Compound microbial agent enhanced organic liquid fertilizer and preparation method thereof

Abstract

The invention belongs to the field of agricultural biotechnology and organic fertilizers, and discloses a compound microbial agent enhanced organic liquid fertilizer and a preparation method thereof.The organic liquid fertilizer is composed of a compound functional microbial agent, a difunctional liquid carrier system and an intelligent activation factor, wherein the composite functional microbial agent comprises nitrogen-fixing bacteria, phosphate solubilizing bacteria and bacillus, and nutrient conversion and rhizosphere micro-ecology construction are promoted through a synergistic metabolism relationship; the difunctional liquid carrier system provides nutrition for crops and forms a liquid phase environment suitable for long-term stable survival of microorganisms; the intelligent activation factor is used for triggering microorganisms to be converted from a low-metabolism silent state to an activated state under the induction of crop rhizosphere secretions and environmental signals, so that stable storage before application and accurate activation release after application are realized. The survival rate and the utilization efficiency of thalli in the liquid microbial fertilizer are effectively improved, the application effect of the fertilizer is improved, and the liquid microbial fertilizer has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of agricultural biotechnology and organic fertilizer, specifically relating to an organic liquid fertilizer enhanced by compound microbial agents and its preparation method. Background Technology

[0002] As modern agriculture develops towards green, efficient, and sustainable practices, microbial fertilizers and organic liquid fertilizers, as environmentally friendly fertilizers, have gradually become important means to improve soil quality and promote healthy crop growth. Microbial fertilizers, through the colonization of active bacterial strains in the rhizosphere and the secretion of their metabolic products, regulate the soil's microecological structure and promote nutrient transformation and absorption. Organic liquid fertilizers, on the other hand, possess advantages such as good solubility, high nutrient utilization efficiency, and convenient application, showing broad application prospects in facility agriculture, saline-alkali land improvement, and the restoration of continuous cropping obstacles.

[0003] However, existing microbial fertilizers and organic liquid fertilizers are mostly single-system products with certain technical limitations. On the one hand, traditional liquid microbial agents often suffer from a significant decrease in microbial activity during storage or transportation due to unstable nutrient environments, fluctuations in osmotic pressure, or improper storage conditions, affecting application efficacy. On the other hand, while some microbial agents possess specific functions, they lack synergistic compatibility with organic nutrient systems, failing to achieve stable coexistence and targeted release in liquid environments. This is especially problematic in complex environments such as saline-alkali land and continuously cropped soils, where microbial colonization is poor and growth-promoting effects are not significant. Furthermore, the control of microbial agent activation mechanisms in existing technologies is relatively crude, making it difficult to achieve targeted release in the crop rhizosphere after application. This can easily lead to waste of microbial resources or delayed effects, reducing the precision of fertilizer response. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide an organic liquid fertilizer enhanced by a composite microbial agent and its preparation method. The fertilizer uses nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus to construct a synergistic microbial community, and combines hydrolyzed protein liquid, molasses hydrolysate and polysaccharide protectant to form a dual-functional carrier system. Furthermore, it introduces intelligent activating factors to achieve stable survival of the bacteria in the liquid and precise activation and efficient growth promotion in the rhizosphere environment.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An organic liquid fertilizer enhanced with compound microbial agents comprises the following raw materials in parts by weight: 5-15 parts compound microbial agents, 20-40 parts organic nitrogen source, 10-25 parts organic carbon source, 1-5 parts polysaccharide protectant, and 0.5-5 parts intelligent activating factor;

[0007] The compound microbial agent is composed of nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus, the organic nitrogen source is hydrolyzed protein solution, the organic carbon source is molasses hydrolysate, the polysaccharide protectant is one or more of chitosan oligosaccharide, sodium alginate and xanthan gum, and the intelligent activating factor is one or more of seaweed oligosaccharide, potassium humate and plant hormone active components.

[0008] More preferably, the nitrogen-fixing bacteria are *Pseudomonas azotocinus* or *Rhizobium*, the phosphate-solubilizing bacteria are *Bacillus megaterium* or *Pseudomonas*, and the *Bacillus* are *Bacillus subtilis* or *Bacillus amyloliquefaciens*.

[0009] More preferably, in the compound microbial agent, the ratio of viable counts of nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus is 2-4:1-2:1-2.

