A carbon component-based high-steep slope soil aggregate modifier and a preparation method thereof

Abstract

This invention provides a carbon-based soil aggregate improver for steep slopes and its preparation method, belonging to the field of soil improvement and ecological restoration. The raw materials for the improver include particulate organic carbon sources, mineral-bound organic carbon sources, nanomaterials, and microbial stabilizers. One method for preparing the improver involves mixing humic acid, leaf mold, and pine needle soil, then adding them to a sodium hexametaphosphate solution. After reaction, the mixture is dried and ground to obtain a mineral-bound organic carbon source. The particulate organic carbon source, mineral-bound organic carbon source, nano-CaCO3, and microbial stabilizers are then mixed evenly, water is added, and fermentation is carried out to obtain a fermentation product. This product is then dried, crushed, and the improver is obtained. The improver of this invention, through the synergistic effect of multiple components, effectively restores the ecological function of degraded soils on steep slopes, enhances the stability of the soil aggregate structure, and strengthens the long-term stability and organic carbon sequestration capacity of the aggregates.

Description

Technical Field

[0001] This invention belongs to the field of soil improvement and ecological restoration, specifically relating to a carbon-based soil aggregate improver for steep slopes and its preparation method. Background Technology

[0002] In the field of slope ecological restoration and soil protection, soil degradation on steep slopes has always been a challenging problem. With the expansion of infrastructure construction, such as the excavation of slopes along highways and railways, the area of ​​steep slopes continues to increase, exacerbating the soil degradation problem. Steep slopes, typically exceeding 35° in gradient and with low vegetation cover, are highly susceptible to rainwater erosion and wind erosion, leading to severe damage to soil structure. The soil on these slopes is characterized by a loose structure and low aggregate content, with an average aggregate size of less than 0.5 mm and a water-stable aggregate content generally below 20%. Under the influence of external forces such as rainfall, the soil is highly susceptible to erosion, resulting in significant sediment loss, clogging river channels and ditches. Simultaneously, soil nutrients are severely depleted, with the content of major nutrients such as nitrogen, phosphorus, and potassium only reaching 30%-50% of that in normal soils. In addition, the low activity of soil microorganisms and the microbial biomass carbon content of less than one-third of that of healthy soil seriously affect vegetation growth and slope stability, exacerbate the deterioration of the ecological environment, and may even trigger geological disasters such as landslides and mudslides, threatening the lives and property of surrounding residents.

[0003] Currently, soil degradation remediation technologies for steep slopes mainly rely on mineral stabilizers (such as clay and bentonite) and organic matter (such as compost and humic acid). However, these traditional remediation methods have significant limitations. From the perspective of organic carbon stability, traditional organic matter amendments such as compost mainly consist of easily decomposable sugars and proteins. Under the action of soil microbial communities (especially fungi and bacteria), the degradation rate can reach 60%-80% within six months, making it difficult to remain in the soil for a long time, resulting in poor durability of soil remediation effects. At the same time, existing amendments lack effective mineral-organic carbon binding mechanisms and cannot fully enhance the stability of soil aggregates. Taking bentonite as an example, although it has a certain water retention capacity, it cannot form a stable chemical bond with organic matter. After 3-5 simulated rainfalls, the aggregate destruction rate of the improved soil exceeds 40%, making it difficult to withstand external forces such as actual rainfall erosion.

[0004] Regarding carbon source utilization, most of the added organic matter cannot effectively combine with soil minerals, resulting in insufficient long-term soil conservation capacity after rapid short-term nutrient release. For example, in soils improved with humic acid, the release rate of nutrients such as nitrogen and phosphorus can reach more than 50% of the total added amount in the initial application period (within 1-2 months), but the nutrient content drops significantly after 3 months, failing to meet the long-term growth needs of plants. This phenomenon not only wastes resources but also fails to achieve long-term optimization of soil fertility and the microbial environment, making it difficult to fundamentally improve the problem of soil degradation on steep slopes.

