RECYCLABLE SYNTHETIC PLANT GROWTH MEDIUM

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional

Application No. 60/782,078, filed March 14, 2006.

TECHNICAL FIELD [0002] The present invention relates to the field of hydroponics, particularly to the area of hydroponic growth media, and more particularly to the field of recyclable synthetic growth media.

BACKGROUND ART

[0003] Hydroponics is crop production using mineral nutrient solutions rather than soil containing silt and clay. Land plants may be grown with roots only in the liquid nutrient (mineral) solution or an inert medium supplied with a liquid nutrient solution and/or gases including but not limited to oxygen, hydrogen and others.

[0004] There are two types of hydroponics - solution culture and medium culture.

Solution culture does not use a solid medium for the roots, just the solution itself. Nutrient solutions used in hydroponics are mostly inorganic and ionic and include cations such as calcium, magnesium, and potassium. Nitrogen, sulfur, and phosphates are also supplied in nutrient solutions in the form of salt solutions with corresponding cations.

[0005] Medium culture utilizes a solid medium for the roots. Typically, nutrient media is delivered to individual plants through feed tubes and individual drippers that supply nutrient media directly to the base of each individual plant. Typical media are sand, gravel, and rockwool. Rockwool is currently the most popular medium. It is made from basalt rock and is prepared for use by heating to a high temperature and spinning it back together to create a "cotton candy" appearance.

[0006] However, there are some problems attached with the use of rockwool. When it is dry, rockwool becomes friable and its mineral particles may be inhaled. It causes a high pH level which requires constant monitoring and removal of leached out minerals. In addition, rockwool can be used for only three or four generations or growth cycles. Finally, rockwool is not recyclable meaning that, after it is no longer usable, it must be disposed of as a hazardous waste thereby adding to its overall cost as well as the overall production cost of the plants grown using a rockwool medium.

[0007] In addition, the root zone oxygen level can be very low when using rockwool due to the low air porosity of rockwool, especially at the later stage when the substrates are compacted. In some cases the oxygen level can drop to as low as 1.8 ppm. [0008] This low oxygen condition can be exacerbated by the use of black tubing to supply nutrient media to plants. The black tubing retains heat and causes the temperature of the growth media to rise reducing its oxygen carrying capacity. This low oxygen condition in rockwool or other growth media can make plants susceptible to root disease as well as reduce their growth potential. [0009] Traditional hydroponic medium culture systems, especially those that utilize rockwool, can develop adverse pH conditions. Because drippers supply water to the surface of the media, some water remains on the surface and leaches out minerals from the rockwool media. Various components of the basaltic rockwool include iron, sodium, aluminum and calcium which can be leached out and raise the pH in the immediate area of the growing plant. This condition requires periodic rinsing of the rockwool in order to bring the pH to acceptable levels.

[0010] In addition it the low oxygen problem, prior art medium culture systems are susceptible to the rapid spread of disease. Because water and nutrients are traditionally delivered using irrigation lines and drippers, if there is a plant disease outbreak, such as Pythium, Fusarium, or Phytophthora, among others, the recirculating systems can spread that disease throughout an entire hydroponic system.

DISCLOSURE OF THE INVENTION

[0011] The present invention broadly comprises a synthetic recyclable plant growth medium including at least one polymer nonwoven material having a fixed form, at least one delivery tube in functional association with the form, and an attachment means attaching the delivery tube to the form. In a preferred embodiment, the delivery tube is fabricated from a form of TYVEK ^® having micropores that open simultaneously when a threshold backpressure is reached. [0012] The present invention also broadly comprises a method of growing plants in a synthetic medium that includes providing a nonwoven polymer material form, with the form having at least one attached delivery tube and wrapped in UV blocking material, forming an opening in said UV blocking material, placing a plant seed or seedling on the nonwoven material form, connecting the delivery tube to a liquid nutrient source, and starting the flow of the liquid nutrient source. In a preferred embodiment, the delivery tube is fabricated from TYVEK ^® . In a

more preferred embodiment, more than one form is utilized with the delivery tubes ot eacn oi tne forms connected together.

