently perforated gas pipe running through the chamber for leakingly piping a gas along the sleeve.

Alternatively, the conduit further comprises a gas pipe running through the base for piping gas along the base of the sleeve, the gas pipe having perforations on an upper surface thereof for leaking gas into the chamber.

In other embodiments of the invention, the base has intermittent ridges thereacross to impede flow of liquid therealong.

In yet other embodiments, the conduit further comprises an access box at an end thereof, the access box comprising: (i) a removable cover above said end and (ii) a cavity therearound.

In other embodiments the conduit further comprises metallic indicators for allowing locating of positions of underground components with a metal detector. Another aspect of the invention is directed to providing a method of subsoil irrigation comprising:

(a) burying a conduit containing an intermittently perforated pipe therealong; the conduit comprising a sleeve fabricated from a base structure comprising an impermeable material and an upper structure thereover coupled to the base structure and comprising a permeable layer, the sleeve defining a chamber between said base and said upper structure, the perforated pipe running along the conduit;

(b) piping an aqueous liquid along the intermittently perforated pipe;

(c) exuding the aqueous liquid from the pipe via perforations therealong into the chamber;

(d) puddling the aqueous liquid onto the base;

(e) wicking the puddled liquid into the upper structure of the sleeve, and

(f) dispersing the aqueous liquid through the upper structure into soil therearound. According to other embodiments, the dispersing step includes diffusing the liquid through the permeable layer into the soil therearound.

According to some embodiments, the method further comprises piping gases through the sleeve and diffusing the gases through the liquid and the permeable fabric. As referred to herein, the word "gas" and variations thereof refer to any gaseous species or mixtures thereof, especially air, oxygen, nitrogen, fertilizers in the gaseous phase, water vapor and the like.

"Liquid" and variations thereof, refer to any liquid, but particularly to water and aqueous solutions. "running freely through" means to being freely removable from and insertable into.

"permeable is a property of a material such as a fabric or spongy textile, that allow liquids and gases to pass therethrough, but holds back solid particles over a minimum size. "dripper pipe", "dripper conduit" etc., refers to intermittently perforated liquid pipes, characterized by having perforations or holes therealong through which a pressured liquid flowing through the pipe will be ejected, using as drips, dribbles or occsionally spurts or spray, depending on pressure, surface tension and the like. BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the invention and to show how it may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings.

With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention; the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Fig. Ia is a schematic illustration of the liquid distribution within ground material obtained with a typical prior art underground dripper pipe;

Fig. Ib is a schematic illustration of the more uniform liquid distribution within the ground material obtained with embodiments of the invention;

Fig. 2 is a vertical cross section through an underground irrigation conduit with an intermittently perforated pipe for supplying liquid inside a sleeve having an essentially flat base of an impermeable material and a chamber, in accordance with a first embodiment of the invention;

Fig. 3 is a section through a dripper pipe and a gas pipe inside a sleeve, in accordance with a second embodiment of the invention; Fig. 4a is a section through a liquid pipe and a sleeve wherein the base of the sleeve comprises a hollow perforated conduit serving as an airpipe, in accordance with a third embodiment of the invention;

Fig. 4b is a section through a gas pipe and a sleeve wherein the base of the sleeve comprises a liquid pipe with intermittent perforations along an upper surface thereof, in accordance with a fourth embodiment of the invention;

Fig. 4c is a section through a sleeve wherein the base of the sleeve comprises both a liquid pipe and a hollow conduit serving as an airpipe, with intermittent perforations along the upper surfaces thereof, in accordance with a fifth embodiment of the invention; Fig. 5 is an isometric view of a section of an underground irrigation conduit including a dripper pipe and a sleeve consisting of a flat base and a wall of fluid-permeable, ground material-impermeable fabric over a support structure, the wall being in contact with the flat base of a water-impermeable material, and the base having raised edges therealong, in accordance with a sixth embodiment of the invention;

