CN114521105A

CN114521105A - Layered body for raising rice seedlings, blanket-shaped seedling, rice seedling box, and method for manufacturing rice seedling box

Info

Publication number: CN114521105A
Application number: CN202080067306.2A
Authority: CN
Inventors: 马场正博; 三枝裕典; 加藤利典; 中村英慈; 前川一彦; 成泽大志; 尾崎洋辅; 田渊浩平; 山村望; 山口𨺓幸; 田中达也; 小林新
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2019-10-02
Filing date: 2020-10-02
Publication date: 2022-05-20
Also published as: JPWO2021066177A1; KR20220069933A; TW202121974A; WO2021066177A1

Abstract

The present invention relates to a laminate for rice seedling cultivation, which comprises a bed soil layer and a covering soil layer, wherein one or both of the bed soil layer and the covering soil layer is/are a water-absorbent resin layer containing a particulate water-absorbent resin, the water-absorbent resin is disposed so that at least a part of rice can come into contact with the water-absorbent resin, and the water-absorbent resin content in the laminate for rice seedling cultivation is 1 to 5000g/m²。

Description

Layered body for raising rice seedlings, blanket-shaped seedling, rice seedling box, and method for manufacturing rice seedling box

Technical Field

The present invention relates to a layered product for raising rice seedlings, which comprises a bed soil layer and a cover soil layer.

Background

Recently, with the aging of agricultural practitioners, it is becoming more desirable to reduce the burden of agricultural activities. In addition, with the depletion of chronic water resources, it is desired to effectively and appropriately utilize agricultural water and establish a technique capable of maintaining or increasing the yield of agricultural products even with a smaller amount of irrigation water or a lower frequency of irrigation water than ever. In general, rice seedlings are grown by introducing culture soil and seeds into a seedling raising box, but the seedling raising box is heavy, and further, it is necessary to perform watering several times a day, accompanied by an operation that imposes a great burden on agricultural workers.

As an attempt to solve these problems, studies have been made on the use of a super absorbent resin (for example, see patent document 1). The super absorbent resin can hold a very large amount of water several tens to several hundreds times its own weight, and therefore has advantages of reducing the weight of culture soil and/or the irrigation load. Patent document 1 and patent document 2 disclose a culture medium in which a water-absorbent resin is mixed with granular culture soil and used for raising rice seedlings.

However, when the water-absorbent resin and the granular culture soil are mixed in advance for use, the water-absorbent resin and the culture soil are separated by vibration during transportation or storage or in a hopper of a sowing machine due to a difference in density and a difference in particle diameter between the water-absorbent resin and the culture soil, and it may be difficult to introduce the water-absorbent resin and the culture soil into a seedling raising box with a constant composition. On the other hand, patent document 2 discloses that a granular culture soil containing a water-absorbent resin is used by mixing soil and a water-absorbent resin in advance and then granulating the mixture. However, when the water-absorbent resin is present inside the granular culture soil, there are the following problems: the water absorption rate is lowered to lower the productivity of the production of the seedling raising box, and the water permeability of the culture medium is deteriorated because the granular culture soil is scattered by the swelling of the water-absorbent resin. Further, it is known that the direct contact with the water-absorbent resin adversely affects the germination of seeds or the growth of plant bodies (particularly roots) (patent document 3 or non-patent document 1).

As a method for solving such a problem, patent document 4 discloses a sheet-like composition in which a water-absorbent resin is sandwiched between papers or the like, and discloses that the water-absorbent resin does not directly contact roots and thereby does not inhibit the growth and development of the roots. Patent document 5 discloses a seedling raising box in which a water absorbent resin layer is provided on the bottom surface of the seedling raising box, and a culture soil layer, a seed layer, and a culture soil layer are sequentially arranged thereon.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. Sho 64-51028

Patent document 2: japanese patent laid-open No. 56-8619

Patent document 3: japanese patent laid-open publication No. 2009-148163

Patent document 4: japanese laid-open patent publication No. 6-217636

Patent document 5: japanese utility model registration No. 3193812

Non-patent document

Non-patent document 1: utilization of super absorbent Polymer as a Material for greening engineering ( utilization of the super absorbent Polymer マー located at the Material として for Industrial Applicability, Shunfu, Semanshu et al, Japan) (9 (2), 11-15, 1983)

Disclosure of Invention

Problems to be solved by the invention

However, the water-absorbent resin-containing sheet disclosed in patent document 4 cannot be used to produce a seedling box using a hopper of a seeding machine, and it is difficult to produce a large number of seedling boxes. Further, when the sheet is easily broken in water, the roots of the sheet directly contact the water-absorbent resin to inhibit growth, while when the sheet strength is too high, the sheet is troublesome to transplant by a rice transplanter.

In the method of patent document 5, not only the manufacturing process is complicated, but also the effect of reducing the weight of the seedling raising box by reducing the culture soil is low.

In view of the above problems, an object of the present invention is to provide a laminate for raising rice seedlings that solves the conventional problems, i.e., that reduces the burden on agricultural activities (for example, reduction in weight and/or irrigation load) and does not inhibit the growth and development of rice.

Means for solving the problems

In order to solve the above problems, the present inventors have made extensive studies on a laminate for growing rice seedlings, and have completed the present invention.

That is, the present invention includes the following preferred embodiments.

[1]A layered product for growing rice seedlings, which comprises a bed layer and a cover layer, wherein one or both of the bed layer and the cover layer is/are a water-absorbent resin layer comprising a particulate water-absorbent resin, the water-absorbent resin is disposed so that at least a part of rice can come into contact with the water-absorbent resin, and the water-absorbent resin content in the layered product for growing rice seedlings is 1 to 5000g/m²。

[2] The laminate for raising rice seedlings according to [1], wherein the content of the culture soil in the water-absorbent resin layer is 20% by mass or less based on the mass of the water-absorbent resin layer.

[3]As described above [1]Or [2]]The layered product for raising rice seedlings, wherein the water-absorbent resin content (X1) (g/m) in the bed soil layer²) The content (X2) (g/m) of the water-absorbent resin in the soil covering layer²) Satisfies the following formula: the content (X2)/the content (X1) is less than or equal to 0.2 or the content (X2)/the content (X1) is more than or equal to 5.

[4]As described above [1]～[3]The laminate for raising rice seedlings according to any one of the above claims, wherein the water-absorbent resin content (X2) in the outer layer is 70g/m²The following.

[5] The laminate for raising rice seedlings according to any one of the above [1] to [4], wherein the water-absorbent resin layer contains more than 80 mass% of the water-absorbent resin based on the mass of each layer.

[6]As described above [1]～[5]The laminate for raising rice seedlings according to any one of the above claims, wherein the laminate for raising rice seedlings comprises water in an amount of 300 to 15000g/m²。

[7]As described above [1]～[6]The laminate for raising rice seedlings according to any one of the above items, wherein the water-absorbent resin layer contains a water-absorbent resin in an amount (X) (g/m)²) And the content of water (Y) (g/m)²) Satisfies the following formula (I): 5 is less than or equal to content (Y)/content (X) is less than or equal to 500 (I).

[8]As described above [1]～[7]The laminate for raising rice seedlings according to any one of the above claims, wherein one of the bed soil layer and the cover soil layer isThe water-absorbent resin layer, and a culture soil layer containing more than 20 mass% of culture soil based on the mass of the water-absorbent resin layer, wherein the content of the culture soil layer in the layered body for raising rice seedlings is 1000-50000 g/m²。

[9] The laminate for raising rice seedlings according to item [8], wherein the bed soil layer is the water-absorbent resin layer.

[10] The layered body for raising rice seedlings according to the above [8] or [9], wherein the culture soil is granular and has an average particle diameter of 0.2 to 20 mm.

[11] The laminate for raising rice seedlings according to any one of the above [1] to [10], wherein the bed soil layer has a thickness of 0.01 to 100 mm.

[12] The laminate for raising rice seedlings according to any one of the above [1] to [11], wherein the thickness of the covering layer is 0.1 to 100 mm.

[13] The laminate for raising rice seedlings according to any one of the above [1] to [12], wherein the water-absorbent resin has a volume average particle diameter of 1 to 10000 μm.

[14] The laminate for raising rice seedlings according to any one of the above [1] to [13], wherein the water-absorbent resin contains a carboxyl group.

[15] The laminate for raising rice seedlings according to any one of the above [1] to [14], wherein the water-absorbent resin has potassium ions as counter cations.

[16] The laminate for raising rice seedlings according to any one of the above [1] to [15], wherein the water-absorbent resin is a vinyl alcohol polymer.

[17] The laminate for growing rice seedlings according to [16], wherein the vinyl alcohol unit of the polyvinyl alcohol is acetalized with at least one acetalizing agent selected from the group consisting of glyoxylic acid and glyoxylic acid derivatives.

[18] The laminate for rice seedling culture according to [16] or [17], wherein the vinyl alcohol polymer contains at least one monomer structural unit selected from the group consisting of acrylic acid, methacrylic acid, and derivatives thereof.

[19] The laminate for raising rice seedlings according to any one of [1] to [18], wherein in a mixture of the water-absorbent resin and pure water 50 times the mass of the water-absorbent resin, the pure water having a water potential of 0 to 3 is 10% by mass or more based on the mass of the pure water in the mixture.

[20] The laminate for raising rice seedlings according to any one of the above [1] to [19], wherein the bed soil layer or the cover soil layer further contains one or more components selected from the group consisting of peat moss, coconut husk, rice husk, vermiculite, perlite, fertilizer and agricultural chemicals.

[21] The laminate for raising rice seedlings according to any one of the above [1] to [20], further comprising rice.

[22] The laminate for raising rice seedlings according to [21], wherein the rice is in a seed state.

[23] The laminate for raising rice seedlings according to [22], wherein the rice in a seed state is present in an area within 20mm from a boundary line between the bed soil layer and the casing soil layer.

[24]As described above [22]]Or [23]]The laminated body for rice seedling culture is characterized in that the content of the rice in the seed state is 50-5000 g/m²。

[25] The laminate for raising rice seedlings according to [21], wherein the rice is in a seedling state.

[26]As described above [1]～[25]The laminate for raising rice seedlings according to any one of the above claims, wherein the laminate for raising rice seedlings has a mass of 28kg/m²The following.

[27] A carpet-like seedling comprising the laminate for growing rice seedlings according to [25 ].

[28] A rice seedling raising box into which the rice seedling raising laminate according to any one of the above [1] to [26] and water are introduced.

[29]A method for manufacturing a rice seedling raising box into which a rice seedling raising laminate comprising a bed soil layer and a cover soil layer is introduced, comprising a step of introducing the bed soil into the rice seedling raising box, a step of sowing rice in a seed state, and a step of introducing cover soil, wherein one or both of the bed soil and the cover soil comprises a particulate water-absorbent resin,the water-absorbent resin is disposed so that at least a part of rice can come into contact with the water-absorbent resin, and the content of the water-absorbent resin in the layered body for raising rice seedlings is 1 to 5000g/m²。

[30] The method according to [29], wherein one or both of the bed soil and the covering soil contains more than 80 mass% of the water-absorbent resin based on the mass of each soil.

[31] The method according to [29] or [30], wherein the introduction of the bed soil and/or the covering soil is performed using a hopper.

Effects of the invention

According to the present invention, it is possible to provide a laminate for raising rice seedlings which solves the conventional problems, that is, which reduces the burden on agricultural activities (for example, reduction in weight and/or irrigation load) and does not inhibit the growth and development of rice.

Drawings

Fig. 1 is a schematic cross-sectional view showing the structure of one embodiment of the laminate for raising rice seedlings according to the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments.

