A method for hydroponical growing of plants as well as a growing device and a system for the practicing of said method

Abstract: In a method of simultaneous hydroponical growing of a number of plants (18), a drip irrigation pipe (14) having outlets (17) disposed along the length thereof is inserted between a pair of flatwise juxtaposed layers (4, 5) of water-impervious mate­ rial of a growing device (10) alongside a first closed longitudinal edge (2) thereof. The growing device (10) including the supply pipe (14) is suspended with said first closed longitudinal edge (2) along a suspension means (15) placed at a substantially horizontal level. Roots (19) of plants (18) are inserted in between said two layers (4, 5) downstreams of said outlets (17) and with the stems (20) extending through throughcuts (11) in one of said two layers (4, 5). Nutrient solution is fed through said supply pipe (14) and outlets (17) and guided to the roots (19) of each plant (18) and is quickly percolated through said roots (19) and collected below the roots (19) for recir­ culation of discharge thereof. The growing device (10) is comprised by two flatwise juxtaposed layers (4, 5) of water-impervious mate­ rial being intersealed along at least one longitu­ dinal edge (20) thereof, said growing device (10) being suspended along said closed longitudinal edge (2) on a suspension means (15) placed at a substantially horizontal level.

Description: The present invention relates to a method for hydroponical growing of plants as well as a growing device and a system for the practicing of said method. Various methods, devices and systems of this kind have been developed through the time. All of the said methods and devices have, however, been based on functions and constructions leaving the plant roots either immersed in the nutrient solution, such as e.g. disclosed in US-PS 3,739,522, or surrounded by a growth medium from time to time saturated with nutrient solution, e.g. by dipping said medium in the nutrient solution, such as disclosed in US-PS 4,118,891. In either situation, the exchange of nutrient solution around the roots is rather slow. As a result the supply of nutrients and oxygen to the roots as well as the removal of waste products from the roots is inadequate so that the conditions for the growth of the plant is unsatisfactory. Experiments have shown that one of the decisive factors in the efforts of optimizing the growth of plants is that the conditions for the roots in taking up the water and exchanging of the neccessary amounts of nutrients and oxygen with waste products is as favourable as possible so as to minimize the stressing of the plants. Further, said experiments have shown that these conditions are favoured by a constant high percentage of relative humidity and oxygen accessible for the roots together with the maintenance of a steady but low concentration of the nutrients necessary in a accessible form and a lowest possible concentration of waste products including waste salts. From said experiments it also appears that even very low concentrations of the nutrients could still be adequate as long as the concentrations are still maintained at a level sufficient to secure the desired uptake of the nutrients necessary. Consequently, a continuous and fast exchange of the nutrient solution around the roots is of the greatest importance in order to ensure a fast removal of waste products and a steady supply of fresh nutrients of the composition and concentration required at the same time as it provides for a high percentage of oxygen accessible to the roots. The main advantage resulting in carrying out a continuous and fast exchange of nutrient solution around the roots is the possibility of minimizing the concentrations of nutrient salts and waste salts around the roots, thereby reducing the osmotic pressure outside the roots, which osmotic pressure is counteracting the uptake of water, at the same time as the necessary nutrient salts are still provided. In DK patent application no. 4420/79, filed on October 19, 1979, a method and a device to overcome this problem is disclosed, wherein a porous growth substrate surrounded by a plastic film in form of a bag is used for developing the roots of a single plant in that the growth substrate is continuously supplied with water containing the additives necessary for the growth of the plant, and whereby the water is collected from below the bottom of the bag and recirculated. As well the production of said device as the mounting thereof in a system including a greater number of said devices is rather time-comsuming and therefore relatively costly. EP-A-0042697 discloses a plant growing unit being formed of flexible plastic material and comprising an upper plant root-ball container being open upwards and a lower reservoir for nutrient solution. The walls of said reservoir have apertures for establishing a maximum level of nutrient solution and a ventilated air space above the nutrient solution. Openings between the container and the reservoir may allow root growth from the container to the reservoir. A wick of capillary material can be inserted to bridge the space between the upper root-ball container and the nutrient solution in the reservoir. The unit might be suspended on a wire, and the nutrient solution may be added on a continuous basis from a drip irrigation pipe in the root-ball container. The object of the present invention is to disclose an improved and simplified method for simultaneously growing several plants as well as a growing device and a system for practicing of said method. The inventive method comprises the steps of: inserting a drip irrigation pipe having outlets disposed along the length thereof in between a pair of flatwise juxtaposed layers of water-impervious material of a plant growing device alongside a first longitudinal edge thereof, suspending said drip irrigation pipe and said growing device on at least one suspension means placed in a substantially horizontal level with said first longitudinal edge and said pipe disposed adjacent said at least one suspension means, and the remaining part of the plant growing device hanging from said suspension means, placing the roots of a number of plants in between said two juxtaposed layers of the growing device, the roots of each plant being disposed downstreams of one of said outlets, continuous feeding of nutrient solution through said drip irrigation pipe and said outlets and guiding it to the roots of each plant, and it characterized by using a plant growing device being closed at said first longitudinal edge and having minor spaced throughcuts through at least one of the layers close to said first closed longitudinal edge, each of said throughcuts being adapted for the insertion of the roots of a plant and with the stem of the plant extending through the throughcut, and allowing said nutrient solution quickly to percolate along the roots of the plants and taking out and collecting percolated excess nutrient solution from below the roots for recirculation or discharge thereof, thereby generating optimal conditions for the roots, including the maintenance of a very thin film of percolating fresh nutrient solution having a low concentration of nutrient salts and waste products on the roots, said film being surrounded by an atmosphere having a nearly 100% relative humidity and a high content of oxygen. By this indicated method a quick exchange and percolation of the nutrient solution are obtained inside an almost completely closed root compartment, whereby