A method for reducing the cadmium content of rice in moderately contaminated soil

Abstract

The present invention relates to the technical field of rice planting, and specifically discloses a method for reducing the cadmium content of rice in moderately polluted soil, comprising: (1) applying a passivating agent to the soil 2-4 days before rice transplanting to reduce the biological effectiveness of soil cadmium and form a root protection film, thereby reducing the absorption and accumulation of cadmium by the rice plant during the growth period, especially the tillering and jointing periods; (2) spraying a leaf surface barrier control agent once during the heading period of rice, and blocking the transport of cadmium ions to grains through complexation with cadmium ions in the rice body and ion channel inhibition. The method is simple to operate, labor-saving and time-saving, and has a high efficiency in reducing cadmium in rice. The method can reduce the cadmium and arsenic content of brown rice in rice fields with moderate cadmium pollution by more than 80%, and increase the rice yield by more than 5%. The method has a stable effect and is suitable for industrial application in rice production in rice fields with less than moderate cadmium pollution.

Description

Technical Field

[0001] The invention relates to the technical field of rice planting, and in particular to a method for reducing the cadmium content of rice in moderately polluted soil. Background Art

[0002] Cadmium has a strong biological toxicity and can enter the human body through the food chain, causing chronic poisoning. The pollutant exceeding the standard rate in China's cultivated soil points is 19.1%, among which cadmium has the highest exceeding rate and is the primary pollutant of heavy metals in my country's soil. Rice has the characteristic of enriching cadmium. Excessive cadmium in rice will seriously threaten people's health. In recent years, the cadmium pollution in Longjiang, Guangxi and the excessive cadmium in rice in Guangdong have attracted great attention from the government and people from all walks of life.

[0003] At present, the following methods are mainly used to solve the problem of safe rice production in cadmium-contaminated paddy fields: soil in-situ passivation remediation measures, agronomic measures, foliar barrier control measures, and plant remediation technical measures. Each technology still has the defects of high cost and insignificant effect. At present, the instability of soil in-situ passivation remediation technology and its short after-effect time are important bottlenecks affecting the promotion and use of this technology. Most passivators often reach saturation in the early stage of rice growth through the adsorption and binding mechanism, and the passivation effect is poor in the late stage of rice growth, and thus the final effect of reducing the cadmium content of rice cannot be achieved. The foliar barrier control technology has the problem of low barrier control efficiency and high labor cost of multiple spraying during the rice growth period. The plant remediation technology also has the problem of slow plant growth and small biomass. Agronomic flooding management technical measures are difficult to guarantee water supply in many mountainous areas and water-scarce areas, and the actual implementation is still difficult. It is understandable that at present, it is still difficult for a single technology to achieve economical and efficient rice production in moderately cadmium-contaminated paddy soil.

[0004] Therefore, how to organically combine multiple technologies to achieve the effect of 1+1>2 is one of the effective ways to solve the problem of safe rice production in moderately cadmium-contaminated paddy fields. The combination of soil passivation in-situ remediation and foliar barrier control technology can effectively control the accumulation of cadmium absorbed by rice and its transport to rice during the entire growth period. The application of passivators in the early stage can effectively passivate the cadmium ions in the soil and reduce the absorption of cadmium by rice. The application of foliar barrier control agents in the late stage of rice growth can chelate the cadmium ions in the plant and reduce the transport of cadmium ions to rice grains, ultimately achieving the effect of reducing the cadmium content in rice. Summary of the invention

[0005] The purpose of the present invention is to provide a method for reducing the cadmium content of rice in moderately contaminated soil, thereby overcoming the defect that the existing single rice barrier technology is difficult to economically and efficiently achieve safe rice production in moderately cadmium-contaminated paddy field soil.

