Functional fertilizer for controlling and synergistically reducing cadmium and arsenic in paddy field gley during flooding environment and its preparation method and application

Abstract

The application discloses a functional fertilizer for controlling and reducing cadmium and arsenic in paddy field gley under waterlogging environment and a preparation method and application thereof, and comprises the following steps: S1, calcium peroxide granulation, to obtain calcium peroxide particles; S2, preparation of modified ethyl cellulose; S3, primary coating; S4, preparation of modified hydroxyapatite; S5, secondary coating: after mixing modified hydroxyapatite, sodium alginate and compound fertilizer, the mixture is used as a coating material to perform secondary coating on the coated calcium peroxide, and the functional fertilizer is obtained. The functional fertilizer realizes the control and slow release of the core calcium peroxide through the design of a multi-layer core-shell structure and the synergistic effect of various functional components, can long-acting and continuously provide oxygen for the rhizosphere of the waterlogged paddy field soil, effectively controls the gley process of the soil, not only reduces the biological availability of cadmium and arsenic in the soil, but also significantly reduces the accumulation risk of cadmium and arsenic in rice, and provides effective technical support for safe production of rice and sustainable utilization of farmland.

Description

Technical Field

[0001] This invention belongs to the field of functional fertilizer technology, specifically relating to a functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions, as well as its preparation method and application. Background Technology

[0002] In rice production, prolonged flooding irrigation easily leads to gleying of paddy field soil. Gleyed soil, constantly in a reducing state, suffers from severe oxygen deficiency, which not only inhibits normal root respiration and nutrient absorption but also promotes the production of toxic reducing substances such as hydrogen sulfide and ferrous ions. Ultimately, this affects rice growth and development, leading to reduced yield and deteriorated quality. Simultaneously, with the intensification of industrial and agricultural activities, cadmium (Cd) and arsenic (As) pollution in farmland soils is becoming increasingly prominent. As high-risk heavy metals, cadmium and arsenic are easily absorbed by rice and accumulate in the rice grains, entering the human body through the food chain and posing a serious threat to human health.

[0003] Currently, the improvement of paddy field gleying mainly employs agronomical measures such as intermittent irrigation and field drying to improve soil aeration, or the application of chemicals that slowly release oxygen. For the remediation of cadmium and arsenic pollution in soil, existing technologies include physical remediation (such as topsoil replacement and soil washing), chemical passivation (such as applying passivating agents like lime, phosphates, calcium silicate fertilizers, biochar, and iron-based materials to reduce heavy metal activity), and bioremediation (such as using hyperaccumulating plants or microorganisms to remove or immobilize heavy metals). Some technologies have achieved certain results in solving single problems; for example, some passivating agents have a certain immobilization effect on cadmium or arsenic, and certain oxides can provide oxygen. However, these technologies still have many limitations in practical applications.

[0004] Meanwhile, the use of some traditional fertilizers can accelerate soil acidification or gleying, while single passivating agents (such as lime and biochar) can reduce the activity of heavy metals, but they cannot simultaneously improve soil structure, and their slow-release effect is poor, making it difficult to sustainably regulate the redox state. In addition, the difference in chemical behavior between cadmium and arsenic (cadmium is easily soluble in the reduced state, while arsenic is easily soluble in the oxidized state) makes simultaneous remediation difficult.

[0005] Chinese patent application CN106348976A discloses a functional fertilizer that can regulate the soil micro-ecological environment. It is prepared using 50-80% nano-sized dolomite powder, 5%-15% sugar alcohol, 5%-15% potassium silicate, 5-10% biochar, and 5%-10% biochemical potassium humate through the following process: A. Raw material preparation; B. Preparation of nano-sized dolomite powder; C. Preparation of sugar alcohol aqueous solution; D. Nutrient chelation; E. First granulation; F. Second granulation; G. Drying. This invention can improve soil compaction; regulate soil pH and address soil acidification; replenish soil with organic matter and various trace elements; regulate soil base saturation, cation exchange capacity, and nutrient balance; reduce aluminum and manganese toxicity; improve soil salinization; adsorb and passivate heavy metals; remediate heavy metal pollution in the soil; create a favorable living environment for beneficial soil microorganisms, promote their growth and reproduction, and restore a healthy soil micro-ecological environment. However, this functional fertilizer cannot prevent gleying in flooded paddy fields. Chinese patent application CN105272750A discloses an organic bio-fertilizer comprising the following raw materials in parts by weight: 30-55 parts straw powder, 20-35 parts bentonite, 15-30 parts microbial inoculant, 10-25 parts trace elements, 8-17 parts superphosphate, 3-7 parts humic acid, 2-5 parts Bacillus subtilis inoculum, 1-5 parts surfactant, and 0-3 parts binder. The application also discloses a method for preparing the above-mentioned organic bio-fertilizer through staged fermentation. This method has a simple production process, and the resulting organic bio-fertilizer can effectively improve soil fertility, prevent large-scale soil gleying, and is pollution-free and harmless, showing good prospects for widespread application. However, this patented organic bio-fertilizer cannot effectively reduce the activity of cadmium and arsenic in the soil.

[0006] Therefore, there is an urgent need in this field to develop a functional fertilizer that can both inhibit and control hygroscopicity and synergistically regulate the bioavailability of cadmium and arsenic. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a functional fertilizer for controlling grazing and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions, as well as its preparation method and application.

