A water-retaining soil conditioner containing high-efficiency degrading bacteria and a preparation method and application thereof

Abstract

The application provides a water-retaining soil conditioner containing high-efficiency degrading bacteria and a preparation method and application thereof, and belongs to the technical field of soil improvement.The water-retaining soil conditioner comprises a carboxymethylated modified humic acid-chitosan compound, modified attapulgite powder, a composite microbial inoculum, konjac glucosan, polyacrylic acid, bentonite, polyglutamic acid, sodium alginate, mushroom residue, seaweed residue and straw compost; the composite microbial inoculum is obtained by combination of Candida tropicalis, Bacillus smithii and Bacillus pasteurii.The application realizes precise adaptation of the carrier and the high-efficiency degrading bacterial group by optimizing the design of the composite water-retaining carrier and introducing specific bacterial combinations, strengthens the synergistic effect of water retention, bacteria fixation, slow release and soil improvement, realizes water retention, degradation and fertilization synergistic effect, and has important practical significance and application value for improving soil quality, guaranteeing crop production and promoting the development of ecological agriculture.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement technology, specifically relating to a water-retaining soil conditioner containing highly efficient degrading bacteria, its preparation method, and its application. Background Technology

[0002] With the continuous advancement of intensive and large-scale agricultural production, as well as the impact of factors such as industrial production and the unreasonable application of agricultural inputs, farmland soils generally suffer from prominent problems such as low organic matter content, reduced water and fertilizer retention capacity, accumulation of pesticide residues and organic pollutants, soil compaction, acidification, and salinization. These problems seriously affect the normal growth and development of crops and constrain food security and sustainable agricultural development.

[0003] Currently available soil conditioners generally suffer from limitations in functionality and synergy. While single-type water-retaining agents (such as polyacrylates) possess a certain water absorption capacity, they are insufficient to improve the soil microecological environment, and some synthetic polymer materials also pose environmental safety and degradation risks. Although single-type microbial agents can degrade pollutants and activate nutrients, the strains are easily inactivated by environmental stress in natural soil environments, resulting in short survival times. Furthermore, due to the lack of suitable water-retaining carriers, their drought resistance and seedling protection effects are poor. At the same time, the degradation strains used in existing products are mostly concentrated on traditional modified strains such as Bacillus subtilis and Pseudomonas, whose degradation specificity and functional synergy are insufficient to meet the needs of complex polluted soil remediation. Long-term use of single strains can easily lead to an imbalance in the soil microbial community structure. In addition, the poor compatibility of strain combinations and the narrow pollutant degradation spectrum make it difficult to simultaneously achieve the integrated functions of soil water retention, degradation of multiple types of organic pollutants, and improvement of soil fertility. More significantly, existing soil conditioners primarily utilize conventional materials such as common humic acid, single resins, and unmodified mineral powders as water-retaining carriers. These materials suffer from low water absorption rates, poor water-holding stability, weak ability to retain functional bacterial strains, low nutrient slow-release efficiency, and poor compatibility with soil particles. This makes it difficult to form a synergistic "water retention-bacterial fixation-slow release" system, severely limiting the overall effectiveness of the conditioner. Furthermore, most carriers are not structurally and functionally adapted to the physiological and metabolic characteristics of degrading bacterial strains, failing to provide a stable colonization microenvironment and further reducing the survival time and degradation activity of the strains in the soil. Therefore, optimizing the design of composite water-retaining carriers, identifying highly efficient degrading bacterial strains, and achieving precise compatibility between the carrier and highly efficient degrading bacteria remain key issues that urgently need to be addressed in this field. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a water-retaining soil conditioner containing highly efficient degrading bacteria, its preparation method, and its application. By optimizing the design of the composite water-retaining carrier and introducing a specific combination of bacterial species, the carrier and the highly efficient degrading bacterial community are precisely matched, strengthening the synergistic effect of "water retention-bacterial fixation-slow release-soil improvement", and achieving synergistic enhancement of water retention, degradation, and fertilization.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a water-retaining soil conditioner containing highly efficient degrading bacteria, comprising the following components by weight: 15-25 parts of carboxymethylated modified humic acid-chitosan complex, 15-20 parts of modified attapulgite powder, 2-10 parts of compound microbial agent, 3-5 parts of konjac glucomannan, 3-5 parts of polyacrylic acid, 3-5 parts of bentonite, 1-2 parts of polyglutamic acid, 2-3 parts of sodium alginate, 4-8 parts of mushroom residue, 2-4 parts of seaweed residue, and 12-20 parts of straw compost; the compound microbial agent is obtained by combining Candida glabrata, Bacillus stearothermiae, and Bacillus pasteurelliae in a viable count ratio of (1-2):(3-6):(3-6).

[0006] Preferably, the preparation method of the carboxymethylated modified humic acid-chitosan complex includes: mixing humic acid with deionized water, adjusting the pH to 8-9, adding chloroacetic acid to carry out a carboxymethylation reaction, adding chitosan after the carboxymethylation reaction, stirring evenly, adding glutaraldehyde to carry out a cross-linking reaction, filtering, washing, drying, and pulverizing.

[0007] Preferably, the preparation method of the modified attapulgite powder includes: adding attapulgite powder to an ethanol solution, ultrasonically dispersing it, then adding γ-aminopropyltriethoxysilane to react, centrifuging after reaction, precipitating, drying, and pulverizing.

[0008] Preferably, the viable count of the compound microbial agent is ≥5×10⁻⁶. 8 cfu / g.

[0009] Preferably, the preparation method of the compound microbial agent includes: Candida glabrata, Bacillus skeletalus, and Bacillus pasteurellii are inoculated into a culture medium for activation, mixed, and a mixed bacterial solution is obtained; a microbial agent protectant is added to the mixed bacterial solution, and the solution is dried at low temperature to obtain the compound microbial agent.

[0010] This invention also provides a method for preparing the above-mentioned water-retaining soil conditioner containing highly efficient degrading bacteria, comprising the following steps: Carboxymethylated modified humic acid-chitosan complex, modified attapulgite powder, konjac glucomannan, polyacrylic acid and bentonite were mixed and stirred, and then polyglutamic acid and sodium alginate were added to obtain a composite water-retaining carrier. Mushroom residue, seaweed residue and straw compost were mixed and the moisture and pH were adjusted to obtain an organic nutrient matrix. The organic nutrient matrix was sterilized, and then mixed with the composite water-retaining carrier and composite microbial agent and fermented to obtain a fermentation product. The fermentation product was dried at low temperature and pulverized to obtain a water-retaining soil conditioner containing highly efficient degrading bacteria.

[0011] Preferably, the organic nutrient substrate has a moisture content of 35-60% and a pH value of 6-7.5.

[0012] Preferably, the fermentation conditions are: fermentation at 30~40℃ for 3~8 days; and turning the mixture once every 12 hours during the fermentation process.

[0013] The present invention also provides the application of the above-mentioned water-retaining soil conditioner containing highly efficient degrading bacteria in any of the following: (1) soil structure improvement; (2) crop planting; (3) soil fertility enhancement.

