On-site soil nutrient detection device and detection method, microchannel chip

Abstract

The present invention relates to an on-site soil nutrient detection device and its detection method, and a micro-channel chip. The on-site soil nutrient detection device includes a pretreatment leaching cell, an on-site real-time detection assembly, and a fresh soil pretreatment transfer assembly. The fresh soil pretreatment transfer assembly transfers the fresh soil leaching sample liquid in the pretreatment leaching cell to the on-site real-time detection assembly. The micro-channel chip of the present invention includes a cover plate layer and a chip substrate. The chip substrate includes a soil leaching liquid introduction groove, a quantitative introduction groove, a reagent storage groove, and a snake-shaped mixing area groove, and the like, and the reaction is driven and controlled by centrifugal force to achieve simultaneous detection of multiple types of soil ions, which has the advantages of being efficient, simple, accurate, and rapid. The on-site soil nutrient detection device and its detection method of the present invention realizes rapid detection of the effective forms of nitrogen, phosphate, and potassium in soil by simultaneously and continuously detecting multiple elements, and further achieves direct and rapid on-site detection of fresh soil nutrients based on the analysis of microfluidics and specific fluorescent quantum dots by combining microfluidics and fluorescence detection analysis.

Description

[Technical field]

[0001] The present invention relates to the technical field of soil nutrient detection, and more particularly to an on-site soil nutrient detection device and detection method, and a microchannel chip. [Background technology]

[0002] Agricultural producers blindly apply large amounts of fertilizer in pursuit of yield, and China's current agricultural production faces the problem of increasing fertilizer without increasing production and low nutrient use efficiency. Meanwhile, soil and water pollution has also become a problem that cannot be ignored. Therefore, realizing accurate soil nutrient management and rational fertilization and improving nutrient use efficiency in agricultural production is an effective way to increase food production and reduce environmental pollution under new circumstances, and is also an urgent need to ensure China's food security and sustainable agricultural development. Accurate soil nutrient management is very important for agricultural use reduction and environmental protection in China, and measurement of the available content of soil nitrogen, phosphorus, and potassium is the basis for realizing accurate soil nutrient management.

[0003] In the prior art, the traditional methods for the available content of soil nitrogen, phosphorus and potassium are mainly to collect and survey in the field, collect soil samples, dry and grind them in the laboratory, and measure the nutrient ion content of the soil samples through laboratory analysis (flame spectrophotometry, flow analysis injector method, total nitrogen digestion method, etc.). These methods have a relatively high measurement accuracy of soil nutrient ion content, but the process is complicated, requiring the consumption of a lot of human, material and financial resources, and often causing delays.

[0004] Currently, the rapid detection of the available forms of nitrogen, phosphorus, and potassium in soil requires different detection methods and equipment for different elements, which is time-consuming, requires complicated operations, and requires a large amount and variety of chemical reagents. The detection period for soil samples using traditional methods is long, making it difficult to realize real-time variable fertilization. Therefore, rapid and accurate detection of the available forms of nitrogen, phosphorus, and potassium in soil is extremely important for the realization of precision agriculture and the development of agriculture.

[0005] In order to achieve the goal of rapid detection, the research and development of simultaneous continuous detection technology for multiple elements is an effective way to realize the rapid detection of the effective forms of soil nitrogen, phosphorus, and potassium. The development of microfluidics combined with fluorescence detection analysis technology can solve this problem.

[0006] Microfluidics technology refers to the controlled supply of minute amounts of liquid by constructing microchannels on the order of microns, and has the advantages of low sample demand, fast mass transfer speed, small size and easy portability, simultaneous detection of multiple channels and multiple samples, and easy combination with optical and other detection methods. Microchips manufactured by microfluidics have extremely low material costs, can be filled with minute amounts of reaction reagents in advance, and materials and minute amounts of reagents do not cause secondary pollution to the environment.

[0007] However, it is still unclear how to rapidly measure soil nutrients on-site using microfluidics and fluorescence technology. Therefore, it is necessary to develop a new method that can rapidly and accurately obtain the available content information of soil nitrogen, phosphorus, and potassium in agricultural fields, and is easy to use, easy for farmers to operate, does not require detailed guidance, is easy to implement, and can guide variable fertilization. In addition, to solve the problems to be solved in soil ion on-site detection research, a centrifugal microfluidic chip with a high level of automation, which can achieve efficient, simple, accurate and rapid simultaneous detection of various ions in soil is also required. Summary of the Invention

[0008] The object of the present invention is to provide an on-site soil nutrient detection device, a detection method thereof, and a microfluidic chip to solve the problem in the prior art that it is difficult to quickly and accurately obtain information on the available content of nitrogen, phosphate, and potassium in soil at agricultural sites.

[0009] In order to achieve the above object, the technical means of the present invention are as follows: 1. An apparatus for on-site detection of soil nutrients, comprising: a pretreatment leaching cell, an in-situ real-time detection assembly, and a fresh soil pretreatment transfer assembly, the fresh soil pretreatment transfer assembly transferring the fresh soil leachate sample liquid in the pretreatment leaching cell into the in-situ real-time detection assembly; a soil reagent micro-channel chip attached to the output shaft of the drive motor assembly by the chip alignment locking groove; an upper surface of the chip substrate is sealed in a case; a soil leachate introduction groove is etched in the center of the upper surface of the chip substrate; a first flow path region, a second flow path region, a third flow path region and a fourth flow path region are etched extending outward from the soil leachate introduction groove; and the first flow path region, the second flow path region, the third flow path region and the fourth flow path region have the same structure.

[0010] the first flow area includes a quantitative introduction groove communicating with the soil leachate introduction groove through a microchannel, the outlets of the reagent storage groove and the quantitative introduction groove are connected through a microchannel, and the outlet of the mixing area groove is connected to the detection area groove through a snake-shaped mixing area groove, the fluorescence exciter and the fluorescence receiver are located on the rotational motion trajectory of the detection area groove, The width of the micropassage at the point where the T-shaped mixing groove is connected to the reagent storage groove and the quantitative introduction groove is smaller than the width of the micropassage at the outlet of the reagent storage groove and the quantitative introduction groove, and the width of the micropassage at the point where the snake-shaped mixing area groove is connected to the detection area groove is smaller than the width of the micropassage at the outlet of the quantitative introduction groove.

[0011] The detection and analysis assembly includes a control processor, a capture card, a fluorescence exciter, a fluorescence receiver, and a soil water heat and salt sensor, wherein the fluorescence exciter is connected to a first control signal output terminal of the control processor, the fluorescence receiver is connected to a first data input terminal of the control processor via the capture card, the data output terminal of the soil water heat and salt sensor is connected to a second data input terminal of the control processor, and the drive motor assembly is connected to the second control signal output terminal of the control processor.

[0012] A sealing membrane is attached to the upper surface of the pretreatment leaching cell, a leaching agent is contained in the pretreatment leaching cell, the number of the pretreatment leaching cells is n, and adjacent pretreatment leaching cells are attached and connected via a mortise and tenon structure.

