HK1141208B - Fluid and nutrient delivery system and associated methods - Google Patents

Description

Fluid and nutrient delivery systems and related methods

Technical Field

The present invention relates generally to systems and methods for watering and providing nutrients to plants, and more particularly to such systems and methods that minimize water use and maximize possible crop density by delivering water and nutrients "on demand".

Background

The need for plant self-watering systems is well established, and since about 70% of the world's fresh water resources are used in agriculture, many products have been designed and built to meet this need to varying degrees. Some systems supply small continuous amounts of water, commonly referred to as drip irrigation, which supplies water to the root zone regardless of the plant's demand. Other systems rely on moisture levels in the soil to indicate water demand. Still others employ capillaries which bring water to the plant based on surface tension and capillary rise effects.

Drip irrigation is a well established method for growing plants in arid areas. Its water utilization efficiency is claimed to be 90% compared to 75-85% of sprinkler systems. Basic drip irrigation systems typically include a ground pipe with a small drip tube/emitter mounted thereon to deliver water from a supply pipe to the roots of the plant on either side of the supply pipe. The drop tube/emitter limits the flow of water to the root, drop by drop, based on the viscous resistance to water flow in the emitter/drop tube. The drip rate is based on calculated requirements for the specific plant, soil conditions, expected rainfall and soil water evaporation transpiration loss rate, and can vary from 1 to 4L/hr per plant.

The need to estimate the water demand of crops or the amount of nutrients provided to water is rarely exact and constant, which results in waste of water. It has been shown that plant roots can control the release of water stored behind a thin porous hydrophilic membrane which is believed to become hydrophobic due to the absorption of organic impurities in the water. The mechanism is not fully understood, although it is speculated that there is a surfactant in the root exudate that opens the pores of the membrane that becomes hydrophobic due to the absorption of organic impurities in the water. The hydrophobic membrane inhibits the flow of water to the plant. However, the roots of plants shed a variety of chemicals, including surfactants, which open the pores of the membrane by making it hydrophilic. This water can now flow to the roots, and when the plant already has enough water, the membrane becomes hydrophobic.

It is also shown that when two reservoirs with membranes (one holding water and the other containing nutrient solution) are provided to the plant, the plant is able to distinguish between the two sources and obtain the required water and the required nutrients. The ratio of water to nutrient may vary from 2-5 to 1 depending on the concentration of the nutrient solution.

Many sub-surface systems have been developed which include tubes that are porous or perforated to allow for the continuous slow release of water. However, such a hydrophobic pipe, which requires a water pressure of up to two atmospheres, cannot automatically stop the delivery of water when the plants already have sufficient water or, for example, rain.

One reason for a commercial irrigation system that does not employ a membrane system may be the difficulty in obtaining a membrane that can provide the necessary amount of water for new plants or seedlings, but also for germinated, fully grown and mature plants that produce fruit and produce. Another possible reason is the reliance on constant traces of organic solutions in water, which will adsorb on the outlet walls of the hydrophilic pore channels of the membrane, converting the membrane into a hydrophobic system, thereby preventing or greatly reducing the flow of water through the membrane. Another reason may be the difficulty of obtaining hydrophilic tubes of suitable wall thickness and diameter, which are sufficiently durable to make the process economical.

The Russian SVET space planting growth system comprises a growth medium with a length of 1000cm²Growing area box greenhouses with rooms for plants up to 40cm high. The roots grow on natural porous zeolite and the high purity water keeps the roots at the desired moisture level. The zero gravity growth chamber used by NASA comprises a microporous ceramic or stainless steel tube through which water with nutrients is passed, providing for irrigation of greenhouse plants. Systems that use porous ceramic, stainless steel or hydrophobic membranes to deliver water and/or nutrients to plants are essentially in the form of drip irrigation, where water/nutrients are always being delivered regardless of the need of the plant. It will be apparent to those skilled in the art that ceramic or stainless steel tubes are relatively thick and that the organic components are absorbed throughout the length of the channel and cannot be removed by the plant's exudates.

