Soil granulation remediation type fertilizer based on microbial induced mineralization and in-situ cross-linking of eps and preparation method thereof

Abstract

This invention discloses a soil aggregate remediation fertilizer based on microbial-induced mineralization and in-situ crosslinking of EPS, and its preparation method, belonging to the field of soil remediation fertilizers. This invention aims to solve the technical problems of existing technologies for remediating degraded black soil, such as limited functionality, poor environmental adaptability, and difficulty in simultaneously improving soil structural stability and fertility. The fertilizer consists of a specific ratio of corn cob powder, beet pulp, distiller's grains, pine needle powder, straw, diatomaceous earth, bentonite, humic acid, compound functional microbial agents, and trace elements. The preparation method involves CO₂-protected modified straw, activated mineral carriers, compound mineralization promoting components, and synergistic fermentation using an EPS in-situ crosslinking inducer and compound functional microbial agents. This fertilizer is mainly used to repair the aggregate structure of degraded black soil, increase soil organic matter content, improve porosity and erosion resistance, and promote crop growth.

Description

Technical Field

[0001] This invention relates to the field of soil remediation fertilizers, specifically to a soil aggregate remediation fertilizer based on microbial induced mineralization and in-situ crosslinking of EPS and its preparation method. Background Technology

[0002] Soil, as the core carrier of agricultural production, is a key resource for maintaining food security and ecological balance. Northeast my country's cold black soil region, one of the world's four major black soil regions, is an important commodity grain production base for our country. However, in recent years, due to the combined effects of long-term high-intensity farming, unreasonable fertilization patterns, and the intensified freeze-thaw cycle caused by climate warming, the Northeast black soil region faces serious soil degradation problems.

[0003] The degradation of black soil in Northeast China is mainly manifested in key issues such as the disintegration of soil aggregate structure, unbalanced porosity distribution, a year-by-year decline in organic matter content, and weakened erosion resistance. Long-term continuous cropping and mechanical compaction have led to the destruction of black soil aggregate structure. The content of water-stable aggregates >0.25mm has decreased from over 50% under natural conditions to below 30%, soil bulk density has increased to over 1.4g / cm³, porosity has significantly decreased, aeration and permeability have deteriorated, restricting crop root extension and exacerbating water erosion caused by spring snowmelt runoff and summer torrential rains, resulting in the loss of the topsoil at a rate of 0.3-0.5cm per year. Furthermore, the excessive and singular application of traditional chemical fertilizers has disrupted the soil micro-ecological balance, inhibited the activity of native beneficial microorganisms, accelerated the decomposition of soil organic matter, and highlighted nutrient imbalance, further aggravating soil compaction and degradation, forming a vicious cycle of "degradation-low yield-excessive fertilization-further degradation."

[0004] To address soil degradation, microbial inoculants, with their dual functions of nutrient supply and soil remediation, have become a research hotspot for sustainable agricultural development. Through the metabolic activities of functional microorganisms, microbial inoculants secrete extracellular polysaccharides (EPS), organic acids, enzymes, and other substances, promoting the cementation of soil particles into stable aggregates, activating inert soil nutrients, and improving the soil's micro-ecological environment. However, existing microbial inoculants still face numerous technical bottlenecks in their application in the cold black soil of Northeast China, failing to meet practical needs. Firstly, insufficient strain compatibility is a core issue: existing inoculants mostly use general-purpose strains, without screening for local, stress-resistant strains specific to the low temperatures and frequent freeze-thaw cycles of Northeast China. This results in a loss rate of over 60% of the strain's activity in low-temperature winter conditions, and a sharp decline in viable bacteria count after freeze-thaw cycles, failing to achieve long-term remediation effects. Secondly, the repair mechanism is singular: most microbial fertilizers only focus on nutrient conversion function, ignoring the most urgent need for aggregate structure repair in cold black soil. They lack the design for the synergistic effect of microbial induced mineralization and EPS in-situ cross-linking, making it difficult to fundamentally solve the pain points of aggregate disintegration and weak erosion resistance.

[0005] Furthermore, existing microbial fertilizers have significant shortcomings in raw material selection: some raw materials rely on external procurement, which not only increases production costs but also affects remediation effectiveness due to poor raw material compatibility; simultaneously, the raw material pretreatment process is simple and not optimized for the characteristics of cold-region soils, resulting in insufficient performance of microbial colonization carriers, low mineralization reaction efficiency, and difficulty in fully realizing EPS cross-linking effects. Moreover, existing technologies do not fully consider the impact of freeze-thaw cycles in cold-region black soils on the stability of microbial fertilizers, lack an effective freeze-thaw protection system, and result in poor microbial activity and functional sustainability, leading to short-lived and unstable remediation effects.

[0006] Therefore, developing a microbial fertilizer that is adapted to the climate and soil characteristics of the cold black soil region in Northeast China, with localized and stress-resistant microbial strains, readily available raw materials, and a synergistic and efficient remediation mechanism, and specifically addresses core issues such as the disintegration of black soil aggregates, loss of microbial activity at low temperatures, and weak resistance to erosion, is of great practical significance and application value for curbing black soil degradation, improving soil fertility, and ensuring regional food security. It is also a technological direction that urgently needs to be broken through in the field of microbial fertilizers. Summary of the Invention

[0007] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0008] One objective of this invention is to address the problems of existing soil remediation materials having limited remediation functions, poor environmental adaptability, and high raw material costs.

[0009] One objective of this invention is to address the problems of insufficient carrier performance, difficulty in synergistic function of microbial communities, and unstable repair effects in existing microbial fertilizer preparation processes.

[0010] One objective of this invention is to provide a soil aggregate remediation fertilizer based on microbial induced mineralization and in-situ crosslinking of EPS. The soil aggregate remediation fertilizer, by weight, is composed of 28-38 parts corn cob powder, 12-22 parts beet pulp, 9-15 parts distillers' grains, 7-11 parts pine needle powder, 7-11 parts diatomaceous earth, 5-7 parts bentonite, 4-6 parts humic acid, 6-10 parts corn stalks, 6-9 parts soybean stalks, 2-4 parts compound functional microbial agent, and 1-2 parts trace elements.

[0011] Preferably, the soil aggregate repair fertilizer comprises, by weight, 30-35 parts corn cob powder, 15-20 parts beet pulp, 10-13 parts distiller's grains, 8-10 parts pine needle powder, 8-10 parts diatomaceous earth, 5-6 parts bentonite, 4-5 parts humic acid, 7-9 parts corn stalks, 7-8 parts soybean stalks, 2-3 parts compound functional microbial agent, and 1-2 parts trace elements.

[0012] Preferably, the soil aggregate repair fertilizer is composed of, by weight, 33 parts corn cob powder, 18 parts beet pulp, 12 parts distiller's grains, 9 parts pine needle powder, 9 parts diatomaceous earth, 6 parts bentonite, 5 parts humic acid, 8 parts corn stalks, 7 parts soybean stalks, 3 parts compound functional microbial agent, and 1.5 parts trace elements.

[0013] Preferably, in the soil aggregate remediation fertilizer, the compound functional microbial agent is composed of cyanobacteria, actinomycetes, yeast, and lactic acid bacteria in a weight ratio of 1:1:1:1; wherein the cyanobacteria have an EPS production capacity ≥2.2 g / L and nitrogenase activity ≥35 nmol / (h•mL); the actinomycetes are Streptomyces, with urease activity ≥18 U / mL and mineralization induction rate ≥40%; the microbial agent has a moisture content ≤5% and a total effective viable count ≥10. 11 CFU / g.

[0014] Preferably, in the soil aggregate remediation fertilizer, the trace elements include zinc, boron, molybdenum, iron and manganese in a weight ratio of 2:1:1:2:2.

[0015] This invention also provides a method for preparing a soil aggregate remediation fertilizer, comprising the following steps: (1) Basic organic raw material pretreatment: corn cobs, beet pulp, liquor lees and pine needles are dried and crushed respectively; (2) Straw modification pretreatment: Cut corn straw and soybean straw into sections, heat them to 130-140℃ at a heating rate of 10-15℃ / min under CO2 protection, maintain for 10-20 minutes, cool and then crush. (3) Pretreatment of mineral carrier: Calcine diatomite and bentonite at 400-450℃ for 1.0-2.0 hours, cool and crush; take 9-11 parts of dolomite powder and mix it evenly with 6-8 parts of calcium dihydrogen phosphate to obtain mineralization promoting component; (4) Preparation of basic mixture: The corn cob powder, beet pulp powder, liquor lees powder, and pine needle powder treated in step (1), the corn stalk powder and soybean stalk powder treated in step (2), the diatomaceous earth powder, bentonite powder, and mineralization promoting components treated in step (3) are mixed with humic acid and chelated trace elements to obtain the basic mixture. (5) Preparation of compound functional microbial agents: Cyanobacteria, actinomycetes, yeasts and lactic acid bacteria are prepared into compound functional microbial agents; (6) Inoculation and fermentation: Inoculate the compound functional microbial agent described in step (5) into the basic mixture, add EPS in situ crosslinking inducer, adjust the moisture content to 38-42%, pile fermentation for 14-16 days, turning the pile during the period, maintaining the moisture content at 34-36% after turning, and controlling the fermentation temperature at 48-55℃; the EPS in situ crosslinking inducer is composed of the following components by weight: 4-6 parts citric acid, 2-3 parts polyethylene glycol 6000, 1-2 parts glycerol, 65 parts deionized water, and 1 part silane coupling agent KH-550; (7) Post-processing granulation: After fermentation, the material is dried and granulated to obtain the soil aggregate repair fertilizer.

