Experimental apparatus and method for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation.

Abstract

This invention discloses an experimental device and method for simulating soil nitrogen cycle under alternating wet and dry conditions in furrow irrigation, relating to the field of agricultural irrigation. The device includes a main module for a furrow irrigation soil column experiment, comprising a vertically arranged, hollow column for layering experimental soil, with an open upper section. A furrow irrigation gas collection module is coaxially positioned at the top of the column and sealed to the opening, used to collect nitrogen gas generated and released by the soil. A leachate uniform collection module is coaxially positioned at the bottom of the column, used to support, filter, and collect downward seepage water formed during furrow irrigation. A wet-dry alternation process control module is located below the leachate uniform collection module, connected to it via an outlet pipe equipped with an outlet valve. This invention can controllably simulate the hydrodynamic process of alternating wet and dry conditions in furrow irrigation and can achieve simultaneous acquisition of nitrogen information from multiple media.

Description

Technical Field

[0001] This invention relates to the field of agricultural irrigation technology, and in particular to an experimental apparatus and method for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation. Background Technology

[0002] Furrow irrigation is a widely used surface irrigation method in agricultural production. Its irrigation process exhibits a cyclical wet-drying pattern characterized by water storage, infiltration, and drying. This hydrodynamic process significantly alters soil moisture distribution and the redox environment, thus having a crucial impact on the migration and transformation of soil nitrogen. Therefore, accurately simulating the wet-drying conditions of furrow irrigation and simultaneously acquiring information on the migration and transformation of soil nitrogen in multiple media is a core prerequisite for quantitatively studying soil nitrogen cycling and flux balance under furrow irrigation conditions.

[0003] To investigate the migration patterns of soil moisture and solutes, various indoor soil column experimental devices have been developed in the current technology. These devices are also commonly used tools for studying soil nitrogen transport. The existing devices use a vertically arranged transparent column as the main experimental body. The column is filled with layers of soil to simulate a farmland soil profile. Multiple sampling holes / interfaces are opened on the side walls of the column to collect soil water samples at different depths. A filtration structure and a leachate collection device are installed at the bottom of the column to collect downward seepage soil water. During the experiment, the device mainly uses top water supply or bottom water level control to allow water to infiltrate or redistribute within the soil column, thereby studying the vertical migration characteristics of water and dissolved solutes in the soil under continuous infiltration or steady hydraulic conditions.

[0004] However, the existing soil column experimental apparatus and supporting methods have insurmountable technical defects when applied to soil nitrogen cycle research under furrow irrigation conditions. These defects are mainly reflected in two aspects: First, the apparatus is designed for continuous infiltration or stable hydraulic conditions, and cannot controllably simulate the dynamic hydrodynamic characteristics of alternating water storage, infiltration, and drying during furrow irrigation. This results in significant deviations between the soil moisture state and aeration conditions in the experiment and the actual environment of furrow-irrigated farmland. Consequently, the conditions for the occurrence of key transformation processes such as nitrogen nitrification and denitrification do not match reality, seriously affecting the authenticity and reproducibility of the experimental results. Second, the apparatus only focuses on the collection and detection of nitrogen in the liquid phase (soil water and leachate), lacking a collection structure and supporting methods for nitrogen gaseous loss. It cannot achieve simultaneous collection of soil water, leachate, and nitrogen gas within the same experimental system, making it difficult to simultaneously quantify nitrogen leaching flux and gaseous loss flux in the study. This makes it impossible to fully construct the mass balance relationship of soil nitrogen under furrow irrigation conditions, greatly limiting the comprehensive and in-depth quantitative research on soil nitrogen cycle processes.