Figure 7 shows the flow of water and nutrient solution for a single plant. In particular, FIG. 7 is a 12cm container by mounting to the bottom of two 285mL reservoirs of the same size and shape (No. 1 for water, No. 2 for nutrient solution)²The memory was embedded in well established ficusidinica potting soil (insert) to show the effect of the water flow pattern when (i) root to membrane contact was established, and (ii) total flow was no longer greater than the water uptake rate (after 24 days). Typically, the flow rate of water is about three times greater than the nutrient solution. It has been shown that a change in nutrient concentration will change the flow rate from both reservoirs. In FIG. 7, the plant root exudates change step 3 of FIG. 8 back to step 1. This has been shown in an experiment by allowing the membrane to close after a specific amount of water has passed through the Amerace-10 membrane. The exit side of the membrane was then purged with alcohol and the water flow through the membrane continued again, eventually stopping when all of the alcohol was purged away, allowing organic impurities to adsorb on the exit wall of the pores, as shown in fig. 8.

Referring again to fig. 8, in step 1, as water leaves the pores of the membrane, it spreads out over the hydrophilic membrane surface. Large droplets form and leave the surface. When the surface is coated by adsorbing hydrophobic impurities in the water, the water leaving the pores of the membrane cannot spread out on the surface and smaller droplets can form (step 2). When the application is continued, there is no room for the water to spread out over the surface, requiring more force to push the water through the hydrophobic areas, as shown in step 3. This is rendered hydrophobic by adsorption of organic impurities in the water and/or nutrient solution. This occludes the pores and prevents water from leaving the membrane under normal pressure conditions. If the pressure is increased, the liquid can flow again because the surface tension of the water can no longer prevent the water from breaking the pores.

Disclosure of Invention

One aspect of the present invention is directed to a system for efficiently delivering an aqueous solution to plants. The system comprises a hydrophilic means, the tip part of which is placed adjacent to the root system of the plant. The hydrophilic means has a lumen therethrough for conducting an aqueous solution from the inlet to the distal portion. The hydrophilic means also has a wall surrounding the lumen. At least part of the wall along the distal portion has pores adapted to allow the aqueous solution to flow therethrough when subjected to root exudates of the surfactant generated by the experimental water pressure of the plant roots.

The system also includes a reservoir adapted to hold an aqueous solution therein. The reservoir is disposed in fluid communication with the hydrophilic means inlet. In one embodiment, positioned between the reservoir and the hydrophilic means is a pressure regulating device for providing at least a minimum pressure value to allow fluid to flow through the hydrophilic means, and at most a maximum pressure value above which fluid will flow through the hydrophilic means even in the absence of surfactant root exudate.

In another aspect, the present invention is directed to a method for efficiently delivering an aqueous solution to plants. This aspect of the invention comprises the step of positioning the distal part of the hydrophilic means adjacent to the root system of a plant, as described in the above system. The aqueous solution is introduced into an inlet of the hydrophilic means and the aqueous solution is directed from the hydrophilic means inlet to the distal end portion. In a specific embodiment, the pressure of the aqueous solution is regulated upstream of the hydrophilic means inlet.

Another aspect of the present invention is directed to a method for creating an effective system for delivering an aqueous solution to plants. This aspect of the method comprises the step of positioning the distal part of the hydrophilic means adjacent to the root system of the plant, as described above.

The pressure of the aqueous solution is regulated upstream of the hydrophilic means inlet, and a reservoir for containing the aqueous solution therein is provided upstream of the pressure regulator. A channel for establishing a flow of the aqueous solution from the reservoir to the inlet of the hydrophilic means is also provided.

The features of the present invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawings.

Drawings

FIGS. 1A and 1B illustrate, in top and cross-sectional views, respectively, a dual irrigation tube for supplying water and nutrients to the roots of plants.

FIG. 2 is a cross-sectional view of a system for watering grass.

Fig. 3 shows an example system for growing plants that can operate without gravity.

Fig. 4 is a side view of an embodiment of a tube with holes covered with a hydrophilic membrane.

Figures 5A and 5B illustrate, in top and cross-sectional views, respectively, a planting system including a surface and an underground portion.

FIG. 6 is a chemical diagram of polyhydroxystyrene.

Figure 7 (prior art) illustrates the flow of water and nutrient solution for a single plant. () absorb water from storage No. 1;and nutrient is absorbed from the No. 2 storage. (from L.A. Errede, Ann. Botany 52, 22-29, 1983.)

