Method for monitoring change of nutrient content of bag-controlled slow-release fertilizer by self-powered chip

Abstract

The invention discloses a method for monitoring the nutrient content change of a bag-controlled slow-release fertilizer through a self-powered chip, and relates to the technical field of forestry fertilization monitoring. According to the method, a controlled release-monitoring dual-function packaging material composed of polyvinyl alcohol, sodium alginate, montmorillonite and the like is researched and developed, a non-contact conductivity detection microchip is embedded into the packaging material in situ, and a self-powered module is combined, so that real-time detection of fertilizer nutrients in a bag is realized. According to the chip, the platinum microelectrode and the submicron insulating layer are cooperatively matched, so that the conductivity detection stability and accuracy are improved, and the problems that the traditional fertilizer nutrient content monitoring depends on manual field operation, the monitoring accuracy is low, monitoring lags behind or monitoring equipment depends on an external power supply and the like are effectively solved; in practical application, after content analysis of nitrogen, phosphorus and potassium is completed, data are transmitted to a background database for storage, the chip can continuously work for more than or equal to 300 days, the detection error is 4-7.2%, and the chip is suitable for long-term accurate monitoring scenes of the content of the nutrients of the bag-controlled slow-release fertilizer in the forest land.

Description

Technical Field

[0001] This invention relates to the field of forestry fertilization monitoring technology, and more particularly to a method for monitoring changes in nutrient content in bagged controlled-release fertilizers using a self-powered, non-contact conductivity detection microchip. This method integrates chip technology with forestry fertilizer nutrient monitoring technology, aiming to provide crucial support for precision forestry fertilization. In forestry production, accurate monitoring of fertilizer nutrients is essential for crop growth, yield improvement, and environmental protection. The self-powered chip technology used in this invention brings new monitoring methods and ideas to this field, possessing significant application value and practical significance. Background Technology

[0002] Fertilizer, as the "food" for tree growth, plays a crucial role in forestry production. Proper fertilization provides trees with essential nutrients such as nitrogen, phosphorus, and potassium, effectively promoting crop growth and significantly increasing tree yields. It is a key factor in ensuring food security and increasing the income of forest farmers.

[0003] Controlled-release fertilizer in bags, as a novel type of fertilizer, effectively reduces nutrient loss and improves fertilizer utilization through special packaging and slow-release technology, which is of great significance to the sustainable development of forestry. Taking eucalyptus planting as an example, traditional fertilization methods result in low fertilizer utilization, easy nutrient loss with rainwater, and phosphorus fixation in the soil, leading to resource waste and potential environmental pollution. However, with controlled-release fertilizer in bags, nutrients are released slowly, meeting the needs of eucalyptus at different growth stages while significantly reducing nutrient loss and improving fertilizer utilization efficiency, providing strong support for the green development of forestry production.

[0004] However, current monitoring of nutrient content changes in bagged controlled-release fertilizers mainly relies on traditional methods of manual sampling followed by laboratory testing. This method has many drawbacks. On the one hand, manual sampling is labor-intensive and time-consuming, resulting in low efficiency. On the other hand, the testing process is cumbersome and lacks timeliness, failing to provide timely decision-making support for forestry production. For example, during critical growth periods, failure to promptly grasp changes in fertilizer nutrient content may lead to untimely or inappropriate fertilization, thereby affecting tree growth and yield. Furthermore, traditional testing methods heavily depend on external power sources. In some remote forest areas, inconvenient power supply makes real-time monitoring difficult, significantly limiting the precise management of nutrients in bagged controlled-release fertilizers.

[0005] With the rapid development of technology, chip technology has been widely applied in numerous fields such as communications, automobiles, medicine, and the Internet of Things. In the communications field, chips enable efficient signal reception, processing, and transmission, ensuring stable and efficient communication. In the automotive field, chips are used to control the engine, braking system, and safety system, driving the intelligent and automated development of automobiles. However, the application of chip technology to monitoring changes in nutrient content in bag-controlled slow-release fertilizers is currently in the exploratory stage, with a significant technological gap. This invention aims to fill this gap by introducing self-powered chip technology into the field of nutrient monitoring in bag-controlled slow-release fertilizers, enabling real-time and accurate monitoring of changes in fertilizer nutrient content, and providing an innovative solution for the intelligent and precise management of forestry production.

[0006] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] This invention aims to provide a method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip. This method addresses the problems of low efficiency, poor timeliness, and reliance on external power sources in existing forest fertilizer nutrient monitoring technologies. It enables real-time, accurate, and self-powered monitoring of nutrient content changes in bag-controlled slow-release fertilizer, providing a scientific basis for precision fertilization in forestry production, effectively improving fertilizer utilization, and reducing resource waste and environmental pollution.

[0008] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0009] A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip includes the following steps:

[0010] (1) Preparation of controlled-release-monitoring dual-function substrate: The substrate is composed of the following components in mass percentage: polyvinyl alcohol 38%-40%, sodium alginate 23%-25%, sodium carboxymethyl cellulose 8%-10%, montmorillonite 10%-12%, attapulgite 6%-8%, polyethylene glycol-400 2%-3%, nano silica 1%-1.5%, citric acid 0.3%-0.5%, with the balance being deionized water and impurities unavoidable during processing;

[0011] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0012] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0013] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0014] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient leaching solution in the bag is periodically detected by the chip, and the self-powered module provides energy. The detection data is wirelessly transmitted to the terminal, and the quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content of fertilizer is completed based on the standard curve.

[0015] Preferably, the preparation of the substrate in step (1) includes:

[0016] (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose are dissolved in deionized water and stirred in a water bath at 60-70℃ for 30-50 min to form a colloid;

[0017] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica are added in sequence and stirred at 250-350 rpm for 15-25 min;

[0018] (c) Molding and curing: Add citric acid to adjust the pH to 6.0-7.0, stir for 8-12 minutes and pour into the mold with the preset chip embedding groove. Vacuum dry at 40-50℃ for 10-14 hours and blow dry at 55-65℃ for 5-7 hours until the moisture content is 1-5%.

[0019] Preferably, the nutrient raw materials in step (2) include urea, potassium dihydrogen phosphate, and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:(1.2-2.8); the nutrient raw materials are dissolved in 40-60 mL of deionized water and then sprayed onto the inner surface of the substrate, and dried in a ventilated environment at 30-40°C for 6-10 hours.

[0020] Preferably, the pretreatment of the non-contact conductivity detection microchip in step (3) includes: rinsing the microchannel with deionized water 2-4 times, and injecting 4-6wt% PDMS solution and baking at 75-85℃ for 8-12 minutes to form a hydrophobic coating;

[0021] Preferably, the sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the embedding depth of the end of the conduit is 0.8-1.2mm.

[0022] Preferably, the self-powered module in step (4) includes a flexible solar cell, an 800-1200mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 40-60 hours.

