Solidified soil, set for producing the same, and method for producing the same

Abstract

To provide solidified culture soil having a high nitrogen content.SOLUTION: The solidified culture soil is a formed body obtained by solidifying granular culture soil containing woody biomass with calcium carbonate, and has soil hardness of 20kPa or more and a nitrogen content of 0. 7mg / g or more. In addition, the present invention provides a method for producing solidified culture soil, including a step of providing a first liquid containing urease and an aqueous medium, a second liquid containing urea and an aqueous medium, and a third liquid containing a calcium salt and an aqueous medium, a step of applying the first liquid, the second liquid, and the third liquid to particulate culture soil containing woody biomass, and a step of leaving the culture soil after the application to stand for 0.5 days or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solidified soil, a set for producing the same, and a method for producing the same. [Background technology]

[0002] With the recent mechanization of agriculture, the method of removing grown seedlings from containers with their root balls using a transplanter and planting them in a field is becoming increasingly common. However, since the root balls often lose their shape even with a slight impact, various methods of solidifying the culture medium used for raising seedlings have been investigated to prevent the root balls from collapsing. Patent Document 1 discloses a technique for solidifying the culture medium by adding a lactic acid resin and a plasticizer to the culture medium and then air-drying it, while Patent Document 2 discloses a technique for solidifying the culture medium by mixing tengusa pieces with the culture medium and then heating and cooling it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-176027 [Patent Document 2] Japanese Patent Application Publication No. 2018-42513 Summary of the Invention [Problem to be solved by the invention]

[0004] The method for producing solidified potting soil described in Patent Document 1 does not involve heat treatment during solidification, thereby reducing CO2 emissions and environmental impact compared to conventional methods that involve heating. However, because lactic acid-based resins and plasticizers are industrially produced, the process of synthesizing the raw materials ultimately places a burden on the environment. The method for producing solidified potting soil described in Patent Document 2 uses pieces of agar seaweed, a natural product, as a potting soil binder, but because heat is used during the solidification process, CO2 is emitted, just like conventional methods, and the production process places a burden on the environment. Furthermore, because the solidified potting soils described in Patent Documents 1 and 2 do not produce nitrogen components such as ammonia nitrogen during their production, an additional step of adding nitrogen-containing fertilizer is required when actually using them for plant growth.

[0005] Therefore, an object of the present invention is to provide a solidified soil with a high nitrogen content that is environmentally friendly and suitable for plant growth, a set for making the same, and a method for manufacturing the same. [Means for solving the problem]

[0006] Some embodiments of the present invention are illustrated below. [1] Solidified soil, which is a compacted body of granular soil containing woody biomass solidified with calcium carbonate, and has a soil hardness of 20 kPa or more and a nitrogen content of 0.7 mg / g or more.

[0007] [2] The solidified soil described in [1], which is for raising seedlings.

[0008] [3] The solidified soil according to [1] or [2], wherein the molded body contains calcium carbonate obtained by reacting calcium ions with a reaction product of urease and urea.

[0009] [4] The solidified soil according to any one of [1] to [3], wherein the calcium carbonate content is 1% by mass or more based on the total mass of the solidified soil.

[0010] [5] The solidified soil according to any one of [1] to [4], wherein calcium carbonate is deposited in the voids of the granular soil and binds adjacent granular soils together.

[0011] [6] A set for preparing solidified soil, comprising a first component containing urease, a second component containing urea, and a third component containing a calcium salt.

[0012] [7] The set for preparing solidified soil described in [6], wherein the second component and the third component are provided as a mixture containing urea and a calcium salt.

[0013] [8] A set for preparing solidified soil according to [6], wherein the first component, the second component, and the third component are each independently provided as a liquid composition.

[0014] [9] A set for preparing solidified soil according to any one of [6] to [8], further comprising granular soil containing woody biomass.

[0015]

[10] The set for preparing solidified culture soil according to any one of [6] to [9], wherein the calcium salt is calcium nitrate, calcium carbonate, calcium phosphate, calcium acetate, calcium sulfate, or a mixture thereof.