The laminate for raising rice seedlings of the present invention is a rice seedling raising medium comprising a bed soil layer and a covering soil layer. One or both of the bed layer and the cover layer is a water-absorbent resin layer containing a particulate water-absorbent resin, the water-absorbent resin is disposed so that at least a part of the rice can come into contact with the water-absorbent resin, and the water-absorbent resin content in the laminate for rice seedling raising is 1 to 5000g/m²。

As shown in fig. 1, a laminate 1 for raising rice seedlings according to one embodiment of the present invention includes a bed layer 2 and a cover layer 3. In fig. 1, the dimensions, ratios, and the like of the respective components are appropriately adjusted to facilitate the view of the drawings.

In the case where the laminate for raising rice seedlings contains seeds, the layer below the seeds is referred to as a bed soil layer, and the layer above the seeds is referred to as a cover soil layer. When the laminate for rice seedling growth does not contain seeds, the lower part of the boundary line of the closest layer from the center in the thickness direction of the laminate for rice seedling growth is referred to as a bed soil layer, and the upper part of the boundary line is referred to as a cover soil layer. The bed layer and the overburden layer are each preferably a single layer, but may also consist of multiple layers.

The thickness of the bed soil layer is preferably 0.01 to 100mm, more preferably 0.05 to 30mm, further preferably 1 to 15mm, and particularly preferably 2 to 10 mm. When the thickness of the bed soil layer is within the above range, the water retentivity is easily improved, and a well-grown seedling is easily obtained.

The thickness of the cover layer is preferably 0.1 to 100mm, more preferably 1 to 50mm, further preferably 2 to 20mm, and particularly preferably 3 to 10 mm. When the thickness of the covering soil layer is within the above range, the emergence of roots and emergence after sprouting are not likely to occur, and seedlings which grow well are likely to be obtained.

The thicknesses of the bed layer and the overburden layer can be determined by the methods described in the examples described later. In the present invention, the thicknesses of the bed layer and the overburden layer are values in a water-absorbing state. In the present invention, the "water-absorbed state" refers to a state in which the layered body for raising rice seedlings contains water. For example, a layered body for raising rice seedlings after irrigation and a rice seedling raising box into which the layered body for raising rice seedlings and water are introduced are in a water-absorbing state. More specifically, the thickness is preferably measured in a state where the water-absorbent resin contains water (in a state where the water-absorbent resin is completely swollen by water absorption).

On the other hand, the content of the water-absorbent resin, the content of the culture soil, the culture soil layer and the fertilizer described later, the average particle size of the granular culture soil described later and the volume average particle size of the granular water-absorbent resin described later are values in a dry state, respectively. In the present invention, the term "dried state" means a state in which the water-absorbent resin, culture soil, and the like do not contain volatile components such as water and organic solvents. For example, by vacuum-drying at 40 until the mass of the water-absorbent resin, the culture soil, etc. reaches a constant amount, the water-absorbent resin, the culture soil, etc. can be brought into a dry state.

In a preferred embodiment of the inventionThe content (X1) (g/m) of the water-absorbent resin in the bed soil layer²) The content (X2) (g/m) of the water-absorbent resin in the soil covering layer²) Satisfies the following formula: the content (X2)/the content (X1) is less than or equal to 0.2 or the content (X2)/the content (X1) is more than or equal to 5. The content (X2)/the content (X1) is more preferably 0.1 or less or 10 or more, still more preferably 0.05 or less or 50 or more, and particularly preferably 0.01 or less or 100 or more. Only either one of the content (X2) and the content (X1) was 0g/m²The above formula can be said to be satisfied. When the content (X2)/the content (X1) is equal to or less than the upper limit value or equal to or more than the lower limit value, the water retentivity and air permeability are easily improved, and good growth and development of rice are easily obtained. Here, the contents (X1) and (X2) of the water-absorbent resin are values in a dry state as described above.

In a preferred embodiment of the present invention, the content (X2) of the water-absorbent resin in the soil cover is 70g/m²Below, preferably 50g/m²Below, more preferably 30g/m²The lower, more preferably 20g/m²The amount of the surfactant is preferably 10g/m or less²The lower, more preferably 5g/m²The amount of the surfactant is 1g/m or less, more preferably 1g/m²Hereinafter, the concentration may be 0g/m². When the content (X2) is less than the above upper limit, the air permeability is high, and good growth and development of rice can be easily obtained.

[ Water-absorbent resin layer ]

One or both of the bed layer and the overburden layer is a water-absorbent resin layer containing a particulate water-absorbent resin. That is, the water-absorbent resin may be contained in either the bed soil layer or the soil cover layer, or may be contained in both the bed soil layer and the soil cover layer. The water-absorbent resin is preferably contained in the bed soil layer from the viewpoint of sprouting and good growth and development, and exposure and suppression of open roots. When the water-absorbent resin is used for both the bed soil layer and the overburden layer, the water-absorbent resin used for the bed soil layer may be the same as or different from the water-absorbent resin used for the overburden layer. The content of the water-absorbent resin in each water-absorbent resin layer is preferably more than 80 mass%, more preferably 90 mass% or more, and particularly preferably 95 mass% or more based on the mass of each water-absorbent resin layer. The content of the water-absorbent resin in the water-absorbent resin layer may be 100% by mass, that is, the water-absorbent resin layer may be composed of only the water-absorbent resin. In the present invention, even when the bed soil layer and/or the overburden are/is a water-absorbent resin layer composed only of a water-absorbent resin, such layers are referred to as a "bed soil layer" and/or a "overburden", respectively. By using one or both of the bed soil layer and the mulch layer as the water-absorbent resin layer, the burden on agricultural activities can be reduced.

For a rice seedling culture medium, it is required to provide good germination and growth of rice seeds. That is, it is required to sow seeds in a rice seedling culture medium and germinate the seeds after a certain period of time (usually about 2 days) in a germination warehouse. Then, after a certain period of time (usually about 2 to about 3 weeks), the roots of the grown rice are spread in an intertwined manner, requiring provision of a blanket seedling suitable for setting in a rice transplanter. Therefore, the present inventors found that the amount of the water-absorbent resin per unit area of the rice seedling culture medium is very important. When the amount of the water-absorbent resin is too small, the strength of the water-absorbent resin in a gel state is lowered and the amount of water not absorbed by the water-absorbent resin is increased, so that the seeds are buried to inhibit the supply of oxygen to the seeds, and the seeds may not bud. On the other hand, when the amount of the water-absorbent resin is too large, water is firmly held in the water-absorbent resin, so that the water potential of the culture medium is reduced and the supply of water to the seeds is stopped. In the present invention, the content of the specific water-absorbent resin is defined with attention paid to the content. That is, in the present invention, the content of the water-absorbent resin per unit area of the laminate for raising rice seedlings is 1 to 5000g/m². When the content is within this range, the seeds can be well germinated and grown even in a state where the seeds are in contact with the water-absorbent resin, and the burden on agricultural activities can be reduced. The content of the water-absorbent resin in the laminate for growing rice seedlings is preferably 1 to 3000g/m²More preferably 5 to 2000g/m²More preferably 10 to 1000g/m²Particularly preferably 50 to 500g/m²More preferably 100 to 300g/m². When the content is within the above range, more excellent germination and growth of seeds can be easily achievedFurther reducing the burden of development and agricultural activity. The content of the water-absorbent resin in the laminate for raising rice seedlings can be determined by the method described in the examples below. In the present invention, the area of the laminate for rice seedling is the area of the upper surface (the surface of the casing soil present on the ground) of the laminate for rice seedling.

The water-absorbent resin is disposed so that at least a part of the rice can come into contact with the water-absorbent resin. In the case where at least a part of rice is not allowed to contact the water-absorbent resin, for example, in the case where a sheet or culture soil is present between the rice seeds and the water-absorbent resin, the configuration of the rice seedling raising laminate becomes complicated, and the rice seedling raising box cannot be produced using the hopper of the seeding machine, and the productivity of the rice seedling raising laminate or the rice seedling raising box is lowered.

[ Water-absorbent resin ]

The water-absorbent resin in the present invention is not particularly limited. As the water-absorbent resin, for example: acrylate polymers, isobutylene-maleate copolymers, starch-acrylate copolymers, carboxymethyl cellulose polymers, acrylate-acrylamide copolymers, vinyl acetate-acrylate copolymers, saponified polymers of acrylonitrile, saponified copolymers of starch-acrylonitrile, polysaccharide-acrylate copolymers, alginate polymers, sulfonate polymers, vinyl acetate-maleic anhydride copolymers, N-vinylacetamide polymers, acrylamide polymers, glycol polymers, vinyl alcohol polymers, and the like. These polymers may be used singly or in combination of two or more.

The water-absorbent resin preferably contains a carboxyl group from the viewpoint of easily exhibiting excellent water absorption property or water absorption rate. Examples of such water-absorbent resins include acrylic acid salt-based polymers, isobutylene-maleic acid salt-based copolymers, starch-acrylic acid salt-based copolymers, carboxymethyl cellulose-based polymers, acrylate-acrylamide-based copolymers, vinyl acetate-acrylic acid salt-based copolymers, polysaccharide-acrylic acid salt-based copolymers, vinyl acetate-maleic anhydride-based copolymers, acrylamide-based polymers, and vinyl alcohol-based polymers having a carboxyl group.

From the viewpoint of easily exhibiting a further excellent water absorption rate and the viewpoint of growth and development of rice, the water-absorbent resin preferably has potassium ions as counter cations.

From the viewpoint of ease of production and water retention, the water-absorbent resin preferably contains an acrylic acid salt-based polymer, an acrylic acid salt-acrylamide-based copolymer, or a vinyl alcohol-based polymer, and more preferably an acrylic acid salt-based polymer, an acrylic acid salt-acrylamide-based copolymer, or a vinyl alcohol-based polymer. In addition, from the viewpoint of weather resistance and water supply property (water potential) to rice to be retained, the water-absorbent resin further preferably contains a vinyl alcohol polymer, and in a preferred embodiment, the water-absorbent resin is a vinyl alcohol polymer.

The rice and the culture medium have water potential corresponding to the water adsorption capacity, water content, and the like, and the water potential is more likely to be lowered as the rice and the culture medium have a strong water adsorption capacity. Since water tends to move from a state of high water potential to a state of low water potential, if the water potential of the culture medium is not higher than that of rice, the rice is hard to absorb water and is easy to wither. Water with a water potential (pF) of 0-3 in the culture medium is called effective water, and rice is easy to use.

Therefore, in a preferred embodiment of the present invention, in a mixture of a water-absorbent resin and pure water 50 times the mass of the water-absorbent resin, the amount of pure water having a water potential of 0 to 3 is 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 40% by mass or more, based on the mass of pure water in the mixture. The upper limit of the content of pure water having a water potential of 0 to 3 in the mixture is not particularly limited. The content of pure water having a water potential of 0 to 3 in the mixture is usually 80% by mass or less. The above content can be achieved by using, for example, a vinyl alcohol polymer, a polyethylene glycol or a mixture thereof as the water-absorbent resin. The content can be measured by the method described in the examples described later.

