Microbial soil conditioner and its preparation method and application

Abstract

This invention belongs to the field of soil conditioner technology, and discloses a microbial soil conditioner, its preparation method, and its application. The microbial soil conditioner comprises the following raw materials by weight: 50-70 parts of fermented modified oyster shell powder, 20-40 parts of natural polymer materials, 1-5 parts of cross-linking agent, and 100-200 parts of deionized water. The fermented modified oyster shell powder is prepared by fermenting oyster shell powder with *Lactobacillus plantarum* BY13205, followed by centrifugation, washing, and drying. The preservation number of *Lactobacillus plantarum* BY13205 is CGMCC No. 35351. This invention uses oyster shell waste as raw material and employs *Lactobacillus plantarum* bio-fermentation technology to regulate the microstructure of oyster shells, and combines it with natural polymer materials to prepare an agricultural water-retaining material with high water retention capacity, environmental friendliness, and low cost.

Description

Technical Field

[0001] This invention belongs to the field of soil conditioner technology, specifically, it relates to a microbial soil conditioner and its preparation method. Background Technology

[0002] Oyster shells are a major waste product from seafood processing. Their main component is calcium carbonate (CaCO3, content >90%), and they also contain small amounts of organic matter and trace elements (such as Mg, Zn, etc.). Traditional oyster shell processing methods (such as calcination, acid treatment, etc.) are energy-intensive, highly polluting, and difficult to effectively control their pore structure, which limits their application in water-retaining materials.

[0003] In recent years, microbial fermentation technology has been widely used in the field of biomass modification due to its green and low-energy characteristics. Chinese invention patent with patent application number CN202110929664.6 discloses a method for activating oyster shells, a mixed liquid, an oyster shell composition and a method for preparing soil conditioner. The method for activating oyster shells includes the following steps: (1) crushing seafood waste / river seafood waste into a slurry; (2) adding compound microbial strains to the slurry in step (1) at an inoculation amount of 5%-10% and fermenting at room temperature for 20-60 hours to obtain the primary product of fermentation; (3) mixing the primary product of fermentation in step (2) and oyster shell powder in a ratio of (1-3):(1-3) and activating for 1-5 days to obtain the activated primary product; (4) centrifuging the activated primary product in step (3) or filtering it with a semi-transparent membrane to obtain the supernatant and filter residue.

[0004] The aforementioned existing oyster shell activation methods involve adding a compound microbial strain to activate the oyster shells. This compound microbial strain includes lactic acid bacteria, Bacillus, yeast, and Aspergillus oryzae in a ratio of (2-8):(1-3):(1-3):1. After the oyster shell powder is made into a soil conditioner, it can improve the soil's water retention, fertilizer retention, and aeration, thereby improving the soil's physical structure, promoting the reproduction of soil microorganisms, and promoting the absorption of soil nutrients by crops, thus achieving the purpose of increasing yield and improving quality. However, the above-mentioned oyster shell activation methods require the addition of multiple different types of microorganisms for fermentation, which reduces the production and use effects. Summary of the Invention

[0005] The main technical problem to be solved by this invention is to provide a microbial soil conditioner and its preparation method. Using oyster shell waste as raw material, the microstructure of oyster shells is controlled by bio-fermentation technology of Bacillus plantarum, and combined with natural polymer materials to prepare an agricultural water-retaining material with high water retention performance, environmental friendliness and low cost.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A microbial soil conditioner comprises the following raw materials by weight: 50-70 parts of fermented modified oyster shell powder, 20-40 parts of natural polymer materials, 1-5 parts of crosslinking agent, and 100-200 parts of deionized water.

[0008] The fermented modified oyster shell powder was prepared by fermenting oyster shell powder with Lactobacillus plantarum BY13205, followed by centrifugation, washing and drying.

[0009] Lactiplantibacillus plantarum BY13205 is deposited at the China General Microbiological Culture Collection Center (CGMCC) on July 23, 2025, with accession number CGMCC No. 35351. The deposit address is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing. The classification name is Lactiplantibacillus plantarum.

[0010] Further optimization: The natural polymer material uses a combination of sodium alginate, humic acid and wheat straw powder, with a mass ratio of sodium alginate, humic acid and wheat straw powder of 1:1:1-2;

[0011] Wheat straw powder is a product made by drying, crushing, and passing wheat straw through an 80-100 mesh sieve.

