WO2004098270A1

WO2004098270A1 - Improved hydroponic growth medium

Info

Publication number: WO2004098270A1
Application number: PCT/US2004/013991
Authority: WO
Inventors: Jeffrey Scott Hurley; James M. Gross
Original assignee: Bki Holding Corporation
Priority date: 2003-05-01
Filing date: 2004-04-30
Publication date: 2004-11-18

Abstract

The present invention relates to a hydroponic plant growth medium. Specifically, the invention provides a method for supporting hydroponic plant growth with the use of a medium containing cellulose fibers, bicomponent fibers, and synthetic fibers.

Description

IMPROVED HYDROPONIC GROWTHMEDIUM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S. C. 119 based on U.S. Provisional Application Ser. No. 60/467,637 which was filed May 1, 2003, which is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a hydroponic growth medium, particularly a multilayered growth medium of cellulose fibers, bicomponent fibers, and synthetic fibers.

BACKGROUND OF THE INVENTION It has been known for many years that plants can be grown without natural soil by substituting a direct source of nutrients. The term "hydroponics" has been coined to describe a variety of soilless culture systems. The basic concept in hydroponics is to feed chemical nutrients, such as, for example nitrogen, potassium, calcium, etc., directly to the plant's roots through the vehicle of an aqueous solution. Hydroponic techniques have been used in the laboratory for decades to achieve precise control of growth variables for scientific study. In recent years, several products have been developed to enable both private and commercial growers to utilize hydroponic principles. When hydroponic equipment and supplies are low enough in cost, carefully controlled hydroponic culture has significant economic advantages over conventional soil culture: plant nutrition is easily optimized; soil-bome diseases are eliminated; there are no weeds to deal with; and the yield and quality is more predictable and generally higher. Under the controlled conditions of hydroponics, the effective growing season can be extended. Overall, this means significantly greater yield per square foot of growing area.

Hydroponic culture is usually coupled with greenhouse facilities in an effort to achieve maximum control of growth factors such as, for example, temperature, light, humidity, nutrients, and water. Growing plants indoors under such controlled conditions means that the growing season can be year-round. Being able to grow vegetables indoors is particularly suited for the far Northern latitudes which may have a natural growing season to short for some crops like tomatoes. The art maybe divided into two basic categories, open systems and closed systems. In open systems the nutrient solution fed to the plants is not recycled but, rather, leaches and drains away. Fresh nutrients are continually supplied and, with the use of "nutrient concentrate injectors" which are mechanisms for supplying nutrients to a water irrigation system on a continual basis, can be regulated with great precision to the plant's growth needs. Closed systems retain the nutrient solution for reuse. The solution is pumped from a reservoir to the plants where it wets the roots through one mechanism or another, and is ultimately returned to the reservoir. The "batch" solution is generally used for a one to four week period, and then discarded and replaced with a fresh batch. In both open and closed systems the nutrient solution is usually applied intermittently. This is done to insure that the roots receive an adequate amount of oxygen.

Open systems have, to date, been the most commonly used hydroponic method. They are inefficient in their nutrient usage, in that a great deal of good nutrients are lost. But they are relatively simple mechanically, and have been very practical. Closed systems offer potentially greater efficiency of nutrient usage and lower cost per yield. Achieving this efficiency, and consequent profitability, in practice depends largely on the cost and design of the supporting equipment.

A wide variety of closed system structures and techniques have already been developed. In some, inert media are used for plant support. Such media include gravel, sand, sawdust, vermiculite, and synthetic plastic materials. These media have no nutrient value themselves, but merely serve as a support matrix for the plant roots and a temporary "sponge" to keep the plant roots in contact with the nutrient solution as well as with oxygen. There are several disadvantages and inefficiencies which have not been overcome by the prior art. The more common products currently sold into this market are phenolic resin coated urethane foams and rockwool, which is a fibrous basalt/chalk blend similar to fiberglass insulation. There is a growing environmental concern about the long-term advisability of placing large amounts of phenolic resins in ordinary landfills. Previous attempts to provide a plant support utilizing low density wet-laid paper have been attempted; however these were not successful based on the collapse of the structure and resulting high density. Furthermore, the wet-laid products contain ingredients, which do not allow the roots of plants to permeate the materials. Another major shortcoming of most prior art systems is the high proportion of manual labor costs. Even though the hydroponic system itself eliminates several manual operations necessary in conventional agriculture, the set-up, planting, plant maintenance, and harvesting are still very labor intensive, and hence costly. Techniques that utilize a medium which may be considered essential for root crops suffer from a number of problems. Adequate drainage can be difficult to achieve. Inefficient drainage can cause oxygen starvation and promote rotting. Initial cost of covering a large area with special media can amount to a substantial sum. That is especially evident when considering that the media must either be replaced for each crop or cleaned and sterilized. If the media is reused, sterilization adds to the cost. Undesirable build up of fine root hairs in reused media will eventually require its replacement. Some media have natural contaminants which must be removed before or during use. Others require physical attention, such as the sharp edges on gravel that can cut or injure plants. A generally ignored drawback to most media is their density, which, if the medium is kept partly fluid, tends to buoy plant roots up to the surface. Low density is particularly an issue with perlite, vermiculite, and plastics, specifically foamed plastics.

