WO2009125023A1

WO2009125023A1 - System, process and module for controlling plant growth

Info

Publication number: WO2009125023A1
Application number: PCT/EP2009/054401
Authority: WO
Inventors: Johannes Christian Quist; Carsten Seidler; Carsten Fredsbo; Linda Elin Noack; Poul Leo Anker
Original assignee: Minaqua Aps
Priority date: 2008-04-11
Filing date: 2009-04-14
Publication date: 2009-10-15
Also published as: EP2108250A1

Abstract

The present invention relates to a system (1, 1') for controlling the growth of at least one plant (23) in a growth medium (24) by determining the moisture content and the aqueous concentration of at least one plant nutrient and by regulating said parameters. The present invention further relates to the use of such a system (1) for growing plants under controlled conditions. The present invention also relates to a detachable module for insertion into a container of a system according to the present invention.

Description

System, process and module for controlling plant growth

The present invention relates to a system for controlling the growth of at least one plant in a growth medium by determining the moisture content and the aqueous concentration of at least one plant nutrient and by regulating said parameters. The present invention further relates to the use of such a system for growing plants under controlled conditions.

Growing and nurturing of plants under controlled conditions is a desired process within commercial and private gardening and horticulture. Plants generally have individual requirements as to the soil water content or the concentration of specific macro- and micro-nutrients. An efficient control on these parameters is therefore key to a successful nurturing of plants .

Small- and medium-scale plant nurturing is typically a non- automated, manual activity that is time-consuming and requires continuous effort and dedication. This goes both for the private use of, for example, ornamental plants, as well as for commercial gardening and plant nurturing such as in garden centers or plant shops.

This situation is complicated even more by the well-known fact that different plant species vary considerably with respect to their nutritional requirements and in their water availability demands. The permanent wilting point of a plant, that is, the soil moisture at which the plant will start to permanently wilt due to lack of water supply, varies from plant to plant, but also between different soil textures. A similar reasoning applies to nutrient requirements.

Accordingly, yet another variable that needs to be accounted for when striving towards optimal plant nurturing is the variation in growth media, such as different types of soils or solid substrates that have different water retentions, pore volumes, or nutrient sorption characteristics.

Other factors, which often vary thus making a controlled plant growth and nurturing process difficult, are the microclimate and the weather. These parameters are of special interest when considering situations in which hobbyists or professional gardeners are not available for a given time period, as may be the case during holidays or periods of illness. Temperature, precipitation, or hours of sunshine may change greatly over time leading the best-laid water-reserve schemes astray.

To date, several systems are known that try to overcome some of these problems. Numerous plant pot systems exist that provide one or more fixed and/or integral water reservoirs that differ in size, location and water transfer characteristics. A simple construction is, for example, a plant pot with one or more openings in its base which is placed onto a water-filled dish. Here, the plant may draw water from the dish through its own water consumption, which lowers the matric potential of the surrounding soil. Due to its simplicity this concept has several drawbacks such as the obvious limitations connected to the dish size and the openness of the water reservoir, as well as the fact that it does not account for the nutritional state of the plant.

U.S. Patent No. 6,345,470 discloses a self-contained automatic watering system for plants. The system comprises a nested plant pot assembly in which the pots together define an annular space, that may serve as a reservoir for water. A controller effects watering cycles using a motor and a pump. While the system may comprise a sensor for determining the fill-level of the water reservoir it does not account for the in-situ conditions of the soil with respect to moisture and/or nutrient concentrations. U.S. Patent No. 7,110,862 provides an apparatus for digitally controlling growth of a plant in a plant pot. The system comprises a moisture sensor and a liquid crystal display that indicates the moisture condition of the soil. Optionally, the system may contain a water tank connected to an electronic valve. A controller may effect the supply of water to the tank. The main drawback of this approach is that it does not account for nutrients, neither for their in-situ concentration nor for their supply to the plant.

In some situations it may be desirable to control the growth of a plant such that the plant is maintained at a state considerably different from its optimum growth conditions. This state may, for example, be a minimum growth state in which plant metabolism is maintained while actual growth is minimized.

U.S. Patent No. 4,340,414 discloses a solution for this requirement by providing a nutritional mixture that contains only trace quantities of phosphate. Thereby, the plant is kept in a "hibernation" state. The main drawback of this approach is the variation in nutritional and physiological requirements between different plant species. The desired effect may be achieved with one solution for a given species, but a different solution for another species. Also, water requirements may vary considerably between species and between different physiological minimum states of different species. Thus, an integrated moisture- and nutrient-control system is needed that is capable of custom-tailoring the desired physiological condition to the specific purpose and plant species.

U.S. Patent Application No. 2007/0220808 concerns a system for computer-controlled irrigation and fertigation of plants. While moisture sensors are placed directly in the soil, chemical sensors are exclusively used on excess water exiting the plant container and collected in a separate container. Thus, nutrient levels and the overall in situ nutrient composition of the soil and/or soil water are unknown. The chemical composition of the collected water will likely differ from the actual soil water composition due to the time lag, different physico-chemical conditions and the resulting susceptibility potential to chemical reactions.

U.S. Patent No. 6,061,957 discloses a gravity-independent plant growth system for utilization in space installations. A series of plants is grown in an elongated root bag containing growth substrate. A fluid pump is used to deliver water from an external reservoir into the root bag. The system may further comprise a nutrient bag containing a solid nutrient concentrate. Sensing probes are used for detecting levels of nutrient ions in the soil and for triggering water supply to the nutrient bag. The main drawback of this approach is the fact that all plants within a growth section are treated with the same nutrient bag, which furthermore contains a fixed mixture of different nutrients, which are simply dissolved in water when needed. Hence, it is not possible to individually supply different nutrients and/or water to individual plants.

International Patent Application WO 2006/068919 relates to a hydroponic plant cultivation system. The system comprises a drip irrigation and fertigation line supplying numerous plant containers with water and fertilizer. Sub-soil sensors, e.g. tensiometers, are employed to determine soil moisture content thus providing signals to a watering control system. While the system may provide for continuous measurement of levels of additives in the fertigation water, the in situ nutrient situation in the soil is unknown and thus cannot be precisely controlled.