[0012] Further optimization: The natural polymer material uses a combination of sodium alginate and humic acid, with a mass ratio of sodium alginate to humic acid of 1:1-3.

[0013] Further optimization: The crosslinking agent is either calcium chloride or citric acid.

[0014] This invention utilizes the above-mentioned technical solution to ferment oyster shells using *Lactobacillus plantarum* BY13205 and combine it with natural polymer materials (such as sodium alginate, humic acid, and wheat straw powder) to prepare a soil conditioner. By optimizing the fermentation process and controlling the porosity and surface properties of oyster shells, and then combining them with natural polymer materials, this invention prepares a highly absorbent, slow-release, and biodegradable environmentally friendly soil conditioner, providing a new approach for agricultural water conservation and waste resource utilization.

[0015] This invention also provides a method for preparing a microbial soil conditioner: the method for preparing the above-mentioned microbial soil conditioner includes the following steps:

[0016] Step 1: Oyster shell pretreatment: Clean the oyster shells to remove surface impurities, then dry them in an oven at 60-80℃ for 8-12 hours. After drying, crush the oyster shells and pass them through a 100-200 mesh sieve to obtain oyster shell powder.

[0017] Step 2: Bio-fermentation modification of oyster shells: Oyster shell powder and fermentation culture medium are mixed at a mass ratio of 1:3-5 to prepare fermentation broth, and the pH value of the fermentation broth is adjusted to 6.0-7.0; then, Lactobacillus plantarum BY13205 is inoculated into the fermentation broth at a volume fraction of 1-5% for fermentation treatment, and then the fermented modified oyster shell powder is obtained after centrifugation, washing and drying.

[0018] Step 3: Preparation of composite soil conditioner: Mix 50-70 parts by weight of fermented modified oyster shell powder, 20-40 parts by weight of natural polymer material and 1-5 parts by weight to obtain a mixture. Add 100-200 parts by weight of deionized water to the mixture and stir until a uniform dispersion is formed. Then granulate the dispersion to obtain the microbial soil conditioner.

[0019] Further optimization: The specific composition of the fermentation medium in step two is based on water as the basic raw material, and the following are added in the following concentration ratios: glucose: 10-30 g / L, peptone: 10-20 g / L, disodium hydrogen phosphate: 2-5 g / L, MgSO4·7H2O: 0.02-0.05 g / L, MnSO4·H2O: 0.20-0.30 g / L, ZnSO4·7H2O: 0.10-0.30 mg / L, FeSO4·7H2O: 0.40-0.60 mg / L, Tween 80: 0.5-1.5 mL / L, thiamine hydrochloride: 0.05-0.15 mg / L, and pyridoxine hydrochloride: 0.04-0.06 mg / L.

[0020] Further optimization: In step two: the fermentation broth is fermented at 30-37℃ and 150-200r / min for 48-72 h; after fermentation, the product is centrifuged at 3000-5000r / min for 10-15 min, the precipitate is washed with deionized water until neutral, and then dried in an oven at 60-80℃ for 12-24 h to obtain fermented modified oyster shell powder.

[0021] Further optimization: In step three, the dispersion is reacted in a water bath at 50-70℃ for 2-4 hours, cooled to room temperature, and then granulated to obtain the microbial soil conditioner.

[0022] Further optimization: In step three: the particle size of the prepared soil conditioner is controlled at 2-5 mm; the moisture content is ≤10%.

[0023] In this invention, *Lactobacillus plantarum* BY13205, as a lactic acid bacterium, can metabolize and produce organic acids (such as lactic acid and acetic acid), which gently dissolve the calcium carbonate in oyster shells to form a porous structure while retaining its natural mineral components. In addition, this strain can also secrete extracellular polysaccharides to enhance the adhesion and stability of the material.

[0024] This invention utilizes organic acids (such as lactic acid and acetic acid) produced by the metabolism of Lactobacillus plantarum BY13205 to react with calcium carbonate on the surface of oyster shell powder, forming irregular pores and holes on the shell surface, which significantly improves the specific surface area and adsorption performance of the material. This method replaces the traditional high-temperature calcination or chemical etching process, effectively reducing energy consumption and environmental pollution.

[0025] In this invention, the hydrophilic groups of sodium alginate (such as -COOH, -OH), the colloidal properties of humic acid, and the cellulose network structure of wheat straw work synergistically to form an "adsorption-water retention" dual system with the pore structure of fermented modified oyster shell powder, which significantly improves the water retention rate (≥300%) and water holding stability of the material.

