Microbial agent coated granular fertilizer and preparation method thereof

Abstract

The invention belongs to the technical field of microbial fertilizers, and particularly relates to a microbial agent coated granulated fertilizer which is of a multi-layer composite structure and sequentially comprises matrix particles, algal polysaccharides, a microbial agent, a polylactic acid-glycolic acid copolymer and polyacrylic acid-polydopamine from inside to outside, according to the microbial agent coated granular fertilizer provided by the invention, the initial viable bacteria retention rate is greater than 90%, the viable bacteria retention rate is still greater than 90% after the fertilizer is stored for 6 months and 12 months, and the organic matter content of soil can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial fertilizers, and particularly relates to a microbial inoculant-coated granular fertilizer. Background Art

[0002] Microbial fertilizers refer to those composed of one or more beneficial microorganisms with the life activities of microorganisms as the core. The microorganisms in microbial fertilizers can decompose organic matter in the soil, improving the nutrient supply capacity; the metabolic activity of microorganisms can produce plant hormones or active substances to stimulate crop growth; the large reproduction of microorganisms can form a dominant population in the rhizosphere soil microecosystem of crops, restricting the growth and reproduction of other pathogenic microorganisms and inhibiting pests and diseases. In the process of the fertilizer effect of microbial fertilizers, the microbial activity plays a key role.

[0003] Traditional granular microbial fertilizers are usually prepared by spraying microorganisms on the surface of carriers. This method has poor film-forming properties, low attached microbial content, and low microbial survival rate. To increase the microbial content and microbial survival rate of granular microbial fertilizers, in the prior art, a Chinese patent application with the authorization publication number of CN 116102375B discloses the preparation of a growth-promoting composite microbial fertilizer and its application to solanaceous crop tomatoes, including the following steps: First, adhere a layer of polydopamine on the surface of spherical carrier particles, and then chelate trace elements Fe 2+ and Zn 2+, and then the fermented bacterial liquid is sprayed on the surface of polydopamine, a layer of molasses is sprayed on the surface of the fermented bacterial liquid, a layer of polydopamine is electrosprayed on the surface of the molasses, and finally a layer of mineral powder is adhered to obtain a compound microbial fertilizer. In this technical solution, the prepared compound microbial fertilizer has a high survival rate of microorganisms during storage, is not easily affected by exposure to the sun and flooding in the soil, can promote the growth of tomatoes, increase the single fruit weight, sugar content and vitamin C content of tomatoes, increase the resistance of tomatoes to bacterial wilt and fusarium wilt, and improve the soil environment. However, it can be seen that this technical solution is relatively complex. Chinese Patent Application with the authorized publication number CN 116102382 B discloses a fungal encapsulated fertilizer, a preparation method and an application. The fertilizer includes matrix particles and an encapsulated film inoculated with functional strains. The functional strains are a combination of Schizophyllum commune and Aspergillus terreus; the fungal encapsulated fertilizer is prepared through processes such as mycelial suspension preparation, extrusion granulation of matrix particles, spraying a mixed solution of fungal suspension and sodium alginate on the matrix particles, soaking and shaping with calcium chloride solution, and cultivation. In this technical solution, the fungal encapsulated fertilizer selects two fungi, Schizophyllum commune and Aspergillus terreus, as functional strains, which can complement and enhance each other's effects: degrade the difficult-to-degrade lignocellulose in cold-waterlogged paddy fields under microaerobic conditions, improve the utilization rate of difficult-to-degrade organic matter, and the degradation products and metabolites can be used as nutrient sources for the growth of other microorganisms. Moreover, it can secrete antibacterial substances, reduce soil-borne diseases, increase the content of available phosphorus and available potassium, improve soil fertility, and promote the growth of rice, with broad application prospects. However, the mechanical stability of alginate gel is poor, and it is easy to absorb water and swell and break, so it will affect the storage stability. Summary of the Invention

