Leaf surface resistance and control method for reducing heavy metal pollution

Abstract

The invention discloses a leaf surface resistance and control method for reducing heavy metal pollution, and belongs to the technical field of heavy metal pollution control, and the method specifically comprises the following steps: mixing sulfydryl modified collagen, tobacco extract, ferric sodium ethylene diamine tetraacetate, manganese sodium ethylene diamine tetraacetate, sugar alcohol silicon original liquid fertilizer, sodium selenite and deionized water to obtain a leaf surface resistance and control agent; according to the method, the composition of the leaf surface resistance and control agent is optimized, the leaf surface resistance and control agent is sprayed in three key growth stages including the tillering stage, the flowering stage and the filling stage of the rice, and the alkaline base fertilizer is used for assisting in adjusting the soil pH and water irrigation field management, so that the heavy metal stress resistance of the rice is improved, and the growth and development of the rice are promoted; the heavy metal content in the rice is reduced, the quality of the rice is improved, and the yield of the rice is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal pollution prevention and control, and particularly relates to a foliar control method for reducing heavy metal pollution. Background Art

[0002] With the acceleration of the global industrialization process, heavy metal pollutants generated by industries such as mining, metal smelting, chemical medicine, electronics and electrical appliances, electroplating, and leather making have increased significantly, and environmental pollution problems have become increasingly serious. In particular, heavy metal pollution has become an important factor threatening agricultural ecological safety and the quality of agricultural products. Heavy metal pollutants enter the soil and water bodies through various channels, and then are absorbed by crops, resulting in excessive heavy metal content in agricultural products, seriously threatening human health.

[0003] In the prior art, the publication number is CN112335676A, which discloses a preparation method and usage steps of a foliar control agent for reducing heavy metal content in rice. It is to grind and sieve diatomite to obtain diatomite powder, mix an aqueous potassium hydroxide solution with the diatomite powder according to the volume-weight ratio and stir evenly to obtain a silicon-potassium mixed slurry, irradiate the silicon-potassium mixed slurry with low-temperature plasma to obtain an activated silicon-potassium mixed slurry, mix humus soil and the activated silicon-potassium mixed slurry according to the weight ratio and stir well to obtain a silicon-potassium organic mixed slurry, irradiate the silicon-potassium organic mixed slurry with low-temperature plasma to obtain a silicon-potassium-based control alkali slurry, first mix citric acid weighed according to the weight ratio with the silicon-potassium-based control alkali slurry, and then perform solid-liquid separation to obtain a foliar control agent for reducing heavy metal content in rice. The usage steps are to dilute the foliar control agent with water by 18 - 22 times and then spray it on the rice leaves. The foliar control agent can promote the growth of rice and reduce the adsorption of harmful heavy metal elements such as mercury and cadmium in the soil by rice.

[0004] However, most of the control agents in the prior art rely on single functional components (such as silicon or selenium), lack the design of multi-component synergistic effect, and it is difficult to take into account multiple objectives such as heavy metal chelation, foliar barrier, and crop nutrition enhancement. Moreover, during the key physiological stages of rice such as the tillering stage, flowering stage, and filling stage, no differential spraying measures are designed for them. Especially in areas with serious heavy metal pollution, the ability of rice to resist heavy metal stress needs to be further improved, which affects the growth and development of rice, resulting in the quality and yield of rice needing to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a foliar control method for reducing heavy metal pollution, which is used to solve the technical problems that the ability of rice planting to resist heavy metal stress and the yield of rice need to be further improved in the prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A foliar control method for reducing heavy metal pollution, comprising the following steps:

[0007] S1. Before transplanting rice, apply alkaline base fertilizer to the field;

[0008] S2. Mix mercapto-modified collagen, tobacco extract, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, sugar alcohol silicon stock fertilizer, sodium selenite and deionized water to obtain a foliar control agent. After diluting the foliar control agent with water, a foliar control dilution solution is obtained;

[0009] S3. Conduct irrigation during the tillering stage, flowering stage, and filling stage of rice, maintain the water layer at 3 - 5 cm, and spray the foliar control dilution solution during the tillering stage, flowering stage, and filling stage. For the rest, follow the conventional field management and harvest the rice.

