Microbial fertilizer and application thereof in improving carbon sequestration capacity of white clay soil and promoting straw decomposition

Abstract

The application discloses a kind of microbial fertilizer and its in improving white pulp soil carbon sequestration capacity and application in promoting straw decomposition, belong to the technical field of microbial fertilizer.The microbial fertilizer includes organic matter, biochar, microbial inoculant, trace element and microbial activator;The microbial inoculant includes bacillus ND2 and bacillus megaterium CICC 22681;The microbial activator includes fulvic acid, gamma-polyglutamic acid and sorbitol.The microbial fertilizer of the application has the dual function of white pulp soil improvement and straw decomposition, can accelerate straw decomposition, improve white pulp soil structure, improve soil fertility and carbon sequestration capacity, help agricultural waste resourceization and soil quality improvement collaborative development, in white pulp soil area or other barren soil area in future agricultural production, it is expected to become important technical support for promoting sustainable development of ecological agriculture, and application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of microbial fertilizer technology, and in particular to a microbial fertilizer and its application in improving the carbon sequestration capacity of alkaline soil and promoting straw decomposition. Background Technology

[0002] Albic soil is a type of barrier soil with a unique profile structure, mainly distributed in Northeast and North my country. Its internal albic layer can cause various serious harms to plant growth. For example, the dense and compact albic layer forms a physical barrier, making it difficult for the taproots of deep-rooted crops such as corn and soybeans to penetrate, typically limiting root depth to less than 20 cm. This significantly reduces the number of secondary roots, leading to decreased lodging resistance. During the rainy season, the albic layer hinders water infiltration, easily forming a temporary water-holding layer in the soil, causing surface water accumulation and leading to root hypoxia and rot. During the dry season, the underlying clay layer further impedes vertical water movement, reducing the soil's water retention capacity by 60% compared to sandy loam, resulting in severe water stress for crops during critical growth stages (such as wheat heading). Furthermore, albic soil generally has an organic matter content below 1.5%, is deficient in available phosphorus and potassium, and has a high ammonium nitrogen fixation rate of up to 75%, leading to nitrogen malnutrition in crops. At the same time, the effective zinc content is often below the critical value, which can easily lead to nutrient deficiency diseases such as "white seedling disease" in corn.

[0003] Currently, the main methods for improving albic soil include physical, chemical, and biological methods. Physical methods, such as deep loosening, can break up the albic layer, but they have problems such as high cost and limited lasting effect. Chemical agents, such as lime, can adjust soil pH, but long-term use can easily cause soil compaction and secondary salinization.

[0004] With the continuous increase in agricultural waste, the resource utilization of organic waste such as straw has become an important direction for sustainable agricultural development. Although the application of straw return to the field has broad prospects, there are still some problems that need to be addressed in practical applications, mainly including low biodegradation efficiency and susceptibility to pests. In cold northern regions, the low temperature and drought conditions after the autumn harvest can prevent straw from fully decomposing before the following year's sowing. In albic soils, due to the dense soil structure and harsh microbial living environment, incomplete decomposition and poor integration with the soil are prone to occur, and even lead to pore blockage, further affecting the aeration of albic soils. These problems have become the main factors restricting the improvement of albic soils and the return of straw to the field. In existing technologies, soil conditioners and straw decomposition agents are mostly used separately, with single functions, and cannot simultaneously achieve straw decomposition and soil improvement. The implementation of multiple measures will undoubtedly increase the burden on the soil. Therefore, developing a microbial fertilizer with multiple functions such as improving albic soils, promoting straw decomposition, and increasing carbon sequestration is of great practical significance for the synergistic development of simultaneously improving soil quality and utilizing agricultural waste resources. Summary of the Invention

[0005] The purpose of this invention is to provide a microbial fertilizer and its application in improving the carbon sequestration capacity of alkaline soil and promoting straw decomposition, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a microbial fertilizer, which comprises the following raw materials in parts by weight: Organic matter 30-45 parts, biochar 25-35 parts, microbial inoculant 8-15 parts, trace elements 3-7 parts, and microbial activator 1-3 parts; The microbial agent contains Bacillus ( Bacillus sp.) ND2 and Bacillus megaterium ( Bacillus megaterium CICC 22681; The microbial activators include humic acid, γ-polyglutamic acid, and sorbitol.