[0023] Preferably, the packaging in step (4) uses a nylon woven outer bag with a thickness of 0.12-0.15mm, heat-seales the edges at 170-190℃, with a sealing width of 4-6mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0024] Preferably, the detection in step (5) involves collecting nutrient leachate every 120-150 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0025] Preferably, the substrate has a porosity of 43%-52%, a pore size of 4-11 μm, a nutrient dissolution rate of 0.4-1.1 mg / h, a release period of 28-47 days, and a release fluctuation range of ±6-10%.

[0026] Preferably, the data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 6-14m. The terminal displays the curves of nitrogen, phosphorus, and potassium content changes and supports access to forestry IoT platforms compatible with the MQTT communication protocol.

[0027] The beneficial effects of this invention compared to the prior art include:

[0028] I. Overcoming the lag in on-site monitoring to achieve real-time dynamic tracking of nutrients.

[0029] In existing technologies, nutrient monitoring of bagged controlled-release fertilizers largely relies on laboratory testing or offline analysis using portable devices. Laboratory testing involves multiple steps, including manual sampling, sample transportation, digestion, and instrumental analysis, which is time-consuming and cannot reflect the real-time release status of fertilizer nutrients. While portable devices can be operated on-site, manual extraction of the leachate from the fertilizer bag is still required, and the sampling process is susceptible to external environmental interference and cannot achieve continuous dynamic monitoring. This invention embeds a chip in situ into the substrate-nutrient composite of the bagged controlled-release fertilizer. The chip can directly contact the nutrient leachate inside the substrate, enabling periodic monitoring without manual intervention. This in-situ integrated design allows the monitoring process to be synchronized with the fertilizer nutrient release process, capturing subtle changes in nutrient content in real time. This fundamentally solves the problem of monitoring lag in existing technologies and provides real-time data support for timely adjustments to fertilization strategies.

[0030] II. Eliminating dependence on external power supply and adapting to diverse forest environments

[0031] Most existing field monitoring equipment relies on external power sources or high-capacity rechargeable batteries. In remote forests, mountain orchards, and other areas without grid coverage, the equipment's range and battery life are severely limited. Battery power requires regular replacement or charging, increasing labor costs and operational complexity. Furthermore, battery stability and lifespan are affected by adverse weather conditions. This invention's self-powered module consists of flexible solar cells, a lithium polymer battery, and a voltage regulator. The flexible solar cells utilize natural forest sunlight for energy harvesting, powering the chip and charging the lithium polymer battery during the day. In the absence of sunlight, the lithium polymer battery continues to power the system, ensuring uninterrupted monitoring. By setting a relatively long detection cycle (e.g., every 120-150 hours), the monitoring system keeps the chip in a low-power sleep or standby state for most of the time, significantly reducing the system's average power consumption. This "low-frequency sampling, long-term monitoring" strategy, combined with the energy harvesting and storage capabilities of the self-powered module, ensures continuous operation of the system during the forest's growing season (≥300 days), overcoming reliance on external power sources or frequent battery replacements. This self-powered design completely eliminates dependence on external power sources; whether in plains forests, remote mountains, or plateau regions, as long as there is natural light, the equipment can operate stably, significantly expanding the applicable scenarios for monitoring technology.

[0032] III. Optimize detection compatibility to ensure the accuracy of test results

[0033] In existing technologies, the packaging materials for controlled-release fertilizers lack compatibility with testing equipment. Unreasonable pore structures in the packaging materials can easily lead to soil particles mixing into the nutrient dissolution solution, and fluctuations in the material's own chemical properties can interfere with the detection signal, thus affecting the accuracy of the test results. Furthermore, non-contact conductivity detection microchips have high requirements for the pH value and solution purity of the detection environment—their platinum microelectrodes are easily affected by impurities adhering to them, affecting signal acquisition, and the submicron-level insulating layer also requires a stable environment to avoid damage. Existing packaging materials cannot meet these compatibility requirements, further reducing detection accuracy. The controlled-release-monitoring dual-function substrate of this invention is specially formulated, with its porosity and pore size precisely controlled. This ensures that nutrients dissolve slowly at a rate of 0.4-1.1 mg / h while filtering out ≥95% of soil particles, preventing impurities from entering the chip's microchannels and damaging the insulating layer. Simultaneously, the citric acid added to the substrate stabilizes the pH value of the detection environment at 6.0-7.0, perfectly matching the optimal response range of the chip's platinum microelectrode, reducing environmental interference with the detection signal. This substrate and its compatible design with the non-contact conductivity detection microchip provide the chip with a stable and pure detection sample, effectively ensuring the accuracy of the detection results.

[0034] IV. Simplify operating procedures and lower the threshold for forestry applications.

[0035] Existing monitoring technologies have complex operational procedures. Whether using laboratory testing or portable devices, they require professionals with expertise in sampling procedures, instrument calibration, and data processing, making it difficult for forestry producers to perform independently. Relying on specialized technicians for monitoring in forestry production increases costs and fails to meet the monitoring needs of large-scale forest areas. This invention employs an integrated packaging design, combining the substrate-nutrient complex, chip, and self-powered module into a single monitoring bag. In use, the monitoring bag is simply buried in the fertilization layer of the forest, eliminating the need for complex assembly and debugging. The chip's detection process is automated, and the data is wirelessly transmitted to a terminal via Bluetooth. Forestry producers can then visually view nutrient content change curves on the terminal without needing specialized testing skills. This simplified operational process lowers the barrier to entry for monitoring technology, allowing forestry producers to easily conduct nutrient monitoring of bag-controlled slow-release fertilizers, facilitating the large-scale application of this technology in forestry production.

[0036] V. Expand the application value of forestry and promote the development of precision forestry

[0037] Existing monitoring technologies are mostly limited to single nutrient content detection functions, failing to provide multi-dimensional support for forestry production and exhibiting low data utilization efficiency. The monitoring technology of this invention not only monitors changes in the nutrient content of bagged controlled-release fertilizers in real time, but its data can also be integrated with forestry IoT platforms. By integrating and analyzing monitoring data from different plots and time periods, forestry producers can clearly understand the changing trends of soil fertility, providing a basis for developing differentiated fertilization plans. Simultaneously, based on long-term monitoring data, it can also provide a reference for selecting tree species, choosing suitable species according to soil nutrient conditions to improve tree yield and quality. Furthermore, the monitoring data can be used to optimize the formulation of bagged controlled-release fertilizers, adjusting the proportion and release cycle of various nutrients in the fertilizer according to the nutrient requirements of different regions and crops, achieving precise fertilizer supply. This multi-dimensional application value provides strong support for the development of precision forestry, promoting forestry production towards a more scientific and efficient direction. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0039] This invention provides a method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip, comprising the following steps:

[0040] (1) Preparation of controlled-release-monitoring dual-function substrate: The substrate is composed of the following components in mass percentage: polyvinyl alcohol 38%-40%, sodium alginate 23%-25%, sodium carboxymethyl cellulose 8%-10%, montmorillonite 10%-12%, attapulgite 6%-8%, polyethylene glycol-400 2%-3%, nano silica 1%-1.5%, citric acid 0.3%-0.5%, with the balance being deionized water and impurities unavoidable during processing;

[0041] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0042] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0043] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0044] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient solution in the bag is periodically detected by the chip, the self-powered module provides energy, and the detection data is wirelessly transmitted to the terminal. The quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content is completed based on the standard curve.

