Planting method for producing low-cadmium selenium-enriched rice in cadmium-polluted cultivated land

Abstract

The invention discloses a planting method for producing low-cadmium selenium-enriched rice in cadmium-polluted cultivated land, and belongs to the technical field of agricultural planting. According to the method, in the whole rice growth process, a selenium-rich bamboo charcoal organic fertilizer (used as a base fertilizer) and a selenium-rich bamboo juice leaf fertilizer which are developed by taking bamboo charcoal and bamboo juice products generated in the high-temperature firing process of selenium-rich adult moso bamboos as main raw materials are applied. Before the seedlings are transplanted, the cadmium-polluted cultivated land is deeply ploughed, and the selenium-rich bamboo charcoal organic fertilizer is adopted to improve the physical and chemical properties of the soil, adsorb and fix cadmium in the soil and activate the selenium element in the soil; in the booting stage and milk-ripe stage of rice, the selenium-rich bamboo juice foliar fertilizer is sprayed to rice plants to prevent cadmium in the rice plants from being transported into rice, and transport and accumulation of selenium into the rice are increased. The planting method is easy to operate, low in cost, environmentally friendly and quick in effect after being used, cadmium accumulation of rice can be remarkably reduced, the selenium content can be remarkably increased, and the planting method has important significance on prevention and treatment of cadmium-polluted rice soil and guarantee of grain safety.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural planting, and in particular relates to a planting method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland. Background Art

[0002] Selenium (Se) is an essential trace element for humans and animals. As a key active center in over 30 selenoproteins and selenoenzymes, it plays a crucial role in maintaining antioxidant, anti-cancer, and immune regulation. Long-term selenium deficiency may lead to diseases such as Keshan disease and Kashin-Beck disease. For those who are selenium-deficient, dietary selenium is the primary source of selenium supplementation, and the safest and most effective way to supplement selenium is through naturally selenium-rich agricultural products.

[0003] Cadmium (Cd) is a toxic heavy metal with a very long half-life. It is one of the persistent pollutants in the environment. It easily enters the biological system and can cause acute and chronic poisoning in humans and animals. It also has strong carcinogenic and teratogenic effects. A large number of studies have found that due to the influence of geological movements, selenium often co-exists with cadmium in the soil, resulting in the widespread threat of cadmium pollution in selenium-rich areas. It is precisely because of the superimposed effect of the co-existence of cadmium in selenium-rich soils and the synergistic effect of selenium and cadmium that the risk of cadmium contamination of agricultural products in selenium-rich soil areas has been aggravated. In order to ensure the high-quality development of selenium-rich agriculture, it is of great significance and urgent to carry out prevention, control and governance of cadmium pollution risk areas in selenium-rich soils.

[0004] At present, the methods for controlling or reducing heavy metal pollution in rice cultivation mainly focus on physical and chemical remediation technologies such as soil importation, vitrification technology, electric technology, soil leaching, etc. These technologies require huge engineering workloads, high investment, and damage to soil structures. They are only suitable for the remediation of small areas of heavily polluted areas, and are not suitable for large-scale arable land soil remediation. Bioremediation technology and combined remediation technology are the future development direction, but for the current arable land soil remediation, the long cycle and slow effect are the difficulties in their promotion. Commonly used paddy field soil cadmium passivators often passivate the activity of selenium in the soil while reducing the effective cadmium in the soil and preventing crops from absorbing cadmium, thereby reducing the effectiveness of soil selenium and reducing the absorption of selenium by crops. Therefore, how to achieve selenium-enriched agricultural products while reducing cadmium absorption in selenium-rich cadmium-contaminated soil has become a technical problem. Summary of the Invention

