Bioactive calcium-based organic soil conditioner and preparation method thereof

Abstract

The invention provides a bioactive calcium-based organic soil conditioner and a preparation method thereof, and belongs to the field of soil conditioners. The method comprises the following steps: carrying out high-temperature calcination on a calcium raw material to convert the calcium raw material into active calcium oxide; performing controllable hydration reaction on the active calcium oxide and the low-temperature water mist to obtain active calcium hydroxide micro powder; the method comprises the following steps: sequentially carrying out composite enzymolysis pretreatment, high-temperature flora degradation and directional humification treatment on mushroom residues to obtain pretreated mushroom residues rich in active humic acid; mixing active calcium hydroxide micro powder, the pretreated mushroom residues and humate, and inoculating acetobacter aceti for fermentation to obtain a fermentation product; and adding a composite biological agent and chitosan into the fermentation product, uniformly mixing, granulating, and drying to obtain the soil conditioner. Therefore, the soil conditioner provided by the invention has the advantages of rapidly neutralizing acidity, lastingly supplying calcium nutrition and efficiently passivating heavy metals.

Description

Technical Field

[0001] This application relates to the field of soil conditioner technology, and in particular to a bio-activated calcium-based organic soil conditioner and its preparation method. Background Technology

[0002] In the fields of agricultural production and environmental remediation, soil degradation has become a significant challenge hindering sustainable development. Soil acidification, calcium deficiency, and heavy metal pollution are three prevalent and interconnected problems. Soil acidification directly leads to increased concentrations of hydrogen ions and toxic ions such as aluminum and manganese, harming crop roots and reducing the availability of essential nutrients like phosphorus, calcium, and magnesium. Traditionally, alkaline substances such as quicklime or calcium carbonate are used to correct acidification. However, these materials dissolve rapidly in the soil, resulting in concentrated and intense neutralization reactions. Their calcium ions are easily fixed by soil colloids or leached away by water, making them difficult for plants to sustainably utilize. Furthermore, long-term use alone can lead to soil compaction. On the other hand, heavy metals (such as cadmium and lead) accumulated in the soil due to industrial activities and unreasonable agricultural inputs seriously threaten agricultural product safety and ecological health. Passivating heavy metals using organic materials (such as humic acid) or mineral materials (such as zeolite) is a common remediation method, but these passivating materials typically lack the ability to significantly regulate soil pH and replenish calcium.

[0003] Currently, some compound soil conditioners exist on the market that physically mix calcium sources, organic matter, and passivating components. However, most of these products are merely simple additives of functional components; the release behavior, reaction sequence, and functional synergy of each component in the soil are not precisely designed, making it difficult to simultaneously achieve the triple goals of "rapid acidification," "long-lasting calcium supply," and "efficient passivation." Specifically, the calcium component is often released too quickly and is easily fixed, while the organic passivating component lacks strong interactions such as chemical bonds with the calcium component, resulting in an unsatisfactory overall effect and insufficient sustainability. Therefore, existing technologies have limitations, and an innovative solution is urgently needed. This application aims to solve the following technical problem: how to provide a soil conditioner that can rapidly neutralize acidity, provide long-lasting calcium nutrition, and efficiently passivate heavy metals. Summary of the Invention

[0004] This application provides a bio-activated calcium-based organic soil conditioner and its preparation method, which provides a soil conditioner that can quickly neutralize acidity, provide long-lasting calcium nutrition, and efficiently passivate heavy metals.

[0005] In a first aspect, embodiments of this application provide a method for preparing a bio-activated calcium-based organic soil conditioner, the method comprising the following steps:

[0006] S1. The calcium raw material is calcined at high temperature to convert it into active calcium oxide;

[0007] S2. Under stirring conditions, the active calcium oxide is subjected to a controlled hydration reaction with low-temperature water mist to obtain active calcium hydroxide micro powder.

[0008] S3. The mushroom residue is subjected to compound enzymatic hydrolysis pretreatment, high-temperature microbial degradation and targeted humification treatment in sequence to obtain pretreated mushroom residue rich in active humic acid.

[0009] S4. Mix the activated calcium hydroxide powder, the pretreated mushroom residue, and humic acid salt, and inoculate with acetic acid bacteria for fermentation to obtain the fermentation product.

[0010] S5. Add the compound biological agent and chitosan to the fermentation product, mix evenly, granulate, and dry to obtain the soil conditioner; the compound biological agent is composed of Bacillus mucilaginosus, Bacillus cereus, and Bacillus subtilis, and the total number of effective viable bacteria in the compound biological agent is ≥10.0×10⁻⁶. 8 CFU / g.

[0011] Optionally, in step S1, the high-temperature calcination temperature is 700℃~900℃, and the calcination time is 1~3h.

[0012] Optionally, in step S2, the controllable hydration reaction satisfies the following conditions: the molar ratio of water to calcium oxide is (0.3~0.5):1, the reaction temperature is 60℃~80℃, and the reaction time is 30~90min.

[0013] Optionally, step S3 specifically includes:

[0014] S31. Add a compound enzyme preparation containing laccase, xylanase and cellulase to the mushroom residue for enzymatic hydrolysis.

[0015] S32. Inoculate the enzymatically hydrolyzed material with thermophilic laterozoans for high-temperature aerobic fermentation;

[0016] S33. After the material cools down, Bacillus subtilis is introduced for mesophilic aerobic fermentation until the material is mature, resulting in pretreated mushroom residue rich in active humic acid.

[0017] Optionally, in step S31, the enzyme activity ratio of laccase, xylanase and cellulase in the compound enzyme preparation is (1-3):(2-5):(1-2).

[0018] The amount of the compound enzyme preparation added is 0.5 to 2.0% of the dry weight of the mushroom residue.

[0019] Optionally, in step S32, the temperature of the high-temperature aerobic fermentation is 60-70°C, and the fermentation time is 3-5 days;

[0020] The inoculum size of *Lactuca thermophila* is 1-5% of the wet weight of the enzymatically hydrolyzed material.

[0021] Optionally, in step S33, the temperature of the mesophilic aerobic fermentation is 45-50°C, and the fermentation time is 7-10 days;

[0022] The inoculation amount of the Bacillus mucilaginosus is 0.5 to 3% of the wet weight of the material after fermentation in step S32.

[0023] Optionally, in step S4, the active calcium hydroxide powder is 20-40 parts by dry weight, the pretreated mushroom residue is 50-70 parts, and the humate is 5-10 parts.

[0024] The amount of acetic acid bacteria inoculated is 1 to 5% of the total weight of the material.

[0025] Optionally, in step S5, the amount of the compound biological agent added is 0.5% to 2% of the dry weight of the fermentation product;

[0026] The amount of chitosan added is 1-3% of the dry weight of the fermentation product;

[0027] The ratio of viable bacteria of the Bacillus subtilis, Bacillus cereus and Bacillus subtilis is (4-6):(3-5):(1-2).

[0028] Secondly, embodiments of this application provide a bio-activated calcium-based organic soil conditioner prepared by the method described in any one of the first aspects, comprising calcium hydroxide micropowder activated by a controllable hydration reaction, pretreated mushroom residue rich in active humic acid, calcium humate fermentation product, compound biological agent, and chitosan.

[0029] The technical solutions provided in this application have the following advantages compared with the prior art:

[0030] This application provides a method for preparing a bio-activated calcium-based organic soil conditioner. Through its unique preparation method, it successfully provides a soil conditioner that combines rapid acidity neutralization, sustained calcium nutrient supply, and efficient heavy metal passivation. The technical implementation path is as follows:

[0031] First, this method, through the sequential design of steps S1 and S2, lays the material foundation for achieving rapid acidity neutralization and sustained calcium supply. Specifically, the active calcium oxide prepared in step S1 is transformed into active calcium hydroxide micropowder with a porous micro / nano structure through the "controlled hydration reaction" in step S2. This unique structure endows it with a huge specific surface area and extremely high surface reactivity. When the conditioner is applied to acidic soil, the active calcium hydroxide micropowder can rapidly react with hydrogen ions in the soil, thereby achieving rapid neutralization of soil acidity. More importantly, this porous structure ensures that its dissolution and reaction are not instantaneous, but can proceed at a relatively mild and continuous rate, providing an initial guarantee for subsequent sustained calcium supply.