the control of the root-environments is very easily carried out, and the depositing of salts at any place of the plant roots is avoided, and which is well suited for the simultaneous growing of several plants under equal and constant conditions. Preferably, this method is characterized by the use of a nutrient solution having a carefully controlled concentration of nutrients well below 2 per thousand, and by feeding nutrient solution in the amount of at least 0.1 l/h for each plant, preferably at least 0.25 l/h for each plant, whereby an extremely rapid growth of the plants is usually obtained. In using a very simple growing device comprising a flattened tubing suspended on a suspension means the upper part of said growing device is placed sloping proportional to the vertical plane containing the suspension means by means of a longitudinal displacement means. Thereby, in an initial phase of the growth, a good contact between the roots and the nutrient solution is ensured. In order to establish said sloping a displacement means, i.e. a wire, could be suspended below and sidewise displaced of the suspension means for the growing device, thereby supporting the upper part of the growing device in a sloping way. The collection of percolated nutrient solution is simplified by using a flattened plastic tubing being closed alongside the bottom edge as well as alongside the top edge except for a discharge opening at the lowest point of the bottom edge. In using a growing device having said pair of flatwise juxtaposed layers sealed together in intermediate lines or zones spaced in the longitudinal direction of the said layers and forming a series of transverse passageways between said zones for the passage of nutrient solution and development of the roots, a good contact between the roots and the nutrient solution is obtainable, even with a freely hanging growing device. In using a flattened plastic tubing, each closed longitudinal edge thereof being provided with a drip irrigation pipe alongside the length thereof, each closed edge and each pipe being suspended on a separate suspension means the intermediate part of the growing device sacking therebetween, the nutrient solution being fed through each of said drip irrigation pipes and upon percolation towards the middle of the growing device taken out through a discharge opening therein, a very favourable method of growing minor plants, such as lettuce, strawberries, beans, and a number of cut flowers, is obtained in which the plants could be placed all over the top surface of the growing device. The inventive growing device comprises a windable length of a pair of flatwise juxtaposed layers of water-impervious material forming first and second longitudinal edges the two layers being interconnected at least along said first longitudinal edge and being adapted for insertion of a drip irrigation pipe having outlets disposed along the length thereof in between said layers alongside said first longitudinal edge, said layers and said pipe further being adapted for suspension on a substantially horizontal suspension means alongside said first interconnected edge and is characterized by said windable length of layers being closed at said first interconnected edge, at least one of said two layers having minor throughcuts spaced along the length thereof and close to said first edge, each of them for the insertion of the roots of a plant adapted to have the stem of the plant extended through the throughcut, said length further being provided with a discharge opening for percolated nutrient solution at the bottom thereof. It is to be stressed that no growing substrate at all is to be inserted between the two layers, and that, consequently, a very cheap growing device for simultaneous growing of a number of plants is obtained. A preferred embodiment of the growing device of the invention is characterized by said length being a flattened tubing of plastic film, with the second longitudinal edge thereof being closed and the discharge opening being provided at the lowest point of said second closed longitudinal edge. A further preferred embodiment of the invention is characterized by said two layers being sealed in sealing zones, having the form of dots or rings or straight or curved lines and being spaced along the longitudinal direction of said layers, said sealing zones leaving longitudinally free passageways alongside said first and second edges and forming a series of successive transverse passageways open to said two longitudinally extending passageways, said transverse passageways having a substantially flat cross-section, said growing device especially being advantageous for use in a vertically suspended position, in which a good contact between the roots and the nutrient solution is still ensured. A further advantageous embodiment of the inventive growing device is characterized by comprising a windable length of a pair of flatwise juxtaposed layers of water-impervious material, said two layers being interconnected along a first longitudinal edge thereof, and said two layers further being sealed along sealing lines extending transverse to and spaced along the longitudinal direction of the length, and where each of said transverse sealing lines extends between a first point located some distance away from the first edge and a second point located some distance away from the opposing second longitudinal edge of said layers, said sealing lines thereby leaving a free longitudinal passageway extending along the length of said first edge and forming a series of successive, transverse passageways separated from each other by the transverse sealing lines and open to the longitudinal passageway at the first edge and to the second edge, said transverse passageways having a substantially flat cross-section. The resulting device is usable for simultaneously growing several plants, and is advantageous in that a series of transverse passageways, each for the growth of one plant and for the percolation of nutrient solution therethrough is provided, thereby minimizing the risk of spreading of disease between the roots. Another preferred embodiment of the growing device of the invention is characterized by a windable, collapsed plastic tubing, its pair of flatwise juxtaposed layers being interconnected along opposing first and second longitudinal, closed edges, respectively, of said collapsed tubing, said two flatwise juxtaposed layers of the collapsed tubing further being sealed along transverse sealing lines extending transverse to and spaced along the longitudinal direction of the length of the tubing, and where each of said transverse sealing lines extends between a first point located some distance away from the first closed edge and a second point located some distance away from the opposing second closed edge of the collapsed tubing, said sealing lines thereby leaving free longitudinal passageways, each extending along the length of a respective one of said closed edges of the collapsed tubing and forming a series of successive, transverse passageways separated from each other by the transverse sealing lines and open to both of said longitudinal passageways. This embodiment is very advantageous, as it is inexpensive and moreover has a further longitudinal passageway for the collection and passing-on of excess nutrient solution from all the transverse passageways. The said growing device is intended for use without any growth substrate therein and in a vertically suspended position with the transverse passageways