[0005] In summary, there is an urgent need to design a technical solution that can controllably simulate the alternating wet and dry hydrodynamic process of furrow irrigation and achieve synchronous acquisition of nitrogen information from multiple media. Summary of the Invention

[0006] The purpose of this invention is to provide an experimental device and method for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation, so as to solve the problems existing in the prior art. It can controllably simulate the hydrodynamic process of alternating wet and dry conditions of furrow irrigation and can realize the synchronous acquisition of nitrogen information in multiple media.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides an experimental apparatus for simulating soil nitrogen cycling under alternating wet and dry conditions of furrow irrigation, comprising: The main module of the furrow irrigation soil column experiment includes a vertically arranged and hollow column, the interior of which is used to fill experimental soil in layers, and the upper part of the column is an open structure. The furrow irrigation gas collection module is coaxially mounted on the top of the column and sealed to the opening at the top of the column, and is used to collect nitrogen gas generated and released by the soil. A seepage fluid uniform collection module, coaxially mounted at the bottom of the column, is used to support, filter, and collect the downward seepage water generated during furrow irrigation; and A wet-dry alternation process control module is located below the leachate uniform collection module. The wet-dry alternation process control module is connected to the leachate uniform collection module through a water outlet pipe, and a water outlet valve is provided on the water outlet pipe.

[0008] In one embodiment, the column sidewall is provided with multiple sampling interfaces in layers along the height direction, each sampling interface corresponding to a different soil depth, and a soil water sampler is sealed and connected to the sampling interface for stratified collection of soil water samples at different depths during furrow irrigation.

[0009] In one embodiment, an air vent valve is provided on the side wall of the lower part of the column to release the air trapped inside the column during the irrigation fluid injection or soil saturation stage.

[0010] In one embodiment, the furrow irrigation gas collection module includes a gas collection hood with an open bottom and a closed top. The bottom opening of the gas collection hood is fixedly and sealed to the top opening of the main body, and a gas sampling interface is provided on the side wall of the gas collection hood.

[0011] In one embodiment, the bottom of the gas collection hood is provided with an annular connecting structure, which is arranged around the lower opening of the gas collection hood. The annular connecting structure has a plurality of bolt holes evenly distributed along the circumferential direction. The top edge of the column is provided with a flange interface that matches the annular connecting structure. The gas collection hood is fixedly connected to the flange interface of the column through the annular connecting structure, and a sealing gasket is provided between the contact surfaces of the annular connecting structure and the flange interface.

[0012] In one embodiment, the leaked fluid uniform collection module includes: A perforated plate, which is installed at the lower end outlet of the column, is used to support the soil and achieve uniform infiltration of the leachate; A leakage fluid collection chamber, located at the bottom of the perforated plate, is used to collect the leakage fluid; and The bottom plate of the water chamber is fixedly and sealed at the lower end of the leakage collection chamber to form a closed bottom of the leakage collection chamber.

[0013] In one embodiment, the perforated plate is provided with a filter screen, which is coaxially arranged with the perforated plate, and the outer edge of the perforated plate is provided with an annular flange edge; the perforated plate is sealed to the bottom of the column through the annular flange edge, and a sealing gasket is provided at the interface between the perforated plate and the column.

[0014] In one embodiment, the outer edge of the water chamber bottom plate extends outward to form an annular flange edge, and the outer edge of the water chamber bottom plate is sealed to the side wall of the leakage collection chamber through the annular flange edge; a water outlet hole is provided in the central area of ​​the water chamber bottom plate, and the water outlet hole is used to connect to one end of the water outlet pipe, thereby guiding the collected leakage liquid to the wet-dry alternating process control module.

[0015] In one embodiment, both the column and the gas collection hood are made of transparent material.

[0016] The present invention also provides an experimental method for simulating soil nitrogen cycling under alternating wet and dry conditions of furrow irrigation, comprising the following steps: Construct the experimental setup and install the stratified sampling system; Experimental soil was layered and filled into the column of the experimental apparatus to construct a soil profile. Irrigation solution was injected through the top of the column to form a furrow irrigation water storage layer, and gas samples were collected. Adjust the outlet valve to control the uniform discharge of leachate from the collection module, realize the infiltration and drying of the column, and collect liquid phase samples; Repeat the alternating wet and dry irrigation process multiple times; collect different liquid and gas samples simultaneously in each round; Calculate nitrogen migration and transformation fluxes and construct nitrogen mass balance relationships.