[0007] Furthermore, the total viable count of the microbial agent is 1-9 × 10⁻⁶. 9 CFU / mL; the Bacillus ( Bacillus sp.) ND2 and the aforementioned Bacillus megaterium ( Bacillus megaterium The ratio of viable bacteria in CICC 22681 is 1:1.

[0008] Optionally, the trace elements include copper humate, zinc molybdate, and boric acid; the mass ratio of copper humate, zinc molybdate, and boric acid is (1-3):1:(0.1-0.6).

[0009] Furthermore, in the microbial activator, the mass ratio of the fulvic acid, the γ-polyglutamic acid and the sorbitol is 1:(3-6):(2-4).

[0010] Optionally, the organic matter includes one or more of straw, soybean meal, and mushroom residue.

[0011] The present invention also provides a method for preparing the above-mentioned microbial fertilizer, comprising the following steps: (1) Microbial inoculants are mixed with organic matter, trace elements and biochar, and fermented twice to obtain fermented materials; (2) The fermented material is mixed with a microbial activator to obtain the microbial fertilizer.

[0012] Furthermore, the fermentation process is as follows: the temperature of the first fermentation is 30-35℃, and the fermentation time is 36-60h; the temperature of the second fermentation is 25-28℃, and the fermentation time is 6-9d.

[0013] Furthermore, before mixing the fermentation material with the microbial activator, the fermentation material is dried to a moisture content of 8%-10%.

[0014] The present invention also provides an application of the above-mentioned microbial fertilizer in the improvement of albic soil, wherein the albic soil improvement includes improving the carbon sequestration capacity of albic soil and improving the soil structure of albic soil.

[0015] The present invention also provides an application of the above-mentioned microbial fertilizer in promoting straw decomposition.

[0016] The present invention discloses the following technical effects: The microbial fertilizer of this invention is composed of organic matter, biochar, microbial agents, trace elements, and microbial activators. Among them, Bacillus ND2 and Bacillus megaterium CICC 22681 are core components, which can efficiently decompose straw cellulose, hemicellulose, and lignin, improving straw decomposition rate and nutrient release rate, and improving soil microecology. The compound activator of fulvic acid, γ-polyglutamic acid, and sorbitol can enhance the activity and survival time of the strains, strengthen the decomposition and improvement effects, and improve the physiological activity of microorganisms in harsh environments such as alkaline soils. Organic matter provides energy for the microorganisms and, after degradation, can replenish soil organic matter. Biochar loosens the soil, reduces bulk density, adsorbs nutrients to reduce loss, and optimizes the microbial living environment. Trace elements can activate the enzyme activity of the strains and replenish deficient elements in the soil.

[0017] This invention's microbial fertilizer combines the dual functions of improving albic soil and composting straw. With a scientifically formulated raw material ratio and simple preparation process, it is suitable for albic soil distribution areas such as Northeast and North China. This fertilizer accelerates straw composting, improves albic soil structure, and enhances soil fertility and carbon sequestration capacity, promoting the coordinated development of agricultural waste resource utilization and soil quality improvement. In the future, it is expected to become an important technological support for promoting the sustainable development of ecological agriculture in albic soil areas or other infertile soil regions, with broad application prospects. Detailed Implementation

[0018] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0019] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0020] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0021] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0022] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0023] The Bacillus involved in the following examples ( Bacillus sp.) ND2 was isolated, identified, and preserved by the College of Agriculture, Heilongjiang Bayi Agricultural Reclamation University, and has been disclosed in the literature "[1] Wang Y, Zhang M, Lu L, et al. Effects of rot-promoting bacteria on decomposition characteristics of corn straw and springsoybean yield in Saline-alkali Land[J]. FRONTIERS IN PLANT SCIENCE, 2025, 16(000).DOI:10.3389 / fpls.2025.1572868.". The following examples involve Bacillus megaterium ( Bacillus megaterium CICC 22681, Bacillus amyloliquefaciens ( Bacillus amyloliquefaciens CICC 10080, Bacillus licheniformis ( Bacillus licheniformis CICC 10037 can be purchased from the China Industrial Microbial Culture Collection Center.

