Water-soluble fertilizer for inhibiting absorption and accumulation of all-metal cadmium of rice grain weight and preparation method of water-soluble fertilizer

Abstract

The invention discloses a water-soluble fertilizer for inhibiting absorption and accumulation of all-metal cadmium of rice grain weight and a preparation method of the water-soluble fertilizer. The water-soluble fertilizer is prepared from the following components in parts by weight: 20 to 25 parts of biochemical fulvic acid, 35 to 40 parts of compound amino acid, 10 to 15 parts of zinc sulfate monohydrate, 3 to 6 parts of ferric sodium ethylene diamine tetraacetate, 0.6 to 0.9 part of manganese sodium ethylene diamine tetraacetate, 0.3 to 0.6 part of boric acid, 0.4 to 0.8 part of pH (Potential of Hydrogen) regulator, 0.7 to 1.2 parts of chelating agent, 0.8 to 1.2 parts of surfactant and 80 to 100 parts of water. The preparation method of the water-soluble fertilizer comprises the following steps: S1, adding biochemical fulvic acid and compound amino acid into water, stirring and dissolving to obtain mother liquor A, S2, adding a pH regulator into the mother liquor A, stirring and dissolving to obtain mother liquor B, s3, respectively adding a chelating agent, zinc sulfate monohydrate, ferric sodium ethylene diamine tetraacetate, manganese sodium ethylene diamine tetraacetate and boric acid into the mother liquor B, stirring and dissolving to obtain mother liquor C; and S4, adding a surfactant into the mother liquor C, stirring and dissolving to obtain the water-soluble fertilizer.

Description

Technical Field

[0001] The invention relates to the technical field of rice planting, and relates to a leaf surface inhibitor, in particular to a water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains, and a preparation method thereof. Background Art

[0002] Heavy metal pollution in soil is an important factor affecting the health of farmland ecosystems and the quality and safety of agricultural products, especially cadmium (Cd). Cadmium (Cd) is a heavy metal element with strong biological toxicity and is easily absorbed by the human body. Therefore, it is a heavy metal element that endangers food security. Cadmium (Cd) can enter the human body through the food chain and cause health problems.

[0003] In recent years, with the development of mining and metallurgy, agricultural sewage irrigation, and illegal application of fertilizers and pesticides, cadmium (Cd) pollution in farmland has become increasingly serious. Data show that 300 million mu of farmland in China is threatened by heavy metal pollution, accounting for 1 / 6 of the total farmland in the country. During the sampling and monitoring of harmful heavy metals in the soil of 300,000 hectares of basic farmland protection areas in my country, it was found that 36,000 hectares of soil heavy metals exceeded the standard, and the excess rate reached 12.1%. At present, more than 10% of the cultivated land area in the country has been polluted by heavy metals. The prevention and control situation is very serious and is showing a trend of continuous intensification. my country's rice planting area is about 30.2132 million hectares, accounting for 27% of the grain planting area. The national rice output is 208.245 million tons, and its sown area, total output and yield per unit area are all ranked first among grain crops;

[0004] As one of the main food crops, rice plays an important role in agricultural production and food security. However, rice is also a crop with a strong ability to absorb and enrich heavy metal cadmium. Therefore, soil cadmium (Cd) pollution poses a serious threat to rice production and food safety. In addition, excessive cadmium in rice is related to health. How to effectively reduce the cadmium content in rice and ensure food security is urgent.

