RU2734883C1 - Biodegradable composite polylactide-based nonwoven material and use thereof for growing plants - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention relates to biodegradable polymer materials and their use in agricultural technologies and can be used for growing plants in conditions of open and closed soil, in personal subsidiary plots, during research in biotechnology and plant breeding. Disclosed is a composite fibrous non-woven material containing polylactide and natural rubber, with the following ratio of components, wt. %: polylactide 85–95, natural rubber 5–15. Invention makes it possible to produce elastic material that preserves biodegradability and mechanical destruction under action of developing root system.

EFFECT: disclosed invention can be used as a base for sowing seeds and growing plants.

6 cl, 7 dwg, 5 tbl

Description

The invention relates to the field of biodegradable polymeric materials and to their use in agricultural technologies and can be used for growing plants in open and closed ground, in personal subsidiary plots, during research in the field of biotechnology and plant breeding.

Current trends towards sustainable green technologies are driving the increasing use of biodegradable materials in agricultural production. This is especially true for crop production, which uses materials, a significant part of which enters the soil directly during their use, bypassing the stages of collection, sorting and processing. Compositions based on polylactic acid (polylactide) are used for pre-sowing seed treatment [US 20110275520 A1, publ. 11/10/2011], as well as for the manufacture of covering and mulching materials [RU 156639 U1, publ. 10.11.2015, CN 105949737 (A), publ. 09/21/2016 and others]. The use of biodegradable materials as carriers for sowing seeds of agricultural crops is described. For example, in the Korean patent application [KR 20080100115 A, publ. 11/14/2008] proposed a method of growing rice, in which seeds are germinated on a non-woven cotton cloth containing many holes, which improve the conditions for plant development. This technology, according to the authors, improves the working conditions of workers and facilitates the fight against unwanted vegetation, however, given the shortage and high cost of natural cotton fiber and large areas of rice plantations, it can hardly be considered promising for widespread use.

In the work [L.S. Shibryaeva, Yu.V. Tertyshnaya, D.D. Palmina, N.S. Levin "Biodegradable polymers as materials for sowing grain crops", Agricultural machines and technologies, No. 6, 2015, p. 14-18] describes the results of a study on the use of nonwoven materials made of poly-3-hydroxybutyrate (PHB) or from a composition as biodegradable carriers for sowing wheat seeds

PHB and synthetic nitrile rubber. The carrier and the plants grown on it have a mutual positive effect on each other. The porous permeable carrier provides the rate of diffusion of water, oxygen and nutrients necessary for effective germination of seeds, thereby stimulating the acceleration of germination and intensive development of the root system, which, in turn, contributes to the mechanical destruction of the material and the acceleration of its further biodegradation. However, the use of synthetic nitrile rubber as a modifying additive does not correspond to the current trend of using natural natural materials, especially in such an environmentally sensitive area as crop production.

Among the biodegradable polymers used in crop production, a special place is occupied by polylactide (polylactic acid, PLA), which decomposes in the soil under the action of a complex of natural factors into carbon dioxide and water. The use of polylactide as a covering material is described, for example, in patent documents [RU 156639 U1, publ. 10.11.2015], [CN 105949737 (A), publ. 09/21/2016] and a number of others.

In work [Shibryeva L., Tertyshnaya Yu., Solovova Yu., Levina N., Zhalnin E. "Effect of plant environment on decomposition of biodegradable materials based on poly-3-hydroxybutyrate and polylactide" Norwegian Journal of development of the International Science , No. 27/2019, V. 1, pp. 11-24], taken by us as a prototype, it was shown that a substrate made of non-woven fibrous material made of polylactide also creates favorable conditions for seed germination and development of wheat seedlings, providing acceleration of plant growth in comparison with the control.

