Saline-alkali soil modification method and structure

Abstract

Irrigation wells and drainage wells are excavated in the diagonal positions of the inner side of a square retention wall correspondingly, a multifunctional ditch is connected between the irrigation wells and the drainage wells, a partition plate is horizontally arranged on the longitudinal middle-upper portion of the multifunctional ditch, the upper portion of the partition plate is an irrigation cavity, and the lower portion of the partition plate is a drainage cavity. One end of the top of the irrigation cavity is connected with an irrigation main pipe installed in the irrigation well, a plug is arranged at the other end of the top of the irrigation cavity, one end of the drainage cavity is communicated with the middle of the drainage well, a ridge body and a ditch body which are adjacent to each other are arranged on the surface of the saline-alkali soil to be modified, and a drainage concealed pipe communicated with the drainage cavity is arranged below the ridge body. An irrigation branch pipe communicated with the irrigation cavity is arranged at one end of the upper part of the ditch body; the dual functions of upper irrigation and lower drainage are achieved through the multifunctional ditch, and specific soil is modified through carbon-based microbial fertilizer added to the roots of saline-alkaline tolerant plants in cooperation with the design of ridge bodies and ditch bodies at the top.

Description

Technical Field

[0001] The invention relates to the field of soil management, and in particular to a saline-alkali land modification method and structure. Background Art

[0002] Salt-alkali land refers to the salt contained in the soil that affects the normal growth of crops. The formation of salt-alkali land in my country is mostly related to the accumulation of carbonates in the soil. Plants can hardly survive in areas with severe saline-alkali soil. The formation of salt-alkali land is the result of the combined effects of natural and human factors. Natural factors include climatic conditions, groundwater levels, topographic conditions, and the influence of rivers and seawater. Climate conditions such as low precipitation and high evaporation can easily lead to the accumulation of salt on the soil surface; the height and salt content of the groundwater level can also affect the degree of soil salinization. A high groundwater level and high salt content can easily lead to soil salinization; topographic conditions such as low-lying terrain and poor drainage can easily lead to salt accumulation; the influence of rivers and seawater, such as lateral infiltration of river water and seawater intrusion, can also form salt-alkali land. Human factors such as improper irrigation: flooding or irrigation without drainage in low-lying areas, leading to rising groundwater levels and salt accumulation. Excessive groundwater extraction in coastal areas: causing seawater to invade groundwater, increasing groundwater salinity.

[0003] Therefore, for the management of saline-alkali land, it is necessary to implement soil salt dilution and discharge operations, and at the same time, attention should be paid to the reduction of groundwater, and comprehensive management should be implemented by planting salt-tolerant plants. During the management operation, attention should be paid to the structural layout of the different regions, and the saline-alkali soil should be diluted and discharged by means of drainage ditches, underground pipes, etc. In terms of pipeline salt discharge, the traditional practice is to discharge the salt in the soil through underground pipes through natural precipitation to achieve the purpose of soil salt washing and salt discharge. In terms of controlling groundwater, the traditional practice is to lower the groundwater level to below the deep layer through underground pipes, thereby effectively controlling the groundwater level and preventing secondary salinization of the soil. The traditional method of salt discharge by two-stage underground pipes of water absorption pipes and water accumulation pipes has certain defects: the laying of underground pipes requires a lot of manual operation, especially the laying of underground pipes with lowered groundwater levels is difficult, the overall project is huge and the cost is high. The secondary pipeline setting of the salt discharge pipeline also has certain defects. The structure of the two-stage underground pipe is relatively complex, and multiple passages need to be set up for connection, and there is a defect of poor water absorption and drainage effect.

[0004] Therefore, the method provided by the present invention is simple and easy to operate, realizes on-site irrigation dilution and purified water backfilling to control the lowest groundwater level, realizes the recycling protection and utilization of water resources, can fully implement the dilution of upper soil salt, improve the efficiency of saline-alkali water discharge, realizes irrigation and saline-alkali water drainage as one through multifunctional ditches, makes full use of the structure of saline-alkali land itself, can realize regional parallel saline-alkali land soil modification operations, saves overall costs, reduces construction difficulty, and is an efficient and convenient saline-alkali land modification method and structure with broad market prospects. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method that is simple and easy to operate, realizes on-site irrigation dilution and purified water backfilling to control the lowest groundwater level, realizes the recycling, protection and utilization of water resources, can fully implement the dilution of upper soil salt, improve the efficiency of saline-alkali water discharge, and realizes irrigation and saline-alkali water drainage in one through multifunctional ditches, fully utilizes the structure of the saline-alkali land itself, can realize regional parallel saline-alkali land soil modification operations, saves overall costs, reduces construction difficulty, and is an efficient and convenient saline-alkali land modification method and structure for overcoming the defects in the prior art.

