A method for ecological regulation of drainage to reduce salinity and alkalinity through coordinated irrigation and drainage

Abstract

This invention discloses a controlled drainage ecological regulation method for synergistic irrigation and drainage to reduce salinity and alkalinity, belonging to the field of soil remediation technology. The method includes: a soaking and dissolving stage, where, with the drainage outlet closed, low-flow irrigation is performed at the farthest point from the drainage ditch, allowing a large amount of irrigation water to enter the small pores of the soil profile and soak and dissolve salts; a diffusion and dispersion stage, where the drainage outlet is raised, and with the outlet height lower than the field surface, large-flow irrigation is performed evenly, filling all pores of the soil profile with irrigation water and enhancing the diffusion and dispersion of salts; a convection desalination stage, where the drainage outlet is opened, and with the outlet depth level with the drainage ditch depth, saline water is evenly discharged from the soil; and a water-saving and emission-reduction stage, where the drainage outlet depth is lower than the crop root zone, breaking the connectivity of small pores and preventing soil salts from moving upwards during crop growth. This synergistic irrigation and drainage achieves the three major goals of salt control, water conservation, and emission reduction.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, specifically to a controlled drainage ecological regulation method for synergistic irrigation and drainage to reduce salinity and alkalinity barriers. Background Technology

[0002] Saline-alkali land is an important reserve of arable land in my country, and its restoration will strongly support increased grain production. Under the dual constraints of water and land resources, the efficient management of saline-alkali land and the prevention of soil salinization are of paramount importance. Drainage technologies such as underground pipes and open ditches are effective measures for preventing salinity damage and have played a crucial role in the management of saline-alkali land in the arid northwest and saline soil along the coast. Uncontrolled free drainage and unreasonable irrigation not only fail to effectively reduce salinity damage but also cause significant water waste and further trigger ecological and environmental problems such as agricultural non-point source pollution. To achieve the ecological goals of water conservation, salt control, and emission reduction, drainage needs to be rationally regulated and coordinated with irrigation.

[0003] Existing farmland drainage methods fail to effectively consider variations in field soil properties and their coordination with irrigation, resulting in low salt leaching efficiency, water waste, and nitrogen and phosphorus loss pollution.

[0004] Therefore, how to provide a drainage method that achieves the ecological goals of efficient salt suppression, reduction of nitrogen and phosphorus pollution in drainage, and conservation of water and fertilizer resources is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] Therefore, this invention provides a controlled drainage ecological regulation method for reducing salinity barriers through coordinated irrigation and drainage, in order to solve the problems of low salt leaching efficiency, water waste, and nitrogen and phosphorus loss pollution caused by the failure to effectively consider the variation of field soil properties and the lack of coordination with irrigation in the existing technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for controlling drainage ecological regulation to reduce salinity and alkalinity barriers through coordinated irrigation and drainage includes the following steps:

[0008] Step S1: Infiltration and dissolution stage. With the drainage outlet closed, a small flow of irrigation is carried out at the farthest end of the drainage ditch pipe, so that a large amount of irrigation water enters the small pores of the soil profile to infiltrate and dissolve the salts.

[0009] Step S2: Diffusion stage. The drainage outlet is raised. Under the condition that the height of the drainage outlet is lower than the field surface, water is evenly distributed and irrigated with a large flow rate to fill the soil profile with irrigation water of all sizes, thereby enhancing the diffusion process of salt.

[0010] Step S3: Convection desalination stage. The drainage outlet is opened, and the saline solution is evenly discharged from the soil under the condition that the depth of the drainage outlet is level with the depth of the drainage ditch.

[0011] Step S4: Water conservation and emission reduction stage, making the depth of the drainage outlet lower than the crop root zone, and on this basis, breaking the small pore connections to block the upward movement of soil salt during crop growth.

[0012] Furthermore, the ratio R of the irrigation water volume in step S1 to that in step S2 im for:

[0013]

[0014] Where, θ s θ represents the soil saturation water content. f For soil field water content, θ r This refers to the residual moisture content of the soil.