extending in a vertical plane. As a result a fast percolation of fresh nutrient solution through each transverse passageway is obtained, thus attaining optimum and uniform conditions for the growth of each plant. The said device is of simple construction and inexpensively manufactured, as it is preferably made by simply welding together of a continuously blown plastic tube along the transverse sealing lines followed by separating the tube into tubings of a length suitable for the purpose of the topic. Furthermore, the device is easy to instal and to use, thereby minimizing the total cost of growth of the plants. The said device may also be made of one or more lengths of plastic film put together in a flatwise juxtaposed position or of other bendable materials impervious to water, such as waterproof paper or other waterproof fibrous fabrics. The interconnections and sealings may be carried out in any known way. The material used is preferably of a type impenetrable to light. More preferably the material is of a light-reflecting type thereby minimizing the amount of heat collected in the growing device. In an advantageous embodiment of the growing device according to the invention the tubing may also comprise a heat-insulating material, such as a foamed or otherwise formed cellular film material, thereby reducing the heat transfer through the tubing and obtaining an economic use of heated nutrient solution. A further preferred embodiment of the growing device of the invention is characterized by both of said longitudinal edges being closed and the length of the two layers being adapted for insertion of a drip irrigation pipe at each edge, and for suspension with said pipes on substantially horizontal suspension means alongside each edge, said two layers being sealed along two parallel longitudinal rows of sealing zones, each sealing zone in a row extending between a first point located some distance away from a closed edge of the length, and a second point located further away from said closed edge and some distance away from the centre line of the length and on the same side thereof as said first point, said rows of sealing zones thereby leaving free longitudinal passageways each extending along the length of a respective one of said closed edges and a free longitudinal, central passageway extending between said two parallel rows of sealing zones, said two rows further forming two series of successive, transverse, flat passageways separated from each other by the sealing zones and each open to a corresponding longitudinal, outer passageway and to the longitudinal, central passageway, the discharge opening being provided at the lowest point of th central passageway. This embodiment is particularly suitable for outdoor growing of plants, as it is very easily mounted in a stable position so that the growing device can resist wind action. Depending on preselected arrangements, this embodiment moreover allows rainwater either to be collected and integrated in the growing system or to be discarded when needed. Depending on the culture grown, it is furthermore possible to grow an increased number of plants per unit length of the growing device without requiring a corresponding larger area of access to the plants by simply placing more plants along the length of each transverse passageway. The sealing zones dividing up in transverse passageways have a simple geometric form, such as dots, rings or straight or curved lines extending perpendicular to, inclined to or parallel with the longitudinal direction of the length or tubing. An embodiment of the growing device having two parallel rows of sealing zones, which is of particular interest from a manufacturing point of view is characteriszed in that the sealing zones of the two rows are formed as lines inclined to the longitudinal direction of the tubing in a substantially symmetrical way with respect to the centre line. Thus the two sides of the growing device display the same properties during production as well as in use of the system. In one embodiment of the inventive device having transverse sealing lines the transverse sealing lines are straight lines inclined at an acute angle of between 0° and 90°, preferably between 0° and 45°, most preferably about 10°, to the longitudinal direction of the device, thereby maintaining a relatively quick percolation of the nutrient solution through the transverse passageways, when the device is suspended with the transverse passageways oriented in a substantially vertical plane. In order to maximise the growing place left above the device within a predetermined level, e.g. inside the roof of a greenhouse, the angle should be as small as possible, whereby the height of the device between the upper and the lower, longitudinal edges thereof is as low as possible for a given length of the transverse passageways. Depending on the type of plants grown, different proportions between the length and the width of the transverse passageways are recommended. For most purposes, however, it is satisfactory that the dimension of the transverse passageway from one longitudinal passageway to the other is about 3-5 times the dimension of the transverse passageway in the longitudinal direction of the device. The choice of width of the longitudinal passageways between the closed edges of the tubing and the row of sealing zones depends on the manner of supplying the nutrient solution, for instance on the dimension of the supply pipes to be used, and on the space necessary for the roots and for the collection and outlet of the percolated water. For most purposes, however, it is satisfactory, that the sealing zones extends between a distance of about 20-80 mm away from a first closed edge of the layers of the collapsed tubing. On the other hand, a considerably greater distance from the second edge or the centre line of the layers or tubing may also be desirable, for instance 80-300 mm. While the above simple form of the growing device functions quite satisfactory in most cases, it is occasionally advantageous to provide the growing device with additional longitudinal sealings along longitudinally extending sealing lines, each additional sealing extending from the end of a transverse sealing line at the first point towards a neighbouring, sealing zone to a point close to said neighbouring, sealing zone and to the adjacent longitudinal passageway, said additional sealings thereby being gently inclined to the inside of the adjacent transverse passageways and leaving a passage from the adjacent longitudinal passageway to each of said transverse passageways for the inlet of nutrient solution therein. This applies especially for devices having very wide transverse passageways separated by sealing zones extending perpendicular to the longitudinal direction of the device. The above arrangement ensures a correct delivery of the supplied nutrient solution to the area of the inserted roots. Any nutrient solution supplied by a supply pipe in the area of a transverse passageway between two adjacent sealing zones is transferred to said transverse passageway through the passage left by the additional, gently inclined, sealing line. Consequently it is easier to place the plant in such a way that the supply of nutrient solution arrives at the area of the inserted roots. It is worth underlining that the growing device is used completely without any kind of growing substrate inside the device, thereby eliminating all costs and other disadvantages therefrom. Moreover, storing and shipping costs are thus kept