Functional water-soluble fertilizer and preparation method thereof

Abstract

The application discloses a kind of functional water-soluble fertilizer and preparation method thereof, and fertilizer component includes urea, potassium dihydrogen phosphate, potassium nitrate, calcium nitrate, water-soluble silicon, potassium fulvic acid, betaine, sodium selenite, magnesium sulfate, EDTA-zinc, EDTA-iron, boric acid, ammonium molybdate and citric acid and the like ingredient.Preparation, calcium nitrate and citric acid are pre-complexed to obtain calcium chelate liquid, potassium fulvic acid is compounded with water-soluble silicon to obtain silicon-fulvic acid complex liquid, macroelement is dissolved as base stock solution with betaine, trace element is chelated as microelement chelate liquid with sodium selenite, then each liquid is mixed according to specific order, and the pH is adjusted to 6.5~8.0, and then homogenized to obtain the fertilizer.The application inhibits the transport of heavy metal cadmium to fruit through calcium, silicon, selenium and fulvic acid multi-target point synergy, reduces the cadmium content of fruit, simultaneously, betaine and silicon are compounded to improve the salt tolerance and stress resistance of crops, and the macroelement and trace element are balancedly supplemented, effectively improves the yield and quality of crops, and the fertilizer system is stable, suitable for water and fertilizer integrated application.

Description

Technical Field

[0001] This invention relates to the field of water-soluble fertilizer technology, specifically to a functional water-soluble fertilizer and its preparation method. Background Technology

[0002] Water-soluble fertilizers are a type of multi-element compound fertilizer that can completely dissolve in water. They can be used in drip irrigation, sprinkler irrigation, and other integrated water and fertilizer systems, and are characterized by comprehensive nutrients, rapid dissolution, and high utilization rate. Based on their function, water-soluble fertilizers can be divided into nutrient-type water-soluble fertilizers and functional-type water-soluble fertilizers. Functional-type water-soluble fertilizers typically contain added plant-, animal-, or mineral-derived active substances such as humic acid, amino acids, and alginic acid to improve soil, stimulate crop growth, and enhance crop quality.

[0003] In greenhouse cultivation, prolonged continuous cropping, excessive application of chemical fertilizers, and high temperature and humidity environments have led to increasingly prominent secondary soil salinization problems. Simultaneously, industrial pollution and soil acidification increase the risk of activation of heavy metals such as cadmium and lead in greenhouse vegetable fields, which easily accumulate in the fruits of solanaceous crops like tomatoes, threatening the safety of agricultural products for consumption. Furthermore, greenhouse cultivation is often accompanied by adverse stresses such as high summer temperatures. The aforementioned salt accumulation, heavy metal activation, and high temperatures often occur in combination, constituting compound stress that severely affects crop yield and quality.

[0004] Most existing functional water-soluble fertilizers are designed to address a single stress or function. For example, they may passivate and repair heavy metals in soil by adding humic acid, compound bacteria, and algae extracts; promote crop root growth by combining potassium dihydrogen phosphate with plant growth regulators; or improve crop heat tolerance by adding γ-aminobutyric acid (GABA). However, these solutions are insufficient to simultaneously address the combined stresses of salt, heavy metals, and high temperatures on crops, and they lack methods to regulate the low accumulation of heavy metals in fruits.

[0005] Therefore, there is a need for a functional water-soluble fertilizer and its preparation method that can inhibit the accumulation of heavy metals in fruits under combined stress conditions, improve the salt tolerance and stress resistance of crops, and balance yield and quality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a functional water-soluble fertilizer and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] On one hand, the present invention provides a functional water-soluble fertilizer, the components of which, by weight, include: 18-30 parts urea, 8-18 parts potassium dihydrogen phosphate, 20-35 parts potassium nitrate, 4-12 parts calcium nitrate, 4-10 parts water-soluble silicon, 10-22 parts potassium humate, 1.5-6 parts betaine, 0.005-0.1 parts sodium selenite, 1-3 parts magnesium sulfate, 0.5-1.5 parts EDTA-zinc, 0.5-1.5 parts EDTA-iron, 0.3-0.8 parts boric acid, 0.05-0.3 parts ammonium molybdate, and 0.3-1.0 parts citric acid.