[0005] Existing soil conditioners or foliar control agents are difficult to accurately control in farmland with different levels of selenium-rich cadmium pollution. Only by combining discrimination technology and precise application technology for farmland with different selenium content and cadmium pollution levels can we effectively control cadmium absorption while achieving the safe production of selenium-rich agricultural products. Based on this, the purpose of the present invention is to provide a planting method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland, specifically adopting the following technical solutions: The present invention provides a planting method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland, comprising the following steps: Step 1: Bamboo charcoal powder and bamboo sap are obtained by high-temperature calcination of selenium-rich bamboo, and bamboo charcoal powder and bamboo sap are used as main raw materials to prepare selenium-rich bamboo charcoal organic fertilizer and selenium-rich bamboo sap foliar fertilizer respectively; Step 2: Select high-quality rice seeds, pre-treat them, and raise them for transplanting; plow and prepare the cadmium-contaminated farmland, apply selenium-rich bamboo charcoal organic fertilizer according to the cadmium content in the soil, and then transplant the rice seedlings; Step 3: When the seedlings grow to the booting stage and milky stage respectively, apply selenium-rich bamboo sap foliar fertilizer according to the cadmium content at the base of the rice stem and in the rice grains, and harvest the rice when it is mature.

[0006] Furthermore, the method for high-temperature burning of selenium-rich bamboo in step one is: take adult bamboo over 5 years old with a selenium content greater than 0.04 mg / kg (dry weight), cut it into tubes and sheets, burn it at a high temperature of more than 800°C (3-5 days), condense and filter to collect bamboo sap, crush and sieve the carbon sheets, carbon tubes and carbon powder after high-temperature burning to obtain bamboo charcoal powder.

[0007] Furthermore, the preparation method of the selenium-rich bamboo charcoal organic fertilizer in step 1 is: weighing 50-60 parts of bamboo charcoal powder, 10-20 parts of bamboo sap, 10-20 parts of calcium sulfate, and 10-20 parts of zinc sulfate by weight, and stirring and mixing (100-150 rpm); the total selenium content of the obtained selenium-rich bamboo charcoal organic fertilizer is greater than 50 mg / kg.

[0008] Furthermore, the preparation method of the selenium-rich bamboo sap foliar fertilizer described in step 1 is: weighing 40-50 parts of bamboo sap, 5-10 parts of polyglutamic acid, 2-5 parts of potassium dihydrogen phosphate, 3-5 parts of biochemical potassium humate, and 30-40 parts of water by weight, stirring and dissolving (100-150 rpm); the total selenium content of the obtained selenium-rich bamboo sap foliar fertilizer is greater than 0.4 g / L.

[0009] Furthermore, the molecular weight of the polyglutamic acid is 10,000-20,000; and on a dry basis, the biochemical fulvic acid content of the biochemical potassium fulvic acid is more than 45%, the total potassium content is more than 10%, and the organic matter content is more than 50%.

[0010] Furthermore, the pretreatment and seedling cultivation in step 2 include: soaking the seeds in warm water, disinfecting with strong chlorine, and germinating and cultivating the seedlings in a pollution-free artificial matrix; and transplanting can be carried out only when the seedlings have four leaves and one heart.

[0011] Furthermore, the plowing and field preparation in step 2 is as follows: deep plowing of about 20 cm is performed 15 days before rice transplanting, the field is flooded with a water layer of about 5 cm for 10 days, and then drained and deep plowed again, and selenium-rich bamboo charcoal organic fertilizer is applied 3 days before rice transplanting.

[0012] Furthermore, in step 2, the application of selenium-rich bamboo charcoal organic fertilizer according to the soil cadmium content is specifically as follows: 3 days before rice transplanting, the soil cadmium content is detected and the cadmium pollution index is calculated. When the cadmium pollution index is 1.0-2.5, 40-80 kg is applied per mu; when the cadmium pollution index is 2.5-5.0, 80-120 kg is applied per mu; when the cadmium pollution index is greater than 5.0, 120-160 kg is applied per mu.

