Observation device for nutrient migration and transformation of crop-soil-underground water continuum

Abstract

The utility model provides a crop-soil-underground water continuum nutrient migration and transformation observation device which comprises a lysimeter arranged in soil, the top of the lysimeter is flush with the ground, a time domain reflectometer and a soil sampler are arranged in the middle of the lysimeter, and the lysimeter is filled with soil; a U-shaped pipe communicated with the lysimeter column is arranged at the bottom of the lysimeter column, and the tail end of the U-shaped pipe extends out of the ground; a filter membrane is arranged at the joint of the evaporation and permeation column and the U-shaped pipe; the water level formed by communicating one side of the U-shaped pipe with the bottom of the lysimeter column is used for representing the water surface of underground water, the other side of the U-shaped pipe is used for observing the underground water, the formed crop-soil-underground water continuum is simple in structure, in addition, a water collecting bottle of the underground water sampler extends into the other side of the U-shaped pipe to directly collect a water sample, the operation is simple and convenient, and the cost is low. The technical problems that in the prior art, an observation device is complex in structure and not easy and convenient to operate are solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of agricultural environmental engineering protection, and relates to an observation device, in particular to an observation device for the migration and transformation of nutrients in a crop-soil-groundwater continuum. Background Art

[0002] Water and fertilizer are essential nutrients for crops. However, improper use of water and fertilizer often causes nutrients (such as C, N, and P) to accumulate and remain in the soil and shallow groundwater, leading to irreversible agricultural non-point source pollution. Only by clarifying the migration and transformation processes of nutrients within the crop-soil-groundwater continuum, including loss, retention, and accumulation, can we ensure the scientific and rational use of water and fertilizers and protect the agricultural ecosystem. Uncovering the nutrient migration and transformation processes presents three challenges: First, the migration and transformation process is complex, involving diverse physical, chemical, and biochemical interactions within different environments, including the root zone (cultivated layer), the subroot soil layer, and the shallow groundwater. Second, the migration and transformation process is dynamic, responding differently to different crops, irrigation, and fertilization. Third, the migration and transformation process is slow, and short-term experimental observations within a single planting season cannot fully reveal the entire migration and transformation process, requiring long-term experimental observations. Current research methods primarily include large-scale field observations (Ye Youliang et al. (2004), Ma Huan et al. (2012), and Wang Li (2017)) and small-scale field seepage tanks (Luo Xiaosheng et al. (2022)) and field lysimeter observations. Field observations are limited to the root zone of crop plants, and groundwater observations are difficult to achieve due to the large scale of the field, which requires the construction of numerous wells. Field seepage tanks (earth pits 1.5 m long, 0.8 m wide, and 0.9 m deep) use containers to collect and test the nitrogen composition and content of seepage liquid from the seepage pits to study nitrogen loss and residual nitrogen. Because the test seepage pits are surrounded by natural soil boundaries, it is impossible to control and prevent water and fertilizer from entering the pits, which would affect the accuracy of the test results. She Yingjun et al. (2022) used a lysimeter (40 cm in diameter, 60 cm in depth, and 0.5 cm in thickness) in a soil-filled winter wheat field to observe nitrogen fertilizer seepage in soil and groundwater. However, the device was small and difficult to operate, making it unsuitable for large-scale crop plantings such as corn. Bai Fangfang et al. (2022) used a lysimeter (1.5 m long, 3 m wide, and 2.8–4.8 m deep) in a summer corn and winter wheat rotation under conditions of varying groundwater depths and nitrogen fertilizer application levels controlled by a Malvern flask water supply system. However, the device was complex, difficult to operate, occupied a large area, was expensive for long-term observations, and had poor adaptability to field conditions. Utility Model Content

[0003] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an observation device for the migration and transformation of nutrients in the crop-soil-groundwater continuum, so as to solve the technical problems of the existing technology that the observation device has a complex structure and is not easy to operate.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A device for observing the migration and transformation of nutrients in a crop-soil-groundwater continuum comprises a lysimeter column disposed in the soil, wherein the top of the lysimeter column is flush with the ground, a time domain reflectometer and a soil sampler are disposed in the middle of the lysimeter column, and the lysimeter column is filled with soil.

[0006] The bottom of the evaporation column is provided with a U-shaped tube connected thereto, and the end of the U-shaped tube extends out of the ground; a filter membrane is provided at the connection between the evaporation column and the U-shaped tube;

[0007] A groundwater sampler is provided in the U-shaped tube, and the groundwater sampler includes a long rod, a water collecting bottle and a water intake pipe which are connected in sequence. A water inlet is provided at the bottom of the water intake pipe, and a float with a diameter larger than the diameter of the water inlet is provided at the water inlet. A hollow limit plate is provided at the upper part of the water intake pipe.

[0008] The utility model also includes the following technical features:

[0009] The water inlet is serrated.

[0010] A vent hole is provided on the side wall of the water collecting bottle.

[0011] The water collecting bottle and the long rod are connected by threads.

[0012] The height of the end of the U-shaped tube extending out of the ground is 10 cm.

[0013] The end of the U-shaped tube is provided with a waterproof cover.