[0009] Preferably, the water-soluble silicon is at least one of sodium metasilicate, potassium metasilicate, and potassium silicate; the potassium fulvate is mineral-derived potassium fulvate; and the betaine is glycine betaine.

[0010] Preferably, the functional water-soluble fertilizer further comprises: 0.5 to 2.5 parts of anti-coagulant and 0.1 to 0.8 parts of surface tension modifier.

[0011] Furthermore, the anti-coagulation agent is selected from at least one of polyaspartic acid, γ-polyglutamic acid, or sodium polyacrylate; the surface tension modifier is selected from at least one of alkyl glycoside, fatty alcohol polyoxyethylene ether, or sodium secondary alkyl sulfonate.

[0012] Preferably, the functional water-soluble fertilizer comprises, by weight, the following components: 25 parts urea, 15 parts potassium dihydrogen phosphate, 30 parts potassium nitrate, 8 parts calcium nitrate, 7 parts water-soluble silicon, 16 parts potassium humate, 4 parts betaine, 0.05 parts sodium selenite, 2 parts magnesium sulfate, 1 part EDTA-zinc, 1 part EDTA-iron, 0.5 parts boric acid, 0.15 parts ammonium molybdate, 0.8 parts citric acid, 1.5 parts polyaspartic acid, and 0.4 parts alkyl glycoside.

[0013] On the other hand, the present invention provides a method for preparing a functional water-soluble fertilizer, the specific steps of which are as follows: S1: Calcium nitrate and citric acid are pre-complexed in water at 50-60℃ to form a calcium chelate solution; S2: Potassium humate and sodium metasilicate are combined in water at 60-70℃ to form a silicon-humic acid composite solution; S3: Dissolve urea, potassium dihydrogen phosphate, potassium nitrate, magnesium sulfate and betaine in water at 40-60℃ to form a base mother liquor; S4: Dissolve EDTA-zinc, EDTA-iron, boric acid, ammonium molybdate and sodium selenite in water at 50-60℃ to form a micro-fertilizer chelate solution; S5: Mix calcium chelate solution, silicon-humic acid composite solution, micro-fertilizer chelate solution and base mother liquor, adjust pH to 6.5-8.0, homogenize, and obtain functional water-soluble fertilizer.

[0014] Preferably, in step S1, the pre-complexation reaction time is 20-40 min, and the pH of the calcium chelate solution is controlled at 3.0-4.5; in step S2, the mass ratio of sodium metasilicate to water is 1:3-1:6, the composite reaction time is 30-50 min, and the pH of the silica-humic acid composite solution is controlled at 9.5-11.0.

[0015] Preferably, in step S4, the total mass ratio of EDTA-zinc, EDTA-iron, boric acid, ammonium molybdate, and sodium selenite to water is 1:5 to 1:10, and the dissolution time is 15 to 30 minutes.

[0016] Preferably, in step S5, the mixing specifically involves: first adding calcium chelate solution to the silicon-humic acid composite solution, then adding micronutrient chelate solution, and finally adding base mother liquor; maintaining the temperature at 40-50°C during the mixing process, homogenizing the mixture for 10-20 minutes, and adjusting the pH using citric acid or phosphoric acid.

[0017] Preferably, the functional water-soluble fertilizer obtained in step S5 is concentrated and then spray-dried to obtain solid powder or granules; the concentration is carried out by vacuum decompression concentration, with the vacuum degree controlled at -0.080 to -0.095 MPa, and the solid content of the concentrated liquid reaches 45% to 60%; the inlet air temperature of the spray drying is controlled at 140 to 160°C, and the outlet air temperature is controlled at 60 to 80°C.