UK Patent Application No. GB 2426908 discloses a plant watering system comprising a moisture sensor buried in the soil. Based on the detected moisture level, a control unit may enable a predetermined amount of water or nutrients to be delivered to the soil. In addition, a nutrient sensor may be placed in the external water tank for delivery to the plant. This system also lacks information about in situ nutrient levels in the soil.

Thus, it is a first aspect of the present invention to provide a system for controlling plant growth, the system accounting for soil moisture as well as for nutrient levels in the soil.

It is a second aspect of the present invention to provide a system for controlling plant growth that is sensitive to the in-situ soil conditions with respect to moisture and/or nutrient concentration.

It is a third aspect of the present invention to provide a system for controlling plant growth in a user-defined fashion, allowing for optimum growth conditions as well as for minimum conditions .

It is a fourth aspect of the present invention to provide an automated use of such a system.

It is a fifth aspect of the present invention to custom-tailor and regulate growth conditions for a wide variety of plant species.

It is a sixth aspect of the present invention to provide a system for controlling plant growth that allows for easily selecting and replacing plant nutrients to be used with the system.

The new and unique way in which the present invention fulfils one or more of the above-mentioned aspects is to provide a system for controlling the growth of at least one plant in a growth medium, said system comprising at least one container with at least one cavity for accommodating the growth medium, at least one water reservoir disposed within the container, at least one nutrient reservoir disposed within the container, first sensor means extending into the cavity for determining the moisture content of the growth medium, second sensor means extending into the cavity for determining the aqueous concentration of at least one plant nutrient in the growth medium, fluid communication means enabling fluid communication between the water reservoir and the cavity, and between the nutrient reservoir and the cavity, respectively, and regulating means for effecting discharge of fluid from at least one of the reservoirs into the cavity.

The system according to the present inventions allows for an efficient and intelligent control of plant growth. It accounts for both changes in moisture and in nutrient concentration in the growth medium, which may be soil or any other plant supporting substrate. Through its sensors and regulation means the system allows for an automated control of plant growth and nurturing .

The container of the present invention may, for example, be a plant pot of cylindrical or frusto-conical shape. The cavity for accommodating the growth medium for the plant may then be the central cavity formed in the plant pot. The plant pot may be double-walled, in which case the water reservoir and one or more nutrient reservoirs may be disposed within the annular compartment surrounding the central cavity of the pot . The water reservoir may contain tap water, or any other suitable irrigation water. The nutrient reservoir will preferably contain an aqueous solution of at least one plant nutrient, for example nitrate, phosphate, or potassium.

The first sensor means for determination of the moisture content of the growth medium may, for example, include a sensor based on well-known soil moisture measurement techniques, such as electrical resistance measurements using gypsum blocks, neutron probe measurements, time-domain reflectometry (TDR) techniques or tensiometer approaches. The second sensor means for determining the aqueous concentration of at least one plant nutrient in the growth medium may, for example, include sensors that are based on electrochemical principles. The sensor means may include potentiometric ion-selective electrodes, amperometric electrodes, ion-selective field effect transistor or any other chemical sensor means. In addition to nutrient sensors the system may comprise one or more pH sensors, metal sensors or sensors for monitoring soil porosity or compaction. Suitable sensors may be selected depending on different parameters such as soil type, texture, average moisture, the type of plant species or the like. In this respect it may be useful to use and/or establish a database correlating these parameters with the usefulness of different types of sensors. It lies within the scope of the present invention to use a nutrient sensor that is capable of measuring a plurality of different compounds. The second sensor means may also comprise more than one sensor, for example three sensors detecting nitrate, phosphate, and potassium ions, respectively.

Both moisture and nutrient sensors extend into the cavity containing the growth medium. Thereby, it is ensured that the sensors gather in situ soil data, e.g. moisture content or nitrate concentrations in the soil water. This is in contrast to prior art approaches where nutrient concentrations were measured in soil percolate only.

The fluid communication means may, for example, be a series of tubing and valves, where each tube is connected to a reservoir, the tubes' ends extend into the cavity and the valves are used for opening and closing water or nutrient solution flow into the cavity. The fluid communication means may also include a wick, a membrane or the like. The regulating means for effecting discharge from the reservoirs to the container cavity may include any suitable means for controlling valves. In an expedient embodiment of the present invention the regulating means comprise a control unit for effecting and controlling discharge of fluid from at least one of the reservoirs into the cavity, wherein the control unit is communicatively connected to the first and second sensor means. In embodiments comprising a water reservoir and a nutrient reservoir containing a solid nutrient composition, the control unit may effect and control transfer of water from the water reservoir to the container cavity, and transfer of water to the nutrient reservoir as well as subsequent discharge of nutrient solution from the nutrient reservoir into the container cavity.

In a preferred embodiment of the present invention, the control unit further comprises a programmable device for at least saving and processing physiological data concerning one or more plant species. Thereby, the control unit is able to carry out one or more activities of the following non-exhaustive list:

(i) receive data from both the first sensor means and the second sensor means, (ii) compare these data with stored plant physiological data on, for example, moisture and nutrient requirements, possibly as a function of soil texture, (iii) assess the necessity of supplying additional water and/or nutrients to the growth medium and thereby to the plant, and (iv) regulate these parameters by discharging water and/or nutrients from the reservoirs to the container cavity.

The nutrients of interest may be chosen from the group of compounds containing nitrogen, phosphorous, potassium, carbon, iron, calcium, manganese, molybdenum, sulphur, boron and zinc. Nutrient compositions used for regulating the aqueous concentration of one or more nutrients in the growth medium may, for example, be aqueous solutions of one or more salts containing one or more nutrients. Another contemplated option is a non-aqueous nutrient composition, for instance a dry fertilizer which may be mixed with water from the water reservoir and thereafter discharged as nutrient solution into the container cavity. In the latter embodiment there is the obvious need for additional fluid communication means connecting the water reservoir with the nutrient reservoir

Preferably, the control unit is communicatively connected to one or more control valves for regulating the discharge of fluid from the reservoirs to the cavity. The control unit may effect the opening and shutting of the control valves for supplying water and/or aqueous nutrient solution to the growth medium. The communicative connection between the control unit and one or more valves may, for example, be an electric connection through wires, cables or the like. Alternatively, it may be a wireless connection.

