Phosphorus solubilizing agent applied to soil for replacing phosphate fertilizer and preparation method and application of phosphate solubilizing agent

Abstract

The invention provides a phosphate solubilizing agent applied to soil for replacing a phosphate fertilizer as well as a preparation method and application of the phosphate solubilizing agent. The phosphate solubilizing agent is prepared from the following raw materials in parts by mass: 1-15 parts of a composite initiator, 1-10 parts of organic acid containing carbon-carbon double bonds, 1-10 parts of unsaturated organic salt containing sulfonic acid, 0.5-5 parts of organic ester containing carbon-carbon double bonds and 1-80 parts of solvent water. The preparation method of the phosphate solubilizing agent is simple, efficient and low in cost, injection of extra inert protective gas is not needed in the industrial production process, potential risks in the industrial production process are reduced, and the cost is further reduced. The phosphate solubilizing agent disclosed by the invention is green, safe and environment-friendly, and the carboxyl group, the sulfonic group and the like of the phosphate solubilizing agent can degrade indissolvable phosphorus salt existing in soil and are not easy to gather, so that the content of available phosphorus in the soil is increased to increase the crop yield, and a new direction is provided for the development of phosphorus additives and alternative chemical fertilizers in the future agricultural field.

Description

Technical Field

[0001] The invention relates to a phosphate dissolving agent used for soil to replace phosphate fertilizer, a preparation method and application thereof, and belongs to the technical field of agricultural application. Background Art

[0002] As a traditional agricultural country, China has rich soil resources. However, according to the data of the third national soil census, the phosphorus content in my country's soil is only 0.44-0.85g kg -1 range, and the content of available phosphorus (referring to the general term for phosphorus in the soil that can be absorbed and utilized by plants) in the soil is insufficient. Even in soils with high phosphorus content, there is not enough available phosphorus to meet the needs of normal growth of crops in that season. Due to the presence of a large amount of free calcium carbonate in the soil, most of the phosphorus becomes insoluble calcium phosphate salts, and the available phosphorus content that can be absorbed and utilized by crops is very low. However, phosphorus is an indispensable element for the formation of nuclear proteins and lecithin in crops. It can accelerate cell division, promote the growth of plant roots, make crops branch more, shorten the differentiation time of flower buds, mature earlier, and improve fruit quality.

[0003] In order to promote the growth of crops and increase their yield, phosphate fertilizers are often applied during the growth stage of crops. Currently, the commonly used phosphate fertilizers mainly include potassium dihydrogen phosphate, calcium magnesium phosphate, etc. The crops planted are harvested quarterly, and the amount of phosphate fertilizer required is large and used multiple times. Long-term use of phosphate fertilizers will mainly cause two negative effects: First, phosphate fertilizers can easily antagonize trace elements in the soil such as zinc, molybdenum, silicon, iron and other elements, causing physiological diseases due to the lack of trace elements in crops. Second, excessive phosphate fertilizers are not easy to lose in the soil, and the absorption and utilization of crops is limited. It is easy to accumulate in the soil and cause soil acidification and compaction. In addition, the current production process of phosphate fertilizers in my country mainly uses sulfuric acid to treat phosphate ore, which will produce a large amount of phosphogypsum. The absorption capacity of phosphogypsum is limited, and the accumulation and storage will cause serious pollution to the environment.

[0004] In order to solve the problem of insufficient effective phosphorus content in the soil and excessive application of phosphorus fertilizer, phosphate dissolving agents can be used to degrade the insoluble phosphate salts contained in the soil itself through chelation and distortion. However, phosphate dissolving agents such as molybdates and tungstates are generally used in the chemical industry. If they are directly applied to the soil, they may cause residues and environmental pollution.

