An improved method for constructing a stable water supply and salt discharge channel for soda saline-alkali soil

Abstract

The present invention relates to saline-alkali soil improvement technology, and in particular to an improvement method for constructing a stable water supply and salt drainage channel for soda saline-alkali soil, comprising the following steps: 1) digging a ditch; 2) pre-treatment of filter materials; 3) filling of filter materials; and 4) in-situ covering operations. The present invention proposes a complete set of physical improvement schemes for the subsoil layer of saline-alkali soil, from ditching, pre-treatment of filter materials to deep burial filling, to improve the subsoil layer of soda saline-alkali soil. Unlike conventional soil improvement methods that only target the topsoil layer, the present invention focuses on the permeability of the subsoil layer, as this helps to improve the connectivity and salt drainage efficiency of each soil layer. Through deep ditch opening and filter material filling technology, a stable water supply and salt drainage channel is established in the subsoil layer, thereby achieving effective connectivity between the subsoil layer concealed pipe and the topsoil layer, further improving the overall salt drainage and improvement efficiency of saline-alkali soil.

Description

Technical Field

[0001] The invention relates to a saline-alkali soil improvement technology, in particular to an improvement method for constructing a stable water delivery and salt discharge channel for soda saline-alkali soil. Background Art

[0002] Research and analysis revealed that the main reason for the poor salt drainage effectiveness of concealed pipes in the soda saline-alkali soils of Northeast China is the inherent "heavy texture and poor permeability" of soda saline-alkali soil, which affects connectivity between soil layers. Furthermore, currently used saline-alkali soil improvement technologies mostly target only the topsoil layer, not the subsoil. Consequently, after leaching of the surface saline-alkali soil, the saline-alkali solution is blocked in the subsoil during infiltration, making it difficult to penetrate further into the concealed pipes in the subsoil layer.

[0003] Internationally, countries like Japan and the United States are using methods such as mechanical deep tillage, filter filling, and culvert formation to enhance soil permeability and improve water flow stability. Domestically, research institutions such as the Heilongjiang Academy of Agricultural Sciences, Jilin Agricultural University, and China Agricultural University have conducted in-depth research on these technologies, particularly deep tillage and straw burial. However, it's worth noting that these studies currently focus primarily on the topsoil layer, not the subsoil itself.

[0004] Soda saline-alkali soils are rich in sodium carbonate and sodium bicarbonate. Their high sodium ion content makes the soil highly dispersible upon contact with water. Specifically, the interaction of sodium ions and water molecules rapidly disperses the soil particles into a slurry, resulting in a loss of cohesion. This phenomenon is particularly pronounced in soda saline-alkali soils, where the particles are smaller than those in normal soils, and the proportion of tiny particles is much greater than in normal soils. These data further emphasize the importance of filter media in the improvement of soda saline-alkali soils.

[0005] Furthermore, this soil characteristic raises two problems. The first problem is that newly opened ditches are prone to large-scale dispersion of soil particles after coming into contact with water, and are carried away by the water, further causing the ditch's shape to become unstable and collapse. Since ditches will inevitably come into contact with water during their operation. If specific treatment measures are not taken, the service life of such ditches may be extremely short, or even only be used once. The second problem is that in order to improve the permeability of the soil, deep tillage and other operations are adopted to form a large number of water-permeable capillary pores in the soil. However, due to the special dispersion of soda saline-alkali soil particles, the capillary pores will quickly close after contact with water, resulting in poor durability and after-effects of deep tillage and other operations.

[0006] Glossary

[0007] Soda saline-alkali soil: Soda saline-alkali soil is a special type of saline-alkali soil, mainly distributed in the Songnen Plain in Northeast China. Rich in sodium carbonate (soda) and sodium bicarbonate (baking soda), it has a heavy, sticky texture, low porosity, and poor permeability.

[0008] Topsoil layer: generally refers to the soil layer of about 0-20 cm. Since deep loosening operations are mainly aimed at this layer, the topsoil layer has larger pores and better water permeability, which can provide a good growth environment for plants.

[0009] Subsoil layer: mainly refers to the soil layer of about 20-40 cm, with a heavy clay texture and small porosity.

