Water-soluble fertilizer prepared from seaweed and preparation method of water-soluble fertilizer

Abstract

The invention discloses a water-soluble fertilizer prepared from seaweed and a preparation method of the water-soluble fertilizer, and belongs to the technical field of fertilizers. According to the method, the seaweed extracting solution is prepared by adopting an optimized chemical extraction mode, an alkaline hydrolysis process adopting three-stage gradient heating and a normal-temperature acidolysis process adopting two-stage acidification are combined, and compared with a traditional chemical extraction method, effective components in seaweed are reserved, and the extraction efficiency is improved.

Description

Technical Field

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

[0002] Seaweed fertilizer uses large brown algae that grows fast in the ocean as raw materials, and uses chemical, physical or biological technologies to extract beneficial ingredients from them to make fertilizers. Applying this fertilizer to plants can provide necessary nutrient support, help promote plant growth and development, increase crop yields, and improve the quality of agricultural products. As a natural organic fertilizer, the efficacy of seaweed fertilizer comes from a series of active substances it contains, such as cytokines, plant hormones (such as auxin, gibberellins, abscisic acid and ethylene), betaine and polyamines.

[0003] In the production process of seaweed fertilizer, the technical challenges mainly focus on how to effectively degrade the main components of seaweed, such as cellulose, pectin and protein, while ensuring the maximum preservation of the original macroelements, trace elements, gibberellins, cytokinin-like substances, polyphenol compounds and components with antibacterial properties in the seaweed. This process requires precise control to ensure that the activity and concentration of these beneficial ingredients are not destroyed, thereby ensuring the effectiveness and quality of the seaweed fertilizer. At present, the production process of seaweed fertilizer mainly adopts physical crushing, chemical extraction and other methods, which cause more damage to the effective active ingredients in seaweed, seriously affecting the effect of later processing and fertilizer production. The biological enzymatic hydrolysis method and microbial bacterial hydrolysis method usually take longer to complete, which affects the widespread implementation of this method in industry. Therefore, how to improve the extraction efficiency while ensuring the effectiveness of seaweed water-soluble fertilizer is a current technical problem. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a water-soluble fertilizer prepared by using seaweed and a preparation method thereof. An optimized chemical extraction method is adopted in the preparation process of the seaweed extract to reduce the destruction of effective ingredients caused by chemical extraction while improving the extraction efficiency.

[0005] The present invention provides a water-soluble fertilizer prepared by using seaweed, characterized in that it comprises the following components in parts by weight: 30-40 parts of seaweed extract, 15-20 parts of water-soluble humic acid, 7-10 parts of potassium chloride, 7-10 parts of magnesium sulfate, 3-5 parts of urea, 3-7 parts of chelating agent, and 2-8 parts of amino acid.

[0006] Preferably, the water-soluble fertilizer prepared by using seaweed provided by the present invention is characterized in that it comprises the following components in parts by weight: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of chelating agent, and 8 parts of amino acids.

[0007] Among them, the seaweed extract is prepared by the following preparation method: S01. Take fresh seaweed, add deionized water according to the mass ratio of material to water of 1:1, grind it to make seaweed slurry, and refrigerate it for later use; S02. Add the seaweed slurry described in step S01 into an atmospheric pressure alkali hydrolysis reactor, add potassium hydroxide solution to adjust the pH to 8.0 - 8.5, open the steam valve to heat the seaweed slurry to 50 - 55 °C, keep it warm and stir for 10 minutes, then heat the seaweed slurry to 60 - 65 °C, keep it warm and stir for 10 minutes, continue to heat the seaweed slurry to 70 - 75 °C, keep it warm and stir for 30 minutes, take out the alkali hydrolysis product from the alkali hydrolysis reactor and filter it to obtain alkali hydrolysis filtrate and alkali hydrolysis residue; S03. Add the alkali hydrolysis residue into an acid hydrolysis reactor, add deionized water at the same time, stir evenly at room temperature and add sulfuric acid solution to adjust the pH value of the system to 3.5 - 4, stir at room temperature for 30 minutes, then continue to add sulfuric acid solution to adjust the pH to 2.5 - 3, stir at room temperature for 30 minutes, take out the acid hydrolysis product from the acid hydrolysis reactor and filter it to obtain acid hydrolysis filtrate and acid hydrolysis residue; S04. Mix the alkali hydrolysis filtrate described in step S02 and the acid hydrolysis filtrate described in step S03 to obtain a mixture, adjust the pH of the mixture to 6.8 - 7.8, and stir evenly to obtain the seaweed extract.

