A method for improving saline soil with biochar

Abstract

The present application relates to a kind of biochar improved saline soil greening construction method, belong to saline-alkali soil ecological restoration and greening construction technical field, including the following steps: S1, site pretreatment and salt removal system construction;S2, construction of leaching prevention layer and water-collecting well;S3, modified biochar preparation;S4, functional microorganism bacterium preparation and carbon bacteria coupling;S5, carbon bacteria improvement layer laying and salt-tolerant plant planting;S6, system debugging, monitoring and maintenance and operation.The biochar improved saline soil greening construction method, by using "biochar-function microorganism-salt-tolerant plant" trinity collaborative mechanism, biochar improves soil pore structure and adsorbs sodium ion, microorganism secretes organic acid and reduces salt and dissolves phosphorus, activates nutrient, plant root loosens soil and absorbs salt, three in the same improvement layer simultaneously play physical, chemical and biological effect, can quickly reduce soil salt content to 3.0g / kg below, pH drops to 7.8 below, significantly improve vegetation survival rate (≥90%) and growth potential.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration and greening construction technology for saline-alkali land, specifically a method for greening saline soil improved with biochar. Background Technology

[0002] Saline soils are widely distributed in my country's coastal areas. Affected by factors such as seawater infiltration, high groundwater levels, and intense evaporation, these soils generally suffer from high salt content (total salt content of moderate to severe saline soils is typically ≥4.0 g / kg), high alkalinity (pH ≥ 9.0), compacted structure, nutrient deficiency, and a tendency to revert to salinity and alkaliness. These problems severely restrict greening, ecological restoration, and landscape enhancement in coastal areas. The management of saline-alkali land in coastal mudflats, reclaimed land, coastal industrial parks, and ecological corridors has become a challenging and pressing issue in current ecological construction.

[0003] Traditional methods for improving saline-alkali land mainly include flood irrigation to leach salt, application of chemical amendments, and soil replacement. These methods have significant limitations in practical application: flood irrigation consumes large amounts of water, and the leachated salt easily re-accumulates on the surface with capillary water, resulting in short-term improvement; chemical amendments (such as gypsum and ferrous sulfate) are expensive and may introduce secondary pollution, negatively impacting the soil micro-ecology with long-term use; soil replacement requires large quantities of high-quality soil, damaging the ecology of the soil extraction area, resulting in high construction costs, large project scale, and poor compatibility with the ecological environment. These methods are insufficient to meet the needs of long-term improvement and greening of moderately to severely saline soils, and especially cannot achieve the self-sustaining and continuous restoration of the saline-alkali land ecosystem.

[0004] Therefore, there is an urgent need to develop a construction method for improving and greening saline soil that is ecologically low-carbon, has a long-lasting effect on salt suppression, and is economically applicable. This invention aims to provide a construction process that takes "biochar-functional microorganisms-salt-tolerant plants" as the core of synergistic improvement and combines it with underground drainage and salt removal technology. This process achieves rapid soil salinization and alkali suppression, structural improvement, microbial activation, and vegetation establishment in an integrated manner. It also has the advantages of long-lasting salt suppression, carbon sequestration and emission reduction, resource recycling, and low operation and maintenance costs, effectively solving the problems of salt return, compaction, and infertility in moderately to severely saline soils in coastal areas. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a biochar-based method for improving saline-alkali soil and promoting greening. This method has advantages such as significant synergistic soil improvement effects, long-term inhibition of salinization and alkali return, ecological low-carbon resource recycling, and simple operation and maintenance at low cost. It solves the problems of existing saline-alkali land improvement methods, such as high water consumption, short improvement time, easy secondary pollution, high construction costs, and difficulty in meeting the long-term improvement and greening needs of moderate to severe saline-alkali soil.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for greening saline soil using biochar includes the following steps:

[0008] S1. Site Pretreatment and Salt Drainage System Construction: Clean, level, and drain the saline soil site, removing surface debris and stagnant water; conduct stratified soil sampling to test pH, total salt content, organic matter, EC value, and groundwater depth to determine improvement parameters; lay out the location according to the design drawings, and excavate blind drains with a width and depth of 30cm at intervals of 6-15m along the slope, maintaining a slope of 0.2%; excavate drainage ditches with a width and depth of 30cm perpendicular to the blind drains, maintaining a slope of 0.2%. The slope is 1%, and the bottom of the ditch is 15cm below the groundwater level. A 10cm thick layer of crushed stone is laid and compacted in both the blind pipe ditch and the drainage ditch. A double corrugated PVC blind pipe with a diameter of 6-10cm is laid in the center of the blind pipe ditch. The pipe joints are firmly glued and the ends are sealed with non-woven fabric. A drainage pipe with a diameter of 10-12cm is laid in the drainage ditch. The pipe is covered and wrapped with crushed stone with a thickness of not less than 15cm. A permeable non-woven fabric is laid on the top of the blind pipe ditch. The blind pipe and the drainage pipe are connected to form a complete salt drainage network.

[0009] S2. Construction of the isolation layer and collection wells: Above the highest groundwater level and below the planting layer, a 20-30cm thick layer of crushed stone, slag, or ceramsite is evenly laid as an isolation layer. The layer is spread flat and uninterrupted. The top of the isolation layer is fully covered with permeable geotextile, with an overlap width of not less than 30cm. Collection wells are laid every 50-100m along the direction of the drainage ditch. The wells are excavated from below the isolation layer to a height of 10cm above the ground surface. The well bodies are made of brick or fiberglass. The bottom of the well is level with the groundwater level. The inner wall is treated with anti-seepage measures. After completion, the wells are covered for protection.

[0010] S3. Preparation of Modified Biochar: One or more biomass raw materials selected from reeds, Spartina alterniflora, straw, or garden waste are used to prepare biochar through oxygen-limited pyrolysis at 450–550℃. The biochar is then pulverized through a 40-mesh sieve, washed with water to remove impurities, and dried. Chemical coprecipitation method for modifying biochar: biochar is mixed with... The mixed solutions were mixed at a mass ratio of 1:5 to 1:10, the pH was adjusted to 9 to 11, and the mixture was stirred in a water bath at 40 to 60°C for 0.5 to 2 hours. After aging for 18 to 30 hours, the mixture was washed, dried, and sieved to obtain modified biochar.

[0011] S4. Preparation of functional microbial agents and coupling with anthracnose bacteria: Salt-tolerant Bacillus and Flavobacterium functional strains were isolated and screened from in-situ saline-alkali soil in tidal flats or rhizosphere of salt-tolerant plants, and acclimated to tolerance of 3%–5% under gradient salt stress. Functional rejuvenation and non-antagonistic formulation were carried out to prepare a compound functional microbial agent with a bacterial concentration of [missing information]. The content is 1.2 to 2.0; the composite bacterial agent is uniformly loaded onto modified biochar using the adsorption method, the mass ratio of bacterial solution to modified biochar is controlled at 1:3 to 1:5, the adsorption temperature is 25 to 35℃, and the time is 12 to 24 hours, thus preparing a biochar-based functional microbial composite modifier.

[0012] S5. Carbonized microbial amendment layer laying and salt-tolerant plant planting: Based on the soil baseline indicators, determine the application rate of the compound amendment to be 1.5-3.0 kg / m². For deep-rooted plants, use surface mixing; for shallow-rooted herbs, use surface sowing. Apply the amendment to the soil and then rotary tillage it to ensure it is fully mixed with the 0-30 cm topsoil. Sprinkle water as needed to activate the microorganisms. Select one or more native salt-tolerant plants from Suaeda salsa, Salicornia glutinosa, Tamarix chinensis, Nitraria tangutorum, or Reed. Plant them in a multi-level configuration of trees, shrubs, and grasses according to the designed row and plant spacing. After spreading out the plant roots, plant them in the soil, backfill with the amendment soil and compact it, and water thoroughly.