[0016] Preferably, in the preparation method, the process parameters for straw modification pretreatment in step (2) are: heating to 135°C at a heating rate of 12°C / min under CO2 protection and maintaining it for 15 minutes.

[0017] Preferably, in the preparation method, the process parameters for the mineral carrier pretreatment in step (3) are: calcining diatomaceous earth and bentonite at 420°C for 1.5 hours.

[0018] Preferably, in the preparation method, in step (6), the turning of the pile is performed once on the 5th day and once on the 10th day during fermentation.

[0019] Preferably, in the preparation method, the post-processing granulation in step (7) specifically includes the following sub-steps: (7a) Drying and pulverizing: After fermentation, the material is dried at 65°C to a moisture content of 12-15%, then pulverized and passed through an 80-mesh sieve; (7b) Granulation: The powder obtained in step (7a) is fed into a disc granulator, and a sodium carboxymethyl starch solution with a mass concentration of 7% is used as a binder. The disc rotation speed is controlled at 45 r / min and the tilt angle is 38° to granulate particles with a particle size of 2-5 mm. (7c) Secondary drying and sieving: The particles obtained in step (7b) are dried at 45°C until the moisture content is ≤8%, and then sieved. (7d) Coating treatment: The sieved particles were coated with a 3% xanthan gum solution by spraying, with the spray amount being 1.8% of the particle mass. The particles were then dried at 40°C for 12 minutes to obtain the soil aggregate repair fertilizer.

[0020] The present invention has at least the following beneficial effects: The fertilizer provided by this invention is made from readily available raw materials in Northeast China, which will not cause secondary pollution to the environment or incur additional costs. It is an environmentally friendly soil remediation product that can remediate different types of degraded black soil in Northeast China, improve soil fertility, enhance soil aeration, and promote crop growth. At the same time, the fertilizer is simple to prepare, easy to operate, and convenient to store, transport, and apply.

[0021] This invention's soil aggregate remediation fertilizer achieves multi-dimensional remediation of degraded soil through the synergistic combination of local agricultural wastes such as corn cob powder, beet pulp, and distiller's grains with specific proportions of diatomaceous earth, bentonite, and functional microbial agents. On one hand, the organic materials continuously provide organic matter and slow-release nutrients during decomposition, while humic acid and mineral carriers enhance the soil's water and fertilizer retention capacity and ion exchange capacity. On the other hand, the introduced composite functional microbial agents serve as the active core; the cyanobacteria and actinomycetes they contain can form biological and chemical cementation between soil particles through secretion of extracellular polysaccharides and induction of mineralization, thereby directly promoting the formation and stabilization of water-stable aggregates. This allows the fertilizer to not only improve basic soil fertility but also specifically rebuild and stabilize soil aggregate structure, improve porosity, and create a more favorable physical environment for crop root growth and soil microbial activity.

[0022] In the preparation method provided by this invention, the straw modification process under CO2 protection improves the specific surface area and adsorption performance of the carrier, providing optimized physical support for microbial colonization and subsequent reactions. The activation of mineral components and the addition of specific mineralization promoting components pre-set key substrates for microbial-induced formation of cementing minerals. By co-fermenting the composite functional microbial agent with an EPS in-situ crosslinking inducer containing a silane coupling agent under controlled conditions, the extracellular polysaccharides secreted by microorganisms are crosslinked and solidified between the carrier surface and particles, realizing the in-situ integrated construction of the "microorganism-carrier-cementing network". This process ensures that the activity of functional microorganisms is maintained and expressed efficiently, so that the final product not only contains rich organic nutrients and active microbial communities, but also has a "pre-made" function that can be immediately activated and continuously carried out structural repair after being applied to the soil.

[0023] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0024] Figure 1 The flowchart shows the preparation method of soil aggregate remediation fertilizer based on microbial induced mineralization and in-situ crosslinking of EPS provided by the present invention.

[0025] Figure 2 This is a diagram illustrating the changes in soil aggregate structure indicators at different growth stages in Example 1 of the present invention.

[0026] Figure 3 This is a diagram illustrating the soil aggregate structure index after freeze-thaw cycles in Embodiment 1 of the present invention.

[0027] Figure 4 This is a diagram illustrating the changes in soil aggregate structure indicators at different growth stages in Example 2 of the present invention. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0029] This invention provides a soil aggregate remediation fertilizer based on microbial induced mineralization and in-situ crosslinking of EPS. The soil aggregate remediation fertilizer, by weight, consists of 28-38 parts corn cob powder, 12-22 parts beet pulp, 9-15 parts distillers' grains, 7-11 parts pine needle powder, 7-11 parts diatomaceous earth, 5-7 parts bentonite, 4-6 parts humic acid, 6-10 parts corn stalks, 6-9 parts soybean stalks, 2-4 parts compound functional microbial agent, and 1-2 parts trace elements.

[0030] In a preferred embodiment, the soil aggregate remediation fertilizer, by weight, comprises 30-35 parts corn cob powder, 15-20 parts beet pulp, 10-13 parts distiller's grains, 8-10 parts pine needle powder, 8-10 parts diatomaceous earth, 5-6 parts bentonite, 4-5 parts humic acid, 7-9 parts corn stalks, 7-8 parts soybean stalks, 2-3 parts compound functional microbial agent, and 1-2 parts trace elements.

[0031] In a preferred embodiment, the soil aggregate remediation fertilizer is composed of, by weight, 33 parts corn cob powder, 18 parts beet pulp, 12 parts distiller's grains, 9 parts pine needle powder, 9 parts diatomaceous earth, 6 parts bentonite, 5 parts humic acid, 8 parts corn stalks, 7 parts soybean stalks, 3 parts compound functional microbial agent, and 1.5 parts trace elements.

[0032] In a preferred embodiment, the soil aggregate remediation fertilizer comprises a compound functional microbial agent consisting of cyanobacteria, actinomycetes, yeast, and lactic acid bacteria in a weight ratio of 1:1:1:1; wherein the cyanobacteria have an EPS production capacity ≥2.2 g / L and nitrogenase activity ≥35 nmol / (h•mL); the actinomycetes are Streptomyces, with urease activity ≥18 U / mL and mineralization induction rate ≥40%; the microbial agent has a moisture content ≤5% and a total effective viable count ≥10. 11 CFU / g.

[0033] In a preferred embodiment, the trace elements in the soil aggregate remediation fertilizer include zinc, boron, molybdenum, iron, and manganese in a weight ratio of 2:1:1:2:2.

[0034] This invention also provides a method for preparing a soil aggregate remediation fertilizer, comprising the following steps: (1) Basic organic raw material pretreatment: corn cobs, beet pulp, liquor lees and pine needles are dried and crushed respectively; (2) Straw modification pretreatment: Cut corn straw and soybean straw into sections, heat them to 130-140℃ at a heating rate of 10-15℃ / min under CO2 protection, maintain for 10-20 minutes, cool and then crush. (3) Pretreatment of mineral carrier: Calcine diatomite and bentonite at 400-450℃ for 1.0-2.0 hours, cool and crush; take 9-11 parts of dolomite powder and mix it evenly with 6-8 parts of calcium dihydrogen phosphate to obtain mineralization promoting component; (4) Preparation of basic mixture: The corn cob powder, beet pulp powder, liquor lees powder, and pine needle powder treated in step (1), the corn stalk powder and soybean stalk powder treated in step (2), the diatomaceous earth powder, bentonite powder, and mineralization promoting components treated in step (3) are mixed with humic acid and chelated trace elements to obtain the basic mixture. (5) Preparation of compound functional microbial agents: Cyanobacteria, actinomycetes, yeasts and lactic acid bacteria are prepared into compound functional microbial agents; (6) Inoculation and fermentation: Inoculate the compound functional microbial agent described in step (5) into the basic mixture, add EPS in situ crosslinking inducer, adjust the moisture content to 38-42%, pile ferment for 14-16 days, turn the pile during the period, maintain the moisture content at 34-36% after turning, and control the fermentation temperature at 48-55℃; the EPS in situ crosslinking inducer is composed of the following components by weight: 4-6 parts citric acid, 2-3 parts polyethylene glycol 6000, 1-2 parts glycerol, 65 parts deionized water, and 1 part silane coupling agent KH-550; (7) Post-processing granulation: After fermentation, the material is dried and granulated to obtain the soil aggregate repair fertilizer.

[0035] In a preferred embodiment, in the preparation method, the process parameters for straw modification pretreatment in step (2) are: heating to 135°C at a heating rate of 12°C / min under CO2 protection and maintaining it for 15 minutes.

[0036] In a preferred embodiment, in the preparation method, the process parameters for the mineral carrier pretreatment in step (3) are: calcining diatomaceous earth and bentonite at 420°C for 1.5 hours.

[0037] In a preferred embodiment, in the preparation method, in step (6), the turning of the pile is performed once on the 5th day and once on the 10th day during fermentation.

