A fertigation system and a method of determining an amount of fertilizer to mix with water in a fertigation system

Abstract

A fertigation system having water supply and irrigation lines to supply a mixture of at least one fertilizer and water to a desired soil region includes: at least one soil sensor (211, 212, 212), wherein the at least one soil sensor (211, 212, 212) is placed under a surface region (203) of the soil and is configured to measure a concentration of the at least one fertilizer or components thereof in the soil over time; and a supply unit (100) for storage of the fertilizer and water, and for mixing of the fertilizer to a desired dilution within the water; and a controller (108) that is operatively connected to the at least one soil sensor (211, 212, 212) and the supply unit (100). The controller (108) is configured to direct an irrigation profile of mixed water and fertilizer delivered from the supply unit (100) to the soil, to thereby maintain a constant value of at least one soil parameter over time.

Description

[0001] A FERTIGATION SYSTEM AND A METHOD OF DETERMINING AN AMOUNT OF FERTILIZER TO MIX WITH WATER IN A FERTIGATION SYSTEM

[0002] RELATED APPLICATIONS

[0003] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 523,234, filed June 26, 2023, entitled “Low Volume Water and Fertilizer Fertigation,” the contents of which are incorporated by reference as if fully set forth herein.

[0004] FIELD OF THE INVENTION

[0005] The field of the invention is generally the application of fertilizer mixed into irrigation water, and more specifically, but not exclusively, to systems and methods for delivery of water and fertilizer in pulses of irrigation with constant delivery of fertilizer at low concentration.

[0006] BACKGROUND OF THE INVENTION

[0007] Irrigation water and fertilizer systems and methods are known as “fertigation”, an idea that encompasses the application of fertilizers into an irrigation system. This is accomplished in two main ways: Venturi Injectors that provide a continuous flow of fertilizers into the irrigation system and positive displacement injectors that provide an intermittent flow.

[0008] In the Venturi injectors, applying the Venturi principle, a pressure difference within the pump draws the fertilizer into the system. A disadvantage of using Venturi injectors is the difficulty in controlling the concentration of the fertilizer delivered to crops. Although continuous, the Venturi injectors only deliver fertilizers where a pressure difference is present and during the irrigation period. The pressure difference is difficult to control, which results in the fertilizer being delivered only at a single time point during the irrigation, and also results in an uneven uptake of the fertilizers into the irrigation system. Therefore, the concentration of the fertilizer may change during the irrigation period.

[0009] A second fertigation system uses positive displacement injectors. These injectors are more accurate than the Venturi injectors in supplying fertilizers into the irrigation lines regardless of water pressure. They inject the fertilizer in pulses at a ratio of fertilizer to water that is dependent on the pump model and type.

[0010] Irrespective of the particular method of irrigation, all current fertigation methods are achieved in one of two ways: a. Supplying all the fertilizer for a short time at the end of the irrigation period; or b. Turning the fertilization-irrigation pump on and off periodically. By pulsing the pump, the concentration of fertilizer in the soil increases or decreases. The concentration of the fertilizer is averaged to achieve a desired application of the fertilizer during the irrigation period.

[0011] One way to measure the degree of uptake of fertilizer in the soil is to measure the electroconductivity of the soil. The electroconductivity is determined, in part, by the presence of certain ions that are delivered via the fertilizer, including potassium, ammonium nitrate, and phosphate. An increase in electroconductivity following application of fertilizer indicates that the soil is overfertilized and that fertilizer is not taken up by the plant. U.S. Patent 10,561 ,081 discloses a system and method of modulating fertilizer application in a fertigation system based on readings from an EC sensor. In this system, an EC sensor is introduced about 30 to 50 cm below the surface of the soil, and measures variation in the EC over a long period of time. A controller receives data from the EC sensor, a solar radiation sensor, an air temperature sensor, and on the basis of this data calculates a flow rate of fertilizer culture solution to be mixed with water. This system, however, utilizes the EC data in order to deliver the fertilizer periodically, as in option (b) described above. This strategy is thus prone to overfertilization for the reasons discussed.

[0012] SUMMARY OF THE INVENTION

[0013] The prior art operates under the premise that the soil behaves as a bucket mixing fertilizer and water. However, in practice, the soil does not retain the fertilizer. As much as 50% of the fertilizer runs off into the ground water. To achieve a predetermined concentration of fertilizer, the current practices require a higher concentration of fertilizer than is needed by the plant, to counteract the runoff.

[0014] Even when the fertilizer is carried in the irrigation line, often the fertilizer and water are not properly mixed. The lack of mixing causes areas that receive small fertilizer or spikes in concentration. Excess fertilizer used to meet the deficiencies caused by non-mixing of the fertilizer in the flowing water stresses the plants and reduces the capacity of the plants to absorb nutrients. This in turn impairs plant vitality. In extreme cases the high concentration of fertilizer may cause plant death. Moreover, the variation in the amount of fertilizer reaching the plant prevents the plant from reaching homeostasis.

[0015] The inventors of the technology disclosed herein have developed systems and methods for fertigation that reduces the amount or concentration of fertilizers used to a bare minimum, and in so doing increasing crops’ vitality and reducing fertilizer-based plant stress. In the systems and methods of the present disclosure, the fertilizer is delivered throughout the entire period of irrigation, at an essentially constant, low concentration. The constant flow of fertilizer in the irrigation line enables the plant to reach homeostasis, thereby optimizing fertilizer uptake. This low concentration is selected so as to provide to the plant the exact amount of fertilizer that is required, without spiking the fertilizer delivered to the plant, which induces osmotic pressure within the plant, and without leaching excess fertilizer into the soil. The methodology disclosed herein additionally has the benefit of avoiding use of excess fertilizer concentration and limiting variation in fertilizer concentration along a field and a watering session.

