A planting method for reducing lead content in wheat by combining chelate induction and foliar surface control

Abstract

The application relates to the field of agricultural planting technology, and discloses a planting method for reducing the lead content of wheat by combining chelation induction and leaf surface control, which comprises the following steps: firstly, detecting and screening the soil lead, implementing differentiated deep plowing and soil conditioner application on lead-free land and low-lead land, adopting standard deep plowing and applying silicon calcium mineral materials and biological agents on the lead-free land; deepening the deep plowing and applying a composite passivation regulator containing calcium dihydrogen phosphate, modified biochar and sepiolite on the low-lead land, shallow plowing before sowing and base application of an EDDS and citric acid compound chelation inducer, implementing differentiated leaf surface nutrient spraying and rhizosphere management at the seedling stage, spraying a leaf surface control agent at the jointing stage to construct a siliconized cell barrier, performing leaf surface control and nutrient synergistic spraying at the booting stage to the filling stage, dynamically monitoring the lead transport risk, and finally detecting the lead content and verifying the quality at the mature stage; through three-level synergistic control of the soil-root-leaf, the lead content of the wheat grains approaches 0.

Description

Technical Field

[0001] This invention relates to the field of agricultural planting technology, specifically a planting method for reducing lead content in wheat through a combination of chelation induction and leaf surface inhibition. Background Technology

[0002] Wheat, as a vital global food crop, has its quality and safety directly impacting human health. However, with accelerated industrialization and the inappropriate use of agricultural inputs, lead pollution in farmland soil is becoming increasingly serious. Lead is a typical heavy metal pollutant with bioaccumulation and neurotoxicity; it can enter the food chain through the soil-crop system, posing a serious threat to human health. Wheat has a strong capacity to accumulate lead, and excessive lead content in its grains has become a key bottleneck restricting safe wheat production.

[0003] Currently, the main technologies for reducing lead content in wheat include: (1) Soil passivation technology, such as applying lime, phosphate and other amendments to fix soil lead, but there are problems such as unstable fixation effect, long-term application can easily lead to soil compaction and nutrient imbalance; (2) Agronomic regulation technology, such as adjusting sowing period and irrigation method, but the lead reduction effect is limited and difficult to quantify and control; (3) Variety screening technology, using low accumulation varieties to reduce lead absorption, but it is difficult to promote due to regional adaptability and yield potential limitations; (4) Chemical chelation technology, by applying chelating agents such as EDTA and EDDS to induce lead activation and prevent its translocation to the aboveground parts, but single chelation treatment is prone to secondary activation risk of lead, and lacks subsequent control over the process of lead translocation to grains.

[0004] The aforementioned technologies primarily target single-stage regulation of lead migration, failing to establish a comprehensive control system encompassing soil, roots, and leaves. This results in inconsistent lead reduction effects, difficulty in lowering grain lead content to safe levels (<0.2 mg / kg), and an inability to achieve the near-zero lead target. Furthermore, existing technologies lack differentiated management strategies for lead-free and low-lead land, failing to simultaneously improve lead reduction and yield / quality.

[0005] Therefore, there is an urgent need to develop a systematic, precise, and quantifiable new technology for lead control in wheat, which can block lead migration at the source, reduce lead bioavailability throughout the process, ensure that the lead content in wheat grains approaches zero, and at the same time guarantee high yield and quality. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a planting method for reducing lead content in wheat through a combination of chelation induction and foliar inhibition. This method has the advantages of significant and stable lead reduction effect, differentiated and precise control, dynamic monitoring throughout the entire process, and being green, safe, and pollution-free. It solves the technical problems of existing technologies, such as single lead reduction steps, uncontrollable effects, lack of differentiated management strategies, difficulty in balancing yield and quality, and environmental risks.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a planting method for reducing lead content in wheat through a combination of chelation induction and foliar inhibition, comprising the following steps:

[0010] Step 1: Soil lead testing and screening: Before wheat sowing, the lead content of the sowing land is tested in a grid pattern and safe land is screened.

[0011] Step 2, Differentiated deep tillage and soil conditioner application: Based on the lead-free and low-lead land types screened in Step 1, differentiated deep tillage and soil conditioner application are carried out.

[0012] Step 3, shallow tillage, pesticide application and sowing: chelation inducer is applied as a base fertilizer and sown based on lead-free or low-lead soil types;

[0013] Step 4, Seedling Management: During the wheat seedling stage, differentiated foliar nutrition and rhizosphere management are carried out based on soil type, and baseline lead content records are established simultaneously.

[0014] Step 5: Constructing a physical barrier: Based on soil type, implement foliar inhibition and silicon nutrition enhancement during the wheat jointing stage to construct a physical barrier;

[0015] Step Six: Foliar inhibition and nutrient synergy: Based on land type, foliar inhibition and nutrient synergy are carried out from the wheat booting stage to the grain-filling stage.

[0016] Step 7, Quality Verification at Maturity: Conduct final lead content testing and quality verification before wheat harvest at maturity, and establish planting records.

