A compound microbial fertilizer containing seaweed extract, its preparation method and application

Abstract

This invention relates to a compound microbial fertilizer containing seaweed extract, its preparation method, and its application. Addressing the problems of traditional encapsulation materials in existing microbial fertilizers, such as easy disintegration in high-salt environments, easy inactivation of microbial agents, and reduced fertilizer effectiveness in high-pH environments, this invention mixes seaweed fermentation broth as a metabolic enhancer with the bacterial solution. Seaweed extract and tannic acid are added to the bacterial solution to form microcapsules. A composite solution of seaweed oligosaccharides and humic acid serves as the outer slow-release layer. The bacterial solution is sprayed onto the surface of the fertilizer particles through a nozzle, creating a gradient coating structure. The method for preparing this compound microbial fertilizer containing seaweed extract allows the fertilizer to form an ion-barrier layer in a high-salt environment. The natural auxins in the seaweed extract and humic acid synergistically activate the metabolism of the microbial strains. The resulting compound microbial fertilizer significantly improves crop growth in high-pH environments after application.

Description

Technical Field

[0001] This invention relates to the field of fertilizer processing technology, specifically to a compound microbial fertilizer containing seaweed extract, its preparation method, and its application. Background Technology

[0002] Microbial fertilizers are products containing specific active microorganisms. Through the life activities of these microorganisms, they enhance soil nutrient supply efficiency, improve soil structure, strengthen crop resistance, and reduce reliance on chemical fertilizers—making them a green agricultural input. Currently, technological innovation in microbial fertilizers focuses on slow-release carriers and microbial community optimization, such as nano-modified biochar carriers, synergistic effects of compound microbial agents, and the use of waste materials to prepare porous biochar with adsorption functions.

[0003] Existing technologies for microbial fertilizers have certain technical bottlenecks. For example, traditional encapsulation materials such as chitosan are prone to disintegration in high-salt environments, leading to the loss of live bacteria during transportation; the high-temperature drying process in the production of solid microbial agents deactivates heat-sensitive substances such as IAA (natural growth factor); and the fertilizers have limited effectiveness in high-pH environments such as saline-alkali soils.

[0004] Seaweed contains abundant natural active substances and endogenous plant growth regulators, and is rich in various trace elements, making it an ideal additive for enhancing fertilizer efficiency. Seaweed extracts, as fertilizer additives, offer advantages such as comprehensive nutrition, soil improvement, and enhanced crop resistance. They can also be used in microbial fertilizers, but their application has certain limitations. Current technologies often involve directly mixing seaweed extracts with bacterial strains, which can easily lead to the decomposition of the active ingredients in the seaweed extract during granulation due to high temperatures, failing to form a synergistic protective system with the bacterial strains.

[0005] Therefore, a novel fertilizer that combines seaweed extract with microorganisms is needed to solve the aforementioned technical problems. Summary of the Invention

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] On one hand, the present invention provides a method for preparing a compound microbial fertilizer containing seaweed extract, comprising the following steps:

[0008] (1) Mix nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and biocontrol bacteria, then add a metabolic synergist to adjust the overall bacterial concentration to 1×10⁻⁶. 9 CFU / mL;

[0009] (2) Add seaweed extract and tannic acid to the bacterial solution to form microcapsules, and spray seaweed oligosaccharide-humic acid composite solution on the surface of the microcapsules;

[0010] (3) The microcapsules obtained in step (2) are sprayed onto the surface of fertilizer granules through an atomizer. The atomization amount is dynamically adjusted according to the temperature of the fertilizer granules to obtain compound fertilizer granules.

[0011] (4) The compound fertilizer particles obtained in step (3) are subjected to infrared radiation to cross-link the seaweed gel network to form a stable coating layer, thereby obtaining the compound microbial fertilizer.

[0012] Preferably, in step (1), the nitrogen-fixing bacteria are Rhodopseudomonas palustris, the phosphate-solubilizing bacteria are Bacillus mucilaginosus, and the biocontrol bacteria are Bacillus subtilis.

[0013] Preferably, in step (1), the mixing ratio of nitrogen-fixing bacteria, phosphate-solubilizing bacteria and biocontrol bacteria is 2:1:1 based on the number of live bacteria, and the metabolic synergist is 5-10% v / v of seaweed fermentation broth.

[0014] Preferably, in step (2), the concentration of seaweed extract is 3-5% w / v, the concentration of tannic acid is 0.5-1% w / v, and the mass ratio of seaweed oligosaccharide to humic acid in the seaweed oligosaccharide-humic acid composite solution is 2:1.