As explained above, each reservoir is advantageously connected to one or more valves via one or more conduits or appropriate tubing. The conduits may transfer water or an aqueous nutrient solution to the container cavity. Opening or shutting of the valves by the control unit controls discharge of the fluid into the cavity. The valves may be inserted at any useful location of the tubing, e.g. close to the periphery of the cavity and the outlet of the tubing. The discharge outlets of the tubing may be arranged at different vertical and horizontal positions with respect to the cavity. Thereby, different localities within the cavity may be regulated in an individual manner. This arrangement may be of particular benefit when using the system according to the present invention with different plant species .

In general, the driving force for the transfer of fluid, for example through conduits or tubing, may be created through different approaches. In one embodiment, the driving force is gravity and/or water pressure. Here, the mere opening of a control valve placed within a conduit will lead to flow and discharge of fluid into the growth medium. In another embodiment, fluid flow is effected by a pump that is powered by, for example, a motor or by solar cells.

Optionally, one or more discharge outlets, that is ends of tubes or conduits, may extend well into the cavity as supported by, for example, rigid conduits between reservoirs and valves, respectively. Another contemplated arrangement is to place one or more discharge outlets above the cavity, so that any fluid draining from the valve precipitates onto the soil and percolates through the growth medium.

According to one embodiment, the system of the present invention comprises two reservoirs, wherein the first reservoir contains water and the second reservoir contains an aqueous solution of at least one plant nutrient. The two reservoirs and their corresponding fluid communication means may be controlled independently of each other by the control unit. The control unit may receive two different signals; the first signal from the first sensor monitoring soil moisture, and the second signal from the second sensor monitoring the concentration of a given nutrient. The data from the sensors are then related to previously stored information on the physiological water requirements and/or nutrient requirements of the plant, whereupon the control unit effects the transfer of a given amount of fluid from one or both reservoirs to the cavity and the growth medium.

In yet another embodiment, the system of the present invention comprises two nutrient reservoirs, wherein the first nutrient reservoir contains an aqueous solution of a first plant nutrient, and the second nutrient reservoir contains an aqueous solution of a second plant nutrient.

In another embodiment the system of the present invention comprises three nutrient reservoirs, wherein the first nutrient reservoir contains an aqueous solution of a first plant nutrient, the second nutrient reservoir contains an aqueous solution of a second plant nutrient, and the third nutrient reservoir contains an aqueous solution of a third plant nutrient.. Each reservoir may be connected to suitable fluid communication means, wherein the outlets of possible tubing or conduits extend into, or are placed at the periphery of, the cavity. The system of this embodiment will advantageously comprise means for determining the aqueous concentration of three different nutrients, for example nitrate, phosphate and potassium ions. Sticking with this example, the first reservoir may contain an aqueous nitrate solution, whereas the second reservoir may contain an aqueous phosphate solution, and the third reservoir contains an aqueous potassium solution. When receiving data from the phosphate sensor indicating that the plant is not adequately supplied with phosphate, the control unit may effect the discharge of a given amount of phosphate- solution into the growth medium. The same principle of regulation may also apply to nitrate and potassium.

In accordance with a broad aspect of the present invention the afore-mentioned regulation may be performed as an interdependent process in which the control unit may use one or more algorithms for regulating plant growth conditions. Again referring to the afore-mentioned example, this algorithm may aid in determining the exact phosphate demand as a function of the current moisture content and the nitrate concentration. This principle may be extended to a number of additional nutrients, each of which may be measured by individual or collective sensors, and to data on light irradiation. Regulation algorithms may be based on multivariate statistical methods such as regression or principal component analysis, for which the control unit will advantageously be equipped with suitable computing capacity.

Optionally, the system of the present invention comprises means for mixing different fluids from at least two reservoirs prior to fluid discharge into the cavity. These different fluids may, for example, be water and one or more nutrient solutions. The mixing process may be enabled by conduits that lead from the different reservoirs into a common mixing reservoir. Each conduit may be equipped with at least one control valve for opening or shutting the flow of fluid towards the mixing chamber. The volume fractions of the individual fluids in the final mixture may advantageously be adjusted by means of the control unit, which controls the control valves and allows for custom-tailoring of a mixture that best meets the physiological requirements of the plant.

According to a preferred embodiment of the present invention the system further comprises at least one detachable module comprising at least one nutrient reservoir, the module being received within a receiving compartment disposed integrally within the container, wherein the module when received in the receiving compartment at least partly surrounds, or abuts against, the cavity. The receiving compartment may be formed as a partly-annular or angular recess formed at the periphery of the cavity of the container, for example as a recess disposed in the cavity-surrounding container wall. The receiving compartment is preferably an integral part of the container. The detachable module may have an arcuate shape and may have an arc length of, for example, 60 degrees. The module comprises one or more nutrient reservoirs, preferably with separate inlets enabling the individual re-filling of the reservoirs. In an alternative use, the entire module may be removed and exchanged with a new module with filled up reservoirs. As used herein, the term "abuts against the cavity" includes embodiments where the module, when received in the receiving compartment, at least partly constitutes a side wall at least partly defining the cavity.