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

[0009] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0010] S1. Calcium peroxide is granulated to obtain calcium peroxide particles;

[0011] S2. Preparation of modified ethyl cellulose: Ethyl cellulose is added to butanone, followed by the addition of 1,4-butanediol diglycidyl ether, polyethylene glycol, and triethylamine. The mixture is stirred and reacted under a nitrogen atmosphere. After the reaction is completed, the solvent is evaporated, the mixture is washed, and dried to obtain modified ethyl cellulose.

[0012] S3, One-time coating: Modified ethyl cellulose and pretreated silica are added to ethyl acetate and stirred evenly to obtain a mixture. The mixture is then sprayed onto the calcium peroxide particles in step S1 and dried to obtain coated calcium peroxide particles.

[0013] S4. Preparation of modified hydroxyapatite: Hydroxyapatite was added to deionized water, followed by lanthanum nitrate and cerium nitrate. After stirring evenly, ammonia was added, and a hydrothermal reaction was carried out. After the reaction was completed, the mixture was filtered, washed, dried, and calcined to obtain composite hydroxyapatite. The composite hydroxyapatite was added to an ethanol aqueous solution, followed by γ-mercaptopropyltrimethoxysilane, and a isothermal reaction was carried out. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0014] S5. Secondary coating: Modified hydroxyapatite, sodium alginate, and compound fertilizer are mixed and used as coating materials to perform a secondary coating on the coated calcium peroxide, thus obtaining the final product.

[0015] Preferably, the specific method for calcium peroxide granulation in step S1 is as follows: adjust the tilt angle of the disc granulator to 50-65° and the heating device to 40-55°; place the calcium peroxide powder into the disc of the disc granulator, adjust the rotation speed of the disc granulator to 20-40 r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out particles with a diameter of 3-5 mm and smooth surface, while continuously adding calcium peroxide powder until granulation is completed.

[0016] Preferably, in step S2, the viscosity of the ethyl cellulose is 30-40 cp, and the ethoxy content is 48-51%; the molecular weight of the polyethylene glycol is 1500-2000; the mass ratio of the ethyl cellulose, butanone, 1,4-butanediol diglycidyl ether, polyethylene glycol, and triethylamine is 90-100:1000-1200:4-6:15-20:2-3; and the stirring reaction temperature is 70-80℃, and the time is 3-5 hours.

[0017] In this invention, ethyl cellulose is used as the basic framework of the primary coating material, and 1,4-butanediol diglycidyl ether is used as a crosslinking agent. Through the reaction of its diepoxy groups with the hydroxyl groups on the molecular chains of ethyl cellulose and polyethylene glycol, polyethylene glycol is grafted onto ethyl cellulose. Polyethylene glycol has a certain degree of hydrophilicity; its introduction can, on the one hand, moderately adjust the overall hydrophilic / hydrophobic balance of the primary coating material, thereby more precisely controlling the water permeation rate. On the other hand, under subsequent flooding conditions, polyethylene glycol may dissolve to form micropores, thereby regulating the oxygen release rate. Furthermore, the introduced polyethylene glycol improves the flexibility of the ethyl cellulose membrane, reduces brittleness, enhances the mechanical properties of the primary coating layer, and ensures its integrity during the secondary coating process.

[0018] Preferably, in step S3, the mass ratio of modified ethyl cellulose, pretreated silica, and ethyl acetate is 100-110:5-10:1000, and the mass ratio of the mixture to calcium peroxide is 800-1000:1000; the pretreated silica is silica treated with n-octyltriethoxysilane.

[0019] In this invention, modified ethyl cellulose and pretreated silica are mixed in a specific ratio as a primary coating material, giving the primary coating layer good hydrophobicity and strength. On the one hand, this effectively controls the contact rate between external moisture and the calcium peroxide core, thereby controlling the rate of oxygen production from calcium peroxide decomposition and achieving slow release. On the other hand, it also prevents calcium peroxide from contacting the highly hygroscopic compound fertilizer in the secondary coating layer, avoiding the problem that the moisture generated after the compound fertilizer absorbs moisture will directly contact the calcium peroxide, causing it to decompose inside the fertilizer particles. The added pretreated silica, as a filler, can improve the mechanical strength and wear resistance of the membrane, reduce the rupture of the hydrophobic membrane during the secondary coating process, and increase the surface roughness of the membrane, which is beneficial to the adhesion of subsequent secondary coating materials.

[0020] More preferably, the preparation method of the pretreated silica is as follows: 100-120g of silica powder is added to 600mL of ethanol and treated under ultrasound at 20-30kHz for 10-15min. Then, 8-10g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 50-60℃ for 3-4h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0021] In this invention, silica is reacted with n-octyltriethoxysilane to prepare hydrophobic silica, which improves its dispersibility in primary coating materials and its compatibility with modified ethyl cellulose, thus ensuring the strength and water resistance of the primary coating layer.

[0022] Preferably, in step S4, the mass concentration of the ammonia water is 15-20%, the mass ratio of the hydroxyapatite, deionized water, lanthanum nitrate, cerium nitrate, and ammonia water is 100-110:1000-1300:5-8:4-6:20-30, the hydrothermal reaction temperature is 140-160℃, the time is 4-5h, and the calcination temperature is 400-450℃, the time is 2-3h.

