An in-situ device for measuring soil nitrogen and phosphorus mineralization

Abstract

This invention discloses an in-situ measurement device for soil nitrogen and phosphorus mineralization, belonging to the field of soil nutrient measurement technology. It includes at least one sampling tube with drawer slots distributed vertically along its surface. A sampling box is removably placed within each drawer slot. The sidewall of the sampling box in contact with the soil is made of a PTFE microporous membrane. An impermeable partition divides the inner cavity of the sampling box into a nitrogen collection chamber and a phosphorus collection chamber. A waterproof and breathable membrane covers the upper end of the sampling tube. A pressure balancing valve is installed on the sampling tube. This invention effectively enables in-situ, synchronous, stratified, and continuous measurement of soil nitrogen and phosphorus mineralization, overcoming many shortcomings of existing technologies and providing strong technical support for related research and applications.

Description

Technical Field

[0001] This utility model relates to the field of soil nutrient determination technology, specifically to an in-situ determination device for soil nitrogen and phosphorus mineralization rate. Background Technology

[0002] Soil nitrogen (N) and phosphorus (P) are essential nutrients for plant growth, and their availability largely depends on the mineralization process of soil organic matter. Soil mineralization refers to the process by which soil microorganisms convert organic nitrogen and phosphorus into inorganic nitrogen (such as ammonium nitrogen NH4) that can be absorbed by plants. + Nitrate nitrogen (NO3) - ) and inorganic phosphorus (such as phosphate PO4) 3- The process of accurately determining soil nitrogen and phosphorus mineralization rate is of great significance for understanding soil nutrient cycling, assessing soil fertility capacity, guiding scientific fertilization, and predicting environmental impacts.

[0003] Currently, the main methods for determining soil nitrogen and phosphorus mineralization include laboratory culture, polyethylene bag culture, top-cover buried tube culture, and ion exchange resin method. Laboratory culture requires sampling, processing, and cultivation, disrupting the original soil condition, and the measurement conditions differ significantly from field conditions. While the polyethylene bag culture method is simple to operate, the soil in the bag can only maintain the initial moisture level of the culture, failing to reflect the dynamic properties of soil moisture fluctuations in the field. The top-cover buried tube culture method, although preserving the original soil condition, requires frequent sampling, resulting in a large workload. The ion exchange resin method, while allowing in-situ determination, typically only measures a single element, and the resin placement method is often not standardized.

[0004] In addition, existing soil mineralization rate measuring devices have the following shortcomings: First, they are mostly focused on the measurement of single elements and lack comprehensive devices that can simultaneously measure nitrogen and phosphorus; second, they either require frequent sampling and analysis or complex sensor systems, making operation complicated; third, some devices have complex structures, cumbersome installation and sampling operations, require professional personnel and tools, and have a large amount of disposable consumables, resulting in high long-term monitoring costs. Utility Model Content

[0005] To address the existing technical problems, this utility model provides an in-situ soil nitrogen and phosphorus mineralization rate measurement device that can simultaneously measure soil nitrogen and phosphorus mineralization rates and is suitable for long-term in-situ monitoring, in order to meet the needs of grassland and agricultural ecosystem research and soil fertility monitoring.

[0006] To achieve the above-mentioned objectives, this utility model provides the following technical solution: An in-situ soil nitrogen and phosphorus mineralization rate determination device includes at least one sampling tube with drawer slots distributed vertically on the sampling tube. A sampling box is removably placed in the drawer slots. The sidewall of the sampling box in contact with the soil is made of PTFE microporous membrane. An impermeable partition is provided inside the sampling box, which divides the inner cavity of the sampling box into a nitrogen collection chamber and a phosphorus collection chamber. The upper end of the sampling tube is covered with a waterproof and breathable membrane. An air pressure balance valve is provided on the sampling tube.

[0007] Preferably, the upper end of the sampling tube is connected to a telescopic rod, and the upper end of the telescopic rod is connected to a rain cover.