Figures 8A-8L (prior art; collectively shown as figure 8) schematically illustrate the microcapillary path of water through a microporous membrane as a function of the length of the hydrophilic region surrounding the microcapillary outlet and how organic impurities in the water are more likely to adhere to the outlet end of the capillary. The initial hydrophilic state of the region surrounding the microcapillary exit is shown in step 1 (FIGS. 8A-8D). D₁Is the diameter of the hydrophilic region, and R₁Is the radius of the water droplet emerging from the outlet, which is much larger than the radius r of the microcapillary outlet. Step 2 (fig. 8E-8H) occurs after some accumulation of the hydrophobic solution around the microcapillary outlet at the periphery of the hydrophilic region. Where D is₁＞D₂> 2R, and R > R₂. Step 3 (FIGS. 8I-8L) is in the final end state, in which the diameter D of the hydrophilic area surrounding the outlet is_fThe constriction is twice the exit radius r. When Δ P is 2 γ/R_fGreater than the applied pressure P_fWhen the flow of water over a given outlet stops. (from L.A.Errede, J.Colloid Interface Sci.100, 414-22, 1984.)

FIG. 9 is a schematic diagram of a system in which a pressure regulating device is incorporated.

FIG. 10 is a schematic diagram of an exemplary pressure regulating device for use in the system of FIG. 9.

Detailed Description

A preferred embodiment of the present invention will now be described with reference to fig. 1-10.

As used herein, the term "tube" refers to a conduit for providing water and/or nutrients. As will be appreciated by those skilled in the art, such a "tube" need not be cylindrical, but may have any suitable shape, and no limitation is intended by the use of these words.

Described herein are systems and methods for supplying water and/or nutrients to the roots of growing plants, wherein the water and/or nutrients required by a single plant are released to the plant. The term "plant" is to be interpreted broadly herein and may include, for example, grass. While not intended as a limitation of the present invention, it is believed that the plant roots are capable of expelling exudates or surfactants when under water pressure, which facilitate the release of water and/or nutrients stored under the conditions described below. In particular, the plants receive a supply of water and/or nutrients from a supply line or pour tube, at least some of which are hydrophilic.

In some embodiments, the tube may include a plurality of pores covered by a hydrophilic membrane; in other embodiments, the entire pipe, portion of the subsurface, or a substantial portion thereof is hydrophilic. In further embodiments, the system may include a surface tube that is water impermeable or hydrophobic, which may be connected to a plurality of hydrophilic tubes that may be inserted into the support medium to supply the roots.

One or more hydrophilic tubes may be inserted into some of the support media such that the tubes are at least partially below the surface of the support media. The support medium may be selected from any suitable medium or mixture of media suitable for supporting growing plants and roots. For example, but not limited to, such support media may include sand, soil, Rockwool, polyurethane-based foam, Fleximat^TMSRI cellulose-based growth media, and the like. Other suitable media known in the art, such as continuous fiber growth media, may also be used.

In a special embodiment, the plants are planted in a support medium, and the individual tubes are connected to a reservoir containing water, nutrients or a mixture thereof. In some embodiments, two pipes may supply a row of plants: water pipes and nutrient pipes. As mentioned above, it has previously been shown that plants are able to distinguish between these tubes. Alternatively, nutrients may be added to the water reservoir for distribution through a pipe.

Thin-walled microporous hydrophilic tubes are commercially available for use as irrigation tubes, which are currently unknown. In specific embodiments, the hydrophilic material comprises Cell-Force^TMAnd Flexi-Sil^TMAnd can be made into hydrophilic tube. Alternatively, some existing hydrophobic thin-walled tubes may be rendered hydrophilic by a process that employs a non-water soluble hydrophilic polymer (e.g., polyhydroxystyrene, U.S. Pat. No. 6045869, incorporated herein by reference; the structure is shown in FIG. 6) as a surface coating. These solutions, applied as coatings and penetrating microporous hydrophobic plastic tubing, have been shown for many years to not clog the pores and remain hydrophilic. Thus, Tyvek with a radius of 5-10mm^RContinuous tubes (Irrigro-International Irrigation Systems) of (a microporous polyethylene material, made of very fine, high density polyethylene fibers, DuPont, Richmond, VA) are used after becoming hydrophilic and have been shown to act as membranes which respond to the roots of plants in sub-Irrigation Systems.

Tyvek^RMany types are available, each with different properties. Although not intended to be limiting, two types are found to be most advantageous for use in the present invention: 1059B and 1073B.

As described above, it has been shown that over time, hydrophilic membranes can become hydrophobic due to the absorption of organic impurities in the water onto the membrane. Due to the variability of impurities in water, we added organic matter to the water that could be absorbed on the outlet pore walls, rendering the membrane hydrophobic, thereby reducing the flow of water or nutrient solution through the membrane. Examples of suitable organic substances include, but are not limited to, humic acid, kerosene, turpentine, pinene, paraffin, and hexadecane. In other embodiments, other suitable C8-C16 saturated hydrocarbons may be employed. The amount added to the irrigation medium is from 10ppb to 10 ppm. It will be appreciated by those skilled in the art that in some embodiments, the addition of organic material is not necessary, depending on the quality of the water.

