A method for safe production and soil quality improvement in a medium-light cadmium contaminated paddy field

Abstract

The application provides a kind of middle light degree cadmium pollution paddy field safe production synergic soil quality promotion regulation method, including planting extraction plant in winter idle season, through the extraction plant absorption accumulation cadmium in soil, then the extraction plant is removed from paddy field before rice transplanting;3-5 days before rice transplanting, spread and apply passivation material and apply alkali modified woody peat material load nitrogen-fixing bacteria material, spread and apply after ploughing and mixing;In rice growing season, spread and apply nitrogen-fixing bacteria agent material, to realize the regulation of middle light degree cadmium pollution paddy field safe production synergic soil quality promotion, the application constructs winter idle season removal+heavy metal passivation combined with fertility promotion in rice season, realizes the dual goal of safe production of middle light degree pollution paddy field and soil quality improvement.

Description

Technical Field

[0001] This invention belongs to the technical field of heavy metal pollution prevention and control, specifically relating to a regulation method for safe production and synergistic soil quality improvement in paddy fields with moderate to mild cadmium pollution. Background Technology

[0002] Current mainstream cadmium pollution control emphasizes "passivation" and "control," that is, reducing the bioavailability of cadmium by altering its existing forms, rather than completely removing it from the soil. Based on this concept, the addition of excessive alkaline materials has become the main method for controlling cadmium pollution in farmland. Although these exogenously added alkaline materials inhibit cadmium activity, they may lead to soil compaction, accelerated decomposition of organic matter, imbalance of microbial communities, and even secondary salinization due to repeated application, resulting in a decline in soil quality.

[0003] Improving soil quality requires enhancing its buffering capacity, aggregate stability, organic carbon content, and biological activity, which often necessitates maintaining relatively active biogeochemical processes. Current soil quality improvement measures, such as increasing organic fertilizer application, planting green manure, and deep tillage, may, however, activate cadmium due to the release of organic acids or changes in redox conditions, leading to excessive levels of cadmium in rice. Therefore, how to improve soil fertility and control heavy metal pollution are urgent technical issues that need to be addressed for the safe production of moderately to lightly polluted farmland. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for regulating and improving soil quality in conjunction with safe production in paddy fields with moderate to mild cadmium pollution, thereby resolving the technical issues in the prior art.

[0005] In a first aspect, the present invention provides the following technical solution: a method for regulating and improving soil quality in conjunction with safe production in paddy fields with moderate to mild cadmium pollution, the method comprising: S1. Planting extractable plants during the winter off-season, allowing the extractable plants to absorb and accumulate cadmium in the soil, and then removing the extractable plants from the paddy field before rice transplanting; S2. 3-5 days before rice transplanting, apply passivation material and alkali-modified woody peat material loaded with nitrogen-fixing bacteria. The amount of passivation material is 100 kg / mu, and the amount of alkali-modified woody peat material loaded with nitrogen-fixing bacteria is 150-250 kg / mu. After application, till and mix thoroughly. S3. During the rice growing season, apply nitrogen-fixing bacterial agent at a rate of 2 kg / mu to achieve safe production and soil quality improvement in rice fields with moderate to mild cadmium pollution.

[0006] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention utilizes the method of extracting cadmium from plants inoculated with enhanced absorption bacteria during the winter fallow season and then removing it, thereby reducing the total amount of cadmium in paddy fields at the source. Through total removal over 3-5 years, the cadmium content in the topsoil of moderately polluted paddy fields can be significantly reduced. Then, before rice transplanting, passivating materials are applied, along with alkali-modified woody peat material loaded with nitrogen-fixing bacteria, and nitrogen-fixing bacteria are applied during the rice growing season to passivate cadmium in the soil and simultaneously improve soil nutrients. This method combines winter fallow removal with heavy metal passivation and fertility enhancement during the rice growing season, achieving the dual goals of safe production and soil quality improvement in moderately polluted paddy fields.

[0007] Preferably, the extracted plant is one or more of rapeseed, milkvetch, and ryegrass inoculated with Bacillus cereus LSE01.

[0008] Preferably, the technical parameters of the passivation material are: CaO 30%-45%, SiO2 5%-8%, pH 11~13.

[0009] Preferably, the passivating material comprises the following raw materials in weight percentages: 32% calcium carbonate, 25% magnesium oxide, and 43% kaolin.

[0010] Preferably, the technical parameters for applying alkali-modified woody peat material loaded with nitrogen-fixing bacteria are: 60%-65% organic matter and 12%-15% free humic acid.