[0006] The technical solution of the present invention is achieved as follows: a saline-alkali land modification method, the method comprising the following steps:

[0007] S1. The saline-alkali land to be modified is divided into different areas by a square retaining wall, and then an irrigation well and a drainage well are excavated at the diagonal position of a single saline-alkali land to be modified, and a multifunctional ditch is excavated at the position connecting the irrigation well and the drainage well, and then an isolation board is installed in the multifunctional ditch to divide the multifunctional ditch into an upper irrigation cavity and a lower drainage cavity;

[0008] S2. Several deep trenches are excavated symmetrically and evenly on both sides of the multifunctional ditch. The depth of the deep trenches is 1.5 to 2 meters. Drainage concealed pipes are laid in the deep trenches. Water retaining plugs are installed at the outer ends of the drainage concealed pipes. The inner ends of the drainage concealed pipes are connected to the drainage cavity. After the laying is completed, the soil is backfilled. A ridge is constructed on the top surface above each drainage concealed pipe. A ditch is formed between two adjacent rows of ridges. Soil modification pits are evenly set at the bottom of the ditch. One end of the drainage cavity is connected to the middle of the drainage well through the canal outlet.

[0009] S3. An irrigation branch pipe is installed on the outer wall of the multifunctional ditch on one side of the top surface of the ditch body. The irrigation branch pipe is connected to the irrigation cavity. The top surface of one end of the irrigation cavity is connected to the irrigation main pipe in the irrigation well. The other end of the irrigation cavity is blocked by a plug. After the installation is completed, a cover plate is laid on the top of the multifunctional ditch, salt-alkali tolerant plants are planted in the soil modification pit, and carbon-based microbial fertilizer is backfilled. Then, a drip irrigation pipe connected to the drip irrigation pipe irrigation branch pipe is laid. The water outlet of the drip irrigation pipe is located between two adjacent soil modification pits. Then, a evaporation suppression burial layer is laid on the top of the drip irrigation pipe.

[0010] S4. Turn on the water pump in the irrigation well. The water in the shallow groundwater layer is pumped to one end of the irrigation cavity through the irrigation main pipe and flows toward one end of the plug. During the flow, the irrigation water enters the ditch through the irrigation branch pipe to implement irrigation operations. The shallow groundwater level is lowered by groundwater irrigation, and at the same time, a water source is provided for the saline-alkali land salt flushing operation;

[0011] S5. When the groundwater irrigation operation is in operation, the irrigation water irrigates and flushes the soil around the roots of the salt-alkali tolerant plants, flushes the salt in the soil and then infiltrates into the lower layer. The infiltrated water is collected through the drainage concealed pipe and then flows back to the drainage cavity, and then flows back to the drainage well through the canal outlet;

[0012] S6. Turn on the water pump installed in the drainage well, extract the saline-alkali water through the saline-alkali water output pipe and transport it to the saline-alkali water purification equipment. When the shallow groundwater level drops to the warning value, the clean water obtained after thorough purification is refilled into the irrigation well. The saline-alkali land is modified through a circulation method of shallow water irrigation, soil surface salt scouring, saline-alkali water underground pipe collection and drainage, and saline-alkali water purification and backfilling.

[0013] A saline-alkali land modification structure comprises saline-alkali land to be modified, wherein a square retaining wall is arranged on the saline-alkali land to be modified, an irrigation well and a drainage well are respectively excavated at diagonal positions on the inner side of the square retaining wall, a multifunctional ditch is connected between the irrigation well and the drainage well, an isolation plate is horizontally arranged in the longitudinal middle and upper part of the multifunctional ditch, the upper part of the isolation plate is an irrigation cavity, the lower part of the isolation plate is a drainage cavity, one end of the top of the irrigation cavity is connected to an irrigation main pipe installed in the irrigation well, a plug is arranged at the other end of the top of the irrigation cavity, one end of the drainage cavity is connected to the middle part of the drainage well, a ridge body and a ditch body adjacent to each other are arranged on the surface of the saline-alkali land to be modified, a drainage concealed pipe connected to the drainage cavity is arranged below the ridge body, and an irrigation branch pipe connected to the irrigation cavity is arranged at one end of the upper part of the ditch body.

[0014] Furthermore, the multifunctional ditch divides the saline-alkali land to be modified inside the square retaining wall into two triangular structures, the ridge bodies are symmetrically arranged on both sides of the multifunctional ditch, the drainage concealed pipes installed under the ridge bodies are symmetrically arranged on both sides of the drainage cavity, the ditch bodies are symmetrically arranged on both sides of the multifunctional ditch, and the irrigation branch pipes installed at one end of the upper part of the ditch body are symmetrically arranged on both sides of the irrigation cavity.

[0015] Furthermore, a number of soil modification pits are evenly arranged at the bottom of the ditch body, the soil modification pits are filled with carbon-based microbial fertilizers, an evaporation suppression burial layer is laid in the ditch body above the carbon-based microbial fertilizers, and the irrigation branch pipe is connected to the drip irrigation pipe laid in the evaporation suppression burial layer.

[0016] Furthermore, the bottom of the irrigation well is connected to the shallow groundwater layer, a water pump connected to the irrigation main pipe is arranged at the bottom of the irrigation well, and a clean water source backfill pipeline is arranged on one side of the top of the irrigation main pipe.

[0017] Furthermore, the side walls and bottom of the drainage well are provided with an anti-seepage isolation layer, and the bottom of the drainage well is located below the multifunctional ditch. At the same time, the bottom of the drainage well is located above the water level of the irrigation well. A water pump is also installed in the drainage well, and the water pump is connected to the saline-alkali water output pipeline, and the saline-alkali water output pipeline is connected to the saline-alkali water purification equipment. The output end of the saline-alkali water purification equipment is connected to the top of the irrigation well through a clean water drainage pipe with a three-way valve.

