Biodegradable macromolecular sustained and controlled release liquid fertilizer and preparation method thereof

Abstract

The preparation method comprises the following steps: uniformly mixing a formaldehyde aqueous solution with urea, carrying out a heating reaction, adding an oxidized sodium carboxymethyl cellulose aqueous solution into the obtained reaction solution, uniformly mixing, and adding potassium dihydrogen phosphate to obtain a solution A; uniformly mixing a gelatin aqueous solution and a sulfydryl polyvinyl alcohol aqueous solution to obtain a solution B; and mixing the solution A with the solution B to obtain the biodegradable polymer sustained and controlled release liquid fertilizer. The slow / controlled-release liquid fertilizer disclosed by the invention has good fertilization uniformity and slow / controlled-release stability, can be applied in manners of drip irrigation, spraying and the like, can reduce the fertilization times, improve the utilization rate of the fertilizer, better save water and fertilizer, improve the yield and quality of crops, and can better adapt to the requirements of sustainable development and a water and fertilizer integration technology.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a biodegradable macromolecular slow-release liquid fertilizer and a preparation method thereof. Background Art

[0002] Fertilizer plays an important role in agricultural production. Traditional fertilizers have low utilization rates and are easy to leach, causing soil, water, and air pollution. The slow-release fertilizer has become a feasible solution to adapt to the sustainable development of agriculture and improve the yield and quality of crops. At present, slow-release fertilizers are mainly granular solid fertilizers. The uneven fertilization can easily cause insufficient nutrient absorption by crops or burn seedlings. Water-fertilizer integration is a technology that has gradually emerged in recent years. By adding water-soluble fertilizers or liquid fertilizers suitable for irrigation during the irrigation process, water application and fertilization can be combined to meet the needs of crops for water and fertilizer in a concentrated, timely and appropriate manner. The introduction of liquid fertilizers with slow-release effects in water-fertilizer integration is conducive to better achieving the effects of saving water, saving fertilizers, and improving fertilizer utilization. In addition, the residue of fertilizers in the soil will cause secondary pollution, have adverse effects on soil structure and properties, and even cause soil compaction, hindering the root development and nutrient absorption of subsequent crops. In order to avoid the above problems, fertilizers are required to have excellent degradable properties. Therefore, in order to adapt to the requirements of sustainable development and water-fertilizer integration technology, reduce the number of fertilization times, improve fertilizer utilization, better save water and fertilizer, and increase the yield and quality of crops, it is necessary to develop biodegradable slow-release liquid fertilizers. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a biodegradable polymer slow-release liquid fertilizer and a preparation method thereof.

[0004] The present invention provides a method for preparing a biodegradable polymer slow-release liquid fertilizer, comprising the following steps:

[0005] S1, mixing the formaldehyde aqueous solution and urea uniformly, adjusting the pH to 7.5-8.5, reacting at 50-80° C. for 1-3 hours, then adding 2-10 wt % oxidized sodium carboxymethyl cellulose aqueous solution to the obtained reaction solution and mixing uniformly, and then adding potassium dihydrogen phosphate to obtain solution A;

[0006] S2, mixing the gelatin aqueous solution and the mercapto polyvinyl alcohol aqueous solution evenly to obtain solution B;

[0007] S3. After mixing the liquid A with the liquid B, the biodegradable polymer slow-release liquid fertilizer is obtained.

[0008] Preferably, in S1, the molar ratio of formaldehyde to urea is 1:1-2, and the concentration of the formaldehyde aqueous solution is 35-45 wt%.

[0009] Preferably, the preparation method of the oxidized sodium carboxymethyl cellulose is as follows: after mixing the sodium carboxymethyl cellulose aqueous solution and the sodium periodate aqueous solution, reacting in the dark for 6 to 24 hours at a pH of 2 to 4 and a temperature of 35 to 50° C., adding ethanol for precipitation after the reaction, washing the obtained precipitate with ethanol and drying.

[0010] Preferably, the mass ratio of sodium carboxymethyl cellulose to sodium periodate is 1:0.5-1.

