System and method for irradiating a plurality of plants

Abstract

Systems and methods are disclosed for irradiating a plurality of plants (11). The system (1) comprises an irradiation system (3) that is configured to irradiate the plurality of plants (11) with radiation having one or more controllable radiation properties, and a data processing system (100), communicatively connected to the irradiation system (3). The data processing system (100) comprises an input interface for receiving a signal indicative of a state of a plant canopy, an output interface for sending a control signal to the irradiation system, and a processor. The processor is configured to receive a signal indicative of a state of a plant canopy formed by the plurality of plants (11), to determine whether or not the plant canopy is closed, based on the received signal indicative of the state of the plant canopy, and to send the control signal to the irradiation system (3), the control signal being based on the determined canopy closure. The irradiation system (3) is configured to switch, based on the received control signal, from irradiating the plurality of plants (11) in accordance with a first radiation recipe to irradiating the plurality of plants (11) in accordance with a second radiation recipe, different from the first radiation recipe.

Description

[0001] System and method for irradiating a plurality of plants

[0002] TECHNICAL FIELD

[0003] This disclosure relates to a system and method for irradiating a plurality of plants, in particular to such system wherein a radiation recipe is determined based on plant properties. This disclosure further relates to a computer-implemented method for irradiating a plurality of plants and to a computer program and computer-readable storage medium for performing such method.

[0004] BACKGROUND

[0005] Indoor production of food in vertical farms (VF) is only economically viable in case plant growth can be done year-round in an efficient way. Light Use Efficiency (LUE), which relates the biomass production to the integral amount of light used for the production, as well as crop quality, for example post-harvest shelf-life, are key value drivers. There is therefore a need in the art to increase light use efficiency without negatively affecting crop quality.

[0006] One aspect that reduces light use efficiency is that in the first growth phase, directly after transplanting young plants from high plant-density trays to a lower-density tray, a (relatively large) fraction of the radiation ends up between the plants. Although this light may — after scattering or reflection on the tray surface — get anew change of being absorbed by the leaves, part of the light energy is lost, leading to a sub-optimal light use efficiency.

[0007] CN1 12015212A describes a system that identifies plant canopy information such as plant biomass, canopy shape, canopy area or plant position with a camera; determines a light-emitting area of a lighting device corresponding to a luminous area covering the canopy area; and controls the lighting device to control the illumination in said luminous area based on said plant canopy information. However, this requires specific lighting devices that can very precisely adjust their luminous area, which most lighting devices currently on the market cannot do.

[0008] US 11089736 B2 describes a horticultural lighting device comprising different groups of LEDs, each group adapted to generate an emission spectrum having a different peak wavelength. The horticultural lighting device also comprises a forward-facing sensor in the form of a low resolution monochromatic CMOS device for measuring plant density. When the measured plant density reaches a pre-determined level, then this indicates that the light spectrum should be changes to a next spectrum required in the plant growing cycle, which can be done by an automatic switching arrangement via control software.

[0009] In light of the above, there is a need in the art for a system and method for irradiating a plurality of plants that increases the light use efficiency.

[0010] SUMMARY

[0011] To that end, a system for irradiating a plurality of plants is disclosed. The system comprises an irradiation system that is configured to irradiate the plurality of plants with radiation having one or more controllable radiation properties, and a data processing system, communicatively connected to the irradiation system. The data processing system comprises an input interface for receiving a signal indicative of a state of a plant canopy, an output interface for sending a control signal to the irradiation system, and a processor. The processor is configured to receive a signal indicative of a state of a plant canopy formed by the plurality of plants, to determine whether or not the plant canopy is closed, based on the received signal indicative of the state of the plant canopy, and to send the control signal to the irradiation system, the control signal being based on the canopy being determined to be closed. The irradiation system is configured to switch, based on the received control signal, from irradiating the plurality of plants in accordance with a first radiation recipe to irradiating the plurality of plants in accordance with a second radiation recipe, different from the first radiation recipe.

[0012] The state of the plant canopy may refer, for instance, to a coverage of the plant canopy, to a density of the plant canopy, to a degree of contiguity of the plant area, or to a different relevant parameter or combination of parameters. For example, the coverage of the plant canopy can be defined as a projected plant canopy area versus a ground (tray) area (e.g., in m2of % ). The density of the plant canopy can be determined, e.g., using light sensor data, based on different absorptive and reflective properties of the plant canopy and the background. The degree of contiguity of the plant canopy, can be defined, e.g., as a number of plant-to-plant overlaps in the plant canopy, or as a number of contiguous areas in the plant canopy (which starts at the number of plants and decreases to 1 when all plants are in contact with each other). The state of the plant canopy may be determined based on data representative of only part of the plant canopy, e.g., a field of view of a camera. The state of the plant canopy can also be a binary state corresponding to (typically) ‘closed’ and ‘not closed’, e.g., based on human input.

[0013] In general, the irradiation system is configured to irradiate the plurality of plants in accordance with the first radiation recipe if the processor has determined that the plant canopy is not closed, and in accordance with the second radiation recipe if the processor has determined that the plant canopy is closed. Typically, the first light recipe (i.e. , before the plant canopy is closed) is optimised for plant growth (in particular lateral growth), as light that is not absorbed by the canopy may be wasted, leading to a relatively low light use efficiency (LUE). However, once the canopy is closed substantially all available light is absorbed by the canopy, and hence the second light recipe may be optimised for stimulating different plant aspects (e.g., dense growth, production of more valuable assimilates, et cetera).

[0014] The irradiation system may comprise one or more controllable radiation sources, and / or one or more controllable radiation filters and / or radiation concentrators (possibly in combination with a ‘fixed’ radiation source, i.e., a radiation source providing radiation with fixed radiation properties).

[0015] In an aspect, this disclosure relates to a horticulture arrangement comprising such a system. The term “horticulture arrangement” especially refers to an arrangement including a plant support wherein or whereon plants may grow, an irradiation system that is configured to direct (horticulture) radiation to the plant support wherein or whereon the plants may grow (or grow), and a control system that controls the (horticulture) radiation. The control system may comprise or be communicatively connected to the data processing system.

[0016] In use, the horticulture arrangement may include a plant support with a plant, or a plant support with a seed, or a plant support with a seedling, etc. Herein, the term “plant” is used for essentially all stages of plant development.