[0004] Based on the defects existing in the prior art, the purpose of the present invention is to provide a microbial agent-coated granular fertilizer. The microbial agent-coated granular fertilizer provided by the present invention has a multi-layer composite structure, and from the inside to the outside, it is successively a matrix particle, an algal polysaccharide, a microbial agent, a poly(lactic-co-glycolic acid) copolymer, and polyacrylic acid-polydopamine, and has excellent stability.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect of the present invention, there is provided a microbial agent-coated granular fertilizer. The microbial agent-coated granular fertilizer has a multi-layer composite structure, and from the inside to the outside, it is successively a matrix particle, an algal polysaccharide, a microbial agent, a poly(lactic-co-glycolic acid) copolymer, and polyacrylic acid-polydopamine.

[0007] Preferably, the raw materials of the matrix particles include organic matter, diopside powder, potassium feldspar powder, biochar, and attapulgite.

[0008] More preferably, the mass ratio of the organic matter, diopside powder, potassium feldspar powder, biochar, and attapulgite is 10-20:5-8:5-8:2-5:2-5.

[0009] Further preferably, the organic matter includes at least one of fermented mushroom residue, fermented furfural residue and fermented soybean meal. The above-mentioned organic matter is a known raw material that can be commercially available and understood by those skilled in the art.

[0010] Further preferably, the biochar includes at least one of straw biochar, coconut shell biochar and bamboo charcoal. The above-mentioned biochar is a known raw material that can be commercially available and understood by those skilled in the art.

[0011] The above-mentioned diopside powder, potassium feldspar powder and attapulgite are all known raw materials that can be commercially available and understood by those skilled in the art.

[0012] Preferably, the algal polysaccharide is fucoidan and / or alginate oligosaccharide.

[0013] Further preferably, the algal polysaccharide is fucoidan.

[0014] Preferably, the microbial inoculant includes Brevibacillus laterosporus powder, Bacillus mucilaginosus powder and Trichoderma harzianum powder.

[0015] Further preferably, the mass ratio of the Brevibacillus laterosporus powder, Bacillus mucilaginosus powder and Trichoderma harzianum powder is 1-3:2-4:1.

[0016] Preferably, the effective viable count of the Brevibacillus laterosporus powder is 50-200 billion CFU / g.

[0017] Preferably, the effective viable count of the Bacillus mucilaginosus powder is 50-100 billion CFU / g.

[0018] Preferably, the effective viable count of the Trichoderma harzianum powder is 50-200 billion CFU / g.

[0019] In the second aspect of the present invention, a method for preparing a coated granular fertilizer with a microbial inoculant is provided, including the following steps:

[0020] S1. Mix the organic matter, diopside powder, potassium feldspar powder, biochar and attapulgite evenly and granulate to obtain matrix granules;

[0021] S2. Mix the algal polysaccharide and water to obtain an algal polysaccharide solution;

[0022] S3. Mix the poly(lactic-co-glycolic acid) copolymer and dimethyl sulfoxide to obtain a poly(lactic-co-glycolic acid) copolymer solution;

[0023] S4. Under nitrogen protection, mix polyacrylic acid, water, and a cross-linking agent evenly, add dopamine hydrochloride, adjust the pH for reaction, dialyze, and freeze-dry to obtain polyacrylic acid-polydopamine. Mix polyacrylic acid-polydopamine and water to obtain a polyacrylic acid-polydopamine solution;

[0024] S5. Spray a layer of algal polysaccharide solution on the surface of the matrix particles, and add a microbial inoculum to obtain matrix particles coated with the microbial inoculum;

[0025] S6. First, spray a layer of poly(lactic-co-glycolic acid) solution on the surface of the matrix particles coated with the microbial inoculum, and then spray a layer of polyacrylic acid-polydopamine solution to obtain the product.

[0026] Preferably, in step S1, the granulated matrix particles are spherical with a particle size of 2 - 5 mm.

[0027] Preferably, in step S2, the mass concentration of the algal polysaccharide solution is 2 - 5%.