[0010] Further, in step S1, the application rate of the alkaline base fertilizer is 70 - 80 kg / mu, and the alkaline base fertilizer is composed of urea, calcium magnesium phosphate fertilizer, potassium carbonate, silicon calcium conditioner and silicon selenium ore powder in a weight ratio of 30 - 35:23 - 26:10 - 16:6 - 8:3 - 5.

[0011] Further, in step S2, the foliar control agent is composed of mercapto-modified collagen, tobacco extract, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, sugar alcohol silicon stock fertilizer, sodium selenite and deionized water in a weight ratio of 7 - 8:3 - 4:1 - 2:1 - 2:2 - 3:0.8 - 1.2:50.

[0012] Further, the foliar control dilution solution is obtained by diluting the foliar control agent and water in a volume ratio of 1:180 - 220.

[0013] Further, the number of times of spraying the foliar control dilution solution during the tillering stage and flowering stage of rice is once, and the spraying periods are the early stage of the tillering stage and the early stage of the flowering stage. The spraying amount of the foliar control dilution solution is 75 - 85 L / mu. The spraying frequency of the foliar control dilution solution during the filling stage is 7 days / time, and the spraying amount of the foliar control dilution solution is 110 - 120 L / mu. The spraying start period is the early stage of the filling stage.

[0014] Further, the preparation method of mercapto-modified collagen is as follows: Mix bovine bone collagen peptide powder and deionized water, stir until the system is dissolved. Under the protection of an inert atmosphere, lower the temperature of the reaction system to 4 - 6 °C, add N-(tetrahydro-2-oxo-3-thienyl)butyramide, ethylenediaminetetraacetic acid, and dithiothreitol to the reaction system, keep the temperature for reaction for 10 - 14 h, and perform post-treatment to obtain mercapto-modified collagen.

[0015] The synthesis reaction mechanism of mercapto-modified collagen is:

[0016] During the reaction, N-(tetrahydro-2-oxo-3-thienyl)butyramide hydrolyzes under low-temperature conditions, releasing a mercapto group. The mercapto group undergoes a nucleophilic substitution reaction with the amino or carboxyl group in the collagen peptide molecule to form a thioether bond or an amide bond, thereby introducing the mercapto group into the collagen peptide molecule. Dithiothreitol is used as a reducing agent to prevent the mercapto group from being oxidized to a disulfide bond and ensure the stability of the mercapto group. After post-treatment to remove unreacted small molecules, mercapto-modified collagen is prepared.

[0017] Furthermore, the dosage ratio of the bovine bone collagen peptide powder, deionized water, N-(tetrahydro-2-oxo-3-thienyl)butyramide, ethylenediaminetetraacetic acid, and dithiothreitol is 10 g: 500 mL: 3 - 4 g: 0.2 - 0.3 g: 1.1 - 1.3 g. The post-treatment includes: after the reaction is completed, the reaction solution is transferred into a dialysis bag with a molecular cut-off of 8000 - 14000 kDa, and then the dialysis bag is placed into a phosphate buffer solution with a pH of 9. The temperature of the phosphate buffer solution is reduced to 4 - 6 °C, and dialysis is carried out for 30 - 36 h. During this period, the phosphate buffer solution is changed every 6 h. Then, the liquid in the dialysis bag is transferred into an evaporator at a temperature of 65 °C and a pressure of -0.1 MPa, and low-boiling substances are removed under reduced pressure to obtain mercapto-modified collagen.

[0018] Furthermore, the tobacco extract is processed by the following steps:

[0019] A1. The tobacco leaves and tobacco dust extract are pulverized and then passed through an 80-mesh sieve to obtain tobacco powder.

[0020] A2. The tobacco powder, deionized water, and α-amylase are mixed and stirred, and the temperature of the reaction system is raised to 45 - 55 °C, and the reaction is carried out for 4 - 6 h with heat preservation. After post-treatment, tobacco extract is obtained.

