Efficient water-soluble fertilizer based on polyglutamic acid and preparation method of efficient water-soluble fertilizer

Abstract

The invention belongs to the technical field of chemical fertilizer preparation, and discloses an efficient water-soluble fertilizer based on polyglutamic acid and a preparation method thereof.The efficient water-soluble fertilizer comprises the following raw materials: polyglutamic acid which is prepared through a microbial fermentation method, has the molecular weight range of 500-1500 kDa and the purity of more than or equal to 95% and serves as a core water and fertilizer retention and nutrient slow release carrier; the high-quality fulvic acid is derived from weathered coal or biochemical extraction, the content of the fulvic acid is greater than or equal to 50%, and the fulvic acid is used for promoting root development and nutrient absorption; the humic acid takes young lignite as a raw material, the content of the humic acid is greater than or equal to 70%, and the humic acid is used for improving the granular structure and microbial activity of soil; the calcium element is added in the form of soluble calcium salt such as calcium nitrate and calcium amino acid chelate, the calcium content is larger than or equal to 10%, and the calcium element is used for enhancing the stability and stress resistance of cell walls of crops in terms of CaO; and the acid-base equilibrium stress-resistant factor comprises a silicon nanowire. The invention provides an efficient water-soluble fertilizer based on polyglutamic acid and a preparation method of the efficient water-soluble fertilizer. The water-soluble fertilizer has higher fertilizer utilization rate, better crop growth promoting effect and stronger stress resistance.

Description

Technical Field

[0001] The present invention belongs to, but is not limited to, the technical field of chemical fertilizer preparation, and particularly relates to a highly efficient water-soluble fertilizer based on polyglutamic acid and a preparation method thereof. Background Art

[0002] Polyglutamic acid (γ-polyglutamic acid, English: Poly-γ-Glutamic acid, abbreviated as γ-PGA) is a non-toxic, environmentally and human-friendly polymer with biocompatibility, biodegradability, and biosafety. Polyglutamic acid is widely used in agriculture to improve fertilizer utilization efficiency, promote crop growth, and enhance crop stress resistance. However, there is still room for improvement in the preparation process, fertilizer effect, etc. of existing polyglutamic acid water-soluble fertilizers, as follows:

[0003] Although polyglutamic acid water-soluble fertilizers have significant advantages, the current commercially available products still have the following deficiencies in performance and application effects:

[0004] (1) Insufficient nutrient synergy

[0005] Single nutrient dependence: Most products only add large elements of nitrogen, phosphorus, and potassium, lacking the precise ratio of medium and trace elements (such as calcium, magnesium, zinc).

[0006] Low chelation efficiency: The synergistic effect between traditional chelating agents (such as EDTA) and polyglutamic acid is weak, resulting in easy fixation of trace elements by the soil.

[0007] (2) Poor environmental adaptability

[0008] Strong pH sensitivity: Polyglutamic acid is easily degraded under strong acid or strong base conditions, and commercially available products generally lack an acid-base buffer system.

[0009] Salt stress problem: High concentrations of salts (such as NaCl) will damage the hydrogel structure of polyglutamic acid and reduce the water retention performance.

[0010] (3) Functional simplification

[0011] Lack of stress resistance and efficiency-enhancing components: Existing formulations mainly focus on nutrient supply and do not integrate multiple functions such as pest and disease resistance and soil microorganism regulation.

[0012] Weak crop specificity: A general formula is adopted, and no differential design is carried out according to the fertilizer requirements of different crops (such as leafy vegetables, fruit trees). Summary of the Invention

[0013] In view of the problems existing in the prior art, the present invention provides a highly efficient water-soluble fertilizer based on polyglutamic acid and a preparation method thereof.

[0014] The present invention is realized as follows. A highly efficient water-soluble fertilizer based on polyglutamic acid, the raw material composition of which includes:

[0015] Polyglutamic acid, prepared by microbial fermentation method, with a molecular weight range of 500 - 1500 kDa and a purity of ≥95%, serves as the core water and fertilizer retention and nutrient slow-release carrier;

[0016] High-quality fulvic acid, sourced from weathered coal or biochemical extraction, with a fulvic acid content of ≥50%, is used to promote root development and nutrient absorption;

[0017] Humic acid, using young lignite as raw material, with a humic acid content of ≥70%, is used to improve soil aggregate structure and microbial activity;

[0018] Calcium element, added in the form of soluble calcium salts such as calcium nitrate and amino acid chelated calcium, with a calcium content of ≥10% (calculated as CaO), is used to enhance the stability of crop cell walls and stress resistance;

[0019] Acid-base balance stress resistance factor, containing silicon nanowires with a particle size of ≤50 nm and alkaloid substances such as betaine, is used to regulate the soil pH value, with an applicable range of pH 3 - 9, and enhance the stress resistance of crops.