[0018] Preferably, during the mixing process in step S5, 0.5 to 2.5 parts by weight of anti-coagulation agent and 0.1 to 0.8 parts by weight of surface tension modifier are added; the anti-coagulation agent is selected from at least one of polyaspartic acid, γ-polyglutamic acid or sodium polyacrylate; the surface tension modifier is selected from at least one of alkyl glycoside, fatty alcohol polyoxyethylene ether or sodium secondary alkyl sulfonate.

[0019] The functional water-soluble fertilizer and its preparation method provided by this invention have the following advantages and effects compared with the prior art: (1) In this invention, calcium is prepared by chelating with citric acid and silicon by compounding with fulvic acid, and then compounded with the base mother liquor. The calcium chelate is added first and the base mother liquor is added last, which avoids the precipitation caused by direct contact between calcium ions and phosphate and silicate ions. This is conducive to the stability of the fertilizer solution system, reduces the risk of phase separation and flocculation, and facilitates storage and integrated water and fertilizer application.

[0020] (2) This invention uses calcium ions to compete with cadmium ions for root absorption channels, silicon to form a silicification barrier by depositing silicon in the cell wall of the root endodermis, sodium selenite to activate antioxidant enzymes and promote the binding of cadmium with phytochelates, and fulvic acid to chelate cadmium in the soil to reduce its bioavailability. It has multiple targets to synergistically inhibit the transport of cadmium to the aboveground parts and fruits, which is beneficial to reduce the content of heavy metals such as cadmium in fruits and ensure the safety of agricultural products for consumption.

[0021] (3) Betaine, as an osmotic regulator, can maintain cell osmotic potential and protect photosynthetic structures. Combined with the inhibition of sodium ion absorption by silicon, it is beneficial to improve the salt tolerance of crops in saline soil. The balanced supplementation of micronutrients such as calcium, magnesium, boron, zinc, and molybdenum is beneficial to improve the yield and quality of crops such as tomatoes. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0023] All materials described in the examples are available from publicly available commercial sources. Example

[0024] This embodiment provides a functional water-soluble fertilizer and its preparation method, including the following steps: S1: Weigh 8g of calcium nitrate and 0.8g of citric acid, add them to 24mL of water, stir and pre-complex at 55℃ for 30min, control the pH of the calcium chelate solution to 3.5, and obtain the calcium chelate solution; S2: Weigh 16g of mineral-derived potassium fulvicate with a fulvic acid content ≥50% and a weight-average molecular weight Mw ≤2000 Da, and 7g of sodium metasilicate (calculated as SiO2) with an effective silica content of approximately 40% and a modulus of 1.5. Add them to 28mL of water, stir and mix at 65℃ for 40min, and control the pH of the composite solution to 10.0 to obtain a silicon-fulvic acid composite solution. S3: Weigh 25g of urea, 15g of potassium dihydrogen phosphate, 30g of potassium nitrate, 2g of magnesium sulfate, and 4g of glycine betaine with a purity ≥98%, add them to 40mL of water, stir and dissolve at 50℃ to obtain the base mother liquor; S4: Weigh 1g of EDTA-zinc with a metal complexation rate ≥99%, 1g of EDTA-iron with a metal complexation rate ≥99%, 0.5g of boric acid, 0.15g of ammonium molybdate, and 0.05g of sodium selenite (calculated as Se), add them to 19mL of water, stir and dissolve at 55℃ for 20min to obtain micro-fertilizer chelation solution. S5: First, add calcium chelate solution to the silicon-humic acid composite solution, then add micro-fertilizer chelate solution, then add base mother liquor, and finally add 1.5g polyaspartic acid and 0.4g alkyl glycoside for mixing. During the mixing process, keep the temperature at 45℃, adjust the pH to 7.0 with phosphoric acid, homogenize for 15min, and obtain liquid functional water-soluble fertilizer. Example