at a minimum. In addition all of the growing device as well as the plant material is burnable after use upon a short air-drying period. According to a further feature of the invention the growing device is initially provided with a minor throughcut through at least one of the layers of the growing device at the end of each transverse passageway close to the longitudinal passageway at the first edge or to the longitudinal outer passageways, respectively, for insertion of a plant and, according to another feature, with at least one opening to the outside from the longitudinal passageway at the second closed edge of the device or the longitudinal central passageway, respectively, for the outlet of excess nutrient solution, thus expediting the correct mounting of the growing device. The throughcuts and openings can be provided prior to or during the mounting of the growing device. A further object of the invention is to provide an improved system for hydroponical growing of plants, where a high degree of functional security is achieved, simultaneous with the cost of initial expenditure as well as the operating costs being kept at a very low level. The inventive system is of the kind comprising a collecting tank for a nutrient solution, a control means for continuously measuring and adjusting the content of nutrient salts and other additives necessary for the growth of plants by adding the necessary amounts of water, macrosubstances, and microsubstances to the nutrient solution, pumps and pipes for continuously carrying nutrient solution to the plants, and at least one gutter for collecting and passing-on of used, excess nutrient solution from the plants to the collecting tank. According to the invention, the system is characterized by further comprising a number of inventive growing devices, a corresponding number of supply pipes inserted therein and of a length at least equal to the length of the growing device (10) and a corresponding number of suspension means for suspending the growing device and each inserted supply pipe in such a manner that each growing device is located above and transverse to the gutter with its lower longitudinal passageway slightly inclined downwards towards said gutter, and with the outlet thereof just above said gutter. The entire system is very simple in its construction. Especi-ally by using supply pipes inserted in and supporting the likewise simple growing devices, a very simplified system is achieved, which is also very reliable. At the same time the mounting of the system and the insertion of the plants is performed in a very simple manner, thus saving a lot of time compared with other systems. In an advantageous embodiment of the inventive system the suspension means comprises at least one suspension member, such as a cord or a wire stretched between at least two posts, and optionally gripping means gripping around the suspension member and the upper part of the growing device holding the supply pipe at suitable places along the length thereof, thereby fastening the growing device to the suspension member, said suspension member being positioned at a level sufficient for keeping the bottom of the growing device just above the top of the gutter. As a result the growing device is kept at a correct position by the suspension member without subjecting the supply pipe to stresses. Moreover, the growing device with supply pipe is easily mounted at or removed from the suspension member. In a further advantageous embodiment of the inventive system the suspension means comprises two parallel wires, tightly stretched between two posts and kept close to each other on either side of the growing device beneath the supply pipe inserted therein, and the suspension means further comprises gripping means, such as hooks, inserted under the wires and the supply pipe and suspended by strings fastened to a mounting means above the growing device, thereby supporting the growing device and the plants inserted therein, the top of said plant being fastened to the string. The use of this construction enables the positioning of the growing device between the two wires with the first longitudinal passageway including the supply pipe situated just above the wires. This results in a very stable suspension of the growing device. The growing device could of course also be suspended on a single wire positioned inside the upper longitudinal passageway alongside the supply pipe therein. Despite the suspension wire or wires being tightly stretched, the wires are slightly bowed in a downward direction when loaded with the growing device. Consequently the lower, second longitudinal passageway is sloped from both ends of the growing device towards the middle, the latter being at the lowermost position. Naturally it is advantageous to place this point above the gutter and to provide the outlet from the second longitudinal passageway at this point. When using the inventive system for growing plants subjected to wind, said system is advantageously characterized by a further supporting means supporting each growing device against being forcibly removed from the substantially vertically suspended hanging position. In this connection one embodiment of said further supporting means comprises at least one suspension member stretched between above-mentioned posts at a level above the lower longitudinal passageway, and a number of locking elements, such as hooks, clamps, straps or pins, securing the growing device to the supporting means. Further in connection therewith anchoring means holding the growing device, such as strings, nets or tapes, may be fastened at anchoring blocks or suspension members secured below the growing device. In a system comprising growing devices having two rows of sealing zones the suspension means advantageously comprises at least one suspension member or weighting member pressing or weighing down the central part of the growing device so that it can resist wind action. Said weighting member may advantageously be at least one sandhose placed loosely on the central part of said growing device. In a particularly advantageous embodiment a system including a growing device with two rows of sealing zones comprises an outer plastic tubing surrounding said growing device and carried by an intermediate carrying means, said outer plastic tubing being closed at each end of the growing device thereby substantially forming a miniature greenhouse around said growing device. The invention is described in greater detail below by means of examples of embodiments and with reference to the accompanying drawings, in which Figure 1 is a diagrammatic, perspective side view of a central section of a preferred embodiment of the inventive growing device with an inserted supply pipe and supported by two wires suspended on posts, Figure 2 is a sectional view along the line II-II of Figure 1, Figure 3 is a diagrammatic side view of a section of another embodiment of the inventive growing device, and Figure 4 is a diagrammatic perspective view of an embodiment of the inventive system including the inventive growing device. Figure 5 is a diagrammatic perspective side view of a further embodiment of the invention including a pair of superposed layers of sheet material, and with further suspension means supporting the lower part of the device, Figure 6 is a similar diagrammatic perspective side view of the preferred embodiment of the invention supported by a helically wound anchoring string fastened at anchoring blocks, Figure 7 is a planar view of a mounted, symmetrically