Nanobiomass charcoal promotes nitrogen and nitrogen composite microbial agent and application thereof

Abstract

The present application relates to a kind of nanometer biochar promotes nitrogen-preserving composite microbial inoculant and its application, belong to compost technical field, the composite microbial inoculant is prepared by following innovative process: (1) the specific particle size (50-100nm) of phosphoric acid modified biochar is coupled with the pore structure of the straw-corn cob carrier (3:1 mass ratio) that is crushed to 2-3mm;(2) first with nitrogen-preserving microbial inoculant (containing nitrogen-fixing enzyme activity methylotrophic spore bacillus, round brown nitrogen-fixing bacteria and spore bacillus) adsorbed in the micropore of porous composite carrier;Again with rot microbial inoculant (Rhizopus, actinomycete and bacillus licheniformis) wrapped in nanometer biochar-carrier complex surface, form double-layer biological activity structure.The interface effect of nanometer biochar of the present application makes microbial inoculant survival period extend to 2 times of conventional preparation, chicken manure composting rotting cycle is shortened by 3-5 days and nitrogen loss rate is reduced to 35%, especially suitable for low carbon-nitrogen ratio agricultural waste rapid humification treatment.

Description

Technical Field

[0001] This invention belongs to the field of composting technology, specifically relating to a nano-biochar-based composite microbial agent for promoting decay and retaining nitrogen, and its application. Background Technology

[0002] Composting is an important technology for converting agricultural waste into organic fertilizer, its core being the acceleration of organic matter decomposition and stabilization through the action of microorganisms. However, traditional composting technologies face several challenges in practical applications, such as long composting times, significant nitrogen loss, and insufficient humification. These problems not only affect the quality of compost products but may also lead to resource waste and environmental burden.

[0003] To improve composting efficiency, functional microbial agents can be added to enhance microbial activity and optimize the material transformation process. Combustion-promoting agents accelerate the decomposition of organic matter, while nitrogen-retaining agents help reduce nitrogen volatilization. However, due to the complex and variable environmental conditions of composting (such as fluctuations in temperature, humidity, and pH), the activity and survival time of microbial agents are often significantly limited, making it difficult for them to maintain their function for an extended period. Furthermore, the structural properties of traditional microbial agent carriers are relatively simple, failing to meet the requirements for long-term microbial survival and stable adsorption, further limiting the application effectiveness of these agents.

[0004] In recent years, nanomaterials have gradually attracted attention due to their unique physicochemical properties. Among them, nano-biochar, with its high specific surface area, abundant pore structure, and excellent adsorption capacity, provides a more suitable living environment for microorganisms and has shown certain application potential in the field of composting. However, current research on the synergistic effect of nano-biochar and microbial agents is still insufficient, and its application in improving the functional stability of microbial agents and composting efficiency still needs further development.

[0005] In summary, existing technologies still have significant shortcomings in promoting decomposition and retaining nitrogen during the composting process. There is an urgent need for a composite microbial agent that can significantly improve the activity and stability of microbial agents, extend their lifespan, and optimize composting efficiency. This invention combines the material properties of nano-biochar with the functional advantages of microbial agents to propose a nano-biochar-based composite microbial agent for promoting decomposition and retaining nitrogen, along with its preparation method, to solve the aforementioned technical challenges. Summary of the Invention

[0006] The purpose of this invention is to provide a nano-biochar-based compound microbial agent for promoting decay and retaining nitrogen, and its application, in order to solve the above-mentioned problems.

[0007] The present invention achieves the above objectives through the following technical solutions:

[0008] This invention provides a nano-biochar-based composite microbial agent for promoting decay and retaining nitrogen, comprising the following steps:

[0009] (1) Phosphoric acid modified biochar of 50-100 nm and wheat straw-corn cob carrier pulverized to 2-3 mm are mixed at a mass ratio of 3:1 to form a porous composite carrier;

[0010] (2) The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, wherein the nitrogen-retaining bacterial agent comprises Bacillus methylotrophicus CICC 20839, Azotobacter chroococcum CICC 22661 and Paenibacillus polymyxa CICC 24260.