[0017] Growing radiation typically comprises a mixture of red and blue radiation. Red radiation may be understood as radiation having a wavelength between 600-700 nm, whereas far-red radiation may be understood as radiation having a wavelength between 700- 780 nm. Blue radiation may be understood as radiation having a wavelength between 400- 500 nm, and may include deep-blue radiation, which may be understood as radiation having a wavelength between 400-425 nm. Green radiation may be understood as radiation having a wavelength between 500-600 nm. Radiation with a wavelength shorter than 400 nm, in particular radiation with a wavelength between 10-400 nm, may be referred to as ultraviolet radiation. Radiation with a wavelength longer than 780 nm, may be referred to as infrared radiation; in particular, radiation with a wavelength between 780-2500 nm may be referred to as near infrared radiation.

[0018] In particular, the term “horticulture radiation” especially refers to radiation having one or more wavelengths in one or more of a first wavelength region of 625-675 nm and a second wavelength region of 400-475 nm. Additionally, green or white light may be added. The relative energies (expressed in, e.g., W / m2) that are provided in these regions may depend upon the type of plant and / or the growth phase. Hence, a recipe may define the ratio, optionally as a function of time, for one or more types of plants. Especially, the term “horticulture radiation” may refer to the PAR region (the photosynthetically active region from 400-700 nm, i.e., red+green+blue). The term “horticulture radiation” may also be used for radiation that is applied to plants in hydroponic applications. As known in the art, in the PAR region the reflection coefficient of leaves is very low (5-10% for red and blue light, 15- 25% for green light). Towards the far-red and near infrared, beyond 700 nm, the reflection coefficient increases. Hence, in specific embodiments, the horticulture radiation, may in addition to PAR radiation also include a small fraction (e.g., <25 % of the power, especially about at maximum 10 % of the power) far-red, i.e., 700-780 nm and near-infrared, e.g., 750- 850 nm.

[0019] When pre-harvest radiation is offered, this is generally meant to stress the plants such that the plants will respond by producing some compound of interest (e.g., nutritional content, colorants, taste compounds, et cetera). Such pre-harvest radiation typically contains a large fraction of blue radiation (e.g., about 450 nm), and / or UV-A radiation (i.e., radiation with a wavelength between 315-400 nm; e.g., 385-400 nm) and / or radiation levels in excess of 50 pmol m2s '. In some cases, UV-B radiation can also be applied beneficially. In general, plants may be sensitive both to absolute intensities of certain wavelengths and to relative intensities of different wavelengths.

[0020] The term “horticulture arrangement” may also refer to a plant farm or climate cell, wherein the plants are grown under controlled conditions, and wherein the plants substantially do not receive natural radiation (daylight). Further, such plant farm may be climatized, such as in the case of a climate cell. Hence, in embodiments, the horticulture arrangement includes such plant farm or climate cell. In other embodiments, the plant farm or climate cell includes at least part of the horticulture arrangement. For instance, a climate cell may comprise the plant support and the irradiation system, and the control system may be configured inside or external from the climate cell. Especially, a plant farm may comprise a climate cell.

[0021] The control system of such horticulture arrangement may control one or more of temperature, humidity, CO2 level, irrigation, nutrient supply, radiation intensity (irradiance) of the horticulture radiation, air conditions including one or more of air temperature, air composition, air flow, etc. The radiation intensity as received by the plurality of plants may refer to, e.g., physical quantity “irradiance” (typically expressed in W / m2) or “photon flux density” (typically expressed in pmol / (m2s)). Such horticulture system may be configured to control one or more of these conditions at different locations in the arrangement. Hence, the irradiation with the horticulture radiation may in embodiments be done in response to, e.g., one or more of time of the day, season of the year, (local) irradiation conditions, age of plant, condition of the plant, planting period, etc. Hence, the irradiation with the horticulture radiation may in embodiments be done in response to plant related data, time related parameters, conditions to which the plant is subjected (such as natural radiation, temperature, relative humidity, CO2 level, irrigation, nutrient supply, etc.).

[0022] The horticulture irradiation system is especially configured to provide horticulture radiation to plants. This may especially imply that the horticulture irradiation system is configured to provide horticulture radiation in a direction of a plant support wherein or whereon plants may grow. Such plant support may be a tray. Especially, the term “plant support” may also refer to a plurality of plant supports, as the plants may be grown in layers one over the other (“multi-layer system”). Hence, racks with each two or more plant supports, with over each plant support a radiation system. Hence, the term “irradiation system” may also refer to a plurality of (individually controlled) irradiation systems.

[0023] Further, the control system is configured to control one or more of a radiation intensity and a spectral distribution of the horticulture radiation. The term “controlling” and similar terms especially refer at least to determining the behaviour or supervising the running of an element. Hence, herein “controlling” and similar terms may, e.g., refer to imposing behaviour to the element (determining the behaviour or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behaviour.

[0024] The phrase “one or more of a radiation intensity and a spectral distribution of the horticulture radiation” may refer to the total spectral distribution of the horticulture radiation, i.e. the power, especially in the visible, provided by the irradiation system. However, in specific embodiments the control system may also be configured to control the spectral distribution, e.g. reducing or increasing parts of the spectral distribution relative to other parts of the spectral distribution. Hence, in embodiments the control system may be configured to control one or more of the intensity and the spectral distribution of the horticulture radiation, for instance in dependence of the one or more optical sensor signals.

[0025] As indicated above, the control system is configured to control one or more of a radiation intensity and a spectral distribution of horticulture radiation in dependence of the canopy being closed in at least part of the horticulture arrangement.

[0026] The controllable radiation sources can be, e.g., LED radiation sources, HID radiation sources, laser radiation sources, or other suitable radiation sources. The one or more controllable radiation sources may include means for controlled interaction with the plants, e.g., through filtering and / or concentrating the generated radiation, and / or through modifying the flow rate of, and hence interaction time with, the plants. The radiation filters may be configured to selectively block, in part or in full, radiation of one or more predetermined wavelength regions. The radiation concentrators may be configured to concentrate radiation on the plants, e.g., using a lens or mirror. Filters and concentrators can also be combined, e.g., by wavelength conversion, reducing an intensity of radiation of a first wavelength (filtering) while increasing radiation of a second wavelength (concentrating).

[0027] The one or more radiation filters may have, for instance, controllable radiation filtering properties and / or a controllable position. Similarly, the one or more radiation concentrators may have, for instance, controllable radiation concentrating properties and / or a controllable position. The controllable position may allow the filters and / or concentrators to be selectively inserted and removed between a radiation source and the plants.