[0016]

[11] A method for producing solidified culture soil, comprising the steps of: providing a first liquid containing urease and an aqueous medium; a second liquid containing urea and an aqueous medium; and a third liquid containing a calcium salt and an aqueous medium; applying the first liquid, the second liquid, and the third liquid to granular culture soil containing woody biomass; and allowing the culture soil after application to stand for 0.5 days or more.

[0017]

[12] A method for producing solidified bed soil described in

[11] , wherein the second liquid and the third liquid are provided as a mixed liquid obtained by adding urea and calcium salt to water.

[0018]

[13] A method for producing solidified soil described in

[11] or

[12] , wherein the step of applying the first liquid, the second liquid, and the third liquid includes immersing the soil in a mixed liquid of the first liquid, the second liquid, and the third liquid.

[0019]

[14] A method for producing solidified potting soil according to any one of

[11] to

[13] , wherein the calcium salt is calcium nitrate, calcium carbonate, calcium phosphate, calcium acetate, calcium sulfate, or a mixture thereof. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a solidified soil having a high nitrogen content that is environmentally friendly and suitable for plant growth, a set for producing the same, and a method for producing the same. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a photograph showing the solidified state of the solidified bed soil in the control area and the experimental area of ​​the example. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described in detail, but these are merely examples and the present invention is not limited to these examples.

[0023] Patent Documents 1 and 2 disclose methods for producing solidified soil with low environmental impact, but both methods only solidify the culture medium. Therefore, in order to produce solidified soil suitable for plant cultivation, it was necessary to mix fertilizer into the soil beforehand or add fertilizer after solidification.

[0024] In the field of civil engineering, cementation technology using calcium carbonate has been attracting attention in recent years as a ground improvement technology. Specifically, this technology solidifies the ground by depositing calcium carbonate in the ground using the urea hydrolysis action of urease. This technology can solidify the ground without putting a burden on the environment, but there is a problem in that ammonia and ammonium ions are generated in the process.

[0025] The present inventors focused on the possibility that the ammonia and ammonium ions generated during the cementation process with calcium carbonate could be used as a nitrogen source to promote plant growth. In other words, they came up with the original idea that if calcium carbonate cementation could be applied to the preparation of solidified soil, it might be possible to prepare solidified soil rich in nitrogen without adding fertilizer, leading to the conception of the present invention. After extensive research, the present inventors discovered that by adding urease, urea, and calcium nitrate to the soil, solidified soil rich in nitrogen suitable for plant growth could be obtained.

[0026] [Solidified soil] The solidified soil in this embodiment is a molded body in which particulate soil containing woody biomass is solidified with calcium carbonate, and has a soil hardness of 20 kPa or more and a nitrogen content of 0.7 mg / g or more.

[0027] Culture soil refers to soil used for growing plants. In the present disclosure, granular culture soil containing woody biomass is used as the culture soil component. The culture soil component may contain other culture soil components in addition to woody biomass. The other culture soil components are not particularly limited as long as they are typically used in agriculture or horticulture, and examples thereof include organic materials, porous inorganic materials, non-porous inorganic materials, soil, etc. Two or more of these culture soil components may be used in combination. The culture soil component is preferably porous. Being porous provides excellent water retention, breathability, and fertilizer retention. Furthermore, the culture soil is preferably granular. Being granular creates voids between particles, which not only provides excellent water permeability and water retention, but also allows calcium carbonate to be deposited in the voids to solidify adjacent particles.

[0028] The volume of woody biomass in the solidified soil is preferably 30% by volume or more, more preferably 40% by volume or more, and even more preferably 50% by volume or more. By having the volume of woody biomass in the soil within the above range, the nitrogen content in the soil can be further increased, as described below. When other solidification components are included from the perspective of moldability and nutrients, the volume of woody biomass in the solidified soil may be 30 to 90% by volume, 40 to 80% by volume, or 50 to 70% by volume.

