Treatment method and treatment system for saline-alkali soil

Abstract

In order to solve the technical problems that in the existing saline-alkali land treatment technology, fresh water irrigation and salt pressing need to be conducted on saline-alkali land regularly, and water sources are wasted, the saline-alkali land treatment system comprises a saline-alkali water returning device, and the saline-alkali water returning device comprises a water distribution pipe network and a plurality of buried dripping seepage pipes. The saline-alkali land treatment method comprises the step of distributing fresh water into the saline-alkali land to be treated, specifically, water is permeated to the position below the surface layer of the saline-alkali land to be treated through the buried dripping and permeating pipes, the water outlet ends of the water distribution pipe network are communicated with the buried dripping and permeating pipes, and then the saline-alkali land to be treated is treated through the buried dripping and permeating pipes. By adopting the saline-alkali soil treatment system and treatment method provided by the invention, water resources can be greatly saved, the saline-alkali water can be continuously desalted, and the salt content of the underground saline-alkali water can be reduced along with continuous water consumption, so that the saline-alkali soil can be radically treated.

Description

Technical Field

[0001] The present invention belongs to the technical field of saline-alkali land improvement, and particularly relates to a treatment method and a treatment system for saline-alkali land. Background Art

[0002] When the salt content in the soil affects the normal growth of crops, such land is called saline-alkali land. According to incomplete statistics of UNESCO and the Food and Agriculture Organization, the area of saline-alkali land in the world is 950 million hectares, of which 99.13 million hectares are in China. The formation of alkali soil and alkalized soil in China is mostly related to the accumulation of carbonates in the soil, so the alkalization degree is generally high. In severely saline-alkali soil areas, plants can hardly survive, which makes the land resources unable to be effectively utilized. Moreover, due to the high salt and alkali content in the soil, it is very difficult for plants to grow normally, resulting in land desertification in the long term. Therefore, countries have increased their efforts in treating saline-alkali land. At present, the treatment of saline-alkali land mainly includes the following methods: In the initial stage of improvement, the focus should be on improving the water condition of the soil. Generally, it is carried out in several steps. First, drain salt, wash salt, and reduce the soil salt content; then plant salt-tolerant plants to fertilize the soil; finally, plant crops. The specific improvement measures are: drainage, irrigation and salt washing, silting improvement, rice planting, fertilization improvement, land leveling and chemical improvement. Control the water discharge volume. By using the above methods, since it is necessary to pre-drain the saline-alkali raw water in the soil and then irrigate the soil after draining the saline-alkali raw water with fresh water to wash the salt and alkali, a large amount of saline-alkali raw water needs to be discharged and a large amount of fresh water needs to be injected during this process, which is a waste of water resources and requires a high labor cost.

[0003] The formation of salinized land is mainly related to shallow underground saline water. Since the shallow underground saline water occupies the shallow geological space of the formation and hinders the formation from storing atmospheric precipitation and surface fresh water, after years of evaporation and concentration, it becomes the root cause of land salinization. Land salinization has caused a large number of low-yield fields and abandoned land, making a large area of land resources unavailable. Therefore, it is necessary to study the technology suitable for the transformation of shallow saline land, replace saline water with fresh water and recycle it, which can not only solve the problem of drought and water shortage but also treat the saline land comprehensively, so that the shallow saline land can restore its development and utilization value. For example, a Chinese invention patent with the patent number 201710568054.1 and the authorized announcement number 107653931 discloses a saline land transformation system and method. The system includes a shallow water level well, a water collection well, a water collecting pipe, a water return pipe, a pump pipe, a jet injector, and a water collecting pipe. The water collecting pipe and the water return pipe are connected to the water collection well. The pump pipe is installed in the water collection well. The lower end of the pump pipe is connected to a submersible electric pump, and the upper end of the pump pipe is connected to the water inlet of the jet injector. After the water suction port of the jet injector passes through a tee, one path is connected to the water collecting pipe, and the other path is connected to the water collecting pipe leading to the shallow water level well. The water discharge port of the jet injector is connected to the water return pipe. The above system and method suck water from the formation through the set water collecting pipe and water return pipe by siphon superposition negative pressure and collect it in the water collection well, then pump out the water in the water collection well and inject external water source into the shallow water well to dilute the groundwater, so as to provide water source for large-area farmland irrigation. Although this method can solve the problem of lack of fresh water required for plant growth, it cannot fundamentally treat the saline land because the salt still remains underground and the saline water will still regularly penetrate into the tillage layer through soil capillary pores, and it is still necessary to irrigate fresh water to suppress salt regularly, which greatly wastes fresh water resources. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for treating saline land in view of the technical problem that the existing saline land treatment technology needs to regularly irrigate fresh water to suppress salt in the saline land, resulting in waste of water resources.