Optionally, The receiving compartment may be established between an inner and an outer plant pot, wherein the inner plant pot at least partly defines the cavity. In this case, the inner and outer plant pot would be considered as together forming the container. One or more reservoirs may extend below and along the sidewalls of the inner plant pot. The inner plant pot may be formed as a double-walled, hollow conical frustum. The annular compartment that is present between the double walls may be open at the base of the frustum's tapered end and may be closed at the base of the frustum's wide end. The central cavity of the hollow frustum may comprise a floor at its tapered end base. The floor allows for physical support of the plant and the growth medium, and is permeable to water. One or more plants may be placed into the central cavity of the hollow frustum together with an appropriate growth medium like soil. The inner pot may then be placed into an outer pot, which may be formed as a dish with a larger diameter than the diameter of the tapered end base of the frustum. The annular cavity of the inner pot may be filled with water or a nutrient solution by means of a check valve close to the upper end, that is, the wide end, of the frustum. Another check valve allows for exiting of gas from the annular cavity to the surroundings. During operation of this assembly water or nutrient solution will be successively transported from the annular cavity of the inner pot into the outer pot, and from there through the water permeable floor of the inner pot to the growth medium and eventually to the plant roots. As the fluid level in the annular cavity is lowered through this transport, a negative gas pressure is created in the headspace above the aqueous phase in the annular cavity. This negative pressure prevents, or slows down, further transport of fluid to the plant. Transport rates may then be enhanced by, for example, transferring additional fluid into the annular cavity through the check valve. Excess gas pressure building up in response to re-filling the fluid may be released through the gas check valve. This process is to be effected and regulated by the control unit. In another embodiment, the inner and the outer plant pot are cast as one piece. The material may, for example, be a polymer, a metal, a metal alloy, clay, ceramic, or terracotta.

According to yet another contemplated embodiment of the present invention, the system further comprises means for rotating the cavity around its vertical axis. If the cavity is formed, for example, as a hollow cylinder, the vertical axis means the central axis of the cylinder. By rotating the cavity around its axis it may advantageously be achieved that the plant is, over time, illuminated from all sides, in situations where the light source is predominantly fixed in a given location. The rotating means may comprise a rotable plate or dish onto which a plant pot assembly is placed. The rotable plate may be driven by an electric motor, or any other rotation mechanism well-known in the art.

In a preferred embodiment, the system of the present invention comprises means for measuring the fill level of at least one of the reservoirs. The fill level of one or more reservoirs, which may contain water or aqueous nutrient solutions, is measured by an appropriate sensor. Examples of such sensors are given in U.S. Patent 4,547,768, U.S. Patent No. 6,769,300, and U.S. Patent No. 7,260,987. Data on the fill level may advantageously be transmitted to the control unit. Similarly to the other data received and processed by the control unit, the data on fill levels of one or more reservoirs may be further transmitted, for example through a wireless connection, to a computer, a mobile phone, or a personal digital assistant (PDA) . Also, the control unit may be programmed such that it, in an automated fashion, effects re-filling of one or more reservoirs from one or more reserve containers.

According to yet another preferred embodiment of the present invention the system further comprises means for wireless communication of data on moisture in the growth medium, aqueous nutrient concentration in the growth medium, fluid discharge rates, radiation, and/or the fill level of one or more of the reservoirs. Wireless data transmission may occur between different components of the system, for example fill level sensors and the control unit, and/or between the control unit and external devices, such as a computer, a mobile phone, or a PDA. Wireless data transmission may furthermore occur between the control unit and a network node, which may further transmit the data to a central server that saves the data in a database.

It lies within the scope of the present invention that the database may continuously gather and accumulate data from the system. Thereby, the database will become an increasingly powerful tool that may aid in improving the system's performance. The system of the present invention may consequently be a learning system, which, based on empirical data gathered during test runs, experiments, or regular operation, is able to classify different plant species into groups requiring the same or a similar treatment. The control unit thus may establish several optimized growth control programs that are custom-tailored to the growth requirements of these groups or classes.

In a further embodiment of the present invention the system comprises means for collecting and storing solar energy for powering the control unit and/or the control valves. These means may advantageously comprise solar cells and rechargeable batteries, and may further be used for powering any component of the system of the present invention.

In a preferred embodiment, the system of the present invention comprises radiometric measurement means. Advantageously, these means comprise one or more light sensors that are sensitive to photosynthetically active radiation (PAR) , which is light with a wavelength of around 380 to 720 nm. The measured parameters may be the irradiance in watt per square meter and/or the spectral irradiance in watt per cubic meter. In an expedient embodiment, the system of the present invention comprises one or more of these light sensor, which are communicatively connected to the control unit. The data from the light sensors are, in combination with the other data such as data on moisture and nutrients, used by the control unit to determine the plant's need for water and/or nutrients. In a contemplated embodiment, the system may comprise means for reducing or excluding light from the plant, for example by mechanically closing an opaque lid over the cavity for accommodating the growth medium, wherein the opening and closing of the opaque lid is based on the aforementioned light data. Hereby, the system of the present invention may advantageously used for creating growth conditions present in different seasons, such as spring or summer.

In another embodiment, the system of the present invention comprises a computer, a PDA, or a mobile phone for wirelessly communicating with the control system.

According to an expedient embodiment of the present invention, the system comprises one or more identification tags for storing and/or transmitting data on plant type, soil texture, nutrient and water requirements, moisture in the growth medium, aqueous nutrient concentration in the growth medium, fluid discharge rates, and/or the fill level of one or more of the reservoirs. These identification tags may, for example, be radio frequency identification (RFID) tags. The tags may be mounted onto, or placed within, each cavity. These tags may be conveniently used for managing plant growth in a system with numerous plant cavities containing different plant species. They may carry information on the plant species, their physiological requirements, their history within the piant- growth control system, or any other data that may be of use to the person skilled in the art. Similarly, identification tags may be placed on different components of the system according to the present invention. Individual tags may be used for one or more reservoirs or cavities. The tags may furthermore be arranged to communicate with a remote control.

Advantageously, the system of the present invention comprises a user interface which allows the user to input plant physiological data, to read data on soil moisture and nutrient concentrations, to manually override pre-programmed nurturing schemes, to effect transfer of water and or nutrients to the growth medium, and/or to visually inspect the system's history with respect to water and/or nutrient supplementation.