[0011] Preferably, the concentration of the sodium carboxymethyl cellulose aqueous solution is 50-100 g / L, and the concentration of the sodium periodate aqueous solution is 50-100 g / L.

[0012] Preferably, in S1, the mass ratio of the reaction solution to the aqueous solution of sodium carboxymethyl cellulose oxide is 1:1-5; in S1, the mass ratio of the reaction solution to potassium dihydrogen phosphate is 1:0.05-0.1.

[0013] Preferably, the concentration of the gelatin aqueous solution is 0.5-1 wt%.

[0014] Preferably, the concentration of the mercapto polyvinyl alcohol aqueous solution is 2-3 wt %.

[0015] Preferably, the preparation method of the mercapto polyvinyl alcohol is: add acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid to a polyvinyl alcohol aqueous solution, react at 30-50°C for 24-72 hours, add ethanol to precipitate after the reaction, wash the obtained precipitate with ethanol and then dry, wherein the mass ratio of polyvinyl alcohol, acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid is 1:5-8:3-5:10-15:0.1-2.

[0016] Preferably, the concentration of the polyvinyl alcohol aqueous solution is 1-3 wt %.

[0017] Preferably, the mass ratio of the aqueous gelatin solution to the aqueous mercaptopolyvinyl alcohol solution is 1:1-3.

[0018] Preferably, in S3, the mass ratio of liquid A to liquid B is 1:1-2.

[0019] In S3, after the liquid A and the liquid B are mixed, the step further includes: diluting the mixture by 20 to 100 times.

[0020] A biodegradable macromolecular slow-release liquid fertilizer is prepared by the preparation method.

[0021] The beneficial effects of the present invention are as follows:

[0022] In the present invention, an aqueous solution of sodium carboxymethyl cellulose oxide and potassium dihydrogen phosphate are added as liquid A to a urea-formaldehyde liquid fertilizer obtained by reacting formaldehyde with urea, and a mixed solution of an aqueous gelatin solution and an aqueous mercapto polyvinyl alcohol solution is added as liquid B. When the two are mixed, the aldehyde groups in the sodium carboxymethyl cellulose oxide, the amino groups in the gelatin, and the mercapto groups in the mercapto polyvinyl alcohol are slowly cross-linked to form a biodegradable network structure, thereby further improving the slow-release performance of nutrients in the liquid fertilizer. The binding force and binding stability of the aldehyde group in the amino group in gelatin and the thiol group in the thiol polyvinyl alcohol are different from those in the sodium carboxymethyl cellulose oxide, and the degradation rate of the thiol group and the aldehyde group cross-linking network is fast, and the plasticity and fluidity are strong, and the cross-linking network binding strength of the amino group and the aldehyde group is high, so the cross-linking network of the amino group in gelatin and the thiol group in the thiol polyvinyl alcohol and the aldehyde group in the sodium carboxymethyl cellulose oxide is introduced at the same time, which can be fully cross-linked, so as to play a good slow-release effect, and can avoid the excessive internal binding force of the liquid fertilizer and cause the soil to clump after application, hinder the root growth of crops, and the uneven distribution of fertilizer application, and the problem of poor fertilizer efficiency, and can realize step-by-step controlled release, improve the uniformity of nutrient release, make nutrient release stable, and improve nutrient utilization. In summary, the slow-release liquid fertilizer of the present invention has good fertilization uniformity and slow-release stability, can be fertilized by drip irrigation, spraying and other methods, can reduce the number of fertilization, improve fertilizer utilization, better save water and fertilizer, improve the yield and quality of crops, and can better adapt to the requirements of sustainable development and water-fertilizer integration technology. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is described in detail below through specific embodiments.

[0024] In the following examples and comparative examples, the polyvinyl alcohol is 1788.