[0010] Subsoil layer: mainly refers to the soil layer below 40 cm. Generally, the concealed pipes are located in the upper part of the subsoil layer.

[0011] Leaching is a commonly used technique for improving saline-alkali soils. This method involves flushing the soil surface with large amounts of water, flushing the salt and alkali in the surface soil into drainage ditches outside the fields, or into deeper soil layers for drainage through concealed pipes. This reduces the salt and alkali content in the surface soil, effectively "diluting the surface."

[0012] Saline solution: water with high salinity and alkali content produced after leaching operations.

[0013] Filter media: usually refers to the granular material used to filter water, here refers to all materials that can transport water.

[0014] Concealed pipes: An underground drainage system specifically designed for saline-alkali soil amelioration. Its surface features a dense microporous structure, allowing moisture from the soil above the pipe to penetrate into it. The pipes are connected to drainage channels and equipped with valves to control water flow. During paddy flooding and salt-alkali leaching, the valves close to prevent water from draining out of the pipes, ensuring the proper water level in the paddy fields. During drainage and salt removal, the valves open, allowing water from the paddy fields to drain through the conduit system into the drainage channels.

[0015] Sand filling: Usually used in underground pipe salt drainage systems, it forms a homogeneous, permeable sand filling layer by injecting sand or other granular materials to increase soil stability and prevent soil erosion or underground pipe system failure caused by unstable water flow.

[0016] Existing technologies for improving saline-alkali soil mainly focus on the study of surface soil, while ignoring the deeper subsoil layer. In particular, soda saline-alkali soil has poor permeability and cannot achieve upper and lower connectivity of the subsoil layer for drainage and salt washing. Summary of the Invention

[0017] This paper proposes an improved method for constructing stable water and salt drainage channels in soda saline-alkali soil. By establishing stable water and salt drainage channels within the subsoil layer, this method addresses the problem of poor salt drainage in traditional concealed pipe systems under soda saline-alkali soil conditions. This method not only improves the overall efficiency of concealed pipe salt drainage in saline-alkali soil but also further optimizes the improvement effect of saline-alkali soil.

[0018] In order to achieve the above object, the present invention provides the following technical solutions:

[0019] An improved method for constructing a stable water supply and salt discharge channel for soda saline-alkali soil comprises the following steps:

[0020] Step 1: Open the trench:

[0021] 1.1. Concealed pipe inspection: confirm the integrity and functionality of the concealed pipe; check the thickness of the sand filling layer;

[0022] 1.2. Trenching Equipment Selection: Choose trenching equipment that can create a ditch with a width of 10-20 cm. The trenching equipment needs to be able to be used in wet and sticky conditions, with a maximum trench depth of 40 cm. The trench walls must be smooth and have a certain degree of solidity that is not prone to collapse.

[0023] 1.3. Ditch parameter setting: set the ditch depth to between 30-40 cm, the ditch width to 10-20 cm; the ditch spacing to 90-220 cm;

[0024] 1.4. Use the trenching equipment selected in step 1.2 to dig the saline-alkali land to form a ditch;

[0025] 1.4.1. Dig trenches in the topsoil layer in a direction perpendicular to the buried pipe direction, and store the excavated topsoil separately;

[0026] The depth of the topsoil layer is 0-20 cm;

[0027] 1.4.2. Continue digging the trench obtained in step 1.4.1, through the subsoil layer to the subsoil layer, and store the excavated subsoil separately;

[0028] The depth of the subsoil layer is 20-40 cm;

[0029] The depth of the subsoil layer is less than 40 cm;

[0030] The trenching depth is between 30-40 cm;

[0031] The concealed pipe is arranged at a depth of 40 cm or less;

[0032] Step 2: Filter material pretreatment:

[0033] 2.1. Filter material screening: Choose organic filter materials as filter materials, such as organic fertilizer, rice husks, and straw;

[0034] 2.2. Filter material pretreatment;

[0035] Step 3: Filling the filter material:

[0036] After the trench is excavated in step 1, the filter material is filled. After filling, compaction is performed again to ensure that the filter material fully fills the entire trench and reaches the appropriate density.