[0005] In summary, existing soil improvement technologies for steep slopes suffer from problems such as poor organic carbon stability, unstable aggregate structure, and low carbon source utilization efficiency. Summary of the Invention

[0006] In view of this, the present invention provides a carbon-based soil aggregate improver for steep slopes and its preparation method, in order to solve the technical problems of poor organic carbon stability, unstable aggregate structure and low carbon source utilization efficiency in existing soil improvement technologies for steep slopes.

[0007] To achieve the above-mentioned objectives, this invention provides a carbon-based soil aggregate improver for steep slopes. The raw materials, by weight, comprise 25-35 parts of particulate organic carbon source, 35-45 parts of mineral-bound organic carbon source, 0.5-1 parts of nano-CaCO3, 0.45-0.6 parts of microbial stabilizer, and 1.2-1.5 parts of additives. The microbial stabilizer consists of live Bacillus licheniformis capsules and cellulase. The additives consist of sodium alginate and attapulgite. The particulate organic carbon source is made from one or more of bamboo shoot shells, lotus root residue, mango kernels, jackfruit seeds, and sacha indica shells. The mineral-bound organic carbon source comprises humic acid, leaf mold, and pine needle soil. Preferably, the mass ratio of the live Bacillus licheniformis capsules to the cellulase is 0.25-0.3:0.2-0.3.

[0008] Preferably, the mass ratio of sodium alginate to attapulgite is 0.2-0.25:1-1.25.

[0009] A method for preparing a carbon-based soil aggregate amendment for steep slopes according to the present invention includes the following steps:

[0010] S1. After cleaning and drying the food processing waste to constant weight, crush it to obtain particulate organic carbon source;

[0011] S2, humic acid, leaf mold, and pine needle soil are mixed in a ratio of 1:1-1.5:1-1.5, and then sieved.

[0012] A composite soil was obtained;

[0013] S3. Add the composite soil to a sodium hexametaphosphate solution with a concentration of 5-6 g / ml and shake to disperse.

[0014] After 18-24 hours, the solution was passed through a 53μm sieve, the filtrate was collected, dried at 50-60℃, and ground to obtain the mineral-bound organic carbon source.

[0015] S4. Mix the particulate organic carbon source, mineral-bound organic carbon source, nano CaCO3, microbial stabilizer and additives evenly, add water to obtain a fermentation mixture with a water content of 50%-60%, and ferment aerobically at 25-30℃ (air flow rate of 0.15vvm) for 7-15 days to obtain the fermentation product.

[0016] S5. The fermentation product is dried and crushed to obtain the soil aggregate improver for steep slopes.

[0017] Preferably, the food processing waste mentioned in S1 is one or more of bamboo shoot shells, lotus root residue, mango pits, jackfruit seeds, and sacha inchi shells.

[0018] Preferably, the average particle size of the particulate organic carbon source in S1 is greater than 53 μm.

[0019] Preferably, the average particle size of the composite soil in S2 is less than 2 mm.

[0020] Preferably, the mass-to-volume ratio of the composite soil to the sodium hexametaphosphate solution in S3 is 1g:5-6ml.

[0021] The application of a carbon-based soil aggregate modifier for steep slopes according to the present invention involves mixing the soil aggregate modifier with the slope soil and then curing it.

[0022] Preferably, the amount of the soil aggregate conditioner added to the steep slope is 10-15% of the slope soil mass.

[0023] Compared to existing technologies that use single organic matter such as compost, rice husk ash, or humic powder as carbon sources, the particulate and mineral-bound organic carbon sources selected in this invention are better suited to the remediation needs of degraded soils on steep slopes in terms of structural composition and chemical activity. Food processing wastes such as bamboo shoot shells, lotus root residue, mango pits, jackfruit seeds, and sacha inchi shells are rich in lignin, cellulose, and hemicellulose complexes, with a moderate C / N ratio. They can slowly decompose under the action of microorganisms and continuously supply carbon, forming a relatively stable organic carbon pool. Compared to conventional compost, these raw materials have a higher aromatic carbon content and a lower proportion of water-soluble organic matter, which can significantly prolong the retention time of organic carbon in the soil and improve its chemical stability.

