PLANT CULTIVATION METHOD AND INSTALLATION

Abstract: There is described a method for the cultivation of plants, comprising positioning a plurality of plants (p1, p2) in a number of vertically spaced rows extending circumferentially about a rotating column (1), and arranging a vertically extending linear array of light sources to illuminate the plants (p1, p2) with light from a horizontal direction. An installation for the cultivation of plants, comprising a vertical column (1) rotatable about its axis, the column (1) having at least one circumferentially extending growing area (2) wherein plants (p1, p2) may be rooted in a growth substrate, the column (1) providing means for supporting and training the plants for growth in a predetermined direction, and the installation further comprising at least one vertically extending linear light source providing illumination to the plants, is also described.

Description: PLANT CULTIVATION METHOD AND INSTALLATION The present invention relates to horticulture, and is particularly concerned with the provision of an apparatus and method for the growing of large numbers of plants in small areas of ground space. The method is particularly suited to the growing of crop-bearing vine type plants such as beans, tomatoes, cucumbers etc, and can be adapted for the production of self-supporting flowering plants. Current methods of producing crops from vine type plants such as tomatoes in greenhouses involves the planting of the tomato plants in twin rows along the length of the greenhouse with paths extending between the pairs of rows. The maximum yield is produced by the conventional methods when the density of vines is three plants per square metre of greenhouse. An objective of the present invention is to provide for an increased population density of plants over conventional methods. It is a further objective of the present invention to provide efficient illumination to the leaves of the vine type plants by ensuring that later developing leaves do not obscure the access of light to earlier developed leaves of the plant. According to one aspect of the present invention, a method for the cultivation of plants comprises positioning a plurality of plants in a number of vertically spaced rows extending circumferentially about a rotating column, and arranging light sources to irradiate the plants from a horizontal direction, preferably generally radially of the column. Preferably, a number of vertically extending linear light sources are arranged to surround the column. However, in a particulariy advantageous embodiment a vertically extending linear light source may be placed within the column, preferably extending along the axis of the column, and may be provided in conjunction with or as an alternative to the external light sources. The columns are preferably circular, but may be polygonal, in horizontal section. An embodiment of present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a vine plant growing column; Figure 2 is a schematic plan view showing the layout of the columns and light sources in a growing house; and Figure 3 is a schematic perspective view of a plant growing column populated with truncated vine plants. Referring now to the drawings, Figure 1 shows a plant growing column for the growing of vine type plants. The column comprises a generally vertical cylinder 1, surrounded by a number of generally horizontal ledges 2. The cylindrical column 1 is preferably formed of an open mesh of wire or other suitable material, or may be formed from perforated sheet material or expanded metal sheet. In an alternative (not illustrated) the column may comprise a number of vertically extending cords or wires hanging from an upper supporting ring, with plants trained up the cords to form a cylindrical array of plants. Extending circumferentially round the column 1 of Figure 1 are a number of horizontal ledges 2. Typically three ledges 2 will be provided on each coiumn 1 , but the number of ledges will depend on the available height in the growing house and the required vertical spacing between the ledges. On each ledge 2 is supported a growth substrate such as a foam slab or mineral wool enclosed in an impervious sleeve, such as are conventionally used for the propagation of tomato or other plants. By providing a column 1 of approximately 800 mm diameter, an area of one square metre of floor can provide approximately 7.5 linear metres of growth substrate in the three circumferential lengths supported by the ledges 2. It is a feature of the present method that vine type plants are rooted at regular spacings in the growth substrate, such that each shelf 2 will accommodate for example ten to twelve plants regularly spaced around the circumference of an 800 mm diameter column 1. Clearly, more plants can be accommodated per ledge if the diameter is increased, or if the spacing between plants is reduced. Using a first technique to take maximum advantage of the plant density obtained, a first plant p1 is trained to grow horizontally round the circumference of the column from its rooting point in the growth substrate. Its neighbouring plant p2 is allowed to grow vertically by a short distance, and is then trained horizontally so as to follow the direction of plant p1. The next plant in the sequence, p3, is allowed to grow vertically by a slightly greater distance than p2, and is then trained to grow horizontally, again following the direction of plant p1. The sequence is repeated for all the plants on each shelf 2. The preferred vertical distance between the trained plants is 12 cm, but greater or smaller distances may be suitable for different plants. As plant p1 continues to grow, it will develop leaves and fruit trusses. By the time the growth tip of plant p1 has moved completely round the circumference of the column 1 and back to its rooting location, the first fruit of plant p1 will have ripened sufficiently to be harvested. This ensures that growth of plant p1 can be allowed to continue without the fresh growth at the tip of plant p1 obscuring the earlier leaves of the plant from light. Ideally, the diameter of the column 1 is so arranged that each truss of fruit developed on the plant p1 is harvested before the growth tip of the plant p1 completes a circumference of the column and reaches the location of the fruit truss. As each successive plant in the series is allowed to grow vertically by a greater extent than its predecessor, the first