Application method for realizing rice nitrogen fertilizer substitution by utilizing photocatalytic nitrogen fixation material

Abstract

The invention discloses an application method for realizing rice nitrogen fertilizer substitution by utilizing a photocatalytic nitrogen fixation material in the technical field of agricultural production. The application method comprises the following steps: S1, pretreating and proportioning a catalyst; s2, reaction container deployment and illumination optimization; s3, carrying out photocatalytic reaction and ammonium nitrogen generation; s4, synergistically applying base fertilizer and additional fertilizer; s5, monitoring and feeding back nitrogen utilization efficiency; the performance of the photocatalyst is improved by adopting a surface doping and composite modification technology, atmospheric nitrogen can be stably and efficiently converted into ammonium nitrogen which can be directly absorbed by rice under a complex environmental condition, and the nitrogen conversion rate and the nitrogen supply efficiency are improved; the AI algorithm is combined with the chlorophyll meter, the soil nitrogen sensor and the water ammonia nitrogen concentration data to predict and dynamically adjust the nitrogen demand of the rice in real time; a closed loop of nitrogen fixation-conversion-absorption-recovery is formed through a segmented application strategy of base fertilizer and topdressing in combination with physical and chemical synergism and a biochar improvement technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural production, more particularly to the field of crop nutrient management and green fertilization, and particularly relates to a method for applying a photocatalytic nitrogen fixation material to replace nitrogen fertilizer for rice. BACKGROUND

[0002] Rice is an important food crop, and its yield and quality depend largely on the level of nitrogen supply. At present, the supply of nitrogen fertilizer in rice fields mainly relies on chemical synthetic nitrogen fertilizers such as urea and ammonium nitrate. These nitrogen fertilizers are prone to ammonia volatilization, runoff and leaching during application, which not only leads to low utilization rate of nitrogen fertilizer (generally 30%-35%), but also causes water eutrophication and increases greenhouse gas emissions. In order to meet the nitrogen demand of crops and reduce nitrogen loss, existing technologies attempt to use slow-release fertilizers, controlled-release fertilizers, organic fertilizers, etc., but there are problems such as high production cost, complex application process, or low matching degree of nutrient release and crop nutrient demand.

[0003] In recent years, photocatalytic nitrogen fixation technology has attracted attention. Using specific photocatalytic materials, nitrogen in the air can be directly reduced to ammonia or ammonium nitrogen under sunlight or artificial light, which can operate at normal temperature and pressure, and has the potential for energy saving and sustainable nitrogen supply. However, most existing photocatalytic nitrogen fixation researches are still in laboratory conditions, and the reactor structure, light conditions, and catalytic efficiency are not optimized for rice field environment; at the same time, the generated ammonia is prone to volatilization and diffusion in an open environment, resulting in low actual nitrogen utilization rate. In addition, existing technologies lack dynamic nitrogen supply methods that match the nitrogen demand of rice at different growth stages, and cannot achieve stable, controllable and efficient nitrogen fertilizer replacement effect in the field.

[0004] Therefore, it is urgent to develop a photocatalytic nitrogen fixation application method that can stably operate in a rice field environment, generate nitrogen, and achieve precise supply, to replace part or all of chemical nitrogen fertilizer, improve nitrogen utilization efficiency, and reduce environmental pollution.

[0005] In view of the problems of low nitrogen utilization rate, serious nitrogen loss, high environmental pollution risk in the existing process of applying nitrogen fertilizer in rice fields, and low application efficiency of photocatalytic nitrogen fixation technology in the field, easy volatilization of ammonia, and difficulty in matching the nitrogen supply process with the nitrogen demand of rice at different growth stages, the present application provides a method for applying a photocatalytic nitrogen fixation material to replace nitrogen fertilizer for rice. It can efficiently catalyze the generation of available nitrogen from air nitrogen in a rice field environment, reduce nitrogen loss through ammonia treatment and slow-release measures, and dynamically control the release of nitrogen according to the nitrogen demand of rice at different growth stages, to achieve a stable, controllable and efficient nitrogen fertilizer replacement effect. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a new technical solution for a method for applying a photocatalytic nitrogen fixation material to replace nitrogen fertilizer for rice.

