Bacillus brevis with ammonia oxidation capacity, ammonia assimilation-ammonia oxidation composite microbial agent and application thereof

Abstract

The application discloses a soil Brevibacillus with ammonia oxidation capacity, an ammonia assimilation-ammonia oxidation composite microbial agent and application thereof. The strain is QN6, which has been preserved in the China General Microbiological Culture Collection Center on December 23, 2024, and the preservation number is CGMCC No.33138. The strain can efficiently convert ammonia nitrogen, increase the total nitrogen content and humic acid content of compost, and accelerate humification. The strain and compost bacillus QY6 (CGMCC No.33139) can be compounded into a double-function composite microbial agent to strengthen the ammonia assimilation and ammonia oxidation paths of compost, and provide an important technical breakthrough for solving the dual difficulties of 'difficult to preserve nitrogen and weak to promote decomposition' of compost. The strain and the double-function composite microbial agent can be used for composting, and the obtained compost product can significantly improve the soil nutrient supply capacity, promote crop growth and improve crop quality, and provide an effective technical means for agricultural waste resource utilization, soil improvement and high-quality crop cultivation.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, specifically to a soil-borne brevicorbacterium with ammonia oxidation capabilities, an ammonia assimilation-ammonia oxidation compound bacterial agent, and their applications. Background Technology

[0002] Composting is a core pathway for the resource utilization of organic solid waste, converting unstable organic matter into stable humic acid through microbial metabolism. However, during aerobic composting, organic nitrogen rapidly mineralizes, producing large amounts of ammonium nitrogen (NH4). + Nitrogen (NH3) is prone to volatilization under high temperature and frequent aeration conditions, resulting in a nitrogen loss rate as high as 74% to 90%. This not only significantly reduces the fertilizer efficiency of compost products but also causes environmental problems such as odor pollution. At the same time, nitrogen loss disrupts the carbon-nitrogen metabolic coupling, severely inhibits the humification process and the formation of stable organic matter such as humic acid, thereby limiting the improvement of compost quality.

[0003] To address the issues of NH3 emissions and nitrogen loss during composting, existing technologies employ ammonia oxidation (nitrification) as a control approach, converting NH4⁺-N into nitrate nitrogen (NO3). - The use of NH4⁺-N to reduce the concentration of NH4⁺-N in the system can, to some extent, inhibit NH3 volatilization, which helps improve total nitrogen retention and creates conditions for the conversion of nitrogen into stable humic nitrogen. However, under actual composting conditions, the ammonia oxidation process is easily affected by factors such as temperature and oxygen levels. Conventional nitrifying bacteria lack adaptability and stability in the high-temperature, high-ammonia environment of composting, resulting in large fluctuations in nitrification efficiency and poor nitrogen retention and humification effects. Therefore, it is urgent to obtain specialized functional strains that can exhibit efficient and stable nitrification capabilities in the composting environment to support continuous nitrogen retention and quality improvement during the composting process.

[0004] Direct application of ammonia-oxidizing bacteria to crops can promote the release of NH4 from the soil or after fertilization. + -N is oxidized in situ to generate NO3. - -N. Leafy vegetables such as cabbage, lettuce, kale, and spinach, grain crops such as corn and soybeans, and cash crops such as tomatoes, peppers, eggplants, cucumbers, and loofahs are all susceptible to NO3. - The absorption and utilization of -N exhibits a clear preference, leading to crops being known as "nitrate-loving crops." Furthermore, compost products and bio-organic fertilizers prepared using ammonia-oxidizing bacteria can sustainably provide crops with absorbable NO3. - -N is used to better match the nitrogen nutrient requirements of nitrate-loving crops, improve crop nitrogen use efficiency, and provide important support for efficient agricultural production and soil quality improvement.

[0005] Furthermore, while the inoculation of ammonia-oxidizing bacteria has shown some effectiveness in the composting process, it largely focuses on the effect of single strains, and some inoculants suffer from limited nitrogen retention efficiency and insufficient humification promotion. On the one hand, ammonia oxidation alone has limited effect on NH4+. + Regulation of -N cannot achieve long-term stable retention of nitrogen. Ammonia oxidation converts NH4+ into nitrogen. + NO3 after -N conversion ⁻ -N remains dissolved inorganic nitrogen, which is prone to denitrification loss in the later stages of composting or in locally hypoxic microenvironments, or to leaching loss during compost product utilization, affecting fertilizer efficiency. Furthermore, ammonia oxidation is not equivalent to fixing nitrogen into a stable organic nitrogen pool, making it difficult to support the introduction of nitrogen-containing functional groups and nitrogen stabilization requirements during humification. Therefore, NH4+... + Rapid consumption and efficient fixation of nitrogen (NH3) are key to achieving a balance between nitrogen conversion and stabilization, which is crucial for suppressing NH3 volatilization in the composting system and achieving efficient nitrogen retention and decomposition during the composting process.

[0006] NH4 + -N, as a core hub in nitrogen transformation, can generate NO3 through ammonia oxidation. - -N reduces the risk of NH3 release in alkaline environments. Furthermore, it can be fixed as organic nitrogen through ammonia assimilation, inhibiting NH3 volatilization and forming a dual barrier of "nitrogen locking and emission reduction." Ammonia assimilation and ammonia oxidation play complementary roles in the nitrogen cycle of composting, jointly influencing composting efficiency and the quality of the final product. Therefore, generating organic nitrogen and nitrates through ammonia assimilation and ammonia oxidation, respectively, can provide nitrogen precursors for humic acid polymerization and simultaneously construct a dual barrier for NH3 emission reduction through nitrogen form conversion.

[0007] Based on this, a highly efficient ammonia-oxidizing functional bacterium suitable for composting was developed, and a synergistic system was further constructed with it and ammonia-assimilating bacteria to synergistically enhance the ammonia assimilation and oxidation processes, effectively promote the synthesis of nitrogen precursors, and synergistically drive humic acid polymerization. This reduces nitrogen loss while improving humification efficiency, thus breaking the dual dilemma of "difficulty in nitrogen retention and weak humification promotion" in composting, and providing a theoretical basis and technological breakthrough for the high-value utilization of organic waste. Therefore, the microbial agents, bio-organic fertilizers, and soil conditioners prepared using this technology are of great significance for solving the pain points of agricultural waste composting and promoting green agricultural development.

[0008] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to provide a soil-borne brevicorbacterium with ammonia oxidation capability and an ammonia assimilation-ammonia oxidation compound bacterial agent, which can be used to improve soil properties, increase soil nutrient content, promote crop growth, and improve crop yield and quality, providing an effective means for the resource utilization of agricultural waste.

[0010] To achieve the above objectives, the present invention first provides a soil-borne breviculobacillus strain with ammonia oxidation capabilities (… Brevibacillus agri This strain was deposited at the China General Microbiological Culture Collection Center on December 23, 2024, with accession number CGMCC No. 33138. This strain can efficiently oxidize NH4 under composting conditions. + -N significantly reduces the amount of NH4 in the system. + -N concentration, thereby inhibiting NH3 volatilization and promoting nitrogen retention.

