Solid water-soluble fertilizer and preparation method thereof

Abstract

The invention relates to a solid water-soluble fertilizer and a preparation method thereof, and belongs to the technical field of water-soluble fertilizer.The solid water-soluble fertilizer is prepared from, by mass, 20-25 parts of potassium nitrate, 6-7 parts of ammonium sulfate, 30-35 parts of urea, 35-40 parts of monopotassium phosphate, 0.4-0.7 part of microelements, 0.4-0.6 part of soluble magnesium salt, 1.3-1.9 parts of polyethylene glycol, 0.4-0.6 part of glycerin and 0.2-0.3 part of polyoxyethylene stearate. And 0.1 to 0.15 part of cocamidopropyl betaine. The solid water-soluble fertilizer disclosed by the invention is balanced in nutrients, high in nutrient content, high in dissolving speed and suitable for a water-fertilizer integrated system (such as drip irrigation and spray irrigation); by chelating trace elements, the absorption efficiency is improved, the nutrient loss is reduced, and the pollution to soil and water is reduced. The polyethylene glycol, the glycerol, the polyoxyethylene stearate and the cocamidopropyl betaine are compounded and added, so that the hygroscopicity of the fertilizer can be improved, the flowability of the fertilizer is enhanced, and the caking phenomenon is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of water-soluble fertilizers, and in particular relates to a solid water-soluble fertilizer and a preparation method thereof. Background Art

[0002] Water-soluble fertilizer, as the name implies, refers to fertilizer that can be dissolved in water and can be used with water. Water-soluble fertilizer has the advantages of simple processing, small dosage, and significant fertilizer effect. The promotion of water-soluble fertilizer is meaningful for energy conservation, emission reduction, and environmental protection. Water-soluble fertilizer is mainly divided into solid water-soluble fertilizer and liquid water-soluble fertilizer.

[0003] Solid water-soluble fertilizer is a solid fertilizer that can be completely dissolved in water, usually in the form of powder or granules. Solid water-soluble fertilizer is an efficient and environmentally friendly form of fertilizer with the following characteristics:

[0004] (1) Water solubility: It can dissolve quickly in water and is easy to apply through irrigation systems (such as drip irrigation and sprinkler irrigation).

[0005] (2) Nutrient balance: The ratio of nitrogen, phosphorus, potassium and trace elements can be precisely adjusted according to crop needs.

[0006] (3) Environmental protection: reduce nutrient loss and reduce pollution to soil and water.

[0007] (4) High efficiency: high nutrient utilization rate and can be quickly absorbed by crops.

[0008] Although solid water-soluble fertilizers have many advantages, they tend to clump, affecting their effectiveness. Summary of the invention

[0009] The present invention aims to provide a solid water-soluble fertilizer and a preparation method thereof. The solid water-soluble fertilizer of the present invention has balanced nutrients, high nutrient content, fast dissolution speed, and is suitable for water-fertilizer integrated systems (such as drip irrigation and sprinkler irrigation); by chelating trace elements, the absorption efficiency is improved, nutrient loss is reduced, and pollution to soil and water bodies is reduced. The compound addition of polyethylene glycol, glycerol, polyoxyethylene stearate and cocamidopropyl betaine can improve the hygroscopicity of the fertilizer, enhance the fluidity of the fertilizer, and reduce the caking phenomenon.

[0010] The technical solution adopted by the present invention to achieve its purpose is as follows:

[0011] A solid water-soluble fertilizer comprises, by weight, 20-25 parts of potassium nitrate, 6-7 parts of ammonium sulfate, 30-35 parts of urea, 35-40 parts of potassium dihydrogen phosphate, 0.4-0.7 parts of trace elements, 0.4-0.6 parts of soluble magnesium salts, 1.3-1.9 parts of polyethylene glycol, 0.4-0.6 parts of glycerol, 0.2-0.3 parts of polyoxyethylene stearate and 0.1-0.15 parts of cocamidopropyl betaine.

[0012] Preferably, the polyethylene glycol is polyethylene glycol 400 or polyethylene glycol 600.

[0013] Preferably, the mass ratio of polyethylene glycol, glycerol, polyoxyethylene stearate and cocamidopropyl betaine is (6-7):2:1:0.5.