[0010] More preferably, the molasses hydrolysate is obtained by the following method: diluting sugarcane molasses with water to a solid content of 40-60%, adding a food-grade acid enzyme mixture at 40-50°C for enzymatic hydrolysis for 2-4 hours to obtain an oligosaccharide solution that can be utilized by microorganisms.

[0011] More preferably, the hydrolyzed protein solution is prepared by the following method: using plant-derived protein as raw material, adding neutral protease, and enzymatically hydrolyzing for 4 to 6 hours under controlled temperature conditions to obtain a protein hydrolysate enriched with short peptides.

[0012] More preferably, the plant-derived protein is selected from one or more of soybean protein, corn protein, and potato protein.

[0013] A method for preparing an organic liquid fertilizer enhanced with a compound microbial agent includes the following steps:

[0014] S1. Prepare a compound microbial agent by culturing nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus to the logarithmic growth phase and then mixing them in proportion;

[0015] S2. Weigh out the organic nitrogen source, organic carbon source and polysaccharide protective agent, mix them evenly under stirring, and adjust the pH to 5.5-6.5;

[0016] S3. Add the intelligent activating factor to the carrier system and stir until homogeneous;

[0017] S4. Add the above compound microbial agent to the premixed liquid system at a temperature below 20°C, stir slowly for 10-30 minutes, and perform homogenization and emulsification treatment to obtain the organic liquid fertilizer.

[0018] More preferably, in step S3, after the smart activator is added to the carrier system, it is slowly stirred at 30-40°C for 10-20 minutes.

[0019] More preferably, the pH value of the liquid fertilizer is 5.5 to 6.5, and the osmotic pressure is controlled at 80 to 150 mmol / kg.

[0020] More preferably, the liquid fertilizer is suitable for improving the rhizosphere microecology of crops and enhancing nutrient absorption efficiency in saline-alkali land, continuously cropped soil, and facility agriculture environments.

[0021] The beneficial effects of this invention are:

[0022] This invention significantly improves the overall performance of organic liquid fertilizers in terms of storage stability, application precision, and growth-promoting effectiveness by constructing a three-dimensional synergistic system of "composite microbial community + dual-functional liquid carrier + intelligent activator." First, the nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, and Bacillus used in this invention are compounded in a specific ratio to form a metabolically complementary microecological structure. In the rhizosphere environment, this structure can achieve multiple functions, including nitrogen fixation, phosphorus release, and root growth promotion, effectively improving the crop's nutrient absorption efficiency. Second, by introducing an organic nitrogen and carbon source system mainly composed of hydrolyzed protein solution and molasses hydrolysate, continuous nutritional support is provided for the microorganisms. Combined with the liquid network structure constructed from chitosan oligosaccharide, sodium alginate, and xanthan gum, the physical adaptability of the microbial community to adverse conditions such as shear force, osmotic pressure changes, and high temperatures is enhanced, enabling the microbial community to survive stably in the liquid environment for a long period. Furthermore, unlike traditional microbial fertilizers that rely solely on natural activation after direct application, this invention introduces intelligent activating factors into a liquid fertilizer system for the first time. Utilizing the responsiveness of seaweed oligosaccharides, potassium humate, and plant hormone-like active components to crop rhizosphere exudates, pH changes, or redox environments, it achieves "silent-activated" state regulation of the microorganisms. This allows them to be in a low-metabolic storage state before application, precisely activated upon entering the soil, rapidly colonizing, and exerting their biological functions. This mechanism significantly improves the utilization rate and targeting of the microbial agent, reducing resource waste. Attached Figure Description

[0023] The invention will now be further described with reference to the accompanying drawings.

[0024] Figure 1 The graphs show the viable bacteria retention rates of organic liquid fertilizer samples from Examples 1-3 and Comparative Examples 1-2 stored at 4°C.

[0025] Figure 2 The graph shows a comparison of the cell growth fold and indoleacetic acid production concentration of the samples from Examples 1-3 and Comparative Examples 1-2 after 48 hours of culture. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] An organic liquid fertilizer enhanced with compound microbial agents comprises the following raw materials in parts by weight: 5 parts compound microbial agents, 20 parts organic nitrogen source, 10 parts organic carbon source, 1 part polysaccharide protectant, and 0.5 parts intelligent activator.