[0011] After obtaining and verifying the function of ammonia-oxidizing bacteria QN6, the present invention further discovered that this strain does not have an antagonistic effect with Bacillus compostii QY6 (CGMCC No. 33139), which is known to have ammonia assimilation ability, and can coexist stably and form a synergistic effect.

[0012] Based on this, the present invention also provides an ammonia assimilation-ammonia oxidation composite bacterial agent, which contains soil brevicorbacterium QN6 and a strain of composting Bacillus ( Bacillus stercoris QY6, in the compound microbial agent, QY6 and QN6 respectively promote the transformation of NH4⁺-N in the composting system through ammonia assimilation and ammonia oxidation, thereby reducing ammonia volatilization in compost, improving nitrogen fixation efficiency, and promoting humification. Among them, Bacillus compostii QY6 was deposited at the China General Microbiological Culture Collection Center on December 23, 2024, at the Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33139.

[0013] Preferably, the compound microbial agent obtained by mixing QN6 and QY6 in a volume ratio of 1 to 2:1 has an effective viable count of not less than 1 × 10⁻⁶. 8 cfu / mL.

[0014] The soil brevicorbacterium or compound microbial agent provided by this invention can be used in the field of composting, especially for the preparation of composting microbial agents, soil conditioners, crop growth promoters or bio-organic fertilizers.

[0015] The present invention also provides a composting method by inoculating soil brevicorbacterium or a compound microbial agent into composting raw materials.

[0016] The present invention also provides a compost product prepared by the above-described composting method.

[0017] The present invention also provides a method for soil improvement and crop growth promotion by applying the above-mentioned compost products and bio-organic fertilizer products prepared using strain QN6 to soil or crop cultivation systems.

[0018] Preferably, the crops used to promote crop growth are selected from rice, rapeseed, and nitrate-nitrogen-loving crops; among which, nitrate-nitrogen-loving crops include radish, carrot, tomato, eggplant, pepper, leek, scallion, onion, leek, spinach, celery, amaranth, lettuce, garland chrysanthemum, daylily, corn, or soybean.

[0019] The application of the soil brevicorbacterium or compound microbial agent provided by the present invention in any of the following includes: promoting nitrogen retention in compost, promoting compost humification, soil improvement, preparing bio-organic fertilizer, and / or promoting crop growth.

[0020] After obtaining and verifying the function of ammonia-oxidizing bacteria QN6, the present invention further discovered that this strain does not have an antagonistic effect with Bacillus compostii QY6 (CGMCC No. 33139), which is known to have ammonia assimilation ability, and can coexist stably and form a synergistic effect.

[0021] Based on this, the present invention also provides an ammonia assimilation-ammonia oxidation composite bacterial agent, which contains soil brevicorbacterium QN6 and a strain of composting Bacillus ( Bacillus stercoris QY6, in the compound microbial agent, QY6 and QN6 work synergistically to enable NH4⁺-N in the composting system to enter the ammonia assimilation pathway and the ammonia oxidation pathway, respectively; the composting Bacillus QY6 was deposited on December 23, 2024 at the China General Microbiological Culture Collection Center, depositary address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, accession number CGMCC No. 33139.

[0022] In the synergistic system, QN6 reacts with the remaining NH4+ through ammonia oxidation. + -N is converted to NO3⁻-N, while QY6 converts NH4 through ammonia assimilation. + -N is fixed as organic nitrogen, thereby reducing NH4+ in the same composting system. + -N enables dual-path utilization, improving NH4 + Improve the overall conversion efficiency of -N and reduce NH3 loss.

[0023] This invention also provides a composting microbial system based on the synergistic effect of ammonia-oxidizing bacteria QN6 and ammonia-assimilating bacteria QY6, and its application in agricultural waste composting. Compared with using QN6 alone, this synergistic microbial system can simultaneously achieve higher NH3 emission reduction rates, total nitrogen retention rates, and humic acid formation during composting; wherein QN6 reduces NH4+ emissions. + -N is oxidized to nitrate nitrogen, and QY6 oxidizes NH4+.+ -N is assimilated into organic nitrogen, thereby enabling the composting system to retain NH4+. + -N forms a dual-pathway utilization to reduce NH3 volatilization and promote humification.

[0024] Preferably, strains QN6 and QY6 are cultured to OD200. 600 =0.80±0.10, and a compound microbial agent is obtained by mixing at a volume ratio of 1~2:1. The effective viable count in the resulting microbial agent is not less than 1×10. 8 cfu / mL.

[0025] The soil brevicorbacterium QN6 or compound microbial agent provided by this invention can be used in the field of composting, including the preparation of composting microbial agents, soil conditioners, crop growth promoters or bio-organic fertilizers.

[0026] The present invention also provides a composting method, which is achieved by inoculating soil brevicorbacterium QN6 or the above-mentioned compound microbial agent into the composting raw materials.

[0027] The present invention also provides a compost product prepared by the above-described composting method.

[0028] The present invention also provides a soil improvement method, which involves applying the above-mentioned compost product to the soil.

[0029] The present invention also provides a method for promoting crop growth by applying the above-mentioned compost product into a crop cultivation system.

[0030] The soil brevicorbacterium QN6 or compound microbial agent provided by this invention can be used in any of the following: composting for nitrogen retention, promoting composting humification, soil improvement, or promoting crop growth.

[0031] The present invention has the following advantages: This invention provides a soil-borne brevicorbacterium QN6 strain with ammonia oxidation capacity. This strain has a strong ammonia oxidation capacity, reducing NH4+ by 48 hours. + The nitrogen-to-nitrogen conversion rate reaches 82.35%, which can significantly reduce ammonia emissions from composting, improve total nitrogen retention, and effectively alleviate nitrogen loss problems.

[0032] Inoculation with strain QN6 can significantly increase the humic acid content in compost, accelerate the humification process, shorten the composting cycle, and improve the stability and agricultural value of compost products.

[0033] This invention combines strain QN6 with Bacillus compostingus QY6 to form a dual-function bacterial agent of "ammonia oxidation + ammonia assimilation," further enhancing nitrogen retention and humification effects, and is adaptable to different raw materials and composting scales. Compared with existing composting regulation technologies that rely solely on ammonia oxidation, this invention introduces the compost-suitable ammonia-oxidizing bacterium QN6 and synergistically applies it with the known ammonia assimilation bacterium QY6, achieving efficient consumption and fixation of NH4⁺-N in the same composting system. This significantly reduces NH3 volatilization, increases total nitrogen retention, and promotes the formation of humic substances such as humic acid.

[0034] Experimental results show that ammonia-oxidizing bacteria QN6 has good functional stability in the composting environment, and its synergistic effect with ammonia-assimilating bacteria QY6 is superior to using QN6 alone in terms of nitrogen retention and humification promotion, indicating that this synergistic system has certain technical advantages and application potential.

[0035] Applying compost products containing QN6 or bio-organic fertilizer products prepared using QN6 can significantly increase soil organic matter, available nutrients and humic acid content, and promote crop growth (cabbage biomass increased by up to 70.81%, and rapeseed thousand-grain weight increased by 27.96%), achieving green efficiency enhancement throughout the entire process of "waste-soil-crop".