[0011] Preferably, the nitrogen-fixing bacterial agent material comprises the following raw materials in parts by weight: 62 parts of nutrient soil, 750 parts of zeolite, 10 parts of vermiculite, and 1 part of arbuscular mycorrhizal fungal agent. Detailed Implementation

[0012] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the scheme, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the scheme are exemplary and intended to explain the embodiments of the present invention, and should not be construed as limiting the present invention.

[0013] Example 1 In Embodiment 1 of the present invention, a method for regulating and improving soil quality in paddy fields with moderate to mild cadmium pollution, the method comprising: S1. Planting extractable plants during the winter off-season, allowing the extractable plants to absorb and accumulate cadmium in the soil, and then removing the extractable plants from the paddy field before rice transplanting; The extracted plant is one or more of rapeseed, milkvetch, and ryegrass inoculated with Bacillus cereus LSE01.

[0014] Specifically, by planting extractable plants with high biomass during the winter fallow season, and inoculating these plants with Bacillus cereus LSE01 which enhances plant absorption, these crops can efficiently absorb and accumulate cadmium in the soil. Then, these plants are removed from the paddy fields before rice transplanting, reducing the total amount of cadmium in the soil at the source. Furthermore, by continuously planting extractable plants for several years, the total amount of cadmium in the soil can be significantly reduced.

[0015] At the same time, the application of passivating materials and nitrogen-fixing bacteria during the rice season further stabilizes residual cadmium and significantly reduces the absorption of cadmium by rice.

[0016] S2. 3-5 days before rice transplanting, apply passivation material and alkali-modified woody peat material loaded with nitrogen-fixing bacteria. The amount of passivation material is 100 kg / mu, and the amount of alkali-modified woody peat material loaded with nitrogen-fixing bacteria is 150-250 kg / mu. After application, till and mix thoroughly. The technical parameters of the passivation material are: CaO 30%-45%, SiO2 5%-8%, pH 11~13; the passivation material includes the following raw materials by weight percentage: calcium carbonate 32%, magnesium oxide 25%, kaolin 43%.

[0017] The technical parameters for applying alkali-modified woody peat material loaded with nitrogen-fixing bacteria are: 60%-65% organic matter and 12%-15% free humic acid.

[0018] Specifically, by combining the application of passivating materials with the application of alkali-modified woody peat material loaded with nitrogen-fixing bacteria, cadmium in the soil can be passivated and soil nutrients in paddy fields can be increased simultaneously. When applied to moderately and lightly polluted land, the combination of the two materials can reduce cadmium absorption by rice by 40%-75%, and when applied to acidic soil, it can increase the pH value by 0.5-1.0 units and increase the total nitrogen in the soil by 3-5 percentage points.

[0019] Among them, alkali-modified woody peat materials loaded with nitrogen-fixing bacteria can provide organic matter (60%-65%) and free humic acid (12%-15%), improve soil aggregate structure, and increase cation exchange capacity; nitrogen-fixing bacteria agents (including arbuscular mycorrhizal fungi) can improve soil nitrogen levels and the nutrient absorption efficiency of rice roots.

[0020] S3. During the rice growing season, apply nitrogen-fixing bacterial agent at a rate of 2 kg / mu to achieve safe production and soil quality improvement in rice fields with moderate to mild cadmium pollution.

[0021] The nitrogen-fixing bacterial agent material includes the following raw materials in parts by weight: 62 parts of nutrient soil, 750 parts of zeolite, 10 parts of vermiculite, and 1 part of arbuscular mycorrhizal fungal agent.

[0022] Specifically, nitrogen-fixing bacteria can further improve soil fertility, and single-season application can increase rice yield, with a reduction in cadmium content in rice of about 35%-55%.

[0023] To further verify the effectiveness of the present invention, field experiments were conducted, as detailed below: Implementation Location: Zhanggong District, Ganzhou City The soil background data are as follows: pH 5.36, total Cd 0.446 mg / kg.

[0024] The experimental group's field treatments were as follows: rapeseed inoculated with Bacillus cereus LSE01 was planted at the end of October. In April of the following year, the rapeseed was harvested and removed from the field at the half-flowering, half-pod stage. 3-5 days before transplanting rice, passivation material and alkali-modified woody peat material loaded with nitrogen-fixing bacteria were applied, at a rate of 100 kg / mu and 150 kg / mu respectively. After application, the soil was tilled and mixed evenly. After the rice turned green, nitrogen-fixing bacteria agent was applied at a rate of 2 kg / mu. The control group's experimental field received no treatment and was planted according to the normal rice planting process.

[0025] The cadmium content in rice was tested after harvest. The rice yield and cadmium content in rice are shown in Table 1.