[0028] In the disclosed system for irradiating a plurality of plants, the first radiation recipe comprises a higher far-red dose than the second radiation recipe. Additionally or alternatively, the first radiation recipe may comprise a lower blue, deep-blue, and / or ultraviolet radiation dose than the second radiation recipe.

[0029] Typically, for a high light use efficiency, the time that it takes to close the canopy, should be as short as possible. It is observed that, by adding far-red light in the spectrum, this time can be shortened. As soon as the canopy is closed, growth will continue, but the effect of additional far-red light will be negligible. Therefore, after closure of the canopy, the far-red light may be removed from the radiation recipe, reducing energy use of the radiation system. By contrast, blue and ultraviolet light tend to reduce the growth rate of the plants (but may have other beneficial effects), and therefore, the first radiation recipe may comprise a relatively low blue / UV dose in order to promote rapid plant growth until the canopy is closed.

[0030] In an embodiment, the signal indicative of the state of the plant canopy is a signal indicating that the plant canopy is closed. In such an embodiment, the data processing system may be configured to determine that the plant canopy is not closed prior to reception of the signal and to determine that the plant canopy is closed after reception of the signal.

[0031] The signal indicating that the plant canopy is closed may be received from, e.g., an image processing system that monitors the plant canopy (as described below), or from a user interface where a human operator toggles a switch when the canopy is considered closed. In the latter case, determining whether or not the canopy is closed may be done by eye.

[0032] In an embodiment, the system further comprises an image processing system configured to receive an image representing a plant canopy formed by the plurality of plants, and to determine, based on the image, whether or not the plant canopy is closed.

[0033] The image processing system may be integrated into the data processing system. Alternatively, the image processing system can be external to the data processing system, e.g., in the form of a smartphone or tablet with image processing software, or in the form of a dedicated monitoring system.

[0034] The plant canopy may be considered to be closed when a predetermined percentage of the pixels in the image represent the plant canopy. The predetermined percentage of the pixels can be at least 80%, at least 85%, at least 90%, 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% of the pixels in the image.

[0035] Counting pixels representing the plant canopy is typically a relatively simple and reliable method. The plant tray or table which usually forms the background, or at least a substantial part thereof, often has a colour that contrasts with the plant canopy; for example, the tray may be configured to reflect the light, while the plants absorb the light. Depending on the light source being active when the image is obtained, pixels representing the plant canopy may be identified, e.g., by a relatively high green value (reflected by the leaves) and / or a relatively low red value (absorbed by the leaves).

[0036] In an embodiment, the plant canopy is considered to be closed when a predetermined percentage of the plurality of plants touches at least a predetermined number greater than zero of its neighbours. For example, the predetermined number of neighbours can be one neighbour, or all neighbours, or all-but-one neighbours, et cetera. The predetermined percentage of the plurality of plants can be, e.g., at least 50 %, at least 75 %, at least 90 %, at least 95 %, at least 99 %, or 100 %.

[0037] In an embodiment, the system further comprises a camera, communicatively connected to the image processing system, for obtaining the image of a plant canopy formed by the plurality of plants. As an example, the camera may be mounted overhead the plurality of plants in order to obtain a top-view of the canopy formed by the plurality of plants.

[0038] In an embodiment, the switch from the first to the second radiation recipe may be delayed by a predetermined amount of time after closure of the canopy.

[0039] For example, the data processing system may be configured to cause the irradiation system to irradiate the plurality of plants in accordance with the first radiation recipe during a predetermined amount of time after a first moment when the plant canopy is considered closed, and in accordance with the second radiation recipe after the predetermined amount of time after the first moment when the plant canopy is considered closed. This may be achieved, for instance, by delaying the sending of the control signal.

[0040] Alternatively, the irradiation system may be configured to switch from irradiating the plurality of plants in accordance with the first radiation recipe to irradiating the plurality of plants in accordance with the second radiation recipe after the predetermined amount of time after the control signal has been received by the irradiation system.

[0041] The predetermined amount of time can be one of: one day, two days, three days, four days, five days, or six or more days.

[0042] Waiting a few days, e.g., about 1-7 days, after the condition is first met ensures that the canopy is sufficiently thick everywhere. The optimal number of days between the canopy closing and switching the light recipes may depend on the plant being grown.

[0043] In an embodiment, each of the first and second radiation recipes defines, for a particular time period, one or more properties of radiation (to be) provided to the plurality of plants.

[0044] The data processing system may be configured to cause the irradiation system to generate radiation such that the radiation has the photon flux and / or photon flux density and / or the spectral power distribution and / or the timing of the irradiation as defined by the first and second radiation recipes, respectively.

[0045] The one or more properties of radiation may comprise at least one of:

[0046] - a photon flux of the radiation as generated by the irradiation system, - a photon flux density of the radiation as received by the plurality of plants,

[0047] - a spectral power distribution of the radiation generated by the irradiation system, and

[0048] - a timing of the irradiation.

[0049] The timing of the irradiation may refer to the photoperiod (expressed as, e.g., a number of hours per day) and / or to the schedule of the irradiation (i.e., at which hours of the day).

[0050] In such an embodiment, the data processing system may be configured to cause the irradiation system to generate radiation such that the radiation has the photon flux and / or photon flux density and / or the spectral power distribution and / or the timing of the irradiation as defined by the first and second radiation recipes, respectively.

[0051] The timing of the irradiation may include temporal variation of the photon flux (density) and / or spectral power distribution, and / or the duration of the irradiation. The photon flux density may be defined, e.g., in pmol / (m2s), or in any other useful quantity.

[0052] In an aspect, the disclosure relates to a computer-implemented method for irradiating a plurality of plants, the method comprising receiving a signal indicative of a state of a plant canopy formed by the plurality of plants; determining whether or not the plant canopy is closed, based on the received signal indicative of the state of the plant canopy; and sending a control signal to an irradiation system, the control signal being based on the determined canopy closure. The control signal may configure the irradiation system to switch from irradiating the plurality of plants in accordance with a first radiation recipe to irradiating the plurality of plants in accordance with a second radiation recipe, different from the first radiation recipe.

[0053] In particular, the control signal may cause the irradiation system to irradiate the plurality of plants in accordance with the first radiation recipe if the plant canopy is not closed, and in accordance with the second radiation recipe if the plant canopy is closed.

