Shallow dry salt elimination system based on charcoal and negative pressure adsorption

Abstract

The invention relates to the technical field of saline-alkali soil improvement, and discloses a charcoal and negative pressure adsorption-based shallow dry salt elimination system, which comprises a film covering module, an exposed module and a driving module, by arranging the film covering module, the exposing module and the driving module connected with the negative pressure structure, salt ions and salt-containing water vapor are effectively adsorbed and directionally migrated and discharged; active migration and discharge of salt are achieved through the negative pressure structure, the salt is effectively prevented from being accumulated again on the surface layer of the soil or other areas, and therefore the occurrence probability of secondary salinization is reduced, and the ecological environment of the soil is improved. The system adopts a mode of alternate arrangement of film covering and exposing, and is convenient to popularize and apply in different types of saline-alkali soil; the biochar layer and the negative pressure structure are buried in the soil, crop planting on the earth surface is not affected, and good agricultural adaptability and practicability are achieved.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land improvement technology, specifically to a shallow dry salt removal system based on biochar and negative pressure adsorption. Background Technology

[0002] Soil salinization is one of the major problems facing global agricultural systems today, severely restricting the efficient use of arable land resources and significantly impacting crop yield and quality. Particularly in the arid and semi-arid regions of Northwest my country, saline-alkali land is widely distributed, with harsh soil environments and poor water and nutrient availability, seriously hindering sustainable agricultural development. Therefore, promoting the efficient improvement of saline-alkali land and enhancing land use efficiency has significant practical importance and strategic value.

[0003] In traditional Chinese practices for saline-alkali land improvement, flood irrigation is commonly used. This method relies on the principle of "salt moving with water" to leach and remove salt from the soil. However, this approach has significant drawbacks: firstly, it easily leads to a rise in the groundwater level, increasing groundwater mineralization and inducing secondary salinization; secondly, the large amount of water consumed is detrimental to ecological protection and agricultural water management in water-scarce areas. Therefore, there is an urgent need to explore more water-saving, efficient, and sustainable technological pathways for saline-alkali land improvement.

[0004] In recent years, with the development of precision agriculture, drip irrigation under mulch film has been widely used in arid regions such as Xinjiang due to its advantages such as water saving, evaporation suppression, and improved fertilizer and water use efficiency. During drip irrigation, salt in the crop root zone gradually migrates outward through the irrigation water and accumulates in the humidity peak area, thus achieving root zone desalination. However, during continuous irrigation and water-salt migration, salt may still migrate back to the crop root zone due to water redistribution, affecting crop growth and development.

[0005] While the aforementioned technologies have improved the scientific and systematic nature of saline-alkali land improvement to some extent, they still have certain shortcomings in practical applications. Traditional salt removal methods generally rely on large-volume irrigation and open ditch drainage, which is not only inefficient and has low water resource utilization, but also easily leads to deep salt accumulation, increases the risk of soil compaction, and is detrimental to the healthy development of crop roots. Meanwhile, while existing drip irrigation systems under plastic film are effective in reducing evaporation and preventing surface runoff, the exposed soil areas between the films remain high-risk areas for salt accumulation. Existing salt removal measures between films, such as mechanical scraping, are not only costly and complex, but may also damage the topsoil structure and induce secondary salinization. Summary of the Invention

[0006] This invention provides a shallow dry desalination system based on biochar and negative pressure adsorption to solve the problems of traditional desalination methods that easily induce secondary salinization and have low desalination efficiency.

[0007] This invention provides a shallow dry salt removal system based on biochar and negative pressure adsorption, comprising: a membrane module, an exposed module, and a driving module; the exposed module is disposed between two adjacent membrane modules, and the exposed module includes a biochar layer buried in a first soil layer and a negative pressure structure disposed in the biochar layer, the biochar layer being in contact with a second soil layer of the membrane module to be suitable for adsorbing salt ions and saline vapor in the membrane module; the driving module is connected to the negative pressure structure to be suitable for driving the negative pressure structure to directionally migrate and discharge the salt ions and saline vapor adsorbed by the biochar layer.

