soil

Abstract

To provide soil that is excellent in breathability and water retention and contributes to improving transportation efficiency. [Solution] The soil contains compost containing carbide, phosphorus, magnesium, and nitrifying bacteria, and gravel derived from granite, wherein the compost content is between 1% and 10% by mass of the soil, and the gravel content is between 70% by mass of the soil. The compost has a particle size distribution in which the fraction with a particle size of 9.5 mm or more is less than 30% by mass of the total weight, the fraction with a particle size of 4 mm or more and less than 9.5 mm is between 25% and 40% by mass of the total weight, the fraction with a particle size of 2 mm or more and less than 4 mm is between 10% and 20% by mass of the total weight, the fraction with a particle size of 1 mm or more and less than 2 mm is between 10% and 20% by mass of the total weight, and the fraction with a particle size of less than 1 mm is less than 15% by mass of the total weight.

Description

[Technical Field]

[0001] One embodiment of the present invention relates to soil. [Background technology]

[0002] In recent years, with the growing interest in renewable energy, the use of biomass has been attracting attention. For example, Patent Document 1 discloses inexpensive agricultural soil in which plant biomass is added to dredged sediment from lakes and marshes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-105036 Summary of the Invention [Problem to be solved by the invention]

[0004] In addition to Patent Document 1, there is a method of mixing compost with sand and gravel to provide inexpensive agricultural soil. However, with this conventional method, the soil for cultivating crops contains a large amount of compost, and the bulk density of the soil is 0.7 to 1.0 g / cm. 3 As a result, the soil becomes too small and is not suitable for transportation. In other words, the soil prepared by the conventional method has the problem of poor transportation efficiency and high transportation costs.

[0005] An object of one embodiment of the present invention is to provide soil that is excellent in breathability and water retention, and also contributes to improving transportation efficiency. [Means for solving the problem]

[0006] A soil according to one embodiment of the present invention comprises compost containing carbide, phosphorus, magnesium, and nitrifying bacteria, and gravel derived from granite, wherein the compost content is 1% by mass or more and 10% by mass or less of the soil, and the gravel content is 70% by mass or more of the soil, and the compost has a particle size distribution in which the fraction with a particle size of 9.5 mm or more is less than 30% by mass of the total weight, the fraction with a particle size of 4 mm or more and less than 9.5 mm is 25% by mass or more and 40% by mass or less of the total weight, the fraction with a particle size of 2 mm or more and less than 4 mm is 10% by mass or more and 20% by mass or less of the total weight, the fraction with a particle size of 1 mm or more and less than 2 mm is 10% by mass or more and 20% by mass or less of the total weight, and the fraction with a particle size of less than 1 mm is less than 15% by mass of the total weight.

[0007] The bulk density of the soil is 1.15 g / cm 3 More than 1.5g / cm 3 It may be less than.

[0008] The soil may have a three-phase distribution, with a solid fraction of 45% to 50%, a liquid fraction of 20% to 30%, and a gas fraction of 20% or more.

[0009] The gravel may be granite. [Effects of the Invention]

[0010] The soil according to one embodiment of the present invention comprises compost containing carbide, phosphorus, magnesium, and nitrifying bacteria, and gravel derived from granite, the compost content being 1% by mass to 10% by mass of the soil, and the gravel content being 70% by mass or more of the soil. The compost has a particle size distribution in which a fraction having a particle size of 9.5 mm or more is less than 30% by mass of the total weight, a fraction having a particle size of 4 mm to less than 9.5 mm is 25% by mass to 40% by mass of the total weight, a fraction having a particle size of 2 mm to less than 4 mm is 10% by mass to 20% by mass of the total weight, a fraction having a particle size of 1 mm to less than 2 mm is 10% by mass to 20% by mass of the total weight, and a fraction having a particle size of less than 1 mm is less than 15% by mass of the total weight. This provides excellent breathability and water retention, making the compost suitable for growing crops. In addition, since the soil contains compost containing carbonized matter, phosphorus, magnesium, and nitrifying bacteria, the soil's bulk density increases, making it possible to transport large amounts of soil at once, thereby improving transportation efficiency. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the structure of magnesium phosphate-containing carbide constituting soil compost according to one embodiment of the present invention. [Figure 2] 1 is a flowchart showing a method for producing soil according to one embodiment of the present invention. [Figure 3] 1 is a graph showing particle size distribution of compost (or decomposed granite soil) in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, various embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0013] In this specification, the term "phosphorus" includes not only elemental phosphorus but also compounds containing phosphorus. Therefore, "phosphorus" also includes phosphoric acid. Here, the term "phosphoric acid" does not only mean phosphoric acid in the narrow sense, i.e., a compound represented by the chemical formula H2PO4, but is also used as a term indicating various phosphates, monohydrogen phosphates, and dihydrogen phosphates in addition to phosphoric acid (H3PO4).

[0014] [1. Soil composition] The soil according to one embodiment of the present invention contains compost and gravel. The compost content is 1% by mass or more and 10% by mass or less relative to the soil. The lower limit of the compost content is 1% by mass, preferably 1.5% by mass, and more preferably 2% by mass. The upper limit of the compost content is 10% by mass, preferably 7.5% by mass, and more preferably 5% by mass. If the compost content is too low, the soil will be unsuitable for growing crops, while if the compost content is too high, the soil will have a low bulk density. The gravel content is 70% by mass or more relative to the soil, preferably 80% by mass or more, and more preferably 90% by mass or more. Details of the components of the compost and gravel will be described later.