[0032] Secondly, the core step S4 of this method is crucial for achieving sustained calcium nutrition and functional integration. In this step, activated calcium hydroxide micropowder undergoes a directional chelation reaction with pretreated mushroom residue and humic acid-rich humic acid-containing humate under the fermentation of acetic acid bacteria. The organic acids produced by the metabolism of acetic acid bacteria continuously dissolve the activated calcium hydroxide micropowder, and the released calcium ions combine with functional groups such as carboxyl groups in the active humic acid and humic acid molecules to form stable calcium humate fermentation products. This transformation is decisive: it converts free calcium ions that are easily fixed or leached by the soil into molecular, water-soluble organic complexed calcium. This calcium humate fermentation product has excellent mobility and stability in the soil, avoiding rapid fixation by soil colloids, thus ensuring that calcium is released slowly and persistently in a form that can be absorbed by plants, achieving a seamless transition and functional upgrade from "rapid acidification" to "long-term calcium supply".

[0033] Finally, this method systematically integrates the ability to efficiently passivate heavy metals through the raw material pretreatment in step S3 and the functional combination in step S5. The pretreated mushroom residue rich in active humic acid prepared in step S3 is itself rich in functional groups with a strong complexing ability for heavy metal ions. In the fermentation system of step S4, this part of active humic acid also participates in the complexation with calcium ions, but its remaining huge complexing capacity, together with the chitosan added in step S5 (whose amino groups are also strong complexing groups), constitutes a "molecular catcher" network for passivating heavy metals. When the conditioner is applied to soil contaminated with heavy metals, the active humic acid component in the calcium humate fermentation product and chitosan can preferentially and strongly chelate and fix heavy metal ions such as cadmium and lead in the soil, converting them into stable forms that are difficult for plants to absorb, thereby effectively blocking heavy metals from entering the food chain.

[0034] In summary, this application, through a progressive process design of "preparing a highly active inorganic calcium source → converting it into organic complex calcium → composite multifunctional passivation components," enables the active calcium hydroxide micropowder, calcium humate fermentation products, pretreated mushroom residue rich in active humic acid, and chitosan in the final product to each perform their respective functions while synergistically enhancing each other. Thus, the composite goals of rapidly neutralizing acidity, providing sustained calcium nutrition, and efficiently passivating heavy metals are simultaneously achieved in a single product. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0036] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic flowchart illustrating a method for preparing a bio-activated calcium-based organic soil conditioner, as provided in an embodiment of this application. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] Figure 1 This is a schematic flowchart illustrating a method for preparing a bio-activated calcium-based organic soil conditioner, as provided in an embodiment of this application.

[0040] like Figure 1 As shown in the embodiments of this application, a method for preparing a bio-activated calcium-based organic soil conditioner is provided, the method comprising the following steps:

[0041] S1. Calcining the calcium raw material at high temperature to convert it into active calcium oxide;

[0042] S2. Under stirring conditions, activated calcium oxide is subjected to a controlled hydration reaction with low-temperature water mist to obtain activated calcium hydroxide micro powder.

[0043] S3. The mushroom residue is subjected to compound enzymatic hydrolysis pretreatment, high-temperature microbial degradation and targeted humification treatment in sequence to obtain pretreated mushroom residue rich in active humic acid.

[0044] S4. Mix activated calcium hydroxide powder, pretreated mushroom residue and humic acid salt, and inoculate with acetic acid bacteria for fermentation to obtain fermentation products;

[0045] S5. Add the compound biological agent and chitosan to the fermentation product, mix evenly, granulate, and dry to obtain the soil conditioner; the compound biological agent is composed of Bacillus mucilaginosus, Bacillus cereus, and Bacillus subtilis, and the total number of effective viable bacteria in the compound biological agent is ≥10.0×10⁻⁶. 8 CFU / g.

[0046] This preparation method is a systematic materials design and bioengineering process that aims to reconstruct basic raw materials into composite materials with high reactivity and multiple soil remediation functions through sequentially controlled physical, chemical, and biological transformations. Its core principle lies in creating and utilizing the unique properties of the products at each step, enabling them to undergo efficient interfacial reactions and molecular assembly in subsequent steps.

[0047] First, activated calcium oxide is prepared through high-temperature calcination. This step fundamentally transforms the calcium source from chemically inert to highly reactive. The detailed principle lies in the thermal decomposition of calcium raw materials (such as calcium carbonate) at high temperatures. This process not only removes crystalline carbon dioxide but, more importantly, disrupts the stable crystal structure of the raw material, generating calcium oxide with defect states and high surface energy. This "activated calcium oxide" has fine grains and a significantly increased specific surface area. The calcium ions on its surface are in a highly unsaturated coordination state with a high chemical potential, making it highly reactive with water molecules or other polar substances in the environment. This provides a highly active source of material for all subsequent calcium ion release and complexation reactions.

[0048] Secondly, activated calcium hydroxide micropowder is prepared through a controlled hydration reaction. This step aims to directionally transform highly active but easily agglomerated calcium oxide into nano- to micron-sized porous calcium hydroxide with superior interfacial properties. The detailed principle lies in this controlled solid-gas (liquid) heterogeneous reaction. By using a "low-temperature water mist" and controlling the "molar ratio of water to calcium oxide" below the theoretical value for complete hydration, the reaction is forced to proceed heterogeneously and to a limited extent on the surface of the calcium oxide particles. Water molecules diffuse and react from the particle surface into its interior, forming a calcium hydroxide crystal layer. Due to insufficient water, the reaction cannot proceed completely to the particle core, ultimately forming a unique "core-shell" or "loose porous" microstructure. This "activated calcium hydroxide micropowder" has a huge specific surface area and abundant surface hydroxyl groups, greatly increasing its contact area and reaction sites with organic molecules such as humic acid in subsequent liquid-phase fermentation.

[0049] Next, pretreated mushroom residue rich in active humic acid was prepared through multi-stage biological pretreatment. This step aims to directionally deconstruct complex plant remains and transform them into a library of small-molecule organic matter rich in specific functional groups (carboxyl groups, phenolic hydroxyl groups). The detailed principle is to simulate and accelerate the natural soil humification process, but through exogenous intervention, to achieve targeted regulation. The process is divided into three stages: The first stage is a compound enzymatic hydrolysis pretreatment, which is based on the specificity and synergy of laccase, xylanase and cellulase to most effectively break down the solid "lignin-carbohydrate complex" in mushroom residue, dissociating it into soluble intermediate products, providing easily assimilated substrates for microbial metabolism; The second stage is thermophilic microbial degradation, which utilizes the high-speed metabolic characteristics of inoculated thermophilic lateral spores at high temperatures to rapidly decompose easily degradable organic matter, achieving rapid stabilization, volume reduction and harmlessness of the material, and accumulating precursor substances for the next stage; The third stage is targeted humification treatment, which utilizes the metabolic characteristics of inoculated Bacillus mucilaginosus to guide the precursor substances produced in the previous stage to be preferentially converted into "active humic acid" with relatively small molecular weight but rich functional groups through microbial condensation and polymerization, with the goal of maximizing the content of oxygen-containing functional groups with strong complexing ability for metal ions in the product.

