WO2012156710A1

WO2012156710A1 - Aeroponics system

Info

Publication number: WO2012156710A1
Application number: PCT/GB2012/051055
Authority: WO
Inventors: John Prewer
Original assignee: Airfarm Limited
Priority date: 2011-05-13
Filing date: 2012-05-11
Publication date: 2012-11-22
Also published as: CA2873166A1; CA2873166C; GB201108138D0

Abstract

An aeroponic propagator (1) for the cultivation of plants comprises two end frames (11), a first support member (12) extended between the two end frames (11) and a substantially opaque sheet (13) for supporting plants to be cultivated, wherein the opaque sheet is suspended from the first support member to form at least one side wall of a chamber (14) between the two frames (11) for roots of plants supported on the opaque sheet (13).

Description

AEROPONICS SYSTEM

The present invention relates to an aeroponics system, in particular an aeroponic propagator for the cultivation of plants.

Aeroponics is a development of hydroponic methods. Hydroponics is the technique of growing plants in water-based solutions of nutrient salts. Although known over 100 years ago it was not used extensively until the Second World War, when it was used to provide troops with green vegetables in parts of the world where normal methods of cultivation were impractical. Hydroponics has since been widely used in many countries and has proved particularly popular in oil producing countries with desert climates.

A hydroponic system known as the nutrient film technique (NFT) was developed during the 1960s at the UK's Glasshouse Crops Research Institute by Dr. Alan Cooper. Although widely acclaimed as a significant advance in hydroponic growth techniques it has a number of drawbacks. The main ones being that - though simple in concept - it tends to be expensive to install and often has been difficult to operate profitably because of disease and nutrient control problems. In spite of these limitations, NFT's appeal to growers is such that it has been used in more than 70 countries.

Aeroponics has gained much publicity over recent years. It is defined by the

International Society for Soil-less Culture as "A system where roots are continuously or discontinuously in an environment saturated with fine drops (a mist or aerosol) of nutrient solution". The method requires no substrate and entails growing plants with their roots suspended in a chamber (the root chamber), with the roots periodically atomised with a fine mist or fog of nutrients, a process which uses significantly less water than alternative growing techniques. Since their inception some 30 years ago, aeroponic techniques have proved very successful for propagation and are widely used in laboratory studies of plant physiology, but have yet to prove themselves on a commercial scale. Aeroponics could also have applications in crisis situations as an aeroponics system can be designed to work in the event of such things as reduced solar radiation levels (e.g. due to high levels of fine volcanic ash particles in the atmosphere) or floods.

However, there are two main limitations associated with commercial aeroponic systems: high equipment costs and low equipment reliability. The present invention aims to at least partly overcome these limitations, desirably by least partly fulfilling one or more of the following objectives;

a) increasing productivity by:

^• at least increasing by 50% the growing surface per unit of land covered by the system

^• improving nutrient uptake in the root areas

^• producing faster growth

^• improving growth through foliar feeding in leaf areas

^• less waste due to disease

^• less waste due to insect attack

b) cutting costs by:

^• simplifying the way the plants are protected from bad weather, insect attack etc.

^• providing easy access to the root areas (e.g. so potatoes can be picked only when they reach a particular size)

^• cutting the level of fertilizer needed

^• cutting or eliminating the need for insecticides

^• reducing or eliminating the need for herbicides

^• significantly reducing the water requirement compared to other cultivation methods

^• using simple and reliable equipment to monitor and control growing conditions

^• minimising use of permanent structures, concrete foundations, ground levelling, etc.

^• collecting and storing rainwater and dew in-situ.

According to one aspect of the present invention there is provided an aeroponic propagator for the cultivation of plants, the propagator preferably comprising: two end frames; a first support member extending between the two end frames; and a substantially opaque sheet for supporting plants to be cultivated, wherein the substantially opaque sheet is suspended from the first support member to form at least one sidewall of a chamber between the end frames for roots of plants supported on the opaque sheet.

Advantageously, such an aeroponic propagator is both reliable and comparatively cheap to construct. The propagator is simple in construction, meaning that there are only a limited number of parts that could go wrong. Further, because the limited number of parts is individually simple, there is little opportunity for the propagator to fail. The simple construction also means that the propagator is particularly useful on sloped land, because the propagator could be erected without the need for terracing the land first.

The substantially opaque sheet preferably blocks at least 75% of light from passing through the sheet, more preferably at least 85% of light, even more preferably at least 90% of light, and still more preferably at least 95% of light.

The propagator is easily customisable. For example, the overall length of the propagator can be easily adjusted by moving the end frames closer or further apart, and the supporting member can be lengthened and shortened accordingly. This is especially advantageous when the supporting member is a rope or line, because they may be easily adjusted in length. This means that the propagator can be easily adjusted to a particular use.

The aeroponic propagator can comprise an end panel arranged to close an end of the root chamber. Such a panel can be provided at both ends of the root chamber. The end panel can comprise a vent flap, which can be remote controlled. Accordingly, the inside of the propagator can be effectively sealed from the outside, thus providing an enclosed space which can be provided with a controlled environment. The use of vent flaps allows the internal environment to be vented to the outside, in the event that the internal environment becomes undesirably hot or pressured for example.

The aeroponic propagator can comprise a repositioning device to reposition the first support member to tilt and / or fold the root chamber. The repositioning device can be a means for tilting and / or folding the two end frames. Accordingly, the propagator root chamber, which forms the main bulk of the propagator, can be repositioned. This is useful when two or more propagators are arranged in close proximity, such as in farming conditions. Repositioning of the root chamber allows for access between the propagators, for example for observation, maintenance or harvesting.

The substantially opaque sheet is preferably reflective, and can comprise UV- stabilised plastics and/or a waterproof paper layer. Accordingly, the sheet reflects back sunlight incident on the sheet towards the foliage of plants supported on the sheet. This provides the plants with additional light for photosynthesis and thus helps increase the rate of plant growth. The provision of UV-stabilised properties for a plastics sheet and waterproof properties for a paper layer ensure that the sheet is durable in all weather conditions and improves the reliability of the propagator.

The aeroponic propagator can comprise a second support member extending between the end frames, wherein the substantially opaque sheet is suspended from both the first and second support members. The use of two, rather than one, support members provides a trapezoidal shape, rather than a triangular shape, to the root chamber. As such, there is increased space between the plants on either side at the top of the root chamber, which may preferable when growing certain plants, for example those with large root systems.

The aeroponic propagator can comprise a tensioning mechanism, preferably a winch, for tightening the first and/or second support members, when they are flexible (for example, when the support members are ropes or lines). This allows for the adjustment of the tension in the support members that can be used to alter the height of the root chamber, for example. In addition, this makes it easier to change the length of the propagator (for example by moving the end frames) because it is then a relatively simple operation to re-adjust the support members to the correct tension. The first and/or second support members can be lines such as an ultra high molecular weight polyethylene rope or recombinant silk, because this is durable and therefore appropriate for use in all weather conditions.

The chamber can be suspended above the ground. As such, the root chamber can be totally separated from the ground, which can be desirable in outside locations, for example, to keep the plant crops away from animals or where the ground is not level. The suspended root chamber also allows for other equipment associated with the propagator to be stored under the root chamber.

The root chamber can further comprise a chamber base, for carrying an energy crop or mushrooms for instance. The root chamber base can be supported by third and fourth support members, each extending between the two end frames below the first support member. The root chamber sidewalls are releasably secured to the third and fourth support members, and the third and fourth support members can be repositionable to alter the shape of the root chamber. The base of the root chamber can thus be held in a fixed shape or repositioned according to the need, and access to the insides of the root chamber can be obtained through releasing the sidewalls from the third or fourth support members.

