Patent Publication Number: US-2022217928-A1

Title: Stress-adaptive irrigation and fertigation

Description:
BACKGROUND 
     Field of Invention 
     The invention relates generally to plant irrigation. More particularly, but not by way of limitation, embodiments of the invention provide systems and methods for stress-adaptive irrigation and fertigation. 
     Description of the Related Art 
     Various systems and methods for plant irrigation and fertigation are known. Irrigation refers to controlled delivery of water; fertigation generally means the injection of fertilizer or other amendment into an irrigation system. As used herein, irrigation may include fertigation. 
     Various stress conditions are known to damage plants and reduce crop yields. Many irrigation systems and methods fail to adequately compensate for such stresses. Moreover, known methods that merely alter an irrigation schedule in response to perceived stress, for example by increasing an irrigation duration in an above-ground sprinkler system, are not generally effective in sub-surface drip irrigation (SDI) systems. Improved stress-adaptive irrigation systems and methods are needed. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention are directed to a sub-surface irrigation system configured to operate in a plant-responsive mode, and further configured to make certain adaptations in response to plant stress. Stress adaptations may include, for example, selectively increasing source pressure of irrigation fluid, heating or chilling the irrigation fluid, and/or injecting fertilizer and/or non-fertilizer amendments into the irrigation fluid. Alternative embodiments, and their advantages, will be described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow diagram of a method for irrigation, according to an embodiment of the invention; 
         FIG. 2  is an assembly view of a delivery tube, illustrated in cross-section, according to an embodiment of the invention; 
         FIG. 3A  is an assembly view of a delivery tube, illustrated in cross-section, according to an embodiment of the invention; 
         FIG. 3B  is an assembly view of a delivery tube, illustrated in cross-section, according to an embodiment of the invention; 
         FIG. 4  is a schematic diagram of an irrigation system, according to an embodiment of the invention; 
         FIG. 5  is a schematic diagram of an irrigation system, according to an embodiment of the invention; 
         FIG. 6  is a schematic diagram of an irrigation system, according to an embodiment of the invention; 
         FIG. 7  is a schematic diagram for the reservoir illustrated in  FIG. 5 ; 
         FIG. 8  is a schematic diagram for the reservoir illustrated in  FIG. 6 ; 
         FIGS. 9A and 9B  are a flow diagram of a method for using the system illustrated in  FIG. 5 or 6 , according to an embodiment of the invention; and 
         FIGS. 10A and 10B  are a flow diagram of a method for using the system illustrated in  FIG. 5 or 6 , according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention are described below with reference to the drawings. Such embodiments are meant to be illustrative and not restrictive. The drawings are not to scale. Certain features illustrated in the drawings may be exaggerated in size, and other features may be omitted altogether, for clarity. 
     The following sections begin with a review of some environmental factors that can be monitored in an effort to assess environmental stress. The description below begins with an overview of plant stress. This document then describes an irrigation method (with reference to  FIG. 1 ), exemplary microporous irrigation tubing (with reference to  FIGS. 2, 3A, and 3B ), exemplary irrigation systems (with reference to  FIGS. 4-8 ), and methods for using such systems (with reference to  FIGS. 9A, 9B, 10A , and  10 B). 
     Section titles are used below for organizational convenience. The description of any claimed feature is not necessarily limited to any section of this specification. 
     Plant Stress 
     Plant stressors result from non-ideal growth conditions that increase the demands on the plant. Abiotic stressors (environmental stressors) are naturally occurring, inanimate factors such as: intense sunlight, high winds, extreme temperatures (hot or cold), drought, flooding, herbicides, pesticides, and poor soil conditions, for example, salinity, acidity, lack of nutrients (macro and micro), and heavy metals. Lesser-known abiotic stressors generally occur on a smaller scale. They include: poor edaphic conditions like rock content and pH levels, high radiation, compaction, and contamination. Any of these stressors can negatively influence plant development and crop productivity. Abiotic stress is considered the most harmful factor concerning the growth and productivity of crops. Abiotic stressors are most harmful when they occur together, in combinations of abiotic stress factors, such as arid, desert climates. 
