Preparation method of humic acid-containing water-soluble organic fertilizer with chelated medium trace elements for synergism

Abstract

The invention relates to the field of organic fertilizer manufacturing, in particular to a preparation method of a humic acid-containing water-soluble organic fertilizer with chelated medium trace elements for synergism, and the preparation method comprises the following steps: S1, adding modified humic acid into deionized water, heating to 40-50 DEG C, stirring for 25-35 minutes, adding hydrated ferrous sulfate, introducing compressed air, and stirring for reaction for 30-50 minutes to obtain a chelating solution and the like; according to the invention, the environmental adaptability of humic acid is improved through molecular structure modification, a composite chelation system is constructed to enhance element stability, a multistage chelation sequence is optimized to prevent ion antagonism, and a physical barrier is innovated to realize a core process path of intelligent controlled release. The functional limitation of a traditional fertilizer in a complex agricultural ecological system is effectively broken through, the nutrient utilization efficiency and agricultural sustainability are remarkably improved, and the fertilizer has wide application prospects in soil remediation, precision agriculture and resource-saving planting systems.

Description

Technical Field

[0001] The invention relates to the field of organic fertilizer manufacturing, in particular to a method for preparing a water-soluble organic fertilizer containing humic acid and capable of enhancing the synergy of trace elements in chelation. Background Art

[0002] Water-soluble organic fertilizer refers to a type of organic fertilizer that comes from plants, animals or microorganisms and is processed by physical, chemical, biological and other processes to make its main nutrients completely soluble in water to form a stable solution. By combining the advantages of organic fertilizers with modern high-efficiency fertilization technology, the precise, efficient and convenient application of organic nutrients can be achieved. It is mainly used in drip irrigation, sprinkler irrigation, micro-sprinkler irrigation and soilless cultivation in organic agriculture.

[0003] In existing technologies, when humic acid-containing water-soluble fertilizers are applied in saline-alkali soils or hard-water irrigation areas, conventional humic acid easily flocculates and precipitates in environments with a pH greater than 7.5, significantly reducing the bioavailability of trace elements. Furthermore, key elements such as iron and zinc compete for binding sites in the composite chelation system, creating strong antagonism and leading to nutrient imbalance in crops. Furthermore, traditional formulas lack a sustained-release design, leading to leaching within 48 hours under irrigation conditions, resulting in loss of active ingredients, especially in sandy soils. While existing technologies attempt to improve performance using synthetic chelating agents or physical coatings, they face a new problem: chelating agents lose their ability to bind to calcium and magnesium ions in hard water, resulting in decreased stability and difficulty in biodegradation.

[0004] Therefore, according to the above-mentioned related technologies, it is urgent to develop a preparation method for chelating trace elements in humic acid-containing water-soluble organic fertilizer. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose a method for preparing a water-soluble organic fertilizer containing humic acid with chelated trace elements to solve the problems of poor environmental adaptability, severe element antagonism and severe element antagonism in the prior art.

[0006] Based on the above objectives, the present invention provides a method for preparing a water-soluble organic fertilizer containing humic acid and enhancing the synergy of trace elements by chelation.

[0007] The preparation method of the water-soluble organic fertilizer containing humic acid and chelated trace elements is characterized in that the preparation steps are as follows: Step S1: adding modified humic acid to deionized water, heating to 40-50°C, stirring for 25-35 minutes, adding hydrated ferrous sulfate, introducing compressed air, stirring and reacting for 30-50 minutes to obtain a chelating solution; Step S2: adding the modified chelating agent and citric acid to the chelating solution, heating to 40-50° C., stirring for 8-12 minutes, adding hydrated zinc sulfate, hydrated manganese sulfate and boric acid, stirring for 15-20 minutes, adding 10% ammonia solution, adjusting the pH to 5-6, stirring and reacting for 50-70 minutes at a speed of 250-350 rpm to obtain a composite chelating solution; Step S3: adding urea to the composite chelating solution, heating to 30-40° C., stirring for 10-20 minutes, adding potassium dihydrogen phosphate and potassium sulfate, stirring for 18-22 minutes at a speed of 250-350 rpm, and continuing stirring for 10-20 minutes to obtain a nutrient chelating mother solution; Step S4: adding the nutrient chelated mother liquor to a concentration tank, reducing the pressure to -0.08 MPa, raising the temperature to 40-50° C., compressing for 50-70 min, adding nano-silicon dioxide and modified starch, stirring for 8-12 min, adding to a high-pressure homogenizer, processing for 5-7 min, at a pressure of 23-27 MPa, filtering, drying, cooling, and passing through an 80-mesh vibrating sieve to obtain a water-soluble organic fertilizer; Because Fe 3+ It is very easy to hydrolyze into colloidal precipitation at pH>4, while in the acidic environment of pH2.5-3.5, the carboxyl and phenolic hydroxyl groups of humic acid can preferentially react with Fe 3+ The formation of a stable five-membered ring chelate prevents its transformation into precipitation. At the same time, as the pH increases, Zn 2+ / Mn 2+ Combined with the o-hydroxyphenylacetic acid group of the modified chelating agent to achieve distributed chelation and element synergistic anti-antagonism Preferably, the mass ratio of the modified humic acid to hydrated ferrous sulfate in step S1 is 2.7-2.8:1; The mass ratio of the modified chelating agent, citric acid, chelating liquid, hydrated zinc sulfate, hydrated manganese sulfate and boric acid in step S2 is 0.016-0.018:0.008-0.009:1:0.008-0.009:0.0045-0.0055:0.003-0.004.

