A compound fish protein and earthworm protein areca anti-yellowing foliar fertilizer

Abstract

The present application relates to the technical field of foliage fertilizer, in particular to a kind of compound fish protein and earthworm protein's arecalyx catechu anti-yellowing foliage fertilizer, it is composed of the following components: fish protein enzymatic polypeptide powder;Earthworm protein enzymatic antibacterial peptide powder;Modified magnesium-loaded porous slow-release microparticles;Fucoidin oligosaccharide;Carboxymethyl chitosan;Available chelated microelement premix;Potassium silicate;Compound penetrant;Gamma-aminobutyric acid;Deionized water: the compound fish protein and earthworm protein's arecalyx catechu anti-yellowing foliage fertilizer provided in the present application, the function of each component is linked to each other, mutually cooperate.Fish protein enzymatic polypeptide powder is prepared from fish processing waste by alkaline protease, papain and flavour protease step-by-step enzymolysis, ultrafiltration and deodorization and debittering, rich in small molecular active peptide and free amino acid, can be directly absorbed by leaf without degradation after spraying, quickly supply carbon and nitrogen nutrition for yellowing plant, provide amino acid precursor for chlorophyll synthesis, conducive to the faster recovery of chlorosis leaf.

Description

Technical Field

[0001] This invention relates to the field of foliar fertilizer technology, specifically to a compound fish protein and earthworm protein-based areca nut anti-yellowing foliar fertilizer. Background Technology

[0002] Areca nut, a perennial evergreen tree belonging to the Arecaceae family and the Areca genus, is widely cultivated in tropical and subtropical regions of my country, such as Hainan and Yunnan, and is an important economic crop. In areca nut production, leaf yellowing is a prominent problem restricting yield and quality. Yellowing plants experience inhibited chlorophyll synthesis, reduced photosynthetic capacity, and delayed fruit development; in severe cases, the entire plant declines, resulting in significant economic losses. Field diagnosis shows that areca nut yellowing often occurs in conjunction with mineral nutrient imbalances, with magnesium deficiency being particularly common. Magnesium is a core component of chlorophyll molecules and participates in the activation of various enzymes within the plant. Magnesium deficiency first manifests as interveinal chlorosis in older leaves, which then gradually spreads to newer leaves.

[0003] To address magnesium deficiency-induced chlorosis, existing foliar fertilizers typically use fast-acting inorganic magnesium salts such as magnesium sulfate as the magnesium source, supplemented with a small amount of trace elements, and then diluted with water for spraying. However, these products have several shortcomings in practical application. First, fast-acting inorganic salts are easily washed away by rainwater after adhering to the leaf surface, resulting in a short-lasting effect. Magnesium content significantly decreases within a few days after spraying, necessitating repeated spraying, which increases labor costs and can easily burn leaves due to improper concentration control. Second, trace elements such as magnesium, iron, zinc, and manganese are often simply mixed in inorganic salt or single chelate salt form. The elements in the spray solution are prone to antagonism and precipitation, resulting in limited actual absorption and utilization rates, making it difficult to meet the balanced needs of leaves for multiple trace elements. Third, existing products have relatively simple functions, mainly focusing on the supplementation of mineral nutrients. They do not contain small-molecule organic nutrients that can be directly utilized by the leaves, nor do they contain active substances that can induce the plant's own disease resistance and stress resistance. However, the stress resistance of yellowing plants is generally reduced, and they are often accompanied by leaf diseases such as anthracnose. Simple foliar fertilizers that supplement nutrients cannot take into account both nutritional repair and disease control.

[0004] Therefore, how to enable foliar fertilizers to rapidly replenish micronutrients while simultaneously achieving the slow release and long-term maintenance of nutrients such as magnesium, and to supplement mineral nutrition while also ensuring the supply of organic nutrients and enhancing the plant's disease resistance and stress tolerance, is a technical problem that urgently needs to be solved in the prevention and control of areca nut yellowing. Summary of the Invention

[0005] The purpose of this invention is to provide a polyurethane concrete for cold regions.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A compound fish protein and earthworm protein areca nut anti-yellowing foliar fertilizer, composed of the following components by weight: 15-28 parts fish protein hydrolysate polypeptide powder; 10-20 parts earthworm protein hydrolysate antibacterial peptide powder; 8-16 parts modified magnesium-loaded porous slow-release microparticles; 5-12 parts alginate oligosaccharide; 3-8 parts carboxymethyl chitosan; 55-150 parts fast-acting chelated trace element premix; 4-10 parts potassium silicate; 2-5 parts compound penetrant; 0.8-2.5 parts γ-aminobutyric acid; and 150-260 parts deionized water.

[0008] As a further technical solution, the fast-acting chelated trace element premix is ​​composed of sugar alcohol magnesium, EDTA-Fe, EDTA-Zn, EDTA-Mn and sodium octaborate tetrahydrate, wherein the mass ratio of Mg, Fe, Zn, Mn and B is 3.0-7.0: 0.8-2.0: 0.3-0.8: 0.2-0.6: 0.1-0.3, respectively.

[0009] As a further technical solution, the preparation method of the modified magnesium-loaded porous sustained-release microparticles includes the following steps:

[0010] A1 calcium source preparation: After washing and drying the seashells, calcine them at 950-1050℃ for 1.5-3.0h to obtain calcium oxide. Then, treat the calcium oxide and water at 80-90℃ for 30-60min at a mass ratio of 1:5 to 1:8 to prepare a calcium hydroxide suspension.

[0011] A2 soft template complexation involves dissolving citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate in deionized water to prepare a 3%–8% (w / v) solution. Then, 4%–10% of the theoretical hydroxyapatite mass is added to the calcium hydroxide suspension from step A1. The mixture is stirred at 30–40°C and 200–400 rpm for 40–60 min to allow the humic acid carboxyl groups to react with the Ca2+. 2+ Pre-complexation forms a soft template;

[0012] A3 coprecipitation: Under conditions of 60–75℃ and pH 10.0–11.0 throughout, 0.3–0.6 mol / L phosphoric acid solution was added dropwise to the A2 system at a Ca / P molar ratio of 1.62–1.70 at a dropping rate of 2–5 mL / min. After the addition was complete, the reaction continued for 2–4 h, and then aged at room temperature for 12–24 h. The solid and liquid were separated and washed until the conductivity of the filtrate was ≤200 μS / cm, and then dried to obtain the precursor.

[0013] A4 calcination to create pores involves calcining the precursor from step A3 at 350–450°C for 1.5–3.0 h to remove the soft template agent and form a mesoporous structure, thus obtaining mesoporous hydroxyapatite.

[0014] A5 involves a two-stage negative pressure impregnation and coating process. In the first stage, a magnesium impregnation solution containing magnesium nitrate is prepared, with a metal ion concentration of 0.4–0.8 mol / L. 2%–4% (by mass of mesoporous hydroxyapatite) of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate is added, along with the mesoporous hydroxyapatite from step A4 at a liquid-to-solid ratio of (6–12) mL:1g. Impregnation is carried out at 40–55℃ and a negative pressure of -0.06–-0.09 MPa for 2–5 hours. After restoring to normal pressure, solid-liquid separation is performed, followed by vacuum drying at 40–50℃ until the moisture content is ≤3%, forming a magnesium-rich outer shell precursor. In the second stage, a mixed iron-zinc-manganese impregnation solution containing ferrous sulfate, zinc sulfate, and manganese sulfate is prepared, with a total metal ion concentration of 0.5–1.0 mol / L and a Fe:Zn:Mn molar ratio of (10–18). Add 3%–6% of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate and 0.2%–0.5% ascorbic acid to the mesoporous hydroxyapatite by mass of 5–9 and add the first-stage precursor at a liquid-solid ratio of (8–15) mL:1g. Impregnate for 2–5 h at 40–55 °C and -0.06–-0.09 MPa negative pressure. After restoring normal pressure, continue stirring for 1–2 h. Separate the solid and liquid, vacuum dry at 40–50 °C until the water content is ≤3%, and air-jet pulverize to D90≤5μm. Finally, disperse the obtained powder in a 1%–3% γ-polyglutamic acid aqueous solution at a solid-liquid ratio of 1:3–1:5, coat at 40–50 °C for 60–90 min, and spray dry to obtain the modified magnesium-loaded porous slow-release microparticles.

