Phosphate solubilizer and soil improvement method

Abstract

To provide a phosphoric acid solubilizer that solubilizes poorly soluble phosphate compounds contained in the soil, releasing phosphate ions and / or available phosphate, and a soil improving method using the phosphoric acid solubilizer.SOLUTION: A phosphoric acid solubilizer contains at least one chelator. The chelator is a crosslinked polymer compound having a functional group capable of chelation, with a volume average particle diameter of 10-200 μm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a phosphate solubilizing agent and a soil improvement method.

Background Art

[0002] Phosphorus is a nutrient necessary for plant growth, along with nitrogen and potassium, etc. The supply of these nutrients is often carried out by fertilizing agricultural land with chemical fertilizers, etc.

[0003] Not all of the nutrients such as phosphorus contained in chemical fertilizers, etc. are utilized as a nutrient source for plants, and may remain in the soil. Some of the nutrients remaining in the soil are utilized as a nutrient source for the next planted plants, but some may remain in the soil without being utilized as a nutrient source due to a change in form.

[0004] For example, in the case of phosphorus, it reacts with metal components such as iron and aluminum in the soil to change into an insoluble phosphate compound, and the insoluble phosphate compound remains in the soil as it is without being absorbed by plants.

[0005] Conventionally, methods for releasing phosphate compounds have been studied in order to effectively utilize the phosphate compounds existing in the soil as fertilizer components.

[0006] For example, Patent Document 1 describes a method for releasing a phosphate compound using a low molecular weight water-soluble polycarboxylic acid such as citric acid. Also, for example, Patent Document 2 describes a method for releasing a phosphate compound using microorganisms.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

[0008] However, the method described in Patent Document 1 uses a low molecular weight (monomer) water-soluble polycarboxylic acid, which can be washed away from the soil by rainfall or irrigation, and may be washed away before it can exert its full effect.

[0009] Furthermore, in the method described in Patent Document 2, depending on the microbial flora in the soil, the microorganisms used may not be able to grow and thus the method may not produce the desired effect.

[0010] Therefore, the present invention aims to provide a phosphate solubilizer that can solubilize poorly soluble phosphate compounds contained in soil and release phosphate ions and / or available phosphate, and a soil improvement method using the phosphate solubilizer. [Means for solving the problem]

[0011] The present inventors have discovered that by using a phosphate solubilizer containing a chelating agent which is a crosslinked polymer compound equipped with a functional group having chelating ability and having a specific volume-average particle size, a complex compound is formed between the chelating agent and iron, aluminum, calcium, etc., contained in poorly soluble phosphate compounds in soil, and consequently, phosphate ions and / or available phosphate are released, leading to the present invention.

[0012] In other words, the present invention relates to a phosphate solubilizer comprising at least one chelating agent, wherein the chelating agent is a crosslinked polymer compound having a chelating functional group and having a volume average particle diameter of 10 to 200 μm; and a soil improvement method comprising: step 1, mixing the phosphate solubilizer at a concentration of 0.1 to 20.0% by weight relative to the weight of soil containing phosphates; and step 2, mixing 1 to 500% by weight of water relative to the weight of soil containing phosphates to release phosphate ions and / or available phosphate. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a phosphate solubilizer that can solubilize poorly soluble phosphate compounds contained in soil and release phosphate ions and / or available phosphate, and a soil improvement method using the phosphate solubilizer. [Modes for carrying out the invention]

[0014] [Phosphate solubilizer] The phosphate solubilizer of the present invention is a phosphate solubilizer comprising at least one chelating agent, wherein the chelating agent is a crosslinked polymer compound having a functional group having chelating ability, and has a volume average particle diameter of 10 to 200 μm.

[0015] (Chelating agent) The phosphate solubilizer of the present invention comprises at least one chelating agent.

[0016] Chelating agents are crosslinked polymer compounds that possess chelating functional groups.

[0017] Examples of functional groups with chelating ability include carboxyl groups, hydroxyl groups, amino groups, imino groups, aldehyde groups, and thiol groups, which have chelating ability with iron, aluminum, and calcium. Because the chelating agent has the above-mentioned functional group, it can form a complex compound with metal ions such as iron, aluminum, and calcium present in the phosphate compound, thereby releasing phosphate ions and / or available phosphate. In particular, carboxyl groups are preferred from the viewpoint of the excellent ability of phosphate compounds to form complexes with metal ions such as iron, aluminum, and calcium.