[0008] This design effectively prevents the impact of rainfall or irrigation water on the measurement results by covering the upper port of the sampling tube with a rain cover.

[0009] Preferably, a guide ring is fitted on the sampling tube near its upper end, the guide ring has a guide groove, and a drain hose is provided on the guide ring at the guide opening of the guide groove.

[0010] In this design, the guide ring is used to intercept rainwater dripping from the edge of the main rain cover or drifting in from the side. The rainwater in the guide ring flows into the drain hose through the guide channel, and the drain hose guides the collected rainwater to a place away from the cultivation area.

[0011] Preferably, it also includes an identification component, which includes a waterproof slot located below the rain cover, into which a record card is inserted.

[0012] Preferably, the sampling tube has pores distributed on its wall, and the diameter of the pores is 1-5 micrometers.

[0013] This design, through pores with a diameter of 1-5 micrometers, can further promote gas exchange while maintaining near-natural soil aeration conditions. These pores can also prevent water from entering due to the surface tension of water, ensuring the accuracy and reliability of the measurement results.

[0014] Preferably, a dust filter is provided at the upper end of the sampling tube.

[0015] This solution, through the design of a dustproof filter, can effectively prevent dust, insects, and other contaminants from entering the sampling tube.

[0016] Preferably, when there are two or more sampling tubes, adjacent sampling tubes are connected end to end by a quick-connect structure, and a double sealing ring is provided at the connection point of the two sampling tubes.

[0017] When the soil being measured is deep, this method can be used to form a sampling tube system by connecting two or more sampling tubes end to end, with the connection between the two sampling tubes sealed by a double sealing ring.

[0018] Preferably, the quick-connect structure includes an internal thread on one of the sampling tubes and an external thread on the other sampling tube that can match the internal thread.

[0019] This scheme connects the two sampling tubes end to end by screwing in the internal and external threads.

[0020] Preferably, the quick-connect structure includes a slot on one of the sampling tubes and a buckle on the other sampling tube that can engage with the slot.

[0021] This solution connects the two sampling tubes end to end through the cooperation of a slot and a buckle.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. Enables in-situ non-destructive continuous monitoring: The drawer-type sampling box allows for repeated sampling of soil at different depths at the same location without damaging the soil profile structure, enabling in-situ, non-destructive, and continuous dynamic monitoring. 2. Simultaneous stratified determination of nitrogen and phosphorus: The dual-chamber design of the sampling box can simultaneously acquire nitrogen and phosphorus mineralization rate data at different soil depths, improving the measurement efficiency and revealing the distribution and transformation patterns of nutrients in the soil profile. 3. Economic, environmentally friendly and sustainable: The main components and adsorption materials can be reused, which reduces the cost of long-term monitoring and meets the requirements of sustainable development; 4. Applicable to various soil types and climate conditions, with a wide range of applications. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of this utility model; Figure 2 for Figure 1 A schematic diagram of the sampling box structure; Figure 3 for Figure 2 Top view in the middle; Figure 4 for Figure 1 A schematic diagram of the structure of the rain cover and telescopic pole in the image; Figure 5 This is a schematic diagram of a first embodiment of the quick-connect structure on the sampling tube of this utility model; Figure 6 This is a schematic diagram of a second embodiment of the quick-connect structure on the sampling tube of this utility model. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0025] In the description of this utility model, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0026] As attached Figure 1 - Appendix Figure 6 The device shown is an in-situ measurement device for soil nitrogen and phosphorus mineralization, comprising at least one sampling tube 1. The sampling tube 1 serves as the main frame of the device and is made of high-strength PVC material. The sampling tube 1 is cylindrical, preferably with an outer diameter of 11 cm, an inner diameter of 10 cm, and a wall thickness of 0.5 cm to ensure sufficient mechanical strength and capacity. The device adopts a segmented design, with each segment being a sampling tube 1. The standard length of each segment is preferably 20 cm. Multiple sampling tubes 1 can be connected via a quick-connect structure according to the required measurement depth. The inner wall of the sampling tube 1 is smoothed to reduce soil friction; the outer wall is treated with UV protection to extend its service life. Depth marks are precisely engraved every 5 cm on the outer wall of the sampling tube 1.

