A composite reducing agent for reducing the production of soil reducing substances in a rice field

Abstract

The application discloses a kind of low production paddy field soil reducing material composite reduction agent, including lime 30-40 parts, medical stone 20-40 parts, magnesium-based hydrotalcite 20-30 parts, calcium peroxide 5-15 parts, metal organic framework material MOF-5 1-5 parts, carboxymethyl cellulose 0.5-2 parts, according to the main obstacle type of soil selection suitable composite reduction agent dosage, the composite reduction agent is pressed into soil with straw, and water is poured to bubble field 3 days after fertilization transplanting rice.The composite reduction agent disclosed in the application can increase dissolved oxygen content, improve pH value and oxidation-reduction potential, reduce the accumulation of reducing substances and accelerate straw decomposition when applied in paddy field through synergistic effect, not only solve the problem of straw decomposition and reducing substance accumulation in paddy field, but also effectively alleviate the loss of fertilizer efficiency, provide necessary silicon, zinc and magnesium and other nutrient elements for rice, promote the growth and development of rice, and comprehensively improve the production capacity.

Description

Technical Field

[0001] This invention belongs to the field of soil reducing agent treatment technology after straw return to low-yield paddy fields, specifically involving a composite agent for reducing soil reducing agents in low-yield paddy fields. Background Technology

[0002] The middle and lower reaches of the Yangtze River are one of my country's main rice-producing areas, where a double or triple cropping system is practiced. However, due to tight farming schedules, frequent cropping, and large amounts of straw returned to the field after early rice harvest, straw return faces numerous challenges. This is especially true in low-yield paddy fields, where the obstacles are mainly categorized as cold-induced, cohesive, and toxic. When fresh straw is returned to the field, under high temperatures and deep flooding conditions, coupled with the application of large amounts of nitrogen fertilizer, the decomposition process rapidly consumes oxygen, easily creating a reducing environment. In the early stages of straw return to the paddy field, the increased oxygen consumption leads to a decrease in dissolved oxygen in the water. Prolonged anaerobic conditions not only affect the soil's redox potential but also disrupt the balance of iron, manganese, sulfur, and nitrogen. Under these conditions, anaerobic microorganisms become the dominant flora, and reducing substances such as Fe(II), Mn(II), and H2S accumulate rapidly in the soil, negatively impacting rice roots, reducing their vitality, and inhibiting tillering. In addition, changes in soil pH and water quality can also have adverse effects on the growth of rice seedlings.

[0003] To improve the above situation, various materials and technologies for improving paddy field soil are currently available on the market. For example, oxygenating agents are mainly made of calcium peroxide and sodium percarbonate, while other amendments include inorganic materials such as lime, oyster shells, and fly ash, as well as organic materials such as livestock and poultry manure, humic acid, and peat, artificially synthesized amendments such as polyacrylamide, natural synthetic copolymers such as humic acid-polyacrylic acid, and even biological amendments such as microbial inoculants. However, these amendments often fail to achieve the expected results in terms of reduction effect and persistence in addressing the problem of the accumulation of reducing substances in low-yield paddy field soil exacerbated by straw return. Therefore, it is necessary to develop a multifunctional, high-efficiency composite soil-reducing agent that can promote straw decomposition, increase dissolved oxygen supply, improve redox potential and pH value, reduce the accumulation of reducing substances, and provide essential nutrients for rice to promote crop growth, thereby achieving the goal of precision agriculture. Summary of the Invention

[0004] This invention provides a compound reducing agent for low-yield paddy field soil, along with its preparation and application methods. This reducing agent aims to address problems such as reduced dissolved oxygen, decreased redox potential and pH, and the accumulation of reducing substances affecting rice development caused by straw return to the field in low-yield paddy fields. By applying the compound reducing agent during straw return, the soil's redox potential and pH can be increased, effectively reducing the accumulation of reducing substances. Simultaneously, it accelerates straw decomposition, replenishes elements such as silicon, magnesium, and zinc, promotes rice growth, and increases crop yield.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A composite soil reducing agent for paddy fields comprises the following six raw materials: by weight, 30-40 parts lime, 20-40 parts maifanite, 20-30 parts magnesium-based hydrotalcite, 5-15 parts calcium peroxide, 1-5 parts metal-organic framework material MOF-5, and 0.5-2 parts carboxymethyl cellulose. Preferably, the composition is 35 parts lime, 30 parts maifanite, 25 parts magnesium-based hydrotalcite, 10 parts calcium peroxide, 4 parts metal-organic framework material MOF-5, and 1 part carboxymethyl cellulose.