fruiting truss of each plant will be spaced from the first fruiting truss of preceding plant both vertically and horizontally, and thus the first fruiting trusses will be arranged in a helix about the column 1. Likewise, as each plant develops a second fruiting truss, these will be arranged in a helical disposition about the column 1. As plant growth continues, each plant may extend a number of times round the column 1. It is preferable that the diameter of the column 1 is so arranged that the time taken by the first fruiting truss to ripen fully is slightly less than the time taken for the growing tip of the plant to complete a circuit of the column 1. Thus, fruit will be harvested from each vine shortly before the growing tip of the plant reaches the location of the fruiting truss. This will simplify harvesting since access to the fruit will not be impeded by the new growth. Alternatively, the vines may be trained round the column to grow with their stems extending along helical paths, with the stems at between 15 and 75 degrees to the horizontal. In a preferred development of the method, the column may be vibrated either continuously or intermittently to influence the stem elongation of the plants. The effect of vibration is to reduce internodal distance, and to cause thickening of the tissue, thus improving fruit weight and quality. By vibrating the column, it may be possible to increase the density of fruit due to the reduced spacing between fruiting trusses on each plant. In a second technique for growing vine-type plants, shown in Figure 3, the vertical spacing between the ledges 2 is decreased, allowing more ledges 2 to be mounted on each column 1. A spacing of 50 to 75 cm is preferred. Rooted cuttings p1 , p2 are planted in a growth medium on the ledges 2 as before, and are grown vertically until a flowering truss has developed. Growth is continued until the stem develops one further leaf, and the growing tip is then pinched off. This effectively stops elongation of the plant stem and the plant then devotes its energy to producing fruit from the flowering truss. When the fruit is ripe, the fruit is harvested and the plant removed from the ledge 2 and discarded or composted to provide a supply of nutrient extracts or growth medium. The pinched-off tips may be rooted, grown on to a transplantable size, and eventually used to replace the plants removed after harvesting. In order to provide uniform illumination to the plants on each column, each column will ideally be surrounded by vertically extending linear light sources which radiate light in a generally horizontal direction towards the column. To further ensure uniformity of illumination, the column 1 may be rotated about its vertical axis. This horizontal illumination of the column and plants effectively overcomes a major problem of the prior art methods, which is that the developing leaf canopy will progressively obscure the lower leaves of the vines from light and thus diminish the potential yield of the plant. By illuminating the columns from the side, using an intense source of light whose radiation wavelengths are readily accessible to the plant, each of the sets of leaves developed by the plant will be illuminated to its maximum capacity for its entire useful life, since new leaves developed by the plant will be spaced from the previous leaves in a direction substantially perpendicular to the incident light. The yield of the plants can be further enhanced by increasing the time for which illumination is provided, and it is envisaged that in a greenhouse or growing enclosure, a number of columns 1 will be mounted in rows, and radiation sources will be placed on either side of these rows to provide lateral illumination for the plants. The columns will preferably be rotated so as to provide uniform illumination to each of the plants, and may be mounted for translational movement so that a number of columns may be placed in an illuminated area in the greenhouse or enclosure, while a further plurality of columns is placed in an unilluminated area to simulate night conditions for the plants. Each column may be rotatably mounted on a base which is movable on the floor of the growing enclosure, this translational movement preferably being achieved by mounting the base on wheels which ride on tracks laid on the floor. To increase further the number of plants which can be accommodated in the enclosure, a number of columns may be mounted on a common base for rotation about their own axes. In a further alternative, a plurality of columns may be mounted on a movable base for both individual rotation about their axes and for rotation as an array about a central vertical axis. It is envisaged that bases will move to and fro along tracks laid along the enclosure, and the rotation of bases and/or columns will be arranged to facilitate columns passing each other closely, without damage to plants growing thereon. Bases or columns may rotate in senses arranged so as to 'mesh' the plants carried on columns which are passing along adjacent tracks in opposite directions. Alternatively, the enclosure may be provided with a fixed array of rotatable columns in ranks and files, and arrays of movable light sources which can be disposed between selected rows of the columns, or round individual columns, to provide illumination to selected plants. Yield can be further improved by closely spacing the columns, with the direction of rotation of each column being in the sense opposite to that of its immediate neighbours. If a daily cycle of twelve hour periods of light and darkness is required for the plants growing on the columns, then the relative numbers of columns 1 and light sources 6 provided in the greenhouse will have to be such that the light sources 6 can illuminate 50% of the columns at any time. If a daily cycle of eight hours of light followed by sixteen hours of darkness is felt sufficient, then an array of light sources 6 sufficient to illuminate one third of the columns 1 will be needed. Either the columns 1 can be made movable, so as to bring the plants into the illuminated area on a sequential basis, or the light sources 6 may be movable so that the light sources can be moved to illuminate the plants in turn. To increase the degree of illumination still further, it is foreseen that an elongated light source may be positioned within the columns, preferably to extend along the axis of each of the columns 1 , so as to emit light in