[0007] The purpose of the present application is achieved by a method for applying nitrogen fertilizer to rice using photocatalytic nitrogen fixation material, comprising the following steps:

[0008] S1, catalyst pretreatment and proportioning: preparing a composite photocatalyst and determining the catalyst proportioning;

[0009] S2, reaction container deployment and light optimization: embedding a solar-driven LED light supplement module, a circulating pump and a pH adjustment system in the reaction container;

[0010] S3, photocatalytic reaction and ammonium nitrogen generation: the catalyst suspension performs photocatalytic reaction on nitrogen in the rice field water body to generate ammonium nitrogen and dissolve in the water body, obtaining an ammonium nitrogen solution;

[0011] S4, base fertilizer and topdressing application: mixing the ammonium nitrogen solution with slow-release urea to prepare a base fertilizer solution, which is applied to the rice field during the tillering stage, the jointing and booting stage and the filling stage;

[0012] S5, nitrogen utilization efficiency monitoring and feedback: real-time monitoring of the nitrogen absorption rate of the rice plant, optimizing the catalyst proportioning and application cycle.

[0013] Further, the composite photocatalyst in S1 uses graphite phase carbon nitride as the core photocatalytic material, and is combined with semiconductor materials such as surface-doped sulfur, nitrogen or metal elements, or modified titanium dioxide and zinc oxide to improve its electron-hole separation efficiency and visible light response range.

[0014] Further, the specific surface area of graphite phase carbon nitride is improved by laser etching or chemical stripping technology; graphite phase carbon nitride is embedded and installed on a metal organic framework to form a heterojunction photocatalyst.

[0015] Further, the catalyst proportioning in S1 is dynamically adjusted according to the nitrogen demand of the rice field at different growth stages;

[0016] The catalyst proportioning is determined to be 2-3g / 300mL, and the catalyst concentration is 3g / 300mL during the tillering stage; the catalyst concentration is reduced to 2.5g / 300mL during the jointing stage; the catalyst concentration is adjusted to 2g / 300mL during the filling stage, and 0.1% of a surfactant is added during preparation, wherein the surfactant is polyvinylpyrrolidone.

[0017] Further, the reaction vessel in S2 is installed in the rice field in a modular manner for floating, and a solar-driven LED light supplement module is embedded in the interior of the reaction vessel for maintaining a minimum light intensity of 1000-2000 lux at night or on cloudy days; a circulating pump is used to continuously circulate the rice field water body and the catalyst suspension in the reaction vessel, and circulates once per hour, and a pH adjusting system is used to control the pH value of the rice field water body to be between 7.0-7.5.

[0018] Further, the preparation process of ammonium nitrogen in S3 is as follows:

[0019] Reaction path optimization: nitrogen molecules in the rice field are captured by aerogel membranes or nanoporous materials, concentrated on the surface of the heterojunction photocatalyst for photocatalytic reaction; nitrate reductase inhibitors are added to prevent further oxidation of ammonia to nitrate;

[0020] Byproduct inhibition technology: through time window control of photocatalytic reaction, after the reaction reaches the peak, nitrate inhibitors are added to control the concentration of nitrate ≤5mg / L; during the grouting period, the pH is gradually reduced to 6.5-6.8 through pH gradient regulation, promoting rapid conversion of ammonia and absorption by rice roots;

[0021] Nitrogen recycling: at the end of the reaction, part of the heterojunction photocatalyst is recovered by using a magnetic separation device or an electrostatic adsorption film, and the heterojunction photocatalyst activity is reactivated by ultrasonic cleaning or chemical regeneration technology; the excess ammonium nitrogen solution after reaction is directly applied to the rice field as liquid fertilizer, or solid nitrogen fertilizer is prepared by evaporation concentration technology.

[0022] Further, the preparation steps of the base fertilizer solution in S4 are as follows:

[0023] Before transplanting, the heterojunction photocatalyst is mixed with slow-release urea to prepare a base fertilizer solution and applied to the rice field;

[0024] During the tillering period, topdressing is carried out using high-concentration base fertilizer solution directly contacting with the rice field water body, while introducing nitrogen-fixing bacteria inoculation;

[0025] During the jointing and heading period and the filling period, medium-concentration and low-concentration base fertilizer solutions are used respectively, and the nitrogen demand is predicted by AI algorithm to dynamically adjust the frequency of topdressing.

[0026] Further, the threshold value of the AI algorithm to predict nitrogen demand is set as follows:

[0027] The nitrogen supply-demand balance threshold is set to 8-12mg / L for the base fertilizer solution and ≥20mg / kg for the soil available nitrogen content;

[0028] If the nitrogen concentration is detected to be lower than the threshold value, i.e., nitrogen supply demand <= 5 mg / L, a topdressing program is started to supplement the catalyst suspension;

[0029] If the concentration is higher than the threshold value, i.e., nitrogen supply demand >= 15 mg / L, a nitrate inhibitor release or nitrogen recovery system is started.

