Compound fertilizer for zizania aquatica planting and preparation method thereof

Abstract

The invention provides a compound fertilizer for zizania aquatica planting and a preparation method thereof. The preparation method mainly comprises the following steps: (1) preparation of calcium peroxide nanoparticles; (2) preparation of a fertilizer core; (3) preparation of a coating agent; the compound fertilizer prepared by the invention has good slow release performance and certain biodegradability, and can provide oxygen for a long time while improving the utilization rate of the fertilizer, so that water eutrophication caused by excessive fertilizer is relieved, and the yield and quality of zizania aquatica are successfully improved.

Description

Technical Field

[0001] The invention relates to the field of fertilizers, and in particular to a compound fertilizer for wild rice stem planting and a preparation method thereof. Background Art

[0002] Wild rice is a perennial aquatic plant that is rich in functional substances such as polysaccharides, amino acids, flavonoids, phenols, etc. It has a unique flavor and delicious taste and is deeply loved by people. At present, wild rice cultivation has become a pillar industry in Zhejiang Province and parts of Jiangsu Province as well as other parts of China. Zhejiang is the province with the largest wild rice cultivation area, with a planting area of ​​about 30,000 hectares in the province, which has high economic value.

[0003] As the area of ​​water chestnut cultivation expands, the amount of fertilizer input for water chestnut cultivation is large and the utilization rate is low. Continuous planting and the direct return of straw to the fields have led to a serious excess of nitrogen, phosphorus and other contents in the water bodies of water chestnut fields, rich organic matter, and a high degree of eutrophication of the water bodies, which has caused algae and aquatic organisms in the water to multiply in large numbers and reduce the oxygen content, thus affecting the growth of the water chestnut root system and causing problems such as root rot, poor tillering development, and poor photosynthesis ability, thereby reducing the yield and quality of water chestnut.

[0004] At present, in order to solve the problem of high eutrophication of water bodies in water chestnut fields, the water chestnut base in Zhejiang Province has carried out a water-dry intercropping planting mode for water chestnut fields, which solves the eutrophication problem of water chestnut fields by covering dry ridges with straw on the spot and exchanging planting furrows with dry ridges when the water chestnut fields are plowed in seasons. However, the water-dry intercropping planting mode requires a certain amount of labor and is more suitable for small-scale growers. Therefore, the present invention studies a compound fertilizer for water chestnut cultivation, which can reduce the eutrophication of water bodies in water chestnut fields while increasing the yield of water chestnut fields. Summary of the invention

[0005] In view of the above problems in the prior art, the present invention provides a compound fertilizer for wild rice cultivation and a preparation method thereof, aiming to improve fertilizer utilization while reducing the eutrophication degree of wild rice paddy fields, thereby improving the yield and quality of wild rice.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A compound fertilizer for wild rice cultivation and a preparation method thereof, the preparation method of the compound fertilizer comprising the following steps: (1) Preparation of calcium peroxide nanoparticles: Calcium chloride was dissolved in deionized water, and 25-28 wt% ammonia water was added dropwise to adjust the pH to 9-10.5, and then the mixture was transferred to an ice water bath, and 30 wt% hydrogen peroxide solution was slowly added dropwise. The mixture was stirred continuously for 1.8-2.2 h. After the reaction was completed, the mixture was centrifuged at 4000-8000 r / min for 10-15 min, and finally rinsed with ethanol for 3-5 times, and dried in a vacuum drying oven at 50-70 °C for 8-10 h to obtain calcium peroxide nanoparticles. (2) Preparation of fertilizer core: nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, calcium peroxide nanoparticles prepared in step (1), and a binder are uniformly mixed, and then placed in a disc granulator for granulation to prepare a fertilizer core with a diameter of 3 to 5 mm; (3) Preparation of coating agent: Sodium carboxymethyl cellulose was dissolved in deionized water and placed in a round-bottom flask. After nitrogen was passed through the flask at 25-28°C for 25-45 min, potassium persulfate was added and reacted for 20-30 min. The flask was heated to 78-82°C and methyl methacrylate (MMA) and N-vinyl pyrrolidone (NVP) were added. The reaction was continued for 3-5 h under nitrogen. After the reaction was completed, the flask was filtered and dried in a vacuum drying oven at 30-50°C for 10-14 h to remove moisture. The flask was washed with methanol for 2-5 times and dried in a vacuum drying oven at 55-65°C for 12-36 h to obtain a coating agent. (4) Preparation of compound fertilizer: First, the coating agent prepared in step (3) is dissolved in tetrahydrofuran to obtain a coating liquid, and then the fertilizer kernel prepared in step (2) is loaded into a coating machine, the rotation speed is maintained at 100-120 r / min, and the coating liquid is injected. After the coating liquid is evenly coated on the surface of the fertilizer kernel, it is heated with hot air at 40-55° C. until the solvent evaporates, and finally a dry compound fertilizer is obtained.