[0029] The preparation steps of the organic liquid fertilizer are as follows:

[0030] S1. *Pseudomonas aeruginosa*, *Bacillus megaterium*, and *Bacillus subtilis* were selected as functional strains and inoculated into sterile liquid LB medium. The cultures were incubated at 37°C in a shaker for 12 hours to allow the bacteria to reach the logarithmic growth phase. The bacterial concentration of each culture was measured and adjusted to 1 × 10⁻⁶. 8 After CFU / mL, mix according to the live bacteria ratio of 3:1:1 to prepare a compound microbial agent, and store it temporarily at 4℃ for later use.

[0031] S2. Pour 200 g of hydrolyzed protein solution and 100 g of molasses hydrolysate into a stainless steel stirred reactor and stir for 30 minutes at room temperature (25±2℃). Then add 10 g of chitosan oligosaccharide powder, continue stirring until fully dissolved, and adjust the pH of the mixture to 5.8 with 1 mol / L citrate buffer to form a homogeneous nutrient carrier solution.

[0032] S3. Take 5 g of seaweed oligosaccharide stock solution and slowly add it dropwise to the above-mentioned pH-adjusted nutrient carrier system. At the same time, place the reactor in a 35°C water bath and maintain constant temperature stirring for 15 minutes. After stirring, let the system cool naturally to 25°C to serve as the premixed solution system for subsequent addition of bacterial agents.

[0033] S4. After cooling the premixed liquid system to below 20°C, slowly add 50 g of the composite microbial agent prepared in step S1, and maintain low-speed stirring for 10 minutes to avoid damaging the bacterial cells. Then, homogenize using a high-shear homogenizing emulsifier at 6000 rpm for 8 minutes, resulting in a pH of 5.8 and an initial viable cell count of approximately 1 × 10⁻⁶. 8 The light brown homogeneous liquid with CFU / mL is the organic liquid fertilizer.

[0034] Example 2

[0035] An organic liquid fertilizer enhanced with compound microbial agents comprises the following raw materials in parts by weight: 15 parts compound microbial agents, 40 parts organic nitrogen source, 25 parts organic carbon source, 5 parts polysaccharide protectant, and 5 parts intelligent activator.

[0036] The preparation steps of the organic liquid fertilizer are as follows:

[0037] S1. *Pseudomonas aeruginosa*, *Bacillus megaterium*, and *Bacillus subtilis* were inoculated into liquid LB medium and cultured at 37°C on a shaker (180 rpm) for 12 hours until the logarithmic growth phase. The viable cell concentration was then determined and adjusted to 1 × 10⁻⁶. 9 After obtaining CFU / mL, mix the bacterial solutions in a 3:1:1 ratio and store at 4°C for later use.

[0038] S2. Mix 400 g of hydrolyzed protein solution and 250 g of molasses hydrolysate at 400 rpm for 20 minutes at room temperature until fully combined. Then add 25 g of chitosan oligosaccharide and 25 g of xanthan gum powder sequentially, and continue stirring for 30 minutes until completely dissolved. Adjust the pH of the system to 6.5 using 1 mol / L citrate-sodium citrate buffer to form a homogeneous and transparent nutrient liquid carrier system.

[0039] S3. Add 25 g of seaweed oligosaccharide liquid stock solution and 25 g of potassium humate solution to the nutrient carrier system after pH adjustment, maintain constant temperature in a 35℃ water bath, and continue stirring for 15 minutes at a stirring speed of 300 rpm to obtain the activated premixed system.

[0040] S4. After cooling the premixed system to no higher than 20°C, slowly pour in 150 g of compound microbial agent, maintaining a stirring speed of 200 rpm for initial mixing for 10 minutes. Then, use a high-shear homogenizer emulsifier with a shear speed of 8000 rpm and an emulsification time of 8 minutes. The resulting liquid fertilizer is a dark brown homogeneous liquid with a pH of 6.5 and an initial viable bacteria concentration of approximately 1 × 10⁻⁶. 9 CFU / mL.

[0041] Example 3

[0042] An organic liquid fertilizer enhanced with compound microbial agents comprises the following raw materials in parts by weight: 10 parts compound microbial agents, 30 parts organic nitrogen source, 17.5 parts organic carbon source, 3 parts polysaccharide protectant, and 2.75 parts intelligent activator.