[0018] Furthermore, the isolation plate is a square plate structure, the top surface of the isolation plate is not lower than the bottom surface of the ditch body, the bottom surface of the irrigation branch pipe is located above the top surface of the isolation plate, and the outer side of the plug is connected to the outer wall of the saline-alkali water drainage well.

[0019] Furthermore, the ridge body is symmetrically distributed on both sides of the multifunctional ditch in a horizontal and vertical cross pattern, and the ditch body is symmetrically distributed on both sides of the multifunctional ditch in a horizontal and vertical cross pattern. The length of the ridge body and the ditch body from the irrigation well to the drainage well gradually shortens. The outer side of the drainage well is the ditch body, and the outer side of the irrigation well is the ridge body. The height of the multifunctional ditch gradually decreases from the irrigation well to the drainage well.

[0020] The present invention has the following positive effects:

[0021] Firstly, the saline-alkali land modification method of the present invention implements modification operations on the saline-alkali land in a circulation mode of shallow water irrigation, soil surface salt flushing, saline-alkali water underground pipe collection and drainage, and saline-alkali water purification and backfilling, divides a single modification area by a retaining wall, and then implements short-distance scientific irrigation operations in the single modification area, and recovers the salt in the soil after flushing with irrigation water. The recovery process is recovered by drainage underground pipes and discharged into a multifunctional ditch. The upper part of the multifunctional ditch is an irrigation cavity, and shallow groundwater is led out through the irrigation cavity to implement irrigation operations. The dual functions of upper irrigation and lower drainage are achieved through a multifunctional ditch. In conjunction with the top ridge and ditch design, the specific soil is modified by using carbon-based microbial fertilizer added to the roots of salt-alkali tolerant plants, and the saline-alkali soil is modified by using root secretions of plants during growth. In conjunction with salt flushing and discharge operations, the saline-alkali land soil is gradually and comprehensively modified. At the same time, in order to ensure that the groundwater level does not fall below the warning red line, the extracted saline water is purified and backfilled into irrigation wells, which helps maintain the overall ecological health of the groundwater in the saline-alkali land.

[0022] Secondly, the present invention provides a saline-alkali land modification structure, which divides the saline-alkali land to be modified in a single area into two triangular areas by using a square retaining wall and a multifunctional ditch, and implements a symmetrical structure of ridges, ditches, drainage concealed pipes and irrigation branch pipes in the two triangular areas. The multifunctional ditch is designed at a 45-degree angle to the structures on both sides, which reduces the drainage distance of saline-alkali water. By draining water diagonally from the proximal end to the middle of the square retaining wall, the saline-alkali water is efficiently discharged, and the saline-alkali water is prevented from excessively penetrating into the deep soil during the drainage process, and the shallow groundwater is prevented from being affected. Pollution, at the same time, the triangular area division method is also convenient for the upper irrigation cavity to evenly implement proximal irrigation towards both ends. The ditch length on both sides of the irrigation cavity facing the irrigation well is the longest, realizing proximal irrigation operations of longer ditches, and the ditch length on both sides of the irrigation cavity facing the drainage well is the shortest, realizing distal irrigation operations of shorter ditches. At the same time, the distal irrigation position is close to the drainage well, which improves the efficiency of irrigation water use and fully realizes the conservation and utilization of water resources. The multifunctional ditch is set in an inclined shape, gradually lowering towards the drainage well, realizing the dual efficient flow operations of irrigation water and saline water.

[0023] Thirdly, the square retaining wall of the present invention can be used in parallel, in series and in an array. The planning operation can be implemented according to the area of ​​the saline-alkali land, and the specific number of irrigation wells and drainage wells can be planned. The expansion can be implemented in the form of sharing one irrigation well or drainage well in two or more sub-regional areas, and then a comprehensive modified structural layout can be implemented in all saline-alkali areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the top view of the saline-alkali land modification structure of the present invention.

[0025] Figure 2 It is a left-side structural schematic diagram of the saline-alkali land modification structure of the present invention.

[0026] Figure 3 It is a right-side structural schematic diagram of the saline-alkali land modification structure of the present invention.

[0027] Figure 4 This is a schematic diagram of the main structure of the multifunctional ditch of the saline-alkali land modification structure of the present invention.

[0028] Figure 5 It is a structural schematic diagram of one of the expansion methods of the alkaline land modification structure of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the following description of the invention, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating directions or positional relationships, are based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. The term "connection" only indicates the connection between devices and has no special meaning.