[0013] Furthermore, in step three, the application of selenium-rich bamboo sap foliar fertilizer according to the cadmium content in the base of the rice stem and the rice grain is specifically as follows: when the stem base cadmium content is less than 2.0 mg / kg and the rice grain cadmium content is less than 0.2 mg / kg, apply it once during the milky stage, and apply 50-100 mL per mu; when the stem base cadmium content is 2.0-4.0 mg / kg and the rice grain cadmium content is 0.2-0.4 mg / kg, apply it once each during the booting stage and the milky stage, and apply 100-200 mL per mu; when the stem base cadmium content is greater than 4.0 mg / kg and the rice grain cadmium content is greater than 0.4 mg / kg, apply it once each during the booting stage and the milky stage, and apply 200-300 mL per mu.

[0014] Furthermore, the spraying method of the selenium-rich bamboo sap foliar fertilizer is: dilute it 400 times with water, spray it on a sunny day without rain, and spray it again if it rains within 6 hours after spraying.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The planting method provided by the present invention applies selenium-rich bamboo charcoal organic fertilizer (as base fertilizer) and selenium-rich bamboo sap foliar fertilizer developed with bamboo charcoal and bamboo sap products produced during the high-temperature burning process of selenium-rich mature bamboo as the main raw materials during the entire rice growth process. The bamboo charcoal has a developed microporous structure inside and is rich in calcium, potassium, sodium, magnesium and other minerals required for plant growth; bamboo charcoal is alkaline and can neutralize acidic substances in the soil, and also has the ability to remove heavy metals (physical adsorption and fixation). Bamboo sap is a liquid substance obtained by cooling the gas generated by pyrolysis of bamboo at room temperature. It contains nearly 300 natural high-molecular organic compounds, including organic acids, alcohols, ketones, aldehydes, esters and trace amounts of alkaline components, etc., and has the characteristics of being rich in selenium and complexing Cd. 2+ , reduce Cd effectiveness, reduce Cd 2+ The invention uses bamboo charcoal and bamboo sap as main raw materials, mixed with plant nutrient solution and microorganisms to produce a highly efficient, pollution-free, ecologically friendly green fertilizer without any inorganic substances. The fertilizer has the functions of nitrogen fixation, phosphorus solubilization, potassium solubilization, and antibacterial. The combined application of the two can effectively reduce the bioavailability of cadmium in the soil and promote the activation of selenium in the soil. The fertilizer has a rapid effect after use, can reduce cadmium accumulation in rice and increase selenium enrichment, and has ideal effects in large-scale applications.

[0016] 2. The planting method provided by the present invention is simple to operate and adopts flooding cultivation throughout the entire growth period of rice, which effectively reduces the cost of cadmium treatment and increases rice yield. It has a short cycle, is environmentally friendly, does not damage the soil structure, and has a significant soil remediation effect. It is of great significance for preventing and controlling cadmium pollution of paddy soil and ensuring food security. DETAILED DESCRIPTION

[0017] To make the objects, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described clearly and completely below in conjunction with the examples. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] Example 1 A planting method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland, comprising: 1. Select selenium-rich mature bamboos aged 5 years or older (selenium content 0.06 mg / kg), cut into tubes and sheets, and transfer them into a high-temperature kiln for carbonization at 850°C for 4 days. During the carbonization process, the liquid is collected through a condenser and filtered through a membrane (pore size 0.4 μm) to obtain selenium-rich bamboo sap. After cooling, the carbon sheets, carbon tubes, and carbon powder obtained from high-temperature carbonization are crushed and sieved (200 mesh) to obtain selenium-rich bamboo charcoal powder.

[0020] 2. Weigh 55 parts of selenium-rich bamboo charcoal powder, 15 parts of selenium-rich bamboo sap, 12 parts of calcium sulfate, and 12 parts of zinc sulfate by weight, and mix thoroughly in a blender (120 rpm) to obtain a selenium-rich bamboo charcoal organic fertilizer (total selenium content: 58.4 mg / kg). Weigh 45 parts of selenium-rich bamboo sap, 8 parts of polyglutamic acid, 3.5 parts of potassium dihydrogen phosphate, 4 parts of biochemical potassium fulvate, and 35 parts of water by weight, and dissolve and mix thoroughly in a blender (120 rpm) to obtain a selenium-rich bamboo sap foliar fertilizer (total selenium content: 0.7 g / L).