Figs. 6a to 6c are side views through of underground irrigation conduits having ridged bases according to a seventh embodiment of the invention, and Figs. 6d and 6e are top views of ridged bases in accordance with an eighth embodiment of the invention; Fig. 7a-d are isometric views of underground irrigation conduits consisting of a dripper pipe within a sleeve, the conduits including access boxes at ends of the pipe, according to a ninth embodiment of the invention;

Fig. 8 is an isometric view of a section of an underground irrigation conduit with multiple dripper pipes connected to a common water source, according to a tenth embodiment of the invention, and

Fig. 9 is an isometric view of a section of an underground irrigation conduit with a metal strip/wire placed along the sleeve, according to an eleventh embodiment of the invention. Fig. 10 is a flowchart illustrating a method of irrigation in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention relates to easily maintained underground irrigation systems with intermittently perforated liquid pipes and the like, included in or inserted into chambers within sleeves, for even distribution of liquid, and sometimes gases and dissolved fertilizers into ground material.

In sub-surface irrigation systems having perforated inner conduits, such as dripper pipes running through porous sleeves, it is advantageous to minimize the fluid pressure applied on the sleeve's inner walls so that the sleeve does not have to be pressure sealed, since pressured systems are more sensitive to leaks. Additionally, systems not requiring pressure sealing may allow the inner conduit to be more easily extracted and reinserted, for maintenance and the like.

Preferably, liquid from the perforated inner conduits is provided at a suitable pressure such that the liquid is released thereout as drips rather than as a spray. Fig. Ia shows a profile of liquid distribution within ground material 6 obtained using typical prior art underground dripper pipes 8. The liquid forms damp patches 4a, 4b, 4c around drippers 5a, 5b and 5c.

With reference to Fig. Ib, using the conduit 10 of the invention, because of a sleeve 20, water 4 is distributed more evenly along the conduit 10. Figure 2 shows a vertical cross section through part of a conduit 100 for underground dispersion of a fluid in accordance with one embodiment of the present invention. The conduit 100 includes a sleeve 120, the sleeve having: (i) an arched upper structure 122 including a layer fabricated from a fluid-permeable, ground material-impermeable material, and (ii) base 123 being essentially flat across its width and being made from a water impermeable material. A chamber 124 is defined by the base 123 and the upper structure 122. The conduit 100 further includes a dripper pipe 8 with drippers 5a, 5b therealong running through chamber 124. A liquid 4, typically water, perhaps with dissolved fertilizer, piped through the dripper pipe 8 at pressure, drips 7 from the drippers 5 out of dripper pipe 8 into the chamber 124, and accumulates on the base 123 of the sleeve 120 as puddles 121.

When laid underground, the upper structure 122 of the sleeve 120 is in direct contact with the ground material 6 thereabout, and allows liquid 4 supplied by the dripper pipe 8 to pass from the upper structure 122 to the ground material 6 by capillary action, while preventing the ground material 6 from pervading the sleeve 120 and blocking the drippers 5 of the dripper pipe 8, as often happens in sub-surface irrigation dripper pipes (Fig. Ia) of the prior art. Drippers 5 are not in direct contact with the upper structure 122, as direct contact has been found to lead to the liquid passing through the permeable layer and into ground material 6 without dispersing along the conduit, thus providing irregular irrigation.

The permeable layer may be made of material such as a woven fabric, non- woven fabric, spongy textile or geo-textile, for example. Fabrication from a non- woven fabric natural fibers, is preferable, since natural fibers are susceptible to rot.