[0038] In a preferred embodiment, the post-processing granulation in step (7) of the preparation method specifically includes the following sub-steps: (7a) Drying and pulverizing: After fermentation, the material is dried at 65°C to a moisture content of 12-15%, then pulverized and passed through an 80-mesh sieve; (7b) Granulation: The powder obtained in step (7a) is fed into a disc granulator, and a sodium carboxymethyl starch solution with a mass concentration of 7% is used as a binder. The disc rotation speed is controlled at 45 r / min and the tilt angle is 38° to granulate particles with a particle size of 2-5 mm. (7c) Secondary drying and sieving: The particles obtained in step (7b) are dried at 45°C until the moisture content is ≤8%, and then sieved. (7d) Coating treatment: The sieved particles were coated with a 3% xanthan gum solution by spraying, with the spray amount being 1.8% of the particle mass. The particles were then dried at 40°C for 12 minutes to obtain the soil aggregate repair fertilizer.

[0039] Figure 1 This is a flowchart illustrating the preparation method of the soil aggregate remediation fertilizer based on microbial-induced mineralization and in-situ crosslinking of EPS provided by this invention. (Combined with...) Figure 1 The following examples illustrate the soil aggregate remediation fertilizer based on microbial induced mineralization and in-situ crosslinking of EPS provided by the present invention and its preparation method.

[0040] Example 1: Particle remediation experiment of degraded black soil in typical farmland of Songnen Plain (freeze-thaw + tillage degradation type) I. Background and Site Overview The Songnen Plain, as the core farmland distribution area of ​​the Northeast Black Soil Region, has long faced the dual stresses of high-intensity farming and seasonal freeze-thaw cycles, leading to severe degradation of the black soil aggregate structure and becoming a core bottleneck restricting the sustainable development of agriculture in the region. The experimental site is located in Sangang Town, Nong'an County, Jilin Province (44°55′N, 125°45′E), which belongs to the mid-latitude continental monsoon climate zone. The average annual temperature is 4.7℃, and the average annual precipitation is 520mm, with precipitation concentrated from June to August, accounting for 65% of the annual total. The extreme low temperature in winter is -28℃, and the freeze-thaw period is from November to March of the following year, with an average of 4-5 freeze-thaw cycles per year and a maximum freezing depth of 1.2m. The soil type of the experimental site is typical degraded black calcareous soil, which was originally natural grassland. After reclamation, it was continuously planted with corn for 25 years without any fallow history. The soil degradation characteristics are obvious: the content of water-stable aggregates >0.25mm is only 28.3%, the soil bulk density is 1.45g / cm³, the total porosity is 42.1%, the organic matter content is 20.3g / kg, and the soil erodibility K value is 0.032t•hm²•h / (hm²•MJ•mm), which belongs to moderately degraded black soil; the soil pH value is 6.8, the available nitrogen is 105mg / kg, the available phosphorus is 12.3mg / kg, and the available potassium is 138mg / kg, which is consistent with the typical physicochemical characteristics of degraded black soil in Songnen Plain farmland. This experiment aims to verify the remediation efficacy of soil aggregate remediation fertilizer based on microbial induced mineralization and in-situ crosslinking of EPS under the dual stress of freeze-thaw cycle and tillage compaction, clarify its influence mechanism on black soil aggregate structure, pore characteristics, soil physicochemical properties and maize growth and development, and provide scientific basis and technical support for the ecological restoration and productivity improvement of large-scale degraded black soil in Songnen Plain.

[0041] II. Experimental Materials and Design (I) Preparation of experimental fertilizers The fertilizer raw materials, by weight, consist of 33 parts corn cob powder, 18 parts beet pulp, 12 parts distiller's grains, 9 parts pine needle powder, 9 parts diatomaceous earth, 6 parts bentonite, 7 parts corn stalks, 7 parts soybean stalks, 5 parts humic acid, 3 parts compound functional microbial agent, 1.5 parts trace elements, and 0.9 parts compound freeze-thaw protectant. The compound functional microbial agent is a mixture of cyanobacteria, actinomycetes, yeast, and lactic acid bacteria in a weight ratio of 1:1:1:1. The cyanobacteria have an EPS production capacity of 2.4 g / L and a nitrogenase activity of 38 nmol / (h•mL), while the actinomycetes have a urease activity of 20.3 U / mL and a mineralization induction rate of 42%. The total number of viable bacteria in the agent is 1.2 × 10¹¹ CFU / g, and the water content is 4.2%. The trace elements are a mixture of zinc, boron, molybdenum, iron, and manganese in a weight ratio of 2:1:1:2:2, and all are agricultural-grade raw materials sourced locally in Northeast China. The compound freeze-thaw protectant is a mixture of beet molasses and corn oligosaccharides in a weight ratio of 3:2, suitable for the low-temperature freeze-thaw environment in Northeast China.

[0042] The fertilizer preparation process is as follows: raw material pretreatment, straw modification, mineral activation, preparation of basic mixture, inoculation and fermentation of microbial agents, and post-treatment granulation: corn cob powder, beet pulp, and baijiu lees are dried with hot air at 65℃ to a moisture content of 12%, and then pulverized through a 70-mesh sieve; pine needle powder is naturally air-dried and then pulverized through an 80-mesh sieve; corn stalks are cut into 2cm sections, heated to 135℃ at 12℃ / min under CO2 protection, held at that temperature for 15min, cooled, and then pulverized through a 70-mesh sieve; diatomaceous earth and bentonite are calcined in a muffle furnace at 420℃ for 1 minute. After 5 hours of cooling, the mixture is pulverized to a 110-mesh sieve. 10 parts of dolomite powder and 7 parts of calcium dihydrogen phosphate are mixed and passed through a 100-mesh sieve to prepare a mineralization promoting component. The pretreated raw materials, modified straw powder, activated minerals and mineralization promoting components, humic acid, and trace elements are placed in a horizontal mixer and mixed at 380 r / min for 30 min to obtain a basic mixture. The compound functional microbial agent is inoculated into the basic mixture at 25℃, and an EPS in-situ crosslinking inducer is added. The in-situ crosslinking inducer contains 5 parts of citric acid, 2.5 parts of polyethylene glycol 6000, 1.5 parts of glycerol, 65 parts of deionized water, and 1.0 part of silane coupling agent KH-550. The mixture is dissolved and cooled at 55℃. The moisture content was adjusted to 38-42%, and the mixture was piled up for fermentation for 15 days. The pile was turned over on the 5th and 10th days, maintaining a fermentation temperature of 48-55℃. The fermentation product was dried at 65℃ to a moisture content of 12-15%, pulverized through an 80-mesh sieve, and granulated using a 7% sodium carboxymethyl starch solution as a binder in a disc granulator to form particles with a diameter of 2-5mm. These particles were then dried at 45℃ to a moisture content of 7%, coated with a 3% xanthan gum solution, and dried at 40℃ for 12 minutes to obtain the finished product. The finished fertilizer's testing indicators were: pH 7.1, organic matter content 42.8%, total nitrogen, phosphorus, and potassium 8.3%, EPS content 0.9g / kg, total viable count of compound functional bacteria 1.1×10¹¹ CFU / g, and a combined percentage of cyanobacteria and actinomycetes of 72%.

[0043] (II) Experimental Design The experiment employed a randomized block design with three treatments and three replicates. Each plot was 20 m² (4 m × 5 m) with a 1 m spacing between plots and a 2 m wide protective row around the perimeter to prevent cross-contamination. Treatment group (T1) received the soil aggregate remediation fertilizer of this invention at a rate of 1200 kg / mu, applied as a base fertilizer in a single application followed by tilling into the soil to a depth of 15 cm, 7 days before sowing. Control group 1 (CK1) received an equal weight of conventional compound fertilizer, applied in the same manner and at the same time as T1. Control group 2 (CK2) received no fertilizer and only underwent conventional tillage and field management. The experimental crop was maize of variety Xianyu 335, with a planting density of 65,000 plants / hectare. The sowing date was April 25, and the harvest date was October 5. Irrigation, weeding, and pest and disease control were all carried out in accordance with local conventional agronomic practices. During the entire growth period, irrigation was carried out twice, once at the jointing stage and once at the tasseling stage, with an irrigation volume of 30 m³ / mu each time. Weeding was carried out manually. Pest and disease control used biological pesticides such as Bacillus thuringiensis and Kasugamycin. All environmental conditions except for fertilizer were kept consistent.

[0044] (III) Measurement Indicators and Methods Soil samples from the top 0-15cm layer were collected at the following times: before fertilization on April 18 (after freeze-thaw cycle), during the corn jointing stage on June 20, during the tasseling stage on July 30, after harvest on October 8, and after freeze-thaw cycle on April 15 of the following year. A five-point pooled sampling method was used, with five sampling points collected from each plot. After removing stones and plant debris, the samples were divided into two parts. One part was fresh and refrigerated at 4℃ for determining the number of viable microorganisms, EPS content, and enzyme activity. The other part was air-dried, ground, and passed through 2mm and 0.25mm sieves for determining soil physicochemical properties, soil aggregate stability, and other indicators.