[0045] The preparation of the substrate in step (1) includes:

[0046] (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose are dissolved in deionized water and stirred in a water bath at 60-70℃ for 30-50 min to form a colloid;

[0047] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica are added in sequence and stirred at 250-350 rpm for 15-25 min;

[0048] (c) Molding and curing: Add citric acid to adjust the pH to 6.0-7.0, stir for 8-12 minutes and pour into the mold with the preset chip embedding groove. Vacuum dry at 40-50℃ for 10-14 hours and blow dry at 55-65℃ for 5-7 hours until the moisture content is 1-5%.

[0049] The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:(1.2-2.8); the nutrient raw materials are dissolved in 40-60mL of deionized water and then sprayed onto the inner surface of the substrate, and dried in a ventilated environment at 30-40℃ for 6-10h.

[0050] The pretreatment of the non-contact conductivity detection microchip in step (3) includes: rinsing the microchannel with deionized water 2-4 times, and injecting 4-6wt% PDMS solution and baking at 75-85℃ for 8-12 minutes to form a hydrophobic coating.

[0051] The sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the insertion depth of the end of the conduit is 0.8-1.2mm.

[0052] The self-powered module mentioned in step (4) includes a flexible solar cell, an 800-1200mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 40-60 hours.

[0053] The packaging in step (4) uses a nylon woven outer bag with a thickness of 0.12-0.15mm, heat-seales the edges at 170-190℃, with a sealing width of 4-6mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0054] The detection in step (5) involves collecting nutrient leachate every 120-150 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0055] The substrate has a porosity of 43%-52%, a pore size of 4-11 μm, a nutrient dissolution rate of 0.4-1.1 mg / h, a release period of 28-47 days, and a release fluctuation range of ±6-10%.

[0056] The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 6-14m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms compatible with the MQTT communication protocol.

[0057] The role of raw materials and their synergistic mechanism:

[0058] (I) The role and synergy of controlled-release and monitoring bifunctional substrate raw materials

[0059] Polyvinyl alcohol (38%-40%): As the matrix skeleton, it forms a three-dimensional network structure through the hydrogen bonding between its molecular chains, providing basic mechanical support for the matrix and ensuring that the matrix is ​​not easily damaged during the burial process in forest land. At the same time, its porous characteristics provide channels for nutrient dissolution.

[0060] Sodium alginate (23%-25%): It has good biocompatibility and film-forming properties. When it works synergistically with polyvinyl alcohol, the carboxyl groups of sodium alginate can form hydrogen bonds with the hydroxyl groups of polyvinyl alcohol, which further enhances the toughness and structural stability of the substrate and prevents the substrate from cracking due to dry-wet cycles. At the same time, its own gel properties can slow down the nutrient release rate.

[0061] Sodium carboxymethyl cellulose (8%-10%): As a binder, it can fill the gaps in the network structure formed by polyvinyl alcohol and sodium alginate, improve the density and formability of the substrate, reduce the shrinkage and deformation of the substrate during the preparation process, and its water solubility can improve the dispersion uniformity between raw materials, ensuring the stability of the substrate performance.

[0062] Montmorillonite (10%-12%): Its layered silicate structure gives it a strong ion adsorption capacity, which can selectively adsorb nitrogen and phosphorus ions in fertilizers and slowly release nutrients through interlayer diffusion. When used in conjunction with sodium alginate, the layered structure of montmorillonite can be embedded in the gel network of sodium alginate to form a "gel-layered" composite controlled-release structure, which further prolongs the nutrient release cycle.

[0063] Attapulgite (6%-8%): Its porous structure gives it a large specific surface area, which can adsorb potassium ions and regulate their release rate. It forms a "complementary adsorption" synergistic effect with montmorillonite - montmorillonite focuses on controlled release of nitrogen and phosphorus, while attapulgite focuses on controlled release of potassium, so as to achieve a balanced release of the three major nutrients in fertilizer. At the same time, its needle-like crystal structure can enhance the mechanical strength of the substrate and prevent the substrate from breaking under the action of external forces in the forest.

[0064] Polyethylene glycol-400 (2%-3%): As a plasticizer, it can be inserted between the molecular chains of polyvinyl alcohol and sodium alginate, reducing the intermolecular forces, improving the flexibility of the substrate, and preventing the substrate from becoming brittle and breaking at low temperatures; at the same time, its hydrophilicity can improve the water absorption performance of the substrate, ensuring that nutrients can be dissolved evenly.

[0065] Nano silica (1%-1.5%): Its nano-sized particles allow it to be uniformly dispersed in the substrate, filling the tiny pores inside the substrate and reducing the rapid loss of nutrients through the pores. At the same time, its chemical stability can enhance the substrate's resistance to microbial degradation, preventing the substrate from being decomposed by microorganisms in forests and causing the controlled-release function to fail. When used in conjunction with sodium carboxymethyl cellulose, nano silica can enhance the substrate's water resistance and prevent the substrate from swelling and deforming due to excessive water absorption.

[0066] Citric acid (0.3%-0.5%): On the one hand, it adjusts the pH value of the substrate to 6.0-7.0, providing a suitable acid-base environment for chip detection and avoiding pH fluctuations from affecting the chip conductivity detection signal; on the other hand, its acidity can slightly activate the adsorption sites of montmorillonite and attapulgite, enhancing their adsorption capacity for nutrient molecules, and at the same time, it undergoes an esterification reaction with the hydroxyl groups of polyvinyl alcohol, further improving the structural stability of the substrate.

[0067] The aforementioned raw materials, through the multi-dimensional synergistic effect of "skeleton support - bonding and molding - ion adsorption - environmental regulation", form a substrate with both precise controlled release and detection compatibility functions. This solves the problems of low controlled release accuracy and poor compatibility with detection equipment in traditional packaging materials, and realizes the integrated integration of "controlled release and monitoring" functions. This meets the requirement of "the overall effect of each technical feature synergistically producing an effect that exceeds the sum of the effects of a single feature" in the inventiveness of combined inventions.

[0068] (ii) Synergy between self-powered modules and chip-related materials

[0069] Flexible solar cells: As the core of energy harvesting, they can convert natural sunlight in the forest into electrical energy to provide continuous power to the chip; when used in conjunction with lithium polymer batteries, the solar cells can power the chip and charge the battery during the day, realizing a closed loop of energy harvesting and storage, ensuring that the system can still operate stably when there is no sunlight.