[0005] In summary, from the perspective of crop nutrition and fertilization, it is of great significance to explore a green, low-cost and stable phosphate degrading agent that can degrade insoluble phosphate salts in the soil. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a dephosphorizing agent for use in soil to replace phosphate fertilizers, and a preparation method and application thereof. The preparation method of the dephosphorizing agent of the present invention is simple, efficient, and low in cost, and no additional inert protective gas injection is required during industrial production, thereby reducing potential dangers during industrial production and further reducing costs. The dephosphorizing agent of the present invention is green, safe, and environmentally friendly, and the carboxyl group, sulfonic acid group, etc. possessed by the dephosphorizing agent can degrade the insoluble phosphate salts in the soil itself and are not easy to aggregate, thereby increasing the effective phosphorus content in the soil to increase crop yields, providing a new direction for the development of phosphorus additives and alternative fertilizers in the future agricultural field.

[0007] The technical solution of the present invention is as follows:

[0008] A phosphate dissolving agent used in soil to replace phosphate fertilizer is prepared by including the following raw materials in parts by weight:

[0009] 1-15 parts of composite initiator, 1-10 parts of organic acid containing carbon-carbon double bond, 1-10 parts of unsaturated organic salt containing sulfonic acid, 0.5-5 parts of organic ester containing carbon-carbon double bond, and 1-80 parts of solvent water.

[0010] Preferably, according to the present invention, the phosphate dissolving agent used in soil to replace phosphate fertilizer is prepared by including the following raw materials in parts by mass:

[0011] 10-11 parts of composite initiator, 3-7 parts of organic acid containing carbon-carbon double bond, 5-7 parts of unsaturated organic salt containing sulfonic acid, 1-2 parts of organic ester containing carbon-carbon double bond, and 5-60 parts of solvent water.

[0012] Preferably, the phosphate dissolving agent used in soil to replace phosphate fertilizer is prepared by the following raw materials in parts by weight:

[0013] 10-11 parts of composite initiator, 5-6 parts of organic acid containing carbon-carbon double bond, 6-7 parts of unsaturated organic salt containing sulfonic acid, 1-2 parts of organic ester containing carbon-carbon double bond, and 5-15 parts of solvent water.

[0014] Further preferably, the phosphate dissolving agent used in soil to replace phosphate fertilizer is prepared by the following raw materials in parts by weight:

[0015] 10.032 parts of composite initiator, 5.8642 parts of organic acid containing carbon-carbon double bond, 6.045 parts of unsaturated organic salt containing sulfonic acid, 1.0738 parts of organic ester containing carbon-carbon double bond, and 10 parts of solvent water.

[0016] According to the preferred embodiment of the present invention, the composite initiator is a combination of two or more of vanadium sulfate, a hydrogen peroxide solution with a mass concentration of 20-30%, sodium persulfate, ammonium persulfate or ammonium bicarbonate. Preferably, the composite initiator is a combination of vanadium sulfate and a hydrogen peroxide solution with a mass concentration of 20-30%; the mass ratio of vanadium sulfate and a hydrogen peroxide solution with a mass concentration of 20-30% is 0.01-0.05:10, preferably 0.032:10.

[0017] According to the preferred embodiment of the present invention, the organic acid containing a carbon-carbon double bond is one or a combination of two or more of maleic anhydride, itaconic acid, acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid or cis-methylbutenedioic acid. Preferably, the organic acid containing a carbon-carbon double bond is a combination of maleic anhydride and itaconic acid; the mass ratio of maleic anhydride to itaconic acid is 1:0.9-3, preferably 1:2.

[0018] According to the preferred embodiment of the present invention, the unsaturated organic salt containing sulfonic acid is one or a combination of sodium methacrylate sulfonate or sodium allyl sulfonate. Preferably, the unsaturated organic salt containing sulfonic acid is a combination of sodium methacrylate sulfonate and sodium allyl sulfonate; the mass ratio of sodium methacrylate sulfonate to sodium allyl sulfonate is 1-2:1, preferably 1.1:1.

[0019] Preferably according to the present invention, the organic ester containing a carbon-carbon double bond is one of hydroxyethyl methacrylate, vinyl acetate or 2-hydroxyethyl acrylate.

[0020] Preferably according to the present invention, the relative molecular mass of the phosphate dephosphorizing agent is 2000-4000.