radial directions to illuminate leaves of the plants from within the column. In such an arrangement, it will of course be advantageous to make the structure of the cylindrical column 1 as open as possible, i.e. maximising the amount of perforation so that light may pass easily through the wall of the column 1. This will not only encourage the growth of leaves on the interior surface of the column 1 which can be directly illuminated from the axial light source, but will also allow any light from the axial light source which is not incident on inwardly facing leaves to pass through the wall of the column 1 and thus be available for the illumination of leaves formed outside the column. It is also foreseen that illumination may be provided only from within the column, with no external light ε ces. In an alte tive configuration of the columns (not shown) the shelves for supporting the growing medium may be omitted, and cup-like receptacles (pots) or blocks of growth substrate may be provided in the cylindrical wall of the column to receive the plants. Alternatively, the columns may be of mesh construction and modified plant pots, to which fixing means have been added, may be attached to the columns or to vertically movable mountings attached to the columns. Each plant pot will be lidded to prevent loss of the growing medium, and irrigation of the plants may be effected by linking each pot to a water supply through a metering valve. The metering valve may be associated with the individual plant pot, and may control the supply of water in dependence on the dryness or moisture of the growing medium therein. The receptacles are so arranged that the plant pots are received with the plant stems extending radially in relation to the cylindrical column, and horizontally. To overcome any geotropic effects, the receptacles may be caused to rotate about their horizontal axes at fixed or variable speeds. A rotational speed of 3 revolutions per hour has been found sufficient to produce growth in a horizontal direction, in a plant whose stem is horizontally aligned. In such an arrangement, stemmed plants such as flowers may be grown in the vertical column structures, using illumination from vertically arranged linear light sources extending between the columns. The amount of natural light received by the plants is made uniform by the cyclic vertical movement of the plants relative to the column, exposing each plant to equal intervals at all vertical locations on the column. In this way, high population densities of potted plants may be grown under uniform controlled conditions of illumination and temperature, as has previously been described in relation to the vine plants. Due to the convex nature of the surface on which the plants are grown, the directions of the stems of neighbouring plants are divergent, and the spacing between stems increases as the stems elongate to provide space for the lateral expansion of the plant. Utilising this effect, the circumferential spacing between adjacent receptacles can be reduced to a distance less than that which has to be provided for potted plants growing on a plane surface. Thus, further concentration of the plant population is possible. It is further foreseen that the speed of rotation of the individual plant receptacles may be controlled, to provide a constant rotation or a stepwise indexing of the plants about their respective axes. In a development of this technique, the potted plants are grown to the required height by maintaining the rotational speed about the horizontal axis at or above 3 revolutions per hour, and then pinching out the growing tip of the stem. The rate of rotation about the horizontal axis is then decreased to below 3 revolutions per hour, either as a constant rotation or as a stepwise indexing motion, which has the effect of producing a fuller, 'bushier' plant. Individual pots or growing medium substrates may, in a further embodiment, be mounted for rotation about horizontal axes and for vertical translational motion on columns, to be used for growing vine-type plants in a generally horizontal direction. In this embodiment, each pot or substrate is planted with one or more cuttings, and is provided round its circumference with a number of parallel stakes extending horizontally, i.e. parallel to the plant stem. The plant is grown between the stakes by controlling the rotational speed to produce a first growth parallel to the stakes, then rotation is slowed to produce radial growth towards a stake. When the plant tip reaches the stake, rotation is speeded up to promote growth along the stake direction. After a determined interval, or when a determined length along the stake is reached, rotation is again slowed to produce radial growth towards an adjacent stake. The cycle is repeated to produce a plant growing spirally in steps between the stakes. Although the method is particularly suited to the growing of crop-bearing vine type plants such as beans, tomatoes, cucumbers etc, it is envisaged that it may be applied also to plants whose normal growth format is generally characterised by horizontal stems from the upper surfaces of which flowers and leaves usually extend generally upwardly. By controlling the rate of rotation of such a plant in a pot mounted horizontally on a column for rotation about a horizontal axis, the usually horizontal stem could be induced to grow in a direction generally away from the pot, i.e. in a direction which will be vertical when the pot is placed upright. The speed of rotation may be controllable to produce linear growth, or spiral growth if the speed is reduced or an indexed rotation applied. Shoots, flowers and leaves could then grow so as to extend generally perpendicularly to the stem, but in various radial directions relative to the stem. As has been briefly discussed, the columns maybe mounted on tracks for movement about the interior of the greenhouse or growing enclosure, and the light sources may likewise be movable. The columns are rotated about their vertical axes to ensure uniform illumination of the plants. Harvesting may take place at a fixed harvesting station, to which the columns are brought in succession, or a mobile harvester unit may pass among rows of columns to effect the collection of fruit or other plant products such as foliage or cuttings. Robotic plant handling and harvesting techniques are considered desirable in conjunction with the growing columns of the present invention.

