Bio-based suspending agent and application thereof in attapulgite clay-based liquid fertilizer

Abstract

The invention discloses a bio-based suspending agent and application thereof in an attapulgite clay-based liquid fertilizer, the bio-based suspending agent is a microbial culture solution obtained by fermenting functional microbial strain leuconostoc mesenteroides by using cane sugar, a seed solution is prepared from the leuconostoc mesenteroides, and the seed solution is prepared into the attapulgite clay-based liquid fertilizer. Inoculating the seed solution into a liquid culture medium to prepare a bio-based suspending agent; and preparing the attapulgite clay-based liquid fertilizer by using the bio-based suspending agent. The bio-based suspending agent disclosed by the invention is a biological agent which is prepared by microbial fermentation and has certain viscosity, has better suspension property, has solubility on common raw materials of liquid fertilizers, and effectively prevents attapulgite clay from precipitating and fertilizer liquid from crystallizing; the attapulgite clay-based liquid fertilizer has good stability, suspension property and flowability, and is rich in nutrition; the bio-based suspending agent is used for replacing a chemical suspending agent, and the preparation process is simple, free of environmental pollution and suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of liquid fertilizers, and in particular relates to a bio-based suspending agent and application thereof in attapulgite clay-based liquid fertilizers. Background Art

[0002] Liquid fertilizers have the advantages of comprehensive nutrient elements, fast fertilizer effect, high fertilization efficiency, and easy to achieve water-fertilizer integration. In arid and semi-arid areas, desert areas, extremely water-deficient areas, large-scale planting areas, and high-value-added economic crop plantations, drip irrigation and sprinkler irrigation are often used for liquid fertilizer application. Dissolve the fertilizer in water, fertilize while watering, and crops obtain the required nutrients in this way. This method can save irrigation water and improve labor productivity. Therefore, liquid fertilizers are widely used in agricultural production and show a growing trend. Among them, suspended liquid fertilizers can integrate other organic raw materials except nitrogen, phosphorus, potassium and trace elements, such as fulvic acid, amino acids, carbon source organic matter and other raw materials, so as to achieve the effect of rooting and nourishing the soil and supplementing a variety of trace elements while supplementing nitrogen, phosphorus and potassium elements to crops, with better fertilizer effect, more uniform nutrition, and more convenient use; good fluidity, no stratification, no caking, and nutrients are not easy to lose, so suspended liquid fertilizers are favored.

[0003] Suspension agents can improve the stability, uniformity and accuracy of nutrient content of liquid fertilizers, making them easier for plants to absorb and utilize. In the context of the continuous promotion of water-fertilizer integration technology, suspension agents help to achieve precise fertilization and improve fertilizer utilization, reducing fertilizer waste and environmental pollution. At the same time, suspension agents can be combined with other functional ingredients to develop liquid fertilizer products with more functions to meet the special needs of different crops and soil conditions. The application prospects of suspension agents in liquid fertilizers are very optimistic and are expected to play a more important role in future agricultural production. However, the quality of suspension agents directly affects the quality of liquid fertilizers. At present, thickening materials such as polyacrylamide and carboxymethyl fiber are usually dissolved as suspension agents, or attapulgite clay and kaolin are modified to make suspension agents. These suspension agents are easy to precipitate and flocculate when used, resulting in uneven fertilizer concentration, and due to the high fertilizer concentration, crystallization is formed, which eventually causes the drip irrigation or sprinkler irrigation system to fail to operate normally. In addition, the addition of suspension agents will increase production costs, which to a certain extent limits its wide application in some crops with low economic value. Therefore, using microorganisms with the function of producing viscous substances and their microbial fermentation technology to produce bio-based suspension concentrates with certain suspension capabilities and reduce production costs is an effective strategy to solve the above problems.