When growing crops in the soil, the addition of nutrients to the continuous base is not necessary; however, when growing crops in sand, Fleximat or Rockwool, nutrient solutions, such as any suitable nutrient Solution known in the art, such as those commonly employed in hydrophobic systems, e.g., Hoegland Solution, Peter's Solution, Miracle-Gro, or other less colored fertilizers, e.g., Schultz Export, can be added to the water supply, or can be supplied directly to the plant in a different tube, as described above, so that the plant roots can allow access to water and nutrients as needed. However, for growth in artificial media, the inclusion of nutrients and micronutrients is important.

Fig. 1A and 1B show a system 10 that employs dual irrigation pipes 11, 12 to deliver water and nutrient solution to plants 13 growing in a growth medium 14. In this example 10, the tubes 11, 12 pass through the root system 15 of the plant 13. It has been found experimentally that the higher the concentration of nutrients employed in the sand and pot plots, the smaller the volume of nutrient solution released to the roots 15, which is an example of the water retention achieved by the present invention.

It will be appreciated by those skilled in the art that the tubes 11, 12 may be a single composite dual lumen tube without departing from the spirit of the present invention. The diameters of the two sections may be commensurate with the plant's water and nutrient requirements, such as doubling the water pipe size, although this is not intended as a limitation.

In some embodiments, because an underground thin-walled microporous tube may collapse under the application of sufficient pressure, a spiral 60, for example comprising plastic, may be placed into, for example, tube 11 or 12 to form a tube 61 that is more resistant to collapse (FIG. 1C).

FIG. 2 shows a system 20 for irrigating grass 21 in which underground pipes 22 are spaced 1-2 feet apart and are supplied with water at approximately constant low pressure, with nutrients added to the aqueous solution as needed.

The irrigation systems and methods described herein are believed to be superior to any other watering system currently employed, and are independent of atmospheric pressure, so that they can be used in space culture or microgravity conditions, as well as others. In one embodiment 30 of the invention (fig. 3), for example, a continuous fiber growth medium 31, such as Rockwool or sponge-like Feximat (from Grow-Tech), may be used to support plants 32 and their roots 33. In this embodiment 30, both reservoirs 34 include a container 35 having an interior space 36 for holding water and nutrient solution. The container 35 is formed like a bellows and is movable between an expanded state containing solution and a recovery state where the solution is removed.

The container 35 also includes a fill inlet 37 in fluid communication with the interior space 36 of the container for adding solution thereto. The dispensing tube 38 is also in fluid communication with the interior space 36 of the container and with the inlet 39 of the hydrophilic tube 40. The dispensing tube 38 also has a one-way valve 41 to prevent backflow of solution from the tube 40 into the interior space 36 of the container.

In the present system, support for plants and their roots may be provided under zero gravity, for example by using a single piece of connecting material, such as Rockwool or Fleximat, a sponge-like hydrophilic porous material produced by Grow-Tech, or a newly developed artificial sponge, such as Agri-LITE (SRI Enviro-Grow). By surrounding a double microporous hydrophilic irrigation tube with these materials, one supplying water and the other supplying nutrient solution, complete maintenance of water and nutrients supplied to the growing plants can be achieved. Such systems may also be used in acidic or desert environments where water conservation is required.

Previous laboratory tests have shown that tomatoes can be grown in sand using nutrients in water by gluing Amerace A10 film 42 (50% silica gel in polyethylene) into the holes 43 of an underground PVC pipe 44 (FIG. 4). The holes 43 of the PVC tube 44 were 12mm in diameter, spaced 10cm apart, drilled into a rigid PVC tube of 17mm internal diameter. The holes 43 are believed to have a limited amount of water and nutrients for growing plants, and this system proves to be inadequate when the plant begins to produce results and requires more membrane area to provide plant needs. The system is improved by drilling and covering more holes to increase the total surface area of the membrane. However, the best mode currently implementing the invention supports the use of coiled tubing. Membrane tubes made of this material are prone to cracking and leakage due to the fragile nature of america.