[0027] Sampling tube 1 is equipped with a pressure balancing valve 6 to ensure pressure balance inside and outside the tube, preventing sample deformation or abnormal moisture migration due to pressure differences. The upper end of sampling tube 1 is covered with a waterproof and breathable membrane. The tube wall has pores with a diameter of 1-5 micrometers, allowing gas molecules to pass freely but preventing liquid water from seeping in. A dust filter is installed at the upper end of sampling tube 1 to prevent dust, insects, and other contaminants from entering the device. This ensures necessary gas exchange between the soil inside sampling tube 1 and the outside atmosphere (e.g., O2 entering, CO2 exiting), simulating natural ventilation conditions.

[0028] The sampling tube 1 has drawer slots 2 distributed vertically. In this embodiment, it is preferable to have one drawer slot 2 every 10 cm. A sampling box 3 is removably placed in the drawer slot 2. The sampling box 3 is preferably injection molded from food-grade PP material. The side wall of the sampling box 3 that contacts the soil is made of PTFE microporous membrane. The pore size of the PTFE microporous membrane is preferably 0.22 micrometers. This PTFE microporous membrane allows ions in the soil solution to pass freely, but effectively prevents fine soil particles from entering the interior of the sampling box 3. The sampling box 3 is equipped with a double silicone sealing ring. When the sampling box 3 is pushed into the drawer slot 2, the double silicone sealing ring can fit tightly against the inner wall of the drawer slot 2 to prevent moisture leakage along the gaps and cross-contamination of samples. The sampling box 3 is equipped with an easy-to-grip handle 31, which allows users to directly pull it out or push it in by hand without the need for tools. The handles 31 on the sampling boxes 3 at different depths can be marked with different colors. Of course, sampling boxes 3 at different depths can also be distinguished by different colors.

[0029] from Figure 2 , Figure 3 As can be seen, the sampling box 3 is equipped with an anti-permeability partition 4, which is made of PP material. This anti-permeability partition 4 divides the inner cavity of the sampling box 3 into a nitrogen collection chamber 41 and a phosphorus collection chamber 42. The nitrogen collection chamber 41 is filled with a pretreated ion exchange resin mixture, which consists of a strong acid cation exchange resin (used to adsorb NH4). + ) and strongly basic anion exchange resins (used for adsorbing NO3) - The components are composed in a specific ratio. The phosphorus collection chamber 42 is filled with phosphate adsorbent material, such as modified alumina particles or commercially available phosphate selective adsorbents. Both adsorbent materials are selected for their high adsorption capacity and selectivity, and ease of elution and regeneration. A semi-permeable membrane can be further coated inside the PTFE microporous membrane of the sampling chamber 3 to enhance selectivity and ensure that only target ions enter the adsorption region.

[0030] Figure 4 Combination Figure 1 As can be seen, to prevent rainfall or irrigation water from affecting the measurement, a telescopic rod 51 is connected to the upper end of the sampling tube 1. The upper end of the telescopic rod 51 is connected to a rain cover 52, which is made of transparent PC material for easy observation. The rain cover 52 has an umbrella-shaped structure, and its outer diameter is 15cm larger than that of the sampling tube 1. A guide ring 53 is fitted on the sampling tube 1 near its upper opening. The guide ring 53 has a guide groove (not shown in the figure) to collect rainwater dripping from the edge of the main rain cover 52 or drifting in from the side. A drainage hose 54 is provided on the guide ring 53 at the guide opening of the guide groove. The water collected in the guide groove is guided by the drainage hose 54 to an area away from the soil at the bottom of the device for discharge.