[0004] Attapulgite clay is often known as the "soil of a thousand soils". It is rich in various trace elements such as sodium, calcium, iron, and aluminum required for plant growth and development. These trace elements from attapulgite clay can well compensate for the lack of soil nutrients and effectively improve the quality and yield of crops. Attapulgite clay has unique advantages as a fertilizer additive. For example, its unique rod-shaped crystal structure can disrupt the highly aggregated soil structure and effectively improve the soil compaction problem caused by factors such as poor water and fertilizer management; the large internal and external specific surface area and rich internal nanopores of attapulgite clay can ensure good water and fertilizer retention, and even provide some acid-base buffering properties. At the same time, it can also absorb various chemicals in the soil that are not conducive to plant growth and development, inhibit the activity of harmful microorganisms, and reduce the resistance of plant growth and development. However, in the application of liquid fertilizers, due to the influence of anions and cations in liquid fertilizers, the dispersibility of attapulgite clay in liquid fertilizers is poor or the colloidal properties are lost. This limits the use of attapulgite clay in liquid fertilizers. Therefore, it is imperative to develop a liquid fertilizer that prevents ions from interfering with the properties of clay colloids. Summary of the invention

[0005] In view of the problems existing in the above-mentioned background technology, the purpose of the present invention is to provide a bio-based suspending agent and its application in attapulgite clay-based liquid fertilizer. The bio-based suspending agent has good suspension properties and can prevent the attapulgite clay in the liquid fertilizer from sinking; the attapulgite clay-based liquid fertilizer has good stability, suspension and fluidity, and is rich in nutrients; the bio-based suspending agent is used to replace the chemical suspending agent, the preparation process is simple, there is no environmental pollution, and it is suitable for large-scale production.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A bio-based suspension concentrate is a microbial culture solution obtained by fermenting sucrose with a functional microbial strain, wherein the viscosity of the microbial culture solution is 115-120 mPa.s; the functional microbial strain is Leuconostoc mesenteroides GSICC 31207 from the Gansu Branch of the China Industrial Microbiological Culture Collection Center.

[0008] A method for preparing a bio-based suspension concentrate comprises the following steps:

[0009] (1) Culture medium preparation:

[0010] (a) Components of solid slant preservation medium and their final concentrations: peptone 2 g / L, sucrose 130 g / L, potassium dihydrogen phosphate 0.3 g / L, sodium dihydrogen phosphate 1.4 g / L, agar 20 g / L, distilled water to 1 L, pH adjusted to 7.0-7.2, and sterilized by high pressure steam at 121°C for 20 min;

[0011] (b) Liquid culture medium components and their final concentrations: peptone 2 g / L, sucrose 130 g / L, potassium dihydrogen phosphate 0.3 g / L, sodium dihydrogen phosphate 1.4 g / L, distilled water to 1 L, pH adjusted to 7.0-7.2, sterilized by high pressure steam at 121°C for 20 min;

[0012] (2) Preparation of Leuconostoc mesenteroides seed solution:

[0013] The Leuconostoc mesenteroides was inoculated from the solid slant preservation medium into a 50 mL triangular flask containing 20 mL of liquid medium, and cultured at room temperature to prepare a Leuconostoc mesenteroides seed solution;

[0014] (3) Preparation of bio-based suspension concentrate:

[0015] The Leuconostoc mesenteroides seed solution is inoculated into the liquid culture medium at a certain inoculation amount, and cultured at room temperature for 60 hours to obtain a microbial culture solution with a certain viscosity and no precipitation, that is, a bio-based suspension.

[0016] Furthermore, the inoculation amount of the Leuconostoc mesenteroides seed solution is 5%.

[0017] A attapulgite clay-based liquid fertilizer comprises urea, monoammonium phosphate, potassium sulfate, attapulgite clay, microbial protein liquid and a bio-based suspending agent.

[0018] Furthermore, the added amount of the attapulgite clay accounts for 1% to 3% by weight of the bio-based suspending agent.

[0019] Furthermore, the particle size of the attapulgite clay is 500 mesh. The above bio-based suspending agent has a good suspension ability for 500 mesh attapulgite clay, and the suspension degree of 500 mesh attapulgite clay in the bio-based suspending agent is maintained at more than 97% after standing for 32 hours.