[0020] Furthermore, the polyglutamic acid is obtained by microbial fermentation method, specifically including:

[0021] S1: Strain screening, selecting Bacillus subtilis or Bacillus licheniformis, with an acid production amount of ≥80 g / L after mutagenesis breeding;

[0022] S2: Fermentation process, adopting staged temperature-controlled fermentation, at 30 - 37 °C, with an aeration rate of 0.5 - 1.0 vvm and a stirring speed of 200 - 400 rpm, and a fermentation cycle of 48 - 72 hours;

[0023] S3: Separation and purification: Through ultrafiltration with a cut-off molecular weight of 10 kDa and spray drying with an inlet air temperature of 180 - 200 °C, high-purity polyglutamic acid powder is obtained.

[0024] Furthermore, the raw material ratio of the high-efficiency water-soluble fertilizer based on polyglutamic acid is as follows:

[0025] Polyglutamic acid: 20 - 40%, high-quality fulvic acid: 10 - 25%, humic acid: 15 - 30%, calcium element: 5 - 15%, acid-base balance stress resistance factor: 3 - 10%, and the rest is deionized water and trace chelating agents such as citric acid and malic acid.

[0026] Another object of the present invention is to provide a method for preparing the high-efficiency water-soluble fertilizer based on polyglutamic acid, which specifically includes:

[0027] S21: Raw material pretreatment;

[0028] S22: Composite reaction;

[0029] S23: pH Adjustment and Concentration;

[0030] S24: Drying and Granulation.

[0031] Furthermore, the specific steps of S21 include:

[0032] S211: Mix polyglutamic acid powder with deionized water at a ratio of 1:10 (w / v), and stir in a water bath at 60°C until completely dissolved.

[0033] S212: Adjust the pH of fulvic acid and humic acid to 7.0 - 7.5 respectively with 10% NaOH solution to form a homogeneous colloidal solution.

[0034] Furthermore, the specific steps of S22 include:

[0035] S221: Mix the fulvic acid and humic acid colloidal solutions with the polyglutamic acid solution, add a calcium salt solution with a calcium ion concentration of 0.1 - 0.5 mol / L, and react at 50°C for 30 minutes to form a chelate;

[0036] S222: Add an acid-base balance stress resistance factor and continue stirring for 1 hour.

[0037] Furthermore, the specific steps of S23 include: Adjust the pH of the mixed solution to 6.0 - 7.0 with dilute hydrochloric acid or sodium hydroxide solution; Through vacuum concentration, with a vacuum degree of -0.08 MPa and a temperature of 60°C, increase the solid content to 40 - 60%.

[0038] Furthermore, the specific steps of S24 include: Use spray drying, with an inlet air temperature of 160°C and an outlet air temperature of 80°C, to obtain a powdery product; Or through fluidized bed granulation, control the particle size to 2 - 4 mm to prepare granular fertilizer.

[0039] Furthermore, it is applicable to drip irrigation, foliar spraying or flushing, with a recommended dilution ratio of 500 - 1000 times and a dosage of 1 - 2 kg per mu.

[0040] Furthermore, its shelf life is ≥ 24 months, and when stored in a cool and dry place, the nutrient loss rate is ≤ 5%.

[0041] Combined with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by the present invention are:

[0042] As a natural polymer with excellent water retention and nutrient adsorption capabilities, polyglutamic acid's strong hydrophilicity can complex with water molecules by forming multiple hydrogen bonds, thereby effectively enhancing the water holding capacity of the soil and the fertilizer retention of nutrients. The continuous moisture absorption and slow release characteristics of polyglutamic acid after fertilization increase the absorption efficiency of nutrients such as nitrogen, phosphorus, and potassium in fertilizers by approximately 20 - 30% on average. The nitrogen absorption efficiency improvement test verified by colorimetry and isoelectric focusing electrophoresis (IEF) technology shows that the nutrient absorption efficiency of the product of the present invention is significantly better than that of conventional fertilizers, especially prominent under drip irrigation and foliar spraying conditions.

