阅读说明：本技术 植物栽培用培养基 (Culture medium for plant cultivation ) 是由 佐佐木秀浩 大贯丞二 于 2020-03-31 设计创作，主要内容包括：本发明的植物栽培用培养基由袋体和破碎物构成,所述破碎物以压缩状态填充到所述袋体中且将由脂肪族聚酯系树脂制成的发泡体破碎而成,填充到所述袋体后的所述破碎物的堆积密度相对于填充到所述袋体前的所述破碎物的堆积密度之比大于1且2以下。(The culture medium for plant cultivation comprises a bag and a crushed material, wherein the crushed material is filled in the bag in a compressed state and is formed by crushing a foam made of an aliphatic polyester resin, and the ratio of the bulk density of the crushed material filled in the bag to the bulk density of the crushed material before filling in the bag is more than 1 and less than 2.)

1. A culture medium for plant cultivation, wherein,

consists of a bag body and a broken object,

the crushed product is filled in the bag body in a compressed state and is formed by crushing a foaming body made of aliphatic polyester resin,

the ratio of the bulk density of the crushed material after filling the bag to the bulk density of the crushed material before filling the bag is greater than 1 and 2 or less.

2. The medium for plant cultivation according to claim 1, wherein,

the specific surface area of the crushed material before filling the bag was 0.5m²/g～2.0m²/g。

3. The medium for plant cultivation according to claim 1 or 2, wherein,

the bulk density of the crushed material before filling the bag is 10kg/m³Above and less than 100kg/m³。

4. The medium for plant cultivation according to any one of claims 1 to 3, wherein,

the bag body is a woven, knitted or nonwoven fabric made of an aliphatic polyester resin.

5. The medium for plant cultivation according to any one of claims 1 to 4, wherein,

the foam is composed of a polylactic acid resin.

Technical Field

The invention relates to a culture medium for plant cultivation.

Background

In recent years, plant factories have come into widespread use which can produce pesticide-free vegetables and the like stably without being affected by weather.

In a plant factory, high temperature management, nutrient solution management and the like are required as compared with conventional open field cultivation, and therefore, it is not rare to replace soil cultivation with overhead cultivation. In the overhead cultivation, a mounting base is installed on the ground or ground surface in a plant factory facility, a cultivation tray placed on the mounting base is filled with a culture medium for plant cultivation as a substitute for soil, and plants are planted and cultivated on the culture medium. As the culture medium for plant cultivation, agricultural materials, for example, rockwool, peat moss, coconut coir, etc., which are relatively light in weight compared to soil, are used.

Among these agricultural materials, peat moss and coconut coir are organic materials derived from plants, and therefore, after being used as a culture medium for plant cultivation, they can be disposed of as general waste, and can also be decomposed by microorganisms in the soil.

However, since rockwool is an inorganic material derived from natural minerals, there is no other treatment method than disposal as industrial waste for disposal in countries and regions where waste classification and recycling are thorough, particularly in the case of waste disposal in japan.

In addition, these agricultural materials have fewer voids and pores capable of holding air than soil, and the so-called root zone around the plant roots is almost occupied by water, nutrient solution, or solid culture medium for plant cultivation, and the space for holding air is small. Therefore, although all agricultural materials have high water retentivity, there is room for improvement in air permeability, because plants have insufficient air taken from their roots, which causes unfavorable conditions in agriculture, such as poor growth and root rot. Therefore, a culture medium for plant cultivation has been proposed which uses, as a main material, resin particles which are light in weight and have excellent water retentivity and air permeability (see, for example, patent documents 1 and 2).

The plant cultivation medium described in patent document 1 is mainly composed of pellets of an aliphatic polyester resin synthesized from a diol and an aliphatic dibasic acid, and pellets obtained by pulverizing a molded article such as a foamed product of the aliphatic polyester resin into a particle size that can pass through a sieve having a mesh opening of 10mm are used as the pellets. In this culture medium for plant cultivation, the aliphatic polyester resin is a synthetic polymer, but since it is biodegradable, mixing the culture medium for plant cultivation with soil can reduce the bulk specific gravity of the soil and improve drainage, water retention and air permeability. In addition, by decomposing the culture medium for plant cultivation with a biological agent, pores are generated in the soil, and the reduction of the bulk density of the soil can be promoted.

The culture medium for plant cultivation described in patent document 2 has a water permeable layer formed of resin particles in which at least a part of air bubbles on the surface of a resin foam is eliminated by heat treatment, and is formed of resin particles in which 50% or more of the resin particles have a particle diameter in the range of 0.5 to 30mm, and the resin particles have an average particle diameter in the range of 5 to 30mm and a true specific gravity in the range of 0.1 to 0.5. In this culture medium for plant cultivation, since the water permeable layer is formed using the resin particles as described above, even if the culture medium for plant cultivation is placed on concrete or the like and filled with the resin particles and plants are planted, the water permeability and water retentivity of the water permeable layer are well balanced, and the plants can be cultivated well.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-26262

Patent document 2: japanese laid-open patent publication No. 8-252031

Disclosure of Invention

Problems to be solved by the invention

However, the culture medium for plant cultivation described in patent document 1 is premised on the fact that the granules as the aliphatic polyester resin foam must be mixed with soil for use. Further, if the pellets are used alone without being mixed with soil, there is a problem that stable plant colonization is difficult to be performed due to pellet flow, floating, and the like when filling the culture tray and supplying the nutrient solution because the true density value is extremely low.