[0007] A method for preparing a composite agent for reducing the reducing properties of paddy field soil includes the following steps:

[0008] (1) Crushing and sieving: Lime, maifanite, magnesium-based hydrotalcite, calcium peroxide and metal-organic framework material MOF-5 are crushed and dried, and then passed through a 100-150 mesh sieve.

[0009] (2) Mix evenly: Take 30-40 parts of lime, 20-40 parts of maifanite, 20-30 parts of magnesium-based hydrotalcite, 5-15 parts of calcium peroxide and 1-5 parts of metal-organic framework material MOF-5 from step (1) and mix evenly; take 0.5-2 parts of carboxymethyl cellulose, dissolve it in water, and then spray it evenly on the surface of the material to ensure uniform distribution;

[0010] (3) Ultrasonic granulation: The material that was mixed evenly in step (2) is added to an ultrasonic granulation device. Ultrasonic waves accelerate the uniform contact and adhesion between the materials to granulate the composite granulator. Preferably, the particle size is 2.1-3.4 mm to facilitate mechanical or drone application.

[0011] Application method of compound soil reducing agent for paddy fields: Analyze the main soil obstacle types to determine the appropriate application rate of the compound reducing agent. The application rate is 20-30 kg / mu for cold-latent soils, 40-50 kg / mu for clay soils, and 50-70 kg / mu for toxic soils. The compound reducing agent is then incorporated into the soil along with straw. After flooding the field for 3 days, fertilizer is applied and rice is transplanted. This reducing agent has a significant and long-lasting effect, making it suitable for paddy fields under long-term flooding conditions where straw decomposition and reducing substances accumulate.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. This invention selects lime, maifanite, magnesium-based hydrotalcite, and calcium peroxide as the main high-efficiency raw materials, which synergistically exert their effects of increasing oxygen, regulating soil pH, reducing reducing substances, promoting straw decomposition, and promoting rice growth. The silicon in maifanite undergoes a redox reaction with calcium peroxide, further enhancing the soil's oxygenation capacity and pH regulation, accelerating the decomposition of organic matter, and its silicon element promotes root development. Magnesium-based hydrotalcite has a layered structure, enhancing soil aeration, and its slow-release calcium and magnesium ions, together with other materials, form a lasting effect in reducing reducing substances.

[0014] 2. The metal-organic framework material MOF-5 is a porous material that can react with components in lime, maifanite, magnesium-based hydrotalcite, and calcium peroxide to form a new microporous network structure. This significantly enhances the soil's oxygenation capacity and prolongs the oxygen release time from calcium peroxide, resulting in a sustained oxygenation effect. It is particularly suitable for paddy fields, which are often flooded, providing a continuous and favorable oxidative environment for rice roots. The zinc element in MOF-5 combines with the magnesium element in magnesium-based hydrotalcite to improve the photosynthetic efficiency and stress resistance of rice. As a metal-organic coordination bond material, MOF-5, in synergy with the alkaline environment of lime, forms a microenvironment that facilitates calcium ion release, resulting in a more lasting and stable pH regulation effect on the soil.

[0015] 3. This invention uses carboxymethyl cellulose as a binder, which can help form a porous structure during the granulation process, regulate the surface tension of the particles, and work together with the metal-organic framework material MOF-5 to increase the mechanical strength and stability of the particles.

[0016] 4. The present invention can not only disperse particles more uniformly through ultrasonic granulation, but also form more microporous structures on the surface of composite reducing agent particles, thereby improving their reactivity.