[0030] Further, the nitrogen utilization efficiency monitoring and feedback in S5 are performed through a chlorophyll meter or a soil nitrogen sensor, and combined with water body ammonia nitrogen concentration data to optimize catalyst ratio and application period; after the end of the irrigation period, the residual catalyst is mixed with microbial inoculant by using a recovery system to be used as biochar material for rice field soil improvement again.

[0031] Further, the surface of the heterojunction photocatalyst is introduced with an amino functional group or a thiol group by a chemical grafting method to enhance the affinity for nitrogen molecules and improve the nitrogen conversion efficiency.

[0032] Compared with the prior art, the present application has the beneficial effects that the present application realizes efficient replacement and precise management of nitrogen fertilizer in the rice planting process, significantly improves the nitrogen utilization efficiency, reduces the dependence on chemical fertilizer and the risk of environmental pollution, and optimizes the nitrogen cycle process of the rice field ecosystem;

[0033] The surface doping and composite modification technology is adopted to improve the performance of the photocatalyst, the modular floating reaction container and the solar light supplement system are combined to ensure that atmospheric nitrogen can be stably and efficiently converted into ammonium nitrogen that can be directly absorbed by rice under complex environmental conditions, reduce the dependence on traditional nitrogen fertilizer, and improve the nitrogen conversion rate and supply efficiency;

[0034] Through the AI algorithm combined with the chlorophyll meter, the soil nitrogen sensor and the water body ammonia nitrogen concentration data, real-time prediction and dynamic adjustment of the nitrogen demand of rice are realized to avoid excessive or insufficient nitrogen, and the catalyst ratio and application period are optimized;

[0035] Through the segmented application strategy of base fertilizer and topdressing, combined with physical and chemical synergy and biochar improvement technology, a closed loop of nitrogen fixation-conversion-absorption-recovery is formed to significantly improve the rice yield, reduce the nitrogen loss rate, and reduce the risk of water eutrophication;

[0036] The present application significantly improves the rice yield and nitrogen utilization efficiency, reduces the environmental burden and agricultural production cost, and has significant ecological and economic benefits.

[0037] Other features of the present application and its advantages will become apparent from the following detailed description of exemplary embodiments thereof and the appended claims, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below only are a part of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor based on the provided drawings.

[0039] Fig. 1 The step flow chart of the present application.

[0040] Fig. 2 The preparation process diagram of ammonium nitrogen of the present application.

[0041] Fig. 3 The preparation step flow chart of base fertilizer solution of the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments only are a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0043] As shown in Figs. 1-3 A method for applying rice nitrogen fertilizer replacement by using photocatalytic nitrogen fixation material, comprising the following steps:

[0044] S1, catalyst pretreatment and proportioning: preparing composite photocatalyst and determining catalyst proportioning;

[0045] S2, reaction container deployment and light optimization: embedding solar-driven LED light supplement module, circulating pump and pH adjusting system in the reaction container;

[0046] S3, photocatalytic reaction and ammonium nitrogen generation: photocatalytic reaction of catalyst suspension on nitrogen in paddy field water body to generate ammonium nitrogen and dissolve in water body, to obtain ammonium nitrogen solution;

[0047] S4, base fertilizer and topdressing cooperative application: mixing ammonium nitrogen solution with slow-release urea to prepare base fertilizer solution and applying in paddy field during tillering period, jointing and booting period and grain filling period;

[0048] S5, nitrogen utilization efficiency monitoring and feedback: real-time monitoring of nitrogen absorption rate of rice plants, optimizing catalyst proportioning and application period.

[0049] In this embodiment, preferably, the composite photocatalyst in S1 uses graphite phase carbon nitride as the core photocatalytic material, and is combined with surface doping of sulfur, nitrogen or metal elements or composite modification of titanium dioxide, zinc oxide semiconductor materials to improve the electron-hole separation efficiency and visible light response range;

[0050] The graphite phase carbon nitride is etched by laser etching or chemical stripping technology to improve the specific surface area of the graphite phase carbon nitride; the graphite phase carbon nitride is embedded and installed on a metal organic framework to form a heterojunction photocatalyst;

[0051] The surface of the heterojunction photocatalyst is introduced with an amino functional group or a mercaptan group by a chemical grafting method to enhance the affinity for nitrogen molecules and improve the nitrogen conversion efficiency;

[0052] It should be noted that by doping sulfur, nitrogen or metal elements on the surface of graphite phase carbon nitride and composite modification of titanium dioxide, zinc oxide and other semiconductor materials, the visible light response range of the catalyst is effectively broadened, the adsorption capacity for nitrogen molecules is enhanced, and the separation efficiency of electron-hole pairs is significantly improved by the heterojunction structure design, reducing the recombination loss of photo-generated carriers, thereby greatly improving the nitrogen conversion rate and ammonia production efficiency.

