Composite reducing agent for reducing substances in low-yield rice field soil

Abstract

The invention discloses a composite reducing agent for reducing substances in low-yield rice field soil, which comprises 30-40 parts of lime, 20-40 parts of medical stone, 20-30 parts of magnesium-based hydrotalcite, 5-15 parts of calcium peroxide, 1-5 parts of a metal organic framework material MOF-5 and 0.5-2 parts of carboxymethyl cellulose, and the proper dosage of the composite reducing agent is selected according to the type of main obstacles of the soil. And turning and pressing the composite reducing agent and straws into soil, irrigating and steeping the field for 3 days, and then fertilizing and transplanting rice. When the composite reducing agent is applied to the rice field, the content of dissolved oxygen can be increased through a synergistic effect, the pH value and the oxidation-reduction potential are improved, accumulation of reducing substances is reduced, straw decomposition can be accelerated, the problem of accumulation of the reducing substances for rice field straw decomposition is solved, and the rice field straw decomposition effect is improved. The fertilizer can also effectively relieve the fertilizer efficiency loss, provide necessary nutrient elements such as silicon, zinc and magnesium for rice, promote the growth and development of rice and comprehensively improve the productivity.

Description

Technical Field

[0001] The invention belongs to the technical field of soil reducing substances treatment after returning straw to low-yield paddy fields, and particularly relates to a composite reducing agent for reducing substances in low-yield paddy field soil. Background Art

[0002] The middle and lower reaches of the Yangtze River are one of the main rice producing areas in my country. The region implements a two-crop or three-crop planting system. However, due to the tight farming season, tight crop rotation, and large amount of straw returned to the field, the return of straw to the field after the early rice harvest faces many challenges. Especially in low-yield rice fields, according to the types of obstacles, there are mainly cold-potential, bonding, and toxic low-yield paddy soils. At this time, after the fresh straw is returned to the field, under high temperature and deep flooding conditions, coupled with the large amount of nitrogen fertilizer applied, its decomposition process consumes oxygen rapidly, and it is easy to form a reducing environment; in the early stage of returning rice straw to the field, the increase in oxygen consumption will lead to a decrease in dissolved oxygen in the water body. The long-term anaerobic environment will not only affect the redox potential of the soil, but also destroy the balance of iron, manganese, sulfur and nitrogen. In this environment, anaerobic microorganisms become the dominant flora, and reducing substances such as Fe(Ⅱ), Mn(Ⅱ), and H2S will accumulate rapidly in the soil, which will have a negative impact on the rice root system, reduce its vitality and inhibit the production of tillers. In addition, changes in soil pH and water quality can also have an adverse effect on the growth of rice seedlings.

[0003] In order to improve the above situation, there are currently a variety of materials and technologies for improving paddy field soil on the market. For example, oxygenators are mainly made of calcium peroxide and sodium percarbonate, while other improvers include inorganic materials such as lime, oyster shells, fly ash, and organic materials such as livestock and poultry manure, humic acid, and peat, as well as artificial synthetic improvers such as polyacrylamide, and natural synthetic copolymers such as humic acid-polyacrylic acid, and even biological improvers such as microbial inoculants. However, these improvers often fail to achieve the expected results in terms of reduction effect and durability in solving the problem of aggravating the accumulation of reducing substances in low-yield paddy field soil after returning straw to the field. Therefore, it is necessary to develop a multifunctional and efficient composite reducer that can not only promote straw decomposition, increase dissolved oxygen supply, increase redox potential and pH value, and reduce the accumulation of reducing substances, but also provide rice with essential nutrients to promote crop growth, so as to achieve the goal of precision agriculture. Summary of the invention

[0004] The present invention provides a composite reducing agent for reducing substances in low-yield paddy soil, and a preparation method and application method thereof. The reducing agent is intended to solve the problems of reduced dissolved oxygen, decreased redox potential and pH value, and reduced substance accumulation affecting rice development caused by returning straw to the field in low-yield paddy fields. By applying the composite reducing agent when returning straw to the field, the redox potential and pH value of the soil can be increased, the accumulation of reducing substances can be effectively reduced, and the decomposition of straw can be accelerated, elements such as silicon, magnesium and zinc can be supplemented, rice growth can be promoted, and crop yield can be increased.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

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

[0007] A method for preparing a composite reducing agent for reducing substances in paddy soil comprises the following steps:

[0008] (1) Grinding and sieving: Grind and dry lime, medical stone, magnesium-based hydrotalcite, calcium peroxide and metal organic framework material MOF-5 respectively, and pass through a 100-150 mesh sieve;

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

[0010] (3) Ultrasonic granulation: The materials uniformly mixed in step (2) are added to an ultrasonic granulation device, and the uniform contact and adhesion between the materials are accelerated by ultrasound to obtain a composite reducing agent by granulation; preferably, the particle size is 2.1-3.4 mm to facilitate mechanical or drone spreading.