[0017] 5. This invention has determined the appropriate application period of the compound soil conditioner and the recommended dosage based on the type of soil obstacle in paddy fields through experiments. Compared with existing soil conditioners on the market, this compound soil conditioner is not only more effective and longer-lasting in increasing dissolved oxygen, oxidation-reduction potential and pH value, reducing reducing substances in the soil and reducing fertilizer loss, but also has a better effect in promoting straw decomposition and increasing rice yield. Attached Figure Description

[0018] Figure 1 The figures show the decomposition of straw by the compound straw reducing agent and other soil conditioners in Example 6 28 days after straw return to the field (treatments 45-50). Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0020] Example 1: Comparative Test of Soil Reducing Substances Generation and High-Efficiency Scaling Agent Materials under Straw Return to Field

[0021] Take a flowerpot with a diameter of 25cm and a height of 40cm, and fill it with 4kg of dry soil. Weigh out 50g of each of the following: calcium peroxide, magnesium peroxide, sodium peroxide, lime powder, dolomite powder, maifanite powder, diatomaceous earth, magnesium-based hydrotalcite powder, and serpentine powder.

[0022] Fresh straw (80% moisture content) was plowed into the soil and watered to a depth of 4 cm. Fertilizer was applied on the third day, and rice seedlings were transplanted. Treatments were set up as follows: Treatment 1: Control, no straw added; Treatment 2: Straw added, no straw reduction agent applied; Treatments 3-5: Straw added, with 0.1g of each of the following straw reduction agents applied: calcium peroxide, magnesium peroxide, and sodium peroxide, respectively; Treatments 6-11:

[0023] Straw was added, and 1g of each of the following materials was applied as a soil reducing agent: lime powder, dolomite powder, maifanite powder, diatomaceous earth, magnesium-based hydrotalcite powder, and serpentine powder; each treatment was repeated in triplicate. On days 4 and 28, dissolved oxygen (measured using an HED-S06 multi-parameter water quality analyzer), oxidation-reduction potential (measured using an HD-QX6550 intelligent portable oxidation-reduction potential meter (saturated calomel electrode)), pH value, and total reducing agent content (obtained by aluminum sulfate extraction) were measured in the soil.

[0024] —Determination by potassium dichromate oxidation method), active reducing substances (determination by potassium permanganate titration method), Fe 2+ Content (determined by the o-phenanthroline colorimetric method) and Mn 2+ The content (determined by potassium periodate colorimetric method) was measured on the 28th day of rice dry weight.

[0025] Application effects: Compared with no straw addition, straw addition reduced dissolved oxygen content, redox potential, and pH.

[0026] The values ​​increased the amount of reducing substances (35.7%-77.0%), indicating that straw return to the field led to the accumulation of reducing substances in the soil. All reducing agent materials reduced the amount of reducing substances. Compared with no reducing agent added, treatment 3 showed the greatest increase in dissolved oxygen (22.4%-24.1%), while treatments 6 and 10 showed the best effects in increasing pH (6.9%-8.6%) and reducing the amount of reducing substances (33.2%-38.5%). Treatment 8 showed the largest increase in rice biomass (10.4%).

[0027] Therefore, in this embodiment, calcium peroxide, lime, maifanite, and magnesium-based hydrotalcite are determined to be the best reducing agent materials.

[0028] Table 1. Production of reducing substances in paddy field soil and the reduction effect of reducing agent materials after straw return.

[0029]

[0030] Table 2. Effects of the rice growth-promoting agent on the reduction of plant growth.

[0031]

[0032] Example 2: Test on the appropriate ratio of main components of a compound soil reducing agent for paddy fields

[0033] Using different proportions of calcium peroxide, lime, maifanite and magnesium-based hydrotalcite as composite reducing agent materials, a pot experiment was conducted as in Example 1. 1g of each proportion of the composite reducing agent was mixed with 50g of fresh straw (80% moisture content) and compacted into the soil, followed by watering to a 4cm water layer. Fertilizer was applied and rice was transplanted on the third day. Treatment 12: No composite reducing agent applied; Treatment 13: A composite reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:2:2:5 was applied; Treatment 14: A composite reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:2:5:2 was applied; Treatment 15: A composite reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:2:3:4 was applied; Treatment 16: A composite reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:2:4:3 was applied; Treatment 17: A composite reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:3:2 was applied. Treatment 18: A compound reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:3:3:3 was applied; Treatment 19: A compound reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:3:4:2 was applied; Treatment 20: A compound reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:4:2:3 was applied; Treatment 21: A compound reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:4:3:2 was applied; Treatment 22: A compound reducing agent with a mass ratio of calcium peroxide:lime:maifanite:magnesium-based hydrotalcite of 1:5:2:2 was applied. Each treatment was repeated in triplicate. Dissolved oxygen, redox potential, pH, total reducing substances, active reducing substances, and Fe were measured in the soil on days 4 and 28. 2+ Content and Mn 2+ The content was determined, and the dry weight of rice was measured on day 28.