[0013] The fresh soil pretreatment transfer assembly includes a negative pressure suction bag, a quick release head is provided at the rear end of the negative pressure suction bag, a fixed quantity liquid storage ring is attached to the front end of the negative pressure suction bag, a suction head is attached to the front end of the fixed quantity liquid storage ring, and a filter block is inserted into the suction head.

[0014] A specific potassium detection reagent is stored in the reagent storage groove of the first flow path region, a specific ammonia nitrogen detection reagent is stored in the reagent storage groove of the second flow path region, a specific nitrate detection reagent is stored in the reagent storage groove of the third flow path region, and a specific phosphorus detection reagent is stored in the reagent storage groove of the fourth flow path region.

[0015] The chip substrate is circular, the soil leachate introduction groove, the quantitative introduction groove, the reagent storage groove and the mixing area groove are all circular, and the first flow path region, the second flow path region, the third flow path region and the fourth flow path region are located on the horizontal and vertical axes of the chip substrate.

[0016] The negative pressure suction bag and the quick release head are made of soft plastic material, the quantitative liquid storage ring and the suction head are made of hard plastic material, and the filter block is made of filter cotton or filter quartz sand.

[0017] The soil reagent micro-channel chip further includes a cover plate layer positioned over the chip substrate.

[0018] The cover plate layer includes a cover plate layer body and a test liquid quantitative introduction hole opened in the center of the cover plate layer body, the test liquid quantitative introduction hole communicating with the soil leachate introduction groove; The cover plate layer main body is further provided with a test liquid guide groove, a detection liquid introduction hole and a visible window, the numbers of the test liquid guide groove, the detection liquid introduction hole, the visible window and the flow path area are the same, the detection liquid introduction hole and the mixing area groove are provided in a one-to-one correspondence, the detection liquid introduction hole is connected to the corresponding mixing area groove, the visible window and the detection area groove are provided in a one-to-one correspondence, the visible window is located directly above the corresponding detection area groove, one end of the test liquid guide groove is connected to the test liquid quantitative introduction hole and the other end is provided with a reservoir, and one side of the reservoir is provided with an air hole connected to the reservoir.

[0019] According to the present invention, there is provided a method for detecting soil nutrients by the on-site soil nutrient detection device according to claim 1, comprising the following steps 91 to 97: Obtaining a concentration curve of fluorescence intensity (step 91): Obtain a linear relationship curve of the target soil concentration value analyzed in the laboratory and the fluorescence intensity. Acquiring water, heat, and salt information (step 92): Inserting a soil water, heat, and salt sensor into the test field, and acquiring water, heat, and salt information by a control processor, where the water, heat, and salt information is water content t, in units of %, Collecting fresh soil samples and leaching (step 93): Collect fresh soil samples and place them in the pretreatment leaching cell. The ratio of fresh soil sample to leaching agent in the pretreatment leaching cell is 1:5. The sample is leached by shaking for 3-5 minutes to obtain the leaching sample liquid. Transfer of leachate sample solution (step 94): The fresh soil pretreatment transfer assembly transfers the leachate sample solution leached in the pretreatment leachate cell into the soil leachate introduction groove of the soil reagent microchannel chip; Centrifugal decomposition using the soil reagent microchannel chip (step 95): The control processor starts the drive motor assembly, and the soil reagent microchannel chip is rotated by the drive motor assembly to perform centrifugal decomposition. The drive motor assembly rotates to perform centrifugal decomposition, and the leachate sample liquid is centrifuged and decomposed in the soil reagent microchannel chip. Acquire fluorescence data (step 96): Activate the fluorescence exciter and the fluorescence receiver by the control processor to acquire fluorescence data of the leaching sample solution in the detection area groove on the soil reagent microchannel chip, and search for a corresponding soil concentration value c from a data table of the linear curve relationship between the soil concentration value and the fluorescence intensity according to the acquired fluorescence data. Obtaining soil nutrient detection results (step 97): The control processor calculates the soil nutrient detection results based on the hydrothermal salt information and the soil concentration value c, i.e., calculates the soil content Xi (unit: mg / kg); Xi=5*c / (1-t) Wherein, Xi is the content of nitrogen, phosphate and potassium, the constant 5 is the coefficient, i.e., 5 times the amount of water is added for every 1g of soil in the pretreatment leaching cell, c is the soil concentration value, and t is the water content (%). A detection method is further provided.

[0020] The step of rotating the drive motor assembly to perform centrifugal disintegration includes the following steps 101 to 104: Step 101: Centrifuge at a low rotation speed, so that the leachate sample uniformly enters the first flow area, the second flow area, the third flow area, and the fourth flow area from the soil leachate introduction groove; Step 102: Centrifuge at a second rotation speed, which is higher than the second rotation speed, so that the leaching sample liquid and the reagent pass through the narrow passage of the T-shaped mixing groove under the driving of centrifugal force and enter the mixing area groove to be further mixed and uniformly mixed and reacted; Step 103: The mixture is kept in a stationary state to be thoroughly mixed and reacted, and then gradually flows into the snake-shaped mixing area groove, and further mixed and reacted in the snake-shaped pipe; Step 104: Centrifuge at a third rotation speed, which is the highest speed, so that the leaching sample liquid passes through the last narrow micro-channel of the elongated snake-shaped mixing region groove and enters the detection region groove.

[0021] According to the present invention, there is provided a microchannel chip including a cover plate layer and a chip substrate, which are provided in this order, The chip substrate includes a chip substrate body, a soil leachate introduction groove provided at the center of the top of the chip substrate body, and a plurality of branch passages provided at the top of the chip substrate body and uniformly distributed along the outer periphery of the soil leachate introduction groove, the branch passages including a quantitative introduction groove, a reagent storage groove, a mixing area groove, a snake-shaped mixing area groove and a detection area groove, the quantitative introduction groove is connected to the soil leachate introduction groove, and a T-shaped mixing groove is provided between the quantitative introduction groove and the reagent storage groove, the quantitative introduction groove and the reagent storage groove are connected by the T-shaped mixing groove and connected to one end of the mixing area groove, the other end of the mixing area groove is connected to one end of the snake-shaped mixing area groove, and the other end of the snake-shaped mixing area groove is connected to the detection area groove via a second capillary valve.

[0022] The cover plate layer includes a cover plate layer body and a test liquid quantitative introduction hole opened in the center of the cover plate layer body, the test liquid quantitative introduction hole communicating with the soil leachate introduction groove; The cover plate layer main body is further provided with a test liquid guide groove, a detection liquid introduction hole and a visibility window, the test liquid guide groove, the detection liquid introduction hole, the visibility window and the passage branch are the same in number, the detection liquid introduction hole and the mixing area groove are provided in a one-to-one correspondence, the detection liquid introduction hole is connected to the corresponding mixing area groove, the visibility window and the detection area groove are provided in a one-to-one correspondence, the visibility window is located directly above the corresponding detection area groove, one end of the test liquid guide groove is connected to the test liquid quantitative introduction hole and the other end is provided with a reservoir, and one side of the reservoir is provided with an air hole connected to the reservoir.

[0023] The snake-shaped mixed region groove has a spiral or meandering shape, and the meandering shape is made up of a plurality of continuous folds.