[0017] Preferably, the soil lead detection and screening process in step one is as follows:

[0018] S1.1. 30-45 days before sowing, conduct grid sampling of the proposed planting area, dividing the area into 19m×19m grids, collecting 3-5 soil mixture samples from each grid, collecting soil from the 0-35cm topsoil layer, and each soil mixture sample weighing 40-50g.

[0019] S1.2 The total lead content of the collected soil samples was determined by atomic absorption spectrophotometry, and the available lead content in the soil was determined by DTPA extraction method. Based on the two test results, the sown land was divided into three categories.

[0020] S1.3. Based on the test results, the planting land is divided into lead-free planting land with a total lead content ≤25mg / kg, low-lead planting land with a total lead content 25-50mg / kg, and medium-high lead planting land with a total lead content ≥50mg / kg. This planting method is only used for the selected lead-free and low-lead land.

[0021] Preferably, the differentiated deep tillage and soil conditioner application process in step two is as follows: 15-20 days before sowing, differentiated deep tillage and soil conditioner application are carried out according to land type, as detailed below;

[0022] (1) For lead-free land, standard deep plowing should be carried out, with the plowing depth controlled at 25-30 cm. After plowing, rotary tillage should be used for fine land preparation. The base fertilizer includes 800-900 kg / mu of decomposed organic fertilizer and 35-40 kg / mu of compound fertilizer. The soil microecological regulator is a mineral material containing silicon and calcium, with an application rate of 40-45 kg / mu. At the same time, Bacillus subtilis biological agent should be applied in combination, with an application rate of 2.5-3.5 kg / mu.

[0023] (2) For low-lead land, deep plowing should be carried out, with the plowing depth controlled at 28-35 cm. After plowing, the land should be finely prepared, and base fertilizer and soil heavy metal passivation regulator should be applied in combination with the land preparation. The amount of base fertilizer is the same as that for lead-free land. The soil heavy metal passivation regulator is a composite passivation material, which is composed of 45%-50% calcium dihydrogen phosphate, 35%-40% modified biochar, 15%-20% sepiolite and 8%-11% silicon-calcium fertilizer by mass percentage. The application rate is 95-105 kg / mu.

[0024] Preferably, in step three, shallow tillage and application of pesticides during sowing: 1-2 days before sowing, the sowing field is shallowly tilled a second time to a depth of 10-15 cm, and a chelation inducer is applied according to the type of lead-free or low-lead soil. The chelation inducer is a compound solution of ethylenediamine disuccinic acid and citric acid in a 1:1 molar ratio. The total amount of chelation inducer applied is determined according to the pollution level: 18-20 kg / mu for lead-free soil and 20-24 kg / mu for low-lead soil. The wheat varieties selected are those with low lead accumulation and strong resistance. The sowing amount is 12-13 kg / mu, the row spacing is 20-25 cm, and the sowing depth is 3-5 cm.

[0025] Preferably, the seedling management process in step four is as follows:

[0026] S2.1 For lead-free soil, apply foliar nutrients. The foliar nutrient solution is a mixture of 0.1%-0.2% sorbitol, 0.1%-0.2% mannitol, 0.05%-0.1% zinc, 0.05%-0.1% iron, 0.05%-0.1% manganese and 0.2%-0.3% silicon. The application rate is 30-40 kg / mu.

[0027] S2.2 For low-lead soil, apply enhanced foliar nutrition. The foliar nutrient solution should be formulated based on the lead-free soil formula, with the addition of a mixture of 0.1%-0.2% humic acid and 0.01%-0.02% sodium selenite. The application rate is 35-45 kg / mu.

[0028] Preferably, in step four, 7-10 days after spraying, samples of the aboveground parts and roots of wheat plants are collected to determine the lead content and nutrient element content, and a baseline value archive is established.

[0029] Preferably, in step five, a physical barrier is constructed:

[0030] (1) For lead-free land, spray a standard foliar inhibitor consisting of 2%-3% potassium silicate, 0.3%-0.5% sorbitol and 0.02%-0.05% surfactant, with a spraying amount of 30-40 kg / mu;

[0031] (2) For low-lead soil, spray an enhanced foliar inhibitor composed of 3.0%-3.5% potassium silicate, 0.5%-0.6% compound sugar alcohol, 0.15%-0.25% humic acid and 0.03%-0.05% surfactant, with a spraying amount of 35-40 kg / mu.

[0032] Preferably, in step five, wheat leaf samples are collected 5-7 days after spraying to determine the silicon and lead content and evaluate the initial control effect. If the measured lead content does not reach the expected level close to 0, the product is sprayed 1-2 more times after an interval of 7-14 days.

[0033] Preferably, the foliar resistance control and nutrient synergy process in step six is ​​as follows:

[0034] (1) For lead-free soil, spray the standard foliar inhibitor 1-2 times during the booting stage and the early grain filling stage. After each spraying, spray the nutrient enhancer together. The nutrient enhancer is a compound solution of 0.1%-0.15% humic acid and 0.3%-0.4% potassium dihydrogen phosphate.