[0034] Application effects: Compared with the untreated compound fertilizer, the application of the compound fertilizer increased dissolved oxygen content, oxidation-reduction potential, and pH value, reduced the amount of reducing substances, and promoted rice development. Among them, the fertilizer reduction effect of treatment 18-20 was obvious and lasted for a long time. The appropriate ratio of calcium peroxide, lime, maifanite and magnesium-based hydrotalcite was 1:3-4:2-4:2-3, at which time the fertilizer had a higher comprehensive effect.

[0035] Table 3. Effects of different composite reducing agent ratios on the reduction of soil reducing substances.

[0036]

[0037] Table 4. Effects of different composite soil reducing agent ratios on soil reducing substances reduction and rice growth.

[0038]

[0039] Example 3: Effect of metal-organic framework material MOF-5 on the function of composite scavenging agent

[0040] A composite slaking agent was prepared by adding a metal-organic framework (MOF-5). The composite slaking agent consisted of the following components by weight: 35 parts lime, 30 parts maifanite, 25 parts magnesium-based hydrotalcite, 10 parts calcium peroxide, and 1 part carboxymethyl cellulose. Treatments were set as follows: Treatment 23: no MOF-5 added; Treatment 24: 1 part MOF-5 added; Treatment 25: 2 parts MOF-5 added; Treatment 26: 3 parts MOF-5 added; Treatment 27: 4 parts MOF-5 added; Treatment 28: 5 parts MOF-5 added. The calcium peroxide, lime, maifanite, magnesium-based hydrotalcite, and MOF-5 were mixed evenly according to the above weight proportions. Carboxymethyl cellulose was then dissolved in water and sprayed evenly onto the material surface. The mixture was then granulated using ultrasonication to obtain composite slaking agent particles. The particle size was controlled within the range of 2.1-3.4 mm, and the particle strength was ≥14.1 N.

[0041] Take a flowerpot with a diameter of 25cm and a height of 40cm, fill it with 4kg of dry soil, add 1g of the prepared compound soil reducing agent and 50g of straw, plow it into the field, and irrigate to a water layer of 4cm. Then, fertilize and transplant rice on the 3rd day. Each treatment was repeated in three groups. Dissolved oxygen, pH value, and total reducing substances in the soil were measured on the 4th, 14th, and 28th days, and the dry weight of rice was measured on the 28th day.

[0042] The results showed that compared with the non-addition of metal-organic framework material MOF-5, the composite scavenging agent with added MOF-5 further increased dissolved oxygen content and pH value, reduced the amount of reducing substances, and promoted rice development. Among them, treatment 27-28 showed a significant scavenging effect, that is, when the amount of metal-organic framework material (MOF-5) reached 4-5 parts, the scavenging agent had a high comprehensive effect.

[0043] Table 5. Effects of different metal-organic framework (MOF-5) addition amounts on the efficacy of the sludge reduction agent.

[0044]

[0045] Example 4: Test on the Appropriate Application Period of the Compound Scaling Agent

[0046] Take a flowerpot with a diameter of 25cm and a height of 40cm, fill it with 4kg of dry soil, weigh out 1g of compound soil reducing agent (lime: maifanite: magnesium-based hydrotalcite: calcium peroxide: metal-organic framework material MOF-5: carboxymethyl cellulose in a mass ratio of 35:30:25:10:4:1) and 50g of straw, plow it into the field and irrigate to a water layer of 4cm. Set up treatments: treatment 29: fertilize and transplant rice on the same day as the compound soil reducing agent is applied; treatment 30: fertilize and transplant rice on the 1st day after the compound soil reducing agent is applied; treatment 31: fertilize and transplant rice on the 2nd day after the compound soil reducing agent is applied; treatment 32: fertilize and transplant rice on the 3rd day after the compound soil reducing agent is applied; treatment 33: fertilize and transplant rice on the 4th day after the compound soil reducing agent is applied; treatment 34: fertilize and transplant rice on the 5th day after the compound soil reducing agent is applied. Each treatment is repeated three times. Soil ammonia volatilization flux was measured on days 1, 3, 7, 15, and 30 after the application of the compound fertilizer. Rice tiller number and root activity were measured on days 15 and 30 (using the α-naphthylamine method).