[0053] In this embodiment, preferably, the catalyst ratio in S1 is dynamically adjusted according to the nitrogen demand of the rice field at different growth stages;

[0054] The catalyst ratio is determined to be 2-3 g / 300 mL, and the catalyst concentration is 3 g / 300 mL during the tillering stage; the catalyst concentration is reduced to 2.5 g / 300 mL during the jointing stage; the catalyst concentration is adjusted to 2 g / 300 mL during the grain filling stage, and 0.1% of a surfactant is added during preparation, wherein the surfactant is polyvinylpyrrolidone;

[0055] It should be noted that by dynamically adjusting the catalyst ratio and introducing a surfactant, the precise supply of nitrogen to rice at different growth stages is realized, and the nitrogen conversion efficiency and the sustainability of resource utilization are significantly improved; polyvinylpyrrolidone as a surfactant enhances the nitrogen adsorption performance, improves the photocatalytic reaction efficiency, and reduces the loss and environmental pollution caused by excessive nitrogen supply; by the phased precise nitrogen supply strategy, the tillering is effectively promoted, the grain development is ensured, and the leaf senescence is delayed, ultimately realizing the simultaneous optimization of rice yield improvement and nitrogen utilization efficiency.

[0056] In this embodiment, preferably, the reaction vessel in S2 is installed in the rice field in a modular floating design, and a solar-powered LED light supplement module is embedded in the interior of the reaction vessel to maintain a minimum light intensity of 1000-2000 lux at night or on cloudy days; a circulating pump is used to continuously circulate the rice field water and the catalyst suspension in the reaction vessel, and circulates once an hour, and a pH adjustment system is used to control the pH of the rice field water between 7.0-7.5;

[0057] It should be noted that the modular floating design allows the reaction vessel to be flexibly adapted to different rice field topography and water conditions, facilitating large-scale deployment and later maintenance; the solar-powered LED light supplement module ensures that the minimum light intensity is maintained at night or on rainy days, improving the nitrogen conversion efficiency; the circulating pump forces the rice field water and the catalyst suspension to circulate every hour, promoting the full contact of nitrogen molecules and catalysts, ensuring reaction uniformity and continuity; the pH adjustment system stabilizes the water pH at 7.0-7.5, optimizing the photocatalytic reaction conditions and reducing catalyst activity decay and nitrogen loss.

[0058] In this embodiment, preferably, the preparation process of ammonium nitrogen in S3 is as follows:

[0059] Reaction path optimization: nitrogen molecules in the rice field are captured by aerogel membranes or nanoporous materials and concentrated on the surface of the heterojunction photocatalyst for photocatalytic reaction; nitrate reductase inhibitors are added to prevent further oxidation of ammonia to nitrate;

[0060] Byproduct inhibition technology: through time window control of photocatalytic reaction, after the reaction reaches the peak, nitrate inhibitors are added to control the concentration of nitrate at ≤5 mg / L; during the grouting period, the pH is gradually reduced to 6.5-6.8 through pH gradient regulation, promoting rapid conversion of ammonia and absorption by rice roots;

[0061] Nitrogen recycling: at the end of the reaction, part of the heterojunction photocatalyst is recovered using a magnetic separation device or an electrostatic adsorption film, and the heterojunction photocatalyst activity is reactivated through ultrasonic cleaning or chemical regeneration technology; the excess ammonium nitrogen solution after the reaction is directly applied to the rice field as a liquid fertilizer, or is prepared into a solid nitrogen fertilizer through evaporation and concentration technology;

[0062] It should be noted that by optimizing the nitrogen capture path, inhibiting the generation of by-products and realizing the recycling of nitrogen, the stability and nitrogen supply efficiency of the photocatalytic nitrogen fixation system are significantly improved, and the loss of nitrogen and environmental impact are reduced; by concentrating the capture of nitrogen molecules through aerogel membranes or nanopore materials, combined with the high reaction characteristics of the heterojunction photocatalyst, the nitrogen conversion efficiency is improved, and the nitrate reductase inhibitor prevents ammonia oxidation to nitrate, reducing nitrogen loss and improving the utilization rate of ammonium nitrogen by rice; using magnetic separation or electrostatic adsorption technology to recover the heterojunction photocatalyst, and through ultrasonic cleaning or chemical regeneration technology to realize the recycling of the catalyst, the material cost is significantly reduced; the excess ammonium nitrogen solution after reaction can be directly used as liquid fertilizer or prepared into solid nitrogen fertilizer by evaporation and concentration, forming a closed-loop system of nitrogen capture, conversion, recovery and reuse.