[0031] Specific embodiments refer to Figure 1 , 2 As shown in , 3, , 4, and 5, a method for modifying saline-alkali land comprises the following steps:

[0032] S1. The saline-alkali land to be modified is divided into regions by a square retaining wall 1, and then an irrigation well 10 and a drainage well 14 are excavated at diagonal positions in a single saline-alkali land divided region to be modified, and a multifunctional ditch 9 is excavated at the position connecting the irrigation well 10 and the drainage well 14, and then an isolation board 7 is installed in the multifunctional ditch 9 to divide the multifunctional ditch 9 into an upper irrigation cavity 18 and a lower drainage cavity 17;

[0033] S2. A number of deep trenches are excavated symmetrically and evenly on both sides of the multifunctional ditch 9. The depth of the deep trenches is 1.5 to 2 meters. Drainage concealed pipes 3 are laid in the deep trenches. Water retaining plugs 4 are installed at the outer ends of the drainage concealed pipes 3. The inner ends of the drainage concealed pipes 3 are connected to the drainage cavity 17. After the laying is completed, the soil is backfilled. A ridge body 2 is constructed on the top surface above each drainage concealed pipe 3. A ditch body 5 is formed between two adjacent rows of ridge bodies. Soil modification pits 6 are evenly arranged at the bottom of the ditch body 5. One end of the drainage cavity 17 is connected to the middle of the drainage well 14 through the canal outlet 19;

[0034] S3, an irrigation branch pipe 8 is installed on the outer wall of the multifunctional ditch 9 on one side of the top surface of the ditch body 5, the irrigation branch pipe 8 is connected to the irrigation cavity 18, the top surface of one end of the irrigation cavity 18 is connected to the irrigation main pipe 11 in the irrigation well 10, and the other end of the irrigation cavity 18 is blocked by a plug 13. After the installation is completed, a cover plate is laid on the top of the multifunctional ditch 9, salt-alkali tolerant plants are planted in the soil modification pit 6, and carbon-based microbial fertilizer is backfilled, and then a drip irrigation pipe connected to the drip irrigation pipe irrigation branch pipe 8 is laid, and the water outlet of the drip irrigation pipe is located between two adjacent soil modification pits 6, and then a evaporation suppression burial layer is laid on the top of the drip irrigation pipe;

[0035] S4, start the water pump 15 in the irrigation well 10, and the water in the shallow groundwater layer is pumped to one end of the irrigation cavity 18 through the irrigation main pipe 11, and flows toward one end of the plug 13. During the flow, the irrigation water enters the ditch body 5 through the irrigation branch pipe 8 to implement irrigation operations, and the shallow groundwater level is lowered by groundwater irrigation, and at the same time, a water source is provided for the salt washing operation of the saline-alkali land;

[0036] S5. When the groundwater irrigation operation is in operation, the irrigation water irrigates and flushes the soil around the roots of the salt-alkali tolerant plants, flushes the salt in the soil and then infiltrates into the lower layer. The infiltrated water is collected through the drainage concealed pipe 3 and then flows back to the drainage cavity 17, and then flows back to the drainage well 14 through the canal outlet 19;

[0037] S6. Turn on the water pump 16 installed in the drainage well 14, extract the saline-alkali water through the saline-alkali water output pipe 12 and transport it to the saline-alkali water purification equipment. When the shallow groundwater level drops to the warning value, the clean water obtained after thorough purification is refilled into the irrigation well 10. The saline-alkali land is modified through a circulation method of shallow water irrigation, soil surface salt scouring, saline-alkali water underground pipe collection and drainage, and saline-alkali water purification and backfilling.

[0038] like Figure 1-5 As shown, a saline-alkali land modification structure includes saline-alkali land to be modified, wherein a square retaining wall 1 is arranged on the saline-alkali land to be modified, and an irrigation well 10 and a drainage well 14 are excavated at diagonal positions on the inner side of the square retaining wall 1, respectively, and a multifunctional ditch 9 is connected between the irrigation well 10 and the drainage well 14, and an isolation plate 7 is horizontally arranged in the longitudinal middle and upper part of the multifunctional ditch 9, the upper part of the isolation plate 7 is an irrigation cavity 18, and the lower part of the isolation plate 7 is a drainage cavity 17, one end of the top of the irrigation cavity 18 is connected to the irrigation main pipe 11 installed in the irrigation well 10, and a plug 13 is arranged at the other end of the top of the irrigation cavity 18, and one end of the drainage cavity 17 is connected to the middle part of the drainage well 14, and a ridge body 2 and a ditch body 5 adjacent to each other are arranged on the surface of the saline-alkali land to be modified, a drainage concealed pipe 3 connected to the drainage cavity 17 is arranged below the ridge body 2, and an irrigation branch pipe 8 connected to the irrigation cavity 18 is arranged at one end of the upper part of the ditch body 5.

[0039] Specifically, the square retaining wall 1 is constructed according to the actual area of ​​the saline-alkali land to be modified. The square retaining wall 1 can be set as a single or parallel, series or array layout structure. The square retaining wall 1 can implement water retaining operations on the ditch position when the irrigation operation is running, so as to prevent the water from overflowing to the outside of the modified position when the irrigation operation uses water. The irrigation well 10 and the drainage well 14 are opened diagonally, which can cover all positions within the area of ​​the square retaining wall 1. The multifunctional ditch is not set at the diagonal position of the irrigation well 10 and the drainage well 14. This setting can save the installation length of the drainage concealed pipe. In the two triangular areas on both sides of the multifunctional ditch, drainage and irrigation operations are carried out towards the diagonal connection position of the saline-alkali land to be modified, shortening the pipeline length and improving the drainage and irrigation efficiency.