[0025] Example 1

[0026] The method for preparing biodegradable polymer slow-release liquid fertilizer is as follows:

[0027] S1. A 37 wt % formaldehyde aqueous solution and urea were mixed evenly in a molar ratio of formaldehyde to urea of ​​1:2, the pH was adjusted to 8, and the mixture was reacted at 60° C. for 2 h, and then a 5 wt % oxidized sodium carboxymethyl cellulose aqueous solution was added to the obtained reaction solution and mixed evenly, and then potassium dihydrogen phosphate was added to obtain a liquid A, wherein the mass ratio of the reaction solution to the oxidized sodium carboxymethyl cellulose aqueous solution was 1:3, and the mass ratio of the reaction solution to potassium dihydrogen phosphate was 1:0.06;

[0028] S2, uniformly mixing a 0.75wt% gelatin aqueous solution and a 1.5wt% mercapto polyvinyl alcohol aqueous solution in a mass ratio of 1:2 to obtain liquid B;

[0029] S3. Mix the liquid A and the liquid B in a mass ratio of 1:1.5 to obtain the biodegradable polymer slow-release liquid fertilizer.

[0030] The preparation method of oxidized sodium carboxymethyl cellulose is as follows: a sodium carboxymethyl cellulose aqueous solution with a concentration of 100 g / L is mixed with a sodium periodate aqueous solution with a concentration of 100 g / L, and the mixture is reacted in the dark at a pH of 3 and a temperature of 40° C. for 12 hours, and after the reaction, ethanol is added for precipitation, and the obtained precipitate is washed with ethanol and then dried to obtain the oxidized sodium carboxymethyl cellulose, wherein the mass ratio of the sodium carboxymethyl cellulose to the sodium periodate is 1:0.8;

[0031] The preparation method of mercapto polyvinyl alcohol is as follows: acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid with a concentration of 98wt% are added to a polyvinyl alcohol aqueous solution with a concentration of 2wt%, and the mixture is reacted at 35°C for 48h. After the reaction, ethanol is added for precipitation, and the obtained precipitate is washed with ethanol and then dried to obtain the product, wherein the mass ratio of polyvinyl alcohol, acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid is 1:6:4:12:0.5.

[0032] Example 2

[0033] The method for preparing biodegradable polymer slow-release liquid fertilizer is as follows:

[0034] A 37 wt % formaldehyde aqueous solution and urea are mixed evenly in a molar ratio of formaldehyde to urea of ​​1:2, the pH is adjusted to 8, and the mixture is reacted at 60° C. for 2 h, and then a 2-10 wt % oxidized sodium carboxymethyl cellulose aqueous solution is added to the obtained reaction solution and mixed evenly, and then potassium dihydrogen phosphate is added to obtain a liquid A, wherein the mass ratio of the reaction solution to the oxidized sodium carboxymethyl cellulose aqueous solution is 1:1, and the mass ratio of the reaction solution to the potassium dihydrogen phosphate is 1:0.05;

[0035] S2, uniformly mixing a 0.5 wt % gelatin aqueous solution and a 2 wt % mercapto polyvinyl alcohol aqueous solution in a mass ratio of 1:1 to obtain liquid B;

[0036] S3. Mix the liquid A and the liquid B in a mass ratio of 1:1 to obtain the biodegradable polymer slow-release liquid fertilizer.

[0037] The preparation method of oxidized sodium carboxymethyl cellulose is as follows: after mixing a sodium carboxymethyl cellulose aqueous solution with a concentration of 50 g / L and a sodium periodate aqueous solution with a concentration of 100 g / L, reacting in the dark for 6 hours under the conditions of pH 2 and temperature 35°C, adding ethanol for precipitation after the reaction, washing the obtained precipitate with ethanol and drying, the mass ratio of sodium carboxymethyl cellulose to sodium periodate is 1:0.5;

[0038] The preparation method of mercapto polyvinyl alcohol is as follows: acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid with a concentration of 98wt% are added to a polyvinyl alcohol aqueous solution with a concentration of 1wt%, and the mixture is reacted at 30°C for 72h. After the reaction, ethanol is added for precipitation, and the obtained precipitate is washed with ethanol and then dried to obtain the product, wherein the mass ratio of polyvinyl alcohol, acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid is 1:5:3:10:0.1.