[0011] (3) The putrefactive agent is coated on the surface of the product (porous composite carrier) obtained in step (2), wherein the putrefactive agent comprises Rhizopus oryzae GDMCC 3.127, Thermoactinomyces vulgaris GDMCC 4.160 and Bacillus licheniformis CICC 21740.

[0012] As a further optimization of the present invention, the preparation method of the phosphoric acid modified biochar includes: impregnating biochar in a 0.5-1.0 mol / L phosphoric acid solution with a solid-liquid ratio of 1:5-1:10, activating it at 80-100℃ for 2-4 hours, and then washing and drying it.

[0013] As a further optimization of the present invention, the ratio of the number of live bacteria in the nitrogen-retaining bacteria agent to the putrefactive bacteria agent is 1:1.5 to 1:2.5.

[0014] As a further optimization of the present invention, the mass ratio of wheat straw to corn cob in the wheat straw-corn cob carrier is 3:1, and it is pretreated with a buffer solution with pH 6.5 to 7.5.

[0015] As a further optimization of the present invention, the nano-biochar in the composite microbial agent accounts for 5% to 15% of the total mass.

[0016] A method for preparing the aforementioned compound microbial agent includes the following steps:

[0017] (1) Phosphoric acid modified nano-biochar was mixed with pretreated wheat straw-corn cob carrier and ultrasonically vibrated for 20-40 min to couple the pores and form a porous composite carrier;

[0018] (2) Slowly add the nitrogen-retaining bacterial agent suspension to the product (porous composite carrier) of step (1) at 70% to 90% of the carrier adsorption saturation, and let it stand at 25 to 30°C for 2 to 4 hours for adsorption;

[0019] (3) Mix the suspension of the putrefactive bacteria with the product of step (2) (a porous composite carrier containing nitrogen-retaining bacteria) at a volume ratio of 1:5 to 1:10, and coat by rotating at 35 to 40 rpm for 30 to 60 minutes.

[0020] In step (2), the OD600 value of the nitrogen-retaining bacterial agent suspension is 1.2–1.8, and in step (3), the spore concentration of the putrefactive bacterial agent suspension is ≥1×10⁻⁶. 7 CFU / mL.

[0021] The above-mentioned nano-biochar-promoting and nitrogen-retaining compound microbial agent is applied in composting. The compound microbial agent is added at 0.5% to 2.0% of the total mass of the composting raw materials, the moisture content of the compost is controlled at 55% to 65%, and the initial C / N ratio is 20 to 25:1.

[0022] When the temperature reaches 50-60℃ during composting, the compound microbial agent is added at a rate of 0.1%-0.3% of the compost mass.

[0023] The beneficial effects of this invention are as follows: This invention uses phosphoric acid modified biochar mixed with wheat straw-corn cob carrier to form a porous composite carrier. Nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and then a composting-promoting bacterial agent is coated on its outer surface. This results in a composite bacterial agent that has a breakthrough effect in improving the activity and stability of the bacterial agent, extending its survival period, and optimizing composting efficiency. Furthermore, the obtained composite bacterial agent can achieve a high-efficiency temperature rise in a short time, shortening the preparation time of the composite bacterial agent and achieving high-efficiency and high-quality fermentation. Detailed Implementation

[0024] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0025] Example 1

[0026] The preparation method of phosphoric acid modified biochar includes: impregnating biochar in 0.5 mol / L phosphoric acid solution with a solid-liquid ratio of 1:5, activating at 80℃ for 2 h, and then washing and drying.

[0027] 50nm phosphoric acid modified biochar and wheat straw-corn cob carrier pulverized to 2mm were mixed at a mass ratio of 3:1 to form a porous composite carrier.

[0028] The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and the nitrogen-retaining bacterial agent contains methylotrophic Bacillus, Azotobacter chrysophytes, and Bacillus-like bacteria;

[0029] The putrefactive bacteria are coated onto the surface of a porous composite carrier loaded with nitrogen-retaining bacteria. The putrefactive bacteria include Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

[0030] The ratio of live bacteria count of nitrogen-retaining bacteria to putrefactive bacteria is 1:1.5;

[0031] The wheat straw to corn cob carrier has a mass ratio of wheat straw to corn cob of 3:1 and is pretreated with a buffer solution of pH 6.5.