[0040] Specifically, the multifunctional ditch 9 is partitioned by the isolation plate 7. After the partition, the upper and lower parts are respectively used for irrigation water output and saline water drainage output, which saves the length of pipeline laying. The irrigation path and the drainage path are efficiently integrated in a one-channel-multiple-purpose manner, reducing the workload of pipeline laying. Compared with the traditional single-sided drainage ditch and irrigation pipeline laying separately, this product greatly saves resources, improves efficiency and saves space.

[0041] Specifically, the ridge body 2 and the ditch body 5 are designed on the surface of the saline-alkali land, and the soil surface pattern design is formed by the undulating surface, which helps the variable layer salt to efficiently infiltrate with the irrigation water during the irrigation operation and be collected through the drainage pipe. The top of the ridge body 2 is designed to be higher, and the ditch body 5 is arranged between two adjacent ridge bodies. The irrigation water is gathered through the ditch body 5, which improves the guiding property of the flow of the irrigation water. In combination with the irrigation branch pipe 8 and the drainage pipe 3, an efficient soil salt water flushing effect is formed as a whole.

[0042] The multifunctional ditch 9 divides the saline-alkali land to be modified inside the square retaining wall 1 into two triangular structures, the ridge bodies 2 are symmetrically arranged on both sides of the multifunctional ditch 9, the drainage concealed pipes 3 installed below the ridge bodies 2 are symmetrically arranged on both sides of the drainage cavity 17, the ditch bodies 5 are symmetrically arranged on both sides of the multifunctional ditch 9, and the irrigation branch pipes 8 installed at one end of the upper part of the ditch bodies 5 are symmetrically arranged on both sides of the irrigation cavity 18. The ridge bodies 2 are symmetrically distributed on both sides of the multifunctional ditch 9 in a horizontal and vertical cross shape, and the ditch bodies 5 are symmetrically distributed on both sides of the multifunctional ditch 9 in a horizontal and vertical cross shape. The length of the ridge bodies 2 and the ditch bodies 5 from the irrigation well 10 to the drainage well 14 is gradually shortened, the outside of the drainage well 14 is the ditch body 5, the outside of the irrigation well 10 is the ridge body 2, and the height of the multifunctional ditch 9 from the irrigation well 10 to the drainage well 14 is gradually reduced.

[0043] Specifically, the length of the drainage concealed pipes 3 on both sides of the multifunctional ditch 9 is gradually shortened, and the length is gradually shortened from one end of the multifunctional ditch 9 close to the irrigation well 10 to the other end. The symmetrical layout is adopted, which is conducive to the planting and care of salt-alkali tolerant plants in the later stage, and is convenient and efficient for irrigation. The drainage concealed pipe 3 is located in the lower layer and connected to the drainage cavity 17, and the irrigation branch pipe 8 is located in the upper layer and connected to the irrigation cavity 18. The drainage and irrigation are integrated into a multifunctional ditch 9 by distinguishing the upper and lower layers, which saves space and improves efficiency.

[0044] The bottom of the ditch body 5 is evenly provided with a number of soil modification pits 6, which are filled with carbon-based microbial fertilizers. An evaporation-inhibiting buried layer is laid in the ditch body 5 above the carbon-based microbial fertilizers, and the irrigation branch pipe 8 is connected to the drip irrigation pipe laid in the evaporation-inhibiting buried layer. The specific soil modification pit 6 is excavated in advance, and when in use, salt-alkali tolerant plants are planted inside it, and then the carbon-based microbial fertilizers are filled and backfilled to mix with the original soil. After the drip irrigation pipe is laid, the evaporation-inhibiting buried layer is covered. When the irrigation operation is running, it is ensured that the irrigation water can efficiently act on the roots of the salt-alkali tolerant plants through the ditch body, and the salt in the soil is taken away by the irrigation water during the infiltration process, and finally discharged into the drainage cavity through the drainage hidden pipe. In order to ensure that the nutrients of the carbon-based microbial fertilizers in the soil are not taken away, the drip irrigation operation is implemented in the soil position between two salt-alkali tolerant plants, and the nutrients are slowly released by the carbon-based microbial fertilizers to avoid being taken away by the irrigation water.

[0045] The bottom of the irrigation well 10 is connected to the shallow groundwater layer. A water pump 15 connected to the irrigation main pipe 11 is arranged at the bottom of the irrigation well 10. A clean water source backfill pipe is arranged on one side of the top of the irrigation main pipe 11. The side wall and bottom of the drainage well 14 are both provided with an anti-seepage isolation layer. The bottom of the drainage well 14 is located below the multifunctional ditch 9. At the same time, the bottom of the drainage well 14 is located above the water level of the irrigation well 10. A water pump 16 is also installed in the drainage well 14. The water pump 16 is connected to the saline-alkali water output pipeline 12. The saline-alkali water output pipeline 12 is connected to the saline-alkali water purification equipment. The output end of the saline-alkali water purification equipment is connected to the top of the irrigation well 10 through a clean water drainage pipe with a three-way valve. The isolation plate 7 is a square plate structure. The top surface of the isolation plate 7 is not lower than the bottom surface of the ditch body 5. The bottom surface of the irrigation branch pipe 8 is located above the top surface of the isolation plate 7. The outer side of the plug 13 is connected to the outer wall of the saline-alkali water drainage well 14.