[0011] Application method of composite reducer for reducing substances in paddy soil: Analyze the main obstacle types of soil, determine the appropriate application amount of composite reducer, the amount of composite reducer for cold potential soil is 20-30kg / mu, the amount of composite reducer for bonding soil is 40-50kg / mu, and the amount of composite reducer for toxic soil is 50-70kg / mu. Press the composite reducer and straw into the soil, irrigate the field for 3 days, and then fertilize and transplant rice. The reducer has significant effect and lasts longer, and is suitable for the environment where straw decomposes and reduces substances accumulate under long-term flooding in paddy fields.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The present invention selects lime, medical stone, magnesium-based hydrotalcite and calcium peroxide as the main efficient raw materials, which can cooperate to increase oxygen, regulate soil pH and reduce reducing substances, promote straw decomposition and rice growth. The silicon in the medical stone and calcium peroxide produce redox reaction, further improve the oxygenation capacity and pH regulating effect of the soil, accelerate the decomposition of organic matter, and its silicon element can promote root development. The magnesium-based hydrotalcite has a layered structure, strengthens the air permeability of the soil, and its slow-release calcium, magnesium ions and other materials form a lasting reducing substance reduction effect.

[0014] 2. The metal-organic framework material MOF-5 is a porous material that can also react with components in lime, medical stone, magnesium-based hydrotalcite and calcium peroxide to form a new microporous network structure, which can significantly enhance the soil's oxygenation capacity and prolong the oxygen release time in calcium peroxide, thereby forming a lasting oxygenation effect. It is particularly suitable for long-term flooding environments such as rice fields, providing a continuous good oxidation environment for rice roots; the zinc element of the metal-organic framework material MOF-5 combined with the magnesium element in magnesium-based hydrotalcite can improve the photosynthesis efficiency and stress resistance of rice; MOF-5, as a metal-organic coordination bond material, synergistically forms a microenvironment with the alkaline environment of lime that helps release calcium ions, and its regulating effect on soil pH is more lasting and stable.

[0015] 3. The present invention uses carboxymethyl cellulose as a binder, which can help form a porous structure during the granulation process, adjust 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 the particles more evenly through ultrasonic granulation, but also form more microporous structures on the surface of the composite reducing agent particles, thereby improving its reaction activity.

[0017] 5. The present invention has determined through experiments the appropriate application period of the composite reducing agent and the recommended dosage according to the type of paddy field soil obstacles, and compared it with the existing soil conditioners on the market. The composite reducing agent is not only more significant and lasting in increasing dissolved oxygen, redox potential and pH value, reducing reducing substances in the soil and reducing fertilizer loss, but also more effective in promoting straw decomposition and increasing rice yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The decomposition of the composite reducing agent and other soil conditioners on the straw 28 days after the straw was returned to the field in Example 6 (treatments 45-50 respectively). DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with specific embodiments. The specific embodiments described herein are only used to explain the present invention rather than to limit the present invention.

[0020] Example 1: Comparison test of the production of soil reducing substances and high-efficiency reduction agent materials under straw return to the field

[0021] Take a flower pot with a diameter of 25 cm and a height of 40 cm and fill it with 4 kg of dry soil. Weigh calcium peroxide, magnesium peroxide, sodium peroxide, lime powder, dolomite powder, medical stone powder, diatomaceous earth, magnesium-based hydrotalcite powder, serpentine powder and 50 g of

[0022] Fresh straw (80% moisture content) was pressed into the soil and watered to a 4 cm water layer, and then fertilized and transplanted rice on the third day. Treatment 1: control, no straw addition; Treatment 2: straw addition, no reduction agent material was applied; Treatments 3-5: straw addition, 0.1 g of reduction agent materials calcium peroxide, magnesium peroxide, and sodium peroxide were applied respectively; Treatments 6-11:

[0023] Straw was added, and 1g of the reducing agent materials lime powder, dolomite powder, medical stone powder, diatomaceous earth, magnesium-based hydrotalcite powder, and serpentine powder were applied respectively; each treatment was repeated three times. On the 4th and 28th days, the dissolved oxygen in the soil (determined by HED-S06 multi-parameter water quality detector), redox potential (determined by HD-QX6550 intelligent portable redox potential meter (saturated calomel electrode)), pH value, and total amount of reducing substances (determined by aluminum sulfate extraction) were measured.