[0008] The fresh seaweed includes one or more of brown algae, sargassum, kelp, and giant kelp.

[0009] The chelating agent includes glucuronic acid and sodium tripolyphosphate.

[0010] The amino acids include one or more of arginine, serine, methionine, leucine, and glutamic acid.

[0011] Preferably, in step S03, when adding deionized water, by weight, the ratio of alkali hydrolysis residue to deionized water is 1:1.

[0012] Preferably, in step S04, the mass ratio of the alkali hydrolysis filtrate to the acid hydrolysis filtrate is 1:1.

[0013] Preferably, in step S04, the pH of the mixture is adjusted to 7.0.

[0014] The present invention also provides a preparation method of a water-soluble fertilizer prepared from seaweed, which is characterized in that the foregoing seaweed extract, water-soluble humic acid, potassium chloride, magnesium sulfate, urea, chelating agent, and amino acids are mixed.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: the present invention adopts a chemical extraction method of alkaline hydrolysis followed by acid hydrolysis, and reduces the destruction of effective components caused by traditional chemical extraction through an optimized chemical extraction process, thereby reducing the extraction efficiency. A three-stage gradient temperature increase process is adopted during the alkaline hydrolysis process to give the seaweed cell wall a sufficient swelling process, thereby preventing direct temperature increase alkaline hydrolysis from damaging the seaweed cell wall. At the same time, normal temperature acid hydrolysis is adopted to reduce the acid hydrolysis pH of the alkaline hydrolysis residue in two stages, thereby further ensuring the effective components in the extraction residue and the extraction purity. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; the technical features designed in the different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0017] Example 1

[0018] A water-soluble fertilizer prepared by using seaweed, the fertilizer contains the following components: by weight, it includes the following components: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of glucuronic acid and sodium tripolyphosphate in total, and 8 parts of glutamic acid; The preparation method of the seaweed extract is as follows: S01 take fresh brown algae, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, grind to make seaweed slurry, refrigerate for later use; S02. adding the seaweed slurry described in step S01 into a normal pressure alkaline hydrolysis reactor, adding potassium hydroxide solution to adjust the pH to 8.0, opening the steam valve to heat the seaweed slurry to 55° C., keeping the temperature and stirring for 10 minutes, then heating the seaweed slurry to 65° C., keeping the temperature and stirring for 10 minutes, and then heating the seaweed slurry to 75° C., keeping the temperature and stirring for 30 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and the same mass of deionized water as the alkaline hydrolysis residue was added, stirred at room temperature, and sulfuric acid solution was added to adjust the pH value of the system to 4. After stirring at room temperature for 30 minutes, sulfuric acid solution was continued to be added to adjust the pH to 3, stirred at room temperature for 30 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed in a mass ratio of 1:1 to obtain a mixture, the pH of the mixture is adjusted to 7, and the mixture is stirred evenly to obtain the seaweed extract.

[0019] The preparation method of the water-soluble fertilizer prepared by using seaweed is to uniformly stir the components of the above fertilizer according to weight parts at room temperature.