[0021] The method for preparing the above-mentioned phosphate dissolving agent used in soil to replace phosphate fertilizer comprises the steps of:

[0022] In solvent water, under the action of a composite initiator, an organic acid containing a carbon-carbon double bond, an unsaturated organic salt containing a sulfonic acid, and an organic ester containing a carbon-carbon double bond undergo a polymerization reaction to prepare a phosphate dissolving agent used in soil to replace phosphate fertilizer.

[0023] Preferably, according to the present invention, the polymerization reaction temperature is 80-100°C, the polymerization reaction time is 3-5h, and the heating rate is 4-6°C / min; preferably, the polymerization reaction temperature is 90°C.

[0024] Preferably, according to the present invention, a method for preparing a phosphate dissolving agent for use in soil to replace phosphate fertilizer comprises the following steps:

[0025] The water is heated at a heating rate of 4-6°C / min; under stirring conditions, organic acids containing carbon-carbon double bonds, unsaturated organic salts containing sulfonic acids, and organic esters containing carbon-carbon double bonds are added into the water and stirred until they are completely dispersed; when the temperature rises to 85°C, a composite initiator is added, and then stirred to react to obtain a phosphate dissolving agent for use in soil as a substitute for phosphate fertilizer.

[0026] The above-mentioned application of the phosphate dissolving agent for use in soil to replace phosphate fertilizer is applied to soil to degrade phosphate in the soil and increase the effective phosphorus content in the soil, thereby increasing the yield and quality of crops.

[0027] The technical features and beneficial effects of the present invention are as follows:

[0028] 1. The preparation method of the present invention is simple, efficient and low in cost. In the present invention, an initiator is added to the synthesis system of an organic acid containing a carbon-carbon double bond, an unsaturated organic salt containing a sulfonic acid, and an organic ester containing a carbon-carbon double bond to improve the reaction polymerization efficiency. At the same time, the initiator generates a protective gas in the polymerization reaction to isolate the oxygen environment, so there is no need to additionally introduce an inert protective gas, thereby avoiding the risk caused by using a large amount of inert protective gas in the large-scale industrial production process and further reducing the production cost.

[0029] 2. The present invention chemically synthesizes a polymer phosphate dissolving agent, broadens the types of phosphate dissolving agents and the varieties of phosphate dissolving agents that can be used in agricultural production, so as to improve the quality and yield of crops, and reduces the shortcomings of existing phosphate dissolving agents such as high volatility, residues in agricultural products, and environmental pollution. The phosphate dissolving agent prepared by the present invention is phosphorus-free but can degrade phosphate salts in the soil; has good stability, low volatility, and long storage time; has good water solubility and low dosage; has little residue in agricultural products, low toxicity, and low environmental pollution.

[0030] 3. Traditional phosphate fertilizers are hydrolyzed to form saturated solutions or acid-lyzed by microorganisms to provide effective phosphorus after being applied to the soil, and the present invention provides a phosphate dissolving agent that can be applied to soil to replace phosphate fertilizers. The phosphate dissolving agent that can be applied to soil to replace phosphate fertilizers of the present invention introduces a high proportion of carboxyl groups in the chemical structure of the copolymer by selecting a specific type of organic acid containing carbon-carbon double bonds, thereby improving the chelating performance of the phosphate dissolving agent. In addition, the unsaturated organic salt containing sulfonic acid in the preparation raw material can make the calcium phosphate crystal nucleus in the soil difficult to aggregate, thereby improving its effect of degrading phosphate salts in the soil. The carboxyl group, sulfonic acid group, etc. possessed by the phosphate dissolving agent of the present invention can degrade the insoluble phosphate salts existing in the soil itself and make them difficult to aggregate, thereby increasing the effective phosphorus content in the soil to increase crop yields, and providing a new direction for the development of phosphorus additives and alternative fertilizers in the future agricultural field.

