FR2988264A1 - Method for culturing plants using mattress retaining from water, involves forming recovery phase of mattress by substrate on height less than or equal to specific cm for culturing plants - Google Patents

Abstract

The method involves manufacturing a mattress (1) with a phase selection mat (2). The phase selection mat is formed with fibrous non-woven material and placed with aqueous solution (31) including acid type polymerizable monomers, acrylic acid and/or standard salt-like acrylic acid, and crosslinking agent of the monomers. A reticulation phase of the monomers forms a super-water absorbent polymer using composite material. A recovery phase of the mattress is formed by a substrate on height less than or equal to 2 cm for culturing plants. Independent claims are also included for the following: (1) a water retaining mattress (2) a tray for culturing plants.

Description

The present invention relates to a plant culture method using a water retentive mattress, the water retentative mat obtained and a culture tray incorporating such a mattress.

It relates more particularly to a plant culture process comprising at least one step of manufacturing said mattress and a step of culturing.

Until now, in the agricultural field, water-retentive mattresses have been used, such as rockwool as a direct support for crops. The water-retentive mattresses are therefore arranged on the soil surface and the cultures directly implanted in said mattress.

It is also known the manufacture of water-absorbing composite material formed from the combination of a fibrous mat and a super-absorbent water polymer as illustrated in EP-0,290,814. Until now, the application of such composite materials in the agricultural field has not developed because of the strong hydrophilic nature of such mattresses. Indeed, the use of such a mattress on the floor has, as a result, under the action of air, a rapid drying of the mattress that becomes brittle and no longer fulfills its purpose. An object of the present invention is therefore to provide a method of plant cultivation, the implementation of which can significantly reduce the amount of irrigation water and the frequency of watering plants without damaging the water status said plants. Another object of the present invention is to provide a method for growing plants whose implementation makes it possible to increase the water reserve retained by the soil or the cultivation substrate and which remains available to the plants. For this purpose, the subject of the invention is a method for cultivating plants using a water-retaining mat, said method comprising at least one step of manufacturing said mattress and a step of culturing, characterized in that in that said water retentive mattress is made of a hydrophilic composite material composed of a fibrous mat and a super-absorbent water polymer, the step of manufacturing said mattress comprises at least one fibrous mat selection phase formed of a nonwoven with at least two layers of fibers of different density, a phase of impregnating the fibrous carpet with an aqueous solution comprising polymerizable monomers of (meth) acrylic acid type and / or acid salt type ( meth) acrylic and a crosslinking agent of said monomers, and a crosslinking phase of said monomers to form said superabsorbent water polymer and, therefore, the hydrophilic composite material, and in that the step of setting e n cultivation of said mattress comprises at least one covering phase of said mattress of a plant culture substrate 15 to a height preferably at least equal to 2 centimeters. The inventors have indeed found that by increasing the strength of the fibrous carpet and by burying the latter to a sufficient depth, it was possible to create, over a long period of time, a reserve of water not subject to evaporation and able to restore water to plants, either by capillary ascension or by direct suction through the roots. The covering height of the mattress is chosen according to the rooting zone of the plant to be planted so that the mattress extends substantially in the lower part of the rooting zone of the plant. Indeed, if the mattress is placed too close to the surface, it may limit root development and dry out by becoming brittle. If it is buried too deep, it may force the plant to develop an extremely deep root system to reach the water supply. The water retentive mattress uses lost rain water (flow, seepage) to form a direct water supply able to supply water to the plant roots. The presence of this mattress provides significant savings in water. The recovery and storage of rainwater can reduce the frequency of watering. A real "artificial water table" is created. Consequently, the presence of such a water-retaining mattress makes it possible to keep in the long term a green, dense and luxuriant vegetation.