[0005] At present, there are three main methods to reduce the absorption and accumulation of cadmium by rice in heavy metal contaminated soil: the first is to directly remove cadmium from the soil, such as using the "guest soil method" to plant super-accumulative crops; the second is to change the occurrence form of heavy metals in the soil, so that it changes from an effective state to a stable state that is difficult to migrate, such as applying passivators; the third is to spray foliar barrier agents to reduce the absorption and accumulation of heavy metals by rice. The first measure requires a lot of money and a long time, and it is difficult to promote on a large scale. The second measure is severely destructive to the soil and will also precipitate the trace elements necessary for rice growth in the soil, leading to a lack of nutrient elements. Therefore, the third measure is obviously more feasible;

[0006] Foliar barrier technology is a widely used technology for safe utilization of agricultural land, which is of great value and significance to the safe production of rice. Traditional foliar barrier technology sprays silicon (Si), selenium (Se), zinc (Zn) and other elements on the leaves to improve crop resistance, inhibit the transport of heavy metals from the crop roots to the aboveground parts or to the edible parts, and reduce the heavy metal content of agricultural products. However, the foliar barrier agents on the market only have the function of blocking cadmium, but cannot provide nutrients for rice. The effect on improving plant resistance and microbial activity is poor, and it cannot effectively increase crop yields. Summary of the invention

[0007] In order to overcome the shortcomings of the existing technical solutions, the present invention provides a water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains and a preparation method thereof, which can effectively solve the technical problems that the foliar inhibitors on the market only have the functional effect of blocking cadmium but cannot provide nutrients for rice, have poor effects on improving plant stress resistance and microbial activity, and cannot effectively increase crop yields.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by weight of rice grains comprises the following components in parts by weight: 20-25 parts of biochemical humic acid, 35-40 parts of composite amino acids, 10-15 parts of zinc sulfate monohydrate, 3-6 parts of sodium ferric ethylenediaminetetraacetate, 0.6-0.9 parts of sodium manganese ethylenediaminetetraacetate, 0.3-0.6 parts of boric acid, 0.4-0.8 parts of pH regulator, 0.7-1.2 parts of chelating agent, 0.8-1.2 parts of surfactant and 80-100 parts of water.

[0009] Furthermore, the composite amino acid is a combination of two or more of glycine, alanine, arginine, proline, leucine, aspartic acid and serine.

[0010] Furthermore, the pH adjuster is one or more combinations of citric acid, potassium citrate and acetic acid.

[0011] Furthermore, the chelating agent is one or more combinations of ethylenediaminetetraacetic acid, sodium ethylenediamine di-o-phenylacetate, and diethylenetriaminepentaacetic acid.

[0012] Furthermore, the surfactant is one or more combinations of polyether-modified trisiloxane, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate, and polyoxyethylene sorbitan monooleate.

[0013] A method for preparing a water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by rice grains, the method comprising the following steps:

[0014] Step S1: preparing biochemical fulvic acid and composite amino acids according to a weight ratio, adding the biochemical fulvic acid and composite amino acids into water, heating them, and stirring them until they are completely dissolved to obtain a mother solution A;

[0015] Step S2: preparing a pH regulator according to a weight ratio, adding the pH regulator to the mother solution A to adjust the pH value, and stirring until completely dissolved to obtain a mother solution B;

[0016] Step S3: preparing a chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid in proportion by weight, and adding the chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid to the mother liquor B for chelation and stirring until completely dissolved to obtain a mother liquor C;

[0017] Step S4: prepare a surfactant according to a weight ratio, add the surfactant into the mother solution C, and stir until it is completely dissolved to obtain a water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains.

[0018] Furthermore, in step S1, the mixed solution of biochemical fulvic acid, complex amino acid and water is heated to a temperature of 45°C to 55°C.

[0019] Furthermore, in step S2, the pH regulator is gradually added to the mother liquor A and fully mixed, and the pH value of the mother liquor B is adjusted to 3-7.

[0020] Furthermore, in step S3, the temperature of the mother liquor B is adjusted to 45°C to 55°C, and then a chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid are added, and the chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid are subjected to a chelating reaction under a temperature condition of 45°C to 55°C.