[0028] Preferably, in step S3, the mass concentration of the poly(lactic-co-glycolic acid) solution is 2 - 5%.

[0029] Preferably, in step S4, the mass ratio of polyacrylic acid, water, cross-linking agent, and dopamine hydrochloride is 1:15 - 20:0.8 - 1:0.5 - 0.6.

[0030] Preferably, the cross-linking agent in step S4 includes 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

[0031] More preferably, the mass ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 0.5 - 0.6:0.3 - 0.4.

[0032] Preferably, the conditions for adjusting the pH for reaction in step S4 are: adjust the pH to 5 - 6 and react at 25 - 30 °C for 10 - 20 h.

[0033] Preferably, the cut-off molecular weight of the dialysis bag used for dialysis in step S4 is 3500 D.

[0034] Preferably, the mass concentration of the polyacrylic acid-polydopamine solution in step S4 is 2 - 5%.

[0035] Preferably, the dosage of the algal polysaccharide solution in step S5 is 0.5 - 1% of the mass of the matrix particles.

[0036] Preferably, the dosage of the microbial inoculum in step S5 is 5 - 10% of the mass of the matrix particles.

[0037] Preferably, the usage amount of the poly(lactic-co-glycolic acid) copolymer solution in step S6 is 0.5-1% of the mass of the matrix particles.

[0038] Preferably, the usage amount of the polyacrylic acid-poly dopamine solution in step S6 is 0.5-1% of the mass of the matrix particles.

[0039] In the present invention, any conventional spraying equipment can be used for spraying, such as a rotary drum, a disk granulator or a fluidized bed.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] In the technical solution of the present invention, the microbial inoculant-coated granular fertilizer is a multi-layer composite structure, which is successively a matrix particle, an algal polysaccharide, a microbial inoculant, a poly(lactic-co-glycolic acid) copolymer and a polyacrylic acid-poly dopamine from the inside to the outside; first, a layer of algal polysaccharide is sprayed on the surface of the matrix particle, and then the microbial inoculant is adhered to the surface of the algal polysaccharide. The algal polysaccharide is fucoidan and / or fuco-oligosaccharide, and its unique carboxyl group can fix the microbial inoculant through hydrogen bonding and electrostatic interaction, so that the microbial inoculant adheres to the surface of the matrix particle; then, the poly(lactic-co-glycolic acid) copolymer is sprayed. The poly(lactic-co-glycolic acid) copolymer has good biocompatibility, reduces the aerobic metabolism loss of microorganisms, and further improves the stability of the microbial inoculant. Finally, the polyacrylic acid-poly dopamine is sprayed, which not only further improves the stability of the microbial inoculant, but also the polyacrylic acid-poly dopamine is easily dissolved when contacting with weakly alkaline soil, releasing the inoculant and nutrients, and improving the fertilizer efficiency. Detailed Embodiments

[0042] In order to have a clearer understanding of the technical features, objectives and effects of the present invention, the specific implementation embodiments will be described in detail below.

[0043] The present invention will be further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are the conventional conditions in the industry. The technical features involved in each implementation manner of the present invention can be combined with each other as long as they do not conflict with each other.

[0044] In the following examples and comparative examples, unless otherwise specified, the raw materials used are all commercially available or prepared by conventional methods in the art.

[0045] The fermented furfural residue was purchased from Liangtian Fertilizer Industry Co., Ltd., Gaocheng District, Shijiazhuang City, with effective content: organic matter 60%, nitrogen, phosphorus and potassium 3%.

[0046] Fucoidan was purchased from Shaanxi Haochen Biotechnology Co., Ltd., specification: fucoidan 95%.

[0047] The diopside powder was purchased from Kunshan Overseas Chinese Science and Technology New Materials Co., Ltd., with a specification of 40 μm.

[0048] The potassium feldspar powder was purchased from Anhui Gerui New Materials Technology Co., Ltd., with a specification of GC-800.

[0049] The straw biochar was purchased from Henan Jiahe Water Purification Materials Co., Ltd., with a specification of 400 mesh.