However, the widespread use of polylactide is difficult due to a number of technological drawbacks, in particular, the relatively high fragility, which makes it difficult to use materials made from it in agricultural production, especially with the use of technical means that create high mechanical loads on the material. One of the possible approaches to improving the physical and mechanical properties of polylactide is based on the introduction of elastoplasts or other additives that contribute to a change in the interphase structure and improve the technological characteristics of the material while maintaining its biodegradability. The series of patents issued by Kimberly-Clark Worldwide, Inc. [RU 2561122 C2, publ. 20.08.2015], [RU 2624303 C2, publ. 03.07.2017], [RU 2618561 C2, publ. 05/04/2017] and others describe the preparation of materials based on polylactic acid modified by the introduction of polymer additives. For example, in the patent [RU 2624303 C2, publ. 07/03/2017] described non-woven

material made from fibers that are obtained from a thermoplastic composition comprising polylactic acid (70 and more wt%) and a polyolefin additive (from 1 to 25 wt%), for example, polypropylene homopolymer PP 3155 (Exxon-Mobil), mixed with each other with the other in the presence of an epoxy modifier that is an epoxy functionalized methacrylic and / or acrylic monomer component, for example, glycidyl acrylate, glycidyl methacrylate, or a combination thereof, or a copolymer of ethylene, methacrylate and glycidyl methacrylate. The invention provides for the production of fibers with good elongation parameters and high strength, however, the introduction of up to 25% of polyolefins and low or high molecular weight epoxy modifiers into the biodegradable material, the decomposition time of which is measured for decades, adversely affects the environmental properties of the material.

In the application [CN 105949737 (A), publ. 09/21/2016] describes a biodegradable mulch film containing 35-42 mass parts of acryl-modified polylactic acid, 18-21 parts of polybutylene succinate, 24-28 parts of polyglutamic acid, 8-12 parts of modified collagen, 0.5-1.8 parts of phenyl salicylate , 0.8-1.4 parts of sodium carboxymethylcellulose, 0.1-0.3 parts of nanosilicon nitride, 1-3 parts of maleic anhydride, 1.6-2.7 parts of antioxidant 1010, 2.3-2.5 parts triphenylphosphite and 0.2-0.5 parts of erucylamide. The composition has a complex composition, which includes not only biodegradable components. The film has high strength, resistance to wind and rain and good transparency, but it cannot be used as a basis for sowing seeds, because due to low permeability, it cannot provide the water and gas exchange necessary for the development of plants, and high strength reduces the ability of the material to biodegradation, one of the stages of which is its mechanical destruction under the influence of external factors.

In the application [CN 1022500451, publ. 11/23/2011] also describes a film containing 60-99 mass. % polylactic acid and 1-40 wt. % natural epoxidized rubber, the degree of epoxidation of which is from 0% (natural rubber) to 75%, preferably 25-50%. The degree of crystallinity, the degree of crosslinking and other characteristics are controlled by the selection of the quantitative composition of the mixture, the degree of epoxidation of the rubber, the time and temperature of annealing. However, as in the previous analogue, the films obtained in this way cannot be used as a basis for sowing seeds, since, unlike non-woven materials, they do not possess

porosity and hygroscopicity, which provide favorable conditions for seed germination and further development of plants.

The problem solved by the present invention is to create a composite fibrous nonwoven fabric based on polylactide, which expands the range of materials that can be used as a biodegradable base for growing plants. Also, the present invention solves the problem of using this material as a base for sowing seeds and growing plants. When solving the problem, we proceeded from the fact that the material must meet the following requirements:

- the presence of a porous structure, which provides the formation of favorable conditions for seed germination and plant development due to effective moisture and gas exchange;

- the ability to hydrolytic and enzymatic degradation in natural conditions with the formation of products that are harmless to the environment and at the same time - stimulate the growth and development of plants;

- the material should combine improved, in comparison with pure polylactide, elasticity indicators, with the ability to mechanical destruction under the influence of natural factors and the developing root system of plants grown on it.

The problem is solved by the proposed composite fibrous nonwoven material containing polylactide, characterized in that it additionally contains natural rubber with the following ratio of components, wt. %:

polylactide 85-95

natural rubber 5-15,

and also its use as a basis for sowing seeds and growing plants.

The technical result is to expand the range of biodegradable materials intended for use as a basis for growing plants. The technical result is achieved by creating a composite biodegradable nonwoven fibrous material with improved elasticity, containing polylactide and natural rubber in the specified mass ratios, the use of which for the specified purpose provides an increase in seed germination and biological productivity of plants.