[0008] Preferably, the mass ratio of urea, composite chelating liquid, potassium dihydrogen phosphate and potassium sulfate in step S3 is 0.05-0.052:1:0.032-0.034:0.024-0.026.

[0009] Preferably, in step S4, the mass ratio of the nutrient chelating mother solution, nano-silicon dioxide and modified starch is 1:0.008-0.012:0.028-0.032.

[0010] Preferably, the preparation steps of the modified humic acid are as follows: Step A1: Add weathered coal powder to a 1.5% potassium hydroxide solution, heat to 60-80°C, stir for 80-100 minutes, and centrifuge for 10-20 minutes at a speed of 3000-5000 rpm to obtain an activated humic acid solution; Step A2: Under a nitrogen atmosphere, add sulfamic acid and 37% formaldehyde solution to the activated humic acid solution, add 10% sodium hydroxide solution, adjust the pH to 9.0-10.0, raise the temperature to 80-90°C, stir and react for 100-140 minutes. After the reaction is complete, cool to 40-60°C, add 10% hydrochloric acid solution, adjust the pH to 2.0-3.0, let it stand and precipitate, centrifuge and wash, and dry to obtain modified humic acid; Sulfonic acid groups are introduced into humic acid molecules through the condensation reaction of aminosulfonic acid and formaldehyde. Sulfonic acid groups are strong acid groups and can be completely ionized into -SO3 in the pH range of 0-14. - , forming a permanent hydrophilic layer, thereby increasing the negative charge density on the molecular surface, and the electrostatic repulsion prevents aggregation and precipitation. At the same time, the sulfonic acid group and the original carboxyl group form a bidentate chelate structure, which can increase the chelate sites.

[0011] Preferably, the mass ratio of the weathered coal powder to the 1.5% potassium hydroxide solution in step A1 is 1:7.8-8.2; The mass ratio of aminosulfonic acid, 37% formaldehyde solution and activated humic acid solution in step A2 is 0.026-0.028:0.0065-0.007:1.

[0012] Preferably, the modified chelating agent is prepared as follows: Add ethylenediamine di-o-hydroxyphenylacetic acid and sodium polyaspartate to deionized water, heat to 43-47°C, stir for 30-40 minutes, add catalyst carbodiimide hydrochloride, add 0.1 mol / L hydrochloric acid solution, adjust the pH to 5.8-6.2, heat to 48-52°C, stir and react for 2-4 hours at a speed of 200-300 rpm. After the reaction is complete, cool to 20-30°C, purify, freeze-dry, crush and sieve to obtain a modified chelating agent; The molecular chain of sodium polyaspartate contains dense carboxyl groups, which can react with Ca in hard water. 2+ / Mg 2+ Form a soluble complex, consume interfering ions, reduce the interference of other ions on EDTA, and at the same time, EDTA iron encounters Ca 2+ When sodium polyaspartate-Ca 2+ The complex preemptively binds free Ca via entropy-driven displacement 2+ , blocking its competition for the coordination site of ethylenediamine di-o-hydroxyphenylacetic acid, while the ortho-phenolic hydroxyl-O - With carboxyl-COO -Forming a rigid octahedral coordination cavity, with Fe 3+ The charge / radius ratio of Fe is perfectly matched, thus reducing 3+ In addition, the long chain of polyaspartic acid is grafted on the outside of the benzene ring of ethylenediamine di-o-hydroxyphenylacetic acid, and its hydrophobic carbon chain physically blocks Ca 2+ Close to the active center of ethylenediamine di-o-hydroxyphenylacetic acid iron.

