An earthworm compost-based microbial synergistic remediation improver for heavy metal-polluted infertile saline-alkali soil and a preparation method thereof

Abstract

The application discloses an earthworm compost-based microbial synergistic remediation modifier for heavy metal-polluted infertile saline-alkali soil and a preparation method of the modifier. The modifier comprises the following raw materials in parts by weight: earthworm compost 40-60 parts, gypsum powder 10-20 parts, humic acid 8-12 parts, seaweed extract 4-6 parts, vermiculite powder 8-12 parts and compound microbial agent 8-12 parts. The application is designed for heavy metal-polluted infertile saline-alkali soil, and can target solving the problem of composite soil, can simultaneously reduce the bioavailability of multiple heavy metals such as lead, cadmium and mercury, and has stronger improvement pertinence, so that an integrated solution scheme for heavy metal (lead, cadmium and mercury) detoxification, saline-alkali regulation and fertility improvement is realized.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, and in particular to a vermicompost-based microbial synergistic remediation agent and its preparation method for heavy metal-contaminated barren saline-alkali soil. Background Technology

[0002] Currently, commonly used soil conditioners in agricultural production include organic conditioners (compost, organic fertilizer), inorganic conditioners (lime, gypsum), and biological conditioners (microbial agents). Vermicompost, rich in organic matter, humic acid, various trace elements, and beneficial microorganisms, is considered a high-quality soil conditioner. Existing vermicompost conditioners are mostly applied directly or through simple mixing. For soils with complex problems such as heavy metal pollution, fertility deficiency, and salinization, current technologies often focus on single improvement targets and fail to form an integrated solution encompassing "heavy metal detoxification - fertility enhancement - salinity regulation," exhibiting the following shortcomings: Limited functionality: It is difficult to simultaneously address the triple problems of heavy metal pollution, fertility depletion, and salinization. Its functional coverage is incomplete, especially lacking the ability to synergistically detoxify multiple heavy metals (lead, cadmium, mercury, etc.). Insufficient targeting: There is a lack of specific formulas for heavy metal-polluted barren saline-alkali soils, the improvement effect is unstable, the synergy between heavy metal detoxification and fertility enhancement is poor, and it is easy to lead to soil acidification or salt accumulation. Weak biological synergy: An efficient symbiotic biological system has not been constructed. Microbial agents are mostly used alone or in simple mixtures, failing to achieve the mutual promotion effect of "earthworm-functional bacteria-plant root fungi", resulting in limited repair efficiency; Non-standard production process: Product quality fluctuates greatly, with significant differences between batches, lack of specific production parameters for soil conditioners with compound pollution, and poor preservation of microbial activity; Inconvenient storage and transportation: High moisture content makes it prone to absorbing moisture and mold, increasing transportation costs and affecting the product's biological activity during its shelf life; The effect evaluation is one-sided: it only focuses on a single indicator (such as heavy metal content or organic matter) and lacks systematic monitoring of ecological indicators such as soil enzyme activity, microbial community structure, and nutrient cycling efficiency. Summary of the Invention

[0003] The main objective of this invention is to provide a vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil and its preparation method, aiming to solve at least one of the aforementioned technical problems.

[0004] To achieve the above objectives, this invention provides a vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated, barren, saline-alkali soil, comprising the following raw materials by weight: 40-60 parts earthworm compost; 10-20 parts of gypsum powder; 8-12 parts of humic acid; 4-6 parts of seaweed extract; 8-12 parts vermiculite powder; 8-12 parts of compound microbial inoculant.

[0005] Furthermore, the specific weight proportions of each raw material are as follows: 50 parts earthworm compost, 15 parts gypsum powder, 10 parts humic acid, 5 parts seaweed extract, 10 parts vermiculite, and 10 parts compound microbial inoculant.

[0006] Furthermore, the compound microbial inoculant includes Azotobacter chrysophyte and arbuscular mycorrhizal fungi.

[0007] This invention also provides a method for preparing the above-mentioned earthworm compost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil, comprising the following steps: (1) Preparation of vermicompost Cow manure, straw, and vegetable leaves are mixed as compost substrate. After adjusting the moisture content and C / N ratio, earthworms are inoculated and cultivated to obtain earthworm compost. (2) Activation of compound microbial agents A compound microbial agent was obtained by mixing Azotobacter chrysophyte and arbuscular mycorrhizal fungi at a weight ratio of 1:1 and activating the mixture. (3) Mixing and synergistic activation Earthworm compost, gypsum powder, humic acid, seaweed extract and vermiculite powder are mixed and stirred. Then, compound microbial agents are added and stirred again. Finally, the mixture is allowed to stand to obtain the initial mixture. (4) Drying and granulation The initial mixture was dried and then granulated to obtain the earthworm compost-based microbial synergistic remediation and improvement agent for heavy metal-contaminated barren saline-alkali soil.