[0015] While the compost content in conventional soil containing gravel is about 20% by mass, as described above, the compost content in the soil according to one embodiment of the present invention is 10% by mass or less, which is significantly lower. This increases the gravel content, but as a result, the bulk density of the soil increases, making it possible to transport large amounts of soil at one time. This improves soil transportation efficiency and reduces transportation costs.

[0016] The bulk density of the soil according to one embodiment of the present invention is, for example, 1.15 g / cm 3 or more, preferably 1.30 g / cm 3 More preferably, it is 1.40 g / cm or more. 3 For example, if the gravel is granite, the bulk density of the soil is 1.5 g / cm 3The bulk density of conventional agricultural soil containing sand and gravel is less than 1.00 g / cm 3 Therefore, the soil according to one embodiment of the present invention is characterized not only by a low compost content but also by a high bulk density.

[0017] Furthermore, the soil according to one embodiment of the present invention has a three-phase distribution suitable for growing crops, despite its low compost content, such as a solid phase ratio of 45% to 50%, a liquid phase ratio of 20% to 30%, and a gas phase ratio of 20% or more.

[0018] [2. Compost composition] [2-1. Compost composition] The soil compost according to one embodiment of the present invention contains charcoal, phosphorus, magnesium, and nitrifying bacteria. Each component of the compost will be described below.

[0019] [2-1-1. Carbide] The charcoal in the compost is a porous material containing carbon as the main component and having pores with cross-sectional diameters ranging from several nanometers to several tens of micrometers. The concentration (composition) of the charcoal in the compost is, for example, 2% by weight to 40% by weight or 5% by weight to 35% by weight. By including the charcoal in the above range, a high composition of nitrifying bacteria, as described below, can be maintained. The specific gravity of the charcoal is 0.05 g / cm 3 More than 0.8g / cm 3 or less, or 0.1g / cm 3 More than 0.5g / cm 3 The specific surface area of ​​the carbide may be, for example, 100 m 2 / g or more 900m 2 / g or less, 100m 2 / g or more 800m 2 / g or less, or 150m 2 / g or more 400m 2 The specific surface area is measured by mercury intrusion porosimetry or a gas adsorption method such as the BJH method or HK method.

[0020] [2-1-2. Rin] The phosphorus in the compost is contained at a concentration of 2.0% by weight or more and 5.0% by weight or less as total phosphorus (i.e., the total amount of phosphorus). At least a portion of the phosphorus in the compost is contained as magnesium ammonium phosphate. As will be described later, in the production of compost, a mixture containing magnesium and a carbide (magnesium-containing carbide) is treated with water containing phosphoric acid. Therefore, magnesium ammonium phosphate is mainly derived from the magnesium in the magnesium-containing carbide and water containing phosphoric acid.

[0021] Another portion of the phosphorus in compost may exist as water-insoluble phosphate. Water-insoluble phosphate is phosphate that is insoluble in water and soluble in a 2% citric acid solution (citric acid-soluble phosphate). Examples of water-insoluble phosphate include calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium phosphate, magnesium monohydrogen phosphate, and magnesium phosphate. The metal ions of these water-insoluble phosphates are derived from the carbides and organic fertilizer sources that are the raw materials for the compost.

[0022] The compost may further contain water-soluble phosphates, such as phosphate salts (lithium phosphate, sodium phosphate, potassium phosphate, ammonium phosphate, etc.), monohydrogen phosphate salts (lithium monohydrogen phosphate, sodium monohydrogen phosphate, potassium monohydrogen phosphate, ammonium monohydrogen phosphate, etc.), and dihydrogen phosphate salts (lithium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, etc.). The metal ions of these water-soluble phosphates are also derived from charcoal or organic fertilizer sources.

[0023] The total amount of phosphorus in compost, i.e., total phosphate, can be determined using ammonium vanadomolybdate spectrophotometry. For example, a given amount of compost is digested with nitric acid or perchloric acid, and then ammonium vanadate(V), hexaammonium heptamolybdate, and nitric acid are added. The total phosphate is then quantified by measuring the absorbance of the resulting phosphorus vanadomolybdate (e.g., at 420 nm) using a UV-visible spectrophotometer.

[0024] The concentration of water-soluble phosphate can be determined, for example, using the ammonium vanadomolybdate spectrophotometric method. In this method, for example, water is added to compost and a predetermined amount of the water-soluble portion is collected as a sample. Nitric acid (1+1) is added to this sample and heated to hydrolyze the non-orthophosphates into orthophosphate ions. Ammonium vanadate(V), hexaammonium heptamolybdate, and nitric acid are then added to produce vanadomolybdate phosphorus. Water-soluble phosphate is quantified by measuring the absorbance of vanadomolybdate phosphorus (e.g., at 420 nm) using a UV-visible spectrophotometer.

