Drainage control ecological regulation and control method for reducing saline-alkali obstacles through irrigation and drainage cooperation

Abstract

The invention discloses a drainage control ecological regulation and control method for reducing saline-alkali obstacles through cooperation of irrigation and drainage, and relates to the technical field of soil remediation, and the method comprises the following steps: in an infiltration and dissolution stage, under the condition that a drainage outlet is closed, small-flow irrigation is performed at the farthest end from a drainage ditch pipe, so that a large amount of irrigation water enters small pores of a soil profile, and salt is infiltrated and dissolved; in the diffusion and dispersion stage, a drainage outlet is raised, and under the condition that the drainage outlet is lower than the field surface, uniform water distribution and large-flow irrigation are performed, so that large and small pores of a soil profile are filled with irrigation water, and the diffusion and dispersion process of salt is enhanced; in the convection desalination stage, a drainage outlet is opened, and salt-containing water is evenly discharged out of the soil under the condition that the drainage outlet is flush with the drainage ditch pipe in depth; in the water-saving and emission-reducing stage, the depth of a drainage outlet is lower than that of a crop root zone, small-pore communication is broken on the basis, and soil salt is prevented from moving upwards in the crop growth period. Irrigation and drainage are coordinated, and the three goals of salt control, water saving and emission reduction are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles. Background Art

[0002] Saline-alkali land is an important reserve resource of arable land in my country. After restoration, it will strongly support my country's grain production increase. Under the dual constraints of water resources and land resources, efficient management of saline-alkali land and prevention of salinization of arable land are of great importance. Drainage technologies such as concealed pipes and open ditches are effective measures to prevent and control saline-alkali hazards, and have played an important role in the management of saline-alkali land and coastal saline soil in the arid northwest region. Uncontrolled free drainage and unreasonable irrigation will not only fail to effectively reduce salinization damage, but will also cause a large amount of water resources to be wasted, and further cause ecological and environmental problems such as agricultural non-point source pollution. In order to achieve the ecological goals of water conservation, salt control and emission reduction, it is necessary to reasonably regulate drainage and coordinate irrigation.

[0003] Existing farmland drainage methods fail to effectively consider field soil property variation and its coordination with irrigation, resulting in low salt washing efficiency, water resource waste, and nitrogen and phosphorus loss pollution.

[0004] Therefore, how to provide a drainage method that can achieve the ecological goals of efficiently suppressing salt, reducing nitrogen and phosphorus pollution in drainage, and saving water and fertilizer resources is a technical problem that needs to be urgently solved by technicians in this field. Summary of the invention

[0005] To this end, the present invention provides a drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles, so as to solve the problems of low salt washing efficiency, water resource waste and nitrogen and phosphorus loss pollution caused by failure to effectively consider field soil property variation and lack of coordination with irrigation in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles, comprising the following steps:

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

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

[0010] Step S3: During the convection desalination stage, the drainage outlet is opened, and the depth of the drainage outlet is flush with the depth of the drainage ditch pipe, so that the salt water is evenly discharged from the soil;

[0011] Step S4: In the water-saving and emission-reduction stage, the depth of the drainage outlet is made lower than the crop root zone, and on this basis, the connectivity of small pores is broken to prevent 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 is im for:

[0013]

[0014] Among them, θ s is the soil saturated moisture content, θ f is the soil moisture content, θ r is 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 method of breaking the connectivity of small pores in step S4 at least includes deep ploughing, deep turning of straw and replacement of a thin layer of soil under the tillage layer.

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

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

[0019] Furthermore, when the salt water is uniformly discharged from the soil in step S3, the desalination is completed after the moisture content of the soil profile returns to the field.

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

[0021] Furthermore, the thin layer of soil under the tillage layer is replaced by direct landfill or bag filling.

[0022] The present invention has the following advantages:

[0023] This application will consider the coordinated implementation path of drainage ecological salt suppression and control by irrigation and drainage, and divide it into the infiltration and dissolution stage, the diffusion and dispersion stage, the convective desalination stage and the water-saving and emission reduction stage. In the infiltration and dissolution stage, under the condition that the drainage outlet is closed, a small flow irrigation is carried out at the farthest end of the drainage ditch pipe, so that more irrigation water can enter the small pores of the soil profile and infiltrate and dissolve the salt; in the diffusion and dispersion stage, the drainage outlet is raised, and under the condition that the drainage outlet height is lower than the field surface, a large flow irrigation is carried out evenly to fill the large and small pores of the soil profile with irrigation water, thereby strengthening the diffusion and dispersion process of salt; in the convective desalination stage, the drainage outlet is opened, and under the condition that the depth of the drainage outlet is flush with the depth of the drainage ditch pipe, the salt water is evenly discharged from the soil; in the water-saving and emission reduction stage, the depth of the drainage outlet is made lower than the crop root zone, and on this basis, the connection between small pores is broken to block the upward movement of soil salt during crop growth.