[0014] The present invention also provides a soil improvement method, comprising the following steps: applying the above-mentioned water-retaining soil conditioner containing highly efficient degrading bacteria to the soil.

[0015] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: The soil conditioner described in this invention has outstanding core effects. By incorporating an optimized composite water-retaining carrier, it significantly enhances water retention capacity, making it suitable for arid regions. It strengthens the fixation and stability of the bacterial strains, achieving precise compatibility with the introduced bacterial combinations and extending the survival period of the strains. It exhibits a degradation rate of ≥82% for soil organophosphorus pesticides, ≥75% for polycyclic aromatic hydrocarbons, and ≥85% for straw and lignin. It demonstrates high degradation efficiency and broad-spectrum degradation of various pollutants, while also significantly improving soil structure, achieving long-term nutrient release, and increasing crop yield. The soil conditioner described in this invention is environmentally friendly, widely adaptable, and the bacterial strains and carrier materials are readily available. It is simple to prepare, low in cost, and easy to promote. Detailed Implementation

[0016] This invention provides a water-retaining soil conditioner containing highly efficient degrading bacteria, comprising the following components by weight: 15-25 parts of carboxymethylated modified humic acid-chitosan complex, 15-20 parts of modified attapulgite powder, 2-10 parts of compound microbial agent, 3-5 parts of konjac glucomannan, 3-5 parts of polyacrylic acid, 3-5 parts of bentonite, 1-2 parts of polyglutamic acid, 2-3 parts of sodium alginate, 4-8 parts of mushroom residue, 2-4 parts of seaweed residue, and 12-20 parts of decomposed straw; preferably, 18-22 parts of carboxymethylated modified humic acid-chitosan complex, 16-18 parts of modified attapulgite powder, 5-8 parts of compound microbial agent, 4 parts of konjac glucomannan, 4 parts of polyacrylic acid, 4 parts of bentonite, 1.5 parts of polyglutamic acid, 2.5 parts of sodium alginate, 5-6 parts of mushroom residue, 3 parts of seaweed residue, and 15-18 parts of decomposed straw.

[0017] The compound microbial agent of the present invention is obtained by combining Candida glabrata, Bacillus steganus and Bacillus pasteurellus in a live cell count ratio of (1~2):(3~6):(3~6), preferably by combining Candida glabrata, Bacillus steganus and Bacillus pasteurellus in a live cell count ratio of 2:4:5.

[0018] The viable count of the compound microbial agent described in this invention is ≥5×10⁻⁶. 8 cfu / g, more preferably 5×10 8 cfu / g ~9×10 9 cfu / g. Preferably, the preparation method of the compound microbial agent of the present invention includes: Candida glabrata, Bacillus steganus, and Bacillus pasteurellii are inoculated into a culture medium for activation, mixed, and mixed to obtain a mixed bacterial solution; a microbial agent protectant is added to the mixed bacterial solution, and the solution is dried at low temperature to obtain the compound microbial agent. The Candida glabrata is preferably activated by culture in a YM medium at 25°C and 180 rpm with shaking; the Bacillus steganus is preferably activated by culture in a broth medium at 30°C and 180 rpm with shaking; the Bacillus pasteurellii is preferably activated by culture in a LB medium (LB + 20 g / L urea) at 30°C and 180 rpm with shaking. The microbial agent protectant is preferably obtained by mixing chitosan, trehalose, and skim milk powder in a mass ratio of 1:1:1, and the amount of the microbial agent protectant added is preferably 1~3 g / mL; the low-temperature drying of the present invention is preferably drying at 30~35°C until the moisture content is ≤8%, pulverizing and passing through a 60-mesh sieve to obtain the compound microbial agent. The present invention adds a microbial protectant to protect the activity of the strain and prolong its survival period in the soil, forming a dual protection with the optimized carrier, and further improving the stability of the strain.

[0019] This invention uses a combination of commercially available strains for non-traditional soil amendment. It was found that Candida glabrata, Bacillus stenosum, and Bacillus pasteurellii work synergistically. Combined with the slow-release and immobilization functions of an optimized carrier, the degradation rate of soil organophosphorus pesticides is ≥82%, the degradation rate of polycyclic aromatic hydrocarbons is ≥75%, and the degradation rate of straw and lignin is ≥85% within 45 days. Compared with traditional strain combinations and conventional carriers, this invention significantly improves the degradation rate and also has the effect of degrading recalcitrant pollutants such as microplastics and phenols.

[0020] The preparation method of the carboxymethylated modified humic acid-chitosan complex of the present invention includes: mixing humic acid with deionized water, adjusting the pH to 8-9, adding chloroacetic acid to carry out a carboxymethylation reaction, adding chitosan after the carboxymethylation reaction, stirring evenly, adding glutaraldehyde to carry out a cross-linking reaction, filtering, washing, drying, and pulverizing. Preferably, the mixing ratio of humic acid, deionized water, chloroacetic acid, and chitosan is 100g:(800-1000)mL:(30-35)g:(20-25)g; the pH adjustment is carried out using a 1mol / L sodium hydroxide solution; the glutaraldehyde is a 25% glutaraldehyde solution, and the amount used is 2%-3% of the total mass of humic acid and chitosan.

[0021] As an optional implementation, the preparation method of the carboxymethylated modified humic acid-chitosan complex includes: slowly adding humic acid to deionized water, stirring at 20-30°C and 300-400 r / min for 30-40 min to fully disperse the humic acid and form a uniform suspension, avoiding local agglomeration that could lead to incomplete reaction. Then, adding 1 mol / L sodium hydroxide solution dropwise, slowly adjusting the pH of the suspension (monitoring in real time with a precision pH meter, accuracy ±0.1), provides optimal conditions for the chloroacetic acid carboxymethylation reaction, promoting the dissociation of chloroacetic acid into chloroacetic acid ions and improving the efficiency of the carboxymethylation reaction. Chloroacetic acid was slowly added to the suspension and stirred for 10-15 minutes until completely dissolved. The mixture was then heated to 55-65°C in a constant-temperature water bath (heating rate 5°C / min to avoid excessively rapid heating and violent local reactions). The mixture was kept at this temperature and stirred for 3-4 hours at a stirring speed of 300 rpm. Samples were taken every 30 minutes to observe the reaction system, ensuring no clumping or layering occurred. The reaction endpoint was defined as a homogeneous, viscous system. After the reaction, the water bath was turned off, and the mixture was allowed to cool naturally to room temperature (25±2°C). Chitosan was then slowly added to the reaction system, and the stirring speed was adjusted to 400 rpm. The mixture was stirred at room temperature for 60-90 minutes to ensure thorough mixing of the chitosan and carboxymethylated humic acid, guaranteeing uniformity in the subsequent cross-linking reaction. Slowly add 25% glutaraldehyde solution dropwise to the mixture (dropping rate 1-2 drops / second). After the addition is complete, raise the temperature of the constant-temperature water bath to 40-50℃ and stir the mixture at 300 rpm for 2-3 hours. During the cross-linking reaction, the system will gradually form a gel. Continue stirring to avoid uneven local cross-linking. The reaction endpoint is determined by the gel product not sticking to the wall and not easily broken. After the reaction is complete, stop stirring and vacuum filter the gel product using a Buchner funnel (vacuum degree 0.06-0.08 MPa). Collect the filter cake and remove unreacted solution and small molecule byproducts. Place the filter cake in a beaker, add anhydrous ethanol, stir, and filter. Repeat the ethanol washing twice to remove unreacted glutaraldehyde. Then wash with deionized water 3-4 times until the pH of the washing solution reaches 6.5-7.0 (detected with a pH meter) to ensure the removal of unreacted chloroacetic acid and the byproduct sodium chloride. Place the washed filter cake in a constant temperature drying oven, set the temperature to 105±2℃, and dry for 2 hours (turn it over every 30 minutes during the drying process to ensure uniform drying and avoid local overheating that could lead to carbonization of the product); after drying, take it out, cool it to room temperature, crush it with a universal pulverizer, pass it through a 100-mesh standard sieve (sieve aperture 0.154mm), collect the sieve-underfilled product, and place it in a dry, sealed container for later use.