[0025] This embodiment provides a functional water-soluble fertilizer and its preparation method, including the following steps: S1: Weigh 4g of calcium nitrate and 0.3g of citric acid, add them to 8mL of water, stir and pre-complex at 50℃ for 25min, control the pH of the calcium chelate solution to 3.0, and obtain the calcium chelate solution; S2: Weigh 10g of mineral-derived potassium fulvicate with a fulvic acid content ≥50% and a weight-average molecular weight Mw ≤2000 Da, and 4g of sodium metasilicate (calculated as SiO2) with an effective silica content of approximately 40% and a modulus of 1.5. Add them to 12mL of water, stir and mix at 60℃ for 35min, and control the pH of the composite solution to 9.5 to obtain a silicon-fulvic acid composite solution. S3: Weigh 18g of urea, 8g of potassium dihydrogen phosphate, 20g of potassium nitrate, 1g of magnesium sulfate, and 1.5g of glycine betaine with a purity ≥98%, add them to 35mL of water, stir and dissolve at 40℃ to obtain the base mother liquor; S4: Weigh 0.5g of EDTA-zinc with a metal complexation rate ≥99%, 0.5g of EDTA-iron with a metal complexation rate ≥99%, 0.3g of boric acid, 0.05g of ammonium molybdate, and 0.005g of sodium selenite (calculated as Se), add them to 7mL of water, stir and dissolve at 50℃ for 15min to obtain micro-fertilizer chelation solution; S5: First, add calcium chelate solution to the silicon-humic acid composite solution, then add micro-fertilizer chelate solution, then add base mother liquor, and finally add 0.5g sodium polyacrylate and 0.1g fatty alcohol polyoxyethylene ether for mixing. During the mixing process, keep the temperature at 40℃, adjust the pH to 6.5 with citric acid, and homogenize for 10 minutes to obtain liquid functional water-soluble fertilizer. Example

[0026] This embodiment provides a functional water-soluble fertilizer and its preparation method, including the following steps: S1: Weigh 12g of calcium nitrate and 1.0g of citric acid, add them to 48mL of water, stir and pre-complex at 60℃ for 40min, control the pH of the calcium chelate solution to 4.5, and obtain the calcium chelate solution; S2: Weigh 22g of mineral-derived potassium fulvicate with a fulvic acid content ≥50% and a weight-average molecular weight Mw ≤2000 Da, and 10g of sodium metasilicate (calculated as SiO2) with an effective silica content of about 40% and a modulus of 1.5. Add them to 60mL of water, stir and mix at 70℃ for 50min, and control the pH of the composite solution to 11.0 to obtain a silicon-fulvic acid composite solution. S3: Weigh 30g of urea, 18g of potassium dihydrogen phosphate, 35g of potassium nitrate, 3g of magnesium sulfate, and 6g of glycine betaine with a purity ≥98%. Add them to 45mL of water and stir at 60℃ to dissolve them, thus obtaining the base mother liquor. S4: Weigh 1.5g of EDTA-zinc with a metal complexation rate ≥99%, 1.5g of EDTA-iron with a metal complexation rate ≥99%, 0.8g of boric acid, 0.3g of ammonium molybdate, and 0.1g of sodium selenite (calculated as Se), add them to 42mL of water, stir and dissolve at 60℃ for 20min to obtain micro-fertilizer chelation solution; S5: First, add calcium chelate solution to the silicon-humic acid composite solution, then add micro-fertilizer chelate solution, then add base mother liquor, and finally add 2.5g γ-polyglutamic acid and 0.8g sodium secondary alkyl sulfonate for mixing. During the mixing process, keep the temperature at 40℃, adjust the pH to 8.0 with citric acid, homogenize for 30min, and obtain liquid functional water-soluble fertilizer. Example

[0027] Based on Example 1, step S6 is added: the liquid functional water-soluble fertilizer obtained in step S5 is concentrated by vacuum decompression, the vacuum degree is controlled at -0.090MPa, and after the solid content reaches 50%, it is spray dried, the inlet air temperature is controlled at 150℃ and the outlet air temperature is controlled at 70℃, thus obtaining the functional water-soluble fertilizer solid powder. Example

[0028] Based on Example 3, step S6 is added: the liquid functional water-soluble fertilizer obtained in step S5 is concentrated by vacuum decompression, the vacuum degree is controlled at -0.095MPa, and after the solid content reaches 60%, it is spray dried, the inlet air temperature is controlled at 160℃ and the outlet air temperature is controlled at 80℃, thus obtaining the functional water-soluble fertilizer solid powder.