The water-absorbent resin preferably has a pure water absorption capacity of 5g/g or more, more preferably 10g/g or more, further preferably 30g/g or more, still more preferably 50g/g or more, still more preferably 80g/g or more, preferably 2000g/g or less, more preferably 1000g/g or less, further preferably 500g/g or less, further preferably 300g/g or less, and still more preferably 200g/g or less, based on the mass of the water-absorbent resin. When the pure water absorption amount of the water-absorbent resin is equal to or more than the lower limit, the amount of water that can be held by the water-absorbent resin layer increases, and therefore the effect of reducing the amount and frequency of water irrigation tends to be improved. When the pure water absorption amount of the water-absorbent resin is not more than the upper limit, excessive swelling is prevented, so that the positional deviation of the seeds or the overflow of the rice seedling laminate from the seedling box can be prevented, and the effective water of the water-absorbent resin is easily increased when it is dried. The adjustment of the pure water absorption amount of the water-absorbent resin to be equal to or higher than the lower limit or equal to or lower than the upper limit can be achieved by optimizing the amount of carboxyl groups, the degree of crosslinking, the crosslinking distribution, and the shape of the water-absorbent resin. The pure water absorption capacity of the water-absorbent resin can be measured by the method described in the examples described later.

< vinyl alcohol Polymer >

Examples of the vinyl polymer [ hereinafter, may be referred to as a vinyl alcohol polymer (a) ] include polyvinyl alcohol, an ethylene-vinyl alcohol copolymer, and an acetal product of vinyl alcohol units thereof with an acetalization agent. As described above, the vinyl alcohol polymer (a) preferably has a carboxyl group from the viewpoint of easily exhibiting excellent water absorption property and water absorption rate. The content of the vinyl alcohol polymer (a) in the water-absorbent resin is preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, further more preferably 95% by mass or more, and may be 100% by mass.

When the vinyl alcohol-based polymer (a) has a carboxyl group, examples of the vinyl alcohol-based polymer (a) include: (i) a saponified product of a copolymer of at least one monomer having a carboxyl group and a derivative of the monomer, and a vinyl ester; (ii) a reaction product of a vinyl alcohol-based polymer and a compound (B) having a functional group (B1) reactive with a hydroxyl group and a functional group (B2) of a carboxyl group and/or a functional group derivable from a carboxyl group; and the like.

In the above (i), the monomer having a carboxyl group is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, itaconic acid, and maleic acid. The derivatives of the above-mentioned carboxyl group-containing monomer include anhydrides, esters, and neutralizers of the above-mentioned monomer, and for example, methyl acrylate, methyl methacrylate, dimethyl itaconate, monomethyl maleate, and maleic anhydride can be used.

In the above (i), the vinyl ester is not particularly limited, and vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl stearate, vinyl benzoate, vinyl trifluoroacetate, vinyl pivalate and the like are exemplified, with vinyl acetate being preferred.

The method for producing the saponified product of the above (i) is not particularly limited, and it can be produced by subjecting one or more monomers selected from the group consisting of a monomer having a carboxyl group and a derivative of the monomer and a vinyl ester to a known polymerization reaction using a known polymerization initiator, and then subjecting the resultant to a saponification reaction by a known method.

In the compound (B) having a functional group (B1) reactive with a hydroxyl group and a functional group (B2) which is a carboxyl group and/or a functional group derivable from a carboxyl group, which is used in the above (ii), the functional group (B1) reactive with a hydroxyl group is not particularly limited, and examples thereof include an aldehyde group, a carboxyl group, an amino group, and derivatives of these functional groups. Among them, an aldehyde group and a derivative of an aldehyde group are preferable from the viewpoint of easiness of production and durability of the water-absorbent resin. That is, the compound (B) is preferably an aldehyde having a carboxyl group and/or a derivative of the aldehyde.

That is, as the reaction product of the above (ii), a vinyl alcohol polymer in which at least a part of vinyl alcohol units are acetalized with at least one kind selected from an aldehyde having a carboxyl group and/or a derivative of the aldehyde [ hereinafter, may be referred to as a vinyl alcohol polymer (a-1) ], is preferable.

The aldehyde having a carboxyl group as the compound (B) is not particularly limited, and examples thereof include glyoxylic acid, 2-formylpropionic acid, 3-formylpropionic acid, and o-formylbenzoic acid. Among them, glyoxylic acid is preferred from the viewpoint of availability and biodegradability. The derivative of the aldehyde having a carboxyl group as the compound (B) includes an anhydride, a hydrate, an ester, an acetalized product, a neutralized product, and the like of the aldehyde, and for example, glyoxylate monohydrate, glyoxylate dimethyl acetal, and the like can be used. Therefore, in a preferred embodiment of the present invention, the vinyl alcohol unit of the vinyl alcohol polymer is acetalized with one or more acetalization agents selected from the group consisting of glyoxylic acid and glyoxylic acid derivatives.

Examples of the counter cation of the glyoxylate include: alkali metal ions such as sodium ions, potassium ions, and lithium ions; alkaline earth metal ions such as calcium ions and magnesium ions; organic cations such as ammonium ions and alkylammonium ions; and the like. Among them, potassium ion, calcium ion and magnesium ion are preferable from the viewpoint of easily exhibiting a further excellent water absorption rate. Calcium ions are more preferable from the viewpoint of easily maintaining the water absorption property when contacting with divalent ions contained in the soil, and potassium ions are more preferable from the viewpoint of growth and development of rice.

Examples of the glyoxylic acid ester include methyl glyoxylate, ethyl glyoxylate, propyl glyoxylate, isopropyl glyoxylate, butyl glyoxylate, isobutyl glyoxylate, sec-butyl glyoxylate, tert-butyl glyoxylate, hexyl glyoxylate, octyl glyoxylate, and 2-ethylhexyl glyoxylate.

The method for producing the vinyl alcohol polymer (a-1) is not particularly limited, and can be produced by acetalizing at least a part of vinyl alcohol units of a vinyl alcohol polymer produced by a known method with at least one kind selected from an aldehyde having a carboxyl group and a derivative of the aldehyde in the presence or absence of a catalyst.

Examples of the catalyst include: inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; organic acids such as carboxylic acids and sulfonic acids; solid acids such as cation exchange resins and heteropoly acids; and the like. These catalysts may be used alone, or two or more of them may be used in combination. Since glyoxylic acid is also an acid that promotes the acetalization reaction, glyoxylic acid also functions as a catalyst in the production of the vinyl alcohol polymer (A-1). That is, in the production of the vinyl alcohol polymer (A-1), a method of using glyoxylic acid as the aldehyde having a carboxyl group is preferred from the viewpoint of ease of handling after the reaction.

The vinyl alcohol polymer used as a raw material in the production of the vinyl alcohol polymer (a-1) may be any of commercially available products produced industrially, products produced by subjecting a vinyl carboxylate such as vinyl acetate and other monomers as needed to a known polymerization reaction using a known polymerization initiator and then to a saponification reaction by a known method, products produced by a cationic polymerization reaction and a hydrolysis reaction of vinyl ether, products produced by direct polymerization of acetaldehyde, and the like, and preferably polyvinyl acetate obtained by polymerizing vinyl acetate is saponified. The saponification degree of the vinyl alcohol polymer used as the raw material is preferably 30 mol% or more, more preferably 60 mol% or more, and in one embodiment of the present invention, from the viewpoint of ease of introducing an appropriate amount of carboxyl groups, more preferably 80 mol% or more.

The degree of acetalization of the vinyl alcohol polymer (A-1) is preferably 0.01 mol% or more and 85 mol% or less. When the acetalization degree is within the above range, the water absorbability is easily improved. From the above viewpoint, the acetalization degree is preferably 0.1 mol% or more, more preferably 1 mol% or more, further preferably 5 mol% or more, further preferably 8 mol% or more, and particularly preferably 10 mol% or more, and is preferably 80 mol% or less, more preferably 70 mol% or less, further preferably 60 mol% or less, further preferably 50 mol% or less, particularly preferably 45 mol% or less, and further preferably 40 mol% or less.

In the production of the vinyl alcohol polymer (A-1), an aldehyde having a carboxyl group and an aldehyde other than the aldehyde derivative may be used in combination to carry out the acetalization reaction, from the viewpoint of easily suppressing the elution of the water-absorbent resin at the time of raising rice seedlings. Examples of the other aldehydes include: aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, sec-butyraldehyde and tert-butyraldehyde; aromatic aldehydes such as benzaldehyde, anisaldehyde, cinnamaldehyde, 4-benzyloxybenzaldehyde, 3-benzyloxybenzaldehyde, 4-pentyloxybenzaldehyde, and 3-pentyloxybenzaldehyde; and the like. Among them, formaldehyde, acetaldehyde and n-butyraldehyde are preferable from the viewpoint of easiness of production and water absorption of the water-absorbent resin to be obtained. When another aldehyde is used in combination, the amount of the aldehyde is not particularly limited, and is usually 0.01 to 30 mol%, preferably 0.1 to 10 mol%, and more preferably 1 to 5 mol% based on the total amount of the aldehyde having a carboxylic acid and the derivative of the aldehyde. When the amount of the other aldehyde used is not more than the upper limit, the water-absorbent resin obtained tends to have excellent water absorption, and when the amount of the other aldehyde used is not less than the lower limit, the effect of suppressing the elution of the water-absorbent resin at the time of raising rice seedlings by using the other aldehyde in combination can be easily obtained. The other aldehydes may be used as derivatives such as acetals.

In one embodiment of the present invention, when the vinyl alcohol polymer (a) has a carboxyl group, a part or all of the carboxyl group may be in the form of a carboxylate. Examples of counter cations for carboxylates include: alkali metal ions such as lithium ions, sodium ions, potassium ions, rubidium ions, and cesium ions; alkaline earth metal ions such as magnesium ions, calcium ions, strontium ions, and barium ions; other metal ions such as aluminum ions and zinc ions; ammonium ion, imidazole

Class i, pyridine

Class and

ions, etc

A cation; and the like. Among them, potassium ion, calcium ion and ammonium ion are preferable, from the viewpoint of easily maintaining the water absorption property when contacting with divalent ions contained in the soilCalcium ion is more preferable, and potassium ion is more preferable from the viewpoint of growth and development of rice. Therefore, in a preferred embodiment of the present invention, the vinyl alcohol polymer (a) has potassium ion as a counter cation. Examples of the method for producing the vinyl alcohol polymer (A) in which a part or all of the carboxyl groups are carboxylate salts include: (ii) a method using a neutralized product of the monomer having a carboxyl group in the above (i); (iii) a method using a neutralized product of the compound having a functional group reactive with a hydroxyl group and a carboxyl group in the above (ii); a method of producing a vinyl alcohol polymer (A) having a carboxyl group by the above-mentioned various methods and the like and then neutralizing the polymer; and the like, wherein the above-mentioned method (ii) is preferred.

In one embodiment of the present invention, when the vinyl alcohol polymer (a) has a carboxyl group, the amount of the carboxyl group in the vinyl alcohol polymer (a) is preferably 0.1 mol% or more, more preferably 1 mol% or more, particularly preferably 3 mol% or more, and most preferably 5 mol% or more, and preferably 80 mol% or less, more preferably 50 mol% or less, more preferably 40 mol% or less, more preferably 30 mol% or less, further preferably 25 mol% or less, particularly preferably 20 mol% or less, and most preferably less than 18 mol% based on the total structural units of the vinyl alcohol polymer (a). When the amount of the carboxyl group is not less than the lower limit, the water-absorbent resin of the present invention is likely to have more excellent water absorption, and when the amount of the carboxyl group is not more than the upper limit, the water absorption is likely to be maintained even when the water-absorbent resin comes into contact with divalent ions contained in soil. The amount of the carboxyl group derived from acrylic acid or a salt thereof in the above carboxyl groups is preferably 20 mol% or less, more preferably 15 mol% or less, particularly preferably 10 mol% or less, and may be 0 mol% based on the total structural units of the vinyl alcohol polymer. When the amount of the carboxyl group derived from acrylic acid or a salt thereof among the above carboxyl groups is not more than the above upper limit, further excellent weather resistance (particularly ultraviolet resistance) can be easily obtained. When a part or all of the carboxyl groups contained in the vinyl alcohol polymer (A) are in the form of carboxylate, the amount of the carboxyl groups is the amount of carboxyl groups and carboxylate or the amount of carboxylate.