[0032] Nano-biochar accounts for 5% of the total mass of the compound microbial agent;

[0033] Preparation method of compound microbial agent: (1) Phosphoric acid modified nano-biochar is mixed with pretreated wheat straw-corn cob carrier and ultrasonically vibrated for 20 min to achieve pore coupling; (2) Nitrogen-retaining microbial agent suspension is slowly added dropwise to the product of (1) at 70% of the carrier adsorption saturation, and allowed to stand at 25℃ for 2 h for adsorption (OD600 value of nitrogen-retaining microbial agent suspension is 1.2); (3) Saprophytic microbial agent suspension is mixed with the product of (2) at a volume ratio of 1:5, and coated by rotating at 35 rpm for 30 min (spore concentration of saprophytic microbial agent suspension is 1×10 7 (CFU / mL).

[0034] Example 2

[0035] The preparation method of phosphoric acid modified biochar includes: impregnating biochar in 0.8 mol / L phosphoric acid solution with a solid-liquid ratio of 1:8, activating at 90℃ for 3 h, and then washing and drying.

[0036] Phosphoric acid modified biochar with a particle size of 60 nm was mixed with wheat straw-corn cob carrier pulverized to 2 mm at a mass ratio of 3:1 to form a porous composite carrier.

[0037] The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and the nitrogen-retaining bacterial agent contains methylotrophic Bacillus, Azotobacter chrysophytes, and Bacillus-like bacteria;

[0038] The putrefactive bacteria are coated onto the surface of a porous composite carrier loaded with nitrogen-retaining bacteria. The putrefactive bacteria include Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

[0039] The ratio of live bacteria count of nitrogen-retaining bacteria to putrefactive bacteria is 1:22;

[0040] The wheat straw to corn cob carrier has a mass ratio of wheat straw to corn cob of 3:1 and is pretreated with a buffer solution of pH 7.

[0041] Nano-biochar accounts for 10% of the total mass of the compound microbial agent;

[0042] Preparation method of compound microbial agent: (1) Phosphoric acid modified nano-biochar is mixed with pretreated wheat straw-corn cob carrier and ultrasonically vibrated for 30 min to achieve pore coupling; (2) Nitrogen-retaining microbial agent suspension is slowly added dropwise to the product of (1) at 80% of the carrier adsorption saturation, and allowed to stand at 27℃ for 3 h for adsorption (OD600 value of nitrogen-retaining microbial agent suspension is 1.6); (3) Saprophytic microbial agent suspension is mixed with the product of (2) at a volume ratio of 1:8 and coated by rotating at 37 rpm for 45 min (spore concentration of saprophytic microbial agent suspension ≥ 1×10 7 (CFU / mL).

[0043] Example 3

[0044] The preparation method of phosphoric acid modified biochar includes: impregnating biochar in 1.0 mol / L phosphoric acid solution with a solid-liquid ratio of 1:10, activating at 100℃ for 4 h, and then washing and drying.

[0045] 100nm phosphoric acid modified biochar and wheat straw-corn cob carrier pulverized to 3mm were mixed at a mass ratio of 3:1 to form a porous composite carrier.

[0046] The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and the nitrogen-retaining bacterial agent contains methylotrophic Bacillus, Azotobacter chrysophytes, and Bacillus-like bacteria;

[0047] The putrefactive bacteria are coated onto the surface of a porous composite carrier loaded with nitrogen-retaining bacteria. The putrefactive bacteria include Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

[0048] The ratio of live bacteria count of nitrogen-retaining bacteria to putrefactive bacteria is 1:2.5;

[0049] The wheat straw to corn cob carrier has a mass ratio of wheat straw to corn cob of 3:1 and is pretreated with a buffer solution of pH 7.5.