[0037] Step 4: In-situ covering operation:

[0038] The subsoil excavated in step 1.4 is backfilled to its original subsoil position, and the topsoil is backfilled to its original topsoil position.

[0039] The method further comprises: step 5, topsoil leveling: after the in-situ covering operation is completed, the backfill soil is compacted and leveled.

[0040] The cross section of the ditch is in the shape of a trapezoid or a rectangle.

[0041] The step 2.2 further comprises:

[0042] 2.2.1. Organic fertilizer pretreatment: Ensure that it is fully fermented and mature. Immature organic fertilizer contains substances that are harmful to plants, such as ammonia or pathogenic microorganisms. If the organic fertilizer contains large debris or lumps, it needs to be pretreated by screening or crushing to ensure uniform distribution.

[0043] 2.2.2. Rice husk pretreatment: Rice husk needs to be pretreated by airing;

[0044] 2.2.3. Straw pretreatment: The straw needs to be pre-treated by shaping, which can include one or more of the following methods:

[0045] 2.2.3.1. Rolling into ropes: Roll the straw into rope-like shapes, i.e. long rice ropes, ensuring the rope diameter is 5-8 cm;

[0046] 2.2.3.2. Weaving into mats: The straw is formed into square rice mats by weaving technology, with a thickness of not less than 20x20 cm;

[0047] 2.2.3.3. Compression into blocks: Use compression technology to compress the straw into blocks or cakes; the volume should be compressed by at least 75%;

[0048] 2.2.3.4. Winding into a ball: Use winding to shape the straw into a spherical shape, forming a ball with a radius of about 4 cm;

[0049] 2.2.3.5. Crushing into segments: Use a crusher to break up the straw into small segments no larger than 8 cm.

[0050] The filter material filling in step 3 adopts a segmented filling method, that is, the filter material is used to fill a section of the ditch, and then a section is left empty and directly covered with soil, and this process is performed alternately.

[0051] To reduce resistance during trenching, deep loosen the planned trenching path before step 1.4.1 to reduce soil compaction.

[0052] The beneficial effects of the present invention are:

[0053] This invention improves the subsoil layer of soda saline-alkali soil. Unlike conventional soil improvement methods, which focus solely on the topsoil, this method focuses on the water permeability of the subsoil layer, as this helps improve connectivity and salt drainage efficiency across the soil layers. By creating deep trenches and filling them with filter material, a stable water and salt drainage channel is established in the subsoil layer, effectively connecting the subsoil concealed pipes with the topsoil layer, further improving the overall salt drainage and improvement efficiency of the saline-alkali soil.

[0054] This invention proposes a comprehensive physical improvement solution for saline-alkali soil layers. From trenching and filter pretreatment to deep filling, each step is designed to improve the soil's physical properties and enhance salt drainage efficiency. This systematic approach provides an efficient and economical solution for the physical improvement of saline-alkali soils.

[0055] Through layered excavation and layered in-situ covering operations, the present invention effectively prevents cross-confusion of soil layers and provides a more scientific and accurate operation basis for subsequent saline-alkali soil improvement work.

[0056] As a renewable organic filter material, straw significantly improves its water permeability and stability after undergoing specific pretreatment steps in the present invention. These pretreatment methods, such as rolling into ropes or weaving into mats, not only enhance the straw's physical properties but also improve its stability and durability in complex saline-alkali soil environments.

[0057] In terms of environmental adaptability, the present invention takes into account the climatic conditions of different regions, such as the low temperature environment in Northeast China, thereby slowing down the decomposition rate of the pre-treated filter material. This ensures that the filter material can maintain its effectiveness in the soil for up to 1-2 years.

[0058] The present invention is also highly compatible with existing concealed pipe drainage systems. By filling the concealed pipes with filter media, the present invention not only increases their service life but also significantly improves their drainage efficiency. Furthermore, the present invention is capable of operating independently even in scenarios where concealed pipes are not present. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a structural schematic diagram of the water delivery and salt discharge channel of the present invention.

[0060] Figure 2 It is a structural diagram of the soil layers and the concealed pipe system of the water conveyance and salt discharge channel of the present invention.

