Compound microbial fertilizer containing seaweed extract as well as preparation method and application of compound microbial fertilizer

Abstract

The invention relates to a compound microbial fertilizer containing a seaweed extract as well as a preparation method and application of the compound microbial fertilizer, and aims to solve the problems that a traditional embedding material in a microbial fertilizer provided by the prior art is easy to disintegrate in a high-salt environment, a microbial inoculum is easy to inactivate, and the effect of the fertilizer in a high-pH environment is relatively small. Adding a seaweed extract and tannic acid into the bacterial liquid to form microcapsules, taking seaweed oligosaccharide and humic acid composite liquid as an outer slow-release layer, and spraying the bacterial liquid onto the surfaces of fertilizer particles through a nozzle, so that the fertilizer forms a gradient coating structure. According to the preparation method of the compound microbial fertilizer containing the seaweed extract, the fertilizer forms an ion barrier layer in a high-salt environment, natural auxin and humic acid in the seaweed extract synergistically activate strain metabolism, and after the prepared compound microbial fertilizer is applied, the growth effect of crops in a high-pH environment can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer processing, and in particular to a composite microbial fertilizer containing seaweed extract, and a preparation method and application thereof. Background Art

[0002] Microbial fertilizers are products containing specific active microorganisms. Through their biological activities, they enhance soil nutrient supply efficiency, improve soil structure, enhance crop resistance, and reduce reliance on chemical fertilizers. Currently, technological innovations in microbial fertilizers focus on slow-release carriers and microbial population optimization, such as nano-modified biochar carriers, synergistic enhancement of composite microbial agents, and the use of waste to prepare porous biochar with adsorption-functional bacteria.

[0003] The microbial fertilizers provided by existing technologies have certain technical bottlenecks. For example, traditional encapsulation materials such as chitosan are prone to disintegration in high-salt environments, resulting in the loss of live bacteria during transportation; the high-temperature drying step in the production of solid bacterial agents inactivates heat-sensitive substances such as IAA (natural growth hormone); fertilizers are less effective in high-pH environments such as saline-alkali land, etc.

[0004] Seaweed is rich in natural active substances and endogenous plant growth regulators, and is enriched with various trace elements, making it an ideal additive for enhancing fertilizer efficiency. Seaweed extracts offer advantages as fertilizer additives, including comprehensive nutrition, soil improvement, and enhanced crop resistance. They can also be used in microbial fertilizers, but their application has certain limitations. Existing technologies often directly mix seaweed extracts with bacterial strains, which can easily lead to the active ingredients in the seaweed extract decomposing at high temperatures during granulation, preventing them from forming a synergistic protective system with the bacterial strains.

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

[0006] To achieve the above object, the present invention adopts the following technical solutions: In one aspect, the present invention provides a method for preparing a composite microbial fertilizer containing seaweed extract, comprising the following steps: (1) Mix nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and biocontrol bacteria, then add metabolic enhancers and adjust the overall bacterial solution concentration to 1×10 9 CFU / mL; (2) adding seaweed extract and tannic acid to the bacterial solution to form microcapsules, and spraying seaweed oligosaccharide-humic acid composite solution on the surface of the microcapsules; (3) spraying the microcapsules obtained in step (2) onto the surface of the fertilizer particles through an atomizer, wherein the atomization amount is dynamically adjusted according to the temperature of the fertilizer particles, to obtain compound fertilizer particles; (4) subjecting the composite fertilizer particles obtained in step (3) to infrared radiation to crosslink the seaweed gel network to form a stable coating layer, thereby obtaining the composite microbial fertilizer.

[0007] Preferably, in step (1), the nitrogen-fixing bacteria is Rhodopseudomonas palustris, the phosphate-solubilizing bacteria is Bacillus subtilis, and the biocontrol bacteria is Bacillus subtilis.

[0008] 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 viable bacteria, and the metabolic enhancer is 5-10% v / v of the seaweed fermentation broth.

[0009] Preferably, in step (2), the concentration of the seaweed extract is 3-5% w / v, the concentration of tannic acid is 0.5-1% w / v, and the mass ratio of seaweed oligosaccharides to humic acid in the seaweed oligosaccharide-humic acid composite solution is 2:1.