[0024] Mineral-bound organic carbon sources (obtained from a composite of humic acid, leaf mold, and pine needle soil) contain a large number of carboxyl groups (–COOH), phenolic hydroxyl groups (–OH), and aromatic carboxyl ring structures, which can form stable binding structures such as coordination bonds or hydrogen bonds with the surface of soil minerals, thereby effectively inhibiting the microbial degradation process of organic carbon and significantly improving its chemical stability in soil.

[0025] Unlike the single humic acid or compost-type raw materials used in existing technologies, the composite carbon source system of this invention uses POC and MAOC to synergistically regulate the short-term and long-term carbon pool structure. It can not only quickly activate microorganisms to promote the formation of aggregates, but also achieve long-term carbon sequestration and structural fixation through mineral binding, thus adapting to the extreme environment of steep slopes with strong surface disturbance and frequent rainfall erosion.

[0026] In this invention, particulate organic carbon source (POC) can provide short-term carbon source and improve microbial activity; mineral-bound organic carbon source (MAOC) can improve long-term carbon sequestration capacity and enhance aggregate stability; nano-CaCO3 (40nm) can promote microbial mineralization and improve pH regulation ability; microbial stabilizer: containing Bacillus licheniformis live bacteria capsules (0.25g-250 million live bacteria) (Shenyang First Pharmaceutical Co., Ltd., Northeast Pharmaceutical Group) and cellulase (0.2g / Guangdong Kangda Biotechnology Co., Ltd.), promotes aggregate formation, organic matter degradation, and improves plant symbiosis ability; auxiliary additives: sodium alginate (0.2g / Guangdong Kangda Biotechnology Co., Ltd.)-attapulgite (1g / mineral products factory) clay composite water-retaining agent, regulates moisture and enhances microbial activity.

[0027] The soil aggregate improver for steep slopes provided by this invention is a multi-component synergistic system. Based on the triple mechanism of carbon component structure regulation, microbial-mineral composite enhancement and interfacial water management, it plays a core role in constructing stable soil aggregate structures, efficient organic carbon sequestration and sustainable plant habitats.

[0028] Particulate organic carbon (POC) provides a carbon source that can be rapidly metabolized by microorganisms, stimulating the initial activity of soil microorganisms, promoting the production of extracellular enzymes and extracellular polymers (EPS), and forming primary cemented aggregate structures. Mineral-bound organic carbon (MAOC) exhibits strong chemical stability, constructing an organic-inorganic composite interface on the surface of soil micro-aggregates, enhancing the long-term stability of the aggregate structure and the mineral-bound sequestration capacity of organic carbon. Nanoscale biomineralized calcium carbonate particles (40 nm) can participate in the aggregate cementation process together with microbial metabolites, forming a microcrystalline carbonate-organic matter composite structure, improving the structure's resistance to disintegration, and effectively regulating the soil's pH buffering capacity, creating a suitable pH environment for microbial growth.

[0029] In the microbial stabilizer complex system, Bacillus licheniformis plays a leading role in aggregate formation and carbon conversion by secreting extracellular polysaccharides and promoting rhizosphere symbiotic metabolism. Cellulase participates in the efficient decomposition of plant residues and POC, improving carbon cycle efficiency and promoting the aggregation and stable binding of humic precursors, thereby enhancing the overall conversion efficiency and structural bonding capacity of soil organic matter. The auxiliary additive sodium alginate-attapulgite complex system constructs a stable water film on the surface of aggregates and between pores, maintaining the moisture state of the soil microenvironment and preventing the structural destruction of microaggregates during wet-dry cycles. The layered structure of attapulgite provides ion exchange and water retention regulation functions, forming a multifunctional slow-release platform for water and trace elements together with the seaweed polysaccharide network.

[0030] This improved system, through the synergistic effect among materials at multiple scales, significantly increased the organic-mineral binding ratio and the intensity of microbial participation in aggregates, enhanced the proportion and average weight diameter of water-stable aggregates, strengthened the spatial protection and structural fixation efficiency of organic carbon, and significantly restored the physical structure, biological activity and carbon storage capacity of degraded soils on steep slopes, providing a stable and sustainable soil ecological support system for slope vegetation restoration.