[0039] Example 3

[0040] The method for preparing biodegradable polymer slow-release liquid fertilizer is as follows:

[0041] A 37 wt % formaldehyde aqueous solution and urea were mixed evenly in a molar ratio of formaldehyde to urea of ​​1:2, the pH was adjusted to 8, and the mixture was reacted at 60° C. for 2 h, and then a 10 wt % sodium carboxymethyl cellulose oxide aqueous solution was added to the obtained reaction solution and mixed evenly, and then potassium dihydrogen phosphate was added to obtain a liquid A, wherein the mass ratio of the reaction solution to the sodium carboxymethyl cellulose oxide aqueous solution was 1:5, and the mass ratio of the reaction solution to potassium dihydrogen phosphate was 1:0.1;

[0042] S2, mixing a 1 wt % gelatin aqueous solution and a 3 wt % mercapto polyvinyl alcohol aqueous solution in a mass ratio of 1:3 to obtain liquid B;

[0043] S3. Mixing the liquid A and the liquid B at a mass ratio of 1:2 to obtain the biodegradable polymer slow-release liquid fertilizer.

[0044] The preparation method of oxidized sodium carboxymethyl cellulose is as follows: a sodium carboxymethyl cellulose aqueous solution with a concentration of 100 g / L is mixed with a sodium periodate aqueous solution with a concentration of 50 g / L, and the mixture is reacted in the dark for 24 hours at a pH of 4 and a temperature of 50° C., and after the reaction, ethanol is added for precipitation, and the obtained precipitate is washed with ethanol and then dried to obtain the oxidized sodium carboxymethyl cellulose, wherein the mass ratio of the sodium carboxymethyl cellulose to the sodium periodate is 1:1;

[0045] The preparation method of mercapto polyvinyl alcohol is as follows: acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid with a concentration of 98wt% are added to a polyvinyl alcohol aqueous solution with a concentration of 3wt%, and the mixture is reacted at 50°C for 24h. After the reaction, ethanol is added for precipitation, and the obtained precipitate is washed with ethanol and then dried to obtain the product, wherein the mass ratio of polyvinyl alcohol, acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid is 1:8:5:15:2.

[0046] Comparative Example 1

[0047] The method for preparing urea-formaldehyde slow-release liquid fertilizer containing nitrogen, phosphorus and potassium is as follows:

[0048] A 37wt% formaldehyde aqueous solution and urea were mixed evenly in a molar ratio of formaldehyde to urea of ​​1:2, the pH was adjusted to 8, and the mixture was reacted at 60°C for 2h, and then deionized water equivalent to 3 times the mass of the reaction solution was added to the obtained reaction solution and mixed evenly, and then potassium dihydrogen phosphate was added and mixed evenly, and then the obtained mixture was mixed evenly with deionized water equivalent to 1.5 times the mass of the mixture to obtain a slow-release liquid fertilizer.

[0049] Comparative Example 2

[0050] The method for preparing biodegradable polymer slow-release liquid fertilizer is as follows:

[0051] S1. A 37 wt % formaldehyde aqueous solution and urea were mixed evenly in a molar ratio of formaldehyde to urea of ​​1:2, the pH was adjusted to 8, and the mixture was reacted at 60° C. for 2 h, and then a 5 wt % oxidized sodium carboxymethyl cellulose aqueous solution was added to the obtained reaction solution and mixed evenly, and then potassium dihydrogen phosphate was added to obtain a liquid A, wherein the mass ratio of the reaction solution to the oxidized sodium carboxymethyl cellulose aqueous solution was 1:3, and the mass ratio of the reaction solution to potassium dihydrogen phosphate was 1:0.06;

[0052] S2, preparing a gelatin aqueous solution with a concentration of 1.25wt% to obtain liquid B;

[0053] S3. Mix the liquid A and the liquid B in a mass ratio of 1:1.5 to obtain a biodegradable polymer slow-release liquid fertilizer.

[0054] The preparation method of oxidized carboxymethyl cellulose sodium is the same as that in Example 1.