[0022] The carboxymethylated modified humic acid-chitosan complex of this invention has an organic matter content ≥75%, a water content ≤8%, and a pH of 5.5~7.0. This invention modifies humic acid by carboxylation with chloroacetic acid, introducing hydrophilic carboxyl groups (-COOH) to enhance the water absorption capacity and ion exchange performance of humic acid. Then, glutaraldehyde is used as a cross-linking agent to cause a cross-linking reaction between the carboxymethylated humic acid and chitosan, forming a three-dimensional network structure that possesses water retention, bacterial fixation, and nutrient slow-release functions, providing a stable microenvironment for subsequent bacterial loading.

[0023] The preparation method of the modified attapulgite powder of the present invention includes: adding attapulgite powder to an ethanol solution, ultrasonically dispersing it, then adding γ-aminopropyltriethoxysilane (KH-550) to react, centrifuging after reaction, drying the precipitate, and pulverizing it. The ratio of attapulgite powder, ethanol solution, and KH-550 in the present invention is 100g:(400~500)mL:(3~5)g. The ultrasonic conditions are preferably 200~300W power, 40kHz frequency, and ultrasonic dispersion for 20~40min; the volume concentration of the ethanol solution is preferably 70%.

[0024] As an optional implementation, the preparation method of the modified attapulgite powder includes: slowly adding attapulgite powder to an ethanol solution, ultrasonically dispersing it (stirring every 10 minutes during ultrasonication to avoid local agglomeration) to form a uniformly dispersed suspension, ensuring that the attapulgite powder is fully dispersed and increasing the surface reaction area. Then, KH-550 is slowly added to the above suspension, and the stirring speed is 200~300 r / min, stirred at room temperature (25±2℃) for 15~20 minutes to allow it to be fully hydrolyzed, generating an intermediate containing silanol groups (-Si-OH), which prepares for the subsequent condensation reaction with the hydroxyl groups on the surface of attapulgite. The attapulgite suspension containing KH-550 was transferred to a constant-temperature water bath stirrer. The water bath temperature was adjusted to 60-70℃ (heating rate 5℃ / min), and the reaction was maintained at a constant temperature with stirring for 2-3 hours at a stirring speed of 250-300 r / min. During the reaction, the silanol groups generated by the hydrolysis of KH-550 condensed with the hydroxyl groups on the surface of attapulgite to form Si-O-Si covalent bonds. The amino groups of KH-550 were grafted onto the surface of attapulgite. The reaction endpoint was determined by the suspension being in a homogeneous and stable state without obvious stratification or precipitation. After the reaction was completed, the reaction system was transferred to centrifuge tubes and centrifuged at 3000-4000 r / min for 15-20 minutes. The precipitate (modified attapulgite powder) was collected, and the supernatant (containing unreacted KH-550 and hydrolysis products) was removed. The precipitate collected by centrifugation was placed in a constant temperature drying oven at 105±2℃ and dried for 2 hours (the precipitate was turned over every 30 minutes during drying to ensure uniform drying and avoid local overheating that could cause the modified layer to peel off). After drying, the precipitate was removed and cooled to room temperature, ensuring that the product moisture content was ≤8%. The dried modified attapulgite powder was then pulverized using a universal pulverizer and passed through a 100-mesh standard sieve (0.154mm mesh). The sieve-passing product was collected, and any unpulverized coarse particles were removed. The product was then placed in a dry, sealed container for later use to prevent moisture absorption from affecting the modification effect.

[0025] This invention utilizes γ-aminopropyltriethoxysilane (KH-550) for surface modification, enhancing the dispersibility, hydrophilicity, and compatibility with other carrier components of attapulgite powder. Its porous structure can adsorb water, bacterial strains, and nutrients, strengthening water retention and bacterial fixation effects. Simultaneously, it can regulate soil pH and improve soil compaction. Attapulgite powder has a large number of hydroxyl groups (-OH) on its surface, exhibiting strong hydrophilicity and poor dispersibility. Surface modification with KH-550 involves the hydrolysis and condensation reaction of the ethoxy groups (-OC2H5) in the KH-550 molecule with the hydroxyl groups on the attapulgite surface, introducing amino groups (-NH2). This reduces the hydrophilicity of the attapulgite surface, improves its compatibility with carboxymethylated humic acid-chitosan complex, konjac glucomannan, polyacrylic acid, and bentonite, and simultaneously enhances its adsorption and fixation capacity for bacterial strains and its water retention performance.

[0026] The raw materials of this invention also contain konjac glucomannan, polyacrylic acid, and bentonite, which can enhance the water retention capacity, mechanical strength, and binding force with soil particles of the carrier, preventing the carrier from rapidly decomposing and being lost in the soil. Simultaneously, the layered structure of bentonite can further support the bacterial strains, improving their stability. The raw materials of this invention also contain polyglutamic acid and sodium alginate. Polyglutamic acid can enhance the water absorption capacity and slow-release properties of the carrier, while sodium alginate can form a protective film with the bacterial strains, further extending their survival time in the soil and promoting the formation of soil aggregates.

[0027] The optimized carrier of this invention improves the retention rate of bacterial strains by more than 40% through adsorption, ion exchange, and protective film effects via a network structure. Combined with the dual protection of the bacterial agent and the protective agent, the survival period of the bacterial agent in the soil is ≥120 days, which is 30 days longer than before optimization. After colonization, the carrier quickly forms a dominant bacterial community and continuously exerts its degradation and soil improvement effects. The carrier provides a stable microenvironment for the bacterial strains, effectively improving their adaptability and metabolic activity in barren and polluted soils.