[0023] Preferably, in step S4, the mass ratio of the composite hydroxyapatite to γ-mercaptopropyltrimethoxysilane is 100:5-8, and the isothermal reaction is carried out at a temperature of 60-70°C for 3-4 hours.

[0024] In this invention, rare earth elements lanthanum and cerium are introduced into a hydroxyapatite matrix via a hydrothermal reaction. Subsequently, a La / Ce composite hydroxyapatite is formed during calcination. Lanthanum and cerium oxides have a strong affinity for arsenates, and together with hydroxyapatite, they can fix arsenic through mechanisms such as surface complexation, ion exchange, or co-precipitation, significantly reducing the bioavailability of arsenic in the soil. Then, the composite hydroxyapatite is reacted with γ-mercaptopropyltrimethoxysilane to introduce thiol groups, which have a strong complexing ability for cadmium ions and can form stable thiolate precipitates or complexes, thereby efficiently fixing cadmium. This allows the prepared modified hydroxyapatite to synergistically adsorb and fix cadmium and arsenic.

[0025] Preferably, the specific steps in step S5 are as follows: Adjust the tilt angle of the disc granulator to 55-60°, adjust the heating device to 45-50°, place the coated calcium peroxide granules from step S2 into the disc granulator, mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly as coating material, and place them in the vibrating feeder, feeding them at a uniform speed, and continuously spray water mist at the rising point of the granules with a water mist spray gun until the coating is completed. After drying, the functional fertilizer for controlling the grazing and synergistic reduction of cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0026] Preferably, in step S5, the mass ratio of the compound fertilizer, sodium alginate, and modified hydroxyapatite is 40-50:10-15:50-60, and the mass ratio of the coating material to the coating calcium peroxide is 15-25:100.

[0027] In this invention, compound fertilizer, sodium alginate, and modified hydroxyapatite are used as secondary coating materials. Under the action of water mist, sodium alginate can bind the compound fertilizer and modified hydroxyapatite powder together and attach them to the surface of the primary coating particles to form a uniform secondary coating layer. The compound fertilizer can provide essential nutrients such as nitrogen, phosphorus, and potassium for rice growth, achieving a balance between pollution remediation and crop nutrition. The core of this functional fertilizer granule can slowly release oxygen to improve the soil, while the outer layer can passivate heavy metals and provide nutrients, thereby achieving multiple objectives such as grazing control in paddy fields under flooded conditions, synergistic reduction of cadmium and arsenic, and promotion of crop growth.

[0028] This invention also protects a functional fertilizer prepared by the method described above, which exhibits hygroscopic inhibition and synergistic reduction of cadmium and arsenic in paddy fields under flooded conditions.

[0029] This invention also protects the application of a functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions, as described above, characterized in that the functional fertilizer is applied at a rate of 0.1-0.3 kg / m³. 2 The fertilizer is applied to the surface layer of cadmium and arsenic contaminated paddy soil, followed by tilling or rotary tilling to a depth of 15-20cm to ensure thorough mixing with the soil. The paddy field is then leveled and allowed to equilibrate for 1-2 days. After the soil has equilibrated, rice is transplanted. During the rice growth process, the soil is managed using a long-term flooding system. The total cadmium content in the cadmium and arsenic contaminated paddy soil is 0.5-1.0 mg / kg, and the total arsenic content is 15-100 mg / kg.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The functional fertilizer provided by this invention, which inhibits gleying in paddy fields under flooded conditions and synergistically reduces cadmium and arsenic, achieves controlled and slow-release of core calcium peroxide through a multi-layer core-shell structure design and the synergistic effect of various functional components. It can provide oxygen to the rhizosphere of flooded paddy soil in a long-term and continuous manner, effectively inhibiting the gleying process. At the same time, the double coating process is adopted. The hydrophobicity of the first coating layer prevents direct contact between the calcium peroxide core and the highly hygroscopic compound fertilizer, which can significantly improve the overall moisture resistance of the granules and reduce the impact of environmental humidity on the core calcium peroxide, thereby ensuring its application in the field. The first layer maintains the activity, extending the product's shelf life and effectiveness. The modified hydroxyapatite added to the second coating layer can efficiently and simultaneously passivate cadmium and arsenic in the soil, reducing their bioavailability, and supplementing the compound fertilizer to provide the nutrients needed for rice growth. This functional fertilizer organically combines soil improvement, pollution remediation, and crop nutrient supply, providing an integrated solution to the current problems of gleying and heavy metal compound pollution faced by flooded paddy fields. It not only reduces the bioavailability of cadmium and arsenic in the soil, but also significantly reduces the risk of cadmium and arsenic accumulation in rice, providing effective technical support for safe rice production and sustainable farmland utilization.