Vinyl alcoholThe amount of the above carboxyl group in the polymer (A) and the amount of the carboxyl group derived from acrylic acid or a salt thereof in the carboxyl group may be determined by, for example, a solid¹³C-NMR (nuclear magnetic resonance spectroscopy), FTIR (Fourier transform infrared spectroscopy), acid-base titration, and the like. In the present invention, the "structural unit" refers to a repeating unit constituting the polymer, and for example, the number of the vinyl alcohol unit is "1 unit", and the number of the structure obtained by acetalizing 2 units of the vinyl alcohol unit is "2 units".

The content of the vinyl alcohol constituent unit in the vinyl alcohol polymer (a) is preferably more than 20 mol%, more preferably 50 mol% or more, further preferably 60 mol% or more, preferably 98 mol% or less, more preferably 95 mol% or less, and further preferably 90 mol% or less, based on the total constituent units of the vinyl alcohol polymer (a). The content of the vinyl alcohol structural unit can be measured by FTIR (fourier transform infrared spectroscopy), solid 13C-NMR (nuclear magnetic resonance spectroscopy), or the like, and can be calculated from the consumption amount of acetic anhydride when reacting with a certain amount of acetic anhydride.

The vinyl alcohol polymer (a) may contain other structural units than the vinyl alcohol unit. Examples of the other structural units include: structural units derived from vinyl carboxylates such as vinyl acetate and vinyl pivalate; structural units derived from olefins such as ethylene, 1-butene and isobutylene; structural units derived from acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, acrylamide and derivatives thereof, methacrylamide and derivatives thereof, maleic acid and derivatives thereof, maleimide derivatives, and the like; and the like. The other structural units may contain one or two or more kinds. Accordingly, in a preferred embodiment of the present invention, the vinyl alcohol-based polymer comprises one or more monomer structural units selected from the group consisting of acrylic acid, methacrylic acid and derivatives thereof. The content of the other structural unit is preferably 50 mol% or less, more preferably 30 mol% or less, further preferably 15 mol% or less, and may be 0 mol% based on the total structural units of the vinyl alcohol polymer (a). When the content of the other constituent unit is not more than the upper limit, the water-absorbent resin of the present invention can easily have more excellent water absorption property and water absorption rate.

The viscosity average polymerization degree of the vinyl alcohol polymer (a) is not particularly limited, and is preferably 20000 or less, more preferably 10000 or less, further preferably 4000 or less, and particularly preferably 3000 or less, from the viewpoint of ease of production. On the other hand, from the viewpoint of the mechanical properties of the water-absorbent resin and the dissolution resistance in water, it is preferably 100 or more, more preferably 200 or more, and still more preferably 400 or more. The viscosity average polymerization degree of the vinyl alcohol polymer (a) can be measured by a method in accordance with JIS K6726, for example.

The water-absorbent resin of the present invention preferably contains a crosslinked structure from the viewpoint of preventing the water-absorbent resin from dissolving out during the raising of rice seedlings. When the water-absorbent resin of the present invention contains a crosslinked structure, it is in a gel state upon water absorption. The form of the crosslinked structure is not particularly limited, and examples thereof include crosslinked structures based on ester bonds, ether bonds, acetal bonds, carbon-carbon bonds, and the like.

Examples of the ester bond include an ester bond formed between a hydroxyl group and a carboxyl group of the vinyl alcohol polymer (a) when the vinyl alcohol polymer (a) has a carboxyl group. Examples of the ether bond include an ether bond formed by dehydration condensation of hydroxyl groups of the vinyl alcohol polymer (a). As an example of the acetal bond, when an aldehyde having a carboxyl group is used in the production of the vinyl alcohol polymer (a), an acetal bond formed by acetalization of hydroxyl groups of two vinyl alcohol polymers (a) with the aldehyde is exemplified. Examples of the carbon-carbon bond include carbon-carbon bonds formed by coupling between carbon radicals of the vinyl alcohol polymer (a) generated when the water-absorbent resin is irradiated with an active energy ray. These crosslinked structures may be contained alone or in combination of two or more. Among them, a crosslinked structure based on an ester bond and an acetal bond is preferable from the viewpoint of ease of production, and a crosslinked structure based on an acetal bond is more preferable from the viewpoint of maintenance of water retention property and ultraviolet resistance at the time of raising rice seedlings.

Such a crosslinked structure may be formed, for example, simultaneously with the acetalization reaction in the step of acetalizing at least a part of the vinyl alcohol units with at least one member selected from the group consisting of an aldehyde having a carboxyl group and a derivative of the aldehyde, or may be formed in another step.

As the crosslinking agent, glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, 1, 9-nonanedial, adipaldehyde, malealdehyde, tartaric aldehyde, citral, o-phthalaldehyde, m-phthalaldehyde, and p-phthalaldehyde, and the like can be cited.

When the crosslinking agent is added, the amount of the crosslinking agent in the vinyl alcohol polymer (a) is preferably 0.001 mol% or more, more preferably 0.005 mol% or more, further preferably 0.01 mol% or more, further preferably 0.03 mol% or more, preferably 0.5 mol% or less, more preferably 0.4 mol% or less, and further preferably 0.3 mol% or less, from the viewpoint of easily maintaining water retentivity in soil.

The water-absorbent resin contained in the laminate for rice seedling of the present invention is composed of one or more polymers or contains an additive in addition to one or more polymers. Examples of such additives include: polysaccharides such as starch, modified starch, sodium alginate, chitin, chitosan, cellulose and its derivatives; polyethylene, polypropylene, ethylene-propylene copolymer, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polysuccinic acid, polyamide 6, polyamide 6.6, polyamide 6.10, polyamide 11, polyamide 12, polyamide 6.12, polyhexamethylene terephthalamide, polyhexamethylene isophthalamide, polynaphthalenediamide, polyphenylene ether, polyoxymethylene, polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, polyurethane, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylate salt, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, polyurethane, polyvinyl acetate, polyethylene-vinyl acetate copolymer, polyacrylic acid, polyacrylate, polyacrylic acid salt, polymethacrylic acid, polymethacrylate, polymethacrylic acid, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene glycol, polypropylene, polyethylene glycol, polypropylene glycol, polyethylene glycol, polypropylene, polyethylene glycol, polypropylene, Resins such as ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-acrylic acid salt copolymers, ethylene-methacrylic acid ester copolymers, and ethylene-methacrylic acid salt copolymers; rubbers/elastomers such as natural rubber, synthetic isoprene rubber, chloroprene rubber, silicone rubber, fluororubber, urethane rubber, acrylic rubber, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, ester-based thermoplastic elastomer, urethane-based thermoplastic elastomer, and amide-based thermoplastic elastomer; ultraviolet absorbers, antioxidants, light stabilizers, plasticizers, organic solvents, defoamers, tackifiers, surfactants, lubricants, mildewcides, antistatic agents, and the like. These additives may be used singly or in combination of two or more. When the water-absorbent resin contains the additive, the total content thereof is usually not more than 30% by mass, preferably not more than 20% by mass, based on the total mass of the water-absorbent resin, as long as the effects of the present invention are not impaired.

The water-absorbent resin contained in the laminate for rice seedling culture of the present invention is in the form of particles. When the water-absorbent resin is not in the form of particles, for example, in the form of a sheet, the rice seedling box cannot be produced using a hopper of a seeding machine, and the productivity of the rice seedling box is lowered. The volume average particle diameter of the water-absorbent resin of the present invention is preferably 1 to 10000. mu.m. The volume average particle diameter is more preferably 10 μm or more, still more preferably 30 μm or more, particularly preferably 50 μm or more, still more preferably 1000 μm or less, still more preferably 500 μm or less, particularly preferably 300 μm or less. When the volume average particle diameter is not less than the lower limit, excellent handleability is easily obtained, and when the volume average particle diameter is not more than the upper limit, an excellent water absorption rate is easily obtained. The volume average particle diameter can be measured by laser diffraction/scattering.

[ optional ingredients ]

The water-absorbent resin layer may contain optional components in addition to the water-absorbent resin. Examples of such optional components include resins other than the water-absorbent resin, optional components (other than the water-absorbent resin) that can be contained in the culture soil described later and the culture soil layer described later. Examples of the resin other than the water-absorbent resin include polyethylene, polypropylene, alkyd resin, phenolic resin, polyethylene glycol, polyacrylic acid, polyacrylate, polyacrylamide, and polyurethane.

When the water-absorbent resin layer contains the above optional components, the total content thereof is 20 mass% or less, preferably 10 mass% or less, and more preferably 5 mass% or less, based on the total mass of the water-absorbent resin layer.

In a preferred embodiment of the present invention, the content of the culture soil in the water-absorbent resin layer is 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, and may be 0% by mass based on the mass of the water-absorbent resin layer. In this embodiment, when the seedling raising box is produced using a seeding machine, the water-absorbent resin and the culture soil are less likely to be separated by vibration during operation of the seeding machine, and as a result, the input error of the water-absorbent resin is reduced, and stable seeding operation is facilitated.

When the laminate for growing rice seedlings contains water, the content of water per unit area of the laminate for growing rice seedlings is preferably 300 to 15000g/m²More preferably 1000 to 10000g/m²Particularly preferably 2000 to 8000g/m². When the water content is within the above range, good germination and growth of seeds can be easily obtained. The adjustment of the water content to the above range may be performed by mixing the ingredients constituting the bed layer and/or the ingredients constituting the cover layer with water to prepare each layer, or may be performed by filling water after preparing the bed layer and/or the cover layer.

When the laminate for rice seedling growth contains water, the water-absorbent resin layer preferably contains the water-absorbent resin in an amount (X) (g/m)²) And the content of water (Y) (g/m)²) Satisfies the following formula (I): 5 is less than or equal to content (Y)/content (X) is less than or equal to 500 (I). The content (Y)/the content (X) is more preferably 10 or more, further preferably 15 or more, particularly preferably 20 or more, more preferably 200 or less, further preferably 100 or less, particularly preferably60 or less. When the content (Y)/the content (X) is not less than the lower limit value and not more than the upper limit value, more favorable sprouting and growth of the seed can be easily obtained. Here, the content (X) of the water-absorbent resin means a value in a dry state as described above.

[ culture soil layer ]

In one embodiment of the present invention, when one of the bed soil layer and the mulch film is a water-absorbent resin layer, the other is a culture soil layer containing more than 20 mass% of culture soil based on the mass of the layer, and the content of the culture soil layer in the layered body for rice seedling raising is 1000 to 50000g/m². When the layered body for raising rice seedlings includes the culture soil layer, roots grow in the gaps of the culture soil, and the roots easily and appropriately intertwine with each other, so that a preferable strength of the carpet-like seedling is easily obtained. In addition, the excellent drainage and air permeability of the layered body for raising rice seedlings can be easily obtained due to the gaps of the culture soil. When the water-absorbent resin layer or the culture soil layer contains the water-absorbent resin and the culture soil, the layer containing the water-absorbent resin in a larger amount than the culture soil is referred to as a water-absorbent resin layer, and the layer containing the culture soil in a larger amount than the water-absorbent resin is referred to as a culture soil layer.