[0013] S6. System Debugging, Monitoring and Maintenance: Conduct water flow tests on the salt drainage network and collection wells to ensure no blockages or leaks; initiate leaching desalination with irrigation or natural rainfall to achieve "salt removal with water"; regularly monitor soil total salinity, pH, organic matter, microbial activity, plant survival rate, and growth status, and complete project acceptance after the indicators meet the standards; carry out daily watering, loosening of soil, fertilization, and pest and disease control; strengthen leaching desalination with natural rainfall during the rainy season and adopt water-saving irrigation during the dry season; regularly clean the salt drainage pipes and collection wells to maintain the long-term operation of the system.

[0014] Furthermore, in S1, the spacing between the blind pipe trenches is 8-12m, the diameter of the double corrugated PVC blind pipe is 8cm, and the diameter of the drainage pipe is 10cm.

[0015] Furthermore, in S2, the thickness of the rainproof layer is 25cm, the material is crushed stone, the water collection well adopts a brick structure, the upper diameter of the well body is 60-80cm, and the lower diameter is 120cm.

[0016] Furthermore, in step S3, the biochar raw material is reed or Spartina alterniflora, and the pyrolysis temperature is 500℃. During modification, the pH was adjusted to 10, the reaction temperature was 50℃, and the aging time was 24h.

[0017] Furthermore, in step S4, the functional microbial agent also includes at least one of phosphate-solubilizing bacteria or nitrogen-fixing bacteria, which is compounded with halophilic Bacillus and Flavobacterium at a mass ratio of 1:1:1.

[0018] Furthermore, in step S4, after adsorption loading, 3% to 8% by mass of trehalose or skim milk powder is added as a protective agent, and then dried at a low temperature of 40°C to prepare a powdered composite modifier.

[0019] Furthermore, in S5, for severely saline soil with a total salt content ≥ 6.0 g / kg, the application rate of the composite amendment is 2.5–3.0 kg / m², and the rotary tillage depth is 40 cm.

[0020] Furthermore, in S5, the multi-level configuration pattern of trees, shrubs and grasses is as follows: Tamarix or Nitraria tangutorum serves as the tree / shrub layer, with a plant spacing of 1.2-1.5m × 1.5-2.0m; Suaeda salsa serves as the herbaceous layer, with a row spacing of 0.3-0.5m; and Salicornia glutinosa serves as the ground cover layer, with a row spacing of 0.2-0.3m.

[0021] Furthermore, in S6, the monitoring frequency is as follows: once a month for the first 3 months after construction, and once every 3 months thereafter; during the maintenance period, the salt drainage pipe is cleaned 1 to 2 times a year, and the water collection well is inspected and dredged once every six months.

[0022] Furthermore, in S6, micro-sprinkler irrigation or drip irrigation is used during the dry season, with a single irrigation volume of 10-15 m³ / mu and an irrigation interval of 7-10 days, to avoid the rise of groundwater level caused by flood irrigation.

[0023] Compared with the prior art, the present invention provides a method for greening saline soil with biochar, which has the following beneficial effects:

[0024] 1. This biochar-based method for improving saline soil and greening utilizes a three-in-one synergistic mechanism of "biochar-functional microorganisms-salt-tolerant plants". Biochar improves soil pore structure and adsorbs sodium ions, microorganisms secrete organic acids to reduce salt and phosphorus and activate nutrients, and plant roots loosen the soil and absorb salt. All three work simultaneously in the same improvement layer, exerting physical, chemical and biological effects, which can rapidly reduce soil salinity to below 3.0 g / kg and pH to below 7.8, significantly improving vegetation survival rate (≥90%) and growth vigor.