Patent document 2 discloses filling resin particles into a water permeable bag, but in order to improve water permeability, the filling amount of the resin particles is made smaller than the capacity of the bag. Further, as the resin foam as a main material of the culture medium for plant cultivation, it is disclosed to use any of polystyrene resin such as polystyrene, polyolefin resin such as polyethylene and polypropylene, and various copolymers such as ABS and MBS, but these resin foams do not have biodegradability. Therefore, a mixture of the resin-based waste that remains without being decomposed by microorganisms in the soil after the plant cultivation and the plant residue rooted in the resin-based waste is generated, and it is necessary to perform disposal such as landfill as an industrial waste as in rockwool. Therefore, as described in patent document 2, when a resin foam having no biodegradability is used as a main material of a culture medium for plant cultivation, there is an economic problem that not only an environmental problem of industrial waste is generated, but also a burden of a treatment procedure of the industrial waste and a burden of treatment cost are increased.

Accordingly, the present inventors have conducted intensive experiments and studies to develop a culture medium for plant cultivation which is lightweight and can stably perform plant permanent planting, has water retentivity and air permeability, and has a small environmental load such as decomposition by microorganisms in soil and composting (compostability) after plant cultivation. Among them, a culture medium for plant cultivation has been developed which is lightweight and stable in plant permanent planting, and which can combine water retention and air permeability by compressing a crushed product obtained by crushing a biodegradable aliphatic polyester resin foam to a specific bulk density range and using the compressed crushed product as a culture medium for plant cultivation. It was confirmed that the culture medium for plant cultivation was composted together with plant residues after use.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a culture medium for plant cultivation which has both water retention and air permeability and which is capable of being decomposed by microorganisms in soil after plant cultivation and which has a small environmental load of composting (compostability).

Technical scheme for solving problems

In order to solve the above problems, the present invention provides a culture medium for plant cultivation, comprising a bag and a crushed material, wherein the crushed material is filled in the bag in a compressed state and is obtained by crushing a foam made of an aliphatic polyester resin, and a ratio of a bulk density of the crushed material filled in the bag to a bulk density of the crushed material before filling in the bag is greater than 1 and 2 or less.

In the culture medium for plant cultivation of the present invention, the specific surface area of the crushed material before filling the bag is preferably 0.5m²/g～2.0m²/g。

In the culture medium for plant cultivation of the present invention, the crushed material is preferably packed in the bag at a bulk density of 10kg/m³Above and less than 100kg/m³。

In the culture medium for plant cultivation according to the present invention, the bag is preferably a woven fabric, a knitted fabric, or a nonwoven fabric made of an aliphatic polyester resin.

In the culture medium for plant cultivation of the present invention, the foam is preferably a polylactic acid resin.

Effects of the invention

According to the culture medium for plant cultivation of the present invention, it is possible to realize a culture medium for plant cultivation that has both water retention and air permeability, and that is capable of being decomposed by microorganisms in soil after plant cultivation and has a small environmental load for composting (compostability).

Drawings

FIG. 1 is a schematic perspective view schematically showing a first embodiment of a culture medium for plant cultivation according to the present invention.

Fig. 2 is a schematic sectional view of section a-a' of fig. 1.

FIG. 3 is a partially cut schematic perspective view schematically showing a plant-cultivation medium according to a second embodiment of the present invention, in which a plurality of the plant-cultivation media according to the first embodiment are arranged in a short direction and packaged with a packaging film.

Fig. 4 is a schematic sectional view of section B-B' of fig. 3.

FIG. 5 is a photograph showing the cross-sectional shape of the tomato root field cultivated in the coconut coir medium in the control area and the plant cultivation medium of the example.

Detailed Description

The culture medium for plant cultivation of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view schematically showing a first embodiment of a culture medium for plant cultivation according to the present invention. Fig. 2 is a schematic sectional view of section a-a' of fig. 1.

The culture medium 1 for plant cultivation of the present embodiment is composed of a bag 3; and a crushed material 2 obtained by crushing a foam made of an aliphatic polyester resin and filled in a compressed state in a bag body 3. The ratio of the bulk density of the crushed material 2 after filling the bag 3 (hereinafter referred to as "crushed material after filling") to the bulk density of the crushed material 2 before filling the bag 3 (hereinafter referred to as "crushed material before filling") is greater than 1 and not more than 2. Specifically, the method is characterized in that a crushed product 2 obtained by crushing a foam made of an aliphatic polyester resin is filled into a bag 3 in a compressed state in which the ratio of the bulk density of the crushed product 2 after filling to the bulk density of the crushed product 2 before filling is greater than 1 and not more than 2.

As described above, although the aliphatic polyester resin is a synthetic polymer, it is biodegradable and has a characteristic of being decomposed by microorganisms in soil. The aliphatic polyester resin contains an aliphatic ester as a main component in its main chain. The aliphatic ester content in the aliphatic polyester resin is at least 60 mol%, preferably 80 to 100 mol%, and more preferably 90 to 100 mol%. The aliphatic polyester resin is a polyester containing an aliphatic polycarboxylic acid component and an aliphatic polyhydric alcohol component or a polyester containing an aliphatic hydroxycarboxylic acid component, and examples thereof include polybutylene succinate, polybutylene adipate, and polylactic acid. Among them, the aliphatic polyester resin constituting the foam is preferably a polylactic acid resin.

The polylactic acid resin is physically stable in a normal use environment and can be used for a long period of time. The used polylactic acid resin is easily decomposed (hydrolyzed) while being kept in an environment of an appropriate moisture and temperature as in compost or soil, and thereafter decomposed (biodegraded) by microorganisms to be completely decomposed into water and carbon dioxide. Therefore, by using a polylactic acid resin as a main material of the culture medium 1 for plant cultivation, composting (composting) treatment can be performed together with plant residues such as stems and leaves, and the cost for discarding the culture medium after use can be significantly reduced.