[0015] As a further technical solution, the preparation method of the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate includes the following steps:

[0016] B1 swelling involves dissolving potassium humate from weathered coal in deionized water to prepare a suspension with a mass-volume concentration of 8%–15%, adjusting the pH to 9.0–10.0 with potassium hydroxide, and stirring at 60–70°C for 40–60 minutes to allow it to fully swell, thereby obtaining a potassium humate swollen solution. The potassium humate from the weathered coal has a humic acid content ≥60%, a K2O content ≥8%, and a weight-average molecular weight of 8000–15000 Da.

[0017] B2 acidification and Fenton-like oxidative depolymerization: Citric acid (4%–10% by dry weight of potassium humate) is added to the swelling solution from step B1 to adjust the pH to 4.0–5.0. Ferrous sulfate and a 30% hydrogen peroxide solution are then added sequentially, wherein Fe... 2+ The molar ratio of potassium humate to H2O2 is 1:25 to 1:50, the amount of hydrogen peroxide solution is 10% to 20% of the dry weight of potassium humate, and the oxidation and depolymerization is carried out at 55 to 65℃ for 90 to 150 min.

[0018] B3 is used to terminate and reduce the reaction. The temperature is raised to 85-90℃ and held for 20-30 minutes to decompose the residual hydrogen peroxide. Then, sodium metabisulfite (0.5%-1.5% by dry weight of potassium humate) is added and the reaction is continued for 10-15 minutes.

[0019] B4 is end-capped and stabilized. The pH is adjusted to 8.0-9.0 with potassium hydroxide. Sodium tripolyphosphate is added at 1%-3% of the dry weight of potassium humate. The reaction is carried out at 50-60℃ for 40-60 min. B5 is dried by spray drying at an inlet air temperature of 160-180℃ and an outlet air temperature of 70-80℃ to obtain the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate.

[0020] As a further technical solution, the preparation method of the fish protein hydrolysate peptide powder includes the following steps:

[0021] C1 After homogenizing the fish processing by-products, add water at a material-to-water mass ratio of 1:1 to 1:2, adjust the pH to 8.5 to 9.5, add alkaline protease at 2000 to 4000 U / g substrate protein, and enzymatically hydrolyze at 52 to 56°C for 2.5 to 4.0 h, and inactivate the enzyme at 95°C for 10 min.

[0022] C2 is cooled to 50℃ and the pH is adjusted to 6.5-7.0. Papain is added at 1500-3000 U / g and flavor protease is added at 1000-2000 U / g. The enzyme is hydrolyzed at 50-54℃ for 1.5-2.5 h, the enzyme is inactivated at 95℃ for 10 min, and the supernatant is collected by centrifugation at 4000-6000 r / min for 15-20 min.

[0023] C3 involves passing the supernatant through an ultrafiltration membrane with a molecular weight cutoff of 3000 Da at 0.15–0.25 MPa and 35–45 °C. The permeate is then desalted by nanofiltration and concentrated to 25%–35% solids. 0.5%–1.5% activated carbon and 1%–2% β-cyclodextrin are added, and the mixture is deodorized and debittered at 45–55 °C for 30–40 min.

[0024] C4 spray drying, with an inlet air temperature of 170-185℃ and an outlet air temperature of 75-85℃, yields the fish protein hydrolysate peptide powder.

[0025] As a further technical solution, the preparation method of the earthworm protease hydrolysis antibacterial peptide powder includes the following steps:

[0026] D1 Take fresh Eisenia fetidae bodies and add 0.05-0.10 mol / L phosphate buffer solution with pH 6.8-7.2 at a material-to-liquid mass-to-volume ratio of 1:2 to 1:4. Homogenize the mixture 2-3 times with a colloid mill and autolyze it at 45-50℃ with pH 6.5-7.0 for 6-10 hours.

[0027] Adjust the pH to 8.0-8.5 with D2, add trypsin at 1500-2500 U / g and alkaline protease at 1500-2500 U / g, hydrolyze at 48-52℃ for 3-5 hours, inactivate the enzyme at 95℃ for 10 minutes, and centrifuge to collect the supernatant.

[0028] The supernatant of D3 was ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 5000 Da, and 2% to 4% of β-cyclodextrin by weight of solids was added to the permeate for encapsulation and deodorization.

[0029] D4 spray drying, with an inlet air temperature of 165-180℃ and an outlet air temperature of 70-80℃, yields the earthworm protease hydrolysed antimicrobial peptide powder.

[0030] As a further technical solution, the alginate oligosaccharide has a degree of polymerization of 2 to 8, and the proportion of components with a degree of polymerization of 2 to 8 is ≥80%. It is obtained by enzymatic hydrolysis of alginate with alginate lyase at 40 to 50°C and pH 6.5 to 7.5 for 3 to 6 hours, followed by desalting and drying.

[0031] As a further technical solution, the carboxymethyl chitosan is N,O-carboxymethyl chitosan with a degree of substitution ≥0.85, a degree of deacetylation ≥90%, and a viscosity of 1% aqueous solution at 25°C of 10-50 mPa·s.

[0032] As a further technical solution, the compound penetrant is composed of rhamnolipid, polyether-modified trisiloxane and propylene glycol.

[0033] As a further technical solution, the mass ratio of rhamnolipid to polyether-modified trisiloxane is 1:1.5 to 1:3, and propylene glycol accounts for 10% to 20% of the mass of the compound penetrant.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] In the compound fish protein and earthworm protein foliar fertilizer for areca nut anti-chlorosis provided by this invention, the functions of each component work synergistically. The fish protein hydrolysate peptide powder is obtained from fish processing byproducts through stepwise enzymatic hydrolysis with alkaline protease, papain, and flavor protease, followed by ultrafiltration and deodorization and debittering. It is rich in small-molecule active peptides and free amino acids, and can be directly absorbed by the leaves without degradation after spraying, rapidly replenishing carbon and nitrogen nutrition for chlorotic plants and providing amino acid precursors for chlorophyll synthesis, thus promoting faster recovery of chlorotic leaves. The earthworm protein hydrolysate antimicrobial peptide powder is obtained from Eisenia fetida as raw material through autolysis and enzymatic hydrolysis with trypsin and alkaline protease. Its antimicrobial peptide components can inhibit areca nut anthracnose and other leaf pathogens. The spore germination and mycelial growth of pathogens are reduced while supplementing organic nitrogen, thus lowering the risk of pathogen infection. Modified magnesium-loaded porous slow-release microparticles use mesoporous hydroxyapatite obtained from calcined seashells as a carrier. Magnesium, iron, zinc, and manganese are loaded into the mesoporous channels through two-stage negative pressure impregnation and coated with γ-polyglutamic acid. After spraying, magnesium and other elements are slowly released along the mesoporous structure, overcoming the shortcomings of fast-acting inorganic magnesium salts, such as easy leaching and short-lasting effects. The citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate used in its preparation acts as a soft template agent during the co-precipitation stage to regulate hydroxyapatite. The mesoporous structure of limestone, on the other hand, acts as a dispersant and stabilizer to promote the uniform loading of magnesium, iron, zinc, and manganese on the carrier; alginate oligosaccharides, as plant immune inducers, can induce increased activity of plant defense enzymes and enhance the plant's tolerance to chlorosis stress; carboxymethyl chitosan has good film-forming and water-retention properties, forming a breathable protective film on the leaf surface after spraying, slowing down the evaporation of the pesticide solution and prolonging the residence time of the active ingredients. Its chelating groups also help maintain the stability of micronutrients in the spray solution; the fast-acting chelated micronutrient premix uses magnesium tannin and EDTA-F e. EDTA-Zn, EDTA-Mn, and sodium octaborate tetrahydrate provide magnesium, iron, zinc, manganese, and boron, which can quickly alleviate nutrient deficiency symptoms; potassium silicate supplements plants with potassium and silicon nutrients, promotes silicification of leaf epidermis, and improves leaf mechanical strength; the compound penetrant, composed of rhamnolipid, polyether-modified trisiloxane, and propylene glycol, can effectively reduce the surface tension of the spray solution and improve the wetting, spreading, and penetration of the solution on the waxy leaf surface; γ-aminobutyric acid (GABA) acts as a signaling molecule to regulate the balance of endogenous hormones in plants and alleviate physiological damage caused by nutrient stress.