Therefore, there is an existing and continual need to improve the hydroponic growth medium.

SUMMARY OF THE INVENTION

The present invention provides a method of growing plants in a novel hydroponic growth medium that overcomes the drawbacks of the prior art. The growth medium of the present invention is a lower density, yet rigid, bonded airlaid structure that has good wet caliper, stiffness, and permeability providing an ideal support for plant growth. Furthermore, the growth medium is recyclable and to a greater degree, biodegradable over the prior art due to the presence of cellulosic fibers. The airlaid process also provides a material into which roots can grow. Additionally, when in contact with water or aqueous solutions, airlaid materials are able to maintain their structure for support. The absence of phenol- formaldehyde resins in the airlaid media and would also encourage recycling and allow safe disposal in a landfill. h a preferred embodiment, the invention provides a hydroponic plant growth medium that includes a fibrous pad made of cellulose fibers, bicomponent fibers, and optionally a second binder. In this preferred embodiment, the plant growth medium is manufactured by an airlaid process. In an alternative preferred embodiment, the invention provides a hydroponic plant growth medium that includes a fibrous dimensionally stable pad made of relatively stiff synthetic fibers, bicomponent binder fibers, and cellulose fibers. In this preferred embodiment, the plant growth medium is also manufactured by an airlaid process. In one embodiment, the fibrous pad of the medium is made of cellulose fibers in an amount of from about 75 percent to about 95 percent by weight based on the total weight of the medium, bicomponent fiber in an amount of from about 10 percent to about 30 percent by weight based on the total weight of the medium, and optionally, a second binder in an amount of up to about 10 percent by weight, based on the total weight of the medium, wherein the total basis weight of the medium is an amount of from about 300 to about 7,000 gsm (grams per square meter), hi a preferred embodiment, the total basis weight of the medium is in an amount of from about 400 to about 1,000 gsm.

In another embodiment, the fibrous pad of the medium is made of polyester fibers in an amount of from about 40 percent to about 75 percent by weight based on the total weight of the medium, bicomponent binder fiber in an amount of from about 15 percent to about 35 percent by weight based on the total weight of the medium, and cellulose fibers in an amount from zero (0) to about 30%, based on the total weight of the medium, wherein the total basis weight of the medium ranges from about 300 to about 7,000 gsm (grams per square meter). In a preferred embodiment, the total basis weight of the medium lies in the range of from about 400 to about 1,000 gsm.

In certain embodiments, the plant growth medium has a caliper of from about 8 mm to about 175 mm. hi a preferred embodiment, the medium has a caliper of from about 50 to about 125 mm. In another preferred embodiment, the medium has a caliper of from about 8 to about 15 mm. In one embodiment, the plant growth medium is present as one layer of fibrous pad. In another embodiment, the plant growth medium is present in 10 plus multiple layers.

In a preferred embodiment, the fibrous pad has a dry density of from about 0.02 to about 0.04 g/cc, preferably from about 0.028 to about 0.035 g/cc. In another embodiment, the fibrous pad has a wet density of from about 0.03 to 0.06 g/cc. In addition, the plant growth medium has an absorbent capacity (water retention capacity) of from about 6 to about 30 g/g. In a preferred embodiment, the medium has an absorbent capacity of from about 15 to about 25 g/g.

In another preferred embodiment, the fibrous pad has a dry density of from about 0.03 to about 0.06 g/cc, preferably from about 0.038 to about 0.05 g/cc, hi another embodiment, the fibrous pad has a wet density of from about 0.03 to 0.08 g/cc. In addition, the plant growth medium has a water retention or absorbent capacity of from about 10 to about 30 g/g. In a preferred embodiment, the medium has an absorbent capacity of from about 15 to about 25 g/g. In another embodiment, the invention also provides for a growth medium which further includes an adjuvant selected from the group consisting of nutrients, fertilizers, fungicides, algaecides, weed killers, pesticides, hormones, bactericides, plant growth regulators, insecticides, and combinations thereof. The present invention also provides for a method of supporting plant growth in a hydroponic plant growth medium by contacting plant material with a growth medium containing a fibrous pad made of cellulose fibers in an amount of from about 75 percent to about 95 percent by weight based on the total weight of the medium, bicomponent fiber in an amount of from about 10 percent to about 30 percent by weight based on the total weight of the medium, and optionally, a second binder in an amount of up to about 10 percent by weight, based on the total weight of the medium, wherein the total basis weight of the medium is an amount of from about 300 to about 7,000 gsm (grams per square meter).