[0010] More preferably, the seaweed extract in step (2) comprises fucoidan, alginic acid and natural auxin (IAA), wherein the fucoidan content is ≥30wt%, the alginic acid content is ≥40wt%, and the IAA content is ≥50mg / kg.

[0011] Preferably, in step (3), the nozzle atomization pressure is 0.3-0.5 MPa and the spraying temperature is 45-60°C.

[0012] Preferably, the dynamic adjustment in step (3) is: regulating the atomization parameters by real-time monitoring of the nozzle temperature, when ΔT=5°C, the flow rate changes by ±10%, and the atomization pressure decreases by 0.1 MPa.

[0013] Preferably, the infrared radiation temperature in step (4) is 60-80° C., and the time is 30-60 seconds.

[0014] On the other hand, the present invention provides a composite microbial fertilizer containing seaweed extract, which is prepared by the above method and contains ≥5×10 viable bacteria per gram of fertilizer. 7 CFU; the retention rate of seaweed active ingredients, calculated as fucoidan, is ≥90%. The surface of the fertilizer granules forms a gradient coating structure: the inner gel layer is a 20-30μm thick bacterial-seaweed polysaccharide complex, the middle cross-linked layer is a 5-10μm thick tannic acid layer, and the outer sustained-release layer is a 10-20μm thick humic acid-seaweed oligosaccharide complex.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for preparing a composite microbial fertilizer containing seaweed extract. The seaweed extract and tannic acid form a microcapsule composite gel network with a core-shell structure, which forms an ion barrier layer (pore size <0.5nm) in the high-salt environment of the fertilizer, thereby improving the survival rate of live bacteria during transportation and storage compared with traditional solid-added bacteria. (2) The present invention provides a method for preparing a composite microbial fertilizer containing seaweed extract. The natural auxin 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 greater than 96.5%, which is higher than that of conventional liquid-added bacteria. (3) The composite 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 DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] Example 1 A method for preparing a composite microbial fertilizer containing seaweed extract comprises the following steps: (1) 2×10 9 CFU / mL of Rhodopseudomonas palustris, 1×10 9 CFU / mL of Bacillus mucilaginosus and 1×10 9 CFU / mL of Bacillus subtilis was mixed, and 7% v / v of seaweed fermentation broth was added as a metabolic enhancer to adjust the overall concentration of the bacterial solution to 1×10 9 CFU / mL; (2) 4% w / v Ascophyllum nodosum extract (containing 38% fucoidan, 42% alginic acid, and 80 mg / kg IAA) and 0.8% w / v tannic acid were added to the bacterial solution to form microcapsules with a particle size of 150 ± 20 μm. The surface of the microcapsules was sprayed with a seaweed oligosaccharide-humic acid complex solution with a mass ratio of 2:1; (3) spraying the microcapsules obtained in step (2) onto the surface of the fertilizer particles through an atomizer, with a nozzle atomization pressure of 0.4 MPa, a spraying temperature of 50°C, an addition amount of 2‰, and a dynamic adjustment of the atomization amount with the temperature of the fertilizer particles. The atomization parameters are controlled by real-time monitoring of the nozzle temperature. When ΔT=5°C, the flow rate changes by ±10%, and the atomization pressure decreases by 0.1 MPa, thereby obtaining compound fertilizer particles; (4) The compound fertilizer prepared in step (3) is subjected to infrared radiation to crosslink the seaweed gel network at a temperature of 75° C. for 40 seconds to form a stable coating layer.

[0018] The composite microbial fertilizer containing seaweed extract is prepared by the method.

[0019] Example 2 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 Ascophyllum nodosum 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.

[0020] The rest is the same as Example 1.

[0021] Example 3 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 Ascophyllum nodosum 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.

[0022] The rest is the same as Example 1.

[0023] Comparative Example 1 The only difference from Example 1 is that no seaweed extract is added in step (2). The rest is the same as Example 1.

[0024] Comparative Example 2 The only difference from Example 1 is that in step (2), the seaweed oligosaccharide-humic acid composite liquid is not sprayed on the surface of the microcapsules. The rest is the same as Example 1.