[0046] Specifically, when the shallow groundwater level of the clean water source backfill pipeline drops to the warning value, the saline water extracted from the drainage well 14 is thoroughly purified before backfilling. During the backfilling process, the groundwater level needs to be tested to avoid excessive water level causing aggravation of salinization in the upper part. The saline water purification treatment adopts multi-stage filtration with ultrafiltration device to completely remove sediment and salt, and disinfection, filtration and purification treatment to ensure the cleanliness of the backfill water resources.

[0047] Embodiment 1: Figure 1 , 2 As shown in Figures 3 and 4, this embodiment uses a square retaining wall to surround all the saline-alkali land to be modified. This embodiment is suitable for saline-alkali land modification operations with a smaller area. When implementing the saline-alkali land modification operation, the square retaining wall 1 is used to surround all the saline-alkali land to be modified, which plays the role of surrounding water retaining during irrigation operations. An irrigation well 10 and a drainage well 14 are excavated at the diagonal position inside the square retaining wall 1, and a multifunctional ditch 9 is excavated at the position connecting the irrigation well 10 and the drainage well 14. Then, an isolation plate 7 is installed in the multifunctional ditch 9 to divide the multifunctional ditch 9 into an upper irrigation cavity 18 and a lower drainage cavity 17. The depth of the irrigation cavity 18 is not greater than the depth of the drainage cavity 17. The top surface of the isolation plate 7 is not lower than the bottom surface of the ditch body 5. The bottom surface of the irrigation branch pipe 8 is located above the top surface of the isolation plate 7. The outer side of the plug 13 is connected to the outer wall of the saline-alkali water drainage well 14. The plug 13 is used to form the irrigation cavity 18 into an upper independent irrigation channel structure.

[0048] Several deep trenches are dug symmetrically and evenly on both sides of the multifunctional ditch 9, with a depth of 1.5 to 2 meters, and drainage pipes 3 are laid in the deep trenches. Water retaining plugs 4 are installed at the outer ends of the drainage pipes 3, and the inner ends of the drainage pipes 3 are connected to the drainage cavity 17. After the laying is completed, the soil is backfilled, and a ridge 2 is constructed on the top surface above each drainage pipe 3. A ditch 5 is formed between two adjacent rows of ridges. Soil modification pits 6 are evenly arranged at the bottom of the ditch 5. One end of the drainage cavity 17 is connected to the middle of the drainage well 14 through the canal outlet 19. The multifunctional ditch 9 divides the saline-alkali land to be modified inside the square retaining wall 1 into two triangular structures. The ridges 2 are symmetrically arranged on both sides of the multifunctional ditch 9, and the drainage pipes 3 installed below the ridges 2 are symmetrically arranged on both sides of the drainage cavity 17. The ditch 5 is symmetrically arranged on both sides of the multifunctional ditch 9, and the irrigation branch pipes 8 installed at one end of the upper part of the ditch 5 are symmetrically arranged on both sides of the irrigation cavity 18.

[0049] The ridge body 2 is symmetrically distributed on both sides of the multifunctional ditch 9 in a horizontal and vertical cross shape, and the ditch body 5 is symmetrically distributed on both sides of the multifunctional ditch 9 in a horizontal and vertical cross shape. The length of the ridge body 2 and the ditch body 5 gradually shortens from the irrigation well 10 to the drainage well 14. The outer side of the drainage well 14 is the ditch body 5, and the outer side of the irrigation well 10 is the ridge body 2. The height of the multifunctional ditch 9 gradually decreases from the irrigation well 10 to the drainage well 14.

[0050] An irrigation branch pipe 8 is installed on the outer wall of the multifunctional ditch 9 on one side of the top surface of the ditch body 5. The irrigation branch pipe 8 is connected to the irrigation cavity 18. The top surface of one end of the irrigation cavity 18 is connected to the irrigation main pipe 11 in the irrigation well 10. The other end of the irrigation cavity 18 is blocked by a plug 13. After the installation is completed, a cover plate is laid on the top of the multifunctional ditch 9, salt-alkali tolerant plants are planted in the soil modification pit 6, and carbon-based microbial fertilizer is backfilled, and then a drip irrigation pipe connected to the drip irrigation pipe irrigation branch pipe 8 is laid, and the water outlet of the drip irrigation pipe is located between two adjacent soil modification pits 6, and then a evaporation suppression burial layer is laid on the top of the drip irrigation pipe. A plurality of soil modification pits 6 are evenly arranged at the bottom of the ditch body 5, and the soil modification pits 6 are filled with carbon-based microbial fertilizers. A evaporation suppression burial layer is laid in the ditch body 5 above the carbon-based microbial fertilizer, and the irrigation branch pipe 8 is connected to the drip irrigation pipe laid in the evaporation suppression burial layer.

