Plant source liquid fertilizer and preparation method thereof

Abstract

The invention relates to a plant source liquid fertilizer and a preparation method thereof, and belongs to the technical field of liquid fertilizer preparation, and the specific preparation method comprises the following steps: S1, collecting a composite plant raw material, and pretreating the raw material to obtain a fermentation substrate; s2, selecting a composite strain, performing fermentation treatment on the fermentation substrate, then filtering, and collecting a fermentation product; and S3, mixing the fermentation product with a system stabilizer. The invention provides a plant source liquid fertilizer and a preparation method thereof. According to the technical scheme, azadirachta indica leaves and agricultural wastes are used as fermentation substrates, and reutilization of plant resources and recycling of the agricultural wastes are realized through a multi-bacteria compound fermentation technology. By introducing the synergistic mechanism of the organic acid and the system stabilizer, the stability and nutrient content of the liquid fertilizer are effectively improved, and the problems of environmental pollution, low fermentation efficiency, poor stability and the like in the preparation and application processes of the existing liquid fertilizer are solved.

Description

Technical Field

[0001] The present application relates to the technical field of liquid fertilizer preparation, and more specifically, to a plant-derived liquid fertilizer and a preparation method thereof. Background Art

[0002] Liquid fertilizer, as an efficient and convenient form of fertilizer, has been widely used in agricultural production in recent years. It usually exists in liquid form, contains various nutrients required by plants, and has the advantages of easy absorption, easy transportation, and easy application. Liquid fertilizer can be quickly absorbed and utilized by plant roots, promote plant growth and development, and improve crop yield and quality.

[0003] However, there are still some obvious deficiencies in the preparation and application of existing liquid fertilizers. First, many liquid fertilizers are prepared by chemical synthesis methods, with a single source of raw materials and often accompanied by environmental pollution problems. The excessive use of chemical fertilizers not only destroys the soil structure, but also leads to increasingly serious environmental problems such as eutrophication of water bodies. Secondly, during the fermentation process of existing liquid fertilizers, due to improper selection of strains or lax control of fermentation conditions, problems such as low fermentation efficiency and low substrate utilization often occur. This not only increases production costs, but also limits the quality improvement of liquid fertilizers.

[0004] In addition, existing liquid fertilizers also have certain problems in terms of stability. Since liquid fertilizers often contain various metal ions and trace elements, if they are not properly handled, these components are prone to precipitation in the system, resulting in a decrease in the quality of the liquid fertilizer. At the same time, some liquid fertilizers lack the necessary stabilizers during the preparation process, making them susceptible to external environmental factors during use, resulting in stratification, agglomeration and other phenomena, which affects the full play of the fertilizer effect.

[0005] Based on the above statements, the present application provides a plant-derived liquid fertilizer and a preparation method thereof. Summary of the invention

[0006] In order to solve the problems raised in the background technology, the present application provides a plant-based liquid fertilizer and a preparation method thereof. The present invention proposes a plant-based liquid fertilizer and a preparation method thereof. The technical solution utilizes neem leaves and agricultural waste as fermentation substrates, and realizes the reuse of plant resources and the resource utilization of agricultural waste through multi-bacteria composite fermentation technology. At the same time, by introducing the synergistic mechanism of organic acids and system stabilizers, the stability and nutrient content of the liquid fertilizer are effectively improved. This not only solves the problems of environmental pollution, low fermentation efficiency, and poor stability of existing liquid fertilizers during preparation and application, but also provides a new type of efficient and environmentally friendly fertilizer option for the sustainable development of modern agriculture.

[0007] The present application provides a method for preparing a plant-derived liquid fertilizer, which adopts the following technical solution:

[0008] A method for preparing a plant-derived liquid fertilizer comprises the following preparation steps:

[0009] S1, collecting composite plant raw materials, pre-treating the raw materials, and obtaining fermentation substrates;

[0010] S2, selecting a composite bacterial strain, fermenting the fermentation substrate obtained in step S1, and then filtering to collect the fermentation product;

[0011] S3. Mixing the fermentation product obtained in step S2 with a system stabilizer to obtain a plant-derived liquid fertilizer.

[0012] Furthermore, in step S1, the composite plant raw material includes neem leaves and agricultural waste, wherein the agricultural waste is at least one of leguminous plant residues, green manure plants, crop straw, fallen leaves and tree prunings.