Another embodiment of the present invention also provides for a method of supporting plant growth in a hydroponic plant growth medium by contacting plant material with a growth medium containing a fibrous pad made of synthetic fibers in an amount of from about 40 percent to about 75 percent by weight based on the total weight of the medium, bicomponent binder fiber in an amount of from about 15 percent to about 35 percent by weight based on the total weight of the medium, and cellulose fibers in an amount from zero (0) to about 30%, based on the total weight of the medium, wherein the total basis weight of the medium is an amount of from about 300 to about 7,000 gsm (grams per square meter). In a preferred embodiment, the total basis weight of the medium is in an amount of from about 400 to about 1,000 gsm.

The plant growth medium useful in the method of the present invention can further include at least one conventional plant growth medium. Such conventional plant growth media include natural soil, soil mixtures, vermiculite, sand, perlite, peat moss, clay, wood bark, coconut fiber, sawdust, fly ash, pumice, plastic particles, glass wool, rock or mineral wool, and polyurethane foams, and combinations thereof. By way of illustration, one hydroponics farm may choose to grow its plants in cubes or blocks of the airlaid medium of the present invention, but place the cubes or blocks on conventional rock wool slabs. Yet another hydroponics farm might use coconut fiber cubes or blocks on airlaid slabs. Any number of combinations could be envisioned.

In one embodiment, the plant material may include a cutting, seed, tuber, bulb, or other plant part capable of growth in the medium. These and other aspects of the invention are discussed more in the detailed description and examples.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a sample of the hydroponic growth medium of the present invention being used within a hydroponic plant system. The figure demonstrates the ability of the growth medium to support the roots and growing plant structure in a hydroponic setting.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for a hydroponic plant growth using a growth medium containing a fibrous pad of biodegradable cellulose fibers, bicomponent binder fibers and optionally, a binder. The present invention also provides a growth medium containing a bonded fibrous pad of matrix fibers, either synthetic or cellulose or both, and bicomponent binder fibers having affinity for the respective matrix fibers, and optionally a second type of binder, which might be applied from a latex spray system.

The fiberized fluff cellulose fibers used in the composite structure of the present invention may be selected from wood cellulose such as Foley Fluffs^® cellulosic pulp, cotton linter pulp, chemically modified cellulose such as crosslinked cellulose fibers or highly purified cellulose fibers, such as Buckeye HPF, each available from Buckeye Technologies Inc., Memphis, Tennessee. Any fluff cellulose fibers may be used in the pad, preferably wood fibers such as airlaid-fluff cellulose, chemically modified cellulose fibers such as for example, cross-linked cellulose fibers, highly purified cellulose, cotton linter fibers, or blends thereof. The fluff fibers may be blended with synthetic fibers such as polyester, PET, nylon, polyethylene or polypropylene. In one embodiment of the invention, the fluff fibers constitute an amount of from about 75 percent to about 95 percent by weight based on the total weight of the medium, preferably in an amount of about 80 percent. In another, preferred embodiment of the invention, the fluff fibers constitute an amount of from about 10 percent to about 20% by weight of the medium.

Mixtures of different fiber types can be used in the invention, however, it is preferred that collectively the matrix fibers constitute most of the fibers in the material, for example at least in an amount of about 75 percent. The term "matrix fiber" as used herein, refers to a synthetic or cellulosic fiber that does not melt or dissolve to any degree during the forming or bonding of an air-laid absorbent structure. A preferred matrix fiber for the execution of this invention is polyethylene terephthalate (PET) staple fiber that is available from a number of fiber manufacturers. Other textile fibers could also be useful as matrix fibers in this invention, including, but not limited to staple fibers of: acetate, acrylic, polypropylene, polyamide (nylon), and rayon. The fiber size can range from about 4 denier to about 20 denier with the preferred size about 6 denier to about 15 denier and the preferred length from about 4 mm to about 15 mm. Denier as used herein is the conventional understanding that denier is the weight in grams of a hypothetical 9000 meters of single filament of the respective fiber. The synthetic fibers may be crimped or straight. The terms "thermal bonding" or "thermal" as used herein refer to the bonding of thermoplastic material to the matrix fiber(s), when heat is applied. In addition, bicomponent thermoplastic fibers or materials are blended with the cellulose or synthetic fibers. Various bicomponent fibers suitable for use in the present invention are disclosed, for example, in U.S. Patents 5,372,885 and 5,456,982, both of which are hereby incorporated by reference in their entirety. Examples of bicomponent fiber manufacturers include KoSa (Salisbury, NC), Trevira (Bobingen, Germany) and ES Fiber Visions (Athens, GA). The preferred thermoplastic fiber is Celbond Type 255 Bico fiber from Hoechst Celanese. Examples of suitable thermoplastic materials include thermoplastic microfϊbers, thermoplastic powders, bonding fibers in staple form, and bicomponent staple fibers. Bicomponent staple fibers are characterized by a high melt temperature core polymer such as, for example, polyethylene terephthalate (PET) or polypropylene surrounded by a low melt temperature sheath polymer, such as, for example, typically polyethylene, modified polyethylene, or copolyesters as in Hoechst-Trevira Type-255 (Charlotte, NC). As used herein, the terms "bicomponent fiber", "bicomponent binder fiber" and "bicomponent thermoplastic fiber" are equivalent and interchangeable.