[0051] The pump 15 in the irrigation well 10 is turned on, and the water in the shallow groundwater layer is pumped to one end of the irrigation cavity 18 through the irrigation main pipe 11, and flows toward one end of the plug 13. During the flow, the irrigation water enters the ditch body 5 through the irrigation branch pipe 8 to implement irrigation operations, and the shallow groundwater level is lowered by groundwater irrigation, while providing a water source for the saline-alkali land flushing operation. When the groundwater irrigation operation is running, the irrigation water irrigates and flushes the soil around the roots of salt-alkali tolerant plants, flushes the salt in the soil and infiltrates into the lower layer, and the infiltrated water is collected by the drainage concealed pipe 3 and flows back to the drainage cavity 17, and then flows back to the drainage well 14 through the canal outlet 19. The side walls and bottom of the drainage well 14 are provided with an anti-seepage isolation layer. The bottom of the drainage well 14 is located below the multifunctional ditch 9. At the same time, the bottom of the drainage well 14 is located above the water level of the irrigation well 10. A water pump 16 is also installed in the drainage well 14. The water pump 16 is connected to the saline water output pipeline 12. The saline water output pipeline 12 is connected to the saline water purification equipment. The output end of the saline water purification equipment is connected to the top of the irrigation well 10 through a clean water drainage pipe with a three-way valve.

[0052] The pump 16 installed in the drainage well 14 is turned on to extract the saline water through the saline water output pipe 12 and then transport it to the saline water purification equipment. When the shallow groundwater level drops to the warning value, the clean water obtained after thorough purification is refilled into the irrigation well 10. The saline-alkali land is modified through a circulation method of shallow water irrigation, soil surface salt scouring, saline water underground pipe collection and drainage, and saline water purification and backfilling.

[0053] As another embodiment of the present invention, Figure 5In combination with 1-4, the difference from the first embodiment is that this embodiment is suitable for large-scale saline-alkali land modification. In specific operation, the square retaining wall 1 performs modification operations on the large-scale saline-alkali land in divided areas, and multiple square retaining walls 1 are arranged in a display structure, such as Figure 5 As shown, it is a top view of the four square retaining walls 1 after being connected. The drainage wells 14 of the four square retaining walls 1 are set at the center of the saline-alkali land to be modified. The four square retaining walls 1 share one drainage well 14. The multifunctional ditch 9 of each square retaining wall 1 is extended toward the center of the saline-alkali land to be modified. The excavation height of the four multifunctional ditches 9 gradually decreases from the four corners of the entire saline-alkali land to be modified toward the center of the saline-alkali land to be modified. The four multifunctional ditches 9 and the drainage well 14 at the center of the saline-alkali land to be modified form a funnel-shaped structure. The inner sides of the four square retaining walls 1 are connected to each other as a whole, forming a cross structure on the entire saline-alkali land to be modified. During specific use, the connection position of the square retaining wall 1 on the inner side of the edge position can also be cancelled, and the inner area of ​​the four square retaining walls 1 can be formed into an overall flat structure. The ridge body 2, the ditch body 5 and the drainage pipe 3 all form a U-shaped structure and are interconnected, thereby improving the irrigation efficiency and drainage efficiency. When the irrigation water meets the basic irrigation needs, the surplus water can quickly carry away the soil salt and be discharged to the drainage well 14 set in the center position.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for modifying saline-alkali land, characterized in that: The method comprises the following steps: S1, dividing the saline-alkali land to be modified into different areas by means of a square retaining wall (1), then digging an irrigation well (10) and a drainage well (14) at diagonal positions within a single saline-alkali land divided area to be modified, and digging a multifunctional ditch (9) at the position connecting the irrigation well (10) and the drainage well (14), and then installing an isolation plate (7) in the multifunctional ditch (9) to divide the multifunctional ditch (9) into an upper irrigation cavity (18) and a lower drainage cavity (17); S2. A plurality of deep trenches are excavated symmetrically and evenly on both sides of the multifunctional ditch (9). The depth of the deep trenches is 1.5 to 2 meters. Drainage concealed pipes (3) are laid in the deep trenches. Water retaining plugs (4) are installed at the outer ends of the drainage concealed pipes (3). The inner ends of the drainage concealed pipes (3) are connected to the drainage cavity (17). After the laying is completed, soil is backfilled. A ridge body (2) is constructed on the top surface above each drainage concealed pipe (3). A ditch body (5) is formed between two adjacent rows of ridge bodies. Soil modification pits (6) are evenly arranged at the bottom of the ditch body (5). One end of the drainage cavity (17) is connected to the middle of the drainage well (14) through the canal outlet (19); S3, an irrigation branch pipe (8) is installed on the outer wall of the multifunctional ditch (9) on one side of the top surface of the ditch body (5), the irrigation branch pipe (8) is connected to the irrigation cavity (18), the top surface of one end of the irrigation cavity (18) is connected to the irrigation main pipe (11) in the irrigation well (10), and the other end of the irrigation cavity (18) is blocked by a plug (13). After the installation is completed, a cover plate is laid on the top of the multifunctional ditch (9), salt-alkali tolerant plants are planted in the soil modification pit (6), and carbon-based microbial fertilizer is backfilled, and then a drip irrigation pipe connected to the drip irrigation pipe irrigation branch pipe (8) is laid, and the water outlet of the drip irrigation pipe is located between two adjacent soil modification pits (6), and then a evaporation suppression burial layer is laid on the top of the drip irrigation pipe; S4, start the water pump (15) in the irrigation well (10), and the water in the shallow groundwater layer is pumped to one end of the irrigation cavity (18) through the irrigation main pipe (11), and flows toward one end of the plug (13). During the flow, the irrigation water enters the ditch body (5) through the irrigation branch pipe (8) to implement irrigation operations, and the shallow groundwater level is lowered by groundwater irrigation, and at the same time, a water source is provided for the salt washing operation of the saline-alkali land; S5. When the groundwater irrigation operation is in operation, the irrigation water irrigates and flushes the soil around the roots of the salt-alkali tolerant plants, flushes the salt in the soil and then infiltrates into the lower layer. The infiltrated water is collected through the drainage concealed pipe (3) and then flows back to the drainage cavity (17), and then flows back to the drainage well (14) through the canal outlet (19); S6. Start the water pump (16) installed in the drainage well (14), extract the saline-alkali water through the saline-alkali water output pipe (12) and transport it to the saline-alkali water purification equipment. When the shallow groundwater level drops to the warning value, the clean water obtained after thorough purification is refilled into the irrigation well (10). The saline-alkali land is modified through a circulation method of shallow water irrigation, soil surface salt flushing, saline-alkali water underground pipe collection and drainage, and saline-alkali water purification and backfilling.