[0016] Generally, systems and methods of the invention permit controlling the application of a fertilizer by monitoring at least one soil parameter, such as electroconductivity (EC) of the soil, during a fertilization session or a period or a season and adjusting the amounts of fertilizers applied to the soil so as to reduce modulation in fertilizer concentrations in the soil and runoff of excess fertilizers. The measured parameter, e.g., EC, provides a direct tool for assessing the degree of fertilizer uptake by the plants. A constant concentration of fertilizer in the soil will generate a constant measurement (or limit a variation in the measured soil parameter), as long as the fertilizer concentration that is taken up by the plants is constant. Seasonal changes, field-specification factors and plant varieties affecting fertilizer uptake may be adjusted and monitored to keep the fertilizer application optimal. If the fertilizer is added in an amount that exceeds the possible uptake of the fertilizer by the plants, or in an amount that is insufficient to supply the daily uptake amount, thereby leaving the soil depleted of the fertilizer, the measured soil parameter, e.g., EC value, will change. The fertilization that is delivered to the plant is adjusted accordingly. In addition to monitoring a soil parameter, systems and methods according to the present disclosure may utilize other sensors that measure plant vitality and plant responsiveness to fertilizer. These sensors may include, for example, leaf temperature sensors and air temperature sensors. The difference between leaf temperature and air temperature over time may serve as an indication of plant vitality and of nutrient uptake.

[0017] Thus, it is an aim of the systems and methods of the present disclosure to provide a fertilization method and system for continuous fertilization of a soil region, such that the amount of the fertilizers in the soil does not vary over the watering or fertilization period.

[0018] In a first of its aspects, the invention provides a fertigation (fertilization-irrigation) system having a water supply and irrigation lines to supply a mixture of at least one fertilizer and water to a desired soil region (typically a soil region in contact with roots of plants). The system includes at least one soil sensor, wherein the at least one soil sensor is placed under a surface region of the soil and is configured to measure the concentration of the at least one fertilizer or components thereof in the soil over time. The system further includes a supply unit for storage of the fertilizer and for mixing of the fertilizer to a desired dilution within the water. A controller is operatively connected to the at least one soil sensor and supply unit. The controller is configured to direct an irrigation profile of mixed water and fertilizer to be delivered from the supply unit to the soil, to thereby maintain a constant value of a soil parameter over time.

[0019] The invention further provides a fertilization-irrigation system, the system comprising water supply and irrigation lines to supply a mixture of at least one fertilizer and water to a desired soil region (typically a soil region in contact with roots of plants), the system further comprises a controller for setting an irrigation profile to provide a substantially constant concentration of the at least one fertilizer in the soil, said constant concentration being determined by a sensor capable of measuring at least one measurable soil parameter e.g., electro-conductance sensor positioned in the soil, and / or other sensors measuring plant uptake of nutrients.

[0020] Advantageously, the maintenance of a constant concentration of the fertilizer in the soil helps ensure that no fertilizer is wasted, and that the soil remains in a balanced and healthy state.

[0021] Systems and methods of the invention allow for an in situ real-time determination of an “irrigation profile" which purpose is to maintain the fertilizer amount minimal and its concentration in the soil constant over time. The irrigation profile includes fertilization concentration, type of fertilization, irrigation amount, length of an irrigation period, frequency of fertigation, etc. The irrigation profile may be modified during the irrigation session to avoid excess fertilization or under-fertilization. Based on a change in the measured soil parameter or other sensor data, e.g., EC of the soil, measured throughout the irrigation session, the irrigation profile may be modified to increase, decrease or maintain constant the fertilization pulses.

[0022] The controller may include a memory and a processor. The memory may be a non-transitory computer-readable medium containing instructions that, when executed by the processor, cause the performance of certain steps described herein. The memory stores information such as time of year data, air temperature data, and soil electro-conductive data associated with the soil location where the fertigation system is located. The processor is configured to determine the irrigation profile and to issue commands to the supply unit in order to produce a fertigation output according to the irrigation profile.

[0023] The controller monitors the soil sensor to maintain a stable fertilizer concentration and controls the one or more pumps to draw a mixture from the containers so that the soil sensor reports a stable EC (or other soil parameter) for the soil. The controller may be configured to control or instruct operation of one or more pumps, fertilizer tank(s) and / or one or more mixing tanks to maintain a stable fertilizer concentration at the soil sensor during an irrigation period.

[0024] In some embodiments, upon a determination by the controller that the soil parameter has changed, the controller is configured to cause the supply unit to modify the irrigation profile. The determination may be based on a change in the measured soil parameter(s) or other sensor data, received from a sensor or a sensor array positioned in a given field. The modification is determined to reverse the change in the soil parameter, to thereby maintain the soil parameter essentially constant.

[0025] In order to supply the fertilizer at the desired concentrations and within the desired timing, the system of the present disclosure includes a supply unit coupled to a water line of an irrigation system. The supply unit may include at least one storage or holding container(s) containing at least one fertilizer or a water solution thereof and at least one or more mixing containers for mixing an amount of a fertilizer and water to a solution of a predetermined concentration, and for delivery of the mixed fertilizer and water to the plants. To enable preparation of various fertilizer concentrations, as may be required for a proper irrigation profile, the at least one storage containers or tanks may be configured to hold water and an amount of the fertilizer and to mix the two components to provide a homogeneous fertilization solution. In some configurations, the system may comprise two or more storage containers. A fertilizer storage container is configured to hold the fertilizer, and a water tank is configured to hold water free of fertilizer. A mixing container may be provided for mixing the water and the fertilizer. Optionally, a second storage container is configured to hold a mixture of a fertilizer and water in a predetermined concentration, for dilution when preparing the fertilizer concentration for the irrigation profile.

[0026] The controller may be operatively coupled to a main irrigation controller of the irrigation system and in communication with the supply unit. The controller is configured to send a signal to the supply unit and the supply unit is configured to inject at least some of the at least one of the fertilizers from the at least one container into the water line in response to receiving the signal from the controller. Alternatively, the controller may be configured to instruct the supply of an amount of the fertilizer solution having a predetermined concentration into the water line.