[0024] A chip fixing hole is provided at the center of the back of the chip substrate body.

[0025] A second air hole communicating with the detection area groove is provided on one side of the detection area groove, and the second air hole and the air hole are provided in one-to-one correspondence, and the second air hole communicates with the corresponding air hole.

[0026] The visible window includes a through hole provided in the cover plate layer body and a light-transmitting film attached to the through hole.

[0027] The detection method for the microchannel chip includes the following steps 1 to 5: Attaching the microfluidic chip (Step 1): Attach the centrifugal microfluidic chip to the centrifugal detector. Injection and flow of test liquid (Step 2): The test liquid is added into the test liquid quantitative introduction hole, and the centrifugal detector is started. The centrifugal detector rotates the microfluidic chip at a rotation speed A1 for T1 seconds. During the rotation of the microfluidic chip, the test liquid flows from the test liquid quantitative introduction hole into the soil leachate introduction groove, and then flows from the soil leachate introduction groove into each quantitative introduction groove. The excess test liquid in the test liquid quantitative introduction hole flows along each test liquid guide groove into the reservoir at the end of each test liquid guide groove. Primary mixing and reaction (step 3): The rotation speed of the centrifugal detector is increased, and the centrifugal detector rotates the microfluidic chip at a rotation speed A2 for T2 seconds. During the rotation of the microfluidic chip, the test liquid and the detection solution flow from the quantitative introduction groove and the reagent storage groove respectively through the T-shaped mixing groove into the mixing area groove. In the mixing area groove, the test liquid and the detection solution are mixed to obtain a mixed liquid, and the test ions in the test liquid react with the detection solution. Secondary mixing and reaction (step 4): The centrifugal detector is stopped, and the mixture in the mixing area groove flows into the snake-shaped mixing area groove, where the test solution and the detection solution in the mixture further mix and react, and then flow into the second capillary valve between the snake-shaped mixing area groove and the detection area groove; Completion of mixing and reaction (step 5): The centrifugal detector is started again, and the centrifugal detector rotates the microfluidic chip at a rotation speed of A3 for T3 seconds. During the rotation of the microfluidic chip, the mixture located between the snake-shaped mixing area groove and the detection area groove passes through the second capillary valve and flows into the detection area groove.

[0028] The different reagent storage grooves are pre-stored with detection solutions for detecting different ions. Effect of the Invention

[0029] Compared with the prior art, the on-site soil nutrient detection device and detection method of the present invention realizes rapid detection of the effective forms of nitrogen, phosphate, and potassium in soil by simultaneously and continuously detecting multiple elements, and further achieves direct and rapid on-site detection of fresh soil nutrients based on the analysis of specific fluorescent quantum dots by combining microfluidics and fluorescence detection analysis.

[0030] The microchannel chip of the present invention realizes simultaneous detection of multiple types of soil ions by driving and controlling reactions using centrifugal force, reducing artificial processes and offering the advantages of efficiency, simplicity, accuracy and speed.

[0031] According to the present invention, on-site rapid detection of soil nutrients with high accuracy can be achieved, and multiple indicators of nitrogen, phosphorus and potassium can be detected simultaneously with high integration degree, which has the advantages of reducing the artificial process, high automation level, simple operation, accuracy and rapidity. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a structural schematic diagram of the soil nutrient field detection device of the present invention. [Diagram 2] FIG. 2 is a structural schematic diagram of the pretreatment leaching cell in FIG. 1 according to the present invention. [Diagram 3] FIG. 2 is a structural schematic diagram of the fresh soil pretreatment transfer assembly in FIG. 1 of the present invention. [Figure 4] FIG. 2 is a structural schematic diagram of the on-site real-time detection assembly in FIG. 1 of the present invention. [Diagram 5] FIG. 2 is a structural perspective view of chip substrate 101 of the soil reagent micro-channel chip of the present invention shown in FIG. [Figure 5-1] 6 is a structural diagram (four flow path regions) of a cover plate layer 102 suitable for the chip substrate in FIG. 5. [Figure 6] 1 is a flow chart showing a procedure of a detection method according to the present invention. [Figure 7] 1 is a three-dimensional view (five branching passages) of a microchannel chip in Example 2 of the present invention. [Figure 8] FIG. 8 is a structural diagram (five channel branches) of the cover plate layer 102 of the micro-channel chip of FIG. 7. [Figure 9] FIG. 8 is a structural diagram (five branching passages) of chip substrate 101 of the micro-channel chip of FIG. 7.

[0033] 1. In-situ real-time detection assembly, 2. Fresh soil pretreatment transfer assembly, 3. Pretreatment leaching cell, 4. Soil water heat-salinity sensor, 5. Capture card, 6. Fluorescence receiver, 7. Fluorescence exciter, 8. Control processor, 9. Drive motor assembly; 10 microfluidic chip, 101 chip substrate, 102 cover plate layer, 1021 test liquid quantitative introduction hole, 1022 test liquid guide groove, 1023 detection liquid introduction hole, 1024 ventilation hole, 1025 visible window, 1026 reservoir; 11 detection area groove, 12 soil leachate introduction groove, 13 chip alignment locking groove, 14 snake-shaped mixing area groove, 15 snake-shaped mixing area groove, 16 T-shaped mixing groove, 17 second vent hole, 18 quantitative introduction groove, 19 microchannel, 20 reagent storage groove; 21 quick release head, 22 negative pressure suction bladder, 23 quantitative liquid storage ring, 24 filtration block; 29 Second capillary valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] In order to make the structural features and effects achieved by the present invention clearer, the following detailed description will be given with reference to preferred embodiments and drawings.

[0035] As shown in Figure 1, the soil nutrient on-site detection device of the present invention includes a pretreatment leaching cell 3, an on-site real-time detection assembly 1, and a fresh soil pretreatment transfer assembly 2. The fresh soil pretreatment transfer assembly 2 transfers the fresh soil sample in the pretreatment leaching cell 3 to the on-site real-time detection assembly 1.

[0036] As shown in Figure 2, the design of the pretreatment leaching cell 3 realizes soil collection and processing at the agricultural site. A sealing membrane is attached to the top surface of the pretreatment leaching cell 3, and the pretreatment leaching cell 3 contains a leaching agent. In actual use, fresh soil can be collected from the surface of the rice field, and after removing crushed stones, etc., it can be directly placed in the pretreatment leaching cell 3. There are multiple pretreatment leaching cells 3, and adjacent pretreatment leaching cells 3 are attached and connected by a mortise and tenon structure, which makes it convenient to use and carry. That is, four cells are arranged in a horizontal row, and in a row, each cell can be easily expanded by the mortise and tenon structure. Each leaching cell contains a soil leaching agent in advance, and is covered and sealed by a PVC membrane. When used in the field, farmers select and assemble the number of leaching cells according to the number of soil samples to be measured, peel off the PVC membrane (sealing membrane), weigh the soil samples and place them in the pretreatment leaching cell 3 in order, and finally cover them with a hard plastic such as PP. The co-agitation improves the leaching efficiency, which achieves in-situ leaching of the soil, eliminating the need to take soil samples back to the laboratory for leaching, and the soil nutrient data obtained is more accurate because fresh soil is used for the measurements.

