GB1597112A

GB1597112A - Hydroponic cultivation of plants

Info

Publication number: GB1597112A
Application number: GB19169/80A
Authority: GB
Inventors: Kenneth Roy Dunn
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-11-18
Filing date: 1976-11-18
Publication date: 1981-09-03

Description

(54) HYDROPONIC CULTIVATION OF PLANTS (71) I, KENNETH Rov DUNN, a British Subject, of 12, The Turnways, Leeds LS6 3DU, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to the growing of plants and is specifically concerned with the growing of edible or inedible plants by hydroponic cultivation-that is, by growing the plants in water, or in water containing nutrients.

Hydroponics as a general field is not novel, although the system has yet to find wide commercial use Several methods of hydroponic cultivation have been tried. One is the so-called nutrient film method, in which plants or seedlings are supported in a trough supplied with a thin film of liquid to which has been added suitable chemical nutrients.

Plants or seedlings can be grown in such conditions, with the liquid/nutrient film providing the nourishment needed by the plant roots, but very careful control of the chemical composition of the film, and of the environment surrounding the growing plants, is needed for any degree of success to be achieved. The system is, for example, highly susceptible to contamination. Another known commercial system involves the use of fluid-irrigated gravel beds, but these, although giving high yields, cannot be readily used for initial germination or small scale research as it requires constant maintenance, large operating areas and large available amounts of water.

The invention is based on the objective of using hydroponic cultivation to achieve germination and rapid growth, without the need for excessive care in the control of the surrounding environment and also without the need for unduly complicated apparatus and checking facilities.

The invention is based on the discovery that for germination a relatively deep, elongated trough may be used allowing similarly deep-water cultivation since in such conditions there will be sufficient natural circulation and aeration of the nutrient fluid to provide the right conditions for germination.

According to the present invention there is provided an apparatus for germinating plants hydroponically from seed, which com- prises a trough and a plurality of individually removable plate containers containing a removable insert holding a plant supporting material and a wick which, in use, connects the plant supporting material with the fluid beneath in the trough.

Preferably the plant containers are adapted to be gripped resiliently in cooperating holding apertures located on the trough, and the inserts are split longitudinally to allow them to be opened when removed from the holding aperture and closed prior to inserting them in the aperture.

In known systems of hydroponic cultivation, including the "film" system referred to above, the growth of the plant roots in the trough has been relatively unimpeded. In contrast, plant seedlings or growing plants are here held in individually removable containers which allow each plant to be removed without disturbing the others. As a further development of the present invention, the plant container may be so constructed that plant roots grow only downwardly from the container towards the nutrient fluid. It has been found that, in such a situation, very rapid growth of the plant is achieved, accompanied by a relatively smaller root growth.This not only allows more plants to be grown side by side in any one trough (thus increasing the overall yield of the trough) but also renders the nutrient fluid far less likely to be contaminated by a mass of roots resting on the bottom of the trough preventing the escape of toxins. The plants are additionally allowed full feeding from the nutrients. A further advantage is that individual growing plants can easily be removed, and either inspected and replaced, or transplanted into soil, peat or other hydroponic apparatus.

The accompanying drawings show, by way of example only, apparatus for use in a method of growing plants hydroponically in accordance with the present invention. In these drawings: Figure I illustrates, in perspective, an apparatus constructed according to the invention; and Figure 2 illustrates, in diagrammatic crosssection, a further form of apparatus embodying the invention.

Reference is directed to my copending Application No. 48053/76 serial No. 1597111 (from which this Application is divided) which discloses apparatus for hydroponic cultivation having means for circulation and aeration of the nutrient fluid. The general operation of the hydroponic cultivation system is described therein and will not be repeated here.

Referring to Figure 1 of the drawings, there is provided a trough 28 of rectangular cross-section, and a number of plant containers 38, having wicks 44, adapted to be supported above the nutrient fluid.

The trough 28 is of considerable length relative to its width and depth, and is deep enough to hold a sufficient depth of liquid to allow the wick 44, and eventually the plant roots, to depend freely into the nutrient solution without contacting the bottom of the trough. It is not closed, but in this embodiment two vertically-spaced grids of squarepatterned mesh 30, 32 are superimposed one on top of another and are held in that position in side channels 34 to form a composite stature which clips removably onto cooperating lipped top edges 36 of the trough 28 along its entire length. In both the embodiments illustrated, the supply piping, baffles, trough components and plant containers are all of suitably non-toxic plastics material.

Individual plant containers 38 are removably inserted into, and gripped by, the bars of the two meshes 30, 32. In this embodiment, the plant containers 38 are elongate cylindrical tubes made of a resilient plastics material.

They could, for example, be constituted by something as practical as a hair-curler, which has the added advantage of having resilient protrusions formed on its outer surface and which could thus be gripped all the more effectively by the bars of the meshes. It is emphasized, however that the inherent resilient deformability of the meshes and/or container body could be enough in itself for a secure location of each plant container. This form of resilient gripping allows the containers to be positioned at a desired height above the intended fluid level.