The aeroponic propagator can comprise a drainage point positioned at the lowest point in the root chamber base for draining the energy or mushroom crop. This allows cultivation of algae, for example, in the base that can be easily removed and used for example as a bio-fuel.

The ground, which may be any surface on which the propagator is positioned (e.g. a roof-top), can form the base of the root chamber or directly support the base of the root chamber when the base comprises, for example, a sheet of plastic. As such, the root chamber is not suspended, and is thus simpler in construction. The substantially opaque sheet can be releasably anchored to the ground at the base of the sidewalls, so forming the root chamber without the use of extra support members such as rigid or semi-rigid tubes, or flexible support members such as ropes or lines. Optionally, the sidewalls can be anchored via the use of water-containing tubes (i.e. tubes filled or partially filled with water). The tubes can be flexible. When the tubes extend along the length of the propagator, this arrangement can provide a seal between the opaque sheet and the surface on which the propagator is provided, thereby sealing the foliage chamber from the outside environment.

The aeroponic propagator can comprise a fogging system to supply a fog to the root chamber. The fogging system can be arranged to collect moisture from the root chamber and re-circulate the moisture in the fog. This allows for roots in the root chamber to be provided with nutrients in the most efficient manner, and minimises wastage by recycling unabsorbed water and nutrients.

The aeroponic propagator can further comprise a substantially transparent sheet arranged over the substantially opaque sheet, so as to form at least a partial enclosure around the root chamber. As such, a space or gap is formed between the two sheets, in which foliage can grow and which can be referred to as a foliage chamber. The second sheet thus protects the foliage from the surrounding environment, for example preventing birds from eating the crops and further reducing the need for insecticides, herbicides and fungicides.

The aeroponic propagator can comprise a blocking device for blocking a gap between the root chamber and the transparent sheet. In particular, at the base of the propagator the gap between the lower edges of the two sheets can be blocked and preferably sealed to contain the atmosphere in the space between the two sheets.

The aeroponic propagator can comprise a vent in the transparent sheet above an uppermost point of the root chamber, and can further comprise a blocking device for blocking the vent in the transparent sheet. This allows for regulation of the environment within the space between the sheets by blocking and unblocking the vent, controlling the flow of air and/or gas and/or fog into the space between the sheets.

Preferably, the blocking devices each comprise an inflatable tube. This is simple and cheap to construct and operate, whilst also providing a cushioning effect that helps ensure as good a seal as possible.

The aeroponic propagator can comprise a fogging system to supply fog, with a median droplet size of 1 to 60 microns, to the space between the root chamber and the partial enclosure, i.e. the foliage chamber. Preferably the median droplet size is 20 microns or less, more preferably 10 microns or less and still more preferably 5 microns or less. This allows for the use of foliar feeding, which increases the growth rate of the plants being cultivated. Similarly, the aeroponic propagator can comprise a system for supplying carbon dioxide rich air and / or temperature controlled air (which can include air that has been heated or cooled) to a space between the root chamber and the partial enclosure, i.e. the foliage chamber, once again to increase the plant growth rate. The fog and / or carbon dioxide rich air and / or temperature controlled air can be applied to both the root and foliage chambers simultaneously.

According to another aspect, there is provided a kit of parts for an aeroponic propagator for the cultivation of plants, the kit comprising two end frames, a first support member and an opaque sheet for supporting plants to be cultivated.

According to another aspect, there is provided a method of cultivating plants using an aeroponic propagator of the first aspect, the method comprising: supporting plants on the opaque sheet so that the plant roots project into the root chamber and the plant foliage projects outside the root chamber; and supplying a nutrient-containing fog to the root chamber for absorption by the plant roots.

The method can further comprise supporting plants on the opaque sheet so that the plant roots project into the root chamber and the plant foliage projects outside the root chamber; and supplying at least one of a nutrient containing fog or carbon dioxide rich air or temperature controlled air to the space between the root chamber and the partial enclosure, i.e. the foliage chamber, for absorption by the plant foliage.

According to another aspect, there is provided an aeroponic propagator for the cultivation of plants, the propagator comprising: a substantially opaque sheet for supporting plants to be cultivated; and wherein the substantially opaque sheet comprises at least one pleated section for supporting the plants. The pleats make it easy for plants to be provided on the sheet and help support the plant during growth and additionally provide means of increasing space between plants by stretching out the pleats as the plants grow, hence increasing the usable area.

The present invention will be described with reference to exemplary embodiments and the accompanying Figures in which;

Fig. 1 is a schematic perspective view of an aeroponic propagator; Fig. 2 is a side view of the end of an aeroponic propagator;

Fig. 3 is an end view of the aeroponic propagator of Fig. 2;

Fig. 4 is a perspective view of the end of another aeroponic propagator;

Fig. 5 is a cross-section through a propagator with inflated vent seals;

Fig. 6 is a cross-section view of the propagator of Fig. 5, but with deflated vent seals; Fig. 7 shows three views of propagators in different tilted and folded positions;

Fig. 8 shows cross-sections through propagators that are not suspended above the ground;

Fig. 9 shows similar propagators to those in Fig. 8, but with a double-layer construction;

Fig. 10 shows the arrangement of a fogging system and the end of a propagator; Fig. 11 shows the arrangement of a fog return pipe and condensate sump at the opposite end of a propagator to that shown in Fig. 10;

Fig. 12 is a schematic plan view of a covered system of propagators.

Fig. 13 is a schematic perspective view of another aeroponic propagator;

Fig. 14 is an end view of the end of the aeroponic propagator of Fig. 13;

Fig. 15 is a plan view of two aeroponic propagators similar to those shown in Fig.

13;

Fig. 16 is a perspective view of a section of a propagator using a pleated sheet covering;

Fig 17 depicts a supporting framework for a pleated sheet such as depicted in the Fig. 16;

Fig. 18 is a detailed view of how a pleat may be formed and supported;

Fig. 19 depicts how several pleats may be held in place; and

Fig 20 depicts alternative pleat arrangements, Fig. 20a showing how a seed stick can be supported in a pleat and Fig. 20b showing how netting may be used to form the pleat.

In the Figures, like parts are identified by like reference numbers.

Figs 1-3 show various views of an aeroponic system, which is an example of an aeroponic propagator 1. The system of Figs 1-3 comprises a root chamber 14 that is suspended over the ground. The ground may be the earth, in a field for example, or another surface such as a roof-top. The suspended configuration simplifies installation and avoids the need for the ground levelling associated with hydroponic systems that operate under glass or polytunnels. Therefore, the surface need not be totally flat. The suspended arrangement is also advantageous in arid environments, as it allows dust and sand to be blown under the root chamber 14, instead of being blown against the side of the root chamber 14. This prevents the accumulation of dust and sand against the sides of the root chamber 14, and allows for easy access along the length of the propagator 1 to be maintained.

For normal operation, the root chamber may be suspended up to about lm above the ground, and preferably about 0.5m to 0.7m above ground level to enable ease of use, for example allowing easy reach to the plants 16 during harvesting or cultivation.

However, the height of the root chamber may be adjustable, for example by the use of supporting end frames 11 that can extend (e.g. by means of a telescoping mechanism), so that the root chamber can be raised in the event of a flood, for example.