[0021] The synthesis reaction mechanism of the tobacco extract is as follows:

[0022] α-Amylase is a hydrolase. During the reaction, it can catalyze the hydrolysis of starch and polysaccharide substances in the tobacco powder to generate small molecular sugars. At the same time, other components such as polyphenols, alkaloids, and organic acids in the tobacco are released into the aqueous phase. By centrifugation and filtration, solid residues and fine particles are removed, and then through concentration, tobacco extract is obtained.

[0023] Furthermore, in step A2, the dosage ratio of the tobacco powder to deionized water is 1 g: 10 mL, and the dosage of α-amylase is 55 - 65 U / g. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, and after centrifugation, the supernatant is filtered through a 0.25-μm nylon filter membrane. Then, the filtrate is transferred into an evaporator at a temperature of 65 °C and a pressure of -0.1 MPa, and low-boiling substances are removed under reduced pressure to obtain tobacco extract.

[0024] The present invention has the following beneficial effects:

[0025] 1. A foliar control method for reducing heavy metal pollution proposed by the present invention adjusts the soil pH through basal fertilizer to reduce the activity of heavy metals. During the three key growth stages of the tillering stage, flowering stage, and filling stage of rice, foliar control agents are sprayed with the assistance of field management of water irrigation. The water irrigation submerges the soil layer, taking advantage of the low solubility of heavy metals in water and the alkaline basal fertilizer to form precipitates of heavy metals, reducing their bioavailability, forming a protection on the soil layer, and blocking the path for heavy metals to enter rice after being absorbed through the soil layer. The foliar control agent acts directly on the leaves, reducing the absorption of heavy metals from atmospheric deposition through the leaves and promoting their excretion. The nutrient components in the control agent promote the growth of rice and can further increase the yield.

[0026] 2. A foliar control method for reducing heavy metal pollution proposed by the present invention mixes urea, calcium magnesium phosphate fertilizer, potassium carbonate, silicon-calcium conditioner, and silicon-selenium ore powder into an alkaline basal fertilizer. In the alkaline basal fertilizer, calcium magnesium phosphate fertilizer, potassium carbonate, and silicon-calcium conditioner jointly raise the soil pH to neutral or weakly alkaline, making lead or cadmium form insoluble metal salts and reducing the amount of exchangeable heavy metals in the soil. Si in the silicon-calcium conditioner and silicon-selenium ore powder competes with Cd for root cell membrane transport proteins, and after absorbing silicon elements, it can deposit in the endodermis of the root, forming a "silicon-suberization double barrier" to inhibit the transport of heavy metals to the xylem. SeO 3 2- forms insoluble complexes with heavy metal ions, reducing the bioavailability of heavy metal ions. The absorption of Se elements upregulates the activity of glutathione peroxidase, alleviates heavy metal-induced lipid peroxidation, and then through field management, a slightly flooded water environment is created during the key growth stage of rice, reducing the redox potential of the rhizosphere soil to -100 to -200 mV, increasing the activity of sulfate-reducing bacteria, and generating S 2- which combines with heavy metal ions to form metal sulfide precipitates, thereby reducing the amount of heavy metals absorbed by the roots and rhizomes and entering the rice.

[0027] 3. A foliar control method for reducing heavy metal pollution proposed by the present invention uses a foliar control agent composed of mercapto-modified collagen, tobacco extract, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, sugar alcohol silicon stock fertilizer, and sodium selenite. Mercapto has a strong affinity for heavy metals and may form stable complexes to prevent heavy metals from entering rice plants. Mercapto-modified collagen chelates heavy metals to prevent them from entering rice plants. In addition, collagen itself may form a protective film to cover the leaf surface, reducing the attachment and penetration of heavy metals. Tobacco contains substances such as alkaloids and polyphenols, and these components have antioxidant effects, which can reduce the oxidative stress caused by heavy metals. In addition, certain components in the tobacco extract may induce the plant's own defense mechanism, such as activating the antioxidant enzyme system, thereby enhancing the tolerance of rice to heavy metals. In sodium ferric ethylenediaminetetraacetate and sodium manganese ethylenediaminetetraacetate, EDTA forms stable chelates with heavy metals, reducing their free concentration in the leaves. Iron and manganese, as essential trace elements, alleviate the nutrient deficiency under heavy metal stress and enhance the photosynthesis efficiency. When sodium ferric ethylenediaminetetraacetate and sodium manganese ethylenediaminetetraacetate enter the irrigation layer of the field soil, Fe 2+ / Mn 2+ oxide colloidal films are formed on the root surface by oxidation to further increase their adsorption capacity for heavy metals. In the sugar alcohol silicon stock fertilizer, silicon promotes the silicification of the cell wall, enhancing the mechanical barrier and restricting the transport of heavy metals to the above-ground parts. Moreover, sugar alcohol, as an osmotic regulator, improves the adhesion of the foliar control agent and extends its action time. Sodium selenite alleviates Cd-induced lipid peroxidation by upregulating the activity of glutathione peroxidase, improves the heavy metal stress resistance of rice, and promotes the growth and development of rice. Specific Embodiments