[0026] Table 1

[0027] According to Table 1: Rice safety analysis: The cadmium content of rice in the control area was 0.216 mg / kg, exceeding the cadmium limit for rice (0.2 mg / kg) in the National Food Safety Standard for Maximum Levels of Contaminants in Food (GB 2762-2022). The cadmium content of rice in the experimental area was 0.047 mg / kg, a reduction of 78.2% (calculated as (0.216-0.047) / 0.216×100%), significantly lower than the national standard, indicating that the method of this invention can effectively control the absorption of cadmium by rice. This is mainly due to: ① plant extraction during the winter fallow season reducing total cadmium in the soil; ② passivation materials increasing pH and adsorbing available cadmium; ③ organic materials and microbial agents improving the rhizosphere microenvironment and reducing the bioavailability of cadmium.

[0028] Changes in soil cadmium availability: The available cadmium content in the control area was 0.331 mg / kg, while in the experimental area it was 0.051 mg / kg, a decrease of 84.6%. Combined with the increase in soil pH from 5.26 to 5.73 (an increase of 0.47), this indicates that the alkaline components such as CaO and SiO2 in the passivation material significantly neutralized soil acidity, promoting cadmium precipitation or complexation. The significant reduction in available cadmium is the direct cause of the decrease in cadmium content in rice.

[0029] Impact on rice yield: The rice yield in the experimental area was 7090.5 kg / hm², slightly higher than the 7063.5 kg / hm² in the control area, representing an increase of 0.38%. Although the yield increase was not significant, it indicates that this method, while ensuring safety, did not negatively impact yield. Considering that plant growth is often inhibited under cadmium stress, this method improved soil nutrient supply and root activity by providing organic matter, nitrogen-fixing bacteria, and humic acid, thus compensating for potential growth inhibition effects.

[0030] Regarding the regulation method for safe production and soil quality improvement in moderately and lightly cadmium-contaminated paddy fields provided in the above embodiments, this invention utilizes the method of planting plants inoculated with enhanced absorption bacteria during the winter fallow season to absorb cadmium and then remove it, thereby reducing the total amount of cadmium in paddy fields at the source. Through total removal over 3-5 years, the cadmium content in the topsoil of moderately and lightly polluted paddy fields can be significantly reduced. Then, before rice transplanting, passivating materials are applied, as well as alkali-modified woody peat materials loaded with nitrogen-fixing bacteria are applied, and nitrogen-fixing bacteria are applied during the rice growing season to passivate cadmium in the soil and simultaneously improve soil nutrients in paddy fields. This method combines winter fallow season removal with heavy metal passivation and fertility improvement during the rice growing season, achieving the dual goals of safe production in moderately and lightly polluted paddy fields while improving soil quality.

[0031] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0032] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for safe production and soil quality improvement in a medium-lightly cadmium-contaminated paddy field, characterized by, The method includes: S1. Planting extractable plants during the winter off-season, allowing the extractable plants to absorb and accumulate cadmium in the soil, and then removing the extractable plants from the paddy field before rice transplanting; S2. 3-5 days before rice transplanting, apply passivation material and alkali-modified woody peat material loaded with nitrogen-fixing bacteria. The amount of passivation material is 100 kg / mu, and the amount of alkali-modified woody peat material loaded with nitrogen-fixing bacteria is 150-250 kg / mu. After application, till and mix thoroughly. S3. During the rice growing season, apply nitrogen-fixing bacterial agent at a rate of 2 kg / mu to achieve safe production and soil quality improvement in rice fields with moderate to mild cadmium pollution.

2. The method according to claim 1, wherein the method is characterized by, The extracted plants are one or more of rapeseed, milkvetch, and ryegrass inoculated with Bacillus cereus LSE01.

3. The method according to claim 1, wherein the method is characterized by, The technical parameters of the passivation material are: CaO 30%-45%, SiO2 5%-8%, pH 11~13.

4. The method according to claim 1, wherein the method is characterized by, The passivation material comprises the following raw materials by weight percentage: calcium carbonate 32%, magnesium oxide 25%, and kaolin 43%.

5. The method according to claim 1, wherein the method is characterized by, The technical parameters for applying alkali-modified woody peat material loaded with nitrogen-fixing bacteria are: 60%-65% organic matter and 12%-15% free humic acid.

6. The method according to claim 1, wherein the method is characterized by, The nitrogen-fixing bacterial agent material comprises the following raw materials in parts by weight: 62 parts of nutrient soil, 750 parts of zeolite, 10 parts of vermiculite, and 1 part of arbuscular mycorrhizal fungal agent.

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