[0037] 4, the in-situ real-time detection assembly 1 includes a drive motor assembly 9 and a detection and analysis assembly. A soil reagent micro-channel chip 10 is attached to the output shaft of the drive motor assembly 9. That is, the soil reagent micro-channel chip 10 is attached to the output shaft of the drive motor assembly 9 in a conventional manner. The drive motor assembly 9 centrifugally rotates the soil reagent micro-channel chip 10.

[0038] The detection and analysis assembly includes a control processor 8, a capture card 5, a fluorescence exciter 7, a fluorescence receiver 6, and a soil water heat-salt sensor 4. The fluorescence exciter 7 is connected to a first control signal output terminal of the control processor 8, and the control processor 8 controls the fluorescence exciter 7 to transmit a fluorescence signal. The fluorescence receiver 6 is connected to a first data input terminal of the control processor 8 via the capture card 5, and the fluorescence receiver 6 acquires the fluorescence data of the fluorescence signal of the fluorescence exciter 7 passing through the detection area groove 11 of the soil reagent micro-channel chip 10. The data output terminal of the soil water heat-salt sensor 4 is connected to a second data input terminal of the control processor 8, and the drive motor assembly 9 is connected to a second control signal output terminal of the control processor 8. Here, according to the design of the soil water heat-salt sensor 4, the soil water heat-salt sensor 4 can be inserted into a test field during use to measure data such as soil temperature, moisture content, and electrical conductivity, thereby achieving the acquisition of soil moisture data. What is done here is the actual detection of fresh soil samples containing moisture, and since there is no step of evaporating the moisture from the soil samples in the laboratory as in the past, in order to achieve the detection of fresh soil containing moisture, it is necessary to take into account the removal of the moisture element when analyzing after measuring the soil moisture.

[0039] As shown in FIG. 3, the fresh soil pretreatment transfer assembly 2 is used to transfer soil leachate. The negative pressure suction bag 22 is used to suck up the soil leachate. The quick release head 21 is attached to the rear end of the negative pressure suction bag 22. The quick release head 21 can easily discharge the sucked soil leachate. The fixed amount liquid storage ring 23 is attached to the front end of the negative pressure suction bag 22. The suction head is attached to the front end of the fixed amount liquid storage ring 23. The filter block 24 is inserted into the suction head. The soil leachate sucked by the suction head is stored in the fixed amount liquid storage ring 23 after being filtered. The capacity of the fixed amount liquid storage ring 23 can be designed according to the actual use needs. Here, the negative pressure suction bag 22 and the quick release head 21 can be made of soft plastic material, the fixed amount liquid storage ring 23 and the suction head can be made of hard plastic material, and the filter block 24 can be filter cotton or filter quartz sand.

[0040] 5, the soil reagent micro-channel chip 10 includes a chip substrate 101. A chip alignment locking groove 13 is provided on the bottom of the chip substrate 101. The chip alignment locking groove 13 is used for mounting and using the drive motor assembly 9. The soil reagent micro-channel chip 10 is mounted on the output shaft of the drive motor assembly 9 via the chip alignment locking groove 13.

[0041] The upper surface of the chip substrate 101 is sealed in a case. A cover plate layer 102 is further provided on the chip substrate 101. A soil leachate introduction groove 12 is etched in the center of the upper surface of the chip substrate 101. According to a conventional design, the portion of the soil leachate introduction groove 12 in the case can be designed to be thin plastic or a structure that is easy to open and close. This makes it easy for the quick release head 21 to introduce the soil leachate into the soil leachate introduction groove 12. A first flow path region, a second flow path region, a third flow path region, and a fourth flow path region are etched extending outward from the soil leachate introduction groove 12. The first flow path region, the second flow path region, the third flow path region, and the fourth flow path region have the same structure.

[0042] The soil reagent micro-channel chip 10 further includes a cover plate layer 102 located on the chip substrate 101. The cover plate layer 102 and the chip substrate 101 are connected to each other. The cover plate layer is not shown in Fig. 4. Fig. 5-1 shows the cover plate layer 102 corresponding to the chip substrate 101 in Fig. 5, which includes four channel regions.

[0043] The cover plate layer 102 includes a cover plate layer body and a test liquid quantitative introduction hole 1021 opened in the center of the cover plate layer body. The test liquid quantitative introduction hole 1021 communicates with the soil leachate introduction groove 12. The cover plate layer body further includes a test liquid guide groove 1022, a detection liquid introduction hole 1023, and a visible window 1025. The test liquid guide groove 1022, the detection liquid introduction hole 1023, the visible window 1025, and the flow path area are the same in number. The detection liquid introduction hole 1023 and the mixing area groove 15 are provided in one-to-one correspondence. The detection liquid introduction hole 1023 communicates with the corresponding mixing area groove 15. The visible window 1025 and the detection area groove 11 are provided in one-to-one correspondence. The visible window 1025 is located directly above the corresponding detection area groove 11. One end of the test liquid guide groove 1022 communicates with the test liquid quantitative introduction hole 1021, and the other end is provided with a reservoir 1026. One side of the reservoir 1026 is provided with an air hole 1024 communicating with the reservoir. The visible window 1025 includes a through hole opened in the cover plate body and a light-transmitting film attached to the through hole.

[0044] The first flow area, the second flow area, the third flow area, and the fourth flow area of ​​the soil reagent microchannel chip 10 are four passages, which respectively measure four indicators, potassium, ammonia nitrogen, nitrate ion, and phosphorus. The specific potassium detection reagent is stored in the reagent storage groove 20 of the first flow area. The specific ammonia nitrogen detection reagent is stored in the reagent storage groove 20 of the second flow area. The specific nitrate ion detection reagent is stored in the reagent storage groove 20 of the third flow area. The specific phosphorus detection reagent is stored in the reagent storage groove 20 of the fourth flow area. Here, the four indicators to be measured are determined by the reagents stored in the reagent storage areas. A predetermined amount of reagents is added to the four reagent storage areas in advance during the chip processing process. These reagents are sealed in the chip. The chip is vacuum-packed and transported to the farmland. The structure and function of each passage are the same, and all are connected via a microchannel. The microchannel is usually 100 um high.

[0045] In order to further improve the centrifugal effect, the first flow region, the second flow region, the third flow region and the fourth flow region are located on the horizontal axis and the vertical axis of the chip substrate 101. Taking the first flow region as an example, the first flow region includes a quantitative introduction groove 18 connected to the soil leachate introduction groove 12 through a microchannel 19. The outlet of the quantitative introduction groove 18 is connected to the reagent storage groove 20 through the microchannel 19 and connected to the mixing region groove 15 through the T-shaped mixing groove 16. The outlet of the mixing region groove 15 is connected to the detection region groove 11 through the snake-shaped mixing region groove 14. The fluorescence exciter 7 and the fluorescence receiver 6 are located on the rotation trajectory of the detection region groove 11. That is, the soil leachate flows from the soil leachate introduction groove 12 to the quantitative introduction groove 18, and then mixes with the reagent storage groove 20, and then flows into the detection region groove 11 through the T-shaped mixing groove 16 and the snake-shaped mixing region groove 14. The fluorescence exciter 7 and the fluorescence receiver 6 are located on the rotation trajectory of the four detection area grooves 11, and their positions are regulated by conventional sensor technology. In order to obtain a higher centrifugal effect, the chip substrate 101 is circular, and the soil leachate introduction groove 12, the quantitative introduction groove 18, the reagent storage groove 20, and the mixing area groove 15 are all circular. In order to improve the liquid conductivity, an air hole 17 can be designed in the detection area groove 11. The air hole 17 is an open-style through hole.