[0015] Furthermore, in step S4, the depth of the drainage outlet from the ground surface is 55-60 cm.

[0016] Furthermore, the methods for breaking the small pore connectivity in step S4 include at least deep plowing, deep straw plowing, and replacement of a thin layer of soil beneath the topsoil.

[0017] Furthermore, during low-flow irrigation in step S1, irrigation is stopped when the soil profile moisture content reaches the field moisture content.

[0018] Furthermore, during the uniform water distribution irrigation in step S2, irrigation stops when the soil profile moisture content reaches saturation.

[0019] Furthermore, in step S3, when the saline solution is uniformly discharged from the soil, the soil profile moisture content returns to the field and the desalination process is completed.

[0020] Furthermore, the replacement thin layer in the soil thin layer replacement under the cultivated layer is 20-30cm below the cultivated layer, the depth of the replacement thin layer is 5-10cm, and the replacement medium in the thin layer is coarse sand and gravel with an average particle size range of 0.5-1.5mm.

[0021] Furthermore, the method for replacing the thin layer of soil beneath the topsoil is direct burial or bag filling.

[0022] The present invention has the following advantages:

[0023] This application considers the coordinated irrigation and drainage ecological salt suppression implementation path, dividing it into four stages: infiltration and dissolution, diffusion and dispersion, convection desalination, and water conservation and emission reduction. In the infiltration and dissolution stage, with the drainage outlet closed, low-flow irrigation is carried out at the farthest point from the drainage ditch, allowing more irrigation water to enter the small pores of the soil profile and infiltrate and dissolve salts. In the diffusion and dispersion stage, the drainage outlet is raised, and with the outlet height lower than the field surface, high-flow irrigation is evenly distributed, filling all pores of the soil profile with irrigation water and enhancing the diffusion and dispersion process of salts. In the convection desalination stage, the drainage outlet is opened, and with the outlet depth level with the drainage ditch depth, saline water is evenly discharged from the soil. In the water conservation and emission reduction stage, the drainage outlet depth is lower than the crop root zone, breaking the connectivity of small pores and preventing soil salts from moving upwards during crop growth.

[0024] This application fully utilizes the dissolving effect of unsaturated flow on a large salt reservoir with small pores, enhances the diffusion and dispersion effect between large and small pores, and thus improves salt discharge efficiency; by cutting off the longitudinal connection channels between large and small pores, it reduces water loss from large pores and salt transport upward through small pores, and inhibits the salt return process; and coordinates irrigation and drainage to achieve the three major goals of salt control, water conservation and emission reduction. Attached Figure Description

[0025] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0026] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0027] Figure 1 The flowchart of a controlled drainage ecological regulation method for reducing salinity and alkalinity barriers through coordinated irrigation and drainage provided by the present invention is shown. Detailed Implementation

[0028] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] To address the problems of low salt leaching efficiency, water waste, and nitrogen and phosphorus loss pollution caused by the failure of existing technologies to effectively consider variations in field soil properties and their coordination with irrigation, a controlled drainage ecological regulation method for mitigating salinity barriers through coordinated irrigation and drainage is proposed, such as... Figure 1 The process, as shown, includes the following steps:

[0030] Step S1: Infiltration and dissolution stage. With the drainage outlet closed, irrigation is carried out at a low flow rate only at the farthest end of the drainage ditch, so that more irrigation water enters the small pores of the soil profile to infiltrate and dissolve salts.

[0031] Step S2: Diffusion stage. The drainage outlet is closed. Under the condition that the height of the drainage outlet is lower than the field surface, water is evenly distributed and irrigated with a large flow rate to fill the soil profile with irrigation water of all sizes, thereby enhancing the diffusion and dispersion of salt.

[0032] Step S3: Convection desalination stage. The drainage outlet is opened, and the saline solution is evenly discharged from the soil under the condition that the depth of the drainage outlet is level with the depth of the drainage ditch.