[0045] The determination indicators and methods are as follows: The composition of water-stable aggregates was determined by wet sieving, and the content of water-stable aggregates >0.25 mm was calculated (WR). 0.25The following parameters were measured: mean weight diameter (MWD), geometric mean diameter (GMD), aggregate destruction rate (PAD), and fractal dimension (D); soil bulk density and total porosity were determined using the ring cutter method; the distribution of macropores (≥100μm), mesopores (1-100μm), and micropores (<1μm) and pore connectivity index were determined using nuclear magnetic resonance; organic matter content was determined using the potassium dichromate oxidation-external heating method; total nitrogen was determined using the Kjeldahl method; available phosphorus was determined using the molybdenum-antimony colorimetric method; available potassium was determined using the flame photometry method; and soil pH was determined using a pH meter. The viable count of multifunctional bacteria and cyanobacteria was determined using the plate dilution coating method. BG11 medium was used for 72 h of incubation at 28℃ under light; actinomycetes were cultured on Gao's No. 1 medium at 28℃ for 48 h; yeast was cultured on PDA medium at 30℃ for 48 h; and lactic acid bacteria were cultured on MRS medium at 37℃ under anaerobic conditions for 24 h. Total EPS was determined by the anthrone colorimetric method, protein content in EPS was determined by the Coomassie brilliant blue method, urease activity was determined by the indophenol blue colorimetric method, and phosphatase activity was determined by the disodium phenyl phosphate colorimetric method. Soil erodibility K-values ​​were calculated using the EPIC-K model. Plant height, stem diameter, leaf area index, root fresh weight, thousand-grain weight, and plot yield of maize were measured. Statistical analysis was performed using SPSS 26.0 software for one-way ANOVA and LSD multiple comparisons, with a significance level set at P < 0.05. Charts were generated using Origin 2023, and data were processed and calculated using Excel.

[0046] III. Experimental Results and Analysis (I) Soil aggregate structure restoration effect Before fertilization, there were no significant differences in soil aggregate structure indices among the treatments. WR 0.25 The average value was 28.1%, MWD was 0.42 mm, GMD was 0.21 mm, and PAD was 68.5%, indicating that the initial soil conditions at the experimental site were consistent and the experimental design was reasonable. After applying the fertilizer of this invention, the aggregate structure indices of the T1 treatment at each growth stage were significantly better than those of CK1 and CK2, and showed a continuous improvement trend (see...). Figure 1 (and Table 1). Post-harvest T1 treatment WR 0.25 The concentration of soil aggregates reached 45.2%, an increase of 34.9% compared to CK1 (33.5%) and 78.6% compared to CK2 (25.3%); the mean square depth (MWD) reached 0.89 mm, an increase of 53.4% ​​compared to CK1 and 140.5% compared to CK2; the mean square depth (PAD) decreased to 32.4%, a decrease of 42.8% compared to CK1 and 56.0% compared to CK2; the fractal dimension (D) decreased to 2.41, a decrease of 6.6% compared to CK1 and 12.3% compared to CK2. The lower the fractal dimension, the more uniform the distribution of soil particles and the more stable the soil aggregate structure. This confirms that the fertilizer of this invention significantly promotes the transformation of small aggregates into large aggregates and improves the stability of aggregates through the synergistic effect of microbial induced mineralization and in-situ crosslinking of EPS, and the effect lasts throughout the entire maize growth period.

[0047] After harvest, the soil underwent a natural freeze-thaw cycle from November to March of the following year. Soil aggregate structure was measured on April 15th of the following year (see...). Figure 2 (and Table 2), T1 process WR 0.25 The percentage remained at 38.6%, an increase of 29.5% compared to CK1 (29.8%) and 74.7% compared to CK2 (22.1%); the MWD was 0.76 mm, an increase of 48.0% compared to CK1 and 130.8% compared to CK2; and the PAD was 40.2%, a decrease of 34.6% compared to CK1 and 47.0% compared to CK2. After freeze-thaw cycles, the aggregate structure indicators of the T1 treatment were still significantly better than those of the control group, indicating that the beet molasses and corn low-compound freeze-thaw protectant polysaccharides in the fertilizer effectively protected the activity of functional microorganisms. The EPS secreted by these microorganisms formed a gel network at low temperatures, buffering the mechanical stress of soil particles caused by freeze-thaw cycles, reducing aggregate disintegration, and maintaining high stability of the aggregate structure after freeze-thaw cycles, which is suitable for the seasonal freeze-thaw climate characteristics of the Songnen Plain.

[0048] Table 1. Changes in soil aggregate structure indices at different growth stages (mean ± standard deviation, n=3) Table 2 Soil aggregate structure indices after freeze-thaw cycles (mean ± standard deviation, n=3) (II) Soil pore characteristics and changes in physicochemical properties After harvest, the total porosity of soil treated with T1 reached 51.3%, an increase of 13.5% compared to CK1 (45.2%) and 22.7% compared to CK2 (41.8%). The macropore content was 18.6%, an increase of 51.2% compared to CK1 (12.3%) and 90.8% compared to CK2 (9.8%). The mesopore content was 22.5%, an increase of 11.9% compared to CK1 and 22.9% compared to CK2. The micropore content was 10.2%, a decrease of 20.3% compared to CK1 and 25.5% compared to CK2 (Table 3). Nuclear magnetic resonance analysis showed that the pore connectivity index of soil treated with T1 was 0.78, significantly higher than that of CK1 and CK2. This indicates that the three-dimensional network structure formed by the calcium carbonate cementation induced by microbial mineralization and the cross-linking of EPS effectively improved the soil pore distribution and connectivity, reduced the proportion of ineffective micropores, and increased the content of aerated and permeable macro and mesopores, providing a favorable spatial environment for maize root growth and microbial activity.

[0049] The soil bulk density of treatment T1 decreased to 1.21 g / cm³, a 12.3% reduction compared to CK1 and a 16.6% reduction compared to CK2, reaching the suitable bulk density range of 1.1-1.3 g / cm³ for maize growth; the organic matter content increased to 23.5 g / kg, a 22.4% increase compared to CK1 and a 32.0% increase compared to CK2, with an average annual increase rate of 1.6 g / kg, which is in line with the reasonable rate of organic matter increase in black soil. In terms of nutrient content, the total nitrogen content of treatment T1 was 1.38 g / kg, an increase of 20.0% compared to CK1 and 27.8% compared to CK2; the available phosphorus content was 18.6 mg / kg, an increase of 31.0% compared to CK1 and 56.3% compared to CK2; and the available potassium content was 165.3 mg / kg, an increase of 16.0% compared to CK1 and 21.7% compared to CK2. The increase in nutrient content is due to the nutrients released from the decomposition of organic raw materials such as corn cob powder, beet pulp, and distiller's grains in the fertilizer, and also to the activation effect of functional microorganisms. The phosphatases secreted by actinomycetes and lactic acid bacteria accelerated the mineralization of soil organic phosphorus, and the nitrogen fixation of cyanobacteria increased the nitrogen input of the soil, thus achieving simultaneous improvement in soil fertility and structure.

[0050] Table 3. Soil porosity characteristics and physicochemical properties after harvest (mean ± standard deviation, n=3) (III) Changes in Microbial Function and EPS Content The total viable count of the complex functional bacteria in the soil treated with T1 after harvest was 3.2 × 10⁻⁶. 7 The CFU / g concentration, with cyanobacteria and actinomycetes accounting for 72%, maintained high activity, while the target functional bacteria were not detected in CK1 and CK2; the viable count of functional bacteria in the T1 treatment after freeze-thaw was 1.8 × 10⁻⁶. 7 The CFU / g survival rate reached 56.2%, indicating that the compound freeze-thaw protectant effectively improved the freeze resistance of microorganisms. The EPS content in the soil of treatment T1 reached a peak of 1.2 g / kg during the tasseling period, which was 200% higher than that of CK1 (0.4 g / kg) and 300% higher than that of CK2 (0.3 g / kg). The polysaccharide content in EPS was 0.75 g / kg and the protein content was 0.45 g / kg. The synergistic effect of polysaccharides and proteins enhanced the cementation effect. The urease activity was 38.6 U / g, which was 45.3% higher than that of CK1 and 68.7% higher than that of CK2. The phosphatase activity was 26.8 U / g, which was 36.7% higher than that of CK1 and 57.6% higher than that of CK2 (Table 4). The soil erodibility K value of T1 treatment decreased to 0.021t•hm²•h / (hm²•MJ•mm), which was 25.0% lower than CK1 and 36.4% lower than CK2. This indicates that the improvement in aggregate structure significantly enhanced the soil's resistance to erosion, meeting the needs of water erosion control in Songnen Plain farmland.

[0051] Table 4. Soil EPS content, enzyme activity, and erodibility during the male emergence period (mean ± standard deviation, n=3) (iv) Maize growth and yield performance The T1 treatment showed significantly higher plant height, stem diameter, and leaf area index than the control group. At harvest, the plant height reached 285 cm, an increase of 12.2% compared to CK1 and 18.8% compared to CK2; the stem diameter was 3.2 cm, an increase of 14.3% compared to CK1 and 23.1% compared to CK2; the leaf area index was 5.8, an increase of 13.7% compared to CK1 and 21.3% compared to CK2; and the root fresh weight was 28.6 g / plant, an increase of 28.5% compared to CK1 and 42.3% compared to CK2 (Table 5). The T1 treatment achieved a corn yield of 826 kg / mu, a 20.6% increase compared to CK1 (685 kg) and a 35.2% increase compared to CK2 (611 kg). The thousand-grain weight was 386 g, a 10.9% increase compared to CK1 and a 19.9% ​​increase compared to CK2. The yield increase was mainly attributed to the improved soil aggregate structure, which optimized the root growth environment, improved nutrient and water supply efficiency, enhanced crop stress resistance, and increased leaf area index, which improved the accumulation of photosynthetic products, ultimately leading to increased yield.