[0026] The present invention also provides an application of the above-mentioned microbial soil conditioner in agricultural water conservation and soil improvement, wherein the amount of soil conditioner added is 0.2% of the total soil weight or 300 kg / mu.

[0027] The fermented modified oyster shell powder (natural calcium carbonate) and natural polymer materials in this invention can be degraded by microorganisms in the natural environment without secondary pollution, which meets the requirements of green agriculture.

[0028] This invention uses oyster shell waste as raw material, which not only reduces production costs but also realizes the recycling of solid waste resources, resulting in significant economic and environmental benefits. Attached Figure Description

[0029] Figure 1 This is a product image of the microbial soil conditioner of the present invention;

[0030] Figure 2 This is a sample image of the microbial soil conditioner used in this invention;

[0031] Figure 3 This is a comparison diagram of the growth status of cherry tomatoes in greenhouse experiments according to the present invention;

[0032] Figure 4 This is a comparison diagram of the control group and the experimental group in the greenhouse experiment of this invention. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention; all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] The *Lactiplantibacillus plantarum* used in this embodiment of the invention was collected by the author and deposited at the China General Microbiological Culture Collection Center (CGMCC) on July 23, 2025, with accession number CGMCC No. 35351. The deposit address is No. 3, No. 1, Beichen West Road, Chaoyang District, Beijing. The classification name is *Lactiplantibacillus plantarum*.

[0035] The process of isolating and identifying *Lactobacillus plantarum* BY13205 in this embodiment of the invention is as follows:

[0036] Isolation, screening and identification of strains

[0037] 1. Isolation and screening of strains:

[0038] The strain was isolated from the soil around the roots of planted cherry tomatoes. The soil was mixed at a ratio of 1:10 (V / V), and after the soil settled naturally, the supernatant was serially diluted and spread on MRS plates (10.0 g peptone, 5.0 g beef meal, 20.0 g glucose, 4.0 g yeast extract, 5.0 g sodium acetate, 2.0 g disodium hydrogen phosphate, 0.20 g magnesium sulfate, 2.0 g triammonium citrate, 0.05 g manganese sulfate, 1 mL Tween 80, 15.0 g agar, 1 L water). The plates were anaerobic at 37 °C for 3 days. Single colonies were selected and purified by streaking on MRS plates three times to obtain the target strain, which was named strain BY13205.

[0039] 2. Molecular biological identification of the strain:

[0040] The 16S rRNA gene of the strain was sequenced using universal bacterial primers. The 16S rRNA gene sequence was identified, and the sequencing assembly results are as follows:

[0041] .

[0042] Test results:

[0043] The strain BY13205 was identified as *Lactiplantibacillus plantarum*.

[0044] Performance testing:

[0045] During fermentation, *Lactobacillus plantarum* metabolizes sugars and produces large amounts of organic acids such as lactic acid and acetic acid. In the performance determination of the strain, compared with the ATCC8014 standard strain (*Lactobacillus plantarum*), the total organic acid produced by *Lactobacillus plantarum* BY13205 is 2.63 times that of the standard strain, indicating that it has a very good basis for the action of calcium carbonate. Therefore, through subsequent condition optimization, it has a very good effect on calcium carbonate.

[0046] The performance test in this invention is described as follows: To evaluate the acid production performance of the strain, the total organic acid content was determined by acid-base titration. *Lactobacillus plantarum* BY13205 and the control standard strain ATCC8014 were cultured separately in MRS liquid medium under the same conditions (e.g., 37℃) for 24 h. The fermentation broth was centrifuged to obtain the supernatant. 5.0 mL of the supernatant was accurately measured and titrated to the endpoint with a standardized 0.1 mol / L sodium hydroxide standard solution using phenolphthalein as an indicator. Uninoculated medium was used as a blank control. The total organic acid content was calculated using the formula "Total acid (g / L) = [C × (V - V0) × 90.08] / 5 × 1000" (where C is the sodium hydroxide concentration, V is the volume of sodium hydroxide consumed by the sample, and V0 is the volume of sodium hydroxide consumed by the blank control).

[0047] The results showed that the total organic acid content produced by the fermentation broth of Lactobacillus plantarum BY13205 was 142.56 g / L (calculated as lactic acid), while the total organic acid content produced by the fermentation broth of the control strain ATCC8014 was 54.21 g / L (calculated as lactic acid).