[0029] Comparative Example 1 Based on Example 1, sodium metasilicate is not added in step S2, while the other raw materials and preparation steps remain unchanged, and water-soluble fertilizer is obtained.

[0030] Comparative Example 2 Based on Example 1, sodium selenite is not added in step S4, while the other raw materials and preparation steps remain unchanged, and a water-soluble fertilizer is obtained.

[0031] Comparative Example 3 Based on Example 1, glycine betaine was not added in step S3, while the other raw materials and preparation steps remained unchanged, and a water-soluble fertilizer was obtained.

[0032] Comparative Example 4 Based on Example 1, step S5 does not include polyaspartic acid and alkyl glycosides, while the remaining raw materials and preparation steps remain unchanged, to obtain a water-soluble fertilizer.

[0033] Experimental Example 1 Water-soluble fertilizer storage stability test This experimental example verifies the phase-separated composite preparation process of the present invention and the effects of anti-coagulation agents and surface tension regulators on the stability of the fertilizer solution system.

[0034] The liquid functional water-soluble fertilizers prepared in Examples 1-3 and the liquid water-soluble fertilizers prepared in Comparative Example 4 were used as test samples. Each sample was filled into a transparent sealed polyethylene plastic bottle and stored in a light-proof environment at 25±5℃ for 90 days. On the 30th, 60th and 90th days, the system was observed by the naked eye to see if precipitation, stratification or flocculation occurred, and the state was recorded.

[0035] The experimental results are shown in Table 1.

[0036] Table 1. Results of storage stability tests for various liquid water-soluble fertilizers Example 1 Clear and transparent, no change Clear and transparent, no change Clear and transparent, with no suspended particles. Example 2 Clear and transparent, no change Clear and transparent, no change Clear and transparent, with no suspended particles. Example 3 Clear and transparent, no change Clear and transparent, no change Clear and transparent, with no suspended particles. Comparative Example 4 A small amount of white flocculent material appeared at the bottom. Obvious flocculent stratification A large amount of hard white sediment was formed at the bottom. Conclusion: Examples 1-3 maintained excellent stability within 90 days. Comparative Example 4, lacking anti-coagulation agents such as polyaspartic acid, underwent phase change and precipitation in the later stage of storage. This indicates that the present invention can effectively ensure the stability of fertilizer solution, making it convenient for long-term storage and integrated water and fertilizer drip irrigation.

[0037] Experimental Example 2 Tomato fruit cadmium reduction and yield quality test This experiment verifies the synergistic effect of the multi-target action of silicon, selenium, humic acid, and calcium in the formulation of this invention on inhibiting the absorption of the heavy metal cadmium by crops. It also verifies the effect of micronutrient supplementation on improving yield and quality. The test crop was tomato, and the test soil was greenhouse garden soil with excessive cadmium content.

[0038] Five treatment groups were established: Example 1, Example 4, Comparative Example 1, Comparative Example 2, and a control group (applied with commercially available conventional water-soluble fertilizer with equal nitrogen, phosphorus, and potassium content). Each treatment group had three replicates arranged in a randomized block design. After transplanting and seedling establishment, topdressing was applied once each during the flowering and fruit setting stage, the young fruit stage, and the fruit enlargement stage. Each time, the fertilizer was diluted with water at a mass-to-volume ratio of 1:100 and then drip-irrigated. The solid powder of Example 4 was first completely dissolved in water. After the fruit matured and was harvested, the average yield per plant and the soluble solids content were measured. At the same time, the cadmium content of fresh fruit samples was determined by graphite furnace atomic absorption spectrometry.