[0024] This application makes full use of the salt-dissolving effect of unsaturated flow on small-pore large salt reservoirs, strengthens the diffusion effect between large and small pores, and thus improves the salt discharge efficiency; by cutting off the longitudinal connecting channels between large and small pores, the water loss of large pores and the upward transport of salt from small pores are reduced, thereby inhibiting the salt return process; and coordinates irrigation and drainage to achieve the three major goals of salt control, water conservation and emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0026] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0027] Figure 1 A flow chart of a drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles provided by the present invention. DETAILED DESCRIPTION

[0028] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In order to solve the problems of low salt washing efficiency, water resource waste and nitrogen and phosphorus loss pollution caused by failure to effectively consider the variation of field soil properties and its coordination with irrigation in the existing technology, a drainage ecological regulation method for controlling salinity and alkali obstacles by synergizing irrigation and drainage is provided. Figure 1 As shown, the following steps are included:

[0030] Step S1: Infiltration and dissolution stage, under the condition that the drainage outlet is closed, a small flow irrigation is only carried out at the farthest end from the drainage ditch pipe, so that more irrigation water enters the small pores of the soil profile to infiltrate and dissolve the salt;

[0031] Step S2: During the diffusion stage, the drainage outlet is closed, and under the condition that the drainage outlet height is lower than the field surface, water is evenly distributed with a large flow rate for irrigation, so that the pores of all sizes in the soil profile are filled with irrigation water, thereby strengthening the diffusion and dispersion of salt;

[0032] Step S3: During the convection desalination stage, the drainage outlet is opened, and the depth of the drainage outlet is flush with the depth of the drainage ditch pipe, so that the salt water is evenly discharged from the soil;

[0033] Step S4: In the water-saving and emission-reduction stage, the depth of the drainage outlet is made slightly lower than the crop root zone. On this basis, the connectivity of small pores is broken to prevent the upward movement of soil salt during crop growth.

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

[0035]

[0036] Among them, θ s is the soil saturated moisture content, θ f is the soil moisture content, θ r is the residual moisture content of the soil.

[0037] According to the ratio of step S1 to step S2, knowing one of the irrigation amounts can infer the other, providing a balance of irrigation amounts at two different stages. Step S1 requires that irrigation be stopped when the soil profile moisture content reaches the field holding moisture content, and step S2 requires that irrigation be stopped when the soil profile moisture content reaches saturation.

[0038] The current high-flow irrigation + uncontrolled free drainage method, due to the existence of large pores in the soil (or preferential flow in the soil), means that a large amount of irrigation water does not have time to dissolve salt and is lost through large pores with less salt content, resulting in low desalination efficiency and a waste of a lot of water resources.

[0039] In step S1, low-flow irrigation allows irrigation water to enter small pores in the soil profile. The capillary adsorption force of small pores in the soil is used to force most of the irrigation water to enter the small pores, effectively infiltrating the largest salt storage reservoir in the soil to dissolve the salt in a large number of small pores. When the soil moisture content reaches the field holding moisture content, irrigation is stopped.

[0040] In step S2, large-flow irrigation fills the large pores of the soil profile with irrigation water, strengthens the molecular diffusion and mechanical dispersion of salt from small pores to large pores, and creates sufficient time for water-salt exchange between large and small pores. When the water content of the soil profile reaches saturation, irrigation stops.

[0041] In step S3, the drainage outlet is opened, and a large amount of salt water is uniformly discharged from the soil by means of the soil gravity potential and the negative pressure formed between large and small pores. When the moisture content of the soil profile returns to the field, desalination is completed.

[0042] Step S4 acts on the crop growth stage. After the first three stages or the cycle of step S2 and step S3, the soil salt is efficiently eluted and enters the stage of efficient utilization of water and fertilizer resources. The drainage ditch outlet control depth in this stage is slightly lower than the crop root zone, generally 55-60cm from the ground surface. On the basis of water saving and emission reduction, a more suitable non-salinity stress environment is created for crops, and deep plowing of the bottom layer, deep turning of straw or replacement of a thin layer of soil under the tillage layer are used to break the connection of soil pores and block the upward movement of soil salt during crop growth.

