Soil carbon sequestration and quality improvement improver for salt marsh soil as well as preparation method and application of soil carbon sequestration and quality improvement improver

Abstract

The invention discloses a soil carbon sequestration and quality improvement modifier for salt marsh soil as well as a preparation method and application thereof. The soil carbon sequestration and quality improvement modifier is mainly prepared from spartina alterniflora charcoal powder and yellow mealworm sand. According to the conditioner, the biochar and the insect sand are mixed according to a specific proportion, the biochar has high stability, carbon elements can be immobilized for a long time, and powerful support is provided for soil carbon sink; the insect sand is rich in various organic nutrients, beneficial microorganisms and trace elements, can effectively improve the soil structure, enhances the water and fertilizer retention capacity of soil, and creates an excellent environment for plant growth. Through the synergistic effect of the two components, the organic carbon content of the soil can be remarkably increased, efficient fixation of carbon is achieved, physical and chemical indexes such as soil acidity and alkalinity and porosity can be adjusted, and conversion and release of nutrients in the soil are promoted. Experiments prove that after the modifier is used, the soil carbon sink function is obviously enhanced, the plant root development is more robust, and the plant growth speed is accelerated.

Description

Technical Field

[0001] The present invention discloses a soil carbon sequestration and quality improvement agent for salt marsh soil, its preparation method and application, belonging to the technical field of ecological environment improvement. Background Art

[0002] Wetlands, as important ecosystems, play a crucial role in the carbon cycle. Although the global wetland area only accounts for 4%-6% of the land area, its carbon storage is as high as 20%-30% of the terrestrial carbon pool. The extensive invasion of Spartina alterniflora in salt marsh wetlands has changed the original vegetation structure of the wetlands, and to a certain extent, disrupted the original carbon cycle balance of the wetlands, affecting the stability of the wetland soil carbon pool. In some salt marsh areas severely invaded by Spartina alterniflora, the soil organic carbon content has fluctuated by 10%-15% in the past decade, reflecting its huge impact on the wetland soil carbon pool.

[0003] The reasonable disposal of Spartina alterniflora straw as a biomass resource has attracted much attention. Traditional treatment methods are often limited to simple incineration or discarding, which not only causes waste of resources but also generates additional carbon emissions due to incineration. Therefore, exploring the resource utilization path of Spartina alterniflora straw and converting it into products beneficial to ecological restoration has become a hot research direction.

[0004] Under this background, it is particularly urgent to develop a technology that can not only effectively utilize Spartina alterniflora straw but also specifically solve the problems of insufficient carbon sink, nutrient imbalance, and degradation of soil physical and chemical properties in salt marsh soil after Spartina alterniflora removal, help restore the wetland soil carbon pool, and meet the requirements of reducing carbon source emissions and increasing the scale of carbon sinks. Summary of the Invention

[0005] Object of the Invention: Aiming at the problems existing in the prior art, the present invention focuses on the effective utilization of Spartina alterniflora straw. In view of the prominent problems such as lack of carbon sink, nutrient imbalance, and degradation of soil physical and chemical properties in salt marsh soil after Spartina alterniflora removal, a special soil carbon sequestration and quality improvement agent is developed to enhance the soil carbon sequestration capacity, optimize the soil nutrient composition, restore and further strengthen the wetland soil carbon pool, and ensure the stable and continuous efficient carbon sequestration function of the wetland soil carbon pool. Relying on the optimization effect of the improvement agent on the soil environment, it helps the growth of native vegetation such as Suaeda salsa, promotes the restoration of wetland biodiversity, and constructs a healthy and stable salt marsh wetland ecosystem, ultimately providing solid technical support and practical solutions for the ecological restoration cause and the smooth realization of the "dual carbon" goal.

[0006] Technical Solution: To achieve the above object of the invention, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a soil carbon sequestration and quality improvement agent for salt marsh soil, and the soil carbon sequestration and quality improvement agent is mainly composed of Spartina alterniflora biochar powder and Tenebrio molitor excrement.

[0008] As a specific implementation, the Spartina alterniflora biochar powder is mainly obtained by pyrolyzing Spartina alterniflora straw under anaerobic conditions; the Tenebrio molitor excrement is mainly the excrement of Tenebrio molitor fed with Spartina alterniflora straw.

[0009] As a specific implementation, the mass ratio of the Tenebrio molitor excrement to the Spartina alterniflora biochar powder is 1:(1 - 3).