[0008] Beneficial effects: This invention provides a shallow dry salt removal system based on biochar and negative pressure adsorption. By setting up a covered module, an exposed module, and a drive module connected to a negative pressure structure, it achieves effective adsorption and directional migration and discharge of salt ions and saline vapor. The biochar layer in the exposed module has excellent adsorption performance, significantly adsorbing salt ions and saline vapor from the covered module. Combined with the directional migration path formed by the negative pressure structure and the drive module, salt is concentrated and efficiently discharged, improving overall salt removal efficiency. Compared to traditional salt removal methods relying on natural evaporation or flood irrigation, this invention achieves active migration and discharge of salt through a negative pressure structure, effectively preventing the re-accumulation of salt in the soil surface or other areas, thereby reducing the probability of secondary salinization and improving the soil ecological environment. The system uses an alternating deployment of covered and exposed modules, facilitating its application in different types of saline-alkali land. The biochar layer and negative pressure structure are buried inside the soil, not affecting surface crop planting, and have good agricultural adaptability and practicality.

[0009] According to some embodiments of the present invention, the mulching module includes a membrane layer covering the second soil layer, and a drainage pipe and a drip irrigation structure disposed between the membrane layer and the second soil layer. The length direction of the drainage pipe is consistent with the width direction of the mulching module. Multiple drainage pipes are provided and spaced apart along the length direction of the mulching module. The length direction of the drip irrigation structure is consistent with the length direction of the mulching module. The drainage pipe and the drip irrigation structure are adapted to drain water into the second soil layer for drip irrigation to dissolve the salts in the second soil layer. The negative pressure structure creates a negative pressure in the biochar layer to cause salt ions and saline vapors in the second soil layer to migrate directionally to the biochar layer of the exposed module.

[0010] According to some embodiments of the present invention, the negative pressure structure includes a drive pump and a plurality of negative pressure pipes, the negative pressure pipes being connected to the drive pump, the drive pump causing a negative pressure state to be formed in the negative pressure pipes, and the drive pump being adapted to blow air into the negative pressure pipes.

[0011] According to some embodiments of the present invention, the negative pressure pipe has a plurality of seepage holes on its wall, and the plurality of seepage holes are spirally distributed around the wall of the negative pressure pipe.

[0012] According to some embodiments of the present invention, the outer wall of the negative pressure pipe is wrapped with a layer of permeable material.

[0013] According to some embodiments of the present invention, the driving pump is a gas ring vacuum pump.

[0014] According to some embodiments of the present invention, the negative pressure pipe is provided with multiple pipes, the length direction of the negative pressure pipe is consistent with the length direction of the exposed module, and the multiple negative pressure pipes are arranged at intervals along the width direction of the exposed module.

[0015] According to some embodiments of the present invention, the drive module includes a solar panel adapted to be electrically connected to the negative pressure structure.

[0016] According to some embodiments of the present invention, the solar panel comprises multiple panels, which are arranged at intervals along the length of the exposed module.

[0017] According to some embodiments of the present invention, the biochar layer is 5-10 cm away from the surface of the first soil layer, and the biochar layer is 5-8 cm thick. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic plan view of a shallow dry salt removal system based on biochar and negative pressure adsorption provided in some embodiments of the present invention; Figure 2 This is a cross-sectional schematic diagram of a shallow dry salt removal system based on biochar and negative pressure adsorption provided in some embodiments of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Membrane-covered module; 11. Drainage pipe; 12. Drip irrigation structure; 13. Diaphragm layer; 2. Exposed module; 21. Biochar layer; 22. Negative pressure structure; 221. Negative pressure pipe; 222. Drive pump; 3. Drive module. Detailed Implementation

[0021] 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 embodiments of the present invention, 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.