[0052] Table 5. Major agronomic traits and yield of maize (mean ± standard deviation, n=3) IV. Discussion The core problem of degraded black soil in the Songnen Plain farmland is the disintegration of aggregates caused by freeze-thaw cycles and structural damage caused by tillage compaction. This invention's fertilizer achieves aggregate repair through the synergistic effect of compound functional microbial agents. Cyanobacteria secrete EPS containing highly viscous dextran and protein complexes, forming a biological crust on the soil surface and cementing soil particles. Actinomycetes catalyze the hydrolysis of urea with urease to produce ammonia, increasing soil pH and inducing calcium ions to combine with carbonate ions to form calcium carbonate cement, achieving microbial-induced mineralization. Yeast and lactic acid bacteria regulate the soil microecological balance, promote organic matter decomposition and nutrient transformation, and provide a carbon source for the growth of functional bacteria. These three factors synergistically enhance the dual effects of in-situ cross-linking and mineralization cementation of EPS, significantly improving aggregate stability.

[0053] Experimental data showed that the content of water-stable aggregates >0.25mm in the soil increased from 28.3% to 45.2% after treatment, consistent with the trend of over 35% increase in aggregates after microbial treatment in related studies. Soil bulk density decreased from 1.45 g / cm³ to 1.21 g / cm³, while porosity increased by 22.7%, improving soil aeration and permeability. The aggregate retention rate after freeze-thaw cycles reached 85.4%, significantly higher than the control group, indicating that the composite freeze-thaw protectant effectively mitigated the damage to microbial activity and aggregate structure caused by low temperatures, adapting to the frequent freeze-thaw cycles characteristic of the Songnen Plain. Soil organic matter content increased by 32.0%, partly due to the decomposition of organic raw materials in fertilizers, and partly due to enhanced gene expression for microbial nitrogen fixation and carbon cycling functions, promoting organic carbon accumulation. The increase in nutrient content was closely related to microbial activation; phosphatase and urease secreted by actinomycetes and lactic acid bacteria accelerated the conversion of phosphorus and nitrogen, improving nutrient availability.

[0054] The 20.6% increase in corn yield confirms the promoting effect of improved soil structure and fertility on crop growth. Optimized root growth environment enhanced the crop's absorption efficiency of water and nutrients, while increased leaf area index improved photosynthetic product accumulation, ultimately leading to increased yield. Simultaneously, the soil erodibility K-value decreased by 36.4%, providing an effective approach for soil and water conservation in the Songnen Plain, meeting the governance needs of the "Northeast Black Soil Protection Plan Outline." In summary, this invention's soil aggregate remediation fertilizer exhibits excellent aggregate remediation effects in freeze-thaw and degraded black soils of the Songnen Plain, simultaneously improving soil fertility and crop yield, and has good potential for widespread application.

[0055] Example 2: Particle remediation experiment of black soil from marshland reclamation in the Sanjiang Plain (high moisture + dispersed structure) I. Background and Site Overview The Sanjiang Plain is the largest distribution area of ​​marshy black soil in my country. In recent years, large-scale marsh reclamation has led to the destruction of black soil structure, forming typical marshy reclamation black soil. This type of black soil, due to long-term high moisture environment, has dispersed soil particles, extremely poor aggregate stability, and an anaerobic environment that inhibits the activity of beneficial microorganisms, resulting in prominent nutrient imbalances. The experimental site is located in Qixingpao Town, Baoqing County, Heilongjiang Province (46°24′N, 132°06′E), belonging to the temperate humid monsoon climate zone, with an average annual temperature of 3.6℃ and an average annual precipitation of 580mm, concentrated in June-August. The soil type is meadow black soil, with a reclamation history of 15 years and continuous soybean planting for 10 years. The soil exhibits significant degradation characteristics: the content of water-stable aggregates (>0.25mm) is only 22.1%, and the soil bulk density is 1.42g / cm³. The soil composition is as follows: total porosity 43.5%, of which ineffective porosity (retained water porosity) accounts for 18.2%; organic matter content 20.3 g / kg; soil redox potential (Eh) -150 mV, indicating a strongly anaerobic environment; soil pH 6.5; available nitrogen 98 mg / kg; available phosphorus 8.7 mg / kg; available potassium 126 mg / kg; soil erodibility K value 0.035 t•hm²•h / (hm²•MJ•mm). This experiment aims to verify the aggregate remediation effect of the fertilizer of this invention under high moisture and anaerobic conditions, clarify its impact on aggregate structure, redox environment, nutrient cycling, and soybean yield in marshland-reclaimed black soil, and provide a technical solution for the improvement of marshland black soil in the Sanjiang Plain.

[0056] II. Experimental Materials and Design (I) Preparation of experimental fertilizers Using the same fertilizer formulation and preparation process as in Example 1, the finished fertilizer had a pH of 7.0, an organic matter content of 43.2%, a total nitrogen, phosphorus, and potassium nutrient content of 8.5%, an EPS content of 0.95 g / kg, a total effective viable count of 1.3 × 10¹¹ CFU / g in the compound functional microbial agent, an EPS production capacity of 2.5 g / L for cyanobacteria, an actinomycete urease activity of 21.1 U / mL, and a mineralization induction rate of 43%.

[0057] (II) Experimental Design The experiment employed a randomized block design with three treatments and three replicates. Each plot was 25 m² (5 m × 5 m) with a 1.5 m spacing and a 2 m wide protective row around the perimeter. Drainage ditches 30 cm deep were installed within each plot to maintain soil moisture at 60-70% of field capacity. Treatment group T2 received the soil aggregate repair fertilizer of this invention at a rate of 1300 kg / mu. In cases of excessive rainfall or high moisture levels, the application rate should be increased appropriately. The fertilizer was applied via furrow application, followed by covering with soil. The furrows were 15 cm deep and 10 cm wide, and applied 10 days before sowing. Control group 1 (CK3) received an equal weight of conventional compound fertilizer, applied via furrow application as in T2. ​​Control group 2 (CK4) received no fertilizer, only conventional drainage and tillage. The experimental crop was soybean variety Heinong 84, sown at a density of 280,000 plants / hectare on May 5th and harvested on October 10th. Field management followed local conventional agronomic practices, with uniform drainage control to ensure consistent conditions except for fertilizer application.

[0058] (III) Measurement Indicators Soil samples from the top 0-15 cm layer were collected on April 25 (before fertilization), June 15 (during soybean branching), July 25 (during flowering), August 30 (during grain filling), and October 12 (after harvest). A five-point pooled sampling method was used. Fresh soil samples were used to determine microbial indicators, EPS content, and redox potential; air-dried soil samples were used to determine soil physicochemical properties and aggregate stability. In addition to the indicators measured in Example 1, soil redox potential, anaerobic microbial abundance, and EPS component analysis were added. The number of root nodules per soybean plant was added as a new soybean growth indicator.

[0059] III. Experimental Results and Analysis (I) Soil aggregate structure restoration effect Before fertilization, there were no significant differences in aggregate structure among the treatments. 0.25 The average was 22.3%, MWD was 0.38 mm, GMD was 0.18 mm, and PAD was 75.2%. After applying the fertilizer of this invention, the aggregate structure indices of the T2 treatment at all growth stages were significantly improved (see...). Figure 4 (and Table 6), Post-harvest T2 treatment WR 0.25The concentration of phosphorus in the T2 treatment reached 38.2%, an increase of 35.5% compared to CK3 (28.2%) and 105.4% compared to CK4 (18.6%); the mean square depth (MWD) was 0.78 mm, an increase of 56.0% compared to CK3 and 151.6% compared to CK4; the particle size distribution (PAD) decreased to 45.3%, a decrease of 31.6% compared to CK3 and 44.3% compared to CK4; and the fractal dimension (D) decreased to 2.45, a decrease of 7.8% compared to CK3 and 12.7% compared to CK4. During the experiment, the soil moisture content of each treatment was maintained at 63-67%, with no significant difference. However, the aggregate stability of the T2 treatment was significantly higher than that of the control group. This is because the cyanobacteria and actinomycetes in the compound functional bacterial agent can still maintain their activity under high moisture conditions. The EPS secreted by cyanobacteria is hydrophilic and sticky, and can form a water-stable cementing layer on the surface of soil particles. The calcium carbonate mineralization product induced by actinomycetes fills the pores and enhances the mechanical stability of the aggregates. The two work together to resist the particle dispersion caused by high moisture.

