Composite cadmium-reducing conditioner based on radix puerariae residue and wormcast and application method

Abstract

The invention discloses a compound cadmium-reducing conditioner based on radix puerariae residue and wormcast and an application method. The cadmium-reducing conditioner comprises the following components in parts by mass: 35-40 parts of oyster shell powder, 30-45 parts of radix puerariae residue and wormcast, 3-5 parts of zinc fulvic acid, 8-10 parts of sodium sulfide and 3-5 parts of manganese sulfate. The cadmium-reducing conditioner is applied to soil before plowing of rice, plowing is performed after standing, and then the rice is transplanted; the earthworm cast is used for activating organic matter components in the radix puerariae residues, the earthworms are used for removing cadmium in the radix puerariae residues, active components in the radix puerariae residues and the earthworm cast and active components such as amino acid in the oyster shell powder act together with zinc fulvic acid, manganese fertilizer and sodium sulfide, and the oyster shell powder and the radix puerariae residues and the earthworm cast are adsorbed and degraded, so that the cadmium-rich organic fertilizer is obtained. The content of cadmium in the brown rice can be synergistically reduced to about 0.1 mg / kg; the operation is simple, and the raw materials are solid wastes and are easily available.

Description

Technical Field

[0001] The invention relates to the technical field of agriculture, and in particular to a composite cadmium-reducing conditioning agent based on kudzu residue and earthworm castings and an application method thereof. Background Art

[0002] The cadmium element has extremely high mobility and bioavailability in the soil environment, making it extremely easy for crops to absorb and accumulate cadmium during their growth process. It then passes through the food chain and eventually enters the human body, posing extremely serious potential hazards to human health. At present, there are a variety of technical means developed for the treatment of soil cadmium pollution. However, each type of technology has obvious limitations. Chemical remediation methods, such as adding chemical modifiers to the soil, can change the occurrence form of cadmium in the soil, thereby reducing its biological effectiveness. However, long-term reliance on such chemical means is likely to cause a series of negative effects such as soil acidification and compaction, seriously interfere with the normal activity of soil microorganisms, and cause irreversible damage to the balance and stability of the soil ecosystem. In the rice planting system, the soil is in a flooded anaerobic environment for a long time, which leads to rapid mineralization and decomposition of soil organic matter, resulting in a decrease in the soil's adsorption capacity for cadmium, which in turn increases the bioavailability of cadmium in rice, greatly increasing the potential risk of cadmium pollution in rice. Traditional cadmium pollution remediation technology has limitations in dealing with the complex problem of coexistence of soil organic matter deficiency and cadmium pollution, and it is difficult to achieve ideal results in rice planting soil management.

[0003] In this context, the present invention proposes a composite cadmium-reducing conditioner based on kudzu residue and earthworm castings; the conditioner can significantly enhance the soil's ability to adsorb and fix heavy metal cadmium, inhibit the activity and migration of cadmium from the source, and provide a scientific, efficient and environmentally friendly systematic solution for the treatment of cadmium pollution in rice-growing soil. Summary of the invention

[0004] The invention aims to overcome the disadvantages of the prior art and provides a composite cadmium-reducing conditioner based on kudzu residue earthworm castings and an application method. The mass ratio of each component in the cadmium-reducing conditioner is: 35-40 parts of oyster shell powder, 30-45 parts of kudzu residue earthworm castings, 3-5 parts of zinc fulvic acid, 8-10 parts of sodium sulfide and 3-5 parts of manganese sulfate. The cadmium-reducing conditioner is applied to the soil before the rice is ploughed, and the soil is ploughed after standing, and then the rice is transplanted. The invention uses earthworm castings to activate organic matter components in the kudzu residue, and uses earthworms to remove cadmium in the kudzu residue. Active ingredients in the kudzu residue earthworm castings and active ingredients such as amino acids in the oyster shell powder act together with zinc fulvic acid, manganese fertilizer and sodium sulfide, and the oyster shell powder and the kudzu residue earthworm castings are adsorbed and degraded, and soil organic matter is increased, so that the cadmium content of rice brown rice is synergistically reduced, and the cadmium content in the rice brown rice can be reduced to 0.1 mg / kg. The operation is simple and the raw materials are easy to obtain.

