Foliar blocking and controlling agent for heavy metal cadmium in rice and application method of foliar blocking and controlling agent

Abstract

The invention relates to a rice heavy metal cadmium leaf surface blocking and controlling agent and an application method thereof, the rice heavy metal cadmium leaf surface blocking and controlling agent is prepared by compounding the following components according to concentration: melatonin 100-300 [mu] mol / L and a nanometer silicon fertilizer 0.1%-0.3% (g / mL), the melatonin is pre-dissolved by ethanol and then is prepared into an aqueous solution with water, the nanometer silicon fertilizer is a SiO dispersion liquid, and the content of SiO is greater than or equal to 350 g / L. The melatonin and the nano silicon fertilizer are used for constructing the organic-inorganic compound leaf surface blocking and controlling agent, the characteristic that the melatonin serves as an endogenous metabolite is utilized, migration of cadmium from the underground part to the overground part is inhibited, the stress resistance of rice is improved, meanwhile, the advantages of the high specific surface area and activity of the nano silicon fertilizer are combined, an effective blocking layer is formed on crop leaf surfaces, and the rice resistance is improved. The cadmium content of rice seeds is remarkably reduced by matching precise spraying (the spraying amount is 10-20 mL / plant) at the flowering stage and the filling stage and surfactant optimization (the adding amount of Tween 60 is 0.02%).

Description

Technical Field

[0001] The invention belongs to the technical field of foliar heavy metal control, and particularly relates to a foliar control agent for heavy metal cadmium in rice and an application method thereof. Background Art

[0002] With the acceleration of global industrialization and the intensification of agriculture, heavy metal contamination in soils has become a major environmental issue threatening ecosystem security and human health. According to the Food and Agriculture Organization of the United Nations, cadmium (Cd) pollution ranks among the top three heavy metal pollutants in agricultural soils. It exhibits strong biotransport properties: ① It competes with essential elements such as calcium and iron for absorption through ion channels, and after absorption by crop roots, it can be transferred to the aboveground part within 72 hours. ② It exhibits significant tissue-specific accumulation in gramineous crops such as rice, with Cd concentrations in grains reaching 8-12 times that in roots (Environ Sci Technol, 2020). This biomagnification effect has resulted in Cd exceeding the standard in rice by 23.7% (GB 2762-2022). Cd accumulates in the human body through the food chain, causing diseases such as osteomalacia and renal dysfunction.

[0003] The current technology framework for remediating Cd-contaminated farmland consists of three main categories: ① Low-accumulation cultivars suffer from poor regional adaptability (cultivar specificity >70%) and long breeding cycles (5-8 years); ② Soil passivation technologies are limited by long remediation cycles (2-3 seasons) and the potential risk of secondary contamination; and ③ Foliar control technologies have become the mainstream solution due to their ease of use (farming time matching >95%), cost-effectiveness (40-60% cost reduction), and yield-increasing effects (average yield increase of 8.5%). Existing foliar control agents can be categorized by their composition: non-metallic elements (such as silicon-based materials), metallic elements (such as zinc and selenium compounds), and organic types (such as humic acid and EDTA). However, the three types of materials have significant technical bottlenecks: (1) Silicon-based materials are subject to pH sensitivity (optimal effect pH 6.5-7.2), and the control efficiency decreases by 38-45% in acidic soil areas (pH < 5.5); (2) Metal element types have a narrow dosage threshold (zinc: 50-100 mg / L) and ecological risks (excessive selenium causes plant toxicity); (3) Organic materials are affected by photolysis and have a short duration of effectiveness (<15 days), and there are problems such as high cost (humic acid purity requirement > 90%). Summary of the Invention

[0004] Technical problem to be solved: The present invention provides a foliar barrier agent for heavy metal cadmium in rice and an application method thereof. The foliar barrier agent of the present invention can reduce the accumulation of heavy metal cadmium in rice seeds by spraying it onto rice leaves, and is safe and pollution-free.