[0024] The calculation methods for the degree of straw decomposition involved in the following examples are based on the method in "[1] Wang Y, Zhang M, Lu L, et al. Effects of rot-promoting bacteria on decomposition characteristics of corn straw and spring soybean yield in Saline-alkali Land[J]. FRONTIERS IN PLANT SCIENCE, 2025, 16(000).DOI:10.3389 / fpls.2025.1572868."

[0025] The inventors' team previously isolated a strain of Bacillus ( Bacillus The strain ND2 was tested and found to promote the decomposition of straw in saline-alkali soil. Based on this, the inventors further investigated whether it had the same effect in alkaline soil and developed a microbial fertilizer that can be used for straw decomposition in alkaline soil. Some of the research process is shown in the following examples.

[0026] Example 1 This embodiment tested the promoting effect of Bacillus ND2 on straw decomposition in alkaline soil. The specific process is as follows: Single colonies of Bacillus ND2 preserved on slant agar were picked and transferred to LB liquid medium. After 24 hours of shaking incubation, they were transferred to PDA medium and cultured until OD200. 600 ≥0.8; collect bacterial cells by centrifugation, and adjust the bacterial concentration to 4×10 using sterile water. 9 CFU / mL. 20-30cm of albic soil was collected from the albic soil area of ​​Zhaodong, Heilongjiang Province, and placed in 25cm deep pots. 60g of corn stalks (3-5cm long) were placed in a nylon mesh bag; the stalks were then soaked in the bacterial solution. After the stalks were completely moistened, the bag was buried in the albic soil. Before covering with soil, urea solution was sprayed according to the C / N ratio of the stalks, adjusting to 30:1. A blank control group was set up, using sterile water instead of the bacterial solution. The experiment lasted for 25 days.

[0027] After the experiment, the degree of straw decomposition (including straw decomposition rate, straw nutrient release rate, and straw cellulose degradation rate, hemicellulose degradation rate, and lignin degradation rate) and the improvement of soil nutrients (soil organic carbon growth rate) were measured. The detection and calculation methods for each indicator are as follows: a. Straw decomposition rate Straw decomposition rate (%) = (W1 - W2) / W1 × 100%; In the formula, W1 is the original weight of straw (g); W2 is the weight of straw after decomposition (g).

[0028] b. Lignin, cellulose, and hemicellulose in straw Cellulose, hemicellulose, and lignin in straw were determined using a modified Van Soest washing fiber method. The degradation rates of cellulose, hemicellulose, and lignin after the experiment were calculated compared to before the experiment.

[0029] c. Soil organic carbon content The organic carbon content of soil samples was determined using a Shimadzu TOC-L analyzer. The increase rate of soil organic carbon after the experiment was calculated compared with that before the experiment.

[0030] The results are shown in Table 1. It can be seen that, compared with the blank control, Bacillus ND2 has a certain promoting effect on the decomposition of corn straw in alkaline soil.

[0031] Table 1. Effect of Bacillus ND2 on the composting of straw in alkaline soil. Example 2 Since the effect of Bacillus ND2 alone on the decomposition of straw in alkaline soil did not meet expectations, this embodiment developed a microbial fertilizer based on Bacillus ND2.

[0032] This example investigated the effects of different bacterial strains combined with Bacillus ND2 on the straw composting effect in alkaline soil, aiming to prepare a microbial inoculant with better straw composting effect in alkaline soil. The specific process is as follows: Bacillus megaterium CICC 22681, Bacillus amyloliquefaciens CICC 10080, and Bacillus licheniformis CICC10037 were respectively compounded with Bacillus ND2. Bacterial solutions were prepared according to the method in Example 1, and the concentration of each solution was adjusted to 4 × 10⁻⁶. 9 CFU / mL was mixed at a volume ratio of 1:1 to prepare a compound microbial agent. Following the method in Example 1, a straw decomposition experiment was conducted using the compound microbial agent, and the degree of straw decomposition (including straw decomposition rate, straw nutrient release rate, straw cellulose degradation rate, hemicellulose degradation rate, and lignin degradation rate) and soil nutrient improvement (soil organic carbon growth rate) were measured.