[0039] The cadmium content reduction rate S = (C0 - C1) × 100% / C0, where C0 is the cadmium content of the fruit in the control group and C1 is the cadmium content of the fruit in each treatment group.

[0040] The experimental results are shown in Table 2.

[0041] Table 2 Results of cadmium reduction and yield / quality tests in tomatoes control group 0.125 / 2.15 4.8 Example 1 0.045 64.0 2.68 6.5 Example 4 0.046 63.2 2.65 6.4 Comparative Example 1 0.085 32.0 2.30 5.2 Comparative Example 2 0.078 37.6 2.45 5.8 Conclusion: The cadmium reduction rates of Examples 1 and 4 both exceeded the design target of 30%, far superior to the control group. Comparative Examples 1 and 2 showed significantly weaker cadmium reduction effects than Example 1, with decreased yield and solids content. This fully demonstrates the significant synergistic effect of this invention in heavy metal control.

[0042] Experimental Example 3 Crop growth and salt tolerance tests under salt stress This experimental example verifies the effect of betaine combined with silicon and other components in this invention on enhancing the stress resistance of crops in secondary salinization soils. The test soil was greenhouse vegetable garden soil with sodium chloride added at a certain mass ratio to achieve the soil conductivity level required for secondary salinization stress.

[0043] Four treatment groups were established: Example 1, Comparative Example 1, Comparative Example 3, and a control group (applied with the same amount of commercially available water-soluble fertilizer containing macroelements). Each treatment group had three replicates. Diluted drip irrigation fertilizer was applied during the flowering and fruit-setting stage of tomatoes. Plant height and above-ground fresh weight were measured during the peak growth period and at harvest. Potassium and sodium ion content were measured on functional leaves from the same location, and the potassium-to-sodium ratio (K2) was calculated. + / Na + ).

[0044] The experimental results are shown in Table 3.

[0045] Table 3. Results of Tomato Growth and Physiological Indicators under Salt Stress control group 65.4 420.5 1.15 Example 1 88.6 685.2 3.42 Comparative Example 1 76.5 550.8 2.05 Comparative Example 3 72.3 510.4 2.38 Conclusion: Under salt stress, the growth of the control group was significantly inhibited; the plant height, fresh weight, and leaf potassium-sodium ratio of Example 1 remained at healthy levels; the biomass of Comparative Example 3 decreased significantly due to cell dehydration caused by the loss of osmotic protection; and the leaf potassium-sodium ratio of Comparative Example 1 was significantly lower than that of Example 1 because it could not effectively limit the transport of sodium ions to the aboveground parts. The experiment demonstrates that the combination of silicon and betaine can effectively maintain ion balance and cell osmotic pressure, significantly improving the salt tolerance and stress resistance of crops.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A functional water-soluble fertilizer, characterized in that, The components, by weight, include: 18-30 parts urea, 8-18 parts potassium dihydrogen phosphate, 20-35 parts potassium nitrate, 4-12 parts calcium nitrate, 4-10 parts water-soluble silicon, 10-22 parts potassium humate, 1.5-6 parts betaine, 0.005-0.1 parts sodium selenite, 1-3 parts magnesium sulfate, 0.5-1.5 parts EDTA-zinc, 0.5-1.5 parts EDTA-iron, 0.3-0.8 parts boric acid, 0.05-0.3 parts ammonium molybdate, and 0.3-1.0 parts citric acid.

2. The functional water-soluble fertilizer according to claim 1, characterized in that, The water-soluble silicon is at least one of sodium metasilicate, potassium metasilicate, and potassium silicate; the potassium humate is mineral-derived potassium humate; and the betaine is glycine betaine.

3. The functional water-soluble fertilizer according to claim 1, characterized in that, The functional water-soluble fertilizer also includes 0.5 to 2.5 parts of anti-coagulant and 0.1 to 0.8 parts of surface tension modifier.

4. The functional water-soluble fertilizer according to claim 3, characterized in that, The anticoagulant is selected from at least one of polyaspartic acid, γ-polyglutamic acid, or sodium polyacrylate; the surface tension modifier is selected from at least one of alkyl glycoside, fatty alcohol polyoxyethylene ether, or sodium secondary alkyl sulfonate.