[0036] The components work synergistically through the complementarity of fast-acting and slow-release components, the synergy of nutrition and disease resistance, and the combination of adhesion and penetration. In terms of nutrient supply, the fast-acting chelated micronutrient premix provides the leaves with available magnesium, iron, zinc, manganese, and boron within hours of application, rapidly relieving the limitations imposed by nutrient deficiency on chlorophyll synthesis and enabling yellowed leaves to quickly turn green again. The modified magnesium-loaded porous slow-release microparticles continuously release magnesium, iron, zinc, and manganese on the leaf surface, extending the effective nutrient supply time to more than 28 days after application, preventing recurrence of yellowing after the effects of the fast-acting components fade. The two components work in a relay-like manner over time. In terms of disease resistance, earthworm protease hydrolysed antibacterial peptide powder directly inhibits leaf pathogens, alginate oligosaccharides induce a systemic defense response in the plant, and fish protease hydrolysed polypeptide powder provides a nitrogen source substrate for the synthesis of defense-related proteins. These three components work synergistically at three levels: direct antibacterial action, immune induction, and nutritional support, making plants in the yellowing repair period less susceptible to diseases such as anthracnose. At the foliar level, the compound penetrant reduces surface tension, allowing active ingredients to quickly penetrate the waxy layer and enter the leaves. The carboxymethyl chitosan film-forming layer reduces water evaporation and loss of active ingredients. This combination of penetration and retention improves nutrient utilization. Potassium silicate and γ-aminobutyric acid enhance plant stress resistance from both structural resistance and physiological regulation perspectives. Silicon deposition strengthens the epidermal barrier, while γ-aminobutyric acid regulates hormone balance and alleviates physiological disorders under chlorosis stress.

[0037] Because the foliar fertilizer of this invention combines small molecule organic nutrients, antibacterial active substances, immune-inducing substances, slow-release trace elements and fast-acting chelated trace elements into one, it not only meets the immediate needs of etiolated plants for a variety of nutrients, but also maintains the long-term supply of nutrients with the help of slow-release carriers, while giving plants disease resistance and stress resistance. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides a compound fish protein and earthworm protein-based areca nut anti-yellowing foliar fertilizer, which, by weight, consists of the following components: 15-28 parts fish protein hydrolysate polypeptide powder; 10-20 parts earthworm protein hydrolysate antibacterial peptide powder; 8-16 parts modified magnesium-loaded porous slow-release microparticles; 5-12 parts alginate oligosaccharide; 3-8 parts carboxymethyl chitosan; 55-150 parts fast-acting chelated trace element premix; 4-10 parts potassium silicate; 2-5 parts compound penetrant; 0.8-2.5 parts γ-aminobutyric acid; and 150-260 parts deionized water.

[0040] In this invention, the preferred amount of the fish protein hydrolysate is 15-28 parts, more preferably 22 parts. The fish protein hydrolysate is obtained from fish processing by-products through compound enzymatic hydrolysis, ultrafiltration, deodorization and debittering, and spray drying. It is rich in small molecule peptides and free amino acids, which can directly supplement the areca nut leaves with organic nitrogen and form complexes with trace elements, thus improving the penetration and absorption efficiency of nutrients on the leaf surface. This invention does not have any special restrictions on the type of fish processing by-products; it can be by-products generated during the processing of tilapia, cod, mackerel, etc., obtained through commercial channels or collected independently. This invention also does not have any special restrictions on the source of the alkaline protease, papain, and flavor protease; commercially available food-grade enzyme preparations can be used. Before use, the enzyme dosage should be calculated based on the enzyme activity indicated on the product label.

[0041] In this invention, the preferred method for preparing the fish protein hydrolysate powder includes the following steps: homogenizing fish processing by-products through a colloid mill, adding water at a material-to-water mass ratio of 1:1 to 1:2, more preferably 1:1.5; adjusting the pH to 8.5 to 9.5 with sodium hydroxide solution, more preferably 9.0; adding alkaline protease at a dosage of 2000 to 4000 U / g of substrate protein, more preferably 3000 U / g; and hydrolyzing at 52 to 56°C for 2.5 to 4.0 hours. The hydrolysis temperature is more preferably 54℃, and the time is more preferably 3.0 h. Enzyme inactivation is performed at 95℃ for 10 min. The temperature is then lowered to 50℃, and the pH is adjusted to 6.5–7.0 with hydrochloric acid solution, more preferably 6.8. Papain is added at 1500–3000 U / g, more preferably 2000 U / g. Flavor protease is added at 1000–2000 U / g, more preferably 1500 U / g. Enzymatic hydrolysis is then performed at 50–54℃ for 1.5–2.5 h, with the hydrolysis temperature being more preferably... The enzyme is inactivated at 52℃ for 2.0 h, then centrifuged at 95℃ for 10 min, and the supernatant is collected after centrifugation at 4000–6000 r / min for 15–20 min. The centrifugation speed is more preferably 5000 r / min and the time is more preferably 18 min. The supernatant is then ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 3000 Da at 0.15–0.25 MPa and 35–45℃, with the ultrafiltration pressure more preferably 0.20 MPa and the temperature more preferably 40℃. The permeate is then desalted and concentrated by nanofiltration. Reduce the solids content to 25%–35%, preferably 30%, add 0.5%–1.5% activated carbon and 1%–2% β-cyclodextrin, and deodorize and debitter at 45–55°C for 30–40 minutes, preferably 50°C and 35 minutes; spray dry at an inlet air temperature of 170–185°C and an outlet air temperature of 75–85°C, preferably 180°C and 80°C, to obtain the fish protein hydrolysate peptide powder.

[0042] In this invention, the preferred dosage of the earthworm proteolytic antimicrobial peptide powder is 10-20 parts, more preferably 15 parts. The earthworm proteolytic antimicrobial peptide powder is obtained from fresh Eisenia fetidae through autolysis, compound enzymatic hydrolysis, ultrafiltration, and spray drying. Besides providing small molecule peptides and amino acid nutrition, it also retains the inherent antimicrobial active peptides within the earthworm, inhibiting the growth of areca nut yellowing-related pathogenic fungi and thus improving the disease resistance of areca nut plants. This invention does not have special restrictions on the source of the Eisenia fetidae; commercially available fresh earthworms are sufficient. Similarly, this invention does not have special restrictions on the source of the trypsin and alkaline protease; commercially available food-grade enzyme preparations are sufficient. Before use, the enzyme dosage should be calculated based on the enzyme activity indicated on the product label.

[0043] In this invention, the preferred method for preparing the earthworm protease hydrolysate antimicrobial peptide powder includes the following steps: Fresh Eisenia fetidae bodies are taken, and 0.05–0.10 mol / L phosphate buffer solution with a pH of 6.8–7.2 is added at a material-to-liquid mass-to-volume ratio of 1:2–1:4. A more preferred material-to-liquid ratio is 1:3, a more preferred buffer concentration is 0.08 mol / L, and a more preferred pH is 7.0. The mixture is homogenized 2–3 times using a colloid mill, and then autolyzed at 45–50°C and pH 6.5–7.0 for 6–10 hours. A more preferred autolyzing temperature is 48°C, a more preferred pH is 6.8, and a more preferred time is 8 hours. The pH is adjusted to 8.0–8.5 with sodium hydroxide solution, a more preferred pH is 8.2. Trypsin is added at a concentration of 1500–2500 U / g, with the enzyme dosage more preferably… Add 2000 U / g of alkaline protease at a concentration of 1500–2500 U / g, with a preferred enzyme concentration of 2000 U / g. Perform enzymatic hydrolysis at 48–52°C for 3–5 hours, with a preferred hydrolysis temperature of 50°C and a preferred hydrolysis time of 4 hours. Inactivate the enzyme at 95°C for 10 minutes. Centrifuge and collect the supernatant. Pass the supernatant through an ultrafiltration membrane with a molecular weight cutoff of 5000 Da at 0.15–0.25 MPa and 35–45°C. Add 2%–4% (by weight of solids) of β-cyclodextrin to the permeate for encapsulation and deodorization, with a preferred β-cyclodextrin concentration of 3%. Spray dry at an inlet air temperature of 165–180°C and an outlet air temperature of 70–80°C, with a preferred inlet air temperature of 170°C and a preferred outlet air temperature of 75°C, to obtain the earthworm protease hydrolyzed antimicrobial peptide powder.