Bicomponent fibers may incorporate a variety of polymers as their core and sheath components. Bicomponent fibers that have a PE (polyethylene) or modified PE sheath typically have a PET or PP (polypropylene) core. The denier of the fiber preferably ranges from about 1.0 dpf to about 4.0 dpf, and more preferably from abo'ut 1.5 dpf to about 2.5 dpf. The length of the fiber is preferably from about 3 mm to about 12 mm, more preferably from about 4.5 mm to about 7.5 mm. Various geometries can be used for the bicomponent fiber of this invention, including concentric, eccentric, islands-in-the-sea, and side-by-side. The relative weight percentages of the core and sheath components of the total fiber may be varied. Preferably, the bicomponent fibers constitute an amount from about 10 percent to about 30 percent by weight based on the total weight of the medium, preferably in an amount of about 15 percent. The present invention optionally includes a second binder. Preferred binders include but are not limited to ethyl vinyl acetate copolymer such as AirFlex 124 (Air Products, Allentown, Pennsylvania) with 10 percent solids and 0.75 percent by weight Aerosol OT (Cytec Industries, West Paterson, New Jersey), which is an anionic surfactant. Other classes of emulsion polymer binders such as styrene-butadiene and acrylic binders may also be used. Binders AirFlex 124 and 192 (Air Products, Allentown, Pennsylvania) having an opacifier and whitener, such as, for example, titanium dioxide, dispersed in the emulsion may also be used. The second binder, when present, constitutes an amount of up to about 10 percent by weight, based on the total weight of the medium, preferably an amount of up to about 5 percent.

The fibrous pad used as the hydroponic growth medium is prepared as an airlaid web. The airlaid web is typically prepared by disintegrating or defiberizing a cellulose pulp sheet or sheets, typically by hammermill, to provide individualized fibers. The individualized fibers are then air conveyed to forming heads on the airlaid web forming machine. Several manufacturers make airlaid web forming machines, including M&J Fibretech of Denmark and Dan- eb, also of Denmark. The forming heads include rotating or agitated drums, generally in a race track configuration which serve to maintain fiber separation until the fibers are pulled by vacuum onto a foraminous condensing drum or foraminous forming conveyor or forming wire. In the M&J machine, the forming head includes a rotary agitator above a screen. Other fibers, such as a synthetic thermoplastic fiber, may also be introduced to the forming head through a fiber dosing system which includes a fiber opener, a dosing unit and an air conveyor. Where two defined layers are desired, two separate forming heads are provided, one for each type of fiber.

The airlaid web is transferred from the forming wire or condensing drum to a calender or other densification stage to densify the web, increase its strength and control web thickness. The fibers of the web are then bonded by application of a latex spray or foam addition system, followed by drying or curing. Alternatively, or additionally, any thermoplastic fiber present in the web may be softened or partially melted by application of heat to bond the fibers of the web. The bonded web may then be calendered a second time to increase strength or emboss the web with a design or pattern. If thermoplastic fibers are present, hot calendering may be employed to impart patterned bonding to the web. Water may be added to the web if necessary to maintain specified or desired moisture content, to minimize dusting and to reduce the buildup of static electricity. The finished growth medium is then rolled or slabbed for future use. The fibrous pad has a caliper of from about 8 to about 175 mm, preferably from about 50 to 125 mm.

Stated another way, in the execution of the hydroponics growth medium of this invention, the synthetic matrix fibers and the bicomponent binder fibers are opened, weighed, and mixed in a fiber dosing system such as a textile feeder supplied by LAROCHE S.A. of Cours-La Ville, France. From the textile feeder, the fibers are air conveyed to the forming heads of the airlaid machine where they are further mixed with the comminuted cellulose pulp fibers from the hammer mills and deposited on the continuously moving forming wire. Vacuum is applied to the bottom of the forming wire within the forming heads of the airlaid machine to cause the dispersed fibers to settle into a uniform mat. After passing under a compaction roll, the mat is carried into a through air dryer to activate (fuse) the bicomponent fiber to itself, and the cellulose and synthetic matrix fibers. Optionally, a second binder can be added through a spray or foaming system. The heating of the web is typically done in one or a series of through air ovens, although infrared or microwave heating could also be used. The finished growth medium is then rolled, slit into slabs, or slit and folded for future converting into the final hydroponics growth medium articles. The fibrous pad has a caliper of from about 5 to about 175 mm, preferably from about 8 to 15 mm. The thickness of a single ply of the growth medium depends on the number of forming heads in the airlaid machine, the throughput of each head, and the capability of the ovens to effectively fuse the binder fibers in the dwell time afforded by the speed of the airlaid machine.

The fibrous pad has a dry density of from about 0.02 g/cc to about 0.04 g/cc, preferably from about 0.28 to 0.035 g/cc. The fibrous pad has a wet density of from about 0.03 g/cc to about 0.06 g/cc. Additionally, the absorbent capacity (water retention capacity) of the fibrous pad is from about 6 to about 30 g/g, preferably from about 15 to about 25 g/g. The terms "absorbent capacity" or "water retention capacity" as used herein are equivalent and interchangeable.