[0063] In this embodiment, preferably, the preparation steps of the base fertilizer solution in S4 are as follows:

[0064] Before transplanting, the heterojunction photocatalyst is mixed with slow-release urea to prepare a base fertilizer solution and applied to the rice field;

[0065] During the tillering stage, topdressing is carried out, and high-concentration base fertilizer solution is directly contacted with the water body in the rice field, while inoculating nitrogen-fixing bacteria;

[0066] During the jointing and heading stage and the filling stage, medium-concentration and low-concentration base fertilizer solutions are used respectively, and the frequency of topdressing is dynamically adjusted according to the nitrogen demand predicted by the AI algorithm;

[0067] It should be noted that by using the phased and concentration-based base fertilizer and topdressing application strategy, combined with the composite use of heterojunction photocatalyst and slow-release urea and the auxiliary role of nitrogen-fixing bacteria, the precision and sustainability of nitrogen supply are significantly improved, and the matching of nutrient demand at different growth stages of rice is optimized, realizing efficient, sustainable and low-cost application of nitrogen fertilizer replacement.

[0068] In this embodiment, preferably, the calculation of the AI algorithm to predict nitrogen demand is as follows:

[0069] ;

[0070] wherein, represents the AI algorithm predicted nitrogen demand value, represents the nitrogen demand threshold based on the growth stage of rice (such as 10-15 mg / L during the tillering stage and 8-12 mg / L during the filling stage); represents the real-time soil nitrogen content obtained by the soil detector (such as effective nitrogen content of 20 mg / kg); represents the base fertilizer solution monitored by the ammonia nitrogen detector (such as 10 mg / L); The nitrogen supply-demand ratio coefficient (adjusted according to the growth stage of the crop, such as tillering stage α = 1.2, and grain filling stage α = 0.8) is represented as The nitrogen loss correction coefficient (adjusted according to the soil type and rainfall, such as clay soil β = 0.3, and sandy soil β = 0.5) is represented as The light enhancement coefficient (adjusted according to the operation state of the light supplementing system, such as natural light sufficient γ = 1.0, and light supplementing operation γ = 1.5) is represented as

[0071] It should be noted that by introducing the multi-parameter fusion AI algorithm, intelligent and dynamic prediction and precise regulation of the nitrogen demand of rice are realized, which significantly improves the adaptability and resource utilization efficiency of the nitrogen fertilizer replacement scheme, while taking into account environmental friendliness and economic benefits. The AI algorithm integrates multi-dimensional data such as the nitrogen demand threshold of the growth stage of rice (such as 10-15 mg / L in the tillering stage and 8-12 mg / L in the grain filling stage), real-time soil nitrogen content (such as effective nitrogen 20 mg / kg), and base fertilizer solution ammonia nitrogen concentration (such as 10 mg / L), and dynamically adjusts the supply-demand ratio coefficient (α), the nitrogen loss correction coefficient (β), and the light enhancement coefficient (γ), to accurately match the nitrogen supply and demand of rice in different growth stages, avoiding yield loss or environmental pollution caused by excessive or insufficient nitrogen.

[0072] In this embodiment, preferably, the threshold of the AI algorithm to predict the nitrogen demand value is set as follows:

[0073] The nitrogen supply-demand balance threshold is set as follows: the base fertilizer solution needs to be maintained at 8-12 mg / L, and the soil effective nitrogen content needs to be ≥20 mg / kg;

[0074] If the nitrogen concentration is detected to be lower than the threshold, i.e. ≤5 mg / L, the topdressing program is started, and the catalyst suspension is supplemented;

[0075] If the concentration is higher than the threshold, i.e. ≥15 mg / L, the nitrate inhibitor release or nitrogen recovery system is started;