[0029] Woody biomass refers to organic resources derived from living organisms, such as wood. Woody biomass is not particularly limited as long as it is derived from wood, but examples include bark, sawdust, and wood flour. One or more of these woody biomass materials may be included. Bark and sawdust may be generated at sawmills, etc. Furthermore, wood flour may be bamboo powder, which is made by grinding bamboo wood produced by cutting abandoned bamboo forests. Woody biomass, particularly wood chips, is known to adsorb ammonia and ammonium ions and inhibit their volatilization and elution. In other words, by incorporating woody biomass into the culture medium, the nitrogen content in the culture medium can be increased through the adsorption effect, further improving the plant growth environment. Furthermore, using waste-derived woody biomass not only enables efficient resource utilization but also reduces the production costs of solidified culture medium. Furthermore, unlike peat moss, which has traditionally been used as a material for solidified culture medium, it is not excavated and collected from nature, making it preferable from an environmental perspective. In addition, unlike coconut peat, which is mainly imported from abroad, there is no restriction on the place of origin, so it can be supplied steadily.

[0030] As the wood, coniferous trees such as cedar, red pine, cypress, and todo fir are preferred. Coniferous trees are widely used for building materials and wood processing materials, and a large amount of offcuts is generated during their production. By using these offcuts, wood for cultivation soil can be supplied in large quantities at low cost. For the same reason, it is also preferable to use bamboo.

[0031] Woody biomass can be obtained by crushing wood scraps and the like using a crusher. By changing the blades and settings of the crusher, the particle size, shape, etc. of the woody biomass can be set as desired. Specifically, woody biomass can be formed into chunks, fibers, chips, powder, etc., depending on the crushing method selected.

[0032] In addition to woody biomass, the solidified soil may additionally contain other organic materials such as coconut shells (coconut peat, etc.), rice husks, bagasse, peat (peat moss, etc.), perc compost, sphagnum moss, lignite, smoked charcoal, bran, charcoal powder, etc. One or more of these soil components may be contained.

[0033] Woody biomass and other organic materials may be air-dried and then passed through a mesh before use. The mesh size is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 2 mm or less. Organic materials of a specific shape and size may be used alone in the culture medium, or organic materials of multiple shapes and sizes may be used in combination. By combining multiple organic materials of different shapes and sizes, a culture medium with an excellent balance of water retention and drainage properties, suitable for plant growth, can be obtained.

[0034] Examples of porous inorganic materials include artificial soil such as vermiculite, attapulgite, diatomaceous earth, sepiolite, zeolite, and perlite, as well as expanded phenolic resin, rock wool, etc. These porous inorganic materials can be used alone or in combination of two or more.

[0035] Examples of non-porous inorganic materials include silica sand, river sand, beach sand, sea sand, alumina sand, talc, calcium carbonate, etc. These non-porous inorganic materials can be used alone or in combination of two or more.

[0036] Examples of soil include black soil, Akadama soil, Kanuma soil, Hyuga soil, leaf mold, Kiryu sand, etc. These soils can be used alone or in combination of two or more types.

[0037] The solidified culture medium may additionally contain a fertilizer. Examples of the fertilizer include nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, calcium compounds such as calcium hydroxide, magnesium compounds such as magnesium hydroxide, and zinc compounds such as zinc oxide. These fertilizers can be used alone or in combination of two or more. The fertilizer preferably contains a slow-release fertilizer (slow-release fertilizer) so that plants can be cultivated efficiently over a long period of time. The slow-release fertilizer is preferably in granular form in order to maintain its effectiveness over a long period of time.

[0038] In this embodiment, "particulate" refers to a state in which fine particles are aggregated. The particle size is not particularly limited, but the particle density is preferably 0.1 to 1.8 g / cm. 3 is preferably 0.1 to 1.5 g / cm 3 More preferably, it is 0.1 to 1.0 g / cm 3 It is more preferable that the particle density is within the above range. Ammonia and ammonium ions can be adsorbed more efficiently. The particle density can be calculated by dividing the mass of a particulate aggregate having a certain volume by that volume.

[0039] In this embodiment, the term "solidified soil" refers to a molded body containing soil that has shape-retaining or solidity and can maintain a predetermined shape without the need for a support. The predetermined shape of the solidified soil is not particularly limited, but may be a cylindrical shape (including one with an oval cross section), a prismatic shape, a conical shape that narrows downward, a truncated cone shape, a pyramidal shape, or a truncated pyramidal shape.