shaped, two-sided growing device, Figure 8 is a sectional view through the growing device of Figure 7 along the line III-III, Figure 9 is a sectional view through the growing device of Figure 7 along the line IV-IV, and Figure 10 is a diagrammatic perspective view of a part of the two-sided growing device including an outer plastic tubing, Figure 11 is a diagrammatic perspective view of a further alternative embodiment of the invention in a simplified form without any sealings and with a single suspension means inside the device and with a displacement means, and Figure 12 a, b, c, d are sections of further alternative embodiments showing sealing zones having various geometric forms. Figures 1 and 2 illustrate a preferred embodiment of the inventive growing device 10. In Figure 1 only a cut-out central section of the growing device is shown. The growing device 10 comprises a collapsed plastic tubing 1 having a first upper, closed longitudinal edge 2 and a second lower, closed longitudinal edge 3 opposing each other. The opposing two layers 4, 5 of the collapsed tubing 1 are sealed together along parallel transverse sealing lines 6 extending transversely to the tubing 1 and inclined at an acute angle α to the longitudinal direction C-C of the tubing 1. Each transverse sealing line 6 extends between two points some distance away from each of the closed longitudinal edges 2, 3, respectively, thereby forming two opposing, longitudinal free passageways 7, 8 parallel to the closed longitudinal edges 2, 3. Between the longitudinal passageways 7, 8, the tubing 1 is divided into a number of parallel, flat transverse passageways 9 separated from each other by the transverse sealing lines 6, but open at both ends to the two longitudinal passageway 7, 8 of the growing device 10. The two opposing layers 4, 5 of the plastic tubing 1 lie flat upon each other. At first the transverse passageways 9 and the longitudinal passageways 7, 8 are completely empty so that the growing devices can assume the form of a coiled-up, endless tube (not shown). The tube can be provided with perforated lines (not shown) to facilitate the separation into suitable lengths of tubing 1, each length forming an individual growing device 10. At the top of each transverse passageway 9 a minor throughcut 11 is made in the layer 4 of the growing device 10, said throughcut enabling the insertion of the roots of a plant into the transverse passageway 9. At the middle of the lower, longitudinal edge 3 an opening 12 is provided acting as an outlet for excess nutrient solution from the growing device 10. Prior to using the growing device a supply pipe 14 for nutrient solution is inserted into the upper longitudinal passageway 7. The growing device is then mounted on suspension means 15 in form of two parallel wires 15 stretched horizontally between two posts 16, 16′, cf. Figure 4. The two wires 15 are positioned on either side of the growing device 10 and just below the upper longitudinal passageway 7 with the inserted supply pipe 14, and kept close to each other. Thus the supply pipe is nested on the two wires 15 and the rest of the growing device 10 is suspended therefrom. Different kinds of supply pipes 14 are usable, provided that they can transfer a continuous flow of nutrient solution into each transverse passageway 9, for instance by drip irrigation. In the preferred embodiment a supply pipe 14 of the type comprising a polyethylene pipe with inserted fittings having outlets 17 opposite each transverse passageway 9 is used. The supply pipes are not a part of this invention, but are included for the sake of clarity. Upon suspension of the growing device 10 nutrient solution is supplied via the supply pipe 14 with outlets 17 and transferred in a continous flow to each transverse passageway 9. A plant 18 is inserted through the throughcut 11 with the roots 19 of the plant positioned inside the transverse passageway 9 and the stem 20 and top 21 of the plant extending through said throughcut 11 outside of the growing device 10. The nutrient solution quickly percolates through the roots 19 and is partially absorbed by said roots. The remaining excess nutrient solution percolates down through the transverse passageway 9 and drains out at the bottom of the transverse passageway for being collected inside the lower longitudinal passagewasy 8 of the growing device 10. As the wires 15 loaded with the growing device 10 are only suspended at their ends, the wires 15 and thus the growing device 10 are curved downwardly. Upon collection in the longitudinal passageway 8 the excess nutrient solution flows towards the opening 12 acting as an outlet at the middle of said passageway. For preventing the wires 15 from separating from each other resulting in the growing device 10 sliding down between them, gripping means, such as hooks 22, are inserted under the wires 15, surrounding said wires and holding then together below the upper longitudinal passageway 7 holding the supply pipe 14. In order to obtain support for the top 21 of a plant 18, the hooks 22 are suspended in strings 23 mounted in mounting means 41, cf. Figure 4. The top 21 of the plant 18 is fastened to said strings 23 in a manner known per se. When employing the hooks 22 one of the wires 15 can be omitted. It is further possible to exclusively use the hooks 22 and the strings 23 for the suspension of the growing device. This is of special relevance in case of a rigid supply pipe 14. Under such circumstances both wires 15 can be omitted. Figure 3 illustrates another embodiment of the inventive growing device 10, where the transverse sealing lines 6 extend substantially perpendicular to the longitudinal direction C-C of the growing device 10. In this embodiment an additional sealing is formed at the top of each transverse passageway, substantially along longitudinally extending sealing lines 26, in order to provide an inlet for the nutrient solution close to the throughcut 11. The additional sealing 26 extends from the end of one transverse sealing line 6 at the upper longitudinal passageway 7 to a point some distance away from the neighbouring transverse sealing line 6 and slopes away from said longitudinal passageway 7. This results in a passage 27 from the longitudinal passageway 7 to a transverse passageway 9, said passage allowing the flow of nutrient solution from the longitudinal passageway 7 to the transverse passageway 9. The throughcut 11 is placed above the passage 27 so that the roots 19 of an inserted plant 18 are positioned in the area of the passage 27. Apart from the differently orientated, transverse-sealing lines 6 and the additional longitudinal sealings 26 the rest of the growing device 10 is as described above in connection with Figures 1 and 2. The additional sealings 26 can, of course, also be introduced in the embodiment of Figures 1 and 2, although they are normally not necessary in connection with a growing device having transverse sealing lines substantially inclined to the longitudinal direction of the growing device. Figure 4 illustrates an embodiment of the inventive improved system for hydroponical growing of plants using the inventive growing device 10. The system includes a plurality of parallel rows of growing devices 10 each mounted on wires 15 supported by posts 16, 16′ and with supply pipes 14 inserted in each growing device. Additional suspension means are provided in form of hooks 22 inserted through the growing device 10 beneath the wires 15 and the supply pipe 14, said hooks being suspended in