In a preferred embodiment, the system of the present invention is used for automatically controlling the growth of at least one plant in a growth medium, the use comprising the steps of monitoring the moisture content of the growth medium and the aqueous concentration of at least one plant nutrient within the growth medium, assessing water and nutrient demand of the plant by comparing the monitored data with plant physiological data saved in the programmable device of the control unit, and discharging water and/or at least one nutrient solution from at least one of the reservoirs into the cavity, wherein the transfer process is controlled by the control unit.. Ideally, all data and processes are managed through the control unit. It may collect concentration data on, for example, nitrate or phosphate, soil moisture data, radiation data, or data on the fill level of one or more reservoirs, either fluid reservoirs or reservoirs filled with non-aqueous nutrient compositions. These data are used by the control unit, in combination with previously stored plant physiological data and potentially with previously stored soil texture data, to determine the water and nutritional requirements linked to a desired growth situation, for example optimum growth. The control unit then may effect the transfer of water and/or aqueous nutrient solution to the growth medium and eventually to the plant. The transfer may be accomplished by means of conduits and control valves that are, for example wirelessly, controlled by the control unit. The data used may be previously stored known data on plant growth requirements. In adition, or alternatively, the data may be gathered and saved during operation of the system of the present invention, so that the system is in fact a learning system building up its own database. If this is combined with observations and resulting data on plant thriving, the plant may actually play an active role in teaching the system to provide the optimal growth conditions.

Another plant growth situation that may be conveniently achieved by using the system according to the present invention is minimum growth. As used herein, minimum growth refers to a plant's growth process which is sub-optimal, that is to say, slower than the optimal growth rate. This may be desired in situations when it is advantageous, for example from an economic point of view, to postpone plant growth. This may be achieved by programming the control unit to that end. The control unit may be programmed such that it consistently keeps one or more nutrients at sub-optimal aqueous concentrations. Alternatively or in addition, soil moisture may be regulated to that end. This use of the present system may be advantageous when growing bonsai plants.

In another embodiment of the present invention the transfer of water and/or at least one nutrient to the growth medium, which is controlled by the control unit, comprises the transfer of water from at least one water reservoir to the growth medium through at least one control valve, and the transfer of an aqueous solution comprising at least one nutrient to the growth medium through at least one control valve, wherein at least one transfer rate is based on the water and nutrient demand.

In another embodiment of the present invention the transfer of water and/or at least one nutrient to the growth medium, which is controlled by the control unit, comprises the transfer of water from at least one water reservoir to the growth medium through at least one control valve, and the transfer of a nonaqueous nutrient composition to the growth medium, wherein at least one transfer rate is based on the water and nutrient demand.

It lies within the scope of the present invention to control the growth of multiple plants in a single system with a central control unit. Industrial scale operation and longterm plant growth maintenance with hundreds or thousands of cavities and plant individuals is envisioned, the moisture and nutrient availability of which is centrally controlled and regulated. Such a system may comprise multiple sensors for soil moisture, aqueous nutrient concentration, and for light. It may further comprise a single or very few fluid reservoirs or single or very few non-aqueous nutrient composition reservoirs that supply the individual cavities with water and or nutrients, as regulated by the control unit.

The present invention also relates to a detachable module for insertion into a container of a system according to the present invention, wherein the module comprises at least one nutrient reservoir. The detachable module is preferably received within a hollow receiving compartment formed integrally within the container, wherein the receiving compartment surrounds, or abuts against, the container cavity. The detachable module preferably has a shape that is complementary to the shape of a suitable receiving compartment formed within the container. In embodiments in which the receiving compartment has an arcuate or partly-annular shape, the detachable module may likewise have an arcuate or partly-annular, for example semi-annular or quarter-annular, shape for being received in the annular compartment. The detachable module comprises one or more reservoirs for receiving plant nutrients. When one or more reservoirs run dry due to discharge of fluid into the container cavity the module may be exchanged with a new module with filled reservoirs. Alternatively, one or more reservoirs of the module may be re-filled with fluid if needed. In this case each reservoir may contain a suitable inlet. The module will preferably also comprise fluid communication means enabling fluid communication between each reservoir and the cavity, respectively. The fluid communication means may, for example, comprise suitable tubing or rigid conduits extending from the reservoir's outlet into the container cavity. One or more valves are preferably incorporated within the fluid communication means so as to enable initiation and shutting-off of fluid discharge from the reservoirs into the cavity.

Optionally, the detachable module may further comprise at least one water reservoir.

In one embodiment the detachable module comprises two nutrient reservoirs with two respective reservoir inlets and two respective reservoir outlets, wherein the first reservoir contains an aqueous solution of a first plant nutrient, and the second reservoir contains an aqueous solution of a second plant nutrient .

In a preferred embodiment the detachable module comprises three nutrient reservoirs with three respective reservoir inlets and three respective reservoir outlets, wherein the first reservoir contains an aqueous solution of a first plant nutrient, the second reservoir contains an aqueous solution of a second plant nutrient, and the third reservoir contains an aqueous solution of a third plant nutrient. The first plant nutrient may be a nitrogen-containing compound, the second plant nutrient may be a phosphorous-containing compound, and the third plant nutrient may be a potassium-containing compound, although other combinations are conceivable. According to another embodiment the detachable module of the present invention further comprises sensor means extending into the cavity for determining the aqueous concentration of at least one plant nutrient in the growth medium. The sensor means may include ion selective electrodes or any other chemical sensor means. In addition to nutrient sensors the detachable module may comprise one or more soil moisture sensors, pH sensors, metal sensors or sensors for monitoring soil porosity or compaction.

In an expedient embodiment of the present invention the module has an arcuate cross section, the module being arranged for disposal within an arcuate receiving compartment formed integrally within the container and at least partly surrounding the cavity.

The present invention also relates to a container for use in the system of the present invention. The container comprises at least one cavity for accommodating the growth medium, at least one water reservoir disposed within the container, and at least one nutrient reservoir disposed within the container. Preferably, the nutrient reservoir is formed as a detachable module received in a receiving compartment formed within the container. The receiving compartment is preferably an annular compartment at least partly surrounding the cavity.