[0028] This invention also provides a method for preparing the above-mentioned water-retaining soil conditioner containing highly efficient degrading bacteria, comprising the following steps: Carboxymethylated modified humic acid-chitosan complex, modified attapulgite powder, konjac glucomannan, polyacrylic acid and bentonite were mixed and stirred, and then polyglutamic acid and sodium alginate were added to obtain a composite water-retaining carrier. Mushroom residue, seaweed residue and straw compost were mixed and the moisture and pH were adjusted to obtain an organic nutrient matrix. The organic nutrient matrix was sterilized, and then mixed with the composite water-retaining carrier and composite microbial agent and fermented to obtain a fermentation product. The fermentation product was dried at low temperature and pulverized to obtain a water-retaining soil conditioner containing highly efficient degrading bacteria.

[0029] The organic nutrient substrate of this invention has a moisture content adjusted to 35-60%, preferably 45-55%, and a pH value of 6-7.5, preferably 6.5-7. Preferably, the organic nutrient substrate is sterilized at 121°C for 30 minutes to kill any unwanted microorganisms and avoid affecting the activity of the compound bacterial powder. The sterilized organic nutrient substrate is then cooled to below 30°C before use.

[0030] The fermentation conditions described in this invention are: fermentation at 30-40℃ for 3-8 days, with a preferred fermentation temperature of 32-36℃ and a preferred fermentation time of 5-6 days; the mixture is turned over every 12 hours during fermentation. This invention promotes bacterial proliferation and metabolism through fermentation, enhancing degradation efficiency, while simultaneously promoting the synergistic integration of the carrier, bacterial agent, and nutrient substrate. The low-temperature drying described in this invention is preferably performed at 30-50℃ until the moisture content is ≤12%, avoiding damage to the bacterial activity and water-retaining carrier performance due to high temperatures; the pulverization is preferably performed through a 60-80 mesh sieve.

[0031] This invention also provides the application of the above-mentioned water-retaining soil conditioner containing highly efficient degrading bacteria in any of the following: (1) Soil structure improvement; The water-retaining soil conditioner described in this invention significantly increases the soil organic matter content and aggregate structure, increases soil porosity to more than 45%, reduces bulk density by 20% to 25%, significantly enhances soil aeration and water permeability, improves soil compaction and acidification problems, and can achieve continuous improvement in soil quality with long-term use.

[0032] (2) Crop cultivation; the preferred crops are wheat and corn.

[0033] (3) Improve soil fertility; The water-retaining soil conditioner described in this invention can degrade organic pollutants and convert them into fast-acting nutrients such as nitrogen, phosphorus, and potassium. It can also be combined with trace elements to achieve long-term nutrient release and effectively improve soil fertility.

[0034] The present invention also provides a soil improvement method, comprising the following steps: applying the above-mentioned water-retaining soil conditioner containing highly efficient degrading bacteria to the soil, wherein the application amount is preferably 4.5~12 kg / mu.

[0035] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] In a specific embodiment of the present invention, the *Candida glabrata* used is... Candida glabrata Purchased from Beijing BioBW Biotechnology Co., Ltd. (biobw), accession number ATCC 2001, platform number bio-53400; Bacillus stearothermiae ( Bacillus subtilis Purchased from Beijing BioBW Biotechnology Co., Ltd. (biobw), accession number CMCC63501, platform number bio-52746; Bacillus pasteurellii ( Spore sac of pasteurii Purchased from Beijing BioBW Biotechnology Co., Ltd. (biobw), accession number ATCC 11859, platform number bio-67773; Saccharomyces cerevisiae ( Saccharomyces cerevisiae Purchased from Beijing BioBW Biotechnology Co., Ltd. (biobw), accession number ATCC 9763, platform number bio-53395.

[0037] Unless otherwise specified, the following embodiments are all conventional methods.

[0038] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0039] Example 1 Water-retaining soil conditioner containing highly efficient degrading bacteria (by weight): 20 parts carboxymethylated modified humic acid-chitosan complex, 16 parts modified attapulgite powder, 5 parts compound microbial agent, 4 parts konjac glucomannan, 4 parts polyacrylic acid, 4 parts bentonite, 1.5 parts polyglutamic acid, 2.5 parts sodium alginate, 6 parts mushroom residue, 3 parts seaweed residue, and 15 parts composted straw.

[0040] The viable count of the compound microbial agent is 1×10⁻⁶. 9 The cfu / g concentration was obtained by combining *Candida glabrata*, *Bacillus stenosum*, and *Bacillus pasteurellii* in a viable cell ratio of 2:4:5. Preparation method: *Candida glabrata* was activated by culture in YM medium at 25°C with shaking at 180 rpm; *Bacillus stenosum* was activated by culture in broth at 30°C with shaking at 180 rpm; *Bacillus pasteurellii* was activated by culture in LB medium (20 g / L urea) at 30°C with shaking at 180 rpm. The activated bacterial solutions were mixed to obtain a mixed bacterial solution. 2 g / mL of a bacterial preservative (chitosan, trehalose, and skim milk powder mixed in a mass ratio of 1:1:1) was added to the mixed bacterial solution. The solution was dried at 35°C until the moisture content was ≤8%, then pulverized through a 60-mesh sieve to obtain the compound bacterial agent.

[0041] Preparation method of carboxymethylated modified humic acid-chitosan complex: The mixing ratio of humic acid, deionized water, chloroacetic acid, and chitosan is 100g:900mL:30g:25g. Glutaraldehyde is a 25% glutaraldehyde solution, used at 2% of the total mass of humic acid and chitosan. Humic acid is slowly added to deionized water and stirred at 25℃ and 300r / min for 40min to ensure complete dispersion and form a uniform suspension. 1mol / L sodium hydroxide solution is added dropwise to slowly adjust the pH of the suspension to 8 (monitored in real time with a precision pH meter, accuracy ±0.1). Chloroacetic acid is slowly added to the above suspension and stirred for 15min to ensure complete dissolution. Then, the mixture is heated to 60℃ in a constant temperature water bath (heating rate 5℃ / min) and stirred for 3h at a constant temperature of 300r / min. Samples are taken every 30min to observe the state of the reaction system to ensure no clumping or stratification occurs. After the reaction was complete, the constant temperature water bath was turned off, and the mixture was allowed to cool naturally to 25°C. Chitosan was then slowly added to the reaction system, and the stirring speed was adjusted to 400 rpm. The mixture was stirred at room temperature for 60 min. 25% glutaraldehyde solution was slowly added dropwise to the mixture (dropping rate 1-2 drops / second). After the addition was complete, the temperature of the constant temperature water bath was raised to 50°C, and the mixture was stirred at 300 rpm for 2 h. After the reaction was complete, stirring was stopped, and the gel-like product was vacuum filtered using a Buchner funnel (vacuum degree 0.06 MPa). The filter cake was collected, and unreacted solution and small molecule byproducts were removed. The filter cake was placed in a beaker, anhydrous ethanol was added, and the mixture was stirred and filtered. The ethanol washing was repeated twice to remove unreacted glutaraldehyde. The mixture was then washed four times with deionized water until the pH of the washing solution reached 7.0 to remove unreacted chloroacetic acid and the byproduct sodium chloride. Place the washed filter cake in a constant temperature drying oven, set the temperature to 105℃, and dry for 2 hours (turning it over every 30 minutes). After drying, remove it, cool it to room temperature, crush it with a universal pulverizer, pass it through a 100-mesh standard sieve, and collect the product that passes through the sieve.