[0013] The present invention also broadly comprises a system for growing plants in a synthetic recyclable medium having at least one polymer nonwoven material with a fixed form, at least one delivery tube in functional association with the fixed form, an attachment means attaching the delivery tube to the form, a trough for holding the fixed form, a nutrient source for storing liquid nutrient solution, at least one distribution line for distributing the nutrient solution to the at least one form, and a valve for connecting the nutrient source to the distribution line.

An alternate embodiment may include apparatus to bubble a selected gas(es) into the nutrient fluid for delivery to the medium through et at least one delivery tube.

[0014] One object of the invention is to supply a synthetic recyclable plant growth medium that provides for improved oxygen delivery to the plant roots.

[0015] A second object of the invention is to provide a synthetic plant growth medium that is reusable through several plant growth cycles. [0016] A third object of the invention is to provide a synthetic plant growth medium that is recyclable.

[0017] An additional object of the invention is to present a synthetic plant growth medium that does not require periodic rinsing of minerals leached out from the growth medium.

[0018] A further object of the invention is to put forth a system for the growth of plants using a synthetic recyclable plant growth medium.

BRIEF DESCRIPTION OF DRAWINGS

[0019] The nature and mode of the operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing Figures, in which:

Figure Ia is a top perspective view of the synthetic water absorbent plant growth medium ("growth medium") of the present invention in which the growth medium is wrapped in a UV resistant wrap;

Figure Ib is a top perspective view of the growth medium of in which the UV resistant wrap is removed showing nutrient delivery tubes attached to the top of the growth medium;

Figure Ic is a top perspective view of an alternate embodiment of the growth medium in which the nutrient delivery tubes are positioned within the growth medium;

Figure 2a is a cross section of the growth medium of the present invention taken along line 2a-2a of Figure Ia and showing the delivery tubes attached on the top surface of the growth medium;

Figure 2b is a cross section of the growth medium of the present invention taken along line 2b-2b of Figure Ib and showing the delivery tubes positioned within the growth medium;

Figure 2c is an enlarged view of the circled area in Figure 2a; Figure 3 is in an enlarged view of the roots of a plant growing in the growth medium with nutrient fluid trapped within the UV wrap and retained around the roots of the plant; and,

Figure 4 is a schematic view a hydroponic plant growth system in which a plurality of growth medium forms of the present invention are connected to form a network of forms.

BEST MODE FOR CARRYING OUT THE rNVENTION [0020] At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical structural elements of the invention.

[0021] While the present invention is described with respect to what is presently considered to be the preferred embodiments, it is understood that the invention is not limited to the disclosed embodiments. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0022] Adverting to the drawings, Figure Ia is a top perspective view of the recyclable synthetic water absorbent plant growth medium ("growth medium") of the present invention in which the growth medium is in the form of at least one nonwoven polymer in the shape of a slab or other shape (form 10") and is wrapped in a UV resistant wrap 13. Also seen is a preferred embodiment in which perforations surround at least one hole cover 14. As will be explained below, in the preferred embodiment, at least one perforated cover(s) 14 is easily removed to reveal at least one hole 14a. Hole 14a allows placement of a plant seed or seedling on or in form 10. [0023] Wrap 13 is an aquaculture wrap having a double purpose. First, it keeps out light and spores that may adversely affect the plants. Second, it retains the nutrients fed to form(s) 10 through tubes 11 as tubes 11 are inside wrap 13. The retention of the nutrients allows the nutrients to concentrate at the roots of the plants. In one embodiment, wrap 13 is comprised of two layers of polyethylene having a gauge of 2.63 mils. As seen in Figure Ib, the two layers include an inner black polyethylene layer 13a (~ 10%), made from low density polyethylene that retains heat and nutrient fluid, and an outer white polyethylene layer 13b (~ 90%) made from a

medium density polyethylene, that blocks UV radiation. Preferably, wrap 13 is manufactured to include holes 14a spaced about 8-12 inches apart, depending on the plant being grown. Holes 14a are easily opened to provide an opening to place the plants onto form 10. Wrap 13 is produced by Peel Plastic Products Ltd., 49 Rutherford Road, South Brampton, Ontario L6W 3J3 Canada.