[0050] The attapulgite clay was purchased from Anhui Mingmei Mineral Chemical Co., Ltd., with a specification of PalyGel FC.

[0051] The effective viable count of the Brevibacillus laterosporus powder is 10 billion CFU / g; it was purchased from Hubei Qiming Bioengineering Co., Ltd.

[0052] The effective viable count of the Bacillus mucilaginosus powder is 10 billion CFU / g; it was purchased from Wuhan Heyuan Green Biotechnology Co., Ltd.

[0053] The effective viable count of the Trichoderma harzianum powder is 10 billion CFU / g; it was purchased from Guangzhou Weiyuan Biotechnology Co., Ltd.

[0054] The weight-average molecular weight of polyacrylic acid is 2000, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number: P299190.

[0055] The molecular weight of the poly(lactic-co-glycolic acid) is 10,000 - 20,000, purchased from Shanghai Yuanye Bio-Technology Co., Ltd., product number: S24436.

[0056] The xanthan gum was purchased from Beijing Wokai Biotechnology Co., Ltd.

[0057] In Examples 1 - 3 and Comparative Examples 1 - 5, the same mass of matrix particles was used: 100 kg.

[0058] Example 1: A microbial inoculant-coated granular fertilizer, the microbial inoculant-coated granular fertilizer is a multi-layer composite structure, which from the inside to the outside is successively a matrix particle, fucoidan, a microbial inoculant, a poly(lactic-co-glycolic acid), and a polyacrylic acid-poly dopamine.

[0059] The raw materials of the matrix particle are composed of fermented furfural residue, diopside powder, potassium feldspar powder, straw biochar, and attapulgite clay.

[0060] The mass ratio of the fermented furfural residue, diopside powder, potassium feldspar powder, straw biochar, and attapulgite clay is 18:6:6:3:3.

[0061] The microbial inoculant is composed of Brevibacillus laterosporus powder, Bacillus mucilaginosus powder, and Trichoderma harzianum powder.

[0062] The mass ratio of the Brevibacillus laterosporus powder, Bacillus mucilaginosus powder and Trichoderma harzianum powder is 2:3:1.

[0063] The preparation method of the microbial inoculant-coated granular fertilizer is as follows:

[0064] S1. Mix the organic matter, diopside powder, potassium feldspar powder, biochar and attapulgite evenly and granulate to obtain matrix granules.

[0065] S2. Mix fucoidan and water to obtain a fucoidan solution.

[0066] S3. Mix poly(lactic-co-glycolic acid) and dimethyl sulfoxide to obtain a poly(lactic-co-glycolic acid) solution.

[0067] S4. Under nitrogen protection, mix polyacrylic acid, water and a cross-linking agent evenly, add dopamine hydrochloride, adjust the pH for reaction, dialyze and freeze-dry to obtain polyacrylic acid-poly dopamine, and mix polyacrylic acid-poly dopamine and water to obtain a polyacrylic acid-poly dopamine solution.

[0068] S5. Spray a layer of fucoidan solution on the surface of the matrix granules, and add the microbial inoculant to obtain matrix granules coated with the microbial inoculant.

[0069] S6. First, spray a layer of poly(lactic-co-glycolic acid) solution on the surface of the matrix granules coated with the microbial inoculant, and then spray a layer of polyacrylic acid-poly dopamine solution to obtain the product.

[0070] The matrix granules after granulation in step S1 are spherical with a particle size of 3 mm.

[0071] The mass concentration of the algal polysaccharide solution in step S2 is 3%.

[0072] The mass concentration of the poly(lactic-co-glycolic acid) solution in step S3 is 3%.

[0073] The mass ratio of the polyacrylic acid, water, cross-linking agent and dopamine hydrochloride in step S4 is 1:18:0.9:0.6.

[0074] The cross-linking agent in step S4 includes 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

[0075] The mass ratio of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 0.5:0.4.