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

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

[0026] The value of straw returned to the field increased the amount of reducing substances (35.7%-77.0%), indicating that returning straw to the field caused the accumulation of reducing substances in the soil. All the reducing agent materials can reduce the amount of reducing substances. Compared with the addition of no reducing agent materials, treatment 3 has the largest increase in dissolved oxygen (22.4%-24.1%), treatments 6 and 10 have the best effect on increasing pH value (6.9%-8.6%) and reducing the amount of reducing substances (33.2%-38.5%), and treatment 8 has the largest increase in rice biomass (10.4%).

[0027] Therefore, this embodiment determines that calcium peroxide, lime, medical stone and magnesium-based hydrotalcite are the best reducing agent materials.

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

[0029]

[0030] Table 2 The reduction and rice growth promotion effects of the reduction agent materials

[0031]

[0032] Example 2 Test on the suitable ratio of main components of composite reducing agent for reducing substances in paddy soil

[0033] A potted plant experiment as in Example 1 was carried out using different proportions of calcium peroxide, lime, medical stone and magnesium-based hydrotalcite as composite reducing agent materials. 1 g of the composite reducing agent in each proportion was mixed with 50 g of fresh straw (80% moisture content) and pressed into the soil and watered to a 4 cm water layer. Fertilizer was then applied and rice was transplanted on the third day. Treatment 12: No composite reducing agent was applied; Treatment 13: A composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:2:2:5 was applied; Treatment 14: A composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:2:5:2 was applied; Treatment 15: A composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:2:3:4 was applied; Treatment 16: A composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:2:4:3 was applied; Treatment 17: A composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:3:2 was applied :4 composite reducing agent; Treatment 18: Apply a composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:3:3:3; Treatment 19: Apply a composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:3:4:2; Treatment 20: Apply a composite reducing agent with a mass ratio of calcium oxide: lime: medical stone: magnesium-based hydrotalcite of 1:4:2:3; Treatment 21: Apply a composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:4:3:2; Treatment 22: Apply a composite reducing agent with a mass ratio of calcium peroxide: lime: medical stone: magnesium-based hydrotalcite of 1:5:2:2. Each treatment was repeated in three groups. Dissolved oxygen, redox potential, pH value, total amount of reducing substances, active reducing substances, Fe in the soil were measured on the 4th and 28th days. 2+ Content and Mn 2+ The dry weight of rice was measured on the 28th day.

[0034] Application effect: Compared with no application of composite reducing agent, the application of composite reducing agent increased the dissolved oxygen content, redox potential, pH value, reduced the amount of reducing substances, and promoted rice development; among them, the reducing effect of treatment 18-20 was obvious and lasted for a long time, that is, the appropriate ratio of calcium peroxide, lime, medical stone and magnesium-based hydrotalcite was 1:3-4:2-4:2-3, and the reducing agent at this time had a higher comprehensive effect.

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

[0036]

[0037] Table 4 Effects of different ratios of composite reducing agents 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 abatement agent

[0040] Add metal organic framework material MOF-5 on the basis of composite reducing agent, the composite reducing agent is composed of the following components: by weight, 35 parts of lime, 30 parts of medical stone, 25 parts of magnesium-based hydrotalcite, 10 parts of calcium peroxide, 1 part of carboxymethyl cellulose, set treatment 23: no MOF-5 added, treatment 24: add 1 part of MOF-5, treatment 25: add 2 parts of MOF-5, treatment 26: add 3 parts of MOF-5, treatment 27: add 4 parts of MOF-5, treatment 28: add 5 parts of MOF-5. Mix calcium peroxide, lime, medical stone, magnesium-based hydrotalcite and metal organic framework material MOF-5 evenly according to the above weight parts, then dissolve carboxymethyl cellulose in water, spray evenly on the surface of the material, and obtain composite reducing agent particles by ultrasonic granulation. The granulation particle size range is controlled at 2.1-3.4mm, and the particle strength is ≥14.1N.

[0041] A flower pot with a diameter of 25 cm and a height of 40 cm was taken, filled with 4 kg of dry soil, 1 g of the composite reducing agent prepared above and 50 g of straw were taken, turned over and returned to the field and watered to a 4 cm water layer, and then fertilized and transplanted rice on the 3rd day. Three groups of replicates were performed for each treatment. The dissolved oxygen, pH value, and total amount of 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 treatment without adding metal organic framework material MOF-5, the composite reducing agent with added MOF-5 further increased the dissolved oxygen content and pH value, reduced the amount of reducing substances, and promoted the development of rice; among them, the reducing effect of treatment 27-28 was obvious, that is, when the amount of metal organic framework material (MOF-5) reached 4-5 parts, the reducing agent had a higher comprehensive effect.