     Biotic stressors include living disturbances such as fungi, bacteria, insects, and weeds. Viruses also cause biotic stress to plants. Fungi cause more diseases in plants than any other biotic stress factor. Microorganisms can cause plant wilt, leaf spots, root rot, or seed damage. Insects can cause severe physical damage to plants. Insects can also spread viruses and bacteria from infected plants to healthy plants. Weeds inhibit the growth of desirable plants by competing for space and nutrients. 
     A plant&#39;s first line of defense against abiotic and biotic stress is in its roots. If the soil holding the plant provides sufficient water and nutrients in response to plant needs, and is otherwise healthy and biologically diverse, the plant will have a higher chance of surviving stressful conditions above ground. Embodiments of the invention monitor plant stressors and provide an appropriate intervention at the rhizosphere to minimize a variety of plant stressors. 
     Exemplary Method for Irrigation 
       FIG. 1  is a flow diagram of a method for irrigation, according to an embodiment of the invention. As shown therein, the process begins in step  105  by performing sub-surface irrigation via microporous tubing treated with a hydrophilic polymer in a root-responsive mode, the root-responsive mode characterized by a relatively low supply pressure (to the tubing) and a closed-end fluid path. Such an irrigation mode is extremely water-efficient, and is the preferred irrigation mode when plants are not under stress. 
     The process then determines a plant stress condition in step  110 . Step  110  may be performed for instance, by comparing sensor data to predetermined threshold, by visual inspection, and/or by performing plant tissue or soil analysis. For example, readings from ambient temperature and/or ground temperature sensors can be compared to predetermined threshold values to determine that an elevated temperature condition exists. Likewise, wind speed data from an anemometer can be compared to predetermined thresholds. Temperature and wind data are preferably integrated over time to model transpiration effects more precisely. As a further example of step  110 , visual inspection, whether performed or aided by humans, local imaging sensors, or overhead assets, can reveal leaf discoloration, plant wilting, lodging (displacement of stems or roots), disease, pest infestation, the presence of weeds, or other evidence of present or emerging plant stressors. Data from subsurface salinity sensors can be compared to a known salt tolerance level for a given plant type. Soil analysis can reveal, for instance, a lack of beneficial microbes in the oil, or the presence of harmful fungi. 
     In step  115 , the process selects a system-delivered treatment based on the plant stress condition, the system-delivered treatment including a relatively high supply pressure and a recirculating fluid path. In the case of temperature-related stress, for example, the selected system-delivered treatment may include chilling or heating the irrigation fluid, and may also include adding a surfactant to the irrigation fluid. For wind stress not accompanied by temperature extremes, the process may select the relatively high supply pressure and the recirculating path alone. When the plant stress condition was determined in step  110  to be a soil condition and/or a mineral imbalance the process may select an agrochemical additive to amend the irrigation fluid to correct the soil deficit or problem in step  115 . Likewise, where biotic stressors are determined to be present, the process may select, for instance, from one or more biological amendments, root/soil activators, organic additive, or pesticides. 
     The relatively high supply pressure (preferred in all treatment cases), and surfactant (when added), will tend to increase the emission rate of irrigation fluid from the tubing to the root sone. The recirculation path (also preferred in all treatment cases) will facilitate a more homogeneous delivery (in terms of temperature and amendment concentration) of the irrigation fluid along the functional length of the subsurface tubing. 
     The process performs the (above-described) system-delivered treatment in step  120 , and determines when to terminate the system-delivered treatment in step  125 . System-delivered treatment is intended to be temporary. The determination in step  125  could be based on a predetermined duration (for example, based on treatment type), on a calculated duration (for instance, based on a severity of determined stressor(s)), or based on evidence of reduced stress (e.g., improvements in data, observations, or analysis relied upon in step  110 ). 
     As indicated by conditional step  135 , if the system-delivered treatment included a fluid amendment, then the process advances to step  140 ; otherwise the process returns directly to step  105 . Clearing step  140  preferably includes supplying the irrigation fluid at the relatively high supply pressure, and using the recirculation fluid path, but without addition of amendments. One exception is that where the system-delivered treatment included amendment with a surfactant, clearing step  140  preferably includes amendment with a thickening agent to counteract the effects of the surfactant on fluid emission. 