[0017] The present invention achieves the following technical effects compared to the prior art: This invention, by setting up a wet-dry alternation process control module and controlling the effluent process, enables the experimental system to form typical furrow irrigation stages of water storage, infiltration, and drying under indoor conditions. This allows the invention to controllably and repeatedly simulate the wet-dry alternation hydrodynamic process of furrow irrigation, improving the consistency and repeatability of experimental conditions with the real furrow irrigation process from the source. Furthermore, this invention integrates a soil water sampler capable of stratified soil water sampling, a furrow irrigation gas collection module, and a leachate uniform collection module, achieving the coordinated collection of multi-media samples of soil water, leachate, and gas. Therefore, it can simultaneously and quantitatively obtain information on nitrogen migration and loss in the aqueous and gas phases, improving the completeness and accuracy of nitrogen cycle flux calculation and mass balance analysis. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the experimental device for simulating soil nitrogen cycle under alternating wet and dry conditions in one or more embodiments of the present invention. Figure 2 This is a schematic diagram of a ring connection structure in one or more embodiments of the present invention; Figure 3 for Figure 2 Side view; Figure 4 This is a schematic diagram of a perforated plate in one or more embodiments of the present invention; Figure 5 for Figure 4 Side view; Figure 6 This is a schematic diagram of the water chamber bottom plate in one or more embodiments of the present invention; Figure 7 for Figure 6 Side view; Figure 8 This is a schematic diagram of a method for simulating soil nitrogen cycle under alternating wet and dry conditions in one or more embodiments of the present invention.

[0020] In the diagram: 1-Furrow irrigation gas collection module, 11-Gas sampling interface, 12-Annular connection structure, 121-First bolt hole, 2-Furrow irrigation soil column experimental main module, 21-Sampling interface, 22-Exhaust valve, 23-Connecting pipe, 3-Permeate uniform collection module, 31-Porous plate, 311-Filter screen, 312-Second bolt hole, 32-Water chamber bottom plate, 321-Third bolt hole, 322-Water outlet hole, 4-Wet-dry alternating process control module, 41-Water outlet valve. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0022] The purpose of this invention is to provide an experimental device and method for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation, so as to solve the problems existing in the prior art. It can controllably simulate the hydrodynamic process of alternating wet and dry conditions of furrow irrigation and can realize the synchronous acquisition of nitrogen information in multiple media.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Existing indoor soil column experiments are typically based on continuous water supply or stable hydraulic conditions, making it difficult to reproduce the alternating wet-dry hydrodynamic characteristics of water storage, infiltration, and drying during furrow irrigation in farmland. This results in soil moisture and aeration changes that do not conform to actual furrow irrigation conditions, leading to deviations in the occurrence conditions of nitrogen migration and transformation processes (such as nitrification and denitrification), thus limiting the authenticity and reproducibility of nitrogen cycle studies under furrow irrigation conditions. Furthermore, existing technologies often lack gas collection structures or multi-media collaborative collection designs, making it difficult to simultaneously acquire soil water, seepage water, and gas samples within the same system. This makes it difficult to quantify nitrogen gaseous loss and leaching flux together, hindering the establishment of nitrogen mass balance. To address this issue, this invention provides an experimental device for simulating soil nitrogen cycle under alternating wet-dry conditions during furrow irrigation. This device constructs a farmland soil profile space under indoor conditions and specifically simulates the periodic hydrodynamic processes of water storage, infiltration, and drying during furrow irrigation, enabling the study of the coordinated migration and transformation of soil nitrogen in the aqueous, gaseous, and solid phases. Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7As shown, the experiment includes a main module 2 for furrow irrigation soil column experiments, a furrow irrigation gas collection module 1, a leachate uniform collection module 3, and a wet-dry alternation process control module 4. The main module 2 for furrow irrigation soil column experiments consists of a vertically arranged, hollow column. The interior of the column is used to fill experimental soil in layers. The upper part of the column is an open structure. Multiple sampling ports 21 are arranged in layers along the height direction on the side wall of the column. Each sampling port 21 corresponds to a different soil depth. A soil water sampler is sealed and connected to the sampling port 21 to collect soil water at different depths during furrow irrigation. The sample is collected in layers. The furrow irrigation gas collection module 1 is coaxially mounted at the top of the column and sealed to the opening at the top of the column to collect nitrogen gas generated and released by the soil. The leachate uniform collection module 3 is coaxially mounted at the bottom of the column to support, filter, and collect the downward seepage water formed during furrow irrigation. The wet-drying process control module 4 is located below the leachate uniform collection module 3 and is connected to the leachate uniform collection module 3 via an outlet pipe equipped with an outlet valve 41. By controlling the opening and closing of the outlet valve 41, the discharge process of the leachate collected by the leachate uniform collection module 3 is controlled, thereby constructing different hydrodynamic stages such as water storage, infiltration, and drying within the main module 2 of the furrow irrigation soil column experiment.