[0054] Thus, a system as described above may be controlled using this method. The method may be executed, for example, by the data processing system described above.

[0055] One aspect of this disclosure relates to a computer comprising a computer readable storage medium having computer readable program code embodied therewith, and a processor, preferably a microprocessor, coupled to the computer readable storage medium, wherein responsive to executing the computer readable program code, the processor is configured to perform any of the methods disclosed herein. One aspect of this disclosure relates to a computer program or suite of computer programs comprising at least one software code portion or a computer program product storing at least one software code portion, the software code portion, when run on a computer system, being configured for executing any of the methods disclosed herein.

[0056] One aspect of this disclosure relates to a non-transitory computer-readable storage medium storing at least one software code portion, the software code portion, when executed or processed by a computer, is configured to perform any of the methods disclosed herein.

[0057] As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, a method or a computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Functions described in this disclosure may be implemented as an algorithm executed by a processor / microprocessor of a computer. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied, e.g., stored, thereon.

[0058] Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer readable storage medium may include, but are not limited to, the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of the present invention, a computer readable storage medium may be any tangible medium that can contain, or store, a program for use by or in connection with an instruction execution system, apparatus, or device.

[0059] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0060] Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber, cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java™, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user’s computer, partly on the user’s computer, as a stand-alone software package, partly on the user’s computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user’s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0061] Aspects of the present invention are described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products as claimed in embodiments of the present invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor, in particular a microprocessor or a central processing unit (CPU), of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer, other programmable data processing apparatus, or other devices create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0062] These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0063] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0064] The flowchart diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products as claimed in various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0065] Moreover, a computer program for carrying out the methods described herein, as well as a non-transitory computer readable storage-medium storing the computer program are provided. A computer program may, for example, be downloaded (updated) to the existing systems (e.g., to the existing control systems) or be stored upon manufacturing of these systems.

[0066] Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise. Embodiments of the present invention will be further illustrated with reference to the attached drawings, which schematically will show embodiments as claimed in the invention. It will be understood that the present invention is not in any way restricted to these specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Aspects of the invention will be explained in greater detail by reference to exemplary embodiments shown in the drawings, in which:

[0068] FIG. 1 schematically illustrates a system for irradiating a plurality of plants according to an embodiment;

[0069] FIG. 2A-2D schematically show a canopy formed by a plurality of plants at various stages of closing; and

[0070] FIG. 2E and 2F show images of a canopy formed by a plurality of plants at various stages of closing;

[0071] FIG. 3A and 3B are flow charts illustrating embodiment of the method;

[0072] FIG. 4 is a graph showing the effect of light spectrum on shelf-life for wild rocket; and

[0073] FIG. 5 illustrates a data processing system according to an embodiment.

[0074] DETAILED DESCRIPTION OF THE DRAWINGS

[0075] In the figures, identical reference numbers indicate identical or similar elements.

[0076] Currently, in vertical farming, radiation recipes are specifically optimized per crop and stay constant during growth, in particular for food production. However, there is ample evidence that plants could benefit from different light treatments depending on their growth phase.

[0077] For example, it is known that for the growth of, e.g., lettuce and similar leafy vegetables, adding far-red (FR, typically about 730 nm) lighting to the standard redblue (RB, typically about 660 nm and about 450 nm, respectively) spectrum, induces stretching of leaves. With this increased leaf area, more light can be intercepted, leading to faster biomass production. However, this addition of far-red radiation in the spectrum might result in a decreased quality in terms of plant morphology, pigment concentration and shelflife. A higher blue dose will have the exact opposite effect on morphology than far-red does: it reduces the final fresh weight significantly, makes plants more compact, and can reduce the number of leaves per plant or canopy area, but can result in an increased quality, pigment concentration, and shelflife.

[0078] Thus radiation recipes have been created that start with a spectrum with a relatively large amount of red and / or far red and a relatively low amount of blue, deep-blue, or ultraviolet. Then, in the last days before harvest, the spectrum is changed to a so-called pre-harvest spectrum with additional blue, deep-blue, and / or ultraviolet in the spectrum and less or no far-red, to improve crop quality, for example to create coloration, to increase vitamin C content or to reduce nitrate content.

[0079] Not only plant quality can benefit from these plant phase dependent radiation recipes, but also the Light Use Efficiency (LUE, typically expressed in gram of harvested crop per mol of photons) can be improved. Dimmable and colour-controllable light fixtures are recently becoming available, offering the possibility to further improve the LUE, while balancing plant yield and quality, by offering radiation recipes depending on the plant growth phase.

[0080] Fig. 1 schematically illustrates a system for irradiating a plurality of plants according to a first embodiment. The system 1 comprises an irradiation system 3 that is configured to irradiate the plurality of plants 11. The irradiation system comprises a plurality of controllable radiation sources 5. The controllable radiation sources may comprise, e.g., a plurality of individually or group-wise controllable LEDs. In this example, the radiation sources 5 are controlled by controller 7. The radiation sources may be configured to provide, e.g., growth or horticulture radiation. The controller may control one or more of: a radiation intensity and a spectral distribution of the horticulture radiation.

[0081] The system 1 also comprises a data processing system 100, communicatively connected to the irradiation system 3. The data processing system comprises a processor, an input interface, and an output interface. The input interface and output interface may be combined in a single I / O interface, e.g., a (general) communication interface. In particular, the data processing system may be configured to generate and transmit control signals, via the output interface, to the controller 7, which controller may be configured to receive said control signals and control the radiation sources 5 accordingly. An example of a data processing system is described in more detail below with reference to Fig. 5.

[0082] The data processing system 100 is configured to receive or determine an indication of whether or not a plant canopy formed by the plurality of plants 11 is closed. For example, the data processing may be configured to receive a signal indicative of a state of a plant canopy formed by the plurality of plants 11 and to determine whether or not the plant canopy is closed, based on the received signal indicative of the state of the plant canopy. The canopy may be defined as an area covered by the plurality of plants, or more specifically covered by photosynthetically active parts of the plants, such as leaves. In the depicted embodiment, the data processing system 100 receives a parameter representative of a canopy state from an image processing system 9. In some embodiments, the image processing system 9 may be part of the data processing system 100. The canopy state can be binary (e.g., open / closed) or multivalued (e.g., a relative area covered by the canopy). Examples of a canopy state are discussed in more detail below with reference to Fig. 2.