[0015] More preferably, the seaweed extract in step (2) includes fucoidan, alginic acid and natural growth factor (IAA), wherein the fucoidan content is ≥30wt%, the alginic acid content is ≥40wt%, and the IAA content is ≥50mg / kg.

[0016] Preferably, in step (3), the nozzle atomization pressure is 0.3-0.5 MPa and the spraying temperature is 45-60℃.

[0017] Preferably, the dynamic adjustment in step (3) is as follows: the atomization parameters are adjusted by real-time monitoring of the nozzle temperature. When ΔT=5℃, the flow rate changes by ±10%, and the atomization pressure decreases by 0.1MPa.

[0018] Preferably, the infrared radiation temperature in step (4) is 60-80℃ and the time is 30-60 seconds.

[0019] On the other hand, the present invention provides a compound microbial fertilizer containing seaweed extract, prepared by the above method, wherein each gram of fertilizer contains ≥5×10⁻⁶ live bacteria. 7 CFU; the retention rate of seaweed active ingredients, calculated as fucoidan, is ≥90%. A gradient coating structure is formed on the surface of the fertilizer granules. The inner gel layer is a 20-30 μm thick bacterial cell-seaweed polysaccharide complex, the middle cross-linked layer is a 5-10 μm thick tannic acid layer, and the outer slow-release layer is a 10-20 μm thick humic acid-seaweed oligosaccharide complex.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The method for preparing compound microbial fertilizer containing seaweed extract provided by the present invention is that seaweed extract and tannic acid form a microcapsule composite gel network with a core-shell structure, and form an ion barrier layer (pore size < 0.5 nm) in the high salt environment of fertilizer, so that the survival rate of live bacteria during transportation and storage is improved compared with traditional solid bacteria addition.

[0022] (2) The method for preparing compound microbial fertilizer containing seaweed extract provided by the present invention has the following advantages: the natural growth hormone and humic acid in the seaweed extract synergistically activate the metabolism of the strain, and the retention rate of key substances such as ACC deaminase is >96.5%, which is higher than that of conventional liquid bacterial addition.

[0023] (3) The compound microbial fertilizer containing seaweed extract provided by the present invention increased rice yield by 28.9% after 21 days of application in a saline-alkali environment, significantly improving the growth effect of crops in a high pH environment. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing a compound microbial fertilizer containing seaweed extract includes the following steps:

[0027] (1) 2×10 9 CFU / mL of Rhodopseudomonas palustris, 1×10 9 CFU / mL of Bacillus mucilaginosus and 1×10 9 A mixture of CFU / mL Bacillus subtilis was added, along with 7% v / v seaweed fermentation broth as a metabolic enhancer, to adjust the overall bacterial concentration to 1×10⁻⁶. 9 CFU / mL;

[0028] (2) Add 4% w / v of *Leptochloa crus-galli* extract (containing 38% fucoidan, 42% alginic acid, and 80 mg / kg IAA) and 0.8% w / v of tannic acid to the bacterial solution to form microcapsules with a particle size of 150 ± 20 μm. Spray a seaweed oligosaccharide-humic acid composite solution with a mass ratio of 2:1 onto the surface of the microcapsules.

[0029] (3) The microcapsules obtained in step (2) are sprayed onto the surface of fertilizer granules through an atomizer. The nozzle atomization pressure is 0.4 MPa, the spraying temperature is 50℃, the addition amount is 2‰, and the atomization amount is dynamically adjusted according to the temperature of the fertilizer granules. The atomization parameters are adjusted by real-time monitoring of the nozzle temperature. When ΔT=5℃, the flow rate changes by ±10%, and the atomization pressure decreases by 0.1 MPa to obtain compound fertilizer granules.

[0030] (4) The compound fertilizer obtained in step (3) is subjected to infrared radiation to cross-link the seaweed gel network. The infrared radiation temperature is 75°C and the time is 40 seconds to form a stable coating layer.

[0031] A compound microbial fertilizer containing seaweed extract was prepared using the above method.

[0032] Example 2

[0033] The only difference from Example 1 is that: in step (1), the metabolic enhancer is 5% v / v seaweed fermentation broth; in step (2), the concentration of the algae extract is 3% w / v and the concentration of tannic acid is 0.5% w / v; in step (3), the nozzle atomization pressure is 0.3 MPa and the spraying temperature is 45°C; in step (4), the infrared radiation temperature is 60°C and the time is 30 seconds.

[0034] The rest is the same as in Example 1.

[0035] Example 3

[0036] The only difference from Example 1 is that: in step (1), the metabolic enhancer is 10% v / v seaweed fermentation broth; in step (2), the concentration of the algae extract is 5% w / v and the concentration of tannic acid is 1% w / v; in step (3), the nozzle atomization pressure is 0.5 MPa and the spraying temperature is 60°C; in step (4), the infrared radiation temperature is 80°C and the time is 60 seconds.