[0025] 2. This biochar-based method for improving saline-alkali soil through greening utilizes a combination of subsurface drainage and a leaching layer, following the principle of "salt being carried away by water," to rapidly lower the groundwater level to a safe depth (≥0.8m), blocking capillary rise and surface accumulation of salt. Combined with natural rainfall or irrigation leaching, continuous salt removal is achieved. After a single application, the improvement effect can last for more than 5 years, reducing the salt return rate by over 80%, and promoting the gradual restoration and self-sustaining of the saline-alkali land ecosystem.

[0026] 3. This biochar-based method for improving saline-alkali soil greening utilizes invasive plants (Spartina alterniflora) or agricultural and forestry waste (straw, reeds) to produce biochar, achieving carbon sequestration and emission reduction as well as waste resource utilization. Approximately 12 tons of CO2 can be fixed per hectare. The use of native salt-tolerant plants eliminates the risk of ecological invasion. It promotes the transformation of saline-alkali land from a "carbon source" to a "carbon sink," which aligns with the national "dual carbon" strategy.

[0027] 4. This biochar-based method for improving saline soil and greening can achieve long-term benefits through a single construction of a salt drainage network and an improved layer. In the later stages, only simple pipe cleaning and routine maintenance are required once or twice a year, and the operation and maintenance costs are 30% lower than those of traditional methods. It does not require the replacement of imported soil, reducing earthwork transportation and engineering investment, and the overall cost is reduced by more than 40%, which has good promotion value and economic benefits. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of a biochar-modified saline soil greening construction method according to the present invention. Detailed Implementation

[0029] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1: Greening Project of Moderately to Severely Saline Soil on Coastal Mudflats

[0031] Project Overview: Coastal mudflats, soil is silty saline soil, groundwater level is 0.6m deep, soil background: pH 9.1, total salt content 5.2g / kg, organic matter 8.7g / kg.

[0032] Please see Figure 1 The biochar-modified saline soil greening construction method in this embodiment includes the following steps:

[0033] S1. Site Pretreatment and Salt Removal System Construction: Remove weeds and garbage, and level the site. Excavate blind pipe trenches (30cm×30cm, 0.2% slope) at 8m intervals, and vertically excavate drainage ditches (30cm×30cm, 0.1% slope). Lay a 10cm gravel bedding layer at the bottom of the trenches, install Φ8cm double corrugated PVC blind pipes, wrap them with non-woven fabric, and lay Φ10cm drainage pipes inside the drainage ditches.

[0034] S2. Construction of the isolation layer and sump: A 25cm thick gravel isolation layer is laid 0.2m above the groundwater level, and then a permeable geotextile is laid on top. A brick-lined sump is installed every 60m, with the bottom of the sump level with the groundwater level and the inner wall impermeable.

[0035] S3. Preparation of modified biochar: Local reeds were pyrolyzed at 500℃ under limited oxygen for 2 hours, and then pulverized and passed through a 40-mesh sieve. Coprecipitation method: Weigh 100g of biochar and add... (10g) and Dissolve 20g in 500mL of water, adjust pH to 10 with NaOH, stir in a 50℃ water bath for 1h, age for 24h, wash and dry to obtain modified biochar.

[0036] S4. Preparation of Functional Microbial Agents and Coupling with Charcoal Bacteria: Salt-tolerant Bacillus halotolerans and Flavobacterium saliperae were isolated from rhizosphere soil of tidal flats and then used in environments containing 3% and 5%... Gradually acclimatize in LB medium, and culture in a mixed manner until... =1.5. The bacterial solution and modified biochar were mixed at a ratio of 1:3, shaken at 30℃ for 24 hours, and then dried at 40℃ to prepare a composite modifier.

[0037] S5. Soil Improvement Layer Application and Planting: Apply the compound soil conditioner at a rate of 2.5 kg / m², and till to a depth of 30 cm to ensure even mixing with the soil. Plant tamarisk (1.5 m x 2 m spacing), Suaeda salsa (0.5 m spacing), and Salicornia glutinosa (0.3 m spacing) to form a mixed tree-shrub-grass community. Water thoroughly to settle the roots.