[0013] Preferably, the mass ratio of ethylenediamine di-o-hydroxyphenylacetic acid, sodium polyaspartate and catalyst is 1:1.4-1.6:0.18-0.22.

[0014] Preferably, the preparation steps of the modified starch are as follows: Add cassava starch to deionized water, heat to 20-30°C, stir for 10-20 minutes, add 3% sodium hydroxide solution, adjust the pH to 8-9, heat to 33-37°C, add octenylsuccinic anhydride, react for 160-200 minutes, add 10% hydrochloric acid solution, adjust the pH to 6.3-6.7, cool and stand, centrifuge and wash, dry and crush to obtain modified starch; Through the directional arrangement of the octenyl long chains, the octenyl hydrophobic chains can be anchored on the starch molecular skeleton to form a dense hydrophobic layer, thereby reducing the water molecule penetration rate and delaying the dissolution of internal nutrients. At the same time, after the modified starch comes into contact with water, the hydrophilic area absorbs water and swells moderately, but the hydrophobic chain network limits unlimited swelling to avoid rupture of the capsule wall. The nanoscale capillaries formed by swelling bind nutrients through surface tension, allowing them to be released slowly. In addition, the carboxyl group ionizes in alkaline soil, and the electrostatic repulsion expands the capillary pore size, accelerating the release; the pore size shrinks under acidic conditions, achieving intelligent response.

[0015] Preferably, the mass ratio of the cassava starch to octenylsuccinic anhydride is 1:0.07-0.09.

[0016] Beneficial effects of the present invention: The present invention provides a method for preparing a water-soluble organic fertilizer containing humic acid with enhanced trace element chelation. The present invention adopts a core process path to improve the environmental adaptability of humic acid through molecular structure modification, enhance element stability through construction of a composite chelation system, optimize the multi-stage chelation sequence to prevent ion antagonism, and realize intelligent controlled release through innovative physical barriers. Compared with the existing technology, the present invention effectively breaks through the functional limitations of traditional fertilizers in complex agricultural ecosystems, significantly improves nutrient utilization efficiency and agronomic sustainability, and has broad application prospects in soil remediation, precision agriculture and resource-saving planting systems. DETAILED DESCRIPTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0018] Example 1: The preparation steps of modified humic acid are as follows: S1: Add 100 g of weathered coal powder to 780 g of 1.5% potassium hydroxide solution, heat to 60°C, stir for 100 min, and centrifuge for 10 min at 5000 rpm to obtain activated humic acid solution; S2: Under a nitrogen atmosphere, add 2.6g of aminosulfonic acid and 0.65g of 37% formaldehyde solution to 100g of activated humic acid solution, add 10% sodium hydroxide solution, adjust the pH to 9.0-10.0, raise the temperature to 80℃, stir and react for 140min. After the reaction is complete, cool to 40℃, add 10% hydrochloric acid solution, adjust the pH to 2.0-3.0, let it stand and precipitate, centrifuge and wash, and dry to obtain modified humic acid.

[0019] Example 2: The preparation steps of modified humic acid are as follows: S1: Add 100 g of weathered coal powder to 800 g of 1.5% potassium hydroxide solution, heat to 70°C, stir for 90 min, and centrifuge for 15 min at 4000 rpm to obtain activated humic acid solution; S2: Under a nitrogen atmosphere, add 2.7g of aminosulfonic acid and 0.68g of 37% formaldehyde solution to 100g of activated humic acid solution, add 10% sodium hydroxide solution, adjust the pH to 9.0-10.0, raise the temperature to 85℃, stir and react for 120min. After the reaction is complete, cool to 50℃, add 10% hydrochloric acid solution, adjust the pH to 2.0-3.0, let it stand and precipitate, centrifuge and wash, and dry to obtain modified humic acid.

[0020] Example 3: The preparation steps of modified humic acid are as follows: S1: Add 100 g of weathered coal powder to 820 g of 1.5% potassium hydroxide solution, heat to 80°C, stir for 80 min, and centrifuge for 20 min at 3000 rpm to obtain activated humic acid solution; S2: Under nitrogen atmosphere, add 2.8g of aminosulfonic acid and 0.7g of 37% formaldehyde solution to 100g of activated humic acid solution, add 10% sodium hydroxide solution, adjust the pH to 9.0-10.0, raise the temperature to 90℃, stir and react for 100min. After the reaction is complete, cool to 60℃, add 10% hydrochloric acid solution, adjust the pH to 2.0-3.0, let it stand and precipitate, centrifuge and wash, and dry to obtain modified humic acid.