[0025] [2-1-3. Magnesium] The compost contains magnesium at a concentration (composition) of 0.01% by weight or more and 10% by weight or less, or 0.1% by weight or more and 5% by weight or less. The magnesium in the compost contains at least magnesium ammonium phosphate and may further contain one or more selected from magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium bicarbonate, and magnesium oxide. The magnesium may also be present as magnesium soluble in an aqueous citric acid solution (citric acid-soluble magnesium). Another portion of the magnesium in the compost may also be present as water-soluble magnesium.

[0026] [2-1-4. Nitrifying bacteria] Compost contains nitrifying bacteria, including ammonia-oxidizing bacteria, ammonia-oxidizing archaea, and nitrite-oxidizing bacteria. For example, ammonia-oxidizing archaea include at least one of Nitrososphaera viennensis and Nitrosopumilus maritimus. The ratio of nitrifying bacteria to the total bacterial population in compost is between 0.04% and 0.10%. The total bacterial and nitrifying bacteria populations in compost can be measured by genome analysis of the compost. Nitrifying bacteria are archaea that oxidize ammonia to nitrite and nitrite to nitrate in soil. Inclusion of nitrifying bacteria in compost can increase the amount of nitrate and nitrite ions in the soil, thereby increasing the nitrogen concentration available as an organic fertilizer source.

[0027] [2-1-5.Other] Compost may also contain potassium, which is an organic fertilizer source, as another component. It may also contain iron as another component. For example, iron may be contained at a concentration (composition) of less than 1% by weight. The iron in the compost may be present in part as iron phosphate, metallic iron (i.e., zero-valent iron), or iron oxide or iron hydroxide.

[0028] [2-2. Compost structure] The structure of the compost is not particularly limited, and it may be in the form of granules such as pellets or plates, or in powder form. Furthermore, when the compost is in the form of granules, the compost may be a granule formed by mixing components and granulating them into granules, or it may be a granule having a so-called core-shell structure in which the core is covered with a coating layer. In the case of a core-shell structure, magnesium may be contained in the core, or the coating layer may contain magnesium. Below, a compost having a core-shell structure will be described as an example.

[0029] Fig. 1 is a schematic diagram showing the structure of magnesium phosphate-containing carbide 100 constituting soil compost according to one embodiment of the present invention. Specifically, Fig. 1(A) is a schematic perspective view of magnesium phosphate-containing carbide 100, and Fig. 1(B) is a schematic cross-sectional view of magnesium phosphate-containing carbide 100 cut along a plane perpendicular to the longitudinal direction.

[0030] As shown in Figures 1(A) and 1(B), magnesium phosphate-containing carbide 100 has a core-shell structure, and as a basic structure, comprises a core 102 and a coating layer 104 covering the core 102. The coating layer 104 may cover the entire surface of the core 102, or may cover only a portion of the surface of the core 102. In the latter case, a portion of the surface of the core 102 is exposed from the coating layer 104. Covering the surface of the core 102 with the coating layer 104 imparts physical strength to the magnesium phosphate-containing carbide 100, and can also include phosphorus or nitrogen, which are effective as an organic fertilizer source.

[0031] The magnesium phosphate-containing carbide 100 may have any shape, such as a pellet as shown in FIG. 1(A), a plate, or a powder. In the pellet form, the magnesium phosphate-containing carbide 100 may have a spherical or cylindrical shape. Although not shown, the magnesium phosphate-containing carbide 100 may have an elliptical cylinder or a polygonal prism having polygonal end faces, such as a triangular, quadrangular, pentagonal, or hexagonal prism. Therefore, the magnesium phosphate-containing carbide 100 may have the shape of a sphere, cylinder, elliptical cylinder, or polygonal prism with a missing portion. The magnesium phosphate-containing carbide 100 does not need to have the shape of a perfect sphere, cylinder, or polygonal prism; for example, it may suffice if the volume of the magnesium phosphate-containing carbide 100 accounts for 75% or more of the total volume of a cylinder with the smallest volume in which the magnesium phosphate-containing carbide 100 is inscribed.

[0032] When the magnesium phosphate-containing carbide 100 is a cylinder or can be regarded as a cylinder, its diameter D may be 1 mm or more and 20 mm or less, 2 mm or more and 11 mm or less, or 3 mm or more and 8 mm or less. Alternatively, the area of ​​the end face of the magnesium phosphate-containing carbide 100 may be 0.8 mm or more. 2 More than 300mm 2 The aspect ratio of the magnesium phosphate-containing carbide 100, i.e., the ratio of the length L to the diameter D (L / D), is also arbitrary and can be, for example, 0.5 to 5.0. Specifically, the length L can be 0.5 mm to 100 mm, 1 mm to 20 mm, 3 mm to 15 mm, or 6 mm to 12 mm.

[0033] When the magnesium phosphate-containing carbide 100 is in powder form, its average particle size may be, for example, 100 μm to 5 mm, 100 μm to 5 mm, 500 μm to 2 mm, or 500 μm to 1 mm. The powdered magnesium phosphate-containing carbide 100 is produced by crushing larger plate- or pellet-shaped magnesium phosphate-containing carbide 100. Therefore, the compost contains powdered magnesium phosphate-containing carbide 100 in which part of the surface of the core 102 is covered with the coating layer 104.

[0034] In this embodiment, compost with an adjusted particle size distribution is used, which will be described later. Here, the configurations of the core 102 and the coating layer 104 will be described in detail.

