GB2272140A - Hydroponic cultivation of plants. - Google Patents

Abstract

Plant cultivation apparatus comprises a reservoir 2 for a nutrient solution 4, a platform 6 above the reservoir, for supporting the root structure of one or more plants, and a pump 16 which lifts nutrient solution by the direct action of rising air, from the reservoir to one end of the platform. Aerated nutrient solution is thus delivered to the platform. Surplus nutrient solution drains from the platform, into the reservoir. <IMAGE>

Description

CULTIVATION OF PLANTS This invention relates to the cultivation of plants.

The invention relates in particular to the horticultural cultivation of plants in glasshouse environments. Aspects of the invention relate to plant cultivation apparatus, a plant cultivation system and a method of cultivating plants.

As is well known, cultivation of plants in glasshouses using hydroponic techniques offers many advantages over the use of soil or compost growing media.

One growing system which is in commercial use in glasshouses employs a long trough above which growing plants are supported, with their root structures on the trough. Nutrient solution is fed to one end of the trough and surplus nutrient solution drains from the other end of the trough. The surplus nutrient solution is pumped back, to be fed back into the trough. Surplus nutrient solution is only ever discarded if it is desired to change the nutrient balance.

A major problem with this system, which is commonly the NFT (nutrient film technique) system, is that a disease of one plant is likely to be transmitted, through the nutrient solution, to all the plants. There are many diseases which can cause serious problems, including the water-loving phycomycete fungi, notably Pythium and Phytophthora spp.

A further problem concerns the oxygen concentration of the nutrient solution. This problem is referred to in Journal of Horticultural Science (1984) 59(3) 439-448. As explained in this article, in NFT systems the nutrient solution can become a barrier to gaseous diffusion.

Oxygen from the air needed to replace that used in respiration is excluded, whilst metabolically generated gases such as carbon dioxide, ethylene oxide and nitrous oxide accumulate. Presumably some aeration of the nutrient solution takes place by a passive process at the interface between the air and the nutrient solution, but this is inadequate to prevent anaerobisis.

The article described above indicates that the use of inorganic, open-structured materials such as PERLITE, ROCKWOOL or CAPOGRO, reduces the likelihood of anaerobisis. Growing systems have been proposed, in which such materials are located in the trough, as growing substrates. The anaerobisis problem is reduced, but the problem of disease transmission referred to above remains.

Sterilising the solution might be thought to be a solution, but is expensive.

A simple growing system which is in commercial use employs inorganic, open-structured growing modules, for example ROCKWOOL blocks, each module supporting a small number of plants. Each module is fed intermittently with nutrient solution. Surplus nutrient solution runs out of the modules and is discarded. This avoids the need for a recirculating pump and associated pipework and, most importantly, means that diseases should not be transmitted from the plants of one module to the plants of another module, by means of the nutrient solution. However this can still happen, if the roots of a plant extend out of the module and into the gutter. Not only is the discarding of the surplus nutrient solution wasteful typically 15-25% runs to waste - it is also unenvironmentally undesirable. Legislation against the discarding of surplus nutrient waste solution may be expected in due course.It is possible to modify this system by recirculating the surplus nutrient solution and sterilising it, but this is expensive.

A further system which has been proposed is known as the GRODAN ADS system. This employs modules of an inorganic growing medium, fed from a reservoir of nutrient solution, with excess nutrient solution returning to the reservoir, having been removed from the inorganic growing medium by a syphonic suction effect, rather than a natural drainage effect. The reservoir is common to a number of modules. After sterilisation, it can be recirculated.

However, trials thus far have not shown the system to work effectively. In certain circumstances the growing medium has sucked water back from the reservoir. Thus, unsterilised surplus nutrient solution can be fed to the modules. Thus, the potential for disease transmission remains. Moreover the system is relatively complicated and expensive and requires sterilisation equipment.

In accordance with a first aspect of the present invention there is provided a plant cultivation unit comprising a reservoir for a nutrient solution, a platform above the nutrient solution on which the root structure of at least one plant to be cultivated is to be located, and means for delivering nutrient solution to the platform from the reservoir.