Preferably, the pad of the growth medium is stacked as multiple thicknesses of up to 10 plus layers, preferably five times in order to achieve maximum support and maximal absorbent capacity. However, the pad may be a single layer to support initial seed germination.

The bonded fibrous pad having synthetic matrix fiber content up to about 70% by weight of the total pad has a dry density of from about 0.02 g/cc to about 0.06 g/cc, preferably from about 0.03 to 0.05 g/cc. Additionally, the absorbent capacity or water retention capacity of the fibrous pad is from about 10 to about 30 g/g, preferably from about 15 to about 25 g/g.

To make up the requisite thickness of hydroponics slabs and cubes, several layers of the airlaid growth medium are stacked. The stacking may be horizontal or, preferably, vertical where the individual plys are on edge during use. The load-bearing property of the bonded airlaid structure is higher when the material is used on edge. However, the pad may be a single horizontal layer to support initial seed germination. The layers of growth medium may be adhesively bonded together using any convenient bonding technique which does not impede root growth across the plys. Preferably, the adhesive would be water-resistant. The method of the present invention pertains to supporting plant growth. By

"support" or "supporting" is meant that the medium assists in providing plant material with a means for subsisting. By "plant material" is meant seeds, germinated seeds, seedlings, sprouts, shoots, tubers, bulbs, plants, or any part of a plant capable of growth on its own, for example cuttings, or the like. In addition, the cellulosic growth medium of the present invention is also suitable to support the growth of mushroom products.

By "contacting" is meant placing the plant growth medium, including the cellulose fibers, bicomponent fibers, and synthetic matrix fibers, sufficiently close to the plant material to enable the plant growth medium to support plant growth. This can include combining the plant material with the plant growth medium, entangling plant material within the fibers of the plant growth medium, inserting plant material by hand within or on the fibers of the plant growth medium, placing plant material on top of the plant growth medium, applying additional plant growth medium around or on top of the plant material, combinations thereof, and the like.

The growth medium of the present invention may be used in various hydroponic growth systems. The medium may be placed into an appropriate water impervious container capable of holding a variable depth of nutrient solution for hydroponic plant growth. The amount of the cellulose and synthetic airlaid fibrous pad used will vary depending on the type and size of the plant material and whether the plant growth medium further includes one or more conventional plant medium. For example, the amount of fibrous pad initially used to germinate a seed can be a single layer only or multiple layers thick, although thicker layers may be used by applying additional pads around or on top of the seed. Once a seed has sprouted into a seedling plant additional pads may be added as needed. The plant growth medium useful in the present invention permits good anchoring of the growing roots. When transplanting, the pads around the plant material remain as a coherent mass making transplanting a facile operation.

In addition to providing adequate water, dissolved nutrients, and oxygen to the roots, the plant growth medium of the present method can exhibit many features and advantages, some of which may depend in part on the type of fiber selected for use in preparing the fibrous pad used herein. These include, for example, resistance to decay or biodegradability, resistance to microbes, low density, and a morphology and density particularly conducive to plant growth. The poor water retention properties of conventional plant media make it necessary to be selective with regard to the type of grain or plant to be cultivated, to avail the need for frequent watering. However, the plant growth medium useful in the present method has very good moisture retention characteristics. For example, the fibrous pads of the present invention have an absorbent capacity of from about 6 to about 30 g/g. Good drainage is also evident from the method of the present invention.

Because of the growth medium's unique morphology, air is retained between the layers of pads, and thus the plant growth medium useful in the present method provides adequate amounts of oxygen to the roots. In addition, this morphology provides good thermal insulation.

Conventional plant growth media are watered from above and kept out of excess water to prevent water wicking to their top surfaces. Water on the top surface of a plant growing media will often kill a seedling via a process known as "damp off." Another highly useful attribute of the present medium is that the pads do not appear to wick water to the surface thus offering the potential to reduce evaporation losses. By not wicking water to their top surfaces, the pads useful in the present invention enables watering plants from the bottom. However, the structure of the pads provides sufficient capillary action for retaining liquids close to plant roots. Such a quality promotes the growth of well-developed plant root systems and enables the use of the present method in hydroponic systems. Depending on the particular type of vegetation being grown, different compositions of the hydroponics growth media of this invention might be preferred.

Environmental harm is reduced by using the present medium and method because nutrients are adsorbed and retained by the plant growth medium and not washed away by rain. In addition, no more fertilizer than necessary need be provided using this method. Thus, the biodegradable fibrous pads of the present invention and the highly synthetic and recyclable compositions can be used in "precision farming." By "precision farming" is meant a farming method wherein a seed, cutting or seedling is placed into the growing medium along with a precisely placed and measured addition of nutrients, pesticides, etc. The advantage provided by precision farming is it avoids the surface application of agricultural chemicals that ultimately are washed away into streams or lakes or enter the water table. Using the biodegradable or recyclable fibers of the present invention together with conventional plant growth material provides a convenient method for precision farming wherein the agricultural chemicals can be added together with the fibrous pads or can be applied after the plant material and fibrous pads are placed in the group.