[0047] The results showed that the soil ammonia volatilization flux was highest on the day of fertilization and transplanting, averaging 0.98 kg / hm². 2 / d, and then gradually decreased; in contrast, after the 3rd day, the difference in ammonia volatilization flux was not significant, all decreasing by more than 50%, while the number of rice tillers and root activity increased by 38.7%-43.7% and 44.0%-49.8%, respectively. This indicates that the compound reducing agent for reducing soil reducing substances of the present invention can prevent the risk of fertilizer efficiency loss when fertilized 3 days after application, and effectively promote rice root development.

[0048] Table 6. Effects of fertilization on soil ammonia volatilization flux after different days of compound ammonia reduction agent application (kg / hm²) 2 / d)

[0049]

[0050]

[0051] Table 7. Effects of fertilization on rice growth and root activity after different number of days following application of compound fertilizer reduction agent.

[0052]

[0053] Example 5: Recommended Dosage Test of Compound Sliming Agent for Paddy Soils with Different Obstacle Types

[0054] Field trials were conducted at three experimental sites: Wuxue and Shayang in Hubei Province, and Jinxian in Jiangxi Province. The soils were classified as cold-potential, cohesive, and toxic low-yield paddy soils, respectively. After the early rice harvest, 4m×8m plots were divided, and field ridges were repaired to prevent water and fertilizer cross-contamination. 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 kg of compound fertilizer (lime:maifanite:magnesium-based hydrotalcite:calcium peroxide:metal-organic framework material MOF-5:carboxymethyl cellulose in a mass ratio of 35:30:25:10:4:1) were weighed and incorporated into the field with straw, simulating application rates of 10, 20, 30, 40, 50, 60, 70, and 80 kg / mu. Treatment 35: no straw incorporation; Treatment 36: straw incorporation; Treatments 37-44: straw incorporation, with 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 kg of compound fertilizer added respectively. Rice was transplanted 3 days after the application of the fertilizer and irrigation. Each treatment was replicated in triplicate. Dissolved oxygen, pH, and reducing agent content in the soil were measured on day 14, and yield was determined at the time of late rice harvest.

[0055] The results showed that returning straw to the field reduced dissolved oxygen and pH in paddy fields, while increasing the amount of reducing substances in the soil. The compound soil reducing agent had the effects of increasing oxygen, raising pH, reducing the amount of reducing substances, and promoting straw decomposition, further increasing rice yield. In toxic soils, when the compound soil reducing agent was applied at a rate of 50-70 kg / mu, it had a significant effect on increasing dissolved oxygen and pH in paddy fields and reducing the amount of reducing substances, at 36.0%-39.2%, 20.1%-23.4%, and 32.9%-42.4%, respectively, resulting in an increase in rice yield of 18.5%-23.3%. In clay soils, when the compound soil reducing agent was applied at a rate of 40-50 kg / mu, it had a significant effect on increasing dissolved oxygen and pH in paddy fields and reducing the amount of reducing substances, at 65.1%-66.7%, 15.5%-16.5%, and 33.8%-41.0%, respectively, resulting in an increase in rice yield of 11.0%-14.6%. In cold-potential soils, when the compound reducing agent is applied at a rate of 20-30 kg / mu, it significantly increases dissolved oxygen and pH levels in paddy fields, and reduces reducing substances by 26.1%-30.6%, 12.2%-13.0%, and 43.1%-34.5%, respectively, resulting in a 16.8%-23.5% increase in rice yield. These results demonstrate that the compound reducing agent for paddy soil reducing substances developed in this invention is suitable for soils with different obstacle types, and has the ability to reduce reducing substances and increase yield.

[0056] Table 8. Effects of application of compound soil mitigation agents on dissolved oxygen, pH, and reducing agent levels in paddy fields for different obstacle types (Day 14)

[0057]

[0058] Table 9. Effects of compound fertilizer application on rice yield and biomass.

[0059]

[0060] Example 6: Comparative test of the efficacy of the composite soil conditioner developed in this invention with other soil conditioners.

