A method and structure for modifying saline-alkali land

Abstract

The invention relates to a saline-alkali land modification method and structure. Irrigation wells and drainage wells are respectively excavated at diagonal positions on the inner side of a square retaining wall. A multifunctional ditch is connected between the irrigation well and the drainage well. An isolation plate is horizontally arranged at the middle and upper part of the multifunctional ditch in the longitudinal direction. The upper part of the isolation plate is an irrigation cavity, and 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 the upper end of the ditch body. The dual functions of upper irrigation and lower drainage are realized through a multifunctional ditch. In conjunction with the design of the ridge body and the ditch body at the top, the specific soil is modified by using carbon-based microbial fertilizer added to the roots of salt-alkali tolerant plants.

Description

Technical Field

[0001] The present invention relates to the field of soil treatment, and particularly to a method and structure for modifying saline-alkali soil. Background Art

[0002] Saline-alkali soil refers to soil in which the salt content affects the normal growth of crops. In China, the formation of saline-alkali soil is mostly related to the accumulation of carbonates in the soil, and plants can hardly survive in severely saline-alkali soil areas. The formation of saline-alkali soil is the result of the combined action of natural and human factors. Natural factors include climatic conditions, groundwater level, topographic conditions, and the influence of rivers and seawater. Climatic conditions such as small precipitation and large evaporation are likely to cause the accumulation of salts on the soil surface; the level and salt content of the groundwater will also affect the degree of soil salinization. High groundwater level and large salt content are likely to form soil salinization; topographic conditions such as low-lying terrain and poor drainage are likely to cause salt accumulation; the influence of rivers and seawater, such as lateral seepage of river water and seawater intrusion, will also form saline-alkali soil. Human factors such as improper irrigation: flood irrigation or only irrigation without drainage in low-lying areas, resulting in the rise of the groundwater level and salt accumulation. Over-extraction of groundwater in coastal areas: causing seawater intrusion into the groundwater, increasing the salinity of the groundwater.

[0003] Therefore, for the treatment of saline-alkali soil, it is necessary to implement the operations of diluting and discharging soil salts, and at the same time, attention should be paid to reducing the groundwater level, and comprehensive treatment should be carried out by taking into account the planting of salt-tolerant plants. During the operation of the treatment, attention should be paid to the structural layout of different regions, and the saline-alkali soil should be diluted and discharged by means of drainage ditches, buried pipes, etc. In terms of pipe drainage of salts, the traditional method is to discharge the salts in the soil through buried pipes by means of natural precipitation to achieve the purpose of soil desalination and salt drainage. In terms of controlling the groundwater level, the traditional method is to lower the groundwater level below the deep layer through buried pipes, so as to effectively control the groundwater level and prevent secondary salinization of the soil. The traditional two-stage buried pipe salt drainage method of suction pipes plus accumulation pipes has certain defects: the laying of buried pipes requires a large amount of manual operation, especially the laying of buried pipe devices for lowering the groundwater level is more difficult, and the overall project is costly and expensive. There are also certain defects in the setting of the secondary pipes of the salt drainage pipes. The two-stage buried pipe structure is relatively complex, requires the setting of multiple passages for connection, and has the defect of poor water absorption and drainage effects.

[0004] Therefore, the present invention provides a saline-alkali soil modification method and structure that are simple and easy to operate, can achieve on-site irrigation dilution and purification water backfill to control the lowest groundwater level, realize the recycling and protection of water resources, can fully implement the dilution of upper soil salts, improve the efficiency of saline-alkali water drainage, integrate irrigation and saline-alkali water drainage through multi-functional ditches, make full use of the self-structure of saline-alkali soil, can realize the parallel operation of saline-alkali soil modification in different regions, save costs overall, reduce the construction difficulty, and are efficient and convenient, and have a broad market prospect. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a method that is simple and easy to operate, realizes on-site irrigation dilution and purification of water backfill to control the lowest groundwater level, realizes the recycling and protection of water resources, can fully implement the dilution of upper soil salts, improve the drainage efficiency of saline-alkali water, integrates irrigation and saline-alkali water drainage through a multi-functional ditch, makes full use of the self-structure of saline-alkali land, can realize the regional parallel soil modification operation of saline-alkali land, saves costs as a whole, reduces the 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 realized as follows: A method for modifying saline-alkali land, the method comprising the following steps:

[0007] S1. Implement regional division of the saline-alkali land to be modified through a square water retaining wall, then dig an irrigation well and a drainage well at the diagonal positions within the divided area of a single saline-alkali land to be modified, and dig a multi-functional ditch at the connecting position of the irrigation well and the drainage well. After that, install a partition board in the multi-functional ditch to divide the multi-functional ditch into an upper irrigation chamber and a lower drainage chamber;

[0008] S2. Symmetrically and equally dig a number of deep trenches on both sides of the multi-functional ditch, the depth of the deep trenches being 1.5 to 2 meters, lay drainage pipes in the deep trenches, install water retaining plugs at the outer ends of the drainage pipes, and connect the inner ends of the drainage pipes to the drainage chamber. After completion of the laying, backfill the soil, construct ridges at the top surface positions above each drainage pipe, form a ditch body between adjacent rows of ridges, evenly arrange soil modification pits at the bottom of the ditch body, and connect one end of the drainage chamber to the middle of the drainage well through a water channel outlet;

[0009] S3. Install an irrigation branch pipe on the outer wall of the multi-functional ditch on one side of the top surface of the ditch body, connect the irrigation branch pipe to the irrigation chamber, connect the top surface of one end of the irrigation chamber to the irrigation main pipe in the irrigation well, block the other end of the irrigation chamber with a plug. After installation, lay a cover plate on the top of the multi-functional ditch, plant salt-tolerant plants in the soil modification pits, backfill carbon-based microbial fertilizer, then lay a drip irrigation pipe connected to the irrigation branch pipe of the drip irrigation pipe, the water outlet of the drip irrigation pipe being located between two adjacent soil modification pits, and then lay an evaporation suppression burial layer on the top of the drip irrigation pipe;

[0010] S4. Start the water pump in the irrigation well, pump the water in the shallow groundwater layer to one end of the irrigation chamber through the irrigation main pipe, and flow towards the plug end. During the flowing process, the irrigation water enters the ditch body through the irrigation branch pipe to carry out irrigation operations, reduce the shallow groundwater level through groundwater irrigation, and at the same time provide water source for the salt flushing operation of the saline-alkali land;

[0011] S5. During the operation of groundwater irrigation, the irrigation water flushes the soil around the roots of the salt-tolerant plants, and after flushing the salt in the soil, it penetrates to the lower layer. The infiltrated water is collected by the subsurface drainage pipe and flows back to the drainage cavity, and then flows back to the drainage well through the water channel outlet.

[0012] S6. Turn on the water pump installed in the drainage well, pump out the saline-alkali water through the saline-alkali water output pipeline and transport it to the saline-alkali water purification equipment. When the shallow groundwater level drops to the warning value, then refill the clean water obtained after thorough purification back into the irrigation well. The saline-alkali land is modified by means of a cycle of shallow water irrigation, soil surface salt flushing, subsurface drainage of saline-alkali water collection, and backfilling after saline-alkali water purification.

[0013] A saline-alkali land modification structure includes the saline-alkali land to be modified. A square water retaining wall is arranged on the saline-alkali land to be modified. An irrigation well and a drainage well are respectively excavated at the diagonal positions inside the square water retaining wall. A multi-functional ditch is connected between the irrigation well and the drainage well. A partition board is horizontally arranged in the upper middle part of the longitudinal direction of the multi-functional ditch. The upper part of the partition board is the irrigation cavity, and the lower part of the partition board is the drainage cavity. One end of the top of the irrigation cavity is connected to the irrigation main pipe installed in the irrigation well, and 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 part of the drainage well. The surface of the saline-alkali land to be modified is provided with adjacent ridge bodies and ditch bodies. A subsurface drainage pipe communicated with the drainage cavity is arranged below the ridge body. One end of the upper part of the ditch body is provided with an irrigation branch pipe communicated with the irrigation cavity.

[0014] Further, the multi-functional ditch divides the saline-alkali land to be modified inside the square water retaining wall into two triangular structures. The ridge bodies are symmetrically arranged on both sides of the multi-functional ditch. The subsurface drainage pipes installed below the ridge bodies are symmetrically arranged on both sides of the drainage cavity. The ditch bodies are symmetrically arranged on both sides of the multi-functional ditch. The irrigation branch pipes installed at one end of the upper part of the ditch bodies are symmetrically arranged on both sides of the irrigation cavity.