[0044] In this invention, the amount of the modified magnesium-loaded porous slow-release microparticles is preferably 8-16 parts, more preferably 12 parts. The modified magnesium-loaded porous slow-release microparticles are prepared from mesoporous hydroxyapatite using seashells as the calcium source. Magnesium, iron, zinc, and manganese are loaded onto the mesoporous channels and particle surface through two-stage negative pressure impregnation, and then coated with γ-polyglutamic acid to form magnesium-loaded porous microparticles with slow-release function. After spraying, the microparticles adhere to the leaf surface, and magnesium and trace elements such as iron, zinc, and manganese are slowly released as the leaves moisten and dry, continuously replenishing the nutrients required by the areca nut leaves and avoiding leaf burn and nutrient loss caused by the one-time release of fast-acting salts. This invention does not have special restrictions on the source of the seashells; oyster shells, scallop shells, clam shells, etc., can be used after being washed with clean water to remove mud and impurities, or they can be obtained through commercial channels. This invention also does not have special restrictions on the source of the magnesium nitrate, ferrous sulfate, zinc sulfate, manganese sulfate, ascorbic acid, and γ-polyglutamic acid; commercially available products well known to those skilled in the art can be used.

[0045] In this invention, the preferred method for preparing the modified magnesium-loaded porous slow-release microparticles includes the following steps: calcium source preparation, washing seashells and drying them to constant weight at 100-110°C, calcining them at 950-1050°C for 1.5-3.0 h, more preferably at 1000°C and for 2.0 h, to obtain calcium oxide, treating it at 80-90°C for 30-60 min at a calcium oxide to water mass ratio of 1:5-1:8, more preferably at 1:6, at 85°C and for 45 min. Prepare a calcium hydroxide suspension; for soft template complexation, dissolve citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate in deionized water to prepare a solution with a mass-volume concentration of 3%–8%, more preferably 5%, and add 4%–10% of the theoretical mass of hydroxyapatite to the above calcium hydroxide suspension, more preferably 7%, and stir at 30–40°C and 200–400 r / min for 40–60 min, more preferably 35°C, more preferably 300 r / min, and more preferably 50 min, so that the carboxyl groups of humic acid react with Ca. 2+Pre-complexation to form a soft template; co-precipitation, under conditions of 60-75℃ and pH 10.0-11.0 throughout, preferably 70℃ and 10.5, 0.3-0.6 mol / L phosphoric acid solution is added dropwise to the above system at a Ca / P molar ratio of 1.62-1.70, preferably 1.66, and the concentration of phosphoric acid solution is preferably 0.45 mol / L, with a dropping rate of 2-5 mL / min, preferably 3 mL / min. After the addition is complete, the reaction continues for 2-4 h, preferably 3 h, and then aged at room temperature for 12-24 h, preferably 18 h. Solid-liquid separation and washing until the conductivity of the filtrate is ≤200 μS / cm, drying at 100-110℃ to constant weight to obtain the precursor. The pH 10.0-11.0 throughout is preferably maintained by sodium hydroxide solution.

[0046] The precursor is calcined to create pores. The precursor is calcined at 350–450°C for 1.5–3.0 h, preferably at 400°C for 2.0 h, to remove the soft template agent and form a mesoporous structure, yielding mesoporous hydroxyapatite. The process involves two stages of negative pressure impregnation and coating. In the first stage, a magnesium impregnation solution containing magnesium nitrate is prepared, with a metal ion concentration of 0.4–0.8 mol / L, preferably 0.6 mol / L. 2%–4% of the mass of the mesoporous hydroxyapatite is added, preferably 3%, at a liquid-to-solid ratio of 6–12 mL:1 g. The above-mentioned mesoporous hydroxyapatite is immersed in a liquid-to-solid ratio of 9 mL:1 g and impregnated at 40–55 °C and -0.06–-0.09 MPa negative pressure for 2–5 h, with a more preferred temperature of 50 °C and a more preferred time of 3 h. After restoring to normal pressure, solid-liquid separation is performed, followed by vacuum drying at 40–50 °C until the water content is ≤3%, with a more preferred vacuum drying temperature of 45 °C, to form a magnesium-rich outer shell precursor. In the second stage, a mixed iron-zinc-manganese impregnation solution containing ferrous sulfate, zinc sulfate, and manganese sulfate is prepared, with a total metal ion concentration of 0.5–1.0 mol / L, more preferably 0.8 mol / L, and a Fe:Zn:Mn ratio of 0.5–1.0 mol / L. The molar ratio is 10–18:5–9:4–7, more preferably 14:7:5. 3%–6% (by mass of mesoporous hydroxyapatite) of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate and 0.2%–0.5% of ascorbic acid are added, more preferably 4% and 0.3% respectively. The precursor obtained in the first stage is added at a liquid-to-solid ratio of 8–15 mL:1 g, more preferably 12 mL:1 g. The mixture is impregnated at 40–55 °C and a negative pressure of -0.06–-0.09 MPa for 2–5 hours. After restoring to normal pressure, stirring is continued for 1–2 hours. More preferably, the solid-liquid separation is carried out for 1.5 hours, followed by vacuum drying at 40-50°C until the moisture content is ≤3%, and air-jet pulverization to D90≤5μm. Finally, the obtained powder is dispersed in a γ-polyglutamic acid aqueous solution with a mass-volume concentration of 1%-3% at a solid-liquid ratio of 1:3 to 1:5, with a more preferably solid-liquid ratio of 1:4 and a more preferably γ-polyglutamic acid solution concentration of 2%. The powder is coated at 40-50°C for 60-90 minutes, with a more preferably coating temperature of 45°C and a more preferably coating time of 75 minutes. The powder is then spray-dried at an inlet air temperature of 160-180°C and an outlet air temperature of 70-80°C to obtain the modified magnesium-loaded porous slow-release microparticles.

[0047] In this invention, the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate plays a dual role in the preparation of the modified magnesium-loaded porous slow-release microparticles. On the one hand, it acts as a soft template agent in the co-precipitation stage to regulate the mesoporous structure of hydroxyapatite; on the other hand, it acts as a complexing dispersant in the negative pressure impregnation stage to promote uniform metal ion loading. This invention does not impose any special restrictions on the source of the weathered coal humate potassium; commercially available products well-known to those skilled in the art can be used. The weathered coal humate potassium has a humic acid content ≥60%, a K2O content ≥8%, and a weight-average molecular weight of 8000–15000 Da. This invention also does not impose any special restrictions on the sources of the citric acid, ferrous sulfate, hydrogen peroxide, sodium metabisulfite, and sodium tripolyphosphate; commercially available analytical grade reagents can be used.

[0048] In this invention, the preferred method for preparing the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate includes the following steps: swelling, dissolving weathered coal potassium humate in deionized water to prepare a suspension with a mass-volume concentration of 8% to 15%, more preferably 12%, adjusting the pH to 9.0 to 10.0 with potassium hydroxide, more preferably 9.5, stirring at 60 to 70°C for 40 to 60 minutes to allow it to fully swell, more preferably at 65°C and for 50 minutes, to obtain a potassium humate swollen solution; Acidification and Fenton-like oxidative depolymerization are performed. Citric acid, at 4%–10% of the dry weight of potassium humate (more preferably 7%), is added to the above-mentioned swollen solution. The pH is adjusted to 4.0–5.0, more preferably 4.5. Ferrous sulfate and a 30% (w / w) hydrogen peroxide solution are then added sequentially, wherein the molar ratio of Fe²⁺ to H₂O₂ is 1:25–1:50, more preferably 1:35. The amount of hydrogen peroxide solution used is 10%–20% of the dry weight of potassium humate (more preferably 15%). The solution is then heated to 55°C. Oxidation and depolymerization are performed at ~65℃ for 90-150 min, with a more preferred temperature of 60℃ and a more preferred time of 120 min. For termination and reduction, the temperature is raised to 85-90℃ and held for 20-30 min to decompose residual hydrogen peroxide, with a more preferred temperature of 88℃ and a more preferred time of 25 min. Then, sodium metabisulfite (0.5%-1.5% of the dry weight of potassium humate) is added, with a more preferred amount of 1.0%, and the reaction continues for 10-15 min, with a more preferred reaction time of 12 min. End-capping and stabilization are achieved by adjusting the solution with potassium hydroxide. Adjust the pH to 8.0–9.0, more preferably 8.5, add 1%–3% sodium tripolyphosphate by dry weight of potassium humate, more preferably 2%, and react at 50–60°C for 40–60 min, more preferably 55°C and more preferably 50 min; dry by spray drying, with an inlet air temperature of 160–180°C and an outlet air temperature of 70–80°C, more preferably 170°C and more preferably 75°C, to obtain the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate.