[0070] Lithium polymer batteries (800-1200mAh): They have high energy density and good charge and discharge performance. They can store the electrical energy collected by solar cells. When used in conjunction with the LM1117-3.3V voltage regulator, the voltage output by the battery is regulated by the regulator to provide a stable 3.3V operating voltage for the chip, avoiding voltage fluctuations that could lead to a decrease in chip detection accuracy or damage.

[0071] Non-contact conductivity detection microchip: Platinum microelectrodes ensure accurate acquisition of conductivity signals, and a submicron-level insulating layer isolates the ionic interference of inorganic fillers (such as montmorillonite and attapulgite) in the substrate; the chip is connected to the substrate through a 0.22μm filter membrane conduit, and the pure leaching solution after the substrate is filtered enters the detection channel, forming a "pretreatment-protection" dual guarantee with the chip insulating layer, and the detection error is controlled within 4-7.2%.

[0072] In summary, this invention achieves an integrated function of "controlled release-monitoring-self-powered supply" through the synergistic effect of various raw materials, solving multiple technical problems in the prior art. Its overall technical effect exceeds the sum of the effects of each individual technical feature.

[0073] To make the present invention more fully disclosed, more specific embodiments are described below.

[0074] Example 1:

[0075] A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip includes the following steps:

[0076] (1) Preparation of controlled-release-monitoring dual-function substrate: The controlled-release-monitoring dual-function substrate is composed of the following components in mass percentage: 38% polyvinyl alcohol, 23% sodium alginate, 8% sodium carboxymethyl cellulose, 10% montmorillonite, 6% attapulgite, 2% polyethylene glycol-400, 1% nano silica, 0.3% citric acid, and the balance being deionized water and impurities that are unavoidable during the processing;

[0077] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0078] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip (CN102641759A) with an integrated thickness controllable insulation layer, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0079] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0080] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient solution in the bag is periodically detected by the chip, the self-powered module provides energy, and the detection data is wirelessly transmitted to the terminal. The quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content is completed based on the standard curve.

[0081] The preparation of the substrate in step (1) includes:

[0082] (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose were dissolved in deionized water and stirred in a water bath at 60°C for 50 min to form a colloid;

[0083] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica were added in sequence and stirred at 250 rpm for 25 min;

[0084] (c) Molding and curing: Add citric acid to adjust the pH to 6.0, stir for 8 minutes and pour into the mold with the preset chip embedding groove, vacuum dry at 40℃ for 14 hours, and blow dry at 55℃ for 7 hours until the moisture content is 5%.

[0085] The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:1.2. The nutrient raw materials are dissolved in 40 mL of deionized water and then sprayed onto the inner surface of the substrate and dried at 30°C for 10 h.

[0086] The pretreatment of the non-contact conductivity detection microchip in step (3) includes rinsing the microchannel twice with deionized water and injecting 4wt% PDMS solution and baking at 75°C for 12 min to form a hydrophobic coating.

[0087] The sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the insertion depth of the end of the conduit is 0.8mm.

[0088] The self-powered module mentioned in step (4) includes a flexible solar cell, an 800mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 60 hours.

[0089] The packaging in step (4) uses a 0.12mm thick nylon woven outer bag, heat-sealed at 170℃ with a sealing width of 4mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0090] The detection in step (5) involves collecting nutrient leachate every 120 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0091] The substrate has a porosity of 43%, a pore size of 4μm, a nutrient dissolution rate of 0.4mg / h, a release period of 28 days, and a release fluctuation range of ±10%.

[0092] The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 6m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms that are compatible with the MQTT communication protocol.

[0093] Example 2:

[0094] A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip includes the following steps:

[0095] (1) Preparation of functional substrate: Preparation of controlled-release-monitoring dual-function substrate: The substrate is composed of the following components by mass percentage: 39% polyvinyl alcohol, 24% sodium alginate, 9% sodium carboxymethyl cellulose, 11% montmorillonite, 7% attapulgite, 2.5% polyethylene glycol-400, 1.2% nano silica, 0.4% citric acid, with the balance being deionized water and impurities unavoidable during processing;

[0096] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0097] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip (CN102641759A) with an integrated thickness controllable insulation layer, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0098] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0099] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient solution in the bag is periodically detected by the chip, the self-powered module provides energy, and the detection data is wirelessly transmitted to the terminal. The quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content is completed based on the standard curve.

[0100] The preparation of the substrate in step (1) includes:

[0101] (a) Preparation of colloidal solution: Preparation of basic colloid: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose were dissolved in deionized water and stirred in a water bath at 65°C for 40 min to form a colloid;

[0102] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica were added in sequence and stirred at 300 rpm for 20 min;

[0103] (c) Molding and curing: Add citric acid to adjust the pH to 6.5, stir for 10 minutes and pour into the mold with the preset chip embedding groove, vacuum dry at 45℃ for 12 hours, and blow dry at 60℃ for 6 hours until the moisture content is 3%.

[0104] The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:2.0. The nutrient raw materials are dissolved in 50 mL of deionized water and then sprayed onto the inner surface of the substrate and dried at 35°C for 8 hours.

[0105] The pretreatment of the non-contact conductivity detection microchip in step (3) includes rinsing the microchannel with deionized water three times and injecting 5wt% PDMS solution and baking at 80°C for 10 min to form a hydrophobic coating.

[0106] The sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the insertion depth of the end of the conduit is 1.0mm.

[0107] The self-powered module mentioned in step (4) includes a flexible solar cell, a 1000mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 50 hours.

[0108] The packaging in step (4) uses a nylon woven outer bag with a thickness of 0.13mm, heat-seales the edges at 180°C with a sealing width of 5mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0109] The detection in step (5) involves collecting nutrient leachate every 130 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0110] The substrate has a porosity of 47%, a pore size of 7 μm, a nutrient dissolution rate of 0.7 mg / h, a release period of 37 days, and a release fluctuation range of ±8%.

[0111] The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 10m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms compatible with the MQTT communication protocol.

[0112] Example 3:

[0113] A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip includes the following steps:

[0114] (1) Preparation of controlled-release-monitoring dual-function substrate: The controlled-release-monitoring dual-function substrate is composed of the following components in mass percentage: 40% polyvinyl alcohol, 25% sodium alginate, 10% sodium carboxymethyl cellulose, 12% montmorillonite, 8% attapulgite, 3% polyethylene glycol-400, 1.5% nano silica, 0.5% citric acid, and the balance being deionized water and impurities that are unavoidable during the processing;

[0115] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0116] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip (CN102641759A) with an integrated thickness controllable insulation layer, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0117] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0118] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient solution in the bag is periodically detected by the chip, the self-powered module provides energy, and the detection data is wirelessly transmitted to the terminal. The quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content is completed based on the standard curve.

[0119] The preparation of the substrate in step (1) includes:

[0120] (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose were dissolved in deionized water and stirred in a water bath at 70°C for 30 min to form a colloid;

[0121] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica were added in sequence and stirred at 350 rpm for 15 min;

[0122] (c) Molding and curing: Add citric acid to adjust the pH to 7.0, stir for 12 minutes and pour into the mold with the preset chip embedding groove, vacuum dry at 50℃ for 10 hours, and blow dry at 65℃ for 5 hours until the moisture content is 1%.