[0013] Furthermore, in step S1, the specific operation of pre-treating the raw material is:

[0014] S11, alkali treatment: after washing and cutting the composite plant raw material, add it into deionized water at a mass volume ratio of 1 g: (10-20) mL, increase the system temperature to 50-80° C., then add alkali solution to the system, adjust the pH value to 9-11, and soak for 1-3 hours to obtain an alkali treatment system;

[0015] S12, enzyme treatment: after cooling the alkali treatment system obtained in S11 to room temperature, adjusting the pH value of the system to neutral, adding complex enzyme to the system, the amount of complex enzyme used is 3-6wt%, and treating at 30-40°C for 30-60 minutes to obtain a fermentation substrate.

[0016] Furthermore, in step S12, the composite enzyme is obtained by mixing cellulase and xylanase in a mass ratio of (1-3):1.

[0017] Furthermore, in step S2, the specific operation of fermenting the fermentation substrate obtained in step S1 is as follows:

[0018] S21, by weight percentage, 83%-93% of the fermentation substrate obtained in step S1, 0.5% MgSO4, 0.5%-0.8% trace elements, 0.5% (NH4)2SO4, 1% KH2PO4 and the remainder urea are mixed, 65% of water by total weight of the aforementioned components is added, stirred evenly and sterilized to obtain a bacterial culture solution;

[0019] S22. Add the composite bacteria into the bacterial culture solution at an inoculation rate of 8-10%, culture on a shaker at a shaking rate of 120-150 rpm, adjust the system pH to 5-6.5, culture temperature to 25°C-35°C, and after fermentation for 55-75 hours, filter through a 270-400 mesh screen to collect the fermentation product.

[0020] Furthermore, the composite bacteria is obtained by mixing Clostridium cellulolyticum, Bacillus subtilis and Propionibacterium according to the live bacteria count ratio of (1-3): (3-5): (1-3).

[0021] Furthermore, in step S21, the trace element is at least one of Fe, Zn, Cu, and Mn.

[0022] Furthermore, in step S3, the system stabilizer is obtained by mixing an amine compound and a polymer component, and the usage amount is 10-30 g / 100 L.

[0023] Furthermore, the amine compound is ethylenediaminetetraacetic acid.

[0024] Furthermore, the polymer is polyvinyl pyrrolidone or polyvinyl alcohol.

[0025] In summary, this application has the following beneficial effects:

[0026] 1. In the technical solution of the present invention, neem leaves and agricultural waste are used as fermentation substrates after pretreatment for the preparation of liquid fertilizer products. On the one hand, plant resources are reused, waste resources are reused, and environmental pollution is reduced. On the other hand, through the fermentation process, the organic matter in neem leaves and agricultural waste is decomposed and converted into nutrients that are more easily absorbed and utilized by plants, thereby increasing the nutrient content in the liquid fertilizer. Neem leaves contain a large amount of active substances with antibacterial and antimicrobial effects, which can inhibit the growth of harmful microorganisms during the fermentation process and improve the stability of the fermentation process.

[0027] 2. In the technical solution of the present invention, Clostridium cellulolyticum, Bacillus subtilis and propionibacterium are used as composite bacterial species to ferment plant raw materials for the preparation of liquid fertilizers. The method of using multi-bacteria composite fermentation can improve the utilization of substrates by bacterial species and improve the degradation effect of plant raw materials. In the composite system, Clostridium cellulolyticum can accelerate the decomposition of plant organic matter and increase the content of humic acid and small molecule organic acids, and propionibacterium further promotes the production of acidic metabolites and promotes the formation of water-soluble humic acid. Bacillus subtilis has good stress resistance and tolerance, which is beneficial to improve the fermentation stability between different bacterial species, reduce harmful competition, and further promote the degradation of substrates.

[0028] 3. In the technical solution of the present invention, organic acid and a system stabilizer containing amine compounds and polymer components are used in the fermentation system to synergistically improve the stability of the system. Humic acid and organic acid components can stabilize the pH value in the liquid fertilizer system, and the system stabilizer can chelate the metal ion components in the liquid fertilizer to prevent metal ion precipitation. Allowing trace elements to participate in the fermentation process together can promote the fermentation activity of the strain and reduce the content of insoluble substances in the system. DETAILED DESCRIPTION

[0029] 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.

[0030] The specific implementation methods of this application involve:

[0031] Clostridium cellulolyticum: Clostridium cellulolyticum H1, numbered ATCC 35319.