[0048] Therefore, it can be seen that the total organic acid content produced by *Lactobacillus plantarum* BY13205 is 2.63 times that of the standard strain, which clearly confirms that *Lactobacillus plantarum* BY13205 in this invention has a significant and stronger organic acid synthesis ability.

[0049] Example 1: Please refer to Figure 1-2 A microbial soil conditioner, comprising the following raw materials by weight: 60 parts fermented modified oyster shell powder, 30 parts natural polymer material, 3 parts crosslinking agent and 150 parts deionized water.

[0050] The natural polymer materials used are sodium alginate, humic acid and wheat straw powder, with a mass ratio of sodium alginate, humic acid and wheat straw powder of 1:1:1.

[0051] Wheat straw powder is a product made by drying, crushing, and passing wheat straw through a 90-mesh sieve.

[0052] The crosslinking agent is either calcium chloride or citric acid.

[0053] This embodiment 1 also provides a method for preparing a microbial soil conditioner, which includes the following steps:

[0054] Step 1: Oyster shell pretreatment: Clean the oyster shells to remove surface impurities, and then dry them in an oven at 70℃ for 10 hours to fully dehydrate them; after drying, crush the oyster shells and pass them through a 150-mesh sieve to obtain oyster shell powder.

[0055] Step 2: Bio-fermentation modification of oyster shells: Oyster shell powder and fermentation culture medium were mixed at a mass ratio of 1:4 to prepare a fermentation broth. The pH of the fermentation broth was adjusted to 6.5 to ensure a suitable fermentation environment. Then, *Lactobacillus plantarum* BY13205 was inoculated into the fermentation broth at a volume fraction of 3%, and fermentation was carried out at 34℃ and 180 r / min for 54 h. After fermentation, the product was centrifuged at 4000 r / min for 13 min. The precipitate was washed with deionized water until neutral and then dried in an oven at 70℃ for 18 h to obtain fermented modified oyster shell powder.

[0056] The fermentation medium in step two is composed of water as the basic raw material, and the following are added in the following concentration ratios: glucose: 20 g / L, peptone: 15 g / L, disodium hydrogen phosphate: 3 g / L, MgSO4·7H2O (magnesium sulfate heptahydrate): 0.04 g / L, MnSO4·H2O (manganese sulfate monohydrate): 0.25 g / L, ZnSO4·7H2O (zinc sulfate heptahydrate): 0.20 mg / L, FeSO4·7H2O (ferrous sulfate heptahydrate): 0.50 mg / L, Tween 80: 1 mL / L, thiamine hydrochloride (vitamin B1): 0.1 mg / L, and pyridoxine hydrochloride (vitamin B6): 0.05 mg / L.

[0057] In this embodiment, organic acids (such as lactic acid and acetic acid) produced by the metabolism of Lactobacillus plantarum BY13205 are used to react with calcium carbonate on the surface of oyster shell powder to form irregular pores and holes on the shell surface, which significantly improves the specific surface area and adsorption performance of the material. This method replaces the traditional high-temperature calcination or chemical etching process, effectively reducing energy consumption and environmental pollution.

[0058] Specific surface area and pore structure analysis:

[0059] The porous structure of the material was characterized by nitrogen adsorption-desorption. Ordinary calcined oyster shell powder (control group) and oyster shell powder treated with organic acid metabolized by Bacillus plantarum BY13205 (experimental group) were degassed under vacuum at 150℃ for 6 h. The nitrogen adsorption-desorption isotherms were measured using a specific surface area and pore size analyzer. The specific surface area was calculated using the BET model and the pore size distribution was analyzed using the BJH model.

[0060] The results showed that the specific surface area of ​​ordinary calcined oyster shell powder was only 2.1 m². 2 / g, average pore size approximately 15.2 nm, total pore volume 0.008 cm³ 3 / g; while the specific surface area of ​​the experimental group was significantly increased to 65.3 m². 2 / g, the average pore size decreased to 5.8 nm, and the total pore volume increased to 0.175 cm³. 3 / g.

[0061] This indicates that the oyster shell powder (experimental group) treated with organic acids by *Lactobacillus plantarum* BY13205 has a richer and denser microporous and mesoporous structure on its surface, making its specific surface area more than 31 times that of the calcined sample (control group), fundamentally enhancing the matrix carrying capacity of the material.