[0020] Example 2

[0021] A water-soluble fertilizer prepared by using seaweed, the fertilizer contains the following components: by weight, it includes the following components: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of glucuronic acid and sodium tripolyphosphate in total, and 8 parts of glutamic acid; The preparation method of the seaweed extract is as follows: S01 take fresh brown algae, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, grind to make seaweed slurry, refrigerate for later use; S02. adding the seaweed slurry described in step S01 into a normal pressure alkaline hydrolysis reactor, adding potassium hydroxide solution to adjust the pH to 8.5, opening the steam valve to heat the seaweed slurry to 50° C., keeping the temperature and stirring for 10 minutes, then heating the seaweed slurry to 60° C., keeping the temperature and stirring for 10 minutes, and then heating the seaweed slurry to 75° C., keeping the temperature and stirring for 30 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and the same mass of deionized water as the alkaline hydrolysis residue was added, stirred at room temperature, and sulfuric acid solution was added to adjust the pH value of the system to 4. After stirring at room temperature for 30 minutes, sulfuric acid solution was continued to be added to adjust the pH to 2.5, stirred at room temperature for 30 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed in a mass ratio of 1:1 to obtain a mixture, the pH of the mixture is adjusted to 7, and the mixture is stirred evenly to obtain the seaweed extract.

[0022] The preparation method of the water-soluble fertilizer prepared by using seaweed is to uniformly stir the components of the above fertilizer according to weight parts at room temperature.

[0023] Comparative Example 1

[0024] A water-soluble fertilizer prepared by using seaweed, the fertilizer contains the following components: by weight, it includes the following components: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of glucuronic acid and sodium tripolyphosphate in total, and 8 parts of glutamic acid; The preparation method of the seaweed extract is as follows: S01 take fresh brown algae, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, grind to make seaweed slurry, refrigerate for later use; S02. adding the seaweed slurry described in step S01 to an alkaline hydrolysis reactor at normal pressure, adding potassium hydroxide solution to adjust the pH to 8.0, opening the steam valve to heat the seaweed slurry to 75° C., keeping the temperature and stirring for 50 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and the same mass of deionized water as the alkaline hydrolysis residue was added, stirred at room temperature, and sulfuric acid solution was added to adjust the pH value of the system to 4. After stirring at room temperature for 30 minutes, sulfuric acid solution was continued to be added to adjust the pH to 3, stirred at room temperature for 30 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed in a mass ratio of 1:1 to obtain a mixture, the pH of the mixture is adjusted to 7, and the mixture is stirred evenly to obtain the seaweed extract.

[0025] The preparation method of the water-soluble fertilizer prepared by using seaweed is to uniformly stir the components of the above fertilizer according to weight parts at room temperature.

[0026] Comparative Example 2

[0027] A water-soluble fertilizer prepared by using seaweed, the fertilizer contains the following components: by weight, it includes the following components: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of glucuronic acid and sodium tripolyphosphate in total, and 8 parts of glutamic acid; The preparation method of the seaweed extract is as follows: S01 take fresh brown algae, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, grind to make seaweed slurry, refrigerate for later use; S02. adding the seaweed slurry described in step S01 into a normal pressure alkaline hydrolysis reactor, adding potassium hydroxide solution to adjust the pH to 8.0, opening the steam valve to heat the seaweed slurry to 55° C., keeping the temperature and stirring for 10 minutes, then heating the seaweed slurry to 65° C., keeping the temperature and stirring for 10 minutes, and then heating the seaweed slurry to 75° C., keeping the temperature and stirring for 30 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and an equal mass of deionized water was added to the alkaline hydrolysis residue, stirred at room temperature and sulfuric acid solution was added to adjust the pH value of the system to 3, stirred at room temperature for 60 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed in a mass ratio of 1:1 to obtain a mixture, the pH of the mixture is adjusted to 7, and the mixture is stirred evenly to obtain the seaweed extract.

[0028] The preparation method of the water-soluble fertilizer prepared by using seaweed is to uniformly stir the components of the above fertilizer according to weight parts at room temperature.