[0020] Further, the attapulgite clay-based liquid fertilizer is made of the following raw materials in parts by weight: 34 parts of urea, 3.35 parts of monoammonium phosphate, 3.85 parts of potassium sulfate, 2.5 parts of 500-mesh attapulgite clay, 15 parts of microbial protein liquid and 85 parts of bio-based suspending agent. In the liquid fertilizer, the main nutrients of the microbial protein liquid are: total free amino acids 53g / L, organic matter 371g / L, total humic acid 218g / L, fulvic acid 243g / L, crude protein 347g / L, total nitrogen (N) 98g / L, phosphorus (P2O5) 0.7g / L, potassium (K2O) 7.9g / L, calcium (Ca) 54g / L, magnesium (Mg) 0.061g / L, iron (Fe) 0.040g / L.

[0021] A method for preparing attapulgite clay-based liquid fertilizer comprises the following steps:

[0022] (1) adding urea, monoammonium phosphate, and potassium sulfate to the bio-based suspending agent in sequence, and stirring until the raw materials are completely dissolved to obtain a mother liquor;

[0023] (2) Adding attapulgite clay and microbial protein solution to the mother liquor, stirring thoroughly until the mixture is uniform, to obtain attapulgite clay-based liquid fertilizer.

[0024] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0025] (1) The bio-based suspension concentrate of the present invention includes a functional microbial strain of Leuconostoc mesenteroides. The bio-based suspension concentrate is a biological preparation with a certain viscosity made by microbial fermentation, which can replace chemical substances in liquid fertilizers and reduce the risk of environmental pollution.

[0026] (2) The bio-based suspending agent of the present invention has a certain suspension ability for attapulgite clay and is soluble in the common raw materials of liquid fertilizers, and can effectively prevent the precipitation of attapulgite clay and the crystallization of fertilizer liquid.

[0027] (3) The attapulgite-based liquid fertilizer of the present invention has good suspension, stability and fluidity, and the suspension degree can be maintained at 94% within 24 hours, the sedimentation rate (expressed as mass fraction) is 5%; the stability coefficient is 0.95; the viscosity is 130mPa.s, and the pH value (1:250 times dilution) is 5.9-6.0. After slight stratification, it can be restored by stirring, and it is rich in attapulgite clay mineral elements and nutrient elements, and has broad application prospects in agricultural production and fertilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of Leuconostoc mesenteroides provided in Example 1 of the present invention;

[0029] Figure 2 is a schematic diagram of the bio-based suspending agent provided in Example 1 of the present invention;

[0030] Figure 3 is a comparison diagram of suspension conditions of different liquid fertilizers provided in Example 3 of the present invention;

[0031] Figure 4 This is a diagram of seed germination rates under different treatments provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific 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.

[0033] Example 1

[0034] Preparation of a bio-based suspension concentrate:

[0035] (1) Culture medium preparation:

[0036] (a) Components of solid slant preservation medium and their final concentrations: peptone 2 g / L, sucrose 130 g / L, potassium dihydrogen phosphate 0.3 g / L, sodium dihydrogen phosphate 1.4 g / L, agar 20 g / L, distilled water to 1 L, pH adjusted to 7.0-7.2, and sterilized by high pressure steam at 121°C for 20 min;

[0037] (b) Liquid culture medium components and their final concentrations: peptone 2 g / L, sucrose 130 g / L, potassium dihydrogen phosphate 0.3 g / L, sodium dihydrogen phosphate 1.4 g / L, distilled water to 1 L, pH adjusted to 7.0-7.2, sterilized by high pressure steam at 121°C for 20 min;

[0038] (2) Preparation of Leuconostoc mesenteroides seed solution:

[0039] Leuconostoc mesenteroides (reference Figure 1 ), which is deposited in the Gansu Branch of China Industrial Microbiological Culture Collection Center, classified and named Leuconostoc mesenteroides, with the deposit number of GSICC31207, and the deposit address is Institute of Biology, Gansu Academy of Sciences, No. 197, Dingxi South Road, Chengguan District, Lanzhou City, Gansu Province, China.