[0062] Adsorption performance test:

[0063] Using the anionic dye methylene blue as a model pollutant, the adsorption capacity of the material was quantitatively evaluated. 0.10 g of each of the control and experimental groups were weighed and placed in 50 mL of methylene blue solution (pH=7.0) with an initial concentration of 50 mg / L. The solutions were shaken in the dark at 25℃ and 150 r / min for 24 h until adsorption equilibrium was reached. After centrifugation, the absorbance at 664 nm was measured using a UV-Vis spectrophotometer, and the equilibrium concentration was calculated. The experimental group adsorbed 52.4 mg / g of methylene blue, while the control group adsorbed only 4.7 mg / g. Further adsorption isotherm fitting revealed that the theoretical maximum adsorption capacity (Langmuir model) of the experimental group was 189.5 mg / g, significantly higher than the 21.3 mg / g of the control group. This result directly confirms that the porous structure formed by bio-etching with *Lactobacillus plantarum* BY13205 improves the adsorption performance of oyster shell powder by more than 10 times, demonstrating a clear technical advantage in the preparation of highly efficient adsorption materials.

[0064] Step 3: Preparation of composite soil conditioner: Mix 60 parts by weight of fermented modified oyster shell powder, 30 parts by weight of natural polymer material and 3 parts by weight to obtain a mixture. Add 150 parts by weight of deionized water to the mixture and stir until a uniform dispersion is formed. Then react in a water bath at 60°C for 3 hours. After cooling to room temperature, granulate the mixture and control the particle size to 3 mm. Finally, dry the mixture at 70°C until the moisture content is ≤10% to obtain the microbial soil conditioner.

[0065] In Example 1, the prepared microbial soil conditioner contains hydrophilic groups of sodium alginate (such as -COOH, -OH), colloidal properties of humic acid, and the cellulose network structure of wheat straw. These work synergistically to form an "adsorption-water retention" dual system with the pore structure of fermented and modified oyster shell powder, significantly improving the water retention rate (≥300%) and water-holding stability of the microbial soil conditioner.

[0066] To verify the performance of the microbial soil conditioner in this invention, the water retention rate and water-holding stability of the complete formulation were tested based on the agricultural water retention evaluation standard, using the composite material without modified oyster shell powder as a blank control.

[0067] The formula used in this invention to calculate the water retention rate is: Water retention rate = [Weight after water absorption (g) - Weight before water absorption (g)] / Weight before water absorption (g) × 100%.

[0068] The water retention rate was tested using the centrifugation method: after the sample was saturated with water, it was centrifuged at 3000 r / min for 20 min, and then the initial water retention rate of the control group and the experimental group was measured.

[0069] Water retention stability was assessed using the repeated wet-dry cycle method: the samples were subjected to 5 cycles of "water absorption-centrifugation-drying at 60℃" before the water retention rate of the control group and the experimental group was tested; the test results are shown in Table 1 below.

[0070] Table 1: Specific test results are as follows:

[0071] detection indicators control group experimental group Initial water retention rate 258% 382% 5th cycle water retention rate 201% 351% Water retention rate 78% 92%

[0072] As shown in the table above, the initial water retention rate of the experimental group reached 382%, which was significantly higher than that of the control group (258%), proving that its "adsorption-water retention" dual system can effectively retain water. The water retention rate of the experimental group remained at 351% in the 5th cycle, with a water retention rate retention rate of 92%, which was much higher than that of the control group (201% in the 5th cycle, with a water retention rate retention rate of 78%). This indicates that the network structure of this microbial soil conditioner is stable and has excellent durability.

[0073] Example 2: Please refer to Figure 1-2 A microbial soil conditioner, comprising the following raw materials by weight: 50 parts fermented modified oyster shell powder, 20 parts natural polymer material, 1 part crosslinking agent and 100 parts deionized water.

[0074] The natural polymer material is sodium alginate and humic acid, with a mass ratio of sodium alginate to humic acid of 1:2.

[0075] The crosslinking agent is either calcium chloride or citric acid.

[0076] This embodiment 2 also provides a method for preparing a microbial soil conditioner, which includes the following steps:

[0077] Step 1: Oyster shell pretreatment: Clean the oyster shells to remove surface impurities, and then dry them in an oven at 60℃ for 8 hours to fully dehydrate them; after drying, crush the oyster shells and pass them through a 100-mesh sieve to obtain oyster shell powder.