[0076] The conditions for adjusting the pH for reaction in step S4 are: adjusting the pH to 6 and reacting at 25°C for 16 h.

[0077] The cut-off molecular weight of the dialysis bag used in dialysis described in step S4 is 3500D.

[0078] The mass concentration of the polyacrylic acid-polydopamine solution described in step S4 is 3%.

[0079] The usage amount of the fucoidan solution described in step S5 is 0.6% of the mass of the matrix particles.

[0080] The usage amount of the microbial inoculant described in step S5 is 8% of the mass of the matrix particles.

[0081] The usage amount of the poly(lactic-co-glycolic acid) solution described in step S6 is 0.6% of the mass of the matrix particles.

[0082] The usage amount of the polyacrylic acid-polydopamine solution described in step S6 is 0.6% of the mass of the matrix particles.

[0083] Example 2

[0084] A microbial inoculant-coated granular fertilizer, the microbial inoculant-coated granular fertilizer is a multi-layer composite structure, which is composed of matrix particles, fucoidan, microbial inoculant, poly(lactic-co-glycolic acid) and polyacrylic acid-polydopamine from the inside to the outside.

[0085] The raw materials of the matrix particles are composed of fermented furfural residue, diopside powder, potassium feldspar powder, straw biochar and attapulgite.

[0086] The mass ratio of the fermented furfural residue, diopside powder, potassium feldspar powder, straw biochar and attapulgite is 18:6:6:3:3.

[0087] The microbial inoculant is composed of Brevibacillus laterosporus powder, Bacillus mucilaginosus powder and Trichoderma harzianum powder.

[0088] The mass ratio of the Brevibacillus laterosporus powder, Bacillus mucilaginosus powder and Trichoderma harzianum powder is 2:3:1.

[0089] The preparation method of the microbial inoculant-coated granular fertilizer is as follows:

[0090] S1. Mix the organic matter, diopside powder, potassium feldspar powder, biochar and attapulgite evenly and granulate to obtain matrix particles;

[0091] S2. Mix the fucoidan and water to obtain a fucoidan solution;

[0092] S3. Mix the poly(lactic-co-glycolic acid) and dimethyl sulfoxide to obtain a poly(lactic-co-glycolic acid) solution;

[0093] S4. Under nitrogen protection, mix polyacrylic acid, water, and a crosslinking agent evenly, add dopamine hydrochloride, adjust the pH to carry out the reaction, dialyze, and freeze-dry to obtain polyacrylic acid-polydopamine. Mix polyacrylic acid-polydopamine and water to obtain a polyacrylic acid-polydopamine solution;

[0094] S5. Spray a layer of fucoidan solution on the surface of the matrix particles, and add a microbial inoculum to obtain matrix particles coated with the microbial inoculum;

[0095] S6. First, spray a layer of poly(lactic-co-glycolic acid) solution on the surface of the matrix particles coated with the microbial inoculum, and then spray a layer of polyacrylic acid-polydopamine solution to obtain the product.

[0096] In step S1, the matrix particles after granulation are spherical with a particle size of 3 mm.

[0097] In step S2, the mass concentration of the algal polysaccharide solution is 3%.

[0098] In step S3, the mass concentration of the poly(lactic-co-glycolic acid) solution is 3%.

[0099] In step S4, the mass ratio of polyacrylic acid, water, crosslinking agent, and dopamine hydrochloride is 1:18:0.9:0.6.

[0100] In step S4, the crosslinking agent includes 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

[0101] The mass ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 0.5:0.4.

[0102] In step S4, the conditions for adjusting the pH to carry out the reaction are: adjust the pH to 6 and react at 25 °C for 16 h.

[0103] In step S4, the cut-off molecular weight of the dialysis bag used for dialysis is 3500 D.

[0104] In step S4, the mass concentration of the polyacrylic acid-polydopamine solution is 3%.

[0105] In step S5, the usage amount of the fucoidan solution is 0.5% of the mass of the matrix particles.