[0040] In this embodiment, the molded body may be formed by placing particulate powder in a container of a desired shape and solidifying the powder to the shape of the container. The container may be of any shape, but when molding solidified soil for raising seedlings, cells, pots, trays, seedling boxes, etc., similar to those conventionally used, can be used, and the type, shape, structure, size, etc. of the container can be selected appropriately. The material of the seedling container is not particularly limited, but resin, glass, wood, etc. can be used.

[0041] In this embodiment, solidification refers to imparting shape retention to an aggregate of particulate matter that cannot maintain a specific shape without support. For example, solidification using cementation with calcium carbonate is preferred. This solidification method does not involve compression, so voids are generated between the particulate culture soil, resulting in excellent permeability and water retention, which is more favorable for plant growth. In addition, nitrogen generated during the solidification process can be incorporated into the culture soil, further promoting plant growth.

[0042] In this embodiment, the solidified hilling soil preferably has a soil hardness of 10 kPa or more from the viewpoint of shape retention. For example, 10 to 1000 kPa is preferred, 20 to 900 kPa is more preferred, and 30 to 850 kPa is even more preferred. A soil hardness of 10 kPa or more allows the soil to be transplanted or transported to a cultivation site while maintaining its shape without the need for a support. Furthermore, a soil hardness of 1000 kPa or less does not inhibit root elongation, thereby further promoting plant growth. Soil hardness can be measured using methods commonly used by those skilled in the art, but is preferably measured using a Yamanaka hardness tester. In particular, even extremely low hardness can be measured by using a Yamanaka hardness tester (flat type) with a disc-tipped end.

[0043] The solidified soil in this embodiment contains ammonia nitrogen. While it is difficult to generalize because it varies depending on the plant being grown, the nitrogen content is preferably 10 mg / g or less, more preferably 8.5 mg / g or less, and even more preferably 6.5 mg / g or less. If the nitrogen content exceeds 6.5 mg / g, the plant will have an excess of nitrogen, which may inhibit growth due to factors such as the reduced absorption of other nutrients such as potassium. Furthermore, a nitrogen content of 0.7 to 6.5 mg / g is preferable. When the nitrogen content in the solidified soil is within the above range, plant growth is further promoted. The nitrogen content can be measured using Soil Environmental Analysis Method V.8 (dry combustion method).

[0044] The ammonia nitrogen includes ammonia nitrogen generated by a reaction product of urease and urea, which will be described later. Furthermore, it may contain ammonia nitrogen that has been added to the culture soil as a fertilizer before or after solidification.

[0045] The solidified soil in this embodiment can be used for raising seedlings and for agricultural purposes. The plants to be cultivated are not particularly limited, but agricultural and horticultural crops such as vegetables, flowers, seedlings, and rice can be cultivated. Seeds or seedlings can be planted in the solidified soil, but sowing seeds is preferred because planting seedlings can cause some of the solidified soil to crumble.

[0046] The solidified soil in this embodiment preferably does not contain water-soluble components that inhibit seed germination. The presence or absence of such components can be determined, for example, by conducting a germination test using an extract of crushed solidified soil suspended in water.

[0047] Plants suitable for solidified soil include, for example, soft plants, which have only a taproot and no or few lateral roots. Because such plants have few roots, it is difficult to form a root ball, and the soil shape can be distorted during transportation. However, by using solidified soil, the soil shape can be stably maintained even during transportation. Soft plants are not particularly limited, but various vegetable crops such as leafy vegetables (e.g., lettuce, Chinese cabbage, kale, broccoli, cauliflower, spinach, garland chrysanthemum, komatsuna, bok choy, green onion, spring onion, asparagus), fruit vegetables (e.g., tomato, cucumber, eggplant), and flower crops (e.g., lisianthus, statice, petunia, stock, pansy, chrysanthemum, etc.) can be grown. Furthermore, since the solidified soil of this embodiment contains a large amount of ammonia nitrogen, it is suitable for growing ammonia-loving plants that prefer ammonia nitrogen as a nutrient source. Examples include rice, tea, cranberry, blueberry, taro, and pineapple.