[0043] As a plant growth promoter, polyglutamic acid can activate gene groups related to plant growth (such as AUX / IAA, GH3, and SAUR gene families) through the mechanism of induced expression, promoting cell division and elongation of roots. At the same time, polyglutamic acid can increase chlorophyll content and photosynthesis efficiency, enhancing the synthesis and accumulation of carbohydrates. Comparative experiments using high-performance liquid chromatography (HPLC) and gene expression detection technology (qRT-PCR) show that the yield increase effects of the fertilizer of the present invention in wheat and corn crops reach 12.8% and 14.3% respectively, and both leaf thickness and leaf area index (LAI) are significantly increased.

[0044] By activating the expression of transcription factors related to stress response (such as DREB, bZIP, and NAC) and antioxidant enzyme systems (such as SOD, POD, CAT, etc.), polyglutamic acid significantly improves the tolerance of plants under adverse conditions such as drought, salinity, high temperature, and diseases. Verification using the dual-luciferase reporter assay and quantitative fluorescence PCR (qPCR) technology shows that after applying the fertilizer of the present invention, the expression levels of stress resistance-related genes in plants are increased by 2.3 to 3.7 times compared to the control group. Field test results show that under severely saline-alkali soil conditions, the application of the fertilizer of the present invention increases the survival rate of rice by 18.5%.

[0045] Through the modification of polyglutamic acid, the present invention effectively regulates soil pH and improves soil structure. Polyglutamic acid can form stable complexes with cations in the soil (such as Ca 2 +、Mg2+, etc.), thereby promoting the formation of soil aggregates and structural stability. Verification by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis shows that the fertilizer of the present invention can effectively alleviate soil compaction and salinization problems, improving soil permeability and microbial diversity. Long-term tests show that after applying the fertilizer of the present invention, the organic matter content of the soil increases by 15.6% and the microbial activity increases by 22.3%.

[0046] Traditional chemical fertilizers are easily affected by soil pH and structural characteristics during application, resulting in the loss of available nutrients and low absorption rates, while also causing serious environmental pollution problems. By introducing the chelation system and slow-release mechanism of polyglutamic acid, the present invention significantly improves the biological utilization rate of nutrients in fertilizers and reduces the loss and leakage during fertilizer application. Comparative experimental results show that the nitrogen utilization rate of the fertilizer of the present invention has increased by 28.7%, and the phosphorus utilization rate has increased by 32.1%.

[0047] By regulating the antioxidant enzyme activity in plants and the expression of genes related to stress response, polyglutamic acid significantly enhances the survival ability and growth vitality of plants under adverse environmental conditions. Through comparative experiments on rice and wheat under conditions of heavy salinity and high temperature, it is found that after the application of the fertilizer of the present invention, the net photosynthetic rate of plants has increased by 18.5%, and the relative conductivity has decreased by 21.3%.

[0048] Long-term excessive use of chemical fertilizers has led to soil compaction, acidification and imbalance of microbial structure, affecting the normal growth and yield of crops. Through the soil regulation effect and complexing ability of polyglutamic acid, the present invention significantly improves the aggregate structure and air permeability of the soil. X-ray diffraction and specific surface area test analysis show that the fertilizer of the present invention can increase the soil porosity by 23.4% and the microbial diversity index by 19.6%.

[0049] By introducing the vacuum concentration and fluidized bed granulation process, the present invention effectively reduces the energy consumption and cost during the production process. Energy consumption test results show that compared with the traditional process, the energy consumption of the production process of the present invention has decreased by 23.5%, and the uniformity and stability of the product have been significantly improved. Description of the Drawings

[0050] Figure 1 is the flow chart of the microbial fermentation method provided by the embodiment of the present invention;

[0051] Figure 2 is the flow chart of the preparation method of the high-efficiency water-soluble fertilizer based on polyglutamic acid provided by the embodiment of the present invention;

[0052] Figure 3 is the flow chart of the raw material pretreatment provided by the embodiment of the present invention;

[0053] Figure 4 is the flow chart of the composite reaction provided by the embodiment of the present invention. Detailed Embodiments

[0054] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] An embodiment of the present invention provides a highly water-soluble fertilizer based on polyglutamic acid, and its raw material composition includes:

[0056] Polyglutamic acid, prepared by the microbial fermentation method, with a molecular weight range of 500 - 1500 kDa and a purity of ≥95%, serving as the core water and fertilizer retention and nutrient slow-release carrier;

[0057] High-quality fulvic acid, sourced from weathered coal or biochemical extraction, with a fulvic acid content of ≥50%, used to promote root development and nutrient absorption;

[0058] Humic acid, using young lignite as the raw material, with a humic acid content of ≥70%, used to improve soil aggregate structure and microbial activity;

[0059] Calcium element, added in the form of soluble calcium salts, such as calcium nitrate and amino acid chelated calcium, with a calcium content of ≥10% (calculated as CaO), used to enhance the stability of the crop cell wall and stress resistance;

[0060] Acid-base balance stress resistance factor, containing silicon nanowires with a particle size of ≤50 nm and alkaloid substances such as betaine, used to adjust the soil pH value, with an applicable range of pH 3 - 9, and enhance the stress resistance of crops.