[0106] In step S5, the usage amount of the microbial inoculum is 5% of the mass of the matrix particles.

[0107] In step S6, the usage amount of the poly(lactic-co-glycolic acid) solution is 0.5% of the mass of the matrix particles.

[0108] The usage amount of the polyacrylic acid - polydopamine solution described in step S6 is 0.5% of the mass of the matrix particles.

[0109] Example 3

[0110] A microbial inoculant - coated granular fertilizer, the microbial inoculant - coated granular fertilizer is a multi - layer composite structure, and from the inside to the outside are successively matrix particles, fucoidan, microbial inoculant, poly(lactic - co - glycolic acid) copolymer, and polyacrylic acid - polydopamine.

[0111] The raw materials of the matrix particles are composed of fermented furfural residue, diopside powder, potassium feldspar powder, straw biochar, and attapulgite clay.

[0112] The mass ratio of the fermented furfural residue, diopside powder, potassium feldspar powder, straw biochar, and attapulgite clay is 18:6:6:3:3.

[0113] The microbial inoculant is composed of Brevibacillus laterosporus powder, Bacillus mucilaginosus powder, and Trichoderma harzianum powder.

[0114] The mass ratio of the Brevibacillus laterosporus powder, Bacillus mucilaginosus powder, and Trichoderma harzianum powder is 2:3:1.

[0115] The preparation method of the microbial inoculant - coated granular fertilizer is as follows:

[0116] S1. Mix the organic matter, diopside powder, potassium feldspar powder, biochar, and attapulgite clay evenly and granulate to obtain matrix particles;

[0117] S2. Mix fucoidan and water to obtain a fucoidan solution;

[0118] S3. Mix poly(lactic - co - glycolic acid) copolymer and dimethyl sulfoxide to obtain a poly(lactic - co - glycolic acid) copolymer solution;

[0119] S4. Under nitrogen protection, mix polyacrylic acid, water, and cross - linker evenly, add dopamine hydrochloride, adjust the pH for reaction, dialyze, and freeze - dry to obtain polyacrylic acid - polydopamine. Mix polyacrylic acid - polydopamine and water to obtain a polyacrylic acid - polydopamine solution;

[0120] S5. Spray a layer of fucoidan solution on the surface of the matrix particles, and add the microbial inoculant to obtain matrix particles coated with the microbial inoculant;

[0121] S6. First, spray a layer of poly(lactic - co - glycolic acid) copolymer solution on the surface of the matrix particles coated with the microbial inoculant, and then spray a layer of polyacrylic acid - polydopamine solution to obtain the product.

[0122] The matrix particles after granulation in step S1 are spherical, with a particle size of 3 mm.

[0123] The mass concentration of the algal polysaccharide solution described in step S2 is 3%.

[0124] The mass concentration of the poly(lactic-co-glycolic acid) copolymer solution described in step S3 is 3%.

[0125] The mass ratio of polyacrylic acid, water, cross-linking agent and dopamine hydrochloride described in step S4 is 1:18:0.9:0.6.

[0126] The cross-linking agent described in step S4 includes 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

[0127] The mass ratio of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 0.5:0.4.

[0128] The conditions for adjusting the pH and reacting in step S4 are: adjusting the pH to 6 and reacting at 25°C for 16 h.

[0129] The cut-off molecular weight of the dialysis bag used for dialysis in step S4 is 3500 D.

[0130] The mass concentration of the polyacrylic acid-poly(dopamine) solution described in step S4 is 3%.

[0131] The usage amount of the fucoidan solution described in step S5 is 0.8% of the mass of the matrix particles.

[0132] The usage amount of the microbial inoculum described in step S5 is 8% of the mass of the matrix particles.

[0133] The usage amount of the poly(lactic-co-glycolic acid) copolymer solution described in step S6 is 0.8% of the mass of the matrix particles.

[0134] The usage amount of the polyacrylic acid-poly(dopamine) solution described in step S6 is 0.8% of the mass of the matrix particles.