[0015] Further, a number of soil modification pits are evenly arranged at the bottom of the ditch body. Carbon-based microbial bacterial fertilizer is filled in the soil modification pits. An evaporation suppression burial layer is laid in the ditch body above the carbon-based microbial bacterial fertilizer. The irrigation branch pipe is communicated with the drip irrigation pipe laid in the evaporation suppression burial layer.

[0016] Further, the bottom of the irrigation well is communicated with the shallow groundwater layer. A water pump communicated with the irrigation main pipe is arranged at the bottom of the irrigation well. A clean water backfill pipeline is arranged on one side of the top of the irrigation main pipe.

[0017] Furthermore, anti-seepage isolation layers are provided on both the side wall and the bottom of the drainage well. The bottom of the drainage well is located below the multi-functional 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 installed in the drainage well. 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 of a square plate-like 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. The outer side of the plug is connected to the outer wall of the saline-alkali water drainage well.

[0019] Furthermore, the ridge bodies are symmetrically distributed on both sides of the multi-functional ditch in a horizontal and vertical cross-shaped pattern. The ditch bodies are symmetrically distributed on both sides of the multi-functional ditch in a horizontal and vertical cross-shaped pattern. The lengths of the ridge bodies and the ditch bodies gradually shorten from the irrigation well to the drainage well. 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 multi-functional ditch gradually decreases from the irrigation well to the drainage well side.

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

[0021] First of all, in the saline-alkali land modification method of the present invention, the saline-alkali land is modified by a cycle of shallow water irrigation, soil surface salt flushing, saline-alkali water collection and drainage through buried pipes, and backfilling after saline-alkali water purification. A water retaining wall is formed to divide individual modification areas, and then short-distance scientific irrigation operations are carried out within the individual modification areas. The salts in the soil are flushed out by irrigation water and then recycled. The recycling process uses buried drainage pipes to recycle and discharge them into the multi-functional ditch. The upper part of the multi-functional ditch is an irrigation cavity. Shallow groundwater is led out through the irrigation cavity for irrigation operations. The multi-functional ditch realizes the dual functions of upper irrigation and lower drainage. With the design of the ridge bodies and ditch bodies on the top, the carbon-based microbial fertilizer added to the roots of salt-tolerant plants is used to modify the specific soil, and the root exudates during the plant growth process are used to modify the saline-alkali soil. Combined with salt flushing and drainage operations, the saline-alkali land soil is gradually and comprehensively modified. At the same time, in order to ensure that the groundwater level is not lower than the warning red line, the extracted saline-alkali water is purified and then backfilled into the irrigation well, which helps to maintain the ecological health of the overall groundwater in the saline-alkali land.

[0022] Secondly, the present invention provides a saline-alkali land modification structure. The saline-alkali land to be modified within a single area is divided into two triangular areas by a square water retaining wall and a multi-functional ditch, and a symmetrical structure of ridges, ditches, subsurface drainage pipes and irrigation branch pipes is arranged in the two triangular areas. The multi-functional ditch is designed at a 45-degree angle with the structures on both sides, reducing the drainage travel of saline-alkali water. Through the method of draining diagonally from the proximal end to the middle of the square water retaining wall, the efficient discharge of saline-alkali water is realized, avoiding excessive infiltration of saline-alkali water into the deep soil during the drainage process and preventing pollution of shallow groundwater. At the same time, the method of triangular area division also facilitates the uniform proximal irrigation of the upper irrigation cavity towards both ends. The ditch bodies on both sides of the irrigation cavity facing the irrigation well have the longest length to realize the proximal irrigation operation of the longer ditch bodies, and the ditch bodies on both sides of the irrigation cavity facing the drainage well have the shortest length to realize the distal irrigation operation of the shorter ditch bodies. At the same time, the distal irrigation position is close to the drainage well, improving the irrigation water use efficiency and fully realizing the conservation and utilization of water resources. The multi-functional ditch is arranged in an inclined shape and gradually decreases towards the drainage well position to realize the dual efficient flow operation of irrigation water and saline-alkali water.

[0023] Thirdly, the square water retaining wall of the present invention can be used in parallel, series and array expansion. According to the area of the saline-alkali land area, planning operations are carried out, and the specific number of irrigation wells and drainage wells is planned. The expansion use can be implemented by sharing one irrigation well or drainage well in two or more sub-divided areas, so as to implement a comprehensive modification structure layout for the entire saline-alkali area. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0027] Figure 4 It is a front view structural schematic diagram of the multi-functional 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 alkali land modification structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] In the following description of the invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. The term "connection" only represents the connection between devices and has no special meaning.