[0046] In order to achieve the effect of centrifugal mixing, the soil reagent microchannel chip 10 adopts a tertiary mixing technique. That is, in the T-shaped mixing area, the primary mixing is performed, and the site where the two passages meet is gradually narrowed and acts as a valve to prevent the soil solution from entering the final detection area when added. After passing through the T-shaped mixing area by centrifugal force, it is further mixed in the circular mixing area. Since the microfluid is in a laminar flow state, the soil test liquid and the reagent need to be thoroughly mixed and reacted. It then enters the snake-shaped mixing area and is further mixed by the repeatedly meandering microchannel. The long and narrow microchannel at the end of the snake-shaped mixing area can also act as a microvalve.

[0047] Therefore, the width of the micropassage 19 at the point where the T-shaped mixing groove 16 is connected to the reagent storage groove 20 and the quantitative introduction groove 18 is smaller than the width of the micropassage 19 at the outlet of the reagent storage groove 20 and the quantitative introduction groove 18. The width of the micropassage 19 at the point where the snake-shaped mixing area groove 14 and the detection area groove 11 are connected is smaller than the width of the micropassage 19 at the outlet of the quantitative introduction groove 18.

[0048] In addition, for ease and accuracy of fluorescence data acquisition, the bottom cover plate of the detection area is made to be on the order of 100 microns thick. This reduces the loss of fluorescence when it passes through the microchannel wall and significantly improves the light intensity utilization rate compared to conventional fluorescence detection. In the detector alignment area, grooves are machined laterally, which makes it easier to align the detector and reduces the wall thickness.

[0049] The present invention further provides a method for detecting soil nutrients by an in-situ detection device, as shown in Figure 6. The method includes the following steps: Obtaining the concentration curve diagram of the fluorescence intensity (step 91): Obtain the linear relationship curve between the soil concentration value analyzed in the laboratory and the fluorescence intensity. The linear relationship curve between the concentration values ​​of the four soil indicators (potassium, ammonia nitrogen, nitrate nitrogen, phosphorus) and the fluorescence intensity is a relationship curve determined in the laboratory, that is, taking a specific ratio of soil concentration values, measuring the corresponding fluorescence intensity, and forming a linear relationship curve between the soil concentration value and the fluorescence intensity. Based on this, the approximate content of the soil concentration value can be obtained according to the fluorescence intensity. In actual use, when the product is used in the rice field, the linear relationship curve has already been input into the control processor 8.

[0050] Acquisition of hydrothermal salt information (step 92): The soil hydrothermal salt sensor 4 is inserted into the test field, and the hydrothermal salt information is acquired by the control processor 8, where the hydrothermal salt information is the water content t (unit %). That is, the water content information is obtained here.

[0051] Collection of fresh soil sample and leaching treatment (step 93): A fresh soil sample is collected and placed in the pretreatment leaching cell 3. The ratio of fresh soil sample to leaching agent in the pretreatment leaching cell 3 is 1:5. The sample is liquified by shaking for 3-5 minutes to obtain a leaching sample liquid (soil leachate).

[0052] Transfer of leachate sample solution (step 94 ): The fresh soil pretreatment transfer assembly 2 transfers the leachate sample solution leached in the pretreatment leaching cell 3 into the soil leachate introduction groove 12 of the soil reagent microchannel chip 10 .

[0053] Centrifugal decomposition using the soil reagent micro-channel chip 10 (step 95): The control processor 8 starts the drive motor assembly 9, which rotates the soil reagent micro-channel chip 10 to perform centrifugal decomposition, and the drive motor assembly 9 rotates to perform centrifugal decomposition, and the leaching sample liquid is centrifuged within the soil reagent micro-channel chip 10 to be decomposed.

[0054] Step 101: Centrifugation is performed at a low rotation speed, and the leachate sample flows uniformly from the soil leachate introducing groove 12 into the first flow path region, the second flow path region, the third flow path region and the fourth flow path region.

[0055] Step 102: Centrifuge at a secondary rotation speed, which is higher than the centrifugal speed at the low rotation speed, and the leaching sample liquid and the reagent pass through the narrow passage of the T-shaped mixing groove 16 under the driving of centrifugal force and enter the mixing area groove 15 to be further mixed, and then uniformly mixed and reacted.

[0056] Step 103: The mixture is kept in a stationary state to sufficiently mix and react, and then gradually flows into the snake-shaped mixing area groove 14, where it is further mixed and reacted in the snake-shaped pipe.

[0057] Step 104: Centrifuge at the third rotation speed, which is the highest speed, so that the leaching sample liquid passes through the last narrow micro-channel of the elongated snake-shaped mixing region groove 14 and enters the detection region groove 11.

[0058] In actual use, the above processes are all designed into an automated process by the drive motor assembly 9, which does not require manual operation and dynamically completes the centrifugal rotation.

[0059] Acquiring fluorescence data (step 96): The control processor 8 activates the fluorescence exciter 7 and the fluorescence receiver 6 to acquire fluorescence data of the leaching sample liquid in the detection area groove 11 on the soil reagent microchannel chip 10, and searches for the corresponding soil concentration value c from a data table of the linear curve relationship between the soil concentration value and the fluorescence intensity based on the acquired fluorescence data.

[0060] Obtaining soil nutrient detection results (step 97): The control processor 8 calculates the soil nutrient detection results based on the hydrothermal salt information and the soil concentration value c, that is, calculates the soil content Xi (unit: mg / kg). Xi=5*c / (1-t) In the formula, Xi is the nitrogen, phosphate and potassium content, the constant 5 is a coefficient, i.e., 5 times the amount of water is added for every 1 g of soil in the pretreatment leaching cell 3, c is the soil concentration value, and t is the water content (%).

[0061] The present invention further provides a microchannel chip 10 that includes a cover plate layer 102 and a chip substrate 101, which are provided in order. The chip substrate 101 includes a chip substrate 101 body, a soil leachate introduction groove 12 provided at the center of the top of the chip substrate 101 body, and a plurality of branch passages provided at the top of the chip substrate 101 body and uniformly distributed along the outer periphery of the soil leachate introduction groove 12. The branch passages include a fixed amount introduction groove 18, a reagent storage groove 20, a mixing area groove 15, a snake-shaped mixing area groove 14, and a detection area groove 11. The groove 18 is connected to the soil leachate introduction groove 12, and a T-shaped mixing groove 16 is provided between the quantitative introduction groove 18 and the reagent storage groove 20. The quantitative introduction groove 18 and the reagent storage groove 20 are connected by the T-shaped mixing groove 16 and connected to one end of the mixing area groove 15. The other end of the mixing area groove 15 is connected to one end of the snake-shaped mixing area groove 14, and the other end of the snake-shaped mixing area groove 14 is connected to the detection area groove 11 via a second capillary valve 29.