[0050] Nano-biochar accounts for 15% of the total mass in the compound microbial agent;

[0051] Preparation method of compound microbial agent: (1) Phosphoric acid modified nano-biochar is mixed with pretreated wheat straw-corn cob carrier and ultrasonically vibrated for 40 min to achieve pore coupling; (2) Nitrogen-retaining microbial agent suspension is slowly added dropwise to the product of (1) at 90% of the carrier adsorption saturation, and allowed to stand at 30℃ for 4 h for adsorption (OD600 value of nitrogen-retaining microbial agent suspension is 1.8); (3) Saprophytic microbial agent suspension is mixed with the product of (2) at a volume ratio of 1:10 and coated by rotating at 40 rpm for 60 min (spore concentration of saprophytic microbial agent suspension is 1×10 7 (CFU / mL).

[0052] Comparative Example 1

[0053] The preparation method of phosphoric acid modified biochar includes: impregnating biochar in 0.8 mol / L phosphoric acid solution with a solid-liquid ratio of 1:8, activating at 90℃ for 3 h, and then washing and drying.

[0054] Phosphoric acid modified biochar with a particle size of 60 nm was mixed with soybean straw-corn cob carrier pulverized to 2 mm at a mass ratio of 3:1 to form a porous composite carrier.

[0055] The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and the nitrogen-retaining bacterial agent contains methylotrophic Bacillus, Azotobacter chrysophytes, and Bacillus-like bacteria;

[0056] The putrefactive bacteria are coated onto the surface of a porous composite carrier loaded with nitrogen-retaining bacteria. The putrefactive bacteria include Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

[0057] The ratio of live bacteria count of nitrogen-retaining bacteria to putrefactive bacteria is 1:22;

[0058] The soybean straw to corn cob carrier has a mass ratio of 3:1 and is pretreated with a buffer solution of pH 7.

[0059] Nano-biochar accounts for 10% of the total mass in the compound microbial agent;

[0060] Preparation method of compound microbial agent: (1) Phosphoric acid modified nano-biochar is mixed with pretreated soybean straw-corn cob carrier and ultrasonically vibrated for 30 min to achieve pore coupling; (2) Nitrogen-retaining microbial agent suspension is slowly added dropwise to the product of (1) at 80% of the carrier adsorption saturation, and allowed to stand at 27℃ for 3 h for adsorption (OD600 value of nitrogen-retaining microbial agent suspension is 1.6); (3) The putrefactive microbial agent suspension is mixed with the product of (2) at a volume ratio of 1:8 and coated by rotating at 37 rpm for 45 min (spore concentration of putrefactive microbial agent suspension ≥ 1×10 7 (CFU / mL).

[0061] Comparative Example 2

[0062] The preparation method of phosphoric acid modified biochar includes: impregnating biochar in 0.8 mol / L phosphoric acid solution with a solid-liquid ratio of 1:8, activating at 90℃ for 3 h, and then washing and drying.

[0063] Phosphoric acid modified biochar with a particle size of 60 nm was mixed with wheat straw-broad bean straw carrier pulverized to 2 mm at a mass ratio of 3:1 to form a porous composite carrier.

[0064] The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and the nitrogen-retaining bacterial agent contains methylotrophic Bacillus, Azotobacter chrysophytes, and Bacillus-like bacteria;

[0065] The putrefactive bacteria are coated onto the surface of a porous composite carrier loaded with nitrogen-retaining bacteria. The putrefactive bacteria include Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

[0066] The ratio of live bacteria count of nitrogen-retaining bacteria to putrefactive bacteria is 1:22;

[0067] The wheat straw to broad bean straw carrier has a mass ratio of wheat straw to broad bean straw of 3:1 and is pretreated with a buffer solution of pH 7.

[0068] Nano-biochar accounts for 10% of the total mass in the compound microbial agent;

[0069] Preparation method of compound microbial agent: (1) Phosphoric acid modified nano-biochar is mixed with pretreated wheat straw-broad bean straw carrier and ultrasonically vibrated for 30 min to achieve pore coupling; (2) Nitrogen-retaining microbial agent suspension is slowly added dropwise to the product of (1) at 80% of the carrier adsorption saturation, and allowed to stand at 27℃ for 3 h for adsorption (OD600 value of nitrogen-retaining microbial agent suspension is 1.6); (3) The putrefactive microbial agent suspension is mixed with the product of (2) at a volume ratio of 1:8 and coated by rotating at 37 rpm for 45 min (spore concentration of putrefactive microbial agent suspension ≥ 1×10 7 (CFU / mL).