As described above, when the crushed pieces 2 of the foamed polylactic acid resin are used as the main material of the culture medium 1 for plant cultivation, the plant can be stably planted while being light in weight, and water retentivity and air permeability can be achieved at the same time. Further, when the crushed pieces 2 of the foamed polylactic acid resin are used as the main material of the culture medium 1 for plant cultivation, the culture medium 1 for plant cultivation with a small environmental load can be realized, which can be hydrolyzed in compost or soil after plant cultivation, or biodegraded by microorganisms, or composted.

The polylactic acid resin is preferably a polymer containing 50 mol% or more of a constituent unit derived from lactic acid. Examples of the polylactic acid resin include (a) a polymer of lactic acid, (b) a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, (c) a copolymer of lactic acid and an aliphatic polyhydric alcohol and an aliphatic polycarboxylic acid, (d) a copolymer of lactic acid and an aliphatic polycarboxylic acid, (e) a copolymer of lactic acid and an aliphatic polyhydric alcohol, and (f) a mixture of any combination of these (a) to (e). The polylactic acid also includes polylactic acids called stereocomplex polylactic acids and stereoblock polylactic acids. Specific examples of lactic acid include L-lactic acid, D-lactic acid, DL-lactic acid, and cyclic dimers thereof, i.e., L-lactide, D-lactide, DL-lactide, and mixtures thereof.

Examples of the other aliphatic hydroxycarboxylic acids in the above-mentioned (b) include glycolic acid, hydroxytyrosic acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxyheptanoic acid, and the like.

Examples of the aliphatic polyhydric alcohol in the above-mentioned (c) and (e) include ethylene glycol, 1, 4-butanediol, 1, 6-hexanediol, 1, 4-cyclohexanedimethanol, neopentyl glycol, decamethylene glycol, glycerol, trimethylolpropane, pentaerythritol, and the like.

Examples of the aliphatic polycarboxylic acid in the above-mentioned (c) and (d) include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, succinic anhydride, adipic anhydride, trimesic acid, propanetricarboxylic acid, pyromellitic anhydride, and the like.

Examples of the foam include a foamed strand, a foamed molded article, an extruded foam, and the like, in addition to foamed particles obtained from resin particles. Among them, the foamed particles are preferable in terms of easily obtaining a fine and uniform cell diameter and a cell film thickness.

In the foam, a foam having a large number of fine cells inside can be obtained by producing resin particles from an aliphatic polyester resin and foaming the resin particles. However, although the foam forms fine cells inside, the surface of the foam is generally smooth, and the performance of the foam due to the fine cells inside is not fully exhibited.

Therefore, in the present invention, the crushed material 2 obtained by crushing the foam is used as a main material of the plant cultivation medium 1, and the fine bubbles in the foam are exposed on the surface of the crushed material 2, thereby increasing the specific surface area of the crushed material 2. The crushed material 2 is filled in the bag 3 in a compressed state. The specific surface area of the crushed product 2 is preferably 0.5m²/g～2.0m²/g。

The average particle diameter of the foam is preferably 3 to 15mm, more preferably 5 to 10 mm. When the average particle diameter of the foam is within the above range, fine and uniform cell diameter and cell film thickness are easily obtained, and the cell diameter and cell film thickness of a crushed product after crushing the foam are easily made uniform, which is preferable.

The foam preferably has an apparent density of 12 to 30kg/m³More preferably 14 to 25kg/m³More preferably 15 to 20kg/m³. When the apparent density of the foam is within the above range, it is preferable because the foam is likely to be a crushed product having excellent light weight.

The average particle diameter of the foam and the apparent density of the foam were determined as follows. First, the foam was left to stand at a relative humidity of 50%, a temperature of 23 ℃ and 1atm for 2 days. Next, a measuring cylinder filled with water having a temperature of 23 ℃ was prepared, and an arbitrary amount of the foam after leaving for 2 days was allowed to sink in the water in the measuring cylinder using a tool such as a metal mesh. Further, the volume [ L ] of the foam read from the water level rising portion is measured in consideration of the volume of a tool such as a metal mesh. The average volume of each foam was calculated by dividing the volume by the number of foams filled in the cylinder. Further, the diameter of a virtual true sphere having the same volume as the obtained average volume was taken as the average particle diameter [ mm ] of the foam. The apparent density of the foam was determined by dividing the mass of the foam placed in the measuring cylinder by the volume.

The average cell diameter of the foam is preferably 30 to 500 μm, more preferably 50 to 250 μm. When the average cell diameter satisfies the above range, the closed cells are broken at the time of breaking the foam, and the foam is broken into a broken product including a sheet-like portion of the cell film derived from the original foam, and is likely to have a shape including a node surrounding an edge of the sheet-like portion of the cell film derived from the original foam and an edge of the gathered edge, whereby the specific surface area can be increased. As a result, it is preferable to easily obtain a culture medium having excellent water retentivity. In addition, the increase in specific surface area increases the contact area with the nutrient solution, and therefore, is an effective means for ensuring a certain water retention property as a culture medium.