[0083] The data processing system 100 is further configured to cause the irradiation system 3 to irradiate the plurality of plants in dependence on the canopy state, in particular in dependence on the canopy formed by the plurality of plants 11 being considered closed or not. For example, the data processing system 100 may cause the irradiation system 3 to switch from a first radiation recipe to a second radiation recipe, different from the first radiation recipe, based on a closure of the canopy. In atypical example, the first radiation recipe is optimised for growth, in particular lateral growth. The first radiation recipe may comprise a relative large amount of red and / or far-red radiation. The second radiation recipe may be optimised for a different parameter; in general, a radiation recipe optimised for fast growth leads to plants that have suboptimal characteristics in other aspects, e.g., shelf life, presence / or concentration of valuable assimilates (such as vitamins, alkaloids, et cetera), plant health, et cetera. In some cases, the second radiation recipe comprises a larger amount of blue radiation, deep-blue, and / or ultraviolet radiation and / or a smaller amount of far-red radiation than the first radiation recipe. The switching moment from the first to the second radiation recipe depends on the canopy of the plurality of plants being closed. The switching moment can be essentially directly after the canopy is considered closed, or with some delay, e.g., one day, two days, three days, four days, five days, or six or more days after the canopy is first considered closed.

[0084] It is noted that the irradiation system need not switch from the first to the second radiation recipe in its entirety at the same time. For example, if only part of the canopy is considered closed, only the irradiation sources irradiating that part of the canopy may switch to the second radiation recipe, whereas the irradiation sources irradiating a nonclosed part of the canopy continue to irradiate according to the first radiation recipe.

[0085] Thus, the system 1 may be configured to improve light use efficiency by promoting growth (in particular lateral growth) when the canopy is not closed in order to maximise the light uptake by the plurality of plants 11. Once the canopy is substantially closed, a differently optimised radiation recipe may be used.

[0086] The irradiation system 3 may comprise at least one radiation source 5. In a typical embodiment, the irradiation system comprises a plurality of radiation sources 5, typically controllable radiation sources, e.g., LEDs, for generating artificial radiation. Additionally or alternatively, the irradiation system 3 may comprise one or more controllable radiation filters and / or radiation concentrators. Such filters and / or concentrators can be used, for example, to control aspects of an artificially generated radiation spectrum that cannot be sufficiently controlled by the radiation sources.

[0087] The irradiation system may further comprise a controller 7. The controller 7 may comprise a processor and a memory communicatively coupled to the processor. The irradiation system 3 may comprise an interface to enable communication with data processing system 100. The irradiation system 3 is configurable to apply at least the first radiation recipe and the second radiation recipe to the plurality of plants 11.

[0088] The controllable radiation sources can be, e.g., LED radiation sources, HID radiation sources, or other suitable radiation sources. The one or more controllable radiation sources may include a radiation source with controlled interaction with the plants, e.g., through filtering and / or concentrating the natural radiation. In some embodiments, the plants are grown in or on a tray which is moveable relative to the radiation sources; in such a system, the interaction may be controlled (additionally or alternatively) through modifying the movement speed, and hence interaction time, of the plants. Alternatively, in such a system, the radiation recipe may ‘move along’ with the tray (while the radiation sources do not move) by having the data processing system or controller adjust the local radiation recipe based on the movement of the tray.

[0089] The radiation filters may be configured to selectively block, in part or in full, radiation of one or more predetermined wavelength regions. The radiation concentrators may be configured to concentrate radiation on the plants, e.g., using a lens or mirror. Filters and concentrators can also be combined, e.g., by wavelength conversion, reducing an intensity of radiation of a first wavelength (filtering) while increasing radiation of a second wavelength (concentrating).

[0090] For example, it is known that for various crops, far-red radiation can increase growth speed, but typically also reduces crop quality, while a high blue-spectrum is known to keep plants more compact (i.e., reduce growth speed), and to enhance e.g. antioxidant concentrations in leaves. Enhanced antioxidant concentrations potentially result in improved shelf life.

[0091] In general, (at least) two growth phases may be distinguished. In the first growth phase of leafy vegetables, when the first radiation recipe is applied, growth can be accelerated. The first radiation recipe typically comprises a relatively large amount, or at least a non-zero amount of far-red radiation. In the second phase, crop quality is prioritised. Therefore, the second radiation recipe typically comprises a relatively large amount, or at least a non-zero amount of blue radiation and / or ultraviolet radiation. Depending on the situation, additional pre-harvest treatments can be used, which may be optimized from, e.g., a light use efficiency and / or crop quality point of view.

[0092] It is noted that in some cases, more than two or three different radiation recipes may be used based on the development stage of the plants.

[0093] Fig. 2A-2D schematically show a canopy formed by a plurality of plants at various stages of closing. For comparison, Fig. 2E and 2F show images of an actual canopy formed by a plurality of plants at various stages of closing.

[0094] Fig. 2A-2D show schematic top views of a (low-density) plant tray 21 comprising a plurality of plants 11 at consecutive moments in time. The current example shows the plants arranged in a square grid, but other arrangements are also possible, e.g., a triangular grid. Evidently, actual plants are not exactly circular as is shown here, but many crops do grow in an approximately circular way (as seen from above), so that it is a reasonable approximation. Similarly, in reality the plants are not all exactly the same size, as shown here, but as they are typically grown in batches under substantially identical circumstances, the plants are typically of roughly equal size. The figures may represent, e.g., camera images obtained by a camera that is mounted overhead the plant tray. The plant tray may extend beyond the field of view of the camera in one or more directions, and the canopy visible in the field of view of the camera may be considered representative for the canopy of the plurality of plants.

[0095] Fig. 2A shows a case where the canopy is not closed. The plants do not remotely touch each other, and only slightly more than half (about 53%) of the area is covered by the plant canopy.

[0096] In Fig. 2B, the plants just start to touch each other. In some embodiments, this may be considered closure of the canopy. As in this schematic, all plants have the same size, they all start making contact with all their neighbours at the same time. In reality, there will be some variation due to variations in size and shape of the individual plants. Therefore, in some embodiments, the canopy may be considered closed if at least a predetermined fraction of neighbours make contact.

