Method to enhance plant growth by foliar spraying with co2-infused water

Abstract

Various factors need to be considered when foliar spraying of plants with CO2-infused water in order to maximize the effects of the foliar spraying on plant growth. One of these factors is the vapor pressure deficit (VPD) of the environment in which the plants are grown. Too low a VPD and the leaves can remain wet for too long for the health of the plant. If the VPD is too high then the leaf can dry before the CO2 in the aqueous solution has had ample opportunity to diffuse through the cuticle. The VPD is measured and used to determine whether to carry out foliar spraying with CO2-infused water. If so, then the light intensity, leaf wetness, and chlorophyll fluorescence are measured and used to determine the frequency and duration of foliar spraying.

Description

[0001] METHOD TO ENHANCE PLANT GROWTH BY FOLIAR SPRAYING WITH CO2-INFUSED WATER

[0002] FIELD OF INVENTION

[0003] [1] This invention relates to agriculture, and more particularly to foliar spraying of plants.

[0004] BACKGROUND

[0005] [2] The plant energy balance (PEB) of a plant is important in determining the amount of photosynthesis carried out by the plant. In order to maximize photosynthesis, the amount of CO2 absorbed by the leaves of the plant must be balanced with the amount of light being absorbed by the plant. If there is too little light, then the amount of C02 usable by the plant in order to carry out photosynthesis is limited, and there is a likely chance of wasted excess C02.

[0006] [3] Foliar feeding is a method of feeding plants by applying liquid fertilizer directly to their leaves rather than through their roots. Plants are able to absorb essential elements through stomata on their leaves, or even across the cuticle and through the epidermis of the leaves. US 5894696 (Ando) teaches the use of C02 infused water to deliver CO2 to plants using foliar spraying, and foliar spraying with CO2-infused water may be an effective way of delivering CO2 to the plant. However, Ando teaches merely that water saturated somewhere between 10 milligram per liter and 2000 milligrams per liter (mg / 1) sprayed on plants would enhance their growth. Ando is mostly silent as to the frequency and duration of foliar spraying, saying that “there is no particular limitation to an amount of the solution to be applied or sprayed though it is commonly enough to spray the solution as much as a leaf surface gets wet”. In the experiment recited in Ando, foliar spraying is carried once per day. [4] The applicant has discovered that spraying a C02 sub-saturated solution in a mist form alone does not necessarily enhance growth, and certainly not at an optimal amount of enhanced growth. For example, in one technology adaptation project, there was no substantive increase in the growth of peppers. This particular project did not have control systems that could record temperature and relative humidity, nor could the system be controlled remotely. Post-project review, temperature and relative humidity data indicated that the vapor pressure deficit for peppers was out of the plant performance range for a significant part of the crop growing cycle. Misting C02 saturated water between 10 mg / 1 and 2000 mg / 1 alone does not guarantee enhanced growth.

[0007] [5] Increased photosynthesis within the plant leads to increased plant growth and, in the case of plants bearing fruit, can lead to increased fruit production. There is a need for a method to impart sufficient CO2 to a plant in given environmental factors to increase photosynthesis within the plant without providing so much CO2 that the plant cannot use it. Although mostly harmless to the plant, providing CO2 to the plant that the plant cannot use effectively is a waste of CO2 and energy, and in the case of foliar spraying a waste of water.

[0008] SUMMARY

[0009] [6] According to one embodiment of the invention, a method of foliar spraying a plant with CO2-infused water is provided. The vapour pressure deficit near the plant is measured. The frequency and duration of foliar spraying the plant is determined based on the measured vapour pressure deficit. In one embodiment, the plant energy balance (PEB) of the plant is measured, and a foliar spraying event is added in the event that the PEB of the plant indicates that photosynthesis is limited by the amount of CO2 present in the plant.