[0024] Figure Ib is a top perspective view of the growth medium showing nutrient delivery tubes 11 ("tubes 11") attached to the top of form 10. In one embodiment, form 10 is approximately 36 inches or one meter in length, about 6 inches wide and about 2.0-5.5 inches in depth. Persons of skill in the art will recognize that other sizes may be more suitable for certain plant growth scenarios. For example, the material of the medium may be formed into one inch cubes or other configurations. In a preferred embodiment, form 10 can be manufactured into any desired length or, after manufacture, cut into any desired length.

[0025] In one embodiment, the medium is comprised of at least one nonwoven polymer fiber ("polymer") and possesses a uniform density throughout the entire formation (slab, cube, etc.). In one example of this embodiment, the polymer comprises 100% polyester (polyethylene terephthalate or PET). Other possible polymers include, but are not limited to, basofϊl (a melamine derivative) PBX Kanekaron (acrylonitrile/vinylidene chloride copolymer), PLA (polyactϊc acid, such as Ingeo™ fiber from Natureworks PLA), polypropylene, acrylic, nylon, propylene, PTA (purified terephthlalic acid), and CAN (acrylonitrile). Still other polymers include, but are not limited to, ethylene dichloride, MEG (monoethylene glycol), ethylene glycol, FDG (polyamide fiber), benzene, and styrene.

[0026] In other embodiments, the medium includes cellulose derivatives distributed throughout the medium again with substantially uniform density. These cellulose fibers include, but are not limited to, rayons, both viscose and acetate rayons, lyocel (regenerated cellulose) and visil, a viscose fiber. Typically, the mixtures range from 80-100% polymer and 0-20% cellulosic material. In a preferred embodiment, the cellulosic material ranges from 1 — 10%. Cellulosic material is defined as the rayon and rayon-type fibers and other fibers that perform the same or similar function as that of rayon in the medium. [0027] Form 10 also includes at least one delivery tube 11 ("tube" or "tubing" 11") attached to form 10 by an attachment means such as a textile staple 12 which attaches tube 11 to form 10 at approximately 6-12 inch intervals. In a preferred embodiment, delivery tube 11 is fabricated from TYVEK ^® . Suitable staples 12 have a length ranging from 2-6 inches. A preferred embodiment is an SPC 1800, 2.875 inch staple (73mm) made by Avery Dennison, Framingham, MA. In an alternate embodiment, the attachment means may be a suitable adhesive able to retain sufficient adhesiveness in a moist or wet environment and if buried

underground. One example of a suitable adhesive is a hot melt glue Hot Melt Bonding Adhesive Resin: Polyolefin-E from International Irrigation Systems, St. Catherines, Ontario, Canada L2T 3N3.

[0028] Tube 11 is considered to be in functional association with form 10 meaning that tube 11 functions to provide water and nutrients to the medium of form 10 which in turns acts as a nutrient source for the growing plants. In a preferred embodiment, form 10 will comprise two or more TYVEK ^® tubes 11, which in one embodiment are attached to the top surface of form 10 using textile staple 12. In a more preferred embodiment, tube 11 is a type of TYVEK ^® comprising micropores averaging about one micron in size which provide for an efficient flow of water and nutrients to each plant without the dangers of over watering. By using a tube 11 that includes these micropores, less water is needed to be supplied to the plants and less maintenance is needed to maintain efficient flow to the plants. In addition, the one micron pore size provides a "biosecurity" feature by preventing harmful microbes from being introduced to the plants through the aqueous nutrient stock fed to the plants. Most infectious microbes are greater than 1 micron in size. Tube 11 with micropores may also be used to supply oxygen, hydrogen and other gases using procedures that are well known to those having skill in the art, such as bubbling the particular gas into the fluid being delivered through tube 11.