In Figs 1-3, at each end of the propagator 1 , a strong triangulated tubular structure 11 is supported on tubular steel screw piles driven to the required depth for local ground conditions. These are examples of end frames. However, end frames 11 may have other constructions, and need not be triangular or constructed from tubular materials or supported on piles. Where there is little or no soil, i.e. on bare rock, the end frames 11 could be set on plates attached to the ground with expanding bolts (as for example, in Fig. 4). That is, the end frames 11 may be supported by any means suitable for the terrain.

Although not shown, the propagator 1 may additionally include one or more supporting frames between the two end frames 11. This construction may be desirable when the propagator is especially long, to provide extra support for the supporting member 12 and the sheets 13, 35.

Fig. 4 shows an alternative propagator 1, with a different end frame 11 to that shown in Figs. 1-3. In Fig. 4, the end frame 11 comprises a substantially upright post with a spar connected cross-wise to the post. The spar and the post are connected at pivot point 45.

Figs. 13-15 show another alternative propagator 1. In this case, end frame 11 is a mast, which is braced against the ground (or other surface underlying the propagator 1). The mast 11 can be attached to the ground via a base plate 131 (as shown in Figs. 13-15). The mast 11 can be positioned so that the base plate 131 is positioned underneath the root chamber 14, and is held in position by the suitable arrangement of lines 12 and 31, which act as support members and which may be tensioned using winches or turnbuckles 21 for example, and which may further be terminated by screw pile caps 101 for example. A rope frame 132 can also be used to provide a suitable shape to which to attach the lines 12 and 31. Of course, other arrangements of lines to those shown in Figs. 13-15 may be used.

Fig. 15 shows how two propagators similar to those shown in Figs. 13 and 14 may be arranged next to each other. In the arrangement shown, the propagators 1 are immediately adjacent each other at the gutter position 151 between the two ridgelines 12. However, a space between the propagators 1 may be opened up through tilting and/or folding methods as described in greater detail below.

As is clear in Fig. 15, the films or sheets 13, 35 can extend all the way to the point at which the mast 11 meets the support member 12. That is, the mast 11 can be within the root chamber 14. In that case, the sheets 13, 35 can extend all the way to the frame 132, and the frame 132 can be covered by a closer panel 34, such as those discussed in more detail below.

In the propagators 1 of Figs 1-4 and 13-15, to keep the structures that enclose the plants 16 as simple and cheap as possible, they are made of either one or two sheets or films - an inner sheet 13 and an outer sheet 35. These films or sheets 13, 35 preferably have good tear, UV light and/or weather resistance characteristics. However, the inner sheet 13 may have different characteristics to the outer sheet 35.

Either one or both of the inner and outer sheets 13,35 can comprise a single layer of material or two or more layers of material. For example, it may be desirable to have two or three layers to provide extra insulation for the propagator 1 , thereby protecting the plant roots and/or foliage from frost in cold climates, for example.

The external face of the inner film 13 is preferably substantially opaque (so that the root chamber 14 is kept dark). The root chamber 14 is desirably kept as dark as is required for normal growth of the particular crop being cultivated, and the inner film 13 is desirably sufficiently opaque to achieve this. The inner film 13 is also desirably sufficiently opaque to prevent the growth of algae on the plant roots inside root chamber 14.

The inner film 13 carries the full weight of mature plants 16. The plants 16 can be attached to the inner film so that they pass through a hole in the inner film 13, so that the plant roots are within the root chamber 14 and the plant foliage is outside the root chamber. The plants 16 may be attached by any suitable means, for example being simply supported by a resilient plastic or paper grommet around the hole in the inner sheet 13 or the use of some form of clip to hold the plant to the inner sheet 13. Netting or stretchable membranes around the plants 16 and/or the holes in the inner sheet 13 may also be used. Such netting or membranes could be arranged in the form of a pouch or pocket around the hole in the inner sheet 13. It is preferable that any such netting or membrane is porous.

The inner film 13 is preferably made of a limited stretch, rip resistant, UV-stabilised plastics film. For example, the inner film 13 may be made nanocellulose (also called micro fibrillated cellulose). Nanocellulose can be produced with high energy efficiency, for example using processes developed by Innventia AB of Stockholm, Sweden. Alternatively, strong waterproof paper with a stretch plastics film (that is UV-stabilised) outer surface could be used. In all cases, it is preferable that the outer face of the inner film 13 is reflective, and preferably white. This reflective face helps keep the root chamber 14 cool in strong sunlight, and reflects light back into foliage supported on the inner film 13 to boost photosynthesis and therefore growth rates.

The inner film 13 forms at least the sidewalls of the root chamber 14. The inner film 13 may be a continuous piece of material forming both sidewalls of the root chamber 14, or may be separate pieces of material (for example, each forming a different sidewall or part of sidewall). Further, the base 15 of the root chamber 14 may also be part of a continuous sheet 13 forming the sidewalls of the root chamber 14. Alternatively, the base 15 may be made from a separate piece of material.

In the Figures, the overall weight of plants 16 and the film 13 is carried by a centrally positioned rope or line 12, which may be made of a metal such as steel or

Dyneema (RTM) (ultra high molecular weight polyethylene), or equivalents. The line 12 may be tightened and loosened via a lever operated winch 21, for example, as shown in Fig. 2. However, instead of a rope or line, an alternative supporting member 12 may be used. For example, the supporting member may be rigid or semi-rigid (for example having hinged portions) and could be a steel or plastics tube for example. One or both ends of the supporting line 12 may be further secured to the surface on which the propagator 1 is situated.

The sheet 13 may be secured to the supporting member 12 via any appropriate method, such as strong acting clips similar to large plastics clothes pegs or by using the deadweight of water, such as in water-filled tubes 39 in Fig. 3 for example.

As shown in Fig. 3, each end of the root chamber 14 is provided with a closer panel 34. Preferably the closer panel 34 is rigid and blocks the end of the root chamber 14, and more preferably forms a seal. At one end of the root chamber 14 the closer panel 34 may have holes in it through which fog nozzles can discharge fog into the root chamber 14. It may also have further holes, through one of which a ventilating fan blows air into the root chamber 14 and through another of which recycled fog is exhausted into the rear of a ventilating fan housed in the fogger/control unit 23. The fogger/control unit 23 is discussed in more detail below.

At the other end of the root chamber 14, the closer panel 34 may have a vent flap 36 that allows air and fog to escape to the open air. The vent flap 36 is preferably remote controlled and may be activated in the event of overheating problems occurring in the root chamber, during hot weather for example, and additionally to maintain the desired or ideal growing conditions in the root chamber. Activation of the vent flap 36 or other control mechanisms can be automated by the use of temperature, carbon dioxide, leaf turgor and/or humidity sensors provided, for example, within the root chamber 14 or the foliage chamber 55. For example, when the sensors register an unacceptable set of conditions within the root chamber 14, the control unit 23 can activate the vent flap 36 to allow external air to mix with the atmosphere inside the root chamber 14. Once the atmosphere inside the root chamber 14 has returned to acceptable conditions, the control unit 23 can close the vent flap 36. The specific parameters for operating the control system will depend on the most suitable conditions for the plants 16 being cultivated.

The vent flap 36 may be part of a system for supplying air to the root chamber 14 and/or foliage chamber 55. The system may comprise a control unit that controls the system in response to the use of oxygen monitors within the root chamber 14 or foliage chamber 55. For example, if the oxygen monitors detect that the level of oxygen in the root chamber is too low, the vent flap 36 is automatically opened to allow flow of air into the chamber to increase the oxygen levels. The flow of air into the chamber may be further assisted, for example, by the use of a fan. Once the level of oxygen in the root chamber 14 returns to a suitable level, the vent flap may be automatically closed. As such, the conditions inside the root chamber 14 can be maintained for optimal growth. Once again, the specific parameters for operating the control system will depend on the most suitable conditions for the plants 16 being cultivated.