The water molecules in contact with the mattress are absorbed by the polymer present on the surface and inside the fibrous tissue. The structure of the fibrous carpet then allows the swelling of the polymer. The development of the roots inside the mattress makes it possible to draw the water directly into the constituted reserve which deflates gradually. Nothing prevents the mattress from reabsorbing water by infiltration and increasing its water supply. The phenomenon of swelling is reversible. In a preferred embodiment of the process, the method comprises, after the crosslinking phase, and before or after a possible phase of drying by blowing hot air of said mattress, a phase of perforation of the mattress. The perforations allow the water to cross the mattress more easily. This is particularly important in the case of certain applications, such as dune fixation where the mattress is applied over large areas. The perforations allow the passage of the roots for a deep growth and a better efficiency in the process of revegetation and fixation of the dunes. Preferably, the impregnating solution further comprises a thickener preferably selected from the group consisting of xanthan gum and colloidal silica. The presence of at least one thickener makes it possible to increase the viscosity of the solution by conferring on it a viscoelastic character. This viscosity is necessary to ensure a good hold of the solution on the fibrous support mat. Indeed, after impregnation and spinning, as will be described below, it is not necessary for the solution to flow from the fibrous carpet, in particular for the one hand, do not damage the manufacturing equipment and in particular the filters of the ultraviolet lamps used to initiate the polymerization, on the other hand, ensure the weight ratio polymer: fibrous support. Preferably, the thickener is chosen so that the solution has a dynamic viscosity of at least 0.3 Pa.s at ambient temperature of 20 ° C. and at atmospheric pressure. Preferably, the impregnating solution further comprises a fertilizer. The presence of such a product further promotes plant growth. Preferably, at the end of the polymerization phase, the water superabsorbent polymer represents between 50 and 90%, preferably about 75%, by weight of the total weight of the mattress. Due to the nature of the fibrous carpet and the method of manufacture adopted, in particular by impregnation (that is to say by soaking or spraying), a high concentration of the polymer mattress is obtained, which allows the mattress to absorb and restore a quantity of water equal to several times the weight of the mattress making the latter particularly effective. Preferably, the impregnating solution further comprises a photoinitiator, preferably of the Irgacure (Trade Mark) type consisting of a 1: 1 by weight mixture of 1-hydroxy-cyclohexyl-phenyl ketone and benzophenone and in that the crosslinking phase comprises at least one ultraviolet irradiation of said mattress. Preferably, the method further comprises, between the impregnation phase and the crosslinking phase, a wringing phase of the mattress, preferably by passing the mat between two rolls. This spinning phase makes it possible to remove, if necessary, the surplus of material and to define, by the value of the interval chosen between rollers, the quantity of desired polymer in said mattress. Preferably, the fibrous mat is a nonwoven formed of at least polyester fibers and bicomponent fibers and whose layer or layers of higher density are densified by needling. The invention also relates to a water-retentive mattress for carrying out a cultivation process of the aforementioned type, characterized in that the water-retaining mat is made of a hydrophilic composite material composed of a mat characterized in that the superabsorbent water polymer contains a (meth) acrylic polymer, in that the fibrous fabric is a nonwoven with at least two layers of wherein said fibers comprise at least polyester fibers and bicomponent fibers and said mat has through apertures. Preferably, the superabsorbent polymer represents by weight at least between 50 and 90%, preferably about 75%, of the total dry weight of the mat. The subject of the invention is also a plant growing tank, characterized in that the bottom of the tank is surmounted by a water-retaining mat of the aforementioned type. The invention will be better understood on reading the following description of exemplary embodiments, with reference to the appended drawings, in which: FIG. 1 represents a diagrammatic sectional view of a mattress according to the invention; Figure 2 shows a schematic view of the different phases of the manufacture of a mattress according to the invention; Figure 3 shows a schematic sectional view of a culture vessel housing a mattress according to the invention.

As mentioned above, the subject of the invention is a process for cultivating plants using a water-retaining mattress 1 and the water-retaining mattress 1 used for carrying out the process. The object of the invention is to use the water retentive mattress 1 as a water reservoir at the rooting zone of the plants. The mattress is therefore used as a direct supply of water to supply the roots of the plants with water, forming a substitute for the water table. To obtain such a result, the culture method thus comprises two steps, namely a step of manufacturing said mattress 1 and a step of culturing. For the manufacture of such a water-retaining mat 1 conforming to the desired characteristics, a selection is first made of a carpet 2 of fibers formed of a nonwoven with at least two layers 21, 22 of fibers of different density. This fibrous mat comprises at least polyester fibers and bi-component fibers. The upper density layer is densified by needling. Thus, a fibrous carpet of the type proposed by the LIBELTEX group under the name Liflet PB gives excellent results. This fibrous mat is stored in the wound state. The carpet is unrolled so that it can be impregnated with an aqueous solution 31. The impregnation may be carried out by dipping or spraying. In the example shown, it is performed by dipping, that is to say by scrolling in a tray containing the impregnating solution 31. This implementation is preferred. The impregnation solution 31 is an aqueous solution comprising at least polymerizable monomers of (meth) acrylic acid type and / or of (meth) acrylic acid salt type and an agent for crosslinking said monomers.