[0021] 3. Select high-yield, high-quality rice varieties (Xizi No. 3) with low cadmium absorption and accumulation. Soak the selected seeds in 25°C warm water for 12 hours. Then soak them in a 350-fold dilution of 85% trichloroisocyanuric acid (Qianglujing) powder for 12 hours. Then soak them in 38°C warm water twice for 5 minutes. Drain and crack the seeds. Turn the pile and thin the seedbed. When the radicle is half the length of the seed, sow the seeds in a non-polluted artificial substrate for normal germination and seedling cultivation. Transplant the seedlings to contaminated farmland when they have four leaves and one heart. Apply potassium dihydrogen phosphate as ear fertilizer after they have reached ear formation.

[0022] 4. Cultivated land in the cadmium pollution control area of Yuanzhou District was selected for the experiment. The topsoil cadmium content in the test fields was 1.51 mg / kg, the selenium content was 0.78 mg / kg, and the pH was 5.45. Fifteen days before transplanting the seedlings, the test fields were plowed to a depth of 20 cm and flooded with approximately 5 cm of water for 10 days. After drainage, the fields were plowed and prepared again. Three days before transplanting, the soil cadmium content was tested and the cadmium pollution index was calculated (cadmium pollution index = measured soil cadmium content / soil cadmium pollution screening value). Selenium-rich bamboo charcoal organic fertilizer was applied based on the cadmium pollution index (mixed with the top 2-4 cm of soil and then flooded with 3-6 cm of water). The fields were then carefully prepared and thoroughly raked and allowed to settle for one day before transplanting the seedlings.

[0023] The diagonal five-point sampling method was used for mixed soil sampling. The total selenium content in soil was determined according to NY / T 1104-2006 Determination of total selenium in soil; the available selenium content in soil was determined according to GB / T 17141-1997 Soil quality - Determination of lead and cadmium - Graphite furnace atomic absorption spectrophotometry; the total cadmium content in soil was determined according to GB / T 17141-1997 Soil quality - Determination of lead and cadmium - Graphite furnace atomic absorption spectrophotometry; and the available cadmium content in soil was determined according to GB / T 23739-2009 Soil quality - Determination of available lead and cadmium - Atomic absorption method.

[0024] Application amount of selenium-rich bamboo charcoal organic fertilizer: when the cadmium pollution index is 1.0-2.5, apply 40-80 kg per mu; when the cadmium pollution index is 2.5-5.0, apply 80-120 kg per mu; when the cadmium pollution index is greater than 5.0, apply 120-160 kg per mu.

[0025] 5. Detect and record the cadmium content at the base of the rice stem at the booting stage and the rice grains at the milky stage. Apply selenium-rich bamboo sap foliar fertilizer based on the cadmium content at the base of the rice stem and the rice grains.

[0026] The total selenium content at the base of rice stems was determined using the National Food Safety Standard for the Determination of Selenium in Foods (GB 5009.93-2017); the inorganic selenium content at the base of rice stems was determined using the Local Food Safety Standard for the Determination of Inorganic Selenium in Selenium-Rich Foods (DBS42 / 010-2018); and the total cadmium content at the base of rice stems was determined using the National Food Safety Standard for the Determination of Cadmium in Foods (GB 5009.15-2023). The total selenium content in rice grains was determined using the National Food Safety Standard for the Determination of Total Selenium in Soils (NY / T 1104-2006); the inorganic selenium content in rice grains was determined using the Local Food Safety Standard for the Determination of Inorganic Selenium in Selenium-Rich Foods (DBS42 / 010-2018); and the total cadmium content in rice grains was determined using the National Food Safety Standard for the Determination of Cadmium in Foods (GB 5009.15-2023).