[0032] Bacillus subtilis: provided by China Industrial Microbiological Culture Collection Center, with the number CICC 24713.

[0033] Propionibacterium sp.: provided by China Industrial Microbiological Culture Collection Center, numbered CICC 20846.

[0034] Example 1

[0035] A method for preparing a plant-derived liquid fertilizer comprises the following preparation steps:

[0036] S1, collecting composite plant raw materials, pre-treating the raw materials, and obtaining fermentation substrates;

[0037] The composite plant raw material is obtained by mixing neem leaves and agricultural waste in a mass ratio of 1:5, and the agricultural waste is leguminous plant residues;

[0038] Among them, the specific operation of pre-treating the raw materials is:

[0039] S11, alkali treatment: after washing and cutting the composite plant raw material, add it into deionized water at a mass volume ratio of 1 g:10 mL, increase the system temperature to 50° C., then add NaOH alkali solution to the system, adjust the pH value to 9, and soak for 1 hour to obtain an alkali treatment system;

[0040] S12, enzyme treatment: after cooling the alkaline treatment system obtained in S11 to room temperature, using HCl to adjust the pH value of the system to neutral, adding a composite enzyme to the system, the composite enzyme usage amount is 3wt%, and after treating at 30°C for 30 minutes, a fermentation substrate is obtained; the composite enzyme is obtained by mixing cellulase and xylanase in a mass ratio of 1:1.

[0041] S2, selecting a composite bacterial strain, fermenting the fermentation substrate obtained in step S1, and then filtering and collecting the fermentation product. The specific operation is as follows:

[0042] S21, by weight percentage, 83% of the fermentation substrate obtained in step S1, 0.5% of MgSO4, 0.5% of trace elements, 0.5% of (NH4)2SO4, 1% of KH2PO4 and the balance of urea are mixed, 65% of the total weight of water of the aforementioned components is added, stirred evenly and sterilized to obtain a bacterial culture solution, wherein the trace element is FeSO4;

[0043] S22. Add the composite bacteria at an inoculation rate of 8% to the bacterial culture solution, culture on a shaker with a shaking speed of 120 rpm, adjust the system pH to 5, and culture at a temperature of 25°C. After fermenting for 55 hours, filter through a 270-mesh screen to collect the fermentation product; the composite bacteria is obtained by mixing Clostridium cellulolyticum, Bacillus subtilis and Propionibacterium in a live bacteria count ratio of 1:3:1.

[0044] S3. Mix the fermentation product obtained in step S2 with a system stabilizer to obtain a plant-derived liquid fertilizer; the system stabilizer is obtained by mixing ethylenediaminetetraacetic acid and polyvinylpyrrolidone in equal weights, and the usage amount of the system stabilizer is 10 g / 100 L.

[0045] Example 2

[0046] A method for preparing a plant-derived liquid fertilizer comprises the following preparation steps:

[0047] S1, collecting composite plant raw materials, pre-treating the raw materials, and obtaining fermentation substrates;

[0048] Wherein, the composite plant raw material is obtained by mixing neem leaves and agricultural waste in a mass ratio of 1:5, and the agricultural waste is crop straw;

[0049] Among them, the specific operation of pre-treating the raw materials is:

[0050] S11, alkali treatment: after washing and cutting the composite plant raw material, add it into deionized water at a mass volume ratio of 1 g:15 mL, increase the system temperature to 65°C, then add NaOH alkali solution to the system, adjust the pH value to 10, and soak for 2 hours to obtain an alkali treatment system;

[0051] S12, enzyme treatment: after cooling the alkaline treatment system obtained in S11 to room temperature, HCl is used to adjust the pH value of the system to neutral, a composite enzyme is added to the system, the composite enzyme usage amount is 4wt%, and after treating at 35°C for 45 minutes, a fermentation substrate is obtained; the composite enzyme is obtained by mixing cellulase and xylanase in a mass ratio of 2:1.