[0061] Field trials were conducted in clayey soil (Shayang) with a soil pH of 5.7. After the early rice harvest, 4m × 8m plots were divided, and field ridges were repaired to prevent water and fertilizer cross-contamination. Two kg each of the following soil conditioners were weighed: a compound soil conditioner (lime: maifanite: magnesium-based hydrotalcite: calcium peroxide: metal-organic framework material MOF-5: carboxymethyl cellulose in a mass ratio of 35:30:25:10:4:1), Tian Shifu soil conditioner (main components: CaO, MgO, K2O, SiO2), and Lvyuanbei soil conditioner (main component: CaO, MgO, K2O, SiO2). Oyster shells (calcined at high temperature), Dierkang soil conditioner (main components: CaO, SiO2, MgO), and Shenzhi soil conditioner (main components: maifanite, actinolite, stalactite, calcite) were used in combination with straw and incorporated into the field, simulating an application rate of 40 kg / mu. Treatment 45: no soil conditioner added; Treatments 46-50: 2 kg of compound soil conditioner, Tian Shifu, Lvyuanbei, Dierkang, and Shenzhi soil conditioner were added respectively. Each treatment was replicated in triplicate. Dissolved oxygen, pH, and reducing agent content in the soil were measured on days 4, 14, and 28. Yield was measured at the late rice harvest.

[0062] The results showed that, compared with other conditioners, the soil compound reducing agent developed in this invention had a greater and longer-lasting effect on increasing dissolved oxygen (47.3%-93.0%) and pH (9.3%-12.3%), and on reducing substances (50.9%-52.6%). The rice yield increased by the largest amount (16.6%) with the compound reducing agent developed in this invention, compared to a yield increase of 4.7-10.4% with other conditioners. These results indicate that the soil compound reducing agent of this invention has a more significant effect on promoting straw decomposition, reducing reducing substances, and increasing yield.

[0063] Table 10. Effects of different conditioner products on dissolved oxygen, pH, and reducing agent content in paddy fields.

[0064]

Claims

1. A composite agent for reducing reducing substances in paddy field soil, characterized in that, By weight, it is composed of the following 6 raw materials: 30-40 parts lime, 20-40 parts maifanite, 20-30 parts magnesium-based hydrotalcite, 5-15 parts calcium peroxide, 1-5 parts metal-organic framework material MOF-5, and 0.5-2 parts carboxymethyl cellulose.

2. The composite agent for reducing reducing substances in paddy field soil according to claim 1, characterized in that: 35 parts lime, 30 parts maifanite, 25 parts magnesium-based hydrotalcite, 10 parts calcium peroxide, 4 parts metal-organic framework material MOF-5, and 1 part carboxymethyl cellulose.

3. A method for preparing a composite reducing agent for reducing substances in paddy field soil, characterized in that, Includes the following steps: (1) Crushing and sieving: lime, maifanite, magnesium-based hydrotalcite, calcium peroxide and metal-organic framework material MOF-5 are crushed and dried respectively, and then passed through an 80-100 mesh sieve; (2) Mix evenly: Take 30-40 parts of lime, 20-40 parts of maifanite, 20-30 parts of magnesium-based hydrotalcite, 10-15 parts of calcium peroxide and 1-5 parts of metal-organic framework material MOF-5 from step (1) and mix evenly; take 0.5-2 parts of carboxymethyl cellulose, dissolve it in water, and then spray it evenly on the surface of the material to ensure uniform distribution; (3) Ultrasonic granulation: The material that was mixed evenly in step (2) is added to an ultrasonic granulation device. Ultrasonic waves accelerate the uniform contact and adhesion between the materials to obtain a composite granulator.

4. The preparation method according to claim 3, characterized in that, The particle size range of the composite reducing agent is 1.5-4.0 mm.

5. The method for applying the compound reducing agent for reducing substances in paddy field soil as described in claim 1, characterized in that: The dosage of compound soil reducing agent is 20-30 kg / mu for cold-potential soil, 40-50 kg / mu for clay soil, and 50-70 kg / mu for toxic soil. The compound soil reducing agent is then mixed with straw and incorporated into the soil. After irrigating the field for 3 days, fertilizer is applied and rice is transplanted.

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