[0043] The replacement thin layer in the replacement of the thin layer of soil under the tillage layer is 20-30cm below the tillage layer, the depth of the replacement thin layer is 5-10cm, and the replacement medium in the thin layer is coarse gravel particles with an average particle size range of 0.5-1.5mm. In addition to hindering the upward movement of salt in step S4, the replacement of the thin layer of soil under the tillage layer can also save water and conserve moisture, and improve the efficiency of water and fertilizer absorption by crop roots. In step S1, the presence of the soil replacement layer can block the downward movement of irrigation water and increase the intensity of infiltration and dissolution. In step S2, the diffusion effect of salt can be enhanced. In step S3, the uniformity of desalination is enhanced, and the desalination efficiency is improved overall.

[0044] There are two ways to replace the thin layer of soil under the tillage layer. One is direct landfill, and the other is to use cloth bags to fill the soil. To prevent the accumulation of sand and gravel, the cloth bags are separated by grids. The filling should not be too full to facilitate laying and leveling.

[0045] This application makes full use of the salt-dissolving effect of unsaturated flow on small-pore large salt reservoirs, strengthens the diffusion effect between large and small pores, and thus improves the salt discharge efficiency; by cutting off the longitudinal connecting channels between large and small pores, the water loss of large pores and the upward transport of salt from small pores are reduced, thereby inhibiting the salt return process; and coordinates irrigation and drainage to achieve the three major goals of salt control, water conservation and emission reduction.

[0046] In order to effectively implement the drainage ecological regulation method, coordinated irrigation and drainage are implemented in multiple scenarios and classifications. The specific scenarios and implementation plans are as follows.

[0047] Example 1

[0048] Coordinated drip irrigation and concealed pipe drainage:

[0049] Step S1: Infiltration and dissolution stage. When the outlet of the concealed pipe is closed, irrigation is performed in a manner that the farther away from the concealed pipe, the greater the irrigation flow rate. The farthest drip irrigation outlet is irrigated with a flow rate greater than 2L / h, and the area close to the concealed pipe is irrigated with a flow rate of about 1L / h. Irrigation stops when the soil profile near the concealed pipe reaches the field holding water content.

[0050] Step S2: Diffusion stage: The concealed pipe remains closed, and 1 day after the end of the previous stage, all drip irrigation outlets begin to irrigate with a large flow rate, and irrigation stops when the soil profile reaches saturation.

[0051] Step S3: Convection desalination stage. The dark pipe is fully opened to allow a large amount of salt water to be evenly discharged from the soil. Desalination ends when the water content of the soil profile returns to the field. If desalination needs to be strengthened, steps S2 and S3 can be repeated. Desalination ends when the water content of the soil profile returns to the field.

[0052] Step S4: Water-saving and emission-reduction stage: In the water and fertilizer resource efficient utilization stage of crop growth, the outlet of the concealed pipe is controlled to be 10 cm below the root zone of the crop, and drip irrigation is performed according to the water demand of the crop.

[0053] In addition, before the start of the four stages, laying drip irrigation tapes combined with surface film covering, deep plowing or replacement of a thin layer of soil under the tillage layer can 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: Infiltration and dissolution stage. Under the condition of closed open ditch outlet, small flow rate surface pulse irrigation is carried out at the farthest end of the open ditch, and irrigation is stopped when the soil profile reaches the field holding water content. The open ditch should be deep and narrow, with a ditch depth of 1.0-1.5m.

[0057] Step S2: Diffusion stage. Under the condition that the open ditch outlet is still closed, large-flow water distribution irrigation starts 2 days after the end of the previous stage, and irrigation stops when the soil profile is saturated. After irrigation stops, a residence time of no less than 24 hours is left to enhance the migration of salt from small pores to large pores.

[0058] Step S3: Convection desalination stage. The open ditch is fully opened, and the soil gravity potential energy and the negative pressure between pores under free drainage are used to promote the efficient precipitation of a large amount of salt water from the soil. Desalination ends when the moisture content of the soil profile returns to the field.

[0059] Step S4: Water-saving and emission-reduction stage. Different from the above-mentioned salt removal stage, during the crop growth period when water and fertilizer resources are efficiently utilized, the open ditch is controlled to have a depth of 20 cm below the crop root zone, and surface irrigation is carried out according to the crop water demand. Before planting crops, deep plowing is performed to break the plow bottom layer, promote the infiltration of irrigation water into salt, and prevent salt evaporation from accumulating in the root zone. The straw is deeply plowed to replace the thin layer of soil below the root zone or below the tillage layer, which cuts off the capillary connection between the tillage layer and the lower soil layer, and reduces the upward evaporation and accumulation of salt.