[0014] The height of the evaporation column is 120 cm, and the distance between the outer wall of the evaporation column and the end of the outer wall of the U-shaped tube is 20 cm.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects:

[0016] (I) The present invention utilizes the water level formed by the connection between one side of the U-shaped tube and the bottom of the evaporation column to represent the groundwater surface, and observes the groundwater on the other side of the U-shaped tube. The structure of the crop-soil-groundwater continuum thus formed is simple. In addition, the water collecting bottle of the groundwater sampler extends into the other side of the U-shaped tube to directly collect water samples, which is easy to operate. This solves the technical problems of the complicated structure and inconvenient operation of the observation device in the prior art.

[0017] (II) The water inlet of the groundwater sampler in the present invention is serrated to prevent clogging by sediment.

[0018] (III) The water collecting bottle of the present invention is provided with a vent, which is more conducive to the water flowing into the water collecting bottle from the water inlet; the water collecting bottle is connected to the long rod with a thread, which is convenient for disassembly and replacement.

[0019] (IV) The utility model has a simple structure, is easy to operate and occupies little space, and is highly applicable in long-term, repeated and comparative tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0021] Figure 2 for Figure 1 Schematic top view of

[0022] Figure 3 for Figure 1 Schematic diagram of the structure of the groundwater sampler.

[0023] The meanings of the various numbers in the figure are: lysimeter column 1, time domain reflectometer 2, soil sampler 3, U-shaped tube 4, groundwater sampler 5, vent 6, waterproof cover 7, filter membrane 8;

[0024] Long pole 501, water collection bottle 502, water intake pipe 503;

[0025] Water inlet 50301, floating plant 50302, hollow limit plate 50303.

[0026] The specific contents of the present invention are further explained in detail below with reference to the embodiments. DETAILED DESCRIPTION

[0027] It should be noted that, unless otherwise specified, all components in the present invention are components known in the art.

[0028] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the scope of protection of the present invention.

[0029] The present invention provides an observation device for the migration and transformation of nutrients in a crop-soil-groundwater continuum, comprising a lysimeter column 1 disposed in the soil, wherein the top of the lysimeter column 1 is flush with the ground, a time domain reflectometer 2 and a soil sampler 3 are disposed in the middle of the lysimeter column 1, and the lysimeter column 1 is filled with soil;

[0030] The bottom of the evapotranspiration column 1 is provided with a U-shaped tube 4 in communication therewith, and the U-shaped tube 4 extends out of the ground at the end thereof; the connecting portion of the evapotranspiration column 1 and the U-shaped tube 4 is provided with a filter membrane 8;

[0031] The U-shaped tube 4 is provided with a groundwater sampler 5, which comprises a long rod 501, a water collecting bottle 502 and a water taking pipe 503 connected in sequence, the bottom of the water taking pipe 503 is provided with a water inlet 50301, the water inlet 50301 is provided with a float 50302 having a diameter larger than that of the water inlet 50301, and the upper portion of the water taking pipe 503 is provided with a hollow limiting disc 50303.

[0032] In the above technology, the water level on one side of the U-shaped tube 2 in communication with the bottom of the evapotranspiration column 1 represents the underground water level, and the underground water is observed on the other side of the U-shaped tube, and the structure of the crop-soil-underground water continuum is simple, in addition, the water collecting bottle of the groundwater sampler extends into the other side of the U-shaped tube to directly collect water samples, which is simple to operate, and solves the technical problems of complex structure and inconvenient operation of the observation device in the prior art.

[0033] Among them, the time domain reflectometer (2) and the soil sampler (3) are both conventional devices.

[0034] Specifically, the water inlet 50301 is sawtooth-shaped, which can effectively prevent the water inlet from being blocked by silt.

[0035] Specifically, the sidewall of the water collecting bottle 502 is provided with a ventilation hole 6.

[0036] In the above technical solution, the ventilation hole 6 is more conducive to the inflow of water into the water collecting bottle; the water collecting bottle and the long rod are connected by threads, which is convenient for disassembly and replacement.

[0037] Specifically, the water collecting bottle 502 and the long rod 501 are connected by threads, which is convenient for installation and disassembly.

[0038] Specifically, the height of the end of the U-shaped tube 4 extending out of the ground is 10 cm, which is used to prevent rainwater from entering.

[0039] Specifically, the end of the U-shaped tube 4 is provided with a waterproof cover 7, which is used to prevent external rainwater from entering the observation system.

[0040] Specifically, the height of the evapotranspiration column 1 is 120 cm, and the distance between the outer wall of the evapotranspiration column 1 and the end of the outer wall of the U-shaped tube 4 is 20 cm.

[0041] Actual measurement example:

[0042] I. Simulation of crop-soil-underground water continuum

[0043] For example, Figure 1Farmland soil was layered according to its natural bulk density within lysimeter column 1. A time-domain reflectometer was installed at a depth of 1 meter in the center of column 1, with the measuring tube approximately 5 cm above the ground surface. The water level in the U-shaped tube remained consistent. Summer corn was planted on the surface of column 1, and winter wheat was planted after harvest, forming a soil and groundwater continuum under the continuous wheat-corn cropping system.