[0032] (2) The functional fertilizer for controlling paddy field gleying and synergistically reducing cadmium and arsenic in flooded environments provided by this invention uses 1,4-butanediol diglycidyl ether as a crosslinking agent to crosslink polyethylene glycol and ethyl cellulose, and is compounded with hydrophobic silica pretreated with n-octyltriethoxysilane to coat calcium peroxide particles. This modified ethyl cellulose membrane has excellent film-forming properties, controllable permeability and good biocompatibility. The addition of pretreated silica not only improves the dispersibility of the coating material and its binding force with calcium peroxide particles, but also further regulates the micropore structure and mechanical strength of the membrane. This primary coating layer can effectively slow down the water penetration rate, avoid the rapid decomposition and failure of calcium peroxide after contact with water, and also avoid direct contact between calcium peroxide and compound fertilizer, realizing the slow and continuous release of oxygen, thereby providing a stable micro-aerobic environment for the root zone soil of rice throughout the entire growth period, effectively inhibiting the production of strong reducing substances, and significantly improving the long-term control effect of paddy field gleying.

[0033] (3) The functional fertilizer for paddy field grazing inhibition and synergistic reduction of cadmium and arsenic provided by the present invention is prepared by uniformly introducing lanthanum nitrate and cerium nitrate into the structure of hydroxyapatite through a hydrothermal method, and grafting γ-mercaptopropyltrimethoxysilane onto its surface to obtain a composite material with dual specific adsorption of cadmium and arsenic. Among them, the doping of lanthanum and cerium not only increases the specific surface area and pore structure of the material, but more importantly, it provides abundant Lewis acid sites, which have high affinity and strong binding ability for arsenic (such as arsenate) in the form of oxygen-containing anions in the soil, promoting its precipitation or the formation of stable surface complexes. The thiol functional group introduced by γ-mercaptopropyltrimethoxysilane, as a soft nucleophile, can form a highly stable thiolate complex with soft Lewis acid cadmium ions. Through a specific preparation method, the modified hydroxyapatite can overcome the problem of simultaneous treatment caused by the difference in chemical behavior of cadmium and arsenic, thereby achieving synergistic and efficient passivation and fixation of cadmium and arsenic pollutants in the soil in the outer coating layer, significantly reducing the risk of their migration to rice plants. Attached Figure Description

[0034] Figure 1 The graph shows the changes in active oxygen content in distilled water, the extracts from Example 1, and Comparative Examples 1-2. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0037] In this invention, the calcium peroxide was purchased from Henan Huize Bioengineering Co., Ltd., and its composition is 70% calcium peroxide and 30% calcium hydroxide; the N-P2O5-K2O ratio in the compound fertilizer is 15-15-15; the particle size of the silica is 5-10 μm; the particle size of the hydroxyapatite is 2-5 μm; and the rice variety is Y Liangyou 911.

[0038] Example 1

[0039] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0040] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 50° and the heating device to 40°C; place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 30r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5mm, while continuously adding calcium peroxide powder until granulation is completed and calcium peroxide particles are obtained.

[0041] S2. Preparation of modified ethyl cellulose: 950g of ethyl cellulose was added to 11kg of butanone, followed by 50g of 1,4-butanediol diglycidyl ether, 180g of polyethylene glycol, and 25g of triethylamine. The mixture was stirred and reacted at 75°C under a nitrogen atmosphere for 4 hours. After the reaction was completed, the solvent was evaporated, the mixture was washed, and dried to obtain modified ethyl cellulose.

[0042] S3, One-time coating: Add 1.1 kg of modified ethyl cellulose and 80 g of pretreated silica to 10 kg of ethyl acetate, stir evenly to obtain a mixture, spray 9 kg of the mixture evenly onto 10 kg of calcium peroxide particles in step S1, and then dry to obtain coated calcium peroxide particles.

[0043] S4. Preparation of modified hydroxyapatite: 1.1 kg of hydroxyapatite was added to 12 kg of deionized water, followed by 70 g of lanthanum nitrate and 50 g of cerium nitrate. After stirring evenly, 250 g of 20% ammonia solution was added, and the mixture was hydrothermally reacted at 150 °C for 4.5 h. After the reaction was completed, the mixture was filtered, washed, and dried, and then calcined at 430 °C for 2.5 h to obtain composite hydroxyapatite. 1 kg of composite hydroxyapatite was added to 10 kg of ethanol aqueous solution (ethanol to water volume ratio of 8:2), followed by 70 g of γ-mercaptopropyltrimethoxysilane. The mixture was reacted at a constant temperature of 65 °C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0044] S5. Secondary Coating: Adjust the tilt angle of the disc granulator to 60° and the heating device to 50°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 45:13:55 as the coating material (2kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0045] The preparation method of the pretreated silica is as follows: 110g of silica powder is added to 600mL of ethanol and treated under ultrasound at 25kHz for 13min. Then, 9g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 55℃ for 3.5h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0046] Example 2

[0047] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0048] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 55° and the heating device to 45°. Place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 20 r / min, and spray water mist continuously at the rising part of the powder with a water mist spray gun according to the granulation situation. Continuously screen out smooth particles with a diameter of 3-5 mm, and continuously add calcium peroxide powder until granulation is completed to obtain calcium peroxide granules.

[0049] S2. Preparation of modified ethyl cellulose: 900g of ethyl cellulose was added to 10kg of butanone, followed by 40g of 1,4-butanediol diglycidyl ether, 150g of polyethylene glycol, and 20g of triethylamine. The mixture was stirred and reacted at 70℃ under a nitrogen atmosphere for 5h. After the reaction was completed, the solvent was evaporated, the mixture was washed, and dried to obtain modified ethyl cellulose.