[0021] Example 4: The steps for preparing the modified chelating agent are as follows: 100 g of ethylenediamine di-o-hydroxyphenylacetic acid and 140 g of sodium polyaspartate were added to 500 mL of deionized water, heated to 43° C., stirred for 40 min, 18 g of catalyst carbodiimide hydrochloride was added, 0.1 mol / L hydrochloric acid solution was added, the pH was adjusted to 5.8-6.2, heated to 48° C., stirred for 4 h at a speed of 200 rpm, and after the reaction was complete, the mixture was cooled to 20° C., purified, freeze-dried, crushed and sieved to obtain a modified chelating agent.

[0022] Example 5: The steps for preparing the modified chelating agent are as follows: 100 g of ethylenediamine di-o-hydroxyphenylacetic acid and 150 g of sodium polyaspartate were added to 500 mL of deionized water, heated to 45° C., stirred for 35 min, 20 g of catalyst carbodiimide hydrochloride was added, 0.1 mol / L hydrochloric acid solution was added, the pH was adjusted to 5.8-6.2, heated to 50° C., stirred for 3 h at a speed of 250 rpm, and after the reaction was complete, cooled to 25° C., purified, freeze-dried, crushed and sieved to obtain a modified chelating agent.

[0023] Example 6: The steps for preparing the modified chelating agent are as follows: 100 g of ethylenediamine di-o-hydroxyphenylacetic acid and 160 g of sodium polyaspartate were added to 500 mL of deionized water, heated to 47° C., stirred for 30 min, 22 g of catalyst carbodiimide hydrochloride was added, 0.1 mol / L hydrochloric acid solution was added, the pH was adjusted to 5.8-6.2, heated to 52° C., stirred for 2 h at a speed of 300 rpm, and after the reaction was complete, cooled to 20° C., purified, freeze-dried, crushed and sieved to obtain a modified chelating agent.

[0024] Example 7: The preparation steps of the modified starch are as follows: Add 100 g of cassava starch to 200 mL of deionized water, heat to 20°C, stir for 20 min, add 3% sodium hydroxide solution, adjust the pH to 8-9, heat to 33°C, add 7 g of octenylsuccinic anhydride, react for 200 min, and after the reaction is complete, add 10% hydrochloric acid solution, adjust the pH to 6.3-6.7, cool and let stand, centrifuge and wash, dry and crush to obtain modified starch.

[0025] Example 8: The preparation steps of the modified starch are as follows: Add 100 g of cassava starch to 200 mL of deionized water, heat to 25 ° C, stir for 15 minutes, add 3% sodium hydroxide solution, adjust the pH to 8-9, heat to 35 ° C, add 8 g of octenylsuccinic anhydride, react for 180 minutes, and after the reaction is complete, add 10% hydrochloric acid solution, adjust the pH to 6.3-6.7, cool and let stand, centrifuge and wash, dry and crush to obtain modified starch.

[0026] Example 9: The preparation steps of the modified starch are as follows: Add 100 g of cassava starch to 200 mL of deionized water, heat to 30°C, stir for 10 min, add 3% sodium hydroxide solution, adjust the pH to 8-9, heat to 37°C, add 9 g of octenylsuccinic anhydride, react for 160 min, and after the reaction is complete, add 10% hydrochloric acid solution, adjust the pH to 6.3-6.7, cool and let stand, centrifuge and wash, dry and crush to obtain modified starch.

[0027] Example 10: Preparation method of water-soluble organic fertilizer containing humic acid with enhanced chelation of trace elements: S1: Add 270 g of modified humic acid to 500 mL of deionized water, heat to 40°C, stir for 35 min, add 100 g of hydrated ferrous sulfate, introduce compressed air, and stir for 30 min to obtain a chelating solution; S2: 1.6 g of modified chelating agent and 0.8 g of citric acid were added to 100 g of chelating liquid, the temperature was raised to 40°C, and the mixture was stirred for 12 min. 0.8 g of hydrated zinc sulfate, 0.45 g of hydrated manganese sulfate, and 0.3 g of boric acid were added, and the mixture was stirred for 15 min. 10% ammonia solution was added, the pH was adjusted to 5-6, and the mixture was stirred for 70 min at a speed of 250 rpm to obtain a composite chelating liquid. S3: Add 5 g of urea to 100 g of the composite chelating solution, raise the temperature to 30° C., stir for 20 min, add 3.2 g of potassium dihydrogen phosphate and 2.4 g of potassium sulfate, stir for 18 min at 350 rpm, and continue stirring for 10 min to obtain a nutrient chelating mother solution; S4: Add 100g of nutrient chelated mother liquor into a concentration tank, reduce the pressure to -0.08MPa, raise the temperature to 40°C, compress for 70min, add 0.8g of nano-silicon dioxide and 2.8g of modified starch, stir for 8min, add into a high-pressure homogenizer, process for 7min, pressure 23Mpa, filter, dry, cool, and pass through an 80-mesh vibrating sieve to obtain a water-soluble organic fertilizer.