[0007] Preferably, in step (1), the ratio of the mass (g) of calcium chloride to the volume (mL) of deionized water and hydrogen peroxide solution is 1:(4-8):(10-15).

[0008] Preferably, in step (2), the mass ratio of nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, calcium peroxide nanoparticles and adhesive is 1: (0.4-0.6): (0.4-0.6): (0.6-0.9): (0.05-0.08).

[0009] Preferably, in step (3), the mass ratio of sodium carboxymethyl cellulose, potassium persulfate, methyl methacrylate (MMA), and N-vinyl pyrrolidone (NVP) is 1: (0.1-0.2): (0.5-0.7): (0.3-0.5), and the mass (g) of sodium carboxymethyl cellulose and the volume (mL) of deionized water is 1: (95-110).

[0010] Preferably, in step (4), the mass (g) of the coating agent: the volume (mL) of tetrahydrofuran: the mass (g) of the fertilizer kernel is 1: (4-6): (7-9).

[0011] Preferably, the nitrogen fertilizer is one or more of ammonium bicarbonate, ammonium sulfate, ammonium chloride, and urea; the phosphate fertilizer is one or more of superphosphate, double superphosphate, monoammonium phosphate, and diammonium phosphate; and the potash fertilizer is one or more of potassium chloride, potassium sulfate, potassium nitrate, and potassium magnesium sulfate.

[0012] Preferably, the binder is one of bentonite, attapulgite powder and kaolin.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The presence of calcium peroxide nanoparticles in the composite fertilizer of the present invention can increase the dissolved oxygen content in the water body to a certain extent. In addition, methyl methacrylate is added in the process of preparing the fertilizer coating agent of the present invention, so that the hydrophobicity of the coating agent is enhanced, and the release of the fertilizer in the coating is significantly delayed. While improving the fertilizer utilization rate, oxygen can be provided for a long time, thereby alleviating the eutrophication of the water body caused by excessive fertilizers, and successfully improving the yield and quality of wild rice stem.

[0014] 2. The hydrophilic component in the coating used for the composite fertilizer of the present invention can enhance the adhesion between it and the internal water-soluble fertilizer, which is beneficial to the transportation and storage of the composite fertilizer. In addition, the hydrolysis of the amide group in N-vinyl pyrrolidone can alleviate the increase in pH caused by the hydrolysis of calcium peroxide, thereby preventing the increase in pH in paddy fields from restricting the normal growth of wild rice. In addition, the coating on the surface of the composite fertilizer has a certain biodegradability, which reduces the adverse effects of the fertilizer on the environment.

[0015] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] none DETAILED DESCRIPTION The present invention is specifically described below by way of examples, which are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. It should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0017] Example 1 (1) Preparation of calcium peroxide nanoparticles: 10 g of calcium chloride was dissolved in 50 mL of deionized water, and 26 wt% ammonia water was added dropwise to adjust the pH to 10. The mixture was then transferred to an ice water bath and 130 mL of hydrogen peroxide solution (30 wt%) was slowly added. The mixture was stirred for 2 h. After the reaction, the mixture was centrifuged at 5000 r / min for 12 min. The mixture was rinsed with ethanol for 4 times and dried in a vacuum oven at 60 °C for 9 h to obtain calcium peroxide nanoparticles. (2) Preparation of fertilizer core: 10 g urea, 5 g monoammonium phosphate, 5 g potassium nitrate, 7 g calcium peroxide nanoparticles prepared in step (1), and 0.6 g bentonite were mixed evenly, and the mixture was placed in a disc granulator for granulation to prepare a fertilizer core with a diameter of 3 to 5 mm. (3) Preparation of coating agent: 1 g sodium carboxymethyl cellulose was dissolved in 100 mL deionized water and placed in a round-bottom flask. After nitrogen was passed at 26°C for 35 min, 0.15 g potassium persulfate was added and reacted for 25 min. The mixture was heated to 80°C and 0.6 g methyl methacrylate (MMA) and 0.4 g N-vinyl pyrrolidone (NVP) were added. The reaction was continued for 4 h under nitrogen. After the reaction was completed, the mixture was filtered and dried in a vacuum drying oven at 40°C for 12 h to remove moisture. The mixture was washed with methanol three times and dried in a vacuum drying oven at 60°C for 24 h to obtain a coating agent. (4) Preparation of compound fertilizer: First, dissolve 1 g of the coating agent prepared in step (3) in 5 mL of tetrahydrofuran to obtain a coating solution. Then, load 8 g of the fertilizer kernel prepared in step (2) into a coating machine, maintain the speed at 110 r / min, and inject the coating solution. After the coating solution is evenly coated on the surface of the fertilizer kernel, heat it with hot air at 50°C until the solvent evaporates, and finally obtain a dry compound fertilizer.