[0036] The strain QN6 and its compound inoculant provided by this invention are suitable for various raw materials such as bacterial residue and chicken manure. They exhibit stability in factory composting and have good environmental protection and agricultural promotion value. Attached Figure Description

[0037] Figure 1 The NH4+ of the six ammonia-oxidizing bacteria initially screened in this invention. + -N conversion capability status.

[0038] Figure 2 The NH4+ of strain QN6 screened in this invention at different times + -N transformation capacity and growth of the strain on streak plates.

[0039] Figure 3 The results of measuring various nitrogen contents and humification indicators after composting were obtained from the inoculation of strain QN6 in a small-scale composting trial.

[0040] Figure 4 This report describes the determination of humic acid, fulvic acid, and HA / FA in the compost after inoculation with QN6 in a small-scale composting trial.

[0041] Figure 5 This study describes the determination of the content of various forms of nitrogen in compost after inoculation with QN6 in large-scale composting.

[0042] Figure 6This report describes the determination of humic acid, fulvic acid, and HA / FA in large-scale compost after inoculation with QN6.

[0043] Figure 7 This study verifies the soil improvement effect of QNO, a compost product obtained after inoculation with QN6.

[0044] Figure 8 Verification of the effect of applying bio-organic fertilizer prepared by inoculating QN6 to potted Chinese cabbage.

[0045] Figure 9 This study verifies the effectiveness of ammonia-oxidizing bacteria agents on rapeseed and rice.

[0046] Figure 10 The results of measuring various nitrogen contents and humification indicators after composting with the compound microbial agent prepared in this invention are shown.

[0047] Figure 11 The results of measuring humic acid, fulvic acid, and HA / FA levels in the compost after inoculation with the compound microbial agent prepared in this invention were obtained.

[0048] Figure 12 The results of measuring various nitrogen contents and humification indicators after composting were obtained by inoculating compound microbial agents with different strain ratios.

[0049] Figure 13 This study describes the determination of humic acid, fulvic acid, and HA / FA levels in compost after inoculation with compound microbial agents of different strain ratios.

[0050] Figure 14 The results of measuring various nitrogen contents and humification indicators after inoculating the compound microbial agent prepared in this invention into industrial large-scale composting.

[0051] Figure 15 The results of measuring humic acid, fulvic acid, and HA / FA levels in the compost after inoculation with the compound microbial agent prepared in this invention during large-scale industrial composting.

[0052] Figure 16 The results of measuring the content of various nitrogen elements and humification indicators in chicken manure compost were obtained by inoculating the compound microbial agent prepared in this invention.

[0053] Figure 17 The results of measuring humic acid, fulvic acid, and HA / FA in chicken manure compost using the compound microbial agent prepared in this invention.

[0054] Figure 18 This document verifies the soil improvement effect of the compost product obtained through fermentation with compound microbial agents in this invention.

[0055] Figure 19This document verifies the effectiveness of the compost product obtained through fermentation with compound microbial agents in the application of it to potted cabbage.

[0056] Figure 20 This study verifies the effectiveness of the compost product obtained by fermentation with compound microbial agents in rapeseed fields. Detailed Implementation

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0058] Note: Unless otherwise specified, the experimental methods in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0059] Example 1: Isolation, Screening and Identification of Ammonia-Oxidizing Bacteria 1. Screening of strains Chicken manure was collected from straw-chicken manure compost, and 15 bacterial strains were obtained through enrichment culture and screening. These strains were then inoculated onto ammonia-oxidizing solid medium, and 6 viable strains were screened from the plates. These strains can utilize NH4+. + -N was used as the nitrogen source for ammonia oxidation, and the colonies were designated QN1 to QN6. Single colonies were picked from the plates and inoculated into 50 mL of sterile ammonia oxidation medium. The ammonia oxidation medium was formulated as follows: 0.5 g ammonium sulfate, 5 g calcium carbonate, 1 g dipotassium hydrogen phosphate, 2 g sodium chloride, 0.5 g magnesium sulfate heptahydrate, 0.03 g ferric sulfate heptahydrate, and 1 L pure water, pH=7.2.

[0060] The initially screened strains were cultured in a shaker at 170 rpm and 33℃ for 48 h. The initial culture medium and the culture medium after 48 h of culture were centrifuged at 6000 rpm for 10 min to obtain supernatants. Then, 200 μL of the supernatant was added to a 20 mL test tube, followed by the addition of 5 mL of sodium phenolate and 5 mL of sodium hypochlorite. The volume was then adjusted to 20 mL with pure water, allowed to stand for 30 min for color development, and the OD was measured. 630 The value of nm was used. An absorbance-concentration standard curve was plotted using ammonium chloride to calculate the NH4 content in the sample. + -N content. Results are shown in... Figure 1 As shown, it can be seen that QN6 contains NH4 + -N conversion ability is the best, NH4 at 48 h +-N conversion capacity reached 82.35%, followed by QN1, and NH4 at 48 h. + -N conversion capability reaches 70.64%.

[0061] 2. Identification of strains The initially screened strain QN6 was activated, and 500 μL of the glycerol culture, stored at -80℃, was added to 49.5 mL of sterile ammonia oxidation medium. The culture was incubated in a shaker at 170 rpm and 33℃. Samples were taken every 12 h after inoculation, and the initial culture medium and culture media at different incubation times were centrifuged at 6000 r / min for 10 min to obtain supernatants. Then, 200 μL of the supernatant from the initial culture medium, and the cultures after 24 h, 48 h, and 72 h of incubation, were added to 20 mL test tubes. 5 mL of sodium phenolate and 5 mL of sodium hypochlorite were added, respectively, and the volume was adjusted to 20 mL with pure water. The tubes were allowed to stand for 30 min for color development, and the OD was measured. 630 The absorbance-concentration standard curve was plotted using ammonium chloride to calculate the NH4 content in the sample. + -N content.

[0062] The results are as follows Figure 2 As shown, where, Figure 2 (a) in the figure represents NH4 at different incubation times. + -N conversion rate, Figure 2 (b) shows the streak plate culture of strain QN6. It can be seen that after 24 h of culture, the NH4+ content of QN6... + -N conversion rate reached 55.6%, and NH4+ was reduced after 72 h of cultivation. + The -N conversion rate reached 85.88%, and the culture was essentially stable. On LB medium, the colonies of strain QN6 were smooth, slightly white, round, and convex in the center. Comparison with the standard classification characteristics in Bergey's Manual of Bacteriology showed that the morphological characteristics and physiological properties of QN6 conformed to the description of the genus *Bacillus*. 16S rRNA gene sequencing yielded a 1446 bp gene fragment. Blast analysis of the sequencing results with the NCBI database identified the strain as *Bacillus spp.*, with the taxonomic name [not specified]. Brevibacillus agri .

[0063] The strain QN6 was deposited on December 23, 2024, at the China General Microbiological Culture Collection Center, Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33138.