[0028] Example 11: Preparation method of water-soluble organic fertilizer containing humic acid with enhanced chelation of trace elements: S1: Add 275 g of modified humic acid to 500 mL of deionized water, heat to 45°C, stir for 30 min, add 100 g of hydrated ferrous sulfate, introduce compressed air, and stir for 40 min to obtain a chelating solution; S2: Add 1.7 g of modified chelating agent and 0.85 g of citric acid to 100 g of chelating liquid, heat to 45 ° C, stir for 10 min, add 0.85 g of hydrated zinc sulfate, 0.5 g of hydrated manganese sulfate and 0.35 g of boric acid, stir for 18 min, add 10% ammonia solution, adjust the pH to 5-6, and stir for 60 min at 300 rpm to obtain a composite chelating liquid; S3: Add 5.1 g of urea to 100 g of the composite chelating solution, raise the temperature to 35°C, stir for 15 minutes, add 3.3 g of potassium dihydrogen phosphate and 2.5 g of potassium sulfate, stir for 20 minutes at 300 rpm, and continue stirring for 15 minutes to obtain a nutrient chelating mother solution; S4: Add 100g of nutrient chelated mother liquor into a concentration tank, reduce the pressure to -0.08MPa, raise the temperature to 45°C, compress for 60min, add 0.1g of nano-silicon dioxide and 3g of modified starch, stir for 10min, add into a high-pressure homogenizer, process for 6min, pressure 25Mpa, filter, dry, cool, and pass through an 80-mesh vibrating sieve to obtain a water-soluble organic fertilizer.

[0029] Example 12: Preparation method of water-soluble organic fertilizer containing humic acid with enhanced chelation of trace elements: S1: Add 280 g of modified humic acid to 500 mL of deionized water, heat to 50°C, stir for 25 min, add 100 g of hydrated ferrous sulfate, introduce compressed air, and stir for 50 min to obtain a chelating solution; S2: Add 1.8 g of modified chelating agent and 0.9 g of citric acid to 100 g of chelating liquid, heat to 50 ° C, stir for 8 min, add 0.9 g of hydrated zinc sulfate, 0.55 g of hydrated manganese sulfate and 0.4 g of boric acid, stir for 20 min, add 10% ammonia solution, adjust the pH to 5-6, stir and react for 50 min at 350 rpm to obtain a composite chelating liquid; S3: Add 5.2 g of urea to 100 g of the composite chelating solution, heat to 40° C., stir for 10 min, add 3.4 g of potassium dihydrogen phosphate and 2.6 g of potassium sulfate, stir for 22 min at 250 rpm, and continue stirring for 20 min to obtain a nutrient chelating mother solution; S4: Add 100g of nutrient chelated mother liquor into a concentration tank, reduce the pressure to -0.08MPa, raise the temperature to 50°C, compress for 50min, add 1.2g of nano-silicon dioxide and 3.2g of modified starch, stir for 12min, add into a high-pressure homogenizer, process for 5min, pressure 27Mpa, filter, dry, cool, and pass through an 80-mesh vibrating sieve to obtain a water-soluble organic fertilizer.

[0030] Comparative Example 1: Compared with Example 10, in this comparative example, all raw materials are directly added during the preparation process of the water-soluble organic fertilizer, and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally the water-soluble organic fertilizer is obtained.

[0031] Comparative Example 2: Compared with Example 10, this comparative example only replaces "modified humic acid" with "humic acid", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a water-soluble organic fertilizer is obtained.

[0032] Comparative Example 3: Compared with Example 10, this comparative example did not add nano silicon dioxide and modified starch during the preparation process of the water-soluble organic fertilizer. The remaining steps and parameters were the same, and this comparative example will not be repeated again to finally obtain the water-soluble organic fertilizer.

[0033] Comparative Example 4: Compared with Example 10, this comparative example only replaces the "modified chelating agent" with the "ethylenediaminetetraacetic acid chelating agent", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally obtains a water-soluble organic fertilizer.