[0035] [2-2-1. Core 102] The core 102 determines the shape of the magnesium phosphate-containing carbide 100 and fixes the coating layer 104, which allows the magnesium phosphate-containing carbide 100 to exhibit the function of fixing phosphorus and nitrogen. The core 102 has a carbide (more specifically, a carbide that is a porous material, and therefore may be referred to as a "porous carbide" hereinafter) as a basic skeleton, and further includes a binder (hereinafter referred to as a "first binder").

[0036] Porous charcoal is produced by heating and carbonizing organic materials under conditions of low oxygen concentration. An example of such organic material is biomass. Here, biomass refers to biologically derived substances and their metabolites. Specific examples include planks and columns of wood, thinned wood, pruning waste, construction waste, powdered sawdust, and wooden molded products such as particle boats. There are no restrictions on the type of wood, and cedar, cypress, and bamboo are also suitable. Other examples of biomass include agricultural waste such as rice husks, bagasse, corn cobs and leaves, and agricultural by-products such as straw, wheat straw, and hay. Other examples include plants that are used to produce fibers, such as hemp, flax, cotton, sisal, abaca, and palm hair. Algae such as seaweed are also suitable. Other examples include food waste and silage obtained from animal manure.

[0037] The first binder functions as an auxiliary component for forming the core 102 in the granulation process described below. The first binder may be an organic binder and / or an inorganic binder. Examples of organic binders include one or more selected from the group consisting of molasses, blackstrap molasses, starch, dextrin, corn starch, rice bran, polyvinyl alcohol, a copolymer of vinyl acetate and ethylene or its saponified form, pulp waste liquor, lignin sulfonate, carboxymethyl cellulose, hydroxypropyl methyl cellulose, sodium alginate, phenolic resin, and tar pitch. Examples of inorganic binders include cement, ground granulated blast furnace slag, fly ash, gypsum (calcium sulfate), calcined gypsum obtained by heating and dehydrating gypsum, and sodium silicate. Inorganic binders are particularly easy to handle and have low solubility in water, resulting in little runoff into water bodies and thus less impact on the environment. Furthermore, inorganic binders are preferred because they have high weather resistance and can provide a core 102 with sufficient strength.

[0038] [2-2-2. Coating layer 104] The coating layer 104 contains a magnesium compound and a binder (hereinafter referred to as a "second binder.") There are no restrictions on the thickness of the coating layer 104, and it may be, for example, from 10 μm to 5 mm, from 20 μm to 3 mm, from 50 μm to 500 μm, or from 100 μm to 300 μm.

[0039] The magnesium compound includes at least magnesium ammonium phosphate, and may further include one or more selected from magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium bicarbonate, and magnesium oxide.

[0040] The second binder can contain materials that can be used in the first binder, and the second binder and the first binder can contain the same materials or different materials.

[0041] [2-2-3. Composition of magnesium phosphate-containing carbide 100] The porous carbide forming the basic skeleton of the core 102 is contained in the magnesium phosphate-containing carbide 100 at a composition of 20% by mass to 99% by mass, 50% by mass to 90% by mass, or 60% by mass to 90% by mass relative to the dry mass of the magnesium phosphate-containing carbide 100 (i.e., the total mass of the core 102 and the coating layer 104 excluding water, which is taken as 100% by mass). By adopting the above composition, a lightweight core 102 having sufficient strength can be formed. The composition of the porous carbide is controlled by adjusting the feed ratio during the production of the magnesium phosphate-containing carbide 100. The composition of the porous carbide in the magnesium phosphate-containing carbide 100 may also be determined from a quantitative carbon value obtained using, for example, combustion and infrared absorption spectroscopy.

[0042] The first binder is contained in the magnesium phosphate-containing carbide 100 in a composition of 1% by mass to 50% by mass, 10% by mass to 40% by mass, or 10% by mass to 30% by mass, based on the total mass of the magnesium phosphate-containing carbide 100. By adopting the above composition, the core 102 can be easily molded and can be provided with sufficient shape stability. The composition of the first binder is controlled by adjusting the mixing ratio during production of the magnesium phosphate-containing carbide 100. The composition of the first binder may also be determined from measured values. For example, when the first binder contains calcium sulfate, the composition may be determined from a quantitative value of sulfur obtained using ICP atomic emission spectroscopy (ICP-AES) or combustion / infrared absorption spectroscopy, or a quantitative value of calcium obtained using atomic absorption spectroscopy (AAS), inductively coupled plasma optical emission spectroscopy (ICP-OES), potassium permanganate volumetric analysis, or the like.

[0043] The magnesium compound contained in the coating layer 104 is contained in a composition of 1% by mass to 30% by mass, 5% by mass to 30% by mass, or 5% by mass to 25% by mass, relative to the total mass of the magnesium phosphate-containing carbide 100. Alternatively, magnesium is contained in a composition of 1% by mass to 40% by mass, 5% by mass to 25% by mass, or 5% by mass to 25% by mass, relative to the total mass of the magnesium phosphate-containing carbide 100. Because the mass of the coating layer 104 is extremely small compared to the mass of the core 102, an extremely high concentration of magnesium is contained in the coating layer 104. Specifically, the magnesium content may be 1% by mass to 30% by mass, relative to the dry mass of the coating layer 104. The magnesium composition may be determined by quantifying magnesium by applying ICP-OES or inductively coupled plasma mass spectrometry (ICP-MS) to the magnesium phosphate-containing carbide 100.