In some cases it may be desirable for the system supplying air to the root chamber to comprise a filter to filter any air coming into the root chamber 14, to ensure that the conditions inside the root chamber are sterile. This would also be desirable when growing pharmaceutical crops. The air can be filtered to remove micro-organisms such as fungal pests, for example.

In some cases (see, for example, Figs. 7 and 8) the outer sheet 35 may not be required. For example, if foliar feeding of plants 16 is not used and insect or bird attack and disease are not problems for the particular crop being cultivated and local conditions, the outer sheet 35 may be omitted. This allows for further simplification of the propagator 1.

As for the inner film 13, the outer film 35 is preferably made from a UV-stabilised plastics film or a nanocellulose material. The outer cover sheet 35 is preferably substantially transparent to visible light to allow the maximum amount of light to reach the leaves of the plants 16.

In particular, the cover sheet 35 is desirably transparent enough to allow the plants 16 to grow and photosynthesise normally. It is particularly preferable that the cover sheet 35 is transparent to red and blue wavelengths. For the red light, the cover sheet 35 is desirably transparent at a wavelength of approximately 660 nm, more preferably transparent over the range of 645 to 700 nm and more preferably transparent over the range of 630 to 740 nm. For the blue light, the cover sheet 35 is desirably transparent at a wavelength of approximately 460 nm, more preferably transparent over the range of 450 to 475 nm and more preferably transparent over the range of 440 to 490 nm.

Desirably, the cover sheet 35 is transparent enough to allow illumination of 100 to 200,000 lux at red and blue wavelengths.

The outer film 35 is supported by lines 37 and 38, which can be of similar construction to line 12 and may be separately tensioned and positioned. Support members 37 support the outer film 35 from the top of the propagators, whilst support members 38 support the outer sheet towards the bottom of the root chamber 14 and hold the outer sheet 35 away from the inner sheet 13. The film 35 may also be weighed down at the bottom, for example using compartmented water-, soil- or stone-filled tubes 39.

The area between the outer sheet 35 and the root chamber 14 provides an outer foliage chamber 55 for the foliage of plants 16 supported on the inner sheet 13. This outer root chamber may be blocked, and preferably sealed, at the bottom by the provision of an inflatable vent seal 33, for example. This is shown in Fig. 3, and is further demonstrated in Figs. 5 and 6 that show cross-sections through a propagator using inflatable vent seals 33. In Fig. 5, the vent seals 33 are inflated, whereas in Fig. 6 the vent seals 33 are deflated. Similarly, the outer sheet 35 may be provided with a vent at the top of the propagator 1. As such, the outer sheet 35 may be one continuous sheet, or it may comprise two or more separate parts. As shown in Figs. 3, 5 and 6 the upper vent may be blocked, and preferably sealed, via an inflatable vent seal 32 similar to the lower vent seals 33. The upper inflatable vent seal 32 can attach to the propagator 1 via any suitable connecting mechanism 32a.

As with the vent flap 36, the operation of the inflatable seals 32, 33 may be controlled automatically by the use of feedback from sensors, e.g. temperature, humidity, leaf turgor or gas sensors. For example, by using temperature sensors in the outer foliage chamber 55 to detect when temperatures rise in the outer foliage chamber 55 to levels where plant growth is affected, the control unit 23 can be activated to deflate the seals 32 and 33. As shown by the arrows in Fig. 6, this allows external air to flow through the outer foliage chamber 55, which reduces the temperature in the outer foliage chamber 55. Once the temperature is returned to acceptable levels, the control unit 23 can re-inflate the seals 32, 33 to maintain the desired temperature.

To provide access to the propagators 1 the end frames 11 can be temporarily tilted and/or folded inwards - thus releasing space for access between parallel rows of propagators 1. In Figs. 1-4 and 13-15 the bottoms of the root chamber 14 are held apart by tensioned ropes 31 that bear the weight of the ground sheet or root chamber base 15. The root chamber 14 can be tilted or folded by pulling on ropes, or other suitable supporting members, 31. This tilting and/or folding operation creates a temporary access space for field workers between the propagators 1.

Fig. 7 demonstrates how the tilting and folding operation may occur. The left-most propagator 1 in Fig. 7 is arranged in the normal configuration for growing plants 16. The central propagator 1 has been configured so that the root chamber 14 is folded or collapsed upon itself by drawing the supporting members 31 towards each other. As such, the inner sheet 13 has been re-positioned and the base 15 has been folded. In the right-most propagator 1 in Fig. 7, the propagator 1 has been tilted. In this example, the relative positions of the supporting members 12 and 31 remain unchanged, so that the tilted root chamber 14 has the same cross-sectional shape as the untilted root chamber 14. However, in some embodiments, it may be desirable to both fold and tilt the root chambers 14 at the same time.

To assist in the tilting and folding, the end frames 11 may also be configured to move position. For example, the Fig. 4 propagator 1 allows the tilting of the root chamber via the pivoting of the spar around pivot point 45 on the upright post. In addition, the spar may contain a slot for the pivot point 45, so that the spar may move laterally as well as rotationally. Similarly, the position of the supporting members 31 on the spar may be re- positionable so that they can be brought closer to each other and therefore allow the folding or collapsing of the chamber 14.

The tilting and folding mechanism allows propagators to be positioned close to each other, and therefore increased productive surface area to be obtained per unit area in plan view. Desirably, the growing surface of the propagator is at least 1.5 times the footprint (i.e. the width of the base 15) of the propagator, and more desirably at least 2 times the footprint, even more desirably up to 3 times the footprint, and still more desirably up to 4 times the footprint. In a preferred example, the growing surface is around 2.5 times the footprint.

As shown in Fig. 4, when the supporting members are ropes or lines, the tilting and folding of the propagator can be achieved using re-positionable anchor posts 46 for the lines 12 and 31. In addition, lines 41 and 42 which are used to control the position of the spar relative to the post of the end frame 11 may also be attached to re-positionable anchor post 46. As well as the anchor posts 46 being re-positionable, the relative tensions in the lines 12, 31, 41 and 42 can be adjusted, preferably using turnbuckles or block and tackle arrangements 43 on the various lines. Similar methods could be used with the propagators of Figs. 1-3, rather than the winch 21.

In the embodiments of Figs. 1-3, the end frames 11 are constructed with an A-frame configuration. In this case, the diagonal sections of the A-frame may be re-positionable and/or hinged to the horizontal member of the A-frame, in order to allow the diagonal members to be re-positioned. As such, the diagonal members of the A-frame may be repositioned along with the chamber 14. In Figs. 1-3, the relative tensions in the lines 12 and 31 can be controlled using the winch 21.

In the configurations of Figs. 1-4, the height of the lines 31 and the base 15 of the chamber 14 can be adjustable to take account of the local terrain and field worker access requirements. As such, the space between the base 15 and the ground may be varied. This space may be used for fog return tubes 24 and rainwater storage bags, for example, which may can in direct contact with the ground. However, it is desirable that the fog return tubes 24 are elevated above the ground (as shown clearly in Fig. 5 for example), in order to avoid creating condensation traps at dips in the ground. That is, by suspending the fog return tubes 24, the formation of local dips along the length of the fog return tube 24 can be avoided, thus avoiding the collection of condensation in the pipe. The floor 15 of the root chamber 14 can, optionally, be used to grow mushrooms or algae varieties, or other energy crops 53, which grow in the dark when fed for example with suitably warm sugar-rich water solutions. Periodically the algae can be drained off through a remotely controlled valve outlet positioned in the root chamber floor 15. Preferably, where the root chamber floor 15 is entirely suspended from lines 31, for example, the valve outlet is positioned substantially centrally in the middle of the root chamber floor 15. This is because the suspended floor forms a catenary along its length and width so that the outlet will always be at the lowest point in the root chamber 14 (in an unfolded or untilted configuration).