[0070] Comparative Example 3

[0071] 60nm biochar and wheat straw-corn cob carrier pulverized to 2mm were mixed at a mass ratio of 3:1 to form a porous composite carrier.

[0072] The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, and the nitrogen-retaining bacterial agent contains methylotrophic Bacillus, Azotobacter chrysophytes, and Bacillus-like bacteria;

[0073] The putrefactive bacteria are coated onto the surface of a porous composite carrier loaded with nitrogen-retaining bacteria. The putrefactive bacteria include Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

[0074] The ratio of live bacteria count of nitrogen-retaining bacteria to putrefactive bacteria is 1:22;

[0075] The wheat straw to corn cob carrier has a mass ratio of wheat straw to corn cob of 3:1 and is pretreated with a buffer solution of pH 7.

[0076] Nano-biochar accounts for 10% of the total mass in the compound microbial agent;

[0077] Preparation method of compound microbial agent: (1) Phosphoric acid modified nano-biochar is mixed with pretreated wheat straw-corn cob carrier and ultrasonically vibrated for 30 min to achieve pore coupling; (2) Nitrogen-retaining microbial agent suspension is slowly added dropwise to the product of (1) at 80% of the carrier adsorption saturation, and allowed to stand at 27℃ for 3 h for adsorption (OD600 value of nitrogen-retaining microbial agent suspension is 1.6); (3) Saprophytic microbial agent suspension is mixed with the product of (2) at a volume ratio of 1:8 and coated by rotating at 37 rpm for 45 min (spore concentration of saprophytic microbial agent suspension ≥ 1×10 7 (CFU / mL).

[0078] 1.1 Experimental Conditions

[0079] ① Application of compound microbial agent in chicken manure composting: Add the compound microbial agent at 1.5% of the total mass of composting raw materials, control the moisture content of the compost pile at 60%, and the initial C / N ratio is 23:1 (when the temperature reaches above 55℃ during the composting process, add the compound microbial agent at 0.2% of the mass of the compost pile).

[0080] ② Divide the above compost into seven equal parts and label them with numbers from 1 to 7;

[0081] ③ The compost-promoting and nitrogen-retaining compound microbial agents prepared in Examples 1-3 and Comparative Examples 1-3 were mixed with compost samples 1-6 respectively, with sample 7 left unmixed as a blank group A. The compost was turned once a day using a turning machine until day 12. From day 13 onwards, the compost was turned once every 3 days. Turning was stopped on day 21.

[0082] The performance of the decomposition-promoting and nitrogen-retaining compound microbial agent samples was tested using the following methods.

[0083] (a) Place a temperature monitoring probe at the midpoint of the cross-section of the compost pile from top to bottom 1 / 2. Place a temperature monitoring probe every 3m along the length of the compost pile to monitor the temperature change inside the compost pile during the composting process. Take the detection data at 10:30 am every day. The results are shown in the table below.

[0084] (ii) Post-curing period: From the point when the temperature of the pile body drops below 40°C and stops rising (referred to as time point A), until the mass ratio of carbon to nitrogen in the pile body is less than 20 (referred to as time point B), this period is called the post-curing period;

[0085] The method for determining the mass ratio of carbon to nitrogen in the compost pile (referred to as carbon-nitrogen ratio): The total carbon and total nitrogen content in the compost pile was determined according to the agricultural industry standards "Determination of Organic Matter in Organic Fertilizers" (NY525-2002) and "Determination of Total Nitrogen in Organic Fertilizers" (NY T297-1995), and the carbon-nitrogen ratio was obtained. The results are shown in the table below.

[0086] As shown in the table:

[0087]

[0088] As can be seen from the table above, the mixed compost sample using the nitrogen-retaining and decomposition-promoting compound microbial agent of Example 2 showed the fastest temperature rise and maintained a high-temperature fermentation period (60°C) for 36 days, with the highest fermentation temperature and the shortest fermentation time.

[0089] The post-curing period of the mixed compost using the nitrogen-retaining and decomposition-promoting compound microbial agent sample from Example 2 was 35 days, which was 21 days shorter than the longest post-curing period of the blank group A (56 days).