The upper structure 122 may be arched as shown, or may consist of separately identifiable walls and roof. The upper structure 122 together with the base 123 defines a chamber 124. The upper structure 122 may be coupled to the base 123 by stitches, mechanical coupling, plastic welding and/or adhesives. As is well known, proper soil aeration is essential for good plant growth. It therefore may be advantageous to supply, in addition to liquid, air or oxygen via the conduit, to supplement air diffusing into the soil from the atmosphere. Fig. 3 shows one such conduit 200 in accordance with a second embodiment of the present invention, in which in addition to the dripper pipe 8 there is also a gas pipe 214 running through the sleeve 220. A gas, typically air, piped through the gas pipe 214 at pressure, flows out of perforations 215 along the gas pipe 214 into the chamber 224 defined by the space between the base 223 and the sleeve's upper structure 222 , and thus gas and/or aerated water diffuse through the fluid- permeable arcuate structure 222 into the ground material 6 thereabout. Alternatively or additionally, the sleeve 220 itself may be connectable to a compressor or fan (not shown), to force air therethrough. Fig. 4a shows conduit 300a according to a third embodiment of the invention, in which the base 323a of the sleeve 320a is itself hollow and perforated on upper surface with perforations 336, and serves as an air supply pipe. Note that although perforations along the lower surface of the base 323a would also serve as a source of air 32 for the ground material, in a conduit 300a with such a base 323a, the supplied air 32 would spread into the ground material less evenly than in conduits where the perforations 336 are only along the upper surface of the base 323a, and the air 32 aerates the irrigation liquid 4. Furthermore, liquid 4 may be lost through such lower perforations. Therefore, the perforations 336 are preferably only along the upper surface of the base 323a.

As shown in Fig. 4b, in conduit 300b the base 323b may comprise a water pipe with intermittent perforations along an upper surface 321 thereof, serving as a source of liquid 4 that wells out and accumulates onto the base 323b. A perforated gas pipe 314 runs through the sleeve 320b, aerating the liquid 4 within the sleeve 320b, thereby supplying air 32 to the ground material. As in the other embodiments of the invention, the water pipe 324b irrigates the ground material around the sleeve 320b by diffusing through the permeable layer in the upper structure 322.

Alternatively, as shown in Fig. 4c, in conduit 300c the base 323c includes both a water pipe and a hollow airpipe, both with intermittent perforations along upper surfaces thereof, serving as sources of liquid 4 and air 32 for supplying to the ground material 6 thereout. Figure 5 shows a section of a conduit 400, in accordance with a fourth embodiment of the present invention. The conduit 400 includes a dripper pipe 8, a sleeve 420 consisting of an upper structure 422 including fluid-permeable ground- material-impermeable layer 425 and a support structure 426; the upper structure is coupled to a flat base 423, and the base 423 has raised edges 427a-b therealong. The edges 427a-b facilitate the spreading of puddles of liquid along the base 423.

The support framework 426 may be made of plastic, metal or alloy, and may be rigid or semi-rigid, with a curved profile as shown, or another shape. It may be meshed as shown, or perforated or with cutouts, for example. Preferably, it has an open structure to allow essentially unimpeded passage and large flux of fluids through the upper structure 422, for irrigation, aeration and/or soil drainage, yet providing a strong and flexible framework for supporting the weight of ground material there above. Usefully, the support structure is rodent proof and prevents rodents from damaging the inner irrigation and air pipes. Alternatively, the upper structure 422 may be self supporting without the support framework 426. The support framework 426 may be placed outside the permeable layer 425, thus providing protection to both the dripper pipe 8 and to the permeable layer 425, or may be placed under the permeable layer 425 as a preferred embodiment, as in Fig. 5, which may provide less protection for the permeable layer 425 from, for example rodents gnawing the sleeve 420, but facilitates the placement of the sleeve 420 underground and/or the construction of the sleeve 420 since the upper structure 422 does not have to be affixed to the support 426. Optionally, the support 426 is affixed to the permeable layer 425 and to the base 423, perhaps by gluing, by ultrasonic welding, or by sewing, or other method that preferably does not appreciably interfere with the wicking of liquid through the permeable layer 425. In order to prevent roots penetrating the upper structure 420, the permeable layer 425 may be pretreated with root control materials, or such root-control materials may be added to the irrigation water, for example, as is customary in drip-line irrigation systems. Indeed, additionally or alternatively, it may be impregnated with other chemical species, such as selected weed killers, rodent poison, fertilizers, and pesticides, for example.