[0028] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0029] In this application, the bovine bone collagen peptide powder is selected from Shandong Pingju Biotechnology Co., Ltd., with a content higher than 99%, and the appearance is crystalline to powder;

[0030] In this application, the CAS number of N-(tetrahydro-2-oxo-3-thienyl) butyramide is 39837-08-6;

[0031] In this application, the CAS number of dithiothreitol is 27565-41-9;

[0032] In this application, the CAS number of sodium ferric ethylenediaminetetraacetate is 15708-41-5;

[0033] In this application, the CAS number of manganese sodium ethylene diamine tetraacetate is 15375-84-5;

[0034] In this application, the sugar alcohol silicon stock solution fertilizer is selected from Shandong Zhenlvmei Biotechnology Co., Ltd., and the content of the active ingredient SiO 2 ≥170 g / L, and the content of compound sugar alcohol ≥100 g / L;

[0035] In this application, the urea is selected from Guangxi Zhuangfang Liyuan Biotechnology Co., Ltd., and the total nitrogen content ≥46.2%;

[0036] In this application, the silicon-calcium conditioner is selected from Shanxi Jiayou Humic Acid Technology Co., Ltd., and the content of the active ingredient is 30%;

[0037] In this application, the calcium magnesium phosphate fertilizer is selected from Jinan Chenxing Chemical Co., Ltd., the main component is organic silicon phosphate fertilizer, the particle size / mesh number is 200 meshes, the moisture content ≤1%, the available phosphorus content ≥12%, and the total phosphorus content ≥12%;

[0038] In this application, the silicon selenium ore powder consists of 25.0-35% calcium oxide, 0.03-0.05% selenium and the balance silicon dioxide, and the mesh number is 325 meshes.

[0039] Example 1

[0040] This example provides a preparation method of a foliar control agent for reducing heavy metal pollution, including the following steps:

[0041] A1. Preparation of mercapto-modified collagen

[0042] Weigh: 100 g of bovine bone collagen peptide powder and 5 L of deionized water, add them to a reaction kettle under nitrogen protection and stir until the system dissolves. Lower the temperature of the reaction kettle to 4 °C, add 30 g of N-(tetrahydro-2-oxo-3-thienyl) butyramide, 2 g of ethylene diamine tetraacetic acid, and 11 g of dithiothreitol to the reaction kettle, keep the temperature for reaction for 10 h, transfer the reaction solution to a dialysis bag with a molecular cut-off of 8000 kDa, then put the dialysis bag into a phosphate buffer solution with pH = 9, lower the temperature of the phosphate buffer solution to 4 °C, dialyze for 30 h, change the phosphate buffer solution every 6 h during this period, and then transfer the liquid in the dialysis bag to an evaporator at a temperature of 65 °C and a pressure of -0.1 MPa, and evaporate and remove the low-boiling substances under reduced pressure to obtain mercapto-modified collagen.

[0043] A2. Preparation of tobacco extract

[0044] Crush the tobacco leaves and tobacco dust extract and pass through an 80-mesh sieve to obtain tobacco powder;

[0045] Weigh: 100 g of tobacco powder, 1 L of deionized water, and add α-amylase to a three-necked flask and stir. Raise the temperature of the three-necked flask to 45 °C, keep the temperature for 4 h, then lower the temperature of the three-necked flask to room temperature, centrifuge, filter the supernatant with a 0.25 μm nylon filter membrane, and transfer the filtrate to an evaporator at 65 °C and a pressure of -0.1 MPa to remove low-boiling substances under reduced pressure to obtain a tobacco extract. Among them, the dosage of α-amylase and tobacco powder is 55 U / g.