[0021] Furthermore, in step S4, the temperature of the mother solution C is adjusted to 45° C. to 55° C. before adding a surfactant.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains uses zinc sulfate monohydrate, sodium ferric EDTA, and sodium manganese EDTA as raw materials. On the one hand, its components are easily absorbed by rice. On the other hand, zinc and cadmium belong to the same family of elements and have similar chemical properties. There is a competitive relationship between the transport of zinc and cadmium in the plasma membrane of rice root cells. Therefore, when zinc exists in large quantities in rice, it can greatly reduce the absorption of cadmium by rice. At the same time, Fe 2+ It can significantly increase the content of iron film on the root surface, thus further inhibiting the absorption of cadmium by rice roots, stems and leaves;

[0024] The water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains uses biochemical fulvic acid and compound amino acids as Zn 2+ , Fe 2+ , Mn 2+ carrier, which can effectively promote the absorption of Zn by rice straw and grains. 2+ , Fe 2+ , Mn 2+ absorption and transport, enhancing the competitive cation Zn 2+ , Fe 2+ , Mn 2+ with cd 2+ antagonistic effect, thereby effectively inhibiting the 2+ The absorption and accumulation of cadmium in rice grains further reduced the cadmium content in rice grains;

[0025] In summary, the water-soluble fertilizer for inhibiting the absorption and accumulation of heavy metal cadmium in rice grains of the present invention can effectively reduce the cadmium content in rice grains. Spraying it on rice leaves and stems can not only better inhibit the absorption and transport of heavy metal cadmium by rice roots and stems, and reduce the absorption and accumulation of heavy metal cadmium in rice grains, but also can be used as a fertilizer to supplement nutrition to rice, thereby promoting rice growth, increasing the number of effective tillers, and improving the rice fruit setting rate and thousand-grain weight, thereby achieving the purpose of improving rice quality, promoting rice production and ensuring rice food safety, and can increase the net photosynthetic rate of leaves, stomatal conductance, intercellular CO2 concentration and transpiration rate, increase the number of effective panicles and biomass, thereby achieving the effect of increasing rice yield and reducing Cd transport to grains. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the preparation method of the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to the present invention;

[0027] Figure 2 The effects of different treatments of the present invention on rice biomass and harvest index;

[0028] Figure 3 The effects of different treatments of the present invention on photosynthetic indexes of rice leaves;

[0029] Figure 4 This is the effect of different treatments of the present invention on the Cd content in various parts of rice. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The invention provides a water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains, comprising the following components in parts by weight: 20 to 25 parts of biochemical fulvic acid, 35 to 40 parts of composite amino acids, 10 to 15 parts of zinc sulfate monohydrate, 3 to 6 parts of sodium ferric ethylenediaminetetraacetate, 0.6 to 0.9 parts of sodium manganese ethylenediaminetetraacetate, 0.3 to 0.6 parts of boric acid, 0.4 to 0.8 parts of a pH regulator, 0.7 to 1.2 parts of a chelating agent, 0.8 to 1.2 parts of a surfactant and 80 to 100 parts of water;

[0032] The composite amino acid is a combination of two or more of glycine, alanine, arginine, proline, leucine, aspartic acid, and serine; the pH regulator is a combination of one or more of citric acid, potassium citrate, and acetic acid; the chelating agent is a combination of one or more of ethylenediaminetetraacetic acid, sodium ethylenediamine di-o-phenylacetate, and diethylenetriaminepentaacetic acid; and the surfactant is a combination of one or more of polyether-modified trisiloxane, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate, and polyoxyethylene sorbitan monooleate.

[0033] like Figure 1 As shown, a method for preparing a water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by rice grains comprises the following steps:

[0034] Step S1: preparing biochemical fulvic acid and composite amino acids according to a weight ratio, adding the biochemical fulvic acid and composite amino acids into water to form a mixed solution, heating the mixed solution to a temperature of 45° C. to 55° C., and then stirring the mixed solution until the biochemical fulvic acid and composite amino acids are completely dissolved to obtain a mother solution A;

[0035] Step S2: preparing a pH regulator according to a weight ratio, gradually adding the pH regulator to the mother solution A, and stirring until the pH regulator is completely dissolved and fully mixed with the mother solution A to obtain a mother solution B, wherein the pH value of the mother solution B is 3 to 7;

[0036] Step S3: preparing a chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid in proportion by weight, adjusting the temperature of the mother solution B to 45° C. to 55° C., adding the chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid, and stirring until completely dissolved, and performing a chelating reaction between the chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid at a temperature of 45° C. to 55° C. to obtain a mother solution C;

[0037] Step S4: prepare a surfactant according to the weight ratio, adjust the temperature of the mother solution C to 45° C. to 55° C., add the surfactant, and stir until the surfactant is completely dissolved to obtain a water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains.