[0060] Table 6. Changes in soil aggregate structure indices at different growth stages (mean ± standard deviation, n=3) (II) Soil pore characteristics and changes in physicochemical properties After harvest, the total porosity of treatment T2 reached 49.8%, an increase of 12.7% compared to CK3 (44.2%) and 16.4% compared to CK4 (42.8%). The content of macropores (≥100μm) was 15.8%, an increase of 50.5% compared to CK3 (10.5%) and 83.7% compared to CK4 (8.6%). The proportion of ineffective pores (i.e., retained water pores) decreased to 12.3%, a decrease of 26.8% compared to CK3 (16.8%) and 32.4% compared to CK4 (18.2%) (Table 7). The improvement in pore structure is mainly attributed to the increase in effective pores and the decrease in ineffective pores after the formation of aggregates, which improved soil aeration and permeability and alleviated the anaerobic environment. The soil redox potential (Eh) of the T2 treatment increased to 50 mV, which was 162.5% higher than that of CK3 (-80 mV) and 225.0% higher than that of CK4 (-120 mV), indicating a significant improvement in the anaerobic environment. The organic matter content increased to 26.8 g / kg, which was 19.1% higher than that of CK3 and 33.3% higher than that of CK4. The increase in Eh was mainly due to the improved soil aeration after the formation of soil aggregates, which enhanced the oxygen diffusion capacity and inhibited the excessive reproduction of anaerobic microorganisms. The accumulation of organic matter was due to the decomposition of organic raw materials from fertilizers and the carbon fixation by microorganisms. In terms of nutrient content, the total nitrogen in the T2 treatment was 1.45 g / kg, an increase of 18.9% compared to CK3 and 28.3% compared to CK4; available phosphorus was 15.3 mg / kg, an increase of 33.0% compared to CK3 and 66.3% compared to CK4; and available potassium was 158.6 mg / kg, an increase of 14.6% compared to CK3 and 23.2% compared to CK4. The increase in available phosphorus was the most significant, which was closely related to the enhanced phosphatase activity secreted by actinomycetes and lactic acid bacteria.

[0061] Table 7. Soil porosity characteristics and physicochemical properties after harvest (mean ± standard deviation, n=3) (III) Changes in Microbial Function and EPS Content The total viable count of the composite functional bacteria in the soil treated with T2 after harvest was 2.8 × 10⁻⁶. 7 CFU / g, cyanobacteria and actinomycetes accounted for 68%, and no target functional bacteria were detected in CK3 and CK4; in terms of the number of methanogens, denitrifying bacteria, and anaerobic microorganisms, the T2 treatment was 1.2 × 10⁻⁶. 4 CFU / g, compared to 3.8×10⁻⁶ for CK3. 4 CFU / g decreased by 68.4%, compared to 5.6×10⁻⁶ in CK4. 4The CFU / g decreased by 78.6%, indicating that improved soil aeration inhibited the reproduction of anaerobic harmful microorganisms. The EPS content in the soil of treatment T2 reached a peak of 1.1 g / kg during the flowering period, which was 266.7% higher than that of CK3 (0.3 g / kg) and 450.0% higher than that of CK4 (0.2 g / kg). The polysaccharide content in EPS was 0.7 g / kg, the protein content was 0.4 g / kg, and the polysaccharide / protein ratio was 1.75, which is conducive to the cementation of soil particles (Table 8). Treatment T2 showed that urease activity was 35.8 U / g, an increase of 46.1% compared to CK3 and 76.4% compared to CK4; phosphatase activity was 24.3 U / g, an increase of 44.6% compared to CK3 and 80.0% compared to CK4; and the soil erodibility K value decreased to 0.023 t•hm²•h / (hm²•MJ•mm), a decrease of 23.3% compared to CK3 and 36.1% compared to CK4. The increased enzyme activity accelerated nutrient cycling, and the decreased erodibility enhanced the soil's resistance to erosion, making it suitable for the concentrated rainy season climate of the Sanjiang Plain.

[0062] Table 8. Soil EPS content, enzyme activity, and erodibility during flowering period (mean ± standard deviation, n=3) (iv) Soybean growth and yield performance The T2 treatment resulted in significantly higher soybean plant height, stem diameter, and root nodule number compared to the control group. At harvest, the plant height reached 85 cm, a 14.9% increase compared to CK3 and a 23.5% increase compared to CK4; stem diameter was 1.2 cm, a 16.5% increase compared to CK3 and a 26.3% increase compared to CK4; and the number of root nodules per plant was 38, a 29.3% increase compared to CK3 and a 46.2% increase compared to CK4 (Table 9). The T2 treatment yielded 235 kg / mu (approximately 0.067 hectares), a 26.3% increase compared to CK3's 186 kg / mu and a 41.5% increase compared to CK4's 166 kg / mu; the thousand-grain weight was 235 g / mu, a 7.8% increase compared to CK3 and a 14.6% increase compared to CK4. The increased yield was mainly due to: 1) improved soil aggregate structure, which optimized the root growth environment, resulting in a 32.6% increase in root fresh weight compared to CK3; 2) reduced anaerobic conditions, leading to enhanced rhizobium activity and improved nitrogen fixation efficiency; and 3) increased nutrient availability, meeting the nutrient requirements of soybeans during their growth period and increasing the accumulation of photosynthetic products.

[0063] Table 9. Major agronomic traits and yield of soybean (mean ± standard deviation, n=3) IV. Discussion The core problem of reclaiming black soil from marshland in the Sanjiang Plain is the dispersion of soil aggregates, anaerobic environment, and nutrient imbalance caused by high moisture content. The fertilizer of this invention achieves restoration through multiple mechanisms: cyanobacteria and actinomycetes work synergistically in a high-moisture environment. The EPS secreted by cyanobacteria forms a water-stable cementing layer, cementing dispersed soil particles into micro-aggregates. The calcium carbonate cement produced by mineralization induced by actinomycetes further assembles the micro-aggregates into macro-aggregates, achieving a dual enhancement of in-situ cross-linking of EPS and mineralization cementation. The formation of aggregates improves soil aeration, increases redox potential, inhibits the reproduction of anaerobic harmful microorganisms, promotes the activity of beneficial microorganisms, and forms a benign micro-ecological cycle. The decomposition of organic raw materials and the activation of microorganisms enhance soil fertility, alleviate nutrient imbalance, and provide a guarantee for crop growth.

[0064] Test data shows that WR 0.25 The concentration of aggregates increased from 22.1% to 38.2%, consistent with the trend observed in related studies where microbial treatments increased aggregates by approximately 35% in different soil types. The redox potential increased from -150mV to 50mV, significantly improving the anaerobic environment and validating the fertilizer's adaptability in high-moisture conditions. Soybean yield increased by 26.3%, demonstrating the synergistic effect of structural repair and fertility enhancement. Compared to the Songnen Plain experiment, the fertilizer application rate in this embodiment increased by 8.3%, mainly because the soil particle dispersion is higher in high-moisture environments, requiring more EPS and mineral products for cementation. The application method, furrow application, avoided fertilizer loss caused by surface application, improving utilization. The experimental results show that the fertilizer of this invention can effectively repair aggregate structure in high-moisture, anaerobic marshy reclaimed black soil, simultaneously improving soil physicochemical properties and crop yield, solving the problem of improving marshy black soil in the Sanjiang Plain.

[0065] Example 3: Improvement of low-lying, flood-prone black soil areas in the Sanjiang Plain (Comparison of EPS in-situ crosslinking strength control effect) This embodiment is based on the exact same experimental design, measurement indicators, and methods as Example 1. The experimental site is located in the low-lying, flood-prone black soil area of ​​the Sanjiang Plain in Jiamusi City, Heilongjiang Province (46°30′N, 130°25′E), belonging to the temperate humid monsoon climate zone. The average annual temperature is 3.8℃, and the average annual precipitation is 590 mm, with precipitation concentrated in June to August. The seasonal waterlogging period lasts for 2-3 months, and snowmelt infiltration leads to a long-term high soil moisture state. The soil type of the experimental site is meadow black soil. After reclamation, soybeans were continuously planted for 12 years, and the soil degradation characteristics were significant: the initial content of water-stable aggregates >0.25 mm (WR) was high. 0.25The soil porosity was only 21.8%, the soil bulk density was 1.43 g / cm³, the total porosity was 43.2%, of which macropores (≥100μm) accounted for only 8.5%, and ineffective pores (retained water pores) accounted for 18.6%. The soil redox potential (Eh) was -145mV, the organic matter content was 20.1 g / kg, and the soil erodibility K value was 0.034t•hm²•h / (hm²•MJ•mm). The typical characteristics were insufficient macropore structure, easy disintegration of aggregates, and prominent anaerobic environment.

[0066] This embodiment aims to compare and verify, under completely identical field conditions, the effect of regulating the "EPS in-situ crosslinking strength" in the inoculation and fermentation stage of fertilizer preparation step (6) on the optimization of pore structure, formation of water-stable aggregates and anti-disintegration ability of low-lying and waterlogged black soil, and to clarify the suitability of this regulation measure for the remediation of black soil under high water stress.

[0067] Comparison of experimental fertilizer preparations: Treatment group T3 fertilizer: Its preparation process is completely consistent with the basic process of fertilizer T1 in Example 1. The composition of the compound functional bacterial agent (cyanobacteria: actinomycetes: yeast: lactic acid bacteria = 1:1:1:1), mineralization induction conditions and porous carrier parameters remain unchanged. Only the key stage of EPS in-situ crosslinking is optimized. The specific detailed operation is as follows: 1. Determination of EPS peak period: On days 8-10 of inoculation and fermentation, the total amount of EPS in the fermentation material is monitored by anthrone colorimetric method. When the EPS content reaches 0.8g / kg or above, it is determined to be the peak period of microbial metabolic EPS, and cross-linking regulation is initiated.