[0005] Technical solution: A foliar barrier for heavy metal cadmium in rice, comprising the following components compounded in concentration: 100-300 μmol / L melatonin and 0.1%-0.3% (g / mL) nano-silicon fertilizer. The melatonin is pre-dissolved in ethanol and then mixed with water to form an aqueous solution. The nano-silicon fertilizer is a SiO2 dispersion with a SiO2 content of ≥350 g / L.

[0006] Preferably, the concentration of melatonin is 200 μmol / L, and the concentration of nano-silicon fertilizer is 0.2% (g / mL).

[0007] The above-mentioned foliar control agent further comprises a surfactant, and the surfactant is selected from at least one of Tween series, fatty acid glyceride, and agricultural silicone.

[0008] Preferably, the surfactant is Tween 60, and its addition amount is 0.02% (g / mL).

[0009] The method for applying the foliar barrier agent comprises the following steps: spraying the foliar surface of rice during its reproductive growth period, spraying twice at a spraying volume of 10 to 20 mL per plant.

[0010] The above-mentioned spraying periods are specifically as follows: the first spraying is during the flowering stage, the second spraying is during the early filling stage, and the interval between the two sprayings is 10 to 15 days.

[0011] The spraying time is within 1 hour after sunset, the ambient temperature is ≤30°C, and the relative humidity is ≥60%.

[0012] During the above-mentioned spraying operation, the droplet diameter is controlled to be 80-120 μm, the leaf surface wetting rate reaches more than 80% and no droplets roll off.

[0013] Beneficial effects: The present invention constructs an organic-inorganic composite foliar barrier agent by combining melatonin and nano-silicon fertilizer, utilizes the characteristics of melatonin as an endogenous metabolite, inhibits the migration of cadmium from the underground part to the aboveground part and improves the stress resistance of rice, and combines the high specific surface area and activity advantages of nano-silicon fertilizer to form an effective barrier layer on the crop leaf surface. Combined with dual-stage precise spraying during the flowering and filling periods (spraying volume 10-20mL / plant) and surfactant optimization (Tween 60 addition amount 0.02%), the cadmium content in rice seeds is significantly reduced; the barrier agent adopts the process of ethanol pre-dissolution and water dilution to achieve stable component compounding, and has the advantages of simplified preparation process, low application cost, and environmental friendliness (biodegradable and non-toxic residue). At the same time, nano-silicon fertilizer is used to enhance crop photosynthesis, stem mechanical strength and stress resistance, forming a comprehensive technical solution integrating heavy metal barrier control, yield guarantee and ecological safety. DETAILED DESCRIPTION

[0014] The following examples are only for illustrating the implementation methods and technical features of the application of the present invention. Its purpose is to allow peers familiar with this invention technology to understand the content of this application and implement it. However, it should be understood by those skilled in the art that the embodiments herein can be changed without departing from the core technology of the present invention. The above embodiments are merely exemplary and should not be used as limitations of the scope of the present invention. In order to better understand the present invention, the present invention will be described in detail below in conjunction with specific embodiments.

[0015] Example 1

[0016] Effects of foliar control agents on heavy metal cadmium content in rice seeds grown in slightly cadmium-contaminated rice fields.

[0017] Test location: Cadmium-contaminated rice field test area, Huibu Town, Changshan County, Quzhou City, Zhejiang Province;

[0018] Trial period: April to October 2022;

[0019] The test site was selected from a farmer's rice field in Huibu Town, Changshan County, Quzhou City, Zhejiang Province. The rice field is safe-use arable land, and the soil heavy metal cadmium content is slightly above the standard, ranging from 0.6 to 0.9 mg / kg. The rice variety tested was Yongyou 1540. The experiment set up one control group and two experimental treatment groups. A randomized block design was used, with three replicates for each treatment and each plot area of 30 m 2 Soil and mature rice seed samples were collected from the site and brought back to the laboratory for analysis of heavy metal cadmium content in the soil and rice seeds. The specific experimental treatment results are shown in Table 1.