[0061] Figure 3 It is a schematic diagram of filling with organic materials in the improved method for constructing a stable water supply and salt discharge channel for soda saline-alkali soil of the present invention. DETAILED DESCRIPTION

[0062] like Figures 1 to 3 As shown, the improved method for constructing a stable water supply and salt discharge channel for soda saline-alkali soil of the present invention comprises the following steps:

[0063] Step 1: Open the trench

[0064] Before trenching operations are carried out, a series of preparatory tasks need to be completed to ensure the effectiveness and accuracy of the operations.

[0065] 1.1. Concealed pipe inspection: confirm the integrity and functionality of the concealed pipe; check the thickness of the sand filling layer.

[0066] The underground pipe is an underground drainage device specially used for improving saline-alkali soil. Its surface has a dense microporous structure, and the water in the soil layer above the underground pipe can penetrate into the underground pipe. The underground pipe is connected to the drainage channel and equipped with a valve to control the water flow. During the process of flooding the fields and washing salt, the valve is closed to prevent the water in the underground pipe from flowing out of the drainage channel, ensuring that the rice fields maintain an appropriate water level. During the drainage and salt removal process, the valve is opened to allow the water in the rice fields to be discharged into the drainage channel through the underground pipe system. Figure 2 As shown, the concealed pipe system is arranged in the subsoil layer.

[0067] Use random point excavation method to conduct random point inspections on concealed pipes, or check through inspection wells to ensure that the concealed pipes are not broken and the holes are not blocked.

[0068] Sand filling is commonly used in underground salt drainage systems. By injecting sand or other granular materials, a homogeneous, permeable sand filling layer is formed to increase soil stability and prevent soil erosion or underground pipe system failure caused by unstable water flow. The sand filling layer is located in the subsoil layer.

[0069] Check the thickness of the sand filling layer to ensure that the permeability coefficient is greater than 10 times that of the surrounding soil and the compaction thickness is not less than 8 cm.

[0070] 1.2. Trenching equipment selection: Choose trenching equipment that can create trenches with a width of 10-20 cm. The trenching equipment needs to be able to be used under wet and sticky conditions. The maximum trenching depth can reach 40 cm. The trench wall must be smooth and have a certain degree of solidity and is not easy to collapse.

[0071] Preferably, the trenching equipment is selected from a plough trencher, a chain trencher or a disc trencher.

[0072] 1.3. Ditch parameter setting:

[0073] Set the trench depth to between 30-40 cm, the trench width to 10-20 cm; the trench spacing to 90-220 cm.

[0074] The trench should be between 30 and 40 cm deep to ensure contact with the sand filling layer above the subsoil pipes, but avoid over-excavation and damage to the sand filling layer. A gap of several centimeters between the sand filling layer and the trench is acceptable. The width and spacing of the trenches should be determined based on a variety of factors, including the performance of the equipment, the expected irrigation volume, and the permeability of the soil.

[0075] Preferably, the ditch width is 10 cm and the ditch spacing is 180 cm. If the salt and alkali cannot be removed, the number of salt washing times can be increased.

[0076] It is particularly important to consider the local salinity concentration as a key factor in determining the width and density of ditches. In areas with higher salinity concentrations, the width and density of ditches should be increased accordingly to improve the efficiency of salt removal. However, considering the overall cost of ditch construction, excessive density and width are not recommended. Salt removal efficiency can be improved by increasing the number of salt washings.

[0077] 1.4. Use the trenching equipment selected in step 1.2 to dig the saline-alkali land to form a ditch;

[0078] 1.4.1. Dig trenches in the topsoil layer in a direction perpendicular to the buried direction of the concealed pipes, and store the excavated topsoil separately.

[0079] The depth of the topsoil layer is 0-20 cm.

[0080] Preferably, in order to reduce the resistance during ditching, deep loosening is performed on the predetermined ditching path before step 1.4.1, thereby reducing the density of the soil. If the pre-field soaking operation is carried out in the spring, it is recommended to carry out deep loosening first and then ditching to effectively reduce the operation resistance and improve the saline-alkali leaching effect. If the operation is carried out after the autumn harvest, the soil is relatively soft due to the relatively high soil moisture content. At this time, there is no need to carry out separate deep loosening, and you only need to wait for the soil moisture content to decrease. Generally, you need to wait for 3-5 days after the autumn harvest before you can operate. After the soil has sufficient bearing capacity, carry out the combined operation of deep loosening, ditching, filter filling and in-situ covering to prevent the problem of machinery sinking.