[0031] Compared with the prior art, the present invention has the following beneficial effects;

[0032] This soil improvement system effectively restores the ecological function of degraded soil on steep slopes through the synergistic effect of multiple components. Specifically, particulate organic carbon (POC) rapidly stimulates microbial activity, promoting the generation of extracellular enzymes and polymers, forming primary cemented aggregate structures. Mineral-bound organic carbon (MAOC), with its chemical stability, constructs an organic-inorganic composite interface, enhancing the long-term stability of aggregates and their organic carbon sequestration capacity. Biomineralized calcium carbonate particles participate in aggregate cementation, forming a microcrystalline carbonate-organic matter composite structure, improving resistance to disintegration. Nano-CaCO3 particles possess a high specific surface area (>50 m²). 2 ·g -1 With its surface hydroxyl activity, Ca can interact with organic carbon components in various chemical and physical ways during fermentation and aggregate formation. On the one hand, Ca... 2+ Ions can form ionic bridges with carboxyl groups (–COOH) and hydroxyl groups (–OH) in humic acid or cellulose decomposition products, promoting the adsorption and cross-linking of organic molecules on the mineral surface, thereby enhancing the cementing strength of the POC–MAOC–mineral complex. On the other hand, CaCO3 microcrystals can nucleate in the extracellular polysaccharide (EPS) matrix secreted by microorganisms, forming an organic-inorganic co-precipitation structure, increasing the microcrystal density and corrosion resistance of the aggregates. Simultaneously, the CaCO3 buffer system can regulate the pH of the fermentation and later-stage maintenance environment (maintaining it at 6.5–7.5), providing an optimal environment for the extracellular enzyme activity of microorganisms and promoting the stable transformation of organic matter. 2+The bridging mechanism can increase the stability of soil aggregates by 20–50%, contributing to the formation of a more durable "organic-mineral-calcium" ternary stable network structure. This invention utilizes this mechanism to enable the aggregate structure formed by the amendment to possess both high stability and high carbon sequestration efficiency.

[0033] In the microbial stabilizer complex system, Bacillus licheniformis secretes extracellular polysaccharides, promotes rhizosphere symbiotic metabolism, and dominates aggregate formation and carbon conversion. The auxiliary additive sodium alginate-attapulgite complex system forms a stable water film on the surface of the aggregates. Attapulgite, combined with seaweed polysaccharides, constructs a slow-release platform for water and trace elements, preventing the aggregates from being damaged by wet-dry cycles.

[0034] With the synergy of multiple scale materials, this system significantly improves the organic-mineral binding ratio of aggregates, the proportion of water-stable aggregates, enhances organic carbon fixation efficiency, and comprehensively restores soil physical structure, biological activity and carbon storage capacity, thus laying a solid soil ecological foundation for slope vegetation restoration. Attached Figure Description

[0035] Figure 1 The percentage of each particle size of the aggregates in the cured slope soil in Example 1 and Comparative Example 1;

[0036] Figure 2 The percentage of each particle size of the aggregates in the cured slope soil in Example 2 and Comparative Example 1;

[0037] Figure 3 The percentage of each particle size of the aggregates in the cured slope soil in Example 3 and Comparative Example 1. Detailed Implementation

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

[0039] The Bacillus licheniformis live bacteria capsules are available in a specification of 0.25g (250 million live bacteria), and the manufacturer is Northeast Pharmaceutical Group Shenyang First Pharmaceutical Co., Ltd.

[0040] The cellulose-degrading enzyme is available in 0.2g form and is sold by Guangdong Kangda Biotechnology Co., Ltd.

[0041] Sodium alginate is available in 0.2g form and is sold by Guangdong Kangda Biotechnology Co., Ltd.

[0042] The specification for paisleyite is 1g, sold by a mineral products factory.

[0043] Example 1

[0044] This embodiment provides a carbon-based soil aggregate amendment for steep slopes, the raw materials of which, by mass, include 25 parts of particulate organic carbon source, 45 parts of mineral-bound organic carbon source, 1 part of nano-CaCO3, 0.3 parts of Bacillus licheniformis live bacteria capsules, 0.3 parts of cellulase, 0.25 parts of sodium alginate and 1.25 parts of attapulgite.