The propagator 1 may be provided with grow lights. Grow lights are designed to emit wavelengths of light necessary for the normal growth of plants. In particular the grow lights preferably emit red and blue wavelengths. For the red light, the grow lights desirably emit light at a wavelength of approximately 660 nm, more preferably transparent over the range of 645 to 700 nm and more preferably transparent over the range of 630 to 740 nm. For the blue light, the grow lights desirably emit light at a wavelength of approximately 460 nm, more preferably transparent over the range of 450 to 475 nm and more preferably transparent over the range of 440 to 490 nm.

The grow lights may be attached to beams 51, (see Fig. 5) which rest on power cables 22, provided above the propagator, and can be spaced according to the type of lamps used. The power cables 22 may be supported by the end frames 11, as shown in Figs. 1-3. Preferably the grow lights are provided in the form of low voltage DC lamps.

The position of the grow lights is preferably adjustable so that, in use, the light from the grow light falls on the outer film 35 at or near a right angle to the outer sheet 35 surface, for example in the range of from 60° to 120° to the surface to the outer sheet, although the angle may need to be outside this range at the base of the outer sheet 35. This allows as much of the light as possible to be transmitted through the outer sheet 35, instead of being reflected away by the outer sheet 35. This in turn means the plants 16 in the propagator 1 receive as much light as possible for photosynthesis. The position of the grow lights may be adjustable, for example, by being provided on a movable joint such as a ball and socket joint.

Figs. 5 and 6 illustrate the use of collection gutters 52 on the outer film 35.

Aeroponic systems create high humidity environments that will sometimes lead to condensation on the inside of the plastics film enclosures. Gutters 52 provide a means for collecting this water, which can then be recycled. Similarly, the gutters 52 can be used to collect rain water and dew from the outer surface of the outer film 35, and this may also be collected and stored, for example, in plastic flexibags which are laid on the ground below the propagators 1.

The propagator 1 could also be built on levelled ground where the chamber 14 is not suspended above the ground. Figs. 8 and 9 show examples of such propagators.

Fig. 8 shows two propagators 1 that do not have an outer sheet 35. The right-most propagator 1 has a single upper support member 12, whilst the left-most propagator 1 has two upper support members 12. As such, the right-most propagator 1 has a root chamber with a triangular cross-section, whilst the left-most propagator 1 has a root chamber 14 with a trapezoidal cross-section.

Compared with the propagators 1 depicted in Figs. 1-7, the propagators of Fig. 8 have inner sheets 13 that reach all the way to the ground. The film 13 may be in direct contact with the ground, or there may be an intermediary layer 81 between the sheets 13 and the ground. The intermediary layer 81 may be some form of geo-textile ground sheet or a layer of gravel, for example.

In Fig 8, the film 13 is held in position against wind loads and the weight of plants 16 inserted in it by tubes 82 filled, or partially filled, with loose soil or water. Water is the preferred medium in partially filled tubes 82 if regular access is required to the root chamber 14. This is because the water may be easily removed and re-filled, and is cheap. These tubes 82, are preferably sufficiently flexible to conform to ground irregularities and seal the grow chambers against the impervious ground sheet 81 to prevent the loss of pressurised air and water fog or nutrient/water fog 54 from the root chamber 14. If desired the tubes 82 can be secured to the ground with metal or plastics pegs preferably with tops that hook over the tubes 82 when they are fully pushed down into the soil beneath the ground sheet 81.

Preferably, tubes 82 are formed integrally with sheet 13.

Alternatively, rather than the tubes 82, other means of weighting the sheet 13 down to form the chamber 14 may be used. However, any such means is preferably releasable, to allow access to the root chamber 14.

The propagators 1 in Fig. 8 may be tilted and re-shaped as previously discussed for the propagators 1 of Figs. 1-7, to allow access between propagators 1 and additionally to control the spacing of the plants relative to the ground. In addition, the inner sheets 13 may be re-positioned so as to change the shape of the root chamber 14 to allow easier access between propagators 1 arranged in parallel.

In particular, in the propagators shown in Fig. 8, there is a particularly advantageous method of re-shaping the root chambers 14 when the tubes 82 filled with water are used to seal the sheet 13 against the ground. The propagators 1 may be arranged such that there is slack available in the support lines 12 when the propagators 1 are in the configurations shown in Fig. 8. In that case, when the line or lines 12 are further tensioned, the inner sheet 13 will be raised. Preferably, the inner sheet 13 may be raised by around 50cm.

As this operation is carried out the fluid- filled tubes 82 holding down sheet 13 are drained of water, and the lifting action causes the film 13 to swing inwards towards the centre line of the chamber 14 and hang substantially vertically. This operation frees space between closely spaced propagators 1 , so aeroponic farmers have room to gain access to crops growing up the film 13 faces of the propagators 1. When access is no longer required, the film 13 can be lowered and stretched tight, to drop onto the ground sheet 81. After the fluid is replaced in tubes 82, the chamber 14 is thus secured back in position and the two sloping faces of the chamber 14 are recreated.

In Figs. 1-7, the fog return tube 24 (part of the fogging system described in more detail below) is shown beneath the chamber 14. In Fig. 8 the fog return tube 24 rests on the bottom of the root chamber 14.

As in Figs 1-7, the chamber 14 of the propagators 1 in Fig. 8 may be provided with a base, for example in the form of a tray resting on the ground or intermediate layer 81. Such a tray may also be used for the cultivation of an energy crop 53 or mushrooms (as shown in Fig. 6).

Fig. 9 depicts two propagators using the double-film construction (i.e. having both an inner film 13 and an outer film 35). As discussed before, such a configuration may be desirable in potentially hostile growing environments, and/or where it is necessary to be able to control growth conditions in order to optimise the speed of plant growth and the quality of produce (e.g. for the organic food market). As in Fig. 3, the outer sheet 35 is suspended from lines 37. The outer sheet 35 is further weighted at ground level in a similar way to the inner sheet 13, for example using filled plastics tubes. Duckboards 91 may be laid over these tubes to allow farmers to move between propagators 1.

The outer sheet 35 creates a protected plant space in which the above ground parts of plants 16 can grow without being attacked by birds or insects, damaged by dust, dirt, sand or hailstones, or to enable foliar feeding, or to protect from other contamination such as chemical or radioactive incidents, or additionally to house a flow of air past sensors positioned at the exit to the foliage chamber where the sensors would be in communication with a control system. As such, this configuration is of use in outside conditions.

Of course, although Figs. 8 and 9 depict the propagators 1 on perfectly levelled ground, this is not necessary. The system will work on a brownfield site, sand, rooftop or even potentially on water if suitable supporting frames are used.

As with the suspended propagators 1 , power cables 22 and light beams 51 may also be provided for the non-suspended propagators of Fig. 8 and Fig. 9.

As already mentioned, the propagators of Figs. 1-9 are provided with fogging systems to provide a fog within the chamber 14. This is now described in more detail with reference to Figs. 10 and 11.