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

[0032] S1. Implement regional division of the saline-alkali land to be modified through the square water retaining wall 1, then excavate the irrigation well 10 and the drainage well 14 at the diagonal positions within the divided area of a single saline-alkali land to be modified, and excavate the multi-functional ditch 9 at the connection position of the irrigation well 10 and the drainage well 14. Then install the isolation board 7 in the multi-functional ditch 9 to divide the multi-functional ditch 9 into the upper irrigation cavity 18 and the lower drainage cavity 17;

[0033] S2. Symmetrically and equally excavate a number of deep ditches on both sides of the multi-functional ditch 9. The depth of the deep ditches is 1.5 to 2 meters, and lay the drainage blind pipe 3 in the deep ditches. Install the water retaining plug 4 at the outer end of the drainage blind pipe 3, and connect the inner end of the drainage blind pipe 3 to the drainage cavity 17. After completion of the laying, backfill the soil. Construct the ridge body 2 at the top surface position above each drainage blind pipe 3. A ditch body 5 is formed between adjacent two rows of ridge bodies. Soil modification pits 6 are equally 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 water channel outlet 19;

[0034] S3. Install the irrigation branch pipe 8 on the outer wall of the multi-functional 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 the plug 13. After the installation is completed, lay the cover plate on the top of the multi-functional ditch 9. Plant salt-tolerant plants in the soil modification pits 6 and backfill the carbon-based microbial fertilizer. Then lay the drip irrigation pipe connected to the irrigation branch pipe 8. The water outlet of the drip irrigation pipe is located between two adjacent soil modification pits 6. Then lay the evaporation suppression burial layer on the top of the drip irrigation pipe;

[0035] S4. Turn on the water pump 15 in the irrigation well 10. The water in the shallow groundwater layer is pumped to one end of the irrigation chamber 18 through the main irrigation pipe 11 and flows towards one end of the plug 13. During the flowing process, the irrigation water enters the trench body 5 through the irrigation branch pipe 8 to carry out irrigation operations. By means of groundwater irrigation, the shallow groundwater level is lowered, and at the same time, water source is provided for the operation of flushing salts in the saline-alkali land.

[0036] S5. When the groundwater irrigation operation is running, the irrigation water irrigates and flushes the soil around the roots of the salt-tolerant plants. After the salts in the soil are flushed, they penetrate to the lower layer. The infiltrated water is collected by the subsurface drainage pipe 3 and flows back to the drainage chamber 17, and then flows back to the drainage well 14 through the water channel outlet 19.

[0037] S6. Turn on the water pump 16 installed in the drainage well 14, pump out 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 re-filled into the irrigation well 10. The saline-alkali land is modified by means of the cycle of shallow water irrigation, soil surface salt flushing, subsurface drainage of saline-alkali water and backfilling after saline-alkali water purification.

[0038] As Figures 1-5 shown, a saline-alkali land modification structure includes the saline-alkali land to be modified. A square water retaining wall 1 is arranged on the saline-alkali land to be modified. An irrigation well 10 and a drainage well 14 are respectively excavated at the diagonal positions inside the square water retaining wall 1. A multi-functional ditch 9 is connected between the irrigation well 10 and the drainage well 14. A partition board 7 is horizontally arranged in the upper middle part of the longitudinal direction of the multi-functional ditch 9. The upper part of the partition board 7 is the irrigation chamber 18, and the lower part of the partition board 7 is the drainage chamber 17. One end of the top of the irrigation chamber 18 is connected to the main irrigation pipe 11 installed in the irrigation well 10, and the other end of the top of the irrigation chamber 18 is provided with a plug 13. One end of the drainage chamber 17 is communicated with the middle part of the drainage well 14. Ridges 2 and trench bodies 5 which are adjacent to each other are arranged on the surface of the saline-alkali land to be modified. A subsurface drainage pipe 3 communicated with the drainage chamber 17 is arranged below the ridges 2. One end of the upper part of the trench body 5 is provided with an irrigation branch pipe 8 communicated with the irrigation chamber 18.