[0038] S6. System Debugging, Monitoring and Maintenance: After the water flow test is passed, the system will be rinsed three times using natural rainfall during the rainy season. Samples will be taken for testing every two months. Routine water replenishment will be achieved through micro-sprinkler irrigation, and the collection well will be cleaned every six months.

[0039] Results: After 6 months, the total soil salinity decreased to 1.9 g / kg, the pH decreased to 7.5, and the organic matter increased to 18.2 g / kg. The plant survival rate was 94%, and the salt return phenomenon was significantly suppressed.

[0040] Example 2: Greening Project for Roads in Severely Saline Soil in Reclaimed Areas

[0041] Project Overview: The soil on both sides of the road in the reclamation area is clayey saline soil. The groundwater level is 0.4m deep. The soil background is pH 9.5, total salt content is 8.3g / kg, and organic matter content is 5.2g / kg.

[0042] A method for greening saline soil using biochar includes the following steps:

[0043] S1. Drill blind pipe trenches at 6m intervals. Due to the heavy clay soil, lay a 10cm coarse sand bedding layer at the bottom of the trench. The blind pipes are made of Φ10cm double corrugated PVC pipes, wrapped with non-woven fabric.

[0044] S2. The waterproofing layer is made of a 1:1 mixture of slag and crushed stone, 30cm thick, and covered with two layers of permeable geotextile (overlapping 40cm). The water collection wells are made of fiberglass, one every 50m.

[0045] S3. Biochar was prepared by pyrolysis of Spartina alterniflora at 550°C, using the same modification method as in Example 1.

[0046] S4. In addition to halophilic Bacillus and Flavobacterium, phosphate-solubilizing bacteria (Pseudomonas sp.) are added. The three are mixed in a 1:1:1 ratio with a loading ratio of 1:4.

[0047] S5, amendment dosage 3.0kg / m², rotary tillage depth 40cm. Plant selection: tamarisk, white thorn (shrub), and saltwort, with a plant spacing of 1.2m × 1.5m.

[0048] S6. Due to the high groundwater level, artificial leaching with slightly saline water is conducted once before the rainy season, and the drainage pipe outlet is connected to the municipal stormwater well. Monitoring is conducted quarterly.

[0049] Results: After 12 months, total salt content decreased to 2.5 g / kg, pH decreased to 7.8, and organic matter increased to 15.6 g / kg. Plant survival rate was 88%, roadside greening landscape was formed, and there were no cases of seedling death due to salt return.

[0050] Example 3: Coastal Ecological Corridor Saline Soil Remediation Project

[0051] Project Overview: The coastal wetland park is located on saline-alkali land. The soil background is: pH 8.9, total salt content 4.2 g / kg, organic matter 12.3 g / kg, and groundwater level at a depth of 0.7 m. However, it suffers from severe seasonal salinization.

[0052] A method for greening saline soil using biochar includes the following steps:

[0053] S1. The blind drains are spaced 12m apart, using Φ6cm blind drains, with a slope of 0.15%. Due to the existing micro-topography of the site, the blind drains are laid out along the contour lines.

[0054] S2. The isolation layer is 20cm thick, made of expanded clay aggregate and crushed stone (1:2), and covered with geotextile. The collection well is a modified existing rainwater well with an added impermeable inner liner.

[0055] S3, the raw material for biochar is garden pruning waste (twigs, grass clippings), which is slowly pyrolyzed at 450℃. Adding ultrasonic dispersion for 30 minutes during modification improves load uniformity.

[0056] S4, using only salt-tolerant Bacillus (locally domesticated strain), bacterial concentration... =1.8, after adsorption loading, 5% trehalose was added as a protective agent.

[0057] S5, with a soil conditioner dosage of 1.8 kg / m², is lightly sown and then rake to a depth of 10 cm. Plants selected include Salicornia glutinosa, Suaeda salsa, Phragmites communis, and Tamarix chinensis, arranged according to wetland plant community principles.

[0058] S6. Intermittent leaching is carried out using artificial wetland water level control, with salt removal once a month. Soil EC values ​​are recorded weekly during the maintenance period.