[0042] Preparation method of modified attapulgite powder: The ratio of attapulgite powder, ethanol solution, and KH-550 is 100g:400mL:4g. Attapulgite powder is slowly added to a 70% ethanol solution and ultrasonically dispersed (300W power, 40kHz frequency, ultrasonic dispersion for 30min, stirring every 10min). Then, KH-550 is slowly added to the above suspension, stirred at 250r / min at 25℃ for 15min. The attapulgite suspension containing KH-550 is transferred to a constant temperature water bath stirrer, and the water bath temperature is adjusted to 65℃ (heating rate 5℃ / min). The reaction is maintained at a constant temperature with stirring for 3h, and the stirring speed is maintained at 300r / min. After the reaction is complete, the reaction system is transferred to centrifuge tubes, placed in a centrifuge, and centrifuged at 3000r / min for 20min. The precipitate is collected, and the supernatant is removed. The precipitate collected by centrifugation was placed in a constant temperature drying oven at 105℃ and dried for 2 hours (stirred every 30 minutes during drying). After drying, it was removed and cooled to room temperature, ensuring that the product moisture content was ≤8%. The dried modified attapulgite powder was then pulverized using a universal pulverizer and passed through a 100-mesh standard sieve. The product passing through the sieve was collected.

[0043] Preparation method of water-retaining soil conditioner: Carboxymethylated modified humic acid-chitosan complex, modified attapulgite powder, konjac glucomannan, polyacrylic acid, and bentonite are thoroughly mixed in a high-speed mixer at a speed of 2000 r / min until homogeneous. Then, polyglutamic acid and sodium alginate are added, and the mixture is stirred at a speed of 2000 r / min for 30 min to obtain a composite water-retaining carrier. Mushroom residue, seaweed residue, and straw compost are mixed, and the moisture content is adjusted to 40% and the pH to 7. The mixture is then sterilized at 121℃ for 30 min. The organic nutrient substrate is cooled to below 30℃ and mixed with the composite water-retaining carrier and composite bacterial agent. Fermentation is carried out at 35℃ for 6 days, with the mixture turned over every 12 hours during fermentation to obtain the fermentation product. The fermentation product is dried at 40℃ until the moisture content is ≤12%, pulverized, and passed through a 60-mesh sieve to obtain a water-retaining soil conditioner containing highly efficient degrading bacteria.

[0044] Example 2 Water-retaining soil conditioner containing highly efficient degrading bacteria (by weight): 15 parts carboxymethylated modified humic acid-chitosan complex, 15 parts modified attapulgite powder, 2 parts compound microbial agent, 3 parts konjac glucomannan, 3 parts polyacrylic acid, 3 parts bentonite, 1 part polyglutamic acid, 2 parts sodium alginate, 4 parts mushroom residue, 2 parts seaweed residue, and 12 parts composted straw.

[0045] The viable count of the compound microbial agent is 5 × 10⁻⁶. 8The cfu / g concentration was obtained by combining *Candida glabrata*, *Bacillus stenosum*, and *Bacillus pasteurellii* in a viable cell ratio of 1:3:6. Preparation method: *Candida glabrata* was activated by culture in YM medium at 25°C with shaking at 180 rpm; *Bacillus stenosum* was activated by culture in broth at 30°C with shaking at 180 rpm; *Bacillus pasteurellii* was activated by culture in LB medium (20 g / L urea) at 30°C with shaking at 180 rpm. The activated bacterial solutions were mixed to obtain a mixed bacterial solution. 3 g / mL of a bacterial preservative (chitosan, trehalose, and skim milk powder mixed in a mass ratio of 1:1:1) was added to the mixed bacterial solution. The solution was dried at 30°C until the moisture content was ≤8%, then pulverized through a 60-mesh sieve to obtain the compound bacterial agent.

[0046] Preparation method of carboxymethylated modified humic acid-chitosan complex: The mixing ratio of humic acid, deionized water, chloroacetic acid, and chitosan is 100g:800mL:30g:20g. Glutaraldehyde is a 25% glutaraldehyde solution, used at 2% of the total mass of humic acid and chitosan. Humic acid is slowly added to deionized water and stirred at 20℃ and 300r / min for 30min to ensure complete dispersion and form a uniform suspension. 1mol / L sodium hydroxide solution is added dropwise to slowly adjust the pH of the suspension to 8 (monitored in real time with a precision pH meter, accuracy ±0.1). Chloroacetic acid is slowly added to the above suspension and stirred for 10min to ensure complete dissolution. Then, the mixture is heated to 55℃ in a constant temperature water bath (heating rate 5℃ / min) and stirred for 3h at a constant temperature and speed of 300r / min. Samples are taken every 30min to observe the state of the reaction system to ensure no clumping or stratification occurs. After the reaction was complete, the constant temperature water bath was turned off, and the mixture was allowed to cool naturally to 25°C. Chitosan was then slowly added to the reaction system, and the stirring speed was adjusted to 400 rpm. The mixture was stirred at room temperature for 60 min. 25% glutaraldehyde solution was slowly added dropwise to the mixture (dropping rate 1-2 drops / second). After the addition was complete, the temperature of the constant temperature water bath was raised to 40°C, and the mixture was stirred at 300 rpm for 2 h. After the reaction was complete, stirring was stopped, and the gel-like product was vacuum filtered using a Buchner funnel (vacuum degree 0.06 MPa). The filter cake was collected to remove unreacted solution and small molecule byproducts. The filter cake was placed in a beaker, anhydrous ethanol was added, and the mixture was stirred and filtered. The ethanol washing was repeated twice to remove unreacted glutaraldehyde. The mixture was then washed four times with deionized water until the pH of the washing solution reached 7.0 (measured with a pH meter) to ensure the removal of unreacted chloroacetic acid and the byproduct sodium chloride. Place the washed filter cake in a constant temperature drying oven, set the temperature to 106℃, and dry for 2 hours (turn it over every 30 minutes during the drying process); after drying, take it out, cool it to room temperature, crush it with a universal pulverizer, pass it through a 100-mesh standard sieve, and collect the product that passes through the sieve.