[0008] Furthermore, in step (1), the contents of each raw material in the compost substrate are 60wt% cow manure, 30wt% straw, and 10wt% vegetable leaves, with the C / N ratio adjusted to 25-30:1 and the moisture content adjusted to 60-70%.

[0009] Furthermore, in step (1), the earthworm species is Eisenia fetida, and the earthworm inoculation density is 1.0 kg / m³. 2 .

[0010] Furthermore, in step (1), the cultivation period is 25 to 35 days, and the pile is turned over 2 to 3 times a day.

[0011] Furthermore, in step (2), the activation culture conditions are 12 hours of culture at a temperature of 30°C and a humidity of 60%.

[0012] Furthermore, in step (3), the settling time is 24 hours.

[0013] Furthermore, in step (4), the drying conditions are to dry at 40-50°C until the moisture content reaches 8-12%.

[0014] The design principle of the present application is: Vermicomposting provides organic matter, humic acid, and basic microbial communities, serving as a carrier for synergistic biological processes. It also promotes the detoxification of heavy metals through earthworm activity, and its secretions can enhance soil particle aggregation. Gypsum powder: Adjusts the pH value of saline-alkali soil (reducing it by 0.7 to 1.0 units), improves soil aggregate structure, reduces soil salinity, and avoids acidification problems caused by biochar or humic acid; Humic acid: enhances the adsorption and complexation capacity of heavy metal ions (lead, cadmium, mercury), improves soil water and fertilizer retention capacity, promotes microbial activity, and its hydrophobic compounds can stabilize the soil DOM structure. Seaweed extract: enhances plant stress resistance, helps improve the adaptability of microorganisms and earthworms, and alleviates the stress effects of heavy metals on organisms; Vermiculite powder: loosens soil structure, adsorbs heavy metal ions, stabilizes soil microenvironment, and its porous structure can protect microorganisms from extreme environmental influences; through the synergistic effect of humic acid and vermiculite, it promotes soil DOM humification and improves soil carbon stability and microbial community diversity.

[0015] Compound microbial inoculants: Azotobacter chrysotile converts atmospheric nitrogen into ammonia nitrogen, increasing the ammonia nitrogen content in the soil by more than 200%; Arbuscular mycorrhizal fungi nourish the soil, reducing nitrogen dissipation by more than 30%, while providing food for earthworms and promoting heavy metal detoxification. The two work synergistically to improve fertility and remediation efficiency.

[0016] The beneficial effects of the present application are embodied in: Precise Adaptability: Specifically designed for barren saline-alkali soils contaminated with heavy metals, it targets and solves complex soil problems. It can simultaneously reduce the bioavailability of multiple heavy metals such as lead, cadmium, and mercury, making the improvement more targeted. It achieves an integrated solution for heavy metal (lead, cadmium, mercury) detoxification, salinity regulation, and fertility enhancement. Synergistic Bio-Effects: An innovative symbiotic system of earthworms, azotobacters chrysophytes, and arbuscular mycorrhizal fungi is constructed. Through nutrient cycling and functional complementarity among the organisms, the system enhances heavy metal detoxification and nitrogen utilization efficiency, achieving a closed loop of "heavy metal detoxification-nitrogen fixation-nitrogen retention." The remediation efficiency is more than 40% higher than that of single materials, and it can also promote the increase of soil microbial community diversity. In addition, the compound microbial agent optimizes the synergistic effect of bio-effects through precise formulation (nitrogen-fixing bacteria: plant root fungi = 1:1) and pre-activation process, with a microbial activity retention rate of ≥85%. Comprehensive and multifunctional: It integrates heavy metal adsorption and detoxification, salinity and pH adjustment, organic matter replenishment, microbial activation, and efficient nitrogen retention, while also enhancing soil enzyme activity (urease, dehydrogenase, etc.), providing more complete functional coverage. Process standardization: Adapt to standardized production processes, clarify key parameters for earthworm compost preparation, microbial activation, mixing and drying, etc., ensuring stable product quality, minimal batch-to-batch variation, and avoiding secondary soil pollution; Easy to store and transport: Drying and granulation process to form a product form that takes into account both storage and transportation and biological activity. It has strong resistance to mold and mildew. After 6 months of storage at room temperature, the microbial activity retention rate is ≥85%, which reduces transportation and storage costs and improves product usability. Eco-friendly: The raw materials are all natural or bio-based, with no chemical additives, which can promote soil DOM humification and improve soil carbon stability; The testing system has been improved: new specific indicators such as heavy metal adsorption rate, ammonia nitrogen content, soil enzyme activity, and microbial community abundance have been added, making product quality quantifiable and improvement effects traceable. Detailed Implementation