[0031] 4. The specific types of composite initiators, organic acids containing carbon-carbon double bonds, unsaturated organic salts containing sulfonic acids, and organic esters containing carbon-carbon double bonds of the present invention, combined with specific ratios, can achieve the excellent phosphorus decomposition effect of the present invention; if the types and ratios of raw materials are not suitable, or one or more components are omitted, the phosphorus decomposition effect will be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a picture of an actual sample of a phosphate dissolving agent that can be used in soil to replace phosphate fertilizer, prepared in Example 1 of the present invention;

[0033] Figure 2 This is a comparison diagram of the phosphate solubilizing agent that can be used in soil to replace phosphate fertilizer prepared in Example 1 of the present invention after phosphate solubilization (left) and before phosphate solubilization (right). DETAILED DESCRIPTION

[0034] The present invention is further described below with reference to specific embodiments, but is not limited thereto.

[0035] Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0036] Example 1

[0037] A phosphate dissolving agent used in soil to replace phosphate fertilizer is prepared by including the following raw materials in parts by weight:

[0038] Composite initiator vanadium sulfate 0.032g, 30% mass concentration of hydrogen peroxide aqueous solution 10g, organic acid maleic anhydride containing carbon-carbon double bonds 1.9612g, itaconic acid 3.903g, unsaturated organic salt containing sulfonic acid sodium methyl propylene sulfonate 3.163g, sodium allyl sulfonate 2.882g, organic ester containing carbon-carbon double bonds hydroxyethyl methacrylate 1.0738g, solvent deionized water 10g.

[0039] The preparation method of the above-mentioned phosphate dissolving agent used in soil to replace phosphate fertilizer comprises the following steps:

[0040] Step 1: Add deionized water into a three-necked flask and adjust the heating rate to 5°C / min;

[0041] Step 2: under stirring conditions, add maleic anhydride, itaconic acid, sodium methacrylic acid, sodium allyl sulfonate, and hydroxyethyl methacrylate to the system of step 1 in sequence, and stir until the monomers are completely dispersed;

[0042] Step 3: When the temperature rises to 85°C, add vanadium sulfate, stir for 60 seconds, then drip a 30% mass concentration of hydrogen peroxide aqueous solution into the system, and drip it within 30 minutes. Then stir and react at 90°C for 4 hours, and finally cool down to collect the product. The above reaction does not require additional inert gas.

[0043] The relative molecular mass of the phosphate dissolving agent used in the soil to replace phosphate fertilizer obtained in this embodiment is 3068 as measured by viscosity method.

[0044] The appearance of the product prepared in this embodiment is as follows Figure 1 As shown, the obtained product is a viscous liquid.

[0045] Example 2

[0046] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that the amount of itaconic acid is 2.602 g; the other raw material compositions are the same as those in Example 1.

[0047] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0048] Example 3

[0049] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that the amount of itaconic acid is 1.952 g; the other raw material compositions are the same as those in Example 1.

[0050] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0051] Example 4

[0052] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that the amount of maleic anhydride is 2.942 g; the other raw material compositions are the same as those in Example 1.

[0053] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0054] Example 5

[0055] A phosphate dissolving agent for use in soil as a substitute for phosphate fertilizer is as described in Example 1, except that the amount of maleic anhydride is 1.471 g; the other raw material compositions are the same as those in Example 1.

[0056] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0057] Example 6

[0058] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that the amount of vanadium sulfate in the initiator is 0.016 g; the other raw material compositions are the same as those in Example 1.

[0059] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0060] Example 7

[0061] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that the amount of vanadium sulfate in the initiator is 0.048 g; the other raw material compositions are the same as those in Example 1.

[0062] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0063] Example 8

[0064] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that the amount of deionized water is 60 g; the other raw material compositions are the same as those in Example 1.

[0065] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1.

[0066] Example 9

[0067] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that hydroxyethyl methacrylate is replaced by vinyl acetate; the other raw material compositions are the same as those in Example 1.

[0068] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0069] Example 10

[0070] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that hydroxyethyl methacrylate is replaced by 2-hydroxyethyl acrylate; the other raw material compositions are the same as those in Example 1.

[0071] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0072] Embodiment 11

[0073] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that itaconic acid is replaced by acrylic acid; the other raw material compositions are the same as those in Example 1.

[0074] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0075] Example 12

[0076] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that vanadium sulfate is replaced by sodium persulfate; the other raw material compositions are the same as those in Example 1.