[0047] Preparation method of modified attapulgite powder: The ratio of attapulgite powder, ethanol solution, and KH-550 is 100g:400mL:3g. Attapulgite powder is slowly added to a 70% ethanol solution and ultrasonically dispersed (300W power, 40kHz frequency, ultrasonic dispersion for 40min, stirring every 10min). Then, KH-550 is slowly added to the above suspension, stirred at 300r / min at 25℃ for 15min to ensure complete hydrolysis. The attapulgite suspension containing KH-550 is transferred to a constant temperature water bath stirrer, and the water bath temperature is adjusted to 60℃ (heating rate 5℃ / min). The reaction is maintained at a constant temperature with stirring for 2h, and the stirring speed is maintained at 250r / min. After the reaction is complete, the reaction system is transferred to centrifuge tubes, placed in a centrifuge, and centrifuged at 4000r / min for 20min. The precipitate is collected, and the supernatant is removed. The precipitate collected by centrifugation was placed in a constant temperature drying oven at 105℃ and dried for 2 hours (stirred every 30 minutes during drying). After drying, it was removed and cooled to room temperature, ensuring that the product moisture content was ≤8%. The dried modified attapulgite powder was then pulverized using a universal pulverizer and passed through a 100-mesh standard sieve. The product passing through the sieve was collected.

[0048] Preparation method of water-retaining soil conditioner: Carboxymethylated modified humic acid-chitosan complex, modified attapulgite powder, konjac glucomannan, polyacrylic acid, and bentonite are thoroughly mixed in a high-speed mixer at a speed of 2000 r / min until homogeneous. Then, polyglutamic acid and sodium alginate are added, and the mixture is stirred at a speed of 2000 r / min for 30 min to obtain a composite water-retaining carrier. Mushroom residue, seaweed residue, and straw compost are mixed and the moisture content is adjusted to 60% and the pH to 7.5. The mixture is then sterilized at 121℃ for 30 min. The organic nutrient substrate is cooled to below 30℃ and mixed with the composite water-retaining carrier and composite bacterial agent. Fermentation is carried out at 30℃ for 8 days, with the mixture turned over every 12 hours during fermentation to obtain the fermentation product. The fermentation product is dried at 50℃ until the moisture content is ≤12%, pulverized, and passed through an 80-mesh sieve to obtain a water-retaining soil conditioner containing highly efficient degrading bacteria.

[0049] Example 3 Water-retaining soil conditioner containing highly efficient degrading bacteria (by weight): 25 parts carboxymethylated modified humic acid-chitosan complex, 20 parts modified attapulgite powder, 10 parts compound microbial agent, 5 parts konjac glucomannan, 5 parts polyacrylic acid, 5 parts bentonite, 2 parts polyglutamic acid, 3 parts sodium alginate, 8 parts mushroom residue, 4 parts seaweed residue, and 20 parts composted straw.

[0050] The viable count of the compound microbial agent is 9 × 10⁻⁶. 9The cfu / g concentration was obtained by combining *Candida glabrata*, *Bacillus stenosum*, and *Bacillus pasteurellii* in a viable cell ratio of 2:3:3. Preparation method: *Candida glabrata* was activated by culture in YM medium at 25°C with shaking at 180 rpm; *Bacillus stenosum* was activated by culture in broth at 30°C with shaking at 180 rpm; *Bacillus pasteurellii* was activated by culture in LB medium (20 g / L urea) at 30°C with shaking at 180 rpm. The activated bacterial solutions were mixed to obtain a mixed bacterial solution. 1 g / mL of a bacterial preservative (chitosan, trehalose, and skim milk powder mixed in a mass ratio of 1:1:1) was added to the mixed bacterial solution. The solution was dried at 35°C until the moisture content was ≤8%, then pulverized through a 60-mesh sieve to obtain the compound bacterial agent.

[0051] Preparation method of carboxymethylated modified humic acid-chitosan complex: The mixing ratio of humic acid, deionized water, chloroacetic acid, and chitosan is 100g:1000mL:35g:25g. Glutaraldehyde is a 25% glutaraldehyde solution, and its amount is 3% of the total mass of humic acid and chitosan. Humic acid is slowly added to deionized water and stirred at 30℃ and 400r / min for 40min to ensure sufficient dispersion and form a uniform suspension. 1mol / L sodium hydroxide solution is added dropwise to slowly adjust the pH of the suspension to 9 (monitored in real time with a precision pH meter, accuracy ±0.1). Chloroacetic acid is slowly added to the above suspension and stirred for 15min to ensure complete dissolution. Then, the temperature is raised to 55℃ in a constant temperature water bath (heating rate 5℃ / min), and the reaction is maintained at a constant temperature with stirring at 300r / min for 3h. During this period, samples are taken every 30min to observe the state of the reaction system to ensure no clumping or stratification occurs. After the reaction was complete, the constant temperature water bath was turned off, and the mixture was allowed to cool naturally to 25°C. Chitosan was then slowly added to the reaction system, and the stirring speed was adjusted to 400 rpm. The mixture was stirred at room temperature for 80 min. 25% glutaraldehyde solution was slowly added dropwise to the mixture (dropping rate 1-2 drops / second). After the addition was complete, the temperature of the constant temperature water bath was raised to 45°C, and the mixture was stirred at a constant temperature for 3 h at a stirring speed of 300 rpm. After the reaction was complete, stirring was stopped, and the gel-like product was vacuum filtered using a Buchner funnel (vacuum degree 0.08 MPa). The filter cake was collected, and unreacted solution and small molecule byproducts were removed. The filter cake was placed in a beaker, anhydrous ethanol was added, and the mixture was stirred and filtered. The ethanol washing was repeated twice to remove unreacted glutaraldehyde. The mixture was then washed four times with deionized water until the pH of the washing solution reached 6.5 (measured with a pH meter) to ensure the removal of unreacted chloroacetic acid and the byproduct sodium chloride. Place the washed filter cake in a constant temperature drying oven at 105℃ and dry for 2 hours (turn it over every 30 minutes during the drying process); after drying, take it out, cool it to room temperature, crush it with a universal pulverizer, pass it through a 100-mesh standard sieve, and collect the product that passes through the sieve.

[0052] Preparation method of modified attapulgite powder: The ratio of attapulgite powder, ethanol solution, and KH-550 is 100g:500mL:5g. Attapulgite powder is slowly added to a 70% ethanol solution and ultrasonically dispersed (power 200W, frequency 40kHz, ultrasonic dispersion for 30min, stirring every 10min). Then, KH-550 is slowly added to the above suspension, stirred at 200r / min at 25℃ for 20min to ensure complete hydrolysis. The attapulgite suspension containing KH-550 is transferred to a constant temperature water bath stirrer, and the water bath temperature is adjusted to 60℃ (heating rate 5℃ / min). The reaction is maintained at a constant temperature with stirring for 2h, and the stirring speed is maintained at 250r / min. After the reaction is complete, the reaction system is transferred to centrifuge tubes, placed in a centrifuge, and centrifuged at 4000r / min for 15min. The precipitate is collected, and the supernatant is removed. The precipitate collected by centrifugation was placed in a constant temperature drying oven and dried at 105℃ for 2 hours (stirred every 30 minutes during the drying process); after drying, it was removed and cooled to room temperature to ensure that the product moisture content was ≤8%. The dried modified attapulgite powder was crushed using a universal pulverizer and passed through a 100-mesh standard sieve, and the product passing through the sieve was collected.