[0046] A3. Preparation of foliar control agent

[0047] Weigh by weight: 7 parts of mercapto-modified collagen, 3 parts of tobacco extract, 1 part of sodium ferric ethylenediaminetetraacetate, 1 part of sodium manganese ethylenediaminetetraacetate, 2 parts of sugar alcohol silicon stock fertilizer, 0.8 part of sodium selenite, and 50 parts of deionized water, mix evenly to obtain a foliar control agent.

[0048] Example 2

[0049] This example provides a preparation method of a foliar control agent for reducing heavy metal pollution, including the following steps:

[0050] A1. Preparation of mercapto-modified collagen

[0051] Weigh: 100 g of bovine bone collagen peptide powder and 5 L of deionized water, add them to a reaction kettle under nitrogen protection and stir until the system dissolves. Lower the temperature of the reaction kettle to 5 °C, add 35 g of N-(tetrahydro-2-oxo-3-thienyl)butyramide, 2.5 g of ethylenediaminetetraacetic acid, and 12 g of dithiothreitol to the reaction kettle, keep the temperature for 12 h, transfer the reaction solution to a dialysis bag with a molecular cut-off of 11,000 kDa, then put the dialysis bag into a phosphate buffer solution with pH = 9, lower the temperature of the phosphate buffer solution to 5 °C, dialyze for 33 h, change the phosphate buffer solution every 6 h during this period, and then transfer the liquid in the dialysis bag to an evaporator at 65 °C and a pressure of -0.1 MPa to remove low-boiling substances under reduced pressure to obtain mercapto-modified collagen.

[0052] A2. Preparation of tobacco extract

[0053] Crush the tobacco leaf and tobacco powder extract and pass through an 80-mesh sieve to obtain tobacco powder;

[0054] Weigh: 100 g of tobacco powder, 1 L of deionized water, and add α-amylase to a three-necked flask and stir. Raise the temperature of the three-necked flask to 50 °C, keep the temperature for 5 h, then lower the temperature of the three-necked flask to room temperature, centrifuge, filter the supernatant with a 0.25 μm nylon filter membrane, and transfer the filtrate to an evaporator at 65 °C and a pressure of -0.1 MPa to remove low-boiling substances under reduced pressure to obtain a tobacco extract. Among them, the dosage of α-amylase and tobacco powder is 60 U / g.

[0055] A3. Preparation of Foliar Control Agent

[0056] Weigh by parts by weight: 7.5 parts of mercapto-modified collagen, 3.5 parts of tobacco extract, 1.5 parts of sodium ferric ethylenediaminetetraacetate, 1.5 parts of sodium manganese ethylenediaminetetraacetate, 2.5 parts of sugar alcohol silicon stock fertilizer, 1.0 part of sodium selenite and 50 parts of deionized water, and mix them evenly to obtain the foliar control agent.

[0057] Example 3

[0058] This example provides a preparation method of a foliar control agent for reducing heavy metal pollution, including the following steps:

[0059] A1. Preparation of mercapto-modified collagen

[0060] Weigh: 100 g of bovine bone collagen peptide powder and 5 L of deionized water, add them to a reaction kettle protected by nitrogen and stir until the system is dissolved. Lower the temperature of the reaction kettle to 6°C, add 40 g of N-(tetrahydro-2-oxo-3-thienyl)butyramide, 3 g of ethylenediaminetetraacetic acid, and 13 g of dithiothreitol to the reaction kettle, and carry out a heat preservation reaction for 14 h. Transfer the reaction solution to a dialysis bag with a molecular cut-off of 14000 kDa, then put the dialysis bag into a phosphate buffer solution with pH = 9, lower the temperature of the phosphate buffer solution to 6°C, and carry out dialysis for 36 h. During this period, change the phosphate buffer solution every 6 h. Then transfer the liquid in the dialysis bag to an evaporator at a temperature of 65°C and a pressure of -0.1 MPa, and evaporate and remove the low-boiling substances under reduced pressure to obtain mercapto-modified collagen.