[0064] Example 2: Application Verification of QN6 Ammonia Oxidation Bio-inoculant in a Small-Scale Composting Test 1. Preparation of biological inoculant: QN6 was inoculated into LB medium and cultured in a shaker at 170 rpm and 33℃ until OD. 600 =0.80±0.10, seed liquid was obtained.

[0065] 2. Composting Experiment Design: Control group (CK): compost raw materials without inoculation with microbial agent; Treatment group (T2): inoculated with ammonia-oxidizing microbial agent (Bacillus brevis 6).

[0066] The composting material consisted of a mixture of shiitake mushroom substrate, oyster mushroom substrate, and distiller's grains in a 20:3:5 ratio. The total organic carbon (TOC) of the mixture was 394.01 g / kg, total nitrogen (TN) was 15.01 g / kg, and the carbon-to-nitrogen ratio (C / N) was 26.25. 30 kg of material was added to an aerobic composting reactor, along with 1% QN6 inoculum. An equal volume of LB liquid culture medium was added to the control group, and the moisture content was adjusted to 55%. The compost was turned on days 0, 2, 5, 9, 16, 23, 30, and 45. After composting, the nitrogen content and humification indicators were measured. The results are as follows: Figure 3 As shown, where, Figure 3 In the figure, a, b, c, d, and e represent the total nitrogen content, cumulative ammonia emissions, and NH4+ content in the system, respectively. + -N content, NO3 - -N content and acid-hydrolyzed organic nitrogen status, where AAN, AN, ASN, and HUN represent amino acid nitrogen, ammonia nitrogen, amino sugar nitrogen, and acid-hydrolyzed unknown nitrogen, respectively. It can be seen that at the end of composting, the addition of microbial agents significantly reduced cumulative NH3 emissions, while the addition of QN6 microbial agents significantly increased NO3 emissions. - -N content; TN content in group T2 was 13.28% higher than that in group CK; cumulative NH3 emissions were 20.70% lower than those in group CK. p <0.05); the NO3⁻-N content in group T2 was 34.15% higher than that in group CK. （p <0.05).

[0067] Further measurements were taken of humic acid (HA), fulvic acid (FA), and the HA / FA ratio in the compost of the two treatment groups. Specific results can be found in the table below. Figure 4 As shown in a, b, and c, the results indicate that adding QN6 inoculant can significantly increase the humic acid content in the composting system. The humic acid content in group T2 was 10.72% higher than that in group CK. p <0.05); the HA / FA ratio in group T2 increased by 7.78% compared to group CK. This indicates that QN6 can effectively promote humic acid synthesis and accelerate composting and humification.

[0068] Example 3: Application of QN6 biological agent in large-scale industrial composting The experiment was conducted by setting up groups, including a control group (CK): compost raw materials that were not inoculated with the microbial agent; and a treatment group (T2): inoculated with the ammonia-oxidizing microbial agent (Bacillus brevis QN6 seed liquid) prepared in Example 2.

[0069] Mushroom residue was selected as the composting material (shiitake mushroom residue, oyster mushroom residue, and distiller's grains were mixed at a ratio of 20:3:5). The TOC of the mixture was 430.83 g / kg, TN was 15.84 g / kg, and C / N ratio was 27.20. Each pile initially contained 30 t of material with a moisture content of 50%. QN6 was added at a 1% (wet weight) inoculum concentration, while the control group was treated with the same volume of sterile LB liquid culture medium. The compost was turned every 2 days for the first 10 days, every 5 days from days 11 to 30, and every 10 days from days 30 to 62, for a total of 62 days of composting.

[0070] The measurement results are as follows Figure 5 As shown, where, Figure 5 In the figure, a, b, c, d, and e represent the total nitrogen content, cumulative ammonia emissions, and NH4+ content in the system, respectively. + -N content, NO3 - -N content and acid-hydrolyzed organic nitrogen status. It can be seen that at the end of composting, the TN content in group T2 was 4.75% higher than that in group CK; the NO3⁻-N content in group T2 was 10.30% higher than that in group CK. p <0.05); the cumulative NH3 emissions of group T2 were 13.81% lower than those of group CK. p <0.05).

[0071] Further measurements were taken of humic acid, fulvic acid, and HA / FA levels in the compost of the two treatment groups. Specific results can be found in the table below. Figure 6 As shown in a, b, and c, the results indicate that the addition of QN6 inoculant increases humic acid content, with the humic acid content in group T2 increasing by 10.72% compared to group CK; the HA / FA ratio in group T2 also increases by 7.78% compared to group CK. This demonstrates that QN6 exhibits good functional stability in large-scale composting.

[0072] Example 4: Soil improvement effect of QN6 compost product QNO Preparation of QNO compost product: The compost product obtained in Example 2 was aged at room temperature for 15 days and then ground through a 5 mm sieve for later use.

[0073] Three treatment groups were set up: NAS (without compost product), CKS (with CKO), and QNS (with QNO). CKO was the final compost product obtained from the CK treatment group after composting, and its soil improvement group was designated CKS. QNO was the final compost product obtained from the T2 treatment group in Example 2, and the soil improved using QNO was designated QNS. The compost product was mixed with the soil at a ratio of 5%, and 1.5 kg of the mixed soil (soil + compost product) was filled into each pot. Water was added to adjust the moisture content to 60%. The soil was watered regularly daily to adjust the soil moisture holding capacity (watering once a day, 100 mL per pot each time). After 30 days of outdoor cultivation, soil samples were taken to determine conventional indicators and nutrient content.

[0074] See results Figure 7 As shown, where, Figure 7 In the table, a, b, c, d, e, f, g, h, and i represent soil pH, soil electrical conductivity, soil organic matter ratio, total organic carbon content, available phosphorus content, available potassium content, available nitrogen content, total nitrogen content, and humic acid content, respectively. The results indicate that the application of QNO altered soil properties and significantly increased soil nutrient content (…). p <0.05). Application of this compost product had no significant effect on soil pH, which remained around 7.40. Compared with other treatments, the soil EC in the QNS group was 48.79% and 20.45% higher, respectively. The higher EC indicates that QNO application enhanced soil activation capacity. Application of the compost product significantly increased soil organic matter and total organic carbon content. p Compared with NAS, the soil organic matter and total organic carbon content in the QNS group were 82.21% and 205.02% higher, respectively. Compared with other treatments, the available phosphorus content in the QNS group was 184.70% and 26.64% higher, and the available potassium content was 349.89% and 9.18% higher, respectively. QNO application can increase the content of available nutrients in the soil, which is beneficial for crop absorption and utilization. Compared with other treatments, the available nitrogen content in the QNS group was 88.09% and 25.72% higher, respectively. Simultaneously, the TN content in the soil of the QNS group was 142.35% and 11.24% higher, respectively, indicating that QNO addition can promote soil nitrogen content, and the increase in available nitrogen content is beneficial for plant nitrogen absorption. Compared with other treatments, the humic acid content in the soil of the QNS group was 128.32% and 7.95% higher, respectively. This increased content can inhibit the leaching of ionic nutrients and increase the proportion of available nutrients in the soil. These results indicate that QNO addition can effectively increase soil nutrient content and improve soil properties.