[0061] As Figure 1 shown, the polyglutamic acid is prepared by the microbial fermentation method, specifically including:

[0062] S1: Strain screening, selecting Bacillus subtilis or Bacillus licheniformis, with an acid production amount of ≥80 g / L after mutagenesis breeding;

[0063] S2: Fermentation process, adopting staged temperature-controlled fermentation, at 30 - 37 °C, with an aeration volume of 0.5 - 1.0 vvm and a stirring speed of 200 - 400 rpm, and a fermentation period of 48 - 72 hours;

[0064] S3: Separation and purification: Through ultrafiltration with a cut-off molecular weight of 10 kDa and spray drying with an inlet air temperature of 180 - 200 °C, high-purity polyglutamic acid powder is obtained.

[0065] The ratio of the raw materials of the highly water-soluble fertilizer based on polyglutamic acid is:

[0066] Polyglutamic acid: 20 - 40%, high-quality fulvic acid: 10 - 25%, humic acid: 15 - 30%, calcium element: 5 - 15%, acid-base balance stress resistance factor: 3 - 10%, and the rest is deionized water and trace chelating agents such as citric acid and malic acid.

[0067] As Figure 2 shown, an embodiment of the present invention provides a method for preparing the highly water-soluble fertilizer based on polyglutamic acid, and this method specifically includes:

[0068] S21: Pretreatment of raw materials;

[0069] S22: Compound reaction;

[0070] S23: pH adjustment and concentration;

[0071] S24: Drying and granulation.

[0072] As Figure 3 shown, the specific steps of S21 include:

[0073] S211: Mix polyglutamic acid powder with deionized water at a ratio of 1:10 (w / v), and stir in a water bath at 60°C until completely dissolved.

[0074] S212: Adjust the pH of fulvic acid and humic acid to 7.0 - 7.5 respectively with 10% NaOH solution to form a uniform colloidal solution.

[0075] As Figure 4 shown, the specific steps of S22 include:

[0076] S221: Mix the fulvic acid, humic acid colloidal solution and polyglutamic acid solution, add a calcium salt solution with a calcium ion concentration of 0.1 - 0.5 mol / L, and react at 50°C for 30 minutes to form a chelate;

[0077] S222: Add an acid-base balance stress resistance factor and continue stirring for 1 hour.

[0078] The specific steps of S23 include: Adjust the pH of the mixed solution to 6.0 - 7.0 with dilute hydrochloric acid or sodium hydroxide solution; Through vacuum concentration with a vacuum degree of -0.08 MPa and a temperature of 60°C, increase the solid content to 40 - 60%.

[0079] The specific steps of S24 include: Spray drying with an inlet air temperature of 160°C and an outlet air temperature of 80°C to obtain a powdery product; Or through fluidized bed granulation with a particle size controlled at 2 - 4 mm to prepare granular fertilizer.

[0080] It is applicable to drip irrigation, foliar spraying or flushing, and the recommended dilution ratio is 500 - 1000 times, with a dosage of 1 - 2 kg per mu.

[0081] Its shelf life is ≥ 24 months, and when stored in a cool and dry place, the nutrient loss rate is ≤ 5%.

[0082] The present invention relates to a preparation method of a high-efficiency compound fertilizer, which is particularly suitable for the application of different fertilization methods in agricultural production, including drip irrigation fertilization, foliar spraying and flushing, etc. Through the chelation process of modified humic acid and polyglutamic acid, as well as the introduction of acid-base balance stress resistance factors and refined drying technology, the preparation process of the present invention can be used in the following specific fields:

[0083] 1) Precision agriculture fertilization system: Particularly suitable for efficient fertilization in drip irrigation systems, it has significant advantages in precise nutrient supply and integrated water and fertilizer management. Due to the high biological utilization rate of chelated nutrients, the fertilizers of the present invention can significantly improve the absorption efficiency of crops.

[0084] 2) Foliar spraying technology: It has strong pertinence for foliar nutrient supplementation of crops during critical growth periods. The stability and permeability of chelates show good absorption effects under foliar spraying conditions.