Tubular Tyvek^R(DuPont) has been used for irrigation purposes in gardens and rows of crops at elevated water pressures. However, the hydrophobic nature of the polyethylene material allows it to be used as a drip source for plants without any control of the emissions through the roots of the plants. The conversion of a hydrophobic surface to a hydrophilic surface has been described (U.S. Pat. No. 6045869) and can be used to make Tyvek^RThe tubes are hydrophilic and respond to the plant's need for water and/or nutrients. When the tube was made hydrophilic by coating and injecting an alcohol solution of polyhydroxystyrene, the tube was found to be permeable to water at very low pressure and showed a decrease in water permeability when organic compounds in the water were adsorbed on the walls of the outlet pores. This can be considered a "conditioning phase" during which permeability can be reduced by 80% by adding hydrocarbons to tap water.

It is first believed that the present invention provides a plurality of supply tubes arranged to extend below the surface of the support medium to feed a plurality of plants or a row of plants. Moreover, the clear advantages of the tube containing hydrophilic material are: a larger area of support medium is supplied with water and nutrients than with a single horizontal membrane.

The invention will now be described by way of example; however, the present invention is not intended to be limited by these examples.

Example 1. Tyvek 4 feet long^RThe tube (#1053D) was made hydrophilic by an alcoholic solution of polyhydroxystyrene, and was buried in plants 4.5 feet by 13cm wide by 10cm deep, covered with soil, and connected to a constant supply of nutrient solution at a constant water head of 35 cm. Ten cherry tomato (Lycopersicon sp.) seeds were planted at uniform distances next to a tube supplying water and nutrients. Fluorescent lighting was provided to the plants 18 hours per day. The average water consumption is 75 +/-10 Ml/hr when the plant is 15cm high, and 125 +/-20 Ml/hr when the plant is 25cm high. When passing throughWhen 100mL of water was sprayed on the bed to simulate precipitation, the water consumption dropped to zero for 2 hours and slowly returned to normal rate over the next 3 hours. The plants grew to two feet high and a large number of tomatoes were harvested.

At the end of the experiment, the system was measured to determine if there was any competition between plants for the space on the membrane. Measurements of the root system indicated that the roots only surrounded the membrane within about 1-2 inches from the stem. This means that the density of plant growth can be increased to such an extent that it is only limited by the available photochemical flux and interference.

When a dual tube system is used to supply water and nutrient separately, the ratio of water consumed to nutrient solution consumed is about 2.5 to 1 for 8 cherry tomato plants in sand. Again, little or no fluctuation was observed when the plant size reached 35cm height.

Example 2. Continuous irrigation pipes are not necessary for plants such as grape vines or kiwi vines that are spaced 20 to 40cm apart from each other. In these cases 50, it is more practical to use a main soft-surface distribution pipe 51 of 20-30mm internal diameter from which the satellite pipes 52 are drawn, supplying short lengths from 10 to 30cm depending on the size of the vine, thin-walled microporous hydrophilic irrigation pipe 53, which irrigation pipe 53 is closed at its end 54, around the root 55 of the vine or shrub, as shown in figures 5A and 5B.

Example 3. Tomato plants were planted in potting soil, in which two microporous hydrophilic tubes with a radius of 1cm and a length of 20cm were also placed. The tube is connected to a reservoir filled with water and nutrients. The soil remained dry and the plants grew to produce a number of tomatoes.

Example 4. Another example uses a Tyvek 1.25m long and 1cm radius^RA tube. The tube was sealed on one end and made from a 3% solution of polyhydroxystyrene in ethanol (novolac grade from TriQuest). The tube was submerged in a 1.4m planter, covered with soil, and connected to a supply of nutrient solution at a constant head of 35cm water. Ten cherry West RedPersimmon (Lycopericon sp) seeds were planted at equal intervals on the sides of the tube through which water and nutrients were supplied. Plants were grown in the conditioning phase while exposed to 16 hours/day of fluorescent lighting. The average water consumption is 75 +/-10 Ml/hr when the plant is 15cm high, and 125 +/-20 Ml/hr when the plant is 25cm high.

When precipitation was simulated by spraying 100mL of water onto the bed, the water consumption dropped to zero for 2 hours and slowly returned to normal rate over the next 3 hours.

The plants grew to 60cm high and a large number of tomatoes were harvested. At the completion of the experiment, the system was measured to determine if there was any competition between plants for the space on the membrane. Measurements of the root system indicated that the roots only surrounded the membrane within a range of about 2.5-5cm from the stem. This finding would indicate that it is possible to increase the density of plant growth to a degree that is limited only by the available light flux and mutual interference.