[0052] S2, selecting a composite bacterial strain, fermenting the fermentation substrate obtained in step S1, and then filtering and collecting the fermentation product. The specific operation is as follows:

[0053] S21, by weight percentage, 87% of the fermentation substrate obtained in step S1, 0.5% of MgSO4, 0.65% of trace elements, 0.5% of (NH4)2SO4, 1% of KH2PO4 and the remainder of urea are mixed, 65% of the total weight of water of the aforementioned components is added, stirred evenly and sterilized to obtain a bacterial culture solution, wherein the trace element is at least one of ZnSO4;

[0054] S22. Add the composite bacteria at an inoculation rate of 9% into the bacterial culture solution, culture on a shaker with a shaking speed of 130 rpm, adjust the system pH to 5.5, and culture at a temperature of 30°C. After fermenting for 65 hours, filter through a 325-mesh screen to collect the fermentation product; the composite bacteria is obtained by mixing Clostridium cellulolyticum, Bacillus subtilis, and Propionibacterium in a live bacteria count ratio of 2:4:2.

[0055] S3. Mix the fermentation product obtained in step S2 with a system stabilizer to obtain a plant-derived liquid fertilizer; the system stabilizer is obtained by mixing ethylenediaminetetraacetic acid and polyvinylpyrrolidone in equal weights, and the usage amount of the system stabilizer is 20 g / 100 L.

[0056] Example 3

[0057] A method for preparing a plant-derived liquid fertilizer comprises the following preparation steps:

[0058] S1, collecting composite plant raw materials, pre-treating the raw materials, and obtaining fermentation substrates;

[0059] The composite plant raw material is obtained by mixing neem leaves and agricultural waste in a mass ratio of 1:5, and the agricultural waste is leguminous plant residues;

[0060] Among them, the specific operation of pre-treating the raw materials is:

[0061] S11, alkali treatment: after washing and cutting the composite plant raw material, add it into deionized water at a mass volume ratio of 1 g:20 mL, increase the system temperature to 80° C., then add alkali solution to the system, adjust the pH value to 11, and soak for 3 hours to obtain an alkali treatment system;

[0062] S12, enzyme treatment: after cooling the alkaline treatment system obtained in S11 to room temperature, HCl is used to adjust the pH value of the system to neutral, a composite enzyme is added to the system, the composite enzyme usage amount is 6wt%, and after treating at 40°C for 60 minutes, a fermentation substrate is obtained; the composite enzyme is obtained by mixing cellulase and xylanase in a mass ratio of 3:1.

[0063] S2, selecting a composite bacterial strain, fermenting the fermentation substrate obtained in step S1, and then filtering and collecting the fermentation product. The specific operation is as follows:

[0064] S21, calculating by weight percentage, mixing 93% of the fermentation substrate obtained in step S1, 0.5% of MgSO4, 0.8% of trace elements, 0.5% of (NH4)2SO4, 1% of KH2PO4 and the balance of urea, adding 65% of water by total weight of the aforementioned components, stirring evenly and sterilizing to obtain a bacterial culture solution, wherein the trace element is FeSO4;

[0065] S22. Add the composite bacteria at an inoculation rate of 10% to the bacterial culture solution, culture on a shaker with a shaking speed of 150 rpm, adjust the system pH to 6.5, and culture at a temperature of 35°C. After fermentation for 75 hours, filter through a 400-mesh screen to collect the fermentation product; the composite bacteria is obtained by mixing Clostridium cellulolyticum, Bacillus subtilis, and Propionibacterium in a live bacteria count ratio of 3:5:3.

[0066] S3. Mix the fermentation product obtained in step S2 with a system stabilizer to obtain a plant-derived liquid fertilizer; the system stabilizer is obtained by mixing ethylenediaminetetraacetic acid and polyvinyl alcohol in equal weights, and the usage amount of the system stabilizer is 30 g / 100 L.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is that in step S11, acid treatment is used instead of the alkali treatment step, and the fermentation substrate is specifically prepared by the following steps:

[0069] S11, acid treatment: after washing and chopping the composite plant raw material, add it into deionized water at a mass volume ratio of 1 g:10 mL, increase the system temperature to 50° C., then add HCl acid solution to the system, adjust the pH value to 2, and soak for 1 hour to obtain an acid-treated system;

[0070] S12, enzyme treatment: After the acid-treated system obtained in S11 is cooled to room temperature, NaOH is used to adjust the pH value of the system to neutral, and a composite enzyme is added to the system in an amount of 3 wt %. After treatment at 30° C. for 30 minutes, a fermentation substrate is obtained.