[0049] In this invention, the amount of alginate oligosaccharide is preferably 5-12 parts, more preferably 8 parts. The alginate oligosaccharide has a degree of polymerization of 2-8, and the proportion of components with a degree of polymerization of 2-8 is ≥80%. It is obtained by enzymatic hydrolysis of alginate with alginate lyase at 40-50℃ and pH 6.5-7.5 for 3-6 hours, followed by desalting and drying. As a plant immune inducer, alginate oligosaccharide can induce a defensive response in areca nut plants and improve the stress resistance of leaves. This invention does not have special restrictions on the source of the alginate oligosaccharide; commercially available products can be used, or it can be prepared by the above method.

[0050] In this invention, the amount of carboxymethyl chitosan used is preferably 3 to 8 parts, more preferably 5 parts. The carboxymethyl chitosan is N,O-carboxymethyl chitosan with a degree of substitution ≥0.85, a degree of deacetylation ≥90%, and a viscosity of 1% aqueous solution at 25°C of 10 to 50 mPa·s. Carboxymethyl chitosan possesses film-forming properties, moisturizing properties, and certain antibacterial activity. After spraying, it can form a water-retaining film on the leaf surface, prolonging the contact time between nutrients and the leaf surface and reducing water evaporation. This invention does not have special restrictions on the source of the carboxymethyl chitosan; commercially available products well-known to those skilled in the art can be used.

[0051] In this invention, the preferred amount of the fast-acting chelated trace element premix is ​​55-150 parts, more preferably 100 parts. The fast-acting chelated trace element premix is ​​composed of magnesium oxyhydroxide, EDTA-Fe, EDTA-Zn, EDTA-Mn, and sodium octaborate tetrahydrate, wherein the mass ratio of Mg, Fe, Zn, Mn, and B is 3.0-7.0:0.8-2.0:0.3-0.8:0.2-0.6:0.1-0.3, and more preferably 5.0:1.4:0.5:0.4:0.2. Magnesium oxyhydroxide, EDTA-Fe, EDTA-Zn, EDTA-Mn, and sodium octaborate tetrahydrate are all commercially available fertilizer-grade chelated trace element products. Any commercially available product well-known to those skilled in the art can be used. When using, the components are mixed evenly after being converted according to the above-mentioned mass ratio.

[0052] In this invention, the amount of potassium silicate used is preferably 4 to 10 parts, more preferably 7 parts. The potassium silicate is commercially available agricultural potassium silicate, and any commercially available product well-known to those skilled in the art can be used. Potassium silicate supplements the areca nut leaves with silicon; the silicon deposits in the leaf epidermal cells to form a silicified layer, which helps to enhance the mechanical strength of the leaves and reduce disease infection.

[0053] In this invention, the amount of the compound penetrant is preferably 2-5 parts, more preferably 3.5 parts. The compound penetrant is composed of rhamnolipin, polyether-modified trisiloxane, and propylene glycol, wherein the mass ratio of rhamnolipin to polyether-modified trisiloxane is preferably 1:1.5-1:3, more preferably 1:2, and propylene glycol accounts for 10%-20% of the mass of the compound penetrant, more preferably 15%. Both rhamnolipin and polyether-modified trisiloxane have excellent wetting and spreading properties, which can reduce the surface tension of the medicinal solution and enable the nutrient solution to spread and penetrate quickly on the surface of areca nut leaves; propylene glycol, as a humectant, can slow down the drying rate of the medicinal solution and prolong the nutrient absorption time. The rhamnolipin is a commercially available biosurfactant, the polyether-modified trisiloxane is a commercially available organosilicon wetting agent, and the propylene glycol is a commercially available industrial-grade propylene glycol; all commercially available products well known to those skilled in the art can be used.

[0054] In this invention, the amount of γ-aminobutyric acid (GABA) is preferably 0.8 to 2.5 parts, more preferably 1.5 parts. As a signaling molecule, GABA can regulate the hormone balance in areca nut plants, alleviate abiotic stress, and promote stomatal regulation and nutrient transport in leaves. The GABA is a commercially available food-grade or feed-grade product; any commercially available product well-known to those skilled in the art can be used.

[0055] In this invention, the amount of deionized water is preferably 150 to 260 parts, more preferably 200 parts.

[0056] This invention also provides a method for preparing the above-mentioned areca nut anti-chlorosis foliar fertilizer, preferably comprising the following steps: adding fast-acting chelated trace element premix and potassium silicate to deionized water, stirring to dissolve at room temperature, then adding γ-aminobutyric acid and stirring to dissolve; then adding fish protein hydrolysate peptide powder, earthworm protein hydrolysate antimicrobial peptide powder, alginate oligosaccharide and carboxymethyl chitosan, stirring until completely dissolved; finally adding modified magnesium-loaded porous slow-release microparticles and compound penetrant, stirring evenly to obtain the compound fish protein and earthworm protein areca nut anti-chlorosis foliar fertilizer. The stirring speed is preferably 200–400 r / min, the stirring time is preferably 20–40 min, and the room temperature is preferably 20–30°C.

[0057] This invention provides a compound fish protein and earthworm protein foliar fertilizer for areca nut anti-chlorosis, which combines fish protein hydrolysate peptide powder and earthworm protein hydrolysate antibacterial peptide powder to synergistically provide small molecule peptide nutrition and antibacterial activity. Modified magnesium-loaded porous slow-release microparticles and fast-acting chelated trace element premixes work together to achieve both rapid supplementation and long-term slow release of trace elements such as magnesium, iron, zinc, manganese, and boron. Alginic acid oligosaccharides and carboxymethyl chitosan synergistically exert immune induction and film-forming moisturizing effects. Combined with potassium silicate, compound penetrant and γ-aminobutyric acid, it can improve the nutritional status of areca nut leaves, promote the regreening of yellowed leaves, enhance the plant's disease resistance and stress resistance, and improve fertilizer utilization.

[0058] Compared with existing technologies, the areca nut anti-yellowing foliar fertilizer provided by this invention uses specific components and works together to form a synergistic system of nutrient supplementation, slow-release enhancement, immune induction, and antibacterial and disease prevention. It can effectively alleviate the yellowing of areca nut leaves, promote leaf regreening, and improve the yield and quality of areca nuts. At the same time, the modified magnesium-loaded porous slow-release microparticles are prepared from seashells, realizing the resource utilization of waste, reducing production costs, and have good promotion and application value.

[0059] To further illustrate the present invention, the following examples provide a detailed description. In the following examples of the present invention: the fish protein hydrolysate peptide powder, earthworm protein hydrolysate antibacterial peptide powder, modified magnesium-loaded porous slow-release microparticles, and citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate used were all prepared by the corresponding steps described above; the weathered coal potassium humate used was commercially available, with a humic acid content ≥60%, K2O content ≥8%, and a weight-average molecular weight of 8000–15000 Da; the alkaline protease, papain, flavor protease, and trypsin used were all commercially available food-grade enzyme preparations, and the amount of enzyme added was calculated according to the enzyme activity indicated on the product label before use; the sugar alcohol magnesium, EDTA-Fe, EDTA-Zn, EDTA-Mn, and sodium octaborate tetrahydrate used were all commercially available fertilizers. This product is a grade chelated trace element product. The alginate oligosaccharide used is commercially available, with components having a degree of polymerization of 2-8 accounting for ≥80%. The carboxymethyl chitosan used is commercially available N,O-carboxymethyl chitosan with a degree of substitution ≥0.85, a degree of deacetylation ≥90%, and a viscosity of 1% aqueous solution at 25℃ of 10-50 mPa·s. The potassium silicate, rhamnolipid, polyether-modified trisiloxane, propylene glycol, γ-aminobutyric acid, γ-polyglutamic acid, magnesium nitrate, ferrous sulfate, zinc sulfate, manganese sulfate, citric acid, hydrogen peroxide, sodium metabisulfite, sodium tripolyphosphate, ascorbic acid, phosphoric acid, potassium hydroxide, sodium hydroxide, hydrochloric acid, and β-cyclodextrin used are all commercially available reagents or commercially available agricultural products.