[0050] Then, calcium humate fermentation product is prepared by acetic acid bacteria fermentation. The purpose of this step is to achieve efficient molecular chelation between active calcium and active organic matter under a mild biochemical environment, constructing a stable organic-inorganic complex. The detailed principle is twofold: first, the H+ released from the organic acids produced by acetic acid bacteria metabolism... + Create and maintain a slightly acidic environment to continuously and gently dissolve "active calcium hydroxide micro powder," releasing Ca at a controllable rate. 2+ Second, the humates in the fermentation system and the active humic acids abundant in the "pretreated mushroom residue" undergo deprotonation of their carboxyl and phenolic hydroxyl groups under suitable pH conditions, forming negatively charged sites. These sites react with free Ca in the solution. 2+ Strong coordination bonds occur, forming a cyclic calcium humate complex. This process transforms inorganic calcium into an organically complexed calcium that is molecularly stable, more mobile in the soil, and more easily absorbed by plants.

[0051] Finally, soil conditioners are prepared through functional compounding and granulation. This step integrates the terminal functional components and achieves physical fixation and activity preservation of the product. The detailed principle involves physically mixing two key functional components into the "calcium humate fermentation product" base matrix. The compound bio-inoculant acts as a living "functional seed," performing long-term ecological regulation after the product is applied to the soil. Chitosan, a natural cationic polysaccharide, has amino groups on its chains that act as a binding agent and complexing synergist through electrostatic attraction. The subsequent "granulation" process tightly binds the component particles, forming particles with a certain strength, which is beneficial for application and the formation of localized repair micro-zones in the soil. "Drying" fixes the product structure in a solid form at low temperatures and ensures the compound bio-inoculant remains dormant to maintain its long-term survival rate.

[0052] In some embodiments, in step S1, the high-temperature calcination temperature is 700℃~900℃, and the calcination time is 1~3h.

[0053] In step S1, the high-temperature calcination temperature range is set at 700℃~900℃, based on the thermodynamics and kinetics of calcium carbonate decomposition. This temperature window ensures that the calcium carbonate decomposition reaction proceeds rapidly and completely (decomposition pressure exceeds ambient total pressure), while avoiding excessively high temperatures (such as exceeding 1000℃) that could cause calcium oxide particles to sinter, recrystallize, and become dense, thus reducing specific surface area and reactivity. The calcination time of 1~3h is to ensure that heat is fully transferred to the interior of the material, allowing raw materials of different particle sizes to complete complete decomposition.

[0054] In some embodiments, in step S2, the controlled hydration reaction satisfies the following conditions: the molar ratio of water to calcium oxide is (0.3 to 0.5):1, the reaction temperature is 60°C to 80°C, and the reaction time is 30 to 90 min.

[0055] In step S2, the molar ratio of water to calcium oxide is strictly limited to (0.3–0.5):1, which is the quantitative core for achieving "controlled incomplete hydration." This ratio ensures that the supplied water is insufficient to completely convert all CaO into Ca(OH)₂, forcing the reaction to stop at the particle surface and near-surface region. This creates numerous nanopores and unreacted calcium oxide "cores" at the microscopic level, a prerequisite for obtaining the ultra-high specific surface area "active calcium hydroxide micropowder" structure. The reaction temperature of 60℃–80℃ provides sufficient thermal energy to accelerate water molecule diffusion and the reaction rate, while avoiding excessively low temperatures that lead to a slow reaction, or excessively high temperatures (such as boiling) that cause rapid evaporation of water, local overheating, and agglomeration. The reaction time of 30–90 min is a kinetic parameter matched to this temperature and molar ratio, designed to allow the controlled hydration reaction to fully reach equilibrium, forming a homogeneous and stable product.

[0056] In some implementations, step S3 specifically includes:

[0057] S31. Add a compound enzyme preparation containing laccase, xylanase and cellulase to the mushroom residue for enzymatic hydrolysis.

[0058] S32. Inoculate the enzymatically hydrolyzed material with thermophilic laterozoans for high-temperature aerobic fermentation;

[0059] S33. After the material cools down, Bacillus subtilis is introduced for mesophilic aerobic fermentation until the material is mature, resulting in pretreated mushroom residue rich in active humic acid.

[0060] In some embodiments, in step S31, the enzyme activity ratio of laccase, xylanase and cellulase in the compound enzyme preparation is (1-3):(2-5):(1-2).

[0061] The amount of compound enzyme preparation added is 0.5 to 2.0% of the dry weight of mushroom residue.

[0062] In some embodiments, in step S32, the temperature of the high-temperature aerobic fermentation is 60-70°C, and the fermentation time is 3-5 days;

[0063] The inoculum size of *Lactuca thermophila* is 1–5% of the wet weight of the enzymatically hydrolyzed material.

[0064] In some embodiments, in step S33, the temperature of the mesophilic aerobic fermentation is 45-50°C, and the fermentation time is 7-10 days.

[0065] The inoculation amount of Bacillus mucilaginosus is 0.5 to 3% of the wet weight of the material after fermentation in step S32.

[0066] In sub-step S31 of step S3, the enzyme activity ratio of laccase, xylanase, and cellulase in the compound enzyme preparation is (1-3):(2-5):(1-2). This ratio is optimized based on the approximate content and structural interweaving characteristics of the three components—lignin, hemicellulose, and cellulose—in mushroom residue. A higher xylanase ratio aims to rapidly break down the hemicellulose layer encapsulating cellulose; a suitable ratio of laccase and cellulase synergistically deconstructs the lignin skeleton and cellulose crystals, achieving the most efficient synergistic degradation. The amount of the compound enzyme preparation added is 0.5-2.0% of the dry weight of the mushroom residue. This range ensures the establishment of an effective enzyme concentration in the material, sufficient to complete the breakdown of the main structure within a set time, while also meeting the cost-effectiveness considerations for industrial applications.

[0067] In sub-step S32 of step S3, the temperature for high-temperature aerobic fermentation is set at 60–70°C. This is the optimal temperature range for the selected strain, *Layus thermophilus*, to grow and produce enzymes, maximizing its metabolic activity. The fermentation time of 3–5 days provides sufficient time for the thermophilic microorganisms to complete their logarithmic growth phase and deeply degrade easily decomposable organic matter. The inoculum size of *Layus thermophilus* is 1–5% of the wet weight of the post-enzymatic hydrolysis material. This inoculum size is sufficient to establish a significant microbial dominance at the initial stage, rapidly controlling the fermentation process, inhibiting contaminating microorganisms, and ensuring efficiency and purity during the high-temperature stage.

[0068] In the S33 sub-step of step S3, the temperature for mesophilic aerobic fermentation is 45–50℃. This temperature range is favorable for the growth and metabolism of mesophilic bacteria such as Bacillus mucilaginosus and the activity of humic acid synthases, while maintaining a certain metabolic rate. The fermentation time is relatively long, 7–10 days, to meet the needs of the complex and relatively slow biochemical synthesis process of "directional humification," providing sufficient time for the full condensation and accumulation of active humic acid molecules. The inoculum size of Bacillus mucilaginosus is 0.5–3% of the wet weight of the preceding material. This inoculum size can effectively introduce and establish functional microbial communities without causing excessive nutrient competition, driving the direction of humification.

[0069] In some embodiments, in step S4, the active calcium hydroxide powder is 20-40 parts by dry weight, the pretreated mushroom residue is 50-70 parts, and the humate is 5-10 parts.

[0070] The inoculation amount of acetic acid bacteria is 1-5% of the total weight of the material.