[0025] This invention, by incorporating a wet-dry alternation process control module 4 at the bottom of the column and controlling the water outflow process, establishes typical water storage, infiltration, and drying stages in furrow irrigation within an indoor experimental setup, thereby controllably and repeatedly simulating the wet-dry alternation hydrodynamic process of furrow irrigation. The invention integrates multiple soil water samplers arranged vertically within the same experimental setup, forming a stratified soil water sampling structure. It also integrates a furrow irrigation gas collection module 1 and a leachate uniform collection module 3, enabling simultaneous acquisition of multi-media samples including soil water, leachate, and gas. This provides a structural basis for analyzing the migration, transformation, and flux of soil nitrogen in the aqueous, gaseous, and solid phases under furrow irrigation conditions. The furrow irrigation gas collection module 1 of this invention features a detachable structure and works in conjunction with the wet-dry alternation process, enabling effective collection of gaseous nitrogen within a set time period without interfering with the furrow irrigation hydrodynamic process. This design further enhances the relevance and practicality of this invention in furrow irrigation nitrogen cycle research.

[0026] In one embodiment, the column is a vertically oriented transparent cylinder with its axis aligned with the direction of gravity, used to simulate the natural vertical structure of farmland soil. The upper end of the main soil column experimental module is open, used to form a short-term water storage layer under furrow irrigation conditions during the experiment, thereby simulating the water accumulation state in furrows. The interior of the column is filled with experimental soil in layers according to the actual farmland soil profile structure, with each soil layer maintaining natural contact to reflect the vertical migration characteristics of water and nitrogen under real farmland conditions. An air vent valve 22 is provided on the lower side wall of the column to release trapped air inside the column during irrigation fluid injection or soil saturation, ensuring the uniformity of soil moisture distribution and the repeatability of experimental conditions during furrow irrigation infiltration.

[0027] In one embodiment, a vertically arranged connecting pipe 23, which is at the same height as the column, is fixedly inserted into the column. The side wall of the connecting pipe 23 has a channel communicating with the inside of the column. A horizontal adapter pipe is connected to the bottom of the connecting pipe 23. The horizontal adapter pipe is sealed through the side wall of the column, and a transparent flexible tube at the same height as the connecting pipe 23 is connected to the end of the horizontal adapter pipe away from the connecting pipe 23. The water level in the transparent flexible tube is the same as the water level of the groundwater surface inside the column. The water level of the groundwater surface inside the column can be observed through the water level in the transparent flexible tube during the furrow irrigation process.

[0028] In one embodiment, the furrow irrigation gas collection module 1 includes a gas collection hood with an open bottom and a closed top. The bottom opening of the gas collection hood is fixedly and sealed to the top opening of the main body. A gas sampling interface 11 is provided on the side wall of the gas collection hood. An annular connecting structure 12 is provided at the bottom of the gas collection hood, forming a connecting flange. The annular connecting structure 12 is arranged around the lower opening of the gas collection hood. Multiple bolt holes are evenly distributed along the circumferential direction on the annular connecting structure 12, which are defined as the first bolt hole 121 in this embodiment. A flange interface matching the annular connecting structure 12 is provided on the top edge of the column. The gas collection hood is detachably installed by bolting to the furrow irrigation soil column experimental main body module 2 through the annular connecting structure 12. A sealing gasket is provided between the contact surfaces of the two to ensure the airtightness of the connection. Through the above structural design, the furrow irrigation gas collection module 1 can be quickly assembled and disassembled while ensuring airtightness, thereby meeting the experimental requirements of collecting gas only at specific stages during the alternating wet and dry furrow irrigation process. The gas collection hood is detachably connected to the main module 2 of the furrow irrigation soil column experiment via a flange structure, allowing it to be selectively installed according to experimental needs. During furrow irrigation, the gas collection hood is installed on the top of the column to form a relatively enclosed gas collection space, and gas samples are collected at set time intervals.