Blockages of some of the drippers in the dripper pipe in irrigation systems tend to cause uneven irrigation. However, in embodiments of the present invention, the drippers are isolated from the ground and roots and separated therefrom by a permeable material and by a chamber. This feature reduces the occurrence of blockages and provides improved distribution of the fluids and compensatory irrigation and/or aeration by drippers adjacent to a blocked dripper.

As shown in Fig. 5, the base 423 is typically flat, thus facilitating the even spreading of the liquid along the conduit and subsequent even distribution of the liquid into the ground material surrounding the conduit 400, even when the surface above the conduit 400 is uneven, or some drippers 5 are blocked.

Preferably, as in the conduit 500a shown in Figure 6a, the conduit has further features for further improving the uniformity of irrigation to uneven terrain. The base 523a of the conduit sleeve 420 may be corrugated, preferably across the base 523a, as shown, thus advantageously hindering or preventing liquid from flowing freely down slopes. Preferably, the base 523a is made of a flexible impermeable material such as polyethylene, for example.

Referring to Figs. 6b-6e, the conduits 500b-500d may have raised barriers 540b- d spaced along the base 523b, the barriers 540b-d being oriented toward the interior of the sleeve 520. In Fig. 6b, the liquid 4 is retained by such raised barriers 540b and forms puddles along the length of the sleeve 520. The barriers 540b may be made from the same material as the floor material such as polyethylene (PE), for example, by pinching the base material upwards or, a second material may be attached to the base material. Alternatively, as shown in Fig. 6c, the barriers 540c may be fabricated from a porous material which may be a woven fabric, a non-woven fabric or felt, a sponge etc. which absorbs some of the liquid 4 by capillary action, the absorbed liquid 4 subsequently passing into the permeable layer, the remaining liquid flowing along the base 523c and being absorbed by an adjacent barrier 540c. Each barrier 540c may absorb liquid from several drippers 5' -5'". Alternatively, with reference to Fig. 6d and 6e, showing isometric views above the base 523d in conduit 50Od, raised protrusions 54Od on the base 523d may guide the liquid 4 toward walls 522 such as when the conduit 50Od is placed at an angle. The structures of the conduits 100-500 shown in Figs. 2 to 6 allow the liquid from the pipes to be transferred along the sleeve, and also enable free movement of gas along the interior of the sleeve and its uniform distribution therewithin. Such gas may pass through the liquid, and diffuse with it through the permeable layer to arerate the ground material, diffuse directly into the soil through the upper structure, and/or be forced into the soil due to pressure differences.

The uniform irrigation and aeration provided by embodiments of the invention have a major impact on the economy of irrigation, water conservation, friendliness to the environment and, potentially, crops yield. In contrast to prior art systems, the present invention provides plants along the conduits with more uniform irrigation, aeration and, when used, fertilization, at a slow rate suitable for gradual uptake, and with minimum waste of the fluids. When using fertilizers, the minimum waste of water leads to minimal usage of fertilizers.

Typically, the sleeve is buried at a depth appropriate to the roots of the crop thereabove. For example, for some lawn grasses, 6" may be an appropriate depth.

An intermittently perforated pipe may be inserted into and threaded through the sleeve before or after the sleeve is laid underground.

Perforated pipes may freely run through conduits 10-500 and thus may be easily extracted out of and inserted into the sleeves, as there is no inherent need for them to be fixed to any other part of the conduit. Some embodiments of the invention afford easy extraction of the underground perforated pipes for maintenance of the conduit, and their subsequent repositioning after the maintenance is completed, or their replacement, as required. Such maintenance may include inspection of drippers, removing blockages, pipe replacement etc. It is noted, that usefully, such maintenance procedures may be carried out without undesirably upsetting the ground material above the conduit, the surface above the conduit and crops, and without need for cessation or interruption of activities performed on the surface.

With reference to Figs. 7a -7d, such underground irrigation conduits may include a dripper pipe 8 within a sleeve 720; the conduits further may include an access box 750a at the upstream end 716a of the dripper pipe 8, the access box 750a may include a removable cover 752 above the end 716a of a dripper pipe 8 and a cavity 754 therearound.