At least one of the polymerizable monomers of the impregnating solution is a monomer chosen from the group formed by 2-acrylamide-2-methylpropanesulphonic acid, 2-acryloyl-ethanesulfonic acid and 2-acryloylacrylic acid. propane sulfonic acid, methacrylic acid and their alkali metal salts or ammonium salts, acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, 2-hydroxyethyl acrylamide, 2-hydroxyethyl methacrylamide, 2-vinylpyridine, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, N, N'-methylene bis-acrylamide, N, N'-methylene bis-methacrylamide, polyethylene glycol diacrylate and polyethylene glycol dimethacrylate, preferably a acrylamide-2-methyl-2-propanesulfonic acid (AMPS) monomer or a monomer of an alkali metal or ammonium salt of said acid, such as sodium acrylamide-2-methyl-2 propanesulfonate. The crosslinking agent may be selected from the group consisting of methylene bisacrylamide. The crosslinking agent is preferably present in the solution at a concentration of between 0.1 and 2.5% expressed by weight relative to the total weight of said solution. Preferably, this crosslinking agent is methylenebisacrylamine. The impregnating solution may also contain a thickener selected from the group consisting of xanthan gum and colloidal silica. This impregnation solution may further comprise a photoinitiator formed of Irgacure 500 (registered trademark). Finally, said solution may include a fertilizer. By way of example, the impregnating solution comprises a composition as follows: Reagent Quantity Unit Water 1250 mL AMPS 1000 g Crosslinking Agent 5 g Photoinitiator (Irgacure) 2.26 mL Xanthane 18.04 g Total Weight 2255 g Total Volume 1954.47 mL The pH of the solution is always adjusted to a value in the range pH 5.5 to pH 7 using a base. The base used here is potash. The impregnation phase is then followed by a dewatering phase during which the fibrous carpet impregnated with the solution is placed between two rollers 5 which define between them an interval depending on the quantity of desired solution in the carpet 2 fibrous. The spinning phase is followed by a crosslinking phase by scrolling the strip inside a tunnel equipped with UV lamps at the level of the ceiling of the first section of the tunnel and at the level of the floor of the second section. of the tunnel. This crosslinking phase may be followed by a drying phase of the mattress during which the mattress passes under at least one hot air blowing mouth 8. Generally, the UV exposure phase corresponds to an exposure time close to 5 seconds at a power density equivalent to 200 MW / cm 2 plus or minus 10%. On the other hand, the distance between the traveling strip and the UV lamps must necessarily be greater than 100 mm in order not to alter the polyester fibers of the fibrous mat. The drying phase is followed by a phase of perforation of the mattress. A perforation die 7, disposed vertically and above the moving mattress 1, and reciprocated up and down can be used as a means of perforation. The mattress 1 obtained may have perforations which comprise at least one opening dimension of at least 24 mm.

The density of perforations may be such that the mattress has a ratio void area / solid area in the range [15% - 25%]. In the example shown, the mattress has through openings 9.

The superabsorbent water polymer represents, by dry weight, 75% of the total weight of the mattress. Once the manufacture is completed, the mattress 1, in the form of a strip, is wound and filmed to preserve it from direct contact with the air. This film will be eliminated at the time of the cultivation stage. The mattress can also be cut into plates and filmed in a manner similar to that described above. During the step of culturing the mattress, the mattress is buried in a layer of plant culture medium to limit contact with the air of the mattress and ensure a predetermined positioning of the mattress in the plant rooting zone. . When the mattress is placed in a culture tank as shown in FIG. 3, the mattress 1 can come into direct contact with the bottom of the tank or be separated from the bottom of the tank by at least one layer of the culture medium which can be of diverse and varied nature.