[0029] In one embodiment, a uniform leachate collection module 3 is disposed at the lower end of the main body module 2 of the furrow irrigation soil column experiment, and is used to support, filter, and collect the downward seepage water formed during furrow irrigation. The uniform leachate collection module 3 includes a perforated plate 31, a leachate collection chamber, and a water chamber bottom plate 32. The perforated plate 31 is disposed at the lower end outlet of the main body module 2 of the furrow irrigation soil column experiment, and is used to support the soil and realize the uniform downward seepage of leachate. In one embodiment, the porous plate 31 includes a filter screen 311 for blocking soil particles, an annular flange edge disposed on the outer edge of the porous plate 31, and a plurality of bolt holes evenly distributed along the circumferential direction of the annular flange edge. In this embodiment, these are defined as second bolt holes 312. In this embodiment, the porous plate 31, the filter screen 311, and the annular flange edge are integrally formed. A plurality of small through holes are opened at the center of the porous plate 31, and the filter screen 311 is integrally formed on one side of the through holes. In another embodiment, the porous plate 31 and the annular flange edge are integrally formed, while the porous plate 31 and the filter screen 311 are separate structures. The porous plate 31 has a plurality of through holes, and the filter screen 311 is attached to or embedded on one side of the porous plate 31, covering the through holes and achieving a filtering effect. The porous plate 31 is sealed to the main body module 2 of the furrow irrigation soil column experiment by bolts, and a sealing gasket is set at the interface between the porous plate 31 and the column body to prevent leakage of seepage liquid from the connection part laterally. The filter screen 311 effectively blocks fine soil particles from entering the lower collection chamber with the water flow, while ensuring that the leachate can pass evenly throughout the entire cross-section of the column, thereby improving the representativeness and stability of leachate collection.

[0030] A water chamber bottom plate 32 is located at the lower end of the leachate collection chamber. Its overall shape is disc-like, forming a closed bottom for the leachate collection chamber. The outer edge of the water chamber bottom plate 32 extends outward to form an annular flange, on which multiple bolt holes are evenly distributed circumferentially. In this embodiment, these are defined as the third bolt hole 321, used to achieve a sealed connection with the side wall of the leachate collection chamber. A water outlet hole 322 is provided in the central area of ​​the water chamber bottom plate 32. The water outlet hole 322 is used to connect to a water outlet pipe, thereby guiding the collected leachate to the wet-dry alternating process control module 4. Through the structural design of the water chamber bottom plate 32, stable hydraulic boundary conditions are formed within the collection chamber, and the leachate can be quantitatively and controllably discharged under the control of the water outlet hole 322, providing a basis for the accurate measurement of leachate flux under furrow irrigation conditions.

[0031] In one embodiment, the control method for realizing the alternating wet and dry irrigation process is not limited to the control structure of the water outlet valve 41 described in the embodiment. Other control methods that can regulate the water discharge process in the soil column can also be used, such as adjusting the opening and closing of the water outlet channel, changing the water outlet resistance, or using other forms of controllable drainage structure. As long as the water storage, infiltration and drying stages can be formed inside the soil column, the purpose of the invention can be achieved.

[0032] Regarding gas collection, the detachable gas collection module used in the embodiment can also be replaced with other structural forms that can collect gases from the soil surface during the alternating wet and dry irrigation process, such as an overall hood structure or a partially sealed collection structure. The specific structural form does not constitute a substantial impact on the purpose of this invention.