[0005] The technical solution for the present invention to solve the technical problem is as follows: A saline land treatment system includes a saline water returning-to-field device. The saline water returning-to-field device includes a water distribution pipe network and a plurality of buried drip infiltration pipes. The buried drip infiltration pipes are used to be arranged below the surface layer of the saline land to be treated. The water outlet ends of the water distribution pipe network are respectively connected to the buried drip infiltration pipes, and the water inlet end of the water distribution pipe network is used to receive fresh water obtained after desalination treatment of saline water; The saline water returning-to-field device further includes a pressure stabilizing tank. The pressure stabilizing tank has a tank body for storing water. The water inlet of the tank body is used to receive fresh water, and the water outlet is connected to the water inlet end of the water distribution pipe network. An air outlet hole is arranged on the tank body of the pressure stabilizing tank and is connected to the external atmosphere; It further includes a saline-alkali water desalination device which desalinates saline-alkali water to obtain concentrated brine and fresh water. The saline-alkali water desalination device includes a reverse osmosis device which converts saline-alkali water into concentrated brine and fresh water. Its concentrated brine outlet is connected to a concentrated brine tank, and its fresh water outlet is communicated with the water inlet of a pressure stabilizing tank. The saline-alkali water desalination device further includes a filtering device which filters impurities in the saline-alkali water. The filtering device includes a quartz sand filter, an activated carbon filter and a precision filter. The water inlet end of the quartz sand filter is connected to the water outlet end of a water pump, its water outlet end is connected to the water inlet end of the activated carbon filter, the water outlet end of the activated carbon filter is connected to the water inlet end of the precision filter, the water outlet end of the precision filter is connected to the water inlet end of the reverse osmosis device, the concentrated water outlet of the reverse osmosis device is connected to the inlet of the concentrated brine tank, and the fresh water outlet of the reverse osmosis device is connected to the water inlet of the fresh water tank. The water inlet end of the water pump is communicated with the saline-alkali water to be treated. It further includes a saline-alkali water collection device which collects and holds the saline-alkali water in the saline-alkali land. The water inlet end of the water pump is located in the saline-alkali water collection device. It further includes a saline-alkali water tank which is located between the water pump and the saline-alkali water collection device. A booster pump is provided between the saline-alkali water tank and the filtering device, and a high-pressure pump is provided between the water outlet end of the filtering device and the reverse osmosis device.

[0006] A method for treating saline-alkali land includes the step of distributing fresh water to the saline-alkali land to be treated. Fresh water is infiltrated below the surface layer of the saline-alkali land to be treated through buried drip irrigation pipes, so that the fresh water is evenly distributed below the surface layer. The infiltration depth is such that the water does not evaporate outward, and the water is evenly distributed below the surface layer. It also includes the steps of collecting saline-alkali water and desalinating the saline-alkali water. First, the saline-alkali water in the saline-alkali land to be treated is collected, and then the collected saline-alkali water is desalinated to obtain the fresh water, and then the fresh water is returned to the field according to the step of distributing fresh water described in claim 1. Before desalinating the saline-alkali water, the saline-alkali water is filtered to remove impurities in the saline-alkali water and then the saline-alkali water is desalinated. At least inject water into the saline-alkali land to be treated and returned to the field twice and repeat the above steps; and / or plant crops on the saline-alkali land in the area to be treated after the fresh water is returned to the field, so that the crops absorb the saline-alkali fertilizers in the soil.