[0018] The chelating agent preferably has an unneutralized carboxyl group concentration of 0.1 to 13.5 mmol / g. When the concentration of unneutralized carboxyl groups is within the above range, it is possible to preferably impart the effect of solubilizing the poorly soluble phosphate compounds contained in the soil and releasing phosphate ions and / or available phosphate. The chelating agent more preferably has an unneutralized carboxyl group concentration of 1.0 to 8.0 mmol / g, and even more preferably 2.0 to 5.0 mmol / g. The concentration of unneutralized carboxyl groups can be measured in terms of acid value (mgKOH / g) according to the description in JIS K 0070 and calculated by the following formula. Carboxyl group concentration (mmol / g) = 1000 × acid value / 56100

[0019] The chelating agent is preferably a polymer having (meth)acrylic acid as a constituent monomer, and more preferably a partial neutralized product of a polymer having (meth)acrylic acid as a constituent monomer [a copolymer having (meth)acrylic acid and a (meth)acrylate (preferably sodium salt) as constituent monomers]. In this specification, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0020] The chelating agent is a crosslinked polymer compound. The chelating agent preferably contains 0.01 to 30% by weight of a crosslinking agent based on the weight of the main chain monomer. Since the chelating agent is a crosslinked polymer compound, it is possible to suppress the outflow of the phosphate solubilizing agent from the soil due to rainfall, irrigation water, etc.

[0021] Examples of crosslinking agents include N,N'-methylenebis(meth)acrylamide, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol triallyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, and sorbitol polyglycidyl ether.

[0022] The chelating agent has a volume-average particle size of 10 to 200 μm. By having a volume-average particle size within the above range of the chelating agent, it is possible to solubilize poorly soluble phosphate compounds contained in the soil and impart the effect of releasing phosphate ions and / or available phosphate. The chelating agent preferably has a volume-average particle size of 15 to 100 μm, and more preferably 20 to 50 μm. In this specification, "volume-average particle diameter" refers to the particle diameter at which the cumulative volume calculated from the smallest diameter side accounts for 50% of the particle diameter distribution measured by laser diffraction.

[0023] The chelating agent preferably has a specific surface area of ​​20,000 to 500,000 (1 / m²). By having a specific surface area within the above range, the chelating agent can effectively solubilize poorly soluble phosphate compounds contained in the soil, thereby releasing phosphate ions and / or available phosphate. The chelating agent preferably has a specific surface area of ​​30,000 to 400,000 (1 / m²). In this specification, "specific surface area" refers to the BET specific surface area measured according to the specific surface area measurement method of JIS K1150.

[0024] Examples of commercially available chelating agents include Sunfresh ST-500MPSA (manufactured by Sanyo Chemical Industries, Ltd., carboxyl group concentration 3.7 mmol / g, volume average particle size 30.5 μm) and Sunfresh IM-1000MPS (manufactured by Sanyo Chemical Industries, Ltd., carboxyl group concentration 3.4 mmol / g, volume average particle size 29.4 μm).

[0025] The chelating agent content is preferably 50-100% by weight, more preferably 60-90% by weight, and even more preferably 70-80% by weight, based on the weight of the phosphate solubilizer. By having a chelating agent content within the above range, it is possible to suitably impart the effect of solubilizing poorly soluble phosphate compounds contained in the soil and releasing phosphate ions and / or available phosphate.

[0026] (Microbial materials) The phosphate solubilizer of the present invention preferably further contains microbial materials.

[0027] Examples of microbial materials include arbuscular mycorrhizal fungi and phosphatase-producing microorganisms. In particular, it is preferable to include arbuscular mycorrhizal fungi, as they can transport phosphate compounds contained in the soil and expand the range over which poorly soluble phosphate compounds contained in the soil can be released.

[0028] When microbial materials are included, their content is preferably 0.0001 to 10% by weight, and more preferably 0.001 to 8% by weight, based on the weight of the phosphate solubilizer.