[0068] 2. Construction of a bivalent ionic crosslinking system: Introducing Ca²⁺ ＋ With Mg² ＋ A complex divalent ion system with Ca² as its core, in which Ca²⁺ ＋ Derived from the mineralization-promoting component dolomite powder in the patented formula, Mg² ＋ By adding additional agricultural-grade magnesium sulfate, the Ca²⁺ content in the crosslinking system is increased. ＋ With a concentration of 25 mmol / L and a Mg²⁺ concentration of 10 mmol / L, the total crosslinking ion concentration was increased from the conventional 25 mmol / L to 35 mmol / L, and the bivalent ions synergistically enhanced the bridging effect between EPS molecules.

[0069] 3. Crosslinking reaction condition control: Adjust the moisture content of the fermentation material to maintain at 35-36%, control the reaction temperature at 45-48℃, and let the reaction stand for 45 minutes. During this period, gently stir once every 15 minutes to ensure that the divalent ions and EPS are in uniform contact and improve the crosslinking density of the three-dimensional network.

[0070] The remaining process steps are completely consistent with the preparation of fertilizer T1 in Example 1. The finished fertilizer test indicators are: pH 7.0, organic matter content 43.0%, total nitrogen, phosphorus and potassium 8.4%, EPS content 1.1 g / kg, and total viable count of compound functional bacteria 1.2×10¹¹CFU / g.

[0071] Control group T1 fertilizer: The T1 fertilizer prepared in Example 1 was used directly as a reference. No additional divalent ions were added during the EPS crosslinking stage. The crosslinking ions were only derived from the natural decomposition of the mineralization promoting components, and the total concentration was 25 mmol / L.

[0072] Comparative analysis of experimental results: The measurement data are compared as follows, under exactly the same initial soil conditions, field management, and measurement time points: 1. Changes in soil aggregate structure indicators Example 3 (T3 treatment): 30 days after fertilization: WR 0.25 The mean weight diameter (MWD) was 29.6 ± 1.2 a, the mean weight diameter (MWD) was 0.52 ± 0.03 a, the mean geometric diameter (GMD) was 0.28 ± 0.02 a, and the aggregate destruction rate (PAD) was 65.3 ± 2.3 c.

[0073] 60 days after fertilization: WR 0.25 The mean value was 36.8 ± 1.5 a, the mean value of MWD was 1.05 ± 0.04 a, the mean value of GMD was 0.42 ± 0.03 a, and the mean value of PAD was 52.1 ± 1.9 d.

[0074] 90 days after fertilization: WR 0.25 The mean value is 40.3±1.7a, the mean value of MWD is 1.38±0.05a, the mean value of GMD is 0.49±0.03a, and the mean value of PAD is 46.5±1.7e.

[0075] Post-harvest: WR 0.25 The mean value is 42.8±1.9a, the mean value of MWD is 1.57±0.05a, the mean value of GMD is 0.54±0.03a, and the mean value of PAD is 43.2±1.6e.

[0076] Control group T1 treatment (post-harvest): WR 0.25 The mean value is 33.5±1.6b, the mean value of MWD is 0.89±0.04b, the mean value of GMD is 0.32±0.02b, and the mean value of PAD is 56.7±2.0b.

[0077] 2. Soil aggregate structure indices after freeze-thaw cycles Example 3 (T3 treatment): WR 0.25The mean value was 36.5±1.6a, the mean value of MWD was 1.36±0.04a, the mean value of GMD was 0.47±0.03a, and the mean value of PAD was 48.3±2.1c.

[0078] Control group T1 treatment (after freeze-thaw): WR 0.25 The mean value was 29.8 ± 1.3 b, the mean value of MWD was 0.76 ± 0.03 b, the mean value of GMD was 0.27 ± 0.02 b, and the mean value of PAD was 61.5 ± 2.7 b.

[0079] 3. Post-harvest soil physicochemical properties and aeration and erosion resistance Example 3 (T3 treatment): Soil bulk density was 1.21±0.03 cg / cm³, total porosity was 51.5±1.2a, macropore content was 17.2±0.7a, ineffective porosity was 12.1±0.6c, saturated hydraulic conductivity was 0.82±0.04a cm / h (18.4% higher than T1), organic matter content was 24.2±0.9 ag / kg, total nitrogen was 1.42±0.06 ag / kg, available phosphorus was 19.3±0.7a mg / kg, available potassium was 168.5±4.3a mg / kg, soil erodibility K value was 0.023±0.001 ct•hm²•h / (hm²•MJ•mm), and redox potential (Eh) was 65±9a mV.

[0080] Control group T1 treatment (post-harvest): soil bulk density 1.38±0.04bg / cm³, total porosity 45.2±1.0b, macropore content 12.3±0.6b, ineffective porosity 16.8±0.8b, saturated hydraulic conductivity 0.69±0.03b cm / h, organic matter content 19.2±0.7bg / kg, total nitrogen 1.15±0.05bg / kg, available phosphorus 14.2±0.6bmg / kg, available potassium 142.5±3.8b mg / kg, soil erodibility K value 0.028±0.001bt•hm²•h / (hm²•MJ•mm), Eh -30±8b mV.

[0081] 4. Post-harvest soil microbial activity and EPS content Example 3 (T3 treatment): Total soil microbial count was 4.1 × 10⁻⁶. 8 ±2.1×10 7The total EPS content was 1.34±0.08 ag / kg (21.6% higher than T1), with EPS polysaccharide content of 0.86±0.05 ag / kg, protein content of 0.48±0.03 ag / kg, urease activity of 39.8±1.6 a U / g, and phosphatase activity of 27.5±1.3 a U / g. The colonization rates of cyanobacteria and actinomycetes were 68.5±3.2 a and 66.3±2.9 a, respectively, accounting for a total of 71%.

[0082] Control group T1 treatment (post-harvest): Total soil microbial count was 2.8 × 10⁻⁶. 8 ±1.8×10 7 b CFU / g, total EPS was 1.10±0.06bg / kg, urease activity was 26.6±1.1b U / g, phosphatase activity was 19.6±0.9b U / g; the colonization rates of cyanobacteria and actinomycetes were 52.3±2.8b and 50.1±2.5b, respectively, accounting for a total of 68%.

[0083] 5. Agronomic traits and yield of soybeans at harvest time Example 3 (T3 treatment): Plant height was 88±4a cm, stem diameter was 1.25±0.05a cm, number of root nodules per plant was 40±3a, fresh root weight was 19.8±1.3ag / plant, number of pods per plant was 45±2a, number of seeds per plant was 92±4a, thousand-seed weight was 242±8a g, and yield was 248±11a kg / mu, which was 6.1% higher than that of T1 treatment (233±10b kg / mu).

[0084] Effect Description: The results of this embodiment show that under high moisture and anaerobic stress in the low-lying, waterlogged black soil area of ​​the Sanjiang Plain, the crosslinking density and mechanical stability of the EPS three-dimensional network can be significantly enhanced by directional regulation of the in-situ crosslinking strength, achieving a dual strengthening effect of "microbial-induced mineralization cementation + high-strength crosslinking of EPS". From the perspective of the dynamic formation process of soil aggregate structure, the T3 treatment showed that at key nodes from 30 days after fertilization to harvest, WR... 0.25 Indicators such as WR and MWD consistently outperformed the T1 treatment, and post-harvest WR was significantly higher. 0.25Compared to T1, the yield increased by 27.8%, and the mean water density (MWD) increased by 76.4%. Even after freeze-thaw cycles, the T3 treatment maintained a high water-stable aggregate content of 36.5%, confirming the inhibitory effect of the high-strength cross-linked network on aggregate disintegration. Regarding soil physicochemical properties, the T3 treatment significantly increased the proportion of macropores and reduced ineffective pores, resulting in an 18.4% increase in saturated hydraulic conductivity and an increase in redox potential from -30mV to 65mV, effectively alleviating the anaerobic environment in low-lying areas. Simultaneously, the soil erodibility K-value decreased by 17.9%, enhancing resistance to water erosion. In terms of microbial activity, the high-strength cross-linked network provided a more stable microenvironment for functional bacteria, increasing the colonization rate of cyanobacteria and actinomycetes by over 30%, significantly improving total EPS and enzyme activity, further promoting nutrient activation and organic matter accumulation. Ultimately, these advantages synergistically translated into a 6.1% increase in soybean yield, fully meeting the core remediation needs of black soil in low-lying, flood-prone areas: "water permeability without instability, and aeration with fertilizer retention." The results clarify that the regulation of in-situ crosslinking strength of EPS is a key technical optimization direction for adapting to degraded black soil with high moisture content. Through this regulation, the adaptability and remediation efficacy of the fertilizer of this invention under different degradation scenarios can be further expanded, and the technical system of "microorganism-EPS-mineralized products" synergistic remediation can be improved.

[0085] Example 4: An example of improving severely lichenified black soil in the Songnen Plain (comparing the effects of microbial-induced mineralization enhancement steps) This embodiment is based on the exact same experimental background, site overview, experimental design, and measurement indicators and methods as Example 1. The experimental site is located in the typical algalized black soil area of ​​the Songnen Plain in Zhaodong City, Heilongjiang Province. The soil has been affected by salinization and structural damage for a long time, resulting in low aggregate content, collapsed pore structure, and poor freeze-thaw stability.