[0081] 1.4.2. Continue digging the trench obtained in step 1.4.1, passing through the subsoil layer directly to the subsoil layer, and store the excavated subsoil separately.

[0082] Specifically, continue digging the trench obtained in step 1.4.1 through the subsoil layer to the sand filling layer in the subsoil layer.

[0083] The depth of the subsoil layer is 20-40 cm.

[0084] The depth of the subsoil layer is below 40 cm.

[0085] The trenching depth of the ditch is between 30-40 cm.

[0086] The arrangement depth of the concealed pipe is 40 cm or less.

[0087] Since the upper part of each underground pipe is covered with tiny holes, water can pass through. Therefore, the direction of the ditch is perpendicular to the direction of the underground pipe burial to achieve the intersection of each water supply and salt discharge channel with multiple underground pipes.

[0088] The arrangement of the ditches serves a dual purpose: first, each ditch connects to the tiny holes in multiple concealed pipes, ensuring efficient drainage of salt and alkali; second, it provides a degree of fault tolerance for the overall salt drainage system. Even if a concealed pipe or ditch section fails, the overall function will not be significantly affected.

[0089] Because salt-alkali leaching is primarily concentrated in the topsoil, the topsoil has a relatively low salinity content, while the subsoil has a relatively high salinity content. This discrepancy is known as "surface desalination." Therefore, during excavation, it is crucial to ensure that the topsoil and subsoil do not mix. If the higher salinity content of the subsoil mixes with the topsoil, this will reduce the surface desalination effect and affect subsequent soil improvement efforts. Specifically, a layered excavation method should be adopted to ensure the separation of the various soil layers. The trenching depth should not be too deep. This is because a layer of sand filling is typically placed above the subsoil pipes to prevent soil from clogging the pipe openings and thus affecting drainage efficiency. Therefore, during trenching, it is important to ensure that the trench is connected to the sand filling layer to avoid damaging it. Furthermore, the trenching depth should not be set too shallow, as this may prevent the subsoil layer of soda saline soil from being fully penetrated, thereby hindering the saline-alkali solution from entering the subsoil pipes.

[0090] The trench walls should be stable enough to prevent collapse and should be kept as flat as possible.

[0091] As for the ditch shape, both trapezoidal and rectangular cross-sections can be used. The trapezoidal cross-section is characterized by being wide at the top and narrow at the bottom, which is more conducive to water ingress; while the rectangular cross-section is equal in width at the top and bottom and is more commonly used.

[0092] Furthermore, the specific width and spacing of the trenches should be determined based on the operating equipment, irrigation volume, and soil permeability.

[0093] Furthermore, although the present invention is based on a concealed pipe system design, it also has the flexibility to operate independently in scenarios without concealed pipes. Specifically, in scenarios equipped with concealed pipes, the ditch is generally flat to allow for more precise docking with the concealed pipe system. In contrast, in the absence of concealed pipes, the ditch needs to be set with a certain slope. The purpose of this is to ensure that the lower end of the ditch is effectively connected to the drainage channel, so that the saline-alkali solution can flow smoothly into the drainage channel.

[0094] When digging trenches in cultivated saline-alkali land, full consideration should be given to the farming season. The best times for digging trenches are before spring flooding and after autumn harvest. Initially, digging trenches should be performed once a year, alternating with digging trenches in untreated areas the following year. The frequency can be gradually reduced, to once every two or three years.

[0095] Step 2: Filter material pretreatment

[0096] After ditching, the filter material needs to be screened and pre-treated.

[0097] 2.1. Filter material screening

[0098] When screening filter materials, choose appropriate filter materials according to actual conditions.

[0099] The present invention uses organic filter materials, including one or more of organic fertilizer, rice husks, and straw, which have excellent water-transport properties. These organic filter materials are not only readily available in farmland, but their decomposition products also improve the physical and chemical properties of the soil.