[0022] Reference Figure 1 and Figure 2 As shown, the present invention provides a shallow dry salt removal system based on biochar and negative pressure adsorption, comprising: a membrane module 1, an exposed module 2, and a driving module 3; the exposed module 2 is disposed between two adjacent membrane modules 1, and the exposed module 2 includes a biochar layer 21 buried in a first soil layer, and a negative pressure structure 22 disposed in the biochar layer 21. The biochar layer 21 is in contact with the second soil layer of the membrane module 1 to be suitable for adsorbing salt ions and saline vapor in the membrane module 1; the driving module 3 is connected to the negative pressure structure 22 to be suitable for driving the negative pressure structure 22 to directionally migrate and discharge the salt ions and saline vapor adsorbed by the biochar layer 21.

[0023] Specifically, by setting up a covered module 1, an exposed module 2, and a drive module 3 connected to a negative pressure structure 22, the system achieves effective adsorption and directional migration and discharge of salt ions and saline vapor. The biochar layer 21 set in the exposed module 2 has excellent adsorption performance, which can significantly adsorb salt ions and saline vapor from the covered module 1. Combined with the directional migration path formed by the negative pressure structure 22 and the drive module 3, the salt is concentrated and efficiently discharged, improving the overall salt removal efficiency. Compared with traditional salt removal methods that rely on natural evaporation or flood irrigation, this invention achieves active migration and discharge of salt through the negative pressure structure 22, effectively avoiding the re-accumulation of salt on the soil surface or in other areas, thereby reducing the probability of secondary salinization and improving the soil ecological environment. The system adopts an alternating arrangement of covered and exposed layers, which is convenient for promotion and application in different types of saline-alkali land. The biochar layer 21 and the negative pressure structure 22 are buried inside the soil, which does not affect the planting of surface crops, and has good agricultural adaptability and practicality.

[0024] Understandably, the biochar used can be prepared from agricultural waste, which is low-cost and reusable. The negative pressure structure 22 combined with the drive module 3 achieves low-energy operation, resulting in low overall system operating costs and good economic efficiency and sustainability. Specifically, high-temperature pyrolysis char is preferred, with straw (straw char) as the raw material. A slow pyrolysis method is used, with a heating rate of <50℃ / min and a yield of 30-40%. The pore structure is relatively well-developed. If the particle size is too small, it will easily clog soil pores and affect water permeability; if it is too large, the specific surface area will be too small, reducing the adsorption efficiency.

[0025] In some embodiments of the present invention, the membrane module 1 includes a membrane layer 13 covering the second soil layer, and a drainage pipe 11 and a drip irrigation structure 12 disposed between the membrane layer 13 and the second soil layer. The length direction of the drainage pipe 11 is consistent with the width direction of the membrane module 1. Multiple drainage pipes 11 are provided and are spaced apart along the length direction of the membrane module 1. The length direction of the drip irrigation structure 12 is consistent with the length direction of the membrane module 1. The drainage pipe 11 and the drip irrigation structure 12 are adapted to drain water and drip irrigate the second soil layer to dissolve the salt in the second soil layer. The negative pressure structure 22 creates a negative pressure in the biochar layer 21 to cause salt ions and salt vapor in the second soil layer to migrate directionally to the biochar layer 21 of the exposed module 2.

[0026] Specifically, the drip irrigation structure 12 can precisely inject water into the second soil layer, causing the salt ions accumulated in the soil to fully dissolve and form a salt solution. Combined with the negative pressure attraction mechanism of the biochar layer, the dissolved salts rapidly migrate directionally to the biochar layer 21 in the exposed module 2, significantly improving the salt migration efficiency. Through the triple synergistic mechanism of drip irrigation salt control, biochar adsorption, and negative pressure migration, the traditional salt removal system, which relies solely on gravity or surface water evaporation, effectively breaks away from the single process of traditional salt removal systems. This achieves a three-dimensional and efficient salt removal path, enhancing the overall system's salt removal capacity and stability.

[0027] Understandably, the drip irrigation structure 12 can be quantitatively controlled based on parameters such as soil salinity and humidity, precisely allocating irrigation amounts. While ensuring sufficient salt dissolution, it significantly reduces water waste, making it particularly suitable for the treatment of saline-alkali land in arid or water-scarce areas. The membrane layer 13, covering the second soil layer, not only reduces water evaporation and controls the rise of surface salt, but also protects the internal structure from external environmental interference, further stabilizing system operation and improving the salt control and drainage stability of the covered area.