[0034] Performance testing: Humic acid alkalinity stability test: Refer to the GB / T35107-2017 "Water-soluble Humic Acid Fertilizer" test standard and use Shimadzu UV-2600 spectrophotometer; 1. Test group: 1.0 g of each of the water-soluble organic fertilizers of Examples 10-12 and Comparative Examples 1-4 was added to 100 mL of a boric acid buffer solution with a pH of 8.5, heated to 25°C, shaken for 24 hours, centrifuged, and the supernatant was filtered. The absorbance was measured at 465 nm and recorded as A. t ; 2. Control group: 1.0 g of each of the water-soluble organic fertilizers of Examples 10-12 and Comparative Examples 1-4 were taken, added to 100 mL of deionized water, centrifuged and filtered, and the absorbance was measured at 465 nm, which was recorded as A0; 3. Calculation of Survival Rate: ; A t : Absorbance after 24 hours, A o : Initial absorbance.

[0035] Table 1 project <![CDATA[A t ]]> <![CDATA[A0]]> Humic acid residual rate (%) Example 10 0.486 0.495 98.2 Example 11 0.483 0.494 97.8 Example 12 0.488 0.496 98.4 Comparative Example 1 0.205 0.496 41.3 Comparative Example 2 0.226 0.495 45.7 Comparative Example 3 0.479 0.495 96.8 Comparative Example 4 0.472 0.494 95.5 Hard Water Chelation Stability Test: Refer to the HG / T5331-2018 "Trace Element Water-soluble Fertilizer" test standard and use inductively coupled plasma emission spectrometer; 1. Preparation of hard water: Add 0.368g of anhydrous calcium chloride and 0.228g of hydrated magnesium chloride into 1000mL of deionized water, stir and dissolve to obtain hard water; 2. Take 0.5 g of each of the water-soluble organic fertilizers of Examples 10-12 and Comparative Examples 1-4, add 100 mL of hard water, shake gently to disperse, heat to 40 ° C, oscillate at a frequency of 150 rpm, react for 120 min, filter, separate, and obtain a filtrate; 3. Take 10 ml of the filtrate and dilute it to 50 ml with deionized water. Determine the concentrations of free iron and zinc. 4. Calculate the degree of chelation: .

[0036] Table 2 project Chelation rate (iron) (%) Chelation rate (zinc) (%) Example 10 96.5 95.8 Example 11 95.7 96.1 Example 12 96.2 95.3 Comparative Example 1 52.3 58.6 Comparative Example 2 94.1 93.7 Comparative Example 3 95.0 94.5 Comparative Example 4 63.8 67.2 Sustained release performance test: Refer to the NY / T 1977-2010 "Slow-release Fertilizer" test standard and use a dialysis bag with a molecular weight cut-off of 8000Da; 1. Take 1.0 g of each of the water-soluble organic fertilizers of Examples 10-12 and Comparative Examples 1-4, put them into a dialysis bag, add 200 mL of deionized water, raise the temperature to 25 ° C, oscillate at a frequency of 100 rpm, and oscillate for 72 hours to obtain an external solution; 2. Take 10 mL of external solution, measure the nutrient dissolution amount, and calculate the cumulative release rate R t (%): , , M t : Cumulative dissolution amount at time point t, M 总 : The theoretical total content of the nutrient in the sample loaded in the dialysis bag, m: sample mass, W: mass fraction of the nutrient in the sample Table 3 project <![CDATA[M 72h (mg)]]> <![CDATA[M 总 (mg)]]> <![CDATA[R t (%)]]> Example 10 49.3 100.0 49.3 Example 11 51.2 100.0 51.2 Example 12 48.7 100.0 48.7 Comparative Example 1 89.1 100.0 89.1 Comparative Example 2 52.8 100.0 52.8 Comparative Example 3 92.6 100.0 92.6 Comparative Example 4 87.9 100.0 87.9 Crop absorption efficiency test: Refer to ISO18644:2016 "Evaluation of the Bioavailability of Trace Elements in Fertilizers" test standard, using the Thermo Fisher iCE3500 atomic absorption spectrometer; 1. Soil pretreatment: Take calcareous soil, heat it to 105℃, dry it for 48 hours to sterilize it, and after cooling, fill it into pots at 5kg per pot and compact it to a bulk density of 1.3g / cm 3 ; 2. Test group: Take the water-soluble organic fertilizers of Examples 10-12 and Comparative Examples 1-4 respectively, apply 1.2g fertilizer per pot, and cover with 1cm of soil after base application; Control group: Take the same amount of conventional fertilizer with the same nutrients, which is urea, potassium dihydrogen phosphate, potassium sulfate and EDTA-Fe / Zn. Apply 1.2g fertilizer per pot and cover with 1cm of soil after base application. Blank group: no fertilizer.