In the example shown, the mattress rests on a layer of sand of a thickness of about 2.5 cm and is surmounted by a layer of sand of 1 cm and a layer of soil of about 3 cm . The depth of burial depends on the nature of the soil and plants. It is known that a sandy soil facilitates the infiltration of water and therefore the swelling of the carpet while a clay soil absorbs part of the water. As an example, for gram inés, generally the mattress is buried in the soil to a depth within the range 15-25 cm. A comparative test was conducted of plants grown in 5 L plastic pots, containing a soil-agricultural-soil-sand mixture (1: 1: 1) in a greenhouse. The experimental conditions are as follows. Three lots of plants were compared. Two batches of eight control plants were grown in pots without water retaining mattresses. One of these two lots was irrigated at 100% of its daily evapotranspirant application and 10 called irrigated control ad libitum. The other of these lots was irrigated to 50% of its daily evapotranspirant application and called water-saving witness. Finally, a third batch of eight plants was grown in pots equipped with a water retaining mat and irrigated to 50% of the irrigated ad libitum.

On a production cycle, it was found that the batch of plants in the pots with water retentive mattresses: 1) produced more biomass than the so-called water-saving control 2) with equivalent biomass production, consumed 16% less water than the irrigated control ad libitum.

Claims (10)

REVENDICATIONS1. A method of cultivating plants with a water-retaining mat (1), said method comprising at least one step of manufacturing said mattress (1) and a culturing step, characterized in that said mattress (1) water retenteur being made of a hydrophilic composite material composed of a fibrous carpet (2) and a superabsorbent water-absorbing polymer (3), the manufacturing step of said mattress (1) comprises at least one least one selection phase of the fibrous carpet (2) formed of a nonwoven with at least two layers of fibers of different density, a phase of impregnating the fibrous carpet (2) with an aqueous solution (31) comprising monomers polymeric acid (meth) acrylic acid and / or (meth) acrylic acid salt type and a crosslinking agent for said monomers, and a crosslinking phase of said monomers to form said superabsorbent polymer (3). water and, consequently, the hydrophilic composite material, and in that the placing step e n culture said mattress (1) comprises at least one covering phase of said mattress (1) of a plant culture substrate to a height preferably at least equal to 2 centimeters. 20 2. Culture method according to claim 1, characterized in that it comprises, after the crosslinking phase, and a possible phase of drying by blowing hot air of said mattress, a phase of perforation of the mattress. 25 3. Culture method according to one of the preceding claims, characterized in that at least one of the polymerizable monomers of the impregnating solution is a monomer chosen from the group formed by 2-acrylamide-2-methyl-acid. propane sulfonic acid, 2-acryloyl sulfonic acid, 2-acryloylpropanesulphonic acid, methacrylic acid and their alkali metal salts or ammonium salts, acrylamide, methacrylamide, N, N- dimethylacrylamide, N, N-dimethylmethacrylamide, 2-hydroxyethylacrylamide, 2-hydroxyethyl methacrylamide, 2-vinylpyridine, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, N, N'-methylenebisacrylamide, N, N'-methylen ebi s-methacrylamide, polyethylene glycol diacrylate and polyethylene dimethacrylate glycol, preferably a monomer of 2-acrylamide-2-methylpropanesulphonic acid (AMPS) or a monomer of an alkali metal or ammonium salt of said acid, such as acrylamide-2-methyl-2 propanesulfonate sodium. 4. Culture method according to one of the preceding claims, characterized in that the impregnation solution further comprises a thickener, preferably selected from the group consisting of xanthan gum and colloidal silica. 5. Culture method according to one of the preceding claims, characterized in that the impregnating solution further comprises a fertilizer. 6. Culture method according to one of the preceding claims, characterized in that the impregnating solution further comprises a photoinitiator, and in that the crosslinking phase comprises at least ultraviolet irradiation of said mattress. 7. Culture method according to one of the preceding claims, characterized in that it further comprises, between the impregnation phase and the crosslinking phase, a wringing phase of the mattress, preferably by passing the mattress between two rolls. 8. Mattress (1) water retentor for carrying out a culture method according to one of claims 1 to 7, characterized in that the mattress (1) retenteur water is in a hydrophilic material noncomposite composed of a fibrous carpet (2) and a water superabsorbent polymer (3), in that the superabsorbent water polymer (3) contains a (meth) acrylic polymer, in that the fibrous carpet (2) is a non-woven fabric with at least two layers of fibers of different densities, said fibers comprising at least polyester fibers and bi-component fibers and in that said mattress comprises apertures (9) therethrough. 9. Mattress (1) according to claim 8, characterized in that the superabsorbent polymer represents by weight at least between 50 and 90%, preferably about 75%, of the total dry weight of the mattress. 10. Tray (4) plant culture, characterized in that the bottom of the tray (4) is surmounted by a mattress (1) 15 retenteur water according to one of claims 8 or 9.