[0044] The second binder is contained in a composition of 0.1% by mass to 10% by mass, 1% by mass to 5% by mass, or 1% by mass to 3% by mass relative to the total mass of the magnesium phosphate-containing carbide 100. The composition of the second binder is also controlled by adjusting the charge ratio during production of the magnesium phosphate-containing carbide 100. As with the first binder, the composition of the second binder may be determined from measured values.

[0045] Furthermore, magnesium phosphate-containing carbide 100 contains relatively high amounts of phosphorus and nitrogen due to the immobilization of phosphorus and nitrogen. For example, the total phosphorus concentration based on the dry mass of magnesium phosphate-containing carbide 100 is 0.1% by mass to 30% by mass, 0.5% by mass to 20% by mass, or 1% by mass to 5% by mass. The total nitrogen concentration based on the dry mass of magnesium phosphate-containing carbide 100 is 0.02% by mass to 6% by mass. Alternatively, the citrate-soluble phosphoric acid concentration (phosphoric acid soluble in a 2% citric acid solution) based on the dry mass of magnesium phosphate-containing carbide 100 is 0.1% by mass to 30% by mass, 0.5% by mass to 20% by mass, or 1% by mass to 5% by mass. The total phosphoric acid concentration, citrate-soluble phosphoric acid concentration, and total nitrogen concentration can be measured using known methods as appropriate. For example, the total phosphate concentration and citrate-soluble phosphate concentration may be measured using molybdenum blue absorptiometry, and the total nitrogen concentration may be measured using alkaline potassium peroxodisulfate ultraviolet absorptiometry.

[0046] [2-3. Compost particle size distribution] In the soil according to one embodiment of the present invention, the compost is prepared to have a predetermined particle size distribution, thereby enabling the soil to have the effects described above. Specifically, the particle size distribution of the compost in the soil according to one embodiment of the present invention has the following characteristics (A) to (E). Here, the total weight refers to the weight of the entire compost. (A) The fraction with a particle size of 9.5 mm or more is 30% by mass or more of the total weight (B) The fraction with a particle size of 4 mm or more and less than 9.5 mm is 25% by mass or more and 40% by mass or less of the total weight (C) The fraction with a particle size of 2 mm or more and less than 4 mm is 10% by mass or more and 20% by mass or less of the total weight (D) The fraction with a particle size of 1 mm or more and less than 2 mm is 10% by mass or more and 20% by mass or less of the total weight (E) The fraction with a particle size of less than 1 mm is less than 15% by mass of the total weight

[0047] In the soil according to one embodiment of the present invention, not only is the compost content in the soil reduced, but the particle size distribution of the compost is adjusted to fall within the above range, thereby increasing the bulk density of the soil and providing the soil with a three-phase distribution suitable for growing crops.

[0048] [3. Composition of Gravel] The gravel of the soil according to one embodiment of the present invention is porous gravel. Such gravel is lightweight and has excellent breathability. In particular, the gravel of the soil according to one embodiment of the present invention is derived from granite. More specifically, granite-derived sand produced by weathering granite can be used as the gravel of the soil according to one embodiment of the present invention. Decomposed sand, which is widely distributed mainly in western Japan, is lightweight but has poor water retention. However, in the soil according to one embodiment of the present invention, even such sand can be improved to a soil suitable for crop cultivation by mixing with compost whose particle size distribution is adjusted to a predetermined range. That is, the soil according to one embodiment of the present invention uses decomposed sand as gravel, and by reducing the amount of compost mixed, the bulk specific gravity is increased, while the particle size distribution of the compost mixed is adjusted, thereby achieving soil with excellent breathability and water retention.

[0049] [4. Soil manufacturing methods] Fig. 2 is a flowchart showing a method for producing soil according to one embodiment of the present invention. The method for producing soil according to one embodiment of the present invention will be described below with appropriate reference to Fig. 2. For convenience, the following description will be given assuming that the soil compost contains granules having a core-shell structure.

[0050] [4-1. Preparation of porous carbide] Porous carbonized materials are produced by heating and carbonizing organic materials in an inert gas atmosphere such as argon gas, a low-oxygen atmosphere, a reducing atmosphere, or a reduced-pressure atmosphere. For example, carbonization can be carried out by heating the organic material at a pressure of 102 Pa to 105 Pa. Alternatively, carbonization can be carried out by heating at normal pressure under conditions where the oxygen concentration is 0.01% to 3% or 0.1% to 2%. The heating temperature for carbonization can be 400°C to 1200°C, 500°C to 1100°C, or 600°C to 1000°C. The heating time can be 10 minutes to 10 days, or 10 minutes to 5 hours.

