Preparation method and application of compound water-soluble fertilizer

Abstract

The invention relates to the technical field of agricultural chemistry, and provides a preparation method and application of a compound water-soluble fertilizer.The preparation method of the compound water-soluble fertilizer.The preparation method comprises the following steps that S1, nutrient elements and a flexibilizer are mixed and then smashed, and a wrapping agent is obtained; s2, dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol aqueous solution; dissolving borax in water to obtain a borax aqueous solution, and adding a disintegrating agent into the borax aqueous solution to obtain a composite solution; s3, after the polyvinyl alcohol aqueous solution is sprayed on urea, a wrapping agent is added, finally, the composite solution is sprayed, and the composite water-soluble fertilizer is obtained after drying. Through the technical scheme, the problems of easy powder removal and low utilization rate of the compound fertilizer in related technologies are solved.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural chemicals, and in particular to a preparation method and application of a composite water-soluble fertilizer. Background Art

[0002] Compound fertilizer plays a significant role in promoting crop growth. First, it can provide comprehensive nutrients for crops, meet the needs of different growth stages, and promote healthy growth of plants. Second, compound fertilizer has high nutrient content and many nutritional elements. One fertilization can supply crops with at least two or more main nutrients at the same time.

[0003] However, simply mixing several fertilizer elements together will form a powder fertilizer that is light in weight and easily blown by the wind. It may be accidentally scattered to other places during the fertilization process, which will not only affect the fertilization effect, but also have an adverse impact on the environment and ecological balance. When the nitrogen fertilizer content in the powder fertilizer is high, the nitrogen fertilizer is easily washed away by water, causing a loss of soil fertility, thereby affecting the yield of crops. Summary of the invention

[0004] The invention provides a preparation method and application of a composite water-soluble fertilizer, which solves the problems of easy powdering and low utilization rate of the composite fertilizer in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a method for preparing a composite water-soluble fertilizer, comprising the following steps: S1, mixing the nutrient elements and the toughening agent, and then crushing them to obtain a coating agent; S2, dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol aqueous solution; dissolving borax in water to obtain a borax aqueous solution, and adding a disintegrant to the borax aqueous solution to obtain a composite solution; S3, spraying the polyvinyl alcohol aqueous solution on urea, adding the encapsulating agent, and finally spraying the composite solution, and obtaining a composite water-soluble fertilizer after drying.

[0006] In the present invention, firstly, the polyvinyl alcohol aqueous solution is sprayed on the surface of urea to play a role of wetting and bonding, and various element materials mixed together can be better wrapped on the urea, and then the borax solution is sprayed on the outer surface to form a three-dimensional space structure with the polyvinyl alcohol, and the wrapped urea will not have a powdering phenomenon, and when fertilizing by hand, there will be no sticky phenomenon. The strength of the wrapped urea is increased by adding a toughening agent, and the disintegrant is dissolved in the borax solution and adheres to the surface of the granular fertilizer as much as possible with the borax solution. When used as a water-soluble fertilizer, it can quickly disintegrate in water and be better dissolved in water.

[0007] As a further technical solution, the nutrient elements include one or more of macroelements, secondary elements, and trace elements.

[0008] As a further technical solution, the mass concentration of the polyvinyl alcohol aqueous solution is 4% to 5%.

[0009] As a further technical solution, the mass concentration of the borax aqueous solution is 3% to 5%.

[0010] As a further technical solution, the mass ratio of the borax aqueous solution to the polyvinyl alcohol aqueous solution is 1:1.

[0011] As a further technical solution, the large amount of elements includes one or both of a phosphorus source and a potassium source.

[0012] As a further technical solution, the phosphorus source includes one or more of monoammonium phosphate, diammonium phosphate and sodium tripolyphosphate; the potassium source includes one or more of potassium nitrate, neutral potassium sulfate and potassium chloride.

[0013] As a further technical solution, at least one of the following technical features is also included: The trace elements include one or two of magnesium sulfate monohydrate and calcium salt tetrahydrate; The trace elements include one or more of EDTA-Zn, EDTA-Fe, and EDTA-Cu; The disintegrant comprises one or both of dry starch and carboxymethyl starch; The toughening agent includes one or two of maltodextrin and curdlan.

[0014] As a further technical solution, in S2, polyvinyl alcohol is stirred at 90° C. for 45 minutes to obtain a polyvinyl alcohol aqueous solution.

[0015] As a further technical solution, in S3, the polyvinyl alcohol aqueous solution is sprayed on the urea, and the encapsulating agent is added after 5 minutes, and finally the composite solution is sprayed, and the composite water-soluble fertilizer is obtained after standing for 15 minutes and drying.

[0016] As a further technical solution, the drying temperature is 90° C. and the drying time is 30 minutes.