[0033] This invention also provides an experimental method for simulating soil nitrogen cycling under alternating wet and dry conditions of furrow irrigation, such as... Figure 8 As shown, it includes the following steps: Step S1: Construct the experimental setup and install the stratified sampling system; set a light-shielding layer on the outer wall of the main module 2 of the furrow irrigation soil column experiment, and install soil water samplers at the corresponding soil depth positions along the height direction, so that they correspond one-to-one with the sampling interfaces set on the side wall of the column, thereby constructing a stratified soil water sampling system.

[0034] Step S2: Fill the column of the experimental device with experimental soil in layers to construct a soil profile; lay a layer of quartz sand on the porous support structure of the leachate uniform collection module 3; then fill the soil column with experimental soil in layers according to the actual farmland soil bulk density parameters to construct a soil profile structure that is close to the actual farmland conditions.

[0035] Step S3: Irrigation liquid is injected through the top of the column to form a furrow irrigation water storage layer; a predetermined volume of irrigation liquid is injected into the column through the opening at the top of the soil column to form a short-term stable water storage layer on the soil surface, simulating the water accumulation state in the furrow during furrow irrigation. The furrow irrigation gas collection module 1 is installed on the top of the soil column.

[0036] Step S4: Adjust the outlet valve 41 to control the water discharge of the leachate uniform collection module 3, realize the infiltration and drying in the column, and collect gas and liquid phase samples; open the outlet valve 41 in the wet-dry alternation process control module 4 to allow the irrigation liquid to infiltrate downward under the action of gravity and form leachate at the bottom of the soil column; collect leachate samples through the leachate uniform collection module 3, and collect soil water through the sealed sampling interface on the side wall of the soil column experimental main module; after the surface water infiltration is completed, the drying stage begins. During the time range before the end of infiltration and during the drying stage, gas samples are continuously collected to obtain information on nitrogen gas generated under the wet-dry alternation conditions of furrow irrigation.

[0037] Step S5: Repeat the alternating wet and dry furrow irrigation process multiple times; repeat steps S3 to S4 to complete the alternating wet and dry furrow irrigation process multiple times; collect soil water samples, leachate samples and gas samples at different depths simultaneously in each round.

[0038] Step S6: Calculate nitrogen migration and transformation fluxes and construct nitrogen mass balance relationships; based on the collected nitrogen index concentration data in soil water, leachate, gas, and soil samples, calculate the nitrogen migration and transformation fluxes in the aqueous, gaseous, and solid phases under furrow irrigation conditions, and construct nitrogen mass balance relationships. This invention's experimental method, by repeatedly performing furrow irrigation water storage, infiltration, and drying processes, and simultaneously collecting multi-media samples in each round, achieves quantitative analysis and mass balance calculation of the soil nitrogen cycle under furrow irrigation conditions.

[0039] In one embodiment, the specific operation sequence, duration of each stage, and number of repetitions of the alternating wet and dry furrow irrigation process can be adjusted according to experimental requirements. As long as the alternating wet and dry furrow irrigation process can be realized and the collection of multi-media samples such as soil water, seepage water, and gas can be completed simultaneously, it should be regarded as an equivalent implementation of the method of the present invention.