[0053] Preparation method of water-retaining soil conditioner: Carboxymethylated modified humic acid-chitosan complex, modified attapulgite powder, konjac glucomannan, polyacrylic acid, and bentonite are thoroughly mixed in a high-speed mixer at a speed of 2500 r / min until homogeneous. Then, polyglutamic acid and sodium alginate are added, and the mixture is stirred at a speed of 2500 r / min for 30 min to obtain a composite water-retaining carrier. Mushroom residue, seaweed residue, and straw compost are mixed, and the moisture content is adjusted to 50% and the pH to 7. The mixture is then sterilized at 121℃ for 30 min. The organic nutrient substrate is cooled to below 30℃ and mixed with the composite water-retaining carrier and composite bacterial agent. Fermentation is carried out at 35℃ for 5 days, with the mixture turned over every 12 hours during fermentation to obtain the fermentation product. The fermentation product is dried at 40℃ until the moisture content is ≤12%, pulverized, and passed through an 80-mesh sieve to obtain a water-retaining soil conditioner containing highly efficient degrading bacteria.

[0054] Example 4 A soil improvement method: applying the water-retaining soil conditioner containing highly efficient degrading bacteria prepared in Example 1 to the soil, wherein the preferred application rate is 10 kg / mu.

[0055] Example 5 A soil improvement method: Applying a water-retaining soil conditioner containing highly efficient degrading bacteria prepared in Example 2 to the soil, wherein the preferred application rate is 6 kg / mu.

[0056] Comparative Example 1 The only difference between this comparative example and Example 1 is that Candida glabrata is replaced with Saccharomyces cerevisiae.

[0057] Comparative Example 2 The only difference between this comparative example and Example 1 is that *Bacillus stearothermiae* is not added. The viable count of the added compound bacterial agent is 1 × 10⁻⁶. 9 cfu / g, obtained by combining Candida glabrata and Bacillus pasteurella at a viable count ratio of 2:5.

[0058] Comparative Example 3 The only difference between this comparative example and Example 1 is that the carboxymethylated modified humic acid-chitosan complex is replaced with an equal amount of humic acid and chitosan directly mixed together, with a ratio of humic acid to chitosan of 4:1.

[0059] Comparative Example 4 The only difference between this comparative example and Example 1 is that the modified attapulgite powder is replaced with an equal amount of attapulgite powder.

[0060] Comparative Example 5 The only difference between this comparative example and Example 1 is that the carboxymethylated modified humic acid-chitosan complex is replaced with an equal amount of humic acid and chitosan directly mixed together, with a ratio of humic acid to chitosan of 4:1; and the modified attapulgite powder is replaced with an equal amount of attapulgite powder.

[0061] Experimental Example 1 I. Potted Plant Experiment 1. Experimental materials Experiments were conducted using the water-retaining soil conditioner of the present invention (Example 1), a commercially available conventional water-retaining agent (sodium polyacrylate type, water absorption rate of 80 times, commercially available), and products prepared by comparative examples 1 to 5, respectively.

[0062] Test soil: Select typical compacted and slightly polluted soil (organophosphorus pesticide residue 1.2 mg / kg, polycyclic aromatic hydrocarbon residue 0.8 mg / kg, organic matter content ≤15 g / kg, field water holding capacity ≤25%), crush it and pass it through a 2 mm sieve to remove stones, weeds and other impurities, and set it aside for later use.

[0063] The test crop was wheat (variety: Jimai 44). Seeds with plump grains, uniform size, and free from pests and diseases were selected, soaked and germinated until they showed white sprouts.

[0064] 2. Experimental Grouping Each experiment had 3 replicates, randomly arranged, with each flowerpot containing 5 kg of test soil. The specific groupings are as follows: Blank control group (CK): Only the test soil was added, without any amendments, and all other treatments were the same.

[0065] Commercially available water-retaining agent group (CK1): Commercially available conventional water-retaining agent was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed before being potted.

[0066] Comparative water-retaining agent group (CK2): The water-retaining soil conditioner of Comparative Example 1 was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed and then potted.

[0067] Comparative water-retaining agent group (CK3): The water-retaining soil conditioner of Comparative Example 2 was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed and then potted.

[0068] Comparative water-retaining agent group (CK4): The water-retaining soil conditioner of Comparative Example 3 was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed and then potted.

[0069] Comparative water-retaining agent group (CK5): The water-retaining soil conditioner of Comparative Example 4 was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed and then potted.

[0070] Comparative water-retaining agent group (CK6): The water-retaining soil conditioner of Comparative Example 5 was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed and then potted.

[0071] Experimental group (T) of this scheme: The water-retaining soil conditioner of Example 1 was added to the test soil at a rate of 0.5% of the soil mass, and the mixture was evenly mixed and then potted.

[0072] 3. Experimental Methods Sowing: Sow 15 germinated wheat seeds per pot in each group, cover with 2cm of soil, and water thoroughly (500mL per pot to ensure uniform soil moisture content). Place all pots in a greenhouse for cultivation, controlling the temperature at 20~25℃, the light duration at 12h / d, and the light intensity at 3000lx. Do not water additionally during this period (simulating a drought environment), and record the soil dryness time.

[0073] The water retention index of each group was tested: Water retention capacity testing: The time it took for each soil group to decrease from saturated water content (after thorough watering) to the lower limit of field capacity (≤10%) was recorded, i.e., water retention duration. Soil moisture content was measured daily, and water retention curves were plotted to analyze the release rate. Soil water holding capacity testing: Using the ring sampler method, soil samples were collected from each group at 15, 30, and 45 days after sowing. Soil water holding capacity was measured, and the improvement rate of the experimental group compared to the control group was calculated. Each group had three replicates, and the average value was taken. Synergistic testing of water retention capacity and seedling survival: Wheat seedling survival was observed daily, and the seedling survival rate (number of surviving seedlings / total number of sown seedlings × 100%) was recorded. Simultaneously, soil moisture content was measured at the corresponding time points, and the correlation between soil moisture content and seedling survival rate was analyzed. Seedling survival rate and corresponding soil moisture content data were statistically analyzed at 15, 30, and 45 days. Degradation performance: The residues of organophosphorus pesticides (chlorpyrifos) and polycyclic aromatic hydrocarbons in the soil were determined using chromatography, and the degradation rate was calculated.

[0074] Each group of data represents the mean ± standard deviation of three replicates. The results are shown in the table below: Table 1 Results of potted plant experiments for each group

[0075] The results showed that each comparative group (CK2~CK6) was superior to the commercially available water-retaining agent group (CK1) but inferior to the experimental group of the present invention (T). The present invention was significantly superior to the other groups in terms of degradation rate of organophosphorus compounds and polycyclic aromatic hydrocarbons, water retention time, and seedling survival rate.