[0010] [7] The present invention provides substantial improvements in the growth rate of plants by taking several factors into account when determining the timing, frequency, and duration of foliar spraying with CO2-infused water, including environmental factors and at least one factor relating to the leaves of the plants. The amount of CO2 taken up by the plant is increased by delivering the C02 in an amount that can best be used by the plant, without wasting water, C02, and energy. Artificial intelligence can be used to further optimize the amount of C02 taken up by the plant without wasting C02.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [8] The features and advantages of embodiments of the invention will become more apparent from the following detailed description of the preferred embodiment(s) with reference to the attached figure, wherein:

[0013] FIG. 1 shows a method of foliar spraying a plant with C02-infused water according to one embodiment of the invention;

[0014] FIG. 2 shows a method of foliar spraying a plant with C02-infused water according to another embodiment of the invention;

[0015] FIG. 3 shows a method of foliar spraying a plant with C02-infused water according to another embodiment of the invention; and

[0016] FIG. 4 shows a method of foliar spraying a plant with C02-infused water according to another embodiment of the invention.

[0017] It is noted that in the attached figures, like features bear similar labels.

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [9] The method of the invention is usually applied to an entire crop of plants. However, for simplicity the invention will be described with reference to a single plant.

[0010] Photosynthesis within a plant depends, generally, on the amount of light reaching the plant and the amount of CO2 absorbed by the leaves of the plant. This can be referred to as the Plant Energy Balance (PEB) of the plant. The amount of photosynthesis being carried out can be determined using chlorophyll fluorescence sensors, such as those produced by Gardin™. These measure the photosynthetic capacity (PC) and the light use efficiency (LUE) of a plant leaf. The chlorophyll fluorescence sensors indicate whether photosynthesis is light limited or whether the photosynthesis is CO2 limited. In other words, a measure can be obtained as to whether photosynthesis can be improved either by increasing the amount of light reaching the plant or by increasing the amount of CO2 being absorbed by the plant leaves.

[0020]

[0011] An effective means of providing CO2 to the plant is by foliar spraying with CO2-infused water. Another method of delivering CO2 to the plant by increasing the amount of CO2 present in the atmosphere surrounding the plant, also called gassing. However, much of the atmosphere does not reach the plant, due for example to leakage from a greenhouse. CO2 is also lost with this method in a greenhouse if the vapour pressure deficit (VPD) is high because the atmosphere is vented so as not to overheat the plant. Furthermore, this method of delivering CO2 to the plant is very difficult, if not impossible, in an open air environment. Much less CO2 is wasted with foliar spraying with CO2-infused water. Foliar spraying with CO2-infused water may be effective even if the VPD is high in a closed environment, because foliar spraying can actually reduce the temperature of the plant. Delivering CO2 through foliar spraying is also possible in a non-sealed structure or in the open, neither situation being conducive to gassing.

[0021]

[0012] Referring to FIG. 1, a method of improving plant energy balance in a plant according to one embodiment of the invention is shown. The embodiment of the invention described with reference to FIG. 1 may be best employed outdoors or in a facility in which the lights and shades cannot be adjusted. This embodiment may of course be employed in a facility in which the lights and / or the shades can be adjusted, but the full advantages of the embodiment described below with reference to FIG. 2 would not be realized.

[0013] At step 102, the daily light integral (DLI) of the environment in which the plant is located is predicted using the LASSI algorithm developed at Cornell University (Albright et al., 2000). The DLI is a measure of how much light will reach the plant for each hour of the day.

[0022]

[0014] At step 104 a foliar spraying protocol is determined based on the DLI predicted at step 102. The protocol defines the frequency of foliar spraying and the timing (what times of day) of foliar spraying. Artificial intelligence (Al) is used to gather information about preferred misting protocols from literature published around the world for the type of crop to which the plant belongs and for the predicted DLI. The artificial intelligence can also gather misting protocol information from similar ongoing projects around the world. Data from all existing projects where aqueous CO2 misting is deployed is continually fed into an Al program which will consist of numerous algorithms and frameworks. The Al program analyzes the data to determine trends that are then used to update the protocol values for each variable at each project. In addition to data from existing projects, hots web scrape relevant articles and the Al program scans these articles in order to extract and analyze the data. As new trends emerge and new values are determined, the Al program will instruct all current projects to function based on these new values at each individual project. This is all a continuous process to ensure that any misting event at any given time is executed based on an analysis of all the available data and the most up to date protocol values. It is not feasible for a human to conduct this type of vast data collection and analysis on a continual basis, hence the utilization of Al.