[0010] In the second aspect, the present invention provides a preparation method of the soil carbon sequestration and quality improvement agent for salt marsh soil, comprising the following steps:

[0011] (1) Preparation of Spartina alterniflora biochar powder: Collect Spartina alterniflora straw, dry it, and under anaerobic conditions, heat it to 500 - 600 °C at a heating rate of 8 - 12 °C·min -1 and pyrolyze for 1.5 - 2.5 h, then cool it, crush it, and sieve it to obtain Spartina alterniflora biochar powder;

[0012] (2) Mix the Spartina alterniflora biochar powder prepared in step (1) with Tenebrio molitor excrement to obtain the product.

[0013] As a preferred scheme, the preparation method comprises the following steps:

[0014] Lay the collected Spartina alterniflora straw flat in a well-ventilated environment to allow it to air dry naturally, ensuring that the moisture inside the straw is fully dissipated to reach a state suitable for subsequent processing.

[0015] After the straw is completely air-dried, put it into a professional pyrolysis device, control the environment to be anaerobic, start the heating program, and continuously heat it at an accurate rate of 10 °C·min -1 until the temperature reaches 550 °C. Under the high temperature condition of 550 °C, maintain the pyrolysis state for 2 hours to allow the Spartina alterniflora straw to fully undergo a carbonization reaction and complete the carbonization process.

[0016] Furthermore, after pyrolysis, wait for the carbonized straw to cool to room temperature, then transfer it to a crushing device for fine crushing, and finally screen it strictly through a 100-mesh sieve to obtain the qualified Spartina alterniflora biochar powder.

[0017] Further, accurately weigh the wormcast and the previously prepared Spartina alterniflora biochar powder according to a specific ratio of 1:(1-3), and place them in a suitable stirring container. Use a professional stirring tool to fully and evenly stir and mix the wormcast and the Spartina alterniflora biochar powder to ensure complete fusion of the two, forming the basic formula of the soil carbon sequestration and quality improvement agent for salt marsh soil.

[0018] In a third aspect, the present invention provides the application of the soil carbon sequestration and quality improvement agent for salt marsh soil in improving salt marsh soil. This improvement agent can increase the total amount of the soil carbon pool, change the components and structure of soil organic carbon, change the physical and chemical properties of the soil, promote plant growth, increase the soil carbon pool management index, and enhance the soil carbon sequestration ability.

[0019] In a fourth aspect, the present invention provides the application of the combined use of Spartina alterniflora biochar powder and Tenebrio molitor wormcast in improving salt marsh soil. The combined use of the two can increase the total amount of the soil carbon pool, change the components and structure of soil organic carbon, change the physical and chemical properties of the soil, promote plant growth, increase the soil carbon pool management index, and enhance the soil carbon sequestration ability.

[0020] As a specific implementation method, the Spartina alterniflora biochar powder is mainly obtained by pyrolyzing Spartina alterniflora straw under anaerobic conditions; the Tenebrio molitor wormcast is mainly the excrement of Tenebrio molitor fed with Spartina alterniflora straw.

[0021] In a fifth aspect, the present invention provides a method for improving salt marsh soil, including using the soil carbon sequestration and quality improvement agent for salt marsh soil to improve salt marsh soil, or adding Spartina alterniflora biochar powder and Tenebrio molitor wormcast to salt marsh soil simultaneously to improve salt marsh soil.

[0022] As a specific implementation method, the method for improving salt marsh soil includes the following steps:

[0023] Spread the soil carbon sequestration and quality improvement agent on the salt marsh soil that needs carbon sequestration and sink enhancement, and mix it evenly with the surface soil; wherein, the mass ratio of the soil carbon sequestration and quality improvement agent to the salt marsh soil is 1:(50-100);

[0024] Or spread Spartina alterniflora biochar powder and Tenebrio molitor wormcast on the salt marsh soil that needs carbon sequestration and sink enhancement simultaneously, and mix it evenly with the surface soil; wherein, the mass ratio of Tenebrio molitor wormcast to Spartina alterniflora biochar powder is 1:(1-3), and the total mass of Tenebrio molitor wormcast and Spartina alterniflora biochar powder to the mass of the salt marsh soil is 1:(50-100).

[0025] As a further preferred scheme, the surface soil refers to the soil layer from 0 to 30 cm downward from the soil surface.