[0027] In some embodiments, the controller includes: a memory storing time of year data, air temperature data, and soil electro-conductive data associated with the soil location where the irrigation system is located; an output configured to be in communication with the supply unit; and a processor coupled to the memory and the output. Alternatively or additionally a computer unit, e.g., an external computer, may be used for processing and instructing the operation of the system. The computer memory may be used to store and manage the irrigation profiles.

[0028] Upon a determination by the processor that the soil parameter(s), e.g., electro- conductive parameters of the soil, or other relevant data have changed, the processor is configured to generate at the output a signal to the supply unit, to cause the supply unit to modify the current irrigation profile; namely, for example, inject at least some of the at least one of the fertilizer from the at least one storage container of the supply unit into the water line; to cease supply of the fertilizer, to modify an irrigation profile of the irrigation system, or introduce any other change into one or more operating conditions (time, sequence, concentration, etc.) of the irrigation profile.

[0029] In some embodiments, the system may comprise any one or more of:

[0030] -at least one fertilizer container; -at least one pump in fluid communication with the fertilizer container;

[0031] -at least one mixing container in fluid communication with the at least one pump; and

[0032] -at least one controller coupled to the pump and the fertilizer container.

[0033] The mixing reduces variation in fertilizer concentration and variation in the EC. The mixing may be achievable by an active or passive means. The active mixing may be in the form of one or more mixing tanks. The passive mixing may be in a form of one or more swirl chambers or tubes with fins, for example. The passive mixer coupled in line after a pump creates turbulence in the irrigation line. This turbulence improves the mixing between water and fertilizer and causes a greater expansion of the pulse, making the irrigation water more homogeneous.

[0034] In some embodiments, the system may comprise two active mixing tanks. As the pump draws fertilizer from a first tank, the second tank may be filled with a predetermined mix of fertilizer and water. The predetermined mix may vary by season, temperature, soil mixture, moisture and other factors affecting plant health, vitality, and growth. The second tank provides a reserve where the demand for fertilizer during irrigation would otherwise exceed the supply.

[0035] The system may further comprise a water level sensor and a water level valve that are coupled to the at least one controller to maintain a predetermined water level in each of the mixing or holding tanks.

[0036] The system includes at least one sensor capable of measuring at least one soil parameter. As used herein, a “soil parameter1’ is one or more detectable parameter that changes due to a change (an increase or a decrease) in the organic and / or ionic content of the soil. Typically, the soil parameter is independent of temperature and can be adapted based on the geographical region, the type of soil, the natural dryness or water content of the soil and other parameters characterizing the field. The soil parameter may be directly related to presence of organic matter or ions in the soil or may relate to any change in the composition of the soil.

[0037] In some configurations, the soil parameter relates to a measure of the NPK content of the soil.

[0038] As such, the sensors used may vary and may be selected from electromagnetic sensors, electrochemical sensors, optical and radiometric sensors. In some embodiments, the sensor is selected to detect a change in the NPK content of the soil. Such sensors may be nitrogen (N), potassium (K) or phosphorus (P) sensors, or a combination thereof.

[0039] In some cases, the sensor is an electromagnetic sensor. The electromagnetic sensor relates to a device (or an element within a device) for sensing presence and / or amount of a particular target substance in a specified location of the soil over time. Non-limiting examples of electromagnetic sensors may include electrical resistance sensors, electrical conductance sensors, current sensors, voltage sensors, power sensors, magnetic sensors, metal ion detectors and others.

[0040] In some embodiments, the sensor is a chemical sensor which may include NPK sensors, oxygen or carbon monoxide detectors, ion selective or redox electrodes, and others.

[0041] In some embodiments, systems of the invention make use of electromagnetic sensors in a form of an electrical resistance sensor or an electrical conductance sensor. In some embodiments, the sensor is an electro-conductance (EC) sensor.

[0042] In some embodiments, a system of the invention may comprise an EC sensor and potentially other sensors such as air temperature sensors, leaf temperature sensors, soil temperature sensors, stem diameter sensors, pH sensors, and others. In some embodiments, the at least one soil sensor comprises arrays of two or more soil sensor configured at different heights of roots of the same plant.

[0043] The sensor may be positioned in the soil at a predetermined location in the irrigation field or may be provided in a form of an array of sensors positioned at predetermined distances within the extent of the field. The depth of the sensor may also vary. The depth may range from the surface of the soil to a depth defined by the depth reached by the plant roots.

[0044] In some configurations, all sensors in a given sensor array are positioned at the same depth. In other configurations, the sensors’ depths may vary along the field. In certain embodiments, two arrays of sensors are placed at different depths. An array of sensors is placed at the bottom of the root zone, for tracking the immediate response of the plant to infusion of fertilizer. An array of sensors is placed at the middle of the root zone, for tracking trends in the free fertilizer that is diffused within the soil around the plant. These different sensors measure different parameters. First, the sensor at the bottom of the plant roots is used to avoid stressing the plant, while the sensor within soil above the bottom is used to determine whether the plant is absorbing the fertilizer. This allows for reducing the fertilizer during the irrigation period to efficiently water and fertilize the plant. The report from the sensor may be used to determine the duration of an irrigation session and the concentration of fertilizer applied.

[0045] The sensor, e.g., EC sensor, is configured to send to the controller a measured value, e.g., an EC value, measured for soil proximate to the water line. The controller is configured to determine, based on at least one of prestored data: a time for initiating injection of the at least one of the fertilizer into the water line; and relative amounts of at least one of the fertilizer to be released upon injection from at least one storage tank into the water line.

[0046] When the system includes an array of air temperature sensors and leaf temperature sensors, the controller is configured to determine a change in the irrigation profile based on a trend in a difference between the leaf temperature and the air temperature.

[0047] According to a second aspect, a method of determining an amount of fertilizer to mix with water in a fertigation system is disclosed. The method includes: measuring at least one soil parameter at a root zone of the plant; calculating a trend in the soil parameter over time; and based on the trend, maintaining or adjusting the amount of fertilizer that is mixed with water in an irrigation profile.