[0006] To achieve the above object, the present invention provides a method for reducing the cadmium content of rice in moderately contaminated soil, comprising:

[0007] (1) 2-4 days before rice transplanting, reduce the bioavailability of soil cadmium and form a root protection film by applying a passivator to the soil to reduce the absorption and accumulation of cadmium by the rice plants during the growth period, especially during the tillering and jointing stages;

[0008] (2) Spray the foliar inhibitor once during the heading stage of rice to block the transport of cadmium ions to the grains by complexing with cadmium ions in the rice body and inhibiting ion channels.

[0009] The early application of passivators can effectively passivate the cadmium ions in the soil and reduce the absorption of cadmium by rice. The application of foliar inhibitors in the early stage of heading can complex the cadmium ions in the plant and reduce the transport of cadmium ions to rice grains, ultimately achieving the effect of reducing the cadmium content in rice.

[0010] Preferably, the passivator comprises the following components by weight: 15-30g of nano-sulfur, 20-40g of nano-ferric oxide, 150-300g of calcium-based bentonite, 80-150g of biochar, 300-500g of silkworm excrement, and 200-400g of shell powder. Calcium-based bentonite, silkworm excrement, etc. can adjust the nutrients in the soil and reduce the biological effectiveness of soil cadmium. Nano-sulfur can form cadmium sulfide precipitation with cadmium in the soil to greatly reduce the biological activity of soil cadmium. Biochar has high porosity and can well absorb cadmium ions in the soil. Nano-sulfur and nano-ferric oxide can form a protective film for the root system, reducing the absorption and accumulation of cadmium by plants during the growth period of rice, especially the tillering and jointing periods.

[0011] Preferably, the preparation method of the passivating agent is as follows:

[0012] A. First, crush the calcium-based bentonite to less than 300 mesh, calcine it at high temperature 400-700℃ for 4 hours, and set aside;

[0013] B. The biochar material is crushed to 200 mesh and set aside;

[0014] C. Crush the shell powder to 200 mesh and set aside;

[0015] D. Dry the silkworm excrement to control the moisture content below 15% and set aside;

[0016] E. Mix and stir the various material components evenly according to the formula ratio to obtain the passivation agent product.

[0017] Preferably, the passivator material is evenly spread together with the base fertilizer at a dosage of 150-300 kg per mu, and then raked evenly with a tractor after spreading.

[0018] Preferably, each liter of the foliar barrier agent contains the following ingredients in parts by weight: 40-75g of potassium dihydrogen phosphate, 10-15g of sodium dodecylbenzenesulfonate, 150-200g of sodium thiosulfate, 50-80g of cystine, 20-35g of citric acid, 40-60g of nano silicon, 20-40g of manganese sulfate, 5-10g of isoamyl acetate, and the rest is water.

[0019] Preferably, the preparation method of the foliar barrier agent is as follows:

[0020] I. First, various solid compounds are dissolved in water separately, and each substance is dissolved close to its solubility;

[0021] II. Slowly add the sodium thiosulfate solution into the citric acid solution, stirring while pouring, and mix thoroughly to obtain a mixed solution B;

[0022] III. Pour the manganese sulfate solution into the mixed solution B, stirring while pouring, and mix thoroughly to obtain a mixed solution C;

[0023] IV. Pour the potassium dihydrogen phosphate solution and the cystine solution into the mixed solution C in sequence, stirring while pouring, to obtain a mixed solution D;

[0024] V. Pour the isoamyl acetate liquid into the sodium dodecylbenzene sulfonate solution while stirring to obtain a mixed solution E;

[0025] VI. 2 hours before use, pour the nano-silicon solution and mixed solution E into mixed solution D in sequence and stir evenly to obtain a complete foliar barrier agent.

[0026] Preferably, a sprayer is used to evenly spray the foliar barrier agent onto the rice leaves.

[0027] Preferably, the dosage of the foliar barrier agent is 200 ml / mu, and it is diluted 100-300 times before use.