strings 23 mounted in a mounting means 41. By means of a pump 32 and via a pressure pipe 31 the nutrient solution is carried from a collecting tank 30 to the individual growing devices 10. The pressure pipe 31 is preferably led through a gutter 33 leading to the collecting tank 30 and extending transverse to the growing devices 10 and midways between the posts 16, 16′ in the ground 34. Nutrient solution is carried to the supply pipe 14 in the growing device 10 through a vertical distribution pipe 35 opposite the growing device and optionally extending through a transverse passageway 9 of the growing device. Especially in case of inclined transverse sealing lines 6, the growing device 10 can be divided into two halves, each mounted on a supply pipe 14 one either side of the gutter 33 between the posts 16, 16′ and the distribution pipe 35, preferably in a laterally reversed manner. At the bottom of each growing device an outlet 12 is formed above the gutter 33. The collecting tank 30 is provided with a control means 36 including a known measuring and dispensing assembly 37, 38, 39. At 37 the measuring assembly measures the content of nutrients and other additives necessary for the growth of plants in the nutrient solution contained in the collecting tank 30. Furthermore it controls the addition of water at 38 and the addition of necessary additives to said solution at 39 in order to obtain a solution with a desired concentration of nutrients. Furthermore the collecting tank 30 is provided with a propeller 40. For using the system the growing devices 10 are mounted on supply pipes 14 and wires 15. An appropriate nutrient solution is prepared and circulated in the system by means of the pump 32 via pressure pipe 31, distribution pipes 35 and supply pipes 14. From the supply pipes 14 the nutrient solution percolates through each transverse passageway 9 of the growing devices 10 and flows out through outlets 12 into the gutter 33 and is returned to the collecting tank 30 for recirculation. Now the roots 19 of the plants 18 are inserted into the transverse passageways 9. The circulating nutrient solution percolates over the roots of the plants, said roots absorbing some of the water and the additives. The excess nutrient solution is returned to the collecting tank 30 together with waste products having been excreted from the roots of the plants. In the collecting tank 30 of the nutrient solution is continuously monitored and adjusted by the control means 36. The collecting tank 30 can be provided with an additional rinsing means (not shown) for removing some of the waste products from the plants 18. A predetermined amount of the return solution is to be discarded, either at intervals or continuously, in order to keep the content of waste products separated from the roots below a predetermined standard. Figure 5 illustrates a further embodiment of the growing device 10 of the invention. The growing device 10 includes a length 1 of two separate layers 4, 5 of sheet material superposed each other, said layers 4, 5 being sealed together along transverse sealing lines 6 as described in connection with Figure 1. The two layers 4, 5 are interconnected along a connection line 2′ at the upper edges 2 of said layers, for instance by welding, seaming or by means of locking elements spaced apart in the longitudinal direction C-C of the device. As in Figure 1, a supply pipe 14 is inserted in the upper longitudinal passageway 7 between the connecting line 2′ and the transverse sealing lines 6. At the lower part of the device 10 a pair of suspension wires 45 is positioned on either side of the device, stretched between the two posts 16, 16′, cf. Figure 4, and kept close to each other by means of clamps 46 inserted through the two layers 4, 5 and surrounding and interlocking the two suspension wires 45. The lower edges 3 of the two layers 4, 5 are left unconnected, thereby leaving a longitudinal opening extending at the bottom of growing device 10 so that excess nutrient solution is let out into the soil or in a gutter (not shown). In Figure 6 the embodiment of the growing device 10 of Figure 1 is shown with supporting means in form of a supporting string 47 would helically around the growing device 10 and fastened at anchoring means, such as anchoring hooks 48 secured in anchoring blocks 49 in the ground 50. Preferably said strings are made of elastic material. Instead of anchoring blocks 49 a single suspension wire or rod 45 at the bottom of the device can be used. Furthermore, instead of the clamps 46 of Figure 5, one end of plastic straps (not shown) can be inserted through the layers 4, 5 and tied to the suspension wire or rod 45 at the bottom of the device, the opposite ends of said straps being provided with enlarged end pieces having shoulders acting as holder. Throughcuts with strengthend edges and for the insertion of said plastic straps are provided in the collapsed tubing simultaneous with the forming of the sealing lines 6, for instance by heat-sealing the two layers of plastic 4, 5 to each other in said areas. Figures 7-10 illustrate another preferred embodiment of the invention, in which the growing device 10 comprising a collapsed tubing 1 is provided with two parallel rows 62, 63 of transverse sealing lines 6 symmetrically placed around the centre line C and with two longitudinal, outer, free passageways 7, 8 at the opposing edges 2, 3 of the tubing 1. Supply pipes 14 for nutrient solution are inserted in said passageways 7, 8. A free longitudinal central passageway 90 is provided between the two rows 62, 63 of transverse sealing lines 6. Transverse passageways 9 between neighbouring transverse sealing lines 6 in a row 62, 63 are open to the respective longitudinal, outer passageway 7, 8 and to the longitudinal central passageway 90, thus forming passages therebetween for the nutrient solution and for the roots of the plants 18. At least one throughcut 12 is provided in the central passageway acting as an outlet 12 for excess nutrient solution. When mounted, each of said edges 2, 3 having longitudinal, outer passageways 7, 8 with supply pipes 14 inserted therein are nested on suspended, opposing wires 15 each streched between two posts 16, 16′ in substantially the same level, cf. Figure 4. The interjacent part of the growing device 10 hangs between and below said wires 15. Midways between the posts 16, 16′ a strap 29 surrounding the opposing wires 15 is tightened thus drawing said wires towards each other. As a result the bottom of the central part of the growing device 10 has a lower position than at the ends of said growing device causing an downward inclination of the central passageway towards the outlet 12, cf. the sectional views along the lines III-III and IV-IV of Figure 7. Moreover the weight of the suspension means 15 and of the growing device 10 with supply pipes 14, plants 18 and nutrient solution weighs down the entire growing device 10 in a curve between the posts 16, 16′ thus intensifying said inclination. When the growing device 10 is mounted outdoors a weighting member 24 in form of at least one sandhose may be placed on the growing device 10 above the central passageway 90, thereby assisting the growing device 10 to resist wind action. The use of this embodiment of the growing device 10 is disclosed in connection with the growing device 10 of Figures 1-6, except that in this case two supply pipes 14 and two series of transverse passageways 9 are provided for each growing device 10. Due to the transverse inclination of the growing device