[0023]

[0015] If there is insufficient information available to the artificial intelligence to determine the misting protocol, or in an embodiment in which artificial intelligence is not used, then initial values are used to define the protocol. For example, if the DLI is predicted to be 400 micromoles / m2 / s during a particular first hour then the foliar spraying is scheduled for two times during that hour. If the DLI is predicted to be 1000 micromoles / m2 / s during a particular second hour later in the day, then the foliar spraying is scheduled for four times during that second hour. In general, the higher the predicted DLI for a particular hour then the higher the protocol will define a higher misting frequency for that hour. However, the protocol will not dictate a misting frequency of more than six times per hour for any given hour.

[0024]

[0016] Misting duration is also a parameter in foliar spraying, but this is determined from other environmental factors as described below.

[0025]

[0017] Using the protocol, a misting schedule is created which indicates the scheduled times at which foliar spraying will be carried out. At step 106 the scheduled time for the next foliar spraying is waited for. Once the scheduled time is reached, then at step 107 the concentration of CO2 in the water to be foliar sprayed is determined. If the concentration is below a CO2 concentration threshold, such as 600 mg / L, then no foliar spraying is carried out at this time as it would be less than optimally effective. An alarm may be sent to a maintenance crew so that troubleshooting can be performed, usually resulting in replacement of a CO2 cylinder. Preferably, the aqueous CO2 concentrations used in the foliar spraying are in the range of 1000 mg / 1 to 1400 mg / 1. The next scheduled time for foliar spraying is awaited at step 106.

[0026]

[0018] If it is determined at step 107 that there is a sufficient concentration of CO2 in the water to be misted onto the plants, then at step 108 the photosynthetic active radiation (PAR) in the vicinity of the plant is measured. The PAR indicates the amount of radiation falling on the plant which can be used in photosynthesis. At step 110 the PAR is compared with a PAR threshold, and if the PAR measured at step 108 is below the PAR threshold, indicating generally that too little light is reaching the plant, then the next scheduled time for foliar spraying is awaited at step 106. The PAR threshold is preferably about 200 micromoles / m2 / s.

[0027]

[0019] If the measured PAR is above the PAR threshold, then at step 114 the vapor pressure deficit (VPD) in the vicinity of the plant is measured. The VPD is an indication of the ambient humidity and temperature. A high VPD is typically an indication of low humidity or high temperature or both, and a low VPD is typically an indication of high humidity or low temperature or both. The VPD affects stomatai opening and closure, which in turn influences transpiration, mass nutrient flow within the plant and photosynthetic potential, all of which are critical to maintaining optimal plant biomass production. When the VPD is too low, there is no room in the air for more water vapor, resulting in reduced transpiration despite the stomata being open. Low VPD is also typically a result of low temperature, and the chemical reactions necessary for photosynthesis are greatly slowed down. When the VPD is too high, the stomata close, therefore there is no water vapor or C02 exchange from the leaf and the plants transpire less. A high VPD is often also a result of high temperature, which can damage the plant. However, a high VPD is of less concern when C02 is delivered to the plant by foliar spraying with C02-infused water. Foliar spraying can both reduce the temperature in the immediate vicinity of the plant through evaporation of water, and can deliver C02 to the plant even if the stomata are closed because the C02 rests on the surface of the leaf and can diffuse through the surface of the leaf.

[0028]

[0020] At step 116 the misting duration is determined. Generally, for a lower measured VPD the misting duration is set lower, and for a higher measured VPD the misting duration is set higher. However, if the VPD is below a VPD threshold then the misting duration is set to 0 s, in other words no foliar spraying is carried out. In such a case there is little point in foliar spraying as foliar spraying would not be very effective at delivering CO2 to the plant and the CO2, water, and energy would mostly be wasted.

[0029]

[0021] Example misting durations for a fogger head with a flow rate of 30 LPH are 5 s if the VPD measured at step 114 is 1.0 kPa and 20 s if the VPD measured at step 114 is 5 kPa. If the VPD measured at step 114 is below 0.5 kPa, then the misting duration is set at 0 s. It should be emphasized that these are example values only, and will depend partly on the flow rate of the fogger head.