[0027] Foliar fertilizer application rate for selenium-rich bamboo sap: When the cadmium content at the base of the stem is less than 2.0 mg / kg and the cadmium content in the rice grain is less than 0.2 mg / kg, apply once during the milky stage at a rate of 50-100 mL per mu. When the cadmium content at the base of the stem is between 2.0-4.0 mg / kg and the cadmium content in the rice grain is between 0.2-0.4 mg / kg, apply once each during the booting and milky stages at a rate of 100-200 mL per mu. When the cadmium content at the base of the stem is greater than 4.0 mg / kg and the cadmium content in the rice grain is greater than 0.4 mg / kg, apply once each during the booting and milky stages at a rate of 200-300 mL per mu. Application method: Dilute 400 times with water and spray on a sunny, rainless day. Re-spray within 6 hours if rain occurs.

[0028] 6. Flooding was used throughout the rice growing season. Shallow irrigation was practiced frequently throughout the growing season, with a 4 cm thin layer of water protecting the fields during the heading stage. Water was cut off from the fields seven days before harvest. During the rice maturity period, rice samples were randomly collected and sent to a third-party testing agency with CMA certification for determination of total selenium and cadmium content, as well as their available forms. The results are shown in Table 1.

[0029] Comparative Example Compound fertilizer (N-P2O5-K2O=15:15:15) was used as the control base fertilizer, with an application of 50 kg per mu. No foliar fertilizer was sprayed on the control group during the same period. 2 kg of potassium dihydrogen phosphate was applied per mu during the booting stage.

[0030] Table 1 Test results of rice samples

[0031] Table 1 shows that, by adopting the planting method of the present invention, Jiangsu Jiaxin Testing Technology Co., Ltd. found that the total cadmium content in rice was reduced from 0.6009 mg / kg to 0.0438 mg / kg, and the cadmium content was reduced from seriously exceeding the standard to extremely low; the total selenium content in rice was increased from 0.0666 mg / kg to 0.0823 mg / kg, an increase of 23.57%; and the organic selenium content was increased from 0.0584 mg / kg to 0.0728 mg / kg, an increase of 24.66%. Testing by the Food Inspection and Testing Institute of the Jiangxi Provincial Inspection, Testing and Certification Institute found that the total cadmium content in rice decreased from 0.6310 mg / kg to 0.0189 mg / kg, from a serious cadmium exceeding the standard to an extremely low content; the total selenium content in rice increased from 0.0680 mg / kg to 0.0900 mg / kg, an increase of 32.35%; the organic selenium content increased from 0.0606 mg / kg to 0.0820 mg / kg, an increase of 35.31%.

[0032] The above experiments have proved that the planting method of the present invention can significantly reduce the cadmium content in rice and effectively increase its selenium content. The rice produced meets the relevant standards of GB / T 22499-2008 and GB2762-2022 (the selenium content meets the requirements of "GB / T22499~2008 Selenium-enriched Rice", and the cadmium content meets the requirements of "National Food Safety Standard Limits of Contaminants in Food" (GB2762~2022)).

[0033] The embodiments described above merely represent several preferred embodiments of the present invention. While the descriptions are relatively specific and detailed, they are not intended to limit the present invention. It should be noted that those skilled in the art will readily appreciate that the present invention is susceptible to various variations and modifications. Any modifications, equivalent substitutions, or improvements within the scope of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A planting method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland, characterized in that: The following steps are involved: Step 1: Bamboo charcoal powder and bamboo sap are obtained by high-temperature calcination of selenium-rich bamboo, and bamboo charcoal powder and bamboo sap are used as main raw materials to prepare selenium-rich bamboo charcoal organic fertilizer and selenium-rich bamboo sap foliar fertilizer respectively; Step 2: Select high-quality rice seeds, pre-treat them, and raise them for transplanting; plow and prepare the cadmium-contaminated farmland, apply selenium-rich bamboo charcoal organic fertilizer according to the cadmium content in the soil, and then transplant the rice seedlings; Step 3: When the seedlings grow to the booting stage and milky stage respectively, apply selenium-rich bamboo sap foliar fertilizer according to the cadmium content at the base of the rice stem and in the rice grains, and harvest the rice when it is mature.

2. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: The method for high-temperature burning of selenium-rich bamboo in step 1 is as follows: taking adult bamboo over 5 years old with a selenium content greater than 0.04 mg / kg, cutting it into tubes and sheets, burning it at a high temperature of more than 800°C, condensing and filtering to collect bamboo sap, crushing and sieving the carbon sheets, carbon tubes and carbon powder after high-temperature burning to obtain bamboo charcoal powder.

3. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: The preparation method of the selenium-rich bamboo charcoal organic fertilizer in step 1 is as follows: 50-60 parts of bamboo charcoal powder, 10-20 parts of bamboo sap, 10-20 parts of calcium sulfate, and 10-20 parts of zinc sulfate are weighed by weight, and the mixture is stirred and evenly mixed; the total selenium content of the obtained selenium-rich bamboo charcoal organic fertilizer is greater than 50 mg / kg.

4. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: The preparation method of the selenium-rich bamboo sap foliar fertilizer described in step 1 is: weighing 40-50 parts of bamboo sap, 5-10 parts of polyglutamic acid, 2-5 parts of potassium dihydrogen phosphate, 3-5 parts of biochemical potassium fulvic acid, and 30-40 parts of water by weight, stirring and dissolving; the total selenium content of the obtained selenium-rich bamboo sap foliar fertilizer is greater than 0.4 g / L.

5. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 4, characterized in that: The molecular weight of the polyglutamic acid is 10,000-20,000; based on dry basis, the biochemical fulvic acid content in the biochemical potassium fulvic acid is more than 45%, the total potassium content is more than 10%, and the organic matter content is more than 50%.

6. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: The pretreatment and seedling raising in step 2 include: soaking the seeds in warm water, disinfecting with strong chlorine, and germinating and raising the seedlings in a pollution-free artificial matrix; transplanting can be carried out only when the seedlings have four leaves and one heart.

7. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: The plowing and field preparation in step 2 is as follows: deep plowing of about 20 cm is performed 15 days before rice transplanting, the field is flooded with about 5 cm of water for 10 days, and then drained and deep plowed again. Selenium-rich bamboo charcoal organic fertilizer is applied 3 days before rice transplanting.

8. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: In step 2, the application of selenium-rich bamboo charcoal organic fertilizer according to the soil cadmium content is specifically as follows: 3 days before rice transplanting, the soil cadmium content is tested and the cadmium pollution index is calculated. When the cadmium pollution index is 1.0-2.5, 40-80 kg per mu is applied; when the cadmium pollution index is 2.5-5.0, 80-120 kg per mu is applied; when the cadmium pollution index is greater than 5.0, 120-160 kg per mu is applied.

9. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 1, characterized in that: In step three, the application of selenium-rich bamboo sap foliar fertilizer according to the cadmium content in the base of the rice stem and the rice grain is specifically as follows: when the stem base cadmium content is less than 2.0 mg / kg and the rice grain cadmium content is less than 0.2 mg / kg, apply it once during the milky stage, and apply 50-100 mL per mu; when the stem base cadmium content is 2.0-4.0 mg / kg and the rice grain cadmium content is 0.2-0.4 mg / kg, apply it once each during the booting stage and the milky stage, and apply 100-200 mL per mu; when the stem base cadmium content is greater than 4.0 mg / kg and the rice grain cadmium content is greater than 0.4 mg / kg, apply it once each during the booting stage and the milky stage, and apply 200-300 mL per mu.

10. The method for producing low-cadmium and selenium-rich rice in cadmium-contaminated farmland according to claim 9, characterized in that: The spraying method of the selenium-rich bamboo sap foliar fertilizer is as follows: dilute it 400 times with water, spray it on a sunny day without rain, and spray it again if it rains within 6 hours after spraying.

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