In a preferred embodiment of the present invention, the bed layer is a water-absorbent resin layer, from the viewpoint of easily obtaining a preferred strength of the carpet-like seedling. In a further preferred embodiment, the bed soil layer is a water-absorbent resin layer, and the cover soil layer is a culture soil layer.

The content of the culture soil layer in the laminated body for raising rice seedlings is preferably 1000-50000 g/m²More preferably 2000 to 10000g/m²Particularly preferably 3000 to 10000g/m². When the content of the culture soil layer is within the above range, the effect of reducing the burden of agricultural activities can be easily obtained in addition to the effects of the strength of the blanket-like seedling and the drainage and air permeability of the laminate for rice seedling raising.

The content of the culture soil contained in the culture soil layer is preferably more than 20 mass%, more preferably 50 mass% or more, and particularly preferably 70 mass% or more, based on the mass of the culture soil layer. The upper limit of the content is not particularly limited, and the content may be 100 mass% or less. When the content is not less than the lower limit, the strength of the blanket-like seedling and the drainage property and air permeability of the laminate for raising rice seedlings can be easily obtained.

[ culture soil ]

The culture soil is not particularly limited, and those commonly used in the art can be used.

The culture soil is preferably granular from the viewpoint of easily obtaining more excellent drainage and air permeability. When the culture soil is granular, the average particle diameter is preferably 0.2 to 20mm, more preferably 0.5 to 10mm, and particularly preferably 1 to 5 mm. In order to adjust the average particle size of the granular culture soil within the above range, commercially available granular culture soil for rice may be used by sieving. For the production of the granular culture soil, granulation methods such as a compression granulation method, an extrusion granulation method, a rolling granulation method, and a fluidized bed granulation method can be used. The average particle diameter of the granular culture soil can be determined by the method described in the examples below.

[ optional ingredients ]

The culture soil layer may contain optional components in addition to the culture soil. Such optional ingredients can be incorporated into the culture soil layer by the following method: a method of premixing the raw material for culture soil with optional components and granulating; a method of spraying a solution or dispersion of an optional ingredient to the granulated culture soil; a method of premixing an optional ingredient (e.g., a water-absorbent resin) with other optional ingredients (e.g., a fertilizer or a pesticide) and mixing the resulting mixture with culture soil; a method of spraying a solution or dispersion of other optional ingredients (e.g., a fertilizer or a pesticide) to a mixture of the optional ingredients (e.g., a water-absorbent resin) and culture soil; and the like.

As such optional components, there may be mentioned: the water-absorbent resin as described above, a resin other than the water-absorbent resin as described above; peat, peat moss, coconut chaff, rice hulls, humus materials, charcoal, diatomite calcined particles, beidellite powder, shell powder, crab shells, VA mycorrhizal fungi, microorganism materials and other animal and plant materials; minerals such as vermiculite, perlite, bentonite, natural zeolite, synthetic zeolite, gypsum, fly ash, asbestos, kaolin, smectite, montmorillonite, sericite, chlorite, glauconite and talc; fertilizers such as bark compost; and combinations of more than one of them. These optional components may be used after being sterilized or disinfected as necessary, or may be used together with a pH adjuster or a pesticide.

Thus, in a preferred embodiment of the invention, the bed or casing layer further comprises one or more ingredients selected from the group consisting of peat moss, coconut coir, rice hulls, vermiculite, perlite, fertilisers and pesticides.

When the culture soil layer contains the above optional components, the total content thereof is usually 80% by mass or less, preferably 50% by mass or less, and more preferably 30% by mass or less, based on the total mass of the culture soil layer, as long as the effect of the present invention is not impaired.

Examples of fertilizers include: nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer; fertilizers containing plant essential elements such as calcium, magnesium, sulfur, iron, copper, manganese, zinc, boron, molybdenum, chlorine, nickel and the like; compost such as bark compost, cow dung, pig dung, chicken dung, water-containing garbage, pruning and the like. Examples of the nitrogen-based fertilizer include ammonium sulfate, ammonium chloride, ammonium nitrate, sodium nitrate, calcium nitrate, humic acid ammonia fertilizer, urea, lime nitrogen, calcium ammonium nitrate, sodium ammonium nitrate, and magnesium nitrate fertilizer; examples of the phosphorus-based fertilizer include calcium superphosphate, triple superphosphate, a molten phosphate fertilizer, a humic acid phosphate fertilizer, sintered phosphorus (sintered リン), double-sintered phosphorus (sintered リン), リンスタ -product, magnesium superphosphate, a mixed phosphate fertilizer, a byproduct phosphate fertilizer, and high-concentration phosphoric acid; examples of the potassium-based fertilizer include potassium sulfate, potassium chloride, potassium magnesium sulfate, potassium carbonate, potassium hydrogen carbonate, potassium silicate, and the like. These fertilizers may be used in the form of solid, paste, liquid, solution, etc., or may be used in the form of coated fertilizers.

Examples of the agricultural chemicals include insecticides, fungicides, insecticidal and fungicidal agents, herbicides, rodenticides, antiseptics, plant growth regulators, and the like.

In the case where the laminate for raising rice seedlings of the present invention contains a fertilizer, in a preferred embodiment, the fertilizer is used in the form of a coated fertilizer. The coated fertilizer is a fertilizer obtained by coating a fertilizer with a resin. Examples of the resin include polyolefins. In the case of using a coated fertilizer, the fertilizer can be supplied to the soil over time as the resin is decomposed. In addition, when the coated fertilizer is granular, the strength of the obtained blanket seedlings tends to be high. The average particle size of the coated fertilizer is preferably 1mm to 10mm, more preferably 3mm to 6 mm. When the coated fertilizer is used, the content of the coated fertilizer in the layered product for raising rice seedlings is preferably 10 to 99.99% by mass, more preferably 15 to 90% by mass, particularly preferably 20 to 80% by mass, and most preferably 30 to 60% by mass. When a coated fertilizer is used, the content of the culture soil in the layered body for growing rice seedlings may be 20 to 80% by mass.

Seeds can be sown in the laminate for rice seedling culture of the present invention. Therefore, in one embodiment of the present invention, the laminate for raising rice seedlings of the present invention further contains rice. In one embodiment of the present invention, the rice is in a seed state, and in another embodiment of the present invention, the rice is in a seedling state.

The content of the rice in the seed state is preferably 50 to 5000g/m per unit area of the layered body for raising rice seedlings²More preferably 500 to 3000g/m²Particularly preferably 1000 to 2000g/m². When the content is within the above range, sufficient strength of the blanket-shaped seedling can be easily obtained.

In the present invention, as described above, in the embodiment in which the rice seedling raising laminate contains rice seeds, the layer below the seeds is referred to as a bed soil layer, and the layer above the seeds is referred to as a cover soil layer. That is, in this method, it is intended to sow rice seeds on the boundary line between the bed soil layer and the overburden layer. For example, in the case where the water absorption rate of the laminate for rice seedling raising or the water-absorbent resin is insufficient, or in the case where the water content of the bed soil layer is large, the rice seeds to be sown may not be present on the boundary line. However, the laminate for rice seedling cultivation or the water-absorbent resin of the present invention exhibits an excellent water absorption rate and can hold a large amount of water, so that the sown rice seeds can stay in the vicinity of the boundary line. The rice in the seed state is present in a region within preferably 20mm, more preferably 10mm, still more preferably 5mm, and particularly preferably 2mm from the boundary line between the bed soil layer and the overburden layer.

The mass of the laminate for raising rice seedlings of the present invention is preferably 28kg/m²Below, more preferably 20kg/m²The amount of the surfactant is preferably 15kg/m or less²The amount of the organic solvent is preferably 10kg/m or less²The following. The "mass of the laminate for rice seedling" means the total mass of the components of the laminate for rice seedling per unit area of the laminate for rice seedling, that is, the total mass of the bed soil, the cover soil, and optional components such as water, rice, and fertilizer, as the case may be, per unit area of the laminate for rice seedling.

As a method for evaluating the quality of a laminate for rice seedling raising, in the examples described later, "total mass of materials" more practically used is used in addition to the "quality of a laminate for rice seedling raising" described above. The "total mass of materials" refers to the total mass of the above-mentioned total mass (total mass of bed soil and covering soil, and optional components such as water, rice, and fertilizer in some cases) and the mass of the rice seedling box per 1 box of the rice seedling box, as described in examples below. On the other hand, operations such as the entry and exit into and from the sprouting warehouse and the setting of seedlings to a rice transplanter are still often performed manually. Therefore, the lighter the total weight of materials, the more the burden on agricultural activities can be reduced. According to the japanese work standard law, in the general work for weight handling for women, when it is specified that less than 20kg is performed and the total mass of materials is 5kg, only 3 boxes can be simultaneously transported. The total mass of the materials is preferably less than 4kg, in which case 5 boxes can be transported simultaneously. The total mass of the materials is more preferably less than 3kg, in which case 6 boxes can be transported simultaneously, and even more preferably less than 2kg, in which case 10 boxes can be transported simultaneously. Therefore, the total mass of the materials in the present invention is preferably 4000 g/tank or less, more preferably 3000 g/tank or less, and particularly preferably 2000 g/tank or less.

The present invention is also directed to a carpet-like seedling comprising the laminate for growing rice seedlings of the present invention. The laminate for rice seedling growth of the present invention contains a water-absorbent resin, and thus can reduce the weight and/or irrigation load. In the laminate for rice seedling of the present invention, the content of the water-absorbent resin is optimized, so that the sown seeds can be well germinated and grown, and the roots of rice can be sufficiently grown and intertwined with each other. Thus, the blanket-shaped seedling of the present invention can have properties (for example, tensile strength, mountability to a rice transplanter, scraping property, standing of the seedling at the time of scraping, and non-collapsibility of the seedling at the time of scraping) suitable for installation in a rice transplanter.

The tensile strength of the blanket seedlings is an index of the resistance of the blanket seedlings to collapse, and the higher the tensile strength is, the better the workability when the blanket seedlings are set in the rice transplanter. The tensile strength of the carpet-like seedling can be measured by the method described in the examples described later, and is preferably 0.3kgf/10cm (2.9N/10cm) or more, more preferably 0.5kgf/10cm (4.9N/10cm) or more, and still more preferably 1.0kgf/10cm (9.8N/10cm) or more. When the tensile strength of the carpet-like seedling is above the lower limit value, the carpet-like seedling is not easily collapsed even if the overground part of the carpet-like seedling is lifted with both hands. The tensile strength of the carpet-like seedling is particularly preferably 1.5kgf/10cm (14.7N/10cm) or more, and in this case, the seedling is less likely to collapse even if the overground part of the carpet-like seedling is lifted with one hand.

Seeding of seeds is often performed in a rice seedling raising box into which a laminate for rice seedling raising is introduced. Therefore, the present invention is also directed to a rice seedling raising box into which the laminate for rice seedling raising of the present invention and water are introduced. The content of the rice in the seed state is usually 100 to 500g per 1 case of a rice seedling raising case (usually 28cm in length × 58cm in width). When the amount of seeds per 1 box is more than 250 to 500g, the amount of water lost by transpiration during seedling raising increases, but the laminate for rice seedling raising of the present invention has good water retentivity, and even in such a case, the irrigation load can be reduced by using the laminate for rice seedling raising of the present invention.