[0028] In some embodiments of the present invention, the negative pressure structure 22 includes a drive pump 222 and a plurality of negative pressure pipes 221. The negative pressure pipes 221 are connected to the drive pump 222. The drive pump 222 causes a negative pressure state to be formed in the negative pressure pipes 221. The drive pump 222 is adapted to blow air into the negative pressure pipes 221.

[0029] Specifically, by setting the drive pump 222 to actively blow air, a negative pressure state can be continuously formed and maintained inside each negative pressure pipe 221. Compared with the method of relying on natural pressure difference or a single suction device, it can effectively enhance the attraction of the system to salt ions and salt vapor, and ensure the long-term effective operation of the negative pressure migration path. Multiple negative pressure pipes 221 are connected to the drive pump 222, which can form negative pressure synchronously or in sections at different locations, and construct planar or point-like negative pressure migration channels, thereby achieving precise control of the direction and speed of salt migration, avoiding salt retention or lateral diffusion in the soil, and enhancing the directionality and depth of salt removal.

[0030] Understandably, the drive pump 222 can flexibly adjust the blowing frequency and intensity according to parameters such as soil salinity, humidity, and negative pressure requirements, making it suitable for saline-alkali land treatment under different soil types and climatic conditions, thus helping to improve the system's applicability in multiple scenarios. The number of negative pressure pipes 221 can be configured according to the land area and salt removal intensity requirements, and their flexible layout is suitable for installation and maintenance under different farming conditions. As a centralized power source, the drive pump 222 facilitates unified control and periodic maintenance, reducing system operation and maintenance costs.

[0031] Salt or saline vapor is first adsorbed and accumulated in the biochar layer 21, and then adsorbed into the negative pressure pipe 221 under negative pressure. This improves the material utilization efficiency and extends the effective service life of the biochar.

[0032] In some embodiments of the present invention, a plurality of seepage holes are provided on the wall of the negative pressure pipe 221, and the plurality of seepage holes are spirally distributed around the wall of the negative pressure pipe 221.

[0033] Specifically, the permeation holes are spirally distributed along the negative pressure pipe 221, creating a spatially encircling layout for the negative pressure adsorption path. This allows for the simultaneous absorption of salts and saline vapors migrating from the biochar layer 21 from multiple directions and angles. Compared to straight or single-sided open structures, this significantly enhances the uniformity and overall efficiency of salt removal. The spiral arrangement also helps to increase the effective contact area between each negative pressure pipe 221 and the surrounding biochar layer 21, allowing the negative pressure effect to be more widely transmitted to the microporous structure between the biochar particles, further accelerating the salt migration rate and improving the salt removal capacity.

[0034] Understandably, under the blowing action of the drive pump 222, the spiral opening can guide air or water vapor to form a spiral turbulent airflow around the negative pressure pipe 221, which strengthens the water vapor disturbance and salt flow in the soil pores, helps to break the static migration bottleneck in the soil and improve the migration power.

[0035] In some embodiments of the present invention, the outer wall of the negative pressure pipe 221 is wrapped with a layer of permeable material.

[0036] Specifically, the permeable material layer effectively prevents tiny impurities such as soil particles and biochar powder from directly entering the seepage holes, significantly reducing the risk of clogging, extending the service life of the negative pressure pipe 221, and improving the long-term stability and reliability of the system. The permeable material also has a certain filtration function, capable of initially purifying water vapor and particles entering the negative pressure pipe 221, preventing contamination of the inside of the negative pressure structure 22, helping to protect core components such as the drive pump 222, and reducing maintenance frequency and operating costs.

[0037] The permeable layer has good water vapor permeability and forms a coating state in its structure, which makes the adsorption range of the negative pressure pipe 221 wider and more continuous. It can increase the effective contact area with the biochar layer 21 while maintaining the adsorption performance, thereby further improving the migration efficiency of salt and salt vapor.