[0038] Test method for the effect of water-soluble fertilizers that inhibit the absorption and accumulation of cadmium in rice grains in rice cultivation on cadmium-contaminated soil:

[0039] 1. Experimental Materials and Methods

[0040] (1) Experimental materials: Soil was taken from a field where rice was grown all year round. The soil physical and chemical properties were as follows: pH 6.60, organic matter 22.72 g / kg, total nitrogen 0.875 g / kg, total phosphorus 1.026 g / kg, total potassium 11.27 g / kg, alkaline nitrogen 78.89 g / kg, available phosphorus 74.60 g / kg, and available potassium 50.16 g / kg. Equal amounts of nitrogen, phosphorus, and potassium were applied to the soil as basal fertilizers at one time. After 10 days of equilibrium, representative rice seedlings with 4 leaves and 1 heart were selected and transplanted into the experimental pots of the four treatment conditions. Each experimental pot was treated three times, for a total of 12 experimental pots, with 2 plants planted in each pot, for a total of 24 plants. Cd-contaminated soil was exogenously added with Cd, with 5 mg Cd applied per 1 kg of soil.

[0041] (2) Experimental design: The treatment conditions of the T1 test pot were: healthy soil + spraying with clean water; the treatment conditions of the T2 test pot were: Cd-contaminated soil + spraying with clean water; the treatment conditions of the T3 test pot were: Cd-contaminated soil + spraying (low concentration) of water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grain weight; the treatment conditions of the T4 test pot were: Cd-contaminated soil + spraying (high concentration) of water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grain weight. The T1 and T2 test pots were sprayed with an equal amount of clean water. The T3 and T4 test pots were treated with a small electric spraying pot to spray the leaves with an equal amount of water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grain weight three times in the middle of rice tillering, the beginning of panicle differentiation, and the heading stage. The spraying amount was 29 ml / pot in the middle of rice tillering, and 58 ml / pot in the beginning of panicle differentiation and heading stages.

[0042] 2. Test indicators and methods

[0043] At the beginning of rice panicle differentiation, photosynthetic characteristic parameters of rice leaves, such as net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate, were measured using a portable photosynthetic instrument (LI-6400XT, USA) from 9:00 to 11:00 on sunny days.

[0044] At the rice maturity stage, the number of effective panicles per plant was calculated, and the rice plants were divided into panicles, leaves, and stems. After threshing, the rice grains were divided into full grains, empty grains, and branches. The total number of grains per panicle, the fruit setting rate, and the thousand-grain weight were calculated. Each part was sterilized at 105℃ for 20 minutes, then adjusted to 75℃ and dried to constant weight, and weighed to obtain the biomass of each part;

[0045] The various parts of rice were crushed by a stainless steel grinder and used for the determination of Cd content. The Cd determination was based on GB 5009.268-2016 "Determination of multiple elements in food" and was determined by microwave digestion using an Agilent 7500cx inductively coupled plasma mass spectrometer (ICP-MS). Excel and SPSS27 were used for data processing, and the Duncan method and LSD were used for variance analysis and multiple comparisons. OriginPro 2024 was used for graphics.