[0039] Specifically, the construction of the square water retaining wall 1 is implemented according to the actual area of the saline-alkali land to be modified. The square water retaining wall 1 can be set as one or a structure with a parallel, series or array layout. The square water retaining wall 1 can carry out water retaining operations on the ditch position during irrigation operations, avoiding water overflow to the outside of the modified position when using water for irrigation. The irrigation well 10 and the drainage well 14 are opened diagonally, which can cover all positions within the area of the square water retaining wall 1. The multi-functional ditch is not arranged at the diagonal position of the irrigation well 10 and the drainage well 14. Through this setting, the installation length of the drainage culvert can be saved. In the two triangular areas on both sides of the multi-functional 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 multi-functional ditch 9 is partitioned by the isolation board 7. After partitioning, the upper and lower parts are respectively used for the output of irrigation water and the drainage output of saline water, saving the pipeline laying length. The irrigation path and the drainage path are efficiently integrated in a way of using one ditch for multiple purposes, reducing the pipeline laying workload. Compared with the traditional separate laying of the unilateral drainage ditch and the irrigation pipeline, 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. The soil surface pattern is designed through the undulating ground surface, which helps the variable-layer salt to infiltrate efficiently with the irrigation water during irrigation operations and be collected through the drainage culvert. 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 gathers through the ditch body 5, improving the guiding property of the irrigation water flow. Cooperating with the irrigation branch pipe 8 and the drainage culvert 3, an efficient soil saline water flushing effect is formed as a whole.

[0042] The multi-functional ditch 9 divides the saline-alkali land to be modified inside the square water retaining wall 1 into two triangular structures. The ridge bodies 2 are symmetrically arranged on both sides of the multi-functional ditch 9. The drainage culverts 3 installed under 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 multi-functional ditch 9. 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 in a horizontal and vertical cross shape on both sides of the multi-functional ditch 9. The ditch bodies 5 are symmetrically distributed in a horizontal and vertical cross shape on both sides of the multi-functional ditch 9. 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 outside of the drainage well 14 is the ditch body 5, and the outside of the irrigation well 10 is the ridge body 2. The height of the multi-functional ditch 9 gradually decreases from the irrigation well 10 to the drainage well 14.

[0043] Specifically, the lengths of the drainage pipes 3 on both sides of the multi-functional ditch 9 gradually decrease, with the length gradually shortening from the end of the multi-functional ditch 9 close to the irrigation well 10 to the other end. The symmetric layout helps with the later planting and maintenance of salt-tolerant plants and enables convenient and efficient irrigation. The drainage pipes 3 are located in the lower layer and are connected to the drainage cavity 17, while the irrigation branch pipes 8 are located in the upper layer and are connected to the irrigation cavity 18. By separating the upper and lower layers, drainage and irrigation are integrated into a single multi-functional ditch 9, saving space and improving efficiency.

[0044] A number of soil modification pits 6 are evenly arranged at the bottom of the ditch body 5. Carbon-based microbial fertilizer is filled in the soil modification pits 6, and an evaporation suppression burial layer is laid in the ditch body 5 above the carbon-based microbial fertilizer. The irrigation branch pipes 8 are connected to the drip irrigation pipes laid in the evaporation suppression burial layer. Specifically, the soil modification pits 6 are dug in advance. When in use, salt-tolerant plants are planted inside, and then backfilled with a mixture of carbon-based microbial fertilizer and the original soil. After the drip irrigation pipes are laid, the evaporation suppression burial layer is covered. During irrigation operation, it is ensured that the irrigation water can efficiently act on the roots of salt-tolerant plants through the ditch body, and the salt in the soil is carried away by the irrigation water during infiltration and finally discharged to the drainage cavity through the drainage pipes. To ensure that the nutrients in the carbon-based microbial fertilizer in the soil are not carried away, drip irrigation operations are carried out at the soil positions between two salt-tolerant plants, and the nutrients in the carbon-based microbial fertilizer are slowly released to avoid being carried 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 provided at the bottom of the irrigation well 10, and a clean water backfill pipe is provided on one side of the top of the irrigation main pipe 11. The side wall and bottom of the drainage well 14 are provided with anti-seepage isolation layers. The bottom of the drainage well 14 is located below the multi-functional ditch 9 and 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 pipe 12, and the saline water output pipe 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 drain pipe with a three-way valve. The partition board 7 has a square plate-like structure. The top surface of the partition board 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 partition board 7. The outer side of the plug 13 is connected to the outer wall of the saline water drainage well 14.