[0017] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0018] Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art. Wherein: Azotobacter chrysophagus was purchased from Beina Chuanglian Biotechnology Co., Ltd., microbial code BNCC192292; Arbuscular mycorrhizal fungi were selected from Rhizospora heteromorpha, purchased from the Arbuscular Mycorrhizal Fungi Germplasm Resource Bank (BGC) of the Institute of Plant Nutrition and Resource Environment, Beijing Academy of Agricultural and Forestry Sciences, with the number BGC heb05. The humic acid was purchased from Jingfeng Humic Acid Co., Ltd. (JINGFENG HUMIC ACID), model JFHA-MFA-P (powder type). Its fulvic acid content is ≥60.00%, and the content of heavy metals (lead, cadmium, mercury, etc.) is ≤0.005mg / kg, which meets the standards for use in agricultural soil improvement. The seaweed extract was purchased from Qingdao Haida Biotechnology Group Co., Ltd. (model HA-100, product standard number: Q / 370212HDSW001-2023). The gypsum powder used is agricultural-grade desulfurized gypsum, purchased from Shandong Lubei Chemical Co., Ltd., model NYSG-01 (calcium oxide content ≥32%, particle size ≤0.5mm); The vermiculite powder is made of horticultural grade expanded vermiculite, purchased from Lingshou County Jihong Mineral Products Trading Co., Ltd., with a specification of 20-40 mesh (expansion ratio ≥ 8 times, moisture content ≤ 5%).

[0019] Example 1 Preparation of a vermicompost-based microbial synergistic remediation and amendment agent for heavy metal-contaminated barren saline-alkali soil The amendment's raw material formula, by weight, is: 50 parts earthworm compost, 15 parts gypsum powder, 10 parts humic acid, 5 parts seaweed extract, 10 parts vermiculite, and 10 parts compound microbial inoculant. The preparation method includes the following steps: (1) Preparation of vermicompost Mix 60 wt% cow manure, 30 wt% corn stalk powder, and 10 wt% chopped cabbage leaves, first dehydrate to a moisture content of 65%, then add urea to achieve a C / N ratio of 25:1 (the amount added is calculated based on the initial carbon and nitrogen content of the cow manure, straw, and cabbage leaves). Use this as the compost substrate, then apply 1.0 kg / m³ of urea. 2 Inoculate earthworms at a certain density and cultivate for 30 days, turning the compost pile 2-3 times a day (monitoring heavy metal content and earthworm activity during turning to ensure earthworm survival rate ≥90%). After cultivation, pass the compost through a 5mm sieve to obtain earthworm compost. The earthworm species used was Eisenia fetida, with healthy adult individuals weighing 0.3-0.5g each. (2) Activation of compound microbial agents Activation medium formula: glucose 20 g / L, peptone 10 g / L, yeast extract 5 g / L, KH2PO4 1 g / L, MgSO4 0.5 g / L H₂O, 0.5 g / L NaCl, 20 g / L agar (solid culture medium), pH 7.0; Azotobacter chrysophyte (BNCC192292) and arbuscular mycorrhizal fungi (BGC heb05) were mixed at a 1:1 weight ratio and then inoculated into activation medium at a 5% (w / w) inoculation ratio. The mixture was then cultured at 30℃ and 60% humidity for 12 hours to enhance the activity of the strains, resulting in a compound microbial inoculum. The concentration of the activated inoculum was ≥1.0×10⁻⁶. 9 cfu / g.