It has also been shown that different plants requiring different water and nutrient ratios can be grown together, each individually being satisfied without monitoring.

Example 5. When a two-membrane system was used to supply water and nutrient separately, the ratio of water consumed to nutrient solution consumed was about 2.5 to 1 for 8 cherry tomato plants in sand. Again, little or no fluctuation was observed when the tomato plant size reached 35cm height.

A planter 115cm long, 13cm wide and 10cm deep was set up in the greenhouse with a double feed film tube for water and nutrients through the center of the bed comprising a 50cm Flexmat and a 50cm rockwool separated by 15cm polyurethane foam. Seeds or seedlings of canola (Brassicaspp), beans (Phaseolus sp), maize (Zea Mays sp) and tomatoes (Lycopersicon sp) are planted in their respective media and in their growth moulds. Growth in Fleximat preference was made normally, with the exception of polyurethane foam, each crop at its own rate of 50-60Mw/cm²And growth under the light flux of (3). Root crops, e.g. carrots (Saucus carota)var sativa sp), radish (Raphanus sativus sp), beetroot (Beta vulgaris sp) and onion (Allium sp) were grown in soil and peat, while potato (Solanum tuberosum sp), parsnip (pastina sativa sp) and parsley (Petroselinum sativum sp) were successfully grown in vermiculite. Cellulosic material (SRI Petrochemical Co.) may also be used as an artificial growth medium.

It was determined that grass (grasses sp) could be irrigated for 3 consecutive years with buried tubular membranes spaced 40-50cm apart.

Example 6. In another example, two hydrophobic planters (30X 30cm) were equipped with membrane tubes for water/nutrient solution, about 7cm from the bottom. The medium allows root crops to produce straight main roots, which consumers are interested in purchasing vegetables. One planter planted parsnip (Saucus carota var sativa sp) seeds. Other planters are parsley (Petroselinum sativum var. tuberosum sp), a binocular crop with leaves and rhizomes. Plant competition controls the over-planting emission of each planter. The plants receive only natural sunlight, reducing the risk of "sifting". Extreme warm temperatures are a concern for plant health.

The roots of Saposhnikovia divaricata grow straight and yield a total weight of 38.9 g. The texture and taste were good. Parsley produces a straight main root, with a total weight of 38.3 g. The resulting leaves had longer petioles than those purchased conventionally, and the total weight was 58.9 g.

It will be appreciated by those skilled in the art that plants with different water requirements can be met by embodiments of the present invention wherein a continuously porous hydrophilic irrigation tube is employed to allow each plant to obtain its required water independently of the other plants. Such a need is often required in greenhouses, where many different plants are grown under a roof.

It has also been shown that a hydrophilic irrigation tube with two channels, one for water and one for nutrients, fully satisfies the needs of the plants and increases their density, limited only by the available light.

It has also been shown that commercially available thin-walled microporous hydrophobic tubes can be converted into hydrophilic tubes, and thus respond to plants and their roots. Such pipes may include, but are not limited to, high pressure irrigation pipes, although their use in the present invention does not require the use of high pressure.

It is also shown how a double membrane tube can be connected to the container for one or more plants, so that the plants can get a supply of water and nutrients from the respective reservoirs as required, without further attention or detection, as long as water is available in the tube reservoir. In a specific example, a 3: 1 ratio of the diameters of the water tubes to the nutrient tubes is optimal, although this is not intended to be limiting and obviously depends on nutrient concentration and plant type.

It has also been shown that a water system that is free of contaminating organic matter and is not responsive to an irrigation system can be made responsive to the irrigation system by adding trace amounts of one or more hydrocarbons to the water supply.

It is also shown that the irrigation system of the present invention can be used to replace emitters in drip irrigation systems, so that the release of water and/or nutrients is responsive to the roots. In a specific embodiment, it has been found that between the known drip irrigation system and the system of the present invention, a factor of 100 to 500 water amount difference is used.

In another embodiment 70 (fig. 9), a pressure regulating device, such as a floating flow control valve 71 (fig. 10), is interposed between reservoirs 72, 73 and tubes 74, 75. In addition, an inlet filter 76 may be added for filtering particular substances. In a specific embodiment, the float controller 71 is operable to regulate pressure between 1 and 3psi, although these values are not intended as limitations. The pressure value is adjustable, for example, by setting the floating flow control valve to a particular level on the tubing 74, 75, for example, 28 inches for specialized tubing materials and systems.