[0025] Comparative Example 3 The only difference from Example 1 is that step (2) is omitted and polyvinyl alcohol is directly sprayed on the surface of the fertilizer for coating. The rest is the same as Example 1.

[0026] Effect test The growth-promoting effects of the microbial fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 on rice in saline-alkali soil (initial pH 8.6) were tested. The results are shown in Table 1.

[0027] Table 1

[0028] As shown in Table 1, after 21 days in a saline-alkali soil environment with an initial pH of 8.6, Examples 1-3 had higher viable bacteria survival rates, higher residual viable bacteria concentrations, and longer fertilizer slow-release periods than Comparative Examples 1-3, and had better improvement effects on soil pH, thereby increasing the yield increase rate of rice in a saline-alkali soil environment. Comparing the three examples with each other, Example 1 had the strongest growth-promoting effect on rice under saline-alkali soil conditions.

[0029] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications and substitutions shall be within the scope of the present invention. Any changes or substitutions that can be readily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A method for preparing a composite microbial fertilizer containing seaweed extract, characterized in that: The following steps are involved: (1) Mix nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and biocontrol bacteria, then add metabolic enhancers and adjust the overall bacterial solution concentration to 1×10 9 CFU / mL; (2) adding seaweed extract and tannic acid to the bacterial solution to form microcapsules, and spraying seaweed oligosaccharide-humic acid composite solution on the surface of the microcapsules; (3) spraying the microcapsules obtained in step (2) onto the surface of the fertilizer particles through an atomizer, wherein the atomization amount is dynamically adjusted according to the temperature of the fertilizer particles, to obtain compound fertilizer particles; (4) subjecting the composite fertilizer particles obtained in step (3) to infrared radiation to crosslink the seaweed gel network to form a stable coating layer, thereby obtaining the composite microbial fertilizer.

2. The preparation method according to claim 1, wherein: In step (1), the nitrogen-fixing bacteria is Rhodopseudomonas palustris, the phosphate-solubilizing bacteria is Bacillus colloids, and the biocontrol bacteria is Bacillus subtilis; the mixing ratio of the nitrogen-fixing bacteria, the phosphate-solubilizing bacteria, and the biocontrol bacteria is 2:1:1 based on the number of viable bacteria; and the metabolic enhancer is 5-10% v / v seaweed fermentation broth.

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

1.

4. The preparation method according to claim 3, wherein: The seaweed extract in step (2) comprises fucoidan, alginic acid and natural auxin (IAA), wherein the fucoidan content is ≥30wt%, the alginic acid content is ≥40wt%, and the IAA content is ≥50mg / kg.

5. The preparation method according to claim 1, wherein: The nozzle atomization pressure in step (3) is 0.3-0.5 MPa, and the spraying temperature is 45-60°C.

6. The preparation method according to claim 1, wherein: The dynamic adjustment in step (3) is as follows: the atomization parameters are controlled by real-time monitoring of the nozzle temperature. When ΔT=5°C, the flow rate changes by ±10% and the atomization pressure decreases by 0.1 MPa.

7. The preparation method according to claim 1, wherein: The infrared radiation temperature in step (4) is 60-80° C. and the time is 30-60 seconds.

8. A composite microbial fertilizer containing seaweed extract prepared by the method according to any one of claims 1 to 7, characterized in that: The number of viable bacteria per gram of fertilizer is ≥5×10 7 CFU; the retention rate of seaweed active ingredients calculated as fucoidan is ≥90%.

9. The composite microbial fertilizer containing seaweed extract according to claim 8, characterized in that: A gradient coating structure is formed on the surface of the fertilizer particles. The inner gel layer is a bacteria-seaweed polysaccharide complex with a thickness of 20-30 μm, the middle cross-linking layer is a tannic acid with a thickness of 5-10 μm, and the outer sustained-release layer is a humic acid-seaweed oligosaccharide complex with a thickness of 10-20 μm.

10. Use of the compound microbial fertilizer containing seaweed extract according to claim 8 or 9 in improving salinized soil.

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