[0026] The soil carbon sequestration and quality improvement agent provided by the present invention proposes an efficient carbon sequestration and quality improvement technology for coastal wetland heavy saline-alkali soil. The core of this technology lies in the resource utilization of waste Spartina alterniflora straw and Tenebrio molitor feces, which are transformed through a process into an innovative material that can both enhance the soil's carbon sequestration potential and comprehensively improve its physical and chemical properties.

[0027] The soil carbon sequestration and quality improvement agent provided by the present invention is applied to the saline-alkali soil to be improved, aiming to deeply optimize the physical and chemical structure of the soil and strengthen its nutrient status. Its working mechanism is reflected in the significant promotion of the salt marsh plant Suaeda salsa, by enhancing its absorption of nitrogen and phosphorus, directly improving the nutrient accumulation of Suaeda salsa, and then stimulating its growth vitality, enhancing the carbon fixation efficiency, and opening up a new way for the natural increase of soil organic carbon content.

[0028] The biochar component of the soil carbon sequestration and quality improvement agent provided by the present invention, with its excellent physical and chemical properties, directly and significantly increases the reserve of soil total organic carbon, provides a valuable carbon source for the soil microbial community, greatly promotes the activity of microbial activities, and thus increases the soil microbial carbon content.

[0029] The Tenebrio molitor feces component of the soil carbon sequestration and quality improvement agent provided by the present invention, with its rich organic nutrients and trace element content, becomes a key factor in optimizing the soil structure and enhancing the soil's water and fertilizer retention capacity. The agent mixes biochar and Tenebrio molitor feces in a specific ratio. Biochar has high stability and can store carbon elements for a long time, providing strong support for the soil carbon sink; Tenebrio molitor feces are rich in various organic nutrients, beneficial microorganisms and trace elements, which can effectively improve the soil structure, enhance the soil's water and fertilizer retention capacity, and create an excellent environment for plant growth. The synergistic effect of the two not only greatly increases the content of soil organic carbon, ensures the efficient fixation and long-term storage of carbon, but also finely adjusts key physical and chemical indexes such as soil pH and porosity, accelerates the transformation and release of nutrients in the soil, and creates a more ideal ecological environment for the healthy growth of plants.

[0030] Technical effect: The soil carbon sequestration and quality improvement agent provided by the present invention, through innovative material design and process optimization, successfully transforms waste Spartina alterniflora straw into an efficient soil improver, not only realizing the recycling of resources, but also providing a patented technical solution for the improvement and carbon sequestration and sink enhancement of coastal wetland heavy saline-alkali soil. By implementing this technology, the physical and chemical properties of the soil in the Spartina alterniflora removal area are improved, and the nutrient content and carbon pool management index in the soil are significantly increased.

[0031] 1. The preparation and application of the soil carbon sequestration and quality improvement agent provided by the present invention. This technology is committed to effectively utilizing Spartina alterniflora straw, reducing the additional carbon emissions caused by traditional incineration treatment methods, cutting carbon source emissions from the source, and realizing the resource utilization of Spartina alterniflora straw, meeting the requirements of the "dual carbon" goal for carbon source control.

[0032] 2. The preparation and application of the soil carbon sequestration and quality improvement agent provided by the present invention. This technology aims at the prominent problems such as insufficient carbon sink, nutrient imbalance and degradation of soil physical and chemical properties in coastal wetlands after the removal of Spartina alterniflora in salt marsh soils. Through innovative material combinations and processes, this modifier is precisely applied to salt marsh soils to enhance the soil carbon sequestration capacity, optimize the soil nutrient status, restore and strengthen the wetland soil carbon pool, and ensure the stable and continuous high-efficiency carbon sequestration function of the wetland soil carbon pool.

[0033] 3. The preparation and application of the soil carbon sequestration and quality improvement agent provided by the present invention. The application of this technology relies on the improvement of the soil environment by the modifier to help local vegetation such as Suaeda salsa grow again in salt marsh wetlands, restore wetland biodiversity, and help build a healthy and stable salt marsh wetland ecosystem. Ultimately, it provides strong technical support and practical implementation plans for global ecological restoration and the successful achievement of the "dual carbon" goal. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Composition of soil stable aggregates after adding the soil carbon sequestration and quality improvement agent.

[0035] Figure 2 Changes in the stem length and root length of Suaeda salsa after adding the soil carbon sequestration and quality improvement agent.