[0018] Example 2 (1) Preparation of calcium peroxide nanoparticles: 10 g of calcium chloride was dissolved in 40 mL of deionized water, and 25 wt% ammonia water was added dropwise to adjust the pH to 9. The mixture was transferred to an ice water bath and 100 mL of hydrogen peroxide solution (30 wt%) was slowly added. The mixture was stirred continuously for 1.8 h. After the reaction was completed, the mixture was centrifuged at 4000 r / min for 15 min. The mixture was rinsed with ethanol three times and dried in a vacuum drying oven at 50 °C for 10 h to obtain calcium peroxide nanoparticles. (2) Preparation of fertilizer core: 10 g of ammonium chloride, 4 g of superphosphate, 4 g of potassium sulfate, 6 g of calcium peroxide nanoparticles prepared in step (1), and 0.5 g of attapulgite powder were mixed evenly, and then placed in a disc granulator for granulation to prepare a fertilizer core with a diameter of 3 to 5 mm; (3) Preparation of coating agent: 1 g sodium carboxymethyl cellulose was dissolved in 95 mL deionized water and placed in a round-bottom flask. After nitrogen was passed through at 25 °C for 25 min, 0.1 g potassium persulfate was added and reacted for 20 min. The mixture was heated to 78 °C and 0.5 g methyl methacrylate (MMA) and 0.5 g N-vinyl pyrrolidone (NVP) were added. The reaction was continued for 3 h under nitrogen. After the reaction was completed, the mixture was filtered and dried in a vacuum drying oven at 30 °C for 14 h to remove moisture. The mixture was washed twice with methanol and dried in a vacuum drying oven at 55 °C for 36 h to obtain a coating agent. (4) Preparation of compound fertilizer: First, 1 g of the coating agent prepared in step (3) was dissolved in 4 mL of tetrahydrofuran to obtain a coating solution. Then, 7 g of the fertilizer kernel prepared in step (2) was loaded into a coating machine, the speed was maintained at 100 r / min, and the coating solution was injected. After the coating solution was evenly coated on the surface of the fertilizer kernel, it was heated with hot air at 40°C until the solvent evaporated, and finally a dry compound fertilizer was obtained.

[0019] Example 3 (1) Preparation of calcium peroxide nanoparticles: 10 g of calcium chloride was dissolved in 80 mL of deionized water, 28 wt% ammonia water was added dropwise to adjust the pH to 10.5, and then the mixture was transferred to an ice water bath, and 150 mL of hydrogen peroxide solution (30 wt%) was slowly added dropwise. The mixture was stirred continuously for 2.2 h. After the reaction was completed, the mixture was centrifuged at 8000 r / min for 10 min, and finally rinsed with ethanol 5 times. The mixture was dried in a vacuum oven at 70 °C for 8 h to obtain calcium peroxide nanoparticles. (2) Preparation of fertilizer core: 10 g of ammonium bicarbonate, 6 g of double superphosphate, 9 g of potassium chloride, 9 g of calcium peroxide nanoparticles prepared in step (1), and 0.8 g of kaolin were mixed evenly, and then placed in a disc granulator for granulation to prepare a fertilizer core with a diameter of 3 to 5 mm; (3) Preparation of coating agent: 1 g sodium carboxymethyl cellulose was dissolved in 110 mL deionized water and placed in a round-bottom flask. After nitrogen was passed through the flask at 28°C for 45 min, 0.2 g potassium persulfate was added and reacted for 30 min. The mixture was heated to 82°C and 0.7 g methyl methacrylate (MMA) and 0.3 g N-vinyl pyrrolidone (NVP) were added. The reaction was continued for 5 h under nitrogen. After the reaction was completed, the mixture was filtered and dried in a vacuum drying oven at 50°C for 10 h to remove moisture. The mixture was washed with methanol 5 times and dried in a vacuum drying oven at 65°C for 12 h to obtain a coating agent. (4) Preparation of compound fertilizer: First, dissolve 1 g of the coating agent prepared in step (3) in 6 mL of tetrahydrofuran to obtain a coating solution. Then, load 9 g of the fertilizer kernel prepared in step (2) into a coating machine, maintain the speed at 120 r / min, and inject the coating solution. After the coating solution is evenly coated on the surface of the fertilizer kernel, heat it with hot air at 55°C until the solvent evaporates, and finally obtain a dry compound fertilizer.