The invention will be explained in greater detail below where further advantageous properties and example embodiments are described with reference to the drawing, in which

Fig. 1 shows a schematic cross-sectional view of one embodiment of the system of the present invention,

Fig. 2 shows a schematic cross-sectional view of another embodiment of the system of the present invention, Fig. 3 shows a functional diagram of another embodiment of the system of the present invention,

Fig. 4 shows a schematic view of another embodiment of the system of the present invention,

Fig. 5 is an exploded perspective view of another embodiment of the system of the present invention,

Fig. 6 is an assembled perspective view of the system of the Fig. 5,

Fig. 7 is a top view of the system of Fig. 6,

Fig. 8 is a transparent side elevation of the system of Fig. 6 as seen in the direction indicated by the arrow A in Fig. 7,

Fig. 9 is a transparent side elevation of the system of Fig. 6 as seen in the direction indicated by the arrow B in Fig. 7, and

Fig. 10 is a longitudinal section through the detachable module along the line X-X in Fig. 5.

In the embodiment shown in Fig. 1, the system 1 for controlling plant growth comprises a plant container 2 with a central cavity 3 for receiving soil and one or more plants (not shown) . The plant container 2 is double-walled in that it comprises an outer sidewall 4 and an inner sidewall 4'. Between these is formed an annular cavity 5 that surrounds the central cavity 3 as separated by the inner side wall 4'. In the embodiment shown in Fig. 1, the annular cavity 5 is used for accommodating a water reservoir 6, a nutrient reservoir 7, and a conduit 8. The nutrient reservoir 7 may contain an aqueous solution of one or more plant nutrients, for example, nitrate or phosphate. The nutrient reservoir 7 is via the conduit 8 connected to a first control valve 9, which may be used for discharging the nutrient solution into the central cavity 3. Similarly, the water reservoir 6 is via another conduit (not shown) connected to a second control valve 10. Within the central cavity 3 is placed a nutrient sensor 11 and a moisture sensor 12. The nutrient sensor 11 may determine the concentration of one or more plant nutrients, for example nitrate or other nitrogen-containing compounds. The moisture sensor 12 may determine the water content or moisture content of the soil. The system 1 in Fig. 1 further comprises a fill-level sensor 13 that is placed within the nutrient reservoir 7. The fill-level sensor 13 enables the accurate determination of the fill-level of the nutrient reservoir 7. The system 1 also comprises a light sensor 31 for measuring irradiation of PAR. All of the aforementioned valves 9, 10 and sensors 11, 12, 13, 31 are communicatively connected to a control unit 14. The control unit 14 comprises a programmable device (not shown) , for example an integrated circuit, which allows for storing of plant physiological data. These physiological data may include optimum soil moisture levels, optimum nutrient concentrations, and optimum light conditions. The control unit 14 is able to read data on nutrient concentrations, moisture content, and light irradiance as transmitted by the nutrient sensor 11, the moisture sensor 12, and the light sensor 31, respectively. The control unit 14 is able to relate these data to the previously stored plant physiological data for determining the in-situ need for water and/or nutrients. The control unit 14 is furthermore able to effect discharge of water and/or nutrient solution from the water reservoir 6 and/or the nutrient reservoir 7 through the first control valve 9 and/or the second control valves 10. In the embodiment shown in Fig. 1 the driving force for this discharge is gravity, however, it lies with the scope of the present invention that other driving forces, for example the force exerted by a fluid pump, may be employed. The communicative connection between the control unit 14 and the valves and the sensors, respectively, may be achieved through wires or through a wireless connection. The control unit 14 is furthermore communicatively connected to a wireless router 15 which may communicate with external devices such as a computer, a mobile phone, or a personal digital assistant (PDA) . The wireless router 15 may communicate data on the in- situ soil conditions with respect to moisture or nutrient concentrations as well as data on the fluid discharge history or fill levels of the reservoirs. The system of Fig. 1 further comprises a solar panels module 16 and a rechargeable battery 17 that is connected to the solar panels module 16 and to the control unit 14 (connections not shown) . The solar panels module 16 collects solar energy, which is stored in the rechargeable battery 17. The latter supplies the power for maintaining the control unit 14 and its processes, such as opening or shutting of valves 9, 10. In the embodiment shown in Fig. 1, the control unit 14, the wireless router 15, the solar panels module 16, the light sensor 31, and the rechargeable battery 17 are integrated into a lid 18 which may be placed on top of the plant container 2. Advantageously, the lid 18 may be made of a translucent material that permits the passage of light. The lid 18 is different from the opaque lid discussed earlier. Yet another component integrated into the lid 18 is a RFID tag 19. The RFID tag 19 may be communicatively connected to the control unit 14, and may carry data on the plant species, its physiological requirements, the soil texture, and/or the plant's nurturing history. The lid 18 may furthermore serve the purpose of reducing moisture loss from the soil by reducing evapotranspiration . The embodiment shown in Fig. 1 further comprises rotational means 27, for example a rotational plate, for rotating the plant container 2, and thereby its central cavity 3, around its vertical axis 28.

The embodiment shown in Fig. 2 differs from the one shown in Fig. 1 in that the system comprises a plant pot assembly of an inner plant pot 29 and an outer plant pot 30. Components that are identical to the ones shown in Fig. 1 are numbered as in Fig. 1. The inner plant pot 29 features a central cavity 3 for receiving soil and one or more plants (not shown) . In between the two plant pots 29, 30 is formed an annular cavity 5 which may be used in the same way as in the embodiment of Fig. 1.