[0123] The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:2.8. The nutrient raw materials are dissolved in 60 mL of deionized water and then sprayed onto the inner surface of the substrate and dried at 40°C for 6 hours.

[0124] The pretreatment of the non-contact conductivity detection microchip in step (3) includes: rinsing the microchannel with deionized water 4 times, and injecting 6wt% PDMS solution and baking at 85°C for 8 minutes to form a hydrophobic coating.

[0125] The sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the insertion depth of the end of the conduit is 1.2mm.

[0126] The self-powered module mentioned in step (4) includes a flexible solar cell, a 1200mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 40 hours.

[0127] The packaging in step (4) uses a nylon woven outer bag with a thickness of 0.15mm, heat-seales the edges at 190℃, with a sealing width of 6mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0128] The detection in step (5) involves collecting nutrient leachate every 150 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on standard curves established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0129] The substrate has a porosity of 52%, a pore size of 11 μm, a nutrient dissolution rate of 1.1 mg / h, a release period of 47 days, and a release fluctuation range of ±6%.

[0130] The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 14m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms compatible with the MQTT communication protocol.

[0131] Example 4:

[0132] A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip includes the following steps:

[0133] (1) Preparation of controlled-release-monitoring dual-function substrate: The substrate is composed of the following components by mass percentage: polyvinyl alcohol 38.5%, sodium alginate 23.5%, sodium carboxymethyl cellulose 8.5%, montmorillonite 10.5%, attapulgite 6.5%, polyethylene glycol-400 2.2%, nano silica 1.1%, citric acid 0.35%, with the balance being deionized water and impurities unavoidable during processing;

[0134] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0135] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip (CN102641759A) with an integrated thickness controllable insulation layer, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0136] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0137] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient solution in the bag is periodically detected by the chip, the self-powered module provides energy, and the detection data is wirelessly transmitted to the terminal. The quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content is completed based on the standard curve.

[0138] The preparation of the substrate in step (1) includes:

[0139] (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose were dissolved in deionized water and stirred in a water bath at 62°C for 45 min to form a colloid;

[0140] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica were added in sequence and stirred at 280 rpm for 22 min;

[0141] (c) Molding and curing: Add citric acid to adjust the pH to 6.2, stir for 9 minutes and pour into the mold with the preset chip embedding groove, vacuum dry at 42℃ for 13 hours, and blow dry at 58℃ for 6.5 hours until the moisture content is 4%.

[0142] The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:1.6. The nutrient raw materials are dissolved in 45 mL of deionized water and then sprayed onto the inner surface of the substrate and dried at 32°C for 9 hours.

[0143] The pretreatment of the non-contact conductivity detection microchip in step (3) includes rinsing the microchannel twice with deionized water and injecting 4.5wt% PDMS solution and baking at 78°C for 11 min to form a hydrophobic coating.

[0144] The sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the insertion depth of the end of the conduit is 0.9mm.

[0145] The self-powered module mentioned in step (4) includes a flexible solar cell, a 900mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 55 hours.

[0146] The packaging in step (4) uses a nylon woven outer bag with a thickness of 0.125mm, heat-seales the edges at 175℃, with a sealing width of 4.5mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0147] The detection in step (5) involves collecting nutrient leachate every 125 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0148] The substrate has a porosity of 45%, a pore size of 5 μm, a nutrient dissolution rate of 0.5 mg / h, a release period of 32 days, and a release fluctuation range of ±9%.

[0149] The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 8m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms compatible with the MQTT communication protocol.

[0150] Example 5:

[0151] A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip includes the following steps:

[0152] (1) Preparation of controlled-release-monitoring dual-function substrate: The substrate is composed of the following components by mass percentage: polyvinyl alcohol 39.5%, sodium alginate 24.5%, sodium carboxymethyl cellulose 9.5%, montmorillonite 11.5%, attapulgite 7.5%, polyethylene glycol-400 2.8%, nano silica 1.4%, citric acid 0.45%, with the balance being deionized water and impurities unavoidable during processing;

[0153] (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite;

[0154] (3) Chip integration: After pre-processing the non-contact conductivity detection microchip (CN102641759A) with an integrated thickness controllable insulation layer, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ;

[0155] (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag;

[0156] (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient leaching solution in the bag is periodically detected by the chip, and the self-powered module provides energy. The detection data is wirelessly transmitted to the terminal, and the quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content of fertilizer is completed based on the standard curve.

[0157] The preparation of the substrate in step (1) includes:

[0158] (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose were dissolved in deionized water and stirred in a water bath at 68°C for 35 min to form a colloid;

[0159] (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica were added in sequence and stirred at 330 rpm for 18 min;

[0160] (c) Molding and curing: Add citric acid to adjust the pH to 6.8, stir for 11 min and pour into the mold with the preset chip embedding groove, vacuum dry at 48℃ for 11 h, and blow dry at 63℃ for 5.5 h until the moisture content is 1%.

[0161] The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate, and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:2.5. The nutrient raw materials are dissolved in 55 mL of deionized water and then sprayed onto the inner surface of the substrate and dried at 38°C for 7 hours.

[0162] The pretreatment of the non-contact conductivity detection microchip in step (3) includes rinsing the microchannel three times with deionized water and injecting 5.5wt% PDMS solution and baking at 83°C for 9 minutes to form a hydrophobic coating.

[0163] The sample inlet of the chip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the insertion depth of the end of the conduit is 1.1mm.

[0164] The self-powered module mentioned in step (4) includes a flexible solar cell, an 1100mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 45 hours.

[0165] The packaging in step (4) uses a nylon woven outer bag with a thickness of 0.14mm, heat-seales the edges at 185℃, with a sealing width of 5.5mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

[0166] The detection in step (5) involves collecting nutrient leachate every 140 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.99.

[0167] The substrate has a porosity of 50%, a pore size of 9 μm, a nutrient dissolution rate of 0.9 mg / h, a release period of 43 days, and a release fluctuation range of ±7%.

[0168] The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 12m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms that are compatible with the MQTT communication protocol.

[0169] Comparative Example 1 (lacking montmorillonite):

[0170] (1) Preparation of functional substrate: The substrate is composed of the following components by mass percentage: 39.5% polyvinyl alcohol, 24.5% sodium alginate, 9.5% sodium carboxymethyl cellulose, 7.5% attapulgite, 2.8% polyethylene glycol-400, 1.4% nano silica, 0.45% citric acid (consistent with Example 5, except for the absence of 11.5% montmorillonite), with the balance being deionized water and impurities unavoidable during processing;

[0171] (2) The parameters of the remaining steps (colloidal solution preparation, stirring in a water bath at 68°C for 35 min, inorganic filler dispersion, stirring at 330 rpm for 18 min, molding and curing, vacuum drying at 48°C for 11 h, nutrient compounding, chip integration (including PDMS coating, baking at 83°C), system packaging, in-situ monitoring and data transmission) are completely consistent with those of Example 5.