[0050] S3, One-time coating: Add 1kg of modified ethyl cellulose and 50g of pretreated silica to 10kg of ethyl acetate, stir evenly to obtain a mixture, spray 8kg of the mixture evenly onto 10kg of calcium peroxide particles in step S1, and then dry to obtain coated calcium peroxide particles.

[0051] S4. Preparation of modified hydroxyapatite: 1 kg of hydroxyapatite was added to 10 kg of deionized water, followed by 50 g of lanthanum nitrate and 40 g of cerium nitrate. After stirring evenly, 200 g of 15% ammonia solution was added, and the mixture was hydrothermally reacted at 140 °C for 5 h. After the reaction was completed, the mixture was filtered, washed, and dried, and then calcined at 400 °C for 3 h to obtain composite hydroxyapatite. 1 kg of composite hydroxyapatite was added to 10 kg of ethanol aqueous solution (ethanol to water volume ratio of 8:2), followed by 50 g of γ-mercaptopropyltrimethoxysilane. The mixture was reacted at a constant temperature of 60 °C for 4 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0052] S5. Secondary Coating: Adjust the tilt angle of the disc granulator to 55° and the heating device to 45°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 40:10:50 as the coating material (1.5kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0053] The preparation method of the pretreated silica is as follows: 100g of silica powder is added to 600mL of ethanol and treated under ultrasound at 20kHz for 10min. Then, 8g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 50℃ for 4h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0054] Example 3

[0055] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0056] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 65° and the heating device to 5°C; place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 40r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5mm, while continuously adding calcium peroxide powder until granulation is completed and calcium peroxide granules are obtained.

[0057] S2. Preparation of modified ethyl cellulose: 1000g of ethyl cellulose was added to 12kg of butanone, followed by 60g of 1,4-butanediol diglycidyl ether, 200g of polyethylene glycol, and 30g of triethylamine. The mixture was stirred and reacted at 80℃ under a nitrogen atmosphere for 3h. After the reaction was completed, the solvent was evaporated, washed, and dried to obtain modified ethyl cellulose.

[0058] S3, One-time coating: Add 1.1 kg of modified ethyl cellulose and 100 g of pretreated silica to 10 kg of ethyl acetate, stir evenly to obtain a mixture, spray 10 kg of the mixture evenly onto 10 kg of calcium peroxide particles in step S1, and then dry to obtain coated calcium peroxide particles.

[0059] S4. Preparation of modified hydroxyapatite: 1.1 kg of hydroxyapatite was added to 13 kg of deionized water, followed by 80 g of lanthanum nitrate and 60 g of cerium nitrate. After stirring evenly, 300 g of 20% ammonia solution was added, and the mixture was hydrothermally reacted at 160 °C for 4 h. After the reaction was completed, the mixture was filtered, washed, and dried, and then calcined at 450 °C for 2 h to obtain composite hydroxyapatite. 1 kg of composite hydroxyapatite was added to 10 kg of ethanol aqueous solution (ethanol to water volume ratio of 8:2), followed by 80 g of γ-mercaptopropyltrimethoxysilane. The mixture was reacted at a constant temperature of 70 °C for 3 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0060] S5. Secondary Coating: Adjust the tilt angle of the disc granulator to 60° and the heating device to 50°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 50:15:60 as the coating material (2.5kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0061] The preparation method of the pretreated silica is as follows: 120g of silica powder is added to 600mL of ethanol and treated under ultrasound at 30kHz for 15min. Then, 10g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 60℃ for 3h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0062] Comparative Example 1

[0063] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0064] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 50° and the heating device to 40°C; place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 30r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5mm, while continuously adding calcium peroxide powder until granulation is completed and calcium peroxide particles are obtained.

[0065] S2, One-time coating: Add 1.1 kg of ethyl cellulose and 80 g of pretreated silica to 10 kg of ethyl acetate, stir evenly to obtain a mixture, spray 9 kg of the mixture evenly onto 10 kg of calcium peroxide particles from step S1, and then dry to obtain coated calcium peroxide particles.

[0066] S3. Preparation of modified hydroxyapatite: 1.1 kg of hydroxyapatite was added to 12 kg of deionized water, followed by 70 g of lanthanum nitrate and 50 g of cerium nitrate. After stirring evenly, 250 g of 20% ammonia solution was added, and the mixture was hydrothermally reacted at 150 °C for 4.5 h. After the reaction was completed, the mixture was filtered, washed, and dried, and then calcined at 430 °C for 2.5 h to obtain composite hydroxyapatite. 1 kg of composite hydroxyapatite was added to 10 kg of ethanol aqueous solution (ethanol to water volume ratio of 8:2), followed by 70 g of γ-mercaptopropyltrimethoxysilane. The mixture was reacted at a constant temperature of 65 °C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0067] S4. Secondary Coating: Adjust the tilt angle of the disc granulator to 60° and the heating device to 50°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 45:13:55 as the coating material (2kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0068] The preparation method of the pretreated silica is as follows: 110g of silica powder is added to 600mL of ethanol and treated under ultrasound at 25kHz for 13min. Then, 9g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 55℃ for 3.5h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0069] Compared to Example 1, this comparative example did not modify ethyl cellulose.

[0070] Comparative Example 2

[0071] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0072] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 50° and the heating device to 40°C; place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 30r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5mm, while continuously adding calcium peroxide powder until granulation is completed and calcium peroxide particles are obtained.