[0033] The results are shown in Table 2. It can be seen that the microbial agent obtained by combining Bacillus megaterium CICC 22681 and Bacillus ND2 has the best effect on the decomposition of alkaline soil straw, and is better than that of a single strain.

[0034] Table 2. Effects of different compound microbial agents on straw composting in alkaline soil. Example 3 The dense structure of alkaline soil provides a harsh environment for microbial survival, limiting microbial growth and resulting in poor composting. Therefore, improving the physiological activity of microorganisms in alkaline soil is crucial for enhancing straw composting. This example investigated the effects of different substances on microbial activity, as detailed below: Single colonies of Bacillus ND2 and Bacillus megaterium CICC 22681 preserved on slant agar were picked and transferred to LB liquid medium. After 24 hours of shaking incubation, they were transferred to PDA medium and cultured until OD500. 600 ≥0.8; collect bacterial cells by centrifugation, and adjust the bacterial concentration to 4×10 using sterile water. 9 CFU / mL. A compound microbial agent was prepared by mixing two bacterial solutions at a volume ratio of 1:1. The compound microbial agent was inoculated at a 10% (v / v) inoculum into LB liquid medium containing different active substances (fulvic acid, γ-polyglutamic acid, sorbitol, or mannitol, all with a final concentration of 10 mg / mL). After inoculation, the medium was incubated at 200 rpm and 25°C for 24 h. Samples were taken at 6, 12, and 24 h, and the viable cell count (CFU / mL) of each group was determined using the serial dilution plate counting method.

[0035] The results are shown in Table 3. It can be seen that among the substances, sorbitol has the best effect on microbial activity, followed by γ-polyglutamic acid, fulvic acid, and mannitol.

[0036] Table 3. Statistical results of viable bacterial counts of strains in different culture media (×10⁻¹⁰) 9 CFU / mL Example 4 Based on the research results of Examples 2 and 3, this invention pre-develops a microbial fertilizer. Several groups of microbial fertilizers were designed, and the optimal microbial fertilizer was selected by testing their effect on the decomposition of straw in alkaline soil. The specific process is as follows: Set up the following groups of microbial fertilizers: Group A: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 in a 1:1 ratio for viable bacteria count, with a total viable bacteria count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and sorbitol in a mass ratio of 1:5:3.

[0037] Group B: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is Bacillus ND2 inoculant with a total viable count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and sorbitol in a mass ratio of 1:5:3.

[0038] Group C: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is Bacillus megaterium CICC 22681 inoculant with a total viable count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and sorbitol in a mass ratio of 1:5:3.

[0039] Group D: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 in a 1:1 ratio for viable bacteria count, with a total viable bacteria count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and mannitol in a mass ratio of 1:5:3.

[0040] Group E: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 in a 1:1 ratio for viable bacteria count, with a total viable bacteria count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; the microbial activator was γ-polyglutamic acid.

[0041] Group F: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 in a 1:1 ratio for viable bacteria count, with a total viable bacteria count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; the microbial activator was sorbitol.

[0042] Group G: By weight, it includes the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter is obtained by mixing straw and soybean residue in a 2:1 mass ratio; the microbial inoculant is obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 in a 1:1 ratio for viable bacteria count, with a total viable bacteria count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; microbial activator was obtained by mixing γ-polyglutamic acid and sorbitol in a mass ratio of 5:3.

[0043] The preparation method of the above-mentioned microbial fertilizer is as follows: Crush straw to 2-3 mm and mix it with soybean residue with a moisture content ≤15% to obtain organic matter; mix the organic matter with trace elements and biochar evenly, and then inoculate with microbial inoculants. First, ferment at 30-35℃ for 48 hours, then lower the temperature to 25-28℃ for 7 days; dry the fermented material at a low temperature (40-45℃) until the moisture content is 8%-10%. Mix the dried material evenly with a microbial activator to obtain the microbial fertilizer.