[0051] Carbonization is carried out using an internal combustion or external heating carbonization furnace. Carbonization of biomass generates pyrolysis gases, resulting in a porous charcoal (also known as biochar) with pores of various shapes and sizes, a complex mixture of pores originating from the biomass structure and pores formed by the desorption of pyrolysis gases. The pyrolysis gases primarily contain flammable or reducing gases, such as hydrogen, carbon monoxide, and alkanes, such as methane, propane, and butane. Because pyrolysis gases are extracted at high temperatures (700°C to 1300°C), their thermal energy and flammability can be utilized as energy sources for power generation and hot water supply. Therefore, the amorphous charcoal obtained from biomass gasification power generation (woody biomass gasification power generation waste charcoal) can be used as the porous charcoal. If pellet-shaped porous charcoal is included in the porous charcoal obtained by carbonization, it is crushed appropriately and processed into powder before the subsequent granulation process.

[0052] [4-2. Granulation of porous carbide] Next, the porous carbide is mixed with a first binder and granulated. At this time, water may be added as needed. Granulation may be performed using a compression granulator, extrusion granulator, roll granulator, blade granulator, melt granulator, spray granulator, or the like. The porous carbide formed by granulation may be appropriately cured. For example, curing may be performed by leaving it at a temperature of room temperature or higher and 50°C or lower for one day or more and one month or less. Through the above steps, the core 102 is formed.

[0053] [4-3. Formation of coating layer] The coating layer 104 can be formed by mixing the magnesium compound and the second binder with the core 102. For example, the magnesium compound and the second binder, or a mixture thereof, may be brought into contact with the core 102 while stirring the core 102. At this time, a solvent such as water or an alcohol such as ethanol or isopropanol may be used as appropriate. The solvent is preferably added in a mist state. The magnesium compound used at this time is selected from magnesium hydroxide, magnesium sulfate, magnesium carbonate, magnesium bicarbonate, and magnesium oxide. Among these magnesium compounds, magnesium hydroxide, magnesium oxide, or magnesium carbonate is preferred, as they can more effectively coat the core 102.

[0054] Alternatively, a dispersion obtained by mixing a mixture of the magnesium compound and the second binder with a solvent may be added to the cores 102. Examples of the solvent include water and alcohol as described above. The dispersion is spray-coated or dip-coated onto the cores 102 to form a coating layer 104 on the surface of the cores 102. After the coating layer 104 is formed, curing may be performed as needed. As with the curing after granulation, curing may be performed by leaving the mixture to stand at a temperature between room temperature and 50°C for a period of one day to one month. By the above process, a magnesium-containing carbide, which is a precursor of the magnesium phosphate-containing carbide 100, is obtained.

[0055] [4-4. Preparation of magnesium phosphate-containing carbide] The magnesium phosphate-containing carbide 100 is prepared by contacting the magnesium phosphate-containing carbide 100 obtained in the above steps with water containing phosphoric acid (hereinafter, "treated water"). The treated water may be prepared by dissolving a phosphate, such as sodium phosphate or potassium phosphate, in water. Alternatively, water from a body of water, such as a river, lake, or ocean, may be used as the treated water. For example, a container filled with magnesium-supported carbide may be placed in a river, lake, or ocean, and the magnesium-supported carbide may be brought into contact with the water from the body of water. This allows phosphoric acid contained in the water from the river, lake, or ocean to react with magnesium compounds, such as magnesium hydroxide, contained in the magnesium phosphate-containing carbide 100, and the phosphate is adsorbed or supported on the carbide as magnesium ammonium phosphate, which has low solubility in water. At the same time, organic compounds containing phosphoric acid and phosphorus are removed from the water. In other words, this method not only enables the low-cost preparation of magnesium phosphate-containing carbide 100, but also allows for the purification and improvement of water quality in various bodies of water.

[0056] [4-5. Composting] Next, composting is carried out using the magnesium phosphate-containing carbide 100 as one of the raw materials, which mainly consists of the processes of mixing with organic fertilizer sources, fermentation, and treatment under aerobic conditions.

[0057] [4-5-1. Mixing of magnesium phosphate-containing carbide and organic fertilizer source] Magnesium phosphate-containing carbide 100 is mixed with an organic fertilizer source. There are no restrictions on the amount of magnesium phosphate-containing carbide 100 relative to the organic fertilizer source; for example, 1% to 40% by weight or 5% to 25% by weight of magnesium phosphate-containing carbide 100 may be added to the organic fertilizer source. If the resulting mixture (primary mixture) has a high viscosity, additional water may be added to adjust the viscosity. Examples of organic fertilizer sources include readily decomposable organic matter of biological origin, such as animal feces and urine (e.g., cow, pig, or chicken), food waste (e.g., food residue), agricultural waste, food waste, and sludge. The amount of carbon dioxide generated after mixing with soil and the content of acid detergent-soluble organic matter (AD-soluble organic matter) can be used as indicators to determine whether a material is readily decomposable.

[0058] [4-5-2. Fermentation treatment] The primary mixture is then subjected to a fermentation treatment. Specifically, the primary mixture is first exposed to an oxygen-containing atmosphere. The oxygen-containing atmosphere may be air or an atmosphere containing oxygen and an inert gas such as nitrogen or argon. The fermentation treatment may be carried out at ambient temperature or in a temperature-controlled environment ranging from 30°C to 60°C. The fermentation treatment time can be set arbitrarily, for example, from 1 day to 120 days, from 10 days to 60 days, or from 15 days to 30 days. This treatment exposes the surface of each mass of the primary mixture to aerobic conditions and the interior to anaerobic conditions. As a result, aerobic fermentation proceeds on the surface of each mass, while anaerobic fermentation proceeds within the interior. Since aerobic fermentation proceeds only on the surface of each mass of the primary mixture, anaerobic fermentation proceeds throughout most of the primary mixture.