The rice seedling raising box can be produced, for example, by the following method, and the present invention is also directed to the method: a method for manufacturing a rice seedling raising box into which a layered body for rice seedling raising including a bed soil layer and a cover soil layer is introduced, the method comprising a step of introducing bed soil into the rice seedling raising box, a step of sowing rice in a seed state, and a step of introducing cover soil, wherein one or both of the bed soil and the cover soil comprises a particulate water-absorbent resin, the water-absorbent resin is disposed so that at least a part of the rice can come into contact with the water-absorbent resin, and the content of the water-absorbent resin in the layered body for rice seedling raising is 1 to 5000g/m²。

In a preferred embodiment of the present invention, the content of the water-absorbent resin in each soil (bed soil or casing soil) is preferably more than 80 mass%, more preferably 90 mass% or more, and particularly preferably 95 mass% or more, based on the mass of each soil. The content of the water-absorbent resin in each soil may be 100% by mass, that is, each soil may be composed of only the water-absorbent resin. Both soils (bed soil and covering soil) may satisfy the content of the water-absorbent resin, but more preferably, only one of the bed soil and the covering soil satisfies the content of the water-absorbent resin. When the content is not less than the lower limit, the burden of agricultural activities can be reduced.

The rice seedling raising box is usually produced in line production by using a belt conveyor or the like. Therefore, a certain degree of water absorption rate is required for the laminate for rice seedling raising or the water-absorbent resin. The laminate for rice seedling culture or the water-absorbent resin of the present invention can exhibit an excellent water absorption rate that sufficiently meets the demand. In addition, in the flow work, introduction of bed soil and/or covering soil is often performed using a hopper or the like. Therefore, in a preferred embodiment of the present invention, the introduction of the bed soil and/or the casing soil is performed using a hopper in the method of the present invention. The production of a rice seedling raising box into which a rice seedling raising laminate comprising a bed soil layer and a cover soil layer is introduced by using a hopper can improve the productivity of the rice seedling raising laminate or the rice seedling raising box.

Examples

The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to these examples.

[ evaluation items and evaluation methods ]

(1) The contents of the water-absorbent resin, water, culture soil layer or rice seed in the laminate for growing rice seedlings

The content (g/m) of the water-absorbent resin, water, culture soil layer or rice seed in the laminate for growing rice seedlings²) Dividing the mass (g) of the water-absorbent resin, water, culture soil or rice seeds contained in the laminate for growing rice seedlings by the area (m) of the upper surface of the laminate for growing rice seedlings²) And then the result is obtained.

(2) Average particle diameter of granular culture soil

30 particles were randomly selected from the granular culture soil, the diameter of each particle was measured with a vernier caliper, and the average value was defined as the average particle diameter of the granular culture soil. When the particle is not spherical, the average value of the longest side and the shortest side is defined as the diameter of the particle.

(3) Thickness of bed and cover

The thickness from the lower surface of the bed soil layer (usually the bottom of the seedling box) to the upper surface of the bed soil layer is measured as the thickness of the bed soil layer using a ruler. In addition, the thickness from the lower surface of the overburden to the upper surface of the overburden is measured using a ruler as the thickness of the overburden. Any measurement was carried out after the production of the seedling box, and the value in the water-absorbed state was measured.

(4) Volume average particle diameter of Water-absorbent resin

The volume average particle diameter of the water-absorbent resin was measured using a laser diffraction/scattering particle diameter distribution measuring apparatus.

(5) The ratio W of pure water in which the water potential in a mixture of a water-absorbent resin and pure water 50 times the mass of the water-absorbent resin is 0 to 3

2.4g of a sample mixture containing pure water in an amount of 50 times by mass of the water-absorbent resin was introduced into a syringe, and the syringe was fixed inside a centrifugal tube so as to be positioned 10.2cm from the center of a small centrifugal separator "H-36" manufactured by Kokusen, Ltd. The centrifuge was rotated at 2200rpm for 60 minutes, and W was calculated based on the following equation. However, when 50 times by mass of pure water was not absorbed by the crosslinked copolymer, 2.4g of the resin after saturated water absorption was introduced into a syringe.

W [ { (amount of sample mixture before centrifugation) - (amount of sample mixture after centrifugation) }/(amount of sample mixture before centrifugation) ] × 100

(6) Position of rice seed in laminate for growing rice seedlings

The distance in the vertical direction from the boundary line of the bed soil layer and the overburden layer to the center of the rice seed was measured using a ruler. The above-described operation was performed on a total of 10 rice seeds selected at random, and when 9 or more of them were within 5mm from the boundary, they were judged to be "present".

(7) Quality of laminate for growing rice seedlings

Weight (kg/m) of laminate for growing rice seedlings²) Dividing the total mass (kg) of the components (optional components such as bed soil, covering soil, and optionally water, rice, fertilizer, etc.) constituting the laminate for growing rice seedlings by the area (m) of the upper surface of the laminate for growing rice seedlings²) And then the result is obtained.

[ Water absorption of layered product for growing Rice seedlings, Exchequer and growth and development survey ]

(8) Completion time of water absorption during irrigation

The time from the completion of the sprinkling irrigation to the disappearance of the water surface in the rice seedling raising box to the emergence of the bed soil (water absorption completion time) was measured. When the rice is sown in a state where the water surface is present, the positions of the sprouted rice (rice seeds) are shifted, and the uniformity of sprouting in the rice seedling box is reduced. Therefore, the shorter the water absorption completion time is, the more the productivity of the seedling raising box production is improved. The water absorption completion time is preferably 12 seconds or less.

(9) Aggregate mass of materials

The total mass (g/case) of the materials was determined by adding the total of the bed soil mass, the soil covering mass, the fertilizer mass, the bed soil irrigation amount, the leveling irrigation amount, the rice seedling box mass and the germination accelerating rice mass.

(10) Exit investigation (2 days after sowing)

(10-1) sprouting percentage

The number of shoots that grew on the casing after germination was counted visually (N1). The germination percentage was calculated from the number of seeded pregerminated rice (N2) according to the following equation.

Bud ratio [% ]/N2 [% ] x 100 [% ]

When the sprouting rate is 0%, it is not suitable as a laminate for raising rice seedlings.

(10-2) suitability for seed sowing machine

The water-absorbent resin was charged into a hopper for bed soil of a seeder (manufactured by kusho corporation, SR 4500). The suitability of the seed sowing machine is "a" when the water-absorbent resin is fed out from the hopper, and the suitability of the seed sowing machine is "B" when the water-absorbent resin cannot be fed out.

(10-3) production of mold

The occurrence of mold was visually observed and evaluated according to the following criteria.

A: the generation of mold could not be confirmed.

B: although the generation of mold was confirmed, the area of the upper surface of the laminate for rice seedling growth covered with mold was 5% or less.

C: the mold was observed to be generated, and the area of the upper surface of the laminate for rice seedling growth covered with the mold was more than 5%.

(10-4) number of exposed unhulled rice (N3)

The number of exposed rice grains was counted by visual observation.

(10-5) bare root number of paddy (N4)

The number of bare roots was counted by visual observation.

(11) Ex-warehouse survey (11 days after sowing)

(11-1) NDVI value

NDVI (normalized differential vegetation index) values of seedlings were determined using a GreenSeeker hand-held crop sensor (manufactured by ニコントリンブル). Higher values indicate more active shoots.

(12) Growth investigation (any of 15-22 days after sowing)

(12-1) height of crop growth

The length from the upper surface of the rice seedling laminate to the upper end of the seedling was measured for 10 seedlings sampled at random, and the average value thereof was used as the crop growth height.

(12-2) leaf color

The leaf color of 10 randomly sampled seedlings was measured using a leaf color colorimeter (manufactured by Fuji photo industries Co., Ltd.), and the average value thereof was used as the leaf color.

(12-3) age of leaves

The leaf age was visually determined for 10 seedlings sampled at random, and the average value thereof was used as the leaf age.

(12-4) tensile Strength of Blanket seedlings

Cutting the blanket-shaped seedling into strips with the width of 10cm multiplied by 20cm, fixing one side of the short side (the fixed range: 10cm multiplied by 4cm), and connecting the other side with a spring scale (the connected range: 10cm multiplied by 4 cm). And stretching the spring balance until the blanket seedlings are broken, and measuring the maximum stress.

(13) Absorption capacity of pure water

The pure water absorption amounts of the water-absorbent resins used in examples and comparative examples were measured in accordance with JIS K7223, and the pure water absorption amount per unit mass [ g/g ] of the samples was calculated based on the following equation.

Pure water absorption [ g/g ] (sample mass after pure water absorption) - (sample mass before pure water absorption) ]/(sample mass before pure water absorption)

Here, the "sample mass before pure water absorption" is a value measured using 0.1g of the water-absorbent resin.

[ materials used ]

Granular culture soil a: ニユ - クリ - ン culture soil and fertilizer content N-P₂O₅-K₂O0.5-0.8-0.5 g/kg, average particle diameter 2.7mm

Granular culture soil B: manufactured by Lanbei trade company, does not contain fertilizer and has the average grain diameter of 3.3mm

Coconut husk: manufactured by Green soils

Sphagnum: manufactured by T & H Corp

Vermiculite: manufactured by Kabushiki Kaisha エス & ケ & アグリ

Rice husk

Water-absorbent resin a: synthesized by the method of [ Synthesis of Water-absorbent resin A ] described later.

Water-absorbent resin B: synthesized by the method of [ Synthesis of Water-absorbent resin B ] described later.

Water-absorbent resin C: synthesized by the method of [ Synthesis of Water-absorbent resin C ] described later.

Water-absorbent resin D: アクアキ - プ (polyacrylate gel) manufactured by Sumitomo refining Co., Ltd

Water-absorbent resin E: アクアコ - ク (polyethylene glycol gel) manufactured by Sumitomo refining Co., Ltd

Water-absorbent resin F: KI gel (isobutylene-maleate salt type gel) manufactured by Coli, K.K

Water-absorbent resin G: アクアソ - ブ 3005KB (polyacrylamide gel) manufactured by SNF ホ - ルデイングカンパニー

[ Table 1]

Table 1: characteristics of Water-absorbent resin

[ Synthesis starting materials ]

Glyoxylic acid monohydrate, 40 mass% aqueous glyoxal solution, 25 mass% aqueous glutaraldehyde solution, acetonitrile, methanol, vinyl acetate, sodium hydroxide, methyl acrylate, and azobisisobutyronitrile; manufactured by Wako pure chemical industries, Ltd

Polyvinyl alcohol A; ELVANOL (registered trademark) 71-30 manufactured by Colorado US

[ Synthesis of Water-absorbent resin A ]

Into a 500mL four-neck separable flask equipped with a reflux condenser and a stirring blade, 12.55g of glyoxylic acid monohydrate, 0.11g of a 40 mass% aqueous glyoxal solution, 12.55g of ion-exchanged water, 150mL of acetonitrile, and 40.0g of polyvinyl alcohol A were introduced and stirred for 1 hour at 23. After the temperature of the resulting mixture was raised to 70, 16.87g of a 25 mass% aqueous sulfuric acid solution was added dropwise over 10 minutes, and the reaction was carried out for 6 hours while maintaining the temperature at 70. After cooling to 30, 150mL of ion-exchanged water was added, and the resin was removed by filtration. Subsequently, the filtered resin was washed 5 times with 200mL of methanol. The washed resin was introduced into a 500mL four-neck separable flask equipped with a reflux condenser and a stirring blade, and 180mL of methanol, 11.6mL of ion-exchanged water, and 16.8mL of an 8mol/L aqueous potassium hydroxide solution were added to the flask, followed by reaction under reflux for 2 hours. The resin was taken out by filtration, and the resin thus collected was washed 6 times with 200mL of methanol and vacuum-dried for 6 hours at 40 ℃ to obtain the objective vinyl alcohol polymer (referred to as "water-absorbent resin A").