In the exemplary float control valve 71 of fig. 10, the water inlet 77 enters the top end 78 of the chamber 79 and is attached to a float 80 that floats on a maintenance level 81. The water flows out through an outlet 82 on the bottom 83 of the chamber 79 and an air vent 84 is provided for maintaining atmospheric pressure. The irrigation pipes 74, 75 are shown as being located below ground level. The height 85 above the tube level can be adjusted and the volume of the chamber can be selected, for example, based on the desired flow rate through the system 70.

It has been found that the addition of the floating flow control valve 71 allows the minimum operating pressure to be maintained without exceeding the maximum pressure. Whether the tubes 74, 75 are the same or different, a minimum pressure is required to pass the fluid. If too much pressure is provided, fluid will flow through the pores of the tubes 74, 75 regardless of the presence or absence of surfactant root exudate.

The system 70 allows for the maintenance of pressure without the need to employ other more expensive types of pressure regulators, electronic valves, or flow regulators. The system 70 is easily hidden in landscape applications and is robust enough for agricultural applications.

Grass parts are known to grow in substantial isolation, for example on golf courses, where the greens are formed on depressions whose ground is filled with earth and are supplied with water and nutrients, either continuously or at predetermined intervals. In such an arrangement, the system of the present invention can ideally provide water and nutrients to the roots of the grass on an as-needed basis, thereby conserving water and nutrients and ensuring optimal nutrients for the green.

Tables 1-4 below include data from experiments performed indoors (table 1) and outdoors (table 2), and flow rates of water and nutrients (table 3), and water feeding results for series and individual plants (fig. 4).

a two separate supply pipes for water and nutrients.

b beets did not mature, although the leaves were abundant.

c the bean roots appeared to crawl down the entire planter and throughout the entire growing medium.

d the system is a model for plant growth in international space stations.

a corn and watermelon are not adopted and grow.

b 1, 1.5 and 2ft intervals of irrigation tubes (40-50cm, 10ft long).

a planter with two tubes, one for water (W) and the other for nutrient solution (N). The reservoirs are periodically interchanged to eliminate any membrane effects. Flow rate unit Ml/hr; the experimental time ranged from 3 months 18 days to 7 months 16 days.

a experiment time: 19 days 2 month to 6 months and 6 days 6 month.

Another aspect of the invention is to make a tube for use in a "water on demand" system. In one method, a thin sheet of low porosity material is coated with the aforementioned polyhydroxystyrene and formed into a cylindrical shape by, for example, thermal, ultrasonic, or impulse means.

Although not intended to be limiting, a possible explanation of the operation of the polyhydroxystyrene polymer (FIG. 6) will be provided below. First, how the polyhydroxystyrene is attached to the membrane: polyhydroxystyrenes have two groups: a hydroxyl group (OH) which is hydrophilic and capable of binding to water hydrogen, and a styrene group which includes a benzene ring (-C)₆H₄-) attached to a vinyl group (═ CH-CH₂-) that are both hydrophobic and can adhere to a hydrophobic polyethylene film, leaving hydrophilic (OH) groups that form weak hydrogen bonds with water.

As described above, the polymer may act as a capillary through the membrane. It has been shown that organic impurities 10 in water⁵-10⁶It is much easier to adhere to the outlet end of the capillary where there is a gas-liquid-solid equilibrium (i.e., air-water-membrane). The organic impurities are held in equilibrium along the capillary wall, where the equilibrium is only between liquid and solid. In this way, the surface of the outlet orifice becomes hydrophobic due to absorption of trace organic impurities in the water and/or nutrient solution.

When the plant requires water, it releases a chemical substance called a release, which may include a surfactant that removes organic compounds adhered at the outlet wall, the fluid from the irrigation pipe now being allowed to flow. This is shown in the prior art as two different membranes, as discussed above in connection with fig. 7-8L.

The high purity water is free of organic impurities. Some domestic water supplies are often purified to such an extent that only very few organic impurities remain. This will result in the closure of the pores only after a large amount of water, which is usually not necessary, has passed through the membrane. This result would be inappropriate due to the time delay between the removal of organics and their deposition on the membrane and the closing of the pores. On the other hand, too much organic capacity in the water can lead to delays in the opening of the closed pores, because of the limited amount of surfactant released through the roots.