[0020] Comparative Example 1 The preparation method of the uncoated composite fertilizer is as follows: (1) Preparation of calcium peroxide nanoparticles: 10 g of calcium chloride was dissolved in 50 mL of deionized water, and 26 wt% ammonia water was added dropwise to adjust the pH to 10. The mixture was then transferred to an ice water bath and 130 mL of hydrogen peroxide solution (30 wt%) was slowly added. The mixture was stirred for 2 h. After the reaction, the mixture was centrifuged at 5000 r / min for 12 min. The mixture was rinsed with ethanol for 4 times and dried in a vacuum oven at 60 °C for 9 h to obtain calcium peroxide nanoparticles. (2) Preparation of compound fertilizer: 10 g of urea, 5 g of monoammonium phosphate, 5 g of potassium nitrate, 7 g of calcium peroxide nanoparticles prepared in step (1), and 0.6 g of bentonite were mixed evenly, and then placed in a disc granulator for granulation to prepare a compound fertilizer with a diameter of 3 to 5 mm.

[0021] Comparative Example 2 The composite fertilizer does not contain N-vinyl pyrrolidone (NVP) when preparing the coating agent, that is, the raw materials for preparing the coating agent are 1g sodium carboxymethyl cellulose and 1g methyl methacrylate (MMA), and the remaining steps are consistent with Example 1.

[0022] Comparative Example 3 The composite fertilizer does not contain methyl methacrylate (MMA) when preparing the coating agent, that is, the raw materials for preparing the coating agent are 1g sodium carboxymethyl cellulose and 1g N-vinyl pyrrolidone (NVP), and the remaining steps are consistent with Example 1.

[0023] Comparative Example 4 The preparation method of the composite fertilizer without coating and calcium peroxide nanoparticles is as follows: Preparation of compound fertilizer: 10g urea, 5g monoammonium phosphate, 5g potassium nitrate and 0.6g bentonite were mixed evenly, and put into a disc granulator for granulation to prepare a compound fertilizer with a diameter of 3-5mm.

[0024] Test methods and results 1. Coating agent performance test: (1) Sustained release performance: Determination of nitrogen (NH4 + ) to evaluate the sustained-release performance of the prepared coating. 100 mg of the sample was placed in a sealed beaker containing distilled water and stirred gently at room temperature. 0.1 mL of the sample was collected at different time intervals and diluted 100 times. Nitrogen (NH4 + ) release amount.

[0025] (2) Biodegradability: Under aerobic conditions, the biodegradability of the films prepared in the Examples and Comparative Examples was compared with that of pure PMMA as a control sample. Round samples (diameter: 15 mm, thickness: 1 mm) were placed in a plastic net to allow microorganisms to enter and to facilitate recovery; they were then buried in the soil at a depth of 3 cm from the surface. After 16 weeks, the samples were removed and carefully cleaned, and weighed to determine the weight loss caused by erosion.

[0026] Table 1 shows the nitrogen (NH4 + ) Release test results show that compared with Comparative Examples 1 and 4, the coating agents of other groups, especially Examples 1 to 3, have good slow-release properties, and the nitrogen release after 25 hours is still less than 45%. In addition, the slow-release performance of Comparative Example 3 is poorer than that of the embodiment, which may be because no MMA is added during the preparation of the coating agent, resulting in poor stability of the composite fertilizer in water, while the reason why the slow-release performance of Comparative Example 2 is slightly better than that of the embodiment may be that MMA replaces the NVP part during the preparation of the coating agent, making the composite fertilizer prepared in Comparative Example 2 more stable in water. Therefore, the coating agent prepared by the present invention has good slow-release properties for internal fertilizers, which is beneficial to improving fertilizer utilization.