The pipe 8 may be connected to a liquid or gas supply line 756a. As in some standard dripline irrigation systems, with reference to Fig. 7bthe pipe 8 may be connected at both sides 716a, 716b to supply lines 756a, 756b thereby providing uniform pressure therealong. As shown in Fig. 7c, for easy insertion of dripper tube 8 into sleeve 720, an end cap 758 may be placed on the downstream end 716b of the pipe 8. The end-cap 758 may have a conical shape or other geometry to ease the manual or mechanical insertion into and extraction of the pipe 8 from the sleeve 720. The end cap 758 may be fixed to pipe end 716b or it may be detachable therefrom. It may also serve to seal the downstream end 716b, in order to prevent free escape of liquid and/or gas from the downstream end 716b and to allow pressure to build up inside the pipe 8.

Preferably, as shown in conduit 70Od in Fig. 7d, the dripper pipe 8 may be inserted into an underground sleeve 720 by: (i) providing access boxes 750a-b at both ends 728a, 728b of the sleeve 720; (ii) extending a string 760 throughout the sleeve 720, such that the string ends be accessible via the access boxes 750a,b; (iii) mounting an endcap 758 onto end 716b of the dripper pipe 8, the endcap 758 being connectable to the end 761b of the string 760; (iv) raising the covers 751a,b of the access boxes 750a,b; (v) connecting the end 761b of the string 760 to the endcap 758 as shown; and (vi) pulling the the string 760 in force and direction suitable for drawing the dripper pipe 8 inside and through the sleeve 720. A reel 762 may be used for pulling the string 760.

The upstream end 716a of the pipe 8 may then be connected to a source of pressurized fluid 756a. Optionally, the endcap 758 may be removed and the downstream end 716b of the pipe 8 may also be connected to a source of pressurized fluid (not shown), thereby providing uniform pressure along the the pipe 8.

For maintenance of the installed dripper pipe 8, the supply of pressurized fluid to the pipe 8 is halted, the endcap 758 may be reconnected to the pipe 8 if not already connected, the string 760 may be reconnected to the endcap 758 and the pipe 8 pulled out of the sleeve 720 in the direction that reextends the string 760 throughout the sleeve 720 for later easy reinstallation of the pipe 8 or another pipe into the sleeve 720. As shown in Fig. 8, in an example of a large irrigation conduit 800, several dripper pipes 8 may be connected to the same source of pressurized fluid 856. Dripper pipes 8, 8', 8" are typically spaced apart at a distance of between 0.3 cm and a meter; however, the total length of each pipe 8 may be up to hundreds of meters. Generally, when an irrigation problem occurs, it may be detected by deterioration in the condition of the irrigated plants, such as yellow patches of turf, or by water logging of parts of the surface. However, in large conduits 800 or if the terrain is not flat, there might be a problem to detect which access box 850 is connected to the problem pipe 8, or where to dig in order to expose the pipe 8.

This problem may be solved by using a sensor (not shown) that detects the conduit 800 or sections of the conduit 800 by measuring, for example, the capacitive or magnetic change between sections of the conduit 800 such as the sleeves 820 or the dripper pipes 8 or the access boxes 850 or by measuring a radar echo from an section of the conduit 800 produced by a RF transmitter or the like. The sensor may be used by approaching in a direction that increases the signal until reaching the detectable section of the conduit 800.

As shown in Fig. 9, in order to increase the sensitivity of such sensors, a strip/wire 970 may be placed in the conduit 900, for example along and above the sleeve 920. The strip/wire 970 may be from a metallic material detectable by a metal detector. Optionally, it may be useful to differentiate between various sub-surface irrigation parts, by using strip/wires 970 that provide different responses to each part, for example, by putting different amounts or kinds of metal in different subsurface conduit parts. With reference to Fig. 10, a method of irrigation according to embodiments of the invention consists of burying a conduit containing an intermittently perforated pipe therealong in accordance with one of the embodiments hereinabove; (b) piping an aqueous liquid along the intermittently perforated pipe; (c) exuding the aqueous liquid from the pipe via perforations therealong into the chamber; (d) puddling the aqueous liquid onto the base; (e) wicking the puddled liquid into the upper structure of the sleeve, and (f) dispersing the aqueous liquid through the upper structure into soil therearound.