[0048] Cementation using calcium carbonate is a technique that uses the urea hydrolysis action of the enzyme urease to deposit calcium carbonate in the ground and solidify the soil. Examples include the MICP (Microbially Induced Calcite Precipitation) method, which uses microorganisms that express urease, and the EICP (Enzyme Induced Calcite Precipitation) method, which directly utilizes urease. These methods allow for the production of solidified soil without placing a burden on the environment, compared to solidification methods that involve heat treatment, which releases CO2. Furthermore, because solidified soil can be produced at the user's own timing, the growth of mold in the soil can be suppressed. The specific reaction formulas are shown below to explain the above method.

[0049] First, the hydrolysis of urea by urease produces ammonia and carbon dioxide (1). CO(NH2)2+2H2O→2NH3+CO2(1) Ammonia reacts with water to produce ammonium ions and hydroxide ions, creating a weakly alkaline environment (2). NH3+H2O→NH4 + +OH - (2) Carbon dioxide dissolves in water (3) and becomes bicarbonate ions and hydrogen ions as shown in equation (4). CO2+H2O→HCO3 - +H + (3) HCO3 - →H + +CO3 2- (4) Calcium carbonate precipitates when calcium ions in the pores react with bicarbonate ions. (5) The precipitated calcium carbonate accumulates and acts as an adhesive, binding the particles together and increasing the soil's strength. Ca 2+ +CO3 2- →CaCo3(5)

[0050] When calcium carbonate cementation is used to solidify the soil, the ammonia nitrogen generated can be absorbed by plants, further promoting plant growth. Furthermore, calcium carbonate has extremely low solubility in water, allowing the soil to remain solidified even during seedling cultivation. Meanwhile, calcium carbonate gradually reacts with hydrogen ions in the soil and decomposes, producing carbon dioxide and water while releasing calcium ions. Calcium binds to a polysaccharide called pectin to strengthen cell membranes, building resistance to pests and diseases, and promoting root growth, thereby further promoting plant growth.

[0051] The solidified soil in this embodiment contains calcium carbonate obtained by reacting calcium ions with the reaction product of urease and urea. The calcium ions may be those originally contained in the soil, or they may be added externally as calcium salts. Examples of calcium salts include calcium nitrate, calcium carbonate, calcium phosphate, calcium acetate, calcium sulfate, or mixtures thereof. However, calcium nitrate is preferred from the viewpoint of supplying nitrogen to the solidified soil. Furthermore, it is preferable to avoid the use of calcium chloride to avoid soil contamination by chloride ions.

[0052] The calcium salt may be naturally occurring or commercially available as a reagent. The calcium salt may be added to the culture medium in powder form or dissolved in liquid form. Adding the calcium salt in liquid form allows the calcium salt to be distributed throughout the culture medium without stirring, making it easy to solidify the culture medium uniformly.

[0053] The calcium carbonate content in the solidified culture soil is preferably 7% by mass or less. The content is more preferably 1 to 5% by mass, even more preferably 1 to 3% by mass, and even more preferably 1 to 2% by mass. When the calcium carbonate content is in the above range, the culture soil can be sufficiently solidified. If the calcium carbonate content exceeds 7% by mass, the culture soil will be excessively solidified, inhibiting root elongation and root respiration, which may impair plant growth. Furthermore, the culture soil will become alkaline, which may inhibit plant growth due to trace element deficiency caused by a decrease in the solubility of trace elements essential for plant growth, and suppressed absorption of calcium, magnesium, etc.

[0054] In this embodiment, the urease used may be one that is rich in urease, a commercially available reagent, or a mixture thereof. Examples of urease-rich substances include the juice of tofu produced using a non-boiling method. Urease may be added to the culture medium in powder form, or it may be dissolved in a liquid and added to the culture medium as a liquid composition. Adding it as a liquid composition allows the urease to be distributed throughout the culture medium without stirring, allowing for easy and uniform solidification of the culture medium. The final concentration of the urease liquid composition to be added is preferably 8500 U / L or less. This concentration allows for more appropriate control of the reaction rate of urea hydrolysis by urease, preventing solidification only on the soil surface. Urease may be extracted from an organism, a recombinant protein, or a mixture thereof. The organism from which urease is extracted is not particularly limited as long as it expresses urease, but from the viewpoint of the amount of urease extracted, it is preferable to use an organism that expresses a large amount of urease, such as a legume such as jack bean.