[0035] (2) For low-lead soil, apply enhanced foliar inhibitors 1-3 times during the heading stage, early grain filling stage and middle grain filling stage. After each application, apply enhanced nutrient synergist. The enhanced nutrient synergist is a compound solution with a mass concentration of 0.15%-0.25% humic acid, 0.2%-0.3% compound sugar alcohol and 0.3%-0.5% potassium dihydrogen phosphate.

[0036] (3) 7-10 days after each spraying, collect flag leaf and young spike samples to determine lead content, silicon content and nutrient content, and dynamically monitor the risk of lead translocation to grains. When the lead content is detected to be increasing, spray 1-2 more times with a stronger inhibitor.

[0037] Preferably, the quality verification process during the maturity period in step seven is as follows:

[0038] S3.1. During the wheat ripening period, conduct the final sample collection and testing before harvest;

[0039] S3.2 Collect wheat grain samples and soil samples from the 0-20 cm topsoil layer, and determine the lead content in the grains, total lead content in the soil, and available lead content, respectively. At the same time, determine the grain yield, thousand-grain weight, protein content, and wet gluten content, and comprehensively evaluate the quality grade of wheat.

[0040] S3.3 After harvest, the lead content test results of the grains are correlated with the lead content test results of the soil and the management measures at each growth stage to form a safety production record.

[0041] Compared with existing technologies, this invention provides a planting method for reducing lead content in wheat through a combination of chelation induction and foliar inhibition, which has the following beneficial effects:

[0042] 1. This invention utilizes a source-precise control system based on grid-based detection, three-level classification of lead levels, differentiated deep tillage, and composite passivation / microecological regulation. For lead-free and low-lead land, it employs silicon-calcium mineral materials and a composite passivating agent of calcium dihydrogen phosphate-modified biochar-sepiolite-silicon-calcium fertilizer to achieve graded and efficient passivation of available lead in the soil. This significantly reduces the bioavailability of lead from the source, laying a solid foundation for subsequent lead reduction.

[0043] 2. This invention utilizes a combined foliar nutrient control technology across the entire growth period, encompassing seedling foliar nutrient control, jointing stage silica barrier construction, and synergistic nutrient control during the heading and grain-filling stages. It differentiates the addition of key components such as humic acid, sodium selenite, potassium silicate, and complex sugar alcohols for different soil types. This achieves multiple synergistic effects, including lead ion complexation on the leaf surface, selenium-lead antagonistic transport inhibition, and the construction of a silicified cell physical barrier. This effectively blocks the lead transport pathway to the grain, stably controlling the lead content in wheat grains on lead-free and low-lead soils to an ultra-low level approaching 0 (≤0.02 mg / kg).

[0044] 3. This invention establishes a closed-loop management mechanism for lead reduction in wheat planting by creating a baseline value record, dynamic monitoring, and feedback adjustment. It establishes a baseline record of lead content in the seedling stage and dynamically adjusts the spraying frequency and plan based on the monitoring results of lead content in leaves and young spikes during the jointing and heading / filling stages. This achieves precise control and ensures the effectiveness of lead reduction in wheat planting. While ensuring that the lead content in wheat grains approaches zero, it also increases wheat yield, thousand-grain weight, and protein content, thus achieving a synergistic effect of lead reduction, high yield, and high quality. Ultimately, it solves the problems of existing technologies such as fragmented soil management and foliar control, lack of differentiated and precise control, unstable lead reduction effects, and difficulty in balancing yield and quality. Attached Figure Description

[0045] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Please see Figure 1 A cultivation method for reducing lead content in wheat through a combination of chelation induction and foliar inhibition includes the following steps:

[0048] Step 1: Soil lead testing and screening: Before wheat sowing, the lead content of the sowing land is tested in a grid pattern and safe land is screened to ensure the safety of the planting base from the source and lay the foundation for subsequent differentiated management;

[0049] Step 2, Differentiated deep tillage and application of soil conditioners: Based on the lead-free and low-lead land types screened in Step 1, differentiated deep tillage and application of soil conditioners are carried out to optimize the soil environment and reduce the risk of lead migration from the source.

[0050] Step 3, shallow tillage, pesticide application and sowing: chelation inducer is applied as a base fertilizer and sown based on lead-free or low-lead soil types;

[0051] Step 4, Seedling Management: During the wheat seedling stage, differentiated foliar nutrition and rhizosphere management are carried out based on soil type to cultivate strong seedlings, strengthen the foundation for lead barrier, and simultaneously establish a baseline record of lead content.

[0052] Step 5: Constructing a physical barrier: During the wheat jointing stage, based on soil type, foliar control and silicon nutrition enhancement are carried out to construct a physical barrier and block lead transport pathways;

[0053] Step Six: Foliar Control and Nutritional Synergy: Based on soil type, foliar control and nutritional synergy are carried out during the wheat booting to grain-filling stage to continuously block lead translocation to grains and ensure yield and quality.

[0054] Step 7: Quality Verification at Maturity: Before harvesting wheat at maturity, conduct final lead content testing and quality verification to confirm that the lead content is close to 0, ensuring wheat safety and quality, and establish planting records.