[0071] The remaining steps are the same as in Example 1.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that in step S1, leguminous plant residues are used instead of the composite plant raw material.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Example 1 is that in step S12, cellulase is used instead of xylanase, and the enzyme usage is maintained at 3 wt %.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Example 1 is that the trace elements do not participate in the fermentation process, and are added to the system in step S2, and the amount used is the same as that in step S21 of Example 1. The specific preparation method is:

[0078] S1, collecting composite plant raw materials, pre-treating the raw materials, and obtaining fermentation substrates;

[0079] S2, selecting a composite bacterial strain, fermenting the fermentation substrate obtained in step S1, and then filtering and collecting the fermentation product. The specific operation is as follows:

[0080] S21, by weight percentage, 83% of the fermentation substrate obtained in step S1, 0.5% of MgSO4, 0.5% of (NH4)2SO4, 1% of KH2PO4 and the remainder of urea are mixed, 65% of water by total weight of the aforementioned components is added, stirred evenly and sterilized to obtain a bacterial culture solution;

[0081] S22. Add the composite bacteria at an inoculation rate of 8% to the bacterial culture solution, culture on a shaker with a shaking speed of 120 rpm, adjust the system pH to 5, and culture at a temperature of 25°C. After fermenting for 55 hours, filter through a 270-mesh screen to collect the fermentation product; the composite bacteria is obtained by mixing Clostridium cellulolyticum, Bacillus subtilis and Propionibacterium in a live bacteria count ratio of 1:3:1.

[0082] S3. Mix the fermentation product obtained in step S2 with a system stabilizer and trace elements to obtain a plant-derived liquid fertilizer, wherein the trace element is FeSO4.

[0083] The remaining steps are the same as in Example 1.

[0084] Comparative Example 5

[0085] The difference between this comparative example and Example 1 is that in step S22, the composite bacteria used is obtained by mixing Bacillus subtilis and Propionibacterium at a live bacteria ratio of 3:1.

[0086] The remaining steps are the same as in Example 1.

[0087] Comparative Example 6

[0088] The difference between this comparative example and Example 1 is that in step S3, the system stabilizer is ethylenediaminetetraacetic acid.

[0089] Performance Testing

[0090] The liquid fertilizer samples prepared in Examples 1-3 and Comparative Examples 1-6 of the present application are now tested for system stability. 500 mL of the prepared liquid fertilizer samples are taken and then centrifuged at 3000 rpm for 30 minutes at room temperature, and the storage stability of different samples is determined by observing the changes in the system state. The liquid fertilizer samples prepared in different groups are frozen at -20°C for 24 hours, and then naturally restored to room temperature, and the changes in the system state are observed to determine the low-temperature stability of the samples.

[0091] Stability level:

[0092] Grade A: The liquid fertilizer system remains unchanged before and after treatment, with no stratification, crystallization, precipitation, etc., and the pH index remains stable.

[0093] Grade B: The liquid fertilizer system shows slight stratification, a small amount of precipitation or crystallization after treatment, and can return to a uniform state after stirring. The pH change rate is <10%.

[0094] Grade C: The liquid fertilizer system shows stratification, crystallization, precipitation and other phenomena after treatment, and the pH change rate is 10%-20%.

[0095] Grade D: The liquid fertilizer system shows stratification, crystallization, precipitation and other phenomena after treatment and is difficult to restore to a uniform state through simple treatment methods such as stirring. The pH change rate is >20%.

[0096] The specific performance test results are shown in Table 1:

[0097] Table 1

[0098]

[0099]

[0100] As can be seen from the results in Table 1, the storage stability and low temperature stability of the liquid fertilizer system prepared in Examples 1-3 are better. As can be seen from the results in Comparative Example 1, alkali treatment changes the structure of the substrate during the fermentation process compared to acid treatment, which can make the plant raw materials more thoroughly treated during the fermentation process, reduce the content of insoluble substances, and improve the stability of the system without reducing the loss of fertilizer efficiency. As can be seen from the results in Comparative Example 6, the use of amine compounds and polymer components in combination can better improve the stability of the product.

[0101] The liquid fertilizer products prepared in Examples 1-3 and Comparative Examples 1-6 are now tested for fertilizer efficiency. Spinach is used as the test object, and the liquid fertilizers prepared in Examples 1-3 and Comparative Examples 1-6 are used to grow spinach, fertilizing once every three days, and the fertilizer application rate is 1.5 mL / m 2 , watered normally. Five test groups were set for each sample, and the harvest was carried out on the 87th day of cultivation. The above-ground plant parts were cut as close to the soil surface as possible and weighed to determine the spinach yield. After recording the fresh weight, the spinach was placed in an oven at 30°C for 105 minutes and then dried at 75°C to a constant weight. The samples were then ground to pass through a 2 mm sieve. The total nitrogen content was determined by the Kjeldahl method, the total phosphorus by Mo-Sb colorimetry, and the total potassium by flame photometry. The yield and quality of the spinach crop were used to judge the fertilizer efficiency of the liquid fertilizer product. The test results are shown in Table 2.