[0100] When choosing filter media, comprehensive considerations are necessary, including availability, affordability, and environmental impact. In this context, it's recommended to choose filter media that is common and readily available locally. Generally speaking, organic filter media, such as straw and rice husks, are not only economically advantageous but also more readily available. These organic filter media are often byproducts of agricultural activities, making them more economical.

[0101] Furthermore, to optimize filter media performance and adaptability, a mixture of different types or sources can be considered. This mixing strategy can provide a more balanced physical and chemical property profile, such as improved water permeability, enhanced stability, or increased adsorption capacity, thereby more effectively responding to varying soil conditions and environmental factors.

[0102] In specific applications, organic fertilizers must be decontaminated and crushed to meet particle size requirements, and usage should be carefully controlled to avoid potential environmental risks. Rice husks should be screened to remove impurities before use. Straw, due to its flexibility and tendency to tangle, requires pretreatment.

[0103] 2.2. Filter material pretreatment

[0104] 2.2.1. Organic Fertilizer Pretreatment: Ensure it is fully fermented and mature. Immature organic fertilizer may contain substances harmful to plants, such as ammonia or pathogenic microorganisms. If the organic fertilizer contains large debris or lumps, it needs to be pretreated by screening or crushing to ensure uniform distribution.

[0105] 2.2.2. Rice husk pretreatment: Rice husk needs to be pretreated by drying.

[0106] 2.2.3. Straw pretreatment: The straw needs to be pre-treated by shaping, which can include one or more of the following methods:

[0107] 2.2.3.1. Rolling into ropes: Roll the straw into rope-like shapes, i.e. long rice ropes, ensuring the rope diameter is 5-8 cm;

[0108] 2.2.3.2. Weaving into mats: The straw is formed into square rice mats by weaving technology, with a thickness of not less than 20x20 cm;

[0109] 2.2.3.3. Compression into blocks: Use compression technology to compress the straw into blocks or cakes; the volume should be compressed by at least 75%;

[0110] 2.2.3.4. Winding into a ball: Use winding to shape the straw into a spherical shape, forming a ball with a radius of about 4 cm;

[0111] 2.2.3.5. Crushing into segments: Use a crusher to break up the straw into small segments no larger than 8 cm.

[0112] These straw pretreatment methods can be selected according to specific application scenarios and requirements to achieve optimal physical properties and economic benefits.

[0113] Furthermore, the durability of the filter material directly determines the stability of water delivery and the durability of the aftereffect. Filter materials that are prone to rot and become ineffective, such as straw.

[0114] The innovation of this invention lies in its pretreatment, particularly compression, which reduces the contact area between straw and air and soil. Furthermore, deep burial and soil covering further reduce the straw's exposure to air, significantly reducing the rate of straw decay. Furthermore, in Northeast China, where temperatures are relatively low, deep burial and dense filling of straw as filter material ensures it will not lose its effectiveness for one to two years.

[0115] Step 3: Filter material filling

[0116] After the trench is excavated in step 1, the filter material is filled. After filling, compaction is performed again to ensure that the filter material fully fills the entire trench and reaches the appropriate density.

[0117] Preferably, filter media is filled in sections, alternating between filling a section of the ditch with filter media and then leaving a section empty and directly covering it with soil. For example, if the filter media is particularly expensive, section-by-section filling may be appropriate. To ensure consistent filling density, continuous pressure is applied to ensure the entire ditch is filled. A space of 0-15 cm or 0-20 cm is reserved at the top for subsequent backfilling and covering with soil.

[0118] To improve filling efficiency, use equipment on the market that is specifically designed for filter media filling.

[0119] In special cases where filter media is particularly expensive, a segmented filling method can be used. Specifically, a section of the ditch is filled with filter media, then a section is left empty and directly covered with soil, alternating between these steps. It should be noted that while this method is feasible, it reduces water delivery efficiency and operational efficiency.

[0120] During the filling process, the filter material should be kept away from mixing with the soil as much as possible to maintain the functionality of the filter material.

[0121] The stable water and salt discharge channel formed by the filter material filling is a hidden channel. After covering with soil, the existence of the underground hidden channel will not affect the planting of surface crops.