A fog of water, preferably containing plant nutrients and enhancing additives is made in a fogger unit 23, which may comprise a nebuliser, for example. The fog may be produced by forcing nutrient-containing water through nozzles by a pump. The fog can be passed into the root chamber 14 and this fog is taken up by the roots, and/or can be passed into the foliage chamber 55 to allow nutrients to be absorbed by the foliage. Several fogger units 23 may be required along the length of a propagator 1 if the propagator 1 is long. The nutrient composition in the fog can be changed to optimise growth. This is done by the fogger/fan control box 23, which also controls the pump/fans. The fog can optionally be condensed and returned to the fogger unit 23 in the return tubes 24. Preferably, to maintain optional growth conditions, the fogger unit 23 is provided with a backup power supply.

In some cases only a single fogger unit 23 is required for a single propagator 1. In other cases, multiple fogger units 23 can be provided for a single propagator 1 or a single fogger unit 23 can supply multiple propagators 1.

The fogger/fan control unit 23, see Fig. 10, may be in the form of a large weatherproof box containing a variable speed fan, water/nutrient pressure pump, heater and/or cooler, water and nutrient suction pump, grow light control unit, fog nozzles, nutrient/water tank, a water/nutrient degassing unit, and computer control system. As previously mentioned, the control system may be linked to sensors measuring growing conditions inside the root chamber 14, and a control system may also be linked to sensors measuring growing conditions in the foliage chamber 55 and where such sensors can also provide feedback control to the control system. Sensors can be used to monitor conditions such as air temperature, air speed, leaf turgor, humidity, nutrient and water pH, nutrient and water levels in the storage tank and daylight levels. The control unit 23 may be linked with RFID (Radio Frequency Identification) chips attached to the plants 16 to monitor and control the growth of the plants 16. The control unit may be linked to a two-way radio communication system, for remote aeroponic system control and system failure alarm functions.

The fog return tube 24 is preferably located centrally. Although shown suspended in Fig. 10, it may also rest either beneath or on the bottom of the root chamber 14 (as shown in Fig. 11). The fog return tube 24 is preferably made from plastics film. The fog return tube 24 is used for recycling excess fog and air from the far end of the root chamber 14 (see Fig. 11) back to the fogger/control unit 23. This recycled fog is blown down the fog return tube 24 by a variable speed fan 111, for example, located near to the end closer panel 34 most distant from the fogger/control unit 23, as shown in Fig. 11.

As previously mentioned, the closer panel 34 at the end of the propagator 1 that is connected to the fogger/control unit 23 (as shown in Fig. 10) can contain holes through which fog can be discharged from the fogger unit 23 into the chamber 14, and through which the fog return pipe 24 can return recycled fog to the fogger unit 23. The

fogger/control unit 23 may also be provided with ventilating fans that blow air into the root chamber through one or more further holes in the closer panel 34, and/or into the foliage chamber 55.

As also previously mentioned, the end panels 34 may be provided with a vent flap

36. The vent flap 36 is preferably provided at the end of the propagator 1 opposite the fogger/control unit 23. However, a vent flap may be provided at either or both ends depending upon how it is desired to control the environment within the chamber 14. The vent flaps 36 may be remotely controlled, as previously described. However, the vent flaps 36 may also be mechanically free to open if the pressure inside the root chamber 14 becomes too high. For example, the vent flaps 36 may be suitably weighted so that they automatically open due to the pressure inside the root chamber 14 when that pressure becomes too high. The provision of vents 36 in this way allows for the root chamber 14 to be maintained at the correct conditions, whilst making it difficult for insects to enter the chamber 14.

The fog return pipe 24 may be suitably arranged so that flow back through the pipe is assisted by the variable speed fan 111. In addition, the fog return pipe 24 may be suitably angled so that flow of any condensed liquid towards the fogger/control unit 23 is assisted by gravity.

Any liquid that does not advance into the fog return pipe 24 may be captured in a dew/condensate sump 112 that is connected to a suction pump on the fan/fogger control unit 23.

The end frames 11 in Figs. 10 and 11 are shown attached to screw pile ground anchors 101. However, the end frame members 11 may be secured to the ground by any suitable method. Figs. 10 and 11 also show grow lights 102 connected to power cable 22.

The fogger/control unit 23 shown in Figs. 10 and 11, or alternatively a second fogger/control unit, may also be used to supply a fog to the foliage chamber 55 between the inner sheet 11 and the outer sheet 35 when the outer sheet 35 is present. The control unit 23 can be arranged to supply water fogs containing water-soluble plant foods to accelerate plant growth to the foliage chamber 55. By creating a high humidity in the foliage chamber 55, the stomata of the plant foliage in the foliage chamber 55 are encouraged to open. As the stomata open, the plants 16 may absorb the nutrients from the fog in the foliage chamber 55 at the same time as absorbing nutrients via their roots from the fog in the root chamber 14.

It may be preferable to use a separate fogger/control unit 23 to differentiate the size of the fog droplets between the root chamber 14 and the foliage chamber 55. Foliar feeding is preferably conducted using fine fogs with median droplet sizes at least 1 micron up to 60 microns. The droplet size is desirably 20 microns or less, more preferably 10 microns or less and still more preferably 5 microns or less. In contrast, root systems prefer slightly coarser droplet sizes and so a larger average droplet size may be desirable in the root chamber 14. To allow control of the droplet size, although this is not necessary, energy- efficient systems such as the μΜίβί (RTM) Platform Technology by Swedish Biomimetics 3000 Limited, of Stockholm, Sweden, can be used.

As with the root chamber 14, the pressure, temperature, humidity, etc, in the foliage chamber 55 may be monitored using sensors and the readings from the sensors may be used to control the supply of fog to the root chamber 14 and / or the movement of air in the root chamber 14.

Pure water fogs may also be supplied to the foliage chamber 55 for use as a screen, to protect the plants 16 from strong sunlight. Pure water fogs may also be used to protect the plants 16 from frost, by reducing radiation heat losses and allowing water vapour in the saturated air to condense onto leaves and release latent heat of fusion. This is much more efficient than providing frost protection by direct heating, for example. Protecting an acre (approximately 4050m²) of orchard from frost by heating involves burning 20-40 gallons (approximately 90-180 litres) of fuel an hour. Water fogs can produce the same level of frost protection using 0.05-0.15 gallons (approximately 0.2-0.7 litres) of fuel (or electricity equivalent) an hour per acre. These figures relate to fogs with median particle diameters ranging from 10-40 microns.

The control of the environments in the root chamber 14 and foliage chamber 55 may desirably be performed in a closed loop system. That is, moisture and nutrients from the fog return tubes 24 may be re-cycled as fog again, with suitable nutrient enrichment, and air within the propagator could be recycled with suitable oxygen and/or carbon dioxide enrichment. Heat levels could be actively controlled using heating and cooling units. Such systems would be desirable when it is necessary to isolate the inside of the propagator from a contaminated external environment, for example after a chemical release or nuclear contamination.

It may be desirable to provide propagators 1 inside a larger covered structure. In that case, the propagators 1 can be configured without the second outer sheet 35. However, it may still be desirable to provide the outer sheet 35 for foliar feeding. Fig. 12 shows a schematic plan of a covered installation comprising five propagators 1 arranged substantially in parallel. As can be seen in Fig. 12, each propagator 1 is provided with its own

fogger/control box. Arrow A indicates the direction of airflow within root chambers 14 of the propagators 1. Arrow B indicates the direction of airflow within the fog return tubes 24 of the propagators 1. The propagators 1 are inside an overall cover 120, which may be a polytunnel or a greenhouse for example. The covering structure 120 has doors 121 to allow access for workers and has ventilating vans 123 and exhaust vents 136 to allow airflow through the structure 120.