Claims: CLAIMS 1. A method for the cultivation of plants, comprising positioning a plurality of plants in a number of vertically spaced rows extending circumferentially about a rotating column, and arranging a vertically extending linear array of light sources to illuminate the plants with light from a horizontal direction. 2. A method according to Claim 1 , wherein a number of vertically extending linear light sources are arranged substantially paraxially with and surrounding the column. 3. A method according to Claim 1 , wherein a vertically extending linear light source is placed within the column. 4. A method according to Claim 3, wherein the linear light source extends along the axis of the column. 5. A method according to Claim 1 , wherein a vertically extending linear light source is placed within the column, and a number of vertically extending linear light sources are arranged substantially paraxially with and surrounding the column. 6. An installation for the cultivation of plants, comprising a vertical column rotatable about its axis, the column having at least one circumferentially extending growing area wherein plants may be rooted in a growth substrate, the column providing means for supporting and training the plants for growth in a predetermined direction, and the installation further comprising at least one vertically extending linear light source providing illumination to the plants. 7. An installation according to claim 6, wherein a number of vertically extending linear light sources are arranged substantially paraxially with and surrounding the column. 8. An installation according to claim 6, wherein a vertically extending linear light source is placed within the column. 9. An installation according to any of Claims 6 to 8, wherein the column is circular in horizontal section. 10. An installation according to any of claims 6 to 8, wherein the column is polygonal in horizontal section. 11. An installation according to any of claims 6 to 8, wherein the column is formed from an open mesh or of wire. 12. An installation according to any of claims 6 to 8, wherein the column is formed from perforated sheet material or expanded metal sheet. 13. An installation according to any of claims 6 to 8, wherein the column comprises a number of vertically extending cords or wires hanging from an upper supporting ring. 14. An installation according to any of Claims 6 to 13, wherein a plurality of columns are mounted in rows in an enclosure, and radiation sources are placed at locations between these rows to provide lateral illumination for the plants, the columns being rotated so as to provide uniform illumination to each of the plants. 15. An installation according to Claim 14, wherein the light sources are fixed to define an illuminated area of the enclosure, and the columns are mounted for translational movement, so that a number of columns may be placed in the illuminated area in the greenhouse while a further plurality of columns may be placed in an unilluminated area. 16. An installation according to Claim 14, wherein the enclosure has a fixed array of rotatable columns and arrays of movable light sources which can be disposed between selective rows of the columns to provide illumination to selected plants. 17. An installation according to Claim 14, wherein each column comprises a plurality of cup-like receptacles (pots) or blocks of growth substrate provided in the cylindrical wall of the column so as to be rotatable about a respective axis extending horizontally and radially in relation to the cylindrical column, each receptacle capable of receiving a plant with the plant stem extending in the direction of that axis. 18. An installation according to Claim 14, wherein each cup-like receptacle or block of growth substrate is movable vertically relative to the column.

Inventors: SPARKES A GRAHAM, SPARKES, A., GRAHAM
Applicants: M & J LTD, SPARKES A GRAHAM, M & J LIMITED, SPARKES, A., GRAHAM
Application year: 1997
Main classification: A01G31
IPC codes: A01G31