[0078] Step 2: Bio-fermentation modification of oyster shells: Oyster shell powder and fermentation culture medium were mixed at a mass ratio of 1:3 to prepare a fermentation broth. The pH of the fermentation broth was adjusted to 6.0 to ensure a suitable fermentation environment. Then, *Lactobacillus plantarum* BY13205 was inoculated into the fermentation broth at a volume fraction of 1%, and fermentation was carried out at 30℃ and 150 r / min for 48 h. After fermentation, the product was centrifuged at 3000 r / min for 10 min. The precipitate was washed with deionized water until neutral and then dried in an oven at 60℃ for 12 h to obtain fermented modified oyster shell powder.

[0079] The fermentation medium in step two is composed of water as the basic raw material, and the following are added in the following concentration ratios: glucose: 10 g / L, peptone: 10 g / L, disodium hydrogen phosphate: 2 g / L, MgSO4·7H2O: 0.02 g / L, MnSO4·H2O: 0.20 g / L, ZnSO4·7H2O: 0.10 mg / L, FeSO4·7H2O: 0.40 mg / L, Tween 80: 0.5 mL / L, thiamine hydrochloride: 0.05 mg / L, and pyridoxine hydrochloride: 0.04 mg / L.

[0080] Step 3: Preparation of composite soil conditioner: Mix 50 parts by weight of fermented modified oyster shell powder, 20 parts by weight of natural polymer material and 1 part by weight to obtain a mixture. Add 100 parts by weight of deionized water to the mixture and stir until a uniform dispersion is formed. Then react in a water bath at 50°C for 2 hours. After cooling to room temperature, granulate the mixture and control the particle size to 2 mm. Finally, dry the mixture at 60°C until the moisture content is ≤10% to obtain the microbial soil conditioner.

[0081] In this Example 2, the prepared microbial soil conditioner contains hydrophilic groups of sodium alginate (such as -COOH, -OH) and the colloidal properties of humic acid, which work synergistically to form an "adsorption-water retention" dual system with the pore structure of fermented and modified oyster shell powder, significantly improving the water retention rate (≥300%) and water holding stability of the microbial soil conditioner.

[0082] Example 3: Please refer to Figure 1-2 A microbial soil conditioner, comprising the following raw materials by weight: 70 parts fermented modified oyster shell powder, 40 parts natural polymer material, 5 parts crosslinking agent and 200 parts deionized water.

[0083] The natural polymer material is made of sodium alginate, humic acid and wheat straw powder, with a mass ratio of sodium alginate, humic acid and wheat straw powder of 1:1:2.

[0084] Wheat straw powder is a product made by drying, crushing, and passing wheat straw through a 100-mesh sieve.

[0085] The crosslinking agent is either calcium chloride or citric acid.

[0086] This embodiment 3 also provides a method for preparing a microbial soil conditioner, which includes the following steps:

[0087] Step 1: Oyster shell pretreatment: Clean the oyster shells to remove surface impurities, and then dry them in an oven at 80℃ for 12 hours to fully dehydrate them; after drying, crush the oyster shells and pass them through a 200-mesh sieve to obtain oyster shell powder.

[0088] Step 2: Bio-fermentation modification of oyster shells: Oyster shell powder and fermentation culture medium were mixed at a mass ratio of 1:5 to prepare a fermentation broth. The pH of the fermentation broth was adjusted to 7.0 to ensure a suitable fermentation environment. Then, *Lactobacillus plantarum* BY13205 was inoculated into the fermentation broth at a volume fraction of 5%, and fermentation was carried out at 37℃ and 200 r / min for 72 h. After fermentation, the product was centrifuged at 5000 r / min for 15 min. The precipitate was washed with deionized water until neutral and then dried in an oven at 80℃ for 24 h to obtain fermented modified oyster shell powder.

[0089] The fermentation medium in step two is composed of water as the basic raw material, and the following are added in the following concentration ratios: glucose: 30 g / L, peptone: 20 g / L, disodium hydrogen phosphate: 5 g / L, MgSO4·7H2O: 0.05 g / L, MnSO4·H2O: 0.30 g / L, ZnSO4·7H2O: 0.30 mg / L, FeSO4·7H2O: 0.60 mg / L, Tween 80: 1.5 mL / L, thiamine hydrochloride: 0.15 mg / L, and pyridoxine hydrochloride: 0.06 mg / L.