[0033] Step S4: Water conservation and emission reduction stage. Make the depth of the drainage outlet slightly lower than the crop root zone. On this basis, break the small pores to prevent soil salt from moving upward during crop growth.

[0034] The ratio R of irrigation water volume in step S1 to that in step S2 im for:

[0035]

[0036] Where, θ s θ represents the soil saturation water content. f For soil field water content, θ r This refers to the residual moisture content of the soil.

[0037] Based on the ratio of step S1 to step S2, knowing the irrigation amount in one step allows us to deduce the other, providing a balance between irrigation amounts at two different stages. Step S1 requires stopping irrigation when the soil profile moisture content reaches field capacity, while step S2 requires stopping irrigation when the soil profile moisture content reaches saturation.

[0038] The current high-flow irrigation combined with uncontrolled free drainage method results in a large amount of irrigation water being lost through the large pores with low salt content before it can leach salts due to the presence of large pores in the soil (or preferential flow in the soil). This leads to low desalination efficiency and waste of a large amount of water resources.

[0039] In step S1, low-flow irrigation allows irrigation water to enter the small pores of the soil profile. The capillary action of these pores facilitates the entry of most of the irrigation water into these pores, effectively saturating the soil's largest salt reservoirs to dissolve a large amount of salt within them. Irrigation is stopped when the soil moisture content reaches field capacity.

[0040] In step S2, high-flow irrigation fills the soil profile, including large pores, with irrigation water, enhancing the molecular diffusion and mechanical dispersion of salts from small pores to large pores, and creating sufficient time for water-salt exchange between pores of different sizes. Irrigation stops when the soil profile reaches saturation.

[0041] In step S3, the drainage outlet is opened, and the negative pressure formed between the soil's gravitational potential and the pores of different sizes promotes the uniform discharge of a large amount of saline water from the soil. Desalination ends when the soil profile moisture content returns to the field.

[0042] Step S4 operates during the crop growth stage. After the first three stages or a cycle of steps S2 and S3, soil salinity is efficiently washed away, leading to a stage of efficient water and fertilizer utilization. During this stage, the drainage ditch outlet is controlled at a depth slightly below the crop root zone, generally 55-60 cm from the surface. Based on water conservation and emission reduction, a more suitable non-salt-stress environment is created for crops through deep plowing of the plow pan, deep turning of straw, or replacement of a thin layer of soil beneath the topsoil to break up soil pore connectivity and prevent soil salinity from migrating upwards during crop growth.

[0043] The replacement layer in the sub-soil thin-layer replacement is 20-30 cm below the tillage layer, with a depth of 5-10 cm. The replacement medium in this thin layer consists of coarse gravel particles with an average particle size ranging from 0.5-1.5 mm. Besides hindering the upward movement of salts in step S4, the sub-soil thin-layer replacement also helps conserve water and moisture, improving the water and fertilizer use efficiency of crop roots. In step S1, the presence of the soil replacement layer impedes the downward movement of irrigation water, increasing the intensity of infiltration and dissolution. In step S2, it enhances the diffusion of salts. In step S3, it improves the uniformity of desalination, thus increasing the overall desalination efficiency.

[0044] There are two ways to replace the thin layer of soil under the topsoil: one is direct burial, and the other is to use cloth bags. To prevent the accumulation of sand and gravel, the cloth bags are sewn with mesh to separate them. The bags should not be filled too full to facilitate laying and leveling.

[0045] This application fully utilizes the dissolving effect of unsaturated flow on a large salt reservoir with small pores, enhances the diffusion and dispersion effect between large and small pores, and thus improves salt discharge efficiency; by cutting off the longitudinal connection channels between large and small pores, it reduces water loss from large pores and salt transport upward through small pores, and inhibits the salt return process; and coordinates irrigation and drainage to achieve the three major goals of salt control, water conservation and emission reduction.

[0046] To effectively implement the ecological regulation and control methods for drainage, a multi-scenario classification approach is adopted to coordinate irrigation and drainage. The specific scenarios and implementation plans are as follows.