[0122] Given the diverse forms and economic considerations of filter media, this invention provides a flexible filter media filling solution. The filter media can be filled in sections, depending on the soil's actual permeability requirements and economic benefits. While staggered filling along the ditch is a viable option, to maximize the filter media's functionality, it is recommended to fill the ditch as densely as possible vertically.

[0123] Step 4: In-situ covering operation

[0124] The subsoil excavated in step 1.4 is backfilled to its original subsoil position, and the topsoil is backfilled to its original topsoil position.

[0125] The reason for backfilling the subsoil layer and the topsoil layer in layers is that the salt content of the two soil layers is different, and backfilling in layers avoids cross contamination.

[0126] Step 5: Level the topsoil

[0127] After the in-situ backfilling operation is completed, the backfill soil is compacted and leveled.

[0128] Because the organic filter fill takes up space, it is not possible to backfill all of it. The excess soil needs to be removed from the field.

[0129] The compaction and leveling operations are mainly carried out according to the path of the previous trenching and covering to improve the physical stability of the soil and reduce the difficulty of subsequent operations caused by uneven soil.

[0130] The best results are achieved in autumn, when the soil freezes and snowfalls in winter naturally trigger a comprehensive salt-alkali washout. During the spring snowmelt, the filter media will fully function as a channel for water and salt removal.

[0131] While compaction and leveling are not essential steps in this method, they offer significant advantages for improving the quality of saline-alkali soil after filter filling. These operations effectively improve soil structure and create a more favorable soil environment for subsequent agricultural activities. Therefore, they should be considered optimization measures in the saline-alkali soil improvement process, aiming to achieve more sustainable and efficient soil improvement results.

[0132] Application examples of the method of the present invention Example 1:

[0133] For example, in the saline-alkali rice paddies near Anda City, Heilongjiang Province, saline-alkali soil seriously impacts agricultural production, particularly rice yield and quality. To address this issue, this study selected soil improvement work for approximately five days after the autumn harvest. Prior to work, a comprehensive assessment of soil moisture and weather conditions determined the optimal timing.

[0134] Step 1: Open the trench

[0135] During the preparatory phase for trenching, the functionality and integrity of the existing underground pipe system were assessed. To this end, the implementation plan employed random excavation to inspect the underground pipes at random locations to ensure their structural integrity and operational conditions. Once the system was confirmed to be free of visible damage and functional, marking was performed to clearly define the pipe's path and location, providing accurate guidance for subsequent trenching operations.

[0136] In this case, a disc trencher was selected as the primary equipment for trenching. Considering soil drainage and saline-alkali leaching, the trench design parameters were set to a width of 10 cm and a depth of 35 cm. This configuration not only meets the local requirement of twice-yearly saline-alkali leaching but also caters to the specific needs of spring rice paddies, thereby improving soil quality and optimizing the crop growth environment.

[0137] Excavation is done in stages, starting with the topsoil layer, which is excavated to a depth of 20 cm. After the topsoil layer is excavated, the subsoil layer is excavated to a depth of 15 cm. After the subsoil layer is excavated, the trench bottom depth should be tested. If the sand filling layer is not reached, the trench depth needs to be deepened.

[0138] Furthermore, the salinity of the subsoil is much higher than that of the topsoil. Therefore, the excavated subsoil should be removed from the field as soon as possible to avoid mixing the high-salinity subsoil with the low-salinity topsoil to avoid secondary contamination.

[0139] Furthermore, if any soil bank at the edge of the field is damaged during the operation, it should be repaired immediately after the operation is completed to prevent it from affecting subsequent flooding operations.

[0140] Step 2: Filter material pretreatment

[0141] Since this operation was carried out after the autumn harvest, a large amount of rice straw would remain after the rice was harvested. The straw was baled using a square baler, cut into 8-10 cm thick blocks, and transported to the fields by truck.

[0142] Step 3: Filter material filling:

[0143] In the pre-dug trench, straw blocks are densely arranged and filled, usually at a height of about 20 cm from the ground surface. The filling process should be accompanied by appropriate compaction.