[0043] The preparation steps of the organic liquid fertilizer are as follows:

[0044] S1. Take *Pseudomonas aeruginosa*, *Bacillus megaterium*, and *Bacillus subtilis*, and inoculate them separately into sterile liquid LB medium. Incubate at 37°C on a shaker (180 rpm) for 12 hours until the logarithmic growth phase. Centrifuge to collect the bacterial cells and resuspend them in sterile physiological saline. Adjust the viable cell concentration to 5 × 10⁻⁶. 8 CFU / mL. The three bacterial solutions were mixed at a live bacteria ratio of 3:1:1 to prepare 100 g of compound bacterial agent, which was then stored at 4℃ for later use.

[0045] S2. Mix 300 g of hydrolyzed protein solution with 175 g of molasses hydrolysate and stir at 350 rpm for 20 minutes at room temperature until homogeneous. Add 15 g of chitosan oligosaccharide and 15 g of sodium alginate powder sequentially, and continue stirring for 30 minutes. Then adjust the pH of the system to 6.0 ± 0.1 with 1 mol / L sodium citrate buffer to serve as the nutrient carrier base solution.

[0046] S3. Add 13.75 g of seaweed oligosaccharide liquid stock solution and 13.75 g of plant hormone active component compound solution (indoleacetic acid and sodium salicylate, both at a concentration of 0.5%) to the above base solution. Heat the system to 35°C and maintain a constant temperature. Set the stirring speed to 300 rpm and stir continuously for 15 minutes to form an activated premix solution.

[0047] S4. After cooling the activated premix to no higher than 20°C, slowly pour in 100 g of the compound microbial agent prepared in step S1, and stir at low speed for 10 minutes for initial dispersion. Then use a high-shear homogenizer, set to 7000 rpm, for emulsification and shearing for 8 minutes to obtain the organic liquid fertilizer.

[0048] Comparative Example 1

[0049] An organic liquid fertilizer enhanced with compound microbial agents comprises the following raw materials in parts by weight: 10 parts compound microbial agents, 30 parts organic nitrogen source, 17.5 parts organic carbon source, and 3 parts polysaccharide protectant;

[0050] The preparation steps of the organic liquid fertilizer are as follows:

[0051] S1. Using the same bacterial strains as in Example 3 (Dazomimonas, Bacillus megaterium, and Bacillus subtilis), the cultures were incubated in liquid LB medium at 37°C and 180 rpm for 12 hours with shaking until the logarithmic growth phase. The bacterial suspensions were centrifuged and resuspended in sterile physiological saline, and the viable cell concentration was adjusted to 5 × 10⁻⁶. 8 After obtaining CFU / mL, mix them at a ratio of 3:1:1 to prepare 100 g of compound bacterial agent, which is stored at 4℃ for later use.

[0052] S2. Take 300 g of hydrolyzed protein solution and 175 g of molasses hydrolysate, and stir at 350 rpm for 20 minutes at room temperature until homogeneous. Then add 15 g of chitosan oligosaccharide and 15 g of sodium alginate, and continue stirring for 30 minutes until completely dissolved. Adjust the pH to 6.0 ± 0.1 using 1 mol / L sodium citrate buffer to form a homogeneous nutrient liquid carrier system.

[0053] S3. Cool the aforementioned carrier system to no higher than 20°C, slowly pour in 100 g of the compound microbial agent, and stir at low speed for 10 minutes to initially disperse the microorganisms. Then, use a high-shear homogenizing emulsifier to process at 7000 rpm for 8 minutes to obtain the organic liquid fertilizer.

[0054] Comparative Example 2

[0055] An organic liquid fertilizer enhanced with compound microbial agents comprises the following raw materials in parts by weight: 10 parts compound microbial agents, 30 parts organic nitrogen source, 17.5 parts organic carbon source, and 2.75 parts intelligent activating factor;

[0056] The preparation steps of the organic liquid fertilizer are as follows:

[0057] S1. Using the same bacterial strains as in Example 3 (Dinofixing Pseudomonas, Bacillus megaterium, Bacillus subtilis), cultured in liquid LB medium at 37°C and 180 rpm for 12 hours until the logarithmic growth phase, and then adjusting the bacterial concentration to 5 × 10⁻⁶. 8 CFU / mL. Mix bacterial solutions at a live bacteria ratio of 3:1:1, with a total volume of 100 g, and store at 4°C for later use.