The essence of the invention is illustrated by the following illustrations:

FIG. 1 shows micrographs of fragments of samples of nonwoven fibrous materials of various compositions (Olympus CX43 (Japan), 100 times magnification).

A. Pure polylactide nonwoven fabric.

B. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 95: 5, respectively.

B. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 90:10, respectively.

D. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 85:15, respectively.

FIG. 2 shows thermograms of samples of nonwoven fibrous materials of various compositions.

A. Initial samples.

B. The same samples after hydrolysis for 180 days at a temperature of 20 ± 2 ° C.

B. The same samples after growing basil plants on them in soil for 60 days, temperature 20 ± 2 ° С.

1. Pure polylactide material.

2. Nonwoven composite material containing polylactide and natural rubber in a mass ratio of 95: 5, respectively.

3. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 90:10, respectively.

4. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 85:15, respectively.

FIG. 3 shows micrographs of fragments of samples of nonwoven fibrous materials after growing basil plants on them in soil for 60 days (Olympus CX43 (Japan), 100 times magnification)

A. Pure polylactide nonwoven fabric.

B. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 95: 5, respectively.

B. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 90:10, respectively.

D. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 85:15, respectively.

FIG. 4. Shown are micrographs of fragments of samples of nonwoven fibrous composite materials after growing basil plants on them - 60 days in soil (Olympus CX43 (Japan), 40 times magnification).

A. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 90:10, respectively.

B. Nonwoven composite material containing polylactide and natural rubber in a weight ratio of 85:15, respectively.

FIG. 5 shows photographs of purple basil plants on the 21st day of vegetation.

A. Plants are grown without a substrate.

B. Plants are grown on a pure polylactide nonwoven backing.

B. Plants are grown on a non-woven substrate containing polylactide and natural rubber in a 90:10 ratio.

FIG. 6 shows photographs of violet basil plants on the 40th day of vegetation, grown on substrates of non-woven polylactide based material with different content of natural rubber in comparison with the control.

K - control;.

100% - pure polylactide backing;

95 + 5% - The backing contains 95% polylactide and 5% natural rubber.

90 + 10% - the backing contains 90% polylactide and 10% natural rubber.

85 + 15% - The backing contains 85% polylactide and 15% natural rubber.

FIG. 7 shows photographs of dried vegetable violet basil plants grown on polylactide-based non-woven substrates with different content of natural rubber in comparison with the control.

1 - pure polylactide substrate;

2 - the backing contains 95% polylactide and 5% natural rubber;

3 - the substrate contains 90% polylactide and 10% natural rubber;

4 - the substrate contains 85% polylactide and 15% natural rubber;

To obtain the material according to the invention, polylactide with a molecular weight of 1.4-1.8 × 10 ⁵ can be used, obtained by any known method, for example, by polymerization of lactic acid obtained from objects of plant origin with different quantitative contents of D and L forms (with different degree of crystallinity), as a composite additive can be

used natural rubber with a molecular weight of 1.4-2.0 × 10 ⁵ from the juice of hevea or other plant raw materials.

The material is obtained by electroforming from a solution, which makes it possible to obtain the necessary porous hygroscopic structure. To prepare the spinning solution, chloroform, carbon tetrachloride or their mixtures are used as a solvent. The concentration of the spinning solution and the conditions for conducting electrospinning are selected empirically, taking into account the viscosity characteristics, which depend on the molecular weight and mass ratio of polymers in the solution. It has been found that in order to obtain a material containing polylactide and natural rubber in the indicated mass ratio range, the molding solution should preferably contain 7-9 mass% of a polymer mixture. At lower concentrations, it is not possible to form a high-quality elementary fiber, an increase in the concentration of the solution for spinning increases its viscosity, which makes it difficult or impossible to electrospin.

To obtain a molding solution, initial solutions of polylactide and natural rubber of the required concentration in the selected solvent are prepared, mixed in the desired ratio, and the resulting solution is homogenized for several minutes at a temperature of 57-60 ° C before being introduced into the electroforming device.

Electrospinning is carried out at an electric field voltage of 17.0-19.0 kV, the distance between the electrodes is 16.5-18 cm at a volumetric flow rate of the molding solution (9-11) × 10 ^-5 g / s and air humidity, preferably not exceeding 25 %, providing effective removal of the solvent, and subsequent complete drying of the resulting nonwoven material at room temperature for 24-32 hours.