[0038] Understandably, permeable material layers can be made of common agricultural materials such as non-woven fabric, fiber felt, and polyester fiber mesh, which are inexpensive and easy to construct. They can be integrally wrapped and formed before the installation of negative pressure pipe 221, which facilitates on-site operations and standardized production, and is suitable for large-scale engineering applications.

[0039] In some embodiments of the present invention, the drive pump 222 is a gas ring vacuum pump.

[0040] Specifically, the gas ring vacuum pump has good negative pressure output stability and can continuously generate a stable negative pressure environment for a long time, ensuring that salt ions and saline vapor in the biochar layer 21 continuously migrate towards the negative pressure pipe 221, thereby improving the operational continuity and salt removal efficiency of the entire salt removal system.

[0041] In some embodiments of the present invention, multiple negative pressure pipes 221 are provided, the length direction of the negative pressure pipes 221 is consistent with the length direction of the exposed module 2, and the multiple negative pressure pipes 221 are arranged at intervals along the width direction of the exposed module 2.

[0042] Specifically, multiple negative pressure pipes 221 are spaced apart inside the exposed module 2, forming a uniformly distributed negative pressure area throughout the exposed area. This significantly improves the adsorption coverage of the biochar layer 21, avoiding adsorption blind spots or low local migration efficiency during salt removal. The negative pressure pipes 221 extend along the length of the exposed module 2, aligning with the salt migration direction, forming multiple parallel directional adsorption channels. This helps guide salt ions and saline vapors in the second soil layer to concentrate and migrate towards the target area. The inner wall of the negative pressure pipes 221 is coated with a hydrophobic polytetrafluoroethylene coating, reducing the adhesion of salt crystals to the pipe wall and enabling automatic detachment of salt crystals from the pipe wall. This achieves efficient dry drainage, improving the orderliness and efficiency of the salt removal process. During the idle period after crop harvest or before the next planting season, the buried negative pressure pipes 221 are first aerated to remove salt crystals, then the pipes are cleaned and recycled. High-pressure water jets are used to flush the inside and outside of the pipes, removing any remaining attached salt crystals, soil, etc., and checking for pore blockage.

[0043] In some embodiments of the present invention, the drive module 3 includes a solar panel adapted to be electrically connected to the negative pressure structure 22.

[0044] Specifically, the solar panels can convert sunlight into electricity to power equipment such as the drive pump 222 in the negative pressure structure 22, avoiding the use of traditional fossil fuels and achieving green and sustainable operation of the system. This is particularly suitable for the high environmental standards required for ecological restoration projects. As a renewable energy source, solar energy requires no additional fuel or electricity costs during operation, resulting in low long-term operating costs. It is especially suitable for large-scale, long-term saline-alkali land remediation projects, significantly reducing system investment throughout its entire life cycle.

[0045] It is understandable that by setting up solar panels in the soil area between the membranes, a high-temperature area can be formed in the exposed module 2, and a temperature difference can be formed between the membrane module 1 and the area between the membranes, which will cause water vapor to accumulate in the high-temperature area and raise the temperature near the negative pressure pipe 221, so that the crystals inside the pipe can be quickly adsorbed onto the pipe wall.

[0046] In some embodiments of the present invention, multiple solar panels are provided and are arranged at intervals along the length of the exposed module 2.

[0047] Specifically, the spaced arrangement of multiple solar panels expands the overall sun-receiving area and extends the duration of sunshine coverage. This helps to continuously and stably acquire solar energy resources at different times and angles of illumination, significantly improving the system's power generation efficiency and supply capacity. The solar panels are arranged at intervals along the length of the exposed module 2, forming a distributed power supply layout on the ground system. This reduces voltage loss caused by single-point deployment, optimizes power transmission paths, and improves power supply response speed and local system energy efficiency.

[0048] In some embodiments of the present invention, the biochar layer 21 is 5-10 cm away from the surface of the first soil layer, and the thickness of the biochar layer 21 is 5-8 cm.