[0043] Table 5 Effect of different metal organic framework material MOF-5 addition amounts on the efficacy of the abatement agent

[0044]

[0045] Example 4 Test on the Suitable Application Period of Composite Subsidy Agent

[0046] Take a flower pot with a diameter of 25 cm and a height of 40 cm, fill it with 4 kg of dry soil, weigh 1 g of composite reducing agent (the mass ratio of lime: medical stone: magnesium-based hydrotalcite: calcium peroxide: metal organic framework material MOF-5: carboxymethyl cellulose is 35:30:25:10:4:1) and 50 g of straw, turn it over and return it to the field, and irrigate it to a 4 cm water layer. Set treatment 29: fertilize and transplant rice on the day of applying the composite reducing agent, treatment 30: fertilize and transplant rice on the first day after applying the composite reducing agent, treatment 31: fertilize and transplant rice on the second day after applying the composite reducing agent, treatment 32: fertilize and transplant rice on the third day after applying the composite reducing agent, treatment 33: fertilize and transplant rice on the fourth day after applying the composite reducing agent, treatment 34: fertilize and transplant rice on the fifth day after applying the composite reducing agent, and each treatment is repeated three times. The soil ammonia volatilization flux was measured on the 1st, 3rd, 7th, 15th and 30th day after the application of the composite ammonia reducing agent, and the rice tiller number and root activity (determined by α-naphthylamine method) were measured on the 15th and 30th day.

[0047] The results showed that the soil ammonia volatilization flux of the fertilized and transplanted soil on the day of the abatement application was the highest with an average of 0.98 kg / hm 2 / d, and then gradually decreased; in contrast, after the third day, the ammonia volatilization flux of fertilization was not much different, and all decreased by more than 50%, and the number of rice tillers and root activity increased by 38.7%-43.7% and 44.0%-49.8%, respectively. This shows that the composite reducing agent for reducing substances in paddy soil of the present invention can prevent the risk of fertilizer loss and effectively promote the development of rice root system by fertilizing 3 days after application.

[0048] Table 6 Effect of fertilization on soil ammonia volatilization flux after application of composite abatement agent at different days (kg / hm 2 / d)

[0049]

[0050]

[0051] Table 7 Effects of fertilization on rice growth and root activity after application of composite reducing agent at different days

[0052]

[0053] Example 5 Test on the recommended dosage of composite abatement agent for paddy field soils with different obstacle types

[0054] Field trials were conducted at three test sites in Hubei Wuxue, Shayang and Jiangxi Jinxian, using low-yield paddy soils of the cold potential type, adhesive type and toxic type, respectively. After the early rice was harvested, the 4m×8m plot was divided, the ridges were repaired to prevent water and fertilizer from flowing, and 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 kg of composite reducing agent (the mass ratio of lime: medical stone: magnesium-based hydrotalcite: calcium peroxide: metal organic framework material MOF-5: carboxymethyl cellulose was 35:30:25:10:4:1) was weighed and returned to the field with straw, simulating the application of 10, 20, 30, 40, 50, 60, 70, and 80 kg / mu of composite reducing agent; treatment 35: no straw returned to the field; treatment 36: straw returned to the field; treatments 37-44: straw returned to the field, adding 0.5, 1, 1.5, 2, 2.5, 3, 3.5, and 4 kg of composite reducing agent respectively. Fertilizer and transplant rice were applied on the third day after the reducing agent was applied to irrigate the field, and three groups of replicates were performed for each treatment. The dissolved oxygen, pH value, and amount of reducing substances in the soil were measured on the 14th day, and the yield was measured when the late rice was harvested.