Because plants can be cultivated without using any natural soil at all, the plant growth medium of the present method can be hygienic. Because certain embodiments of the plant growth medium of the present method are prepared from synthetic fibers, the medium can be sterile and can be particularly suited for growing sensitive plants. The fibrous pads of the plant growth medium can be resistant to microbes and thus less susceptible to bacterial, viral, fungal and insect infestation. Thus, utilization of such plant growth medium would alleviate the need to use environmentally hazardous fungicides, insecticides or other infestation controlling chemicals and make more desirable distribution of plants marketed intact with root systems.

The plant growth medium of the present invention is particularly suitable for use as a growth medium for seed germination testing. Nurseries test seed germination rates and are confronted with the difficulty of finding consistent, reproducible growth media. Conventional growth media vary due to different points of origin as well as due to aging effects. For example, organic material such as peat moss degrades over time giving the medium a higher acid content. The fibrous pads of the present invention overcome these difficulties by providing a sterile, consistent growth medium for seed germination testing.

Once a crop has been harvested, biodegradable plant growth medium useful in the present invention is much more suitable for composting due to its degradable nature. Biodegradable fibrous pads can be used in a field as needed and readily plowed under because they would physically come apart. The individual fibers of the pad can be allowed to degrade more slowly since degradation would no longer be required to achieve the "plowed under" capability. Other plant growth mediums of this invention are more suited to recycling or disposal in landfills due to the high synthetic polymer content and environmentally benign nature than resin bonded mediums, in particular, the phenol-formaldehyde resin bonded mediums.

Although the material of the fibrous pads provides no source of plant nutrition, it does demonstrate good nutrient adsorption characteristics. Thus, the method of the present invention can further include contacting the plant growth medium, the plant material, or both, with at least one plant adjuvant. Contacting via spraying, dipping, irrigating, and/or the like with a balanced nutrient liquid is easily achieved in accordance with known hydroponic, agricultural, or horticultural principles. Likewise, the method of the present invention can further include providing light and heat as needed to foster growth.

Water-soluble adjuvants for use in preferred embodiments of the present invention include nutrients, fertilizers, fungicides, algaecides, weed killers, pesticides, hormones, bactericides, plant growth regulators, insecticides, combinations thereof, and the like. Numerous water-soluble plant fertilizers and other nutrients are available commercially. Suitable fungicides include benomyl and other benzimidazoles such as, for example,

Benlate^® sold by E. I. du Pont de Nemours and Company, flusilazole and other triazoles such as, for example, Nustar^® sold by E. I. du Pont de Nemours and Company, metalaxyl and other acylalanines such as, for example, Ridomil^® sold by Ciba-Geigy Corp., and tridemorph and other morphlines such as, for example, Calixine^® sold by BASF, among others. Suitable insecticides include oxamyl and other related carbamates such as, for example, Vydate^® sold by E. I. duPont de Nemours and Company, acephate such as, for example, Orthene^® sold by Chevron Chemical Co., resmethrin and other pyrethrodis such as for example, Synthrine^® sold by Fairfield American Corp., among others. Suitable herbicides include chlorsulfuron and other sulfonylureas such as, for example, Glena^® sold by E. I. du Pont de Nemours and Company among others. Combinations of fungicides, insecticides and fertilizers help protect young germinating seedling plants from disease and insect damage while supplying needed nutrients.

The plant growth medium useful in the method of the present invention can further include at least one conventional plant growth medium. Such conventional plant growth media include natural soil, soil mixtures, vermiculite, sand, perlite, peat moss, clay, wood bark, sawdust, fly ash, pumice, plastic particles, glass wool, and polyurethane foams, and combinations thereof.

With the growing demand for soil for plants used as decoration for room interiors and cultivated on balconies or rooftops, particularly in urban areas, the present invention is useful in providing a plant growth medium as a soil substitute, including for hydroponic cultivation, as a soil supplement in flower pots, balcony planters, or in rooftop areas to cultivate plants, or as a supplement to other conventional plant growth media. In addition, by increasing the scale, the present method can also be used for processed horticulture and in raising grain. EXAMPLES

The present invention will be better understood by reference to the following Examples, which are provided as exemplary of the invention, and not by way of limitation. EXAMPLE 1: Sample Hydroponic Growth Medium

The present Example demonstrates a controlled production of the target hydroponic growth medium. The Example provides a high caliper, low density product at the desired absorbent capacity for use in a hydroponic plant growth system.

The raw materials used in the production of the medium included Foley Fluff, Trevia 2 dpf x 6 mm bicomponent fiber, and AF 192 binder to minimize possible excessive dusting. The manufacturing process was a standard airlaid process. The following table summarizes the control strategy for the manufacture of the growth medium. The final product had an average thickness of 11.2 mm, overall density of 0.035 g/cc, and a core diameter of 3 inches. The average basis weight was 458 gsm. The medium is a homogenous product containing 360 gsm Foley fluff (80.0%) and 90 gsm Trevira 2.0 bico type 1661 (20.0%).