The following examples describe the preparation, properties and characteristics of the obtained materials, as well as their use for growing plants using the example of vegetable purple basil.

Example 1. Obtaining and properties of nonwoven composite materials containing polylactide and natural rubber.

To obtain materials according to the invention, granules of polylactic acid (polylactide) grade 4032D (Nature Works, USA) with a molecular weight of 1.7 × 10 ⁵ g / mol, a density of 1.24 g / cm ³ , tensile strength of 52-56 MPa were used, and natural rubber brand SVR 3L (Vietnam) - the content of non-rubber impurities is not more than 0.03%, ash is not

more than 0.5%, tensile strength 22-24 MPa, molecular weight 1.6 × 10 ⁵ g / mol, density 0.913 g / cm ³ .

Prepare initial 9% solutions of polymers in chloroform, mix them in the required ratio, and stir for 2-3 minutes at a temperature of about 60 ° C before being introduced into the electroforming device until a homogeneous molding solution is obtained. Electrospinning is carried out at room temperature and air humidity no more than 25% in a single-capillary device EFV-1 (Russia). Specific conditions for electrospinning are selected for each solution individually in the following ranges: volumetric flow rate of the molding solution (9-11) × 10 ^-5 g / s, electric field voltage 17.0-19.0 kV, distance between electrodes 16.5-18 cm The finished nonwoven fibrous material is dried in air at room temperature for 24-32 hours. Samples of composite fibrous nonwoven materials containing polylactide and natural rubber in mass ratios (95-85) :( 5-15) mass. %, respectively.

The structure of the materials is investigated by optical polarizing microscopy on an Olympus CX43 device (Japan). It is shown that the diameter of an elementary fiber is practically independent of the rubber content and is 5-7 microns. The thickness of the samples of the obtained nonwoven fibrous materials is 35-45 microns.

FIG. 1 shows micrographs of samples of the obtained materials (B - D) in comparison with a sample of a nonwoven fabric made of pure polylactide (A). The photographs show that the introduction of natural rubber into polylactide in an amount of 5-15 mass. % does not noticeably affect the structure of the material and does not worsen its porosity in comparison with a non-woven fabric made of pure polylactide.

The impact of the aquatic environment is an important component of the complex of natural factors that ensure the biodegradation of material in nature. Given in Table. 1, the indicators of water absorption of the obtained materials indicate that the introduction of natural rubber into polylactide within the indicated limits does not reduce the hygroscopicity of the material and does not worsen the conditions for the delivery of water-soluble nutrients to the seeds of plants grown on it.

The ability to hydrolytic decomposition is characterized by the value of the sample weight loss Δm after exposure to an aqueous medium for a certain period of time, as well as by the results of measuring the thermophysical characteristics of the test materials samples before and after prolonged exposure to the aqueous medium. The measurement results are presented in Table. 2. Pre-weighed samples of material with a size of 3 × 3 cm are kept in water at room temperature for 180 days, after which the samples, dried in air at a temperature of 35-40 ° C for 30 minutes, are weighed again and the weight loss is determined by the formula:

where m ₀ is the mass of the original sample, m _i is the mass of the sample after exposure to water.

The ability of the samples to biodegrade in the soil is assessed by the change in the thermophysical characteristics of the samples upon completion of growing basil plants on them. After removing the grown plants, the material is removed from the soil, washed in water and dried at room temperature. Thermal characteristics - a glass transition temperature T _c and the melting temperature _Tm were determined by differential scanning calorimetry (DSC) on a differential scanning calorimeter DSC 204 F1 Netzsch (Germany) at a heating rate 8 ° C / min. Calibration for indium with T _pl = 156.6 ° C, weight 5-6 mg. The accuracy of determining T _pl and T _c is ± 0.1 ° C. The standard deviations of the experimental areas of the melting peaks of the samples (at least 10 replicates) are ± 8%. The magnitude of the degree of crystallinity α _{cr is} calculated as described in [Tertyshnaya Yu.V., Karpova SG, Popov AA. Influence of the aqueous environment on the molecular mobility of polylactide // Chemical Physics. 2017. T. 36. No. 6. S. 84-91.] By the formula

where ΔH _m is the heat of fusion obtained experimentally, ΔH _m * the heat of fusion of an ideal PLA crystal, equal to 93.1 J / g [Lim LT., Auras R., Rubino M. Processing technologies for poly (lactic acid) // Progress Poly. Sci. 2008. V. 33. P. 820].