[0027] Table 1 Nitrogen (NH4 + ) Release test results Table 2 shows the test results of biodegradability of the films prepared in the embodiments and comparative examples. According to the weight loss data, compared with pure PMMA, the films of embodiments 1 to 3 and comparative examples 2 to 3 all have certain biodegradability, and compared with comparative example 2, the biodegradability of comparative example 3 and embodiments 1 to 3 is better, indicating that MMA has a certain adverse effect on the biodegradability of the films. Therefore, the films used in the composite fertilizer of the present invention have biodegradability.

[0028] Table 2 Test results of weight loss of the coatings obtained in Examples and Comparative Examples 2. Test of wild rice stem growth: The compound fertilizers prepared according to the examples and comparative examples were applied in the field treatment of wild rice, with 30 kg / mu of base fertilizer and 10 kg / mu of pregnant wild rice fertilizer. Each treatment was repeated 3 times, and the area of ​​each plot was 67 m 2 High dikes were built between treatments, and the spacing between rice stems was 1.0 m × 0.4 m. The daily management of rice stem fields was carried out according to farmers' habits. The test methods for rice stem growth indicators, yield, and water quality in rice stem fields are as follows: (1) Determination of Zizania latifolia growth indicators: When Zizania latifolia was harvested, an equal number of Zizania latifolia plants were randomly selected from each experimental field to measure the number of effective tillers per plant, leaf length, leaf width, and plant height. Each indicator was measured six times each time.

[0029] (2) Determination of water chestnut yield: After the water chestnut matured, nine 2 m × 2 m areas were randomly selected in each experimental field as the yield measurement areas. After manual harvesting, the length, width, hairy water chestnuts, and net water chestnut mass were measured. The water chestnut yield was the sum of the water chestnut yields during the entire harvesting period, and the water chestnut yield was recorded.

[0030] (3) Determination of water quality in rice fields: After the rice stems matured, water quality testing instruments were used to measure the pH and dissolved oxygen in the paddy fields. Without disturbing the phytoplankton, water from five points on the field surface was drawn to form a mixed sample. About 500 mL of the water sample was taken for hydration analysis. After filtering with filter paper, the total phosphorus content in the field surface water was determined by the potassium persulfate digestion method, and the total nitrogen content in the field surface water was determined by the alkaline potassium persulfate oxidation digestion method.

[0031] Table 3 and Table 4 are the test results of the growth index and yield of the embodiment and the comparative example. It can be seen from the data in the two tables that the growth indexes of the wild rice stem in embodiments 1 to 3 are better than those in comparative examples 1 to 4, and the yields are higher than those in comparative examples 1 to 4, indicating that the compound fertilizer prepared by the present invention can effectively improve the yield and quality of wild rice stem. Comparing embodiments 1 to 3 with comparative example 1, and comparative example 1 with comparative example 4, respectively, it is shown that the presence of the coating agent and the calcium peroxide nanoparticles have a certain promoting effect on the growth of wild rice stem.

[0032] Table 3 Test results of wild rice stem growth indexes in Examples and Comparative Examples Table 4 Results of measurement of wild rice stem yield in the examples and comparative examples Table 5 is the water quality measurement results of the embodiments and comparative examples of the rice field. Comparing the data of comparative examples 1 and 4, it can be seen that the calcium peroxide nanoparticles can increase the content of dissolved oxygen in the water of the rice field to a certain extent, but will increase the pH value of the water body, and the increase in pH value may affect the normal growth of the rice field. Compared with comparative example 1, the release rates of fertilizers such as nitrogen and phosphorus and oxygen in embodiments 1 to 3 and comparative examples 2 to 3 are reduced due to the slow release performance of the coating. These coatings extend the oxygen release time while alleviating the increase in the total nitrogen and total phosphorus content in the water body, avoiding the oxygen being consumed in advance, thereby maintaining the dissolved oxygen content in the water body. Among them, the lack of MMA in the coating of comparative example 3 leads to a slightly poor slow release performance, which makes its control effect on the total phosphorus, total nitrogen and dissolved oxygen content in the water body slightly worse than that of embodiments 1 to 3. In addition, Examples 1 to 3 can better control the increase in pH value. Specifically, compared with Comparative Example 2, Examples 1 to 3 have better effects in controlling pH value, which may be because the coating agent in Comparative Example 2 lacks NVP and cannot alleviate the problem of pH increase caused by calcium peroxide hydrolysis. Therefore, the composite fertilizer prepared by the present invention can comprehensively control pH value, dissolved oxygen and nitrogen and phosphorus content, thereby alleviating eutrophication of water bodies caused by excessive fertilizers.