[0077] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0078] Example 13

[0079] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that sodium methyl propylene sulfonate is not added; other raw material compositions are the same as those in Example 1.

[0080] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0081] Embodiment 14

[0082] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that sodium allyl sulfonate is not added; other raw material compositions are the same as those in Example 1.

[0083] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0084] Embodiment 15

[0085] A phosphate dissolving agent used in soil to replace phosphate fertilizer is as described in Example 1, except that maleic anhydride is not added; other raw material compositions are the same as those in Example 1.

[0086] The preparation method of the above-mentioned phosphate dissolving agent for use in soil to replace phosphate fertilizer is as described in Example 1, with the same differences as above.

[0087] Comparative Example 1

[0088] A phosphate dissolving agent, as described in Example 1, except that hydroxyethyl methacrylate is not added; other raw material compositions are the same as those in Example 1.

[0089] The preparation method of the above-mentioned phosphate degrading agent is as described in Example 1, except that the differences are the same as above.

[0090] Since there is no hydroxyethyl methacrylate in this comparative example, the reaction product is stratified.

[0091] Comparative Example 2

[0092] A dephosphorizing agent, as described in Example 1, except that the composite initiator is replaced by 6g of ammonium persulfate; the other raw material compositions are the same as those in Example 1.

[0093] The preparation method of the above-mentioned phosphate degrading agent is as described in Example 1, except that the differences are the same as above.

[0094] In this comparative example, due to the lack of protective gas protection, the initiator used did not initiate the reaction and ultimately the target product was not obtained.

[0095] Comparative Example 3

[0096] A dephosphorizing agent, as described in Example 1, except that the composite initiator is replaced by 6g of sodium persulfate; the other raw material compositions are the same as those in Example 1.

[0097] The preparation method of the above-mentioned phosphate degrading agent is as described in Example 1, except that the differences are the same as above.

[0098] In this comparative example, due to the lack of protective gas protection, the initiator used did not initiate the reaction and ultimately the target product was not obtained.

[0099] Test Example 1

[0100] Phosphate solubilization experiment

[0101] Prepare solution: dissolve 25 g of calcium nitrate in 100 mL of water to prepare calcium nitrate solution; dissolve 6.8 g of potassium dihydrogen phosphate and 1.9 g of sodium hydroxide in 100 mL of water to prepare orthophosphate solution.

[0102] Step 1: Add 200 mL of water to a beaker, then add 5 mL of calcium nitrate solution and 5 mL of orthophosphate solution to the beaker, and stir with a glass rod to form a turbid phosphate solution.

[0103] Step 2: Add the phosphate dissolving agent drop by drop into the beaker, stir continuously with a glass rod until the solution is clear and start timing.

[0104] Table 1 Phosphorus dissolution effect

[0105]

[0106]

[0107] Note: Under stirring conditions, use a pipette to titrate the phosphate dissolving agent into the phosphate solution at a uniform speed until the phosphate solution becomes clear, and record the amount of phosphate dissolving agent used; the time from the start of titration to the clarification of the phosphate solution is the phosphate dissolving time. Stability refers to the state of the phosphate dissolving agent after being placed at room temperature for 72 hours.

[0108] It can be seen from the test results in Table 1 that the phosphate dissolving agent obtained by the method of the present invention, which can be applied to soil to replace phosphate fertilizer, has the advantages of excellent phosphate dissolving effect, small dosage, good stability, etc. The dosage and phosphate dissolving time of the phosphate dissolving agent obtained in Example 1 of the present invention are both optimal, and compared with the phosphate dissolving agent prepared by not introducing organic ester into the raw material, it has excellent stability. Figure 2The comparison diagram of the phosphate solubilizer prepared in Example 1 of the present invention and applicable to soil instead of phosphate fertilizer after phosphate solubilization (left) and before phosphate solubilization (right) shows that the phosphate solubilizer of the present invention successfully achieves phosphate solubilization.

Claims

1. A phosphate dissolving agent used in soil to replace phosphate fertilizer, characterized in that: The raw materials comprising the following parts by weight are prepared: 1-15 parts of composite initiator, 1-10 parts of organic acid containing carbon-carbon double bond, 1-10 parts of unsaturated organic salt containing sulfonic acid, 0.5-5 parts of organic ester containing carbon-carbon double bond, and 1-80 parts of solvent water.