[0102] Table 2

[0103]

[0104]

[0105] It can be seen from the results shown in Table 2 above that the fertilizer efficiency of the liquid fertilizers prepared in Examples 1-3 of the present application is significantly better than that of the products prepared in Comparative Examples 1-6, that is, within the technical solution defined in the present application, the liquid fertilizer products prepared have excellent comprehensive performance.

[0106] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0107] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a plant-derived liquid fertilizer, characterized in that: The method comprises the following preparation steps: S1, collecting composite plant raw materials, pre-treating the raw materials, and obtaining fermentation substrates; S2, selecting a composite bacterial strain, fermenting the fermentation substrate obtained in step S1, and then filtering to collect the fermentation product; S3. Mixing the fermentation product obtained in step S2 with a system stabilizer to obtain a plant-derived liquid fertilizer.

2. The method for preparing a plant-derived liquid fertilizer according to claim 1, characterized in that: In step S1, the composite plant raw material includes neem leaves and agricultural waste, wherein the agricultural waste is at least one of leguminous plant residues, green manure plants, crop straw, fallen leaves and tree prunings.

3. The method for preparing a plant-derived liquid fertilizer according to claim 1, characterized in that: In step S1, the specific operation of pre-treating the raw material is as follows: S11, alkali treatment: after washing and cutting the composite plant raw material, add it into deionized water at a mass volume ratio of 1 g: (10-20) mL, increase the system temperature to 50-80° C., then add alkali solution to the system, adjust the pH value to 9-11, and soak for 1-3 hours to obtain an alkali treatment system; S12, enzyme treatment: after cooling the alkali treatment system obtained in S11 to room temperature, adjusting the pH value of the system to neutral, adding complex enzyme to the system, the amount of complex enzyme used is 3-6wt%, and treating at 30-40°C for 30-60 minutes to obtain a fermentation substrate.

4. The method for preparing a plant-derived liquid fertilizer according to claim 3, characterized in that: In step S12, the composite enzyme is obtained by mixing cellulase and xylanase in a mass ratio of (1-3):

1.

5. The method for preparing a plant-derived liquid fertilizer according to claim 1, characterized in that: In step S2, the specific operation of fermenting the fermentation substrate obtained in step S1 is as follows: S21, by weight percentage, 83%-93% of the fermentation substrate obtained in step S1, 0.5% MgSO4, 0.5%-0.8% trace elements, 0.5% (NH4)2SO4, 1% KH2PO4 and the remainder urea are mixed, 65% of water by total weight of the aforementioned components is added, stirred evenly and sterilized to obtain a bacterial culture solution; S22. Add the composite bacteria into the bacterial culture solution at an inoculation rate of 8-10%, culture on a shaker at a shaking rate of 120-150 rpm, adjust the system pH to 5-6.5, culture temperature to 25°C-35°C, and after fermentation for 55-75 hours, filter through a 270-400 mesh screen to collect the fermentation product.

6. The method for preparing a plant-derived liquid fertilizer according to claim 5, characterized in that: The composite bacterial strain is obtained by mixing Clostridium cellulolyticum, Bacillus subtilis and propionic acid bacteria according to the live bacteria count ratio of (1-3): (3-5): (1-3).

7. The method for preparing a plant-derived liquid fertilizer according to claim 5, characterized in that: In step S21, the trace element is at least one of Fe, Zn, Cu, and Mn.

8. The method for preparing a plant-derived liquid fertilizer according to claim 1, characterized in that: In step S3, the system stabilizer is obtained by mixing an amine compound and a polymer component, and the usage amount is 10-30 g / 100 L.

9. The method for preparing a plant-derived liquid fertilizer according to claim 8, characterized in that: The amine compound is ethylenediaminetetraacetic acid, and the polymer is polyvinyl pyrrolidone or polyvinyl alcohol.

10. A liquid fertilizer obtained by the method for preparing a plant-derived liquid fertilizer according to any one of claims 1 to 9.

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