[0071] In step S4, the proportions by dry weight are: 20-40 parts activated calcium hydroxide powder, 50-70 parts pretreated mushroom residue, and 5-10 parts humate. This proportion scientifically balances the calcium ion supply, organic matter carrier amount, and humic acid precursor amount. It ensures sufficient calcium source for chelation, adequate active organic matter as a reaction matrix and buffer system, and exogenous humate as a "seed" and supplement, jointly creating the most favorable material environment for calcium humate formation. The inoculum amount of Acetobacter is 1-5% of the total material weight. This inoculum concentration ensures the initial cell density in the fermentation broth, enabling the acid production process to start quickly and maintain a stable acidic microenvironment, which is crucial for the continuous dissolution of calcium and the smooth progress of the chelation reaction.

[0072] In some embodiments, in step S5, the amount of compound biological agent added is 0.5% to 2% of the dry weight of the fermentation product;

[0073] The amount of chitosan added is 1-3% of the dry weight of the fermentation product;

[0074] The ratio of viable Bacillus mucilaginosus, Bacillus cereus and Bacillus subtilis was (4-6):(3-5):(1-2).

[0075] In step S5, the amount of compound biological agent added is 0.5–2% of the dry weight of the fermentation product. This ratio aims to implant a sufficiently high density of functional microbial "seeds" into the final product, ensuring that they reach the effective threshold in the soil. The amount of chitosan added is 1–3% of the dry weight of the fermentation product. This amount effectively utilizes its role as a cationic polyelectrolyte in particle bonding and functional enhancement without increasing costs or potentially affecting microbial activity due to excessive amounts. Within the compound biological agent, the viable count ratio of Bacillus mucilaginosus, Bacillus cereus, and Bacillus subtilis is (4–6):(3–5):(1–2). This specific ratio is an optimized formulation based on the functional strength of each of the three strains and their niche compatibility in the mixed system. It aims to ensure that the product simultaneously possesses strong mineral activation ability, plant growth promotion ability, and biocontrol potential, with mutual promotion or compatibility between the strains without strong inhibition. The total effective viable count of the compound biological agent is required to be ≥10.0 × 10⁻⁶. 8 CFU / g is the quantitative basis for ensuring that the above functional ratios can achieve the expected results in practical applications, thus ensuring the reliability of the product's performance.

[0076] Based on a general inventive concept, embodiments of this application provide a bio-activated calcium-based organic soil conditioner prepared by any of the above methods, comprising calcium hydroxide micro powder activated by a controlled hydration reaction, pretreated mushroom residue rich in active humic acid, calcium humate fermentation product, compound biological agent, and chitosan.

[0077] This bio-activated calcium-based organic soil conditioner is a composite material that achieves efficient soil remediation through component design and functional synergy. Its core components each perform a specific function, forming a synergistic and effective overall system through precise interactions. The functions of each core component are as follows:

[0078] Calcium hydroxide micropowder activated by controlled hydration reaction serves as a core inorganic calcium source and acid-base regulator. Its unique porous micro / nano structure provides a huge specific surface area and high reactivity, and its main function is to continuously and gently release calcium ions into the soil and neutralize soil acidity.

[0079] Pretreated mushroom residue rich in active humic acid serves as a core organic matter carrier and functional group library. It is rich in small-molecule active humic acid (such as fulvic acid), providing a large number of functional groups such as carboxyl and phenolic hydroxyl groups. Its main function is to chelate (fix) heavy metal ions in the soil through these functional groups and to serve as a high-quality carbon source for soil microorganisms.

[0080] Calcium humate fermentation products: serving as a key organic-inorganic bridging component and a stable slow-release carrier. It is the Ca in activated calcium hydroxide micropowder. 2+ The stable complex formed by fermentation chelation with active humic acid mainly functions to convert easily lost inorganic calcium into an organic complex calcium form that is more mobile and easier for plants to absorb, and to improve the overall structural stability.

[0081] Compound biological agents: acting as the biological executors of the system. They are composed of Bacillus mucilaginosus, Bacillus cereus, and Bacillus subtilis in specific proportions. Their main function is to perform long-term ecological regulation functions such as potassium and silicon release, secretion of plant growth hormones, and inhibition of soil-borne diseases after colonization in the soil.

[0082] Chitosan: As an auxiliary physicochemical functional modifier. As a natural cationic polysaccharide, its main function is to assist in the binding and shaping of conditioning agent particles through the protonation of its amino groups, and to further enhance the adsorption and fixation capacity of heavy metal ions.

[0083] More importantly, the synergistic effects among the components constitute a multi-layered functional network:

[0084] First, the calcium hydroxide micropowder activated by a controlled hydration reaction undergoes a basic synergistic reaction with the pretreated mushroom residue rich in active humic acid during fermentation. The calcium hydroxide micropowder continuously releases Ca... 2+ The calcium is captured by the abundant functional groups of active humic acid in the mushroom residue, thus generating calcium humate fermentation products in situ during fermentation. This process not only achieves the organicification and stabilization of calcium, but also tightly links the inorganic and organic phases through chemical bonding.

[0085] Secondly, the fermentation products of calcium humate act as a central link, bridging the functions of other components. On the one hand, it stabilizes the form of calcium; on the other hand, its organic matter provides a good colonization carrier and initial nutrition for the compound biological agent, protecting and promoting the survival and reproduction of functional strains after application to the soil. Simultaneously, chitosan binds to negatively charged components such as calcium humate and mushroom residue through electrostatic interactions, forming a physical coating during granulation, further reinforcing the overall particle structure and providing additional protection for the compound biological agent.

[0086] Ultimately, the synergistic effect of all components is fully expressed in the soil environment. After the conditioner is applied to the soil, calcium humate and residual active humic acid work together to exert a powerful passivation effect on heavy metals; calcium hydroxide micropowder continuously adjusts the acidity and provides calcium nutrition; the compound biological agent is activated, using the aforementioned organic components as an energy source to proliferate and exert its biological function; and chitosan helps to enhance the heavy metal fixation effect. This multi-level synergy from chemical chelation and physical adsorption to biological activation jointly achieves the combined goals of soil pH regulation, efficient calcium replenishment, long-term passivation of heavy metals, and ecological improvement of the micro-ecosystem.

[0087] In summary, the bio-activated calcium-based organic soil conditioner and its preparation method provided in this application have multi-level systematic advantages. Its core lies in the fact that through careful material design and process control, it has achieved a full-chain innovation from raw material activation and functional modification to end product integration, and finally obtained a soil remediation material with synergistic effects and superior performance.

[0088] First, this application possesses fundamental innovative advantages in terms of technical principles and process design. Unlike traditional processes involving simple mixing or single treatment, this scheme constructs a sequential reaction system of "physical activation-biotransformation-chemical chelation." In particular, the two core steps of "controlled hydration reaction" and "multi-stage biological pretreatment," through targeted regulation of the reaction process and microbial metabolic pathways, respectively create highly active calcium hydroxide micropowder with unique micro / nano structures and active humic acid organic matter rich in specific functional groups. This precise design and preparation of intermediate products lays an irreplaceable material foundation for subsequent efficient molecular assembly and functional integration, demonstrating significant non-obviousness.

[0089] Secondly, in terms of product composition and functional integration, this application achieves a deep multi-effect synergistic advantage. The final product is not a physical mixture of individual functional components, but an organic whole with "calcium humate fermentation products" as a stable matrix. Among them, calcium hydroxide micropowder activated by controlled hydration reaction provides the foundation for continuous acid regulation and calcium supplementation; pretreated mushroom residue rich in active humic acid and chitosan jointly construct a strong heavy metal ion passivation network; and the composite biological agent, as a living functional unit, is embedded in and relies on the aforementioned organic-inorganic composite matrix. Each component performs its own function in the soil environment while promoting each other: organic matter provides nutrients for the microbial agent, and microbial metabolic activities further activate nutrients and consolidate the aggregate structure, forming a virtuous cycle of "chemical conditioning - biological activation - ecological restoration". This multi-layered synergistic effect from the molecular to the ecological level ensures that the comprehensive efficacy of the product in solving complex problems such as soil acidification, calcium deficiency, heavy metal pollution, and soil fertility decline far exceeds the simple superposition of single-function products.