     Microporous Irrigation Tubing Examples 
       FIGS. 2, 3A, and 3B  are each an assembly view of a delivery tube, illustrated in cross-section, according to alternative embodiments of the invention. As shown in  FIG. 2 , a microporous membrane  205  is welded along regions  215  to a backer  210  to form an irrigation tube having a lumen  220 . The embodiments illustrated in  FIGS. 3A and 3B  each provide an irrigation tube without a backer  210 . Instead, in these examples, a microporous membrane  305  is wrapped upon itself to form an irrigation delivery tube having a lumen  320 . The embodiment in  FIG. 3A  includes a flat seam weld  310  with a bead  315 ; the embodiment in  FIG. 3B  includes a fin weld  325 . 
     The microporous membrane  205 ,  305 , may be, for instance, manufactured from polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET, a/k/a polyester) or other suitable material. As an example, the microporous membrane  205 ,  305 , may be DuPont Tyvek™ or other non-woven or spun-bonded fabric. Preferably, the microporous membrane  205 ,  305 , is treated (entirely or selectively) with a hydrophilic polymer to enhance responsiveness to root exudate. 
     For the tubing embodiment in  FIG. 2 , the backer  210  is preferably a less expensive material than the microporous membrane  205 . The backer  210  is also preferably much less porous (i.e., effectively non-porous) compared to the microporous membrane  205 . For thermal compatibility, where the microporous membrane  205  is PE, the backer  210  is preferably also manufactured from PE; where the microporous membrane  205  is PP, the backer  210  is preferably PP; and where the microporous membrane is  205  is PET, the backer  210  may be PET. The surface area of the microporous membrane  205  and the surface area of the backer  210  need not be equal for any given length of tubing. 
     Other microporous irrigation tubing configurations and weld types are possible, and could also be used in combination with one or more stress-adaptative systems and methods disclosed herein. Moreover, some features or embodiments may be equally applicable to surface and sub-surface applications of microporous irrigation tubing. 
     Exemplary Systems 
     Exemplary systems for performing the above method, and variants thereof, are described below with reference to  FIGS. 4-8 . 
       FIG. 4  is a schematic diagram of an irrigation and fertilization system, according to an embodiment of the invention. The embodiment illustrated in  FIG. 4  might be applicable, for instance, to a large commercial farming operation. As shown therein, a supply system  405  feeds a header pipe  485  that is coupled to multiple sub-surface microporous irrigation delivery tubes  493 . Multiple plants  495  have roots  497  within a functional distance of delivery tubes  493 . The delivery tubes  493  could be constructed, for example, as described above with reference to  FIG. 2, 3A , or  3 B. 
     The supply system  405  includes a reservoir (RES)  410  coupled to receive fluid from well pump (W)  415 , city water connection (CW)  420 , and recirculation pump (RE)  425 . Each of these reservoir  410  inputs could be coupled via a valve (not shown). In the illustrated embodiment, the reservoir  410  includes a heater (HT)  430 . Valves  440 ,  445  are coupled to outputs of the reservoir  410 . An in-line chiller (CH)  435  is coupled to an output of valve  445 . 
     Suitable recirculation pumps  425  are manufactured, for instance, by Blue Torrent Pool Products, Floject, Flotec, and other suppliers, according to application requirements. The heater  430  could be, for example, a glass-encased electric heating element, although geo-thermal or other heating modalities could also be applied according to design choice. The in-line chiller  435  could be or include, for instance, a TropiCool®, Heatwave, GBB (Great Big Bopper by AquaCal), or other water-source heat pump. 
     In the supply system  405 , the reservoir  410  output is further coupled to filters (F)  450 , and also coupled to tanks (T)  455 ,  460 ,  465 , and  470  and to pressure regulator  480 . Any of the tanks  455 ,  460 ,  465 ,  470  could include a pump (not shown). 