[0090] Step 3: Preparation of composite soil conditioner: Mix 70 parts by weight of fermented modified oyster shell powder, 40 parts by weight of natural polymer material and 5 parts by weight to obtain a mixture. Add 200 parts by weight of deionized water to the mixture and stir until a uniform dispersion is formed. Then react in a water bath at 70°C for 4 hours. After cooling to room temperature, granulate the mixture and control the particle size to 5 mm. Finally, dry the mixture at 60°C until the moisture content is ≤10% to obtain the microbial soil conditioner.

[0091] In this Example 3, the prepared microbial soil conditioner contains hydrophilic groups of sodium alginate (such as -COOH, -OH) and the colloidal properties of humic acid, which work synergistically to form an "adsorption-water retention" dual system with the pore structure of fermented and modified oyster shell powder, significantly improving the water retention rate (≥300%) and water holding stability of the microbial soil conditioner.

[0092] Example of results: Please refer to Figure 3-4 :

[0093] This study tested the effect of microbial soil conditioner on the growth performance of cherry tomatoes through a greenhouse experiment. Two treatments were set up: Field 1 (control group) received no microbial soil conditioner, while Field 2 (experimental group) received any of the microbial soil conditioners prepared in Examples 1-3, at a dosage of 0.2% of the total soil weight or 300 kg / mu. The experimental fields were located in the greenhouse of Shandong Beiyou Biotechnology Co., Ltd. (detailed address: Puzhuangyuan Farm, 023 Township Road, Houzhen Town, Shouguang City, Shandong Province) to ensure a stable and controllable environment. After 45 days of normal cultivation, once the seedlings had grown, the plants were subjected to drought stress treatment, controlling soil moisture at approximately 40% of normal water holding capacity and reducing watering frequency to 50% of normal. After 60 days, the photosynthetic rate, relative water content, chlorophyll content, aboveground dry weight, and plant height of each group of cherry tomatoes were measured. The average results of each group were taken, and the results are shown in Table 2 below.

[0094] Table 2: Physiological characteristics of plants under different treatment conditions

[0095] serial number Photosynthetic rate μmol / (m·s) Relative moisture content (%) Chlorophyll content (mg / g) Dry weight of above-ground portion (g) Above-ground plant height (cm) No. 1 (Control Group) 7.58±0.34 57.66±3.65 1.89±0.11 48.68±2.76 0.92±0.15 Group 2 (Experimental Group) 10.32±0.45 69.33±2.94 2.47±0.23 65.88±3.95 1.26±0.11

[0096] The results showed that, compared with the control group, the microbial soil conditioner of this invention can significantly improve the photosynthetic rate, relative water content and chlorophyll content of cherry tomato leaves, promote the growth rate of aboveground parts and dry matter accumulation, and prove that the microbial soil conditioner can enhance the drought resistance of cherry tomatoes in arid environments and ensure their growth and development.

[0097] and combined Figure 3-4 It can be seen that among them Figure 3 Centered on the center line of the image, the left side shows the cherry tomatoes grown in the experimental group; the right side shows the cherry tomatoes grown in the control group. Figure 4 visible, Figure 4 The left image shows cherry tomatoes grown in the control group, while the right image shows cherry tomatoes grown in the experimental group. This demonstrates that applying the microbial soil conditioner described in this invention to the crop planting substrate can significantly improve the growth status of cherry tomatoes, ensure their growth and development, and promote the yield and quality of cherry tomatoes.

[0098] For those skilled in the art, any changes, modifications, substitutions, and variations made to the embodiments without departing from the principles and spirit of the present invention, based on the teachings of the present invention, still fall within the protection scope of the present invention.

Claims

1. A microbial soil conditioner, characterized in that: The ingredients, by weight, include the following: 50-70 parts of fermented modified oyster shell powder, 20-40 parts of natural polymer materials, 1-5 parts of crosslinking agent, and 100-200 parts of deionized water. The fermented modified oyster shell powder was prepared by fermenting oyster shell powder with *Lactobacillus plantarum* BY13205. The oyster shell powder was mixed with the fermentation medium at a mass ratio of 1:3-5 to obtain the fermentation broth, and the pH of the broth was adjusted to 6.0-7.