Preferably the unit includes means for permitting surplus nutrient solution to drain from the platform into the reservoir. Thus, a preferred plant cultivation unit in accordance with the present invention permits recirculation of nutrient solution and so is of modular design. There is no possibility for transmission of diseases from one unit to another unit, through the agency of nutrient solution.

Preferably, a plant cultivation unit in accordance with the present invention includes means for aerating the nutrient solution.

Preferably, the means for delivering nutrient solution to the platform from the reservoir comprises a pump in which the nutrient solution is impelled directly by air. Pumps of this type are cheap and have no moving parts. They are in common use in aquaria, where they include a filter which is not required when used in a plant cultivation unit in accordance with the present invention.

Preferably, the platform is of elongate form on which a plurality of plants to be cultivated are to be located, the platform being slightly inclined to the horizontal, wherein the means for delivering nutrient solution to the platform from the reservoir delivers the nutrient solution to the higher end region of the platform, and the surplus nutrient solution can drain into the reservoir from the lower end region of the platform.

Preferably, the length of the reservoir is in the range 30cm-200cm.

Preferably the reservoir has outlet means, for example an aperture, located beneath the level of the platform, but above the normal surface level of nutrient solution in the reservoir, so that in the event of an inadvertent over-supply of nutrient solution, or of a deliberate flushing operation, nutrient solution can drain from the reservoir without flooding the platform. Means may be provided for sensing an inadvertent over-supply of nutrient solution, leading to the draining of nutrient solution from the reservoir, and for shutting off the supply of nutrient solution to the reservoir in response.

In accordance with a second aspect of the present invention there is provided plant cultivation apparatus comprising a reservoir for nutrient solution within which the root structure of one or more plants to be cultivated is to be immersed, and means for aerating the nutrient solution. Preferably, in plant cultivation apparatus in accordance with the second aspect of the present invention, the means for aerating the nutrient solution comprises a pump having a lower inlet immersed, in use, in the nutrient solution and an upper outlet located in use above the nutrient solution, and a conduit therebetween, nutrient solution being impelled from the inlet to the outlet by air fed into the conduit and rising to the outlet end, from which aerated nutrient solution falls, thereby to aerate and agitate the nutrient solution in the reservoir.

In accordance with a third aspect of the present invention there is provided plant cultivation apparatus comprising a plurality of reservoirs for nutrient solution, a common nutrient solution supply source, means connecting the common nutrient solution supply source to each of the reservoirs, a respective pump for each reservoir, each pump being able to pump nutrient solution by the direct action of air, a common air propulsion means, and means for connecting the common air propulsion means to each of the pumps.

Preferably, a reservoir employed in the third aspect of the present invention, is part of a plant cultivation unit in accordance with the first aspect of the present invention Suitably, therefore, each reservoir has above it a respective platform on which the root structure of at least one plant to be cultivated is to be located, the respective pump for each reservoir being adapted to pump aerated nutrient solution to the platform from the reservoir, the surplus nutrient solution being able to drain from the platform into the reservoir.

In other embodiments of the third aspect of the present invention, a reservoir is part of a plant cultivation apparatus in accordance with the second aspect of the present invention.

In accordance with a fourth aspect of the present invention there is provided a method of cultivating plants, using a plant cultivation unit or apparatus in accordance with the first or the second or the third aspect of the present invention.

The invention will now be further described, by way of example, with reference to Figs. 1 to 3 in which: Fig. 1 is a schematic side view of a plant cultivation unit; Fig. 2 is a schematic end view of the plant cultivation unit of Fig. 1.

Fig. 3 is a schematic end view of a plant cultivation unit of different type; and Fig. 4 is a schematic plan view of an array of plant cultivation units.

The units shown in Figs. 1 and 2 comprise a reservoir in the form of a moulded plastics trough 2. The reservoir contains a nutrient solution 4. At the upper open side of the reservoir, above the nutrient solution, is a platform 6 having a flat base wall 8 and inclined side walls 10, and no end walls. The base wall is parallel to be bottom wall of the reservoir. In use in a glasshouse, it is slightly inclined to the horizontal, by virtue of a corresponding slight inclination of the floor of the glasshouse.

The platform 8 is supported within the box by means of two plastics supports 12. These have bent over end regions 10 which engage over the upper edge regions of the side walls of the reservoir and, between the end regions 14, a flat web to support the platform.