[0047] Example 1

[0048] Synergistic drip irrigation and concealed pipe drainage:

[0049] Step S1: Irrigation and Dissolution Stage. With the drip irrigation outlet closed, irrigation is carried out with a higher flow rate the further away from the drip irrigation outlet. The flow rate at the furthest drip irrigation outlet is set at greater than 2 L / h, while the flow rate closer to the drip irrigation outlet is set at approximately 1 L / h. Irrigation stops when the soil profile near the drip irrigation outlet reaches field capacity moisture content.

[0050] Step S2: Diffusion Stage. The underground pipes remain closed. One day after the end of the previous stage, all drip irrigation outlets begin high-flow irrigation. Irrigation stops when the soil profile reaches saturation.

[0051] Step S3: Convection desalination stage. The underground pipes are fully opened to allow a large amount of saline solution to be evenly discharged into the soil. Desalination ends when the soil profile moisture content returns to field hold. If further desalination enhancement is required, steps S2 and S3 can be repeated. Desalination ends when the soil profile moisture content returns to field hold.

[0052] Step S4: Water Conservation and Emission Reduction Stage. During the stage of efficient utilization of water and fertilizer resources in crop growth, the depth of the submerged pipe outlet is controlled to be 10cm lower than that of the crop root zone, and drip irrigation is carried out according to the crop's water requirements.

[0053] In addition, before the four stages begin, drip irrigation tape is laid in combination with surface mulching and deep tillage or replacement of the soil layer below the topsoil to slow down the accumulation of salt in the root zone during crop growth.

[0054] Example 2

[0055] Coordinated surface irrigation and open ditch drainage:

[0056] Step S1: Immersion and Dissolution Stage. With the open ditch outlet closed, perform low-flow surface pulse irrigation at the farthest point from the open ditch. Stop irrigation when the soil profile reaches field-hold moisture content. The open ditch should be deep and narrow, with a depth of 1.0-1.5m.

[0057] Step S2: Diffusion Stage. With the open ditch outlet still closed, begin high-flow irrigation 2 days after the end of the previous stage, stopping irrigation when the soil profile is saturated. Allow a residence time of at least 24 hours after irrigation stops to enhance salt migration from micropores to macropores.

[0058] Step S3: Convective desalination stage. The open ditch is fully opened, utilizing the soil's gravitational potential energy and negative pressure within the pores under free drainage to efficiently precipitate a large amount of saline solution from the soil. Desalination ends when the soil profile moisture content returns to field capacity.

[0059] Step S4: Water Conservation and Emission Reduction Stage. Unlike the salt leaching stage described above, during the crop growth period when water and fertilizer resources are utilized efficiently, the depth of open ditches is controlled to be 20cm below the crop root zone, and surface irrigation is carried out according to the crop's water requirements. Before planting, deep plowing is performed to break up the plow pan, promoting the infiltration of irrigation water to leach salts and preventing salt evaporation and accumulation in the root zone. Straw is deeply plowed below the root zone or replaced with a thin layer of soil below the topsoil, severing capillary connections between the topsoil and the underlying soil layers, reducing the upward evaporation and accumulation of salts.

[0060] Example 3

[0061] Coordinated furrow irrigation and underground pipe drainage:

[0062] Step S1: Immersion and Dissolution Stage. With the outlet of the underground pipe closed, furrow irrigation is carried out with a flow rate decreasing as the soil gets closer to the underground pipe. Irrigation is stopped when the soil profile reaches field capacity moisture content. The irrigation furrows are arranged parallel to the underground pipe.

[0063] Step S2: Diffusion Stage. The outlet of the underground pipe remains closed. 1.5 days after the end of the previous stage, all irrigation ditches simultaneously begin high-flow-rate irrigation until the soil is saturated. After stopping irrigation, allow a residence time of at least 24 hours to enhance the migration of salts from micropores to macropores.

[0064] Step S3: Convection desalination stage. The outlet of the underground pipe is opened and the control depth of the outlet is gradually reduced until it is fully opened, so that a large amount of saline water is evenly discharged from the soil. When the soil profile moisture content returns to the field, the drainage ditch is closed.