[0046] Specifically, when the shallow groundwater level drops to the warning value, the saline-alkali water pumped out from the drainage well 14 is thoroughly purified and then used for backfilling. During the backfilling process, the groundwater level needs to be monitored to avoid the aggravation of upper-layer salinization caused by too high water level. The purification treatment of saline-alkali water adopts multi-stage filtration combined with an ultrafiltration device to thoroughly remove sediment and salt, and perform disinfection, filtration, and purification treatment to ensure the cleanliness of the backfilled water resources.

[0047] Example 1: As Figure 1 , 2 , 3, and 4 show, in this example, a square water retaining wall is used to surround all the saline-alkali land to be modified. This example is suitable for the modification operation of saline-alkali land with a small area. When implementing the saline-alkali land modification operation, the square water retaining wall 1 is used to surround all the saline-alkali land to be modified, playing a role in blocking water around during the irrigation operation. Irrigation wells 10 and drainage wells 14 are excavated at the diagonal positions inside the square water retaining wall 1, and a multi-functional ditch 9 is excavated at the connection position of the irrigation well 10 and the drainage well 14. Then, a partition board 7 is installed in the multi-functional ditch 9 to divide the multi-functional ditch 9 into an upper irrigation chamber 18 and a lower drainage chamber 17. The depth of the irrigation chamber 18 is not greater than the depth of the drainage chamber 17. The top surface of the partition board 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 partition board 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 an upper independent irrigation channel structure for the irrigation chamber 18.

[0048] A number of deep ditches are symmetrically and equally excavated on both sides of the multi-functional ditch 9. The depth of the deep ditches is 1.5 to 2 meters, and drainage pipes 3 are laid in the deep ditches. A water-blocking plug 4 is installed at the outer end of the drainage pipe 3. The inner end of the drainage pipe 3 is connected to the drainage chamber 17. After the laying is completed, the soil is backfilled. Ridges 2 are constructed at the top surface position above each drainage pipe 3. A ditch body 5 is formed between adjacent rows of ridges. Soil modification pits 6 are equally arranged at the bottom of the ditch body 5. One end of the drainage chamber 17 is connected to the middle of the drainage well 14 through a water channel outlet 19. The multi-functional ditch 9 divides the saline-alkali land to be modified inside the square water retaining wall 1 into two triangular structures. The ridges 2 are symmetrically arranged on both sides of the multi-functional ditch 9. The drainage pipes 3 installed below the ridges 2 are symmetrically arranged on both sides of the drainage chamber 17. The ditch bodies 5 are symmetrically arranged on both sides of the multi-functional ditch 9. The irrigation branch pipes 8 installed at one upper end of the ditch bodies 5 are symmetrically arranged on both sides of the irrigation chamber 18.

[0049] The ridges 2 are symmetrically distributed in a horizontal and vertical cross shape on both sides of the multi-functional ditch 9. The ditch bodies 5 are symmetrically distributed in a horizontal and vertical cross shape on both sides of the multi-functional ditch 9. The lengths of the ridges 2 and the ditch bodies 5 gradually shorten from the irrigation well 10 to the drainage well 14. The outside of the drainage well 14 is the ditch body 5, and the outside of the irrigation well 10 is the ridge 2. The height of the multi-functional ditch 9 gradually decreases from the irrigation well 10 to the drainage well 14 side.

[0050] An irrigation branch pipe 8 is installed on the outer wall of the multi-functional ditch 9 on one side of the top surface of the ditch body 5. The irrigation branch pipe 8 is communicated with the irrigation cavity 18. One end of the top surface of the irrigation cavity 18 is communicated with 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 installation, a cover plate is laid on the top of the multi-functional ditch 9. Salt-tolerant plants are planted in the soil modification pit 6, and carbon-based microbial fertilizer is backfilled. Then, a drip irrigation pipe communicated with the irrigation branch pipe 8 of the drip irrigation pipe is laid. The water outlet of the drip irrigation pipe is located between two adjacent soil modification pits 6. Then, an 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. Carbon-based microbial fertilizer is filled in the soil modification pits 6. An evaporation suppression burial layer is laid in the ditch body 5 above the carbon-based microbial fertilizer. The irrigation branch pipe 8 is communicated with the drip irrigation pipe laid in the evaporation suppression burial layer.