[0086] This embodiment aims to compare and verify, under completely identical field conditions, the effect of strengthening the "microbial-induced mineralization reaction regulation" operation in step S6 of the fertilizer preparation process on the stability of soil aggregates and freeze-thaw resistance.

[0087] Comparison of experimental fertilizer preparations: Treatment group T4 fertilizer: Its preparation method is consistent with the core process of preparing fertilizer T1 in Example 1, including bacterial community isolation and culture, porous slow-release carrier, EPS in-situ cross-linking matrix, and the distribution ratio of each group. The difference is: In step S6, the original mineralization induction stage was changed from a conventional static reaction to a slow-release carbonate-organic acid dual-regulated mineralization induction mode. Specifically, after the formation of the microbial-EPS composite system, slow-release calcium carbonate particles were added at 3.5% of the carrier mass, along with an organic acid buffer system mainly composed of gluconic acid, to maintain the system pH stably at 7.2±0.1. The reaction was then induced for 40 minutes at 32℃ and a stirring rate of 120 rpm to promote the synergistic deposition of microbial metabolites and mineral ions. The remaining granulation and 38℃ low-temperature drying processes were completely consistent with those in Example 1.

[0088] Control group T1 fertilizer: The T1 fertilizer prepared in Example 1 was used directly as a comparative reference.

[0089] Comparative analysis of experimental results: Under the same initial soil conditions and field management, the measured data are compared as follows: 1. Changes in soil aggregate structure indicators (comparison of key nodes) Example 4 (T4 treatment): 60 days after fertilization: 0.25–5 mm aggregates accounted for 43.6%, MWD was 1.58 mm, and water-stable aggregates accounted for 39.4%.

[0090] After harvest: 0.25–5 mm aggregates accounted for 45.2%, MWD was 1.63 mm, and water-stable aggregates accounted for 41.1%.

[0091] 2. Soil aggregate structure indices after freeze-thaw cycles Example 4 (T4 treatment): 0.25–5 mm aggregates accounted for 38.9%, MWD was 1.41 mm, and water-stable aggregates accounted for 35.8%.

[0092] 3. Post-harvest soil physicochemical properties and erosion resistance Example 4 (T4 treatment): Soil bulk density was 1.19 g / cm³, aeration porosity was 17.6%, organic matter content was 24.5 g / kg, available nitrogen was 146 mg / kg, available phosphorus was 29.6 mg / kg, available potassium was 148 mg / kg, and erodibility K value was 0.0221 t·hm²·h / (hm²·MJ·mm).

[0093] 4. Post-harvest soil microbial activity Example 4 (T4 treatment): Total soil microbial count was 4.3 × 10⁻⁶. 8 The CFU / g concentration was 38.6 U / g, the urease activity was 30.2 U / g, and the colonization rate of Bacillus licheniformis was 73.8%, that of Bacillus subtilis was 76.5%, that of Streptomyces was 69.1%, and that of cyanobacteria was 61.7%.

[0094] 5. Agronomic traits and yield of maize at harvest time Example 4 (T4 treatment): Plant height was 282cm, stem diameter was 3.61cm, root dry weight was 34.1g / plant, ear length was 23.0cm, number of grains per ear was 602, thousand-grain weight was 385g, and yield was 734kg per mu.

[0095] Results: The results of this embodiment demonstrate that, without altering the microbial community composition and the in-situ cross-linking pathway of EPS, precise control of the microbial-induced mineralization reaction environment can significantly enhance the "bridging" effect of mineralized products within the aggregate framework, thereby improving the freeze-thaw stability and erosion resistance of the aggregates. This optimized pathway verifies the technical reliability of this invention in systematically improving the structural stability of black soil through multi-dimensional regulation of the synergistic process of microorganisms, minerals, and organic matter. Although the embodiments of this invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for this invention. Further modifications can be readily implemented by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, this invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A soil aggregate remediation fertilizer based on microbial-induced mineralization and in-situ crosslinking of EPS, characterized in that, The soil aggregate repair fertilizer, by weight, consists of 28-38 parts corn cob powder, 12-22 parts beet pulp, 9-15 parts distillers' grains, 7-11 parts pine needle powder, 7-11 parts diatomaceous earth, 5-7 parts bentonite, 4-6 parts humic acid, 6-10 parts corn stalks, 6-9 parts soybean stalks, 2-4 parts compound functional microbial agent, and 1-2 parts trace elements.

2. The soil aggregate remediation fertilizer as described in claim 1, characterized in that, The soil aggregate repair fertilizer, by weight, consists of 30-35 parts corn cob powder, 15-20 parts beet pulp, 10-13 parts distillers' grains, 8-10 parts pine needle powder, 8-10 parts diatomaceous earth, 5-6 parts bentonite, 4-5 parts humic acid, 7-9 parts corn stalks, 7-8 parts soybean stalks, 2-3 parts compound functional microbial agent, and 1-2 parts trace elements.

3. The soil aggregate remediation fertilizer as described in claim 2, characterized in that, The soil aggregate repair fertilizer, by weight, consists of 33 parts corn cob powder, 18 parts beet pulp, 12 parts distillers' grains, 9 parts pine needle powder, 9 parts diatomaceous earth, 6 parts bentonite, 5 parts humic acid, 8 parts corn stalks, 7 parts soybean stalks, 3 parts compound functional microbial agent, and 1.5 parts trace elements.

4. The soil aggregate remediation fertilizer as described in claim 3, characterized in that, The compound functional microbial agent is composed of cyanobacteria, actinomycetes, yeast, and lactic acid bacteria in a weight ratio of 1:1:1:1; wherein the cyanobacteria have an EPS production capacity ≥2.2 g / L and nitrogenase activity ≥35 nmol / (h•mL); the actinomycetes are Streptomyces, with urease activity ≥18 U / mL and mineralization induction rate ≥40%; the microbial agent has a water content ≤5% and a total effective viable count ≥10. 11 CFU / g.

5. The soil aggregate remediation fertilizer as described in claim 3, characterized in that, The trace elements include zinc, boron, molybdenum, iron, and manganese, in a weight ratio of 2:1:1:2:

2.

6. A method for preparing the soil aggregate remediation fertilizer as described in any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Basic organic raw material pretreatment: corn cobs, beet pulp, liquor lees and pine needles are dried and crushed respectively; (2) Straw modification pretreatment: Cut corn straw and soybean straw into sections, heat them to 130-140℃ at a heating rate of 10-15℃ / min under CO2 protection, maintain for 10-20 minutes, cool and then crush. (3) Pretreatment of mineral carrier: Calcine diatomite and bentonite at 400-450℃ for 1.0-2.0 hours, cool and crush; take 9-11 parts of dolomite powder and mix it evenly with 6-8 parts of calcium dihydrogen phosphate to obtain mineralization promoting component; (4) Preparation of basic mixture: The corn cob powder, beet pulp powder, liquor lees powder, and pine needle powder treated in step (1), the corn stalk powder and soybean stalk powder treated in step (2), the diatomaceous earth powder, bentonite powder, and mineralization promoting components treated in step (3) are mixed with humic acid and chelated trace elements to obtain the basic mixture. (5) Preparation of compound functional microbial agents: Cyanobacteria, actinomycetes, yeasts and lactic acid bacteria are prepared into compound functional microbial agents; (6) Inoculation and fermentation: Inoculate the compound functional microbial agent described in step (5) into the basic mixture, add EPS in situ crosslinking inducer, adjust the moisture content to 38-42%, pile up for fermentation for 14-16 days, turn the pile during the period, maintain the moisture content at 34-36% after turning the pile, and control the fermentation temperature at 48-55℃. The EPS in-situ crosslinking inducer is composed of the following components by weight: 4-6 parts citric acid, 2-3 parts polyethylene glycol 6000, 1-2 parts glycerol, 65 parts deionized water, and 1 part silane coupling agent KH-550. (7) Post-processing granulation: After fermentation, the material is dried and granulated to obtain the soil aggregate repair fertilizer.

7. The preparation method according to claim 6, characterized in that, In step (2), the process parameters for straw modification pretreatment are: under CO2 protection, heating to 135°C at a heating rate of 12°C / min and maintaining for 15 minutes.

8. The preparation method according to claim 6, characterized in that, In step (3), the process parameters for mineral carrier pretreatment are: calcining diatomaceous earth and bentonite at 420°C for 1.5 hours.

9. The preparation method according to claim 6, characterized in that, In step (6), the turning of the pile is performed once on the 5th day and once on the 10th day during fermentation.

10. The preparation method according to claim 6, characterized in that, The post-processing granulation in step (7) specifically includes the following sub-steps: (7a) Drying and pulverizing: After fermentation, the material is dried at 65°C to a moisture content of 12-15%, then pulverized and passed through an 80-mesh sieve; (7b) Granulation: The powder obtained in step (7a) is fed into a disc granulator, and a sodium carboxymethyl starch solution with a mass concentration of 7% is used as a binder. The disc rotation speed is controlled at 45 r / min and the tilt angle is 38° to granulate particles with a particle size of 2-5 mm. (7c) Secondary drying and sieving: The particles obtained in step (7b) are dried at 45°C until the moisture content is ≤8%, and then sieved. (7d) Coating treatment: The sieved particles were coated with a 3% xanthan gum solution by spraying, with the spray amount being 1.8% of the particle mass. The particles were then dried at 40°C for 12 minutes to obtain the soil aggregate repair fertilizer.

Images