5. The functional water-soluble fertilizer according to claim 4, characterized in that, The functional water-soluble fertilizer components, by weight, include: 25 parts urea, 15 parts potassium dihydrogen phosphate, 30 parts potassium nitrate, 8 parts calcium nitrate, 7 parts water-soluble silicon, 16 parts potassium humate, 4 parts betaine, 0.05 parts sodium selenite, 2 parts magnesium sulfate, 1 part EDTA-zinc, 1 part EDTA-iron, 0.5 parts boric acid, 0.15 parts ammonium molybdate, 0.8 parts citric acid, 1.5 parts polyaspartic acid, and 0.4 parts alkyl glycoside.

6. The method for preparing functional water-soluble fertilizer according to claim 1, characterized in that, The specific steps are as follows: S1: Calcium nitrate and citric acid are pre-complexed in water at 50-60℃ to form a calcium chelate solution; S2: Potassium humate and water-soluble silicon are combined in water at 60-70℃ to form a silicon-humic acid composite solution; S3: Dissolve urea, potassium dihydrogen phosphate, potassium nitrate, magnesium sulfate and betaine in water at 40-60℃ to form a base mother liquor; S4: Dissolve EDTA-zinc, EDTA-iron, boric acid, ammonium molybdate and sodium selenite in water at 50-60℃ to form a micro-fertilizer chelate solution; S5: Mix calcium chelate solution, silicon-humic acid composite solution, micro-fertilizer chelate solution and base mother liquor, adjust pH to 6.5-8.0, homogenize, and obtain functional water-soluble fertilizer; Wherein, the water-soluble silicon is at least one of sodium metasilicate, potassium metasilicate, and potassium silicate; the potassium humate is mineral-derived potassium humate; and the betaine is glycine betaine.

7. The method for preparing functional water-soluble fertilizer according to claim 6, characterized in that, In step S1, the pre-complexation reaction time is 20-40 min, and the pH of the calcium chelation solution is controlled to be 3.0-4.5; In step S2, the mass ratio of sodium metasilicate to water is 1:3 to 1:6, the composite reaction time is 30 to 50 min, and the pH of the silica-humic acid composite solution is controlled at 9.5 to 11.

0. The total amount of EDTA-zinc, EDTA-iron, boric acid, ammonium molybdate, and sodium selenite is in a mass ratio of 1:5 to 1:10 with water, and the dissolution time is 15 to 30 minutes.

8. The method for preparing functional water-soluble fertilizer according to claim 6, characterized in that, In step S5, the mixing process specifically involves: first adding calcium chelate solution to the silicon-humic acid composite solution, then adding micronutrient chelate solution, and finally adding base mother liquor; maintaining the temperature at 40-50℃ during the mixing process, homogenizing for 10-20 minutes, and adjusting the pH using citric acid or phosphoric acid.

9. The method for preparing functional water-soluble fertilizer according to claim 6, characterized in that, It also includes step S6: The functional water-soluble fertilizer obtained in step S5 is concentrated and then spray-dried to obtain solid powder or granules; the concentration is carried out by vacuum decompression concentration, with the vacuum degree controlled at -0.080 to -0.095 MPa, and the solid content of the concentrated liquid reaches 45% to 60%; The inlet air temperature of the spray dryer is controlled at 140-160℃, and the outlet air temperature is controlled at 60-80℃.

10. The method for preparing functional water-soluble fertilizer according to claim 6, characterized in that, In the mixing process described in step S5, 0.5 to 2.5 parts by weight of anti-coagulation agent and 0.1 to 0.8 parts by weight of surface tension modifier are added. The anticoagulant is selected from at least one of polyaspartic acid, γ-polyglutamic acid, or sodium polyacrylate. The surface tension modifier is selected from at least one of alkyl glycosides, fatty alcohol polyoxyethylene ethers, or sodium secondary alkyl sulfonate.