[0040] The Leuconostoc mesenteroides was inoculated from the solid slant preservation medium into a 50 mL Erlenmeyer flask containing 20 mL of liquid medium, and cultured at room temperature to prepare a Leuconostoc mesenteroides seed solution;

[0041] (3) Preparation of bio-based suspension concentrate:

[0042] The inoculum of 5% was inoculated into the liquid culture medium, and the culture medium was incubated for 60 h at room temperature (25°C to 28°C) to obtain a microbial culture medium with a viscosity of 115 to 120 mPa.s without precipitation. Figure 2 , i.e. bio-based suspension concentrate.

[0043] The relationship between the viscosity of the bio-based suspension and the fermentation culture time of Enterobacter mesenteroides is shown in Table 1. The seed solution of Enterobacter mesenteroides was inoculated into a 50mL triangular flask containing 20mL of liquid culture medium at a 5% inoculation rate, and the culture was cultured at room temperature. The time was recorded and the viscosity of the culture solution was measured. When the liquid culture medium was not inoculated with Enterobacter mesenteroides, the viscosity of the culture solution was 0.7mPa.s (the viscosity after sterilization was 0.6mPa.s). As the fermentation culture time increased, the viscosity of the culture solution gradually increased. After 60h of culture, the viscosity of the culture solution tended to be stable, and the sterilization treatment had little effect on the viscosity of the culture solution. Therefore, combined with the preparation time cost of the bio-based suspension, the preparation fermentation time and viscosity of the bio-based suspension were determined to be 60h and 115-120mPa.s.

[0044] Table 1 Relationship between viscosity of bio-based suspension and fermentation culture time of Leuconostoc mesenteroides

[0045] Time (h) Viscosity of bio-based suspension concentrate (mPa.s) Viscosity of bio-based suspension after sterilization (mPa.s) 0 1.70 1.75 12 1.85 1.45 24 1.85 1.85 36 22.00 31.35 60 120.00 110.67 84 123.33 122.00 108 116.00 108.00 132 127.33 121.00

[0046] Example 2

[0047] A attapulgite clay-based liquid fertilizer is prepared from the following raw materials in parts by weight: 34 parts of urea, 3.35 parts of monoammonium phosphate, 3.85 parts of potassium sulfate, 2.5 parts of 500-mesh attapulgite clay, 15 parts of microbial protein liquid and 85 parts of bio-based suspending agent. The added amount of attapulgite clay accounts for 1% to 3% of the weight of the bio-based suspending agent. In the liquid fertilizer, the main nutrients of the microbial protein liquid are: 53g / L of free amino acids, 371g / L of organic matter, 218g / L of total humic acid, 243g / L of fulvic acid, 347g / L of crude protein, 98g / L of total nitrogen (N), 0.7g / L of phosphorus (P2O5), 7.9g / L of potassium (K2O), 54g / L of calcium (Ca), 0.061g / L of magnesium (Mg) and 0.040g / L of iron (Fe).

[0048] The bio-based suspending agent has a good suspension ability for 500-mesh attapulgite clay. After standing for 32 hours, the suspension degree of 500-mesh attapulgite clay in the bio-based suspending agent is maintained at more than 97%.

[0049] Analysis of the effect of bio-based suspending agent on the suspension properties of attapulgite clay:

[0050] Prepare 500 mesh attapulgite clay water suspension, bio-based suspension and commercial liquid fertilizer suspension, respectively, attapulgite clay / carrier liquid is 5g / 100mL. The specific steps are: use a measuring cylinder to measure 25mL of carrier liquid and pour it into a 50mL beaker, then pour 1.25g of attapulgite clay, mix evenly with a magnetic stirrer (15min); then pour the dispersed attapulgite clay suspension into a 25mL plunger measuring cylinder until the 25mL scale line, and then seal it; stand and observe, and record the sedimentation and stratification scale of the suspension as the suspension value at this time. The suspension of the attapulgite clay suspension with the addition of the bio-based suspension agent is significantly higher than that of the attapulgite clay water suspension and the commercial liquid fertilizer suspension (see Table 2), and the bio-based suspension agent has a certain suspension ability for attapulgite clay.