[0029] A type of TYVEK ^® tube 11 possessing one micron pores is manufactured and supplied by International Irrigation Systems as WHD+C TYVEK ^® tubing. In a more preferred embodiment, WHD+C TYVEK ^® may include a noncompressible plastic insert placed within TYVEK ^® tube 11 during its manufacture allowing it to be buried thereby protecting tube 11 from destruction by UV exposure, vermin and small animals such as rodents. In addition, as explained below, use of WHD+C TYVEK ^® tubes enables even distribution of water-borne nutrients to the plants placed onto form 10. In the custom or continuous medium roll embodiment, tube 11 is attached to form 10 as form 10 is unrolled. Connection fittings are used to attach the ends of reels of tubing 11 together during this assembly process. [0030] Figure Ib also depicts a preferred embodiment of form 10 in which the nonwoven polymer is formed into a densified top layer 10a adjacent to a lower less dense layer 10b. Densified layer 10a is about 0.25-1.25 inches thick at the top surface of form 10. This densified layer serves to better support the plants placed onto the slab. The densified layer is preferably between 1.25 and 4 times denser than the lower portion of form 10. The same polymer materials and cellulosic materials described above are present in the densified layer in the same proportion as the remainder of form 10. These mixtures of polymer and cellulosic fibers and their methods of making and densifying (varying density) are well known to those skilled in the art. For example, a 100% polyester form and a 90-10% polyester-rayon blend, both suitable for use as

recyclable synthetic growth media, are manufactured by Fybon Industries, Ltd, of York, Ontario Canada having a weight of 30 oz./sq. yd. and a width of 43 inches and a overall length of about 22 yards.

[0031] Figure Ic is a top perspective view of an alternate embodiment of the growth medium in which the nutrient delivery tubes are positioned within the growth medium. In this embodiment, a roll of tubing 11 is unrolled and incorporated into form 10 as form 10 is fabricated forming an interstial space around tubing 11 with nonwoven polymer material both above and below tubing 11. [0032] Figure 2a is a cross section of the growth medium of the present invention taken along line 2a-2a of Figure Ia and showing the delivery tubes attached on the top surface of form 10. Figure 2b is a cross section of the growth medium of the present invention taken along line 2b-2b of Figure Ib and showing the delivery tubes positioned within the growth medium. Figure 2c is enlarged view of the circled area of Figure 2a showing delivery tube 11. Also seen is noncollapsible insert lib and micropores lie in the walls of delivery tube 11. [0033] Figure 3 is in an enlarged view of the roots of plant 20 growing in the growth medium with nutrient fluid trapped within UV resistant wrap 13 and retained around the roots of the plant. Plant 20 is seen emerging from form 10 through hole 14a. Plant 20 may be any type of plant. Some examples well known in the art include cucumbers, strawberries, peppers and tomatoes, however, these examples are not intended to limit the type of plants able to be grown in the synthetic plant growth medium of the present invention. Roots 22 are seen extending from densified layer 10a through layer 10b to the bottom of form 10. Wrap 13 acts as a root barrier to keep plant 20 confined to within form 10. Wrap 13 is a watertight barrier that holds nutrient 11a within the confines of the wrapped form 10. As plants mature, slits are cut into wrap 13 to drain depleted nutrient fluid 11 and allow new nutrient fluid 11 to be supplied to form 10. The arrows signify nutrient solution 11a flowing down from tubes 11 and concentrating around roots 22 as shown by the arrows.

[0034] Figure 4 is a schematic drawing of a hydroponic system utilizing the medium of the present invention configured as a slab or form 10. Tank 30 is connected to several forms 10 through hose 31. Valve 32 may be a simple on-off valve or a pressure control valve positioned to control the flow of nutrient fluid 11a from tank 30. Forms 10 are held in troughs 34 and are connected to each other by connection fittings 18. Connections 18 for different types of tubing 11 are well known to those of skill in the art. Form 10 is contained within wrap 13 (not shown in Figure 4) except for hole 14a in the top for placing the plants to be grown. Nutrient solution 11a is fed from tank 30 through hose or pipe 31 and into tubes 11 in either a gravity fed or a pressurized system. Slits made in wrap 13 allow the nutrient fluid 11a to drain into trough 34

and be replenished by new nutrient fluid 11a from tank 30 maintaining constant access to replenished or new nutrient fluid 11a by the plants. The fluid passes from tank 30 or other source through a series of one or more hoses or pipes fitted with a pressure compensating flow controller to produce an automatic watering/feed effect. Pressure compensating flow controllers are supplied by International Irrigation Systems. As described below, in the preferred embodiment of the system shown in Figure 4, tubing 11 is WHD+C TYVEK ^® the micropores of which open simultaneously only after a back pressure of 4-10 psi is reached. After the micropores open, the plants at the downstream end of the connected forms 10 receive the nutrient fluid at the same flow rate as the plants at the upstream end of form 10. Pressure compensating flow controllers 23 control the feed flow and pressure entering tubing 11.