2. The phosphate dissolving agent used for soil replacement of phosphate fertilizer according to claim 1, characterized in that: The phosphate dissolving agent used for replacing phosphate fertilizer in soil is prepared by including the following raw materials in parts by weight: 10-11 parts of composite initiator, 3-7 parts of organic acid containing carbon-carbon double bond, 5-7 parts of unsaturated organic salt containing sulfonic acid, 1-2 parts of organic ester containing carbon-carbon double bond, and 5-60 parts of solvent water.

3. The phosphate dissolving agent used for soil replacement of phosphate fertilizer according to claim 2, characterized in that: The phosphate dissolving agent used for replacing phosphate fertilizer in soil is prepared by the following raw materials in parts by mass: 10-11 parts of composite initiator, 5-6 parts of organic acid containing carbon-carbon double bond, 6-7 parts of unsaturated organic salt containing sulfonic acid, 1-2 parts of organic ester containing carbon-carbon double bond, and 5-15 parts of solvent water.

4. The phosphate dissolving agent used in soil to replace phosphate fertilizer according to claim 1, characterized in that: The composite initiator is a combination of two or more of vanadium sulfate, a hydrogen peroxide solution with a mass concentration of 20-30%, sodium persulfate, ammonium persulfate or ammonium bicarbonate; preferably, the composite initiator is a combination of vanadium sulfate and a hydrogen peroxide solution with a mass concentration of 20-30%; the mass ratio of vanadium sulfate and a hydrogen peroxide solution with a mass concentration of 20-30% is 0.01-0.05:10, preferably 0.032:

10.

5. The phosphate dissolving agent used in soil to replace phosphate fertilizer according to claim 1, characterized in that: The organic acid containing a carbon-carbon double bond is one or a combination of two or more of maleic anhydride, itaconic acid, acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid or cis-methylbutene dicarboxylic acid; preferably, the organic acid containing a carbon-carbon double bond is a combination of maleic anhydride and itaconic acid; the mass ratio of maleic anhydride to itaconic acid is 1:0.9-3, preferably 1:

2.

6. The phosphate dissolving agent used in soil to replace phosphate fertilizer according to claim 1, characterized in that: The unsaturated organic salt containing sulfonic acid is one or a combination of sodium methacrylate sulfonate or sodium allyl sulfonate; preferably, the unsaturated organic salt containing sulfonic acid is a combination of sodium methacrylate sulfonate and sodium allyl sulfonate; the mass ratio of sodium methacrylate sulfonate to sodium allyl sulfonate is 1-2:1, preferably 1.1:

1.

7. The phosphate dissolving agent used in soil to replace phosphate fertilizer according to claim 1, characterized in that: The organic ester containing a carbon-carbon double bond is one of hydroxyethyl methacrylate, vinyl acetate or 2-hydroxyethyl acrylate.

8. The phosphate dissolving agent used in soil to replace phosphate fertilizer according to claim 1, characterized in that: The relative molecular mass of the phosphate-dissolving agent is 2000-4000.

9. A method for preparing a phosphate dissolving agent for use in soil as a substitute for phosphate fertilizer according to any one of claims 1 to 8, comprising the steps of: In solvent water, under the action of a composite initiator, an organic acid containing a carbon-carbon double bond, an unsaturated organic salt containing a sulfonic acid, and an organic ester containing a carbon-carbon double bond undergo a polymerization reaction to prepare a phosphate dissolving agent used in soil to replace phosphate fertilizer; Preferably, the polymerization reaction temperature is 80-100°C, the polymerization reaction time is 3-5h, and the heating rate is 4-6°C / min; preferably, the polymerization reaction temperature is 90°C.

10. The use of a phosphate dissolving agent as claimed in any one of claims 1 to 8 as a substitute for phosphate fertilizer in soil, characterized in that: It is applied to soil to degrade phosphates in the soil and increase the effective phosphorus content in the soil, thereby improving crop yield and quality.

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