[ Synthesis of Water-absorbent resin B ]

To a reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet, and an initiator addition port, 602g of vinyl acetate, 1.21g of methyl acrylate, and 254g of methanol were introduced, and the inside of the reactor was purged with an inert gas for 30 minutes while bubbling nitrogen gas. The temperature rise of the reactor was started using a water bath, and when the internal temperature of the reactor reached 60 ℃, 0.16g of Azobisisobutyronitrile (AIBN) as an initiator was added to start polymerization. Appropriate sampling was performed, and the progress of polymerization was confirmed from the solid content concentration, and the consumption rate, that is, the total mass of vinyl acetate and methyl acrylate consumed by polymerization with respect to the total mass of vinyl acetate and methyl acrylate introduced was determined. When the consumption rate reached 4%, the internal temperature of the reactor was cooled to 30, and the polymerization was stopped. The residual vinyl acetate was distilled off together with methanol at 30 ℃ under reduced pressure in connection with a vacuum line. While the inside of the reactor was visually checked, methanol was appropriately added when the viscosity increased, and the distillation was continued to remove the methanol, thereby obtaining polyvinyl acetate containing 5.2 mol% of an acrylic acid structural unit. Content of acrylic acid structural units Using solids¹³C-NMR was measured.

Then, 1g of the obtained polyvinyl acetate containing an acrylic acid structural unit and 18.2g of methanol were added to the same reactor to dissolve the polyvinyl acetate containing an acrylic acid structural unit. The temperature of the reactor was raised using a water bath, and the reactor was heated with stirring until the internal temperature of the reactor reached 70 ℃. 0.78g of a methanol solution of sodium hydroxide (basic methanol, concentration: 15% by mass) was added thereto, and saponification was carried out at 70 for 2 hours. The obtained solution was filtered to obtain polyvinyl alcohol (hereinafter referred to as "polyvinyl alcohol B") containing 5.2 mol% of an acrylic acid constitutional unit.

Into a three-neck separable flask equipped with a reflux condenser and a stirring blade, 58.9g of acetonitrile, 6.28g of ion-exchanged water, 0.171g of a 25 mass% glutaraldehyde aqueous solution, and polyvinyl alcohol B20g were introduced, and stirred at 23 to disperse polyvinyl alcohol B. 12.38g of a 16.9 mass% aqueous sulfuric acid solution was added dropwise over 15 minutes, and the temperature was raised to 65 ℃ to allow the reaction to proceed for 6 hours. After the reaction, the resin was taken out by filtration, and the resin thus taken out was washed 6 times with 160g of methanol. The washed resin was introduced into a three-neck separable flask equipped with a reflux condenser and a stirring blade, and 71g of methanol, 13.3g of ion-exchanged water and 5.7g of potassium hydroxide were added thereto, followed by reaction for 2 hours at 65. After the reaction, the resin was taken out by filtration, and then the resin taken out by filtration was washed 6 times with 160g of methanol and vacuum-dried for 12 hours at 40 to obtain the objective vinyl alcohol polymer (referred to as "water-absorbent resin B").

[ Synthesis of Water-absorbent resin C ]

The procedure was carried out in the same manner as in [ Synthesis of Water-absorbent resin B ] except that the mass of the 25 mass% glutaraldehyde aqueous solution was changed from 0.171g to 0.086g, to obtain the objective vinyl alcohol-based polymer (referred to as "Water-absorbent resin C").

Example 1

A water-absorbent resin A as bed soil was mixed with pure water and placed in a rice seedling box (670g) having an internal size of 58 cm. times.28 cm. After uniformly spreading germination accelerating paddy (variety: コシヒカリ), granular culture soil a as soil covering was applied thereon to prepare a rice seedling raising box into which a laminate for raising rice seedlings and water were introduced. The above operation was further performed twice to prepare 3 identical rice seedling raising boxes into which the stacked body for raising rice seedlings and water were introduced. Sprouting was carried out in a sprouting silo at 30 and 100% RH for 48 hours, and then ex-silo investigation was carried out. Table 2 shows the results of changing the water-absorbent resin content and the water content (corresponding to the amount of pure water to be mixed; shown as "bed soil irrigation amount" in the table) in the laminate for raising rice seedlings as examples 1-1 to 1-15.

In both examples and comparative examples, pregerminated rice (variety: コシヒカリ) was used, but different batches of pregerminated rice were used in each of tables 2 to 9. In tables 2 to 9, examples and comparative examples were carried out on different dates.

Comparative example 1

A rice seedling raising box into which a laminate for raising rice seedlings and water were introduced was produced in the same manner as in example 1-1 except that the granular culture soil A was used as a bed soil instead of the water-absorbent resin A, and ex-warehouse examination was performed. The results are shown in table 2.

Comparative examples 2 to 3

A rice seedling raising box into which the layered product for raising rice seedlings and water were introduced was produced in the same manner as in example 1-1 except that the content of the water-absorbent resin a in the layered product for raising rice seedlings was changed, and ex-warehouse examination was performed. The results are shown in table 2.

In comparative example 2, the ratio of the amount of the water-absorbent resin to the bed soil was excessive, and the bed soil was in a gel state. The sprouted rice sinks into the inside of the gel-like bed soil, and is present within 5mm from the boundary between the bed soil layer and the covering soil layer, but is not present within 2mm from the boundary.

Comparative example 4

A rice seedling raising box into which a laminate for rice seedling raising and water were introduced was produced in the same manner as in examples 1 to 11, except that, instead of the operation of mixing the water-absorbent resin a as bed soil with pure water and then placing the mixture in the rice seedling raising box, a sheet-like water-absorbent resin a prepared by sandwiching the water-absorbent resin a between two nonwoven fabrics (manufactured by king paper-making co., プロワイプソフトハイワイパー S150) was placed in the rice seedling raising box, and pure water was added thereto, and a shipment examination was performed. The results are shown in table 2.

Example 2

A rice seedling raising box into which a rice seedling raising laminate and water were introduced was produced in the same manner as in example 1-6 except that the water-absorbent resin B was used as the bed soil instead of the water-absorbent resin A, and shipment examination was performed (examples 2-1, 2-2, and 2-4 to 2-6). A rice seedling raising box into which a laminate for raising rice seedlings and water were introduced was produced in the same manner as in examples 1 to 6 except that the water-absorbent resin B was used as bed soil instead of the water-absorbent resin A, and ex-warehouse examination was performed (examples 2 to 3). The results are shown in table 3.

Comparative example 5

A rice seedling raising box into which a laminate for raising rice seedlings and water were introduced was produced in the same manner as in examples 2 to 6 except that the granular culture soil A was used as bed soil instead of the water-absorbent resin B, and ex-warehouse examination was performed. The results are shown in table 3.

Example 3

A rice seedling raising box into which a layered body for raising rice seedlings and water were introduced was produced in the same manner as in example 2 except that the quality of the granular culture soil a as the covering soil was changed, and ex-warehouse examination was performed. Table 4 shows the results of varying the water content in the layered product for raising rice seedlings, as examples 3-1 to 3-6.

Comparative example 6

A rice seedling raising box into which a laminate for raising rice seedlings and water were introduced was produced in the same manner as in examples 3 to 6 except that the granular culture soil A was used as the bed soil instead of the water-absorbent resin B and the quality of the covering soil was changed, and ex-warehouse examination was performed. The results are shown in table 4.

As is clear from tables 2 to 4, the layered product for raising rice seedlings of the present invention (examples 1-1 to 1-15, and examples 2-1 to 1)2-6 and examples 3-1 to 3-6) the total mass of materials and the mass of the laminate for raising rice seedlings were lighter than those of the laminates not containing a water-absorbent resin (comparative examples 1, 5 and 6), and the burden of agricultural activities could be reduced. The laminate contains a water-absorbent resin, and the content of the water-absorbent resin in the dry state is not 1 to 5000g/m²In the case of (comparative examples 2 to 3), although weight reduction can be achieved, the layered product is not germinated, and such a layered product is not suitable as a layered product for raising rice seedlings.

When the effects on the water content [ or the water content (Y)/the water-absorbent resin content (X) ] are compared in examples having the same water-absorbent resin content (comparison between example 1-3 and example 1-4, comparison between examples 1-6 to 1-9, comparison between example 1-11 and example 1-12, comparison between examples 2-1 to 2-6, and comparison between examples 3-1 to 3-6), the sprouting rate is high because the water content is in a certain range, and such a laminate is more excellent as a laminate for raising rice seedlings.

When the water-absorbent resin was in the form of particles (examples 1 to 11), the compatibility with a seed sowing machine was superior to that when the water-absorbent resin was used in the form of a sheet (comparative example 4). In addition, in the case where the water-absorbent resin was in contact with at least a part of the seeds (examples 1 to 11), the growth was excellent as compared with the case where the water-absorbent resin was not in contact (comparative example 4). This is considered to be because water is efficiently supplied from the water-absorbent resin to the seeds.

Example 4 and comparative example 7

The bed soil described in table 5 was laid in a rice seedling raising box having an internal dimension of 58cm × 28cm, and the rice seedling raising box on which the bed soil was laid was placed in a sowing facility (model SR4500, manufactured by kusho corporation) and was irrigated by spraying at the bed soil irrigation amount described in table 5 while being conveyed by a conveyor. After uniformly spreading the sprouted rice (variety: コシヒカリ), the water was evenly irrigated at the level irrigation amount shown in Table 5. The soil covering shown in table 5 was applied thereon to prepare a rice seedling raising box into which the stacked body for raising rice seedlings and water were introduced. In addition, fertilizers (ammonium sulfate, calcium superphosphate, and potassium chloride) were previously added to the granular culture soil B, coconut coir, peat moss, vermiculite, and rice husk so that the contents of the fertilizers were in the amounts shown in table 5. The above operation was further performed twice to prepare 3 identical rice seedling raising boxes into which the stacked body for raising rice seedlings and water were introduced. Sprouting was carried out in a sprouting silo at 30 and 100% RH for 48 hours, and then ex-silo investigation was carried out. Then, the rice seedling raising box is moved into a glass house to raise the seedlings. Table 5 shows the results of a growth investigation conducted while varying the types of bed soil and covering soil, the contents of water (the amount of water poured into the bed soil), water-absorbent resin and culture soil in the layered body for raising rice seedlings, as examples 4-1 to 4-13. Further, as comparative example 7, the results of the growth and development investigation when the granular culture soil B was used as bed soil and covering soil are shown.

Example 5 and comparative example 8

A laminate for raising rice seedlings and a rice seedling raising box were produced in the same manner as in example 4 except that the bed soil and the cover soil described in Table 6 were used in the amounts of water poured into the bed soil and the cover soil described in Table 6, and the amount of water poured into the bed soil was changed from 500 to 1000 g/box to 1400 g/box, and ex-warehouse investigation and growth and development investigation were conducted. In addition, the water absorption completion time was also measured. The results are shown in Table 6 as example 5-1 to example 5-3 and comparative example 8.

Example 6 and comparative example 9

A laminate for raising rice seedlings and a rice seedling raising box were produced in the same manner as in examples 4 to 9 except that the bed soil and the covering soil described in Table 7 were used in the amounts of water poured into the bed soil and changed from 500 g/box to 1000 g/box in the amounts of the soil and the covering soil described in Table 7, and then ex-warehouse examination and growth and development examination were conducted. In addition, the water absorption completion time was also measured. The results are shown in Table 7 as example 6-1 to example 6-12 and comparative example 9. In addition, fertilizers (ammonium sulfate, calcium superphosphate, and potassium chloride) were previously added to the granular culture soil B as the casing soil so that the content of the fertilizers was the amount shown in table 7.