     The pressure regulator  480  is preferably configured to output a relatively low-pressure fluid flow from the supply system  405  to the header pipe  485 , for instance for a setting within the range of 0.5-5.0 PSI, for compatibility with the microporous delivery tubes  493 . An exemplary regulator  480  is the Model  3865  diaphragm regulator manufactured by Ziggity Systems, Inc. The desired pressure setting for such an adjustable pressure regulator may vary accordingly to properties of the delivery tubes  493 . In alternative embodiments, other pressure settings and/or other regulators  480  could be used. 
     In operation, the reservoir  410  is selectively supplied by well pump  415 , city water connection  420 , and/or recirculation pump  425 . Fluid is selectively heated in the reservoir  410  via heater  430 ; fluid is selectively cooled at an output of the reservoir  410  using in-line chiller  435  via operation of valves  440 ,  445 . In some modes of operation, fluid in supply system  405  is not heated or chilled. Flow through filters  450  may also be selective (for instance via additional valves, not shown) according to fluid amendment and recirculation status. Generally, each tank  455 ,  460 ,  465 , and  470  could contain a unique type of fluid amendment. For example, tank  455  could contain a fertilizer, tank  460  could contain a surfactant, tank  465  could contain a thickening agent, and tank  470  could contain particulate for a suspended load. Contents (or a portion) of each tank  455 ,  460 ,  465  and  470  can be selectively added to irrigation fluid in the supply system  405 , alone or in any combination, via operation of a corresponding valve  475 . Regulator  480  controls a supply pressure of irrigation fluid to header pipe  485  and delivery tubes  493 . During selective recirculation (i.e., according to status of the recirculation pump  425 ), irrigation fluid is returned to the supply system  405  via recirculation path  490 . 
     The supply system  405  may be operated in alternative modes. For instance, in a normal low-pressure plant-responsive mode, the heater  430  and chiller  435  may be inactive, valve  440  may be open, valves  445  and  475  may be closed, the regulator  480  may be adjusted for a relatively low pressure (for instance 1.5 psi), and the recirculation pump  425  could be turned off. In a treatment mode, the heater  430  or chiller  435  may be on, one or more valves  475  may be open, the regulator  480  may be set at a relatively high pressure (for instance 5.0 psi), and the recirculation pump  425  may be on. 
     Variations to the system illustrated in  FIG. 4  and described above are possible. For instance, some embodiments do not require well pump  415 , city water connection  420 , or recirculation pump  425 . In alternative embodiments, heater  430  could be placed in-line, external to the reservoir  410 . The heater  430  could be combined with the chiller  435 , for instance in a heat pump unit. The number and sequential placement of filters  450  and tanks  455 ,  460 ,  465 , and  470  could vary. In an automated or semi-automated embodiment, the supply system  405  could include a controller; the controller could receive signals from one or more environmental sensors, and the controller could output control signals to the recirculation pump  425 , heater  430 , in-line chiller  435 , valves  440 ,  445 ,  475 , and/or pressure regulator  480 . 
       FIG. 5  is a schematic diagram of an irrigation system, according to an embodiment of the invention. As shown therein, a supply system  500  feeds a header pipe  505  that is coupled to multiple sub-surface microporous irrigation delivery tubes  493 . Multiple plants  495  have roots  497  within a functional distance of delivery tubes  493 . The delivery tubes  493  could be constructed, for example, as described above with reference to  FIG. 2, 3A , or  3 B. Each of the delivery tubes is fluidically coupled to the footer  506 . Sensors  508  could be or include, for example, in-ground temperature and/or salinity sensors. 
     Supply system  500  is configured so that a pressurized water source (W/S)  501  can be serially coupled to a diverter  502 , a first pressure regulator  503  (which is set for a relatively low pressure output, for instance 1.0 psi), a diverter  504 , and the header pipe  505 . For some applications, RDI model APR-Z053 may be suitable for the first pressure regulator  503 . 