[0044] Following the experimental method of Example 1, the functions of the microbial fertilizers in each group were tested: Topsoil from the albic soil area of ​​Zhaodong, Heilongjiang Province (0-20cm depth) was collected and placed in pots 25cm deep. A suspension of the microbial fertilizer to corn stalks was prepared using sterile water at a ratio of 1g:10mL, with a mass ratio of 0.5:60. This suspension was evenly sprayed onto the corn stalks, which were then placed in nylon mesh bags. The moisture content was adjusted to 50%-55% with sterile water, and the bags were buried in the albic soil. Before covering with soil, urea solution was sprayed according to the straw C / N ratio, adjusting it to 30:1. Sterile water was used as a blank control instead of the suspension. The experiment lasted 25 days. After the experiment, following the method of Example 1, the degree of straw decomposition (including straw decomposition rate, straw nutrient release rate, and straw cellulose degradation rate, hemicellulose degradation rate, and lignin degradation rate) and the improvement of soil nutrients (soil organic carbon growth rate) were measured.

[0045] The results are shown in Table 4. It can be seen that in the microbial fertilizer system, the combined use of Bacillus ND2 and Bacillus megaterium CICC22681 achieved better results in improving alkaline soil and composting straw. The results also indicate that the composition of the microbial activator also has a certain impact on the improvement of alkaline soil and the composting effect of straw; the best effect is achieved when fulvic acid, γ-polyglutamic acid, and mannitol are used in combination.

[0046] Table 4. Effects of different microbial fertilizers on the composting of straw in alkaline soil. Example 5 A field trial was conducted based on the research results of the microbial fertilizer in Group A of Example 4. Field plots with a topsoil layer of 20-40cm thick albic soil were selected as experimental plots and randomly divided into 4 plots, each 20m². 2 The groups were designated as a blank control group, Experiment 1, Experiment 2, and Experiment 3. The microbial fertilizers used in Experiments 1 through 3 were as follows: Experiment 1: The microbial fertilizer, by weight, included the following raw materials: 40 parts organic matter, 30 parts biochar, 12 parts microbial inoculant, 5 parts trace elements, and 2 parts microbial activator. The organic matter was obtained by mixing straw and soybean residue at a mass ratio of 2:1; the microbial inoculant was obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 at a viable count ratio of 1:1, with a total viable count of 5 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 2:1:0.5; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and sorbitol in a mass ratio of 1:5:3.

[0047] Experiment 2: The microbial fertilizer, by weight, included the following raw materials: 30 parts organic matter, 35 parts biochar, 15 parts microbial inoculant, 7 parts trace elements, and 3 parts microbial activator. The organic matter was obtained by mixing straw and soybean residue at a mass ratio of 2:1; the microbial inoculant was obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 at a viable count ratio of 1:1, with a total viable count of 1×10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 1:1:0.6; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and sorbitol in a mass ratio of 1:3:4.

[0048] Experimental Group 3: The microbial fertilizer, by weight, included the following raw materials: 45 parts organic matter, 25 parts biochar, 8 parts microbial inoculant, 3 parts trace elements, and 1 part microbial activator. The organic matter was obtained by mixing straw and soybean residue at a mass ratio of 2:1; the microbial inoculant was obtained by mixing Bacillus ND2 and Bacillus megaterium CICC 22681 at a viable count ratio of 1:1, with a total viable count of 9 × 10⁻⁶. 9 CFU / mL; trace elements were obtained by mixing copper humate, zinc molybdate, and boric acid in a mass ratio of 3:1:0.1; microbial activator was obtained by mixing fulvic acid, γ-polyglutamic acid, and sorbitol in a mass ratio of 1:6:2.