[0017] As a further technical solution, in S3, urea is placed in a round pot, the rotation speed of the round pot is adjusted to 100-200 rpm, and the polyvinyl alcohol aqueous solution is sprayed.

[0018] The invention also provides a method for preparing a composite water-soluble fertilizer and the composite water-soluble fertilizer is prepared.

[0019] The present invention also provides a composite water-soluble fertilizer or a composite water-soluble fertilizer obtained by a preparation method of the composite water-soluble fertilizer and application of the composite water-soluble fertilizer in agricultural planting.

[0020] The working principle and beneficial effects of the present invention are: In the present invention, (1) the composite water-soluble fertilizer formed by granulation and packaging contains almost all the nutrient elements required by crops, has the functions of long-term effect when applied dry and quick effect when applied wet, can meet the needs of crops at different stages, reduce the number of fertilizations, and save costs; (2) urea is hygroscopic, and the packaging needs to be moisture-proof. The packaging of polyvinyl alcohol and borax hydrogel can play a moisture-proof role; (3) the three-dimensional space structure formed by polyvinyl alcohol and borax can better make various elements evenly wrapped on urea, play a fixing role, especially when spreading, there will be no sticky phenomenon; (4) polyvinyl alcohol (PVA) is used as a thickener, borax (Na 2 B 4 O 7 10H 2 O, Borax) is a crosslinking agent. When the two substances are mixed, a borate ester bond is formed to obtain Borax-PVA hydrogel. The principle is that the borate ion B(OH) 4- It cross-links with the hydroxyl groups of polyvinyl alcohol to form a hydrogel, thereby forming a three-dimensional network space structure with ordered pores and morphological structures. This structure is easy to decompose and has high stability. It also provides storage space for various substances wrapped on the surface of urea to prevent powdering. Boron can also be used as a trace element for crops, thereby improving the utilization rate of compound fertilizers and solving the problem of easy powdering and low utilization rate of compound fertilizers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] Figure 1 This is the infrared spectrum of the borate ester bond formed after the polyvinyl alcohol aqueous solution and the borax aqueous solution are cross-linked in Example 1. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the following examples and comparative examples: Urea, nitrogen content: 46.53%, particle size 0.6~1.4mm; polyvinyl alcohol, alcoholysis degree 98%~99%, molecular weight 70000~80000; borax, content ≥99.5%; monoammonium phosphate, nitrogen content: 12%, phosphorus content: 61%; diammonium phosphate, nitrogen content: 20%, phosphorus content: 54%; sodium tripolyphosphate, phosphorus content: 57%; potassium nitrate, potassium content: 46%; neutral potassium sulfate, potassium content: 52%; potassium chloride, potassium content: 62%; magnesium sulfate monohydrate , magnesium content: 9.58%; tetrahydrate calcium salt: Jiaocheng County Zhibaowang Fertilizer Co., Ltd., white crystal, calcium content: 17%; EDTA-Zn, zinc content: 14.52%; EDTA-Fe, iron content: 13.14%; EDTA-Cu, copper content: 14.60%; dry starch was purchased from Hebei Jinfeng Starch Sugar Alcohol Co., Ltd.; carboxymethyl starch was purchased from Hebei Jinfeng Starch Sugar Alcohol Co., Ltd.; maltodextrin was purchased from Shandong Xiwang Sugar Co., Ltd.; curdlan was purchased from Shandong Xiwang Sugar Co., Ltd.

[0025] Example 1 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of monoammonium phosphate, 100 g of potassium nitrate, 30 g of magnesium sulfate monohydrate, 1 g of EDTA-Zn and 10 g of maltodextrin respectively, mix them thoroughly, and then grind them to 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 3g of polyvinyl alcohol and dissolve it in 97g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 4g of borax in 96g of water to obtain a borax aqueous solution, and then add 3g of dry starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into a round pot, adjust the round pot speed to 100rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wet, after 5min, add the wrapping agent that mixes well, when the wrapping agent is all wrapped on urea, then spray the composite solution, after 15min, take out the urea after wrapping, put into 90 DEG C of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer. The infrared spectrum of the boric ester bond formed after the polyvinyl alcohol aqueous solution and the borax aqueous solution are cross-linked in the present embodiment is as follows Figure 1 As shown, from Figure 1 It can be seen that compared with the absorption peak of PVA, the cross-linked product formed by mixing PVA and borax is at 1640 cm -1 There is an absorption peak of bending vibration (boric acid ester bond is a special double bond), that is, a boric acid ester bond is formed. PVA is at 3600~3400cm -1 There is a broad absorption band at 3460 cm, which is caused by the stretching vibration of OH (PVA polymer), while the cross-linked product -1The broad peak at is reduced to a sharp peak, which is due to the borate ester bond formed between polyvinyl alcohol and borax, forming a cross-linked structure and reducing the amplitude of OH vibration.