[0060] Example 3

[0061] Coordinated ditch irrigation and concealed pipe drainage:

[0062] Step S1: Infiltration and dissolution stage. When the outlet of the concealed pipe is closed, the furrow irrigation is carried out in a manner that the flow rate decreases as the distance to the concealed pipe decreases. When the soil profile reaches the field holding water content, the irrigation is stopped. The irrigation furrow is arranged in parallel with the concealed pipe.

[0063] Step S2: Diffusion stage. The outlet of the blind pipe is still closed. 1.5 days after the end of the previous stage, all irrigation ditches start to irrigate at a high flow rate until the soil is saturated. After stopping irrigation, leave a residence time of no less than 24 hours to strengthen the migration of salt from small pores to large pores.

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

[0065] Step S4: Water-saving and drainage-reduction stage. This stage acts on the efficient utilization of water and fertilizer resources during the crop growth period. The depth of the drainage ditch is controlled to be 10 cm lower than the crop root zone, and irrigation is carried out in rotation according to the crop water demand.

[0066] In addition, before the start of the four stages, the plow bottom layer is broken to promote the infiltration of irrigation water and salt, and the crop straw is deeply plowed below the root zone or the thin layer of soil under the tillage layer is replaced to prevent the accumulation of salt upwards. Then the land is prepared and irrigation ditches are dug between the crop rows. Small ditches with a width of 35-50cm are preferably used.

[0067] The drainage ecological regulation method provided in this application implements drainage regulation in stages and scenarios based on full consideration of the impact of soil pore structure on water-salt movement and synergistic salt inhibition by irrigation and drainage, thereby achieving the ecological goals of efficient desalination and salt inhibition, reducing drainage nitrogen and phosphorus pollution, and saving water and fertilizer resources.

[0068] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A drainage ecological control method for coordinated irrigation and drainage to reduce saline-alkali obstacles, characterized in that: The following steps are involved: Step S1: In the infiltration and dissolution stage, under the condition that the drainage outlet is closed, a small flow irrigation is carried out at the farthest end from the drainage ditch pipe, so that a large amount of irrigation water enters the small pores in the soil profile to infiltrate and dissolve the salt; Step S2: During the diffusion stage, the drainage outlet is raised. Under the condition that the drainage outlet height is lower than the field surface, water is evenly distributed and a large flow rate is irrigated to fill the pores of all sizes in the soil profile with irrigation water, thereby strengthening the diffusion process of salt. Step S3: During the convection desalination stage, the drainage outlet is opened, and the depth of the drainage outlet is flush with the depth of the drainage ditch pipe, so that the salt water is evenly discharged from the soil; Step S4: In the water-saving and emission-reduction stage, the depth of the drainage outlet is made lower than the crop root zone, and on this basis, the connectivity of small pores is broken to prevent the upward movement of soil salt during crop growth.

2. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 1, characterized in that: The ratio R of the irrigation water volume in step S1 to that in step S2 im for: Among them, θ s is the soil saturated moisture content, θ f is the soil moisture content, θ r is the residual moisture content of the soil.

3. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed 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 drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 1, characterized in that: The method of breaking the connection between small pores in step S4 at least includes deep ploughing, deep turning of straw and replacement of the thin layer of soil under the tillage layer.

5. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 1, characterized in that: During the small flow irrigation in step S1, the irrigation is stopped when the moisture content of the soil profile reaches the field holding moisture content.

6. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 1, characterized in that: During the uniform water distribution irrigation in step S2, the irrigation stops when the water content of the soil profile reaches saturation.

7. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 1, characterized in that: When the salt water is uniformly discharged from the soil in step S3, the desalination is completed after the moisture content of the soil profile returns to the field.

8. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 4, characterized in that: The replacement thin layer in the replacement of the thin layer of soil under the tillage layer is 20-30 cm below the tillage layer, the depth of the replacement thin layer is 5-10 cm, and the replacement medium in the thin layer is coarse gravel particles with an average particle size range of 0.5-1.5 mm.

9. The drainage ecological regulation method for coordinated irrigation and drainage to reduce saline-alkali obstacles as claimed in claim 4, characterized in that: The method for replacing the thin layer of soil under the tillage layer is direct landfilling or bag filling.

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