[0044] Nine evaporation column observation experiments were arranged according to step 1, with three N fertilization levels (high, medium, and low) and three replicates for each fertilization level.

[0045] Schedule fertilization frequency and dosage based on the crop growth cycle. In this example, the total fertilizer amount for a single crop season is applied evenly in three applications. The irrigation schedule and amount are the same for all crops.

[0046] 2. Monitoring of moisture and nutrients in crops and soil

[0047] Time domain reflectometry was used to measure soil moisture content (volume moisture content) at different depths (20 cm, 40 cm, 60 cm, 60 cm, and 80 cm). The results can reveal the temporal and spatial variations of soil moisture in the crop-soil relationship.

[0048] Arrange 1-2 different sampling points in each lysimeter column, and use a soil sampler to collect soil profile samples at different depths at each point, such as 0-20cm, 20-40cm, 40-60cm, 60-80cm, etc. The samples from different points of the same lysimeter column 1 are evenly mixed into a sample of one point. The soil profile samples of the three points of the lysimeter column 1 are evenly mixed to obtain a mixed soil profile sample. Therefore, three soil profile samples were collected for the three N fertilization levels. The sampling frequency is arranged according to the crop growth cycle and one week after fertilization. Generally, 3-4 sampling times are arranged for a single crop.

[0049] 3. Soil samples are sent to the laboratory for nutrient testing.

[0050] 3. Groundwater nutrient monitoring

[0051] 1. If Figure 3 Place a groundwater sampler 5 in the left side of the U-shaped tube and extend the water intake pipe 503 below the water surface. Float 50302, under the buoyancy of the water, moves upward to the hollow limit plate (50303). Water from the water intake flows into the water collection bottle 502. When the water collection bottle is filled with about 100mL of water, lift the long rod 501, and the float falls back to the middle of the water intake to block the water inflow. Remove the groundwater sampler 5, and the water in the water collection bottle 502 is transferred to the sampling bottle. The frequency of groundwater sampling is the same as that of soil sampling.

[0052] 2. Groundwater samples are sent to the laboratory for nutrient content testing.

[0053] 4. Test Results

[0054] The following results can be obtained through the above experiments:

[0055] (1) Crop yield - N fertilizer application amount relationship;

[0056] (2) The spatio-temporal distribution of nutrients under different N fertilizer application amounts, which reveals the migration and transformation of nutrients in crops-soil, and the potential of nutrients flowing into groundwater and polluting the groundwater.

[0057] (3) The test results are used to calibrate and check the mathematical simulation model. The calibrated mathematical simulation model can be used to predict the nutrient residue, migration, accumulation and flow direction of soil and groundwater under actual large-scale farmland planting, which can provide a theoretical basis for scientific fertilization, pollution control and improvement in agriculture.

Claims

1. An observation device for the migration and transformation of nutrients in a crop-soil-groundwater continuum, characterized in that: The invention comprises a lysimeter column (1) arranged in the soil, wherein the top of the lysimeter column (1) is flush with the ground, a time domain reflectometer (2) and a soil sampler (3) are arranged in the middle of the lysimeter column (1), and the lysimeter column (1) is filled with soil; A U-shaped tube (4) is provided at the bottom of the evaporation column (1) and is in communication therewith, with the end of the U-shaped tube (4) extending above the ground; a filter membrane (8) is provided at the connection between the evaporation column (1) and the U-shaped tube (4); A groundwater sampler (5) is provided in the U-shaped tube (4), and the groundwater sampler (5) comprises a long rod (501), a water collecting bottle (502), and a water intake pipe (503) which are connected in sequence. A water inlet (50301) is provided at the bottom of the water intake pipe (503), and a floating plant (50302) having a diameter larger than that of the water inlet (50301) is provided at the water inlet (50301). A hollow limiting plate (50303) is provided at the upper portion of the water intake pipe (503).

2. The device for observing the migration and transformation of nutrients in the crop-soil-groundwater continuum according to claim 1, characterized in that: The water inlet (50301) is serrated.

3. The device for observing the migration and transformation of nutrients in the crop-soil-groundwater continuum according to claim 1, characterized in that: A vent hole (6) is provided on the side wall of the water collecting bottle (502).

4. The device for observing the migration and transformation of nutrients in the crop-soil-groundwater continuum according to claim 1, characterized in that: The water collecting bottle (502) and the long rod (501) are connected by threads.

5. The device for observing the migration and transformation of nutrients in the crop-soil-groundwater continuum according to claim 1, characterized in that: The height of the end of the U-shaped tube (4) extending above the ground is 10 cm.

6. The device for observing the migration and transformation of nutrients in the crop-soil-groundwater continuum according to claim 5, characterized in that: A waterproof cover (7) is provided at the end of the U-shaped tube (4).

7. The device for observing the migration and transformation of nutrients in the crop-soil-groundwater continuum according to claim 1, characterized in that: The height of the evaporation column (1) is 120 cm, and the distance between the outer wall of the evaporation column (1) and the end of the outer wall of the U-shaped tube (4) is 20 cm.

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