[0062] As shown in FIG. 7, the cover plate layer 102 and the chip substrate 101 are bonded. As shown in FIG. 9, the reagent storage groove 20 is previously stored with the detection solution. The structure of the chip substrate 101 body includes the soil leachate introduction groove 12, the quantitative introduction groove 18, the reagent storage groove 20, the snake-shaped mixing area groove 14, the T-shaped mixing groove 16, the second capillary valve 29, the mixing area groove 15, the detection area groove 11, and the second air hole 17. The body structure of the chip substrate 101 is consistent in thickness and distributed on one side of the chip substrate 101, and the other side is provided with a chip fixing hole structure for connecting the microchannel chip and the centrifugal detector. The chip fixing hole corresponds to the centrifugal detector fixing structure, and the thickness does not penetrate the chip substrate 101, and does not destroy the body structure on the other side of the chip substrate 101.

[0063] The soil leachate introduction groove 12 is used for receiving the test liquid in the chip substrate 101 and distributing it evenly to the surrounding passage branches. The quantitative introduction groove 18 is used for receiving a fixed volume of test liquid, which is distributed symmetrically along the soil leachate introduction groove 12, and can realize high-precision control of the test liquid involved in the reaction under the action of centrifugal drive. The reagent storage groove 20 is used for receiving a certain volume of detection liquid. The detection solution is a solution containing nano-probe material and is stored here in advance. The structure of the T-type mixing groove 16 is designed between the reagent storage groove 20 and the quantitative introduction groove 18 and the mixing area groove 15, and both kinds of solutions are held at the front end of the T-type mixing groove 16 before mixing. The middle part of the T-type mixing groove 16 is a capillary structure, which as a whole constitutes a first capillary valve. The snake-shaped mixing area groove 14 is used to further improve the mixing and reaction between the test liquid and the detection solution. One end is connected to the mixing area groove 15, and the mixed liquid reacted in the mixing area groove 15 directly enters the snake-shaped mixing area groove 14 under the action of capillary force, and the other end is connected to the detection area groove 11 through the second capillary valve 29 structure, and the mixed liquid thoroughly mixed and reacted in the snake-shaped mixing area groove 14 is held at the front end of the second capillary valve 9. The T-shaped mixing groove 16 and the second capillary valve 29 are two passive microvalves, and this structure completes the liquid flow control in the microchannel chip. Driven by centrifugal force, the internal pressure of the liquid breaks through the capillary valve and enters the next area, thereby realizing the operation mode of the microchannel chip driven by centrifugal force. The T-shaped mixing groove 16 and the second capillary valve 29 have different structural dimensions, and only when driven at different centrifugal rotation speeds can they break through the liquid retention performance of the capillary valve. The test liquid and the detection solution pass through the structure of the T-shaped mixing groove 16 by the drive of centrifugal force and enter the mixing area groove 15. In the process of filling the mixing area groove 15, the flow rate of the liquid slows down in the microchannel environment, and the two solutions mix and react. The reacted mixed solution passes through the second capillary valve 29 between the snake-shaped mixing area groove 14 and the detection area groove 11 by the drive of centrifugal force, and slowly fills and stores in the detection area groove 11 area, waiting for fluorescence detection.The second vent hole 17 is vertically connected to the corresponding vent hole 1024 in the cover plate layer 102, and is designed in an open style to maintain air pressure balance in each region of the micro-channel chip.

[0064] The cover plate layer 102 includes a cover plate layer body and a test liquid quantitative introduction hole 1021 opened in the center of the cover plate layer body, the test liquid quantitative introduction hole 1021 communicates with the soil leachate introduction groove 12, The cover plate layer main body is further provided with a test liquid guide groove 1022, a detection liquid introduction hole 1023 and a visible window 1025, and the test liquid guide groove 1022, the detection liquid introduction hole 1023, the visible window 1025 and the passage branches are the same in number, the detection liquid introduction hole 1023 and the mixing area groove 15 are arranged in a one-to-one correspondence, the detection liquid introduction hole 1023 is connected to the corresponding mixing area groove 15, the visible window 1025 and the detection area groove 11 are arranged in a one-to-one correspondence, the visible window 1025 is located directly above the corresponding detection area groove 11, one end of the test liquid guide groove 1022 is connected to the test liquid quantitative introduction hole 1021, and the other end is provided with a reservoir portion 1026, and one side of the reservoir portion 1026 is provided with an air vent 1024 connected to the reservoir portion.

[0065] As shown in FIG. 8, the test liquid quantitative introduction hole 1021 is the introduction position of the test liquid of the microchannel chip, and is designed to have a cylindrical structure, but is not limited thereto, and can accommodate a certain amount of test liquid, and is vertically connected to the soil leachate introduction groove 12 in the chip substrate 101 to realize the purpose of introducing the test liquid into the chip substrate 101. Each test liquid guide groove 1022 is uniformly arranged radially along the test liquid quantitative introduction hole 1021. The test liquid guide groove 1022 has a microchannel structure, and can accommodate the excess test liquid that has escaped from the test liquid quantitative introduction hole 1021, and introduce the test liquid into the end reservoir 1026, thereby realizing the quantitative introduction of the test liquid. The detection liquid introduction hole 1023 and the reagent storage groove 20 of the chip substrate 101 are provided in one-to-one correspondence and are vertically connected. After the cover layer 102 of the microchannel chip and the chip substrate 101 are sealed and bonded, a detection solution containing a nano-probe material is introduced into the reagent storage groove 20 of the chip substrate 101 through the detection solution introduction hole 1023. The vent hole 1024 and the second vent hole 17 of the chip substrate 101 are connected vertically and are used to maintain air pressure balance in each region of the microchannel chip. The visible window 1025 and the detection region groove 11 of the chip substrate 101 are provided in one-to-one correspondence and are the detection channel of the fluorescence transmitting / receiving device. By attaching a layer of light-transmitting film, the detection region can be sealed and the fluorescence detection performance can be improved.

[0066] The snake-shaped mixed region groove 14 has a spiral or meandering shape, and the meandering shape is made up of a plurality of continuous folds.

[0067] A chip fixing hole is provided at the center of the back of the chip substrate 101 body.

[0068] The chip fixing hole is located on the back of the chip substrate 101 body, on the opposite side to the surface on which the soil leachate introduction groove 12 etc. are provided in the chip substrate 101 body; when viewed from Figures 5 and 9, it is the back of the chip substrate 101 body, and when viewed from Figure 7, it is the underside of the chip substrate 101 body.

[0069] A second air hole (17) communicating with the detection area groove (11) is provided on one side of the detection area groove (11), and the second air hole (17) and the air hole (1024) are provided in one-to-one correspondence, and the second air hole (17) communicates with the corresponding air hole (1024).

[0070] The visible window (1025) includes a through hole provided in the cover plate layer (102) body and a light-transmitting film attached to the through hole.