Persons skilled in the art will appreciate that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the appended claims and includes both combinations and sub combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description. In the claims, the word "comprise", and variations thereof such as

"comprises", "comprising" and the like indicate that the components listed are included, but not generally to the exclusion of other components.

Claims

1. A conduit for dispersion of a fluid underground, the conduit comprising a sleeve; the sleeve comprising a base structure and an upper structure thereover and coupled thereto, thereby defining a chamber between said base structure and said upper structure; the base structure comprising an impermeable material, with an upper surface having a cross-section with a substantial flat or raised center to encourage liquid thereon to flow towards outer edges thereof, and the upper structure comprising a permeable material to allow fluid flow therethrough.

1. The conduit of claim 1, the upper structure comprising walls and roof.

2. The conduit of claim 1, the upper structure being arched.

3. The conduit of claim 1, said permeable layer being permeable to liquid and to gas and being selected from the group comprising woven fabrics, non-woven fabrics, sponges and geo-textiles.

4. The conduit of claim 4, wherein the permeable layer is a non- woven fabric devoid of biodegradable fibers.

5. The conduit of claim 1, the upper structure further comprising a support framework for supporting the permeable layer.

6. The conduit of claim 6, the framework being rodent proof.

7. The conduit of claim 6, the framework comprising a material selected from the group of plastics, metals and alloys.

8. The conduit of claim 1, said coupling comprising at least one of the group comprising stitches, mechanical coupling, plastic welding and adhesives.

9. The conduit of claim 1, the permeable layer being impregnated with at least one active ingredient selected from the group comprising rodent repellent, root growth inhibitors and fertilizers.

10. The conduit of claim 1 further comprising at least an intermittently perforated pipe therealong for leaking a fluid into the chamber for dispersing the fluid through the permeable layer.

11. The conduit of claim 1 further comprising an intermittently perforated liquid pipe running freely through the chamber for leakingly piping a liquid along the sleeve such that the intermittently perforated pipe leakingly dispenses said liquid onto the base structure and the liquid wicks through the permeable layer.

12. The conduit of claim 1 further comprising a liquid pipe running through the base for piping liquid along the base of the sleeve, the liquid pipe having perforations on an upper surface thereof for leaking liquid onto the base.

13. The conduit of claim 12, the liquid comprising water and dissolved fertilizer.

14. The conduit of claim 1 further comprising an intermittently perforated gas pipe running freely through the chamber for leakingly piping a gas along the sleeve.

15. The conduit of claim 1 further comprising a gas pipe running through the base for piping gas along the base of the sleeve, the gas pipe having perforations on an upper surface thereof for leaking gas into the chamber.

16. The conduit of claim 1, the base having intermittent ridges thereacross to impede flow of liquid therealong.

17. The conduit of claim 1, further comprising an access box at an end thereof, the access box comprising: (i) a removable cover above said end and (ii) a cavity therearound.

18. The conduit of claim 1, further comprising metallic indicators for allowing locating of positions of underground components with a metal detector.

19. A method of subsoil irrigation comprising:

(a) burying a conduit containing an intermittently perforated pipe therealong; the conduit comprising a sleeve fabricated from a base structure comprising an impermeable material and an upper structure thereover coupled to the base structure and comprising a permeable layer, the sleeve defining a chamber between said base and said upper structure, the perforated pipe running along the conduit; (b) piping an aqueous liquid along the intermittently perforated pipe;

(d) puddling the aqueous liquid onto the base;

(e) wicking the puddled liquid into the upper structure of the sleeve, and

(f) dispersing the aqueous liquid through the upper structure into soil therearound.

20. The method of claim 19, said step of dispersing comprising diffusing the liquid through the permeable layer into the soil therearound.