[0028] Preferably, choose sunny weather to spray the foliar barrier control agent. If it rains within 4 hours after spraying, repeat the spraying once. The amount of foliar barrier control agent used is 1 / 3 to 1 / 2 of the normal amount.

[0029] Compared with the existing technology, the present invention has the following beneficial effects:

[0030] 1. The present invention applies a passivator before rice planting to effectively passivate the cadmium ions in the soil and reduce the absorption of cadmium by rice. The application of a foliar inhibitor in the early stage of heading can complex the cadmium ions in the plant and reduce the transport of cadmium ions to rice grains, ultimately achieving the effect of reducing the cadmium content of rice.

[0031] 2. Calcium-based bentonite, silkworm feces, etc. can adjust the nutrients in the soil and reduce the biological effectiveness of soil cadmium. Nano-sulfur can react with cadmium in the soil to form cadmium sulfide precipitation, which greatly reduces the biological activity of soil cadmium. Biochar has high porosity and can well absorb cadmium ions in the soil. Nano-sulfur and nano-ferric oxide can form a protective film for the root system, reducing the absorption and accumulation of cadmium by rice plants during the growth period, especially the tillering and jointing stages.

[0032] 3. The foliar agent of the present invention adds sodium dodecylbenzene sulfonate and isoamyl acetate components. Sodium dodecylbenzene sulfonate acts as a surfactant to increase the activity of the effective ingredients of the foliar agent on the rice leaves, while isoamyl acetate acts on the wax layer on the leaf surface to promote the effective absorption of amino acids, sodium thiosulfate, silicon, manganese and other ingredients by rice, thereby greatly improving the application efficiency of the effective ingredients of the foliar agent and the heavy metal cadmium blocking effect.

[0033] 4. The method of the present invention is simple to operate, labor-saving and time-saving, and has high efficiency in reducing cadmium in rice. The method can reduce the cadmium and arsenic content of brown rice by more than 80% in rice fields with moderate cadmium pollution, and increase the rice yield by more than 5%. The method has a stable effect and is suitable for industrial application in rice production in rice fields with moderate cadmium pollution or below. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0035] Example 1

[0036] The cadmium content of paddy field soil was 1.21 mg / kg, and the soil pH was 6.5. The time was late rice, and the rice variety was Guangliangxiang No. 2 conventional rice. The comparative treatments were set as follows: (1) application of the passivation agent of the present application; (2) application of comparative passivation agent 1; (3) application of comparative passivation agent 2; (4) no application of passivation agent - control.

[0037] The formula of the passivator in this application: each 1kg of passivator contains 25g of nano-sulfur, 35g of nano-ferric oxide, 200g of calcium-based bentonite, 120g of biochar, 400g of silkworm feces, and 220g of shell powder.

[0038] Comparative passivation agent 1: lime, which is currently the most widely used;

[0039] Comparative passivator 2: The commercial passivators purchased on the market have superphosphate, magnesium, sepiolite, zeolite powder, fly ash and the like as their main ingredients.

[0040] How to use: Apply with base fertilizer

[0041] After the paddy field is plowed and harrowed, 3 days before rice transplanting, evenly spread the passivator material at a dosage of 200kg per mu together with the base fertilizer, and then harrow it evenly with a tractor. After balancing for 3 days, transplant the rice seedlings.

[0042] The main data of the test are shown in Table 1:

[0043]

[0044] As can be seen from Table 1, the cadmium content in the soil and rice was significantly reduced in different growth stages when the passivator was applied compared with that when no passivator was applied. At the same time, the rice yield of the passivator was also increased accordingly. The effect of applying the passivator of the present application was better than that of applying the comparative passivator 1 and the comparative passivator 2. Relatively speaking, the cadmium reduction effect was significant in the tillering stage, and the reduction effect in the maturity stage was relatively weakened.