[0144] Step 4: In-situ covering operation

[0145] Carry out backfilling in layers, ensuring that the subsoil layer is backfilled to the subsoil layer and the topsoil layer is backfilled to the topsoil layer. Excess soil needs to be removed in time.

[0146] Step 5: Level the topsoil

[0147] In this example, no topsoil leveling is required.

Claims

1. An improved method for constructing a stable water supply and salt discharge channel for soda saline-alkali soil, characterized by comprising the following steps: Step 1: Open the trench: 1.

1. Concealed pipe inspection: confirm the integrity and functionality of the concealed pipe; check the thickness of the sand filling layer; 1.

2. Trenching Equipment Selection: Choose trenching equipment that can create a ditch with a width of 10-20 cm. The trenching equipment needs to be able to be used in wet and sticky conditions, with a maximum trench depth of 40 cm. The trench walls must be smooth and have a certain degree of solidity that is not prone to collapse. 1.

3. Ditch parameter setting: set the ditch depth to between 30-40 cm, the ditch width to 10-20 cm; the ditch spacing to 90-220 cm; 1.

4. Use the trenching equipment selected in step 1.2 to dig the saline-alkali land to form a ditch; 1.4.

1. Dig trenches in the topsoil layer in a direction perpendicular to the buried pipe direction, and store the excavated topsoil separately; The depth of the topsoil layer is 0-20 cm; 1.4.

2. Continue digging the trench obtained in step 1.4.1, through the subsoil layer to the subsoil layer, and store the excavated subsoil separately; The depth of the subsoil layer is 20-40 cm; The depth of the subsoil layer is less than 40 cm; The trenching depth is between 30-40 cm; The concealed pipe is arranged at a depth of 40 cm or less; Step 2: Filter material pretreatment: 2.

1. Filter material screening: Select organic filter material as the filter material, which can be one or more of organic fertilizer, rice husk, and straw; 2.

2. Filter material pretreatment; Step 3: Filling the filter material: After the trench is excavated in step 1, the filter material is filled. After filling, compaction is performed again to ensure that the filter material fully fills the entire trench and reaches the appropriate density. Step 4: In-situ covering operation: The subsoil excavated in step 1.4 is backfilled to its original subsoil position, and the topsoil is backfilled to its original topsoil position.

2. The improved method according to claim 1, characterized in that: The method further comprises: Step 5: Leveling the topsoil: After the in-situ backfilling operation is completed, the backfill soil is compacted and leveled.

3. The improved method according to claim 1 or 2, characterized in that: The cross section of the ditch is in the shape of a trapezoid or a rectangle.

4. The improved method according to claim 1 or 2, characterized in that: The step 2.2 further comprises: 2.2.

1. Organic fertilizer pretreatment: Ensure that it is fully fermented and mature. Immature organic fertilizer contains substances that are harmful to plants, including ammonia or pathogenic microorganisms. If the organic fertilizer contains large debris or lumps, it needs to be pretreated by screening or crushing to ensure uniform distribution. 2.2.

2. Rice husk pretreatment: Rice husk needs to be pretreated by airing; 2.2.

3. Straw pretreatment: The straw needs to be pre-treated by shaping, which can include one or more of the following methods: 2.2.3.

1. Rolling into ropes: Roll the straw into rope-like shapes, i.e. long rice ropes, ensuring the rope diameter is 5-8 cm; 2.2.3.

2. Weaving into mats: The straw is formed into square rice mats by weaving technology, with a thickness of not less than 20x20 cm; 2.2.3.

3. Compression into blocks: Use compression technology to compress the straw into blocks or cakes; the volume should be compressed by at least 75%; 2.2.3.

4. Winding into a ball: Use winding to shape the straw into a spherical shape, forming a ball with a radius of about 4 cm; 2.2.3.

5. Crushing into segments: Use a crusher to break up the straw into small segments no larger than 8 cm.

5. The improved method according to claim 1 or 2, characterized in that: The filter material filling in step 3 adopts a segmented filling method, that is, the filter material is used to fill a section of the ditch, and then a section is left empty and directly covered with soil, and this process is performed alternately.

6. The improved method according to claim 1 or 2, characterized in that: To reduce resistance during trenching, deep loosen the planned trenching path before step 1.4.1 to reduce soil compaction.

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