[0005] In order to achieve the above technical effects, the following technical solutions are adopted: A composite cadmium-reducing conditioner based on kudzu residue earthworm castings comprises the following components: Oyster shell powder, kudzu worm castings, zinc fulvic acid, sodium sulfide and manganese sulfate.

[0006] Furthermore, the composite cadmium-reducing conditioning agent component formula is: 35-40 parts of oyster shell powder, 30-45 parts of kudzu worm castings, 3-5 parts of zinc fulvic acid, 8-10 parts of sodium sulfide and 3-5 parts of manganese sulfate.

[0007] Furthermore, the mesh size of the oyster shell powder is 50-100 meshes.

[0008] Furthermore, the kudzu residue earthworm castings are dried and crushed into 80-150 meshes.

[0009] Furthermore, the zinc fulvic acid, sodium sulfide and manganese sulfate are crushed into 80-150 meshes.

[0010] Furthermore, the preparation method of the kudzu residue earthworm castings is specifically as follows: Step S1: taking fresh kudzu vine residue, adjusting the moisture content to 60%-70%, composting and fermenting for 20-25 days, turning the compost every 5-8 days, and controlling the compost temperature at 50-60°C; Step S2: placing earthworm seeds in the material obtained by fermentation in step S1, with a density of 10 to 15 earthworm seeds per kilogram of dry material, re-adding once every 20 days, and then separating the earthworms from the earthworm castings to obtain kudzu residue earthworm castings; Among them, the living temperature of earthworms is set at 25±10℃ to ensure the normal reproduction of earthworms.

[0011] Furthermore, the application method is specifically: The composite cadmium-reducing conditioner is applied to the soil before the rice is ploughed, and the soil is ploughed after being left to stand, and then the rice is transplanted.

[0012] Furthermore, the compound is applied to the soil 5-10 days before the rice is ploughed.

[0013] Furthermore, the dosage of the composite cadmium-reducing conditioner is 150-250 kg / mu.

[0014] The beneficial effects of the present invention are: The invention discloses a composite cadmium-reducing conditioner based on kudzu residue earthworm castings and an application method. The mass proportions of the components in the cadmium-reducing conditioner are as follows: 35-40 parts of oyster shell powder, 30-45 parts of kudzu residue earthworm castings, 3-5 parts of zinc fulvic acid, 8-10 parts of sodium sulfide and 3-5 parts of manganese sulfate. The cadmium-reducing conditioner is applied to the soil before ploughing the rice, and the soil is ploughed after standing, and then the rice is transplanted. The invention uses earthworm castings to activate organic matter components in the kudzu residue, and uses earthworms to remove cadmium in the kudzu residue. Active ingredients in the kudzu residue earthworm castings and active ingredients such as amino acids in the oyster shell powder act together with zinc fulvic acid, manganese fertilizer and sodium sulfide, and the oyster shell powder and the kudzu residue earthworm castings are adsorbed and degraded to increase soil organic matter, so as to synergistically reduce the cadmium content of rice brown rice, and the cadmium content in the rice brown rice can be reduced to 0.1 mg / kg. The operation is simple, and the raw materials are easy to obtain. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0018] The preparation method of the kudzu residue earthworm castings in the following examples and comparative examples is specifically as follows: Step S1: taking fresh kudzu vine residue, adjusting the moisture content to 65%, composting and fermenting for 25 days, turning the compost every 6 days, and controlling the compost temperature at 55°C; Step S2: placing earthworm seeds in the material obtained by fermentation in step S1, with a density of 12 earthworm seeds per kilogram of dry material, re-adding once every 20 days, and then separating the earthworms from the earthworm castings to obtain kudzu residue earthworm castings; Among them, the living temperature of earthworms is set at 28℃ to ensure the normal reproduction of earthworms.

[0019] Embodiment 1: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu worm castings of 150 mesh, 3 parts of zinc fulvic acid of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 1.

[0020] Embodiment 2: 40 parts of oyster shell powder of 50 mesh, 30 parts of kudzu worm castings of 80 mesh, 5 parts of zinc fulvic acid of 80 mesh, 10 parts of sodium sulfide of 80 mesh and 3 parts of manganese sulfate of 80 mesh were mixed evenly to obtain composite cadmium-reducing conditioning agent 2.