[0020] Control group: blank control group, normal rice planting.

[0021] Treatment group 1: 0.02% (g / mL) Tween 60 was sprayed once during the flowering stage and the grain filling stage, respectively.

[0022] Treatment group 2: The rice was sprayed with the foliar barrier control agent of the present invention once at the flowering stage and the grain filling stage respectively. The ingredient formula was a mixed preparation of 200 μmol / L melatonin, 0.2% (g / mL) nano-silicon fertilizer and 0.02% (g / mL) Tween 60.

[0023] Table 1 Total cadmium content in each experimental treatment and rice seeds (mg / kg)

[0024]

[0025] Note: Data are mean values with two decimal places (n=3). Lowercase letters indicate differences between treatments. Different letters indicate significant differences between treatments according to Duncan's new multiple range method (p<0.05).

[0026] As can be seen from the test results in Table 1, there was no significant difference in the cadmium content in the soil of each test unit. Compared with the blank control group, the total cadmium content in the rice seeds to which the above-mentioned foliar barrier agent was applied was significantly reduced, with an average reduction of 74.2%, which did not exceed the limit value standard of 0.2 mg / kg for rice in the "National Food Safety Standard for Limits of Contaminants in Food" (GB2762-2022). The average reduction in the rice seed enrichment coefficient was 72.5%. The research results show that when planting the Yongyou 1540 rice variety in this region, the auxiliary application of the above-mentioned foliar barrier agent can solve the agricultural product safety problem caused by excessive cadmium in rice seeds and realize the safe use of contaminated arable land. At the same time, the addition of the surfactant Tween 60 has little effect on the accumulation of cadmium in rice seeds.

[0027] In order to verify the effect of a single component and concentration of foliar barrier agents on reducing the heavy metal cadmium content in rice seeds, concentration gradient experiments of melatonin and nano-silicon fertilizer were set up respectively.

[0028] The melatonin concentration gradient test included one blank control group, one surfactant control group, and three melatonin treatment groups (100 μmol / L, 200 μmol / L, and 300 μmol / L) (Table 2). Three replicates were set for each treatment, and the other experimental conditions were the same as above.

[0029] Control group: blank control group, normal rice planting.

[0030] Treatment group 1: 0.02% (g / mL) Tween 60 was sprayed once during the flowering stage and the grain filling stage, respectively.

[0031] Treatment group 2: Rice was sprayed with a mixture of 100 μmol / L melatonin and 0.02% (g / mL) Tween 60 once at the flowering stage and the grain filling stage, respectively.

[0032] Treatment group 3: The rice was sprayed with a mixture of 200 μmol / L melatonin and 0.02% (g / mL) Tween 60 once at the flowering stage and the grain filling stage, respectively.

[0033] Treatment group 4: The rice was sprayed with a mixture of 300 μmol / L melatonin and 0.02% (g / mL) Tween 60 once at the flowering stage and the grain filling stage, respectively.

[0034] Table 2 Effects of different concentrations of melatonin on the total cadmium content in rice seeds (mg / kg)

[0035]

[0036] Note: Data are mean values with two decimal places (n=3). Lowercase letters indicate differences between treatments. Different letters indicate significant differences between treatments according to Duncan's new multiple range method (p<0.05).

[0037] As can be seen from the test results in Table 2, there was no significant difference in the soil cadmium content among the experimental units. Compared with the blank control group, after applying different concentrations of melatonin preparations, as the concentration of melatonin preparations increased, the total cadmium content in rice seeds showed a trend of first decreasing and then increasing, but all were lower than the control group. Among them, the application of 200μmol / L melatonin had the best cadmium reduction effect, with an average reduction of 50%, which did not exceed the limit value standard of 0.2mg / kg for rice in the "National Food Safety Standard Limit of Contaminants in Food" (GB2762-2022). The average reduction in the rice seed enrichment coefficient was 55.3%. The results of the study showed that when the Yongyou 1540 rice variety was planted in this area, the auxiliary application of melatonin preparations could effectively reduce the accumulation of heavy metal cadmium content in rice seeds, but it showed a significant concentration effect, and 200μmol / L melatonin had the best cadmium reduction effect.