[0020] (3) Mixing and synergistic activation Earthworm compost, gypsum powder (pre-dried to a moisture content ≤5% and pulverized to a particle size ≤0.5mm), humic acid, seaweed extract, and vermiculite powder (pre-dried to a moisture content ≤5% and pulverized to a particle size ≤0.5mm) are mixed and stirred at 30r / min for 15 minutes. Then, a compound microbial agent is added, and stirring is continued for 15 minutes. Finally, the mixture is allowed to stand for 24 hours for synergistic activation, promoting the stable combination of microorganisms and earthworm compost carrier to obtain the initial mixture. (4) Drying and granulation The initial mixture is dried at a low temperature of 45℃ (to avoid high temperature damaging microbial activity and heavy metal adsorption structure) until the moisture content reaches 10%, and then granulated using a granulator with a particle size of 2-5mm (to ensure uniform application and ease of feeding for earthworms), thus obtaining an earthworm compost-based microbial synergistic remediation and improvement agent for heavy metal-contaminated barren saline-alkali soil.

[0021] Experimental Example 1 Improvement effect experiment The soil amendment was mixed with heavy metal-contaminated barren saline-alkali soil at a dosage of 15g of amendment per 1kg of soil. The mixture was left at room temperature for 60 days, and the changes in relevant indicators before and after soil treatment were detected. The results are shown in Table 1 below. Table 1

[0022] Experimental Example 2 Based on Example 1, by adjusting factors and comparing the effects, the final confirmed range and optimal values ​​of process parameters are shown in Table 2: Table 2

[0023] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A vermicompost-based microbial synergistic remediation and amendment agent for heavy metal-contaminated barren saline-alkali soil, characterized in that, By weight, it includes the following ingredients: 40-60 parts earthworm compost; 10-20 parts of gypsum powder; 8-12 parts of humic acid; 4-6 parts of seaweed extract; 8-12 parts vermiculite powder; 8-12 parts of compound microbial inoculant.

2. The vermicompost-based microbial synergistic remediation and amendment agent for heavy metal-contaminated barren saline-alkali soil as described in claim 1, characterized in that, The specific weight proportions of each raw material are as follows: 50 parts earthworm compost, 15 parts gypsum powder, 10 parts humic acid, 5 parts seaweed extract, 10 parts vermiculite, and 10 parts compound microbial agent.

3. The vermicompost-based microbial synergistic remediation and amendment agent for heavy metal-contaminated barren saline-alkali soil as described in claim 1 or 2, characterized in that, The compound microbial inoculant includes Azotobacter chrysophyte and arbuscular mycorrhizal fungi.

4. The preparation method of the vermicompost-based microbial synergistic remediation agent for heavy metal-contaminated barren saline-alkali soil as described in claim 1, 2, or 3, characterized in that, Includes the following steps: (1) Preparation of vermicompost Cow manure, straw, and vegetable leaves are mixed as compost substrate. After adjusting the moisture content and C / N ratio, earthworms are inoculated and cultivated to obtain earthworm compost. (2) Activation of compound microbial agents A compound microbial agent was obtained by mixing Azotobacter chrysophyte and arbuscular mycorrhizal fungi at a weight ratio of 1:1 and activating the mixture. (3) Mixing and synergistic activation Earthworm compost, gypsum powder, humic acid, seaweed extract and vermiculite powder are mixed and stirred. Then, compound microbial agents are added and stirred again. Finally, the mixture is allowed to stand to obtain the initial mixture. (4) Drying and granulation The initial mixture was dried and then granulated to obtain the earthworm compost-based microbial synergistic remediation and improvement agent for heavy metal-contaminated barren saline-alkali soil.

5. The preparation method of the vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil as described in claim 4, characterized in that, In step (1), the contents of each raw material in the compost substrate are 60wt% cow manure, 30wt% straw, and 10wt% vegetable leaves, with the C / N ratio adjusted to 25-30:1 and the moisture content adjusted to 60-70%.

6. The preparation method of the vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil as described in claim 4 or 5, characterized in that, In step (1), the earthworm species used is Eisenia fetida, and the earthworm inoculation density is 1.0 kg / m³. 2 .

7. The preparation method of the vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil as described in claim 4 or 5, characterized in that, In step (1), the cultivation period is 25 to 35 days, and the pile is turned over 2 to 3 times a day.

8. The preparation method of the vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil as described in claim 4 or 5, characterized in that, In step (2), the activation culture conditions are 12 hours of culture at a temperature of 30℃ and a humidity of 60%.

9. The preparation method of the vermicompost-based microbial synergistic remediation agent for heavy metal-contaminated barren saline-alkali soil as described in claim 4 or 5, characterized in that, In step (3), the settling time is 24 hours.

10. The preparation method of the vermicompost-based microbial synergistic remediation modifier for heavy metal-contaminated barren saline-alkali soil as described in claim 4 or 5, characterized in that, In step (4), the drying conditions are to dry at 40-50°C until the moisture content reaches 8-12%.

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