2. A saline-alkali land modification structure, comprising saline-alkali land to be modified, characterized in that: A square retaining wall (1) is arranged on the saline-alkali land to be modified. An irrigation well (10) and a drainage well (14) are excavated at diagonal positions inside the square retaining wall (1). A multifunctional ditch (9) is connected between the irrigation well (10) and the drainage well (14). An isolation plate (7) is horizontally arranged in the middle and upper part of the multifunctional ditch (9). The upper part of the isolation plate (7) is an irrigation cavity (18). The lower part of the isolation plate (7) is a drainage cavity (17). One end of the top of the irrigation cavity (18) is connected to the installation cavity. The irrigation main pipe (11) in the irrigation well (10) is connected, a plug (13) is arranged at the other end of the top of the irrigation cavity (18), one end of the drainage cavity (17) is connected to the middle of the drainage well (14), and a ridge body (2) and a ditch body (5) adjacent to each other are arranged on the surface of the saline-alkali land to be modified, a drainage concealed pipe (3) connected to the drainage cavity (17) is arranged below the ridge body (2), and an irrigation branch pipe (8) connected to the irrigation cavity (18) is arranged at one end of the upper part of the ditch body (5).

3. The saline-alkali land modification structure according to claim 1, characterized in that: The multifunctional ditch (9) divides the saline-alkali land to be modified inside the square retaining wall (1) into two triangular structures, the ridge body (2) is symmetrically arranged on both sides of the multifunctional ditch (9), the drainage concealed pipes (3) installed below the ridge body (2) are symmetrically arranged on both sides of the drainage cavity (17), the ditch body (5) is symmetrically arranged on both sides of the multifunctional ditch (9), and the irrigation branch pipes (8) installed at one end of the upper part of the ditch body (5) are symmetrically arranged on both sides of the irrigation cavity (18).

4. The saline-alkali land modification structure according to claim 1, characterized in that: A plurality of soil modification pits (6) are evenly arranged at the bottom of the ditch body (5), the soil modification pits (6) are filled with carbon-based microbial fertilizer, a evaporation suppression burial layer is laid in the ditch body (5) above the carbon-based microbial fertilizer, and the irrigation branch pipe (8) is connected to the drip irrigation pipe laid in the evaporation suppression burial layer.

5. The saline-alkali land modification structure according to claim 1, characterized in that: The bottom of the irrigation well (10) is connected to a shallow groundwater layer. A water pump (15) connected to an irrigation main pipe (11) is arranged at the bottom of the irrigation well (10). A clean water source backfill pipeline is arranged on one side of the top of the irrigation main pipe (11).

6. The saline-alkali land modification structure according to claim 1, characterized in that: The side walls and the bottom of the drainage well (14) are both provided with an anti-seepage isolation layer. The bottom of the drainage well (14) is located below the multifunctional ditch (9). At the same time, the bottom of the drainage well (14) is located above the water level of the irrigation well (10). A water pump (16) is also installed in the drainage well (14). The water pump (16) is connected to the saline-alkali water output pipeline (12). The saline-alkali water output pipeline (12) is connected to the saline-alkali water purification equipment. The output end of the saline-alkali water purification equipment is connected to the top of the irrigation well (10) through a clean water drainage pipe with a three-way valve.

7. The saline-alkali land modification structure according to claim 1, characterized in that: The isolation plate (7) is a square plate structure, the top surface of the isolation plate (7) is not lower than the bottom surface of the ditch body (5), the bottom surface of the irrigation branch pipe (8) is located above the top surface of the isolation plate (7), and the outer side of the plug (13) is connected to the outer wall of the saline-alkali water drainage well (14).

8. The saline-alkali land modification structure according to claim 3, characterized in that: The ridge bodies (2) are symmetrically distributed on both sides of the multifunctional ditch (9) in a horizontal and vertical cross shape, and the ditch bodies (5) are symmetrically distributed on both sides of the multifunctional ditch (9) in a horizontal and vertical cross shape. The lengths of the ridge bodies (2) and the ditch bodies (5) gradually shorten from the irrigation well (10) to the drainage well (14). The outer side of the drainage well (14) is the ditch body (5), and the outer side of the irrigation well (10) is the ridge body (2). The height of the multifunctional ditch (9) gradually decreases from the irrigation well (10) to the drainage well (14).

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