[0045] Example 2

[0046] The cadmium content of paddy field soil was 1.21 mg / kg, and the soil pH was 6.5. The time was late rice, and the rice variety was Guangliangxiang No. 2 conventional rice. The comparative treatments were: (1) spraying the foliar barrier agent of the present application; (2) spraying the comparative foliar barrier agent 1; (3) spraying the comparative foliar barrier agent 2; (4) no foliar barrier agent was applied - control.

[0047] The foliar barrier control agent formula of this application: 1000ml foliar barrier control agent contains 70g of potassium dihydrogen phosphate, 12g of sodium dodecylbenzene sulfonate, 185g of sodium thiosulfate, 70g of cystine, 30g of citric acid, 55g of nano silicon, 25g of manganese sulfate, and 8g of isoamyl acetate.

[0048] Comparison of foliar control agent 1: a foliar fertilizer product commonly used on the market (Zhengsebao);

[0049] Comparison of foliar control agent 2: a foliar control agent containing trace elements commonly used on the market (cadmium-free);

[0050] Directions:

[0051] Choose sunny weather and spray the above-mentioned foliar inhibitor once during the heading period of rice, with a dosage of 200 ml / mu and diluted 200 times before use.

[0052] Comparative foliar control agent: Apply according to the dosage and method specified in the product instructions.

[0053] Control spraying water treatment: During the heading period of rice, spray water on the same day, the dosage is 200ml / mu, diluted 200 times before use.

[0054] The main test data are shown in Table 2:

[0055]

[0056] As can be seen from Table 2, the foliar barrier agent of the present application has a better cadmium removal effect than the control group and the foliar barrier agent purchased on the market.

[0057] Example 3

[0058] The method of soil passivation combined with foliar control was used. When the soil cadmium content was 1.15 mg / kg, the soil pH was 6.0, the time was early rice, and the rice variety was Guang 8 You Yu Xiang hybrid rice variety. Five experimental comparisons were set up: (1) soil passivation + foliar control (2) foliar control spraying once; (3) foliar control spraying twice; (4) soil passivation; (5) control

[0059] Passivator formula: Each 1kg of passivator contains 25g of nano-sulfur, 35g of nano-ferric oxide, 200g of calcium-based bentonite, 120g of biochar, 400g of silkworm feces, and 220g of shell powder.

[0060] How to use: Apply with base fertilizer

[0061] After the paddy field is plowed and harrowed, 3 days before rice transplanting, evenly spread the passivator material at a dosage of 200kg per mu together with the base fertilizer, and then harrow it evenly with a tractor. After balancing for 3 days, transplant the rice seedlings.

[0062] Foliar control agent formula: 1000ml foliar control agent contains 70g potassium dihydrogen phosphate, 12g sodium dodecylbenzene sulfonate, 185g sodium thiosulfate, 70g cystine, 30g citric acid, 55g nano silicon, 25g manganese sulfate, and 8g isoamyl acetate.

[0063] Directions:

[0064] Foliar spray once: Choose sunny weather and spray the above foliar fertilizer once during the heading period of rice, the dosage is 200ml / mu, diluted 200 times before use.

[0065] Foliar spraying twice: In fine weather, the first foliar spraying is 4 days before the rice heading stage by spraying the foliar inhibitor with a sprayer, the dosage is 150ml / mu, diluted 150 times; the second foliar spraying is when the rice is heading by spraying the foliar inhibitor with a sprayer, the dosage is 150ml / mu, diluted 150.

[0066] Control treatment: spray clean water twice in sunny weather, 4 days before the rice booting stage and at the rice heading stage, spray clean water 150ml / mu through a sprayer, diluted 150 times;

[0067] The main test data are shown in Table 3:

[0068]

[0069] As can be seen from Table 3, the use of soil passivation + foliar barrier control method is better than simply applying soil passivators or foliar barrier control agents in terms of both cadmium reduction effect on rice and increase in rice yield.