The average cell diameter of the foam can be determined as follows based on an enlarged photograph of a cut surface approximately bisecting the foam taken with a microscope. In the enlarged photograph of the cut surface of the foam, 4 line segments from one surface of the foam to the other surface are drawn through the approximate center of the cut surface of the foam. However, the line segment is drawn so as to form radial straight lines extending in 8 directions at equal intervals from the approximate center of the cut surface of the bubble to the surface of the cut particle. Next, the number of bubbles intersecting each of the 4 line segments (N1 to N4) was counted, and the total number N of bubbles intersecting each line segment was found to be N1+ N2+ N3+ N4 (pieces). Then, the total L (μm) of the lengths of the 4 line segments was obtained, and the average cell diameter (d') of the expanded beads was obtained from the total L and the total N according to the following formula (1).

d′＝L/(0.616×N)···(1)

This operation was performed for 10 foams selected at random, and the average cell diameter of each foam was added and averaged to be referred to as the average cell diameter (d) of the foam. The above equation (1) is a calculation equation for calculating the average diameter of the cell spheres when the cells are spherical and have a substantially uniform size, and is described in "handbook of foamed plastics (プラスチックフォームハンドブック) (publisher: news agency of the journal industry, published by showa 48, 2.28 th.c)" page 37.2.2 ".

The average cell film thickness of the foam is preferably 3 μm or less, more preferably 2 μm or less, and still more preferably 1.5 μm or less. When the average cell film thickness satisfies the above range, a crushed product obtained by crushing the foam is preferably in the form of a sheet and the bulk density of the crushed product is low. On the other hand, from the viewpoint of suppressing the excessively broken cell film from being excessively broken by the breaking and the excessively thinned broken product, it is preferably 0.5 μm or more, and more preferably 0.7 μm or more.

The average cell film thickness of the foam was calculated from the average cell diameter d measured by the above method using the following formula (2).

V_S＝(ρf-ρg)/(ρs-ρg)＝[(d+T)³-d³]/(d+T)³···(2)

Wherein, V_SIs the volume fraction of the base resin, and ρ f is the apparent density (g/cm) of the expanded beads³) And ρ s is the density (g/cm) of the base resin³) And ρ g is the gas density (g/cm) in the bubble³) D is the average cell diameter (μm), and T is the average cell thickness (μm). The above equation is a relational expression between the average cell diameter and the average cell film thickness, and is described in "1.3.2" on page 222 of handbook of foamed plastics (プラスチックフォームハンドブック) (publisher: journal of Industrial News, Showa, 48, 2.28 th month). By determining the average cell diameter of the expanded beads of the present invention according to the formula (2), the average cell film thickness (T) of the expanded beads is determined.

The method for producing the aliphatic polyester resin foam can be suitably used by conventionally known methods, and various additives such as a foaming agent generally used for producing the foam may be added thereto without lowering the hydrolyzability or biodegradability of these resins and without inhibiting the growth and development of plants. As a method for producing the foam, for example, a method of obtaining the foam by secondary foaming of a melt foam molding method is preferable. In this method, first, as "primary foaming", resin beads of an aliphatic polyester resin or a polylactic acid resin are dispersed in a water-based dispersant in a closed container, and the resin beads are immersed in a foaming agent at a high temperature and a high pressure, and released to a pressure range lower than the internal pressure of the closed container to foam the resin beads. The pre-expanded particles of the aliphatic polyester-based resin, the polylactic acid-based resin obtained by primary expansion may be referred to as "primary expanded particles".

Further, as the "secondary foaming", for example, the primary foamed particles are pressurized with an inorganic gas such as air in a pressure-resistant container, and are further foamed by steam heating after applying an internal pressure. The pre-expanded particles of the aliphatic polyester-based resin obtained by the secondary expansion may be referred to as "secondary expanded particles".

The thus obtained foam of the aliphatic polyester resin can be suitably crushed by a conventionally known method, and examples thereof include crushing treatment with a commercially available crusher. The particle size of the crushed material 2 obtained can be made to be equal to or smaller than a predetermined value by a method such as separation of undersize components.

In the present invention, the specific surface area of the crushed material 2 before filling is preferably 0.5m²/g～2.0m²(ii) g, more preferably 1.0m²/g～2.0m²Per g, more preferably 1.2m²/g～1.8m²(ii) in terms of/g. When the specific surface area is within the above range, the fine bubbles of the crushed material 2 favorably retain the nutrient solution or air, so that the plant does not suffer from root rot and can achieve both water retentivity and air permeability suitable for the growth and development of the plant at a high level. In the present specification, the value of the "specific surface area" is measured by low-temperature low-humidity physical adsorption of an inert gas (e.g., nitrogen) using the BET method.

The crushed material before filling preferably passes through a sieve having a mesh opening of 4mm at a ratio of 90 mass% or more, and more preferably passes through a sieve having a mesh opening of 1.7mm at a ratio of 90 mass% or more. On the other hand, from the viewpoint that when the crushed material is too small, the bulk density of the crushed material increases, it is preferable that the proportion of the crushed material before filling that does not pass through a sieve having a pore size of 45 μm is 90 mass% or more. The mesh opening size is determined in accordance with JIS Z8801-1: 2006 nominal mesh size of the screen.

The number of fractures can be calculated based on the following formula (3).

(number of crushing) (average particle diameter of foam before crushing)/(mesh opening diameter of crushed material before filling 90 mass% or more of sieve) · (3)

The number of the crushed pieces is preferably 1.1 to 5, more preferably 1.5 to 4. When the number of disrupted cells is within the above range, the foam is suitably disrupted, and the water retentivity and air permeability of the plant cultivation medium can be easily achieved.

In the culture medium 1 for plant cultivation of the present invention, the bag 3 is filled with the crushed material 2. The crushed material 2 is compressed inside the bag 3, and thus the inter-particle distance of the crushed material 2 becomes uniform, and a capillary phenomenon is likely to occur. Therefore, the water retention as a culture medium is improved. In this specification, the process of compressing the volume of the crushed material 2 is referred to as a compacting process.