[0059] Anaerobic fermentation is promoted by the action of anaerobic microorganisms contained in the organic fertilizer source. Therefore, anaerobic microorganisms that promote the decomposition of organic matter may be added when mixing the magnesium phosphate-containing carbide 100 with the organic fertilizer source. Examples of anaerobic microorganisms include nitrate-reducing bacteria, iron-reducing bacteria, sulfate-reducing bacteria, acid-producing bacteria, acetogenic bacteria, and methanogenic archaea, with iron-reducing bacteria and methanogenic archaea being preferred.

[0060] Fermentation treatment increases the amount of nitrifying bacteria in the soil. This increase in nitrifying bacteria also increases the amount of nitrate and nitrite ions in the soil, increasing the nitrogen concentration, which is effective as an organic fertilizer source.

[0061] [4-6. Compost classification] Next, the compost is classified into predetermined fractions. Specifically, the compost is classified into (A) a fraction with a particle size of 9.5 mm or more, (B) a fraction with a particle size of 4 mm or more but less than 9.5 mm, (C) a fraction with a particle size of 2 mm or more but less than 4 mm, (D) a fraction with a particle size of 1 mm or more but less than 2 mm, and (E) a fraction with a particle size of less than 1 mm. Classification of the compost can be performed, for example, by sieving using multiple sieves, but is not limited to this.

[0062] [4-7. Mixing compost and gravel] Before mixing the compost with gravel, the compost is prepared by mixing the fractions (A) to (E) described above so that the compost has a predetermined particle size distribution. Then, the compost prepared to have the predetermined particle size distribution is mixed with gravel in a predetermined ratio. This produces soil according to one embodiment of the present invention.

[0063] To prepare a compost with a predetermined particle size distribution, the fractions (A) to (E) are mixed in the following proportions. As a result, the proportions of the fractions (A) to (E) in the compost prepared to have the predetermined particle size distribution will be the respective proportions relative to the total weight of the compost (100% by mass). (A) 30% by mass or more of the fraction with a particle size of 9.5 mm or more (B) A particle size fraction of 4 mm or more and less than 9.5 mm is 25% by mass or more and 40% by mass or less (C) A particle size fraction of 2 mm or more and less than 4 mm is 10% by mass or more and 20% by mass or less (D) A particle size fraction of 1 mm or more and less than 2 mm is 10% by mass or more and 20% by mass or less (E) Fraction of particle size less than 1 mm is less than 15% by mass

[0064] The compost prepared to have a predetermined particle size distribution is mixed with gravel so that the compost content is 1% to 10% by mass of the soil, i.e., the compost content is 1% to 10% by mass of the soil, and the gravel content is 70% by mass or more of the soil.

[0065] As described above, according to the soil of one embodiment of the present invention, even if a relatively small amount of compost is mixed with gravel, the compost has a predetermined particle size distribution, so that soil with excellent breathability and water retention, i.e., soil suitable for growing crops, can be provided. Furthermore, because the bulk density of the soil can be increased, it is possible to transport large amounts of soil at one time, improving transportation efficiency. [Example]

[0066] Hereinafter, the soil according to one embodiment of the present invention will be described in more detail based on examples.

[0067] [1. Soil Production] [1-1. Preparation of magnesium phosphate-containing carbide] Irregularly shaped charcoal (waste charcoal from woody biomass gasification power generation), magnesium hydroxide powder and / or magnesium oxide powder, blast furnace slag powder as a binder, and water were mixed and kneaded at room temperature for 30 minutes to obtain a powder mixture. The obtained powder mixture was then placed in a granulator and formed into pellets with a diameter of 4 mm and a height of 10 mm. The formed granules were then dried (cured) at 20°C for 24 hours to obtain a magnesium-containing carbide.

[0068] The magnesium content of the magnesium-containing carbide was determined by crushing the carbide and measuring the magnesium content using flame atomic absorption spectrometry (MgO equivalent) in accordance with the Fertilizer Testing Methods (Agriculture, Forestry and Fisheries Materials Consumption Safety Technology Center). As a result, it was confirmed that the magnesium content of the magnesium-containing carbide was 9.37% by weight.

[0069] The obtained magnesium-containing carbide was packed into a glass column, and a sewage sludge dewatering separated liquid containing 100 mg / L of phosphoric acid was passed through it at a flow rate of 23 L / day for 12 days. The sewage sludge dewatering separated liquid used here was the supernatant obtained by centrifuging sludge at a sewage treatment plant in Kanagawa Prefecture. The obtained magnesium phosphate-containing carbide was then dried at room temperature for 24 hours to prepare a magnesium phosphate-containing carbide.

[0070] [1-2. Compost preparation] Cow manure was used as the organic fertilizer source. In Examples 1 and 2, a primary mixture of the organic fertilizer source and magnesium phosphate-containing carbide (weight ratio: organic fertilizer source: magnesium phosphate-containing carbide = 1:0.05 to 1:1) was prepared, and this primary mixture was filled into a resin bottle (capacity: approximately 500 L), sealed, and fermented at 60°C for 5 days. During the fermentation process, the primary mixture was stirred once a day.