[0036] Figure 3 Changes in the fresh weight and dry weight of Suaeda salsa after adding the soil carbon sequestration and quality improvement agent. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention will be further described below in conjunction with the embodiments.

[0038] Example 1:

[0039] (1) Raw material preparation: Collect Spartina alterniflora straw and lay it flat in a well-ventilated environment to naturally air-dry, ensuring that the internal moisture is fully dissipated to provide suitable conditions for subsequent processing. The Tenebrio molitor frass is derived from the excrement produced during the breeding of Tenebrio molitor.

[0040] (2) Biochar preparation: Put the air-dried Spartina alterniflora straw into a professional pyrolysis device, heat it up to 550 °C at a rate of 10 °C per minute in an oxygen-free state, and maintain this temperature for 2 hours to fully carbonize the straw. After the carbonized straw is cooled to room temperature, it is finely pulverized and screened through a 100-mesh sieve to obtain the qualified Spartina alterniflora biochar powder.

[0041] (3) Preparation of soil carbon sequestration and quality-improving modifier: Weigh the Tenebrio molitor frass and Spartina alterniflora biochar powder accurately according to a specific mass ratio of 1:1. Place the weighed frass and biochar powder in a suitable stirring container, and use professional stirring tools to stir and mix them fully and evenly to ensure complete fusion of the two, forming the basic formula of the modifier.

[0042] (4) Collect the Spartina alterniflora-removed trace soil, put it into bags, manually remove the plant residues (>2 mm) in the soil, pre-sow the seeds in this soil, and thin the seedlings in the seedling tray when the seedlings grow to 4-5 cm. Select the seedlings with healthy growth and consistent growth vigor and transplant them into flower pots filled with 1 kg of Spartina alterniflora-removed trace soil, with 5 seedlings reserved in each pot. Add 10 g of soil carbon sequestration and quality-improving modifier to the soil, and cultivate it in a greenhouse at 25 °C. During this period, maintain the maximum water holding capacity at 70%, and the cultivation period is 90 days.

[0043] (5) At the 90th day of cultivation, conduct destructive sampling and measurement. The detection indicators include the physical and chemical properties of the soil (aggregates, porosity, electrical conductivity, pH, redox potential, nutrient content), the composition of soil organic carbon (total soil organic carbon, easily oxidizable organic carbon, dissolved organic carbon, soil microbial carbon, inert organic carbon), and the physiological and biochemical indicators of plants (fresh weight of Suaeda glauca, dry weight of Suaeda glauca, stem length, root length). Calculate the physical and chemical properties of the soil, the soil carbon sequestration capacity, and the plant growth status based on these.

[0044] Example 2:

[0045] (1) Raw material preparation: Collect Spartina alterniflora straws and lay them flat in a well-ventilated environment to dry naturally to ensure that the internal moisture is fully dissipated, providing suitable conditions for subsequent processing. The Tenebrio molitor frass is from the excrement produced during the breeding of Tenebrio molitor.

[0046] (2) Biochar preparation: Put the air-dried Spartina alterniflora straws into a professional pyrolysis device, heat them up to 550 °C at a rate of 10 °C per minute in an anaerobic state, and maintain this temperature for 2 hours to fully carbonize the straws. After the carbonized straws are cooled to room temperature, conduct fine grinding and screening through a 100-mesh sieve to obtain the qualified Spartina alterniflora biochar powder.

[0047] (3) Preparation of soil carbon sequestration and quality-improving modifier: Weigh the Tenebrio molitor frass and Spartina alterniflora biochar powder accurately according to a specific mass ratio of 1:2. Place the weighed frass and biochar powder in a suitable stirring container, and use professional stirring tools to stir and mix them fully and evenly to ensure complete fusion of the two, forming the basic formula of the modifier.

[0048] (4) Collect the Spartina alterniflora - removed bare - land soil, bag it, manually remove the plant residues (>2 mm) in the soil, pre - sow the seeds in this soil, thin out the seedlings in the seedling tray when the seedlings grow to 4 - 5 cm, select the healthy and uniformly growing seedlings and transplant them into flower pots filled with 1 kg of Spartina alterniflora - removed bare - land soil, with 5 seedlings reserved in each pot. Add 15 g of soil carbon sequestration and quality improvement agent to the soil, cultivate in a 25°C greenhouse, maintain the maximum water - holding capacity at 70% during the period, and the cultivation period is 90 d.