[0014] Preferably, the trace elements include 0.2-0.3 parts of soluble iron salt, 0.05-0.1 parts of soluble manganese salt, 0.05-0.1 parts of soluble zinc salt, 0.05-0.1 parts of soluble copper salt, and 0.05-0.1 parts of sodium borate.

[0015] Preferably, the soluble iron salt is EDTA iron, the soluble manganese salt is EDTA manganese, the soluble zinc salt is EDTA zinc, and the soluble copper salt is EDTA copper.

[0016] Preferably, the soluble magnesium salt is magnesium sulfate.

[0017] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0018] S1. Prepare the raw materials in the following parts by mass: 20-25 parts of potassium nitrate, 6-7 parts of ammonium sulfate, 30-35 parts of urea, 35-40 parts of potassium dihydrogen phosphate, 0.4-0.7 parts of trace elements, 0.4-0.6 parts of soluble magnesium salts, 1.3-1.9 parts of polyethylene glycol, 0.4-0.6 parts of glycerol, 0.2-0.3 parts of polyoxyethylene stearate, and 0.1-0.15 parts of cocamidopropyl betaine;

[0019] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0020] S3. Adding trace elements and soluble magnesium salts to the premix, mixing evenly, granulating, and drying to obtain a mixture;

[0021] S4. The polyethylene glycol and glycerol are added to the reaction vessel and heated to 60-70 ° C, stirred until completely dissolved, polyoxyethylene stearate is added, stirring is continued until uniformly dispersed, cocamidopropyl betaine is added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0022] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry it to obtain a solid water-soluble fertilizer.

[0023] Preferably, in step S3, the particle size of the granulation is controlled to be 2-5 mm, and the drying temperature is controlled to be 50-60°C.

[0024] Preferably, in step S5, the drying temperature is controlled at 50-60°C.

[0025] The beneficial effects of the present invention are:

[0026] The solid water-soluble fertilizer of the present invention selects nitrate nitrogen, ammonium nitrogen, urea nitrogen three forms of nitrogen combination for use, can meet different nitrogen requirements. In the present invention, total nitrogen, total phosphorus, total potassium are relatively balanced, provide main nutrients, meet crop growth needs; At the same time, trace elements in iron, manganese, zinc, copper, boron, and magnesium are added, and nutrition is rich, so that the solid water-soluble fertilizer of the present invention has a wide range of applications. By adding polyethylene glycol, glycerol, polyoxyethylene stearate, and cocamidopropyl betaine compound, the nutrients in the water-soluble fertilizer can be protected, the contact between the nutrients in the water-soluble fertilizer and the air is blocked, the formation of crystal bridges is hindered, and intercrystalline bonding is prevented. Polyethylene glycol and glycerol ensure that the water solubility of the fertilizer is not affected, and polyoxyethylene stearate and cocamidopropyl betaine can also improve the dispersibility of the fertilizer. DETAILED DESCRIPTION

[0027] Example 1

[0028] A solid water-soluble fertilizer comprises, by mass, 20 parts of potassium nitrate, 6 parts of ammonium sulfate, 35 parts of urea, 40 parts of potassium dihydrogen phosphate, 0.2 parts of EDTA iron, 0.05 parts of EDTA manganese, 0.1 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.1 parts of sodium borate, 0.5 parts of magnesium sulfate, 1.3 parts of polyethylene glycol 600, 0.4 parts of glycerol, 0.2 parts of polyoxyethylene stearate and 0.1 parts of cocamidopropyl betaine.

[0029] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0030] S1. Prepare the raw materials according to the above mass parts;

[0031] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0032] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 60 ° C to obtain a mixture;

[0033] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 70 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, stirring was continued until uniformly dispersed, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0034] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 60° C. to obtain a solid water-soluble fertilizer.

[0035] Example 2

[0036] A solid water-soluble fertilizer comprises, by mass, 25 parts of potassium nitrate, 7 parts of ammonium sulfate, 30 parts of urea, 35 parts of potassium dihydrogen phosphate, 0.3 parts of EDTA iron, 0.1 parts of EDTA manganese, 0.05 parts of EDTA zinc, 0.1 parts of EDTA copper, 0.05 parts of sodium borate, 0.4 parts of magnesium sulfate, 1.8 parts of polyethylene glycol 600, 0.6 parts of glycerol, 0.3 parts of polyoxyethylene stearate and 0.15 parts of cocamidopropyl betaine.