[0048] Optionally, the measuring step includes measuring the at least one soil parameter at a bottom of the root zone and at a middle of the root zone.

[0049] Optionally, the trend calculated from EC data measured at the middle of the root zone is a trend of EC concentration in the soil over time. The trend calculated from EC data measured at the bottom of the root zone may be a trend in the height of the peak caused following addition of new fertilizer into the soil.

[0050] Optionally, the method further includes measuring a difference of leaf temperature compared to surrounding air temperature following a change in the irrigation profile, and based on a trend in the difference, maintaining or reversing the change in the irrigation profile.

[0051] Optionally, the method includes delivering the fertilizer mixed with water according to the irrigation profile in a constant concentration throughout a fertigation session. Exposure to the fertilizer is controlled at a lower concentration than is typical in known fertigation systems, so that variation in the concentration of fertilizer at the plant roots, during the irrigation period, is reduced. By reducing the EC of the soil and by keeping the EC constant during the irrigation period, the plants are less stressed and the intake of the fertilizer by the plants is increased. This allows for using less fertilizer at a lower volume of water.

[0052] According to a third aspect, a method of fertigation is disclosed. The method includes delivering fertilizer at a constant concentration throughout an irrigation session. The fertigation session may last a substantial period of time, e.g. 30 minutes or more, and may deliver a low, constant supply of fertilizer to the plant, so as to avoid spikes in osmotic pressure and enable the plant to achieve homeostasis.

[0053] Optionally, the delivering step comprises delivering pulses of mixed water and fertilizer from a positive displacement pump. The delivering step may further include passing the mixed water and fertilizer though a passive mixer downstream of the positive displacement pump, to thereby homogenize the mixed water and fertilizer.

[0054] BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Fig. 1 A is a graph of EC against time for the application of fertilizer at the end of a two-hour irrigation period as known in the art;

[0056] Fig. 1 B is a graph of EC against time for the pulsed application of fertilizer every several minutes within a two-hour irrigation period, according to the prior art;

[0057] Fig. 1C is a graph of EC against time for the essentially constant application of fertilizer throughout a two-hour irrigation period, according to embodiments of the present disclosure;

[0058] Fig. 2 is a block diagram of a system according to some embodiments of the present disclosure;

[0059] Fig. 3 is a schematic view of sensors arranged in relation to a plant according to some implementations of the present disclosure;

[0060] FIG. 4A illustrates trends in EC soil data collected from the middle of the root zone, according to embodiments of the present disclosure;

[0061] FIG. 4B illustrates trends in EC soil data collected from the bottom of the root zone, according to embodiments of the present disclosure.

[0062] DETAILED DESCRIPTION OF THE INVENTION

[0063] Plants are affected quickly by changes in electroconductivity (EC). Because of this, averaging fertilization (e.g., delivering fertilization in relatively large quantities and with large time gaps in between deliveries) is not effective. These changes in fertilizer concentration in the soil are reflected in changes in the EC. Soils with a high concentration of fertilizer and high EC stress the plants and adversely affect plant vitality. The systems and methods of the present disclosure are aimed at providing low concentrations of fertilizer throughout the irrigation. This low and stable concentration of fertilizer allows the plant to adjust and absorb all the fertilizer that is applied.

[0064] The EC data is a proxy for the capacity and demand of plants to use fertilizer. By maintaining a stable concentration as described herein the plants are not stressed and receive an adequate amount of a water-fertilizer mixture. This is an advantage over the swings of EC and by extension fertilizer concentration in terms of plant health, capacity to use fertilizer, and avoiding waste of fertilizer to runoff. This results in more efficient fertilization and less use of fertilizers. The environmental impact of less fertilizer use is improved water quality including a lower incidence of algae blooms and the resulting depletion of available dissolved oxygen in bodies of water. The data from the system may be used to improve biodiversity in lakes and streams.

[0065] The systems and methods may be implemented as a solution to the technical problem in an embodiment that has a controller coupled to one or more soil sensors 211 and 212, as depicted in Figures 2 and 3. The controller is generally configured to supply fertilizer based on the following data:

[0066] -fertilizer concentration information from soil sensors 211 , 212; and

[0067] -optionally, leaf and air temperature information taken from temperature sensors 213, 214; to supply the amount of fertilizer at a rate that the plants can consume. This delivery of the fertilizer is essentially constant, subject to only to technical limitations of the pump that is used to deliver the mixture of fluid and fertilizer. A pumping cycle of water and fertilizer may occur every second, for example, or even more than once per second.

[0068] The system and method utilize the following components in order to implement this fertilization:

[0069] -a fertilizer and water mixture which may be actively and passively mixed (Fig.

[0070] 2);

[0071] -a pulsed pump used to reduce modulation in the peaks of fertilizer concentration (Fig. 2).

[0072] By receiving data from the soil sensors and optionally the additional sensors, the system and method provide various advantages over prior practice. The system provides a way to deliver the application of fertilizer only in the amount that the plant can consume, hence avoiding over-fertilization that stresses or adversely affects plant vitality.

[0073] Another advantage is that the system of the present disclosure includes mixing tanks and a passive mixer, which thoroughly mix the fertilizer and water to avoid fertilizer spikes.

[0074] Another advantage is that the pumps are pulsed to keep the EC data stable while fertilizer is applied. The controller operates the pump in a way to pulse the pumps to avoid the spikes in fertilizer concentration, by smoothing the spikes as compared to the trend seen in Fig. 1 b.

[0075] The systems and methods of the present disclosure are an advance over the current practice of adding fertilizer to the end of an irrigation period or the pulsed administration of fertilizer in a fertigation system at intervals of several minutes or longer without monitoring the fertilizer concentration near the plant roots. The present invention stabilizes the concentration of fertilizer at the target plants’ roots. The stable concentration allows the plant to avoid stress and to lower the overall fertilizer load because it reduces runoff of fertilizer and thus allows for a less intensive and lower cost application of fertilizer.