Closely fitting within each container is an insert consisting of an initially rectangular plastics sheet which has been rolled into a tube 40 and pushed into the container 38. In Figure 1 the container and the rolled sheet insert are shown separately, and the construction of the two meshes and their supporting side channels is also shown in detail.

The insert surrounds and holds a seed or growing plant, in a suitably porous wad or bed 42 of supporting material, so that the plant grows upwardly out of the top of the insert and its roots grow downwardly out of the bottom of the insert towards the nutrient liquid flowing through the trough. This construction allows easy removal of the seedling from the container when this is required.

The "wick" 44 (such as a strip of blotting paper or a "tail" of cotton wool) initially connected the plant-supporting material 42 with the fluid beneath in the trough 28. As the seed germinates and the seedling grows and begins to extend its own roots towards the fluid, the wick can be removed or can, in certain instances, be so designed that it is automatically displaced by the growing root5. Alternatively the wick could be made of a material into which roots will form and grow, and thus becomes a part of the growing plant.

The meshes 30, 32 along the length of the trough, house many plant containers, each of which has its own individual plant growing within it. Although the containers themselves are also of perforated mesh form, in this particular embodiment, it will be noted that the inserts 40 are not perforated and that the plant is thus constrained to grow out of each end of the container without being able to grow through it. This not only makes insertion and removal of individual plant containers extremely easy and simple; it also partially restricts the root growth of individual plants, without in any way impairing the growth of the plant at the top of the container, thus making it possible to grow many plants in a relatively confined space and with very little space between individual plants.

Individual inserts 40 can be removed from their plant containers, unrolled to check the plant or to take it out altogether and transplant it into another trough or a soil bed, and the insert then re-rolled into tubular form and pushed back into the container, without having to remove the conainer from the holding meshes.

The dimensions of the trough 28 ensure that there is sufficient natural circulation and aeration of nutrient fluid to germinate the seed and support the seedling until root growth is established. Once this stage has been reached it is preferred to transfer the seedling to an apparatus such as that described in my copending Application, No.

48053/76 serial No. 1597111 where external means for nutrient circulation and aeration are provided, to ensure maximum plant growth. The trough 28 used in the present invention may, of course, be provided with circulation and/or aeration but these are not necessary for germination and need not be used.

In Figure 2, there is shown a cross-section of an apparatus in which the environment around the trough is fully controlled. The embodiment of Figure 1 could be modified to operate as shown in this Figure. Two membranes 56, 58 are provided, which between them enclose the entire growing trough along its length. The membranes are removably clipped to the side channels of the trough 28 which support the double mesh layer 30, 32 along the top of the trough, and either or both membranes could be suitably coloured to either increase or decrease the admission of light or heat to the plants growing in the trough. They could be clipped to the trough sides, and could be permeable.

Inside the inner skin 56, the atmosphere is controlled by ventilation inlets and outlets, to suit the needs of the plants germinating or growing within. The air flow within and along the inner membrane is preferably relatively slow-moving, but continuously circulating. Between the membranes 56, 58 relatively colder or hotter air moves in a relatively higher through-flow. This has the effect of stabilising the environmental conditions within the inner membrane 56. The outer membrane 58 comes right down to the bottom edges of the trough 28 and so also stabilises the temperature of the nutrient fluid within the trough.

In this embodiment, the base of the trough incorporates a thermal blanket 6Cksuch as a cold or hot water reservoir-to allow further controlled variation of the temperature of nutrient fluid within the trough.

Any condensation which forms on the inner membrane can be collected within the ventilation system, or can be allowed to flow down to the joint between the membrane and the trough and then collected for re-use.

Gases other than air could of course be used if appropriate.

Modifications can be made to these described embodiments. A single mesh layer could be used to hold the plant containers, for example during germination, or more than two superimposed spaced meshes could be used. The plant container inserts could be formed as a tube, with a split along part of its length to allow the insert to be opened to check the plant or seed growth. Further modifications are envisaged within the scope of the claims which will follow.

For germination, where static fluid can be used, the apparatus need only comprise the trough, the containers and inserts, and the mesh. Seedlings in the containers are connected by a capillary wick, as previously described, to the fluid. Frequent checks of the seedlings can be made, owing to the construction of the plant containers and inserts which also allow undamaged transfer to the full "circulating" apparatus at the appropriate growth stage. Fluid flow rates, and nutrient concentration, can thereafter be increased as gradually as necessary for optimum growth and eventual high yield.

WHAT I CLAIM IS: 1. Apparatus for germinating plants hydroponically from seed, which comprises a trough and a plurality of individually removable plant containers containing a removable insert holding a plant supporting material and a wick which, in use, connects the plant supporting material with the fluid beneath in the trough.

2. Apparatus as claimed in claim 1 in which the plant containers are adapted to be gripped resiliently in cooperating holding apertures located on the trough, and the inserts are split longitudinally to allow them to be opened when removed from the container and closed prior to inserting them in the container.

3. Apparatus according to claim 2 in which the container is removable from its holding aperture, and the insert is removable from the container without first having to remove the container from its holding aperture.