[0135] Comparative Example 1

[0136] The difference from Example 1 is that a layer of fucoidan solution is not sprayed on the surface of the matrix particles, and the microbial inoculum is directly added; the rest are the same.

[0137] Comparative Example 2

[0138] The difference from Example 1 is that fucoidan is replaced with xanthan gum of the same mass; the rest are the same.

[0139] Comparative Example 3

[0140] The difference from Example 1 is that a layer of poly(lactic-co-glycolic acid) copolymer solution is not sprayed on the surface of the matrix particles coated with the microbial inoculant, and a layer of polyacrylic acid-poly dopamine solution is directly sprayed; the rest are the same.

[0141] Comparative Example 4

[0142] The difference from Example 1 is that only a layer of poly(lactic-co-glycolic acid) copolymer solution is sprayed on the surface of the matrix particles coated with the microbial inoculant, and a layer of polyacrylic acid-poly dopamine solution is not sprayed; the rest are the same.

[0143] Comparative Example 5

[0144] The difference from Example 1 is that the polyacrylic acid-poly dopamine solution is replaced with an equal mass of poly dopamine solution; the preparation method of the poly dopamine solution is: under nitrogen protection, dopamine hydrochloride and Tris-HCl buffer solution with a pH value of 8.5 are mixed, and the mass concentration of the poly dopamine solution is 3%; the rest are the same.

[0145] Performance test:

[0146] 1. Initial viable bacteria retention rate: Detect the number of effective viable bacteria in the microbial inoculant-coated granular fertilizer just prepared / the actual number of effective viable bacteria added to the microbial inoculant-coated granular fertilizer × 100%;

[0147] 2. Viable bacteria retention rate after storage under different conditions: Detect the number of effective viable bacteria in the microbial inoculant-coated granular fertilizer after storage under different conditions / the actual number of effective viable bacteria added to the microbial inoculant-coated granular fertilizer × 100%; The number of effective viable bacteria is detected according to GB 20287-2006, and the results are shown in Table 1.

[0148] 3. Planting experiment: Crop: lettuce, application rate is 80 kg / hm 2 , after harvesting lettuce (40 days after fertilization), detect the organic matter content in the soil. The detection method uses the dichromate oxidation-external heating method. The organic matter content of the original soil is 11.5 mg / kg, and the pH is 7.5. The results are shown in Table 1.

[0149] Table 1

[0150]

[0151]

[0152] As can be seen from Table 1, the microbial inoculant-coated granular fertilizers provided in Examples 1-3 of the present invention not only have excellent initial viable bacteria retention rate, but also the viable bacteria retention rate after 6 months and 12 months of storage is still greater than 90%, and the organic matter content is higher than 15 mg / kg.

[0153] Comparative Example 1, Comparative Example 3 and Comparative Example 4 show that when any one layer is missing, the initial viable bacteria retention rate of the microbial inoculant-coated granular fertilizer obtained, the viable bacteria retention rates after 6 months and 12 months of storage are significantly reduced, and the organic matter content significantly decreases. It shows that to achieve an initial viable bacteria retention rate greater than 90%, and the viable bacteria retention rates after 6 months and 12 months of storage are still greater than 90%, and the organic matter content is high; algal polysaccharide, poly(lactic-co-glycolic acid) and polyacrylic acid-poly dopamine are all indispensable.

[0154] From Comparative Example 2 and Comparative Example 5, it can be seen that when fucoidan is replaced by xanthan gum; when poly(lactic-co-glycolic acid) is replaced by poly dopamine, the initial viable bacteria retention rate of the microbial inoculant-coated granular fertilizer obtained, the viable bacteria retention rates after 6 months and 12 months of storage are significantly reduced. It shows that to achieve an initial viable bacteria retention rate greater than 90%, and the viable bacteria retention rates after 6 months and 12 months of storage are still greater than 90%, and the organic matter content is high; specific algal polysaccharide and polyacrylic acid-poly dopamine must be used.