The propagators 1 may be further supplied with temperature controlled air such as heated air (which may be obtained from a waste heat source such as a manufacturing plant) or cooled air, and / or air rich in carbon dioxide (i.e. having a higher concentration of carbon dioxide than standard air). This air may be supplied to either the roots or the foliage.

Higher carbon dioxide levels are known to enhance plant growth, and so the carbon dioxide rich air will assist in the growing of plants 16 in the propagator 1.

The carbon dioxide rich air may be obtained from any source, including waste sources such as cement production or power plants. If the waste source is local to the propagator, the waste carbon dioxide could be piped directly into the gap between the inner 13 and outer 35 layers (i.e. the foliage chamber) or into the root chamber 14. However, the most benefit would be obtained by directing the carbon dioxide rich air to the foliage chamber 55. Desirably, the supply of carbon dioxide rich air is controlled in response to the carbon dioxide level detected by carbon dioxide monitors within the foliage chamber. For example, if the carbon dioxide monitors detect that the level of carbon dioxide in the foliage chamber is too low, the supply of carbon dioxide rich air into the foliage chamber may be automatically increased to increase the carbon dioxide levels. Once the level of carbon dioxide in the foliage chamber returns to a suitable level, the supply of carbon dioxide rich air may be automatically reduced. As such, the conditions inside the foliage chamber can be maintained for optimal growth. Once again, the specific parameters for operating the control system will depend on the most suitable conditions for the plants 16 being cultivated.

The control unit 23 may be further configured to control the supply of the carbon dioxide. Alternatively, a separate control mechanism for the supply of carbon dioxide may be supplied.

The propagator 1 may also make use of waste heat from local sources. Once again, waste heat may be piped between layers 13 and 35 (i.e. into the foliage chamber 55) or directly into the root chamber 14. Once again, the control of the supply of waste heat could be performed by the control unit 23, or a further control mechanism. The supply of the waste heat can be controlled in response to temperature sensors within the propagator, to avoid overheating the plants 16.

In some cases it may be desirable for the inner sheet 13 to have a pleated

arrangement. This is described below with reference to Figs. 16-20.

Fig 16 is a schematic perspective view of the pleated arrangement. As such, the structural supporting elements of the overall propagator 1 , such as the end frames 11 , are not shown. However, the pleated arrangement may be used with any of the structural configurations of the propagator 1 previously discussed.

As can be seen, the inner sheet 13 is provided with pleated sections 161 running lengthwise along the propagator 1. That is, the pleats 161 run substantially parallel to the supporting members 12 and 31.

The pleats 161 form lengthwise pockets or slits in the inner sheet 13, which are open on the outer surface of the inner sheet 13. That is, the pleats 161 hang inside the root chamber 14. Fig. 17 depicts one way in which the pleats 161 can be formed and supported. Two 'C channels form a structure 171, which forms part of a framework on which pleat- supporting members 175 can be provided. In some arrangements, the end frames 11 may act as structures 171, as part of the pleat-supporting framework.

The structure 171 of Fig 17 can be anchored to the ground and/or supported by support members 31 and/or attached to certain elements of the end frame. A joint 172 can be formed between the two 'C sections at support member 12. The joint 172 can be a hinge, for example a fabric hinge, which may be notched to enable support member 12 to slide above or adjacent to it into the desired location. The two sections of the structure 171 can be locked into position relative to each other by a locking means 174 such as a bolt that extends through both 'C sections.

The pleat-supporting members 175 can be ropes or lines or any other suitable supporting member as previously described with reference to support members 12 and 31. In Fig. 17, ropes or lines 175 extend between at least two structures 171, only one of which is shown, and each line 175 passes through a hole in the depicted structure 171. The end of each of the lines 175 is attached to a weight 176 to keep the line 175 in tension. A similar arrangement may be used at the other end of each line 175.

Alternative tensioning methods could be used. For example, a line 175 can be wedged in place with a peg through the hole in the structure 171. In some cases, for example when using three structures 171 spaced so that one structure 171 is in the middle of the propagator 1, it may be desirable to fixedly attach (e.g. via a knot when using a rope or line) the line 175 to the central structure 171.

In Fig. 18, the pleat-supporting members 175 are provided in pairs. This allows the formation of a pleat 161 in the inner sheet 13 by pulling or pushing a section of the inner sheet 13 through the gap between the pair of pleat-supporting members 175. In effect, a pocket of the material of the inner sheet 13 is created inside the root chamber 14, so that the pocket opens to the outer surface of the inner sheet 13.

One way to hold the pleats 161 in place is to use clips or some other fastening means at suitable intervals to attach sheet 13 to the pleat-supporting members 175. Fig. 19 shows an example in which a tape 162 is used to fasten across multiple pleats 161. The tape 162 is attached by a means such as welding, gluing or stitching to the sheet 13. By applying the tape 162 across the pleats 161, the pleats 161 are held in position and do not fall out if a lower section of the sheet 13 is pulled or weighted down with plants 16, for example. An alternative configuration to that depicted would be to provide an inner sheet 13 in which the pleats 161 are pre-formed. For example, the sheet 13 could be manufactured with the pleats 161 formed and held in place by a means such as welding, gluing or stitching at periodic intervals along the pleat 161, or with tape 162 already in place. In such a case, the pleat-supporting members and the structures 171 may be omitted from the propagator 1 if the pleats 161 are held together strongly enough.

The pleated arrangement has several advantages.

As shown in Figs. 20a and 20b, the pleats 161 can act as a channel for locating seeds, seedlings or seed or plant-bearing porous media (such as a cellulose fibre seed stick 201), or as a channel where the roots or tubers of root crops such as potatoes or carrots can be carried. The support of the pleat 161 helps avoid the roots and tubers pulling on the rest of plant 16, as may happen if they hang free in chamber 14. Alternatively, the roots / tubers can be located in the root chamber 14, with only the foliage located in the pleat 161.

The pleats 161 can also help to collect rainwater 191 (where there is no outer sheet 35) and dew or condensed fog. This is shown in Fig. 19.

To allow access between the pleats 161 and the root chamber 14 (i.e. so that the nutrient fog 54 in the root chamber can still be absorbed by plants 16 whose roots are supported in the pleats 161), there are various possibilities. The pleats 161 may be formed from a material that allows the transmission of the moisture and nutrients. The pleats 161 can be provided with perforations 192 on the bottoms and / or sides of the pleats 161, as shown in Figs 18 and 19. Such perforations would still restrict or prevent light penetrating into the root chamber, so as to maintain the inner sheet 13 as being substantially opaque and thus preventing algae growing on plant roots (which would use water and nutrients otherwise available to plant roots), and also would still inhibit the escape of fog.

Alternatively the pleat 161 may be made of a different material to the bulk of the inner sheet 35 such as a netting material 202 as shown in Fig. 20b. One advantage of using a fibrous seed stick 201 in such a situation (which could be made from various materials, for example cellulose, as mentioned above) is that it helps fill the pleat 161 and therefore assists in preventing light from reaching the root chamber when the pleat 161 material is not itself opaque. Alternatively, the inner sheet 35 may be maintained as providing a substantially opaque covering for the propagator by providing only a narrow opening for the pleat 161 on the outer surface of the inner sheet 13. The present invention has been described above with reference to specific embodiments. It will be understood that the above description does not limit the present invention, which is defined in the appended claims.