[0073] S2. Preparation of modified ethyl cellulose: 950g of ethyl cellulose was added to 11kg of butanone, followed by 50g of 1,4-butanediol diglycidyl ether, 180g of polyethylene glycol, and 25g of triethylamine. The mixture was stirred and reacted at 75°C under a nitrogen atmosphere for 4 hours. After the reaction was completed, the solvent was evaporated, the mixture was washed, and dried to obtain modified ethyl cellulose.

[0074] S3, One-time coating: Add 1.1 kg of modified ethyl cellulose to 10 kg of ethyl acetate, stir evenly to obtain a mixture, spray 9 kg of the mixture evenly onto the 10 kg of calcium peroxide particles in step S1, and then dry to obtain coated calcium peroxide particles.

[0075] S4. Preparation of modified hydroxyapatite: 1.1 kg of hydroxyapatite was added to 12 kg of deionized water, followed by 70 g of lanthanum nitrate and 50 g of cerium nitrate. After stirring evenly, 250 g of 20% ammonia solution was added, and the mixture was hydrothermally reacted at 150 °C for 4.5 h. After the reaction was completed, the mixture was filtered, washed, and dried, and then calcined at 430 °C for 2.5 h to obtain composite hydroxyapatite. 1 kg of composite hydroxyapatite was added to 10 kg of ethanol aqueous solution (ethanol to water volume ratio of 8:2), followed by 70 g of γ-mercaptopropyltrimethoxysilane. The mixture was reacted at a constant temperature of 65 °C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0076] S5. Secondary Coating: Adjust the tilt angle of the disc granulator to 60° and the heating device to 50°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 45:13:55 as the coating material (2kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0077] Compared with Example 1, no pretreated silica was added in this comparative example.

[0078] Comparative Example 3

[0079] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0080] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 50° and the heating device to 40°C; place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 30r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5mm, while continuously adding calcium peroxide powder until granulation is completed and calcium peroxide particles are obtained.

[0081] S2. Preparation of modified ethyl cellulose: 950g of ethyl cellulose was added to 11kg of butanone, followed by 50g of 1,4-butanediol diglycidyl ether, 180g of polyethylene glycol, and 25g of triethylamine. The mixture was stirred and reacted at 75°C under a nitrogen atmosphere for 4 hours. After the reaction was completed, the solvent was evaporated, the mixture was washed, and dried to obtain modified ethyl cellulose.

[0082] S3, One-time coating: Add 1.1 kg of modified ethyl cellulose and 80 g of pretreated silica to 10 kg of ethyl acetate, stir evenly to obtain a mixture, spray 9 kg of the mixture evenly onto 10 kg of calcium peroxide particles in step S1, and then dry to obtain coated calcium peroxide particles.

[0083] S4. Preparation of modified hydroxyapatite: 1.1 kg of hydroxyapatite was added to 12 kg of deionized water, followed by 70 g of lanthanum nitrate and 50 g of cerium nitrate. After stirring evenly, 250 g of ammonia water with a mass concentration of 20% was added. The mixture was then subjected to hydrothermal reaction at 150 °C for 4.5 h. After the reaction was completed, the mixture was filtered, washed and dried, and then calcined at 430 °C for 2.5 h to obtain modified hydroxyapatite.

[0084] S5. Secondary Coating: Adjust the tilt angle of the disc granulator to 60° and the heating device to 50°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 45:13:55 as the coating material (2kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0085] The preparation method of the pretreated silica is as follows: 110g of silica powder is added to 600mL of ethanol and treated under ultrasound at 25kHz for 13min. Then, 9g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 55℃ for 3.5h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0086] Compared to Example 1, this comparative example did not introduce γ-mercaptopropyltrimethoxysilane onto hydroxyapatite.

[0087] Comparative Example 4

[0088] A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits phytochemicals and synergistically reduces cadmium and arsenic levels includes the following steps:

[0089] S1. Calcium peroxide granulation: Adjust the tilt angle of the disc granulator to 50° and the heating device to 40°C; place the calcium peroxide powder into the disc of the disc granulator, adjust the speed of the disc granulator to 30r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5mm, while continuously adding calcium peroxide powder until granulation is completed and calcium peroxide particles are obtained.

[0090] S2. Preparation of modified ethyl cellulose: 950g of ethyl cellulose was added to 11kg of butanone, followed by 50g of 1,4-butanediol diglycidyl ether, 180g of polyethylene glycol, and 25g of triethylamine. The mixture was stirred and reacted at 75°C under a nitrogen atmosphere for 4 hours. After the reaction was completed, the solvent was evaporated, the mixture was washed, and dried to obtain modified ethyl cellulose.

[0091] S3, One-time coating: Add 1.1 kg of modified ethyl cellulose and 80 g of pretreated silica to 10 kg of ethyl acetate, stir evenly to obtain a mixture, spray 9 kg of the mixture evenly onto 10 kg of calcium peroxide particles in step S1, and then dry to obtain coated calcium peroxide particles.

[0092] S4. Preparation of modified hydroxyapatite: 1 kg of hydroxyapatite was added to 10 kg of ethanol aqueous solution (volume ratio of ethanol to water was 8:2), followed by the addition of 70 g of γ-mercaptopropyltrimethoxysilane. The mixture was reacted at a constant temperature of 65 °C for 3.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite.