[0076] Fig.1 A is a graph showing the prior art application of fertilizer at the end of an irrigation period. The water is delivered over a period lasting approximately 120 minutes, and the fertilizer is delivered approximately during minutes 100 to 120. The graph over time shows that the application of fertilizer in the current practice comes late in the period and results in a dramatic increase in EC. The EC in the graph is measured in deciSiemens per meter (dS / m).

[0077] Fig. 1 B illustrates another current practice illustration of the intermittent pulse application of the fertigation pump. In this practice, the fertilizer is delivered approximately every 8 minutes. The amplitude of the EC measurements shows a swift reaction. Therefore, achieving an average concentration, which is desirable as is known in the industry, requires higher peaks to establish the desired concentration as a mean.

[0078] FIG. 1 C schematically illustrates the profile of EC measurements in soil over the duration of a 120 minute irrigation session according to embodiments of the present disclosure. The EC remains essentially constant throughout the entire irrigation period, and generally ranges between 5 and 10 dS / m, subject to the degree of dilution of the fertilizer.

[0079] The system of the present disclosure combines three elements working together: at least one subsoil sensor configured to measure a signal or measurement, e.g. an EC signal, as a measure of fertilizer concentration, optionally in concert with additional sensors; a controller that receives that information, determines an amount of fertilizer to apply and whether to increase or decrease the current amount of fertilizer during an irrigation session, and operates the system to apply fertilizer, and one or more mixers that produce a uniform concentration of fertilizer in the irrigation water. The system is configured to deliver rapid pump pulses to stabilize the concentration of fertilizer by reducing the amplitude of spikes in concentration of fertilizer.

[0080] FIG. 2 schematically illustrates different components of supply unit 100, according to embodiments of the present disclosure. Supply unit 100 is an exemplary system for preparing fertigation mixtures with different concentrations of fertilizer in the irrigation water, according to the needs that are determined for each plant at a given time. In FIG. 2, solid lines represent piping or physical connections, whereas dashed lines represent electrical connections.

[0081] In general, supply unit 100 is connected to a source of irrigation water. Water enters the system via water inlet 101. The water inlet flows through flow meter 102 and check valve 103. The check valve 103 prevents rearward flow of the water from pump 105 to the source of irrigation water. Water exiting the check valve 103 enters vacuum releaser 104. The function of vacuum releaser 104 is to ensure that operation of pump 105 does not cause a vacuum condition in the water line. A vacuum condition is also possible because of the length of the irrigation line and drop in elevation of the irrigation lines from the source of water (not shown here). The pump in combination with the irrigation lines can cause cavitation or a “water hammer”. A cavitation or water hammer reduces the efficiency of the pump and in some cases, it may cause damage to the water lines and pump. The vacuum releaser permits air into the system to thereby prevent such phenomena. Following passage through the vacuum releaser, the water enters pump 105.

[0082] Supply unit 100 also includes a source of fertilizer. The fertilizer is stored in a fertilizer tank 110. Fertilizer tank 110 is connected to a fertilizer level sensor which is used to indicate when it is necessary to refill the tank. The tank 110 is also connected to a filter 111 (to ensure that residue in the fertilizer tank does not enter into and clog the pump), flow meter 112, and then to NC (normally closed) solenoid valve 113. The NC valve 113 is opened when fertilizer is being supplied to the pump 105.

[0083] Pump 105 receives inlets both from the water source and from the fertilizer source. Pump 105 delivers the water and fertilizer to one of solenoid valve 106 or solenoid valve 115. When the water and fertilizer are ready to be delivered to the plants, the mixture is delivered to valve 106. When the water and fertilizer are to be mixed, they are delivered through valve 115, to a mixing portion of the supply unit 100.

[0084] Specifically, in the mixing scenario, water exiting the pump 105 through valve 115 opens to a water level control valve 117. The water level control valve 117 functions as a flow restrictor, for controlling the volume of water and fertilizer entering mixing tank 118. The water and fertilizer then enter mixing tank 118. Mixing tank 118 is equipped with a water level sensor 119 which is connected to controller 108. The water level sensor 119 is used to monitor volumes of water and fertilizer entering the mixing tank, to thereby confirm that the desired amount of both ingredients is included in the mixture.

[0085] In exemplary embodiments, mixing tank is an active mixer. The active mixer mixes the water and fertilizer through any suitable mechanism known to those in the art, such as stirring, vibrating, vortexing, etc.

[0086] After exiting mixing tank 118, the mixture goes through filter 116 and normally open solenoid valve 114 (which is closed only during the mixing process), and is returned to pump 115. Optionally, the mixture may be pumped through the mixing tank more than once, if it is desired to dilute the fertilizer mixture by more than the dilution obtained through one run-through.

[0087] In certain embodiments, the flow capacity of the water from the water source is up to about 18-20 times the flow capacity of the fluid that is drawn into the pump 105 from either normally closed valve 113 or normally open valve 114.

[0088] The degree of dilution of the fertilizer within water is controlled through operation of a duty cycle of NC valve 113. When water flows through the water inlet 101 , the water flows at a constant rate through the pump 105, into the mixing tank 118, through normally open valve 114, and back to the pump 105 and to the irrigation lines. Fertilizer is mixed with the water by pumping of the fertilizer through normally closed valve 113 into pump 105 and from the pump 105 into the mixing tank 118. The flow rate of the fertilizer is limited by the maximum drawing capacity of the pump. As discussed, the drawing capacity of the pump may be around 1 / 18 the flow capacity of the water. Thus, at maximum, the mixed water and fertilizer reentering the pump is diluted 18-fold. If the duty cycle of the fertilizer is set at a lower level than the maximum, then the fertilizer is diluted even more. Obviously, the power of the pump may be raised, or more than one pump may be utilized, if a lesser degree of dilution is desired. The mixture of water and fertilizer is diluted again, by the same factor, through mixture of water flowing from water inlet 101 and the mixed water and fertilizer reentering the pump 105. Thus, cumulatively, in this example, the fertilizer is diluted by a factor of 1 :324 (1 :18 squared), or approximately to a total dilution of 3 parts per thousand. Because liquid fertilizer is usually extremely concentrated, this degree of dilution is actually still very high, for most applications. The dilution is even lower if the normally closed valve is closed during a portion of the time that is required to fill the mixing tank.