[0049] (5) At the 90 - d cultivation time, conduct destructive sampling and measurement. The detection indexes include the physical and chemical properties of the soil (aggregate, porosity, conductivity, pH, redox potential, nutrient content), the composition of soil organic carbon (total soil organic carbon, easily oxidizable organic carbon, dissolved organic carbon, soil microbial carbon, inert organic carbon), and the physiological and biochemical indexes of plants (fresh weight of Suaeda glauca, dry weight of Suaeda glauca, stem length, root length). Calculate the physical and chemical properties of the soil, the soil carbon sequestration capacity, and the plant growth status based on these.

[0050] Example 3:

[0051] (1) Raw material preparation: Collect Spartina alterniflora straws and spread them out in a well - ventilated environment to air - dry naturally, ensuring that the internal moisture is fully dissipated to provide suitable conditions for subsequent processing. The Tenebrio molitor frass is from the excrement produced during the breeding of Tenebrio molitor.

[0052] (2) Biochar preparation: Put the air - dried Spartina alterniflora straws into a professional pyrolysis device, heat up to 550°C at a rate of 10°C per minute in an anaerobic state, and maintain this temperature for 2 hours to fully carbonize the straws. After the carbonized straws are cooled to room temperature, conduct fine pulverization and screening through a 100 - mesh sieve to obtain the qualified Spartina alterniflora biochar powder.

[0053] (3) Preparation of soil carbon sequestration and quality improvement agent: Accurately weigh the Tenebrio molitor frass and Spartina alterniflora biochar powder according to a specific mass ratio of 1:3. Place the weighed frass and biochar powder in a suitable stirring container, and use a professional stirring tool to stir and mix them fully and evenly to ensure complete fusion of the two, forming the basic formula of the improvement agent.

[0054] (4) Collect the Spartina alterniflora - removed bare - land soil, bag it, manually remove the plant residues (>2 mm) in the soil, pre - sow the seeds in this soil, thin out the seedlings in the seedling tray when the seedlings grow to 4 - 5 cm, select the healthy and uniformly growing seedlings and transplant them into flower pots filled with 1 kg of Spartina alterniflora - removed bare - land soil, with 5 seedlings reserved in each pot. Add 20 g of soil carbon sequestration and quality improvement agent to the soil, cultivate in a 25°C greenhouse, maintain the maximum water - holding capacity at 70% during the period, and the cultivation period is 90 d.

[0055] (5) At 90 d of cultivation, destructive sampling was carried out for determination. The detection indexes included the physical and chemical properties of the soil (aggregates, porosity, electrical conductivity, pH, redox potential, nutrient content), the composition of soil organic carbon (total soil organic carbon, easily oxidizable organic carbon, dissolved organic carbon, soil microbial carbon, inert organic carbon), and the physiological and biochemical indexes of plants (fresh weight of Suaeda salsa, dry weight of Suaeda salsa, stem length, root length). Based on these, the calculation of the physical and chemical properties of the soil, the soil carbon sequestration capacity, and the plant growth status was carried out.

[0056] After the implementation of the salt marsh soil carbon sequestration and quality improvement agent, the nutrient content of the soil was significantly increased (Table 1). The available nitrogen content increased by 1.83% - 10.87%, the available potassium content increased by 41.55% - 105.15%, and the available phosphorus content increased by 12.53%. The increase in nutrient content can promote the growth of salt marsh vegetation (such as Figure 2 , 3 ) and improve the vegetation biomass, thereby enhancing the vegetation carbon sequestration efficiency.

[0057] Table 1 Nutrient improvement effects obtained in the examples

[0058] Alkalytic nitrogen (mg / kg) Available potassium (mg / kg) Available phosphorus (mg / kg) Before implementation 63.08 192.49 13.73 Example 1 64.24 272.47 12.56 Example 2 68.61 344.01 14.55 Example 3 69.94 394.89 15.45

[0059] After the implementation of the salt marsh soil carbon sequestration and quality improvement agent, the physical properties of the soil were significantly improved (Table 2). The redox potential increased by 13.27% - 20.38%, the alkalinity decreased by 8.53% - 10.88%, the electrical conductivity increased by 20.78% - 47.62%, and the porosity decreased by 0.18% - 1.04%. The proportion of soil stable aggregates changed with the increase of the addition concentration. The content changed, such as Figure 1 , the addition of the modifier can promote the formation of soil >2 mm and 2 - 0.25 mm aggregates, and inhibit the formation of 0.25 - 0.053 mm and <0.053 mm aggregates, indicating that the addition of the modifier can promote the formation of large aggregates, and it is positively correlated with the addition concentration. The soil without the conditioner is not easy to form aggregates.