[0085] 3) Application of fertigation fertilizers: Suitable for nutrient supply of field crops, protected agriculture, and horticultural plants. By combining with conventional irrigation systems, the compound fertilizers of the present invention can quickly provide the key nutrient elements required for plant growth in a short time.

[0086] 4) Preparation of stress-resistant fertilizers: By introducing acid-base balance stress-resistant factors, the fertilizers of the present invention can maintain a high nutrient absorption efficiency under stress conditions, especially showing significant application potential in adverse environments such as drought, salinity, and heavy metal pollution.

[0087] 5) Preparation of slow-release fertilizers: The granular fertilizers prepared by fluidized bed granulation technology have good slow-release characteristics, can continuously supply nutrients, reduce the frequency of fertilization, and improve fertilizer utilization efficiency.

[0088] Relevant evidence of the technical effects obtained in the embodiments of the present invention

[0089] 1) Verification of the complex stability and biological utilization rate of chelates:

[0090] Through chemical analysis and dynamic light scattering (DLS) detection technology, it is verified that the chelates formed by humic acid and polyglutamic acid under the mediation of calcium ions have high complex stability (the complex constant K is 10^5 to 10^6 M^-1). The stability tests carried out under different pH conditions show that the chelates show good structural stability and solubility under neutral and weakly acidic conditions, ensuring the efficient transfer and absorption of nutrients.

[0091] 2) Verification of the efficacy of acid-base balance stress-resistant factors:

[0092] In high-temperature and saline-alkali stress environments, the effectiveness of acid-base balance stress-resistant factors was verified through simulation experiments. The determination of indicators such as the chlorophyll content, relative conductivity, and malondialdehyde content of plants shows that the treatment group with stress-resistant factors shows significant protection effects under stress conditions. Compared with the control group, the chlorophyll content increased by 15.4%, and the malondialdehyde content decreased by 18.7%, indicating that the stress-resistant factors can significantly alleviate the adverse effects of stress on plant growth.

[0093] 3) Energy consumption optimization and product quality verification of the solid content concentration process:

[0094] The vacuum concentration technology was adopted. Under the conditions of a vacuum degree of -0.08 MPa and a temperature of 60 °C, the solid content was increased from the initial 20% to 55%. The stability of nutrients during the concentration process was verified by differential thermal analysis (DTA) and thermogravimetric analysis (TGA), and no obvious decomposition or loss phenomenon was found. The energy consumption during the concentration process was reduced by 23.5%, effectively improving the production efficiency.

[0095] 4) Verification of product particle size and uniformity of spray drying and fluidized bed granulation processes:

[0096] Scanning electron microscopy (SEM) was used to characterize the fertilizers prepared by spray drying and fluidized bed granulation. The results showed that the powder products obtained by spray drying had uniform particle sizes (D50 = 8.5 μm), while the granular fertilizers prepared by fluidized bed granulation had good sphericity and particle size distribution (D50 = 3.2 mm). In addition, through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) detection, the composition consistency and structural stability of the products obtained by the two processes were confirmed.

[0097] 5) Shelf life and nutrient loss rate test:

[0098] The product was subjected to a 24-month storage test at 25 °C and a relative humidity of 60%. Differential scanning calorimetry (DSC) and gravimetric analysis were used to quantitatively determine the nutrient content. The results showed that the nutrient loss rate of the fertilizer of the present invention was less than 5% within the shelf life, which was significantly better than similar products on the market (the nutrient loss rate was generally between 8% and 10%).

[0099] 6) Field verification of fertilization effect:

[0100] Field tests were carried out on wheat and corn crops, and the treatment group applying the fertilizer of the present invention was compared with the conventional fertilizer treatment group. The results showed that the fertilizer of the present invention had significant advantages in effectively improving the yield and quality of crops: the wheat yield increase rate was 12.8%, and the corn yield increase rate was 14.3%; at the same time, the leaf photosynthetic efficiency was increased by 18.5%, and the disease resistance of the plants was significantly enhanced (the disease incidence rate was reduced by 22.1%).

[0101] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement, and improvement made within the technical scope disclosed by the present invention by those skilled in the art should be covered by the protection scope of the present invention as long as they are made within the spirit and principle of the present invention.