[0051] Table 2 Effect of different carrier liquids on the suspension properties of attapulgite clay suspensions

[0052] time Water (suspension degree, %) Commercially available liquid fertilizer (suspension degree, %) Bio-based suspending agent (suspension degree, %) 10min 64.67 13.60 100.00 2h 47.00 13.60 100.00 6h 41.33 13.60 98.00 32h 34.67 13.60 97.60 44h 34.67 13.60 79.60 56h 34.17 13.60 58.40 68h 34.00 13.60 51.60

[0053] Analysis of the influence of dispersion time of attapulgite clay in bio-based suspending agent on the suspension properties of attapulgite clay:

[0054] Prepare 500-mesh attapulgite clay suspensions with bio-based suspending agents added, and the attapulgite clay / bio-based suspending agent is 5g / 100mL. The specific steps are: use a measuring cylinder to measure 25mL of bio-based suspending agent and pour it into a 50mL beaker, then pour 1.25g of attapulgite clay, stir evenly with a magnetic stirrer, and stir for 5, 10, 15, 20, and 25 minutes respectively; then pour the dispersed attapulgite clay suspension into a 25mL plunger measuring cylinder until the 25mL scale line, and then seal it; let it stand and observe, and record the sedimentation and stratification scale of the suspension as the suspension value at this time. After 15 minutes of dispersion of attapulgite clay in the bio-based suspending agent, the attapulgite clay has the best suspension, and the suspension degree is maintained above 95% after standing for 72 hours (see Table 3).

[0055] Table 3 Relationship between the suspension properties and dispersion time of attapulgite clay suspension with bio-based suspending agent added

[0056]

[0057] Analysis of the influence of different amounts of attapulgite clay added on the suspension of attapulgite clay in bio-based suspension concentrate: 500-mesh attapulgite clay suspensions with bio-based suspension concentrates were prepared, and the attapulgite clay / bio-based suspension concentrates were 1g / 100mL, 2g / 100mL, 3g / 100mL, 4g / 100mL, and 5g / 100mL, respectively, that is, the amount of attapulgite clay added was 1% to 5%. The specific steps are: use a measuring cylinder to measure 25mL of bio-based suspension concentrate and pour it into a 50mL beaker, then pour 0.25, 0.5, 0.75, 1, and 1.25g of attapulgite clay, and mix evenly with a magnetic stirrer (15min); then pour the dispersed attapulgite clay suspension into a 25mL plunger measuring cylinder to the 25mL mark, and then seal it; let it stand for observation, and record the sedimentation and stratification scale of the suspension as the suspension value at this time. When the addition amount of attapulgite clay is in the range of 1% to 3%, the attapulgite clay suspension with the addition of the bio-based suspending agent has good suspension properties. After standing for 41 hours, the suspension degree is maintained at 94% and above (see Table 4).

[0058] Table 4 Relationship between the concentration of attapulgite clay in suspension and its suspension

[0059]

[0060] Example 3

[0061] The solubility of bio-based suspension concentrate in urea, monoammonium phosphate, and potassium sulfate, which are commonly used raw materials in commercial liquid fertilizers, was investigated in the hope that the bio-based suspension concentrate could be applied to liquid fertilizers with attapulgite clay added to reduce precipitation and material crystallization. The specific steps are: different masses of urea (N 46%), monoammonium phosphate (N 12%, P2O5 62%), and potassium sulfate (K2O 52%) were added to the bio-based suspension concentrate to dissolve, and the maximum solubility and viscosity of the bio-based suspension concentrate at room temperature (20-25°C) were measured. The initial viscosity of the bio-based suspension concentrate was 116.00 mPa.s. The solubility of urea, monoammonium phosphate, and potassium sulfate in 100g of bio-based suspension concentrate was 70, 16.67, and 7.69g, respectively, and the viscosity of the bio-based suspension concentrate decreased with the increase of the mass of urea and potassium sulfate; the viscosity of the bio-based suspension concentrate increased with the increase of the mass of monoammonium phosphate (see Table 5).