[0007] The advantages and beneficial effects of the present invention are: By using the saline-alkali land treatment system and treatment method proposed by the present invention, since the micro-infiltration irrigation technology is adopted to accurately deliver fresh water into the saline-alkali land, water resources can be greatly saved. Moreover, since fresh water is delivered below the soil surface layer through the micro-infiltration technology, it can prevent the saline-alkali water below the ground surface from moving upward to the ground surface. The fresh water layer in the plough layer soil is below the ground surface, which will greatly reduce the evaporation of water, greatly reduce the amount of fresh water used, and by continuously distributing water below the ground surface, it can inhibit the penetration of saline-alkali water into the plough layer through soil capillary pores, and can continuously desalinate the saline-alkali water, so as to fundamentally treat the saline-alkali land.

[0008] By using the saline-alkali land treatment system and treatment method of the present invention, the saline-alkali water desalination device is used to desalinate the saline-alkali water, and the desalinated water is sent into the buried drip infiltration pipe. The required fresh water does not need to be supplemented by external fresh water. Instead, the existing saline-alkali water in the system is converted into fresh water and the salt is removed through the equipment host. Therefore, the salt content of the saline-alkali water below the ground surface will become less and less with continuous water use, so that the saline-alkali land can be completely cured. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a block diagram of the saline-alkali land treatment system of the present invention; Figure 2 It is a block diagram of the structure of the saline-alkali water desalination device of the saline-alkali land treatment system. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be further described in detail below through specific embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0011] Such as Figure 1 And Figure 2As shown in the figure, the method for treating saline-alkali land of the present invention includes the steps of collecting the raw saline-alkali water from the saline-alkali land to be treated and pumping out the raw saline-alkali water. Through this step, the raw saline-alkali water is collected in one or more designated areas, which form the water intake points around the saline-alkali land to be treated, hereinafter referred to as water intake points, and the collected raw saline-alkali water is pumped out from the water intake points. It also includes the step of desalinating the pumped raw saline-alkali water to separate the salt and alkali from the water. Through the saline-alkali water desalination technology, the salt and alkali are separated from the water to obtain two substances: salt and alkali, and fresh water with low or no salt and alkali content. The third step is to disperse and reflux the obtained fresh water to below the surface layer through micro-infiltration irrigation technology, so that the fresh water evenly infiltrates below the treated surface layer, and the obtained fresh water is returned to the field. Further, the depth of the fresh water infiltrating underground is based on the condition that the water does not evaporate. Furthermore, the saline-alkali water is repeatedly collected and desalinated, and the desalinated fresh water is reinjected into the field for irrigation, and the salt and alkali in the treated area are repeatedly dissolved, so that the salt and alkali are separated from the soil. Since the water located below the surface will penetrate upward under the action of the external soil environment, the water flowing into the area to be treated will return upward, and the returned water further dissolves the water below the surface, enabling the salt and alkali to be further dissolved. By repeating the processes of returning fresh water to the field and desalinating saline-alkali water, the salt and alkali content in the soil of the area to be treated is gradually reduced, and finally the soil meets the normal tillage conditions. Specifically, the following saline-alkali land treatment system can be used to implement the method of the present invention.