[0071] On the other hand, in Comparative Example 2, the organic fertilizer source was subjected to fermentation treatment under the same conditions as in Examples 1 and 2, without using magnesium phosphate-containing carbide.

[0072] After the fermentation treatment, the ammonia contained in the sample was evaporated according to the distillation method in 4.1.2.a of the Fertilizer Testing Method (Agriculture, Forestry and Fisheries Agricultural Materials Inspection Center).

[0073] [1-3. Mixing compost with gravel] In Examples 1 and 2, and Comparative Example 2, compost was classified using multiple sieves into (A) a fraction with a particle size of 9.5 mm or more, (B) a fraction with a particle size of 4 mm or more but less than 9.5 mm, (C) a fraction with a particle size of 2 mm or more but less than 4 mm, (D) a fraction with a particle size of 1 mm or more but less than 2 mm, and (E) a fraction with a particle size of less than 1 mm. To produce soil containing only sand and gravel without compost in Comparative Example 1, decomposed granite soil was classified according to the above-mentioned classifications (A) to (E). In Examples 1 and 2, and Comparative Example 2, the compost was prepared by mixing the above-mentioned fractions (A) to (E) so as to have the particle size distribution shown in Table 1. In Comparative Example 1, the decomposed granite soil was prepared by mixing the above-mentioned fractions (A) to (E) so as to have the particle size distribution shown in parentheses in Table 1. In order to visually confirm the particle size distribution of the compost (or granite soil) in Example 1, Example 2, Comparative Example 1, and Comparative Example 2, a graph of the particle size distribution of the compost (or granite soil) in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 is shown in Figure 3.

[0074] [Table 1]

[0075] Subsequently, the compost with the particle size distribution adjusted in the proportions shown in Table 2 was mixed with gravel to obtain soil for each of Examples 1 and 2, Comparative Examples 1 and 2.

[0076] [Table 2]

[0077] [2. Soil Evaluation] The soil's three-phase distribution was measured to evaluate its suitability for crop cultivation. A 100 mL cylindrical tube was attached to a Yamanaka-type air-dried fine soil bulk density analyzer. A sample with a moisture content of pF 1.5 was gently placed in the tube without applying pressure, and the tube was dropped five times from a height of 5 cm to fill the sample. The measured three-phase distribution was evaluated as suitable for crop cultivation, i.e., a solid fraction of 45% to 50%, a liquid fraction of 20% to 30%, and a gas fraction of 20% or more, with a rating of "Good." Any other range was evaluated as "Poor." The soil three-phase distribution results are shown in Table 3.

[0078] [Table 3]

[0079] As can be seen from Table 3, the three-phase distribution in the soil of the Example was within the optimum range for all of the solid, liquid, and gas phase ratios. On the other hand, the three-phase distribution in the soil of Comparative Example 1 or Comparative Example 2 was outside the optimum range for any of the solid, liquid, and gas phase ratios. In other words, the soil of the Example had a well-balanced three-phase distribution and was excellent in air permeability and water retention, making it suitable for growing crops.

[0080] The bulk density of the soil in Example 1 was 1.42 g / cm 3 The bulk density of the soil in Example 2 was 1.41. In contrast, the bulk density of the soil containing granite soil in which the compost content was 20 mass % relative to the soil, as in the conventional method, was 1.05 g / cm 3 Therefore, it was found that the bulk density of the soils in Examples 1 and 2 was large.

[0081] The above-described embodiments of the present invention can be combined as appropriate as long as they are not mutually inconsistent. A product in which a person skilled in the art appropriately adds or deletes components or modifies the design based on each embodiment is also included within the scope of the present invention as long as it includes the gist of the present invention.

[0082] Even if there are other effects and advantages different from those brought about by the above-described embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0083] 100: magnesium phosphate carbide, 102: core, 104: coating layer

Claims

1. Compost containing charcoal, phosphorus, magnesium, and nitrifying bacteria; A soil comprising: sand and gravel derived from granite; The content of the compost is 1% by mass or more and 10% by mass or less with respect to the soil, The content of the gravel is 70% by mass or more relative to the soil, The compost is The fraction having a particle size of 9.5 mm or more is less than 30% by mass of the total weight, a particle size fraction of 4 mm or more and less than 9.5 mm is 25% by mass or more and 40% by mass or less of the total weight, a particle size fraction of 2 mm or more and less than 4 mm is 10% by mass or more and 20% by mass or less of the total weight, a particle size fraction of 1 mm or more and less than 2 mm is 10% by mass or more and 20% by mass or less of the total weight, A particle size distribution in which the fraction with a particle size of less than 1 mm is less than 15% by mass of the total weight. soil.

2. The bulk density of the soil is 1.15 g / cm ３ 1.5g / cm or more ３ The soil of claim 1, wherein the water content is less than 100%.

3. The soil is The solid fraction is 45% or more and 50% or less, The liquid phase rate is 20% or more and 30% or less, A three-phase distribution with a gas phase ratio of 20% or more. The soil according to claim 1.

4. The soil according to claim 1 , wherein the gravel is decomposed granite soil.

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