[0089] The duty cycle of the normally closed valve 113 may be expressed as a scale of 1 to 10, in which “10” refers to the state of the valve always being open, and 1 refers to the valve being open only 10% of the time. This scale of 1 to 10 may be utilized in place of absolute values. This scale may be referred to when evaluating the concentration of the fertilizer and adjusting it in response to sensor data, as will be discussed further herein.

[0090] While there are various ways to dilute fertilizer with water in varying concentrations, the system and method discussed above has particular advantages. Most notably, it is possible to achieve the desired range of dilutions without ever changing the flow rate of the water. In addition, the concentration of the fertilizer may easily be adjusted through operation of the controller on the pump and solenoid valves.

[0091] Once the mixture is diluted to the desired concentration, the mixture is then pumped through valve 106, and optionally through static mixer 107, and to the irrigation lines. The static mixer may be, for example, a series of bends, a labyrinth, or one or more constriction points. The static mixer helps counteract variability in the output of the pump that may result from laminar flow.

[0092] The pump 105 is thus configured to deliver the fluid, pre-mixed with fertilizer, to the plant. The frequency of delivery of the fertilizer to the plant is thus subject only to the periodicity of the pump. For example, if the pump delivers fluid every second, then the fertilizer is delivered to the plant every second. However, due to the action of the static mixer and the subsequent mixing in the irrigation lines, each one second pulse becomes intertwined with a subsequent one. At lower frequencies of pumping, or when a duty cycle is employed, a wave pattern in the delivery of fertilizer may be observed. The controller 108 includes a processor and a memory. The memory may be a non-transitory computer-readable medium containing instructions that, when executed by the processor, cause the performance of certain steps described herein. The controller may be housed on a computer connected to the other elements of the system 100 via a wired connection, or may be a cloud-based computer configured to receive information and provide instructions wirelessly.

[0093] The controller 108 has two functions: first, to control the operations of the supply unit 100 to deliver timely and consistent mixtures of water and fertilizer, as described, and second, to take the data from one or more soil sensors and temperature sensors and use this data to calculate the desired concentration of fertilizer in a predetermined range. With respect to the first function, the controller 108 is connected to various elements that control the volumes of water and fertilizer that enter into a fertigation mixture. These include solenoid valves 106 and 115, water flow meter 102, fertilizer flow meter 112, water level sensor 119, and fertilizer level sensor 109. With respect to the second function, the controller 108 receives data input from the various sensors 120 that are implemented around the plants, including soil sensors and optionally temperature sensors. The memory of the controller stores information such as time of year data, air temperature data, and soil electro-conductive data associated with the soil location where the fertigation system is located. The controller includes software configured to execute the algorithms described herein to thereby determine suitable concentrations of fertilizer to supply to the plants in view of the sensor data and changes of trends in uptake of nutrients from the soil, as discussed herein.

[0094] As may be recognized by those of skill in the art, supply unit 100 may be arranged in a different manner or incorporate different components. For example, instead of having a single mixing tank, the system could have two mixing tanks. One mixing tank may have a permanent, concentrated solution of fertilizer, which may be diluted as desired in a second mixing tank. In addition, in the illustrated embodiment, there is only a single pump 105, through which fluid and fertilizer are routed (at least) twice, once prior to mixing and once following mixing. In alternative embodiments, these roles may be distributed to two separate pumps or groups of pumps, one prior to mixing and one after mixing.

[0095] Advantageously, system 100 may be used to provide fertigation at a constant concentration of fertilizer within the irrigation water. A constant concentration avoids two challenges manifest in current methods of fertigation: the osmotic pressure caused by spikes in fertilizer concentration, and the prevention of homeostasis in the plant due to even minor changes in fertilizer concentration. The constant concentration is delivered over a long fertigation session lasting 30 minutes, 1 hour, 2 hours, or even longer. Because of mixing downstream of the pump 105, as discussed, the system achieves this constant concentration even when the pump does not deliver a constant flow of fertigation fluid. For example, the pump may deliver a pulse every 1 second, every 10 seconds, every 30 seconds, or even less frequently, and the fluids will mix within the irrigation tubing to ensure a constant flow.

[0096] FIG. 3 illustrates a setup 200 of sensors on and around a plant 201 , according to embodiments of the present disclosure. A first EC sensor (or other soil sensor) 211 may be configured under the surface region 203 of the soil, at the bottom of a root zone 202, approximately 50 cm below the surface region 203 (the depth may vary depending on the type of plant). A second EC sensor (or other soil sensor) 212 may be configured at the middle of root zone 201 , approximately 20 cm below the surface of the ground (the depth may vary depending on the type of plant). As discussed above, the soil sensors may be any other suitable type of sensor for measuring an indication of fertilizer concentration in soil, such as an electromagnetic sensor. In addition, the setup 200 optionally includes two temperature sensors. Temperature sensor 213 measures ambient air temperature, and temperature sensor 214 measures leaf temperature. A fertigation line 216 delivers water and fertilizer mixture 217 to the soil area. As is apparent, the illustration of FIG. 3 is schematic, and there may be multiple sensors and irrigation lines instead of the single examples shown herein. Likewise, while in the illustrated embodiment the soil sensors are adjacent to plant roots, in alternative embodiments the soil sensors may be elsewhere in the field. One advantage of distancing the soil sensors from the irrigation lines is that it is possible to measure the travel of a plume of fertilizer from the irrigation line through a field.

[0097] FIGS. 4A and 4B illustrate how the soil sensor data may be analyzed in order to evaluate uptake of nutrients by the plant. FIG. 4A illustrates representative data from soil sensor 212 which is placed in the middle of the root zone. The EC is measured over the course of a week (168 hours). Periodically during this period, irrigation is supplied for a short period of time (such as around two hours). During this irrigation, fertilizer is supplied at an essentially constant rate, as discussed.