[0055] Specifically, the soil lead testing and screening process in step one:

[0056] S1.1. 30-45 days before sowing, conduct grid sampling of the proposed planting area. Divide the area into 19m×19m grids and collect 3-5 soil mixed samples from each grid. Focus on collecting soil samples from the 0-35cm topsoil layer. The sampling should cover the entire proposed planting area. The sampling size of each soil mixed sample should be 40-50g. After removing stones, weeds and other impurities, seal and store fresh.

[0057] S1.2 The total lead content of the collected soil samples was determined by atomic absorption spectrophotometry, and the available lead content in the soil was determined by DTPA extraction method. Based on the two test results, the sown land was divided into three categories.

[0058] S1.3. Based on the test results, the planting land is divided into lead-free planting land (total lead content ≤25mg / kg), low-lead planting land (total lead content 25-50mg / kg), and medium-high lead planting land (total lead content ≥50mg / kg, requiring remediation or adjustment of planting structure). This planting method is only used for the selected lead-free and low-lead land. The use of medium-high lead land for planting is strictly prohibited to ensure the safety and controllability of the planting base and to provide the basic conditions for reducing the lead content of wheat to near zero in the future.

[0059] Specifically, the differentiated deep tillage and soil conditioner application process in step two involves: 15-20 days before sowing, differentiated deep tillage and soil conditioner application are carried out according to land type to ensure that the soil conditions are suitable for the lead reduction requirements of the corresponding land type, as detailed below:

[0060] (1) For lead-free land, standard deep plowing should be carried out, with the plowing depth controlled at 25-30 cm. After plowing, rotary tillage should be used to finely prepare the land to ensure that the soil is loose and uniform, which is conducive to the growth of wheat roots. Base fertilizer and soil microecological regulator should be applied simultaneously with land preparation. The base fertilizer includes 800-900 kg / mu of well-rotted organic fertilizer and 35-40 kg / mu of compound fertilizer (N-P2O5-K2O is 15-15-15) to ensure the basic nutrition required for wheat growth. The soil microecological regulator is a mineral material containing silicon and calcium. The application rate is as follows: The dosage is 40-45 kg / mu, used to supplement the available silicon and calcium content in the soil, promote the absorption of silicon by wheat roots, enhance the mechanical strength of cell walls, build a physical barrier to block the potential impact of exogenous lead (such as atmospheric deposition and irrigation water carrying), consolidate the advantages of lead-free soil, and help maintain the lead content of wheat close to 0; at the same time, it is used in conjunction with the application of Bacillus subtilis biological agent (with an effective viable bacteria count ≥200 million / gram), at a dosage of 2.5-3.5 kg / mu, to optimize the rhizosphere microecology, enhance root vitality, and improve the stress resistance of wheat;

[0061] (2) For low-lead soil, deep plowing should be carried out, with the plowing depth controlled at 28-35 cm. The aim is to turn the relatively rich lead in the topsoil into the lower layer, and at the same time turn the relatively clean soil in the lower layer to the surface, thereby reducing the absolute lead content in the topsoil and laying the foundation for subsequent passivation treatment. After plowing, the land should be finely prepared to ensure that there are no large soil particles and that the soil moisture is uniform. Base fertilizer and soil heavy metal passivation regulator should be applied in conjunction with land preparation. The amount of base fertilizer should be the same as that used for lead-free land to ensure nutrient supply. The soil heavy metal passivation regulator is a composite passivation material, which, by mass percentage, consists of 45%-50% calcium dihydrogen phosphate, 35%-40% modified biochar, 15%-20% sepiolite, and 8%-11% silicon-calcium fertilizer. Its application rate is 95-105 kg / kg. The treatment method involves several steps: First, calcium dihydrogen phosphate reacts with available lead in the soil via phosphate ions, converting lead into a stable state. Second, modified biochar, with its well-developed pore structure and high specific surface area, adsorbs and complexes lead ions in the soil, reducing lead migration. Third, sepiolite replaces adsorbed lead in the soil through ion exchange, further reducing lead activity. Fourth, silicon-calcium fertilizer replenishes silicon and calcium in the soil, helping to strengthen wheat cell walls and synergistically enhancing passivation effects. These multiple mechanisms work together to reduce the content of available lead in the soil, reducing lead migration to wheat roots at the source and providing core support for reducing wheat lead content to near zero. For low-lead land, biological agents are not applied alone to avoid the possibility that their metabolites might increase the risk of lead activation, thus affecting the lead-reducing effect.

[0062] Specifically, in step three, shallow tillage, pesticide application, and sowing: 1-2 days before sowing, the sowing field is shallowly tilled a second time to a depth of 10-15 cm. A chelation inducer is applied according to the type of lead-free or low-lead soil. The chelation inducer is a compound solution of ethylenediamine disuccinic acid (EDDS) and citric acid in a 1:1 molar ratio. The total amount of chelation inducer applied is determined according to the pollution level: 18-20 kg / mu for lead-free soil and 20-24 kg / mu for low-lead soil. Wheat varieties with low lead accumulation and strong resistance (such as Yangmai series or Ningmai series) are selected. The sowing rate is 12-13 kg / mu, the row spacing is 20-25 cm, and the sowing depth is 3-5 cm.