[0076] It should be noted that by setting the nitrogen supply and demand balance threshold and combining the real-time response mechanism of the AI algorithm, the precision, intelligence and dynamics of rice nitrogen supply are realized, and the adaptability and resource utilization efficiency of the nitrogen fertilizer replacement scheme are significantly improved; the AI algorithm can accurately judge the nitrogen supply and demand state by dynamically monitoring the ammonia nitrogen concentration (8-12 mg / L) of the base fertilizer solution and the soil available nitrogen content (≥20 mg / kg), avoiding growth restriction due to nitrogen deficiency or nitrogen loss and environmental pollution caused by excessive supply; when the nitrogen concentration is detected to be lower than the threshold (≤5 mg / L), the topdressing program is automatically started to supplement the catalyst suspension to quickly improve the nitrogen supply; when the concentration is higher than the threshold (≥15 mg / L), the nitrate inhibitor is released or the nitrogen recovery system is started to reduce the waste of nitrogen and the accumulation risk of nitrate nitrogen, and the nitrogen utilization efficiency is optimized.

[0077] In this embodiment, preferably, the nitrogen utilization efficiency monitoring and feedback in S5 are optimized by a chlorophyll meter or a soil nitrogen sensor, and combined with water body ammonia nitrogen concentration data to optimize the catalyst ratio and application period; after the irrigation period ends, the residual catalyst is mixed with microbial inoculant by the recovery system and used as biochar material for rice field soil improvement again;

[0078] It should be noted that through the intelligent nitrogen monitoring system and closed-loop recycling mechanism, the precision of nitrogen supply, resource recycling efficiency and soil improvement effect are significantly improved, and the nitrogen waste and environmental load are reduced, providing an efficient and sustainable nitrogen fertilizer replacement technology path for rice planting.

[0079] In this embodiment, preferably, the catalyst ratio is calculated as follows:

[0080] ;

[0081] wherein, represents the new catalyst ratio, represents the original catalyst ratio; represents the ratio adjustment range; represents the set nitrogen utilization efficiency threshold; represents the minimum nitrogen utilization efficiency; represents the current nitrogen utilization efficiency;

[0082] The application period is calculated as follows:

[0083] ;

[0084] wherein, represents the new application period; represents the original application period; represents the nitrogen loss amount; The nitrogen content of the soil is expressed as the sum of the nitrogen content of the soil and the base fertilizer solution.

[0085] It should be noted that the nitrogen use efficiency is calculated by the following formula:

[0086] ;

[0087] wherein, is expressed as the current leaf chlorophyll index (measured by a chlorophyll meter); is expressed as the chlorophyll index under the optimal growth state of rice (such as 25-30); is expressed as the nitrogen content of the soil (such as the effective nitrogen content of 20 mg / kg) obtained in real time by a soil detector; is expressed as the base fertilizer solution (such as 10 mg / L) monitored in real time by an ammonia nitrogen detector; is expressed as the amount of nitrogen loss (calculated by the change of nitrogen concentration in water or soil nitrogen detection data);

[0088] By dynamically calculating the catalyst ratio and application period, combined with the nitrogen use efficiency monitoring and feedback mechanism, the intelligent, precise and sustainable management of the nitrogen fertilizer replacement technology is realized, which significantly improves the nitrogen conversion efficiency, resource utilization rate and agricultural ecological benefits.

[0089] Specific embodiments are as follows:

[0090] Field application of photocatalytic nitrogen fixation materials in rice nitrogen fertilizer replacement:

[0091] Test site and conditions: The test paddy soil type is clay loam, and the previous crop is wheat. The field water source is irrigation canal water, and the conventional rice cultivation management mode is adopted during the test period, with a water layer depth of 3-5 cm to ensure normal growth of rice during the whole growth period.

[0092] Test design

[0093] A randomized block design is adopted, and 5 treatments are set: CK (blank control, no nitrogen fertilizer); NF (single application of chemical fertilizer); OF (application of organic fertilizer + chemical fertilizer); SF (side deep application of fertilizer); PF (photocatalytic nitrogen fixation). Each treatment has 3 replicates, with a plot area of 20 m². The field is isolated by building ridges, and water is independently discharged.

[0094] CK: no nitrogen fertilizer; NF: base fertilizer with compound fertilizer (15-15-15, containing 15% nitrogen) 135 kg N / hm2, tillering fertilizer with urea 81 kg N / hm2, and ear fertilizer with urea 54 kg N / hm2, total nitrogen application amount 270 kg N / hm2; OF: base fertilizer with organic fertilizer (containing 4% nitrogen) 135 kg N / hm2, tillering fertilizer with urea 81 kg N / hm2, and ear fertilizer with urea 54 kg N / hm2, total nitrogen application amount 270 kg N / hm2; SF: one-time side deep application of slow-release fertilizer (22-8-12) 270 kg N / hm2; PF: photocatalytic nitrogen fixation treatment, floating photocatalytic reaction device was arranged in the field, 3 g g-C3N4 / 300 mL water was added to the reaction cavity in proportion, and was connected with the field water, under natural sunlight, photocatalytic air nitrogen generated ammonium (NH4+), catalyst suspension was supplemented every 7 days, the ammonia nitrogen concentration in the field water was maintained at about 3 mg / L, and nitrogen was continuously supplied during the whole growth period without additional chemical nitrogen fertilizer.