[0033] Table 5 Test results of water quality in rice field of Example and Comparative Example The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A compound fertilizer for wild rice cultivation and a preparation method thereof, characterized in that: The preparation method of compound fertilizer comprises the following steps: (1) Preparation of calcium peroxide nanoparticles: Calcium chloride was dissolved in deionized water, and 25-28 wt% ammonia water was added dropwise to adjust the pH to 9-10.5, and then the mixture was transferred to an ice water bath, and 30 wt% hydrogen peroxide solution was slowly added dropwise. The mixture was stirred continuously for 1.8-2.2 h. After the reaction was completed, the mixture was centrifuged at 4000-8000 r / min for 10-15 min, and finally rinsed with ethanol for 3-5 times, and dried in a vacuum drying oven at 50-70 °C for 8-10 h to obtain calcium peroxide nanoparticles. (2) Preparation of fertilizer core: nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, calcium peroxide nanoparticles prepared in step (1), and a binder are uniformly mixed, and then placed in a disc granulator for granulation to prepare a fertilizer core with a diameter of 3 to 5 mm; (3) Preparation of coating agent: Sodium carboxymethyl cellulose was dissolved in deionized water and placed in a round-bottom flask. After nitrogen was passed through the flask at 25-28°C for 25-45 min, potassium persulfate was added and reacted for 20-30 min. The flask was heated to 78-82°C and methyl methacrylate (MMA) and N-vinyl pyrrolidone (NVP) were added. The reaction was continued for 3-5 h under nitrogen. After the reaction was completed, the flask was filtered and dried in a vacuum drying oven at 30-50°C for 10-14 h to remove moisture. The flask was washed with methanol for 2-5 times and dried in a vacuum drying oven at 55-65°C for 12-36 h to obtain a coating agent. (4) Preparation of compound fertilizer: First, the coating agent prepared in step (3) is dissolved in tetrahydrofuran to obtain a coating liquid, and then the fertilizer kernel prepared in step (2) is loaded into a coating machine, the rotation speed is maintained at 100-120 r / min, and the coating liquid is injected. After the coating liquid is evenly coated on the surface of the fertilizer kernel, it is heated with hot air at 40-55° C. until the solvent evaporates, and finally a dry compound fertilizer is obtained.

2. The method for preparing the composite fertilizer according to claim 1, characterized in that: In step (1), the ratio of the mass (g) of calcium chloride to the volume (mL) of deionized water and hydrogen peroxide solution is 1:(4-8):(10-15).

3. The method for preparing the composite fertilizer according to claim 1, characterized in that: In step (2), the mass ratio of nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, calcium peroxide nanoparticles and adhesive is 1: (0.4-0.6): (0.4-0.6): (0.6-0.9): (0.05-0.08).

4. The method for preparing the composite fertilizer according to claim 1, characterized in that: In step (3), the mass ratio of sodium carboxymethyl cellulose, potassium persulfate, methyl methacrylate (MMA), and N-vinyl pyrrolidone (NVP) is 1: (0.1-0.2): (0.5-0.7): (0.3-0.5), and the mass (g) of sodium carboxymethyl cellulose and the volume (mL) of deionized water is 1: (95-110).

5. The method for preparing the compound fertilizer according to claim 1, characterized in that: In step (4), the mass (g) of the coating agent: the volume (mL) of tetrahydrofuran: the mass (g) of the fertilizer kernel is 1: (4-6): (7-9).

6. The method for preparing the compound fertilizer according to claim 3, characterized in that: The nitrogen fertilizer is one or more of ammonium bicarbonate, ammonium sulfate, ammonium chloride, and urea; the phosphate fertilizer is one or more of superphosphate, double superphosphate, monoammonium phosphate, and diammonium phosphate; the potassium fertilizer is one or more of potassium chloride, potassium sulfate, potassium nitrate, and potassium magnesium sulfate.

7. The method for preparing the compound fertilizer according to claim 3, characterized in that: The binder is one of bentonite, attapulgite powder and kaolin.

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