towards the central passageway 90 this embodiment is suitable for growing several plants in each transverse passageway 9 thereby obtaining an intensive utilization of the area of the growing device. The embodiment illustrated in Figure 10 is further provided with an outer plastic tubing 25 surrounding the suspended growing device 10, said plastic tubing being supported by an intermediate carrying means 28 in form of three parallel wires suspended triangularly and roof-shaped above the growing device 10 between two end frames 52 each clamped on a post 16, 16′. In this case also the wires 15 are suspended between said two end frames 52. An outer plastic tubing 25 rests on above three parallel wires and is weighed down by a weighting member 51 inserted inside the bottom of the tubing 25. Instead of the three parallel wires the carrying means 28 can also be made of spirally wound steel strings or another type of upwards curved frames resting on top of the growing device 10 or mounted in end frames 52. At the ends of the growing device 10 the outer plastic tubing 25 can be closed outside of the end frames 52, thereby ensuring the maintainance of elevated temperatures and relative humidity inside the tubing. Figure 11 illustrates a further simplified embodiment of the inventive growing device (10). This growing device 10 comprises a collapsed plastic tubing (1) having a first upper, closed longitudinal edge 2 and a second lower, closed longitudinal edge (3) opposing each other, the opposing intermediate two layers (4, 5) of the collapsed tubing (1) being without any sealing therein. Said growing device (10) is used suspended on a single wire (15) inserted therein alongside the supply pipe (14) inside the upper longitudinal passageway (7), and the upper part of said growing device (10) is placed in a sloping way by means of a displacement means (55) in the form of a wire suspended parallel with, below and sideways displaced from the suspension wire (15). Optionally, said layers (4, 5) could be provided with pleatings (56) extending parallel with, inclined to or perpendicular to the direction of length for the growing device (10). The effect of said pleatings (56) is that the nutrient solution on meeting such a pleating (56) will tend to follow said pleating, thereby guiding the water to the roots. Of course, it would also be possible to use this embodiment of the growing device (10) suspended on wires (15) inserted in each of the longitudinal passageways (7, 8) together with two supply pipes, as disclosed in connection with Figures 7-10, however, in this connection without using any displacement means (55). In Figures 12a, b, c, d is illustrated various geometric forms of sealing zones (6) applicable in connection with the invention in addition to the previously mentioned forms. The advantage of said forms of sealing zones (6) is that depending on the composition and thickness of the material of the layers (4, 5) the way of suspension of the growing device (10) and the kind of plants grown therein various forms of sealing zones are desirable. In figure 12a the sealings are ring-formed, in Figure 12b in the form of spot weldings, and in Figures 12c and d in the form of short sealing lines of a length of between 5 and 15 cm and extending parallel with, inclined to or perpendicular to the direction of length of the growing device (10).

Claims: A method of hydroponical growing of plants comprising the steps of: inserting a drip irrigation pipe (14) having outlets (17) disposed along the length thereof in between a pair of flatwise juxtaposed layers (4, 5) of water-impervious material of a plant growing device (10) alongside a first longitudinal edge (2) thereof, suspending said drip irrigation pipe and said growing device on at least one suspension means (15) placed in a substantially horizontal level with said first longitudinal edge and said pipe disposed adjacent said at least one suspension means, and the remaining part of the plant growing device (10) hanging from said suspension means, placing the roots (19) of a number of plants (18) in between said two juxtaposed layers of the growing device, the roots of each plant being disposed downstream of one of said outlets, continuous feeding of nutrient solution through said drip irrigation pipe and said outlets and guiding it to the roots of each plant, characterized by using a plant growing device (10) being closed at said first longitudinal edge (2) and having minor spaced throughcuts (11) through at least one of the layers (4, 5) close to said first closed longitudinal edge (2) each of said throughcuts being adapted for the insertion of the roots (19) of a plant (18) and with the stem (20) of the plant extending through the throughcut (11), and allowing said nutrient solution quickly to percolate along the roots of the plants and taking out and collecting percolated excess nutrient solution from below the roots for recirculation or discharge thereof, thereby generating optimal conditions for the roots, including the maintenance of a very thin film of percolating fresh nutrient solution having a low concentration of nutrient salts and waste products on the roots, said film being surrounded by an atmosphere having a nearly 100% relative humidity and a high content of oxygen. A method as claimed in claim 1, characterized by using a nutrient solution having a carefully controlled concentration of nutrients well below 2 per thousand, and by feeding nutrient solution in the amount of at least 0.1 l/h for each plant, preferably at least 0.25 l/h for each plant. A method as claimed in claim 1 or 2, characterized by placing an upper part of the plant growing device (10) sloping proportionally to the vertical plane containing the suspension means (15), by means of a longitudinal displacement means (55). A method as claimed in any of claims 1-3, characterized by using a flattened plastic tubing (1) being closed alongside the bottom edge (3) as well as alongside the top edge (2), except for a discharge opening (12) at the lowest point of the bottom edge (3). A method as claimed in any of claims 1-4, characterized by using a growing device having said pair of flatwise juxtaposed layers (4, 5) sealed together in intermediate lines or zones (6) spaced in the longitudinal direction of the said layers and forming a series of transverse passageways (9) between said zones (6) for the passage of nutrient solution and development of the roots (19). A method as claimed in any of claims 1-5, characterized by using a flattened plastic tubing (1), each closed longitudinal edge (2, 3) thereof being provided with a drip irrigation pipe (14) alongside the length thereof, each closed edge (2, 3) and each pipe being suspended on a separate suspension means (15), the intermediate part of the growing device sagging therebetween, the nutrient solution being fed through each of said drip irrigation pipes (14) and upon percolation towards the middle (C) of the growing device taken out through a discharge opening therein. A growing device (10) for hydroponical growing of plants comprising: a windable length (1) of a pair of flatwise juxtaposed layers (4, 5) of water-impervious material forming first and second longitudinal edges (2, 3), the two layers (4, 5) being interconnected at least along said first longitudinal edge (2) and being adapted for insertion of a drip irrigation pipe (14) having outlets (17) disposed along the length thereof inbetween said layers (4, 5) alongside said first longitudinal edge (2), said layers (4, 5) and