FIG. 2 shows the thermograms of the original samples (A) and the same samples after soaking in water for 180 days (B) and after being in the soil for 60 days (C) at room temperature. Table 2 shows the change in the thermophysical characteristics of samples of nonwoven materials of different composition under the influence of an aqueous medium and soil.

As can be seen from the table, under the influence of an aqueous environment for six months, the weight loss of all samples, regardless of the content of natural rubber in them, is 2-3%, which indicates the occurrence of hydrolysis with the formation of water-soluble products. The degree of crystallinity of the samples increases by 8-10%, indicating that the partial destruction of the amorphous phase of the polymer due to hydrolysis and optionally of secondary crystallization on the background of the plasticizing effect of water These processes explain the almost complete smoothing thermograms glass transition temperature _Tg peaks (cm. Fig. 2 - A and B).

It should be noted that, under the influence of soil, even for a relatively short 60-day period in nonwoven composite materials, as well as in a material made of pure polylactide, signs of degradation are observed: although the thermophysical characteristics practically do not change within the accuracy, nevertheless, a tendency towards a decrease in the degree of crystallinity, and the thermogram (Fig.2B) shows the appearance of a low-temperature shoulder at the melting peak, which indicates

the course of processes of changing the crystal structure. Signs of incipient biodegradation of the material are visible in FIG. 3, which shows micrographs of fragments of samples of nonwoven materials made of pure polylactide (A) and composite materials with different ratios of polylactide and natural rubber after growing plants on them in soil for 60 days. The presence of darkening of elementary fibers, which are not removed by additional washing of the samples, indicates the onset of biodegradation processes under the influence of metabolic products by soil microorganisms. In the photographs shown in FIG. 4, damage to the samples associated with the germination of plant roots through them is visible, which also confirms the applicability of the obtained materials for the specified purpose.

Thus, the given data show that the introduction of natural rubber into polylactide in an amount of 5-15 mass. % does not have a negative effect on its hygroscopicity and ability to degradation under the influence of micromycetes of the soil and aquatic environment.

Table. 3 shows the physical and mechanical characteristics of the materials obtained - the elongation at break ε and the relative strength σ, determined according to GOST 25.061065-72 using a tensile testing machine RM-3-1, as well as the melt flow rate (MFR) determined according to GOST 11645-73, characterizing the behavior of thermoplastic elastomer in a viscous state.

These data show that the introduction of natural rubber into polylactide in the range of 5-15 wt. % has no significant effect on the rheological properties of the resulting nonwoven fabric.

The table shows that the value of the relative elongation at break ε increases with an increase in the content of natural rubber in the sample: an increase in the content of NA from 5 to 15 wt. % leads to an increase in the value of ε by 1.7-3.6 times, while the strength of the samples depends little on the content of rubber in the material. These results show that the introduction of natural rubber into the polylactide in the specified quantitative limits does not significantly affect the strength characteristics of the material, but significantly increases its elasticity and elongation, which makes the material less brittle, improves its consumer qualities and facilitates the use of technical means for its application.

Example 2 The use of nonwoven composites containing polylactide and natural rubber for growing plants.

The possibility of using the proposed material for growing plants is demonstrated by the example of growing a spicy-aromatic plant, vegetable purple basil. Seed germination and plant cultivation were carried out in the phytotron of FGBNU FNATS VIM (Moscow).

In the same containers are placed 200 ± 20 g of soil of the brand "Soil Kev for Vegetables", pH 5.5-7.0 (Gera LLC), on which, with a depth of 10-15 mm, samples of nonwoven materials with a size of 65 × 65 mm are placed, evenly spread on them the seeds of basil (from the agro-firm "Aelita"), sprinkle with a layer of moistened soil. The containers are placed in a phytotron (temperature 20 ± 2 ° C, natural light) and the soil is kept moist without adding any fertilizers. Seed germination is determined on the 10th day after sowing, the full growing cycle is 60 days, at the end of which the plants are removed from the soil, and samples of non-woven material after washing and drying are used for thermophysical measurements.