[0051] The water pump 15 in the irrigation well 10 is turned on. 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 towards the end of the plug 13. During the flowing process, the irrigation water enters the ditch body 5 through the irrigation branch pipe 8 to carry out irrigation operations. The shallow groundwater level is lowered by the way of groundwater irrigation, and at the same time, water sources are provided for the operation of flushing salts in saline-alkali land. When the groundwater irrigation operation is running, the irrigation water irrigates and flushes the soil around the roots of the salt-tolerant plants. After the salts in the soil are flushed, they penetrate to the lower layer. The permeated water is collected by the drainage blind pipe 3 and flows back to the drainage cavity 17, and then flows back to the drainage well 14 through the water channel outlet 19. Anti-seepage isolation layers are arranged on the side wall and the bottom of the drainage well 14. The bottom of the drainage well 14 is located below the multi-functional 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 communicated with the saline-alkali water output pipe 12. The saline-alkali water output pipe 12 is communicated with 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.

[0052] The water pump 16 installed in the drainage well 14 is turned on. The saline-alkali water is pumped out through the saline-alkali water output pipe 12 and transported 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 re-filled into the irrigation well 10. The saline-alkali land is modified by means of a cycle of shallow water irrigation, soil surface salt flushing, saline-alkali water collection and drainage through the blind pipe, and backfilling after saline-alkali water purification.

[0053] As another embodiment of the present invention, such as Figure 5As shown in Figures 1-4, the difference from the first embodiment is that this embodiment is suitable for the modification of large areas of saline-alkali land. During specific operation, the square water retaining wall 1 performs the modification operation of dividing areas on the large area of saline-alkali land. Moreover, multiple square water retaining walls 1 are arranged in an array structure. As Figure 5 shown, it is a top view of the connection of four square water retaining walls 1. The drainage wells 14 of the four square water retaining walls 1 are arranged at the center of the saline-alkali land to be modified. The four square water retaining walls 1 share one drainage well 14. The multi-functional ditches 9 of each square water retaining wall 1 extend towards the center of the saline-alkali land to be modified. The four multi-functional ditches 9 are dug from the four corner positions of the whole saline-alkali land to be modified towards the center of the saline-alkali land with gradually decreasing heights. The four multi-functional 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 water retaining walls 1 are connected to form a whole, forming a cross structure on the whole saline-alkali land to be modified. During the specific use process, the connection position of the square water retaining wall 1 on the inner side of the edge position can also be cancelled, and the inner side areas of the four square water retaining walls 1 form a whole flat structure. The ridge body 2, the ditch body 5, and the drainage pipe 3 all form a square structure and are interconnected, improving the irrigation efficiency and drainage efficiency, so that when the irrigation water meets the basic irrigation requirements, the surplus accumulated water can quickly carry away the soil salt and be discharged into the drainage well 14 arranged at the center position.