     Diverter  502  is also coupled to multiple injector valves  517  and bypass valve  518 . Each of the injector valves  517  is serially coupled to an input of a corresponding inline injector  511 . Inline injectors  511  are preferably configured for accurate addition of soluble fertilizer or other amendments. Outputs of the inline injectors  511  are coupled to an output of the bypass valve  518  and to a first input of a reservoir  510 . A first output of the reservoir  510  is serially coupled to a pump  512  and chiller/heater  513 . In alternative embodiments, the chiller/heater  513  could be a chiller, or a heater, instead of a combined chiller/heater. An output of the chiller/heater  513  is coupled to a second input of the reservoir  510 . A second output of the reservoir  510  is serially coupled to a recirculation pump  519 , a second pressure regulator  514  (which is set for a relatively high pressure output, for instance 5.0 psi) and the diverter  504 . For some applications, RDI model APR-M758 may be suitable for the second pressure regulator  503 . The footer  506  is serially coupled to the recirculation valve  509  and a third input to the reservoir  510 . 
     Controller  516  is an optional component, according to design choice. If included, controller  516  could be configured to receive data from the sensors  508 , and could control the operation of any one or more components illustrated as part of supply system  500  (with the exception of directly controlling the pressurized water source  501 ). Recirculation pump  520  is also an optional component, based on application needs. Recirculation pump  520  may be required, for instance, if the reservoir  510  is disposed at a much higher elevation than the footer  506 . 
     In a normal (and most water-efficient) mode, unamended irrigation fluid can be supplied by the supply system  500  to the header pipe  505  at a relatively low pressure and with a termination point at the recirculation valve  509 . 
     In the case of system-delivered treatment in response to plant stress, the supply system  500  can be configured to supply irrigation fluid to the header pipe  505  at a relatively high pressure, with or without amendment from one or more inline injectors  511 , and with or without heating or cooling enabled by the chiller/heater  513 . Operation during system-delivered treatment preferably includes a recirculation path through an open recirculation valve  509 , and with the aid of recirculation pump  519  (and recirculation pump  520 , if applicable). 
       FIG. 6  is a schematic diagram of an irrigation system, according to an embodiment of the invention. The irrigation system illustrated in  FIG. 6  is substantially similar to the irrigation system illustrated in  FIG. 5  except for minor differences between supply system  600  and the supply system  500 . In particular, supply system  600  deletes the pump  512 , replaces reservoir  510  with reservoir  610 , and couples the chiller/heater inline. Supply system  600  requires that selected inline injectors  511  can provide sufficient flow for the selected chiller/heater  513 . With that caveat, the supply system  600  can supply the same “normal” and “system-delivered treatment” modes described above with reference to supply system  500 . As noted above, in alternative embodiments, the chiller/heater  513  could be a chiller, or a heater, instead of a combined chiller/heater. 
       FIG. 7  is a schematic diagram for the reservoir  510  illustrated in  FIG. 5 . Reservoir  510  includes thermally-insulated walls  705 , three inputs  710 ,  715 ,  720 , two outputs  725 ,  730 , and a drain  735 . Fluid  740  is maintained below a predetermined fill line  745 , for instance with aid of a float switch (not shown). With reference to  FIG. 5 : input  710  may be from outputs of the inline injectors  511  and bypass valve  518 ; input  715  may be from the chiller/heater  513 ; and input  720  may be coupled to the recirculation valve  509 . Output  725  may be to the pump  512 , and output  730  may be to the recirculation pump  519 . 
       FIG. 8  is a schematic diagram for the reservoir  610  illustrated in  FIG. 6 . Compared to reservoir  510 , reservoir  610  deletes input  710  and output  725 . 