[0055] The results showed that returning straw to the field reduced the dissolved oxygen and pH value of the paddy field and increased the amount of soil reducing substances; the composite reducing agent had the effects of increasing oxygen, raising the pH value, reducing the amount of reducing substances and promoting the decomposition of straw, further increasing the rice yield. In toxic soil, when the composite reducing agent was used at a dosage of 50-70 kg / mu, the effect of increasing the dissolved oxygen and pH value of the paddy field and reducing the amount of reducing substances was greater, which were 36.0%-39.2%, 20.1%-23.4% and 32.9%-42.4% respectively, and the rice yield increased by 18.5%-23.3%. In adhesive soil, when the composite reducing agent was used at a dosage of 40-50 kg / mu, the effect of increasing the dissolved oxygen and pH value of the paddy field and reducing the amount of reducing substances was greater, which were 65.1%-66.7%, 15.5%-16.5% and 33.8%-41.0% respectively, and the rice yield increased by 11.0%-14.6%. In cold latent soil, when the dosage of the composite reducing agent is 20-30 kg / mu, the effect of increasing the dissolved oxygen and pH value of the paddy field and reducing the amount of reducing substances are 26.1%-30.6%, 12.2%-13.0% and 43.1%-34.5% respectively, and the rice yield increases by 16.8%-23.5%. The above results show that the composite reducing agent for reducing substances in paddy soil developed by the present invention is suitable for soils of different barrier types and has the ability to reduce reducing substances and increase production.

[0056] Table 8 Effects of application of soil composite reducers of different obstacle types on dissolved oxygen, pH and reducing substances in paddy fields (14th day)

[0057]

[0058] Table 9 Effects of compound reducing agent application on rice yield and biomass

[0059]

[0060] Example 6 Comparative test of the efficacy of the composite reducing agent developed by the present invention and other soil conditioners

[0061] Field tests were conducted in cohesive soil (Shayang) with a soil pH of 5.7. After early rice harvest, 4m×8m plots were divided, and the ridges were repaired to prevent water and fertilizer from flowing into the field. 2kg of composite abatement agent (the mass ratio of lime: medical stone: magnesium-based hydrotalcite: calcium peroxide: metal organic framework material MOF-5: carboxymethyl cellulose was 35:30:25:10:4:1), Tianshifu soil conditioner (the main components are: CaO, MgO, K2O, SiO2), and Luyuanbei soil conditioner (the main components are: Ca O, oyster shells calcined at high temperature), Dierkang soil conditioner (main components: CaO, SiO2, MgO), Shenzhi soil conditioner (main components: medical stone, actinolite, stalactite, calcite) and straw were turned over and returned to the field, simulating an application rate of 40kg / mu; treatment 45: no soil conditioner was added; treatments 46-50: 2kg of composite reduction agent, Tianshifu, Luyuanbei, Dierkang and Shenzhi soil conditioner were added respectively. Each treatment was repeated in three groups. The dissolved oxygen, pH value and amount of reducing substances in the soil were measured on the 4th, 14th and 28th days, and the yield was measured when the late rice was harvested.

[0062] The results show that compared with other conditioning agents, the soil composite reduction agent developed by the present invention has a greater effect on improving dissolved oxygen (47.3%-93.0%) and pH value (9.3%-12.3%) and reducing the effect of reducing substances (50.9%-52.6%), and the duration is longer; the rice yield increase of the composite reduction agent developed by the present invention is up to 16.6%, and the yield increase is 4.7-10.4% points higher than other conditioning agents. The above results show that the soil composite reduction agent of the present invention has more significant effects on promoting straw decay, reducing reducing substances and increasing yield.

[0063] Table 10 Effects of different conditioner products on dissolved oxygen, pH and reducing substances in rice fields

[0064]

Claims

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

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

3. A method for preparing a composite reducing agent for reducing substances in paddy soil, characterized in that: The following steps are involved: (1) Grinding and sieving: Grind and dry lime, medical stone, magnesium-based hydrotalcite, calcium peroxide and metal organic framework material MOF-5 respectively, and pass through a 80-100 mesh sieve; (2) Mixing uniformly: Take 30-40 parts of lime crushed in step (1), 20-40 parts of medical stone, 20-30 parts of magnesium-based hydrotalcite, 10-15 parts of calcium peroxide and 1-5 parts of metal organic framework material MOF-5 and mix them uniformly; take 0.5-2 parts of carboxymethyl cellulose and dissolve it in water, and then evenly spray it on the surface of the material to ensure uniform distribution; (3) Ultrasonic granulation: The materials uniformly mixed in step (2) are added to the ultrasonic granulation equipment, and the uniform contact and adhesion between the materials are accelerated by ultrasound to obtain the composite reducing agent by granulation.

4. The preparation method according to claim 3, characterized in that: The particle size range is 1.5-4.0 mm.

5. The method for applying the composite reducing agent for reducing substances in paddy soil according to claim 1, characterized in that: The dosage of the composite reducer for cold potential soil is 20-30 kg / mu, the dosage of the composite reducer for adhesive soil is 40-50 kg / mu, and the dosage of the composite reducer for toxic soil is 50-70 kg / mu. The composite reducer and straw are pressed into the soil, and the field is irrigated and soaked for 3 days before fertilizing and transplanting rice.

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