[0070] In summary, applying a passivator before rice planting can effectively passivate the cadmium ions in the soil and reduce the absorption of cadmium by rice. Applying a foliar barrier before heading can complex the cadmium ions in the plant and reduce the transport of cadmium ions to rice grains, ultimately achieving the effect of reducing the cadmium content in rice. The method is simple to operate, labor-saving and time-saving, and has a high efficiency in reducing cadmium in rice. Using this method, the cadmium and arsenic content of brown rice in rice fields with moderate cadmium pollution was reduced by more than 80%, and the rice yield was increased by more than 5%. This method has a stable effect and is suitable for industrial application in rice production in rice fields with moderate cadmium pollution or below.

[0071] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for reducing the cadmium content of rice in moderately contaminated soil, characterized in that: include: (1) 2-4 days before rice transplanting, reduce the bioavailability of soil cadmium and form a root protection film by applying a passivator to the soil to reduce the absorption and accumulation of cadmium by the rice plants during the growth period, especially during the tillering and jointing stages; The preparation method of the passivating agent is as follows: 15-30g of nano sulfur, 20-40g of nano ferric oxide, 150-300g of calcium-based bentonite, 80-150g of biochar, 300-500g of silkworm feces, and 200-400g of shell powder; The passivation agent material is evenly spread together with the base fertilizer at a dosage of 150-300 kg per mu, and then raked evenly with a tractor after spreading; (2) Spraying the foliar inhibitor once during the heading period of rice can prevent the transport of cadmium ions to the grains by complexing with cadmium ions in the rice body and inhibiting ion channels; Each liter of the leaf control agent contains the following ingredients by weight: 40-75g of potassium dihydrogen phosphate, 10-15g of sodium dodecylbenzene sulfonate, 150-200g of sodium thiosulfate, 50-80g of cystine, 20-35g of citric acid, 40-60g of nano silicon, 20-40g of manganese sulfate, 5-10g of isoamyl acetate, and the rest is water; The dosage of the foliar barrier agent is 200 ml / mu, and it is diluted 100-300 times before use.

2. The method for reducing the cadmium content of rice in moderately contaminated soil according to claim 1, characterized in that: A. First, crush the calcium-based bentonite to less than 300 mesh, calcine it at high temperature 400-700℃ for 4 hours, and set aside; B. The biochar material is crushed to 200 mesh and set aside; C. Crush the shell powder to 200 mesh and set aside; D. Dry the silkworm excrement to control the moisture content below 15% and set aside; E. Mix and stir the various material components evenly according to the formula ratio to obtain the passivation agent product.

3. The method for reducing the cadmium content of rice in moderately contaminated soil according to claim 1, characterized in that: The preparation method of the foliar barrier agent is as follows: I. First, various solid compounds are dissolved in water separately, and each substance is dissolved close to its solubility; II. Slowly add the sodium thiosulfate solution into the citric acid solution, stirring while pouring, and mix thoroughly to obtain a mixed solution B; III. Pour the manganese sulfate solution into the mixed solution B, stirring while pouring, and mix thoroughly to obtain a mixed solution C; IV. Pour the potassium dihydrogen phosphate solution and the cystine solution into the mixed solution C in sequence, stirring while pouring, to obtain a mixed solution D; V. Pour the isoamyl acetate liquid into the sodium dodecylbenzene sulfonate solution while stirring to obtain a mixed solution E; VI. 2 hours before use, pour the nano-silicon solution and mixed solution E into mixed solution D in sequence and stir evenly to obtain a complete foliar barrier agent.

4. The method for reducing the cadmium content of rice in moderately contaminated soil according to claim 1, characterized in that: Use a sprayer to evenly spray the foliar barrier agent on the rice leaves.

5. The method for reducing the cadmium content of rice in moderately contaminated soil according to claim 1, characterized in that: Choose sunny weather to spray foliar control agents. If it rains within 4 hours after spraying, repeat the spraying. The amount of foliar control agent used is 1 / 3 to 1 / 2 of the normal amount.

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