[0037] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0038] S1. Prepare the raw materials according to the above mass parts;

[0039] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0040] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 50 ° C to obtain a mixture;

[0041] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 60 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, stirring was continued until uniformly dispersed, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0042] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 50° C. to obtain a solid water-soluble fertilizer.

[0043] Example 3

[0044] A solid water-soluble fertilizer comprises, by mass, 22 parts of potassium nitrate, 6 parts of ammonium sulfate, 34 parts of urea, 39 parts of potassium dihydrogen phosphate, 0.2 parts of EDTA iron, 0.05 parts of EDTA manganese, 0.1 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.05 parts of sodium borate, 0.55 parts of magnesium sulfate, 1.4 parts of polyethylene glycol 600, 0.4 parts of glycerol, 0.2 parts of polyoxyethylene stearate and 0.1 parts of cocamidopropyl betaine.

[0045] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0046] S1. Prepare the raw materials according to the above mass parts;

[0047] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0048] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 55 ° C to obtain a mixture;

[0049] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 65 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, stirring was continued until uniformly dispersed, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0050] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 55° C. to obtain a solid water-soluble fertilizer.

[0051] Example 4

[0052] A solid water-soluble fertilizer comprises, by weight, 23 parts of potassium nitrate, 6.5 parts of ammonium sulfate, 32 parts of urea, 38 parts of potassium dihydrogen phosphate, 0.3 parts of EDTA iron, 0.1 parts of EDTA manganese, 0.05 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.1 parts of sodium borate, 0.4 parts of magnesium sulfate, 1.4 parts of polyethylene glycol 600, 0.4 parts of glycerol, 0.2 parts of polyoxyethylene stearate and 0.1 parts of cocamidopropyl betaine.

[0053] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0054] S1. Prepare the raw materials according to the above mass parts;

[0055] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0056] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 55 ° C to obtain a mixture;

[0057] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 70 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, stirring was continued until uniformly dispersed, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0058] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 55° C. to obtain a solid water-soluble fertilizer.

[0059] Example 5

[0060] A solid water-soluble fertilizer comprises, by mass, 20 parts of potassium nitrate, 6 parts of ammonium sulfate, 35 parts of urea, 40 parts of potassium dihydrogen phosphate, 0.2 parts of EDTA iron, 0.05 parts of EDTA manganese, 0.1 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.1 parts of sodium borate, 0.5 parts of magnesium sulfate, 1.9 parts of polyethylene glycol 600, 0.5 parts of glycerol, 0.3 parts of polyoxyethylene stearate and 0.1 parts of cocamidopropyl betaine.

[0061] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0062] S1. Prepare the raw materials according to the above mass parts;

[0063] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0064] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 60 ° C to obtain a mixture;

[0065] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 70 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, stirring was continued until uniformly dispersed, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0066] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 60° C. to obtain a solid water-soluble fertilizer.

[0067] Example 6

[0068] A solid water-soluble fertilizer comprises, by weight, 25 parts of potassium nitrate, 7 parts of ammonium sulfate, 30 parts of urea, 35 parts of potassium dihydrogen phosphate, 0.3 parts of EDTA iron, 0.1 parts of EDTA manganese, 0.05 parts of EDTA zinc, 0.1 parts of EDTA copper, 0.05 parts of sodium borate, 0.4 parts of magnesium sulfate, 1.8 parts of polyethylene glycol 600, 0.5 parts of glycerol, 0.2 parts of polyoxyethylene stearate and 0.15 parts of cocamidopropyl betaine.

[0069] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0070] S1. Prepare the raw materials according to the above mass parts;

[0071] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0072] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 50 ° C to obtain a mixture;

[0073] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 60 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, stirring was continued until uniformly dispersed, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0074] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 50° C. to obtain a solid water-soluble fertilizer.

[0075] Comparative Example 1

[0076] A solid water-soluble fertilizer comprises, by weight, 20 parts of potassium nitrate, 6 parts of ammonium sulfate, 35 parts of urea, 40 parts of potassium dihydrogen phosphate, 0.2 parts of EDTA iron, 0.05 parts of EDTA manganese, 0.1 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.1 parts of sodium borate, 0.5 parts of magnesium sulfate, 1.3 parts of polyethylene glycol 600, 0.4 parts of glycerol, and 0.2 parts of polyoxyethylene stearate.