[0071] The present invention further provides a detection method using the microchannel chip, comprising the following steps 1 to 5: Attachment of the microfluidic chip (step 1): Attach the centrifugal microfluidic chip to the centrifugal detector. Injection and flow of test liquid (Step 2): The test liquid is added into the test liquid quantitative introduction hole 1021, and the centrifugal detector is started, which rotates the micro-channel chip at a rotation speed A1 for T1 seconds, during which the test liquid flows from the test liquid quantitative introduction hole 1021 into the soil leachate introduction groove 12, and then flows from the soil leachate introduction groove 12 into each quantitative introduction groove 18, and the excess test liquid in the test liquid quantitative introduction hole 1021 flows along each test liquid guide groove 1022 into the reservoir 1026 at the end of each test liquid guide groove 1022. In one embodiment, the value of A1 is 200 rpm / min, and the value of T1 is 30 seconds. Primary mixing and reaction (step 3): The rotation speed of the centrifugal detector is increased, and the centrifugal detector rotates the microfluidic chip at a rotation speed A2 for T2 seconds. During the rotation of the microfluidic chip, the test liquid and the detection solution flow from the quantitative introduction groove 18 and the reagent storage groove 20 respectively through the T-shaped mixing groove 16 into the mixing area groove 15, where the test liquid and the detection solution are mixed to obtain a mixed liquid, and the test ions in the test liquid react with the detection solution. In one embodiment, the value of A2 is 800 rpm / min, and the value of T2 is 10 seconds. Secondary mixing and reaction (step 4): The operation of the centrifugal detector is stopped, and the mixture in the mixing area groove 15 flows into the snake-shaped mixing area groove 14, where the test liquid and the detection solution in the mixture further mix and react with each other, and flow to the second capillary valve 29 between the snake-shaped mixing area groove 14 and the detection area groove 11. Completion of mixing and reaction (step 5): The centrifugal detector is started again, and the centrifugal detector rotates the microfluidic chip at a rotation speed A3 for T3 seconds. During the rotation of the microfluidic chip, the mixture between the snake-shaped mixing region groove 14 and the detection region groove 11 passes through the second capillary valve 29 and flows into the detection region groove 11. In one embodiment, the value of A3 is 1500 rpm / min, and the value of T3 is 20 seconds.

[0072] The different reagent storage grooves 20 are pre-stored with detection solutions for detecting different ions.

[0073] Each branch of the passage is provided with a reagent storage groove 20. The reagent storage groove 20 is filled with a detection solution for detecting different ions to detect different ions. The detection solution includes a fluorescent nano-material probe having specific discrimination ability and a corresponding solvent. The fluorescent nano-material probe is uniformly dispersed in the solvent and has a specific fluorescence excitation wavelength and emission wavelength. After the detection solution and the test liquid are mixed, the nano-material probe in the detection solution can discriminate the test ion and cause a rapid and significant change in the fluorescence wavelength, and the detection component can be used to realize quantitative detection on site. The nano-material probe adopts a chemical organic synthesis method to synthesize a nano-probe with different structures and specific discrimination ability for different ions. This probe has the advantages of high selectivity, high sensitivity, and visualized quantitative detection. When a specific ion is to be detected, the branch of the passage corresponding to this ion can be used. This allows multiple types of ions to be detected simultaneously in one go, improving the detection efficiency.

[0074] The microchannel chip and detection method of the present invention use a multi-stage capillary valve structure to solve the problem of flow control of the test liquid and detection liquid, and use centrifugal force drive to solve the problem of accurate control of the reaction and detection process, thereby solving the problem that it is difficult to realize automatic, simple, accurate and rapid on-site detection, and thereby achieving the technical effect of on-site rapid detection, which can instantly obtain detection data after a sample is injected into the system.

[0075] The probe of the present invention is made of nanomaterials. The probe is combined with a microchannel to simultaneously detect various ions in soil, and the type and concentration information of ions in soil can be obtained instantly through the specific reaction of the nanomaterial to ions and the change in fluorescence before and after the reaction. This technology has the ability to identify ions specifically, effectively solving the problem of simultaneous detection of various ions in soil, and the fluorescence detection method can eliminate the interference of visible light, improving the sensitivity and reliability of ion detection. The centrifugal microchannel chip of the present invention can realize the simultaneous detection of various ions in soil, and can efficiently, simply, accurately and quickly obtain the type and concentration information of ions in soil, which is favorable for the strengthening and development of the automatic acquisition and detection technology of modern agricultural sensors.

[0076] The above describes the basic principle, main features and advantages of the present invention. It is understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and the description in the specification are only the principles of the present invention, and the present invention can be further modified and improved without departing from the spirit and scope of the present invention, and all of these modifications and improvements are included in the protection scope of the present invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. 1. A field in situ detection device for soil nutrients, comprising: The present invention includes a pretreatment leaching cell (3), a farm site real-time detection assembly (1), and a fresh soil pretreatment transfer assembly (2), the fresh soil pretreatment transfer assembly (2) transferring the fresh soil leaching sample liquid in the pretreatment leaching cell (3) into the farm site real-time detection assembly (1); The farm site real-time detection assembly (1) includes a drive motor assembly (9) and a detection and analysis assembly. A soil reagent micro-channel chip (10) is attached to the output shaft of the drive motor assembly (9). The soil reagent micro-channel chip (10) includes a chip substrate (101). A chip alignment locking groove (13) is provided on the bottom of the chip substrate (101). The soil reagent micro-channel chip (10) is connected to the drive motor assembly ( 9), a soil leachate introduction groove (12) is etched in the center of the upper surface of the chip substrate (101), a first flow path region, a second flow path region, a third flow path region and a fourth flow path region are etched extending outward from the soil leachate introduction groove (12), the first flow path region, the second flow path region, the third flow path region and the fourth flow path region are identical in structure, and the upper surface of the chip substrate (101) is covered by a case so that the first flow path region, the second flow path region, the third flow path region and the fourth flow path region are formed in an enclosed state; The fresh soil pre-treatment transfer assembly (2) includes a negative pressure suction bag (22), a quick release head (21) is provided at the rear end of the negative pressure suction bag (22), a fixed quantity liquid storage ring (23) is attached to the front end of the negative pressure suction bag (22), a suction head is attached to the front end of the fixed quantity liquid storage ring (23), and a filter block (24) is inserted into the suction head, which is a field detection device for soil nutrients.

2. 2. The field in-situ detection device for soil nutrients according to claim 1, characterized in that a sealing membrane is attached to the upper surface of the pre-treatment leaching cell (3), a leaching agent is contained in the pre-treatment leaching cell (3), the number of the pre-treatment leaching cells (3) is n, and adjacent pre-treatment leaching cells (3) are attached and connected via a mortise and tenon structure.

3. 2. The field detection device for detecting soil nutrients according to claim 1, wherein the reagent storage groove (20) in the first flow region stores a specific potassium detection reagent, the reagent storage groove (20) in the second flow region stores a specific ammonia nitrogen detection reagent, the reagent storage groove (20) in the third flow region stores a specific nitrate ion detection reagent, and the reagent storage groove (20) in the fourth flow region stores a specific phosphorus detection reagent.