[0055] Instead of urease, microorganisms expressing urease may be added to the culture medium. The microorganisms are preferably added in a liquid suspension (microorganism suspension). Examples of microorganisms highly expressing urease include bacteria selected from the genera Bacillus, Sporosarcina, Sporolactobacillus, Clostridium, and Desulfotomaculum.

[0056] The urease-expressing microorganisms may be commercially available or may be microorganisms isolated from soil used in gardening or agriculture and cultured. Using microorganisms isolated from soil can reduce the impact on the environment.

[0057] The microbial suspension may contain a source of nutrients necessary for the growth of the microorganisms.

[0058] There are no particular limitations on the nutrient sources used for the microorganisms, and examples thereof include meat extract, sugars such as glucose, and polysaccharides such as starch. The content may be 1 to 30 g or 4 to 20 g per liter of water.

[0059] In this embodiment, the urea may be a fertilizer containing urea, or commercially available urea as a reagent. Urea may be added to the culture medium in powder form, but it is preferable to add it to the culture medium in a liquid dissolved state. Adding urea in liquid form allows the urea to be distributed throughout the culture medium without stirring, allowing the culture medium to be easily and uniformly solidified. When adding urea in liquid form, the final urea concentration is preferably 6 to 20 g / L, and more preferably 8 to 15 g / L. When the urea content is within the above range, the permeability of the urea-containing liquid into the solidified culture medium is maintained within a good range, a sufficient amount of carbonate ions can be generated to solidify calcium ions, and the cost is also advantageous from the viewpoint of the effect relative to the content.

[0060] [Solidified soil manufacturing set] In this embodiment, urease, urea, and calcium salts can be provided as a solidified soil preparation set comprising a first component containing urease, a second component containing urea, and a third component containing a calcium salt. Each of the above components can be provided as a liquid composition, or a mixture of the first component, the second component, and the third component can be provided. By adding each component of the solidified soil preparation set to any soil, a solidified soil with a high nitrogen content can be prepared.

[0061] The first component containing urease is preferably provided as a powdered urease and an aqueous medium separately. By providing urease in powder form, the time until urease is inactivated can be significantly extended. The solvent is not particularly limited as long as it is an aqueous medium in which urease does not lose its activity, but a buffer solution such as a phosphate buffer solution is preferred, and the pH is preferably 6.0 to 8.0. Since the optimum pH for urease is approximately 6.0, using a buffer solution with a pH within the above range allows urease to maintain high enzymatic activity. The aqueous medium may also contain a protease inhibitor to prevent decomposition of urease.

[0062] The second component containing urea and the third component containing a calcium salt may be provided as solutions with higher concentrations than those actually used, and may be diluted with water before use. By providing them as highly concentrated solutions, the amount of liquid required can be reduced.

[0063] In this embodiment, the water may be ion-exchanged water, distilled water, tap water, or the like.

[0064] The solidified soil preparation set may further include a soil containing woody biomass. By using a soil containing woody biomass, which has a high adsorption effect of ammonia and ammonium ions, a solidified soil with a higher nitrogen content can be prepared.

[0065] [Method of manufacturing solidified soil] According to some embodiments, a method for producing solidified culture soil can be provided, comprising the steps of (Step 1) providing a first liquid containing urease and an aqueous medium, a second liquid containing urea and an aqueous medium, and a third liquid containing a calcium salt and an aqueous medium, and (Step 2) applying the first, second, and third liquids to a granular culture soil containing woody biomass. This method may additionally comprise (Step 3) allowing the culture soil to stand for 0.5 days or more after applying the first, second, and third liquids.

[0066] This manufacturing method makes it possible to produce solidified soil with a high nitrogen content, which can further promote plant growth.

[0067] Step 1 includes providing a first liquid containing urease and an aqueous medium, a second liquid containing urea and an aqueous medium, and a third liquid containing a calcium salt and an aqueous medium. The above steps may include adding urease, urea, and the calcium salt to water. When adding, each may be added independently to water contained in separate containers, or urea and the calcium salt may be added to water in the same container.