[0037] 3. Sow 5 corn kernels per pot and keep 3 healthy seedlings after emergence. Culture conditions: 25±1℃, 16h light, 60%±5% humidity, maintain soil moisture content at 60% WHC, and culture for 30 days. 4. Take the third fully expanded leaf, rinse with deionized water, heat to 105°C, fix for 30 minutes, cool to 70°C, dry, crush and sieve, weigh 0.2g, add 5mL concentrated nitric acid, microwave digest, dilute to 25mL, filter and test; 5. Data calculation: nutrient content: , absorption gain rate:

[0038] Table 4 project <![CDATA[C Fe (mg / kg)]]> <![CDATA[Gain Fe (%)]]> <![CDATA[C zn (mg / kg)]]> <![CDATA[Gain zn (%)]]> Example 10 142.6 82.4 58.3 90.2 Example 11 144.9 85.1 51.8 88.7 Example 12 140.9 80.6 59.1 91.5 Comparative Example 1 78.5 15.3 59.1 19.8 Comparative Example 2 86.7 28.7 32.1 86.4 Comparative Example 3 138.2 76.5 57.5 87.9 Comparative Example 4 92.4 35.6 41.7 483 Data Analysis: As can be seen from Tables 1-4, the chelated trace element synergistic water-soluble organic fertilizer containing humic acid prepared by the present invention has better nutrient slow-release properties, anti-ion antagonism ability and crop absorption efficiency; In Comparative Example 1, due to the direct mixing of all raw materials, the iron and zinc ions were strongly antagonistic in the alkaline environment. The reason was that Fe 3+ At pH>4, it preferentially hydrolyzes to form colloidal precipitation, blocking the chelating sites of humic acid; at the same time, Zn 2+ with Fe 3+ The competition for chelating ligands results in a decrease in the bioavailability of both, and the step-by-step chelation process controls the pH gradient to allow the carboxyl groups of humic acid to bind to Fe in a directional manner. 3+ Form a five-membered ring chelate to prevent precipitation and transformation from the source; In Comparative Example 2, since modified humic acid was replaced with humic acid, it flocculated and precipitated in soil at pH 8.2. This was because the carboxyl group of conventional humic acid suddenly lost its ionization in an alkaline environment. The intermolecular hydrogen bonding and π-π stacking increased the particle size to the micron level, encapsulating the trace elements and co-precipitating them. At the same time, the modified humic acid maintained a strong ionization state in the pH range of 0-14 through sulfonic acid grafting. The electrostatic repulsion reduced the Zeta potential from -15mV to -38mV, effectively inhibiting aggregation. In Comparative Example 3, since no nano-SiO2 and modified starch were added, its 72h leaching rate reached 92%. The reason is that the fertilizer particles lack a physical barrier, allowing water to directly penetrate and dissolve nutrients. At the same time, the long octenyl chains of the modified starch form a dense hydrophobic layer, which binds nutrient molecules through the pressure generated by the nanocapillaries. In addition, the nano-SiO2 fills the pores and reduces the swelling rate, synergistically extending the release period to 240h. Comparative Example 4 replaces the modified chelating agent with EDTA chelating agent, resulting in a 76% decrease in zinc chelation stability in hard water. The reason is that EDTA reacts with CaCl2. 2+ The binding constant is much higher than that of Zn 2+ Calcium ions compete to occupy the coordination sites, and the carboxyl clusters of sodium polyaspartate in the modified chelator preferentially bind to Ca 2+ Forming a soluble complex that blocks calcium interference through an entropy-driven effect; in addition, the rigid octahedral cavity of EDTA binds to Zn 2+ Perfect match for specific chelation protection.

[0039] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0040] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a water-soluble organic fertilizer containing humic acid and chelated trace elements, characterized in that: The preparation steps are as follows: Step S1: adding modified humic acid to deionized water, heating to 40-50°C, stirring for 25-35 minutes, adding hydrated ferrous sulfate, introducing compressed air, stirring and reacting for 30-50 minutes to obtain a chelating solution; Step S2: adding the modified chelating agent and citric acid to the chelating solution, heating to 40-50° C., stirring for 8-12 minutes, adding hydrated zinc sulfate, hydrated manganese sulfate and boric acid, stirring for 15-20 minutes, adding 10% ammonia solution, adjusting the pH to 5-6, stirring and reacting for 50-70 minutes at a speed of 250-350 rpm to obtain a composite chelating solution; Step S3: adding urea to the composite chelating solution, heating to 30-40° C., stirring for 10-20 minutes, adding potassium dihydrogen phosphate and potassium sulfate, stirring for 18-22 minutes at a speed of 250-350 rpm, and continuing stirring for 10-20 minutes to obtain a nutrient chelating mother solution; Step S4: adding the nutrient chelated mother liquor to a concentration tank, reducing the pressure to -0.08 MPa, raising the temperature to 40-50° C., compressing for 50-70 min, adding nano-silicon dioxide and modified starch, stirring for 8-12 min, adding to a high-pressure homogenizer, processing for 5-7 min, at a pressure of 23-27 MPa, filtering, drying, cooling, and passing through an 80-mesh vibrating sieve to obtain a water-soluble organic fertilizer.