[0040] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. An experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation, characterized in that: include: The main module of the furrow irrigation soil column experiment includes a vertically arranged and hollow column, the interior of which is used to fill experimental soil in layers, and the upper part of the column is an open structure. The furrow irrigation gas collection module is coaxially mounted on the top of the column and sealed to the opening at the top of the column. It is used to collect nitrogen gas generated and released by the soil. The furrow irrigation gas collection module can be quickly assembled and disassembled while ensuring airtightness, meeting the experimental requirements of gas collection only at specific stages during the alternating wet and dry furrow irrigation process. The furrow irrigation gas collection module adopts a detachable structure and works in conjunction with the alternating wet and dry furrow irrigation process, thereby achieving effective collection of gaseous nitrogen within a set time period without interfering with the furrow irrigation hydrodynamic process. A uniform leakage collection module is coaxially mounted at the bottom of the column to support, filter, and collect the downward leakage water formed during furrow irrigation. as well as A wet-dry alternation process control module is located below the leachate uniform collection module. The wet-dry alternation process control module is connected to the leachate uniform collection module through a water outlet pipe, and a water outlet valve is provided on the water outlet pipe. An air vent valve is provided on the lower side wall of the column to release the air trapped inside the column during the irrigation fluid injection or soil saturation stage. The leaked fluid uniform collection module includes: A perforated plate, which is installed at the lower end outlet of the column, is used to support the soil and achieve uniform infiltration of the leachate; A leakage fluid collection chamber, located at the bottom of the perforated plate, is used to collect the leakage fluid; and The bottom plate of the water chamber is fixedly and sealed at the lower end of the leakage collection chamber to form a closed bottom of the leakage collection chamber; A water outlet hole is provided in the central area of ​​the bottom plate of the water chamber. The water outlet hole is used to connect to one end of the water outlet pipe, thereby guiding the collected leachate to the wet-dry alternation process control module. By opening and closing the water outlet valve, the discharge process of the leachate collected by the leachate uniform collection module is controlled, thereby constructing the water storage, infiltration and drying hydrodynamic stages inside the main module of the furrow irrigation soil column experiment.

2. The experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions under furrow irrigation as described in claim 1, characterized in that: The column sidewall is provided with multiple sampling interfaces in layers along the height direction. Each sampling interface corresponds to a different soil depth. A soil water sampler is sealed and connected to each sampling interface for stratified collection of soil water samples at different depths during furrow irrigation.

3. The experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions under furrow irrigation as described in claim 1, characterized in that: The furrow irrigation gas collection module includes a gas collection hood with an open bottom and a closed top. The bottom opening of the gas collection hood is fixedly and sealed to the top opening of the column. The side wall of the gas collection hood is provided with a gas sampling interface.

4. The experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions under furrow irrigation as described in claim 3, characterized in that: The bottom of the gas collection hood is provided with an annular connecting structure, which is arranged around the lower opening of the gas collection hood. Multiple bolt holes are evenly distributed along the circumferential direction on the annular connecting structure. The top edge of the column is provided with a flange interface that matches the annular connecting structure. The gas collection hood is fixedly connected to the flange interface of the column through the annular connecting structure, and a sealing gasket is provided between the contact surfaces of the annular connecting structure and the flange interface.

5. The experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions under furrow irrigation as described in claim 1, characterized in that: The perforated plate is provided with a filter screen, which is coaxially arranged with the perforated plate. The outer edge of the perforated plate is provided with an annular flange. The perforated plate is sealed to the bottom of the column through the annular flange. A sealing gasket is provided at the interface between the perforated plate and the column.

6. The experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation according to claim 1, characterized in that: The outer edge of the water chamber bottom plate extends outward to form an annular flange edge, and the outer edge of the water chamber bottom plate is sealed to the side wall of the leakage collection chamber through the annular flange edge.

7. The experimental apparatus for simulating soil nitrogen cycle under alternating wet and dry conditions of furrow irrigation according to claim 3, characterized in that: Both the column and the gas collection hood are made of transparent material.

8. A method for simulating soil nitrogen cycling under alternating wet and dry conditions under furrow irrigation, based on the experimental apparatus for simulating soil nitrogen cycling under alternating wet and dry conditions according to any one of claims 1 to 7, characterized in that: Includes the following steps: Construct the experimental setup and install the stratified sampling system; Experimental soil was layered and filled into the column of the experimental apparatus to construct a soil profile. Irrigation solution was injected through the top of the column to form a furrow irrigation water storage layer, and gas samples were collected. Adjust the outlet valve to control the uniform discharge of leachate from the collection module, realize the infiltration and drying of the column, and collect liquid phase samples; Repeat the alternating wet and dry irrigation process multiple times; collect different liquid and gas samples simultaneously in each round; Calculate nitrogen migration and transformation fluxes and construct nitrogen mass balance relationships.

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