[0038] The nano-silicon fertilizer concentration gradient test set up a blank control group, a surfactant control group and three concentrations (0.1%, 0.2%, 0.3%) of nano-silicon fertilizer treatment groups (Table 3), and each treatment was repeated three times. The other experimental conditions were the same as above.

[0039] Control group: blank control group, normal rice planting.

[0040] Treatment group 1: 0.02% (g / mL) Tween 60 was sprayed once during the flowering stage and the grain filling stage, respectively.

[0041] Treatment group 2: A mixture of 0.1% (g / mL) nano-silicon fertilizer and 0.02% (g / mL) Tween 60 was sprayed once during the flowering and grain filling stages of rice, respectively.

[0042] Treatment group 3: A mixture of 0.2% (g / mL) nano-silicon fertilizer and 0.02% (g / mL) Tween 60 was sprayed once during the flowering and grain filling stages of rice, respectively.

[0043] Treatment group 4: A mixture of 0.3% (g / mL) nano-silicon fertilizer and 0.02% (g / mL) Tween 60 was sprayed once during the flowering and grain filling stages of rice, respectively.

[0044] Table 3 Effects of different concentrations of nano-silicon fertilizer on the total cadmium content in rice seeds (mg / kg)

[0045]

[0046] Note: Data are mean values with two decimal places (n=3). Lowercase letters indicate differences between treatments. Different letters indicate significant differences between treatments according to Duncan's new multiple range method (p<0.05).

[0047] The test results in Table 3 show no significant differences in soil cadmium content among the experimental units. Compared to the blank control group, after applying different concentrations of nano-silicon fertilizer, total cadmium content in rice seeds initially decreased and then stabilized as the concentration of the melatonin preparation increased, but remained lower than the control group. Applications of 0.2% and 0.3% nano-silicon fertilizers were most effective in reducing cadmium, with an average reduction of approximately 40%, slightly exceeding the 0.2 mg / kg limit for rice grains set in the "National Food Safety Standard for Contaminants in Food" (GB2762-2022). The average reductions in the rice seed enrichment factor were 39.6% and 41.7%, respectively. The results indicate that supplementing the application of nano-selenium fertilizer with the Yongyou 1540 rice variety in this region can effectively reduce the accumulation of heavy metal cadmium in rice seeds, but there was a significant concentration effect. The 0.2% and 0.3% nano-silicon fertilizers showed the best cadmium reduction effects, with similar differences. Considering the overall application cost, the 0.2% nano-silicon fertilizer is recommended.

[0048] Based on the above experimental data, it can be concluded that both melatonin and nano-silicon fertilizer can reduce the accumulation of heavy metal cadmium in rice seeds, with significant concentration effects. Furthermore, the combined use of the two ingredients can produce a significant combined effect. The two ingredients have different mechanisms of action in regulating heavy metal cadmium accumulation in rice seeds and can produce a synergistic effect.

[0049] Example 2

[0050] Effects of foliar control agents on heavy metal cadmium content in rice seeds grown in heavily cadmium-contaminated rice fields.

[0051] Test location: Cadmium-contaminated rice field test area, Huibu Town, Changshan County, Quzhou City, Zhejiang Province;

[0052] Trial period: April to October 2023;

[0053] The test site was selected from a farmer's rice field in Huibu Town, Changshan County, Quzhou City, Zhejiang Province. The rice field is strictly controlled arable land, and the soil heavy metal cadmium content is seriously exceeded, with the soil cadmium content ranging from 1.5 to 2.0 mg / kg. The rice variety tested was Yongyou 1540. A total of 1 control group and 3 experimental treatment groups were set up in the experiment. A randomized block design was used, with 3 replicates for each treatment and each plot area of 10m 2 Soil and mature rice seed samples were collected from the site and brought back to the laboratory for analysis of heavy metal cadmium content in the soil and rice seeds. The specific test treatment results are shown in Table 4.