Specifically, the compressed state of the crushed material 2 is characterized by being set to a compressed state in which the ratio of the bulk density of the crushed material 2 after filling to the bulk density of the crushed material 2 before filling is greater than 1 and not greater than 2. In the present specification, the value of "bulk density of crushed material before filling" is determined by a general test method for thermosetting plastics according to JIS K6911-1995. The bulk density of the crushed product 2 before filling was calculated based on the following formula (4).

Bulk density (kg/m) of crushed material before filling³) (mass of cylinder filled with crushed material (kg) — mass of cylinder) (m) internal volume of cylinder (m)³)〕···(4)

The bulk density of the crushed product 2 after filling was calculated based on the following formula (5).

Bulk density (kg/m) of the crushed material after filling³) (mass of filled crushed material (kg) — bag mass (kg) }/{ internal volume of filled crushed material (m)³)}···(5)

The internal volume of the crushed material after filling is determined from the outer diameter of the bag body in which the crushed material is filled in a compressed state.

When the ratio of the bulk density of the crushed material 2 after filling to the bulk density of the crushed material 2 before filling is within the above range, when the crushed material 2 after compaction treatment is used for the culture medium 1 for plant cultivation, the inter-particle distance of the crushed material 2 becomes uniform, and capillary phenomenon is likely to occur, and as a result, the water retention rate of the culture medium can be improved.

As a method of controlling the ratio of the bulk density of the crushed material 2 after filling to the bulk density of the crushed material 2 before filling, for example, the filling amount of the crushed material 2 in the bag 3 is adjusted.

There is a tendency that the bulk density of the broken foam is generally higher than that of the original foam. The crushing treatment is nothing more than the action of breaking the closed cell structure of the foam, which reduces the so-called gas phase and solid phase composite, i.e. the proportion of the volume of the gas phase in the foam. Therefore, the bulk density of the foam after crushing tends to be higher than that of the foam before crushing. In the present invention, the bulk density of the crushed product 2 before filling is preferably 10kg/m³Above and less than 100kg/m³More preferably 10kg/m³Above 40kg/m³Hereinafter, more preferably 12kg/m³Above and 30kg/m³The following. When the bulk density is within the above range, the desired water retention performance can be exhibited, and the plant colonization can be stably performed.

The bag 3 of the crushed product 2 filled with the foam is not particularly limited as long as it has biodegradability similar to that of the crushed product 2, and for example, a knitted fabric, a woven fabric, or a nonwoven fabric made of an aliphatic polyester resin is preferable. The bag 3 preferably has stretchability. In the present specification, the term "knit fabric" refers to a fabric product obtained by forming a shape one by a method of tying a knot with a thread or a fiber. In the present specification, the term "woven fabric" refers to a fabric product obtained by producing a fabric piece by piece in a structure in which a plurality of warp threads and one or a plurality of weft threads are crossed.

The threads constituting the bag body 3 are preferably three-dimensional crimp threads made of an aliphatic polyester resin, and particularly preferably temporary crimp threads which are one of multifilament threads made of a polylactic acid resin. As the stretch property of such a line, for example, the CR value is preferably 10% or more, more preferably 20% or more, and still more preferably 40% or more. The CR value is an abbreviation for Compliance coefficient (Compliance Ratio) and is one of indexes for evaluating a relationship between a load applied to a fiber and an elongation of the fiber. The CR value is an intrinsic value that varies depending on the type of fiber, and the higher the CR value is, the greater the stretchability of the fiber is.

Examples of the woven bag 3 include a stretchable woven bag. Examples of the woven bag body 3 include a spandex woven fabric. The bag 3 of nonwoven fabric may be a spandex nonwoven fabric. The method for producing these bag bodies 3 is not particularly limited, and examples thereof include a method of mechanically knitting, melt-blowing a nonwoven fabric by a fully automatic knitting machine, or the like. The bag 3 may be formed by obtaining a tubular knitted fabric, woven fabric, or nonwoven fabric having both ends open and then sealing one end by heat fusion or the like, or the bag 3 may be formed by previously sealing one end.

For example, when filling the stretchable woven bag with the crushed material 2, the degree of compaction of the crushed material 2 after filling is preferably in the range of 1.05 to 1.4. By setting the degree of compaction within the above range, a culture medium for plant cultivation excellent in water retentivity can be obtained.

The degree of compaction was calculated based on the following formula (6).

(degree of compaction) (bulk density of crushed product before filling)/(bulk density of crushed product after filling) · (6)

Such control of the degree of compaction and control of the ratio of the bulk density of the crushed material 2 after filling to the bulk density of the crushed material 2 before filling can be achieved by adjusting the amount of the crushed material 2 to be filled into the bag 3.

For example, the open end of the bag body 3 of the crushed product 2 filled with the foam is sealed by tying or sewing with a string or the like made of a three-dimensional crimp-processed yarn made of an aliphatic polyester resin, or by thermally melting a resin component with a sealer or the like incorporating an electric heating wire.

The outer diameter of the plant cultivation medium 1 thus produced is not particularly limited as long as it can be stored in a cultivation tray or other plant cultivation container. Of course, when the ratio of the bulk density of the crushed material 2 after filling to the bulk density of the crushed material 2 before filling is within a predetermined numerical range, the crushed material 2 of the foam can be stored in the bag 3 in an arbitrary shape depending on the internal shape of the plant cultivation container in which the plant cultivation medium 1 is stored. Considering the shape of the cultivation tray used in a large-scale plant factory, for example, a long bag 3 having a length of about 1000mm is preferably used. In addition, the diameter is preferably about 50mm to 150mm in consideration of handling, portability, and the like of the culture medium 1 for plant cultivation.