[0021] All comparative examples are based on Example 1.

[0022] Comparative Example 1: 80 parts of kudzu residue earthworm castings with a mesh size of 150, 3 parts of zinc fulvic acid with a mesh size of 150, 8 parts of sodium sulfide with a mesh size of 150 and 5 parts of manganese sulfate with a mesh size of 150 were uniformly mixed to obtain a composite cadmium-reducing conditioner 3.

[0023] Comparative Example 2: 80 parts of oyster shell powder of 100 mesh, 3 parts of zinc fulvic acid of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 4.

[0024] Comparative Example 3: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu worm castings of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 8 parts of manganese sulfate of 150 mesh were mixed evenly to obtain composite cadmium-reducing conditioning agent 5.

[0025] Comparative Example 4: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu worm castings of 150 mesh, 11 parts of zinc fulvic acid of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain composite cadmium-reducing conditioner 6.

[0026] Comparative Example 5: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu worm castings of 150 mesh, 8 parts of zinc fulvic acid of 150 mesh and 8 parts of sodium sulfide of 150 mesh were mixed evenly to obtain composite cadmium-reducing conditioning agent 7.

[0027] Comparative Example 6: 80 parts of kudzu residue earthworm castings with a mesh size of 150, 8 parts of sodium sulfide with a mesh size of 150 and 8 parts of manganese sulfate with a mesh size of 150 were mixed evenly to obtain a composite cadmium-reducing conditioner 8.

[0028] Comparative Example 7: 80 parts of kudzu residue earthworm castings with a mesh size of 150, 3 parts of zinc fulvic acid with a mesh size of 150 and 13 parts of manganese sulfate with a mesh size of 150 were mixed evenly to obtain a composite cadmium-reducing conditioner 9.

[0029] Comparative Example 8: 80 parts of kudzu worm castings with a mesh size of 150, 8 parts of zinc fulvic acid with a mesh size of 150, and 8 parts of sodium sulfide with a mesh size of 150 were uniformly mixed to obtain a composite cadmium-reducing conditioning agent 10.

[0030] Comparative Example 9: 80 parts of oyster shell powder of 100 mesh, 8 parts of sodium sulfide of 150 mesh and 8 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 11.

[0031] Comparative Example 10: 80 parts of oyster shell powder of 100 mesh, 3 parts of zinc fulvic acid of 150 mesh and 13 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 12.

[0032] Comparative Example 11: 80 parts of oyster shell powder of 100 mesh, 8 parts of zinc fulvic acid of 150 mesh, and 8 parts of sodium sulfide of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 13.

[0033] Comparative Example 12: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu worm castings of 150 mesh and 16 parts of manganese sulfate of 150 mesh were mixed evenly to obtain composite cadmium-reducing conditioner 14.

[0034] Comparative Example 13: 35 parts of oyster shell powder with a mesh size of 100, 45 parts of kudzu worm castings with a mesh size of 150 and 16 parts of sodium sulfide with a mesh size of 150 were mixed evenly to obtain a composite cadmium-reducing conditioning agent 15.

[0035] Comparative Example 14: 35 parts of oyster shell powder with a mesh size of 100, 45 parts of kudzu worm castings with a mesh size of 150, and 16 parts of zinc fulvic acid with a mesh size of 150 were mixed evenly to obtain a composite cadmium-reducing conditioning agent 16.

[0036] Comparative Example 15: 80 parts of 150-mesh kudzu residue earthworm castings and 16 parts of 150-mesh manganese sulfate were mixed evenly to obtain a composite cadmium-reducing conditioning agent 17.

[0037] Comparative Example 16: 80 parts of 150-mesh kudzu worm castings and 16 parts of 150-mesh sodium sulfide were mixed evenly to obtain a composite cadmium-reducing conditioner 18.

[0038] Comparative Example 17: 80 parts of 150-mesh kudzu residue earthworm castings and 16 parts of 150-mesh zinc fulvic acid were mixed evenly to obtain a composite cadmium-reducing conditioner 19.