[0097] In a simple embodiment, the area covered by the canopy may be obtained by segmenting an image in canopy pixels and other pixels, and counting the canopy pixels. If the fraction of pixels representing the canopy (i.e., the canopy pixels) is above a predetermined threshold, the canopy may be considered closed, and if the fraction is below the threshold, the canopy may be considered not closed. The threshold for when the canopy is considered closed may depend on the geometry of the plant tray. For example, assuming circular plants like in Fig. 2B, the moment neighbouring plants start to touch each other corresponds to a canopy area of about 79% in a square grid, and to an area of about 91% in a triangular grid. Thus the threshold may be chosen as, e.g., 79%, 80%, 85%, or any intermediate value for a square grid, or, e.g., 90%, 91%, 95%, or any intermediate value for a triangular grid.

[0098] In Fig. 2C, the plants have grown even further, and cover about 96% of the area. Although part of the tray (about 4% of the area) is not yet covered by the plant canopy, neighbouring plants may start to have a negative influence on each other, e.g., one plant partially shading the leaves of the neighbouring plant. Thus, in general, a balance may be sought between light use efficiency (which is, in principle, maximal if the entire plant tray is covered with the canopy, as in that case, all light can be absorbed by the plants), and photosynthetic efficiency (which is, in principle, maximal if the plant is not shaded by, e.g., its neighbours).

[0099] Therefore, the predetermined threshold may be determined based on a balance between area coverage and coverage by neighbouring plants. This balance may again depend on the geometry of the plant tray. The threshold may be determined as, e.g., 90%, 95%, 96%, 97%, 98%, or 99%.

[0100] Fig. 2D shows a completely closed canopy, where 100% of the area is covered by the plant canopy. Assuming circular plants, this corresponds to an overlap of about 36% for a square grid arrangement and about 17% for a triangular grid arrangement.

[0101] As noted, the overlap may be determined using a camera, e.g., a camera that is mounted above the plant tray. However, different methods to determine the overlap are also possible, such as: human inspection, monitoring using a mobile device (e.g., a smart phone or tablet), sensors in the plant tray, light sensors measuring the light intensity of light reflected by the plant tray, et cetera. Existing software may be used to determine the canopy coverage, e.g., the Easy Leaf Area app installed on a smart phone.

[0102] For example, the canopy area fraction can be obtained by analysing the percentage of pixels that are green (assuming a white light source) compared to the total number of pixels in the image by using image processing software, or the pixels that have a low red pixel value. This can be done manually by a user, or automatically started. Alternatively, a machine-learning algorithm is used, such as a Mask R-CNN.

[0103] Fig. 2E and 2F show images of a canopy formed by a plurality of plants at various stages of closing. Although the small plants in Fig. 2E (shortly after transfer of the plants to the low-density tray) have irregular forms, the larger plants in Fig. 2F have an approximately circular circumference, as indicated by the dashed circle.

[0104] Fig. 3 A is a flow chart illustrating an embodiment of a method for irradiating a plurality of plants. This method may be performed by a system as described above. A step 31 comprises irradiating the plurality of plants in accordance with a first radiation recipe. The irradiation may be performed by a controllable irradiation system as described above. The first radiation recipe can be optimised for light use efficiency and / or rapid growth of the plant. In a typical example, the first radiation recipe comprises a relatively high amount of red and / or far-red light, and a relatively low amount of blue, deep-blue or ultraviolet light. For example, the amount of red radiation may be 80 % or more or even 85 % or more. The amount of far-red radiation may be at least 6 %, usually between 6-12 %. Adding more far- red radiation may increase fresh weight, but typically does not further increase light use efficiency.

[0105] A step 33 comprises receiving a signal indicative of a state of a plant canopy formed by the plurality of plants. A step 35 comprises determining whether or not a canopy formed by the plurality of plants is closed. This step may comprise, e.g., comparing a canopy area fraction to a predetermined threshold. Steps 33 and 35 are typically performed by a data processing system as described above.

[0106] If the canopy is not considered closed, the irradiation system continues to irradiate 31 the plurality of plants in accordance with a first radiation recipe. Typically, steps 33 and 35 will be repeated, possibly periodically, until the canopy is closed. In some embodiments, a signal will only be received once the canopy is considered closed. In such embodiments, step 35 will always evaluate to “yes”. In other embodiments, several signals may be received (at different moments in time). As described elsewhere in more detail, the signal received in step 33 can also be, e.g., an image of the canopy to be analysed by the data processing system in order to determine whether or not the canopy is considered to be closed. In such embodiments, steps 33 and 35 are typically repeated multiple times.

[0107] An optional step 37 comprises irradiating the plurality of plants in accordance with the first radiation recipe during a predetermined amount of time after a first moment when the plant canopy is considered closed. The predetermined amount of time can be one of: one day, two days, three days, four days, five days, or six or more days. Waiting a few days, e.g., about 1-7 days, after the canopy is first considered closed ensures that the canopy is sufficiently thick everywhere. The optimal number of days between the canopy closing and switching the light recipes may depend on the plant being grown. If the comparison yields that the canopy is considered closed, and optional step 37 has been executed as applicable, a step 39 comprises irradiating the plurality of plants in accordance with a second radiation recipe, different from the first radiation recipe. For example, the second radiation recipe may be optimised for plant quality, e.g., increasing the shelf-life of the plurality of plants, or parts thereof.

[0108] Fig. 3B is a flow chart illustrating essentially the same embodiment as Fig. 3 A, except that this method may be performed entirely by a data processing system. Steps 33 and 35 may be as described above for Fig. 3A.

[0109] Additionally, a step 32 comprises configuring the controllable irradiation system to irradiate the plurality of plants in accordance with the first radiation recipe, and a step 38 comprises configuring the controllable irradiation system to irradiate the plurality of plants in accordance with the second radiation recipe. For example, the data processing system may generate and transmit control signals to the controllable irradiation system. Although not shown, this embodiment may comprise an optional waiting step analogous to step 37, during which the controllable irradiation system is or remains configured to irradiate the plurality of plants according to the first radiation recipe.

[0110] Thus, when the canopy is closed, the plants mostly or completely cover the surface area of the growth table, i.e., the plant canopy covers a substantial part of the plant support. A “substantial part” may refer to at least 80% of the full plant support, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% of full plant support coverage. At that moment the far-red part of the spectrum can be switched off, and eventually replaced by blue light. By continuously monitoring growth, the result of the calculated plant surface coverage can be registered to serve as an input for a control system such as the GrowWise Control System (GWCS). The GrowWise Control System is Signify’s radiation control system that schedules the radiation according to a user-defined radiation recipe.