[0090] In summary, the advantages of this application are mainly reflected in the following aspects: at the process level, through innovative sequential step design, it achieves targeted enhancement and efficient preparation of key component properties; at the product level, through precise compatibility and synergistic design among components, it achieves systematic integration and long-term effectiveness of soil remediation functions. This makes it more efficient, more durable, and more adaptable than existing technologies in addressing complex soil obstacles, thus constituting outstanding technological progress and significant industrial application value.

[0091] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0092] Example 1

[0093] (1) Raw material preparation

[0094] Calcium source: dried oyster shells (main component is CaCO3), crushed to pass through a 100-mesh sieve.

[0095] Mushroom residue: taken from the waste mushroom substrate produced by the industrialization of enoki mushrooms (total organic carbon 388.2g / kg, total nitrogen 12.57g / kg, carbon-nitrogen ratio 30.64, moisture <10%), and then air-dried for later use.

[0096] Humate: Potassium humate (humic acid content ≥55%, CAS No.: 68514-28-3), purchased from Shandong Huayuan Humic Acid Ecological Agriculture Technology Co., Ltd.

[0097] Compound enzyme preparation: a solid mixed enzyme containing laccase (enzyme activity 50U / mg, CAS No.: 80498-15-3), xylanase (enzyme activity 1000U / mg, CAS No.: 9025-57-4) and cellulase (enzyme activity 500U / mg, CAS No.: 9012-54-8).

[0098] Microbial inoculant: Thermophilic Laterophyllum spore suspension (spore concentration 1×10⁻⁶) 8 CFU / mL, purchased from Beina Biotechnology (BNCC186105), Bacillus mucilaginosus bacterial suspension (5×10⁻⁶ viable cells). 8 CFU / mL, purchased from Shandong Ruichen Biotechnology Co., Ltd.; Acetobacter bacillus bacterial suspension (live count 1×10⁻⁶). 9 CFU / mL (purchased from Shanghai Bohu Biotechnology Co., Ltd.) and compound biological agent (Bacillus mucilaginosus: Bacillus cereus: Bacillus subtilis viable count ratio of 5:4:1, total viable count of 2.0×10⁻⁶ CFU / mL) and compound biological agent (Bacillus mucilaginosus: Bacillus cereus: Bacillus subtilis viable count ratio of 5:4:1 9(CFU / g) Bacillus cereus was purchased from Beijing Naphthalene Biochemical Technology Co., Ltd. (Bacillus cereus ATCC11778), and Bacillus subtilis was purchased from Shandong Yihao Biotechnology Co., Ltd.

[0099] Chitosan (deacetamide degree ≥90%, CAS No.: 9012-76-4).

[0100] (2) This embodiment provides a method for preparing a bio-activated calcium-based organic soil conditioner, comprising the following steps:

[0101] S1. Preparation of activated calcium oxide

[0102] Take 1 kg of processed oyster shell powder, place it in a muffle furnace, calcine it at 800℃ for 2 hours, and obtain active calcium oxide powder after natural cooling.

[0103] S2. Controlled hydration preparation of activated calcium hydroxide micro powder

[0104] The above-mentioned activated calcium oxide was placed in a reactor equipped with stirring and temperature control. Stirring was turned on (200 rpm), and the temperature inside the reactor was raised to 70°C. Deionized water was atomized into low-temperature water mist using an ultrasonic atomizer and introduced into the reactor to react with the activated calcium oxide. The molar ratio of water to calcium oxide was controlled at 0.4:1, and the reaction was continued for 60 minutes. After the reaction was completed, loose, microporous activated calcium hydroxide powder was obtained and discharged for later use.

[0105] S3. Preparation of pretreated mushroom residue rich in active humic acid

[0106] S31. Compound Enzymatic Hydrolysis: Take 1 kg of dry mushroom residue and adjust the moisture content to 60%. Weigh out 15 g of compound enzyme preparation (accounting for 1.5% of the dry weight of mushroom residue) according to the enzyme activity ratio (laccase:xylanase:cellulase = 1.5:3.5:1.5) and sprinkle it evenly into the mushroom residue. Let it stand at 50℃ for 36 h for enzymatic hydrolysis.

[0107] S32. High-Temperature Microbial Degradation: Inoculate the enzymatically hydrolyzed material with 50 mL of thermophilic Lateral spore suspension (inoculation amount is 5% of the wet weight of the material), mix thoroughly, and pile up (approximately 1.2 meters high). Cover with a breathable membrane for aerobic fermentation. Control the pile temperature at around 65℃, turn the pile every 24 hours, and continue high-temperature fermentation for 4 days.

[0108] S33. Targeted Humicification Treatment: After the pile temperature naturally drops below 48℃, add 30mL of Bacillus mucilaginosus bacterial solution (inoculation amount is 1.5% of the current wet weight of the material) and mix thoroughly. Control the pile temperature at around 48℃ for mesophilic aerobic fermentation, turning the pile every 48 hours, and fermentation continues for 8 days. When the material turns dark brown, loose, and odorless, and the seed germination index (GI) is measured to be 85%, it is considered fully decomposed. Dry the decomposed material at 55℃ to constant weight, crush it through a 60-mesh sieve, and obtain pretreated mushroom residue.

[0109] S4. Fermentation preparation of calcium humate fermentation products

[0110] Weigh out 30 parts by dry weight of activated calcium hydroxide powder, 60 parts by weight of pretreated mushroom residue, and 8 parts by weight of potassium humate, and mix them thoroughly in a mixer. Transfer the mixture to a fermenter and adjust the moisture content to 55%. Inoculate with 30 mL of Acetobacter acetic acid bacteria solution (inoculation amount is 3% of the total weight of materials), and ferment in a sealed container at 35℃ for 3 days to obtain the calcium humate fermentation product.

[0111] S5, Functional Compounding and Granulation

[0112] Add 1.5% (by dry weight) of a compound biological agent (i.e., 1.5g per 100g of dry fermentation product) and 2% (by dry weight) of chitosan powder to the above fermentation product, and mix thoroughly in a twin-screw mixer. Feed the mixture into a disc granulator, spray in a small amount of water mist, and produce wet granules with a particle size of 3–4 mm. Dry the wet granules in an oven at 50°C until the moisture content is below 12%, thus obtaining the finished bio-activated calcium-based organic soil conditioner.

[0113] Example 2

[0114] S1. Preparation of activated calcium oxide

[0115] Take 1 kg of processed oyster shell powder (passed through a 100-mesh sieve), place it in a muffle furnace, calcine at 700℃ for 1 hour, and obtain active calcium oxide powder after natural cooling.

[0116] S2. Controlled hydration preparation of activated calcium hydroxide micro powder

[0117] The above-mentioned activated calcium oxide was placed in a reactor equipped with stirring and temperature control. The stirring was turned on (200 rpm), and the temperature inside the reactor was raised to 60°C. Deionized water was atomized into low-temperature water mist using an ultrasonic atomizer and introduced into the reactor to react with the activated calcium oxide for hydration. The molar ratio of water to calcium oxide was controlled at 0.3:1, and the reaction was carried out for 30 minutes. After the reaction was completed, loose, microporous activated calcium hydroxide powder was obtained and discharged for later use.

[0118] S3. Preparation of pretreated mushroom residue rich in active humic acid

[0119] S31. Compound Enzymatic Hydrolysis: Take 1 kg of dry mushroom residue and adjust the moisture content to 58%. Weigh out 5 g of compound enzyme preparation (0.5% of the dry weight of mushroom residue) according to the enzyme activity ratio (laccase:xylanase:cellulase = 1:2:1), sprinkle it evenly into the mushroom residue, and let it stand at 50℃ for 36 h for enzymatic hydrolysis.