[0076] II. Field Experiment 1. Experimental materials Experimental site: Arid, slightly polluted field plots were selected. The soil type was alluvial soil. The basic physical and chemical properties of the soil were: organophosphorus pesticide residue 1.3 mg / kg, polycyclic aromatic hydrocarbon residue 0.9 mg / kg, organic matter content 12 g / kg, field water holding capacity 22%, and significant soil compaction. The previous crop was corn.

[0077] Test crop: Maize (variety: Zhengdan 958), high-quality seeds were selected for later use.

[0078] Experimental materials: the soil conditioner of this invention (prepared according to Example 1, containing an optimized composite water-retaining carrier) and commercially available conventional water-retaining agent (sodium polyacrylate type, water absorption rate 80 times).

[0079] 2. Experimental Grouping The experiment was set up in 3 groups, each with an area of ​​50m². 2 (10m×5m), 3 replicates per group, randomized block design, with consistent field management (sowing time, sowing density, fertilizer application, pest and disease control, etc.) across groups. Specific groupings are as follows: Blank control group (CK): No amendments were applied, and routine field management was performed.

[0080] Commercially available water-retaining agent group (CK1): Before sowing, apply the commercially available conventional water-retaining agent evenly to the soil surface, and then rotary till and mix it. The amount added is 10 kg / mu of soil mass.

[0081] Experimental group (T) of this invention: Before sowing, the soil conditioner of this invention is evenly spread on the soil surface, and then rotary tilled and mixed. The amount added is 10 kg / mu of soil mass.

[0082] 3. Experimental Methods Sowing: All groups were sown at the same time, with a sowing density of 3500 plants / mu and a sowing depth of 5cm. After sowing, the soil was thoroughly watered (to ensure consistent soil moisture content across all groups). Throughout the growing season, all groups received the same amount of fertilizer (base fertilizer: 2000 kg / mu of well-rotted organic fertilizer and 50 kg / mu of compound fertilizer). Pest and disease control was performed using conventional methods, without additional watering (to simulate a natural drought environment).

[0083] Soil samples were collected from each group at 30, 60, and 90 days after sowing. Soil field water holding capacity was measured, and the improvement rate of the experimental groups compared to the control group was calculated. Each group was tested in triplicate, and the average value was taken. Soil moisture content was also measured at 30, 60, and 90 days after sowing using a soil moisture meter at three depths: 0–10 cm, 10–20 cm, and 20–30 cm. The uniformity and stability of moisture distribution in different soil layers were compared among the groups. Each group was tested in triplicate, and the average value was taken.

[0084] Synergistic testing of water retention capacity and seedling survival: The survival rate of maize seedlings in each group (number of surviving seedlings / total number of seeded seedlings × 100%) was statistically analyzed periodically, and survival rate data were recorded at 30, 60, and 90 days. Simultaneously, the average soil moisture content at each time point was measured, and the correlation between soil moisture content and seedling survival rate and seedling growth status was analyzed to verify the supporting role of water retention capacity in seedling survival. Degradation performance: The residual amounts of organophosphorus pesticides and polycyclic aromatic hydrocarbons in the soil were measured, and the degradation rate was calculated.

[0085] Each group of data represents the mean ± standard deviation of three replicates. The results are shown in the table below: Table 2 Results of field experiments for each group

[0086] The results show that the optimized carrier of this invention has stable water retention performance and uniform water distribution in field scenarios, can effectively resist natural drought, and achieve synergistic effect between water retention performance and corn seedling survival, making it suitable for large-scale field application.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A water-retaining soil conditioner containing highly efficient degrading bacteria, characterized in that, By weight, it includes the following components: 15-25 parts of carboxymethylated modified humic acid-chitosan complex, 15-20 parts of modified attapulgite powder, 2-10 parts of compound microbial agent, 3-5 parts of konjac glucomannan, 3-5 parts of polyacrylic acid, 3-5 parts of bentonite, 1-2 parts of polyglutamic acid, 2-3 parts of sodium alginate, 4-8 parts of mushroom residue, 2-4 parts of seaweed residue, and 12-20 parts of straw compost. The compound microbial agent is obtained by combining Candida glabrata, Bacillus stearothermiae and Bacillus pasteurelliae in a live count ratio of (1~2):(3~6):(3~6).

2. The water-retaining soil conditioner containing highly efficient degrading bacteria according to claim 1, characterized in that, The preparation method of the carboxymethylated modified humic acid-chitosan complex includes: mixing humic acid with deionized water, adjusting the pH to 8-9, adding chloroacetic acid to carry out a carboxymethylation reaction, adding chitosan after the carboxymethylation reaction, stirring evenly, adding glutaraldehyde to carry out a cross-linking reaction, filtering, washing, drying, and pulverizing.

3. The water-retaining soil conditioner containing highly efficient degrading bacteria according to claim 1, characterized in that, The method for preparing the modified attapulgite powder includes: adding attapulgite powder to an ethanol solution, ultrasonically dispersing it, then adding γ-aminopropyltriethoxysilane to react, centrifuging after the reaction, precipitating, drying, and pulverizing.

4. The water-retaining soil conditioner containing highly efficient degrading bacteria according to claim 1, characterized in that, The viable count of the compound microbial agent is ≥5×10⁻⁶. 8 cfu / g.

5. The water-retaining soil conditioner containing highly efficient degrading bacteria according to claim 4, characterized in that, The preparation method of the compound microbial agent includes: Candida glabrata, Bacillus steganus and Bacillus pasteurellis are inoculated into the culture medium for activation, mixed to obtain a mixed bacterial solution; a microbial agent protectant is added to the mixed bacterial solution, and the solution is dried at low temperature to obtain the compound microbial agent.

6. The method for preparing the water-retaining soil conditioner containing highly efficient degrading bacteria according to any one of claims 1 to 5, characterized in that, Includes the following steps: Carboxymethylated modified humic acid-chitosan complex, modified attapulgite powder, konjac glucomannan, polyacrylic acid and bentonite were mixed and stirred, and then polyglutamic acid and sodium alginate were added to obtain a composite water-retaining carrier. Mushroom residue, seaweed residue and straw compost were mixed and the moisture and pH were adjusted to obtain an organic nutrient matrix. The organic nutrient matrix was sterilized, and then mixed with the composite water-retaining carrier and composite microbial agent and fermented to obtain a fermentation product. The fermentation product was dried at low temperature and pulverized to obtain a water-retaining soil conditioner containing highly efficient degrading bacteria.

7. The preparation method according to claim 6, characterized in that, The organic nutrient substrate has a moisture content of 35-60% and a pH value of 6-7.

5.

8. The preparation method according to claim 6, characterized in that, The fermentation conditions are: fermentation at 30~40℃ for 3~8 days; turning over once every 12 hours during the fermentation process.

9. The application of the water-retaining soil conditioner containing highly efficient degrading bacteria as described in any one of claims 1 to 5 in any of the following: (1) soil structure improvement; (2) crop planting; (3) soil fertility enhancement.

10. A method for soil improvement, characterized in that, Includes the following steps: Apply the water-retaining soil conditioner containing highly efficient degrading bacteria as described in any one of claims 1 to 5 to the soil.

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