4. The agricultural on-site detection device for soil nutrients according to claim 1, characterized in that the chip substrate (101) is circular, the soil leachate introduction groove (12), the quantitative introduction groove (18), the reagent storage groove (20) and the mixing area groove (15) are all circular, and the first flow area, the second flow area, the third flow area and the fourth flow area are located on the horizontal axis and the vertical axis of the chip substrate (101).

5. 2. The field detection device for soil nutrients as claimed in claim 1, characterized in that the negative pressure suction bag (22) and the quick release head (21) are made of soft plastic material, the quantitative liquid storage ring (23) and the suction head are made of hard plastic material, and the filter block (24) is filter cotton or filter quartz sand.

6. 2. The field in-situ detection apparatus for soil nutrients according to claim 1, wherein the soil reagent micro-channel chip (10) further comprises a cover plate layer (102) located on the chip substrate (101).

7. The cover plate layer (102) includes a cover plate layer body and a test liquid quantitative introduction hole (1021) opened in the center of the cover plate layer body, the test liquid quantitative introduction hole (1021) communicates with a soil leachate introduction groove (12), The cover plate body further has a test liquid guide groove (1022), a detection liquid introduction hole (1023), and a visible window (1025), and the numbers of the test liquid guide groove (1022), the detection liquid introduction hole (1023), the visible window (1025), and the flow path area are the same, and the detection liquid introduction hole (1023) and the mixing area groove (15) are provided in one-to-one correspondence, and the detection liquid introduction hole (1023) communicates with the corresponding mixing area groove (15), and the visible window (1 7. The agricultural land on-site detection device for soil nutrients as described in claim 6, characterized in that the visible window (1025) and the detection area groove (11) are provided in one-to-one correspondence, the visible window (1025) is located directly above the corresponding detection area groove (11), one end of the test liquid guide groove (1022) communicates with the test liquid quantitative introduction hole (1021) and the other end is provided with a reservoir section (1026), and one side of the reservoir section (1026) is provided with an air hole (1024) communicating with the reservoir section.

8. A microchannel chip (10) including a cover plate layer (102) and a chip substrate (101) provided in this order, The chip substrate (101) includes a chip substrate (101) body, a soil leachate introduction groove (12) provided in the center of the upper surface of the chip substrate (101) body, and a plurality of branch passages provided on the upper surface of the chip substrate (101) body and uniformly distributed along the outer periphery of the soil leachate introduction groove (12). The branch passages include a fixed amount introduction groove (18), a reagent storage groove (20), a mixing area groove (15), a snake-shaped mixing area groove (14), and a detection area groove (11). The fixed amount introduction groove (18) communicates with the soil leachate introduction groove (12), and a T-shaped mixing groove (16) is provided between the quantitative introduction groove (18) and the reagent storage groove (20), and the quantitative introduction groove (18) and the reagent storage groove (20) are connected by the T-shaped mixing groove (16) to one end of the mixing area groove (15), the other end of which communicates with one end of the snake-shaped mixing area groove (14), and the other end of the snake-shaped mixing area groove (14) is connected to the detection area groove (11) via a second capillary valve (29); The cover plate layer (102) includes a cover plate layer body and a test liquid quantitative introduction hole (1021) opened in the center of the cover plate layer body, the test liquid quantitative introduction hole (1021) communicates with a soil leachate introduction groove (12), The cover plate body further has a test liquid guide groove (1022), a detection liquid introduction hole (1023) and a visible window (1025), the test liquid guide groove (1022), the detection liquid introduction hole (1023), the visible window (1025) and the passage branch are the same in number, the detection liquid introduction hole (1023) and the mixing area groove (15) are provided in one-to-one correspondence, the detection liquid introduction hole (1023) is connected to the corresponding mixing area groove (15), A microchannel chip, characterized in that the visible windows (1025) and the detection area grooves (11) are provided in one-to-one correspondence, the visible windows (1025) are located directly above the corresponding detection area grooves (11), one end of the test liquid guide groove (1022) communicates with a test liquid quantitative introduction hole (1021) and the other end has a reservoir (1026), and one side of the reservoir (1026) is provided with an air vent (1024) communicating with the reservoir.

9. 9. The microchannel chip according to claim 8, wherein the snake-shaped mixing region groove (14) is spiral or meandering, and the meandering shape is formed of a plurality of continuous folds.

10. 9. The microchannel chip according to claim 8, wherein a chip fixing hole is provided at the center of the back of the chip substrate (101) body.

11. The microchannel chip of claim 8, characterized in that a second air hole (17) communicating with the detection area groove (11) is provided on one side of the detection area groove (11), the second air hole (17) and the air hole (1024) are provided in one-to-one correspondence, and the second air hole (17) communicates with the corresponding air hole (1024).

12. 9. The microchannel chip according to claim 8, wherein the visible window (1025) includes a through-hole provided in the cover plate layer (102) body and a light-transmitting film attached to the through-hole.

13. A detection method using the microchannel chip according to any one of claims 8, 11 and 12, comprising the following steps 1 to 5: Attachment of the microfluidic chip (Step 1): Attach the centrifugal microfluidic chip to the centrifugal detector. Injection and flow of test liquid (Step 2): The test liquid is added into the test liquid quantitative introduction hole (1021), the centrifugal detector is started, and the centrifugal detector rotates the micro-channel chip at a rotation speed A1 for T1 seconds. During the rotation of the micro-channel chip, the test liquid flows from the test liquid quantitative introduction hole (1021) into the soil leachate introduction groove (12), and then flows from the soil leachate introduction groove (12) into each quantitative introduction groove (18). The excess test liquid in the test liquid quantitative introduction hole (1021) flows along each test liquid guide groove (1022) into the reservoir (1026) at the end of each test liquid guide groove (1022). Primary mixing and reaction (step 3): The rotation speed of the centrifugal detector is increased, and the centrifugal detector rotates the micro-channel chip at a rotation speed A2 for T2 seconds. During the rotation of the micro-channel chip, the test liquid and the detection solution flow from the quantitative introduction groove (18) and the reagent storage groove (20) respectively through the T-shaped mixing groove (16) into the mixing area groove (15). In the mixing area groove (15), the test liquid and the detection solution are mixed to obtain a mixed liquid, and the test ions in the test liquid react with the detection solution. Secondary mixing and reaction (step 4): The operation of the centrifugal detector is stopped, and the mixture in the mixing area groove (15) flows into the snake-shaped mixing area groove (14), where the test solution and the detection solution in the mixture further mix and react, and flow into the second capillary valve (29) between the snake-shaped mixing area groove (14) and the detection area groove (11); Completion of mixing and reaction (step 5): The centrifugal detector is started again, and the centrifugal detector rotates the microfluidic chip at a rotation speed A3 for T3 seconds. During the rotation of the microfluidic chip, the mixed liquid located between the snake-shaped mixing area groove (14) and the detection area groove (11) passes through the second capillary valve (29) and flows into the detection area groove (11), which is the detection method.

14. 14. The method according to claim 13, wherein the different reagent storage grooves (20) are pre-stored with detection solutions for detecting different ions.

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