[0046]

[0047] Table 1 Rice yield and yield components under different treatments

[0048] 3. Results and Analysis

[0049] 1. Effects of different treatments on rice yield and its components

[0050] As shown in Table 1, spraying water-soluble fertilizers that inhibit the absorption and accumulation of cadmium in rice grain weight can significantly increase the weight of rice grains. Compared with the T2 treatment, the grain weights of the T3 and T4 treatments increased by 81.7% and 48.57%, respectively. The number of effective panicles was the highest in the T3 treatment, followed by the T4 treatment, which increased by 66.67% and 40.00%, respectively, compared with the T2 treatment. There were no significant differences in the total number of grains per panicle, the fruit setting rate and the 1000-grain weight of the T2, T3 and T4 treatments.

[0051] 2. Effects of different treatments on rice biomass and harvest index

[0052] like Figure 2 It can be seen that compared with the T2 treatment, the biomass of the T3 and T4 treatments increased by 53.14% and 24.32%, respectively, and the differences reached a significant level. There was no significant difference in the harvest index among the treatments.

[0053] (III) Effects of different treatments on photosynthetic indicators of rice leaves

[0054] Depend on Figure 3It can be seen that compared with the T2 treatment, the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate of the T3 treatment increased by 9.72%, 42.76%, 7.30% and 17.05%, respectively, and the differences were significant. There was no significant difference in the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration and transpiration rate of the T3 treatment compared with the control (T1).

[0055] (IV) Effects of different treatments on cadmium content in various parts of rice

[0056] Depend on Figure 4 It can be seen that there are differences in Cd content in various parts between T2 and T3 treatments, but they are not significant. The Cd content in full grains and empty grains + branches in T3 treatment is 33.11% and 28.24% lower than that in T2 treatment, respectively. Compared with T2 treatment, T3 treatment significantly increased the proportion of Cd in stems and leaves, but significantly reduced the proportion of Cd in full grains and empty grains + branches (decreased by 31.77% and 25.66, respectively).

[0057] IV. Conclusion

[0058] (1) From Table 1 and Figure 2 It can be seen that the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains of the present invention contains a large amount of nutrients such as amino acids, organic matter and Zn. Whether spraying a high concentration or a low concentration of the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains, it can promote rice tillering and increase biomass, thereby increasing yield;

[0059] (2) A large number of studies have shown that Zn, Fe, and Mn can compete with Cd for absorption and transport systems, inhibiting the absorption of Cd by rice. According to research reports, Fe can promote the formation of a large amount of iron film in the rice root system, preventing the root system from absorbing Cd, thereby reducing the Cd content of rice. Mn and Zn have antagonistic effects with Cd in the plant, competing for Cd transport carriers, inhibiting the transport of Cd, and significantly reducing the Cd content in rice stems, leaves, and grains. Figure 4 It can be known that the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by rice grain weight of the present invention contains amino acids, organic matter, Zn, Fe, Mn, and B elements. Therefore, after spraying the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by rice grain weight on the leaves, Zn, Fe, and Mn can inhibit the transport of Cd to the aboveground part, especially to the solid grains, resulting in a significant decrease in the proportion of Cd in the grains.

[0060] Compared with traditional technology: The water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains uses zinc sulfate monohydrate, sodium ferric EDTA, and sodium manganese EDTA as raw materials. On the one hand, its components are easily absorbed by rice. On the other hand, zinc and cadmium belong to the same family of elements and have similar chemical properties. There is a competitive relationship between the transport of zinc and cadmium in the plasma membrane of rice root cells. Therefore, when zinc exists in large quantities in rice, it can greatly reduce the absorption of cadmium by rice. At the same time, Fe 2+ It can significantly increase the content of iron film on the root surface, thus further inhibiting the absorption of cadmium by rice roots, stems and leaves;

[0061] The water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains uses biochemical fulvic acid and compound amino acids as Zn 2+ , Fe 2+ , Mn 2+ carrier, which can effectively promote the absorption of Zn by rice straw and grains. 2+ , Fe 2+ , Mn 2+ absorption and transport, enhancing the competitive cation Zn 2+ , Fe 2+ , Mn 2+ with cd 2+ antagonistic effect, thereby effectively inhibiting the 2+ The absorption and accumulation of cadmium in rice grains further reduced the cadmium content in rice grains;