[0060] Example 1: By weight, the amounts of each component are as follows: 15 parts fish protein hydrolysate peptide powder, 10 parts earthworm protein hydrolysate antimicrobial peptide powder, 8 parts modified magnesium-loaded porous slow-release microparticles, 5 parts alginate oligosaccharide, 3 parts carboxymethyl chitosan, 55 parts fast-acting chelated trace element premix, 4 parts potassium silicate, 2 parts compound penetrant, 0.8 parts γ-aminobutyric acid, and 150 parts deionized water.

[0061] Step 1: Preparation of Citric Acid-Hydrogen Peroxide Synergistic Depolymerization Modified Potassium Humate. Weathered coal potassium humate with a humic acid content ≥60%, K₂O content ≥8%, and weight-average molecular weight 8000–15000 Da was dissolved in deionized water to prepare an 8% (w / v) suspension. The pH was adjusted to 9.0 with potassium hydroxide, and the solution was stirred at 60°C for 40 min to allow for complete swelling, resulting in a swollen potassium humate solution. Citric acid (4% by dry weight of potassium humate) was added to the swollen solution to adjust the pH to 4.0. Ferrous sulfate and a 30% (w / v) hydrogen peroxide solution were then added sequentially, with a Fe²⁺ to H₂O₂ molar ratio of 1:25. The amount of hydrogen peroxide solution used was 10% of the dry weight of potassium humate. Oxidation and depolymerization were carried out at 55°C for 90 min. The temperature was raised to 85°C and held for 20 min to decompose residual hydrogen peroxide. Then, sodium metabisulfite (0.5% by dry weight of potassium humate) was added, and the reaction was continued for 10 min. The pH was adjusted to 8.0 with potassium hydroxide, and sodium tripolyphosphate (1% by dry weight of potassium humate) was added. The mixture was reacted at 50°C for 40 min. The mixture was then spray-dried at an inlet air temperature of 160°C and an outlet air temperature of 70°C to obtain citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate.

[0062] Step 2: Preparation of modified magnesium-loaded porous slow-release microparticles. Oyster shells were washed and dried to constant weight at 105℃, then calcined at 950℃ for 1.5 h to obtain calcium oxide. The calcium oxide was then treated at 80℃ for 30 min at a calcium oxide to water mass ratio of 1:5 to prepare a calcium hydroxide suspension. The citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate obtained in Step 1 was dissolved in deionized water to prepare a 3% (w / v) solution. This solution was added to the above calcium hydroxide suspension at 4% of the theoretical hydroxyapatite mass, and stirred at 30℃ and 200 r / min for 40 min to allow the humic acid carboxyl groups to react with the calcium hydroxide. 2+A soft template was formed through pre-complexation. At 60°C and pH 10.0 throughout, a 0.3 mol / L phosphoric acid solution was added dropwise to the above system at a Ca / P molar ratio of 1.62 at a dropping rate of 2 mL / min. After the addition was complete, the reaction continued for 2 h, followed by aging at room temperature for 12 h. Solid-liquid separation was performed, and the filtrate was washed until its conductivity was ≤200 μS / cm. The filtrate was then dried at 105°C to constant weight to obtain the precursor. The precursor was calcined at 350°C for 1.5 h to remove the soft template agent and form a mesoporous structure, yielding mesoporous hydroxyapatite. A magnesium impregnation solution containing magnesium nitrate was prepared with a metal ion concentration of 0.4 mol / L. Citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate was added at 2% of the mass of mesoporous hydroxyapatite. The mesoporous hydroxyapatite was added at a liquid-solid ratio of 6 mL: 1 g. The solution was impregnated at 40 °C and -0.06 MPa negative pressure for 2 h. After restoring normal pressure, the solid and liquid were separated, and the solution was vacuum dried at 40 °C until the water content was ≤3%, forming a magnesium-rich outer shell precursor. A mixed impregnation solution containing ferrous sulfate, zinc sulfate, and manganese sulfate was prepared, with a total metal ion concentration of 0.5 mol / L and a Fe:Zn:Mn molar ratio of 10:5:4. 3% (by mass of mesoporous hydroxyapatite) of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate and 0.2% ascorbic acid were added. The precursor obtained in the first stage was added at a liquid-to-solid ratio of 8 mL:1 g. The solution was impregnated at 40℃ and -0.06 MPa for 2 h, and after restoring to normal pressure, stirring was continued for 1 h. Solid-liquid separation was performed, followed by vacuum drying at 40℃ until the moisture content was ≤3%, and then air-jet milling to a D90 ≤5 μm. The resulting powder was dispersed in a 1% (w / v) γ-polyglutamic acid aqueous solution at a solid-to-liquid ratio of 1:3, coated at 40℃ for 60 min, and spray-dried at an inlet air temperature of 170℃ and an outlet air temperature of 75℃ to obtain modified magnesium-loaded porous slow-release microparticles.

[0063] Step 3: Preparation of fish protein hydrolysate powder. Tilapia processing by-products were homogenized using a colloid mill, and water was added at a material-to-water ratio of 1:1. The pH was adjusted to 8.5 with sodium hydroxide solution. Alkaline protease was added at a concentration of 2000 U / g of substrate protein, and the mixture was hydrolyzed at 52℃ for 2.5 h, followed by enzyme inactivation at 95℃ for 10 min. The mixture was then cooled to 50℃, and the pH was adjusted to 6.5 with hydrochloric acid solution. Papain was added at a concentration of 1500 U / g, and flavor protease at a concentration of 1000 U / g. The mixture was hydrolyzed at 50℃ for 1.5 h, followed by enzyme inactivation at 95℃ for 10 min. The mixture was centrifuged at 4000 r / min for 15 min, and the supernatant was collected. The supernatant was ultrafiltered through a 3000 Da molecular weight cutoff membrane at 0.15 MPa and 35℃. The permeate was desalted by nanofiltration and concentrated to 25% solids. 0.5% activated carbon and 1% β-cyclodextrin were added, and the mixture was deodorized and debittered at 45℃ for 30 min. Spray drying was performed at an inlet air temperature of 170℃ and an outlet air temperature of 75℃ to obtain fish protein hydrolysate peptide powder.

[0064] Step 4: Preparation of earthworm proteolytic antimicrobial peptide powder. Fresh Eisenia fetidae bodies were taken and added to a 0.05 mol / L phosphate buffer solution (pH 6.8) at a material-to-liquid mass-to-volume ratio of 1:2. The mixture was homogenized twice using a colloid mill and autolyzed at 45℃ and pH 6.5 for 6 hours. The pH was adjusted to 8.0 with sodium hydroxide solution. Trypsin and alkaline protease were added at 1500 U / g each, and the mixture was enzymatically hydrolyzed at 48℃ for 3 hours. The enzymes were inactivated at 95℃ for 10 minutes, and the supernatant was collected by centrifugation at 5000 r / min for 15 minutes. The supernatant was ultrafiltered through a 5000 Da molecular weight cutoff membrane at 0.20 MPa and 40℃. β-cyclodextrin (2% by weight of solids) was added to the permeate for encapsulation and deodorization. The mixture was spray-dried at an inlet air temperature of 165℃ and an outlet air temperature of 70℃ to obtain earthworm proteolytic antimicrobial peptide powder.

[0065] Step 5: Prepare the fast-acting chelated trace element premix. Calculate the amount of each raw material using magnesium sugar alcohol, EDTA-Fe, EDTA-Zn, EDTA-Mn, and sodium octaborate tetrahydrate according to the mass ratio of Mg, Fe, Zn, Mn, and B of 3.0:0.8:0.3:0.2:0.1, mix and stir evenly to obtain the fast-acting chelated trace element premix.

[0066] Step 6: Prepare the compound penetrant. Mix rhamnolipid and polyether-modified trisiloxane at a mass ratio of 1:1.5, then add propylene glycol at 10% of the mass of the compound penetrant, and stir until homogeneous to obtain the compound penetrant.

[0067] Step 7: Prepare foliar fertilizer. Add 55 parts of fast-acting chelated micronutrient premix and 4 parts of potassium silicate to 150 parts of deionized water, and stir at 300 rpm for 30 minutes at 25°C. Add 0.8 parts of γ-aminobutyric acid and continue stirring for 10 minutes. Add 15 parts of fish protein hydrolysate peptide powder, 10 parts of earthworm protein hydrolysate antimicrobial peptide powder, 5 parts of alginate oligosaccharide, and 3 parts of carboxymethyl chitosan, and stir until completely dissolved. Finally, add 8 parts of modified magnesium-loaded porous slow-release microparticles and 2 parts of compound penetrant, and stir evenly to obtain the compound fish protein and earthworm protein areca anti-yellowing foliar fertilizer.