[0063] Specifically, in step four, the seedling management process involves applying foliar nutrients and managing the rhizosphere according to soil type 15-20 days after wheat emergence (three-leaf stage). This provides sufficient nutrition for wheat growth while mitigating the risk of lead activation. Details are as follows:

[0064] S2.1 For lead-free soil, foliar nutrient spraying is applied. The foliar nutrient solution is a mixture of 0.1%-0.2% sorbitol, 0.1%-0.2% mannitol, 0.05%-0.1% zinc, 0.05%-0.1% iron, 0.05%-0.1% manganese, and 0.2%-0.3% silicon, with a spraying rate of 30-40 kg / mu. This is used to promote vigorous seedling growth, enhance root vitality, consolidate the growth advantage in a lead-free environment, and ensure that the lead content of wheat remains close to 0. In terms of rhizosphere management, selective topdressing with a biological agent containing Bacillus subtilis (1-2 kg / mu) is applied to maintain the rhizosphere microecological balance and further enhance the root system's stress resistance.

[0065] S2.2 For low-lead soil, apply enhanced foliar nutrition. The foliar nutrient solution should be based on the lead-free soil formula, with the addition of a mixture of 0.1%-0.2% humic acid and 0.01%-0.02% sodium selenite. Apply 35-45 kg / mu. Humic acid can chelate lead ions on the leaf surface, reducing their entry into mesophyll cells, while sodium selenite, through selenium-lead antagonism, can inhibit lead transport within the plant. This dual action helps reduce lead content to near zero. For rhizosphere management, do not apply biological agents to avoid potential activation risks and prevent an increase in available lead content in the soil.

[0066] Specifically, in step four, 7-10 days after spraying, samples of the above-ground parts and roots of wheat plants are collected to determine the lead content and nutrient element content, establish a baseline value file, record the specific values ​​of nutrient element content as a control benchmark, compare with subsequent test data, dynamically adjust management measures, and ensure that the lead reduction target is steadily achieved.

[0067] Specifically, step five involves constructing a physical barrier: when wheat plants are 20-25 cm tall, foliar inhibitors are sprayed according to soil type to enhance silicon nutrient supply and build a protective barrier on the leaves, thus laying a solid defense to reduce lead content to near zero. The details are as follows:

[0068] (1) For lead-free soil, spray a standard foliar inhibitor, consisting of 2%-3% potassium silicate (by mass). It consists of 0.3%-0.5% sorbitol and 0.02%-0.05% surfactant (calculated as organosilicon), and the spraying rate is 30-40 kg / mu. Its focus is on building a silicified cell barrier in the leaves, preventing lead pollution from atmospheric deposition, and continuously maintaining the lead content of wheat close to 0.

[0069] (2) For low-lead soil, spray with an enhanced foliar inhibitor, consisting of potassium silicate with a mass concentration of 3.0%-3.5% (or similar). It consists of 0.5%-0.6% compound sugar alcohol, 0.15%-0.25% fulvic acid and 0.03%-0.05% surfactant. The spraying rate is 35-40 kg / mu. The enhanced barrier agent strengthens the physical barrier by increasing the silicon concentration, and at the same time, it uses the complexation effect of fulvic acid to further block the penetration of lead, thus doubly enhancing the barrier effect and accelerating the lead content to approach 0.

[0070] Specifically, in step five, wheat leaf samples are collected 5-7 days after spraying to determine the silicon and lead content and assess the initial control effect. If the measured lead content does not reach the expected level of close to 0, spraying is repeated 1-2 times after an interval of 7-14 days to ensure that the control effect meets the standard.

[0071] Specifically, in step six, the foliar control and nutrient synergy process involves applying foliar inhibitors 2-3 times during the wheat heading and grain-filling stages, depending on the soil type, while simultaneously supplementing nutrients to achieve the dual goals of "lead inhibition + yield protection," pushing the lead content in wheat down to near zero, as detailed below:

[0072] (1) For lead-free land, standard foliar inhibitors are sprayed 1-2 times during the booting stage and early grain filling stage. After each spraying, a nutrient enhancer is sprayed in conjunction. The nutrient enhancer is a compound solution of 0.1%-0.15% humic acid and 0.3%-0.4% potassium dihydrogen phosphate. The focus is on ensuring full grain filling and yield formation, while continuously consolidating the lead-free advantage and ensuring that the lead content of wheat grains approaches 0.

[0073] (2) For low-lead soil, apply enhanced foliar inhibitors 1-3 times during the heading stage, early grain filling stage and mid grain filling stage. After each application, apply enhanced nutrient synergist. The enhanced nutrient synergist is a compound solution with a mass concentration of 0.15%-0.25% humic acid, 0.2%-0.3% compound sugar alcohol and 0.3%-0.5% potassium dihydrogen phosphate. While ensuring grain filling and increasing yield, continuously enhance the lead control effect, further inhibit lead transfer to grains, and ensure that the lead content in grains is reduced to close to 0.

[0074] (3) 7-10 days after each spraying, collect flag leaf and young spike samples to determine lead content, silicon content and nutrient content, and dynamically monitor the risk of lead translocation to grains. When the lead content is detected to be increasing, spray 1-2 more times with a stronger inhibitor to ensure that the lead reduction target is not deviated from.