Claims

1. An aeroponic propagator for the cultivation of plants, the propagator comprising:

two end frames;

a first support member extending between the two end frames; and a substantially opaque sheet for supporting plants to be cultivated, wherein the substantially opaque sheet is suspended from the first support member to form at least one sidewall of a chamber between the end frames for roots of plants supported on the opaque sheet.

2. The aeroponic propagator according to any one of the preceding claims, wherein the first support member is a support line.

3. The aeroponic propagator according to claim 2, further comprising a tensioning mechanism, preferably a winch, for tightening the support line.

4. The aeroponic propagator according to claim 2 or 3, wherein the support line is an ultra high molecular weight polyethylene rope.

5. The aeroponic propagator according to any one of the preceding claims, further comprising a substantially transparent sheet arranged over the substantially opaque sheet, so as to form at least a partial enclosure around the chamber.

6. The aeroponic propagator according to claim 5, wherein the substantially transparent sheet is transparent to light at wavelengths of from 630 to 740 and from 440 to

490 nm.

7. The aeroponic propagator according to claim 5 or 6, further comprising a blocking device for blocking a gap between the chamber and the transparent sheet.

8. The aeroponic propagator according to any one of claims 5 to 7, further comprising a vent in the transparent sheet above an uppermost point of the chamber.

The aeroponic propagator according to claim 8, further comprising a blocking device for blocking the vent in the transparent sheet.

The aeroponic propagator according to any one of claims 7 to 9, wherein the blocking device is an inflatable tube.

The aeroponic propagator according to any one of claims 5 to 10 further comprising a fogging system to supply fog, with a median droplet size of 1 to 60 microns, to a space between the chamber and the at least partial enclosure.

The aeroponic propagator according to any one of claims 5 to 11 further comprising a system for supplying carbon dioxide rich air or temperature controlled air to a space between the chamber and the at least partial enclosure.

The aeroponic propagator according to any one of claims 5 to 12, further comprising one or more support members, arranged to support the transparent sheet.

The aeroponic propagator according to any one of the previous claims, further comprising an end panel arranged to close an end of the chamber.

The aeroponic propagator according to claim 14, wherein the end panel comprises a vent flap that is optionally remote controlled.

The aeroponic propagator according to any one of the preceding claims, further comprising a repositioning device to reposition the first support member to tilt the chamber.

The aeroponic propagator according to claim 16, wherein the repositioning device is a means for tilting and / or folding the two end frames.

The aeroponic propagator according to any one of the preceding claims, wherein said substantially opaque sheet is reflective.

The aeroponic propagator according to any one of the preceding claims, wherein said substantially opaque sheet comprises UV-stabilised plastics.

The aeroponic propagator according to claim 16, wherein the substantially opaque sheet further comprises a waterproof paper layer.

The aeroponic propagator according to any one of the preceding claims, further comprising a second support member extending between the end frames, and wherein the substantially opaque sheet is suspended from both the first and second support members.

22. The aeroponic propagator according to any one of the preceding claims, wherein the chamber is suspended above the ground.

23. The aeroponic propagator according to claim 22, further comprising a chamber base for supporting an energy crop.

24. The aeroponic propagator according to claim 23, wherein the chamber base is

supported by third and fourth support members extending between the two end frames below the first support member.

25. The aeroponic propagator according to claim 24, wherein the chamber sidewalls are releasably secured to the third and fourth support members.

26. The aeroponic propagator according to claim 24 or claim 25, wherein the third and fourth support members are repositionable to alter the shape of the chamber.

27. The aeroponic propagator according to any one of claims 22 to 26, further

comprising a drainage point positioned at the lowest point in the chamber base for draining the energy crop.

28. The aeroponic propagator according to any one of claims 1 to 21, wherein the ground either forms the base of the chamber or directly supports a base of the chamber.

The aeroponic propagator according to claim 28, wherein the substantially opaque sheet is releasably anchored to the ground at the base of the sidewalls, optionally by a water-containing tube.

The aeroponic propagator according to any one of the preceding claims, further comprising a fogging system to supply a fog to the chamber.

The aeroponic propagator according to claim 30, wherein the fogging system is arranged to collect moisture and the nutrients contained therein from the chamber and re-circulate the moisture and nutrients in the fog.

The aeroponic propagator according to any one of the preceding claims, further comprising an intermediary frame positioned between the two end frames.

The aeroponic propagator according to any one of the preceding claims, wherein the substantially opaque sheet blocks at least 75% of light from passing through the sheet, preferably at least 85% of light, even more preferably at least 90%> of light, and still more preferably at least 95% of light.

The aeroponic propagator according to any one of the preceding claims, wherein one or more of the support members and/or one or more of the end frames and/or one or more of the intermediary frames is secured to a surface on which the aeroponic propagator is provided.

The aeroponic propagator according to any one of the preceding claims, wherein the substantially opaque sheet and/or the substantially transparent sheet each comprises two or more layers.

The aeroponic propagator according to any one of the preceding claims, further comprising grow lights arranged to shine, in use, on the foliage of plants supported on the substantially opaque sheet.

37. The aeroponic propagator according to any one of the preceding claims, further comprising a system for supplying air to the chamber.

38. The aeroponic propagator according to claim 37, wherein the system for supplying air to the chamber comprises a filter to remove micro-organisms from the air supplied to the chamber.

39. The aeroponic propagator according to claim 37 or claim 38, further comprising:

an oxygen sensor in the chamber, and/or at least one sensor in the chamber for monitoring at least one of temperature, humidity, carbon dioxide and/or leaf turgor, and

a control unit configured to control the rate at which air is supplied to the chamber in response to feedback from the oxygen sensor and/or at least one sensor.

40. The aeroponic propagator according to any one of claims 37 to 39 when dependent from claim 5, further comprising:

an oxygen sensor in a space between the chamber and the at least partial enclosure, and/or

at least one sensor in the chamber and/or in a space between the chamber and the at least partial enclosure for monitoring at least one of temperature, humidity, carbon dioxide and/or leaf turgor, and

a control unit configured to control the rate at which air is supplied to the chamber and/or the at least partial enclosure in response to feedback from the oxygen sensor and/or at least one sensor.

41. The aeroponic propagator according to any one of the previous claims, wherein the substantially opaque sheet comprises at least one pleated section for supporting the plants.

42. A kit of parts for an aeroponic propagator for the cultivation of plants, the kit

comprising two end frames, a first support member and an opaque sheet for supporting plants to be cultivated. A method of cultivating plants using an aeroponic propagator according to claim 30 or claim 31, the method comprising:

supporting plants on the opaque sheet so that the plant roots project into the chamber and the plant foliage projects outside the chamber; and

supplying a nutrient-containing fog to the chamber for absorption by the plant roots.

An aeroponic propagator for the cultivation of plants, the propagator comprising: a substantially opaque sheet for supporting plants to be cultivated; and wherein the substantially opaque sheet comprises at least one pleated section for supporting the plants.

A method of cultivating plants using an aeroponic propagator according to claim 11 or claim 12, the method comprising:

supplying at least one of a nutrient containing fog, temperature controlled air or carbon dioxide rich air to a space between the chamber and the partial enclosure, for absorption by the plant foliage.

An aeroponic propagator constructed and arranged substantially as hereinbefore described or as illustrated in any one of the accompanying drawings.

A kit of parts for an aeroponic propagator for the cultivation of plants substantially as hereinbefore described or as illustrated in any one of the accompanying drawings.

A method of cultivating plants using an aeroponic propagator substantially as hereinbefore described or as illustrated in any one of the accompanying drawings.