[0031] It also includes an identification component, which includes a waterproof slot 55 located below the rain cover 52. A record card is inserted into the waterproof slot 55 for on-site handwritten records. Each sampling tube 1 has a fixed label that can be written and read with information such as the sample point number, deployment time, and person in charge. A durable QR code containing information such as the device ID is printed on the outer wall of the sampling tube 1.

[0032] When the soil depth being measured is relatively deep, two or more sampling tubes 1 are required. In this case, two adjacent sampling tubes 1 are connected end to end by a quick-connect structure, and a double sealing ring 7 is provided at the connection point of the two sampling tubes 1.

[0033] refer to Figure 5 The diagram shows a quick connection structure according to Embodiment 1. In this embodiment, the quick connection structure includes an internal thread on one of the sampling tubes 1 and an external thread on the other sampling tube 1 that matches the internal thread. The two sampling tubes 1 can be quickly and detachably connected by screwing the internal thread and the external thread together.

[0034] refer to Figure 6 The diagram below is a schematic diagram of the second embodiment of the quick connection structure. In this embodiment, the quick connection structure includes a slot 81 on one of the sampling tubes 1 and a buckle 82 on the other sampling tube 1 that can be engaged with the slot 81. When connecting, the two sampling tubes 1 are connected by fastening the buckle 82 into the slot 81.

[0035] Of course, the quick connection structure can also adopt a rotary interface design. After aligning and tightening, the two sampling tubes 1 can be locked together.

[0036] Alternatively, anti-rotation positioning pins can be installed at the interface where the two sampling tubes 1 are connected to ensure that the connected tube segments do not rotate relative to each other, thereby keeping the opening direction of all drawer slots 2 consistent with the direction of the sampling box 3.

[0037] An in-situ method for determining soil nitrogen and phosphorus mineralization, applicable to Figures 1-6 The soil nitrogen and phosphorus mineralization rate in-situ measurement device shown includes the following steps: S1, Device setup: Select a representative grassland plot, use a soil drill or special tool to drill a hole vertically to the predetermined depth according to the outer diameter of the sampling tube 1, and vertically place the assembled device (at this time, the sampling box 3 does not contain adsorbent) into the drill hole, ensuring that the tube wall of the sampling tube 1 fits well with the hole wall, and backfill the soil taken from the drill hole into the sampling tube 1 in its original state, trying to maintain the original bulk density and structure of the soil, so as to bury the sampling tube 1 in the soil to be tested; S2, Start cultivation: After the device stabilizes, take out the sampling box 3, put the pretreated nitrogen adsorption material into the nitrogen collection chamber 41, put the pretreated phosphorus adsorption material into the phosphorus collection chamber 42, and then reinsert the sampling box 3 into the drawer slot 2 at the corresponding depth, record the start time T0, and start in-situ cultivation. S3, Sample Collection: According to the experimental design, samples are collected at predetermined incubation time points (e.g., 7 days, 14 days, 30 days, etc., denoted as T). 1, To perform sampling (T2, T3...), simply extract the sampling box 3 at the target depth. After extraction, rinse the surface of the sampling box 3 with a small amount of deionized water to remove the soil particles. After removing the old sampling box 3, you can immediately place the sampling box 3 containing the new adsorbent into it to start the measurement of the next culture cycle, thereby achieving continuous monitoring. S4, Sample processing and elution: Take the sample box 3 back to the laboratory, carefully open the sample box 3, and transfer the adsorbent material in the nitrogen collection chamber 41 and the adsorbent material in the phosphorus collection chamber 42 completely into the marked containers (such as beakers or centrifuge tubes). (1) For nitrogen adsorption materials: add an appropriate amount (e.g., 50 mL) of 2 mol / L KCl solution, shake thoroughly to extract for a period of time (e.g., 1 hour), then filter or centrifuge to obtain the supernatant, which is the nitrogen eluent; (2) For phosphorus adsorbent materials: Select a suitable eluent according to the properties of the adsorbent. For example, for alumina adsorbent, add an appropriate amount (e.g., 50 mL) of 0.5 mol / L NaOH solution or a specific concentration of acidic solution (e.g., HCl), shake thoroughly to extract, filter or centrifuge to obtain the supernatant, which is the phosphorus eluent. S5, Sample Analysis: Determine the ion concentration in the eluent using standard chemical analysis methods; (1) Nitrogen eluent: for the determination of NH4 + -N and NO3 - The concentration of -N, for example, using a continuous flow analyzer or spectrophotometry; (2) Phosphorus eluent: for determining PO4 3- The concentration of -P, for example, using the molybdenum blue colorimetric method; S6, Mineralization rate calculation: Based on the measured ion concentration (C, mg / L) in the eluent, the eluent volume (V, L), the soil dry weight (M, kg) at the corresponding layer in the culture tube, and the culture time (ΔT = T). n - T0, days), calculate net mineralization rate (R, mg / kg / d); Net nitrogen mineralization rate R_N = [(C_NH4) - N + C_NO3-N) × V] / (M × ΔT) Net phosphate mineralization rate R_P = (C_PO4) - (P × V) / (M × ΔT) (Note: Soil dry weight M is usually calculated by taking samples and measuring the moisture content at the beginning or end of the experiment.) S7. Device Recovery and Regeneration: After the experiment, the entire device can be taken out. After cleaning the sampling tube 1, sampling box 3 and other components, they can be reused. The used adsorption resin and adsorbent can be regenerated according to standard methods (e.g., acid and alkali rinsing). After regeneration, its adsorption performance is tested. If it is qualified, it can be used again for subsequent experiments.