In the compacting treatment of the plant cultivation medium 1 of the present invention, after the filling amount of the crushed material 2 of the foam in the bag 3 is adjusted to a compressed state, soil, sand, or other conventional plant cultivation medium such as rockwool, peat moss, or coconut husk can be layered on the bag 3 filled with the crushed material 2, and further the compacting treatment can be performed.

In this manner, when the plant cultivation medium 1 is formed into a laminated structure with soil and other agricultural materials and compacted, the plant cultivation medium 1 is preferably disposed generally on the root zone side or the lowermost part. By arranging the culture medium 1 for plant cultivation at the lowermost portion, the roots of the plants mainly extend into the culture medium 1 for plant cultivation, and the influence on the root zone of the soil and other agricultural materials can be minimized. Further, since the bag 3 is wrapped outside the culture medium 1 for plant cultivation, the plant cultivation culture medium 1, which contains the plant residue of the bag 3 and is easily composted, can be easily separated from the soil and other agricultural materials after the plant cultivation.

As the compacting treatment other than the compacting treatment of the present invention, for example, the following methods are available. The first method is a method in which the crushed pieces 2 of the foam are directly arranged in a layered manner at the lowermost portion without being filled in the bag body, and soil or the like is arranged on the crushed pieces 2 of the foam arranged in a layered manner. In this case, the crushed material 2 is compacted by the mass of the soil disposed on the crushed material 2. The second method is a method in which the broken pieces 2 of the foam are not filled in a compressed state in the bag (that is, the filling amount of the broken pieces 2 of the foam is smaller than the bag capacity), the bag filled with the broken pieces 2 of the foam is disposed at the lowermost portion, and soil is disposed on the bag. In this case, the crushed material 2 in the bag body is compacted by the mass of the soil, as described above. The third method is a method of compacting the crushed product 2 of the foam by molding the same in a compressed state in a mold to form a foamed molded article.

The method of using the culture medium 1 for plant cultivation according to the present embodiment will be described in detail below.

When the culture medium 1 for plant cultivation is used, it is preferable to immerse the medium in water in advance so that the fine bubbles on the surface of the crushed product 2 of the foam can retain sufficient moisture. For example, the immersion time is preferably about 12 hours to 24 hours. When the immersed culture medium is pulled up from the water and drained, the remaining water is drained from the bag 3, and the water content is changed to a water content suitable for the growth and development of plants.

The water content of the plant cultivation medium 1 can be determined from the normal water retention rate. The bucket is filled with water, and the plant cultivation medium is immersed in the water completely and then left for 24 hours or more. After standing, the medium was pulled up with a strainer of a sufficient size, and the normal water retention rate was calculated from the difference between the mass of the medium 1 for plant cultivation measured 1 hour after pulling up and the dry mass (initial mass) of the medium 1 for plant cultivation measured in advance. The drainage from the plant cultivation medium 1 is natural drainage by gravity. The dry mass of the plant cultivation medium 1 was measured after storing it at 23 ℃ and 50% humidity for 24 hours or more.

The calculation formula of the normal water retention rate was calculated based on the following formula (7).

(Normal Water Retention Rate vol%) { ((mass of culture Medium for plant cultivation 1 hour after starting pulling up) - (mass of culture Medium for plant cultivation 1 in dried state))/(Density of Water) }/(volume of culture Medium for plant cultivation calculated from external dimensions) × 100 · (7)

As described above, the aqueous culture medium 1 for plant cultivation can be used as a medium for replacing part or all of the soil in soil cultivation or planting cultivation, in addition to the medium for overhead cultivation. In particular, the plant cultivation medium 1 of the present invention is excellent in lightweight property, and therefore can be suitably used as a culture medium for overhead cultivation.

Specific applications of the culture medium 1 for plant cultivation of the present invention include, for example, a culture medium for cultivation of fruits and vegetables such as tomato (solanaceae) and strawberry (rosaceae), and a culture medium for cultivation of leaf materials such as lettuce (compositae). In general, there is no particular limitation as long as the plant species used as a cultivar is cultivated. Examples thereof include capsicum, eggplant and the like of the same genus and genus as tomato, cruciferae such as cabbage and the like, cucurbitaceae such as cucumber, bitter gourd and the like. In addition, plants of Gramineae, Umbelliferae, Alliaceae, Compositae, Convolvulaceae, Iridaceae, etc. can also be cultivated.

Next, another embodiment of the culture medium for plant cultivation according to the present invention will be described with reference to the drawings. In the following embodiments, the same components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be omitted or simplified.

FIG. 3 is a schematic perspective view schematically showing a second embodiment of the medium for plant cultivation according to the present invention. Fig. 4 is a schematic sectional view of section B-B' of fig. 3.

In the plant cultivation medium 1a of the present embodiment, as schematically shown in fig. 3 and 4, a plurality of the plant cultivation medium 1 of the first embodiment in which the crushed pieces 2 of the foam are filled in the bag body 3 are arranged in the short direction, and the outside thereof is wrapped with a resin film (hereinafter, referred to as a wrapping film 4) or the like as a wrapping material. The wrapping film 4 is preferably an aliphatic polyester resin such as a polylactic acid resin, but is not necessarily biodegradable, and may be made of a polypropylene resin, a polystyrene resin, a polyethylene resin, or the like.

In the plant cultivation medium 1a, holes for plant permanent planting may be provided in the packaging film 4 on the upper surface side, or slits for drainage may be provided in the packaging film 4 on the lower side. By providing the packaging film 4 with a hole or a notch, the crushed material 2 of the foam filled in the bag 3 does not leak out, and stable planting of the plant can be promoted, and the remaining moisture in the culture medium can be discharged.