[0120] S32. High-Temperature Microbial Degradation: Inoculate 10 mL of thermophilic Lateral spore suspension (1% of the wet weight of the material) into the enzymatically hydrolyzed material, mix thoroughly, and pile up (approximately 1.0 meter high). Cover with a breathable membrane for aerobic fermentation. Control the pile temperature at around 60℃, turn the pile every 24 hours, and continue high-temperature fermentation for 3 days.

[0121] S33. Targeted Humicification Treatment: After the pile temperature naturally drops below 45℃, inoculate with 5mL of Bacillus mucilaginosus bacterial solution (inoculation amount is 0.5% of the current wet weight of the material) and mix thoroughly. Control the pile temperature at around 45℃ for mesophilic aerobic fermentation, turning the pile every 48 hours, and fermentation continues for 7 days. When the material turns dark brown, loose, and odorless, and the seed germination index (GI) is measured to be 82%, it is considered fully decomposed. Dry the decomposed material at 55℃ to constant weight, crush it through a 60-mesh sieve, and obtain pretreated mushroom residue.

[0122] S4. Fermentation preparation of calcium humate fermentation products

[0123] Weigh 20 parts by dry weight of activated calcium hydroxide powder, 70 parts by pretreated mushroom residue, and 5 parts by dry weight of potassium humate, and mix thoroughly in a mixer. Transfer the mixture to a fermenter and adjust the moisture content to 52%. Inoculate with 10 mL of Acetobacter acetic acid bacteria solution (1% of the total weight of the materials), and ferment in a sealed container at 35°C for 3 days to obtain the calcium humate fermentation product.

[0124] S5, Functional Compounding and Granulation

[0125] Add 0.5% (by dry weight) of a compound biological agent to the above fermentation product (i.e., 0.5g per 100g of dry fermentation product; the ratio of viable Bacillus mucilaginosus: Bacillus cereus: Bacillus subtilis in this agent is 4:3:1, and the total viable count is 1.2 × 10⁻⁶). 9 The mixture of 1% (CFU / g) and 1% chitosan powder (with a deacetamide degree ≥90%) is thoroughly mixed in a twin-screw mixer. The mixture is then fed into a disc granulator, where a small amount of water mist is sprayed in to produce wet granules with a particle size of 3-4 mm. The wet granules are dried in an oven at 50°C until the moisture content is below 12%, yielding the finished bio-activated calcium-based organic soil conditioner.

[0126] Example 3

[0127] S1. Preparation of activated calcium oxide

[0128] Take 1 kg of processed oyster shell powder (passed through a 100-mesh sieve), place it in a muffle furnace, calcine at 900℃ for 3 hours, and obtain active calcium oxide powder after natural cooling.

[0129] S2. Controlled hydration preparation of activated calcium hydroxide micro powder

[0130] The above-mentioned activated calcium oxide was placed in a reactor equipped with stirring and temperature control. The stirring was turned on (220 rpm), and the temperature inside the reactor was raised to 80°C. Deionized water was atomized into low-temperature water mist using an ultrasonic atomizer and introduced into the reactor to react with the activated calcium oxide for hydration. The molar ratio of water to calcium oxide was controlled at 0.5:1, and the reaction was carried out for 90 minutes. After the reaction was completed, loose, microporous activated calcium hydroxide powder was obtained and discharged for later use.

[0131] S3. Preparation of pretreated mushroom residue rich in active humic acid

[0132] S31. Compound Enzymatic Hydrolysis: Take 1 kg of dry mushroom residue and adjust the moisture content to 62%. Weigh out 20 g of compound enzyme preparation (accounting for 2.0% of the dry weight of mushroom residue) according to the enzyme activity ratio (laccase:xylanase:cellulase = 3:5:2), sprinkle it evenly into the mushroom residue, and let it stand at 52℃ for 48 h for enzymatic hydrolysis.

[0133] S32. High-Temperature Microbial Degradation: Inoculate the enzymatically hydrolyzed material with 50 mL of thermophilic Lateral spore suspension (inoculation amount is 5% of the wet weight of the material), mix thoroughly, and then pile up (approximately 1.5 meters high). Cover with a breathable membrane for aerobic fermentation. Control the pile temperature at around 70℃, turn the pile every 24 hours, and continue high-temperature fermentation for 5 days.

[0134] S33. Targeted Humicification Treatment: After the pile temperature naturally drops below 48℃, inoculate with 60mL of Bacillus mucilaginosus bacterial solution (inoculation amount is 3% of the current wet weight of the material) and mix thoroughly. Control the pile temperature at around 50℃ for mesophilic aerobic fermentation, turning the pile every 48 hours, and fermentation continues for 10 days. When the material turns dark brown, loose, and odorless, and the seed germination index (GI) is measured to be 88%, it is considered fully decomposed. Dry the decomposed material at 55℃ to constant weight, crush it through a 60-mesh sieve, and obtain pretreated mushroom residue.

[0135] S4. Fermentation preparation of calcium humate fermentation products

[0136] Weigh out 40 parts of activated calcium hydroxide powder, 50 parts of pretreated mushroom residue, and 10 parts of potassium humate by dry weight, and mix them thoroughly in a mixer. Transfer the mixture to a fermenter and adjust the moisture content to 58%. Inoculate with 50 mL of Acetobacter acetic acid bacteria solution (inoculation amount is 5% of the total weight of materials), and ferment in a sealed container at 38℃ for 4 days to obtain the calcium humate fermentation product.

[0137] S5, Functional Compounding and Granulation

[0138] Add 2.0% (by dry weight) of a compound biological agent to the above fermentation product (i.e., 2.0g per 100g of dry fermentation product; the ratio of viable Bacillus mucilaginosus: Bacillus cereus: Bacillus subtilis in this agent is 6:5:2, and the total viable count is 2.5 × 10⁻⁶). 9 CFU / g and 3% chitosan powder (deacetamide degree ≥90%) are mixed evenly in a twin-screw mixer. The mixture is then fed into a disc granulator, where a small amount of water mist is sprayed in to produce wet granules with a particle size of 3-4 mm. The wet granules are dried in an oven at 55°C until the moisture content is below 12%, yielding the finished bio-activated calcium-based organic soil conditioner.

[0139] Comparative Example 1

[0140] This comparative example is modified from the one disclosed in Example 1 as follows:

[0141] Step S2 (controllable hydration preparation of active calcium hydroxide micro powder) is completely omitted.

[0142] Specifically, after obtaining the active calcium oxide powder in step S1, a controlled hydration reaction is not performed. Instead, excess water (molar ratio of water to calcium oxide is 1.2:1) is directly added to the powder, and the mixture is stirred at room temperature until the reaction is complete to generate ordinary calcium hydroxide. This ordinary calcium hydroxide powder is then used to replace the "active calcium hydroxide micro powder" in subsequent step S4, while all other raw materials, steps, and parameters remain exactly the same as in Example 1.

[0143] Comparative Example 2

[0144] This comparative example is modified from the one disclosed in Example 1 as follows:

[0145] Step S3 (preparing pretreated mushroom residue rich in active humic acid) is completely omitted and replaced with conventional compost.

[0146] Specifically, dried mushroom residue of the same source and weight as in Example 1 was taken, and the moisture content was adjusted to 60%. Conventional aerobic composting was then carried out (without adding compound enzymes or specific functional microbial agents, natural inoculation, and a compost temperature fluctuating between ambient temperature and 55°C). The composting period was 20 days, until the material was fully decomposed (brown in color and without foul odor). This conventional compost product was then dried at 55°C, pulverized through a 60-mesh sieve, and used in subsequent step S4 to replace the "pretreated mushroom residue." All other raw materials, steps, and parameters were exactly the same as in Example 1.