[0049] Specifically, the biochar layer 21 is buried within a range of 5–10 cm from the surface layer, which is beneficial for effectively covering the main channels of salt migration. This allows salt ions and saline vapors in the second soil layer to rapidly contact the adsorption layer in the vertical direction, thereby improving the overall salt removal efficiency. Setting the thickness of the biochar layer 21 to 5–8 cm ensures sufficient adsorption capacity while maintaining good pore structure and permeability, enhancing the penetration and migration capacity of water vapor, and avoiding the reduction of negative pressure effect or airflow stagnation caused by excessively thick layers.

[0050] It is understandable that planting salt-tolerant crops, such as alfalfa and goji berries, on the first soil layer of the bare module 2 increases vegetation cover and improves the ecological stability of farmland. This not only improves the utilization rate of the field land, but also absorbs the salt remaining between the films, indirectly reducing soil salinity and improving the salt removal effect of the entire field system.

[0051] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A system for shallow desalination based on biochar and negative pressure adsorption, characterized in that, The application relates to a salt ion and salt water vapor directional migration and removal device. The device comprises: a mulch module (1); a bare module (2) arranged between two adjacent mulch modules (1), wherein the bare module (2) comprises a biochar layer (21) embedded in a first soil layer and a negative pressure structure (22) arranged in the biochar layer (21), the biochar layer (21) is in contact with a second soil layer of the mulch module (1) to adsorb salt ions and salt water vapor in the mulch module (1); 2. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 1, wherein, a driving module (3) connected with the negative pressure structure (22) to drive the negative pressure structure (22) to directionally migrate and remove the salt ions and salt water vapor adsorbed by the biochar layer (21).

3. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 1, wherein, The mulch module (1) comprises a diaphragm layer (13) arranged on the second soil layer, and a drainage pipe (11) and a drip irrigation structure (12) arranged between the diaphragm layer (13) and the second soil layer, the length direction of the drainage pipe (11) is consistent with the width direction of the mulch module (1), the drainage pipe (11) is provided with a plurality of drainage pipes (11) and is arranged at intervals along the length direction of the mulch module (1), the length direction of the drip irrigation structure (12) is consistent with the length direction of the mulch module (1), the drainage pipe (11) and the drip irrigation structure (12) are adapted to drain and drip irrigate the second soil layer to dissolve the salt ions in the second soil layer, and the negative pressure structure (22) forms a negative pressure in the biochar layer (21) to make the salt ions and salt water vapor in the second soil layer directionally migrate to the biochar layer (21) of the bare module (2).

4. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 3, characterized in that, The negative pressure structure (22) comprises a driving pump (222) and a plurality of negative pressure pipes (221), the negative pressure pipes (221) are in communication with the driving pump (222), the driving pump (222) forms a negative pressure state in the negative pressure pipes (221), and the driving pump (222) is adapted to blow air into the negative pressure pipes (221).

5. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 4, characterized in that, A plurality of water permeation holes are formed in the wall of the negative pressure pipe (221) and are distributed in a spiral manner around the wall of the negative pressure pipe (221).

6. The biochar-based and negative pressure adsorption shallow layer salt drainage system according to any one of claims 3 to 5, characterized in that, The outer wall of the negative pressure pipe (221) is wrapped with a water permeable material layer.

7. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 3, characterized in that, The driving pump (222) is a gas ring type vacuum pump.

8. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 1, wherein, The negative pressure pipe (221) is provided with a plurality of negative pressure pipes (221), the length direction of the negative pressure pipe (221) is consistent with the length direction of the bare module (2), and the plurality of negative pressure pipes (221) are arranged at intervals along the width direction of the bare module (2).

9. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 8, characterized in that, The driving module (3) comprises a solar panel, and the solar panel is adapted to be electrically connected with the negative pressure structure (22).

10. The charcoal-based and negative pressure adsorption shallow layer salt drainage system according to claim 1, wherein, The solar panel is provided with a plurality of solar panels and is arranged at intervals along the length direction of the bare module (2). The biochar layer (21) is 5-10 cm away from the surface of the first soil layer, and the biochar layer (21) has a laying thickness of 5-8 cm.

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