[0061] A2. Preparation of tobacco extract

[0062] Crush the tobacco leaves and tobacco dust extract and pass them through an 80-mesh sieve to obtain tobacco powder;

[0063] Weigh: 100 g of tobacco powder, 1 L of deionized water, and α-amylase, add them to a three-necked flask and stir. Raise the temperature of the three-necked flask to 55°C, carry out a heat preservation reaction for 6 h, lower the temperature of the three-necked flask to room temperature, centrifuge, filter the supernatant with a 0.25-μm nylon filter membrane, and then transfer the filtrate to an evaporator at a temperature of 65°C and a pressure of -0.1 MPa, and evaporate and remove the low-boiling substances under reduced pressure to obtain the tobacco extract. Among them, the dosage of α-amylase and tobacco powder is 65 U / g.

[0064] A3. Preparation of foliar control agent

[0065] Weigh by parts by weight: 8 parts of mercapto-modified collagen, 4 parts of tobacco extract, 2 parts of sodium ferric ethylenediaminetetraacetate, 2 parts of sodium manganese ethylenediaminetetraacetate, 3 parts of sugar alcohol silicon stock fertilizer, 1.2 parts of sodium selenite and 50 parts of deionized water, and mix them evenly to obtain the foliar control agent.

[0066] Example 4

[0067] This embodiment provides a foliar control method for reducing heavy metal pollution, including the following steps:

[0068] S1. Applying basal fertilizer

[0069] Select a field plot with an average annual heavy metal deposition of lead and cadmium in the atmosphere of 26.5 mg / m 2 / yr and 1.8 mg / m 2 / yr as the experimental plot,

[0070] Mix urea, calcium magnesium phosphate fertilizer, potassium carbonate, silicon-calcium conditioner and silicon-selenium ore powder evenly according to a weight ratio of 30:23:10:6:3 to obtain an alkaline basal fertilizer for standby;

[0071] Before transplanting rice, apply the alkaline basal fertilizer to the experimental plot at an application rate of 70 kg / mu.

[0072] S2. Diluting the foliar control agent

[0073] Mix the foliar control agent prepared in Example 1 and drinking water evenly according to a volume ratio of 1:180 to obtain a foliar control dilution.

[0074] S3. Conduct irrigation during the tillering stage, flowering stage, and filling stage of rice, maintaining the water layer at 3 cm. Spray the foliar control dilution once at a spraying rate of 75 L / mu in the early stage of the tillering stage and the early stage of the flowering stage of rice. Starting from the early stage of the filling stage, spray the foliar control dilution at a frequency of once every 7 days and a spraying rate of 110 L / mu each time. The rest is managed according to conventional field management, and then harvest the rice.

[0075] Example 5

[0076] This embodiment provides a foliar control method for reducing heavy metal pollution, including the following steps:

[0077] S1. Applying basal fertilizer

[0078] Select a field plot with an average annual heavy metal deposition of lead and cadmium in the atmosphere of 26.5 mg / m 2 / yr and 1.8 mg / m 2 / yr as the experimental plot,

[0079] Mix urea, calcium magnesium phosphate fertilizer, potassium carbonate, silicon-calcium conditioner and silicon-selenium ore powder evenly according to a weight ratio of 33:25:13:7:4 to obtain an alkaline basal fertilizer for standby;

[0080] Before transplanting rice, apply the alkaline basal fertilizer to the experimental plot at an application rate of 75 kg / mu.

[0081] S2. Diluting the foliar control agent

[0082] Mix the foliar control agent prepared in Example 2 and drinking water evenly at a volume ratio of 1:200 to obtain a foliar control dilution.

[0083] S3. Conduct irrigation during the tillering stage, flowering stage, and filling stage of rice, maintain the water layer at 4 cm, spray the foliar control dilution once at a spraying amount of 80 L / mu in the early stage of the tillering stage and the early stage of the flowering stage of rice, and start spraying the foliar control dilution at a frequency of once every 7 days and a spraying amount of 115 L / mu each time in the early stage of the filling stage, and the rest is carried out according to conventional field management, and then harvest the rice.