Samples were tested as soon as they came off of the line for basis weight and caliper (density). Once on target they were tested for absorbent capacity. The average absorbent capacity was 25.1 g/g. The absorbent capacity is optimized as per control strategy againgtA _tt < _f i§fe target specifications. Testing was conducted in water with a 1 minute soak and a 30 second drain in the horizontal position with no load. This is the key independent variable. The caliper was optimized as per control strategy against target specs. Changes were made as necessary to meet the absorbent capacity.

EXAMPLE 2: Using Hydroponic Growth Medium

This example demonstrates the germination of seeds and their subsequent growth into plants in the plant medium useful in the present method.

The growth medium was prepared as described in Example 1.

Seeds were planted into square planters containing 7 to 9 horizontal layers of the fibrous pad growth medium. The seeds were placed on top of the surface of the planting medium. The seeds were then watered with 15 mis of demineralized water containing liquid plant food. Watering was done 3-5 times per week thereafter.

Within two days, the seeds began to germinate and continued to grow in the plant medium as shown in Figure 1.

EXAMPLES 3-8: Hydroponics Medium from Laboratory Pad-former Experiments

These examples employed a laboratory airlaid handsheet apparatus which lays down a 35.5 X 35.5 cm (14 X 14 inch) pad suitable for range-finding experiments before going to the actual airlaid machine. Pre-weighed amounts of the various fibers are added to a mixing chamber where jets of air fluidize and mix the fibers. The fluidized cloud of fibers was pulled down onto the forming wire by a vacuum source. The cellulose fluff was Foley

Fluffs® cellulose pulp from Buckeye Technologies, Inc. of Memphis, TN. Before feeding to the handsheet apparatus, the pulp sheet was previously passed through a hammer mill to comminute the pulp into individual fibers. The binder fiber was Type MO-226-1 copolyester sheath 2 dpf x 6 mm bicomponent fiber and the matrix fiber was 6 dpf by 4 mm Type T-224 PET fiber (polyethylene terephthalate) both from KoSa of Salisbury, NC or Type 375X2, also 6 denier by 4 mm PET fiber by Wellman International of Mullagh, Kells, Ireland. The handsheet apparatus is used to build a pad in layers. After each fourth of the total weight of fibers is added, the sample is turned 90 degrees in the apparatus. This procedure helps to minimize air turbulence artifacts. In this step-wise fashion the entire 500 gsm airlaid pad is formed. The pad is pressed to a target thickness in a heated laboratory press and held there to activate the bicomponent fiber, hi Each of Examples 3-8, the weight ratio of PET to bico fiber was 70/30. The results are shown in Table 1, below. Example 3 had no cellulose fluff, Example 4 had 5% fluff by weight, Example 5 had 10% fluff, Example 6 had 15%, Example 7 had 20%, and Example 8 had 25% fluff.

EXAMPLE 9: Continuous Production Hydroponic Growth Medium

Example 9 illustrates the production of the target hydroponic growth medium on a conventional continuous airlaid production line.

The raw materials used in the production of the medium on a continuous conventional airlaid machine included Foley Fluffs® cellulose pulp from Buckeye Technologies, Inc. of Memphis, TN, Type IJP-477 copolyester sheath 2 dpf x 6 mm bicomponent fiber and 6 dpf by 4 mm Type T-224 PET fiber (polyethylene terephthalate) both from KoSa of Salisbury, NC. The manufacturing process was a standard airlaid process.

The final product had an average thickness of 15 mm, overall density of 0.032 g/cc, and an average basis weight of 479 gsm. The medium was a homogenous product containing 10% Foley Fluffs, 27% bico type IJP-477, and 63% PET. Type T-224.

Samples were tested as soon as they came off of the line for basis weight and caliper (for density calculation). Fluid handling performance testing was conducted in colored water on a bundle of five or six pads cut with a rotary shears to 6.35 x 7.62 mm (2.5 x 3 inches). The use of a rotary shears avoided crimped edge effects, which could arise from the extreme compaction of the cut fibers caused by a bypass or anvil cutter. The height of a stack of five or six pads under no load was recorded as the beginning thickness. The same block of material was used in turn from one test to the next to minimize variability in results. The first fluid test was vertical wicking and the dry pads are stood on edge as a bundle in a dry flat dish. Water was slowly introduced to the bottom of the bundle from a squeeze bottle until no more wicking was observed. The height of the liquid front was measured in several places around the block and averaged. The bundle of vertically-oriented pads was then transferred to a mesh basket and immersed in water for 2 minutes. The basket was removed from the water bath without tipping and the sample allowed to drain for 10 minutes before weighing. The water retention capacity was expressed as the weight in grams water retained after the 10 minute drain per gram of dry growth media. The width of the vertical stack was measured across the top of the plys after the draining time to calculate the wet collapse as a percentage of the original dry thickness. The drained block was loaded into a plastic box with a perforated bottom. The plastic box had internal dimensions of 6.19 cm by 6.83 cm by 10 cm high. One wall of the box in the 6.19 cm dimension was designed to be movable with a thumbscrew to conform to the shape of the bundle if wet collapse had occurred. The adjustable side was found to be necessary to prevent water from flowing around the sample and causing an artificially high permeability measurement. The box was mounted over a catch pan and colored water poured through the material at a rate sufficient to maintain a slight hydrostatic head. After reaching a steady flow rate, a stopwatch was started as an empty catch pan was moved under the draining box. The vertical permeability was expressed as grams water per second. The control was cut from a rockwool hydroponics slab manufactured by Rockwool/Grodan of Melick-Herkenbosch, The Netherlands. The rockwool block was used throughout the fluid tests in the same orientation as if it were still a part of its original slab. Table 1 - Working Examples 3-9