[0030]

[0022] Once the misting duration is determined, then the leaf wetness is measured at step 118 using a leaf wetness sensor. If at step 120 it is determined that the leaf wetness sensor indicates that the leaf surface is too wet, typically more than 20% wet, then the next scheduled time for misting is awaited at step 106. If on the other hand it is determined that the leaf surface is not too wet, the foliar spraying can be safely carried out without risking keeping the leaf so wet that rot sets in. Foliar spraying is carried out at step 126 for the duration determined at step 116 and for the duration dictated by the protocol determined at step 104. Preferably, the size of the microdroplets in the CO2 misting solution is between 30 and 60 microns.

[0031]

[0023] In this way, the duration, timing, and frequency of foliar spraying is determined by the VPD, the leaf wetness, the measured PAR, and the predicted DLL

[0032]

[0024] In order to achieve plant energy balance (PEB), the timing of foliar spraying may be adjusted. At step 128 the PEB of the plant is measured using a chlorophyll fluorescence sensor, such as produced by Gardin™. The measured PEB indicates whether photosynthesis within the leaf is limited by the amount of light reaching the leaf, whether photosynthesis within the leaf is limited by the amount of CO2 within the leaf, or whether there is complete PEB.

[0033]

[0025] At step 130 it is determined whether the measured PEB indicates that photosynthesis within the leaf is light limited, for example by the measured PEB being below a first PEB threshold in the case of the Gardin™ sensor. If photosynthesis is light limited, then the next scheduled misting time is awaited at step 106. If it is not determined that photosynthesis is light limited, then at step 134 it is determined from the measured PEB whether photosynthesis within the leaf is CO2 limited, for example by the measured PEB being above a second PEB threshold in the case of the Gardin™ sensor. If it is not determined that photosynthesis is CO2 limited, then the next scheduled misting time is awaited at step 106.

[0034]

[0026] If it determined that photosynthesis is CO2 limited, then this suggests that not enough CO2 is reaching the interior of the leaf for effective photosynthesis. At step 136 it is determined whether the time for the next misting is more than 20 minutes away, and if so, then the misting schedule is adjusted at step 138 by adding a scheduled misting time for 10 minutes from the current time. If the next misting time is scheduled for less than 20 minutes away, then no additional misting is scheduled. In either case the next scheduled misting time is awaited at step 106.

[0027] Referring to FIG. 2, a method of improving plant energy balance in a plant according to another embodiment of the invention is shown. The embodiment described with reference to FIG. 2 is applicable if the plant is being grown in an environment in which lighting can be adjusted, such as a greenhouse provided with artificial lighting and adjustable shading.

[0035]

[0028] At step 202, the daily light integral (DLI) of the environment in which the plant is located is predicted using the LASSI algorithm.

[0036]

[0029] At step 203 the amount of light reaching the plant is adjusted, for example by adjusting lights, adjusting shades, or both. The amount by which the lights and / or the shades are adjusted is determined using the LASSI algorithm and the predicted DLL Artificial intelligence may be used to gather information about a desired DLI from literature published around the world for the type of crop to which the plant belongs. The artificial intelligence can also gather desired DLI information from similar ongoing projects around the world.

[0037]

[0030] The lights and / or the shades are adjusted until the LASSI algorithm predicts that the desired DLI will reach the plant. The type of adjustment will depend on the facility. For example, in addition to lights that can be adjusted, a greenhouse may be provided with mechanically adjustable shades, such as translucent covers that can be drawn over the greenhouse, or electronically tintable windows. The desired DLI is based on the type of plant and on the facility in which the plant is grown. If the literature, such as that perused by artificial intelligence, is silent as to the desired DLI for the type of plant and not enough project analysis data for this type of plant has been accumulated, then desired DLI is determined for the closest variety for which data is available is determined. For example, if the type of plant being grown is Bahama Bomb tomatoes but there is insufficient data for this variety, the data for a similar variety such as Sugar Bomb tomatoes is used if available, or the next closest variety for which data is available is used. The predicted DLI is then determined again based on the adjustments made to the lighting.