[0068] Step 2 involves adding the first, second, and third liquids to the granular culture medium containing woody biomass. While each liquid can be added to the culture medium in any order, it is preferable to add a mixture of all liquids. Adding a premix allows calcium carbonate to be deposited more uniformly throughout the culture medium, resulting in a solidified culture medium with a more uniform hardness overall. The culture medium may be immersed in the mixture of the first, second, and third liquids and then immediately placed in a container of the desired shape, or the container may be immersed in the mixture of the first, second, and third liquids while still in the container of the desired shape.

[0069] Step 3 includes allowing the culture medium to stand for 0.5 days or more after application of the first, second, and third liquids. Allowing the culture medium to stand for a certain period of time allows the culture medium to harden. It is preferable to allow the culture medium to stand while immersed in the first, second, and third liquids. The time required for the standing is, for example, 0.5 to 15 days at room temperature. Specifically, the standing time is preferably about 3 days in a greenhouse, about 1 day in a germination room controlled at a temperature of 25 to 28°C and humidity of approximately 0%, or about 1 week indoors in an environment similar to that of an agricultural worker, such as a house or barn. The culture medium may be further air-dried after the standing time. The moisture content of the seedling-raising medium after air-drying can be adjusted appropriately depending on the type of agricultural produce being raised. [Example]

[0070] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0071] Example 1: Formation of solidified body by injection of solidification solution This experiment was conducted as a preliminary step to the preparation of solidified soil, in order to confirm that the solidified soil produced had no problems in strength (would not collapse).

[0072] <Method> The materials used to make the soil were bamboo powder (Moso bamboo from Gifu Prefecture, chipped bamboo further processed with a shokusenki machine), sawdust (Japanese cedar, Shimada Kowari Seisakusho), and coco peat (Sri Lankan, Ltd.). In the experiments, bamboo powder and coco peat, or sawdust and coco peat, were placed in a 2 L plastic bottle at a volume ratio of 1:1 (500 mL each). The mixture was mixed for approximately 1 minute at 1500 rpm using a Braun food processor, air-dried for 24 hours, and then passed through a 2 mm mesh sieve. The solidification solution used was a 1:1 mixture of 0.1 g / L (170 U / mg) urease solution and 1 M urea-calcium nitrate solution. The 1 M urea-calcium nitrate solution was prepared by dissolving urea and calcium nitrate tetrahydrate (both Fujifilm Wako Pure Chemicals) in purified water to a final concentration of 1 M. The experimental procedure is as follows. A 1.50 mL syringe was loosely filled with 30 mL of a bamboo powder-coco peat mixed sample (bamboo mixed sample) or a sawdust-coco peat mixed sample (sawdust mixed sample) to prepare a test specimen (density of the test specimen was 0.21 ± 0.02 g / cm). 3 ). 2. Experimental and control sections were prepared, and 25 ml of a solidification solution made by mixing 0.1 g / L urease solution and 1 M urea-calcium nitrate mixed solution was injected into the test specimens in the experimental section at a rate of approximately 12.5 ml / min. Any solution not adsorbed by the specimens was drained. In the control section, pure water (pH 7.3) was used instead of the solidification solution. The above procedure was repeated eight times every 12 hours. 3. After the eight injections and drainages were completed, the syringes were disassembled with a hot knife and the solidified bodies of the bamboo and sawdust blend samples were extracted. Photographs of the solidified bodies are shown in Figure 1. 4. The unconfined compressive strength (kPa) of the extracted solidified material was measured using a Yamanaka hardness tester (plane type). The nitrogen content was also measured using the soil environmental analysis method V.8 (dry combustion method). The results are shown in Table 1.

[0073] [Table 1]

[0074] The bamboo-blended control samples maintained their shape even after removal from the syringe, whereas the sawdust-blended control samples lost their shape. Furthermore, when attempting to measure the hardness of either control sample using a Yamanaka hardness tester (flat type), the samples collapsed and could not be measured. In contrast, both experimental samples maintained their shape, and hardness measurements ranged from 50 to 200 kPa for the bamboo-blended samples and 30 to 100 kPa for the sawdust-blended samples. This indicates that the soil in the experimental samples can be solidified by injecting a 0.1 g / L urease solution and a 1 M urea-calcium nitrate mixed solution. Furthermore, the nitrogen content in the experimental samples was higher than that in the control samples.