[0045] A method for preparing a carbon-based soil aggregate amendment for steep slopes, as described in this embodiment, includes the following steps:

[0046] S1. Bamboo shoot shells, lotus root residue, mango kernels, jackfruit seeds, and sacha in a mass ratio of 1:1:1:1:1 were washed, dried to constant weight, and crushed to obtain particulate organic carbon source with an average particle size of 100 μm.

[0047] S2, humic acid, leaf mold and pine needle soil are mixed in a ratio of 1:1:1 and sieved to obtain composite soil with an average particle size of less than 2mm.

[0048] S3. The composite soil was added to a sodium hexametaphosphate solution with a concentration of 5 g / ml and shaken for 18 h. The mass ratio of the composite soil to the sodium hexametaphosphate solution was 1 g: 5 ml. The mixture was passed through a 53 μm sieve, and the filtrate was dried at 50 °C and ground to obtain a mineral-bound organic carbon source.

[0049] S4. After uniformly mixing the particulate organic carbon source, mineral-bound organic carbon source, nano CaCO3, microbial stabilizer and additives, water is added to obtain a fermentation mixture with a water content of 50%. Aerobic fermentation is carried out at 25°C (air flow rate of 0.15 vvm) for 15 days to obtain the fermentation product.

[0050] S5. The fermentation product is dried and crushed to obtain the soil aggregate improver for steep slopes.

[0051] The application of the carbon-based soil aggregate modifier for steep slopes described in this embodiment involves mixing 10g of the soil aggregate modifier with 100g of slope soil, adding water to adjust the water content to 60% of the field capacity, and then curing at room temperature for 20 days.

[0052] Example 2

[0053] This embodiment provides a carbon-based soil aggregate amendment for steep slopes. The raw materials, by weight, include 30 parts of particulate organic carbon source, 40 parts of mineral-bound organic carbon source, 0.6 parts of nano-CaCO3, 0.28 parts of Bacillus licheniformis live bacteria capsules, 0.25 parts of cellulase, 0.23 parts of sodium alginate, and 1.2 parts of attapulgite.

[0054] A method for preparing a carbon-based soil aggregate amendment for steep slopes, as described in this embodiment, includes the following steps:

[0055] S1. Bamboo shoot shells, lotus root residue, mango kernels, jackfruit seeds, and sacha in a mass ratio of 1:1:1:1:1 were washed, dried to constant weight, and crushed to obtain particulate organic carbon source with an average particle size of 100 μm.

[0056] S2, humic acid, leaf mold and pine needle soil are mixed in a ratio of 1:1.5:1.5 and sieved to obtain a composite soil with an average particle size of less than 2 mm.

[0057] S3. The composite soil was added to a sodium hexametaphosphate solution with a concentration of 6 g / ml and shaken for 24 h. The mass ratio of the composite soil to the sodium hexametaphosphate solution was 1 g: 6 ml. The mixture was passed through a 53 μm sieve, and the filtrate was dried at 60 °C and ground to obtain a mineral-bound organic carbon source.

[0058] S4. After uniformly mixing the particulate organic carbon source, mineral-bound organic carbon source, nano CaCO3, microbial stabilizer and additives, water is added to obtain a fermentation mixture with a water content of 60%. Aerobic fermentation is carried out at 30°C (air flow rate of 0.15 vvm) for 7 days to obtain the fermentation product.

[0059] S5. The fermentation product is dried and crushed to obtain the soil aggregate improver for steep slopes.

[0060] The application of the carbon-based soil aggregate modifier for steep slopes described in this embodiment involves mixing 15g of the soil aggregate modifier with 100g of slope soil, adding water to adjust the water content to 60% of the field capacity, and then curing at room temperature for 20 days.