[0037] The rest is the same as in Example 1.

[0038] Comparative Example 1

[0039] The only difference from Example 1 is that no seaweed extract is added in step (2). The rest is the same as in Example 1.

[0040] Comparative Example 2

[0041] The only difference from Example 1 is that the seaweed oligosaccharide-humic acid composite solution is not sprayed onto the surface of the microcapsules in step (2). The rest is the same as in Example 1.

[0042] Comparative Example 3

[0043] The only difference from Example 1 is that step (2) is omitted, and polyvinyl alcohol is directly sprayed onto the fertilizer surface for coating. The rest is the same as in Example 1.

[0044] Effect test

[0045] The microbial fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 were tested to promote the growth of rice in saline-alkali land (initial pH 8.6). The results are shown in Table 1.

[0046] Table 1

[0047]

[0048] As shown in Table 1, after 21 days in a saline-alkali soil environment with an initial pH of 8.6, Examples 1-3 showed a higher survival rate of live bacteria, a higher concentration of residual live bacteria, a longer slow-release period of fertilizer, and a better effect on improving soil pH, thereby increasing the yield of rice in a saline-alkali soil environment. Among the three examples, Example 1 had the strongest effect on promoting the growth of rice under saline-alkali soil conditions.

[0049] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications and substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for preparing a complex microbial fertilizer containing seaweed extract, characterized by, The method comprises the following steps: (1) mixed nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, and biocontrol bacteria, and then added a metabolic synergist to adjust the overall concentration of the bacterial solution to 1 x 10 9 CFU / mL, wherein the nitrogen-fixing bacteria are Rhodopseudomonas palustris, the phosphorus-solubilizing bacteria are Bacillus mucilaginosus, the biocontrol bacteria are Bacillus subtilis, and the metabolic synergist is 5-10% v / v seaweed fermentation broth; (2) adding seaweed extract and tannic acid to the bacterial solution to form microcapsules, and spraying a seaweed oligosaccharide-humic acid complex solution on the surface of the microcapsules, wherein the seaweed extract comprises fucoidan, alginate and natural auxin IAA; (3) spraying the microcapsules prepared in step (2) on the surface of the fertilizer particles through an atomizer, and dynamically adjusting the atomization amount according to the temperature of the fertilizer particles to obtain composite fertilizer particles; (4) crosslinking the seaweed gel network of the composite fertilizer particles prepared in step (3) through infrared radiation to form a stable coating layer, and forming a gradient coating structure on the surface of the fertilizer particles, wherein the inner gel layer is a bacterial-fucoidan complex with a thickness of 20-30 μm, the middle crosslinked layer is tannic acid with a thickness of 5-10 μm, and the outer slow-release layer is a humic acid-seaweed oligosaccharide complex with a thickness of 10-20 μm, thereby obtaining the composite microbial fertilizer.

2. The method of claim 1, wherein: The mixing ratio of the nitrogen-fixing bacteria, phosphorus-dissolving bacteria and biocontrol bacteria in step (1) is 2:1:1 in terms of viable bacterial count.

3. The method of claim 1, wherein: In step (2), the concentration of the seaweed extract is 3-5% w / v, the concentration of the tannic acid is 0.5-1% w / v, and the mass ratio of seaweed oligosaccharide to humic acid in the seaweed oligosaccharide-humic acid complex solution is 2:

1.

4. The method of claim 3, wherein: In the seaweed extract of step (2), the content of fucoidan is ≥30 wt%, the content of alginate is ≥40 wt%, and the content of IAA is ≥50 mg / kg.

5. The method of claim 1, wherein: In step (3), the atomization pressure of the nozzle is 0.3-0.5 MPa, and the spraying temperature is 45-60℃.

6. The method of claim 1, wherein: In step (3), the dynamic adjustment is as follows: by monitoring the temperature of the nozzle in real time to control the atomization parameters, when ΔT=5℃, the flow rate changes by ±10%, and the atomization pressure decreases by 0.1 MPa.

7. The method of claim 1, wherein: In step (4), the infrared radiation temperature is 60-80℃, and the time is 30-60 seconds.

8. The compound microbial fertilizer containing seaweed extract prepared by the method according to any one of claims 1-7, characterized in that: Each gram of fertilizer contains ≥5×10 7 CFU of live bacteria; retention rate of active ingredients of seaweed ≥90% based on fucoidan.

9. Application of the seaweed extract-containing composite microbial fertilizer of claim 8 in the improvement of salinized soil.

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