[0035] Typically, hydroponic plant systems produce uneven growth and fruition as the plants positioned near the upstream or entry point of the nutrient fluid will absorb a greater proportion of the nutrients than the plants further downstream from the nutrient entry point. Using the preferred WHD+C TYVEK ^® tubing enables each plant on a particular form to receive equal amounts of nutrient thereby providing even plant growth throughout the slab. The micropores of the WHD+C TYVEK ^® tubing 11 are designed to open simultaneously due to back pressure created in tube 11. The micropores are about 1 micron in diameter. As the nutrient fluid enters and fills tube 11, the micropores remain closed creating back pressure in the tube. When sufficient back pressure is created, typically about 4-10 psi, all the micropores open simultaneously allowing for evenly balanced distribution of nutrient fluid throughout form 10. Once initiated, this even distribution is continued as long as flow to form 10 is maintained. [0036] It should be noted that the nutrient fluid may be unique for each type of plant and even for each geographic area. Moreover, the nutrient fluid may change in type or concentration of nutrient component as the particular plant matures. Such changes do not affect the performance of the medium of form 10 or TYVEK ^® tubing 11.

[0037] Another unexpected advantage over the prior art, including the use of rock wool plant growth media, is the lack of salting out of the nonwoven polymer and polymer — cellulosic media and the consequent reduced amount of water needed to be supplied to the plants. Using rock wool and the usual drip tube method causes the rock wool media to salt out thereby exposing the plants to an abnormally high level of salts. This causes stress in the plants and reduces their growth and yield. This salting out effect accelerates as the rock wool media is reused for additional plant growth cycles. Use of the nonwoven media of the present invention allows the grower better control over the flow of water and nutrient fluid and reduces the overall amount of water needed to be supplied to the plants. The nonwoven medium retains water in the medium, especially when contained in wrap 13. The water is not drawn to the surface of the

media where it evaporates, preventing salts from collecting on the surface of the media near the plants through water evaporation. This reduces or eliminates the need to flood the media with water to leach out the collected salts. Because there is less runoff, less evaporation at the surface and less need for leaching out salts formed at the media surface, use of the polymer and polymer- cellulosic media reduces the total amount of water and nutrient fluid needed to grow a crop as compared to use of prior art (rock wool) media. Moreover, in addition to reducing the stress on the growing plants, the lack of salting out allows the media to be reused without significant loss of growth and yield in successive plantings. [0038] Nutrient fluids previously known to those skilled in the art may be used with the medium comprising form 10. Typically, formulas for nutrient fluids are not only unique to each type of plant, but often differ as to geographic region and even by individual grower. Each nutrient fluid comprises nitrogen, phosphates, and potassium in various ratios. The polymer and polymer/cellulosic media described are capable of using any of these various nutrient formulas to initiate and maintain growth from seeds and/or seedlings to mature plant with ripened fruit ready for harvesting.

[0039] The medium provides advantages over the prior art in that it is recyclable and consequently significantly reduces the pressure on landfills that currently receive unrecyclable synthetic growth media such as rock wool. The nonwoven polymer media, such as polyester, provides structure and air porosity. In the preferred embodiments that include cellulosic material such as rayon, the cellulosic material enables the medium to retain water until the roots of the plants mature sufficiently to retain water on their own. Moreover, roots from previous plantings are also retained in the medium to help retain water for new plantings. Using the medium of form 10, it is possible to use the same form 10 for at least three different plantings, meaning growth from seed or seedling to mature fruiting plant. In addition, the old roots from prior plantings can be chlorinated or brominated to kill any disease carrying organisms present in the media.

[0040] Moreover, the preferred embodiment of tubing 11, having micropores of 1 micron aid in preventing disease microorganisms from infecting the plants as the small size of the micropores prevents larger sized disease organisms that may be present in nutrient fluid 11a from contacting and infecting the plants. Finally, after usage, the nonwoven polymer form can be recycled to reclaim the polymer using techniques well known in the recycling arts. [0041] Thus it is seen that the objects of the invention are efficiently obtained, although changes and modifications to the invention should be readily apparent to those having ordinary skill in the art, which changes would not depart from the spirit and scope of the invention as claimed.