[0065] Step S4: Water Conservation and Emission Reduction Stage. This stage focuses on the efficient use of water and fertilizer resources during the crop growth period. The depth of drainage ditches is controlled to be 10cm below the crop root zone, and alternating irrigation is carried out according to the crop's water requirements.

[0066] In addition, before the four stages begin, the plow pan is broken up to promote the infiltration of irrigation water to leach salts. At the same time, crop straw is deeply plowed into the root zone or replaced in a thin layer of soil below the topsoil to prevent salt from accumulating upwards. Then, the land is prepared and irrigation ditches are dug between the crop rows. Small ditches, 35-50 cm wide, are recommended.

[0067] The drainage ecological regulation method provided in this application, based on fully considering the influence of soil pore structure on water and salt movement and the synergistic salt suppression effect of irrigation and drainage, implements drainage regulation in stages and scenarios, thereby achieving the ecological goals of efficient desalination and salt suppression, reducing nitrogen and phosphorus pollution in drainage, and saving water and fertilizer resources.

[0068] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for controlling drainage ecological regulation to reduce salinity and alkalinity barriers through coordinated irrigation and drainage, characterized in that, Includes the following steps: Step S1: Infiltration and dissolution stage. With the drainage outlet closed, a small flow of irrigation is carried out at the farthest end of the drainage ditch pipe, so that a large amount of irrigation water enters the small pores of the soil profile to infiltrate and dissolve the salts. Step S2: Diffusion stage. The drainage outlet is raised. Under the condition that the height of the drainage outlet is lower than the field surface, water is evenly distributed and irrigated with a large flow rate to fill the soil profile with irrigation water of all sizes, thereby enhancing the diffusion process of salt. Step S3: Convection desalination stage. The drainage outlet is opened, and the saline solution is evenly discharged from the soil under the condition that the depth of the drainage outlet is level with the depth of the drainage ditch. Step S4: Water conservation and emission reduction stage, making the depth of the drainage outlet lower than the crop root zone, and on this basis, breaking the small pore connections to block the upward movement of soil salt during crop growth.

2. The controlled drainage ecological regulation method for reducing salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 1, characterized in that, The ratio R of irrigation water volume in step S1 to that in step S2 im for: Where, θ s θ represents the soil saturation water content. f For soil field water content, θ r This refers to the residual moisture content of the soil.

3. The method for controlling drainage and ecological regulation to reduce salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 1, characterized in that, In step S4, the depth of the drainage outlet from the ground surface is 55-60 cm.

4. The controlled drainage ecological regulation method for reducing salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 1, characterized in that, The methods for breaking the connectivity of small pores in step S4 include at least deep plowing, deep turning of straw, and replacement of a thin layer of soil beneath the topsoil.

5. The controlled drainage ecological regulation method for reducing salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 1, characterized in that, In step S1, when irrigating with a low flow rate, irrigation is stopped when the soil profile moisture content reaches the field moisture content.

6. The controlled drainage ecological regulation method for reducing salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 1, characterized in that, In step S2, when water is evenly distributed for irrigation, irrigation stops when the soil profile moisture content reaches saturation.

7. The method for controlling drainage and ecological regulation to reduce salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 1, characterized in that, In step S3, when the saline solution is uniformly discharged from the soil, the soil profile moisture content returns to the field and the desalination process ends.

8. The method for controlling drainage and ecological regulation to reduce salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 4, characterized in that, The replacement thin layer in the soil thin layer replacement is 20-30cm below the topsoil, and the depth of the replacement thin layer is 5-10cm. The replacement medium in the thin layer is coarse sand and gravel with an average particle size range of 0.5-1.5mm.

9. The controlled drainage ecological regulation method for reducing salinity and alkalinity barriers through coordinated irrigation and drainage as described in claim 4, characterized in that, The method for replacing the thin layer of soil beneath the topsoil is direct burial or filling with cloth bags.

Images