[0095] Structure and use method of photocatalytic reaction device:

[0096] The device adopts floating design, which is composed of a reaction cavity, a photocatalyst carrier plate, an air inlet, a liquid outlet, and a slow-release module. The catalyst carrier plate uniformly lays g-C3N4 powder, a transparent light window is opened above the reaction cavity to ensure direct sunlight, the device floats on the water surface, the bottom liquid outlet is connected with the field water, and the generated ammonium nitrogen is diffused with water for root absorption. When the catalyst suspension is supplemented in the field, the liquid level in the reaction cavity is kept consistent with the field water.

[0097] Test index and method:

[0098] Tiller number, plant height, and leaf area index (LAI) were investigated at different stages during growth;

[0099] At the harvest stage, the number of effective spikes, grain number per spike, seed setting rate, and thousand-grain weight were measured, the theoretical yield and actual yield were calculated, and the ammonia nitrogen concentration in the field water was determined by the Nash reagent spectrophotometric method.

[0100] Test results:

[0101] The photocatalytic nitrogen fixation treatment (PF) can maintain a suitable ammonia nitrogen concentration (about 3 mg / L) in the field water during the whole growth period, effectively promote tiller growth, and reach more than 150 tillers per 10 holes at the tiller peak stage. At the harvest stage, the number of effective spikes, grain number per spike, and seed setting rate of the PF treatment all reach the conventional fertilization level, and the thousand-grain weight is slightly higher than that of the conventional fertilizer. The theoretical yield of the PF treatment reaches 5702.45 kg / acre, and the actual yield is 5415.36 kg / acre, which has no significant difference (P>0.05) with the yield of the conventional fertilization (NF), but the nitrogen fertilizer amount is reduced by 100%, significantly reducing the nitrogen input. The PF treatment reduces ammonia volatilization loss, and water quality monitoring shows that the ammonia volatilization amount in the field water during the whole growth period is more than 40% lower than that of the conventional fertilization.

[0102] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that for those skilled in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for replacing nitrogen fertilizer for rice using a photocatalytic nitrogen-fixing material, characterized by: The following steps are involved: S1. Catalyst pretreatment and proportioning: preparing composite photocatalyst and determining catalyst proportion; S2. Reaction vessel deployment and lighting optimization: A solar-powered LED lighting module, a circulation pump, and a pH adjustment system are embedded in the reaction vessel. S3. Photocatalytic reaction and ammonium nitrogen generation: The catalyst suspension undergoes a photocatalytic reaction on nitrogen in the paddy water to generate ammonium nitrogen, which dissolves in the water to obtain an ammonium nitrogen solution; S4. Coordinated application of basal fertilizer and topdressing: Mix ammonium nitrogen solution with slow-release urea to prepare a basal fertilizer solution, which is applied to the rice field during the tillering, jointing and booting stages, and grain filling stages; S5. Nitrogen utilization efficiency monitoring and feedback: Real-time monitoring of nitrogen absorption rate of rice plants to optimize catalyst ratio and application cycle.

2. The method for replacing nitrogen fertilizer for rice using photocatalytic nitrogen-fixing materials according to claim 1, characterized in that: The composite photocatalyst in S1 uses graphite phase carbon nitride as the core photocatalytic material, and is combined with semiconductor materials such as surface doped sulfur, nitrogen or metal elements or composite modified titanium dioxide and zinc oxide to improve its electron-hole separation efficiency and visible light response range.

3. The method for replacing nitrogen fertilizer for rice using photocatalytic nitrogen-fixing materials according to claim 1, characterized in that: The graphite phase carbon nitride is etched by laser etching or chemical stripping technology to increase the specific surface area of ​​the graphite phase carbon nitride; the graphite phase carbon nitride is embedded and installed on the metal organic framework to form a heterojunction photocatalyst.