[0012] The saline-alkali land treatment system of the structure of the embodiment of the present invention includes a saline-alkali water raw water collection device, a saline-alkali water desalination device, and a fresh water returning to the field device. The saline-alkali water raw water collection device serves as the raw water intake point. A water pump is connected between the saline-alkali water desalination device and the saline-alkali water raw water collection device. The water inlet of the water pump is communicated with the inner cavity of the saline-alkali water raw water collection device, and the water outlet of the water pump is connected to the water inlet of the saline-alkali water desalination device. The desalinated saline-alkali outlet of the saline-alkali water desalination device is communicated with a concentrated brine water tank, or can also be directly connected to the water inlet of a concentrated brine drying device. The concentrated brine drying device performs drying treatment on the concentrated brine. The concentrated brine drying device can adopt an automatic evaporation device. The salt outlet of the concentrated brine drying device is communicated with a storage container such as a salt tank. Or there can be a concentrated saline-alkali water tank below to collect and store the separated concentrated saline-alkali water, and then the concentrated saline-alkali water is evaporated by an evaporation device to obtain dry salt. The water outlet of the saline-alkali water desalination device is communicated with the water inlet of a fresh water tank, and the water outlet of the fresh water tank is communicated with the water inlet of the fresh water returning to the field device. The fresh water returning to the field device adopts a buried irrigation system. The buried irrigation system includes a water distribution pipe network and buried drip infiltration pipes. The buried drip infiltration pipes are used to be buried below the surface layer, and their water outlets are located inside the saline-alkali land soil layer, so that the returned water seeps into the ground below the surface of the saline-alkali land. Multiple buried drip infiltration pipes are set in a treatment area, and each buried drip infiltration pipe is connected to the water outlet of the saline-alkali water desalination device through the water distribution pipe network. The buried drip infiltration pipes are buried underground. The burial depth of the buried drip infiltration pipes is based on the standard that the exuded water will not evaporate. The spacing between them is based on the standard that the water is evenly distributed and covers the area in the area to be treated. Generally, it is located 300-400 mm below the surface layer. The spacing of the buried drip infiltration pipes is between 500-800 mm. In this way, the obtained fresh water can be redissolved with the saline-alkali remaining in the soil after infiltration, so that the saline-alkali is collected into the saline-alkali water raw water collection device from the underground soil, which is convenient for the secondary treatment of the saline-alkali land. The fresh water that seeps into the ground below the surface layer will infiltrate up, down, left, and right due to the infiltration effect, so that there is water below the surface soil layer. In this way, the water absorbs the saline-alkali in the soil and dissolves the saline-alkali in the water. By using this device and method, since the saline-alkali water raw water is treated by the saline-alkali water desalination device to obtain fresh water, the fresh water can reach the standard of pure water, or it can be water with a salt content equivalent to that of natural water sources. After this water is reinjected and returned to the ground below the surface, since the salt content in the water has reached the standard of pure water or water sources, it can be supplied for plants to absorb and utilize after being returned to the field by reinjection, enabling the plants to obtain a better living condition than before. After the fresh water is returned to the field by reinjection, it can further dissolve the saline-alkali in the soil, making the saline-alkali enter the water, preparing for the next cycle of saline-alkali separation.In the present invention, a buried drip irrigation pipe is adopted to send the fresh water generated after being treated by the saline-alkali desalination device back into the underground soil. Therefore, no external water resources are required. Since the micro-infiltration irrigation technology below the ground surface is adopted for returning fresh water to the field, the amount of water required is very small. It can evenly wet the underground soil, dissolve the fertilizers in the land for plants to absorb and utilize. Thus, no external water source is needed, which is extremely convenient and beneficial for the treatment of saline-alkali land in arid and water-scarce areas. This method and this system are also applicable to the treatment of saline-alkali land in arid areas. For the treatment of saline-alkali land in arid areas, since its saline-alkali raw water is very little or cannot be taken out, fresh water transported from the outside can be distributed into the surface layer of the saline-alkali land through the underground micro-infiltration irrigation technology first, so that the saline-alkali in the area to be treated is dissolved in the fresh water distributed underground, and then collected into the saline-alkali water raw water collection device, and then treated by the saline-alkali water desalination device. In this way, the treatment of saline-alkali land in arid areas can be realized, and the goal of complete treatment can be achieved with very little water resources. More advantageously, since the obtained fresh water penetrates into the ground below the surface layer through the buried drip irrigation pipe, the evaporation of water can be reduced. Especially when it is buried below the depth where evaporation cannot occur, usually below 300 - 400 mm, it basically does not participate in evaporation. Therefore, the salt and alkali redissolved in the fresh water will not form saline-alkali. They will be collected at the water intake point and separated and desalted again by the saline-alkali water desalination device, so that the saline-alkali in the treated area only decreases and does not increase. Especially, when crops are planted in the treated saline-alkali land and fertilizers or drugs for crop growth are added to the fresh water, since the fertilizers and drugs are input below the ground surface along with the fresh water and the water does not evaporate, saline-alkali will not be formed either. Therefore, the treated land can be prevented from salinizing again, and the treatment of the saline-alkali land enters a virtuous cycle, and the saline-alkali land can be completely treated and transformed. The opening time of the fresh water returning device can be controlled according to the technological requirements. For example, when plants need to be planted in this plot and the soil needs to contain moisture and oxygen, when the collection of the saline-alkali water raw water in the treatment area is completed and no new saline-alkali water raw water infiltrates into the saline-alkali water raw water collection device or the infiltration amount is very small, fresh water is returned to the field by injection. When returning by injection, finally backfill the saline-alkali water raw water collection device to prevent the reverse flow of saline-alkali. When plants do not need to be planted in this plot or the planted plants are drought-tolerant varieties, the saline-alkali water can be desalinated and returned to the field by injection at the same time. This is like washing the ground in a cycle, which can improve the efficiency of saline-alkali land treatment. Moreover, the crops can absorb a certain amount of saline-alkali as fertilizers, further reducing the saline-alkali content of the saline-alkali land. It is best to set a pressure stabilizing tank in the system. The water inlet of the pressure stabilizing tank is connected to the water outlet of the fresh water tank, and its water outlet is connected to the water inlet of the water distribution network. An air outlet is provided on the tank body of the water storage tank of the pressure stabilizing tank and is connected to the outside atmosphere, so that the water in the pressure stabilizing tank body is normal-pressure water, and the pressure stabilizing tank stores fresh water.The pressure stabilizing tank is preferably of the structure of the water and fertilizer supply device in the patent application with the patent name of "An Adaptive Water and Fertilizer Supply Device and an Adaptive Water and Fertilizer Supply System", the patent application number of CN 202410558412.0, and the publication number of CN118216333A. Of course, the structure of a conventional pressure stabilizing tank can also be adopted, as long as it can provide pressure and water source to the buried drip irrigation pipe.