Shown in Fig. 1 but not, for clarity, in Fig. 2, is an air bubble pump 16 and a nutrient solution feed head 18, arranged to intermittently feed nutrient solution into the reservoir. The air bubble pump is of plastics material and comprises two tubular limbs 20, 22 joined together in side by side relation, and with a connecting port 24 therebetween. The first limb 20 is sealed at its lower end, whilst the second limb 22 is open at its lower end. The upper end of the second limb 22 is bent over, and is open. The upper end of the first limb 20 is straight and open, and is connected to flexible tubing 26.

As shown in Fig. 1, the lower end of the pump is immersed in the nutrient solution, whilst the upper end of the second limb 22 is located above the higher end of the platform.

In use, air is blown under low pressure in the direction of the arrow A, through the first tubing, thence into the first limb 20. It must pass through the port 24 into the second limb 22. It rises within the second limb 22 and as it does so it impels nutrient solution with it.

Further nutrient solution is drawn into the second limb 22 at its lower end, as shown by the arrow B. The air/nutrient solution mixture leaves the pump and falls onto the platform. The nutrient solution trickles along the platform, through the plant roots, and surplus nutrient solution drops back into the reservoir at the other end of the platform.

For clarity, the plants located in the platform are not shown, but they are located and supported in conventional manner. In this embodiment the length of the platform is approximately 90cm, and its width approximately 20cm, and it is intended for growing two cucumber plants.

The embodiment shown in Fig. 3 comprises a pump 16 as described above and a reservoir 2 as described above, containing a nutrient solution 4. There is no platform.

Plant root structure is located within the nutrient solution 4. The pump 16 serves to aerate and agitate the nutrient solution, so preventing root anaerobisis. In another embodiment not employing a platform air could simply be bubbled into nutrient solution in a reservoir, although it may be more difficult thereby to obtain good agitation/mass flow.

Fig. 4 shows plant cultivation apparatus comprising a plurality of reservoirs. These could be of the type described with reference to Fig. 1 or Fig. 3, or other types in accordance with different aspects of the present invention. Preferably, however, they are of the type shown in Fig. 1. Also shown is ductwork 30 leading from a common nutrient solution source (not shown) to outlet nozzles 18, one for each reservoir. Also shown is air supply ductwork 32 leading from a common air source (not shown) to pump 16, one for each reservoir as described above. The air source is preferably a large volume low pressure rotary blower. Each ductwork shown may be part of a "ring-main" ductwork system, or of a ductwork system employing "spurs".

In relation to the apparatus shown in all of the enclosed drawings, the pump(s) is/are selected and/or the air supply rate adjusted such that recirculation of the nutrient solution is relatively rapid. In preferred embodiments the entire nutrient solution is recirculated within 10-15 minutes.

Trials using the embodiment described in Fig. 1 have taken place, and have shown that cucumber plants remain healthy for their natural lifetime in glasshouse conditions. Early plant loss through anaerobisis appears to be avoided. Moreover crop yields are high. Plant diseases cannot be spread from one unit to another through the agency of nutrient solution. The units are extremely cheap and simple to operate. Aeration is continuous.

There are no particular requirements in relation to the levelness or tilt of the glasshouse site. The apparatus lends itself to flexible glasshouse management. When it is desired to change from a crop which grows well in a hydroponic environment, for example cucumber, to a crop which does not, such as lettuce, the apparatus can be easily dissembled, and removed for storage. Stackable reservoirs may be selected. The apparatus lends itself to use by large commercial glasshouse growers as well as to smaller growers and amateurs. There is no necessity for sterilisation of nutrient solution and no effluent to remove.

In the embodiment such as that of Fig. 1, employing a platform, a conventional inorganic material such as ROCKWOOL may be used as the growing medium. The inorganic medium is located on the platform. Alternatively, such a growing medium may not be used, the roots structure being open to the environment, and located directly on the platform. It should be appreciated that during the propagation stages the plant is likely to have been grown on in a small e.g. 500cc block of inorganic material, but thereafter the roots are free to grow in the aerial/aqueous environment. That is to say, they do not grow within an inorganic medium.