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures. Such modifications are intended to fall within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A hydroponic growth medium comprising: (A) cellulose fibers in an amount of from about 75 percent to about 95 percent by weight based on the total weight of the medium, (B) bicomponent fibers in an amount of from about 10 percent to about 30 percent by weight based on the total weight of the medium, and

(C) optionally, a second binder in an amount up to about 10 percent by weight based on the total weight of the medium.

2. The medium of Claim 1 , wherein the medium has a basis weight of from about

300 to about 7,000 gsm.

3. The medium of Claim 1 , wherein the medium has a basis weight of from about 400 to about 1000 gsm.

4. The medium of one of the previous claims, wherein the medium has a caliper of from about 8 mm to about 175 mm.

5. The medium of one of the previous claims, wherein the medium has a caliper of from about 50 mm to about 125 mm.

6. The medium of one of the previous claims, wherein the medium has a dry density of from about 0.02 to about 0.04 g/cc.

7. The medium ofone ofthe previous claims, wherein the medium has a dry density of from about 0.028 to about 0.035 g/cc.

8. The medium of one of the previous claims, wherein the medium has an absorbent capacity of from about 6 to about 30 g/g.

9. The medium of one of the previous claims, wherein the medium has an absorbent capacity of from about 15 to about 25 g/g.

10. The medium of one of the previous claims, wherein the medium has been

/ manufactured by an airlaid process .

11. The medium of one of the previous claims further comprising an adjuvant selected from the group consisting of nutrients, fertilizers, fungicides, algaecides, weed killers, pesticides, hormones, bactericides, plant growth regulators, insecticides, and combinations thereof.

12. A method of supporting plant growth in a hydroponic growth medium comprising contacting plant material with the growth medium of one of Claims 1-11.

13. The method of Claim 12, wherein plant material is a cutting, seed, tuber, bulb or other plant part capable of growth in the medium.

14. A hydroponic growth medium comprising:

(A) matrix fibers in an amount of from about 40 percent to about 75 percent by weight based on the total weight of the medium, (B) binder fibers in an amount of from about 15 percent to about 35 percent by weight based on the total weight of the medium, and

(C) cellulose fibers in an amount from zero (0) up to about 30 percent by weight based on the total weight of the medium.

15. The medium of Claim 14, wherein the matrix fibers are synthetic staple fibers.

16. The medium of Claim 15, wherein the staple fibers are polyester.

17. The medium of Claim 14, wherein the binder fibers are bicomponent fibers.

18. The medium of Claim 17, wherein the bicomponent fibers are have a polyester core and a copolyester sheath.

19. The medium of one of Claims 14-18, wherein the medium has abasis weight of from about 300 to about 7,000 gsm.

20. The medium of Claim 19, wherein the medium has a basis weight of from about 400 to about 1000 gsm.

21. The medium of one of Claims 14 to 20, wherein the medium has a caliper of from about 5 mm to about 175 mm.

22. The medium of Claim 21 , wherein the medium has a caliper of from about 8 mm to about 15 mm.

23. The medium of one of Claims 14 to 22, wherein the medium has a dry density offrom about 0.02 to about 0.06 g/cc.

24. The medium of Claim 23, wherein the medium has a dry density of from about 0.03 to about 0.05 g/cc.

25. The medium of one of Claims 14 to 24, wherein the medium has a water retention capacity offrom about 10 to about 30 g/g.

26. The medium of Claim 25, wherein the medium has a water retention capacity offrom about 15 to about 25 g/g.

27. The medium of one of Claims 14 to 26, wherein the medium has been manufactured by an airlaid process.

28. The medium of one of Claims 14 to 27 further comprising an adjuvant selected from the group consisting of nutrients, fertilizers, fungicides, algaecides, weed killers, pesticides, hormones, bactericides, plant growth regulators, insecticides, and combinations thereof.

29. A method of supporting plant growth in a hydroponic growth medium comprising contacting plant material with the growth medium of one of Claims 14 to 28.

30. The method of Claim 29, wherein plant material is a cutting, seed, tuber, bulb or other plant part capable of growth in the medium.

31. Use of the hydroponic growth medium of one of Claims 1 or 14 for supporting plant growth.