[0172] Comparative Example 2 (Deviation of colloidal solution preparation temperature)

[0173] (1) In the preparation of functional substrate, the colloidal solution preparation step is as follows: polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose are dissolved in deionized water and stirred in a water bath at 50°C for 35 min to form a colloid (the temperature deviates from 68°C in Example 5, and the stirring time is the same as in Example 5).

[0174] (2) The proportions of the remaining raw materials (containing 11.5% montmorillonite, which is exactly the same as in Example 5) and the parameters of the steps (dispersing inorganic fillers at 330 rpm and stirring for 18 min, molding and curing at 48°C and vacuum drying for 11 h, nutrient compounding, chip integration, system packaging, in-situ monitoring and data transmission) are all exactly the same as in Example 5.

[0175] Comparative Example 3 (without self-powered module)

[0176] (1) System packaging steps: The self-powered module was not assembled (flexible solar cell + 1100mAh lithium polymer battery + LM1117-3.3V voltage regulator were removed), and an external 220V power supply (converted to 3.3V DC voltage via adapter) was used to power the detection chip;

[0177] (2) The parameters of the remaining steps (raw material ratio and process for functional substrate preparation, nutrient compounding, chip integration (including PDMS coating), in-situ monitoring and data transmission) are completely consistent with those of Example 5.

[0178] Comparative Example 4 (Chip without preprocessing)

[0179] (1) Chip integration steps: The non-contact conductivity detection microchip was not coated with PDMS (the microchannel was rinsed with deionized water 3 times, skipping the filling of 5.5wt% PDMS solution and baking at 83℃), and was directly embedded in the substrate-nutrient composite.

[0180] (2) The parameters of the remaining steps (raw material ratio and process for functional substrate preparation, nutrient compounding, system packaging (including self-powered module), in-situ monitoring and data transmission) are completely consistent with those of Example 5.

[0181] Single-factor experiment:

[0182] The core parameters of the original Example 5 were: colloidal solution preparation temperature 68℃, inorganic filler stirring rate 330 rpm, vacuum drying temperature 48℃, PDMS coating baking temperature 83℃, and nutrient drying temperature 38℃. Temperature parameters were uniformly spaced at 3℃ intervals, and rate parameters were uniformly spaced at 30 rpm intervals. The remaining parameters were consistent with those of the original Example 5. The test results are as follows:

[0183] 1. Screening experiment for the preparation temperature of colloidal solutions

[0184] The process is basically the same as that of the optimal embodiment 5, except that the colloidal solution preparation temperature is set at five levels: 62℃, 65℃, 68℃, 71℃, and 74℃. The results are shown in Table 1.

[0185]

[0186] Conclusion Analysis:

[0187] Below 68℃ (Group 1 and Group 2): for every 3℃ decrease in temperature, the uniformity of the colloid decreases by 4.7-4.9 percentage points, the porosity of the substrate decreases by 3.5 percentage points, and the fluctuation range of nutrient release increases by 0.8-1.7 percentage points. This is because the degree of polyvinyl alcohol solubility gradually decreases, the uniformity of the pore structure deteriorates, and the controlled release stability weakens.

[0188] At temperatures above 68℃ (Groups 4 and 5): for every 3℃ increase in temperature, the uniformity of the colloid decreases by 2.3-5.5 percentage points, the porosity of the substrate increases by 2.2-3.3 percentage points, and the fluctuation range increases by 0.6-2.6 percentage points. This is because the thermal stability of sodium alginate decreases, the gel network is damaged, and the increase in large pores leads to faster nutrient loss.

[0189] Group 3 (the 68°C parameter of the original Example 5) can simultaneously achieve high colloid uniformity, porosity adaptation, and controlled release with low fluctuations, making it the optimal choice.

[0190] 2. Screening experiment on stirring rate of inorganic packing

[0191] The process is basically the same as that of the optimal embodiment 5, except that the stirring rate of the inorganic packing is set to five levels: 270 rpm, 300 rpm, 330 rpm, 360 rpm, and 390 rpm. The results are shown in Table 2.

[0192]

[0193]

[0194] Conclusion Analysis:

[0195] At speeds below 330 rpm (Group 1 and Group 2): for every 30 rpm decrease in speed, the uniformity of filler dispersion decreases by 9.3 percentage points, the mechanical strength of the substrate decreases by 0.1-0.6 MPa, and the nutrient dissolution rate decreases by 0.1-0.2 mg / h. Due to insufficient stirring intensity, filler agglomeration leads to a decrease in structural support and severe nutrient encapsulation.

[0196] At speeds above 330 rpm (Groups 4 and 5): for every 30 rpm increase in speed, the dispersion uniformity decreases by 2.7-6.2 percentage points, the mechanical strength decreases by 0.2-0.4 MPa, and the dissolution rate increases by 0.2 mg / h. This is because high-speed stirring introduces a large number of air bubbles, forming ineffective pores, damaging the structural integrity and causing nutrients to be easily lost.

[0197] Group 3 (the 330 rpm parameter of the original Example 5) is the optimal choice because it balances filler dispersion, structural strength and nutrient release rate.

[0198] 3. Vacuum drying temperature screening experiment

[0199] The process is basically the same as that of the optimal embodiment 5, except that the vacuum drying temperature is set at five levels: 42°C, 45°C, 48°C, 51°C and 54°C. The results are shown in Table 3.

[0200]

[0201]

[0202] Conclusion Analysis:

[0203] At temperatures below 48℃ (Group 1 and Group 2): for every 3℃ decrease in temperature, the moisture content of the substrate increases by 1.1-1.7 percentage points, the shrinkage rate increases by 0.3-0.6 percentage points, and the nutrient retention rate decreases by 1.4-2.5 percentage points. Due to insufficient drying, residual moisture provides conditions for microbial reproduction, and nutrient decomposition is accelerated.

[0204] At temperatures above 48℃ (Groups 4 and 5): for every 3℃ increase in temperature, the moisture content decreases by 0.2-0.4 percentage points, the shrinkage rate increases by 0.5-0.8 percentage points, and the retention rate decreases by 0.8-1.7 percentage points. Due to excessively rapid drying, microcracks are generated by stress concentration inside the substrate, and nutrients are lost through the cracks.

[0205] Group 3 (the 48°C parameter of the original Example 5) can achieve low moisture residue, low structural shrinkage and high nutrient retention, making it the optimal choice.

[0206] 4. PDMS coating baking temperature screening experiment

[0207] The process is basically the same as that of the optimal embodiment 5, except that the PDMS coating baking temperature is set at five levels: 77°C, 80°C, 83°C, 86°C and 89°C. The results are shown in Table 4.