[0061] Example 3

[0062] This embodiment provides a carbon-based soil aggregate improver for steep slopes. The raw materials, by weight, include 35 parts of particulate organic carbon source, 35 parts of mineral-bound organic carbon source, 0.5 parts of nano-CaCO3, 0.25 parts of Bacillus licheniformis live bacteria capsules, 0.2 parts of cellulase, 0.2 parts of sodium alginate, and 1 part of attapulgite.

[0063] A method for preparing a carbon-based soil aggregate amendment for steep slopes, as described in this embodiment, includes the following steps:

[0064] S1. Bamboo shoot shells, lotus root residue, mango kernels, jackfruit seeds, and sacha in a mass ratio of 1:1:1:1:1 were washed, dried to constant weight, and crushed to obtain particulate organic carbon source with an average particle size of 100 μm.

[0065] S2, humic acid, leaf mold and pine needle soil are mixed in a ratio of 1:1.3:1.2 and sieved to obtain composite soil with an average particle size of less than 2 mm.

[0066] S3. The composite soil was added to a sodium hexametaphosphate solution with a concentration of 5.5 g / ml and shaken for 20 h. The mass ratio of the composite soil to the sodium hexametaphosphate solution was 1 g: 5.5 ml. The mixture was passed through a 53 μm sieve, and the filtrate was collected, dried at 55 °C, and ground to obtain a mineral-bound organic carbon source.

[0067] S4. After uniformly mixing the particulate organic carbon source, mineral-bound organic carbon source, nano CaCO3, microbial stabilizer and additives, water is added to obtain a fermentation mixture with a water content of 55%. Aerobic fermentation is carried out at 28°C (air flow rate of 0.15 vvm) for 10 days to obtain the fermentation product.

[0068] S5. The fermentation product is dried and crushed to obtain the soil aggregate improver for steep slopes.

[0069] The application of the carbon-based soil aggregate modifier for steep slopes described in this embodiment involves mixing 12g of the soil aggregate modifier with 100g of slope soil, adding water to adjust the water content to 60% of the field capacity, and then curing at room temperature for 20 days.

[0070] Comparative Example 1

[0071] Take 100g of the same slope soil as in Example 1, add water to adjust to 60% of field capacity, and cure at room temperature for 20 days.

[0072] The slope soils cured in Examples 1-3 and Comparative Example 1 were used to measure the content of aggregates larger than 0.25 mm, the water-stable aggregate index (WSA), and the mean weight diameter (MWD). Water-stable soil aggregate particle groups were prepared using the wet sieving method. A set of sieves with apertures of >2, 2-1, 1-0.5, 0.5-0.25, and <0.25 mm were placed in a settling cylinder containing an appropriate amount of water. The soil placed on the top sieve was soaked in water for 5 minutes, then vibrated at a frequency of 30 times per minute for 3 minutes. After standing for 5 minutes, each sieve surface was carefully rinsed with water. The rinsed suspension was collected in a beaker, allowed to settle completely, dried, and weighed to calculate the particle size and distribution of each grade of aggregate.

[0073] Figure 1 The percentages of different particle sizes of aggregates in the cured slope soil of Example 1 and Comparative Example 1 are shown. Figure 2 The percentages of different particle sizes of aggregates in the cured slope soil of Example 2 and Comparative Example 1 are shown. Figure 3Table 1 shows the percentage of different particle sizes of aggregates in the cured slope soil of Example 3 and Comparative Example 1. The core indicators of aggregate stability are shown in Table 1.

[0074] Table 1 Core Indicators of Aggregate Stability

[0075]

[0076] The content of soil aggregates larger than 0.25 mm is a key indicator of soil stability. These large aggregates, formed by the cementation of organic matter and microbial secretions, have stronger resistance to water erosion and mechanical damage, and can effectively improve soil structure and ecological function. Figure 1-3 The data in Table 1 regarding the proportion of aggregates larger than 0.25 mm demonstrate the remarkable effect of the soil conditioner in promoting the formation of large aggregates. It significantly enhances the soil's resistance to erosion, improves its aeration, water permeability, and nutrient retention capacity, providing a reliable scientific basis for soil structure improvement. International standards (such as FAO) and domestic industry standards (NY / T 1121.19-2008) both use the content of aggregates larger than 0.25 mm as a core indicator for evaluating large aggregates. In this study, all treatments far exceeded the ideal threshold for agricultural soils (>50%), with some even reaching the high standards required for ecological restoration projects (>70%), highlighting the significant advantages and application potential of this soil improvement technology.