[0068] Example 2: By weight, the amounts of each component are as follows: 28 parts fish protein hydrolysate peptide powder, 20 parts earthworm protein hydrolysate antimicrobial peptide powder, 16 parts modified magnesium-loaded porous slow-release microparticles, 12 parts alginate oligosaccharide, 8 parts carboxymethyl chitosan, 150 parts fast-acting chelated trace element premix, 10 parts potassium silicate, 5 parts compound penetrant, 2.5 parts γ-aminobutyric acid, and 260 parts deionized water.

[0069] Step 1: Preparation of Citric Acid-Hydrogen Peroxide Synergistic Depolymerization Modified Potassium Humate. Weathered coal potassium humate with a humic acid content ≥60%, K₂O content ≥8%, and weight-average molecular weight 8000–15000 Da was dissolved in deionized water to prepare a 15% (w / v) suspension. The pH was adjusted to 10.0 with potassium hydroxide, and the solution was stirred at 70°C for 60 min to allow for complete swelling, resulting in a swollen potassium humate solution. Citric acid (10% by dry weight of potassium humate) was added to the swollen solution, and the pH was adjusted to 5.0. Ferrous sulfate and a 30% (w / v) hydrogen peroxide solution were then added sequentially, with a Fe²⁺ to H₂O₂ molar ratio of 1:50. The amount of hydrogen peroxide solution used was 20% of the dry weight of potassium humate. The solution was then oxidatively depolymerized at 65°C for 150 min. The residual hydrogen peroxide was decomposed by heating to 90℃ and holding for 30 min. Then, sodium metabisulfite (1.5% by weight of potassium humate dry basis) was added, and the reaction was continued for 15 min. The pH was adjusted to 9.0 with potassium hydroxide, and sodium tripolyphosphate (3% by weight of potassium humate dry basis) was added. The reaction was carried out at 60℃ for 60 min. The mixture was then spray-dried at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate.

[0070] Step 2: Preparation of modified magnesium-loaded porous slow-release microparticles. Oyster shells were washed and dried to constant weight at 105℃, then calcined at 1050℃ for 3.0 h to obtain calcium oxide. The calcium oxide was then treated at 90℃ for 60 min at a calcium oxide to water mass ratio of 1:8 to prepare a calcium hydroxide suspension. The citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate obtained in Step 1 was dissolved in deionized water to prepare an 8% (w / v) solution. 10% of the theoretical hydroxyapatite mass was added to the above calcium hydroxide suspension, and the mixture was stirred at 40℃ and 400 r / min for 60 min to allow the humic acid carboxyl groups to react with the calcium hydroxide. 2+A soft template was formed through pre-complexation. At 75°C and pH 11.0 throughout, a 0.6 mol / L phosphoric acid solution was added dropwise to the above system at a Ca / P molar ratio of 1.70 at a dropping rate of 5 mL / min. After the addition was complete, the reaction continued for 4 h, followed by aging at room temperature for 24 h. Solid-liquid separation was performed, and the filtrate was washed until its conductivity was ≤200 μS / cm. The filtrate was then dried at 105°C to constant weight to obtain the precursor. The precursor was calcined at 450°C for 3.0 h to remove the soft template agent and form a mesoporous structure, yielding mesoporous hydroxyapatite. A magnesium impregnation solution containing magnesium nitrate was prepared with a metal ion concentration of 0.8 mol / L. Citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate was added at 4% of the mass of mesoporous hydroxyapatite. The mesoporous hydroxyapatite was added at a liquid-solid ratio of 12 mL: 1 g. The solution was impregnated at 55 °C and -0.09 MPa negative pressure for 5 h. After restoring normal pressure, the solid and liquid were separated, and the solution was vacuum dried at 50 °C until the water content was ≤3%, forming a magnesium-rich outer shell precursor. A mixed impregnation solution containing ferrous sulfate, zinc sulfate, and manganese sulfate was prepared, with a total metal ion concentration of 1.0 mol / L and a Fe:Zn:Mn molar ratio of 18:9:7. Citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate (6% by mass of mesoporous hydroxyapatite) and 0.5% ascorbic acid were added. The precursor obtained in the first stage was added at a liquid-to-solid ratio of 15 mL:1 g. The solution was impregnated at 55 °C and -0.09 MPa negative pressure for 5 h, and after restoring to normal pressure, stirring was continued for 2 h. Solid-liquid separation was performed, followed by vacuum drying at 50 °C until the moisture content was ≤3%, and then air-jet milling to a D90 ≤5 μm. The resulting powder was dispersed in a 3% (w / v) γ-polyglutamic acid aqueous solution at a solid-to-liquid ratio of 1:5, coated at 50 °C for 90 min, and spray-dried at an inlet air temperature of 170 °C and an outlet air temperature of 75 °C to obtain modified magnesium-loaded porous slow-release microparticles.

[0071] Step 3: Preparation of fish protein hydrolysate powder. Tilapia processing by-products were homogenized using a colloid mill, and water was added at a material-to-water ratio of 1:2. The pH was adjusted to 9.5 with sodium hydroxide solution. Alkaline protease was added at a concentration of 4000 U / g of substrate protein, and the mixture was hydrolyzed at 56℃ for 4.0 h, followed by enzyme inactivation at 95℃ for 10 min. The mixture was then cooled to 50℃, and the pH was adjusted to 7.0 with hydrochloric acid solution. Papain was added at a concentration of 3000 U / g, and flavor protease at a concentration of 2000 U / g. The mixture was hydrolyzed at 54℃ for 2.5 h, followed by enzyme inactivation at 95℃ for 10 min. The mixture was centrifuged at 6000 r / min for 20 min, and the supernatant was collected. The supernatant was ultrafiltered through a 3000 Da molecular weight cutoff membrane at 0.25 MPa and 45℃. The permeate was desalted by nanofiltration and concentrated to 35% solids. 1.5% activated carbon and 2% β-cyclodextrin were added, and the mixture was deodorized and debittered at 55℃ for 40 min. Spray drying was performed at an inlet air temperature of 185℃ and an outlet air temperature of 85℃ to obtain fish protein hydrolysate peptide powder.

[0072] Step 4: Preparation of earthworm proteolytic antimicrobial peptide powder. Fresh Eisenia fetidae bodies were taken and added to a 0.10 mol / L phosphate buffer solution (pH 7.2) at a material-to-liquid mass-to-volume ratio of 1:4. The mixture was homogenized three times using a colloid mill and autolyzed at 50℃ and pH 7.0 for 10 hours. The pH was adjusted to 8.5 with sodium hydroxide solution. Trypsin and alkaline protease were added at 2500 U / g each, and the mixture was enzymatically hydrolyzed at 52℃ for 5 hours. The enzymes were then inactivated at 95℃ for 10 minutes, and the mixture was centrifuged at 5000 rpm for 15 minutes to collect the supernatant. The supernatant was ultrafiltered through a 5000 Da molecular weight cutoff membrane at 0.20 MPa and 40℃. 4% (by weight of solids) of β-cyclodextrin was added to the permeate for encapsulation and deodorization. The mixture was spray-dried at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain earthworm proteolytic antimicrobial peptide powder.

[0073] Step 5: Prepare the fast-acting chelated trace element premix. Calculate the amount of each raw material by adjusting the mass ratio of Mg, Fe, Zn, Mn, and B to 7.0:2.0:0.8:0.6:0.3, and mix them evenly to obtain the fast-acting chelated trace element premix.

[0074] Step 6: Prepare the compound penetrant. Mix rhamnolipid and polyether-modified trisiloxane at a mass ratio of 1:3, then add propylene glycol at 20% of the mass of the compound penetrant, and stir until homogeneous to obtain the compound penetrant.