[0049] Before the experiment, soil samples were collected from the top 0-20 cm layer to test soil bulk density and soil carbon content. Corn stalks were collected, shredded to a length of less than 5 cm, and evenly spread on the experimental field at a dosage of 500 kg / mu. Microbial fertilizer was prepared into a suspension with sterile water at a ratio of 1 g:10 mL, and evenly sprayed onto the corn stalks. After mixing thoroughly, the soil was deeply tilled in the 0-40 cm layer to incorporate the stalks into the soil. The blank control group used sterile water instead of the suspension. After treatment, soybeans (Nongqingdou 28) were sown. Fertilization and irrigation during soybean cultivation were carried out according to local conventional management practices. The experiment lasted throughout the soybean growth period. After the experiment, soil samples were collected from the bottom 20-40 cm layer to test soil bulk density and soil organic carbon content. Based on the soil bulk density and carbon content data measured before and after the experiment, the rate of change in soil bulk density and carbon content were calculated.

[0050] The results are shown in Table 5. It can be seen that the soil bulk density change rate in the blank control group was positive, indicating that directly returning straw to the albic soil without the use of microbial fertilizer may increase the soil burden. The carbon content in the blank control group increased, indicating that although it imposed a certain burden on the soil, the straw could still decompose due to the action of the microorganisms in the albic soil, thereby improving carbon sequestration. Compared with the blank control group, the soil bulk density change rate in Experiments 1-3 was negative, indicating that the soil bulk density decreased, the soil was more loose and permeable than before the experiment, and the carbon content also increased significantly. This shows that the microbial fertilizer of the present invention can improve the soil structure of albic soil and increase carbon sequestration by promoting straw decomposition.

[0051] Table 5. Results of the effects of different microbial fertilizers on soil bulk density and carbon content. The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A microbial fertilizer, characterized in that, The microbial fertilizer comprises the following raw materials in parts by weight: Organic matter 30-45 parts, biochar 25-35 parts, microbial inoculant 8-15 parts, trace elements 3-7 parts, and microbial activator 1-3 parts; The microbial agent contains Bacillus ( Bacillus sp.) ND2 and Bacillus megaterium ( Bacillus megaterium CICC 22681; The microbial activators include humic acid, γ-polyglutamic acid, and sorbitol.

2. The microbial fertilizer according to claim 1, characterized in that, The total viable count of the microbial agent is 1-9 × 10⁻⁹. 9 CFU / mL; the Bacillus ( Bacillus sp.) ND2 and the aforementioned Bacillus megaterium ( Bacillus megaterium The ratio of viable bacteria in CICC 22681 is 1:

1.

3. The microbial fertilizer according to claim 1, characterized in that, The trace elements include copper humate, zinc molybdate, and boric acid; the mass ratio of copper humate, zinc molybdate, and boric acid is (1-3):1:(0.1-0.6).

4. The microbial fertilizer according to claim 1, characterized in that, In the microbial activator, the mass ratio of fulvic acid, γ-polyglutamic acid and sorbitol is 1:(3-6):(2-4).

5. The microbial fertilizer according to claim 1, characterized in that, The organic matter includes one or more of straw, soybean meal, and mushroom residue.

6. A method for preparing microbial fertilizer according to any one of claims 1-5, characterized in that, Includes the following steps: (1) The microbial agent is mixed with organic matter, trace elements and biochar and subjected to two fermentation processes to obtain fermented material; (2) The fermented material is mixed with a microbial activator to obtain the microbial fertilizer.

7. The preparation method according to claim 6, characterized in that, The fermentation process is as follows: the temperature of the first fermentation is 30-35℃, and the fermentation time is 36-60h; the temperature of the second fermentation is 25-28℃, and the fermentation time is 6-9d.

8. The preparation method according to claim 6, characterized in that, Before mixing the fermentation material with the microbial activator, the fermentation material is dried to a moisture content of 8%-10%.

9. The application of the microbial fertilizer according to any one of claims 1-5 in the improvement of alkaline soil, characterized in that, The improvement of albic soil includes enhancing the carbon sequestration capacity of albic soil and improving the soil structure of albic soil.

10. The application of the microbial fertilizer according to any one of claims 1-5 in promoting straw decomposition.

Images