[0077] The stability of soil aggregates after improvement was systematically evaluated using the mean weight diameter (MWD) index (Table 1). This result shows that all treatments significantly improved soil structural stability. From the perspective of soil mechanical properties, the increase in MWD value directly reflects the optimization of aggregate particle size distribution. The MWD of all improved soil groups exceeded 1.7 mm, far higher than the ideal threshold (1.5 mm) for agricultural soils, indicating that the amendment effectively promoted the transformation of micro-aggregates into macro-aggregates. Particularly noteworthy is that the MWD of the soil treated in Example 1 approached 1.85 mm, a value reaching that of organic-rich clay, demonstrating its particularly significant improvement effect. An increase in MWD value of over 60% has significant value in engineering practice and can provide reliable technical support for slope protection and farmland improvement.

[0078] The effectiveness of the soil amendment was evaluated using the Water Stable Aggregate Index (WSA). Data showed that the WSA values ​​in Examples 1 and 2 significantly increased by 4.92% and 3.76% respectively compared to the original value (89.85%). The soil treated in Example 1 exhibited the best WSA performance, increasing it to 94.375%, reaching an extremely stable level (>90%). The soil treated in Example 2 also showed excellent performance, increasing its WSA to 93.333%. The soil treated in Example 3 (89.897%) had a WSA that was essentially the same as the control, only slightly higher. This invention demonstrates the advantages of the soil amendment in promoting the formation of organic-mineral complexes.

[0079] Although Example 3 showed a relatively small increase in water-stable aggregate (WSA) content, increasing by only 0.05%, its WSA still reached 89.897%, which was better than the unmodified original soil (89.85%). However, Example 3 showed significant improvements in other indicators such as aggregate content >0.25mm (%) and average particle diameter MWDwet (mm), reflecting the synergistic enhancement effect of the overall formulation of the amendment in Example 3 on the multifunctionality of the soil.

[0080] The soil conditioner of this invention demonstrates its superior performance in improving soil structural stability. The overall particle size of the aggregates increases, significantly enhancing resistance to mechanical damage. The proportion of water-stable aggregates reaches an extremely high level, exhibiting exceptional resistance to water erosion. The proportion of large-size aggregates increases significantly, improving pore structure and water retention.

[0081] Soil carbon, nitrogen, phosphorus and available phosphorus content were measured in the soils of Examples 1-3 and Comparative Example 1 after curing. The measurement results are shown in Table 2.

[0082] Table 2 Soil carbon, nitrogen, phosphorus and available phosphorus content

[0083]

[0084] The data in the table show that, compared to Comparative Example 1, the soil organic carbon content in Examples 1, 2, and 3 increased significantly. The organic carbon content (g·kg) of the improved soil in Examples 1-3 is shown in the table. -1 The concentrations were all higher than those of the soil in Comparative Example 1 (36.86), especially in Example 3 where it reached 46.54 g·kg⁻¹. -1 Compared to Comparative Example 1, this represents an increase of approximately 26.3%. This indicates that both added POC and MAOC can significantly enhance the soil carbon pool, especially in the treatment with increased POC proportion (Example 3), where the effect is more pronounced. POC, as an active carbon source, is more likely to increase the total carbon content in the short term.

[0085] The data in the table show that, compared to Comparative Example 1, the total nitrogen content of the soils in Examples 1, 2, and 3 decreased, especially in Example 3 where it was the lowest. This is due to the increased carbon-to-nitrogen ratio in the amendment (the input of high-carbon components intensifies competition for nitrogen among microorganisms), and some nitrogen is temporarily fixed during microbial assimilation or initial organic matter decomposition, resulting in a decrease in total nitrogen. However, this "temporary sequestration" of nitrogen is a reversible process in ecological restoration, which is beneficial for long-term nutrient cycling and steady-state nitrogen supply from plants.