[0060] Table 2 Effects of changes in soil physical properties in the examples

[0061] Redox potential (mV) Alkalinity (ESP) % Conductivity (us / cm) Porosity (%) Before implementation 64.5 53.05 142.17 68 Example 1 73.06 47.28 171.71 67.29 Example 2 75.8 46.67 169.19 67.56 Example 3 77.65 48.52 209.88 67.88

[0062] After the implementation of the salt marsh soil carbon sequestration and quality improvement agent, the organic carbon content of the soil was significantly increased, and the organic carbon composition changed (Table 3). The soil organic carbon content increased by 33.89% - 63.76%, and the inert carbon content increased by 27.56% - 92.89%. It shows that the addition of the modifier promoted the fixation of soil carbon.

[0063] Table 3 Soil carbon improvement effects obtained in the examples

[0064]

[0065] The specific embodiments listed above are only for explaining the present invention and are not limited to the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention in principle.

Claims

1. A soil carbon fixation and quality improvement agent for salt marsh soil, characterized in that: The soil carbon fixation and quality improvement agent is mainly composed of Spartina alterniflora biochar powder and yellow mealworm sand.

2. The soil carbon fixation and quality improvement agent for salt marsh soil according to claim 1, characterized in that: The Spartina alterniflora biochar powder is mainly obtained by pyrolysis of Spartina alterniflora straw under anaerobic conditions; the mealworm sand is mainly the excrement of mealworms fed on Spartina alterniflora straw.

3. The soil carbon fixation and quality improvement agent for salt marsh soil according to claim 1, characterized in that: The mass ratio of the yellow mealworm sand to the Spartina alterniflora biochar powder is 1:(1-3).

4. The method for preparing the soil carbon fixation and quality improvement agent for salt marsh soil according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Preparation of Spartina alterniflora biochar powder: Spartina alterniflora straw was collected, dried, and heated at 8-12 °C min under anaerobic conditions. -1 The heating rate is raised to 500-600° C. and pyrolyzed for 1.5-2.5 h, cooled, crushed, and sieved to obtain Spartina alterniflora biochar powder; (2) Mixing the Spartina alterniflora biochar powder obtained in step (1) with Tenebrio molitor sand to obtain the biochar.

5. Use of the soil carbon fixation and quality improvement agent for salt marsh soil according to any one of claims 1 to 3 in improving salt marsh soil.

6. Application of Spartina alterniflora biochar powder and mealworm sand in improving salt marsh soil.

7. The use according to claim 6, characterized in that: The Spartina alterniflora biochar powder is mainly obtained by pyrolysis of Spartina alterniflora straw under anaerobic conditions; the mealworm sand is mainly the excrement of mealworms fed on Spartina alterniflora straw.

8. A method for improving salt marsh soil, characterized in that: The method comprises improving the salt marsh soil by using the soil carbon fixation and quality improvement agent for salt marsh soil according to any one of claims 1 to 3, or simultaneously adding Spartina alterniflora biochar powder and yellow mealworm sand to the salt marsh soil to improve the salt marsh soil.

9. The method for improving salt marsh soil according to claim 8, characterized in that: The following steps are involved: Spreading the soil carbon fixation and quality improvement agent in the salt marsh soil that needs to fix carbon and increase carbon sink, and mixing it evenly with the surface soil; wherein the mass ratio of the soil carbon fixation and quality improvement agent to the salt marsh soil is 1: (50-100); Alternatively, the Spartina alterniflora biochar powder and yellow mealworm sand are simultaneously spread on the salt marsh soil that needs to fix carbon and increase carbon sink, and are evenly mixed with the topsoil; wherein the mass ratio of yellow mealworm sand to Spartina alterniflora biochar powder is 1:(1-3), and the mass ratio of the total mass of yellow mealworm sand and Spartina alterniflora biochar powder to the mass ratio of salt marsh soil is 1:(50-100).

10. The method for improving salt marsh soil according to claim 9, characterized in that: The surface soil refers to the soil layer from 0 to 30 cm below the soil surface.

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