[0075] [Example 2 Germination test] To verify whether the solidified soil samples can be used for plant growth, a germination test was carried out using the extract from the solidified soil samples.

[0076] <Method> The solidified body and solidified soil prepared in Example 1 were broken into pieces and air-dried. The sample passed through a 2 mm sieve was placed in an Erlenmeyer flask, and boiling water was poured into it at a ratio of 1:5 (w / w) relative to the sample. The extract was then filtered through gauze to obtain a liquid extract. 10 mL of the resulting extract was added to a petri dish containing approximately three sheets of filter paper. 15 komatsuna seeds were sown therein and allowed to stand in a constant temperature room (25°C) for 8 days. After 8 days, the number of germinated seeds was visually counted, and the germination rate was calculated. The germination rate was evaluated according to the following criteria. ◎: Germination rate is 90% or more. ○: Germination rate is between 80% and 90%. △: Germination rate is 70% or more but less than 80%.

[0077] The results are shown in Table 2.

[0078] [Table 2]

[0079] The manufacturer's guaranteed germination rate for the komatsuna seeds used in this study was 90%. In this test, all samples achieved a germination rate of 90% or higher, demonstrating that the water-soluble components contained in the solidified product obtained by this disclosure do not inhibit the germination of komatsuna. Because the solidified soil in the experimental area had a high nitrogen content, it is highly likely to be excellent for plant growth after germination. Since no adverse effects on germination were observed in the experimental area in this test, the solidified soil of the present invention is considered useful as a solidified soil for growing seedlings from seeds.

Claims

1. It is a compact in which granular soil containing woody biomass is solidified with calcium carbonate, The soil hardness is 20 kPa or more, A solidified soil having a nitrogen content of 0.7 mg / g or more.

2. The solidified soil according to claim 1, which is for raising seedlings.

3. The solidified soil according to claim 1 or 2, wherein the formed body contains calcium carbonate obtained by reacting calcium ions with a reaction product of urease and urea.

4. 3. The solidified soil according to claim 1, wherein the content of calcium carbonate is 1% by mass or more based on the total amount of the solidified soil.

5. 3. The solidified soil according to claim 1, wherein calcium carbonate is deposited in the voids of the granular soil and binds adjacent granular soils together.

6. a first component comprising urease; a second component comprising urea; and A solidified soil making set comprising a third component containing a calcium salt.

7. The set for making solidified soil according to claim 6, wherein the second component and the third component are provided as a mixture containing urea and a calcium salt.

8. The set for making solidified soil according to claim 6, wherein the first component, the second component, and the third component are each independently provided as a liquid composition.

9. The solidified soil making set according to any one of claims 6 to 8, further comprising particulate soil containing woody biomass.

10. The solidified soil preparation set according to any one of claims 6 to 8, wherein the calcium salt is calcium nitrate, calcium carbonate, calcium phosphate, calcium acetate, calcium sulfate, or a mixture thereof.

11. a first liquid comprising urease and an aqueous medium; a second liquid comprising urea and an aqueous medium; and providing a third liquid comprising a calcium salt and an aqueous medium; Applying the first liquid, the second liquid, and the third liquid to a particulate culture medium containing woody biomass; and The step of leaving the applied soil for 0.5 days or more is included. Method for manufacturing solidified soil.

12. The method for producing solidified bed soil according to claim 11, wherein the second liquid and the third liquid are provided as a mixed liquid obtained by adding urea and calcium salt to water.

13. A method for producing solidified soil as described in claim 11 or 12, wherein the step of applying the first liquid, the second liquid, and the third liquid includes immersing the soil in a mixed liquid of the first liquid, the second liquid, and the third liquid.

14. The method for producing solidified soil according to claim 11 or 12, wherein the calcium salt is calcium nitrate, calcium carbonate, calcium phosphate, calcium acetate, calcium sulfate, or a mixture thereof.

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