[0026] Example 2 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 200 g of diammonium phosphate, 200 g of neutral potassium sulfate, 40 g of calcium salt tetrahydrate, 2 g of EDTA-Fe and 15 g of curdlan respectively, mix them thoroughly, and then grind them into 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 4g of polyvinyl alcohol and dissolve it in 96g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 5g of borax in 95g of water to obtain a borax aqueous solution, and then add 4g of carboxymethyl starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 200rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray the composite solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0027] Example 3 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of sodium tripolyphosphate, 100 g of potassium chloride, 50 g of magnesium sulfate monohydrate, 1 g of EDTA-Cu and 20 g of maltodextrin respectively, mix them thoroughly, and then grind them to 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 5g of polyvinyl alcohol and dissolve it in 95g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 4g of borax in 96g of water to obtain a borax aqueous solution, and then add 5g of dry starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 100rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray the composite solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0028] Example 4 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 200 g of monoammonium phosphate, 200 g of potassium nitrate, 30 g of calcium tetrahydrate, 1 g of EDTA-Zn and 20 g of maltodextrin respectively, mix them thoroughly, and grind them into 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 3g of polyvinyl alcohol and dissolve it in 97g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 5g of borax in 94g of water to obtain a borax aqueous solution, and then add 3g of dry starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 100rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray the composite solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0029] Example 5 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of diammonium phosphate, 200 g of potassium chloride, 50 g of magnesium sulfate monohydrate, 2 g of EDTA-Fe and 10 g of maltodextrin respectively, mix them thoroughly, and then grind them into 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 5g of polyvinyl alcohol and dissolve it in 95g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 4g of borax in 96g of water to obtain a borax aqueous solution, and then add 4g of dry starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 200rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray the composite solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0030] Example 6 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 200 g of sodium tripolyphosphate, 200 g of potassium chloride, 50 g of calcium tetrahydrate, 2 g of EDTA-Fe and 10 g of curdlan respectively, mix them thoroughly, and grind them into 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 5g of polyvinyl alcohol and dissolve it in 95g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 5g of borax in 95g of water to obtain a borax aqueous solution, and then add 5g of carboxymethyl starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 200rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray the composite solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0031] Comparative Example 1 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of monoammonium phosphate, 100 g of potassium nitrate, 30 g of magnesium sulfate monohydrate, 1 g of EDTA-Zn and 10 g of maltodextrin respectively, mix them thoroughly, and then grind them to 400 meshes with a pulverizer to obtain a coating agent; S2, dissolving 4 g of borax in 96 g of water to obtain a borax aqueous solution, and then adding 3 g of dry starch to fully dissolve to obtain a composite solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 100rpm, spray water on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray the composite solution, after 15min, take out the urea after the wrapping, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0032] Comparative Example 2 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of monoammonium phosphate, 100 g of potassium nitrate, 30 g of magnesium sulfate monohydrate, 1 g of EDTA-Zn and 10 g of maltodextrin respectively, mix them thoroughly, and then grind them to 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 3 g of polyvinyl alcohol and dissolve it in 97 g of water, stir at 90 ° C for 45 min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 3 g of dry starch in 96 g of water and fully dissolve to obtain a starch aqueous solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 100rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray starch aqueous solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0033] Comparative Example 3 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of monoammonium phosphate, 100 g of potassium nitrate, 30 g of magnesium sulfate monohydrate, 1 g of EDTA-Zn, 10 g of maltodextrin and 4 g of borax respectively, mix them thoroughly, and then grind them into 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 3g of polyvinyl alcohol and dissolve it in 97g of water, stir at 90°C for 45min, and cool to room temperature to obtain a polyvinyl alcohol aqueous solution; dissolve 3g of dry starch in 96g of water and fully dissolve to obtain a starch aqueous solution; S3, weigh 500g urea, put into round pot, adjust the round pot rotating speed to 100rpm, spray polyvinyl alcohol aqueous solution on urea, make it all wetted, after 5min, add the wrapping agent mixed, when the wrapping agent is all wrapped on urea, and then spray starch aqueous solution, after 15min, take out the urea after the package, put into 90 ℃ of baking ovens and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0034] Comparative Example 4 A method for preparing a composite water-soluble fertilizer comprises the following steps: S1. Weigh 100 g of monoammonium phosphate, 100 g of potassium nitrate, 30 g of magnesium sulfate monohydrate, 1 g of EDTA-Zn, and 10 g of maltodextrin respectively, mix them thoroughly, and then grind them into 400 meshes with a pulverizer to obtain a coating agent; S2, weigh 500g urea, put into a round pot, adjust the round pot rotating speed to 100rpm, spray water on the urea to make it all wetted, after 5min, add the mixed wrapping agent, when the wrapping agent is all wrapped on the urea, and then spray water, after 15min, take out the urea after the wrapping, put into 90 ° C baking oven and dry, take out after 30min, obtain composite water-soluble fertilizer.