[0054] Control group: blank control group, normal rice planting.

[0055] Treatment group 1: 0.02% (g / mL) Tween 60 was sprayed once during the flowering stage and the grain filling stage, respectively.

[0056] Treatment group 2: The rice was sprayed with the foliar control agent once at the flowering stage and the grain filling stage respectively.

[0057] Treatment group 3: soil conditioner (main component of which was calcium aluminum hydrotalcite) was applied before planting.

[0058] Treatment group 4: Soil conditioner (main component: calcium aluminum hydrotalcite) was applied before planting, and a mixture of 200 μmol / L melatonin, 0.2% (g / mL) nano-silicon fertilizer and 0.02% (g / mL) Tween 60 was sprayed once during the flowering and filling stages of rice.

[0059] Table 4 Total cadmium content in each experimental treatment and rice seeds (mg / kg)

[0060]

[0061] Note: Data are mean values with two decimal places (n=3). Lowercase letters indicate differences between treatments. Different letters indicate significant differences between treatments according to Duncan's new multiple range method (p<0.05).

[0062] From the test results in Table 4, it can be seen that there is no significant difference in the cadmium content in the soil of each test unit. Compared with the blank control group, the total cadmium content in the rice seeds of the treatment group 2 (treated group 2) applied with the above-mentioned foliar barrier alone was significantly reduced, with an average reduction of 65.4%, slightly exceeding the limit value standard of 0.2 mg / kg, and the average reduction in the rice seed enrichment coefficient was 65.9%. When the above-mentioned foliar barrier treatment was superimposed on the soil conditioner (the main component of which is calcium aluminum hydrotalcite), the average total cadmium content in the rice seeds was only 0.15 mg / k, which was 80.8% lower than the control group and lower than the limit value standard of 0.2 mg / kg for rice. The results of the study showed that when the Yongyou 1540 rice variety is planted in this area, the auxiliary application of the above-mentioned foliar barrier can significantly reduce the accumulation of cadmium in rice seeds. At the same time, it can produce a composite effect when used together with soil conditioners and other means to solve the problem of safe utilization of heavily cadmium-contaminated cultivated land.

Claims

1. A foliar control agent for heavy metal cadmium in rice, characterized in that: The invention is prepared by compounding the following components according to their concentrations: 100-300 μmol / L melatonin and 0.1%-0.3% (g / mL) nano-silicon fertilizer. The melatonin is pre-dissolved in ethanol and then mixed with water to form an aqueous solution. The nano-silicon fertilizer is a SiO2 dispersion with a SiO2 content of ≥350 g / L.

2. The foliage control agent according to claim 1, characterized in that: The melatonin concentration is 200 μmol / L, and the nano-silicon fertilizer concentration is 0.2% (g / mL).

3. The foliage control agent according to claim 1, characterized in that: The invention also comprises a surfactant, which is selected from at least one of Tween series, fatty acid glyceride and agricultural silicone.

4. The foliage control agent according to claim 3, characterized in that The surfactant is Tween 60, and its addition amount is 0.02% (g / mL).

5. The method for applying the foliar control agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: Spray the leaves twice during the reproductive growth period of rice, with a spraying volume of 10 to 20 mL per plant.

6. The application method according to claim 5, characterized in that The spraying period is specifically as follows: the first spraying is at the flowering stage, the second spraying is at the early filling stage, and the interval between the two sprayings is 10 to 15 days.

7. The application method according to claim 5, characterized in that The spraying time is within 1 hour after sunset, the ambient temperature is ≤30°C, and the relative humidity is ≥60%.

8. The application method according to claim 5, characterized in that During the spraying operation, the droplet diameter is controlled to be 80-120 μm, the leaf surface wetting rate reaches more than 80% and no droplets roll off.

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