[0055] Comparative Example 3

[0056] The method for preparing biodegradable polymer slow-release liquid fertilizer is as follows:

[0057] S1. A 37 wt % formaldehyde aqueous solution and urea were mixed evenly in a molar ratio of formaldehyde to urea of ​​1:2, the pH was adjusted to 8, and the mixture was reacted at 60° C. for 2 h, and then a 5 wt % oxidized sodium carboxymethyl cellulose aqueous solution was added to the obtained reaction solution and mixed evenly, and then potassium dihydrogen phosphate was added to obtain a liquid A, wherein the mass ratio of the reaction solution to the oxidized sodium carboxymethyl cellulose aqueous solution was 1:3, and the mass ratio of the reaction solution to potassium dihydrogen phosphate was 1:0.06;

[0058] S2, preparing a 1.25 wt % mercapto polyvinyl alcohol aqueous solution to obtain solution B;

[0059] S3. Mix the liquid A and the liquid B in a mass ratio of 1:1.5 to obtain a biodegradable polymer slow-release liquid fertilizer.

[0060] The preparation method of oxidized sodium carboxymethyl cellulose and mercapto polyvinyl alcohol is the same as that in Example 1.

[0061] Test example

[0062] (1) Sustained release performance test

[0063] The slow-release performance of the slow-release liquid fertilizer of Example 1 and Comparative Examples 1 to 3 was tested by leaching method. The test method is as follows: the intermittent leaching method is adopted, the soil is first loaded into the leaching column pre-filled with quartz sand, and then the liquid fertilizer is fully mixed with the soil, and a control group without fertilizer is set. During the test, the water content of each group of soil is maintained at 70% of the saturated water content by replenishing water. Each group of samples is cultured under the condition of 25±2℃, and leached with water once at the 10th, 20th, 30th, 40th and 50th days of culture. The leaching solution is collected after each leaching, and the total nitrogen content of the leaching solution is tested by potassium persulfate oxidation-ultraviolet spectrophotometry, and the cumulative release rate of N is calculated. The test results are shown in Table 1.

[0064] Table 1

[0065]

[0066] It can be seen from Table 1 that the biodegradable polymer slow-release liquid fertilizer of the present invention has stable slow-release performance, and its 50d cumulative release rate is significantly lower than that of the urea-formaldehyde slow-release liquid fertilizer of Comparative Example 1, which is beneficial to prolonging the fertilizer effect period, and the nutrient release is stable, which can improve the uniformity of fertilizer release and improve nutrient utilization.

[0067] (2) Fertilizer efficiency test

[0068] The controlled-release liquid fertilizers of Example 1 and Comparative Examples 1 to 3 were used to test the fertilizer efficiency of tomatoes. The fertilization method is: 15-15-15 compound fertilizer is used as base fertilizer, and the amount of base fertilizer is 100 kg / mu; and the controlled-release liquid fertilizer is used for topdressing by drip irrigation on the 30th, 80th and 110th days after tomato planting, and the amount of liquid fertilizer used for each topdressing is 50 kg / mu. The controlled-release liquid fertilizer is diluted 50 times before use. After harvesting, the per-acre yield of tomatoes is counted, and the quality traits of tomato fruits are tested. The results of the fertilizer efficiency test are shown in Table 2:

[0069] Table 2

[0070]