[0054] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for modifying saline-alkali land, comprising saline-alkali land to be modified, wherein 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 respectively 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), and the top of the irrigation cavity (18) is One end of the drainage cavity (17) is connected to an irrigation main pipe (11) installed in an irrigation well (10); the other end of the top of the irrigation cavity (18) is provided with a plug (13); one end of the drainage cavity (17) is connected to the middle of the drainage well (14); a ridge body (2) and a ditch body (5) adjacent to each other are provided on the surface of the saline-alkali land to be modified; a drainage concealed pipe (3) connected to the drainage cavity (17) is provided below the ridge body (2); an irrigation branch pipe (8) connected to the irrigation cavity (18) is provided at one end of the upper part of the ditch body (5); the invention is characterized in that: The method includes the following steps: S1. Divide the saline-alkali land to be modified into regions by means of a square water retaining wall (1). Then, dig an irrigation well (10) and a drainage well (14) at the diagonal positions within the divided region of a single saline-alkali land to be modified, and dig a multi-functional ditch (9) at the position connecting the irrigation well (10) and the drainage well (14). After that, install a partition board (7) in the multi-functional ditch (9) to divide the multi-functional ditch (9) into an upper irrigation cavity (18) and a lower drainage cavity (17); S2. Symmetrically and equally dig a number of deep ditches on both sides of the multi-functional ditch (9). The depth of the deep ditches is 1.5 to 2 meters, and lay drainage pipes (3) in the deep ditches. Install water retaining plugs (4) at the outer ends of the drainage pipes (3). The inner ends of the drainage pipes (3) are connected to the drainage cavity (17). After completion of the laying, backfill the soil. Construct ridges (2) at the top surface positions above each drainage pipe (3). A ditch body (5) is formed between two adjacent rows of ridges. Soil modification pits (6) are equally 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 a water channel outlet (19); S3. Install an irrigation branch pipe (8) on the outer wall of the multi-functional 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). One end of the top surface of the irrigation cavity (18) is connected to an 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, lay a cover plate on the top of the multi-functional ditch (9). Plant salt-tolerant plants in the soil modification pits (6), and backfill carbon-based microbial fertilizers. Then, lay a drip irrigation pipe connected to the irrigation branch pipe (8) of the drip irrigation pipe. The water outlet of the drip irrigation pipe is located between two adjacent soil modification pits (6). Then, lay an evaporation suppression burial layer on the top of the drip irrigation pipe; S4. Start the water pump (15) in the irrigation well (10). 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 towards the end of the plug (13). During the flowing process, the irrigation water enters the ditch body (5) through the irrigation branch pipe (8) to perform irrigation operations. The shallow groundwater level is lowered by means of groundwater irrigation, and at the same time, water sources are provided for the operation of flushing salts from the saline-alkali land; S5. During the operation of groundwater irrigation, the irrigation water irrigates and flushes the soil around the roots of the salt-tolerant plants. After the salts in the soil are flushed, they penetrate to the lower layer. The penetrated water is collected by the drainage pipes (3) and flows back to the drainage cavity (17), and then flows back to the drainage well (14) through the water channel outlet (19); S6. Start the water pump (16) installed in the drainage well (14). Pump out the saline-alkali water through the saline-alkali water output pipeline (12) and transport it to the saline-alkali water purification equipment. When the shallow groundwater level drops to the warning value, then refill the clean water obtained after thorough purification back into the irrigation well (10). Modify the saline-alkali land by means of a cycle of shallow water irrigation, flushing of soil surface salts, collection and drainage of saline-alkali water through the drainage pipes, and backfilling after purification of the saline-alkali water.

2. The saline-alkali land modification method according to claim 1, characterized in that: The described multi-functional ditch (9) divides the saline-alkali land to be modified inside the square water retaining wall (1) into two triangular structures. The ridge bodies (2) are symmetrically arranged on both sides of the multi-functional ditch (9). The subsurface drainage 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 multi-functional ditch (9). 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).

3. The saline-alkali land modification method according to claim 1, characterized in that: Several soil modification pits (6) are evenly arranged at the bottom of the described ditch body (5). Carbon-based microbial fertilizer is filled in the soil modification pits (6). An evaporation suppression burial layer is laid in the ditch body (5) above the carbon-based microbial fertilizer. The irrigation branch pipe (8) is communicated with the drip irrigation pipe laid in the evaporation suppression burial layer.

4. The saline-alkali land modification method according to claim 1, characterized in that: The bottom of the described irrigation well (10) is communicated with the shallow groundwater layer. A water pump (15) communicated with the irrigation main pipe (11) is arranged at the bottom of the irrigation well (10). A clean water backfill pipe is arranged on one side of the top of the irrigation main pipe (11).

5. The saline-alkali land modification method according to claim 1, wherein: The side wall and the bottom of the described drainage well (14) are both provided with anti-seepage isolation layers. The bottom of the drainage well (14) is located below the multi-functional ditch (9). At the same time, the bottom of the drainage well (14) is 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 communicated with the saline-alkali water output pipe (12). The saline-alkali water output pipe (12) is communicated with the saline-alkali water purification equipment. The output end of the saline-alkali water purification equipment is communicated with the top of the irrigation well (10) through a clean water drain pipe with a three-way valve.

6. The saline-alkali land modification method according to claim 1, characterized in that: The described isolation plate (7) is a square plate-like 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).

7. The saline-alkali land modification method according to claim 2, wherein: The described ridge bodies (2) are symmetrically distributed in a horizontal and vertical cross shape on both sides of the multi-functional ditch (9). The described ditch bodies (5) are symmetrically distributed in a horizontal and vertical cross shape on both sides of the multi-functional ditch (9). 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 outside of the drainage well (14) is the ditch body (5). The outside of the irrigation well (10) is the ridge body (2). The height of the multi-functional ditch (9) gradually decreases from the irrigation well (10) to the drainage well (14).

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