Both approaches described in the previous paragraph have been tested. When an organic growing medium has been employed, yields of cucumbers have been found to correspond closely to those achieved in conventional inorganic modular systems, where the nutrient solution runs to waste. However, surprisingly, yields of cucumbers achieved when an inorganic growing medium is not employed have been found to be substantially higher. Comparative trials establishing this conclusion will now be described.

In the middle of a one acre commercial cucumber production house, under confidential conditions, 10 units of the type shown in Figs. 1 and 2 were set up. Twenty cucumber plants (variety Rubella) were placed, two in each unit at the same time as the rest of the house was planted. The units were placed on each side of a gutter running the width of the glasshouse. On one side of the gutter the plants were planted directly onto the platform of the unit. On the other side the plants were placed on a ROCKWOOL mat which had been placed on the platform. The irrigation was managed according to the needs of the conventional system.

The rest of the glasshouse employed a conventional "run to waste" ROCKWOOL cultivation system.

The numbers of cucumbers harvested from the two systems were recorded.

Both sets of plants grown in the units, with and without ROCKWOOL, grew for 232 days, the full lifetime of the conventionally grown crop. There were no visible differences between the plants. Up to 214 days after planting (the last day that data was available) the plants in the units using ROCKWOOL modules had produced 562 cucumbers, and the plants in the 5 units with no ROCKWOOL had produced 651 cucumbers. This represents an increase of 15.8%. In both cases the cucumbers were of normal, commercially acceptable size. The cucumbers from the units with no ROCKWOOL mats were not noticeably smaller than those from the units with ROCKWOOL mats. The yield in the conventional "run to waste" system corresponded to that of the units with ROCKWOOL mats.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (12)

CLIAMS

1. A plant cultivation unit comprising a reservoir for a nutrient solution, a platform above the nutrient solution on which the root structure of at least one plant to be cultivated is to be located, and means for delivering nutrient solution to the platform from the reservoir, and means for permitting surplus nutrient solution to drain from the platform into the reservoir.

2. A plant cultivation unit according to Claim 1, including means for aerating the nutrient solution.

3. A plant cultivation unit according to Claim 2, wherein the means for delivering nutrient solution to the platform from the reservoir comprises a pump in which the nutrient solution is impelled directly by air.

4. A plant cultivation unit according to Claim 3, wherein the platform is of elongate form on which a plurality of plants to be cultivated are to be located, the platform being inclined to the horizontal, wherein the means for delivering nutrient solution to the platform from the reservoir delivers the nutrient solution to the higher end region of the platform, and the surplus nutrient solution can drain into the reservoir from the lower end region of the platform.

5. Plant cultivation apparatus comprising a reservoir for nutrient solution within which the root structure of one or more plants to be cultivated is to be immersed, and means for aerating the nutrient solution.

6. Plant cultivation apparatus as claimed in Claim 5, wherein the means for aerating the nutrient solution comprises a pump having a lower inlet immersed, in use, in the nutrient solution and an upper outlet located in use above the nutrient solution, and a conduit therebetween, nutrient solution being impelled from the inlet to the outlet by air fed into the conduit and rising to the outlet end, from which aerated nutrient solution falls, thereby to aerate and agitate the nutrient solution in the reservoir.

7. Plant cultivation apparatus comprising a plurality of reservoirs for nutrient solution, a common nutrient solution supply source, means connecting the common nutrient solution supply source to each of the reservoirs, a respective pump for each reservoir, each pump being able to pump nutrient solution by the direct action of air, a common air propulsion means, and means for connecting the common air propulsion means to each of the pumps.

8. Plant cultivation apparatus as claimed in Claim 7, wherein each reservoir is part of a plant cultivation unit as claimed in any of Claims 1 to 4.

9. A method of cultivating plants, by use of a plant cultivation unit or apparatus according to any preceding claim.

10. A method of cultivating plants as claimed in any of Claims 1 to 4 or 8, wherein the root structure of the or each plant is located directly on the platform.

11. Plant cultivation as substantially hereinbefore described with reference to any one of the accompanying drawings.

12. A method of cultivating plants according to Claim 9 or 10 and substantially as hereinbefore described.