[0058] S2. Mix 300 g of hydrolyzed protein solution with 175 g of molasses hydrolysate, stir at 350 rpm for 20 minutes at room temperature until fully mixed, and then adjust the pH of the system to 6.0±0.1 using 1 mol / L sodium citrate buffer to form the basic nutrient liquid carrier system.

[0059] S3. Slowly add 13.75 g of seaweed oligosaccharide stock solution and 13.75 g of plant hormone solution to the above carrier, maintain constant temperature in a 35°C water bath, set the stirring speed to 300 rpm, and stir continuously for 15 minutes to form a premix.

[0060] S4. Cool the activated premixed liquid to below 20°C, slowly add 100 g of compound microbial agent, stir at low speed for 10 minutes, and then perform high-shear emulsification treatment. Process using a high-speed homogenizing emulsifier at 7000 rpm for 8 minutes to obtain the organic liquid fertilizer.

[0061] Performance testing

[0062] 1. Viability retention rate test

[0063] The viable bacterial content in the samples was determined using the standard plate dilution method. Organic liquid fertilizer samples prepared in Examples 1-3 and Comparative Examples 1-2 were taken, and the initial viable bacterial count was measured immediately after preparation as the data for day 0. Subsequently, each sample was sealed and stored at 4°C in the dark, and samples were taken at 15, 30, and 45 days of storage. After each sampling, serial dilutions were performed using sterile physiological saline, and the appropriate dilution was evenly spread on the surface of nutrient agar medium. The samples were incubated at 37°C for 48 hours, and the number of colonies formed was counted. The viable bacterial concentration (CFU / mL) of the sample was calculated. The viable bacterial retention rate was calculated as the ratio of the viable bacterial count measured at each time point to the initial viable bacterial count. The results are shown in Table 1 below.

[0064] Table 1. Retention rate of different samples during storage

[0065] sample Initial viable count (CFU / mL) 15-day retention rate (%) 30-day retention rate (%) 45-day retention rate (%) Example 1 <![CDATA[1.0×10 8 ]]> 93 88 82 Example 2 <![CDATA[1.0×10 9 ]]> 96 91 87 Example 3 <![CDATA[5.0×10 8 ]]> 94 88 82 Comparative Example 1 <![CDATA[5.0×10 8 ]]> 82 72 62 Comparative Example 2 <![CDATA[5.0×10 8 ]]> 78 60 48

[0066] As shown in Table 1, Examples 1-3 all maintained high viable bacterial stability within 45 days, with Example 2 exhibiting the highest retention rate at 87%, demonstrating the positive effect of high-dose formulations on bacterial survival. In contrast, Comparative Example 1, lacking the addition of a smart activator, resulted in metabolic imbalances in the bacteria during storage, leading to a significant decrease in activity and a retention rate of only 62%. Comparative Example 2, by removing the polysaccharide protectant, exacerbated bacterial sedimentation and death, resulting in a retention rate of only 48% after 45 days. This invention, through the introduction of polysaccharide encapsulation and a smart activation mechanism, effectively delays bacterial death while enhancing the bacteria's resistance to osmotic pressure and cryogenic protection.

[0067] 2. Storage stability test

[0068] Samples from Examples 1-3 and Comparative Examples 1-2 were placed in transparent sample vials, sealed, and stored at a constant temperature of 25°C for 45 days. During this period, the samples were observed every 7 days for any obvious precipitation or stratification, and the time when stratification first became visible to the naked eye was recorded. pH values ​​were measured on day 0 and day 45, and the maximum change ΔpH was calculated. Simultaneously, the sedimentation rate on day 45, i.e., the percentage of the precipitate volume to the total liquid volume, was determined using the static graduated cylinder method. The test results are shown in Table 2.