[0077] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0078] S1. Prepare the raw materials according to the above mass parts;

[0079] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0080] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 60 ° C to obtain a mixture;

[0081] S4. The polyethylene glycol and glycerol were added to the reaction vessel and heated to 70 ° C, stirred until completely dissolved, polyoxyethylene stearate was added, and stirring was continued until uniformly dispersed, and cooled to obtain a mixed solution;

[0082] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 60° C. to obtain a solid water-soluble fertilizer.

[0083] Comparative Example 2

[0084] A solid water-soluble fertilizer comprises, by weight, 20 parts of potassium nitrate, 6 parts of ammonium sulfate, 35 parts of urea, 40 parts of potassium dihydrogen phosphate, 0.2 parts of EDTA iron, 0.05 parts of EDTA manganese, 0.1 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.1 parts of sodium borate, 0.5 parts of magnesium sulfate, 1.3 parts of polyethylene glycol 600, 0.4 parts of glycerol, and 0.1 parts of cocamidopropyl betaine.

[0085] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0086] S1. Prepare the raw materials according to the above mass parts;

[0087] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0088] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix well, granulate, control the particle size to 2-5 mm, and dry at 60 ° C to obtain a mixture;

[0089] S4. The polyethylene glycol and glycerol were added to a reaction vessel and heated to 70 ° C, stirred until completely dissolved, cocamidopropyl betaine was added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution;

[0090] S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry at 60° C. to obtain a solid water-soluble fertilizer.

[0091] Comparative Example 3

[0092] A solid water-soluble fertilizer comprises, by weight, 20 parts of potassium nitrate, 6 parts of ammonium sulfate, 35 parts of urea, 40 parts of potassium dihydrogen phosphate, 0.2 parts of EDTA iron, 0.05 parts of EDTA manganese, 0.1 parts of EDTA zinc, 0.05 parts of EDTA copper, 0.1 parts of sodium borate and 0.5 parts of magnesium sulfate.

[0093] A method for preparing a solid water-soluble fertilizer comprises the following steps:

[0094] S1. Prepare the raw materials according to the above mass parts;

[0095] S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix;

[0096] S3. Add EDTA iron, EDTA manganese, EDTA zinc, EDTA copper, sodium borate and magnesium sulfate to the premix, mix evenly, granulate, control the particle size to 2-5 mm, dry at 60° C. to obtain a solid water-soluble fertilizer.

[0097] Experimental Example 1

[0098] Anti-caking test: The fertilizer is placed under a pressure of 50kg in an environment with a temperature of 45℃ and a relative humidity of 80% for 30 days. The compressed sample is dropped freely from a height of 1m twice (once up and once down), and the sample is weighed and recorded as m 0 The sample was sieved with a 7 mm sieve for 3 min, and the mass on the sieve was measured with an electronic balance, recorded as m 1 , agglomeration rate = m 1 / m 0 × 100%. See Table 1 for the results.

[0099] Table 1

[0100]

[0101]

[0102] As can be seen from Table 1, the solid water-soluble fertilizer of the present invention has excellent anti-caking effect, and has obvious anti-caking effect compared with Comparative Example 3. By comparing Examples 1-6 with Comparative Examples 1-2, it can be seen that the compounding of polyethylene glycol, glycerol, polyoxyethylene stearate, and cocamidopropyl betaine has a synergistic effect and can improve the anti-caking effect.

[0103] Experimental Example 2

[0104] For the water solubility test, 10 g of solid water-soluble fertilizer was added to 100 mL of normal temperature water, stirred at 200 rpm at room temperature, and the time required for complete dissolution was recorded. The solution was filtered, the mass of the undissolved residue was measured, and the dissolution rate was calculated. The results are shown in Table 2.

[0105] deal with Dissolution time / s Residue mass / g Dissolution rate / % Example 1 185 0.141 98.59 Example 2 188 0.139 98.61 Example 3 184 0.140 98.60 Example 4 186 0.141 98.59 Example 5 185 0.142 98.58 Example 6 185 0.140 98.60 Comparative Example 1 183 0.139 98.61 Comparative Example 2 172 0.135 98.65 Comparative Example 3 146 0.117 98.83

[0106] It can be seen from Table 2 that the dissolution rate and dissolution rate of the solid water-soluble fertilizer of the present invention are relatively high. Although the dissolution time is slightly longer than that of Comparative Example 3, the solid water-soluble fertilizer of the present invention still achieves excellent water-solubility effect in terms of the anti-caking effect.