[0084] Example 6

[0085] This example provides a foliar control method for reducing heavy metal pollution, including the following steps:

[0086] S1. Apply base fertilizer

[0087] Select a field plot with an average annual heavy metal deposition of lead and cadmium in the atmosphere of 26.5 mg / m 2 / yr and 1.8 mg / m 2 / yr as the experimental plot,

[0088] Mix urea, calcium magnesium phosphate fertilizer, potassium carbonate, silicon-calcium conditioner, and silicon-selenium ore powder evenly at a weight ratio of 35:26:16:8:5 to obtain an alkaline base fertilizer for standby;

[0089] Before transplanting rice, apply the alkaline base fertilizer to the experimental plot at an application rate of 80 kg / mu.

[0090] S2. Dilute the foliar control agent

[0091] Mix the foliar control agent prepared in Example 3 and drinking water evenly at a volume ratio of 1:220 to obtain a foliar control dilution.

[0092] S3. Conduct irrigation during the tillering stage, flowering stage, and filling stage of rice, maintain the water layer at 5 cm, spray the foliar control dilution once at a spraying amount of 85 L / mu in the early stage of the tillering stage and the early stage of the flowering stage of rice, and start spraying the foliar control dilution at a frequency of once every 7 days and a spraying amount of 120 L / mu each time in the early stage of the filling stage, and the rest is carried out according to conventional field management, and then harvest the rice.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 6 is that potassium carbonate, silicon-calcium conditioner, and silicon-selenium ore are not added to the alkaline base fertilizer.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 6 is that in step S3, the irrigation treatments during the tillering stage, flowering stage, and filling stage of rice are cancelled.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 6 is that when preparing the foliar control agent used, step A1 is cancelled, and the bovine bone collagen peptide powder in step A1 is used to replace the mercapto-modified collagen in step A3.

[0099] Comparative Example 4

[0100] The difference between this comparative example and Example 6 is that when preparing the foliar control agent used, step A2 is cancelled, and no tobacco extract is added in step A3.

[0101] Performance test:

[0102] Refer to the national food safety standard "Determination of multiple elements in foods" GB 5009.268-2016 to determine the lead and cadmium contents in the harvested rice in Examples 4-6 and Comparative Examples 1-4;

[0103] Refer to the operating specification for rice yield determination "DB33 / T 2517-2022" to determine the yields of the harvested rice in Examples 4-6 and Comparative Examples 1-4. The specific test results are shown in Table 1 below.

[0104] Table 1 - Data table of performance test data of samples

[0105]

[0106]

[0107] Data analysis:

[0108] By comparing and analyzing the data in Table 1 above, the lead content in the rice prepared by the present invention is reduced to 0.118 mg / kg, the cadmium content is reduced to 0.082 mg / kg, and the yield is increased to 625 kg / mu. All performance parameters are better than those of the comparative examples. This shows that the foliar control method for reducing heavy metal pollution provided by the present invention sprays a foliar control agent composed of mercapto-modified collagen, tobacco extract, sodium ferric ethylenediaminetetraacetate, etc. at three key growth stages of the tillering stage, flowering stage, and filling stage of rice, and is assisted by field management such as adjusting the soil pH with alkaline base fertilizer and water irrigation to improve the heavy metal stress resistance of rice and promote the growth and development of rice. Thus, while reducing the heavy metal content in rice, the yield of rice is increased.

[0109] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A leaf surface control method for reducing heavy metal pollution, characterized in that: The following steps are involved: S1. Apply alkaline base fertilizer to the field before transplanting rice; S2, mixing thiol-modified collagen, tobacco extract, sodium iron ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, sugar alcohol silicon stock fertilizer, sodium selenite and deionized water to obtain a foliar barrier control agent, and diluting the foliar barrier control agent with water to obtain a foliar barrier control dilution solution; S3. Irrigate during the tillering, flowering and filling stages of rice, maintain the water layer at 3-5cm, and spray the leaf surface with diluted barrier control liquid during the tillering, flowering and filling stages. The rest is based on conventional field management and rice is harvested.