It has been found that the area of membrane required for a plant is best achieved by a tube having a diameter of approximately 1cm radius, a maximum thickness of 0.5mm, and a pore size of from 0.1 to 5um, preferably with an average value of 0.4um, although this is not intended to be limiting and other pore values may be used. This part of the membrane will come into contact with the roots of the plant. A short section of membrane tubing may be supplied with water and/or nutrients through the small diameter tubing, but care must be taken to prevent air lock-up in the tubing. A 1cm inner diameter tube is not considered too large. Since the supply line is exposed to light (sunlight or artificial light), it is necessary to use an opaque tube, otherwise the sun-activated light will cause the generation of algae, which will eventually block the hole. It is believed that the coating of the hydrophobic membrane primarily allows the resulting hydrophilic surface to become hydrophobic and close the pores. Leaving the inner bore uncoated restricts water flow through the membrane.

In the foregoing description, certain terms have been used for brevity, clearness, and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirement of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. Moreover, the embodiments of the apparatus illustrated and described herein are examples only, and the scope of the present invention is not limited to the exact details of construction.

The present invention, the construction, operation and use of the preferred embodiments, and the advantageous new and useful results attained thereby, have been described. New and useful structures, as well as reasonable mechanical equivalents, which are apparent to those skilled in the art, are set forth in the following claims.

Claims (9)

1. A system for delivering water and nutrients to plants, comprising:

a microporous tube comprising a hydrophilic polymer, a distal portion of the tube positioned adjacent to a root system of a plant, the tube having a lumen therethrough for conducting an aqueous solution from an inlet to the distal portion, the tube having pores that allow the aqueous solution to flow therethrough when acted upon by a root exudate comprising a surfactant;

a reservoir adapted to hold an aqueous solution therein; and

a pressure regulating device in fluid communication at an upstream end with the reservoir and at a downstream end with the inlet of the tube to provide at least a minimum pressure value to allow fluid to flow through the tube and at most a maximum pressure value above which fluid will flow through the tube even in the absence of the surfactant-containing root exudate.

2. The system of claim 1, wherein the pressure regulating device provides a pressure value in the range of 1 to 3 psi.

3. The system of claim 1, wherein the pressure regulating device comprises a floating flow control valve.

4. The system of claim 1, wherein the pressure regulating device is adjustable to achieve a plurality of operating pressures.

5. The system of claim 1, wherein the hydrophilic polymer is a polyhydroxystyrene.

6. The system of claim 5, wherein the multi-well tube comprises a first multi-well tube, the reservoir comprising a first reservoir to hold at least water, further comprising:

a second microporous tube coated and impregnated with a hydrophilic polymer and having a distal end portion positioned adjacent to said plant root system, the second tube having a lumen therethrough for conducting a nutrient solution from an inlet to the distal end portion, the second microporous tube having pores adapted to allow a nutrient solution to flow therethrough when acted upon by a root exudate including a surfactant, the second microporous tube fluidly connected to the downstream end of said pressure regulating device at the inlet; and

a second reservoir for holding a nutrient solution therein, the second reservoir being in fluid communication with the upstream end of the pressure regulating device.

7. The system of claim 1, wherein the memory comprises:

a container having an interior space for containing an aqueous solution therein, the container being movable between an expanded state when containing the solution and a contracted state when the solution has been removed;

a fill inlet in fluid communication with the interior space of the container for adding a solution thereto; and

a dispensing tube in fluid communication with the interior space of the container and the tube inlet for providing a solution to the interior space of the hydrophilic means via the pressure regulating device, the dispensing tube having a one-way valve therein for preventing backflow of the solution from the tube interior space to the interior space of the container.

8. Method for establishing a system according to claim 1 for plants, comprising the steps of:

joining the lateral ends of a hydrophilic sheet comprising a hydrophilic polymer to form a tube;

placing the distal end portion of the tube in an artificial plant growing medium;

planting a plant in the growth medium, the plant having a root system adjacent the tube end;

placing the inlet of the tube proximal to the reservoir suitable for containing the aqueous solution; and

the pressure of the aqueous solution upstream of the inlet of the pipe is regulated.

9. Method for establishing a system according to claim 1 for plants, comprising the steps of:

applying a hydrophilic polymer to a microporous hydrophobic sheet;

joining the side ends of the sheet to form a tube;

placing the distal end portion of the tube in an artificial plant growing medium;

planting a plant in the growth medium, the plant having a root system adjacent the tube end;

placing the inlet of the tube proximal to the reservoir suitable for containing the aqueous solution; and

the pressure of the aqueous solution upstream of the inlet of the pipe is regulated.