0. *Lactobacillus plantarum* BY13205 was then inoculated into the fermentation broth at a volume fraction of 1-5%. The fermentation was carried out at 30-37℃ and 150-200 r / min for 48-72 h. After fermentation, the product was centrifuged at 3000-5000 r / min for 10-15 min, the precipitate was washed with deionized water until neutral, and then dried in an oven at 60-80℃ for 12-24 h to obtain the fermented modified oyster shell powder. Lactobacillus plantarum BY13205 is deposited at the China General Microbiological Culture Collection Center (CGMCC) on July 23, 2025, with accession number CGMCC No. 35351. The deposit address is No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing. Its classification name is Lactobacillus plantarum. Lactiplantibacillus plantarum; The prepared fermented modified oyster shell powder has the following properties: specific surface area: 65.3 m² 2 / g; Average pore size: 5.8 nm; Total pore volume: 0.175 cm³ 3 / g; Methylene blue adsorption capacity: 52.4 mg / g; Theoretical maximum adsorption capacity is 189.5 mg / g; The natural polymer materials are a combination of sodium alginate, humic acid and wheat straw powder or a combination of sodium alginate and humic acid. The mass ratio of sodium alginate, humic acid and wheat straw powder is 1:1:1-2; the wheat straw powder is the product of wheat straw that has been dried, crushed and passed through an 80-100 mesh sieve. The mass ratio of sodium alginate to humic acid is 1:1-3; The crosslinking agent is calcium chloride.

2. A method for preparing a microbial soil conditioner: The method is used to prepare the microbial soil conditioner according to claim 1, characterized in that: Includes the following steps: Step 1: Oyster shell pretreatment: Clean the oyster shells to remove surface impurities, then dry them in an oven at 60-80℃ for 8-12 hours. After drying, crush the oyster shells and pass them through a 100-200 mesh sieve to obtain oyster shell powder. Step 2: Bio-fermentation modification of oyster shells: Oyster shell powder and fermentation culture medium are mixed at a mass ratio of 1:3-5 to prepare fermentation broth, and the pH value of the fermentation broth is adjusted to 6.0-7.0; then, Lactobacillus plantarum BY13205 is inoculated into the fermentation broth at a volume fraction of 1-5% for fermentation treatment, and then the fermented modified oyster shell powder is obtained after centrifugation, washing and drying. In step two: the fermentation broth is fermented at 30-37℃ and 150-200 r / min for 48-72 h; after fermentation, the product is centrifuged at 3000-5000 r / min for 10-15 min, the precipitate is washed with deionized water until neutral, and then dried in an oven at 60-80℃ for 12-24 h to obtain fermented modified oyster shell powder. Step 3: Preparation of composite soil conditioner: Mix 50-70 parts by weight of fermented modified oyster shell powder, 20-40 parts by weight of natural polymer material and 1-5 parts by weight to obtain a mixture. Add 100-200 parts by weight of deionized water to the mixture and stir until a uniform dispersion is formed. Then granulate the dispersion to obtain the microbial soil conditioner.

3. The method for preparing a microbial soil conditioner according to claim 2, characterized in that: The fermentation medium in step two is specifically composed of water as the base material, with the following added in the following concentration ratios: glucose: 10-30 g / L, peptone: 10-20 g / L, disodium hydrogen phosphate: 2-5 g / L, MgSO4·7H2O: 0.02-0.05 g / L, MnSO4·H2O: 0.20-0.30 g / L, ZnSO4·7H2O: 0.10-0.30 mg / L, FeSO4·7H2O: 0.40-0.60 mg / L, Tween 80: 0.5-1.5 mL / L, thiamine hydrochloride: 0.05-0.15 mg / L, pyridoxine hydrochloride: 0.04-0.06 mg / L.

4. The method for preparing a microbial soil conditioner according to claim 2, characterized in that: In step three: the dispersion is reacted in a water bath at 50-70℃ for 2-4 hours, cooled to room temperature and then granulated to obtain the microbial soil conditioner.

5. The method for preparing a microbial soil conditioner according to claim 2, characterized in that: In step three: the particle size of the prepared soil conditioner is controlled at 2-5 mm; the moisture content is ≤10%.

6. An application of the microbial soil conditioner according to claim 1 in agricultural water conservation and soil improvement, characterized in that: The amount of soil conditioner added is 0.2% of the total soil weight or 300 kg / mu.

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