[0062] Table 5 Solubility of common raw materials in commercial liquid fertilizers in bio-based suspension concentrates

[0063]

[0064] In order to further consider the application of bio-based suspending agent, attapulgite clay and microbial protein solution in liquid fertilizer, combined with the requirements of the national industry standard "Water-soluble fertilizer containing humic acid" (NY 1106-2010), the present invention develops the raw material ratio and preparation process in attapulgite clay-based liquid fertilizer.

[0065] The attapulgite clay-based liquid fertilizer is prepared from the following raw materials in parts by weight: 34 parts of urea, 3.35 parts of monoammonium phosphate, 3.85 parts of potassium sulfate, 2.5 parts of attapulgite clay (500 meshes), 15 parts of microbial protein liquid, and 85 parts of bio-based suspending agent.

[0066] The preparation method of attapulgite clay-based liquid fertilizer comprises the following specific steps:

[0067] (1) Preparation of mother liquor: Add 34 parts of urea, 3.35 parts of monoammonium phosphate, and 3.85 parts of potassium sulfate to 85 parts of bio-based suspending agent in sequence, stir the solution thoroughly until the raw materials are completely dissolved, and set aside.

[0068] (2) Add 2.5 parts of attapulgite clay and 15 parts of microbial protein solution to the mother liquor, stir thoroughly (magnetic stirrer, 20-25° C., 15 min) to mix evenly, and obtain the attapulgite clay-based liquid fertilizer. Put it into a container, seal it and store it.

[0069] Attapulgite clay-based liquid fertilizer has good suspension, stability and fluidity. The suspension degree can be maintained at 94% within 24 hours (refer to Figure 3 ), the precipitation rate (expressed by mass fraction) is 5%; the stability coefficient is 0.95; the viscosity is 130mPa.s, and the pH value (1:250 dilution) is 5.9-6.0.

[0070] The main nutrients and their contents of attapulgite clay-based liquid fertilizer include: macroelements (N+P2O5+K2O) ≥ 200g / L, among which N ≥ 160g / L, P2O5 ≥ 20g / L, K2O ≥ 20g / L, humic acid ≥ 30g / L, organic matter ≥ 55g / L, attapulgite clay ≥ 25g / L, and it is rich in attapulgite clay mineral elements.

[0071] Analysis of the effect of attapulgite clay-based liquid fertilizer on seed germination: Prepare a 9 cm diameter culture dish and cover it with filter paper, add 10 mL of the treatment solution diluted 500 times, and fully moisten the filter paper. After evenly placing 10 commercially available radish seeds on the filter paper, place the culture dish in a dark environment at 28-30°C for 3 days, observe and record the number of seed germination, and keep the filter paper moist every day. The treatment solutions were set as: distilled water (blank treatment), attapulgite clay-based liquid fertilizer, and nutrient mixture, with 3 replicates for each treatment. The nutrient mixture is the main substance in the commercially available liquid fertilizer used in the present invention, and is prepared from 34 parts of urea, 3.35 parts of monoammonium phosphate, 3.85 parts of potassium sulfate, 25 parts of microbial protein solution, and 75 parts of water. The main nutrients and their contents include: macroelements (N+P2O5+K2O) ≥ 200g / L, of which N ≥ 160g / L, P2O5 ≥ 20g / L, K2O ≥ 20g / L, total humic acid ≥ 60g / L, and organic matter ≥ 100g / L. The effects of the three treatment solutions on seed germination are shown in the figure. Figure 4 shown.