[0075] Specifically, the quality verification process during the maturity stage in step seven:

[0076] S3.1. During the wheat maturity stage (late waxy maturity stage), conduct the final sample collection and testing before harvest to ensure that the test results accurately reflect the lead content and quality of the wheat.

[0077] S3.2 Collect wheat grain samples and soil samples from the 0-20 cm topsoil layer to determine the lead content in the grains, total lead content in the soil, and available lead content, respectively. The lead content in the grains must be lower than the national food safety standard limit (0.2 mg / kg), with the core objective being to reduce the lead content in the grains to near zero. For wheat grown on low-lead land, the lead content in the grains must be lower than 0.02 mg / kg to ensure a higher safety margin and to approach the zero-lead standard as closely as possible. Simultaneously, determine the grain yield (converted to yield per mu), thousand-grain weight, protein content, and wet gluten content to comprehensively evaluate the quality grade of the wheat and ensure the achievement of the goals of "lead reduction (approaching zero), high yield, and high quality."

[0078] S3.3 After harvest, the grain lead content test results are correlated with the soil lead test results and the management measures at each growth stage to form a safety production file, providing data support for the next year's planting decisions. At the same time, the soil is tested again after harvest. If the available lead content in the low-lead soil has not dropped to near zero, a compound passivation regulator can be applied once during the fallow period to lay the foundation for further reducing lead content in subsequent plantings.

[0079] The method of the present invention was applied to the following embodiments, with a comparative example used as a control group, as follows:

[0080] Example 1 (Combined application of chelation induction and foliar inhibition in lead-free soil)

[0081] Test site: Lead-free land with a total lead content ≤25mg / kg, which meets the screening criteria of step one. Steps two to seven constitute the complete technical process of this invention.

[0082] Comparative Example 1 (Lead-free soil treated with only chelation inducers, without foliar inhibition, to verify the necessity of foliar inhibition)

[0083] Differences from Example 1: The application of foliar inhibitors in steps five and six of this invention is deleted, and only the basal application of chelation inducers in step three is retained. The remaining management measures are exactly the same as in Example 1.

[0084] Expected results: Although it has a certain lead-reducing effect, it lacks the physical barrier of leaves and cannot block the later atmospheric deposition of lead and the transport of lead in the phloem. The lead content in the grain is significantly higher than that in Example 1.

[0085] Example 2 (Combined application of chelation induction and foliar inhibition in low-lead soil)

[0086] Test location: Low-lead soil with a total lead content of 35 mg / kg (range of 25-50 mg / kg). Steps two through seven constitute the complete technical process of this invention.

[0087] Comparative Example 2 (low lead soil with only foliar inhibition and no chelation inducer applied as a base, to verify the necessity of chelation induction)

[0088] Differences from Example 2: The application of chelation inducer (EDDS + citric acid compound solution) in step 3 was removed, and only the foliar control measures in steps 5 and 6 were retained. The remaining management measures were exactly the same as in Example 2.

[0089] Expected results: Due to the lack of root chelation induction, the migration of available lead from the soil to the roots was not effectively blocked. Although there was some control on the leaves, the amount of lead absorbed by the roots was high, the lead content in the grains was significantly higher than in Example 2, and the lead reduction effect was unstable.

[0090] Example 3 (Combined application of chelation induction and foliar inhibition in low-lead soil)

[0091] Test location: Same as Example 2 (low-lead soil with a total lead content of 35 mg / kg).

[0092] Differences from Example 2: Regarding the optimization of spraying frequency in step six, adjustments were made based on dynamic monitoring results: Seven days after spraying the enhanced foliar inhibitor during the heading stage, the lead content in the flag leaf was measured to be 0.08 mg / kg (higher than expected), so one more application of the enhanced inhibitor was added; normal spraying was performed in the early and middle stages of grain filling, and the remaining technical measures were the same as in Example 2.

[0093] Expected results: Through dynamic monitoring and frequency optimization, the lead content in the grains will be further ensured to approach 0 (<0.01 mg / kg), verifying the effectiveness of the "monitoring-feedback-adjustment" mechanism.

[0094] Comparative Example 3 (Low-lead soil treated with conventional passivation technology, compared with existing technology)

[0095] Differences from Example 2: Traditional agronomic practices are used instead of the core technology of this invention. In step two, only conventional lime passivating agent (100 kg / mu) is applied, without deep tillage and stratification control, and without modified biochar, sepiolite, or other composite passivating materials. In step three, no chelation inducer is applied, and only conventional sowing is performed. In steps four to six, no foliar inhibition is performed, and only conventional foliar fertilizer (0.3% potassium dihydrogen phosphate) is sprayed twice. There is no silicon nutrient fortification, no humic acid complexation, and no selenium-lead antagonism. The remaining management measures (variety, sowing rate, base fertilizer) are the same as in Example 2.

[0096] Expected results: Conventional passivation technology has limited effect on soil lead fixation and lacks foliar control to block lead translocation, making it difficult to reduce grain lead content to a safe level (expected >0.1 mg / kg), and thus failing to achieve the goal of approaching zero.