Fig. 3 shows a functional diagram of a further embodiment of system 1 of the present invention. The system 1 features four nutrient reservoirs 7, 7', 7'', 7''' which may each be filled with a different aqueous nutrient solution. Each nutrient reservoir 7, 7', 7'', η^{r r r} features a gas valve 20 for exchanging gas with the atmosphere and a fluid inlet 21 for refilling of fluid into the reservoir (exemplified only for reservoir 7 in Fig. 3) . The system further comprises a water reservoir 6 which also features a gas valve 20' and a fluid inlet 21' that serve the same purpose as for the nutrient reservoirs 7, 7', 7'', 7'''. Each nutrient reservoir 7, 7', 7'', 7''' is connected to a mixed solution reservoir 22 via a conduit 8 and a first control valve 9 (exemplified only for reservoir 7 in Fig. 3) . Similarly, the water reservoir 6 is connected to the mixed solution reservoir 22 via a conduit 8' and a second control valve 10. All control valves are controllable by the control unit 14. The latter is furthermore communicatively connected to a set of nutrient sensors 11, 11', H'', H''' and to a moisture sensor 12 placed within the soil. Each nutrient sensor 11, 11', H'', H''' is sensitive to a specific nutrient corresponding to the different solutions in the nutrient reservoirs 7, 7', 7'', 7'''. Other shown components include a solar panels module 16, a rechargeable battery 17, and a wireless router 15, all of which serve the same general purpose as in the embodiment shown in Fig. 1. During operation the control unit 14 acts as an interface between all the valves and the sensors. The valves may be opened or shut individually as dependent on the requirements of the plant. The resulting mixed solution in the mixed solution reservoir 22 may accordingly vary over time. The mixed solution is in contact with the soil in which one or more plants are placed. This contact may, for example, be achieved by placing the mixed solution reservoir 22 underneath the central cavity 3 of Fig. 1. Between the cavity and the reservoir may be placed a porous plate or a plate with holes, both of which allow capillar fluid transfer towards the soil and the plant.

The control unit 14 may furthermore be equipped with a user interface that allows the user to select different growth strategies, for example optimum growth, sub-optimal growth, or minimum growth. Accordingly, the control unit 14 will custom- tailor specific water and nutrient transfer rates that lead to the desired results for different plant species.

In the embodiment shown in Fig. 4 the system of the present invention comprises a set of plant containers 2, 2', 2'', 2'" each of which contain a plant 23 and a growth medium 24, for example soil (exemplified only for plant container 2 in Fig. 4) . Each plant container comprises a nutrient sensor 11 and a moisture sensor 12 (exemplified only for plant container 2 in Fig. 4) . The system 1 further comprises a water reservoir 6 and a nutrient reservoir 7, neither of which is an integral part of the plant containers 2, 2', 2' ' , 2' ' ' . The nutrient reservoir 7 and the water reservoir 6 are via a first and a second conduit network 25, 25' connected to a first series of control valves 9, 9', 9'', 9''' and a second series of control valves 10, 10', 10'', 10''', respectively. The system further comprises a control unit 14 that is connected to a wireless router 15 which may wirelessly communicate with a remote computer 26. The control unit 14 may effect opening and shutting of the control valves 9, 9', 9", 9'", 10, 10', 10", 10'", for example through wireless communication. The nutrient reservoir may contain an aqueous solution of one or more plant nutrients, or it may contain a non-aqueous nutrient composition, for example a dry fertilizer. The sensors 11, 12 may transmit data on the water content and the aqueous concentration of one or more nutrients to the control unit 14. The control unit 14 may identify the individual plant species present in the different plant containers 2, 2' , 2' ' , 2' ' ' by accessing information on RFID tags that may be present on each of the plant containers 2, 2', 2'', 2' ' ' (RFID tags not shown in Fig. 4) . Although the embodiment in Fig. 4 only shows four plant containers, any additional number of plant containers lie within the scope of the present invention.

While in the embodiment in Fig. 4 several of the system's components are physically separated from each other it is certainly contemplated to include all components of the system as integral parts of a single plant container. This may be implemented by using double- or triple-walled plant containers with one or more internal cavities. Into these cavities components like reservoirs or a control unit may be placed. Alternatively, one or more components of the system may be releasably or permanently attached to the exterior of a plant container.

Figs. 5-10 show another embodiment of the system 1' of the present invention. As in all figures, the same reference numerals denote the same or corresponding parts.

A frusto-conical plant container 2 comprises a central cavity 3 for receiving a suitable growth substrate such as soil and one or more plants (not shown) . Within the container 2 is disposed a detachable module 32, which comprises one or more nutrient reservoirs 7 which may, for example, contain aqueous solutions of nitrate, phosphate and/or potassium ions. The module 32 is received in a receiving compartment 37 as is best seen in the exploded view of the system 1' shown in Fig. 5. The module 32, when received in the receiving compartment, abuts against the cavity 3, as is best seen in Fig. 7. The reservoirs 7 may be filled through their respective inlet openings 34. Each opening may be closed with a screw cap or the like. For the sake of illustration the side elevational views of Fig. 8 and 9 are shown as if the containers outer side wall were transparent. As is best seen in Fig. 8 the reservoir 7 may be in fluid communication with the cavity 3 by means of conduits 33 and individually controllable valves 39. Figures 10 shows that the module comprises in total three separate reservoirs 7, 7', 7'' with three respective reservoir inlets 34, 34', 34'' and three respective reservoir outlets 35, 35', 35'' connected to three respective conduits 33, 33', 33'' featuring three respective valves 39, 39', 39''. The valves 39, 39', 39'' may permit or shut off fluid flow through the conduits 33, 33', 33''. Fluid flowing from each reservoir through the conduits and valves may be discharged from openings 40 into the cavity 3. Alternatively to what is shown in Fig. 9 the conduits 33 and/or the valves 39 may extend beyond the inner side wall 4' into the cavity 3.

The detachable module 32 further comprises at least one sensor 11 for determining the concentration of one or more nutrients in the soil. As is best seen in Fig. 9, the sensor 11 extends a short distance into the cavity. All sensors and valves are communicatively connected to a control unit 14 disposed within the module 32. In addition, the embodiment of Figs. 5-10 comprises a ring-shaped lid 36 with solar panels disposed thereon. The latter may be used to charge a rechargeable battery disposed within the system. Alternatively or in addition, the system may comprise an electric plug 38 supplying power to the control unit 14, the valves 39 and/or the sensors 11.