[0069] Table 2 Physical stability of different samples under room temperature storage conditions

[0070] sample 45-day settlement rate (%) Time to initial stratification (days) pH change range (ΔpH) Example 1 4 ＞45 0.2 Example 2 2 ＞45 0.1 Example 3 3 ＞45 0.2 Comparative Example 1 8 21 0.4 Comparative Example 2 12 14 0.6

[0071] As shown in Table 2, Examples 1-3 did not exhibit significant stratification during 45 days of storage at room temperature, with sedimentation rates below 4% and pH changes controlled within 0.2, indicating a stable liquid fertilizer structure. Example 2 showed the lowest sedimentation rate and the most stable pH, demonstrating the best performance. In contrast, Comparative Example 1, lacking the synergistic regulation of intelligent activating factors, exhibited a looser structure, with stratification occurring earlier and a sedimentation rate reaching 8%. Comparative Example 2, lacking the addition of polysaccharide protectants, lacked spatial encapsulation and complexation fixation of the microbial cells and dissolved components, resulting in significant physical instability. Within 45 days, the sedimentation rate reached 12%, stratification occurred as early as day 14, and pH fluctuations were significant.

[0072] 3. Intelligent activation response performance test

[0073] Samples from Examples 1-3 and Comparative Examples 1-2 were inoculated into simulated rhizosphere culture medium containing 2 mM citrate buffer (pH 5.0) and incubated statically at 37°C for 24 h and 48 h, respectively. After sampling, the cell concentration (CFU / mL) was determined using the dilution plating method, and the fold increase compared to the initial cell count was calculated. Simultaneously, the concentration of indoleacetic acid (IAA) in the culture medium was determined using the Salkowski colorimetric method as one of the biomarkers for microbial metabolic initiation. The test results are shown in Table 3 below.

[0074] Table 3. Activation response performance of different samples under simulated rhizosphere environment

[0075] sample 24-hour bacterial cell growth rate 48-hour bacterial cell growth rate 48-hour IAA concentration (mg / L) Example 1 1.8 3.5 18.2 Example 2 2.2 4.1 21.5 Example 3 2.0 3.8 19.6 Comparative Example 1 1.2 1.5 9.4 Comparative Example 2 1.4 2.0 11.3

[0076] Table 3 shows that Examples 1-3 all exhibited significant cell activation and metabolic initiation capabilities under simulated rhizosphere conditions. Example 2 showed the highest proliferation rate and IAA concentration, demonstrating the high responsiveness of the intelligent activator under low pH and organic acid induction conditions. In contrast, Comparative Example 1, lacking the activator, experienced limited cell growth, with only a 1.5-fold increase and IAA synthesis levels below 10 mg / L. Comparative Example 2, lacking a protective system, showed a slightly better cell response than Comparative Example 1, but still significantly lower than the Example groups. These results fully validate that the seaweed oligosaccharides, fulvic acid, or plant hormone-like factors introduced in this invention can induce the bacterial community to transition from a quiescent state to a highly metabolically active state in the rhizosphere environment, achieving rapid activation and promoting growth after application.

[0077] 4. Growth-promoting effect test

[0078] To evaluate the actual promoting effect of the liquid fertilizer of this invention on plant growth, wheat seedlings were selected as the model crop. A seedling tray sand culture system was configured, with five groups set up: Examples 1-3 and Comparative Examples 1-2, each with 6 pots and 10 wheat seeds sown in each pot. The corresponding liquid fertilizer (diluted 100 times) was applied starting on the 3rd day after emergence, once every 3 days, for 14 consecutive days. Routine watering was provided during this period, and greenhouse conditions were maintained at 25±2℃ with 12 h of light per day. After the experiment, the seedling height, root length, aboveground fresh weight, chlorophyll content (SPAD value), and root activity (TTC reduction method) of each wheat group were measured. The results are shown in Table 4.

[0079] Table 4. Growth-promoting effects of different sample treatments on wheat seedlings

[0080] sample Seedling height (cm) Root length (cm) Fresh weight (g) SPAD value <![CDATA[Root activity (OD 490 )]]> Example 1 18.2 15.4 1.96 38.2 0.62 Example 2 19.6 16.7 2.21 40.5 0.71 Example 3 19.0 16.1 2.08 39.4 0.67 Comparative Example 1 15.8 13.3 1.52 33.6 0.48 Comparative Example 2 16.4 13.9 1.60 34.8 0.51