[0097] The planting process data of the examples and the comparative examples are compared, and the specific data are shown in Table 1 below:

[0098] Table 1

[0099] Total lead content in soil (mg / kg) ≤25 ≤25 35 35 35 35 Available lead content in soil (mg / kg) <1.0 <1.0 <2.5 8-12 <2.0 15-25 Lead content in grains (mg / kg) <0.01 0.05-0.08 <0.02 0.08-0.15 <0.01 >0.1 Grain yield (kg / mu) 480-520 470-510 450-490 440-480 460-500 420-460 1000-grain weight (g) 42-45 41-44 40-43 39-42 41-44 38-41 Protein content (%) 13.5-14.5 13.2-14.2 13.0-14.0 12.8-13.8 13.2-14.2 12.5-13.5 Leaf surface silicon content (%) 2.5-3.5 1.2-1.8 3.0-4.0 2.8-3.5 3.5-4.5 0.8-1.2 Lead reduction compliance rate 100% 60% 100% 40% 100% 10%

[0100] Table 1 shows that the lead content in the grains of Examples 1 and 2 both reached the target of near-zero (<0.02 mg / kg), while the lead content in the grains of Comparative Example 1 (without foliar inhibition) and Comparative Example 2 (without chelation induction) was 5-8 times and 4-7.5 times higher, respectively, demonstrating a significant synergistic effect between chelation induction and foliar inhibition. Example 3 increased the spraying frequency through monitoring feedback, achieving a lead content in the grains of <0.01 mg / kg on low-lead soil, a reduction of more than 50% compared to Example 2, verifying the effectiveness of the monitoring-adjustment mechanism. Comparative Example 3 used conventional... Conventional passivation technology resulted in lead content in grains >0.1 mg / kg, posing a high risk of exceeding the standard. However, Example 2 reduced lead content by more than 80% under the same land conditions, and its yield and quality indicators were superior to those of conventional technology, achieving the triple goals of reducing lead, maintaining yield, and improving quality. The soil available lead content in Examples 2 and 3 was reduced to <2.5 mg / kg, while Comparative Examples 2 and 3 maintained at 8-12 mg / kg and 15-25 mg / kg, respectively. This demonstrates that the basal application of chelation inducers combined with compound passivation regulators can effectively fix soil lead from the source and reduce its bioavailability.

[0101] In summary, the chelation-induced and foliar inhibition combined planting method for reducing wheat lead content provided by this invention, through a three-level inhibition system of soil-root-leaf, achieves the technical goal of maintaining wheat lead content close to 0 in lead-free land and reducing wheat lead content in low-lead land to <0.02 mg / kg or even <0.01 mg / kg. Compared with comparative schemes lacking any key link and existing conventional technologies, this method has significant technical advantages and application value, providing a systematic solution for clean wheat production.

[0102] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A planting method for reducing lead content in wheat through a combination of chelation induction and foliar inhibition, characterized in that, Includes the following steps: Step 1: Soil lead testing and screening: Before wheat sowing, the lead content of the sowing land is tested in a grid pattern and safe land is screened. Step 2, Differentiated deep tillage and soil conditioner application: Based on the lead-free and low-lead land types screened in Step 1, differentiated deep tillage and soil conditioner application are carried out. Step 3, shallow tillage, pesticide application and sowing: chelation inducer is applied as a base fertilizer and sown based on lead-free or low-lead soil types; Step 4, Seedling Management: During the wheat seedling stage, differentiated foliar nutrition and rhizosphere management are carried out based on soil type, and baseline lead content records are established simultaneously. Step 5: Constructing a physical barrier: Based on soil type, implement foliar inhibition and silicon nutrition enhancement during the wheat jointing stage to construct a physical barrier; Step Six: Foliar inhibition and nutrient synergy: Based on land type, foliar inhibition and nutrient synergy are carried out from the wheat booting stage to the grain-filling stage. Step 7, Quality Verification at Maturity: Conduct final lead content testing and quality verification before wheat harvest at maturity, and establish planting records.

2. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, The soil lead detection and screening process in step one: S1.

1. 30-45 days before sowing, conduct grid sampling of the proposed planting area, dividing the area into 19m×19m grids, collecting 3-5 soil mixture samples from each grid, collecting soil from the 0-35cm topsoil layer, and each soil mixture sample weighing 40-50g. S1.2 The total lead content of the collected soil samples was determined by atomic absorption spectrophotometry, and the available lead content in the soil was determined by DTPA extraction method. Based on the two test results, the sown land was divided into three categories. S1.

3. Based on the test results, the planting land is divided into lead-free planting land with a total lead content ≤25mg / kg, low-lead planting land with a total lead content 25-50mg / kg, and medium-high lead planting land with a total lead content ≥50mg / kg. This planting method is only used for the selected lead-free and low-lead land.

3. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, The differentiated deep tillage and soil conditioner application process in step two is as follows: 15-20 days before sowing, differentiated deep tillage and soil conditioner application are carried out according to land type, as detailed below; (1) For lead-free land, standard deep plowing should be carried out, with the plowing depth controlled at 25-30 cm. After plowing, rotary tillage should be used for fine land preparation. The base fertilizer includes 800-900 kg / mu of decomposed organic fertilizer and 35-40 kg / mu of compound fertilizer. The soil microecological regulator is a mineral material containing silicon and calcium, with an application rate of 40-45 kg / mu. At the same time, Bacillus subtilis biological agent should be applied in combination, with an application rate of 2.5-3.5 kg / mu. (2) For low-lead soil, deep plowing should be carried out, with the plowing depth controlled at 28-35 cm. After plowing, the land should be finely prepared, and base fertilizer and soil heavy metal passivation regulator should be applied in combination with the land preparation. The amount of base fertilizer is the same as that for lead-free soil. The soil heavy metal passivation regulator is a composite passivation material, which is composed of 45%-50% calcium dihydrogen phosphate, 35%-40% modified biochar, 15%-20% sepiolite and 8%-11% silicon-calcium fertilizer by mass percentage. The application rate is 95-105 kg / mu.

4. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, In step three, shallow tillage, pesticide application, and sowing: 1-2 days before sowing, the sowing field is shallowly tilled a second time to a depth of 10-15 cm. A chelation inducer is applied according to the type of lead-free or low-lead soil. The chelation inducer is a compound solution of ethylenediamine disuccinic acid and citric acid in a 1:1 molar ratio. The total amount of chelation inducer applied is determined according to the pollution level: 18-20 kg / mu for lead-free soil and 20-24 kg / mu for low-lead soil. Wheat varieties with low lead accumulation and strong resistance are selected. The sowing rate is 12-13 kg / mu, the row spacing is 20-25 cm, and the sowing depth is 3-5 cm.

5. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, The seedling management process in step four: S2.1 For lead-free soil, apply foliar nutrients. The foliar nutrient solution is a mixture of 0.1%-0.2% sorbitol, 0.1%-0.2% mannitol, 0.05%-0.1% zinc, 0.05%-0.1% iron, 0.05%-0.1% manganese and 0.2%-0.3% silicon. The application rate is 30-40 kg / mu. S2.2 For low-lead soil, apply enhanced foliar nutrition. The foliar nutrient solution should be formulated based on the lead-free soil formula, with the addition of a mixture of 0.1%-0.2% humic acid and 0.01%-0.02% sodium selenite. The application rate is 35-45 kg / mu.

6. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 5, characterized in that, In step four, 7-10 days after spraying, samples of the aboveground parts and roots of wheat plants are collected to determine the lead content and nutrient element content, and a baseline value archive is established.

7. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, In step five, a physical barrier is constructed: (1) For lead-free land, spray a standard foliar inhibitor consisting of 2%-3% potassium silicate, 0.3%-0.5% sorbitol and 0.02%-0.05% surfactant, with a spraying amount of 30-40 kg / mu; (2) For low-lead soil, spray an enhanced foliar inhibitor composed of 3.0%-3.5% potassium silicate, 0.5%-0.6% compound sugar alcohol, 0.15%-0.25% humic acid and 0.03%-0.05% surfactant, with a spraying amount of 35-40 kg / mu.

8. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 7, characterized in that, In step five, wheat leaf samples are collected 5-7 days after spraying to determine the silicon and lead content and evaluate the initial control effect. If the measured lead content does not reach the expected level close to 0, spraying is repeated 1-2 times after an interval of 7-14 days.

9. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, The process of foliar inhibition and nutrient synergy in step six: (1) For lead-free soil, spray the standard foliar inhibitor 1-2 times during the booting stage and the early grain filling stage. After each spraying, spray the nutrient enhancer together. The nutrient enhancer is a compound solution of 0.1%-0.15% humic acid and 0.3%-0.4% potassium dihydrogen phosphate. (2) For low-lead soil, apply enhanced foliar inhibitors 1-3 times during the heading stage, early grain filling stage and middle grain filling stage. After each application, apply enhanced nutrient synergist. The enhanced nutrient synergist is a compound solution with a mass concentration of 0.15%-0.25% humic acid, 0.2%-0.3% compound sugar alcohol and 0.3%-0.5% potassium dihydrogen phosphate. (3) 7-10 days after each spraying, collect flag leaf and young spike samples to determine lead content, silicon content and nutrient content, and dynamically monitor the risk of lead translocation to grains. When the lead content is detected to be increasing, spray 1-2 more times with a stronger inhibitor.

10. The planting method for reducing wheat lead content through a combination of chelation induction and foliar inhibition as described in claim 1, characterized in that, The quality verification process during the maturity stage in step seven: S3.

1. During the wheat ripening period, conduct the final sample collection and testing before harvest; S3.2 Collect wheat grain samples and soil samples from the 0-20 cm topsoil layer, and determine the lead content in the grains, total lead content in the soil, and available lead content, respectively. At the same time, determine the grain yield, thousand-grain weight, protein content, and wet gluten content, and comprehensively evaluate the quality grade of wheat. S3.3 After harvest, the lead content test results of the grains are correlated with the lead content test results of the soil and the management measures at each growth stage to form a safety production record.

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