said pipe (14) further being adapted for suspension on a substantially horizontal suspension means (15) alongside said first interconnected edge (2), characterized by said windable length (1) of layers (4, 5) being closed at said first interconnected edge (2), at least one of said two layers (4, 5) having minor throughcuts (11) spaced along the length thereof and close to said first edge (2), each of them for the insertion of the roots (19) of a plant (18), adapted to have the stem (20) of the plant (18) extended through the throughcut (11), said length (1) further being provided with a discharge opening (12) for percolated nutrient solution at the bottom thereof. A growing device (10) as claimed in claim 7, characterized by said length (1) being a flattened tubing (1) of plastic film, with the second longitudinal edge (3) thereof being closed and the discharge opening (12) being provided at the lowest point of said second closed longitudinal edge (3). A growing device (10) as claimed in claim 7 or 8, characterized by said two layers (4, 5) being sealed in sealing zones (6), having the form of dots or rings or straight or curved lines and being spaced along the longitudinal direction of said layers (4, 5), said sealing zones (6) leaving longitudinally free passageways (7, 8) alongside said first and second edges (2, 3) and forming a series of successive transverse passageways (9) open to said two longitudinally extending passageways (7, 8), said transverse passageways (9) having a substantially flat cross-section. A growing device (10) as claimed in claim 7 and for the practicing of the method of claim 6, characterized by both of said longitudinal edges (2, 3) being closed and the length (1) of the two layers (4, 5) being adapted for insertion of a drip irrigation pipe (14) at each edge (2, 3), and for suspension with said pipes (14) on substantially horizontal suspension means (15) alongside each edge (2, 3), said two layers (4, 5) being sealed along two parallel longitudinal rows (62, 63) of sealing zones (6), each sealing zone in a row extending between a first point (6') located some distance away from a closed edge (2, 3) of the length (1), and a second point (6'') located further away from said closed edge (2, 3) and some distance away from the centre line (C) of the length (1) and on the same side thereof as said first point (6'), said rows (62, 63) of sealing zones (6) thereby leaving free longitudinal passageways (7, 8) each extending along the length of a respective one of said closed edges (2, 3) and a free longitudinal, central passageway (90) extending between said two parallel rows (62, 63) of sealing zones (6), said two rows of sealing zones further forming two series of successive, transverse, flat passageways (9) separated from each other by the sealing zones (6) and each open to a corresponding longitudinal, outer passageway (7, 8) and to the longitudinal, central passageway (90), the discharge opening (12) being provided at the lowest point of the central passageway (90). A system for hydroponical growing of plants, comprising a collection tank (30) for a nutrient solution, a control means (36) for continuously measuring and adjusting the content of nutrient salts and other additives necessary for the growth of plants by adding the necessary amounts of water, macrosubstances, and microsubstances, to the nutrient solution, pumps (32) and pipes (31, 35) for continuously carrying of nutrient solution to the plants (18), and at least one gutter (33) for collecting and passing-on of used, excess nutrient solution from the plants (18) to the collecting tank (30), characterized by further comprising a number of growing devices (10) as claimed in any of the claims 7-10, a corresponding number of supply pipes (14) inserted therein and of a length at least equal to the length of the growing device (10) and a corresponding number of suspension means (15, 24) for suspending the growing device (10) and each inserted supply pipe (14) in such a manner that each growing device (10) is located above and transverse to the gutter (33) with its lower longitudinal passageway (8) or central passageway (90), respectively, slightly inclined downwards towards said gutter (33) and with the outlet (12) thereof just above said gutter. A system as claimed in claim 11, characterized in that the suspension means (15, 24) comprises at least one suspension member, such as a cord or a wire (15), stretched between at least two posts (16, 16'), and optionally gripping means (22) gripping around the suspension member (15) and the upper part of the growing device (10), holding the supply pipe (14) at suitable places along the length thereof, thereby fastening the growing device (10) to the suspension member (15), said suspension member being positioned at a level sufficient for keeping the bottom of the growing device (10) just above the top of the gutter (33). A system as claimed in claim 12, characterized in that the suspension means (15) comprises two parallel wires (15), tightly stretched between two posts (16, 16'), and kept close to each other on either side of the growing device (10) beneath the supply pipe (14) inserted therein, and in that the suspension means (15) further comprises gripping means (22), such as hooks, inserted under the wires (15) and the supply pipe (14) and suspended by strings (23) fastened to a mounting means (41) above the growing device (10), thereby supporting the growing device (10) and the plants (18) inserted therein, the top (21) of said plants being fastened to the strings (23). A system as claimed in any of the preceding claims 11-13, characterized by a further supporting means (45-48) supporting each growing device against being forcibly removed from said substantially vertically suspended hanging position, for instance by means of wind, said supporting means comprising at least one suspension member (45) stretched between said posts (16, 16') at a level just above the lower longitudinal passageway (8), and a number of locking elements, such as hooks, clamps, straps or pins (46), securing the growing device (10) to the suspension members (45), said supporting means including anchoring means (47) such as tapes, nets or strings to be fastened at anchoring blocks (48) or suspension members (45) secured below the growing device. A system as claimed in claim 12, in which said suspension means (15, 24) comprises at least one suspension member or weighting member (24) pressing or weighing down the central part of the growing device (10). A system as claimed in any of the preceding claims 11-13 and 15, and including a growing device as claimed in claim 10, wherein the opposing closed edges (2, 3) of said growing device (10) having supply pipes (14) inserted in the longitudinal outer passageways (7, 8) thereof are nested on suspension members (15) located opposite each other and substantially on the same level, and with the interjacent part of the growing device (10) in a hanging position between and below said suspension members (15), and further including an outer plastic tubing (25) surrounding said growing device (10) and carried by an intermediate carrying means (28), said outer plastic tubing being closed at each end of the growing device (10). A method as claimed in any of claims 1 to 7, characterized by welding together said pair of layers (4, 5) along said first longitudinal edge (2).

Inventors: AHM POUL HENRIK, AHM, POUL HENRIK
Applicants: BENTLE PRODUCTS AG
Application year: 1990
Main classification: A01G31
IPC codes: A01G31