[0062] In summary, the water-soluble fertilizer for inhibiting the absorption and accumulation of heavy metal cadmium in rice grains of the present invention can effectively reduce the cadmium content in rice grains. Spraying it on rice leaves and stems can not only better inhibit the absorption and transport of heavy metal cadmium by rice roots and stems, and reduce the absorption and accumulation of heavy metal cadmium in rice grains, but also can be used as a fertilizer to supplement nutrition to rice, thereby promoting rice growth, increasing the number of effective tillers, and improving the rice fruit setting rate and thousand-grain weight, thereby achieving the purpose of improving rice quality, promoting rice production and ensuring rice food safety, and can increase the net photosynthetic rate of leaves, stomatal conductance, intercellular CO2 concentration and transpiration rate, increase the number of effective panicles and biomass, thereby achieving the effect of increasing rice yield and reducing Cd transport to grains.

[0063] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by rice grains, characterized in that: The invention comprises the following components in parts by weight: 20 to 25 parts of biochemical fulvic acid, 35 to 40 parts of complex amino acid, 10 to 15 parts of zinc sulfate monohydrate, 3 to 6 parts of sodium ferric ethylenediaminetetraacetate, 0.6 to 0.9 parts of sodium manganese ethylenediaminetetraacetate, 0.3 to 0.6 parts of boric acid, 0.4 to 0.8 parts of pH regulator, 0.7 to 1.2 parts of chelating agent, 0.8 to 1.2 parts of surfactant and 80 to 100 parts of water.

2. The water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 1, characterized in that: The composite amino acid is a combination of two or more of glycine, alanine, arginine, proline, leucine, aspartic acid and serine.

3. The water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 2, characterized in that: The pH adjuster is one or more combinations of citric acid, potassium citrate and acetic acid.

4. The water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 3, characterized in that: The chelating agent is one or more combinations of ethylenediaminetetraacetic acid, sodium ethylenediamine di-o-phenylacetate, and diethylenetriaminepentaacetic acid.

5. The water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 4, characterized in that: The surfactant is one or more combinations of polyether-modified trisiloxane, fatty alcohol polyoxyethylene ether, sodium lauryl sulfate, and polyoxyethylene sorbitan monooleate.

6. The method for preparing the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium by rice grains according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Step S1: preparing biochemical fulvic acid and composite amino acids according to a weight ratio, adding the biochemical fulvic acid and composite amino acids into water, heating them, and stirring them until they are completely dissolved to obtain a mother solution A; Step S2: preparing a pH regulator according to a weight ratio, adding the pH regulator to the mother solution A to adjust the pH value, and stirring until completely dissolved to obtain a mother solution B; Step S3: preparing a chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid in proportion by weight, and adding the chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid to the mother liquor B for chelation and stirring until completely dissolved to obtain a mother liquor C; Step S4: prepare a surfactant according to a weight ratio, add the surfactant into the mother solution C, and stir until it is completely dissolved to obtain a water-soluble fertilizer that inhibits the absorption and accumulation of cadmium in rice grains.

7. The method for preparing the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 6, characterized in that: In step S1, the mixed solution of biochemical fulvic acid, compound amino acid and water is heated to a temperature of 45°C to 55°C.

8. The method for preparing the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 7, characterized in that: In step S2, the pH regulator is gradually added to the mother solution A and fully mixed, and the pH value of the mother solution B is adjusted to 3-7.

9. The method for preparing the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 8, characterized in that: In step S3, the temperature of the mother solution B is adjusted to 45°C to 55°C, and then a chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid are added. The chelating agent, zinc sulfate monohydrate, sodium ferric ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, and boric acid are subjected to a chelating reaction at a temperature of 45°C to 55°C.

10. The method for preparing the water-soluble fertilizer for inhibiting the absorption and accumulation of cadmium in rice grains according to claim 9, characterized in that: In step S4, the temperature of the mother solution C is adjusted to 45°C to 55°C, and then a surfactant is added.

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