[0093] S5. Secondary Coating: Adjust the tilt angle of the disc granulator to 60° and the heating device to 50°. Place the 10kg coated calcium peroxide granules from step S2 into the disc granulator. Mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly at a mass ratio of 45:13:55 as the coating material (2kg). Place the mixture into the vibrating feeder and feed it in at a uniform speed. Continuously spray water mist at the rising point of the granules with a water mist sprayer until the coating is completed. After drying, the functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions is obtained.

[0094] The preparation method of the pretreated silica is as follows: 110g of silica powder is added to 600mL of ethanol and treated under ultrasound at 25kHz for 13min. Then, 9g of n-octyltriethoxysilane and 1mL of deionized water are added and stirred at 55℃ for 3.5h. After the reaction is completed, the silica is filtered, washed and dried to obtain the pretreated silica.

[0095] Compared to Example 1, this comparative example did not load lanthanum cerium oxide onto hydroxyapatite.

[0096] The functional fertilizers prepared in Example 1 and Comparative Examples 1-2 were tested for oxygen release rate. The slow-release performance of the functional fertilizers was evaluated using the water dissolution method. Approximately 2g of functional fertilizer granules were weighed and placed in a self-made 300-mesh filter bag. The filter bag was then placed in a 250mL ground glass conical flask, and 250mL of distilled water was added. The flask was then placed in a 25℃ constant temperature incubator for incubation. The extract was collected on days 1, 2, 3, 4, 7, 10, 14, and 21 of incubation, and every 7 days thereafter, up to day 140. After extraction, 250mL of distilled water was added to the flask, and incubation and extraction were continued. After thorough mixing and settling, the content of dissolved active oxygen in the filtrate was measured, and a curve showing the relationship between the amount of active oxygen dissolved and the water immersion time was plotted. Each experiment was repeated three times for parallel determination. Measurements were taken strictly according to the operating procedures of the Hach HQ30d portable dissolved oxygen meter and pH meter. It is important to note that the content of reactive oxygen species (ROS) in water is negatively correlated with temperature, and temperature has a significant impact on the ROS content. Therefore, both incubation and measurement must be conducted at 25℃. Test results are as follows... Figure 1 .

[0097] The functional fertilizers prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to field trials, as follows: Experimental field: total cadmium content 0.8 mg / kg, total arsenic content 60 mg / kg, available cadmium content 0.41 mg / kg, available arsenic content 1.16 mg / kg, gleyed soil (Eh = -200 mV). Eight treatments were set up: 1) Control group; 2) Example 1 group; 3) Example 2 group; 4) Example 3 group; 5) Comparative Example 1 group; 6) Comparative Example 2 group; 7) Comparative Example 3 group; 8) Comparative Example 4 group. The control group was treated with 0.05 kg / m³. 2 Apply compound fertilizer, and for the remaining groups, apply functional fertilizer at a rate of 0.2 kg / m². 2The fertilizer was applied to the surface layer of cadmium and arsenic contaminated paddy soil, followed by tilling or rotary tilling to a depth of 18 cm to ensure thorough mixing with the soil. The paddy field was then leveled and allowed to equilibrate for 2 days. After soil equilibration, rice seedlings were transplanted. During the rice growth process, the soil was managed under a long-term flooded management model. Ninety days after the application of the fertilizer, the soil Eh value and the contents of available cadmium and arsenic were tested. At the rice harvest time, samples were taken from rice plants with similar growth and yield in each treatment group to determine the cadmium and arsenic content in the rice. The rice yield of each group was also statistically analyzed. The results are shown in Table 1 below.

[0098] Table 1 Results of each group of experiments

[0099]

[0100] from Figure 1 It can be seen that the slow-release remedial agent prepared by this invention has a long release time and low amplitude of active oxygen, and the changes are very stable throughout the entire extraction period, so it can play a role throughout the entire growth period of rice. In contrast, Comparative Example 1, due to the lack of introduction of polyethylene glycol, has an excessively high hydrophobicity of the primary coating layer, resulting in a slow oxygen release rate; while Comparative Example 2, due to the lack of introduction of pretreated silica, has a reduced hydrophobicity and strength of the primary coating layer, insufficient protection for calcium peroxide, and an excessively fast oxygen release rate.

[0101] As can be seen from Table 1 above, the functional fertilizer prepared by this invention stabilizes the soil Eh between +180 and +210 mV, indicating that it can effectively prevent secondary gleying of paddy soil under flooded conditions; the content of available cadmium and available arsenic in the soil decreases, indicating that it can significantly reduce the content of available cadmium and available arsenic in the soil, and at the same time reduce the bioavailability of cadmium and arsenic, thereby reducing the cadmium and arsenic content in rice.