[0039] Comparative Example 18: 80 parts of oyster shell powder with a mesh size of 100 and 16 parts of manganese sulfate with a mesh size of 150 were uniformly mixed to obtain a composite cadmium-reducing conditioning agent 20.

[0040] Comparative Example 19: 80 parts of oyster shell powder with a mesh size of 100 and 16 parts of sodium sulfide with a mesh size of 150 were mixed evenly to obtain a composite cadmium-reducing conditioning agent 21.

[0041] Comparative Example 20: 80 parts of oyster shell powder with a mesh size of 100 and 16 parts of zinc fulvic acid with a mesh size of 150 were mixed evenly to obtain a composite cadmium-reducing conditioner 22.

[0042] Comparative Example 21: 96 portions of 150-mesh kudzu residue earthworm castings were mixed evenly to obtain a composite cadmium-reducing conditioning agent 23.

[0043] Comparative Example 22: 96 parts of oyster shell powder with a mesh size of 100 were mixed evenly to obtain a composite cadmium-reducing conditioner 24.

[0044] Comparative Example 23: 35 parts of bentonite with a mesh size of 100, 45 parts of kudzu worm castings with a mesh size of 150, 3 parts of zinc fulvic acid with a mesh size of 150, 8 parts of sodium sulfide with a mesh size of 150 and 5 parts of manganese sulfate with a mesh size of 150 were uniformly mixed to obtain a composite cadmium-reducing conditioner 25.

[0045] Comparative Example 24: 35 parts of quicklime of 100 mesh, 45 parts of kudzu worm castings of 150 mesh, 3 parts of zinc fulvic acid of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 26.

[0046] Comparative Example 25: 35 parts of attapulgite with a mesh size of 100, 45 parts of kudzu worm castings with a mesh size of 150, 3 parts of zinc fulvic acid with a mesh size of 150, 8 parts of sodium sulfide with a mesh size of 150 and 5 parts of manganese sulfate with a mesh size of 150 were uniformly mixed to obtain a composite cadmium-reducing conditioner 27.

[0047] Comparative Example 26: 35 parts of oyster shell powder of 100 mesh, 45 parts of cow dung of 150 mesh, 3 parts of zinc fulvic acid of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 28.

[0048] Comparative Example 27: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu worm castings of 150 mesh, 3 parts of zinc sulfate of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioner 29.

[0049] Comparative Example 28: 35 parts of oyster shell powder of 100 mesh, 45 parts of kudzu slag of 150 mesh, 3 parts of zinc sulfate of 150 mesh, 8 parts of sodium sulfide of 150 mesh and 5 parts of manganese sulfate of 150 mesh were mixed evenly to obtain a composite cadmium-reducing conditioning agent 30; Preparation method of kudzu vine residue: take fresh kudzu vine residue, adjust the moisture content to 65%, compost and ferment for 25 days, turn the pile every 6 days, control the temperature of the pile at 55℃, and dry after fermentation; Comparative Example 29: 35 parts of oyster shell powder with 100 mesh, 45 parts of sweet potato residue earthworm castings with 150 mesh, 3 parts of zinc sulfate with 150 mesh, 8 parts of sodium sulfide with 150 mesh and 5 parts of manganese sulfate with 150 mesh were mixed evenly to obtain composite cadmium-reducing conditioner 31; the preparation method of sweet potato residue earthworm castings is the same as that of kudzu residue earthworm castings.

[0050] The composite cadmium-reducing conditioning agent in Examples 1-2 and Comparative Examples 1-29 is evaluated below: A field experiment was conducted in a safe utilization area in Xinyu City. The soil pH of the experimental field was 5.42, the total cadmium content was 0.85 mg / kg, and the organic matter content was 28.8 g / kg. It was a latent paddy soil with medium overall fertility. The entire field was divided into 96 plots, each with an area of ​​20m 2 , the ridges were cut in half between the plots and covered with film. Each treatment was repeated 3 times, with a total of 32 treatment plots. Treatment plot 1 was the blank control group CK (no cadmium-reducing conditioner material was applied), and treatment plots 2-32 were the composite cadmium-reducing conditioners in Examples 1-2 and Comparative Examples 1-29, respectively; all plots were planted with the medium-grain rice Cenliangyou 1810.