When the culture medium 1a for plant cultivation is used, water can be injected through the water injection port, which is a planting hole provided in advance in the packaging film 4. After the water injection, the film is left to stand for about 12 to 24 hours, and a water drainage slit is formed in the lower portion of the side surface of the packaging film 4, so that the excess water can be drained from the slit.

The plant cultivation medium 1a containing water and adjusted in water content in this manner can be used as a substitute medium for a part or all of soil in soil cultivation or planting cultivation, for example, in addition to being used as a medium for overhead cultivation, as in the first embodiment.

In addition, when a biodegradable resin film is used as the wrapping film 4 after the plant cultivation, the plant residue together with the wrapping film 4 and the culture medium 1a for plant cultivation can be composted. On the other hand, when a resin film having no biodegradability is used as the wrapping film 4, the plant residue and the culture medium for plant cultivation 1a are composted after the wrapping film 4 is removed.

The following examples are given, but the medium for plant cultivation according to the present invention is not limited to these examples at all.

Examples

1. Measurement of Normal Water-Retention Rate of Medium for plant cultivation

< example 1 >

5kg of foamed particles of a polylactic acid resin having a bulk expansion ratio 100 times that of a foam (apparent density: 20 kg/m) was charged from a charging port of a screen mill (HA8-2542-25, manufactured by HORAI (R) ホーライ, Ltd.) equipped with a 1.5-mesh screen at a charging speed of 50kg/hr³Average particle diameter 5.3mm, average bubble diameter 188 μm, bubble film thickness 1.0 μm) and crushed.

The ratio of foaming by stacking of the polylactic acid resin foamed particles,A1L measuring cylinder is prepared, foamed particles are filled into a 1L scale of the measuring cylinder, the mass (g) of the filled foamed particles is measured, and the bulk density (kg/m) is obtained by unit conversion³) Then, the resin density of polylactic acid was adjusted to 1.25 (g/cm)³) The value obtained by dividing the above bulk density is referred to as the bulk foaming ratio.

The apparent density of the polylactic acid resin foamed particles was measured as follows. First, the expanded beads were left to stand at a relative humidity of 50%, a temperature of 23 ℃ and 1atm for 2 days. Next, a measuring cylinder filled with water having a temperature of 23 ℃ was prepared, and the foamed particles left to stand for 2 days were allowed to sink in the water in the measuring cylinder using a metal mesh. Further, the volume [ L ] of the foam read from the water level rising portion was measured in consideration of the volume of the metal mesh. The apparent density of the foamed particles was determined by dividing the mass of the foamed particles charged into the measuring cylinder by the volume and converting the unit.

The average cell diameter of the polylactic acid resin foamed particles is determined as follows based on an enlarged photograph taken with a microscope of a cut surface that approximately bisects the foamed body. In the enlarged photograph of the cut surface of the foam, 4 line segments from one surface of the foam to the other surface are drawn through the approximate center of the cut surface of the foam. However, the line segment is drawn so as to form radial straight lines extending in 8 directions at equal intervals from the approximate center of the cut surface of the bubble to the surface of the cut particle. Next, the number of bubbles intersecting each of the 4 line segments (N1 to N4) was counted, and the total number N of bubbles intersecting each line segment was found to be N1+ N2+ N3+ N4 (pieces). Next, the total L (. mu.m) of the lengths of the 4 line segments was determined, and the average cell diameter (d') of the expanded beads was determined from the total L and the total N according to the formula (1). This operation was performed for 10 foamed bodies selected at random, and the value obtained by adding and averaging the average cell diameters of the foamed particles was referred to as the average cell diameter (d) of the foamed particles of the polylactic acid resin.

Since the thickness of the cell film of the polylactic acid resin foamed particles is (ρ f and ρ s) > ρ g in the formula (2), when ρ g is 0 (g/cm)³) When Vs is equal to ρ f/ρ s. Therefore, the average bubble film thickness T (μm) was calculated based on the following equation (8).

T＝d〔(X/(X-1))^1/3-1〕···(8)

Wherein ρ s is the density of the base resin, and the resin density of the polylactic acid is 1.25 (g/cm)³) And thus is 1.25. ρ f is an apparent density of the expanded particles, and therefore is 0.020 (g/cm)³)。

100% of the crushed material obtained passes through a sieve with a mesh opening size of 1.4 mm.

Further, when the specific surface area of the crushed pieces of the obtained foam was measured by a multipoint method using a BET adsorption tester (product name: Smart VacPrep, manufactured by Mimmerit Co., Ltd.) using Kr gas, the value of the specific surface area was 1.28m²/g。

The crushed material before filling was determined as follows by passing through 90 mass% or more of the mesh opening of the sieve. The crushed material was sieved using a screen smaller than the screen of the sieve mill and having the closest nominal mesh size (5 minutes of shaking). In the case where the crushed material passes through 90 mass% or more, the same screening is performed by a screen having a smaller nominal mesh size. By the above operation, the crushed material was sieved until the crushed material passed through 90 mass% or more, and the minimum nominal mesh diameter at which the crushed material passed through 90 mass% or more was shown in table 1.