[0035] Comparative Example 5 The only difference between this comparative example and Example 1 is that the polyvinyl alcohol aqueous solution and the boric acid aqueous solution are replaced by water, and maltodextrin is not added.

[0036] Comparative Example 6 The only difference between this comparative example and Example 1 is that maltodextrin is not added.

[0037] Comparative Example 7 The only difference between this comparative example and Example 1 is that 100 g of monoammonium phosphate, 100 g of potassium nitrate, 30 g of magnesium sulfate monohydrate, 1 g of EDTA-Zn, 10 g of maltodextrin, 3 g of polyvinyl alcohol, 4 g of borax, 3 g of dry starch, and 500 g of urea are directly mixed and evenly mixed, and then crushed to obtain a composite water-soluble fertilizer.

[0038] 30 grains of the composite water-soluble fertilizers prepared in Examples 1 to 6 and Comparative Examples 1 to 6 were taken respectively, and their hardness was tested. The test results are shown in Table 1.

[0039] Table 1 Hardness test results of composite water-soluble fertilizer

[0040] It can be seen from Table 1 that, compared with Comparative Examples 1 to 6, the hardness of the composite water-soluble fertilizer prepared in Examples 1 to 6 is greater than that of Comparative Examples 1 to 6, indicating that the three-dimensional network structure gel outer film formed by polyvinyl alcohol and borax can increase the hardness of the composite water-soluble fertilizer, reduce powdering, and improve the utilization rate of the composite water-soluble fertilizer.

[0041] Taking four-season Chinese cabbage as the test material, 5 g of the composite water-soluble fertilizer prepared in Examples 1 to 6 and Comparative Examples 1 to 4 and 7 were weighed respectively and evenly scattered in the flower pot as base fertilizer, covered with 2 cm thick soil, poured with 300 mL of water, and planted 3 four-season Chinese cabbage seeds. The weight of the four-season Chinese cabbage on the 15th day was tested, and the average weight of the three four-season Chinese cabbages was taken, and water was used as a blank group; the test results are shown in Table 2.

[0042] Table 2 Weight results of four-season Chinese cabbage in Examples 1 to 6 and Comparative Examples 1 to 4 and 7 after 15 days

[0043] It can be seen from Table 2 that, compared with Comparative Examples 1 to 4 and Comparative Example 7, when the composite water-soluble fertilizer prepared in Examples 1 to 6 acts on four-season Chinese cabbage, the weight increase of four-season Chinese cabbage is higher than that of Comparative Examples 1 to 4 and Comparative Example 7, indicating that the utilization rate of the composite water-soluble fertilizer prepared in the present invention is improved, and the crop yield can be significantly increased.

[0044] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite water-soluble fertilizer, characterized in that: The following steps are involved: S1, mixing the nutrient elements and the toughening agent, and then crushing them to obtain a coating agent; S2, dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol aqueous solution; dissolving borax in water to obtain a borax aqueous solution, and adding a disintegrant to the borax aqueous solution to obtain a composite solution; S3, spraying the polyvinyl alcohol aqueous solution on urea, adding the encapsulating agent, and finally spraying the composite solution, and obtaining a composite water-soluble fertilizer after drying.

2. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: The nutrient elements include one or more of macroelements, secondary elements and trace elements.

3. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: The mass concentration of the polyvinyl alcohol aqueous solution is 4% to 5%.

4. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: The mass concentration of the borax aqueous solution is 3% to 5%.

5. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: The mass ratio of the borax aqueous solution to the polyvinyl alcohol aqueous solution is 1:

1.

6. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: The large amount of elements includes one or both of a phosphorus source and a potassium source.

7. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: The phosphorus source includes one or more of monoammonium phosphate, diammonium phosphate and sodium tripolyphosphate; the potassium source includes one or more of potassium nitrate, neutral potassium sulfate and potassium chloride.

8. The method for preparing a composite water-soluble fertilizer according to claim 1, characterized in that: Also includes at least one of the following technical features: The trace elements include one or two of magnesium sulfate monohydrate and calcium salt tetrahydrate; The trace elements include one or more of EDTA-Zn, EDTA-Fe, and EDTA-Cu; The disintegrant comprises one or both of dry starch and carboxymethyl starch; The toughening agent includes one or two of maltodextrin and curdlan.

9. A composite water-soluble fertilizer prepared according to the method for preparing a composite water-soluble fertilizer according to any one of claims 1 to 8.

10. Use of the composite water-soluble fertilizer according to claim 9 or the composite water-soluble fertilizer obtained by the preparation method of the composite water-soluble fertilizer according to any one of claims 1 to 8 in agricultural planting.

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