[0111] In an embodiment, the control system acquires and analyses the camera images. The definition of the canopy being closed can be part of the light recipe, based on user input, or based on a default value. An example of such definition is that the canopy is called ‘closed’ when the surface area of the plants is at least 95% of the surface area of the growth table. Another definition is that the canopy is called closed 1 day after the time that the surface area of the plants is 100% of the surface area of the growth table. Other examples are given elsewhere in this disclosure. At the first moment that the canopy is closed, according to the current definition, the control system switches off the far-red radiation. Alternatively, the far-red radiation is substantially reduced, for example by a factor of at least 2.

[0112] In an alternative embodiment, the image processing system is equipped with edge computing possibilities in order to generate a ‘canopy closed’ signal that is sent to the control system. In case the control system receives a ‘canopy closed’ signal from one or more or a majority of the cameras, the far-red radiation may be switched off or reduced. Alternatively, the spectrum may be switched locally; e.g. for each light source, the spectrum is determined based on the coverage as determined based on images from a camera that is closest to that light source. Other alternatives are readily apparent to the skilled person.

[0113] Having an automated feedback input towards the control system, to organize the moment of switching radiation settings, is beneficial because the growth speed very much depends on species, varieties, and climate settings. Another advantage of automated growth speed monitoring is related to the fact that the moment of canopy closing becomes predictable if no changes in other growth parameters will occur in the meantime. This makes further optimization with respect to light use efficiency (LUE) even more accessible for vertical farm systems. Furthermore, the canopy closing time can act as a predictor for an optimal harvest time.

[0114] Fig. 4 is a graph showing the effect of light spectrum on shelf-life for wild rocket. This figure was obtained from Nicole et al. ‘Chapter 1.4: Postharvest quality of leafy greens growing in a plant factory’, in: Anpo et al. eds., Plant Factory using Artificial Lighting (Elsevier 2019) pages 33-43, which is hereby incorporated by reference.

[0115] Fig. 4 shows the Overall Visual Quality (OVQ) against the number of days in storage at 4 °C, for three different light spectra: red-white (RW, triangles), red-blue (RB, diamonds), and red-white-far-red (RWFr, circles). The overall visual quality crosses the consumer acceptance line (OVQ = 6) at 24 days, 26 days, and 20 days, respectively. Each data point is the average of the overall visual quality of three individual samples. The plants were grown under the respective spectrum for the entire crop cycle, i.e., from seedling to harvest.

[0116] Thus, compared to the red-white reference spectrum, the addition of far-red light reduces shelf-life. This shows that plant quality (in this case, shelflife) may be improved by using a second radiation recipe (after closure of the canopy) that contains no, or only a small amount of far-red light. At the same time, a first radiation recipe (before closure of the canopy) containing a relatively large amount of far-red light improves light use efficiency by stimulating plant growth.

[0117] For example, it is known that for the growth of lettuce and similar leafy vegetables, adding far-red (FR) lighting to the standard red-blue (RB) spectrum induces stretching of leaves. With this increased leaf area, more light is intercepted, leading to faster biomass production. However, as shown in Fig. 4, this addition of far-red radiation in the spectrum can result in a decreased quality in terms of plant morphology, pigment concentration and shelflife. A higher blue dose has, in general, an opposite effect on morphology as far-red does. It reduces the final fresh weight significantly, makes plants more compact, and can reduce the number of leaves per plant or canopy area.

[0118] Fig. 5 depicts a block diagram illustrating a data processing system as claimed in an embodiment.

[0119] As shown in Fig. 5, the data processing system 100 may include at least one processor 102 coupled to memory elements 104 through a system bus 106. As such, the data processing system may store program code within memory elements 104. Further, the processor 102 may execute the program code accessed from the memory elements 104 via a system bus 106. In one aspect, the data processing system may be implemented as a computer that is suitable for storing and / or executing program code. It should be appreciated, however, that the data processing system 100 may be implemented in the form of any system including a processor and a memory that is capable of performing the functions described within this specification.

[0120] The memory elements 104 may include one or more physical memory devices such as, for example, local memory 108 and one or more bulk storage devices 110. The local memory may refer to random access memory or other non-persistent memory device(s) generally used during actual execution of the program code. A bulk storage device may be implemented as a hard drive or other persistent data storage device. The processing system 100 may also include one or more cache memories (not shown) that provide temporary storage of at least some program code in order to reduce the number of times program code must be retrieved from the bulk storage device 110 during execution.

[0121] Input / output (I / O) devices depicted as an input device 112 and an output device 114 optionally can be coupled to the data processing system. Examples of input devices may include, but are not limited to, a keyboard, a pointing device such as a mouse, a touch-sensitive display, an external control system referred to herein, or the like. Examples of output devices may include, but are not limited to, a monitor or a display, speakers, the LED driver, or the like. Input and / or output devices may be coupled to the data processing system either directly or through intervening I / O controllers.

[0122] In an embodiment, the input and the output devices may be implemented as a combined input / output device (illustrated in Fig. 5 with a dashed line surrounding the input device 112 and the output device 114). An example of such a combined device is a touch sensitive display, also sometimes referred to as a “touch screen display” or simply “touch screen”. In such an embodiment, input to the device may be provided by a movement of a physical object, such as, e.g., a stylus or a finger of a user, on or near the touch screen display.

[0123] A network adapter 116 may also be coupled to the data processing system to enable it to become coupled to other systems, computer systems, remote network devices, and / or remote storage devices through intervening private or public networks. The network adapter may comprise a data receiver for receiving data that is transmitted by said systems, devices and / or networks to the data processing system 100, and a data transmitter for transmitting data from the data processing system 100 to said systems, devices and / or networks. Modems, cable modems, and Ethernet cards are examples of different types of network adapter that may be used with the data processing system 100.

[0124] As pictured in Fig. 5, the memory elements 104 may store an application 118. In various embodiments, the application 118 may be stored in the local memory 108, the one or more bulk storage devices 110, or apart from the local memory and the bulk storage devices. It should be appreciated that the data processing system 100 may further execute an operating system (not shown in Fig. 5) that can facilitate execution of the application 118. The application 118, being implemented in the form of executable program code, can be executed by the data processing system 100, e.g., by the processor 102. Responsive to executing the application, the data processing system 100 may be configured to perform one or more operations or method steps described herein.

[0125] In one aspect of the present invention, the data processing system 100 may represent a control system of a LED driver as described herein.