       FIGS. 9A and 9B  are a flow diagram of a method for using the system illustrated in  FIG. 5 or 6 , according to an embodiment of the invention. Step  905  is supplying fluid from a pressurized water source  501  to subsurface microporous irrigation tubing  493  via a first pressure regulator  503  at a relatively low set pressure, the tubing  493  being treated with a hydrophilic polymer, a fluidic path through the tubing being terminated at a closed recirculation valve  509 . Step  910  is determining a plant stress condition and selecting at least one amendment based on the plant stress condition. Step  915  is diverting the fluid from the pressurized water source  501  to at least one injector  511  instead of the first pressure regulator  503 , each of the at least one injectors  511  being associated with a corresponding one of the at least one amendments. Step  920  is injecting each of the at least one amendments using the at least one injectors  511 , outputs of the at least one injectors being combined to produce an amended irrigation fluid. Step  925  is outputting the amended irrigation fluid to the tubing  493  via a second pressure regulator  514  at a relatively high set pressure, the relatively high set pressure being higher than the relatively low set pressure. Step  930  is opening the recirculation valve  509 , and activating at least one recirculation pump  519 ,  520 , the fluidic path through the tubing being converted by the opening and the activating to a recirculation path fluidically coupling the second pressure regulator  514 , the tubing  493 , the recirculation valve  509 , and the at least one recirculation pump  519 ,  520 . Step  935  is terminating the injecting, terminating the outputting of the amended irrigation fluid, and coupling the pressurized water source  501  to the recirculation path using a bypass valve  518 . Step  940  is waiting for a predetermined time after terminating the injecting and terminating the outputting of the amended irrigation fluid. Step  945  is closing the bypass valve  518 , closing the recirculation valve  509 , deactivating the at least one recirculation pump  519 ,  520 , diverting the fluid from the pressurized water source  501  to the tubing  493  via the first pressure regulator  503  at the relatively low set pressure. 
     Accordingly, in embodiments of the invention, amendments introduced during system-delivered treatments are cleared from subsurface irrigation tubing by supplying only unamended fluid at relatively high pressure in the recirculation path for a predetermined time before returning to the relatively low-pressure and closed-ended root-responsive mode. 
       FIGS. 10A and 10B  are a flow diagram of a method for using the system illustrated in  FIG. 5 or 6 , according to an embodiment of the invention. Step  1005  is supplying fluid from a pressurized water source  501  to subsurface microporous irrigation tubing  493  via a first pressure regulator  503  at a relatively low set pressure, the tubing  493  being treated with a hydrophilic polymer, a fluidic path through the tubing being terminated at a closed recirculation valve  509 . Step  1010  is determining a plant stress condition and selecting at least one amendment based on the plant stress condition, the at least one amendment including a surfactant. Step  1015  is diverting the fluid from the the pressurized water source  501  to at least one injector  511  instead of the first pressure regulator  503 , each of the at least one injectors  511  being associated with a corresponding one of the at least one amendments. Step  1020  is injecting each of the at least one amendments using the at least one injectors  511 , outputs of the at least one injectors being combined to produce an amended irrigation fluid. Step  1025  is outputting the amended irrigation fluid to the tubing  493  via a second pressure regulator  514  at a relatively high set pressure, the relatively high set pressure being higher than the relatively low set pressure. Step  1030  is opening the recirculation valve  509 , and activating at least one recirculation pump  519 ,  520 , the fluidic path through the tubing being converted by the opening and the activating to a recirculation path fluidically coupling the second pressure regulator  514 , the tubing  493 , the recirculation valve  509 , and the at least one recirculation pump  519 ,  520 . Step  1035  is terminating the injecting of the at least one amendment, and newly injecting at least one thickening agent using the at least one injectors  511 , outputs of the at least one injectors being combined to produce a thickened irrigation fluid. Step  1040  is outputting the thickened irrigation fluid to the tubing  493  via the second pressure regulator  514  at the relatively high set pressure. Step  1045  is waiting for a predetermined time after terminating the injecting and terminating the outputting of the amended irrigation fluid. Step  1050  is closing the bypass valve  518 , closing the recirculation valve  509 , deactivating the at least one recirculation pump  519 ,  520 , diverting the fluid from the pressurized water source  501  to the tubing  493  via the first pressure regulator  503  at the relatively low set pressure. 
     Accordingly, in embodiments of the invention, the effects of surfactants introduced during system-delivered treatments are at least partially countered in from subsurface irrigation tubing by supplying water with a thickening agent at relatively high pressure in the recirculation path for a predetermined time before returning to the relatively low-pressure and closed-ended root-responsive mode. 
     CONCLUSION 
     Those skilled in the art can readily recognize that numerous variations and substitutions may be made in the invention, its use and its configuration to achieve substantially the same results as achieved by the embodiments described herein. For example, features described with reference to different embodiments in this application can be combined in ways not expressly described. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many variations, modifications and alternative constructions fall within the scope and spirit of the disclosed invention.