[0208]

[0209]

[0210] Conclusion Analysis:

[0211] At temperatures below 83℃ (Group 1 and Group 2): for every 3℃ decrease in temperature, the coating curing degree decreases by 5.3 percentage points, the solution residue rate increases by 0.6-1.2 percentage points, and the detection error increases by 0.6-1.1 percentage points. This is because the curing reaction is incomplete, the coating is not hydrophobic enough, and the solution easily adheres to the walls of the microchannels.

[0212] At temperatures above 83℃ (Groups 4 and 5): for every 3℃ increase in temperature, the degree of curing decreases by 1.8-5.2 percentage points, the residual rate increases by 0.4-1.7 percentage points, and the error increases by 0.4-1.7 percentage points. This is because the coating becomes brittle due to excessive cross-linking, and local peeling forms uneven surfaces, resulting in solution residue.

[0213] Group 3 (the 83°C parameter of the original Example 5) can achieve full curing of the coating and low solution residue, ensuring detection accuracy, and is the optimal choice.

[0214] 5. Nutrient drying temperature screening experiment

[0215] The process is basically the same as that of the optimal embodiment 5, except that the nutrient drying temperature is set at five levels: 32℃, 35℃, 38℃, 41℃ and 44℃. The results are shown in Table 5.

[0216]

[0217]

[0218] Conclusion Analysis:

[0219] Below 38℃ (Group 1 and Group 2): for every 3℃ decrease in temperature, the uniformity of crystallization decreases by 4.7 percentage points, the initial burst power decreases by 0.1mg / h, and the release cycle is shortened by 3.2-3.6 days. This is because the slow evaporation of water and uneven growth of nutrient crystals lead to the formation of small crystals, resulting in insufficient release in the early stage.

[0220] At temperatures above 38℃ (Groups 4 and 5): for every 3℃ increase in temperature, uniformity decreases by 2.7-5.2 percentage points, explosive power increases by 0.1-0.2 mg / h, and the cycle is shortened by 2.5-3.2 days. This is because rapid evaporation of water leads to excessively large nutrient crystal particles and an accelerated dissolution rate in the early stages, resulting in a shorter cycle.

[0221] Group 3 (the 38°C parameter of the original Example 5) can achieve uniform nutrient crystallization, burst power that matches the needs of crop seedlings, and a cycle that covers the entire growth period, making it the optimal choice.

[0222] Performance index test data:

[0223] The performance testing method is basically the same as that of the optimal embodiment 5. The test samples include 5 embodiments and 4 comparative examples. The results are shown in Table 6.

[0224]

[0225]

[0226] Data comparison and theoretical analysis:

[0227] 1. Nutrient controlled release performance: As can be seen from the table data, the nutrient release fluctuation range of Example 5 is ±7.0%, which is the best among all tested subjects, and has a significant advantage over other examples and comparative examples.

[0228] Compared with Examples 1-4: the decrease was 33.3% compared to Example 1 (±10.5%), 20.5% compared to Example 2 (±8.8%), 10.3% compared to Example 3 (±7.8%), and 26.3% compared to Example 4 (±9.5%). The core reason is that Example 5 used a single-factor experiment to determine the colloidal solution preparation temperature of 68℃ (colloidal uniformity 99.1%) and the inorganic filler stirring rate of 330rpm (dispersion uniformity 99.2%), which allowed montmorillonite and attapulgite to be uniformly embedded in the gel network, forming a structure with uniform pore size and stable controlled-release channels. In contrast, Example 1 had a lower colloidal temperature (62℃) resulting in insufficient gel dissolution, and Example 3 had a higher stirring rate (350rpm) which introduced air bubbles, both of which caused defects in the controlled-release structure, with fluctuations greater than those in Example 5.

[0229] Compared with the comparative example: it decreased by 54.0% compared with comparative example 1 (±15.2%) and by 61.7% compared with comparative example 2 (±18.3%), further confirming the key role of montmorillonite (not present in comparative example 1) and optimal temperature (deviation from comparative example 2) in the stability of controlled release. The controlled release system of Example 5 can meet the needs of crops such as wheat and corn for stable nutrient release without sudden increases or decreases throughout the entire growth period (the industry allows fluctuations of ≤±8%).

[0230] 2. Detection accuracy: Example 5 has a detection error of 4.0%, which is the best among all tested objects, and the accuracy is significantly improved compared with other examples and comparative examples.

[0231] Compared with Examples 1-4: the error was reduced by 44.4% compared to Example 1 (7.2%), 27.3% compared to Example 2 (5.5%), 16.7% compared to Example 3 (4.8%), and 38.5% compared to Example 4 (6.5%). This is because Example 5 used a PDMS coating baking temperature of 83℃ (the optimal value in the single-factor experiment). At this temperature, the PDMS coating curing degree reached 99.3%, and the microchannel solution residue rate was only 1.8%, which could avoid the interference of solution adhesion on the conductivity detection signal. In contrast, Example 2 had a lower PDMS baking temperature (80℃), resulting in insufficient coating curing (curing degree 96.8%) and a residue rate of 2.4%, which directly led to an increase in detection error.

[0232] Compared with comparative examples: the error was reduced by 56.5% compared with comparative example 4 (9.2%), 24.5% compared with comparative example 1 (5.3%), 34.4% compared with comparative example 2 (6.1%), and 21.6% compared with comparative example 3 (5.1%). Comparative example 4, due to the lack of PDMS coating, had a high hydrophilicity of the microchannel inner wall, resulting in a nutrient solution residue rate exceeding 8% and doubling the detection error. This highlights the necessity of the PDMS coating process parameters in Example 5. Its 4.0% error is lower than the industry average detection error (5%-8%), ensuring the reliability of quantitative analysis of nitrogen, phosphorus, and potassium.

[0233] 3. Substrate mechanical strength: The substrate mechanical strength of Example 5 is 2.6 MPa, which is the best among all tested objects, and it has stronger structural stability than other examples and comparative examples.

[0234] Compared with Examples 1-4: the performance was improved by 44.4% compared to Example 1 (1.8 MPa), 13.0% compared to Example 2 (2.3 MPa), 8.3% compared to Example 3 (2.4 MPa), and 23.8% compared to Example 4 (2.1 MPa). The core reason is that the amount of montmorillonite added to the substrate in Example 5 was 11.5%, and its layered structure can form an organic-inorganic interpenetrating network with polyvinyl alcohol and sodium alginate, filling the voids inside the substrate and enhancing tensile and impact resistance; while in Example 1, the amount of montmorillonite added was reduced (only 10.0%) to improve the range, resulting in insufficient structural support and a significant reduction in mechanical strength.

[0235] Compared with the comparative examples: the strength is improved by 73.3% compared with comparative example 1 (1.5MPa), 4.0% compared with comparative example 2 (2.5MPa), and 4.0% compared with comparative example 4 (2.5MPa), and is only on par with comparative example 3 (2.6MPa). Comparative example 1 suffers from structural integrity damage and a sharp drop in strength due to the lack of montmorillonite; the 2.6MPa strength of example 5 can withstand the impact of forestry farming machinery (maximum impact force ≤2.5MPa) and soil compression, avoiding nutrient leakage and chip damage caused by substrate cracking, and is suitable for complex forestry application environments.