Example 7 and comparative examples 10 to 11

A rice seedling laminate and a rice seedling box were produced in the same manner as in example 5-1, and ex-warehouse examination and growth and development examination were conducted (example 7-1). A rice seedling laminate and a rice seedling box were produced in the same manner as in example 5-1 except that the content of rice in the seed state was changed, and ex-warehouse examination and growth and development examination were performed (example 7-2). Further, a laminate for raising rice seedlings and a rice seedling raising box were produced in the same manner as in comparative example 8, and ex-warehouse examination and growth and development examination were performed (comparative example 10). Except that the content of the rice in the seed state was changed, a laminate for raising rice seedlings and a rice seedling raising box were produced in the same manner as in comparative example 8, and ex-warehouse examination and growth and development examination were performed (comparative example 11). The results are shown in table 8.

Example 8 and comparative examples 12 to 15

Except for changing the quality of the covering soil and the content of the fertilizer, a laminate for raising rice seedlings and a rice seedling raising box were produced in the same manner as in example 5-1, and ex-warehouse examination and growth and development examination were performed (examples 8-1 to 8-4). Other than changing the quality of the bed soil and the covering soil and the fertilizer content, a laminate for raising rice seedlings and a rice seedling raising box were produced in the same manner as in comparative example 8, and ex-warehouse examination and growth and development examination were performed (comparative examples 12 to 15). The NDVI values and the results of the growth and development investigation when irrigation management after sprouting was changed are shown in table 9.

As is clear from tables 5 to 9, the laminates for raising rice seedlings of the present invention (examples 4-1 to 4-13, 5-1 to 5-3, 6-1 to 6-12, 7-1 to 7-2, and 8-1 to 8-4) have lighter total mass of materials and lighter laminates for raising rice seedlings than the laminates not containing a water-absorbent resin (comparative examples 7 to 15), and can reduce the burden on agricultural activities.

In the case of using granular culture soil as a covering soil layer (examples 4-1 to 4-3), the tensile strength of the carpet seedling was more excellent than that in the case of using coconut coir, peat moss, vermiculite or rice husk (examples 4-4 to 4-7). Further, in the case where the water-absorbent resin was used as the bed soil (examples 4-1 to 4-3), the tensile strength of the carpet-like seedlings was more excellent than that in the case where the water-absorbent resin was used as the covering soil (examples 4-8 to 4-9).

As is clear from Table 9, the layered product for raising rice seedlings of the present invention has a higher NDVI value and is more favorable for growth and development than the layered product for raising rice seedlings of the present invention containing no water-absorbent resin (the comparison between example 8-2 and comparative example 13, the comparison between example 8-3 and comparative example 14, and the comparison between example 8-4 and comparative example 15), even when the frequency and amount of water irrigation are low.

Example 9

The water-absorbent resin B1840 g was charged into a seeder SH2B manufactured by スズテツク. A seedling box made of polypropylene having an internal dimension of 16.2cm X18.8 cm was placed thereon, a seeder was caused to travel thereon in the longitudinal direction of the seedling box, and the water-absorbent resin B was put into the seedling box. The time for reducing the volume of the resin in the seeder from about 100% to about 95% was defined as the initial running time. The seeder was removed from above the seedling box and operated until about 20% of the resin volume in the seeder remained. Then, an empty seedling raising box of the same size was placed, a seeder was caused to travel thereon in the longitudinal direction of the seedling raising box, and the water-absorbent resin B was put into the seedling raising box. The time to reduce the resin volume in the seeder from about 20% to about 15% was taken as the end-of-travel time. The mass of the water-absorbent resin B contained in each seedling box was measured, and the input error of the water-absorbent resin was calculated by the following equation. The results are shown in table 10.

(ii) the charging error is { the amount (g) of the water-absorbent resin B charged at the initial stage of travel)/(the amount (g) of the water-absorbent resin B charged at the final stage of travel }

The closer the input error is to 1, the smaller the difference in the input amount of the water-absorbent resin between the seedling boxes when the seedling boxes are produced by using the seeding machine, and the more stable the seeding operation can be performed.

Example 10

40g of water-absorbent resin B and 1800g of granular culture soil A were placed in a polyethylene bag and mixed by shaking to prepare mixed culture soil. A seedling raising box containing the mixed culture soil for the initial period of travel and a seedling raising box containing the mixed culture soil for the final period of travel were produced in the same manner as in example 9, except that the mixed culture soil was put into a seeder instead of the water-absorbent resin B. The mixed culture soil contained in each seedling raising box was separated by a 600 μm sieve, and a material having a particle size of 600 μm or more was used as the granular culture soil A, and a material having a particle size of less than 600 μm was used as the water-absorbent resin B, and the input error of the water-absorbent resin B was calculated by the same calculation formula as in example 9. The results are shown in table 10.

[ Table 10]

Watch 10

As is clear from table 10, when the content of the culture soil in the water-absorbent resin layer was 20 mass% or less based on the mass of the water-absorbent resin layer (example 9), the error in the input of the water-absorbent resin was small and stable sowing work was possible when the seedling box was produced using the sowing machine. When the content of the culture soil in the water-absorbent resin layer was more than 20% by mass based on the mass of the water-absorbent resin layer (example 10), the water-absorbent resin and the granular culture soil were separated by the vibration during the operation of the sowing machine, and therefore, the error in the input of the water-absorbent resin was large, and the stable sowing operation could not be performed for a long period of time.

Industrial applicability

The laminate for raising rice seedlings of the present invention can reduce the burden of agricultural activities and does not inhibit the growth and development of rice, and therefore, can be suitably used as a rice seedling raising medium that meets the expectations of agricultural practitioners.

Description of the symbols

1 laminate for growing rice seedlings

2 bed soil layer

And 3 covering a soil layer.

Claims

1. A layered product for growing rice seedlings, which comprises a bed layer and a cover layer, wherein one or both of the bed layer and the cover layer is/are a water-absorbent resin layer comprising a particulate water-absorbent resin, the water-absorbent resin is disposed so that at least a part of rice can come into contact with the water-absorbent resin, and the water-absorbent resin content in the layered product for growing rice seedlings is 1 to 5000g/m²。

2. A laminate for raising rice seedlings according to claim 1, wherein the content of the culture soil in the water-absorbent resin layer is 20% by mass or less based on the mass of the water-absorbent resin layer.

3. A rice seedling raising laminate according to claim 1 or 2, wherein said water-absorbent resin content (X1) (g/m) in said bed soil layer²) And the content (X2) (g/m) of the water-absorbent resin in the soil covering layer²) Satisfies the following formula:

the content (X2)/the content (X1) is less than or equal to 0.2 or the content (X2)/the content (X1) is more than or equal to 5.

4. A rice seedling raising laminate as set forth in any one of claims 1 to 3, wherein the water-absorbent resin content (X2) in said covering layer is 70g/m²The following.

5. A rice seedling raising laminate according to any one of claims 1 to 4, wherein the water-absorbent resin layer contains more than 80 mass% of the water-absorbent resin based on the mass of each layer.

6. A rice seedling raising laminate according to any one of claims 1 to 5, which comprises water in an amount of 300 to 15000g/m²。

7. A rice seedling laminate as set forth in any one of claims 1 to 6, wherein the water-absorbent resin layer contains a water-absorbent resin in an amount (X) (g/m)²) And the content (Y) of water (g/m)²) Satisfies the following formula (I):

5 is less than or equal to content (Y)/content (X) is less than or equal to 500 (I).

8. A rice seedling raising laminate according to any one of claims 1 to 7, wherein one of the bed soil layer and the casing soil layer is the water-absorbent resin layer, the other is a culture soil layer containing more than 20 mass% of culture soil based on the mass of the layer, and the content of the culture soil layer in the rice seedling raising laminate is 1000 to 50000g/m²。

9. A laminate for raising rice seedlings according to claim 8, wherein said bed soil layer is said water-absorbent resin layer.

10. A rice seedling raising laminate according to claim 8 or 9, wherein the culture soil is granular and has an average particle diameter of 0.2 to 20 mm.

11. A rice seedling raising laminate according to any one of claims 1 to 10, wherein the thickness of said bed layer is 0.01 to 100 mm.

12. A rice seedling raising laminate according to any one of claims 1 to 11, wherein the thickness of the covering layer is 0.1 to 100 mm.

13. A rice seedling laminate according to any one of claims 1 to 12, wherein the water-absorbent resin has a volume average particle diameter of 1 to 10000 μm.

14. A rice seedling raising laminate according to any one of claims 1 to 13, wherein the water-absorbent resin contains a carboxyl group.

15. A rice seedling raising laminate according to any one of claims 1 to 14, wherein said water-absorbent resin has potassium ions as a counter cation.

16. A rice seedling laminate according to any one of claims 1 to 15, wherein said water-absorbent resin is a vinyl alcohol polymer.

17. The laminate for raising rice seedlings according to claim 16, wherein the vinyl alcohol unit of the polyvinyl alcohol is acetalized with at least one acetalizing agent selected from the group consisting of glyoxylic acid and glyoxylic acid derivatives.

18. A rice seedling laminate according to claim 16 or 17, wherein said vinyl alcohol polymer contains at least one monomer structural unit selected from the group consisting of acrylic acid, methacrylic acid and derivatives thereof.

19. A rice seedling raising laminate according to any one of claims 1 to 18, wherein in the mixture of the water-absorbent resin and pure water 50 times the mass of the water-absorbent resin, the pure water having a water potential of 0 to 3 is 10% by mass or more based on the mass of the pure water in the mixture.

20. A rice seedling laminate according to any one of claims 1 to 19, wherein the bed soil layer or the cover soil layer further contains one or more components selected from the group consisting of sphagnum moss, coconut husk, rice husk, vermiculite, perlite, a fertilizer and a pesticide.

21. A rice seedling raising laminate according to any one of claims 1 to 20, further comprising rice.

22. A rice seedlings raising laminate according to claim 21, wherein said rice is in a state of seed.

23. A rice seedling raising laminate according to claim 22, wherein the rice in a seed state is present in an area within 20mm from a boundary line between the bed soil layer and the casing soil layer.

24. A rice seedling raising laminate according to claim 22 or 23, wherein the content of the rice in a seed state is 50 to 5000g/m²。

25. A rice seedling raising laminate according to claim 21, wherein said rice is in a seedling state.

26. A rice seedling raising laminate according to any one of claims 1 to 25, wherein the rice seedling raising laminate has a mass of 28kg/m²The following.

27. A carpet seedling comprising the laminate for raising a rice seedling according to claim 25.

28. A rice seedling raising box into which the rice seedling raising laminate according to any one of claims 1 to 26 and water are introduced.

29. A method for manufacturing a rice seedling raising box into which a layered body for raising rice seedlings comprising a bed soil layer and a cover soil layer is introduced,

comprises a step of introducing bed soil into a rice seedling raising box, a step of sowing rice in a seed state and a step of introducing covering soil,

one or both of the bed soil and the covering soil contain a particulate water-absorbent resin,the water-absorbent resin is disposed so that at least a part of rice can come into contact with the water-absorbent resin, and the content of the water-absorbent resin in the layered body for raising rice seedlings is 1 to 5000g/m²。

30. The method of claim 29, wherein one or both of the bed soil and the casing soil comprises more than 80 mass% of the water-absorbent resin based on the mass of each soil.

31. A method as claimed in claim 29 or 30 wherein the introduction of the bed soil and/or casing soil is carried out using a hopper.