[0075] Example 5: Effects of applying bio-organic fertilizer to potted cabbage 1. Preparation of bio-organic fertilizer QN6 was inoculated into nitrification medium and fermented at 35℃ and 180 r / min for 72 h until the viable cell count in the bacterial culture reached 5 × 10⁶. 8 The microbial fermentation broth was obtained at a concentration of CFU / mL. The fermentation broth was then mixed with organic fertilizer at a mass ratio of 1:9 and subjected to a secondary fermentation at room temperature for 7 days. The moisture content of the fermented product was maintained below 30%, and the viable cell count was >2×10⁻⁶. 8 CFU / g yields bio-organic fertilizer (QNN). Organic fertilizer without added microorganisms is Yiji brand organic fertilizer, whose main raw materials are fungal residue, tobacco dust, humic acid, distiller's grains, and straw.

[0076] 2. Experimental Design Three treatment groups were set up: NAP (no organic fertilizer added), CKP (with Yiji brand organic fertilizer added), and QNP (with QNN bio-organic fertilizer added).

[0077] Mix the compost product with the soil at a ratio of 5%, and fill each pot with 1.5 kg of the mixed soil (soil + compost product). Add water to adjust the moisture content to 60%. Transplant seedlings of equal size into the pots one week after emergence, and water regularly every day to adjust the soil moisture holding capacity (water once a day, 100 mL / pot each time). After 30 days of outdoor cultivation, take samples to determine the agronomic traits and quality indicators of the Chinese cabbage.

[0078] 3. Application Effect See results Figure 8 As shown, where, Figure 8 In the figure, a, b, c, d, e, f, g, and h represent plant height, root length, fresh weight biomass, dry weight biomass, chlorophyll content, soluble sugar content, soluble protein content, and total nitrogen content, respectively. The results showed that compared with other treatments, the QNP group had 44.33% and 17.76% higher plant height, 62.31% and 29.55% higher root length, 62.66% and 30.28% higher fresh weight biomass, and 38.90% and 14.47% higher dry weight biomass, respectively. This indicates that QNN bio-organic fertilizer has a significant promoting effect on the growth of Chinese cabbage. p <0.05). Compared with the other treatments, the chlorophyll content of the QNP group was 17.50% and 9.30% higher, respectively, indicating that the application of bio-organic fertilizer can effectively promote plant photosynthetic capacity and increase chlorophyll content. The soluble sugar content of the QNP group was 215.05% and 44.33% higher than that of the other groups, respectively. p<0.05), applying bio-organic fertilizer is beneficial for the synthesis of soluble sugars and avoids external stress on Chinese cabbage. Compared with other treatments, the soluble protein content of the QNP group was 20.59% and 3.67% higher, respectively, and the total nitrogen content of plants was 8.99% and 5.33% higher, respectively. This indicates that applying bio-organic fertilizer has a strong nitrogen supply capacity for Chinese cabbage growth, which is conducive to the absorption of nitrogen in the soil and its conversion into plant nitrogen, thereby reducing nitrogen loss and improving the quality of Chinese cabbage.

[0079] Example 6: Application effect of ammonia-oxidizing bacteria inoculant on rapeseed and rice. To study the adaptability of ammonia-oxidizing bacteria in dryland and flooded soils, the ammonia-oxidizing bacteria QN6 was applied to rapeseed and rice, respectively, and its growth-promoting and yield-increasing effects were evaluated.

[0080] 1. Preparation of biological inoculant: QN6 was inoculated into LB medium and cultured in a shaker at 170 rpm and 33℃ until OD600=0.80±0.10 to obtain seed culture.

[0081] 2. Rapeseed field trial setup: A control group without bacterial treatment (CK) and an ammonia-oxidizing bacterial agent treatment group (T1) were set up. In the treatment group, 50 mL of bacterial agent was applied to each rapeseed plant by root irrigation.

[0082] Rice field experiment setup: A control group without bacterial treatment (RC) and an ammonia-oxidizing bacterial agent treatment group (R1) were set up. The bacterial agent was applied to the treatment group by spraying, so that the bacterial agent formed a continuous mist of droplets on the surface of rice to ensure that the leaves, leaf sheaths and stem bases were fully covered with bacteria.

[0083] 3. Application Effect The effects of ammonia-oxidizing bacteria on rapeseed: Figure 9 As shown in the figure, compared with the control group (CK), ammonia-oxidizing bacteria significantly promoted rapeseed growth and improved yield and quality traits under field conditions. p <0.05). Among them, the aboveground dry weight and underground dry weight of group T1 increased by 29.35% and 11.78% respectively compared with group CK. p <0.05); the thousand-kernel weight and oil content of the kernels increased by 35.29% and 18.84% respectively compared with the CK group. p <0.05).

[0084] The effects of ammonia-oxidizing bacteria on rice: Figure 9 As shown in eh. Compared with the control group (RC), ammonia-oxidizing bacteria significantly promoted rice growth and increased yield under field conditions: ammonia-oxidizing bacteria increased rice seed setting rate by 3.14%, significantly increased rice root length by 21.18%, rice plant height by 16.71%, and the measured yield per mu increased by 13.12% ( ). p <0.05).

[0085] The above results indicate that ammonia-oxidizing bacteria can promote the accumulation of rapeseed biomass, improve grain yield composition and increase oil content, and have a clear effect on increasing yield and improving quality in the field; at the same time, it can promote the growth and development of rice, improve grain filling performance and achieve increased yield, showing good field application effects.

[0086] Example 7: A compound microbial agent YN and its effect in composting This embodiment provides a compound microbial agent comprising the aforementioned *Bacillus brevis* QN6, and also includes a strain of *Bacillus compostii* QY6, the taxonomic name of which is... Bacillus stercoris It was deposited on December 23, 2024, at the China General Microbiological Culture Collection Center (CGMCC), located at Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33139. The specific preparation is as follows:

[0087] QY6 and QN6 were inoculated into LB medium and cultured in a shaker at 170 rpm and 33°C until OD. 600 =0.80±0.10, seed liquid was obtained.

[0088] By streaking QY6 and QN6 onto LB agar plates, cross-streaks were performed. After 48 hours of incubation, the two strains were found to grow together without any antagonism. A 1:1 volume ratio of QY6 and QN6 was then used to obtain a highly efficient bifunctional microbial agent (YN) for regulating nitrogen conversion in compost.

[0089] The experimental design included: control group (CK): uninoculated bacterial residue; treatment group (YN): inoculated with compound bacterial agent YN (Bacillus compostii QY6 + Bacillus brevis 6).

[0090] Mushroom residue was selected as the raw material, consisting of shiitake mushroom residue, oyster mushroom residue, and distiller's grains, mixed in a ratio of 20:3:5. The resulting mixture had a TOC of 394.01 g / kg, a TN of 15.01 g / kg, and a C / N ratio of 26.25. Each pile initially contained 30 kg of material with a moisture content of 55%. YN was added at a 1% (wet weight) inoculum concentration, while the control group received the same volume of sterile LB liquid culture medium. The mixture was thoroughly mixed with the mushroom residue before composting. The internal temperature of the compost pile was measured daily. The pile was turned and samples were taken on days 0, 2, 5, 9, 16, 23, 30, and 45 for a total of 45 days of composting.