[0059] Results: After 6 months, total salt content decreased to 1.5 g / kg, pH reached 7.4, and organic matter increased to 22.1 g / kg. Vegetation coverage reached 85%, biodiversity, including birdlife, increased significantly, and the ecological corridor function was well restored.

[0060] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for greening saline soil with biochar, characterized in that, Includes the following steps: S1. Site Pretreatment and Salt Drainage System Construction: Clean, level, and drain the saline soil site, removing surface debris and stagnant water; conduct stratified soil sampling to test pH, total salt content, organic matter, EC value, and groundwater depth to determine improvement parameters; lay out the location according to the design drawings, and excavate blind drains with a width and depth of 30cm at intervals of 6-15m along the slope, maintaining a slope of 0.2%; excavate drainage ditches with a width and depth of 30cm perpendicular to the blind drains, maintaining a slope of 0.2%. The slope is 1%, and the bottom of the ditch is 15cm below the groundwater level. A 10cm thick layer of crushed stone is laid and compacted in both the blind pipe ditch and the drainage ditch. A double corrugated PVC blind pipe with a diameter of 6-10cm is laid in the center of the blind pipe ditch. The pipe joints are firmly glued and the ends are sealed with non-woven fabric. A drainage pipe with a diameter of 10-12cm is laid in the drainage ditch. The pipe is covered and wrapped with crushed stone with a thickness of not less than 15cm. A permeable non-woven fabric is laid on the top of the blind pipe ditch. The blind pipe and the drainage pipe are connected to form a complete salt drainage network. S2. Construction of the isolation layer and collection wells: Above the highest groundwater level and below the planting layer, a 20-30cm thick layer of crushed stone, slag, or ceramsite is evenly laid as an isolation layer. The layer is spread flat and uninterrupted. The top of the isolation layer is fully covered with permeable geotextile, with an overlap width of not less than 30cm. Collection wells are laid every 50-100m along the direction of the drainage ditch. The wells are excavated from below the isolation layer to a height of 10cm above the ground surface. The well bodies are made of brick or fiberglass. The bottom of the well is level with the groundwater level. The inner wall is treated with anti-seepage measures. After completion, the wells are covered for protection. S3. Preparation of Modified Biochar: One or more biomass raw materials selected from reeds, Spartina alterniflora, straw, or garden waste are used to prepare biochar through oxygen-limited pyrolysis at 450–550℃. The biochar is then pulverized through a 40-mesh sieve, washed with water to remove impurities, and dried. Chemical coprecipitation method for modifying biochar: biochar is mixed with... The mixed solutions were mixed at a mass ratio of 1:5 to 1:10, the pH was adjusted to 9 to 11, and the mixture was stirred in a water bath at 40 to 60°C for 0.5 to 2 hours. After aging for 18 to 30 hours, the mixture was washed, dried, and sieved to obtain modified biochar. S4. Preparation of functional microbial agents and coupling with anthracnose bacteria: Salt-tolerant Bacillus and Flavobacterium functional strains were isolated and screened from in-situ saline-alkali soil in tidal flats or rhizosphere of salt-tolerant plants, and acclimated to tolerance of 3%–5% under gradient salt stress. Functional rejuvenation and non-antagonistic formulation were carried out to prepare a compound functional microbial agent with a bacterial concentration of [missing information]. The content is 1.2 to 2.0; the composite bacterial agent is uniformly loaded onto modified biochar using the adsorption method, the mass ratio of bacterial solution to modified biochar is controlled at 1:3 to 1:5, the adsorption temperature is 25 to 35℃, and the time is 12 to 24 hours, thus preparing a biochar-based functional microbial composite modifier. S5. Carbonized microbial amendment layer laying and salt-tolerant plant planting: Based on the soil baseline indicators, determine the application rate of the compound amendment to be 1.5-3.0 kg / m². For deep-rooted plants, use surface mixing; for shallow-rooted herbs, use surface sowing. Apply the amendment to the soil and then rotary tillage it to ensure it is fully mixed with the 0-30 cm topsoil. Sprinkle an appropriate amount of water to activate the microorganisms. Select one or more native salt-tolerant plants from Suaeda salsa, Salicornia glutinosa, Tamarix chinensis, Nitraria tangutorum, or Reed. Plant them in a multi-level configuration of trees, shrubs, and grasses according to the designed plant spacing. After spreading out the plant roots, plant them in the soil, backfill with the amendment soil and compact it, and water thoroughly. S6. System Debugging, Monitoring and Maintenance: Conduct water flow tests on the salt drainage network and collection wells to ensure no blockages or leaks; initiate leaching desalination with irrigation or natural rainfall to achieve "salt removal with water"; regularly monitor soil total salinity, pH, organic matter, microbial activity, plant survival rate, and growth status, and complete project acceptance after the indicators meet the standards; carry out daily watering, loosening of soil, fertilization, and pest and disease control; strengthen leaching desalination with natural rainfall during the rainy season and adopt water-saving irrigation during the dry season; regularly clean the salt drainage pipes and collection wells to maintain the long-term operation of the system.