[0029] Comparative Example 3

[0030] A water-soluble fertilizer prepared by using seaweed, the fertilizer contains the following components: by weight, it includes the following components: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of glucuronic acid and sodium tripolyphosphate in total, and 8 parts of glutamic acid; The preparation method of the seaweed extract is as follows: S01 take fresh brown algae, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, ground to make seaweed slurry, refrigerated standby; S02. adding the seaweed slurry described in step S01 into a normal pressure alkaline hydrolysis reactor, adding potassium hydroxide solution to adjust the pH to 8.0, opening the steam valve to heat the seaweed slurry to 55° C., keeping the temperature and stirring for 20 minutes, then continuing to heat the seaweed slurry to 75° C., keeping the temperature and stirring for 30 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and the same mass of deionized water as the alkaline hydrolysis residue was added, stirred at room temperature, and sulfuric acid solution was added to adjust the pH value of the system to 4. After stirring at room temperature for 30 minutes, sulfuric acid solution was continued to be added to adjust the pH to 3, stirred at room temperature for 30 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed in a mass ratio of 1:1 to obtain a mixture, the pH of the mixture is adjusted to 7, and the mixture is stirred evenly to obtain the seaweed extract.

[0031] The preparation method of the water-soluble fertilizer prepared by using seaweed is to uniformly stir the components of the above fertilizer according to weight parts at room temperature.

[0032] Comparative Example 4

[0033] A water-soluble fertilizer prepared by using seaweed, the fertilizer contains the following components: by weight, it includes the following components: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of glucuronic acid and sodium tripolyphosphate in total, and 8 parts of glutamic acid; The preparation method of the seaweed extract is as follows: S01 take fresh brown algae, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, grind to make seaweed slurry, refrigerate for later use; S02. adding the seaweed slurry described in step S01 to an alkaline hydrolysis reactor at normal pressure, adding potassium hydroxide solution to adjust the pH to 8.0, opening the steam valve to heat the seaweed slurry to 75° C., keeping the temperature and stirring for 50 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and an equal mass of deionized water was added to the alkaline hydrolysis residue, stirred at room temperature and sulfuric acid solution was added to adjust the pH value of the system to 3, stirred at room temperature for 60 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed in a mass ratio of 1:1 to obtain a mixture, the pH of the mixture is adjusted to 7, and the mixture is stirred evenly to obtain the seaweed extract.

[0034] The preparation method of the water-soluble fertilizer prepared by using seaweed is to uniformly stir the components of the above fertilizer according to weight parts at room temperature.

[0035] The seaweed extracts prepared in Examples 1-2 and Comparative Examples 1-4 were respectively taken to determine the contents of alginate, seaweed oligosaccharides, gibberellins and indoleacetic acid. The results are shown in Table 1.

[0036] Table 1 Results of determination of the contents of various components in seaweed extract Seaweed extract alginic acid Seaweed oligosaccharides / ppm Gibberellic acid / ppm Indoleacetic acid / ppm Example 1 2.4% 556 356 365 Example 2 2.5% 494 321 359 Comparative Example 1 1.8% 368 192 281 Comparative Example 2 1.9% 395 186 310 Comparative Example 3 2.0% 385 232 289 Comparative Example 4 1.8% 336 154 221

[0037] The water-soluble fertilizers of Examples 1-2 and Comparative Examples 1-4 were used to test fertilizer efficiency. The test location was Fushan, Yantai.

[0038] The test crop was strawberry. Six treatments of the seaweed water-soluble fertilizer of the present invention (A1, A2, B1, B2, B3, B4) were set up in the test. A1, A2, B1, B2, B3, B4 were the seaweed water-soluble fertilizers prepared in Examples 1-2 and Comparative Examples 1-4 respectively. The above treatments were repeated 3 times and arranged randomly. The strawberries were planted in single ridges with double rows. The large row spacing was 75 cm, the small row spacing was 30 cm, and the plant spacing was 20 cm. About 100 plants were planted in each ridge. It was irrigated with roots after being diluted 400-500 times with water. It was applied once every 10 days starting from the seedling stage, and a total of 3 times were applied.

[0039] The development of strawberry roots is shown in Table 2. It can be seen from Table 2 that there were significant differences in the root development of strawberries in the treatments using the seaweed water-soluble fertilizer of the examples of the present invention compared with the comparative examples. Thus, it can be seen that applying the seaweed water-soluble fertilizer of the present invention can increase the growth of crop roots.