[0091] The measurement results are as follows Figure 10 As shown, where, Figure 10In the figure, a, b, c, d, and e represent the total nitrogen content, cumulative ammonia emissions, and NH4+ content in the system, respectively. + -N content, NO3 - -N content and acid-hydrolyzed organic nitrogen content, where AAN, AN, ASN, and HUN represent amino acid nitrogen, ammonia nitrogen, amino sugar nitrogen, and acid-hydrolyzed unknown nitrogen, respectively. It can be seen that the experimental group with added bifunctional compound microbial inoculant (YN) can reduce nitrogen loss and increase compost nitrogen content. Specifically, the TN content in the YN group was 18.10% higher than that in the CK group. p <0.05); cumulative NH3 emissions were 28.92% lower than CK ( p <0.05); NH4 + -N content was 37.34% lower than CK ( p <0.05); NO3 - -N increased by 21.95% compared to CK ( p <0.05); the content of acid-hydrolyzed organic nitrogen was 7.57% higher than that of CK. This indicates that the addition of bifunctional compound microbial agent can effectively reduce ammonia emissions in composting and increase nitrogen retention in the system.

[0092] Further measurements were taken of humic acid (HA), fulvic acid (FA), and the HA / FA ratio in the compost of the two treatment groups. Specific results can be found in the table below. Figure 11 As shown in a, b, and c. The results indicate that the addition of YN bacterial agent significantly promotes humic acid synthesis ( p <0.05), the humic acid content in the YN group was 14.28% higher than that in the CK group; there was no significant difference in fulvic acid content between the two groups, but the YN group was 10.76% lower than that in the CK group; the HA / FA ratio in the YN group was 27.78% higher than that in the CK group ( p <0.05). This indicates that adding the bifunctional compound microbial agent can effectively promote humic acid synthesis, accelerate the composting process, and shorten the composting cycle.

[0093] Example 8: Effect of compound microbial agent YN1 with different strain ratios on composting QY6 and QN6 were inoculated into LB medium and cultured in a shaker at 170 rpm and 33°C until OD. 600 =0.80±0.10, seed liquid was obtained. QY6 and QN6 were compounded at a volume ratio of 2:1 to obtain a bifunctional microbial agent (YN1) that efficiently regulates nitrogen conversion in compost. A control group (CK) was set up: uninoculated compost residue; the treatment group (YN1) was inoculated with the bifunctional compound microbial agent YN1.

[0094] Mushroom residue was selected as the raw material, consisting of shiitake mushroom residue, oyster mushroom residue, and distiller's grains, mixed in a ratio of 9:7.16:1.8. The total organic matter (TOC) of the mixture was 484.67 g / kg, total organic matter (TN) was 16.07 g / kg, and the C / N ratio was 30.16. Each pile initially contained 30 kg of material with a moisture content of 55%. YN1 was added at a 1% (wet weight) inoculum concentration, while the control group received the same volume of sterile LB liquid culture medium. The mixture was thoroughly mixed with the mushroom residue before composting. The internal temperature of the compost pile was measured daily. The pile was turned and samples were taken on days 0, 2, 5, 9, 16, 23, 30, and 45 for a total of 45 days of composting.

[0095] The measurement results are as follows Figure 12 As shown, where, Figure 12 In the figure, a, b, c, d, and e represent the total nitrogen content, cumulative ammonia emissions, and NH4+ content in the system, respectively. + -N content, NO3 - -N content and acid-hydrolyzed organic nitrogen content were analyzed, with AAN, AN, ASN, and HUN representing amino acid nitrogen, ammonia nitrogen, amino sugar nitrogen, and acid-hydrolyzed unknown nitrogen, respectively. It can be seen that the addition of the bifunctional compound microbial agent (YN1) significantly promoted nitrogen retention in compost and improved the quality of the compost product. The TN content of the YN1 group was 24.78 g / kg, which was 23.32% higher than that of CK1. p <0.05); cumulative NH3 emissions were 35.17% lower than CK1 ( p <0.05); NH4 + -N content was 30.67% lower than CK1 ( p <0.05); NO3 - -N improved by 17.65% compared to CK1 ( p <0.05); the content of acid-hydrolyzed organic nitrogen was 16.89% higher than that of CK1 ( p <0.05).

[0096] Further measurements were taken of humic acid (HA), fulvic acid (FA), and the HA / FA ratio in the compost of the two treatment groups. Specific results can be found in the table below. Figure 13 As shown in a, b, and c. The results indicate that the addition of YN1 bacterial agent significantly promotes the polymerization of humic acid ( p <0.05), accelerating composting and humification. The humic acid content in group YN1 was 80.54 g / kg, which was 20.85% higher than that in group CK1 ( p <0.05); the fulvic acid content in group YN1 was 40.75 g / kg, which was not significantly different from that in group CK1; the HA / FA ratio in group YN was 1.99, which was 18.45% higher than that in group CK. p <0.05). This indicates that the addition of the bifunctional compound microbial agent YN1 can effectively promote humic acid synthesis, accelerate the composting and humification process, and shorten the composting cycle.

[0097] Example 9: Effect of Compound Microbial Agent YN in Industrial Composting Mushroom residue was selected as the raw material, consisting of shiitake mushroom residue, oyster mushroom residue, and distiller's grains, mixed in a ratio of 20:3:5. The resulting mixture had a TOC of 430.83 g / kg, a TN of 15.84 g / kg, and a C / N ratio of 27.20. Each pile initially contained 30 t of material with a moisture content of 50%. YN was added at a 1% (wet weight) inoculum concentration, while the control group received the same volume of sterile LB liquid culture medium. The mixture was thoroughly mixed with the mushroom residue before composting. The internal temperature of the compost pile was measured daily. For the first 10 days of composting, the pile was turned every 2 days; from days 11 to 30, every 5 days; and from days 30 to 62, every 10 days. Samples were taken to measure relevant indicators during each turn. The composting process lasted a total of 62 days.

[0098] The measurement results are as follows Figure 14 As shown, where, Figure 14 In the figure, a, b, c, d, and e represent the total nitrogen content, cumulative ammonia emissions, and NH4+ content in the system, respectively. + -N content, NO3 - -N content and acid-hydrolyzed organic nitrogen status, where AAN, AN, ASN, and HUN represent amino acid nitrogen, ammonia nitrogen, amino sugar nitrogen, and acid-hydrolyzed unknown nitrogen, respectively. It can be seen that adding 1% bifunctional compound microbial agent (YN) can promote nitrogen retention in large-scale microbial residue composting and has good functional stability. TN content was 22.36% higher than the control group. p <0.05); cumulative NH3 emissions were 22.64% lower than the control group ( p <0.05); NH4 + -N content was 18.31% lower than that of the control group. p <0.05); NO3 - -N increased by 6.67% compared to the control group; the content of acid-hydrolyzed organic nitrogen was 10.94% higher than that of the control group.