[0090] Experimental conditions are referenced in 1.1.

[0091] The performance of the above-mentioned composting and nitrogen-retaining compound microbial agent samples was tested using the following methods.

[0092] Determination of seed germination index after decomposition

[0093] The specific method for detecting seed germination index is as follows: Following the method described in the article "Zhang Ming, Gao Tianpeng, Liu Lingling, et al. Study on the composting process of wheat straw and sheep manure mixed at high temperature. Journal of China Agricultural University, 2011, Vol. 11, pp. 566-569", the seed germination index was measured three times. The results are shown in the table below.

[0094] As shown in the table:

[0095]

[0096] As can be seen from the table above, the germination index of the compost prepared using the nitrogen-retaining and decomposition-promoting compound microbial agent sample prepared in Example 2 was 92% after decomposition, which was 13% higher than that of the worst-performing Comparative Example 4 (79%).

[0097] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A nano-biochar-based compound microbial agent for promoting decay and retaining nitrogen, characterized in that, Includes the following steps, (1) Phosphoric acid modified nano-biochar of 50-100 nm and wheat straw-corn cob carrier pulverized to 2-3 mm are mixed at a mass ratio of 3:1 to form a porous composite carrier. The mass ratio of wheat straw to corn cob in the wheat straw-corn cob carrier is 3:1, and it is pretreated with a buffer solution of pH 6.5-7.

5. (2) The nitrogen-retaining bacterial agent is loaded into the micropores of the porous composite carrier, wherein the nitrogen-retaining bacterial agent comprises methyltrophic Bacillus, Azotobacter chrysophytes and Bacillus-like bacteria; (3) The putrefactive agent is coated on the surface of the porous composite carrier obtained in step (2), wherein the putrefactive agent includes Rhizopus oryzae, common thermophilic actinomycetes and Bacillus licheniformis.

2. The compound microbial agent according to claim 1, characterized in that, The preparation method of the phosphoric acid modified nano-biochar includes: immersing biochar in a 0.5-1.0 mol / L phosphoric acid solution with a solid-liquid ratio of 1:5-1:10, activating it at 80-100℃ for 2-4 hours, and then washing and drying it.

3. The compound microbial agent according to claim 1, characterized in that, The ratio of live bacteria count of the nitrogen-retaining bacteria agent to the putrefactive bacteria agent is 1:1.5 to 1:2.

5.

4. The compound microbial agent according to any one of claims 1 to 3, characterized in that, In the compound microbial agent, phosphoric acid-modified nano-biochar accounts for 5% to 15% of the total mass.

5. A method for preparing the compound microbial agent according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Phosphoric acid modified nano-biochar was mixed with pretreated wheat straw-corn cob carrier and ultrasonically vibrated for 20-40 min to couple the pores and form a porous composite carrier; (2) Slowly add the nitrogen-retaining bacterial agent suspension to the porous composite carrier in step (1) at 70% to 90% of the carrier adsorption saturation, and let it stand at 25 to 30°C for 2 to 4 hours for adsorption; (3) Mix the suspension of the putrefactive bacteria with the porous composite carrier containing the nitrogen-retaining bacteria in step (2) at a volume ratio of 1:5 to 1:10, and coat by rotating at 35 to 40 rpm for 30 to 60 minutes.

6. The preparation method according to claim 5, characterized in that, In step (2), the OD600 value of the nitrogen-retaining bacterial agent suspension is 1.2–1.8, and in step (3), the spore concentration of the putrefactive bacterial agent suspension is ≥1×10⁻⁶. 7 CFU / mL.

7. The application of the compound microbial agent according to any one of claims 1 to 4 in chicken manure composting, characterized in that: The compound microbial agent is added at 0.5% to 2.0% of the total mass of the composting raw materials, the moisture content of the compost pile is controlled at 55% to 65%, and the initial C / N ratio is 20 to 25:

1.

8. The application according to claim 7, characterized in that, When the temperature reaches 50-60℃ during composting, the compound microbial agent is added at a rate of 0.1%-0.3% of the compost mass.

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