[0086] The data in the table show that, compared to Comparative Example 1, the total phosphorus content of the soils in Examples 1, 2, and 3 was slightly increased, with the total phosphorus content of the improved soils remaining stable at 0.96–0.97 g·kg⁻¹. -1 The value was higher than that of Comparative Example 1 (0.85), indicating that the modifier of the present invention has a certain effect on phosphorus retention, which is related to the phosphorus passivation inhibition effect induced by organic matter encapsulation, microbial mineralization and nano-CaCO3.

[0087] The data in the table show that the available phosphorus content in the soils of Examples 1, 2, and 3 was significantly increased compared to Comparative Example 1. Comparative Example 1 had a content of only 10.56 mg·kg⁻¹. -1 Example 1 achieved 40.72 mg·kg -1 The improvement was nearly 3.9 times, indicating that the organic carbon and microbial active components added to the improver have a significant effect on promoting phosphate dissolution and phosphate mineralization.

[0088] In summary, the modifier in Example 1 has the most balanced effect, while Example 3, although it has limited improvement in WSA, shows long-term carbon sequestration potential in terms of organic carbon accumulation.

[0089] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A soil aggregate modifier for steep slopes based on carbon components, characterized in that, The raw materials, by weight, include 25-35 parts of particulate organic carbon source, 35-45 parts of mineral-bound organic carbon source, 0.5-1 parts of nano-CaCO3, 0.45-0.6 parts of microbial stabilizer, and 1.2-1.5 parts of additives. The microbial stabilizer is composed of live Bacillus licheniformis capsules and cellulase, with a mass ratio of 0.25-0.3:0.2-0.

3. The additives are composed of sodium alginate and attapulgite, with a mass ratio of 0.2-0.25:1-1.

25. The particulate organic carbon source is made from one or more of bamboo shoot shells, lotus root residue, mango kernels, jackfruit seeds, and sacha inchi shells. The raw materials for the mineral-bound organic carbon source include humic acid, leaf mold, and pine needle soil.

2. A method for preparing a carbon-based soil aggregate amendment for steep slopes according to claim 1, characterized in that, Includes the following steps: S1. After cleaning and drying the food processing waste to constant weight, crush it to obtain particulate organic carbon source; S2, humic acid, leaf mold, and pine needle soil are mixed in a ratio of 1:1-1.5:1-1.5, and then sieved. A composite soil was obtained; S3. Add the composite soil to a sodium hexametaphosphate solution with a concentration of 5-6 g / ml and shake to disperse. After 18-24 hours, the solution was passed through a 53μm sieve, the filtrate was collected, dried at 50-60℃, and ground to obtain the mineral-bound organic carbon source. S4. The particulate organic carbon source, mineral-bound organic carbon source, nano-CaCO3, and microorganisms are added to the mixture. After the stabilizer and additives are mixed evenly, water is added to obtain a fermentation mixture with a water content of 50%-60%. The mixture is then fermented aerobically at 25-30℃ for 7-15 days to obtain the fermentation product. S5. The fermentation product is dried and crushed to obtain the soil aggregate improver for steep slopes.

3. The preparation method according to claim 2, characterized in that, The food processing waste mentioned in S1 is one or more of the following: bamboo shoot shells, lotus root residue, mango pits, jackfruit seeds, and sacha inchi shells.

4. The preparation method according to claim 2, characterized in that, The average particle size of the particulate organic carbon source described in S1 is greater than 53 μm.

5. The preparation method according to claim 2, characterized in that, The average particle size of the composite soil described in S2 is less than 2 mm.

6. The preparation method according to claim 2, characterized in that, The mass-to-volume ratio of the composite soil to the sodium hexametaphosphate solution described in S3 is 1g:5-6ml.

7. An application of a carbon-based soil aggregate conditioner for steep slopes as described in claim 1, characterized in that, The specific steps involve mixing the soil aggregate improver for steep slopes with the slope soil and then curing it.

8. The application according to claim 7, characterized in that, The amount of the soil aggregate amendment for steep slopes added is 10-15% of the soil mass of the slope.

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