4. The method for replacing nitrogen fertilizer for rice using photocatalytic nitrogen-fixing materials according to claim 1, characterized in that: The catalyst ratio in S1 is dynamically adjusted according to the nitrogen demand of the rice field at different growth stages; The catalyst ratio was determined to be 2–3 g / 300 mL, and the catalyst concentration was 3 g / 300 mL during the tillering stage; the catalyst concentration was reduced to 2.5 g / 300 mL during the jointing stage; the catalyst concentration was adjusted to 2 g / 300 mL during the filling stage, and 0.1% of a surfactant was added during the preparation, wherein the surfactant used was polyvinyl pyrrolidone.

5. The method for replacing nitrogen fertilizer for rice using photocatalytic nitrogen-fixing materials according to claim 1, characterized in that: The reaction container in S2 is installed in a modular manner in the rice field for floating, and a solar-powered LED supplementary lighting module is embedded in the interior of the reaction container to maintain the minimum light intensity at night or on cloudy days, and the light intensity is maintained at 1000-2000 lux; a circulation pump is used to continuously circulate the rice field water and the catalyst suspension in the reaction container, and circulates once per hour, and uses a pH adjustment system to control the pH value of the rice field water between 7.0-7.

5.

6. The method of using a photocatalytic nitrogen-fixing material to replace nitrogen fertilizer for rice according to claim 2, characterized in that: The preparation process of the ammonium nitrogen in S3 is as follows: Reaction pathway optimization: Nitrogen molecules in rice paddies are captured using aerogel membranes or nanoporous materials and concentrated on the surface of heterojunction photocatalysts for photocatalytic reactions. Nitrate reductase inhibitors are added to prevent the generated ammonia from being further oxidized to nitrate. Byproduct suppression technology: By controlling the photocatalytic reaction time window, a nitrate inhibitor is added after the reaction reaches its peak to control the nitrate concentration to ≤5mg / L. During the grain filling period, the pH is gradually lowered to 6.5–6.8 through pH gradient control to promote rapid ammonia conversion and absorption by rice roots. Nitrogen recycling: At the end of the reaction, a portion of the heterojunction photocatalyst is recovered using a magnetic separation device or electrostatic adsorption membrane, and the activity of the heterojunction photocatalyst is reactivated through ultrasonic cleaning or chemical regeneration technology; the excess ammonium nitrogen solution after the reaction is directly applied to the rice field as liquid fertilizer, or solid nitrogen fertilizer is prepared through evaporation concentration technology.

7. The method of claim 1 for replacing nitrogen fertilizer for rice using a photocatalytic nitrogen-fixing material, characterized in that: The preparation steps of the base fertilizer solution in described S4 are as follows: Before transplanting, the heterojunction photocatalyst is mixed with slow-release urea to prepare a base fertilizer solution and applied to the rice field; Topdressing is carried out during the tillering stage, using a high-concentration base fertilizer solution in direct contact with the paddy water, and at the same time introducing nitrogen-fixing bacteria inoculation; Medium-concentration and low-concentration base fertilizer solutions are used during the jointing and booting stages and the grain-filling stages, respectively. The nitrogen demand is predicted through AI algorithms, and the frequency of topdressing is dynamically adjusted.

8. The method for replacing nitrogen fertilizer for rice using photocatalytic nitrogen-fixing materials according to claim 6, characterized in that: The threshold value of the nitrogen demand value predicted by the AI ​​algorithm is set as follows: To set the nitrogen supply and demand balance threshold, the base fertilizer solution needs to be maintained at 8–12 mg / L and the soil available nitrogen content needs to be ≥20 mg / kg; If the nitrogen concentration is detected to be lower than the threshold, i.e., nitrogen supply and demand ≤ 5 mg / L, the topdressing procedure is initiated and the catalyst suspension is replenished; If the concentration is higher than the threshold, that is, nitrogen supply and demand ≥15 mg / L, the nitrate inhibitor release or nitrogen recovery system is activated.

9. The method of claim 1 for replacing nitrogen fertilizer for rice using a photocatalytic nitrogen-fixing material, characterized in that: The nitrogen utilization efficiency in S5 is monitored and fed back through a chlorophyll meter or soil nitrogen sensor, and combined with water ammonia nitrogen concentration data to optimize the catalyst ratio and application cycle; after the filling period, the residual catalyst is mixed with microbial agents using a recovery system and reused as biochar material for paddy field soil improvement.

10. The method of using photocatalytic nitrogen-fixing materials to replace nitrogen fertilizer for rice according to claim 3, characterized in that: The surface of the heterojunction photocatalyst is introduced with amino functional groups or thiol groups by a chemical grafting method to enhance the affinity for nitrogen molecules and improve the nitrogen conversion efficiency.

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