[0040] Table 2 Development of strawberry roots deal with Longest root length / cm Root fresh weight / g A1 15.1 2.7 A2 16.8 3.0 B1 13.5 1.7 B2 14.0 2.0 B3 12.6 2.3 B4 11.8 1.9

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-soluble fertilizer prepared using seaweed, characterized in that: The composition comprises the following components in parts by weight: 30-40 parts of seaweed extract, 15-20 parts of water-soluble humic acid, 7-10 parts of potassium chloride, 7-10 parts of magnesium sulfate, 3-5 parts of urea, 3-7 parts of chelating agent and 2-8 parts of amino acid.

2. The water-soluble fertilizer prepared by using seaweed as claimed in claim 1, characterized in that: The seaweed extract is prepared by the following preparation method: S01 take fresh seaweed, according to the material-water ratio mass ratio of 1: 1 ratio of deionized water, grind to make seaweed slurry, refrigerate for later use; S02. adding the seaweed slurry described in step S01 into a normal pressure alkaline hydrolysis reactor, adding potassium hydroxide solution to adjust the pH to 8.0-8.5, opening the steam valve to heat the seaweed slurry to 50-55° C., keeping the temperature and stirring for 10 minutes, then heating the seaweed slurry to 60-65° C., keeping the temperature and stirring for 10 minutes, then heating the seaweed slurry to 70-75° C., keeping the temperature and stirring for 30 minutes, taking out the alkaline hydrolysis product from the alkaline hydrolysis reactor and filtering it to obtain an alkaline hydrolysis filtrate and an alkaline hydrolysis residue; S03. The alkaline hydrolysis residue was added to the acid hydrolysis reactor, and deionized water was added, stirred at room temperature, and sulfuric acid solution was added to adjust the pH value of the system to 3.5-4. After stirring at room temperature for 30 minutes, sulfuric acid solution was continued to be added to adjust the pH to 2.5-3, stirred at room temperature for 30 minutes, and the acid hydrolysis product was removed from the acid hydrolysis reactor and filtered to obtain an acid hydrolysis filtrate and an acid hydrolysis residue; S04. The alkaline hydrolysis filtrate of step S02 and the acid hydrolysis filtrate of step S03 are mixed to obtain a mixture, the pH of the mixture is adjusted to 6.8-7.8, and the mixture is stirred evenly to obtain the seaweed extract.

3. The water-soluble fertilizer prepared by using seaweed according to claim 2, characterized in that: The fresh seaweed includes one or more of brown algae, sargassum, kelp and giant kelp.

4. The water-soluble fertilizer prepared by using seaweed according to claim 1, characterized in that: The composition includes the following components in parts by weight: 40 parts of seaweed extract, 20 parts of water-soluble humic acid, 10 parts of potassium chloride, 10 parts of magnesium sulfate, 5 parts of urea, 7 parts of chelating agent and 8 parts of amino acid.

5. The water-soluble fertilizer prepared by using seaweed according to claim 4, characterized in that: The chelating agent includes glucuronic acid and sodium tripolyphosphate.

6. The water-soluble fertilizer prepared by using seaweed according to claim 4, characterized in that: The amino acids include one or more of arginine, serine, methionine, leucine and glutamic acid.

7. The water-soluble fertilizer prepared by using seaweed according to claim 2, characterized in that: Deionized water is added in step S03, and the ratio of the alkaline hydrolysis residue to the deionized water is 1:1 in parts by weight.

8. The water-soluble fertilizer prepared by using seaweed according to claim 2, characterized in that: The mass ratio of the alkaline hydrolysis filtrate to the acid hydrolysis filtrate in step S04 is 1:

1.

9. The water-soluble fertilizer prepared by using seaweed according to claim 2, characterized in that: In step S04, the pH of the mixture is adjusted to 7.

0.

10. A method for preparing a water-soluble fertilizer using seaweed according to any one of claims 1 to 9, characterized in that: The seaweed extract, water-soluble humic acid, potassium chloride, magnesium sulfate, urea, chelating agent and amino acid are mixed.