[0013] In the method of the present invention, after the first saline-alkali water desalination treatment and fresh water return to the field are completed, planting can be carried out on the land. Salt-tolerant plants are planted in the first year. Since the saline-alkali water desalination treatment has been carried out once, the pH value of the saline-alkali soil will be reduced to 7.1-8.5, and the crop growth environment has been greatly improved. It can also be that a saline-alkali land is subjected to multiple collections of raw saline-alkali water and multiple desalinations until it meets the normal growth conditions of plants before planting plants.

[0014] In the method and system of the present invention, the saline-alkali collection device can be a saline-alkali collection well, a collection pit or a collection ditch. The saline-alkali collection device is arranged in the area that needs saline-alkali treatment, and its bottom is below the surface layer, generally about 2-10 meters below the surface layer, located in the shallow stratum. Multiple saline-alkali raw water collection devices can be set as water intake points in a treatment area, and the saline-alkali raw water in the treatment area is collected into the saline-alkali raw water collection device by the natural infiltration of the saline-alkali raw water. Such an approach is relatively economical. Usually, there will be a relatively low-lying area in the environment of a treatment area where there will be accumulated water. Setting the saline-alkali collection device at this position is very suitable for desertified saline-alkali land, and the natural collection speed of its saline-alkali raw water is relatively fast. After the saline-alkali raw water is collected into the saline-alkali raw water collection device, the saline-alkali raw water is sent to the saline-alkali desalination device by a water pump. The saline-alkali desalination device can adopt existing seawater salt extraction devices, seawater desalination devices such as the structure of the device for transforming coastal saline-alkali land and seawater desalination, or can also adopt reverse osmosis devices in the field of water treatment, such as reverse osmosis membrane separation devices or nanofiltration membrane separation devices, etc., as long as the saline-alkali can be separated from the water. Preferably, the saline-alkali raw water is filtered before reverse osmosis treatment, and a filter is set in front of the reverse osmosis device. The filtered saline-alkali raw water passes through to the reverse osmosis device for solid-liquid separation to avoid blocking the osmosis device. The filter can adopt a structure combining a quartz sand filter, an activated carbon filter and a precision filter. The water inlet end of the quartz sand filter is connected to the water outlet end of the water pump, its water outlet end is connected to the water inlet end of the activated carbon filter, the water outlet end of the activated carbon filter is connected to the water inlet end of the precision filter, and the water outlet end of the precision filter is connected to the water inlet end of the reverse osmosis device. The concentrated water outlet of the reverse osmosis device is communicated with the inlet of the concentrated brine tank, and the fresh water outlet of the reverse osmosis device is communicated with the water inlet of the fresh water tank. After the above filtration, pure and impurity-free fresh water is obtained. Preferably, a booster pump is set between the filtration device and the saline-alkali water tank to increase the pressure of the raw water. Preferably, a high-pressure pump is set between the water outlet of the filtration device and the water inlet of the reverse osmosis device to improve the reverse osmosis filtration ability. The obtained fresh water enters the fresh water tank, and the concentrated brine tank is connected to the automatic evaporation device. The salt obtained by evaporating the concentrated brine through the automatic evaporation device enters the salt box.