[0098] Generally, plants do not take up nutrients in fertilizer at the same rates throughout a weekly period. Specifically, a plant actively engages in photosynthesis only during daytime hours. Thus, the decline in fertilizer nutrients in a plant is primarily during daytime hours, whereas the soil nutrient level remains essentially constant at night.

[0099] In addition, the presence of water in soil also influences electroconductivity of the soil. Thus, during an irrigation session, the electroconductivity of the soil increases a certain amount because of the water, and an additional amount due to the presence of the ions from the fertilizer.

[0100] FIG. 4A illustrates trends in EC following fertigation sessions which are spaced once every two days (48 hours). Each peak in EC represents a fertigation session. The water of the fertigation session is absorbed quickly, resulting in a corresponding drop following the peak. The fertilizer ions are absorbed less quickly over the course of the next 48 hours. The EC data is analyzed to review the trend of the EC sensor. This trend represents how much fertilizer is not absorbed by the plant. This time period is divided between nighttime periods in which the EC of the soil is essentially flat, and daytime periods in which the EC of the soil is dropping. If the amount of fertilizer is applied correctly, then the trend should be identical over the course of each 48 hour period. If the trend line is going down, then more fertilizer is added. If the trend line is going up, then the amount of fertilizer is reduced. The goal of the evaluation is to keep the trendline as close as possible to flat. In the present example, the trend indicates a downward slope, signifying that the net EC of the soil is decreasing over time. As a result, corrective measures are required in the form of increasing the fertilizer concentration.

[0101] FIG. 4B illustrates data from sensor 211 , measuring at the bottom of the root area. At this location, what is of interest is the height of the peak that is caused by the irrigation of water and fertilizer. The height of the peak represents the amount of fertilizer that is included in the water. As discussed in connection with FIG. 4A, the addition of water always causes a peak in EC. However, the peak reaches a higher point if the soil had been previously saturated with ionic nutrients due to overfertilization. This data is used to see how the previous change of fertilizer ratio affected the plant. If the peak that is caused by the fertigation is higher than typical, this indicates that too much fertilizer was previously added to the mixture, resulting in excess residual fertilizer in the plant and an inability of the plant to take up the expected amount of nutrients. The paired soil sensors 211 , 212 may be used to determine other information as well. Specifically, the use of multiple soil sensors at varying depths allows for the controller to measure the time that water travels from the surface to the plant roots. With this information the timing of an irrigation period can be adjusted.

[0102] The temperature sensors 213, 214 may also be used in order to evaluate the plant’s uptake of nutrients. During the photosynthesis process, water is needed to convert light and CO2 into sugars. The stronger the photosynthesis process, the more water the leaf uses. The more water the leaf uses, the colder it will be compared to the environment.

[0103] When the plant receives the optimal conditions, the photosynthesis process will be the strongest. If the plant is stressed due to lack of water or too much fertilizer, then the photosynthesis process will weaken and the temperature difference will drop.

[0104] Accordingly, the trend in the temperature difference is used to check if the change in fertilizer ratio was good for the plant or if it increased stress. In case the temperature difference went up (the leaf is cooler) then the change was good. If the temperature difference went down (the leaf is hotter) then the change was detrimental. The temperature difference is evaluated within a suitable time after delivery of the fertigation in order for the temperature difference to be impacted, e.g., within the first 1 to 2 days, or up to the next irrigation cycle. In order to ensure that the change is not attributable to other factors, the same fertigation ratio may be provided for a second consecutive day. If the changed ratio persists, then the controller reverts the system to the previous fertigation ratio.

[0105] One exemplary protocol for controlling the amount of fertilizer that is supplied to the field proceeds as follows. The controller is configured to select from between 10 concentrations (or “levels”) of fertilizers that can be supplied to the field. This may be controlled, as discussed, by the time the NC valve 113 controlling the fertilizer is open during corresponding flow of irrigation water into the pump 105 - between 0 to 50 minutes at 5 minutes increments. An initial value of 1 to 10 may be set based on the farmer’s expected need for fertilization, in view of the crop that is being grown, location, weather, progress of growth, etc.

[0106] The algorithm uses the data from the EC sensors placed at 20 cm during nighttime (between 20:00-06:00). The data from nighttime is evaluated so that the trendline is not affected by the daily uptake of nutrients by the plant during photosynthesis, as discussed. As seen, for example, in FIG. 4A, during the nighttime period, the soil EC remains fairly constant.

[0107] A 7-day data is interpolated into a linear line: y=ax+b

[0108] A 1 -day data is averaged into c.

[0109] If a<0, indicating a downward trend in soil fertilizer, then the fertilizer level is increased by 1 . This is done once every 3 days unless c (daily average) is lower than b (weekly average). If c is lower than b, or otherwise significantly different than b, then further time is taken to assess the trend and determine that the weekly average is not resulting from a recent phenomenon.

[0110] If a>0, indicating that the amount of nutrients in the soil is increasing, then the fertilizer level is decreased by 1. This is done once every 3 days unless c (daily average) is higher than b (weekly average).

[0111] The algorithm may consider both soil sensors at the same time. For example, if both sensors indicate that an excess of nutrients is being provided to the plant, then the fertilizer level may be decreased by 2. If both sensors indicate that not enough fertilizer is being provided to the plant, then the fertilizer level may be decreased by 2. If one of the sensors indicates a change and one indicates no change, then the fertilizer level may be changed by 1 . If the sensors provide conflicting indications, then no change in fertilizer level is called for. Following a change in fertilizer level, measures of plant health as indicated by the delta between leaf temperature and air temperature are used as a retrospective check to confirm that a change in fertilizer concentration was beneficial for the plant.