[0099] Further measurements were taken of humic acid (HA), fulvic acid (FA), and the HA / FA ratio in the compost of the two treatment groups. Specific results can be found in the table below. Figure 15 As shown in a, b, and c. The results indicate that adding 1% YN inoculant can promote the humification process, but there is no significant difference compared with the control group ( p >0.05). The humic acid content in the YN group was 6.36% higher than that in the CK group; the fulvic acid content was not significantly different between the two groups; the HA / FA ratio in the YN group was 1.91, which was 17.18% higher than that in the CK group. This indicates that adding 1% of the bifunctional compound microbial agent can effectively promote humic acid synthesis, accelerate the composting and humification process, and improve the quality of compost products.

[0100] Example 10: Effect of Compound Microbial Agent YN on Chicken Manure Composting Chicken manure compost was selected as the raw material, and rice straw was used to control the C / N ratio to 26.2:1. The resulting mixture had a TOC of 533.62 g / kg and a TN of 20.37 g / kg. Each pile initially contained 30 t of material with a moisture content of 53%. YN was added at a 2% (wet weight) inoculum concentration, while the control group received the same volume of sterile LB liquid culture medium. The mixture was thoroughly mixed with the materials before composting. The internal temperature of the compost pile was measured daily. For the first 10 days of composting, the pile was turned every 2 days; from days 11 to 30, every 5 days; and from days 30 to 62, every 10 days. Samples were taken to measure relevant indicators during the 62-day composting period.

[0101] The measurement results are as follows Figure 16 As shown, where, Figure 16 In the figure, a, b, c, d, and e represent the total nitrogen content, cumulative ammonia emissions, and NH4+ content in the system, respectively. + -N content, NO3 - -N content and acid-hydrolyzed organic nitrogen status, where AAN, AN, ASN, and HUN represent amino acid nitrogen, ammonia nitrogen, amino sugar nitrogen, and acid-hydrolyzed unknown nitrogen, respectively. It can be seen that the addition of the bifunctional compound microbial agent (YN) significantly promotes nitrogen retention in chicken manure compost. p <0.05), improving the quality of compost products. The TN content in the YN group was 25.53 g / kg, which was 29.39% higher than that in the CK group ( p <0.05); NH3 emissions were 26.59% lower than the control group ( p <0.05); NH4 + -N content was 26.74% lower than that of the control group. p <0.05); NO3 - -N increased by 16.18% compared to the control group ( p <0.05); the content of acid-hydrolyzed organic nitrogen was 16.92% higher than that of the control group ( p <0.05).

[0102] Further measurements were taken of humic acid (HA), fulvic acid (FA), and the HA / FA ratio in the compost of the two treatment groups. Specific results can be found in the table below. Figure 17 As shown in a, b, and c. The results indicate that adding 2% YN inoculant significantly promotes humic acid polymerization and accelerates composting and humification. p <0.05). The humic acid content in the YN group was 70.66 g / kg, which was 16.58% higher than that in the CK group. p <0.05); the fulvic acid content in the YN group was 5.65% lower than that in the CK group; the HA / FA ratio in the YN group was 2.06, which was 20.10% higher than that in the CK group ( p <0.05). This indicates that adding 2% bifunctional compound microbial agent can effectively promote humic acid synthesis and improve the quality of compost products.

[0103] Example 11: Effect of YNO, a compost product of compound microbial agent YN, on soil improvement. Preparation of compost product YNO: The compost product obtained from the YN treatment group in Example 5 was aged at room temperature for 15 days to promote its stability. The aged compost product was then ground and passed through a 5 mm sieve for later use.

[0104] Three treatments were set up: NAS (without compost product), CKS (with CKO), and YNS (with YNO). CKO was the final compost product obtained from the CK treatment group in Example 5, and its soil-improved group was designated CKS. YNO was the final compost product obtained from the YN treatment group in Example 5, and the soil improved using YNO was designated YNS. The compost product was mixed with the soil at a ratio of 5%, and 1.5 kg of the mixed soil (soil + compost product) was filled into each pot. Water was added to adjust the moisture content to 60%. The soil was watered regularly daily to adjust the soil moisture holding capacity (100 mL / pot once a day). After 30 days of outdoor cultivation, soil samples were taken to determine conventional indicators and nutrient content.

[0105] By comparing the changes in soil physicochemical properties and nutrient content after the soil improvement experiment, the results are shown in […]. Figure 18 As shown, where, Figure 18 In the equation, a, b, c, d, e, f, g, h, and i represent soil pH, soil electrical conductivity, soil organic matter ratio, total organic carbon content, available phosphorus content, available potassium content, available nitrogen content, total nitrogen content, and humic acid content, respectively. The results indicate that the application of YNO altered soil properties and significantly increased soil nutrient content (…). p <0.05). See also Figure 18 The application of compost products had no significant effect on soil pH, which remained around 7.40. Compared with other treatments, the soil EC in the YNS group was 35.29% and 9.52% higher, respectively. The higher EC indicates that the application of YNO enhanced soil activation capacity. The application of compost products significantly increased soil organic matter and total organic carbon content. p <0.05), compared with NAS, the soil organic matter and total organic carbon content in the YNS group were 73.51% and 175.09% higher, respectively; compared with other treatments, the available phosphorus content in the YNS group was 185.55% and 27.05% higher, respectively; the available potassium content in the YNS group was 298.26% higher than that in NAS. Applying YNO can increase the content of available nutrients in the soil, which is beneficial for crop absorption and utilization. Compared with other treatments, the available nitrogen content in the YNS group was 103.09% and 35.74% higher, respectively. Meanwhile, the soil TN content in the YNS group was 146.94% and 13.35% higher, respectively. pThe concentration of nitrogen (<0.05) indicates that the addition of YNO can promote soil nitrogen content, and the increased available nitrogen content is beneficial for plant nitrogen absorption. Compared with other treatments, the humic acid content in the YNS group was 138.94% and 12.97% higher, respectively. This increased content can inhibit the leaching of ionic nutrients and increase the proportion of available nutrients in the soil. These results demonstrate that the addition of YNO can effectively increase soil nutrient content and improve soil properties.

[0106] Example 12: Effect of applying compost product YNO to potted Chinese cabbage. Preparation of compost product YNO: The compost product obtained from the YN treatment group in Example 5 was aged at room temperature for 15 days to promote its stability. The aged compost product was then ground and passed through a 5 mm sieve for later use.

[0107] Three treatments were set up: NAP (without compost product), CKP (with CKO), and YNP (with YNO). CKO was the compost product obtained after final composting in the CK treatment group of Example 5, and its plant growth-promoting group was designated CKP. YNO was the compost product obtained after final composting in the YN treatment group of Example 5, and its plant growth-promoting group was designated YNP. The compost product was mixed with soil at a ratio of 5%, and 1.5 kg of the mixed soil (soil + compost product) was filled into each pot. Water was added to adjust the moisture content to 60%. One week after emergence, seedlings of equal size were transplanted into pots, and watering was carried out regularly to adjust soil moisture holding capacity (watering once a day, 100 mL / pot each time). After 30 days of outdoor cultivation, samples were taken to determine the agronomic traits and quality indicators of the Chinese cabbage.