Claims

1. A saline-alkali land treatment system, characterized in that: It includes a saline-alkali water return device, which comprises a water distribution pipe network and a plurality of buried drip infiltration pipes. The buried drip infiltration pipes are used to be arranged below the surface layer of the saline-alkali land to be treated. The water outlet ends of the water distribution pipe network are respectively connected to the buried drip infiltration pipes, and the water inlet end of the water distribution pipe network is used to receive the fresh water obtained after the desalination treatment of the saline-alkali water.

2. The saline-alkali land treatment system according to claim 1, characterized in that: The saline-alkali water return device further includes a pressure stabilizing tank. The pressure stabilizing tank has a tank body for storing water. The water inlet of the tank body is used to receive fresh water, and the water outlet is connected to the water inlet end of the water distribution pipe network. An air outlet hole is arranged on the tank body of the pressure stabilizing tank and is connected to the outside atmosphere.

3. The saline-alkali land treatment system according to claim 1, characterized in that: It further includes a saline-alkali water desalination device, which performs desalination treatment on the saline-alkali water to obtain concentrated brine and fresh water. The saline-alkali water desalination device includes a reverse osmosis device. The saline-alkali water is converted into concentrated brine and fresh water through the reverse osmosis device. Its concentrated brine outlet is connected to a concentrated brine tank, and its fresh water outlet is connected to the water inlet of the pressure stabilizing tank.

4. A saline-alkali land treatment system according to claim 3, characterized in that, The saline-alkali water desalination device further includes a filtering device, which filters the impurities in the saline-alkali water. The filtering device includes a quartz sand filter, an activated carbon filter and a precision filter. The water inlet end of the quartz sand filter is connected to the water outlet end of a water pump, and its water outlet end is connected to the water inlet end of the activated carbon filter. The water outlet end of the activated carbon filter is connected to the water inlet end of the precision filter. The water outlet end of the precision filter is connected to the water inlet end of the reverse osmosis device. The concentrated water outlet of the reverse osmosis device is connected to the inlet of the concentrated brine tank, and the fresh water outlet of the reverse osmosis device is connected to the water inlet of the fresh water tank. The water inlet end of the water pump is connected to the saline-alkali water to be treated.

5. The saline-alkali land treatment system according to claim 1, characterized in that, It further includes a saline-alkali water collection device, which collects the saline-alkali water in the saline-alkali land and holds the saline-alkali water. The water inlet end of the water pump is located in the saline-alkali water collection device.

6. The saline-alkali land treatment system according to claim 1, characterized in that, It further includes a saline-alkali water tank, which is located between the water pump and the saline-alkali water collection device. A booster pump is arranged between the saline-alkali water tank and the filtering device, and a high-pressure pump is arranged between the water outlet end of the filtering device and the reverse osmosis device.

7. A method for treating saline-alkali land, characterized in that, It includes the step of distributing fresh water to the saline-alkali land to be treated. The fresh water is infiltrated through the buried drip infiltration pipes below the surface layer of the saline-alkali land to be treated, so that the fresh water is evenly distributed below the surface layer.

8. The method for treating saline-alkali land according to claim 7, characterized in that, The infiltration depth is based on that the water does not evaporate outward, and the water is evenly distributed below the surface layer. It further includes the step of collecting saline-alkali water and the step of desalination treatment of saline-alkali water. First, the saline-alkali water is collected from the saline-alkali land to be treated, and then the collected saline-alkali water is desalinated to obtain the fresh water, and then the fresh water is returned to the field according to the step of distributing fresh water described in claim 1.

9. The method for treating saline-alkali land according to claim 8, characterized in that, Before desalinating the saline-alkali water, the saline-alkali water is filtered to remove the impurities in the saline-alkali water and then the desalination treatment of the saline-alkali water is carried out.

10. A saline-alkali land treatment system according to claim 9, characterized in that, At least inject water into the saline-alkali land to be treated and return it to the field twice and repeat one of the steps described in claims 7-9; and / or plant crops on the saline-alkali land in the area to be treated after the fresh water is returned to the field, so that the crops absorb the saline-alkali fertilizer in the soil.

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