[0081] Table 4 shows that the wheat seedlings treated in Examples 1-3 were significantly superior to those in Comparative Examples 1 and 2 in terms of seedling height, root length, fresh weight, chlorophyll content, and root activity, indicating that the liquid fertilizer of this invention has a significant promoting effect on early crop growth. Example 2 showed the best overall performance, with seedling height and root length reaching the highest levels, and fresh weight and SPAD values ​​significantly increased, indicating that the plant's photosynthetic capacity and biomass accumulation were simultaneously enhanced. Combined with the root activity results, it can be seen that this invention effectively improves root metabolic activity and nutrient absorption capacity through the synergistic effect of the composite microbial community and the bifunctional liquid carrier system. Simultaneously, the intelligent activating factor is triggered in the rhizosphere environment, promoting rapid colonization of functional bacteria and the release of growth-promoting metabolites, thereby significantly improving the rhizosphere microecology. Comparative Example 1 lacked an activation and regulatory mechanism, resulting in limited growth-promoting effects; Comparative Example 2 also showed significantly weakened effects due to insufficient bacterial stability.

[0082] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0083] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. An organic liquid fertilizer enhanced with a compound microbial agent, characterized in that, It contains the following raw materials in parts by weight: 5-15 parts of compound microbial agent, 20-40 parts of organic nitrogen source, 10-25 parts of organic carbon source, 1-5 parts of polysaccharide protectant, and 0.5-5 parts of intelligent activator. The compound microbial agent is composed of nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus, the organic nitrogen source is hydrolyzed protein solution, the organic carbon source is molasses hydrolysate, the polysaccharide protectant is one or more of chitosan oligosaccharide, sodium alginate and xanthan gum, and the intelligent activating factor is one or more of seaweed oligosaccharide, potassium humate and plant hormone active components.

2. The organic liquid fertilizer according to claim 1, characterized in that, The nitrogen-fixing bacteria are *Pseudomonas azotocinus* or *Rhizobium*, the phosphate-solubilizing bacteria are *Bacillus megaterium* or *Pseudomonas*, and the *Bacillus* are *Bacillus subtilis* or *Bacillus amyloliquefaciens*.

3. The organic liquid fertilizer according to claim 1, characterized in that, In the compound microbial agent, the ratio of viable counts of nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus is 2-4:1-2:1-2.

4. The organic liquid fertilizer according to claim 1, characterized in that, The molasses hydrolysate is obtained by diluting sugarcane molasses with water to a solid content of 40-60%, adding a food-grade acid enzyme mixture at 40-50°C for enzymatic hydrolysis for 2-4 hours to obtain an oligosaccharide solution that can be utilized by microorganisms.

5. The organic liquid fertilizer according to claim 1, characterized in that, The hydrolyzed protein solution is prepared by the following method: using plant-derived protein as raw material, adding neutral protease, and enzymatically hydrolyzing for 4 to 6 hours under controlled temperature conditions to obtain a protein hydrolysate enriched with short peptides.

6. The organic liquid fertilizer according to claim 5, characterized in that, The plant-derived protein is selected from one or more of soybean protein, corn protein, and potato protein.

7. A method for preparing an organic liquid fertilizer enhanced with a compound microbial agent, characterized in that, Includes the following steps: S1. Prepare a compound microbial agent by culturing nitrogen-fixing bacteria, phosphate-solubilizing bacteria and Bacillus to the logarithmic growth phase and then mixing them in proportion; S2. Weigh out the organic nitrogen source, organic carbon source and polysaccharide protective agent, mix them evenly under stirring, and adjust the pH to 5.5-6.5; S3. Add the intelligent activating factor to the carrier system and stir until homogeneous; S4. Add the above compound microbial agent to the premixed liquid system at a temperature below 20°C, stir slowly for 10-30 minutes, and perform homogenization and emulsification treatment to obtain the organic liquid fertilizer.

8. The preparation method according to claim 7, characterized in that, In step S3, after the intelligent activating factor is added to the carrier system, it is slowly stirred at 30-40°C for 10-20 minutes.

9. The organic liquid fertilizer according to claim 1, characterized in that, The liquid fertilizer has a pH value of 5.5 to 6.5 and an osmotic pressure controlled at 80 to 150 mmol / kg.

10. The organic liquid fertilizer according to claim 1, characterized in that, The liquid fertilizer is suitable for improving the rhizosphere microecology of crops and enhancing nutrient absorption efficiency in saline-alkali land, continuously cropped soil, and facility agriculture environments.

Images