Table 4 shows the effect of the composition of the substrate material on seed germination, which is defined as the percentage of the number of germinated seeds to the total number of seeds sown.

From these data, it can be seen that the use of non-woven fibrous material based on polylactide for sowing basil seeds leads to an increase in the germination rate by 6-35% compared to the control - the traditional method of sowing seeds directly into the soil. Such a positive effect is due to the fact that the porous permeable structure of nonwoven fibrous materials promotes effective water and gas exchange and provides favorable conditions for seed germination in the soil. In addition, hydrolysis of polylactide proceeding in an aqueous medium according to the scheme

leads to local accumulation of lactic acid, which serves as additional fertilizing for seeds.

Plant care includes regular soil moisture, maintaining a temperature of 20 ± 2 ° C and a natural light regime. In the photographs shown in FIG. 5 and FIG. 6, made, respectively, on the 21st and 40th days after sowing the seeds in the ground, it can be seen that the plants grown on substrates made of fibrous nonwoven material containing polylactide in a composition with natural rubber are characterized by more friendly shoots, develop more actively, form a wider sheet plate than in the control.

On the 60th day of vegetation, the plants are removed from the soil to determine their morphophysical characteristics. FIG. 7 is a photograph of air-dried at room temperature basil plants grown on a non-woven fibrous material of the invention compared to a control. The photograph shows that the plants grown on the material according to the invention are superior in size and development to the control plants grown under normal conditions. This is confirmed by the measurement results given in Table. five.

From the data in Table. 4 it follows that the cultivation of basil plants on substrates made of materials containing polylactide in combination with natural rubber has a beneficial effect on the development of plants: the height of the aboveground part increases by an average of 30-60%, the length of the roots increases by 18-35%, an increase in green mass, characterizing the yield is 40-120% compared to the control. Although these indicators are somewhat inferior to the material from pure polylactide in some positions, they nevertheless demonstrate a clear advantage over the indicators of control plants grown in the traditional way.

Thus, the claimed composite non-woven fibrous material containing polylactide and natural rubber in the stated ratios is characterized by a higher elasticity compared to the prototype, retains the biodegradability and the ability to mechanical destruction under the influence of the developing root system. When used as a basis for sowing seeds and growing plants, it helps to increase seed germination and increase the biological productivity of plants. The increase in elasticity due to the introduction of natural rubber into the composition facilitates the use of the material in industrial technologies using technical means. The material meets the requirements for "green" technologies, and can be used for growing plants in open and closed ground, in personal subsidiary plots, in research in the field of biotechnology and plant breeding.

The given example of the use of the material as a substrate for growing basil plants is a particular example that does not cover all possible options for its similar use for growing various herbal, vegetable, grain and other agricultural crops. In general, the application

The proposed material as a biodegradable base for growing plants includes placing the material on a soil layer, placing seeds on the material, covering them with a soil layer maintained in a moist state and further care for the seedlings in accordance with varietal agricultural techniques.

Claims (7)

1. Biodegradable fibrous nonwoven material containing polylactide, characterized in that it additionally contains natural rubber at the following ratio of components, wt. %: polylactide 85-95 natural rubber 5-15 2. Material according to claim 1, characterized in that it is obtained by electrospinning from solution. 3. Material according to claim 2, characterized in that the molding solution is a 7-9% solution of a mixture of polymers in chloroform or carbon tetrachloride or in a mixture of these solvents. 4. Material according to claim 2, characterized in that the electrospinning is carried out at an electric field voltage of 17.0-19.0 kV, the distance between the electrodes is 16.5-18 cm at a volumetric flow rate of the molding solution (9-11) × 10 ^-5 g / s. 5. The use of material according to claim 1 for growing plants, characterized in that it is used as a basis for sowing seeds and growing plants. 6. Application according to claim 5, characterized in that it includes placing the material on the soil layer, placing the seeds on the material, covering them with a layer of soil that is kept in a moist state and further care for the seedlings in accordance with varietal agricultural techniques.

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