From the thus obtained crushed pieces of the polylactic acid resin foam, 4.19L in volume and 152.5g in mass were taken, and filled into a stretchable woven bag having a total length of 1000mm, one end of which was closed by heat-fusion and the other end of which was an open end, and the open end was heat-fused to obtain a culture medium for plant cultivation. The outer dimension of the medium was a substantially cylindrical shape with a diameter of 70mm and a length of 990 mm. The volume of the disrupted material after filling, which was calculated from the outer dimensions of the culture medium, was 3.81L. Since the volume was 4.19L and the mass was 152.2g, the bulk density of the crushed material before filling was 36.3kg/m as calculated by dividing the mass by the volume³. Since the volume was 3.81L and the mass was 152.2g, which is the same as that of the crushed material before filling, the bulk density of the crushed material after filling was calculated to be 39.9kg/m³。

The bucket is filled with water, and the plant cultivation medium is allowed to stand for 24 hours after being completely immersed in water. After leaving, the medium was pulled up with a strainer of a sufficient size, and from the difference between the mass of the medium 1 for plant cultivation measured after 1 hour of pulling up and the dry mass (initial mass) of the medium 1 for plant cultivation measured in advance, the normal water retention rate was calculated based on the formula (7). The drainage from the plant cultivation medium 1 is natural drainage by gravity. The dry mass of the plant cultivation medium 1 was measured after being stored at 23 ℃ and 50% humidity for 24 hours or more.

< example 2 >

A plant cultivation medium was produced and immersed in water in the same manner as in example 1, except that the mesh diameter of the screen attached to the screen mill was changed to Φ 3.

< example 3 >

A plant cultivation medium was produced and immersed in water in the same manner as in example 1, except that the mesh opening size of the screen attached to the screen mill was changed to Φ 1.7.

< example 4 >

A plant cultivation medium was produced and immersed in water in the same manner as in example 1, except that the mesh diameter of the screen attached to the screen mill was changed to Φ 4.

< comparative example 1 >

A plant cultivation medium was produced in the same manner as in example 1, and immersed in water, except that the bag was filled with a foamed polylactic acid resin having a stacking expansion ratio of 100 times without crushing the foamed material using a screen mill.

< comparative example 2 >

A plant cultivation medium was produced and immersed in water in the same manner as in example 1, except that the mesh diameter of the mesh attached to the mesh mill was changed to Φ 3, and the bag was filled with the crushed material so that the degree of compaction was 1.00.

The results of measuring various characteristic values of the culture media for plant cultivation of examples 1 to 4 and comparative examples 1 to 2 are shown in table 1.

[ Table 1]

As shown in Table 1, it was confirmed that the crushed material before filling passed through a sieve having a mesh size of 90 mass% or more, and the specific surface area of the crushed material before filling into the bag increased, as well as the number of crushed pieces increased, and that the normal water retention value of the culture medium increased.

2. Cultivation test of tomato Using culture Medium for plant cultivation

Then, a tomato cultivation test was performed using 3 bags of the plant cultivation medium of example 3 arranged in parallel in the longitudinal direction and a culture medium packed with a polyethylene resin-made packing film.

On the day before the field planting of the tomatoes, a notch for water injection is opened on the upper surface of the packaging film, and the whole culture medium is soaked in water, filled with water until the inside of the packaging film is filled with water and placed for 24 hours. After the placement, the water injection cut provided on the upper surface of the packaging film is enlarged to the same extent as the bottom surface of the seedling raising pot and serves as a planting hole, and a plurality of cutting grooves for drainage are provided on the lower portions of both side surfaces of the packaging film. The water draining device is placed on a big strainer, and residual water is drained naturally by means of gravity.

The bottom of the seedling pot was hollowed out in cooperation with a planting hole provided in a packaging film of the drained culture medium, and a tomato (Furutika (フルティカ) < registered variety >) seedling was placed on the culture medium for secondary seedling. During field planting, the distance between plants is 15cm, the distance between beds is 110cm, and each bed is 26 plants. The nutrient solution after planting was managed in a circulating manner, and water was periodically poured using a dropper (manufactured by Natefme (ネタフィム)). The frequency of filling was carried out in 30 minutes 1 time with a small amount of high frequency. The liquid discharge rate was set to 20%. The environment in the greenhouse was set to 28 ℃/15 ℃ for the day temperature (ventilation temperature)/night temperature (heating temperature).

After the tomatoes were cultivated under such conditions and the results were confirmed, the fruits were thinned to 1 fruit cluster and 4 fruits were kept and cultivated until harvest. After harvesting the tomatoes, the packaging film was removed from the culture medium for plant cultivation, and the compost was poured without separating the plant residue, the bag body, and the crushed pieces of the foam.

< results >

50 tomatoes cultivated in the medium for plant cultivation of examples were randomly selected, and the weight and the sugar degree were measured, respectively, and the weight average and the sugar degree average were obtained by arithmetic averaging these values. The tomato cultured using the medium for plant cultivation of the example had an average weight of 19.9g and an average sugar degree of 5.9%. The sugar content was measured using a sugar meter (product name "PAL-1" manufactured by ITUP (アタゴ)). On the other hand, the weight average of tomatoes cultivated in a coconut husk medium, which is one of conventional plant cultivation media, was 19.3g, and the sugar degree average was 5.7%. As described above, it was confirmed that tomato fruits cultivated using the culture medium for plant cultivation of the examples had substantially the same quality as tomato fruits cultivated using a coconut husk culture medium, which is one of the conventional culture media for plant cultivation.

In addition, it was confirmed that when the culture medium was cut in the depth direction after removing the packaging film from the plant cultivation medium of the example, the roots of tomatoes were mainly thin roots during hydroponic cultivation and extended so as to be concentrated in the central part of the culture medium and the lower part of the culture medium, as shown in fig. 5. In addition, when compost was put without separating plant residues, the bag of the plant cultivation medium of the example, and the crushed material of the foam, it was confirmed that biodegradation was performed.

Description of the reference numerals

1.1 a culture medium for plant cultivation

2 crushing of the material

3 bag body

4 packaging film