[0071] As can be seen from Table 2, the biodegradable polymer slow-release liquid fertilizer in Example 1 of the present invention can significantly improve the per-acre yield of tomatoes and the soluble sugar and lycopene content in tomato fruits compared with the urea-formaldehyde slow-release liquid fertilizer in Comparative Example 1, which shows that the slow-release liquid fertilizer of the present invention can effectively increase the yield and quality of crops. Comparing the urea-formaldehyde slow-release liquid fertilizer in Comparative Example 1 with the biodegradable polymer slow-release liquid fertilizer in Comparative Example 2, the yield and quality shape of tomatoes are not significantly improved. This is because the biodegradable polymer slow-release liquid fertilizer in Comparative Example 2 only introduces a cross-linked network of amino groups in gelatin and aldehyde groups in sodium oxidized carboxymethyl cellulose. Due to the excessive internal binding force of the groups in the liquid fertilizer, the soil caking occurs after application, which not only makes the nutrient distribution uneven and cannot be well absorbed and utilized by crops, resulting in poor fertilizer efficiency, but also hinders the root growth of crops and affects the growth and development of crops. Comparing the urea-formaldehyde slow-release liquid fertilizer in Comparative Example 1 with the biodegradable polymer slow-release liquid fertilizer in Comparative Example 3, the improvement on tomato yield and quality shape is also very limited. This is because the biodegradable polymer slow-release liquid fertilizer in Comparative Example 3 only introduces a cross-linked network of thiol groups in thiol polyvinyl alcohol and aldehyde groups in oxidized carboxymethyl cellulose sodium. Since the binding force between the thiol groups and the aldehyde groups is not strong enough and the degradation rate of the cross-linked network is fast, it degrades quickly in the soil. Therefore, the biodegradable polymer slow-release liquid fertilizer in Comparative Example 3 has a poor slow-release effect on nutrients, and the nutrient release is not smooth enough, and the nutrient utilization rate cannot be effectively improved.

[0072] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a biodegradable polymer slow-release liquid fertilizer, characterized in that: The steps include: S1, mixing the formaldehyde aqueous solution and urea uniformly, adjusting the pH to 7.5-8.5, reacting at 50-80° C. for 1-3 hours, then adding 2-10 wt % oxidized sodium carboxymethyl cellulose aqueous solution to the obtained reaction solution and mixing uniformly, and then adding potassium dihydrogen phosphate to obtain solution A; S2, mixing the gelatin aqueous solution and the mercapto polyvinyl alcohol aqueous solution evenly to obtain solution B; S3. After mixing the liquid A with the liquid B, the biodegradable polymer slow-release liquid fertilizer is obtained.

2. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: In S1, the molar ratio of formaldehyde to urea is 1:1-2, and the concentration of the formaldehyde aqueous solution is 35-45 wt%.

3. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: The preparation method of the oxidized sodium carboxymethyl cellulose is as follows: after mixing the sodium carboxymethyl cellulose aqueous solution and the sodium periodate aqueous solution, reacting them in the dark for 6 to 24 hours at a pH of 2 to 4 and a temperature of 35 to 50° C., adding ethanol for precipitation after the reaction, washing the obtained precipitate with ethanol and drying the obtained precipitate; The mass ratio of sodium carboxymethyl cellulose to sodium periodate is 1:0.5-1; The concentration of the sodium carboxymethyl cellulose aqueous solution is 50-100 g / L, and the concentration of the sodium periodate aqueous solution is 50-100 g / L.

4. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: In S1, the mass ratio of the reaction solution to the aqueous solution of sodium carboxymethyl cellulose oxide is 1:1-5; in S1, the mass ratio of the reaction solution to potassium dihydrogen phosphate is 1:0.05-0.

1.

5. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: The concentration of the gelatin aqueous solution is 0.5-1 wt %.

6. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: The concentration of the mercapto polyvinyl alcohol aqueous solution is 2-3 wt %.

7. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: The preparation method of the mercapto polyvinyl alcohol comprises: adding acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid to a polyvinyl alcohol aqueous solution, reacting at 30-50° C. for 24-72 hours, adding ethanol for precipitation after the reaction, washing the obtained precipitate with ethanol and drying, wherein the mass ratio of the polyvinyl alcohol, acetic anhydride, glacial acetic acid, thioglycolic acid and concentrated sulfuric acid is 1:5-8:3-5:10-15:0.1-2; The concentration of the polyvinyl alcohol aqueous solution is 1-3 wt %.

8. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: The mass ratio of the gelatin aqueous solution to the mercapto polyvinyl alcohol aqueous solution is 1:1-3.

9. The method for preparing the biodegradable polymer slow-release liquid fertilizer according to claim 1, characterized in that: In S3, the mass ratio of the liquid A to the liquid B is 1:1-2.

10. A biodegradable polymer slow-release liquid fertilizer, characterized in that: The method is prepared according to any one of claims 1 to 9.

Images