[0072] The results showed (see Table 6 and Figure 4 ), attapulgite clay-based liquid fertilizer was beneficial to seed germination, with a germination rate of 96.7%, while the germination rate of the nutrient mixture containing higher humic acid and organic matter was only 90%, indicating that adding bio-based suspending agent and attapulgite clay to liquid fertilizer is beneficial to seed germination.

[0073] Table 6 Effects of different treatment solutions on seed germination rate

[0074] deal with Seed germination rate Distilled water (blank treatment) 100％ Attapulgite clay based liquid fertilizer 96.7％ Nutrient mixture 90％

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bio-based suspending agent, characterized in that: The bio-based suspension concentrate is a microbial culture solution obtained by fermenting sucrose with a functional microbial strain, and the viscosity of the microbial culture solution is 115-120 mPa.s; the functional microbial strain is Leuconostocmesenteroides GSICC 31207 from the Gansu Branch of the China Industrial Microbiological Culture Collection Center.

2. A method for preparing a bio-based suspension concentrate as claimed in claim 1, characterized in that: The following steps are involved: (1) Culture medium preparation: (a) Components of solid slant preservation medium and their final concentrations: peptone 2 g / L, sucrose 130 g / L, potassium dihydrogen phosphate 0.3 g / L, sodium dihydrogen phosphate 1.4 g / L, agar 20 g / L, distilled water to 1 L, pH adjusted to 7.0-7.2, and sterilized by high pressure steam at 121°C for 20 min; (b) Liquid culture medium components and their final concentrations: peptone 2 g / L, sucrose 130 g / L, potassium dihydrogen phosphate 0.3 g / L, sodium dihydrogen phosphate 1.4 g / L, distilled water to 1 L, pH adjusted to 7.0-7.2, sterilized by high pressure steam at 121°C for 20 min; (2) Preparation of Leuconostoc mesenteroides seed solution: The Leuconostoc mesenteroides was inoculated from the solid slant preservation medium into a 50 mL triangular flask containing 20 mL of liquid medium, and cultured at room temperature to prepare a Leuconostoc mesenteroides seed solution; (3) Preparation of bio-based suspension concentrate: The Leuconostoc mesenteroides seed solution is inoculated into the liquid culture medium at a certain inoculation amount, and cultured at room temperature for 60 hours to obtain a microbial culture solution with a certain viscosity and no precipitation, that is, a bio-based suspension.

3. The preparation method according to claim 2, characterized in that: The inoculation amount of the Leuconostoc mesenteroides seed solution is 5%.

4. A attapulgite clay-based liquid fertilizer, characterized in that: The liquid fertilizer comprises urea, monoammonium phosphate, potassium sulfate, attapulgite clay, microbial protein liquid and the bio-based suspension concentrate according to claim 1.

5. The attapulgite clay-based liquid fertilizer according to claim 4, characterized in that: The added amount of the attapulgite clay accounts for 1% to 3% of the weight of the bio-based suspending agent.

6. The attapulgite clay-based liquid fertilizer according to claim 4, characterized in that: The particle size of the attapulgite clay is 500 meshes.

7. The attapulgite clay-based liquid fertilizer according to claim 4, characterized in that: The attapulgite clay-based liquid fertilizer is prepared from the following raw materials in parts by weight: 34 parts of urea, 3.35 parts of monoammonium phosphate, 3.85 parts of potassium sulfate, 2.5 parts of 500-mesh attapulgite clay, 15 parts of microbial protein liquid and 85 parts of bio-based suspending agent.

8. A method for preparing the attapulgite clay-based liquid fertilizer according to any one of claims 4 to 7, comprising the following steps: (1) adding urea, monoammonium phosphate, and potassium sulfate to the bio-based suspending agent in sequence, and stirring until the raw materials are completely dissolved to obtain a mother liquor; (2) Adding attapulgite clay and microbial protein solution to the mother liquor, stirring thoroughly until the mixture is uniform, to obtain attapulgite clay-based liquid fertilizer.

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