[0051] Rice seedlings were grown in the field. Within 3 days before rice transplanting, 40 kg / mu of compound fertilizer (total nutrient content 45%, of which N-P2O5-K2O=15-15-15) was applied. 150 kg / mu of the composite cadmium-reducing conditioner described in Example 1-2 and Comparative Example 1-29 was applied to different treatment areas at the same time (the blank control group CK did not apply any cadmium-reducing conditioner material), and manual plowing was performed to ensure that the fertilizer and the composite cadmium-reducing conditioner were fully mixed with the soil. Manual transplanting was adopted in the transplanting process. After the rice turned green, 10 kg / mu of urea was applied during the tillering period. Other field water and fertilizer management methods and pest and disease control methods were consistent with traditional methods. After the rice matured, each plot was harvested and measured for yield, and the cadmium content in the brown rice was determined.

[0052] The method for determining the cadmium content of brown rice is as follows: take 0.1g brown rice powder sample, add 5mL nitric acid and 3.0mL hydrogen peroxide solution, cover and cold digest overnight, digest for 2h using a graphite digester and dilute to 25mL, and analyze and determine the cadmium concentration in the digestion solution using an inductively coupled plasma mass spectrometer. The test results are shown in Table 1: Table 1 Differences in rice yield and cadmium content in brown rice among treatments Processing Area deal with Rice yield (kg / mu) Cadmium content in brown rice (mg / kg) 1 Blank control CK 651±20 0.761±0.067 2 Example 1 661±17 0.113±0.012 3 Example 2 663±14 0.108±0.015 4 Comparative Example 1 652±16 0.180±0.018 5 Comparative Example 2 651±15 0.186±0.015 6 Comparative Example 3 654±11 0.169±0.019 7 Comparative Example 4 656±13 0.194±0.013 8 Comparative Example 5 652±17 0.192±0.020 9 Comparative Example 6 647±13 0.237±0.021 10 Comparative Example 7 649±12 0.241±0.023 11 Comparative Example 8 645±16 0.223±0.021 12 Comparative Example 9 651±11 0.239±0.025 13 Comparative Example 10 646±12 0.246±0.016 14 Comparative Example 11 641±11 0.226±0.019 15 Comparative Example 12 643±13 0.235±0.024 16 Comparative Example 13 647±17 0.257±0.021 17 Comparative Example 14 634±15 0.243±0.023 18 Comparative Example 15 636±11 0.356±0.031 19 Comparative Example 16 631±12 0.378±0.033 20 Comparative Example 17 639±17 0.356±0.030 21 Comparative Example 18 643±12 0.361±0.025 22 Comparative Example 19 635±16 0.394±0.034 23 Comparative Example 20 637±17 0.392±0.032 24 Comparative Example 21 629±10 0.449±0.038 25 Comparative Example 22 626±12 0.478±0.041 26 Comparative Example 23 622±17 0.237±0.016 27 Comparative Example 24 632±11 0.229±0.015 28 Comparative Example 25 651±11 0.204±0.011 29 Comparative Example 26 653±17 0.227±0.015 30 Comparative Example 27 650±8 0.201±0.013 31 Comparative Example 28 647±12 0.367±0.007 32 Comparative Example 29 657±10 0.209±0.011 Note 1: Except for the different treatment methods, the other conventional cultivation methods of each group in the table are the same.

[0053] Note 2: According to the requirements of "GB 2762-2022 National Food Safety Standard Limits of Contaminants in Food", the cadmium content of qualified rice is less than or equal to 0.2 mg / kg.

[0054] According to the experimental results of the above embodiments, the present invention utilizes earthworm castings to activate organic matter components in kudzu residue, and utilizes earthworms to remove cadmium in kudzu residue. The active ingredients in kudzu residue earthworm castings and active ingredients such as amino acids in oyster shell powder work together with zinc fulvic acid, manganese fertilizer and sodium sulfide. In addition, the adsorption and degradation of oyster shell powder and kudzu residue earthworm castings increase the effects of soil organic matter, and synergistically reduce the cadmium content of rice brown rice. The cadmium content in rice brown rice can be reduced to 0.1 mg / kg, which solves the technical problem that the prior art cannot reduce the cadmium content of rice brown rice to below 0.15 mg / kg.