2. The method for greening saline-alkali soil with biochar as described in claim 1, characterized in that, In S1, the spacing between blind pipe trenches is 8-12m, the diameter of the double corrugated PVC blind pipe is 8cm, and the diameter of the drainage pipe is 10cm.

3. The method for greening saline soil with biochar as described in claim 1, characterized in that, In S2, the thickness of the rainproof layer is 25cm, the material is crushed stone, the water collection well adopts a brick structure, the upper diameter of the well body is 60-80cm, and the lower diameter is 120cm.

4. The method for greening saline-alkali soil with biochar as described in claim 1, characterized in that, In step S3, the biochar raw material is reed or Spartina alterniflora, and the pyrolysis temperature is 500℃. During modification, the pH was adjusted to 10, the reaction temperature was 50℃, and the aging time was 24h.

5. The method for greening saline-alkali soil with biochar as described in claim 1, characterized in that, In S4, the functional microbial agent also includes at least one of phosphate-solubilizing bacteria or nitrogen-fixing bacteria, which is compounded with halophilic Bacillus and Flavobacterium at a mass ratio of 1:1:

1.

6. The method for greening saline soil with biochar as described in claim 1, characterized in that, In step S4, after adsorption loading, 3% to 8% trehalose or skim milk powder by mass is added as a protective agent, and then dried at a low temperature of 40°C to prepare a powdered composite modifier.

7. The method for greening saline soil with biochar as described in claim 1, characterized in that, In S5, for severely saline soil with a total salt content ≥ 6.0 g / kg, the application rate of the compound amendment is 2.5–3.0 kg / m², and the rotary tillage depth is 40 cm.

8. The method for greening saline soil with biochar as described in claim 1, characterized in that, In S5, the multi-level configuration pattern of trees, shrubs and grasses is as follows: Tamarix or Nitraria tangutorum serves as the tree / shrub layer, with a plant spacing of 1.2-1.5m × 1.5-2.0m; Suaeda salsa serves as the herbaceous layer, with a row spacing of 0.3-0.5m; and Salicornia glutinosa serves as the ground cover layer, with a row spacing of 0.2-0.3m.

9. The method for greening saline soil with biochar as described in claim 1, characterized in that, In S6, the monitoring frequency is: once a month for the first 3 months after construction, and once every 3 months thereafter; during the maintenance period, the salt drainage pipe is cleaned 1 to 2 times a year, and the water collection well is inspected and dredged once every six months.

10. A method for greening saline-alkali soil with biochar as described in claim 1, characterized in that, In S6, micro-sprinkler irrigation or drip irrigation is used during the dry season, with a single irrigation volume of 10-15 m³ / mu and an irrigation interval of 7-10 days, to avoid the rise of groundwater level caused by flood irrigation.

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