[0236] 4. Battery Life and Communication: Battery Life: Example 5 has a battery life of 45.0 hours, which is lower than Example 1 (60.0 hours), Example 4 (56.0 hours), and Example 2 (52.0 hours), but higher than Example 3 (41.0 hours). It also demonstrates greater applicability to all scenarios compared to Comparative Example 3 (which requires an external power supply). In forest environments without power grids, Comparative Example 3 cannot operate independently, while the self-powered module of Example 5 (flexible solar cell + 1100mAh lithium battery) can meet the 45-hour battery life requirement, adapting to monitoring needs at night and in rainy weather, without sacrificing structural integrity in pursuit of extreme battery life.

[0237] Communication distance: The communication distance of Example 5 is 12.0m, which is lower than that of Example 3 (13.8m), but higher than that of Example 1 (6.5m), Example 2 (10.2m), and Example 4 (8.2m), and is on par with all comparative examples (12.0-12.2m). In forestry and forest land monitoring, terminals are usually deployed on field ridges or next to irrigation equipment (distance ≤10m). A communication distance of 12.0m is sufficient to meet the requirements, avoiding the situation in Example 3 where the module size was increased to pursue a longer distance, thus encroaching on nutrient storage space (leading to a shortened release cycle).

[0238] 5. Overall Performance Conclusion: Example 5 achieves optimal performance in three core indicators—nutrient release fluctuation amplitude, detection error, and substrate mechanical strength—as well as balanced performance in two non-core indicators—endurance and communication. This demonstrates a comprehensive advantage in controlled release accuracy, reliable detection, structural stability, and scenario adaptability. Compared to Examples 1-4, it has no significant performance shortcomings (e.g., Example 1 has long endurance but weak strength, and Example 3 has accurate detection but short endurance). Compared to Comparative Examples 1-4, it addresses pain points such as poor controlled release, high error, low strength, and reliance on external power for monitoring equipment. Its overall performance is significantly superior to all tested objects.

[0239] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the inventive concept, and all such substitutions or modifications should be considered within the scope of protection of the present invention.

[0240] Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made without departing from the spirit and scope of the invention. Furthermore, the scope of the invention is not limited to the specific embodiments of the processes, methods, and steps described in the specification. From the disclosure of this invention, those skilled in the art will readily utilize existing or future processes, methods, steps that substantially perform the same function or achieve the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to cover such processes, methods, steps.

Claims

1. A method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip, characterized in that, Includes the following steps: (1) Preparation of controlled-release-monitoring dual-function substrate: The substrate is composed of the following components in mass percentage: polyvinyl alcohol 38%-40%, sodium alginate 23%-25%, sodium carboxymethyl cellulose 8%-10%, montmorillonite 10%-12%, attapulgite 6%-8%, polyethylene glycol-400 2%-3%, nano silica 1%-1.5%, citric acid 0.3%-0.5%, with the balance being deionized water and impurities unavoidable during processing; (2) Nutrient compounding: The nutrient raw materials are compounded with the substrate obtained in step (1) to form a substrate-nutrient composite; (3) Chip integration: After pre-processing the non-contact conductivity detection microchip, it is embedded in the preset chip embedding groove of the substrate-nutrient composite in situ; (4) System packaging: Assemble the self-powered module and connect it to the chip, and package it to form a monitoring bag; (5) In-situ monitoring and data transmission: The electrical conductivity signal of the fertilizer nutrient leaching solution in the bag is periodically detected by the chip, and the self-powered module provides energy. The detection data is wirelessly transmitted to the terminal, and the quantitative monitoring of the changes in nitrogen, phosphorus and potassium nutrient content of fertilizer is completed based on the standard curve.

2. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The preparation of the substrate in step (1) includes: (a) Preparation of colloidal solution: Polyvinyl alcohol, sodium alginate and sodium carboxymethyl cellulose are dissolved in deionized water and stirred in a water bath at 60-70℃ for 30-50 min to form a colloid; (b) Inorganic filler dispersion: Montmorillonite, attapulgite, polyethylene glycol-400 and nano silica are added in sequence and stirred at 250-350 rpm for 15-25 min; (c) Molding and curing: Add citric acid to adjust the pH to 6.0-7.0, stir for 8-12 minutes and pour into the mold with the preset chip embedding groove. Vacuum dry at 40-50℃ for 10-14 hours and blow dry at 55-65℃ for 5-7 hours until the moisture content is 1-5%.

3. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The nutrient raw materials mentioned in step (2) include urea, potassium dihydrogen phosphate and potassium nitrate, and the ratio of their total mass to the mass of the substrate is 1:(1.2-2.8); the nutrient raw materials are dissolved in 40-60mL of deionized water and then sprayed onto the inner surface of the substrate, and dried in a ventilated environment at 30-40℃ for 6-10h.

4. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The pretreatment of the non-contact conductivity detection microchip in step (3) includes: rinsing the microchannel with deionized water 2-4 times, and injecting 4-6wt% PDMS solution and baking at 75-85℃ for 8-12 minutes to form a hydrophobic coating.

5. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The sample inlet of the non-contact conductivity detection microchip is connected to the interior of the substrate through a 0.22μm filter membrane conduit, and the embedding depth of the end of the conduit is 0.8-1.2mm.

6. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The self-powered module mentioned in step (4) includes a flexible solar cell, an 800-1200mAh lithium polymer battery and an LM1117-3.3V voltage regulator. After assembly, the output voltage is stable at 3.3V±0.1V and can provide power continuously for 40-60 hours.

7. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The packaging in step (4) uses a nylon woven outer bag with a thickness of 0.12-0.15mm, heat-seales the edges at 170-190℃, with a sealing width of 4-6mm, and retains a Bluetooth signal window with a size of 2cm×3cm.

8. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The detection in step (5) involves collecting nutrient leachate every 120-150 hours, acquiring conductivity signals using a platinum microelectrode on a non-contact conductivity detection microchip, and performing quantitative analysis based on a standard curve established using potassium chloride, phosphate, and nitrate standard solutions. The coefficient of determination R of the standard curve is... 2 ≥0.

99.

9. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The substrate has a porosity of 43%-52%, a pore size of 4-11 μm, a nutrient dissolution rate of 0.4-1.1 mg / h, a release period of 28-47 days, and a release fluctuation range of ±6-10%.

10. The method for monitoring changes in nutrient content of bag-controlled slow-release fertilizer using a self-powered chip according to claim 1, characterized in that, The data transmission in step (5) is achieved through a BLE5.0 Bluetooth module with a communication distance of 6-14m. The terminal displays the curves of nitrogen, phosphorus and potassium content changes and supports access to forestry IoT platforms compatible with the MQTT communication protocol.

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