2. The method for preparing a chelated trace element synergistic water-soluble organic fertilizer containing humic acid according to claim 1, wherein: The mass ratio of the modified humic acid to hydrated ferrous sulfate in step S1 is 2.7-2.8:1; The mass ratio of the modified chelating agent, citric acid, chelating liquid, hydrated zinc sulfate, hydrated manganese sulfate and boric acid in step S2 is 0.016-0.018:0.008-0.009:1:0.008-0.009:0.0045-0.0055:0.003-0.

004.

3. The method for preparing a chelated humic acid-containing water-soluble organic fertilizer with enhanced trace element synergy according to claim 1, wherein: The mass ratio of urea, composite chelating liquid, potassium dihydrogen phosphate and potassium sulfate in step S3 is 0.05-0.052:1:0.032-0.034:0.024-0.

026.

4. The method for preparing a chelated humic acid-containing water-soluble organic fertilizer with enhanced trace element synergy according to claim 1, wherein: In step S4, the mass ratio of the nutrient chelating mother solution, nano-silicon dioxide and modified starch is 1:0.008-0.012:0.028-0.

032.

5. The method for preparing a chelated trace element synergistic water-soluble organic fertilizer containing humic acid according to claim 1, wherein: The preparation steps of the modified humic acid are as follows: Step A1: Add weathered coal powder to a 1.5% potassium hydroxide solution, heat to 60-80°C, stir for 80-100 minutes, and centrifuge for 10-20 minutes at a speed of 3000-5000 rpm to obtain an activated humic acid solution; Step A2: Under a nitrogen atmosphere, add sulfamic acid and 37% formaldehyde solution to the activated humic acid solution, add 10% sodium hydroxide solution, adjust the pH to 9.0-10.0, raise the temperature to 80-90°C, stir and react for 100-140 minutes. After the reaction is complete, cool to 40-60°C, add 10% hydrochloric acid solution, adjust the pH to 2.0-3.0, let it stand and precipitate, centrifuge and wash, and dry to obtain modified humic acid.

6. The method for preparing a chelated trace element synergistic water-soluble organic fertilizer containing humic acid according to claim 5, characterized in that: The mass ratio of the weathered coal powder to the 1.5% potassium hydroxide solution in step A1 is 1:7.8-8.2; The mass ratio of aminosulfonic acid, 37% formaldehyde solution and activated humic acid solution in step A2 is 0.026-0.028:0.0065-0.007:

1.

7. The method for preparing a water-soluble organic fertilizer containing humic acid and chelated trace elements according to claim 1, wherein: The modified chelating agent preparation steps are as follows: Add ethylenediamine di-o-hydroxyphenylacetic acid and sodium polyaspartate to deionized water, heat to 43-47°C, stir for 30-40 minutes, add catalyst carbodiimide hydrochloride, add 0.1 mol / L hydrochloric acid solution, adjust the pH to 5.8-6.2, heat to 48-52°C, stir and react for 2-4 hours at a speed of 200-300 rpm. After the reaction is complete, cool to 20-30°C, purify, freeze-dry, crush and sieve to obtain a modified chelating agent.

8. The method for preparing a water-soluble organic fertilizer containing humic acid and chelated trace elements according to claim 7, wherein: The mass ratio of ethylenediamine di-o-hydroxyphenylacetic acid, sodium polyaspartate and catalyst is 1:1.4-1.6:0.18-0.

22.

9. The method for preparing a chelated trace element synergistic water-soluble organic fertilizer containing humic acid according to claim 1, characterized in that: The preparation steps of the modified starch are as follows: Add cassava starch to deionized water, heat to 20-30°C, stir for 10-20 minutes, add 3% sodium hydroxide solution, adjust the pH to 8-9, heat to 33-37°C, add octenylsuccinic anhydride, react for 160-200 minutes, add 10% hydrochloric acid solution, adjust the pH to 6.3-6.7, cool and let stand, centrifuge and wash, dry and crush to obtain modified starch.

10. The method for preparing a water-soluble organic fertilizer containing humic acid and chelated with trace elements according to claim 9, characterized in that: The mass ratio of the cassava starch to octenylsuccinic anhydride is 1:0.07-0.09.