[0029] (Other ingredients) The phosphate solubilizer of the present invention may optionally contain soil improvement materials such as peat, charcoal, diatomaceous earth, zeolite, vermiculite, perlite, bentonite, polyethyleneimine-based materials, or polyvinyl alcohol-based materials. If other components are included, their content is preferably 0.001 to 5% by weight, based on the weight of the phosphate solubilizer.

[0030] (Method of manufacturing a phosphate solubilizer) The method for producing the phosphate solubilizer of the present invention is not particularly limited, and the chelating agent, microbial material, and other components as needed may be mixed by known methods.

[0031] [Soil Improvement Methods] The soil improvement method of the present invention comprises: step 1, mixing the above-mentioned phosphate solubilizer of the present invention with soil containing phosphate in an amount of 0.1 to 20.0% by weight; and step 2, mixing with 1 to 500% by weight of water relative to the weight of soil containing phosphate to release phosphate ions and / or available phosphate.

[0032] (Process 1) In step 1, the phosphate solubilizer of the present invention is mixed with soil containing phosphates in an amount of 0.1 to 20.0% by weight relative to the weight of the soil. By including a phosphate solubilizer within the above range, phosphate compounds contained in the soil can be solubilized without worsening the soil's aeration and drainage, thereby sufficiently releasing phosphate ions and / or available phosphate. The phosphate solubilizer of the present invention is preferably mixed in an amount of 1.0 to 15.0% by weight relative to the weight of the soil containing phosphate, and more preferably in an amount of 2.0 to 10.0% by weight.

[0033] The method for mixing the phosphate solubilizer of the present invention with soil containing phosphates in proportion to the soil weight is not particularly limited, and any known method may be appropriately selected.

[0034] (Process 2) In step 2, phosphate ions and / or available phosphate are released by mixing 1 to 500% by weight of water relative to the weight of the soil containing phosphate. By mixing water within the above range, the phosphate solubilizer absorbs water and expands, providing a good contact interface with the soil. In step 2, the amount of water to be mixed is preferably 1 to 400% by weight relative to the weight of the soil containing phosphate.

[0035] Step 2 is preferably performed after Step 1, after allowing it to stand for at least 0.5 hours, from the standpoint of allowing it to blend well with water.

[0036] The method of mixing the water is not particularly limited; any known method can be appropriately selected.

[0037] This specification discloses the following:

[0038] (1) of this disclosure is a phosphate solubilizer comprising at least one chelating agent, wherein the chelating agent is a crosslinked polymer compound having a chelating functional group and having a volume average particle diameter of 10 to 200 μm.

[0039] Disclosure (2) is a phosphate solubilizer according to Disclosure (1), wherein the concentration of unneutralized carboxyl groups of the chelating agent is 0.1 to 13.5 mmol / g.

[0040] Disclosure (3) is a phosphoric acid solubilizer according to Disclosure (1) or (2), wherein the chelating agent is a polymer having (meth)acrylic acid as a constituent monomer.

[0041] Disclosure (4) is a phosphate solubilizer according to any one of Disclosures (1) to (3), further comprising a microbial material.

[0042] The present disclosure (5) is a soil improvement method comprising: step 1, mixing a phosphate solubilizer described in any of the present disclosures (1) to (4) in an amount of 0.1 to 20.0% by weight relative to the weight of soil containing phosphate; and step 2, freeing phosphate ions and / or available phosphate by mixing 1 to 500% by weight of water relative to the weight of the soil containing the phosphate. [Examples]

[0043] The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples unless it deviates from the spirit of the invention. Unless otherwise specified, parts refer to parts by weight, and % refers to % by weight.

[0044] (Soil containing phosphates) 50g of soil from a field (Kyoto Prefecture, collected in 2020) that had been treated with chemical fertilizers for 20 years was air-dried in a 30°C dryer for one week, and then sieved through a 2mm soil sieve to prepare dried soil (A-1).