[0147] Comparative Example 3

[0148] This comparative example is modified from the one disclosed in Example 1 as follows:

[0149] In step S5, the addition of the compound biological agent and chitosan is omitted.

[0150] Specifically, after obtaining the "calcium humate fermentation product" in step S4, without adding any compound biological agents or chitosan, the fermentation product is directly fed into a disc granulator for granulation and drying. All other raw materials, steps, and parameters are exactly the same as in Example 1.

[0151] The physicochemical properties of the soil conditioners prepared in Examples 1-3 and Comparative Examples 1-3 were tested, and the results are shown in Table 1. The testing methods are as follows:

[0152] pH determination method: Refer to agricultural standard NY / T1377-2007. Weigh 10.0g of conditioner sample that has passed through a 2mm sieve, add 50mL of carbon dioxide-free distilled water at a solid-liquid ratio of 1:5, shake in a shaker at 25℃ for 30min, let stand for 30min, and then measure the pH value of the supernatant using a calibrated precision pH meter.

[0153] Effective calcium content determination method: Refer to the "Calcium and Magnesium Content Determination" section of industry standard HG / T3276-2012. Water-soluble and weakly acid-soluble calcium in the sample are extracted using a 1% citric acid solution. After appropriate dilution, the extract is titrated with disodium ethylenediaminetetraacetate (EDTA) standard titrant using calcium carboxylic acid as an indicator.

[0154] Method for determining cation exchange capacity: Refer to forestry standard LY / T1243-1999. A 1 mol / L ammonium acetate solution at pH 7.0 is used as the exchanger. Multiple exchanges are performed on the sample to ensure all exchangeable cation sites are saturated with ammonium ions. The displaced ammonium ions are determined by the Kjeldahl method or by distillation titration.

[0155] Organic matter content method: Refer to agricultural standard NY / T1121.6-2006. The potassium dichromate oxidation-external heating method is used. In the presence of concentrated sulfuric acid, the organic carbon in the sample is oxidized with a known excess of potassium dichromate solution. The remaining potassium dichromate is back-titrated with a ferrous sulfate standard solution, and the organic matter content is calculated based on the amount consumed.

[0156] Specific surface area determination method: Refer to national standard GB / T19587-2017. The nitrogen adsorption method is adopted. At the liquid nitrogen temperature (77K), the adsorption-desorption isotherm of nitrogen on the sample is determined using a specific surface area and pore size analyzer. The specific surface area of ​​the sample is calculated by the BET (Brunauer-Emmett-Teller) model.

[0157] Table 1 Physicochemical properties of soil conditioners

[0158] Test Project pH value Available calcium content (g / kg) <![CDATA[Cation Exchange Capacity (CEC, cmol + / kg)]]> Organic matter content (g / kg) <![CDATA[Specific surface area (m 2 / g)]]> Example 1 10.3 185.6 62.5 455.2 15.8 Example 2 10.1 162.3 58.1 472.5 12.1 Example 3 10.5 198.4 65.8 438.7 16.5 Comparative Example 1 12.6 152.7 45.3 448.9 5.3 Comparative Example 2 9.9 143.2 40.2 465.3 14.6 Comparative Example 3 9.8 170.5 55.4 465.8 15.2

[0159] As shown in Table 1, the physicochemical properties of the soil conditioner exhibit balanced and excellent characteristics in key performance aspects, and form a clear and logical comparison with the comparative examples, thus highlighting the technical contribution of the key steps in this invention.

[0160] First, regarding indicators reflecting the basic chemical properties of the materials, the products in the examples exhibited moderate and stable alkalinity (pH 10.1–10.5), which is beneficial for the safe and effective neutralization of acidic soils. In contrast, Comparative Example 1, by omitting the "controlled hydration" step and directly using ordinary calcium hydroxide, had a pH as high as 12.6, which is excessively alkaline and poses a potential risk of disrupting the soil microecology and burning crop roots in practical applications. Furthermore, the effective calcium content of the products in the examples (162.3–198.4 g / kg) was generally higher than that of the comparative examples, especially significantly higher than that of Comparative Example 1 (152.7 g / kg) and Comparative Example 2 (143.2 g / kg). This directly reflects the efficient activation and effective retention of calcium through the synergistic effect of "controlled hydration" and "directional pretreatment."

[0161] Secondly, the examples demonstrate significant advantages in revealing the core indicators of material reactivity and fertilizer retention capacity. The cation exchange capacity (CEC, 58.1–65.8 cmol) of the examples is [not specified in the original text]. + The concentration of CEC 40.2 cmol / kg was significantly higher than that of all comparative examples. Comparative example 2 (CEC 40.2 cmol / kg) was the highest. + The lowest value ( / kg) strongly demonstrates that the organic matter obtained by replacing "directed humification treatment" with conventional composting has insufficient quantity and activity of surface functional groups (such as carboxyl groups and phenolic hydroxyl groups), resulting in a significant decrease in the product's ability to retain and exchange nutrient ions. Comparative Example 1 (CEC 45.3 cmol) + The low ( / kg) indicates that the unactivated calcium source structure is not conducive to forming efficient complexes with organic matter.

[0162] Finally, the data provided intuitive evidence for key indicators characterizing the material's physical structure and reaction interface. The specific surface area of ​​the products in the example (12.1–16.5 m²) 2 The g / g ratio was significantly greater than that of Comparative Example 1 (5.3m). 2 / g). This order-of-magnitude difference directly confirms the decisive role of the "controlled hydration reaction" in creating the unique structure of the loose, porous "active calcium hydroxide micropowder". A larger specific surface area implies a more complete contact interface in the subsequent fermentation chelation reaction, and a milder reaction kinetics after application to the soil. The specific surface areas of Comparative Examples 2 and 3 are similar to those of the examples, indicating that this indicator is mainly affected by the form of the calcium source, and less affected by the organic matter treatment method and end-of-life additives.

[0163] The application performance of the soil conditioners prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 2. The testing methods are as follows:

[0164] Soil pH-raising effect test method: Acidic farmland soil with a pH of 5.2 was collected, air-dried, and sieved. An experimental group and a blank control group were set up. In the experimental group, a conditioner was uniformly mixed in at a ratio of 2% by weight of the soil, and the soil was placed in a constant temperature and humidity incubator (25℃) for 30 days, maintaining a field water holding capacity of 60%. After the incubation period, the soil pH was measured according to the method of NY / T1377-2007, and the difference (ΔpH) between the experimental group and the blank control group was calculated.

[0165] Method for testing the passivation rate of available cadmium: The above-mentioned culture experiment was conducted in contaminated soil with a total cadmium content of 2.5 mg / kg. After the culture was completed, available cadmium in the soil was extracted using the DTPA (diethylenetriaminepentaacetic acid) extraction method (refer to HJ491-2019), and its content was determined using atomic absorption spectrometry. Passivation rate (%) = [(available cadmium content in the control group - available cadmium content in the treatment group) / available cadmium content in the control group] × 100%.

[0166] Calcium ion continuous release test method: A soil column leaching simulation device was used. Soil mixed with 2% conditioner was placed into a soil column to simulate the intensity of natural rainfall (e.g., equivalent to 100 mm of rainfall per week), and intermittent leaching was performed with deionized water. All leachate was collected from day 1 to day 28, and the calcium ion concentration was measured. The percentage of cumulative calcium ion release relative to the total calcium content of the conditioner was calculated.

[0167] Plant biological effect testing method: A pot experiment of Chinese cabbage was conducted in the above-mentioned contaminated soil. Ten seeds were sown in each pot, and five seedlings were transplanted after germination. The plants were grown for 35 days under the same light, temperature, and water and fertilizer management conditions. After harvest, the fresh weight of the aboveground parts of the Chinese cabbage was measured, and the biomass increase rate relative to the blank contaminated soil control group (whose biomass was recorded as 100%) was calculated.