[0108] See results Figure 19 As shown, where, Figure 19 In the diagram, a, b, c, d, e, f, g, and h represent plant height, root length, fresh biomass, dry biomass, chlorophyll content, soluble sugar content, soluble protein content, and total nitrogen content, respectively. The results showed that compared to the other treatments, the YNP group had plant heights that were 56.52% and 27.71% higher, and root lengths that were 70.94% and 36.44% higher, respectively. p <0.05); Biomass is a comprehensive indicator for assessing plant growth and soil fertility. Compared with other treatments, the biomass (fresh weight) of the YNP group was 70.81% and 36.80% higher, respectively, and the biomass (dry weight) was 42.34% and 17.30% higher, respectively, indicating that YNO compost products have a significant promoting effect on the growth and development of Chinese cabbage. p <0.05). Compared with the other treatments, the chlorophyll content of the YNP group was 15.00% and 6.98% higher, respectively, indicating that the application of YNO can effectively promote plant photosynthetic capacity and increase chlorophyll content. The soluble sugar content of the YNP group was 290.32% and 78.82% higher than that of the other groups, respectively. p<0.05), applying YNO is beneficial for the synthesis of soluble sugars and helps prevent Chinese cabbage from being subjected to external stress. The content of soluble protein directly affects the plant's osmotic regulation system and is a key indicator of the plant's drought resistance. Compared with other treatments, the soluble protein content of the YNP group was 23.97% and 3.18% higher, respectively, and the total nitrogen content of the plant was 18.42% and 14.43% higher, respectively. This indicates that applying YNO has a strong nitrogen supply capacity for the growth of Chinese cabbage, which is conducive to the absorption of nitrogen in the soil and its conversion into plant nitrogen. This can reduce nitrogen loss and improve the quality of Chinese cabbage.

[0109] Example 13: Effects of applying compost product YNO in rapeseed fields Preparation of compost product YNO: The compost product obtained from the YN treatment group in Example 6 was aged at room temperature for 15 days to promote its stability. The aged compost product was then ground and passed through a 5 mm sieve for later use.

[0110] The obtained compost product was aged at room temperature for 15 days to promote its stability. After aging, the compost product was ground and passed through a 5mm sieve for later use. Three treatments were set up: NAP1 (no compost product added), CKP1 (CKO added), and YNP1 (YNO added). CKO was the compost product obtained after the final composting of the CK treatment group in Example 6, and its plant growth promotion group was designated as CKP1. YNO was the compost product obtained after the final composting of the YN treatment group in Example 6, and the plant growth promotion group using YNO was designated as YNP1. The compost product was applied at a ratio of 50 g / plant before seedling transplanting. Except for the addition of compost product, all other conditions were the same, and the results were measured on the whole rapeseed plant at maturity.

[0111] See results Figure 20 As shown, where, Figure 20 In the figure, a, b, c, d, e, f, g, and h represent plant height, root length, thousand-grain weight, oil content, chlorophyll content, soluble sugar content, soluble protein content, and total nitrogen content of the plant, respectively. The results showed that, compared with the control group, the addition of YNO significantly promoted the growth of rapeseed. p <0.05). Compared with other treatments, the rapeseed plant height in the YNP1 group was 7.49% and 3.35% higher, respectively, and the root length was 36.30% and 13.77% higher, respectively. Thousand-seed weight is an important indicator of rapeseed seed development and quality; its increase signifies a significant improvement in the accumulation of nutrients in the seeds, which directly affects rapeseed yield and oil content. Compared with other treatments, the thousand-seed weight in the YNP1 group was 27.96% and 16.62% higher, respectively. p<0.05), with oil content 16.28% and 6.38% higher, respectively, indicating that the application of compost product YNO can effectively improve the economic benefits of rapeseed. Chlorophyll is an important indicator reflecting plant photosynthesis, and its content can characterize the photosynthetic efficiency and growth potential of plant leaves. Compared with other treatments, the chlorophyll content of the YNP1 group increased by 21.33% and 6.43%, respectively. The soluble sugar content of the YNP1 group was 20.98% and 4.77% higher than that of NAP1 and CKP1, respectively, indicating that compost product YNO can promote the synthesis of soluble sugars to enhance the plant's stress resistance. Soluble protein, as an important osmotic regulator in plants, plays an important role in cell water retention and biomembrane protection. Compared with other treatments, the soluble protein content of the YNP1 group was 28.53% and 10.32% higher, respectively, and the total nitrogen content of the plant was 26.93% and 10.02% higher, respectively, indicating that compost product YNO can enhance the nitrogen use efficiency of rapeseed, reduce nitrogen loss, and thus improve crop quality.

[0112] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A soil-borne short-spore bacillus with ammonia-oxidizing ability ( Brevibacillus agri ), characterized in that, The strain is QN6, which was deposited on December 23, 2024, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 33138.

2. A compound bacterial agent for ammonia assimilation and ammonia oxidation, characterized in that, The product comprises the soil brevicorbacterium QN6 as described in claim 1, and further comprises a composting brevicorbacterium ( Bacillus stercoris QY6, in the compound microbial agent, QY6 and QN6 respectively promote the transformation of NH4⁺-N in the composting system through ammonia assimilation and ammonia oxidation, thereby reducing ammonia volatilization in composting, improving nitrogen retention efficiency, and promoting humification; wherein, the composting Bacillus QY6 was deposited on December 23, 2024 at the China General Microbiological Culture Collection Center, depositary address: Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, accession number CGMCC No. 33139.

3. The compound microbial agent according to claim 2, characterized in that, The compound microbial agent is prepared by mixing QN6 and QY6 in a volume ratio of 1 to 2:1, and its effective viable count is not less than 1 × 10⁻⁶. 8 cfu / mL.

4. The application of the soil brevicorbacterium as described in claim 1 or the compound microbial agent as described in any one of claims 2-3 in the field of composting.

5. The application according to claim 4, characterized in that, The applications include the preparation of composting agents, soil conditioners, crop growth promoters, or bio-organic fertilizers.

6. A composting method, characterized in that, Inoculate the compost raw materials with the soil-borne short-spore bacillus as described in claim 1 or the compound microbial agent as described in any one of claims 2-3.

7. A compost product, characterized in that, It is prepared by the composting method described in claim 6.

8. A method for soil improvement and promoting crop growth, characterized in that, The compost product as described in claim 7 and the bio-organic fertilizer product prepared using QN6 are applied to soil or crop cultivation systems.

9. The method according to claim 8, characterized in that, The crops are selected from rice, rapeseed, and nitrate-nitrogen-loving crops; wherein, the nitrate-nitrogen-loving crops include radish, carrot, tomato, eggplant, pepper, leek, scallion, onion, leek, spinach, celery, amaranth, lettuce, garland chrysanthemum, daylily, corn, or soybean.

10. The application of the *Bacillus brevis* of claim 1 or the compound microbial agent of any one of claims 2-3 in any of the following, comprising: Promotes nitrogen retention in compost; Promotes composting and humification; Soil improvement; Preparation of bio-organic fertilizer; or Promotes crop growth.

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