The container 2 is double-walled with an inner side wall 4 'and an outer sidewall 4. Within the annular cavity 5 formed between the side walls 4', 4 may be formed at least one water reservoir

(not shown) . In addition, a soil moisture sensor may be disposed in the annular cavity 5, extending into the central cavity 4. The annular cavity 5 may at least partly surround the central cavity 4. The water reservoir formed within the annular cavity 4 may, for example, fill a circular arc of 180°. At the regions adjacent to the receiving compartment 37, the annular compartment may be filled up with solid material (not shown) to ensure a stable and defined receiving compartment 37 for the detachable module. Alternatively, the container may comprise two receiving compartments for two respective detachable modules, the first module comprising one or more reservoirs for nutrient solutions and one or more nutrient sensors, and the other module comprising a reservoir for water and a soil moisture sensor. Other combinations and quantities of modules, reservoirs and receiving compartments are conceivable.

The system of the present invention may advantageously be used for nurturing of specific plant species. To this end, a single container with its one or more receiving compartments may be combined with different types of detachable modules. These different types may be defined by specific combinations of nutrients and suitable sensors. For many applications, a nutrient module containing nitrogen, phosphorous and potassium will be suitable. Other plant species or growth requirements may necessitate another combination. Once one or more reservoirs of a module are empty the control unit may register and signal this, so that the user exchanges or refills the module. To this end, one or more reservoir fill sensors may be used.

The system according to the present invention allows for a precise and efficient control of plant growth since it takes into account important in-situ parameters and furthermore comprises means to manipulate soil moisture and nutrient concentrations. The combination with the sensor arrangement allows for a detailed monitoring of the moisture and nutrient concentration changes effected by the system. The embodiments shown in the figures exemplify the present invention and should not be understood as limiting the invention to the specific features or arrangements shown therein.

Claims

1. A system (1, 1') for controlling the growth of at least one plant (23) in a growth medium (24), said system (1, 1') comprising at least one container (2) with at least one cavity (3) for accommodating the growth medium (24), at least one water reservoir (6) disposed within the container (2 ) , - at least one nutrient reservoir (7) disposed within the container (2), first sensor means (12) extending into the cavity (3) for determining the moisture content of the growth medium (24), - second sensor means (11) extending into the cavity

(3) for determining the aqueous concentration of at least one plant nutrient in the growth medium (24), fluid communication means (8, 33) enabling fluid communication between the water reservoir (6) and the cavity (3), and between the nutrient reservoir

(7) and the cavity (3), respectively, and regulating means (14) for effecting discharge of fluid from at least one of the reservoirs (6, 7) into the cavity (3) .

2. A system (1, 1') according to claim 1, wherein the regulating means comprise a control unit (14) for effecting and controlling discharge of fluid from at least one of the reservoirs (6, 7) into the cavity (3), wherein the control unit (14) is communicatively connected to the first and second sensor means (11, 12) .

3. A system (1, 1') according to claim 2, wherein the control unit (14) comprises a programmable device for saving and processing physiological data concerning one or more plant species.

4. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') comprises two nutrient reservoirs (7, 7'), wherein the first nutrient reservoir (7) contains an aqueous solution of a first plant nutrient, and the second nutrient reservoir (7') contains an aqueous solution of a second plant nutrient.

5. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') further comprises a third nutrient reservoir (7 ' ' ) containing an aqueous solution of a third plant nutrient.

6. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') further comprises at least one detachable module (32) comprising at least one nutrient reservoir (7), the module being received within a receiving compartment (37) disposed integrally within the container (2), wherein the module (32) when received in the receiving compartment (37) at least partly surrounds, or abuts against, the cavity (3) .

7. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') further comprises radiometric measurement means (31) .

8. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') further comprises means for rotating (27) the cavity around its vertical axis (28) .

9. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') further comprises means (13) for measuring the fill level of at least one of the reservoirs (6, 7) .

10. A system (1, 1') according to any any of the preceding claims, wherein the system (1, 1') further comprises means for wireless communication of data on moisture in the growth medium, aqueous nutrient concentration in the growth medium, fluid discharge rates, and/or the fill level of one or more of the reservoirs (6, 7) .

11. A system (1, 1') according to any of the preceding claims, wherein the system (1, 1') further comprises one or more identification tags (19) for storing and/or transmitting data on plant type, soil texture, nutrient and water requirements, moisture in the growth medium, aqueous nutrient concentration in the growth medium, fluid discharge rates, and/or the fill level of one or more of the reservoirs

12.An automated use of a system (1, 1') according to any of the preceding claims for controlling the growth of the at least one plant in the growth medium, the use comprising the steps of monitoring the moisture content of the growth medium and the aqueous concentration of at least one plant nutrient within the growth medium, assessing water and nutrient demand of the plant by comparing the monitored data with plant physiological data saved in the programmable device of the control unit, and discharging water and/or at least one nutrient solution from at least one of the reservoirs (6, 7) into the cavity (3), wherein the transfer process is controlled by the control unit (14) .

13. A detachable module (32) for insertion into a container

(2) of a system (1, 1') according to any one of claims 1- 11, wherein the module comprises at least one nutrient reservoir ( 7 ) .

14. A detachable module (32) according to claim 13, wherein the module (32) comprises two nutrient reservoirs (7, 7') with two respective reservoir inlets (34, 34') and two respective reservoir outlets (35, 35'), wherein the first reservoir (7) contains an aqueous solution of a first plant nutrient, and the second reservoir (7') contains an aqueous solution of a second plant nutrient.

15. A detachable module (32) according to claim 14, wherein the module (32) further comprises a third reservoir (7 ' ' ) with a respective reservoir inlet (34'') and a respective reservoir outlet (35'') wherein the third reservoir (7 ' ' ) contains an aqueous solution of a third plant nutrient.

16. A detachable module (32) according to any of claims 13-

15, wherein the module further comprises sensor means

(11) extending into the cavity (3) for determining the aqueous concentration of at least one plant nutrient in the growth medium (24) .

17. A detachable module according to any one of claims 13-16, wherein the module has an arcuate cross section, the module being arranged for disposal within an arcuate receiving compartment formed integrally within the container (2) and at least partly surrounding the cavity (3) .