[0155] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A microbial inoculant-coated granular fertilizer, characterized in that, The microbial inoculant-coated granular fertilizer is a multi-layer composite structure, which consists of a matrix particle, algal polysaccharide, microbial inoculant, poly(lactic-co-glycolic acid), and polyacrylic acid-poly(dopamine) from the inside to the outside in sequence.

2. The microbial inoculant-coated granular fertilizer according to claim 1, wherein The raw materials of the matrix particle include organic matter, diopside powder, potassium feldspar powder, biochar, and attapulgite; the mass ratio of the organic matter, diopside powder, potassium feldspar powder, biochar, and attapulgite is 10-20:5-8:5-8:2-5:2-5.

3. The microbial inoculant-coated granular fertilizer according to claim 2, characterized in that, The organic matter includes at least one of fermented mushroom residue, fermented furfural residue, and fermented soybean meal.

4. The microbial inoculant-coated granular fertilizer according to any one of claims 1-3, characterized in that, The algal polysaccharide is fucoidan and / or algal oligosaccharide.

5. The microbial inoculant-coated granular fertilizer according to claim 4, wherein The algal polysaccharide is fucoidan.

6. The microbial inoculant-coated granular fertilizer according to claim 5, wherein, The microbial inoculant includes Brevibacillus laterosporus powder, Bacillus mucilaginosus powder, and Trichoderma harzianum powder; the mass ratio of the Brevibacillus laterosporus powder, Bacillus mucilaginosus powder, and Trichoderma harzianum powder is 1-3:2-4:

1.

7. The microbial inoculant-coated granular fertilizer according to claim 1, wherein The effective viable count of the Brevibacillus laterosporus powder is 50-200 billion CFU / g; the effective viable count of the Bacillus mucilaginosus powder is 50-100 billion CFU / g; the effective viable count of the Trichoderma harzianum powder is 50-200 billion CFU / g.

8. The preparation method of the microbial inoculant-coated granular fertilizer according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Mix the organic matter, diopside powder, potassium feldspar powder, biochar, and attapulgite evenly and granulate to obtain the matrix particle. S2. Mix the algal polysaccharide and water to obtain an algal polysaccharide solution. S3. Mix the poly(lactic-co-glycolic acid) and dimethyl sulfoxide to obtain a poly(lactic-co-glycolic acid) solution. S4. Under nitrogen protection, mix polyacrylic acid, water, and crosslinking agent evenly, add dopamine hydrochloride, adjust the pH for reaction, dialyze, and freeze-dry to obtain polyacrylic acid-poly(dopamine), and mix the polyacrylic acid-poly(dopamine) and water to obtain a polyacrylic acid-poly(dopamine) solution. S5. Spray a layer of algal polysaccharide solution on the surface of the matrix particle, and add the microbial inoculant to obtain the matrix particle coated with the microbial inoculant. S6. First, spray a layer of poly(lactic-co-glycolic acid) solution on the surface of the matrix particle coated with the microbial inoculant, and then spray a layer of polyacrylic acid-poly(dopamine) solution to obtain the product.

9. The preparation method of the microbial inoculant-coated granular fertilizer according to claim 8, characterized in that The mass concentration of the algal polysaccharide solution in step S2 is 2-5%. The mass concentration of the poly(lactic-co-glycolic acid) solution in step S3 is 2-5%. The mass concentration of the polyacrylic acid-poly(dopamine) solution in step S4 is 2-5%.

10. The preparation method of the microbial inoculant-coated granular fertilizer according to claim 8, characterized in that, The usage amount of the algal polysaccharide solution in step S5 is 0.5-1% of the mass of the matrix particle. The usage amount of the microbial inoculant in step S5 is 5-10% of the mass of the matrix particle. The usage amount of the poly(lactic-co-glycolic acid) solution in step S6 is 0.5-1% of the mass of the matrix particle. The usage amount of the polyacrylic acid-poly(dopamine) solution in step S6 is 0.5-1% of the mass of the matrix particle.

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