2. A leaf surface control method for reducing heavy metal pollution according to claim 1, characterized in that: In step S1, the application amount of the alkaline base fertilizer is 70-80 kg / mu, and the alkaline base fertilizer is composed of urea, calcium magnesium phosphate fertilizer, potassium carbonate, silicon calcium conditioner and silicon selenium mineral powder in a weight ratio of 30-35:23-26:10-16:6-8:3-5.

3. A leaf surface control method for reducing heavy metal pollution according to claim 1, characterized in that: In step S2, the foliar barrier agent is composed of thiol-modified collagen, tobacco extract, sodium iron ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, sugar alcohol silicon stock fertilizer, sodium selenite and deionized water in a weight ratio of 7-8:3-4:1-2:1-2:2-3:0.8-1.2:

50.

4. A leaf surface control method for reducing heavy metal pollution according to claim 1, characterized in that: The foliar barrier control dilution liquid is obtained by diluting the foliar barrier control agent and water at a volume ratio of 1:180-220.

5. The leaf surface control method for reducing heavy metal pollution according to claim 1, characterized in that: The frequency of spraying the foliar barrier control diluted liquid during the tillering stage and flowering stage of rice is once, and the spraying period is the early stage of the tillering stage and the early stage of the flowering stage. The spraying amount of the foliar barrier control diluted liquid is 75-85L / mu. The frequency of spraying the foliar barrier control diluted liquid during the filling stage is 7 days / time, and the spraying amount of the foliar barrier control diluted liquid is 110-120L / mu. The spraying starts in the early stage of the filling stage.

6. A leaf surface control method for reducing heavy metal pollution according to claim 1, characterized in that: The preparation method of thiol-modified collagen is as follows: bovine collagen peptide powder and deionized water are mixed, stirred until the system is dissolved, the temperature of the reaction system is lowered to 4-6°C under the protection of an inert atmosphere, N-(tetrahydro-2-oxo-3-thienyl)butanamide, ethylenediaminetetraacetic acid, and dithiothreitol are added to the reaction system, the reaction is kept warm for 10-14 hours, and post-processed to obtain thiol-modified collagen.

7. A leaf surface control method for reducing heavy metal pollution according to claim 6, characterized in that: The amount ratio of the bovine collagen peptide powder, deionized water, N-(tetrahydro-2-oxo-3-thienyl)butyramide, ethylenediaminetetraacetic acid and dithiothreitol is 10g:500mL:3-4g:0.2-0.3g:1.1-1.3g. The post-treatment comprises: after the reaction is completed, transferring the reaction solution to a dialysis bag with a molecular cutoff of 8000-14000kDa, then placing the dialysis bag in a phosphate buffer with a pH of 9, lowering the temperature of the phosphate buffer to 4-6°C, dialyzing for 30-36h, changing the phosphate buffer every 6h, and then transferring the liquid in the dialysis bag to an evaporator with a temperature of 65°C and a pressure of -0.1MPa, and removing low-boiling substances under reduced pressure to obtain thiol-modified collagen.

8. The leaf surface control method for reducing heavy metal pollution according to claim 1, characterized in that: Tobacco extract is obtained by the following steps: A1. Grind tobacco leaves and tobacco dust extract and pass through an 80-mesh sieve to obtain tobacco powder; A2. Tobacco powder, deionized water and α-amylase are mixed and stirred, the temperature of the reaction system is raised to 45-55° C., the reaction is kept warm for 4-6 hours, and post-processed to obtain a tobacco extract.

9. A leaf surface control method for reducing heavy metal pollution according to claim 8, characterized in that: In step A2, the tobacco powder and deionized water are used in a ratio of 1 g:10 mL, and the amount of α-amylase is 55-65 U / g. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, centrifuged, the supernatant is filtered with a 0.25 μm nylon filter membrane, and the filtrate is transferred to an evaporator at a temperature of 65° C. and a pressure of -0.1 MPa, and low-boiling substances are evaporated under reduced pressure to obtain a tobacco extract.

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