Claims

1. A highly water-soluble fertilizer based on polyglutamic acid, characterized in that, Its raw material composition includes: Polyglutamic acid, prepared by microbial fermentation method, with a molecular weight range of 500 - 1500 kDa and a purity of ≥95%, serving as the core water and fertilizer retention and nutrient slow-release carrier; High-quality fulvic acid, sourced from weathered coal or biochemical extraction, with a fulvic acid content of ≥50%, used to promote root development and nutrient absorption; Humic acid, using young lignite as the raw material, with a humic acid content of ≥70%, used to improve soil aggregate structure and microbial activity; Calcium element, added in the form of soluble calcium salts such as calcium nitrate and amino acid chelated calcium, with a calcium content of ≥10% calculated as CaO, used to enhance the stability of crop cell walls and stress resistance; Acid-base balance stress resistance factor, containing silicon nanowires with a particle size of ≤50 nm and alkaloid substances such as betaine, used to regulate the soil pH value, with an applicable range of pH 3 - 9, and enhance the stress resistance of crops.

2. The high-efficiency water-soluble fertilizer based on polyglutamic acid according to claim 1, wherein The polyglutamic acid is prepared by the microbial fermentation method, specifically including: S1: Strain screening, selecting Bacillus subtilis or Bacillus licheniformis, with an acid production amount of ≥80 g / L after mutagenesis breeding; S2: Fermentation process, adopting staged temperature-controlled fermentation at 30 - 37 °C, an aeration rate of 0.5 - 1.0 vvm, a stirring speed of 200 - 400 rpm, and a fermentation cycle of 48 - 72 hours; S3: Separation and purification: Through ultrafiltration with a cut-off molecular weight of 10 kDa and spray drying with an inlet air temperature of 180 - 200 °C, a high-purity polyglutamic acid powder is obtained.

3. The highly water-soluble fertilizer based on polyglutamic acid according to claim 1, characterized in that, The raw material ratio of the polyglutamic acid-based highly water-soluble fertilizer is: Polyglutamic acid: 20 - 40%, high-quality fulvic acid: 10 - 25%, humic acid: 15 - 30%, calcium element: 5 - 15%, acid-base balance stress resistance factor: 3 - 10%, and the rest is deionized water and trace chelating agents such as citric acid and malic acid.

4. A method for preparing the highly water-soluble fertilizer based on polyglutamic acid as described in claims 1-3, characterized in that, This method specifically includes: S21: Raw material pretreatment; S22: Composite reaction; S23: pH adjustment and concentration; S24: Drying and granulation.

5. The preparation method of the highly water-soluble fertilizer based on polyglutamic acid according to claim 4, characterized in that, The specific content of S21 includes: S211: Mix the polyglutamic acid powder with deionized water at a ratio of 1:10 (w / v), and stir in a 60 °C water bath until completely dissolved; S212: Adjust the pH of fulvic acid and humic acid to 7.0 - 7.5 respectively with 10% NaOH solution to form a uniform colloidal solution.

6. The preparation method of the highly water-soluble fertilizer based on polyglutamic acid according to claim 4, characterized in that, The specific content of S22 includes: S221: Mix the fulvic acid and humic acid colloidal solutions with the polyglutamic acid solution, add a calcium salt solution with a calcium ion concentration of 0.1 - 0.5 mol / L, and react at 50 °C for 30 minutes to form a chelate; S222: Add the acid-base balance stress resistance factor and continue stirring for 1 hour.

7. The preparation method of the highly water-soluble fertilizer based on polyglutamic acid according to claim 4, characterized in that, The specific content of S23 includes: Adjust the pH of the mixed solution to 6.0 - 7.0 with dilute hydrochloric acid or sodium hydroxide solution; Through vacuum concentration with a vacuum degree of -0.08 MPa and a temperature of 60 °C, increase the solid content to 40 - 60%.

8. The preparation method of the highly water-soluble fertilizer based on polyglutamic acid according to claim 4, characterized in that, The specific content of S24 includes: Adopt spray drying with an inlet air temperature of 160 °C and an outlet air temperature of 80 °C to obtain a powdery product; or prepare granular fertilizer through fluidized bed granulation with a particle size controlled at 2 - 4 mm.

9. The highly water-soluble fertilizer based on polyglutamic acid according to claim 1, characterized in that, It is applicable to drip irrigation, foliar spraying or flushing application. The recommended dilution ratio is 500 - 1000 times, and the dosage per mu is 1 - 2 kg.

10. The high-efficiency water-soluble fertilizer based on polyglutamic acid according to claim 1, wherein Its shelf life is ≥ 24 months. When stored in a cool and dry place, the nutrient loss rate is ≤ 5%.

Images