[0031] At step 204 a foliar spraying protocol is determined based on the predicted DLL Step 204 is similar to step 104 described above with reference to FIG. 1.

[0038]

[0032] Using the protocol, a misting schedule is created which indicates the scheduled times at which foliar spraying will be carried out. At step 206 the scheduled time for the next foliar spraying is waited for. Once the scheduled time is reached, then at step 207 the concentration of CO2 in the water to be foliar sprayed is determined. If the concentration is below a CO2 concentration threshold, such as 600 mg / L, then no foliar spraying is carried out at this time as it would be less than optimally effective. An alarm may be sent to a maintenance crew so that troubleshooting can be performed, usually resulting in replacement of a CO2 cylinder. Preferably, the aqueous CO2 concentrations used in the foliar spraying are in the range of 1000 mg / 1 to 1400 mg / 1. The next scheduled time for foliar spraying is awaited at step 206.

[0039]

[0033] If it is determined at step 207 that there is a sufficient concentration of CO2 in the water to be misted onto the plants, then at step 208 the PAR in the vicinity of the plant is measured. At step 210 the PAR is compared with a PAR threshold, and if the PAR measured at step 208 is below the PAR threshold, indicating generally that too little light is reaching the plant, then at step 212 the lighting within the facility is adjusted so as to increase the lumens reaching the plant up to at least 200 mm / m2 / s. The next scheduled time for foliar spraying is then awaited at step 206. The PAR threshold is preferably about 200 micromoles / m2 / s.

[0040]

[0034] If the measured PAR is above the PAR threshold, then at step 214 the vapor pressure deficit (VPD) in the vicinity of the plant is measured.

[0041]

[0035] At step 216 the misting duration is determined. Generally, for a lower measured VPD the misting duration is set lower, and for a higher measured VPD the misting duration is set higher. However, if the VPD is below a VPD threshold then the misting duration is set to 0 s, in other words no foliar spraying is carried out.

[0036] Example misting durations for a fogger head with a flow rate of 30 LPH are 5 s if the VPD measured at step 214 is 1.0 kPa and 20 s if the VPD measured at step 214 is 5 kPa. If the VPD measured at step 214 is below 0.5 kPa, then the misting duration is set at 0 s. It should be emphasized that these are example values only, and will depend partly on the flow rate of the fogger head.

[0042]

[0037] Once the misting duration is determined, then the leaf wetness is measured at step 218 using a leaf wetness sensor. If at step 220 it is determined that the leaf wetness sensor indicates that the leaf surface is too wet, typically more than 20% wet, then the next scheduled time for misting is awaited at step 206. If on the other hand it is determined that the leaf surface is not too wet, the foliar spraying can be safely carried out without risking keeping the leaf so wet that rot sets in. Foliar spraying is carried out at step 226 for the duration determined at determined at step 216 and for the duration dictated by the protocol determined at step 204. Preferably, the size of the microdroplets in the CO2 misting solution is between 30 and 150 microns, and a pressure of between 30 psi and 100 psi is used.

[0043]

[0038] In this way, the duration, timing, and frequency of foliar spraying is determined by the VPD, the leaf wetness, the measured PAR, and the predicted DLL

[0044]

[0039] In order to achieve plant energy balance (PEB), the timing of foliar spraying may be adjusted. At step 228 the PEB of the plant is measured using a chlorophyll fluorescence sensor, such as produced by Gardin™.

[0045]

[0040] At step 230 it is determined whether the measured PEB indicates that photosynthesis within the leaf is light limited, for example by the measured PEB being below a first PEB threshold in the case of the Gardin™ sensor. If photosynthesis is light limited, then the next scheduled misting time is awaited at step 206. If it is not determined that photosynthesis is light limited, then at step 234 it is determined from the measured PEB whether photosynthesis within the leaf is CO2 limited, for example by the measured PEB being above a second PEB threshold in the case of the Gardin™ sensor. If it is not determined that photosynthesis is C02 limited, then the next scheduled misting time is awaited at step 206.