4. Apparatus according to either of claims 2 or 3 in which the holding apertures are defined by the bars of a mesh extending along the trough above the intended fluid level, insertion of the plant container between the bars causing the bars to be resiliently pushed apart, or the container to be resiliently squeezed inwardly, or both.

5. Apparatus according to claim 4 in which the mesh is detachable from the trough without first having to remove the plant containers from the mesh.

6. Apparatus according to any of claims 2 to 5 in which the plant container has a series of externally formed protrusions, each of which locates the container in the holding aperture at a given height above the intended fluid level, the resilience of the fit between the container and its holding aperture allowing the protrusions to be pushed successively through the aperture and so locate the container at several alternative heights above the intended fluid level.

7. Apparatus according to any of claims 1 to 6 in which the plant containers allow growth of the plant only through the top and the bottom of the container, and positively prevent growth through the sides of the

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Claims

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seedling to an apparatus such as that described in my copending Application, No.

48053/76 serial No. 1597111 where external means for nutrient circulation and aeration are provided, to ensure maximum plant growth. The trough 28 used in the present invention may, of course, be provided with circulation and/or aeration but these are not necessary for germination and need not be used.

In Figure 2, there is shown a cross-section of an apparatus in which the environment around the trough is fully controlled. The embodiment of Figure 1 could be modified to operate as shown in this Figure. Two membranes 56, 58 are provided, which between them enclose the entire growing trough along its length. The membranes are removably clipped to the side channels of the trough 28 which support the double mesh layer 30, 32 along the top of the trough, and either or both membranes could be suitably coloured to either increase or decrease the admission of light or heat to the plants growing in the trough. They could be clipped to the trough sides, and could be permeable.

Inside the inner skin 56, the atmosphere is controlled by ventilation inlets and outlets, to suit the needs of the plants germinating or growing within. The air flow within and along the inner membrane is preferably relatively slow-moving, but continuously circulating. Between the membranes 56, 58 relatively colder or hotter air moves in a relatively higher through-flow. This has the effect of stabilising the environmental conditions within the inner membrane 56. The outer membrane 58 comes right down to the bottom edges of the trough 28 and so also stabilises the temperature of the nutrient fluid within the trough.

In this embodiment, the base of the trough incorporates a thermal blanket 6Cksuch as a cold or hot water reservoir-to allow further controlled variation of the temperature of nutrient fluid within the trough.

Any condensation which forms on the inner membrane can be collected within the ventilation system, or can be allowed to flow down to the joint between the membrane and the trough and then collected for re-use.

Gases other than air could of course be used if appropriate.

Modifications can be made to these described embodiments. A single mesh layer could be used to hold the plant containers, for example during germination, or more than two superimposed spaced meshes could be used. The plant container inserts could be formed as a tube, with a split along part of its length to allow the insert to be opened to check the plant or seed growth. Further modifications are envisaged within the scope of the claims which will follow.

For germination, where static fluid can be used, the apparatus need only comprise the trough, the containers and inserts, and the mesh. Seedlings in the containers are connected by a capillary wick, as previously described, to the fluid. Frequent checks of the seedlings can be made, owing to the construction of the plant containers and inserts which also allow undamaged transfer to the full "circulating" apparatus at the appropriate growth stage. Fluid flow rates, and nutrient concentration, can thereafter be increased as gradually as necessary for optimum growth and eventual high yield.

WHAT I CLAIM IS: 1. Apparatus for germinating plants hydroponically from seed, which comprises a trough and a plurality of individually removable plant containers containing a removable insert holding a plant supporting material and a wick which, in use, connects the plant supporting material with the fluid beneath in the trough.
2. Apparatus as claimed in claim 1 in which the plant containers are adapted to be gripped resiliently in cooperating holding apertures located on the trough, and the inserts are split longitudinally to allow them to be opened when removed from the container and closed prior to inserting them in the container.
3. Apparatus according to claim 2 in which the container is removable from its holding aperture, and the insert is removable from the container without first having to remove the container from its holding aperture.
4. Apparatus according to either of claims 2 or 3 in which the holding apertures are defined by the bars of a mesh extending along the trough above the intended fluid level, insertion of the plant container between the bars causing the bars to be resiliently pushed apart, or the container to be resiliently squeezed inwardly, or both.
5. Apparatus according to claim 4 in which the mesh is detachable from the trough without first having to remove the plant containers from the mesh.
6. Apparatus according to any of claims 2 to 5 in which the plant container has a series of externally formed protrusions, each of which locates the container in the holding aperture at a given height above the intended fluid level, the resilience of the fit between the container and its holding aperture allowing the protrusions to be pushed successively through the aperture and so locate the container at several alternative heights above the intended fluid level.
7. Apparatus according to any of claims 1 to 6 in which the plant containers allow growth of the plant only through the top and the bottom of the container, and positively prevent growth through the sides of the

container.
8. Apparatus according to any of claims I to 7 in which membrane is arched over, and sealed to, the trough so as to enclose the growing plants in a localised atmosphere, means being provided to vary the atmospheric conditions within the sealed membrane.
9. Apparatus according to claim 8 in which there are two spaced membranes and means are provided to vary the conditions between the membranes.
10. Apparatus for germinating plants hydroponically from seeds substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.