[0168] Table 2 Application Performance of Soil Conditioners

[0169] Group Soil pH rise (ΔpH) Effective cadmium passivation rate (%) Sustained release of calcium ions (%) Bok choy biomass increase rate (%) Example 1 1.9 68.5 42.30 35.6 Example 2 1.7 62.1 38.70 31.2 Example 3 2.0 71.3 45.10 37.8 Comparative Example 1 2.8 41.8 78.50 10.5 Comparative Example 2 1.2 48.5 35.20 22.4 Comparative Example 3 1.5 60.2 40.80 28.7

[0170] As shown in Table 2, the results of the application performance test of the soil conditioner indicate that the products prepared in Examples 1-3 of this invention are significantly superior to the comparative examples in terms of comprehensive performance in simulating actual soil environments. This directly verifies that the products have the combined functions of "rapidly neutralizing acidity, providing long-lasting calcium nutrition, and efficiently passivating heavy metals", and ultimately manifest as excellent plant growth promotion effects.

[0171] First, regarding the direct effects of soil improvement, the examples demonstrated "mild and lasting" acidification characteristics and "highly efficient and stable" passivation capabilities. The examples maintained a stable pH increase (ΔpH) of 1.7 to 2.0 in acidic soils, achieving effective improvement without the risk of excessive alkalization. In contrast, Comparative Example 1 (ΔpH 2.8), due to the use of strongly alkaline ordinary calcium hydroxide, resulted in an overly drastic adjustment that could potentially disrupt soil balance. More importantly, the examples achieved a passivation rate of 62.1% to 71.3% for available cadmium, significantly superior to all comparative examples. Comparative Example 1 (41.8%) and Comparative Example 2 (48.5%) had the lowest passivation rates, directly demonstrating that the porous structure created by "controlled hydration" and the highly active humic acid generated by "directional pretreatment" are two indispensable key factors for achieving efficient heavy metal complexation and fixation.

[0172] Secondly, regarding the nutrient supply mode, the examples exhibit excellent "slow-release" characteristics. The cumulative release rate of calcium ions in the examples remained at a low level of 38.7% to 45.1% over 28 days, indicating a gradual and sustained release of calcium nutrients. In contrast, Comparative Example 1 showed a release rate as high as 78.5%, indicating that the unactivated calcium source dissolved and leached too quickly in the soil, failing to provide a sustained supply. This slow-release characteristic is corroborated by the higher specific surface area and cation exchange capacity (CEC) of the examples in Table 1, suggesting that the active structure and organic matter synergistically played a buffering and controlled-release role.

[0173] Ultimately, all the above advantages are reflected in the crop's physiological response. The treatment group in the example showed the highest biomass increase rate in the pakchoi (31.2%–37.8%), thanks to the creation of an optimal root zone environment characterized by "moderate pH, reduced toxicity, and continuous nutrient supply." Although Comparative Example 1 increased the pH, due to alkalinity damage, poor passivation, and rapid calcium loss, the biomass increase rate was only 10.5%, the worst effect. Comparative Examples 2 and 3 showed intermediate biomass promotion effects, further indicating that providing only basic nutrients (comparative Example 2 had low organic matter activity) or lacking biostimuli (comparative Example 3 lacked functional microbial agents) cannot achieve the optimal synergistic growth-promoting effect achievable by the present invention.

[0174] The range descriptions in this document, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used in this document mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used in this document can all be obtained through commercial purchase or prepared by existing methods.

[0175] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a bio-activated calcium-based organic soil conditioner, characterized in that, The method includes the following steps: S1. The calcium raw material is calcined at high temperature to convert it into active calcium oxide; S2. Under stirring conditions, the active calcium oxide is subjected to a controlled hydration reaction with low-temperature water mist to obtain active calcium hydroxide micro powder. S3. The mushroom residue is subjected to compound enzymatic hydrolysis pretreatment, high-temperature microbial degradation and targeted humification treatment in sequence to obtain pretreated mushroom residue rich in active humic acid. S4. Mix the activated calcium hydroxide powder, the pretreated mushroom residue, and humic acid salt, and inoculate with acetic acid bacteria for fermentation to obtain the fermentation product. S5. Add the compound biological agent and chitosan to the fermentation product, mix evenly, granulate, and dry to obtain the soil conditioner; the compound biological agent is composed of Bacillus mucilaginosus, Bacillus cereus, and Bacillus subtilis, and the total number of effective viable bacteria in the compound biological agent is ≥10.0×10⁻⁶. 8 CFU / g.

2. The method for preparing the bio-activated calcium-based organic soil conditioner according to claim 1, characterized in that, In step S1, the high-temperature calcination temperature is 700℃~900℃, and the calcination time is 1~3h.

3. The preparation method of the bio-activated calcium-based organic soil conditioner according to claim 1, characterized in that, In step S2, the controlled hydration reaction satisfies the following conditions: the molar ratio of water to calcium oxide is (0.3~0.5):1, the reaction temperature is 60℃~80℃, and the reaction time is 30~90min.

4. The preparation method of the bio-activated calcium-based organic soil conditioner according to claim 1, characterized in that, Step S3 specifically includes: S31. Add a compound enzyme preparation containing laccase, xylanase and cellulase to the mushroom residue for enzymatic hydrolysis. S32. Inoculate the enzymatically hydrolyzed material with thermophilic laterozoans for high-temperature aerobic fermentation; S33. After the material cools down, Bacillus subtilis is introduced for mesophilic aerobic fermentation until the material is mature, resulting in pretreated mushroom residue rich in active humic acid.

5. The method for preparing the bio-activated calcium-based organic soil conditioner according to claim 4, characterized in that, In step S31, the enzyme activity ratio of laccase, xylanase and cellulase in the compound enzyme preparation is (1-3):(2-5):(1-2); The amount of the compound enzyme preparation added is 0.5 to 2.0% of the dry weight of the mushroom residue.

6. The method for preparing the bio-activated calcium-based organic soil conditioner according to claim 4, characterized in that, In step S32, the temperature of the high-temperature aerobic fermentation is 60-70℃, and the fermentation time is 3-5 days; The inoculum size of *Lactuca thermophila* is 1-5% of the wet weight of the enzymatically hydrolyzed material.

7. The method for preparing the bio-activated calcium-based organic soil conditioner according to claim 4, characterized in that, In step S33, the temperature of the mesophilic aerobic fermentation is 45-50℃, and the fermentation time is 7-10 days; The inoculation amount of the Bacillus mucilaginosus is 0.5 to 3% of the wet weight of the material after fermentation in step S32.

8. The method for preparing the bio-activated calcium-based organic soil conditioner according to claim 1, characterized in that, In step S4, based on dry weight, the active calcium hydroxide powder is 20-40 parts, the pretreated mushroom residue is 50-70 parts, and the humate is 5-10 parts. The amount of acetic acid bacteria inoculated is 1 to 5% of the total weight of the material.

9. The method for preparing the bio-activated calcium-based organic soil conditioner according to claim 1, characterized in that, In step S5, the amount of the compound biological agent added is 0.5-2% of the dry weight of the fermentation product; The amount of chitosan added is 1-3% of the dry weight of the fermentation product; The ratio of viable bacteria of the Bacillus subtilis, Bacillus cereus and Bacillus subtilis is (4-6):(3-5):(1-2).

10. A bio-activated calcium-based organic soil conditioner prepared by the method according to any one of claims 1 to 9, characterized in that, It contains calcium hydroxide micron powder activated by a controlled hydration reaction, pretreated mushroom residue rich in active humic acid, calcium humate fermentation products, compound biological agents, and chitosan.

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