[0107] Experimental Example 3

[0108] Fertilization effect

[0109] Water-soluble fertilizer was sprayed at a dosage of 3kg / mu at a fertilizer-water ratio of 1:500. The target was Zhongsu No. 4 tomato, and the growth and yield of the tomato were observed. The results are shown in Table 3.

[0110] Table 3

[0111]

[0112] It can be seen from Table 3 that after applying the solid water-soluble fertilizer of the present invention, the yield of tomatoes is high and the fruit cracking rate is low.

Claims

1. A solid water-soluble fertilizer, characterized in that: Calculated by mass, it includes 20-25 parts of potassium nitrate, 6-7 parts of ammonium sulfate, 30-35 parts of urea, 35-40 parts of potassium dihydrogen phosphate, 0.4-0.7 parts of trace elements, 0.4-0.6 parts of soluble magnesium salts, 1.3-1.9 parts of polyethylene glycol, 0.4-0.6 parts of glycerol, 0.2-0.3 parts of polyoxyethylene stearate, and 0.1-0.15 parts of cocamidopropyl betaine.

2. A solid water-soluble fertilizer according to claim 1, characterized in that, The polyethylene glycol is polyethylene glycol 400 or polyethylene glycol 600.

3. A solid water-soluble fertilizer according to claim 1, characterized in that, The mass ratio of polyethylene glycol, glycerin, polyoxyethylene stearate and cocamidopropyl betaine is (6-7):2:1:0.

5.

4. A solid water-soluble fertilizer according to claim 1, characterized in that, The trace elements include 0.2-0.3 parts of soluble iron salt, 0.05-0.1 parts of soluble manganese salt, 0.05-0.1 parts of soluble zinc salt, 0.05-0.1 parts of soluble copper salt and 0.05-0.1 parts of sodium borate.

5. A solid water-soluble fertilizer according to claim 4, characterized in that, The soluble iron salt is EDTA iron, the soluble manganese salt is EDTA manganese, the soluble zinc salt is EDTA zinc, and the soluble copper salt is EDTA copper.

6. A solid water-soluble fertilizer according to claim 1, characterized in that, The soluble magnesium salt is magnesium sulfate.

7. A method for preparing a solid water-soluble fertilizer, characterized in that: The following steps are involved: S1. Prepare the raw materials in the following parts by mass: 20-25 parts of potassium nitrate, 6-7 parts of ammonium sulfate, 30-35 parts of urea, 35-40 parts of potassium dihydrogen phosphate, 0.4-0.7 parts of trace elements, 0.4-0.6 parts of soluble magnesium salts, 1.3-1.9 parts of polyethylene glycol, 0.4-0.6 parts of glycerol, 0.2-0.3 parts of polyoxyethylene stearate, and 0.1-0.15 parts of cocamidopropyl betaine; S2. Potassium nitrate, ammonium sulfate, urea and potassium dihydrogen phosphate were added to a mixer and mixed to obtain a premix; S3. Adding trace elements and soluble magnesium salts to the premix, mixing evenly, granulating, and drying to obtain a mixture; S4. The polyethylene glycol and glycerol are added to the reaction vessel and heated to 60-70 ° C, stirred until completely dissolved, polyoxyethylene stearate is added, stirring is continued until uniformly dispersed, cocamidopropyl betaine is added, stirred until completely dissolved and dispersed, and cooled to obtain a mixed solution; S5. Spray or apply the mixed solution obtained in step S4 onto the surface of the mixed material obtained in step S3, and dry it to obtain a solid water-soluble fertilizer.

8. The method for preparing a solid water-soluble fertilizer according to claim 7, characterized in that: In step S3, the particle size of the granulation is controlled to be 2-5 mm, and the drying temperature is controlled to be 50-60°C.

9. The method for preparing a solid water-soluble fertilizer according to claim 7, wherein: In step S5, the drying temperature is controlled at 50-60°C.

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