[0112] A similar type of analysis may be performed in order to evaluate the ideal timing of irrigation pulses. The EC data may be used to determine whether to increase or decrease the irrigation volume or frequency. The volume of irrigation may also be scaled from 1 to 10, and may also be increased or decreased incrementally, based on the long-term trends in the EC data.

[0113] The fertilizer used in methods and systems of the invention may be any fertilizer known in the art. In some embodiments, the fertilizer is a macronutrient such as nitrogen, phosphorus and potassium. Other macronutrients may include boron, cobalt, copper, iron, manganese, molybdenum, silicon, vanadium, and zinc, as well as multinutrients such as NPK fertilizers.

[0114] Features, integers characteristics, described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example unless incompatible therewith. All of the features disclosed herein (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing examples or embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) or to any novel one, or any novel combination, of the steps of any method or process disclosed. A skilled person will understand additional features and use of the system and method.

Claims

Claims1. A fertigation system having water supply and irrigation lines to supply a mixture of at least one fertilizer and water to a desired soil region, the system comprising: at least one soil sensor, wherein the at least one soil sensor is placed under a surface region of the soil and is configured to measure a concentration of the at least one fertilizer or components thereof in the soil over time; and a supply unit for storage of the fertilizer and water, and for mixing of the fertilizer to a desired dilution within the water; and a controller that is operatively connected to the at least one soil sensor and the supply unit, wherein the controller is configured to direct an irrigation profile of mixed water and fertilizer delivered from the supply unit to the soil, to thereby maintain a constant value of at least one soil parameter over time.

2. The system of claim 1 , wherein the irrigation profile comprises one or more of: concentration of fertilizer within the irrigation fluid, type of fertilization, irrigation amount, length of an irrigation period, frequency of fertigation pulses, and / or sequence of irrigation.

3. The system according to any of the previous claims, wherein the controller includes: a memory storing time of year data, air temperature data, and soil electro-conductive data associated with the soil location where the fertigation system is located; and a processor configured to determine the irrigation profile and to issue commands to the supply unit in order to produce a fertigation output according to the irrigation profile.

4. The system according to any one of the preceding claims, wherein upon a determination by the controller that the soil parameter has changed, the controller is configured to cause the supply unit to modify the irrigation profile.

5. The system according to claim 4, wherein the modification of the irrigation profile is determined to reverse the change in the soil parameter.

6. The system according to any one of the preceding claims, wherein the at least one soil parameter is a measure of organic and / or ionic content of the soil.

7. The system according to claim 6, wherein the at least one soil parameter relates to is a measure of NPK content of the soil.

8. The system according to claim 1 , wherein the sensor is selected from electromagnetic sensors, electrochemical sensors, optical and radiometric sensors.

9. The system according to claim 1 , wherein the at least one soil sensor is selected to detect a change in the NPK content of the soil.

10. The system according to claim 9, wherein the sensor is a nitrogen (N), or a potassium (K) or a phosphorus (P) sensor, or a combination thereof.

11. The system according to claim 1 , wherein the at least one soil sensor is an electromagnetic sensor.

12. The system according to claim 11 , wherein the electromagnetic sensor is selected from electrical resistance sensors, electrical conductance sensors, current sensors, voltage sensors, power sensors, magnetic sensors, and metal ion detectors.

13. The system according to any one of claims 1 , wherein the at least one soil sensor is a chemical sensor selected from NPK sensors, oxygen or carbon monoxide detectors, ion selective and redox electrodes.

14. The system according to claim 1 wherein the at least one soil sensor is an electroconductance (EC) sensor.

15. The system according to claim 14, wherein the EC sensor is configured to send to the controller a measured EC value, measured for soil proximate to the water line, and wherein the controller is configured to determine, based on at least one of prestored data: a time for initiating injection of the at least one of the fertilizer into the water line; and relative amounts of the at least one fertilizer to be released upon injection from at least one storage tank into the water line.

16. The system according to any of the previous claims, wherein the at least one soil sensor comprises arrays of two or more soil sensors configured at different heights of roots of the same plant.

17. The system according to any of the previous claims, further comprising an array of air temperature sensors and leaf temperature sensors, wherein the controller is configured to determine a change in the irrigation profile based on a trend in a difference between the leaf temperature and the air temperature.

18. A method of determining an amount of fertilizer to mix with water in a fertigation system, comprising: measuring at least one soil parameter at a root zone of the plant; calculating a trend in the at least one soil parameter over time; and based on the trend, maintaining or adjusting the amount of fertilizer that is mixed with water in an irrigation profile.

19. The method of claim 18, wherein the measuring step comprises measuring the at least one soil parameter at a bottom of the root zone and at a middle of the root zone.

20. The method of claim 19, wherein the trend calculated from EC data measured at the middle of the root zone is a trend of EC concentration in the soil over time.21 . The method of claim 19, wherein the trend calculated from EC data measured at the bottom of the root zone is a trend in the height of the peak caused following addition of new fertilizer into the soil.

22. The method of claim 19, wherein the trend calculated from EC data measured at the middle of the root zone is a trend of EC concentration in the soil over time and the trend calculated from EC data measured at the bottom of the root zone is a trend in the height of the peak caused following addition of new fertilizer into the soil, and wherein both trends are considered cumulatively in order to determine a degree of change in the amount of fertilizer that is mixed with water.

23. The method of claim 18, further comprising measuring a difference of leaf temperature compared to surrounding air temperature following a change in theirrigation profile, and based on a trend in the difference, maintaining or reversing the change in the irrigation profile.

24. The method of claim 18, further comprising delivering the fertilizer mixed with water according to the irrigation profile in a constant concentration throughout a fertigation session.

25. A method of fertigation, comprising delivering fertilizer at a constant concentration throughout an irrigation session.

26. The method of claim 25, wherein the delivering step comprises delivering pulses of mixed water and fertilizer from a positive displacement pump.

27. The method of claim 26, wherein the delivering step further comprises passing the mixed water and fertilizer though a passive mixer downstream of the positive displacement pump to thereby homogenize the mixed water and fertilizer.

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