[0038] The preferred embodiments of this utility model have been described above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this utility model through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. An in-situ device for measuring soil nitrogen and phosphorus mineralization, characterized in that: It includes at least one sampling tube (1), on which drawer slots (2) are distributed vertically. A sampling box (3) is removably placed in the drawer slots (2). The sidewall of the sampling box (3) in contact with the soil is made of PTFE microporous membrane. An anti-permeability partition (4) is provided inside the sampling box (3). The anti-permeability partition (4) divides the inner cavity of the sampling box (3) into a nitrogen collection chamber (41) and a phosphorus collection chamber (42). The upper end of the sampling tube (1) is covered with a waterproof and breathable membrane. A pressure balance valve (6) is provided on the sampling tube (1).

2. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 1, characterized in that: The upper end of the sampling tube (1) is connected to a telescopic rod (51), and the upper end of the telescopic rod (51) is connected to a rain cover (52).

3. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 2, characterized in that: A guide ring (53) is fitted on the sampling tube (1) near its upper end. A guide groove is provided on the guide ring (53), and a drain hose (54) is provided on the guide ring (53) at the guide opening of the guide groove.

4. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 2, characterized in that: It also includes an identification component, which includes a waterproof slot (55) located below the rain cover (52) into which a record card is inserted.

5. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 1, characterized in that: The sampling tube (1) has pores distributed on its wall, and the diameter of the pores is 1-5 micrometers.

6. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 1, characterized in that: The sampling tube (1) is equipped with a dust filter at the upper end of the tube opening.

7. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 1, characterized in that: When there are two or more sampling tubes (1), the two adjacent sampling tubes (1) are connected end to end by a quick connection structure, and a double sealing ring (7) is provided at the connection of the two sampling tubes (1).

8. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 7, characterized in that: The quick-connect structure includes an internal thread on one of the sampling tubes (1) and an external thread on the other sampling tube (1) that can match the internal thread.

9. The in-situ soil nitrogen and phosphorus mineralization rate determination device according to claim 7, characterized in that: The quick-connect structure includes a slot (81) on one of the sampling tubes (1) and a buckle (82) on the other sampling tube (1) that can engage with the slot (81).

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