[0046]

[0041] If it is determined that photosynthesis is CO2 limited, then this suggests that not enough CO2 is reaching the interior of the leaf for effective photosynthesis. At step 236 it is determined whether the time for the next misting is more than 20 minutes away, and if so, then the misting schedule is adjusted at step 238 by adding a scheduled misting time for 10 minutes from the current time. If the next misting time is scheduled for less than 20 minutes away, then no additional misting is scheduled. In either case the next scheduled misting time is awaited at step 206.

[0047]

[0042] In one embodiment, the VPD, the light intensity, the leaf wetness, and the chlorophyll fluorescence are measured remotely, and the frequency and duration of foliar spraying is determined and set remotely.

[0048]

[0043] The plant is preferably of the class C3 and C4 plants both with leaves, so that the CO2-infused water is able to cover the top of the leaf surface. A fdm of the CO2-infused water covers the entire (or most of) the leaves of the plant, primarily the top of the leaves and also some of the bottom of leaves.

[0049]

[0044] The invention has been described as measuring the PEB and possibly adjusting the misting schedule in response to the measured PEB. Alternatively, the PEB is not measured and the misting schedule is not adjusted accordingly. This embodiment of the invention is shown in FIG. 3 and FIG. 4, the latter being for use in facilities in which the lighting can be adjusted. The methods shown in FIG. 3 and FIG. 4 are identical to those described with reference to FIG. 1 and FIG. 2 respectively, except the steps relating to measuring the PEB are omitted, and after foliar spraying at step 126 of FIG. 3 or step 226 of FIG. 4 the next scheduled misting time is awaited.

[0050]

[0045] The invention has been described as using the LASSI algorithm to predict the DLI and, in one embodiment, to determine how lighting within the facility should be adjusted in order to achieve a desired DLI. Alternatively, the LASSI protocol can be not used. In such an embodiment, the DLI is not predicted and the lighting not adjusted to achieve a desired DLL The protocol determined at step 104 or step 204 is set based solely on initial values which may be determined by historical data for this facility and this crop.

[0051]

[0046] The invention has been described as using artificial intelligence to gather information about the preferred misting protocol and about the desired DLI from literature published around the world and from similar ongoing projects around the world. Alternatively, no artificial intelligence could be used, and the desired DLI and misting protocol are determined from initial values or from historical data concerning the particular crop and facility in which the method is carried out.

[0052]

[0047] The embodiments presented are exemplary only and persons skilled in the art would appreciate that variations to the embodiments described above may be made without departing from the spirit of the invention. The scope of the invention is solely defined by the appended claims.

Claims

I / WE CLAIM:

1. A method of foliar spraying a plant with C02-infused water, comprising:measuring the vapour pressure deficit (VPD) near the plant; anddetermining a frequency and a duration of foliar spraying the plant based on the measured VPD.

2. The method of claim 1 wherein determining the frequency and duration of foliar spraying uses artificial intelligence.

3. The method of claim 1 further comprising:measuring the plant energy balance (PEB) of the plant; andadding a foliar spraying event in the event that the PEB of the plant indicates that photosynthesis is limited by the amount of CO2 present in the plant.

4. The method of claim 3 further comprising:using the LASSI algorithm to predict a predicted daily light integral (DLI) in the environment in which the plant is being grown; andusing the predicted DLI when determining the frequency and duration of foliar spraying.

5. The method of claim 4 further comprising:determining a desired DLI; andadjusting the light available to the plant until the predicted DLI determined by the LASSI algorithm matches the desired DLL6. The method of claim 5 wherein determining the desired DLI uses artificial intelligence.

7. The method of claim 1 further comprising:using the LASSI algorithm to predict a predicted daily light integral (DLI) in the environment in which the plant is being grown; andusing the predicted DLI when determining the frequency and duration of foliar spraying.

8. The method of claim 7 further comprising:determining a desired DLI; andadjusting the light available to the plant until the predicted DLI determined by the LASSI algorithm matches the desired DLL9. The method of claim 8 wherein determining the desired DLI uses artificial intelligence.

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