[0126] In another aspect, the data processing system 100 may represent a client data processing system. In that case, the application 118 may represent a client application that, when executed, configures the data processing system 100 to perform the various functions described herein with reference to a “client”. Examples of a client can include, but are not limited to, a personal computer, a portable computer, a mobile phone, or the like. In yet another aspect, the data processing system 100 may represent a server. For example, the data processing system may represent an (HTTP) server, in which case the application 118, when executed, may configure the data processing system to perform (HTTP) server operations.

[0127] Various embodiments of the invention may be implemented as a program product for use with a computer system, where the program(s) of the program product define functions of the embodiments (including the methods described herein). In one embodiment, the program(s) can be contained on a variety of non-transitory computer-readable storage media, where, as used herein, the expression “non-transitory computer readable storage media” comprises all computer-readable media, with the sole exception being a transitory, propagating signal. In another embodiment, the program(s) can be contained on a variety of transitory computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., flash memory, floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. The computer program may be run on the processor 102 described herein.

[0128] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0129] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of embodiments of the present invention has been presented for purposes of illustration, but is not intended to be exhaustive or limited to the implementations in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present invention. The embodiments were chosen and described in order to best explain the principles and some practical applications of the present invention, and to enable others of ordinary skill in the art to understand the present invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS:

1. A system (1) for irradiating a plurality of plants (11) on a plant support (21), the system (1) comprising: an irradiation system (3) that is configured to irradiate the plurality of plants(11) with radiation having one or more controllable radiation properties; and a data processing system (100) comprising an input interface (116) for receiving a signal indicative of a state of a plant canopy, an output interface (116) for sending a control signal to the irradiation system (3), and a processor (102), , the processor (102) being configured to:- receive a signal indicative of a state of a plant canopy formed by the plurality of plants (11);- determine whether or not the plant canopy is closed, based on the received signal indicative of the state of the plant canopy, where the plant canopy is closed when the plant canopy covers a substantial part of the plant support (21); and- send the control signal to the irradiation system (3), the control signal being based on the canopy determined to be closed; wherein the irradiation system (3) is configured to switch, based on the received control signal, from irradiating the plurality of plants (11) in accordance with a first radiation recipe to irradiating the plurality of plants (11) in accordance with a second radiation recipe, different from the first radiation recipe; wherein the first radiation recipe comprises a higher far-red dose than the second radiation recipe and / or wherein the first radiation recipe comprises a lower blue, deep-blue and / or ultraviolet radiation dose than the second radiation recipe.

2. The system as claimed in claim 1, wherein the signal indicative of the state of the plant canopy is a signal indicating that the plant canopy is closed, and wherein the processor (102) is configured to determine that the plant canopy is not closed prior to reception of the signal and determine that the plant canopy is closed after reception of the signal.

3. The system as claimed in any one of the preceding claims, further comprising an image processing system configured to: receive an image representing a plant canopy formed by the plurality of plants; determine, based on the image, the state of the plant canopy; and send the signal indicative of the state of the plant canopy to the data processing system (100).

4. The system as claimed in claim 3, wherein the state of the plant canopy is based on an absolute or relative number of pixels in the image representing the plant canopy, and wherein determining that the canopy is closed comprises determining that at least a predetermined absolute or relative number of the pixels in the image represent the plant canopy.

5. The system as claimed in claim 4, wherein the predetermined number is a relative number equal to at least 80%, at least 85%, at least 90%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% of the pixels in the image.

6. The system as claimed in any one of claims 1-3, wherein the state of the plant canopy is based on an absolute or relative number of plants touching one or more of its respective neighbours, and wherein determining that plant canopy is closed comprises determining that the absolute or relative number of plants touching one or more of its respective neighbours is at least equal to a predetermined threshold.

7. The system as claimed in any one of claims 3-6, further comprising a camera, communicatively connected to the image processing system, for obtaining the image of a plant canopy formed by the plurality of plants.

8. The system as claimed in claim 7, wherein the camera is positioned overhead the plurality of plants; and / or wherein the camera is integrated into the image processing system and wherein the image processing system is positioned overhead the plurality of plants; and / or wherein the camera is integrated into the irradiation system.

9. The system as claimed in any one of the preceding claims, wherein the processor (102) is configured to send the control signal to the irradiation system (3) after a predetermined amount of time after a first moment when the plant canopy is determined to be closed; or wherein the irradiation system (3) is configured to switch from irradiating the plurality of plants (11) in accordance with the first radiation recipe to irradiating the plurality of plants (11) in accordance with the second radiation recipe after the predetermined amount of time after the control signal has been received by the irradiation system.

10. The system as claimed in claim 9, wherein the predetermined amount of time is one of: one day, two days, three days, four days, five days, or six or more days.

11. The system as claimed in any one of the preceding claims, wherein each of the first and second radiation recipes defines, for a particular time period, one or more radiation properties provided to the plurality of plants, wherein the one or more radiation properties comprise at least one of:- a photon flux of the radiation as generated by the irradiation system,- a photon flux density of the radiation as received by the plurality of plants,- a spectral power distribution of the radiation generated by the irradiation system, and- a timing of the irradiation; and wherein the data processing system is configured to cause the irradiation system to generate radiation such that the radiation has the photon flux and / or photon flux density and / or the spectral power distribution and / or the timing of the irradiation as defined by the first and second radiation recipes, respectively.

12. A computer-implemented method for irradiating a plurality of plants (11) on a plant support (21), the method comprising:- receiving a signal indicative of a state of a plant canopy formed by the plurality of plants (i i);- determining whether or not the plant canopy is closed, based on the received signal indicative of the state of the plant canopy, where the plant canopy is closed when the plant canopy covers a substantial part of the plant support (21); and- sending a control signal to an irradiation system (3), the control signal being based on the determined canopy closure, the control signal configuring the irradiation system to switch from irradiating the plurality of plants (11) in accordance with a first radiation recipe to irradiating the plurality of plants (11) in accordance with a second radiation recipe, different from the first radiation recipe; wherein the first radiation recipe comprises a higher far-red dose than the second radiation recipe and / or wherein the first radiation recipe comprises a lower blue, deep-blue and / or ultraviolet radiation dose than the second radiation recipe.

13. A computer program comprising instructions which, when executed by a data processing system of a system as claimed in one of claims 1 to 11, causes the system to perform the method as claimed in claim 12.

14. A computer-readable storage medium having stored thereon a computer program as claimed in claim 13.

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