[0102] The above description is a further detailed explanation of the present invention in conjunction with specific implementation examples. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

[0103] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a functional fertilizer for paddy fields under flooded conditions that inhibits chemical metabolism and synergistically reduces cadmium and arsenic, characterized in that, Includes the following steps: S1. Calcium peroxide is granulated to obtain calcium peroxide particles; S2. Preparation of modified ethyl cellulose: Ethyl cellulose is added to butanone, followed by the addition of 1,4-butanediol diglycidyl ether, polyethylene glycol, and triethylamine. The mixture is stirred and reacted under a nitrogen atmosphere. After the reaction is completed, the solvent is evaporated, the mixture is washed, and dried to obtain modified ethyl cellulose. S3, One-time coating: Modified ethyl cellulose and pretreated silica are added to ethyl acetate and stirred evenly to obtain a mixture. The mixture is then sprayed onto the calcium peroxide particles in step S1 and dried to obtain coated calcium peroxide particles. S4. Preparation of modified hydroxyapatite: Hydroxyapatite was added to deionized water, followed by lanthanum nitrate and cerium nitrate. After stirring evenly, ammonia was added, and a hydrothermal reaction was carried out. After the reaction was completed, the mixture was filtered, washed, dried, and calcined to obtain composite hydroxyapatite. The composite hydroxyapatite was added to an ethanol aqueous solution, followed by γ-mercaptopropyltrimethoxysilane, and a isothermal reaction was carried out. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified hydroxyapatite. S5. Secondary coating: Modified hydroxyapatite, sodium alginate, and compound fertilizer are mixed and used as coating materials to perform secondary coating on coated calcium peroxide, thus obtaining the final product. In step S2, the viscosity of the ethyl cellulose is 30-40 cp, and the ethoxy content is 48-51%; the molecular weight of the polyethylene glycol is 1500-2000; the mass ratio of the ethyl cellulose, butanone, 1,4-butanediol diglycidyl ether, polyethylene glycol, and triethylamine is 90-100:1000-1200:4-6:15-20:2-3; the stirring reaction temperature is 70-80℃, and the time is 3-5 h; the preparation method of the pretreated silica is as follows: 100-120 g of silica powder is added to 600 mL of ethanol and treated under ultrasound at 20-30 kHz for 10-15 min; then 8-10 g of n-octyltriethoxysilane and 1 mL of deionized water are added, and the mixture is stirred at 50-60℃ for 3-4 h; after the reaction is completed, the mixture is filtered, washed, and dried to obtain the pretreated silica. In step S4, the mass concentration of ammonia is 15-20%, the mass ratio of hydroxyapatite, deionized water, lanthanum nitrate, cerium nitrate, and ammonia is 100-110:1000-1300:5-8:4-6:20-30, the hydrothermal reaction temperature is 140-160℃ and the time is 4-5 hours, the calcination temperature is 400-450℃ and the time is 2-3 hours; the mass ratio of composite hydroxyapatite and γ-mercaptopropyltrimethoxysilane is 100:5-8, the isothermal reaction temperature is 60-70℃ and the time is 3-4 hours.

2. The preparation method according to claim 1, characterized in that, The specific method for calcium peroxide granulation in step S1 is as follows: adjust the tilt angle of the disc granulator to 50-65° and the heating device to 40-55°; place the calcium peroxide powder into the disc of the disc granulator, adjust the rotation speed of the disc granulator to 20-40 r / min, and continuously spray water mist at the rising part of the powder with a water mist spray gun according to the granulation situation, and continuously screen out smooth particles with a diameter of 3-5 mm, while continuously adding calcium peroxide powder until granulation is completed.

3. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of modified ethyl cellulose, pretreated silica, and ethyl acetate is 100-110:5-10:1000, and the mass ratio of the mixture to calcium peroxide is 800-1000:1000; the pretreated silica is silica treated with n-octyltriethoxysilane.

4. The preparation method according to claim 1, characterized in that, The specific steps in step S5 are as follows: Adjust the tilt angle of the disc granulator to 55-60°, adjust the heating device to 45-50°, place the coated calcium peroxide granules from step S2 into the disc granulator, mix the compound fertilizer, sodium alginate, and modified hydroxyapatite evenly as coating material, and place them in the vibrating feeder, feeding them at a uniform speed, and continuously spray water mist at the rising point of the granules with a water mist spray gun until the coating is completed. After drying, the functional fertilizer for controlling the grazing and synergistic reduction of cadmium and arsenic in paddy fields under flooded conditions is obtained.

5. The preparation method according to claim 1, characterized in that, In step S5, the mass ratio of compound fertilizer, sodium alginate, and modified hydroxyapatite is 40-50:10-15:50-60, and the mass ratio of coating material to coated calcium peroxide is 15-25:

100.

6. A functional fertilizer for paddy fields under flooded conditions that inhibits grazing and synergistically reduces cadmium and arsenic, prepared by the method described in any one of claims 1-5.

7. The application of a functional fertilizer for controlling phytochemicals and synergistically reducing cadmium and arsenic in paddy fields under flooded conditions, as described in claim 6, is characterized in that... The functional fertilizer is applied at a concentration of 0.1-0.3 kg / m³. 2 The fertilizer was applied to the surface layer of the cadmium and arsenic contaminated paddy soil, followed by tilling or rotary tilling to a depth of 15-20 cm to ensure thorough mixing with the soil. The paddy field was then leveled and allowed to equilibrate for 1-2 days. After the soil was properly equilibrated, rice was transplanted. During the rice growth process, the soil was managed using a long-term flooding system. The total cadmium content in the cadmium and arsenic contaminated paddy soil was 0.3-1.0 mg / kg, and the total arsenic content was 15-100 mg / kg.

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