[0045] (Phosphate solubilizer) (B-1): "Sunfresh ST-500MPSA" (crosslinked polymer compound (a copolymer composed of acrylic acid and sodium acrylate as monomers), manufactured by Sanyo Chemical Industries, Ltd.) (B-2): "Sunfresh IM-1000MPS" (crosslinked polymer compound (a copolymer composed of acrylic acid and sodium acrylate as monomers), manufactured by Sanyo Chemical Industries, Ltd.) (polymer compound) (B'-1): "Sunfresh ST-500D * (Cross-linked polymer compound (a copolymer composed of acrylic acid and sodium acrylate as constituent monomers), manufactured by Sanyo Chemical Industries, Ltd.) The carboxyl group concentration and volume-average particle size of each phosphate solubilizer were measured and calculated using the method described herein and are shown in Table 1.

[0046] (Example 1) 1 g of dry soil (A-1), 30 mg of phosphate solubilizer (B-1), and 99 g of ultrapure water were measured into an ointment jar (125 ml), lightly mixed, and left to stand at room temperature for 4 days. Next, the mixture was shaken at 150 rpm for 30 minutes using a shaker (MIGHTY SHAKER AS-1N, manufactured by AS ONE Corporation). Subsequently, to prevent column clogging in ion chromatography, the mixture was filtered through a funnel lined with filter paper (No. 5C), and the filtrate was further filtered through a 0.45 μm syringe filter. Subsequently, the phosphate concentration of the filtrate obtained by ion chromatography (labeled "recovered phosphate concentration" in Table 1) was quantified. The measurement conditions are as follows.

[0047] <Measurement conditions> Equipment: Liquid transfer pump RHPLC Pump PU-4180 Autosampler HPLC Autosampler AS-4050 Column Oven CO-4060 (All three items listed above are manufactured by JASCO Corporation.) Detector CM-8020 (manufactured by Tosoh Corporation) Column: PCI-201S column for anion analysis (manufactured by Toa DKK Co., Ltd.) Column temperature: 40℃ Eluent: The eluent was prepared using the following method. 0.498g of phthalic acid, 0.332g of trishydroxymethylaminomethane, and 12.4g of boric acid were mixed and diluted to 1L with ultrapure water. The mixture was then stirred for 5 hours until completely homogenized. Flow rate: 1ml / min Injection volume: 20μl Calibration curve: A single calibration curve using calibration solution (for 20 μl anion loop) IA-AS1 (manufactured by Toa DKK Co., Ltd.).

[0048] (Example 2) The phosphoric acid concentration of the obtained filtrate was quantified in the same manner as in Example 1, except that phosphoric acid solubilizer (B-1) was replaced with phosphoric acid solubilizer (B-2).

[0049] (Comparative Example 1) The phosphate concentration of the obtained filtrate was quantified in the same manner as in Example 1, except that the phosphate solubilizer (B-1) was changed from 30 mg to 0 mg (i.e., no phosphate solubilizer was used).

[0050] (Comparative Example 2) The phosphoric acid concentration of the obtained filtrate was quantified in the same manner as in Example 1, except that the phosphoric acid solubilizer (B-1) was replaced with a polymer compound (B'-1).

[0051] [Table 1]

[0052] As shown in Table 1, in the examples using a phosphate solubilizer that is a crosslinked polymer compound having chelating functional groups and having a volume-average particle size of 10 to 200 μm, it was confirmed that phosphate compounds could be solubilized and phosphate ions released.

Claims

1. A phosphate solubilizer containing at least one chelating agent, The chelating agent is a crosslinked polymer compound having a functional group with chelating ability, and having a volume-average particle diameter of 10 to 200 μm. The chelating agent is a polymer having (meth)acrylic acid as a constituent monomer, and the concentration of unneutralized carboxyl groups is 0.1 to 13.5 mmol / g. The chelating agent contains 0.01 to 30% by weight of the crosslinking agent relative to the weight of the main chain monomer. The crosslinking agent is a phosphate solubilizer, which is at least one selected from the group consisting of N,N'-methylenebis(meth)acrylamide, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol triallyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, and sorbitol polyglycidyl ether.

2. The phosphate solubilizer according to claim 1, further comprising a microbial material.

3. Step 1 involves mixing the phosphate solubilizer according to claim 1 or 2 in an amount of 0.1 to 20.0% by weight relative to the weight of the soil containing phosphate, A soil improvement method comprising step 2, which involves mixing 1 to 500% by weight of water relative to the weight of the soil containing the phosphate to release phosphate ions and / or available phosphate.

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