[0055] In summary, the invention discloses a composite cadmium-reducing conditioner based on kudzu residue earthworm castings and an application method. The mass proportions of the components in the cadmium-reducing conditioner are: 35-40 parts of oyster shell powder, 30-45 parts of kudzu residue earthworm castings, 3-5 parts of zinc fulvic acid, 8-10 parts of sodium sulfide and 3-5 parts of manganese sulfate. The cadmium-reducing conditioner is applied to the soil before plowing the rice, and the soil is plowed after standing, and then the rice is transplanted. The invention uses earthworm castings to activate organic matter components in the kudzu residue, and uses earthworms to remove cadmium in the kudzu residue. Active ingredients in the kudzu residue earthworm castings and active ingredients such as amino acids in the oyster shell powder act together with zinc fulvic acid, manganese fertilizer and sodium sulfide, and the oyster shell powder and the kudzu residue earthworm castings are adsorbed and degraded, and soil organic matter is increased, so that the cadmium content of rice brown rice is synergistically reduced, and the cadmium content in the rice brown rice can be reduced to 0.1 mg / kg. The operation is simple, and the raw materials are easy to obtain.

[0056] At this point, those skilled in the art recognize that, although the embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the contents disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A composite cadmium-reducing conditioning agent based on kudzu residue earthworm castings, characterized in that: The composite cadmium reduction conditioning agent comprises the following components: Oyster shell powder, kudzu worm castings, zinc fulvic acid, sodium sulfide and manganese sulfate; The composite cadmium reduction conditioning agent component formula is: 35-40 parts of oyster shell powder, 30-45 parts of kudzu worm castings, 3-5 parts of zinc fulvic acid, 8-10 parts of sodium sulfide and 3-5 parts of manganese sulfate.

2. A composite cadmium-reducing conditioning agent based on kudzu residue earthworm castings as claimed in claim 1, characterized in that: The mesh number of the oyster shell powder is 50-100 meshes.

3. A composite cadmium-reducing conditioning agent based on kudzu slag earthworm castings as claimed in claim 1, characterized in that: The kudzu residue earthworm castings are dried and crushed into 80-150 meshes.

4. A composite cadmium-reducing conditioning agent based on kudzu slag earthworm castings as claimed in claim 1, characterized in that: The zinc fulvic acid, sodium sulfide and manganese sulfate are crushed into 80-150 meshes.

5. A composite cadmium-reducing conditioning agent based on kudzu slag earthworm castings as claimed in claim 1, characterized in that: The preparation method of the kudzu residue earthworm castings is specifically as follows: Step S1: taking fresh kudzu vine residue, adjusting the moisture content to 60%-70%, composting and fermenting for 20-25 days, turning the compost every 5-8 days, and controlling the compost temperature at 50-60°C; Step S2: placing earthworm seeds into the material obtained by fermentation in step S1, with a density of 10 to 15 earthworm seeds per kilogram of dry material. The earthworm seeds are Taiping No. 2, and are re-placed every 20 days. Then, the earthworms are separated from the earthworm castings to obtain kudzu residue earthworm castings.

6. A composite cadmium-reducing conditioning agent based on kudzu residue earthworm castings as claimed in claim 5, characterized in that: The living temperature of the earthworms is set at 25±10° C. to ensure the normal reproduction of the earthworms.

7. The method for applying the composite cadmium-reducing conditioner based on kudzu residue earthworm castings as claimed in claim 1, characterized in that: The application method is specifically: The composite cadmium-reducing conditioner is applied to the soil before the rice is ploughed, and the soil is ploughed after being left to stand, and then the rice is transplanted.

8. The method for applying the composite cadmium-reducing conditioner based on kudzu slag earthworm castings as claimed in claim 7, characterized in that: The method is applied to the soil 5-10 days before rice tillage.

9. The method for applying the composite cadmium-reducing conditioner based on kudzu slag earthworm castings as claimed in claim 7, characterized in that: The dosage of the composite cadmium-reducing conditioner is 150-250kg / mu.