[0075] Step 7: Prepare foliar fertilizer. Add 150 parts of fast-acting chelated micronutrient premix and 10 parts of potassium silicate to 260 parts of deionized water, and stir at 300 rpm for 30 minutes at 25°C. Add 2.5 parts of γ-aminobutyric acid and continue stirring for 10 minutes. Add 28 parts of fish protein hydrolysate peptide powder, 20 parts of earthworm protein hydrolysate antimicrobial peptide powder, 12 parts of alginate oligosaccharide, and 8 parts of carboxymethyl chitosan, and stir until completely dissolved. Finally, add 16 parts of modified magnesium-loaded porous slow-release microparticles and 5 parts of compound penetrant, and stir evenly to obtain a compound fish protein and earthworm protein areca anti-yellowing foliar fertilizer.

[0076] Example 3: By weight, the amounts of each component are as follows: 22 parts fish protein hydrolysate peptide powder, 15 parts earthworm protein hydrolysate antimicrobial peptide powder, 12 parts modified magnesium-loaded porous slow-release microparticles, 8 parts alginate oligosaccharide, 5 parts carboxymethyl chitosan, 100 parts fast-acting chelated trace element premix, 7 parts potassium silicate, 3.5 parts compound penetrant, 1.5 parts γ-aminobutyric acid, and 200 parts deionized water.

[0077] Step 1: Preparation of Citric Acid-Hydrogen Peroxide Synergistic Depolymerization Modified Potassium Humate. Weathered coal potassium humate with a humic acid content ≥60%, K₂O content ≥8%, and weight-average molecular weight 8000–15000 Da was dissolved in deionized water to prepare a suspension with a mass-volume concentration of 12%. The pH was adjusted to 9.5 with potassium hydroxide, and the solution was stirred at 65°C for 50 min to allow for complete swelling, resulting in a swollen potassium humate solution. Citric acid (7% by dry weight of potassium humate) was added to the above swollen solution to adjust the pH to 4.5. Ferrous sulfate and a 30% by mass hydrogen peroxide solution were then added sequentially, with a Fe²⁺ to H₂O₂ molar ratio of 1:35. The amount of hydrogen peroxide solution used was 15% of the dry weight of potassium humate. The solution was then oxidatively depolymerized at 60°C for 120 min. The residual hydrogen peroxide was decomposed by heating to 88℃ and holding for 25 min. Then, sodium metabisulfite (1.0% by dry weight of potassium humate) was added, and the reaction was continued for 12 min. The pH was adjusted to 8.5 with potassium hydroxide, and sodium tripolyphosphate (2% by dry weight of potassium humate) was added. The reaction was carried out at 55℃ for 50 min. The mixture was then spray-dried at an inlet air temperature of 170℃ and an outlet air temperature of 75℃ to obtain citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate.

[0078] Step 2: Preparation of modified magnesium-loaded porous slow-release microparticles. Oyster shells were washed and dried to constant weight at 105℃, then calcined at 1000℃ for 2.0 h to obtain calcium oxide. The calcium oxide was then treated at 85℃ for 45 min at a calcium oxide to water mass ratio of 1:6 to prepare a calcium hydroxide suspension. The citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate obtained in Step 1 was dissolved in deionized water to prepare a 5% (w / v) solution. 7% of the theoretical hydroxyapatite mass was added to the above calcium hydroxide suspension, and the mixture was stirred at 35℃ and 300 r / min for 50 min to allow the humic acid carboxyl groups to react with the calcium hydroxide. 2+A soft template was formed through pre-complexation. At 70°C and pH 10.5 throughout, a 0.45 mol / L phosphoric acid solution was added dropwise to the above system at a Ca / P molar ratio of 1.66 at a dropping rate of 3 mL / min. After the addition was complete, the reaction continued for 3 h, followed by aging at room temperature for 18 h. Solid-liquid separation was performed, and the filtrate was washed until its conductivity was ≤200 μS / cm. The filtrate was then dried at 105°C to constant weight to obtain the precursor. The precursor was calcined at 400°C for 2.0 h to remove the soft template agent and form a mesoporous structure, yielding mesoporous hydroxyapatite. A magnesium impregnation solution containing magnesium nitrate was prepared with a metal ion concentration of 0.6 mol / L. Citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate was added at a mass of 3% of the mesoporous hydroxyapatite. The mesoporous hydroxyapatite was added at a liquid-to-solid ratio of 9 mL:1 g. The solution was impregnated at 50 °C and -0.08 MPa negative pressure for 3 h. After restoring normal pressure, the solid and liquid were separated, and the solution was vacuum dried at 45 °C until the water content was ≤3%, forming a magnesium-rich outer shell precursor. A mixed impregnation solution containing ferrous sulfate, zinc sulfate, and manganese sulfate was prepared, with a total metal ion concentration of 0.8 mol / L and a Fe:Zn:Mn molar ratio of 14:7:5. 4% (by mass of mesoporous hydroxyapatite) of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate and 0.3% ascorbic acid were added. The precursor obtained in the first stage was added at a liquid-to-solid ratio of 12 mL:1 g. The solution was impregnated at 50 °C and -0.08 MPa negative pressure for 3 h, and after restoring to normal pressure, stirring was continued for 1.5 h. Solid-liquid separation was performed, followed by vacuum drying at 45 °C until the moisture content was ≤3%, and then air-jet milling to a D90 ≤5 μm. The resulting powder was dispersed in a 2% (w / v) γ-polyglutamic acid aqueous solution at a solid-to-liquid ratio of 1:4, coated at 45 °C for 75 min, and spray-dried at an inlet air temperature of 170 °C and an outlet air temperature of 75 °C to obtain modified magnesium-loaded porous slow-release microparticles.

[0079] Step 3: Preparation of fish protein hydrolysate powder. Tilapia processing by-products were homogenized using a colloid mill, and water was added at a material-to-water ratio of 1:1.5. The pH was adjusted to 9.0 with sodium hydroxide solution. Alkaline protease was added at 3000 U / g substrate protein, and the mixture was hydrolyzed at 54℃ for 3.0 h, followed by enzyme inactivation at 95℃ for 10 min. The mixture was cooled to 50℃, and the pH was adjusted to 6.8 with hydrochloric acid solution. Papain was added at 2000 U / g, and flavor protease at 1500 U / g, and the mixture was hydrolyzed at 52℃ for 2.0 h, followed by enzyme inactivation at 95℃ for 10 min. The mixture was centrifuged at 5000 r / min for 18 min, and the supernatant was collected. The supernatant was ultrafiltered through a 3000 Da molecular weight cutoff membrane at 0.20 MPa and 40℃. The permeate was desalted by nanofiltration and concentrated to 30% solids. 1.0% activated carbon and 1.5% β-cyclodextrin were added, and the mixture was deodorized and debittered at 50℃ for 35 min. Spray drying was performed at an inlet air temperature of 180℃ and an outlet air temperature of 80℃ to obtain fish protein hydrolysate peptide powder.

[0080] Step 4: Preparation of earthworm proteolytic antimicrobial peptide powder. Fresh Eisenia fetidae bodies were taken and added to a 0.08 mol / L phosphate buffer solution (pH 7.0) at a material-to-liquid mass-to-volume ratio of 1:3. The mixture was homogenized twice using a colloid mill and autolyzed at 48℃ and pH 6.8 for 8 hours. The pH was adjusted to 8.2 with sodium hydroxide solution. Trypsin and alkaline protease were added at 2000 U / g each, and the mixture was enzymatically hydrolyzed at 50℃ for 4 hours. The enzymes were inactivated at 95℃ for 10 minutes, and the supernatant was collected by centrifugation at 5000 rpm for 15 minutes. The supernatant was then ultrafiltered through a 5000 Da ultrafiltration membrane at 0.20 MPa and 40℃. β-cyclodextrin (3% by weight of solids) was added to the permeate for encapsulation and deodorization. The mixture was spray-dried at an inlet air temperature of 170℃ and an outlet air temperature of 75℃ to obtain earthworm proteolytic antimicrobial peptide powder.

[0081] Step 5: Prepare the fast-acting chelated trace element premix. Calculate the amount of each raw material using magnesium sugar alcohol, EDTA-Fe, EDTA-Zn, EDTA-Mn, and sodium octaborate tetrahydrate according to the mass ratio of Mg, Fe, Zn, Mn, and B of 5.0:1.4:0.5:0.4:0.2, mix and stir evenly to obtain the fast-acting chelated trace element premix.

[0082] Step 6: Prepare the compound penetrant. Mix rhamnolipid and polyether-modified trisiloxane at a mass ratio of 1:2, then add propylene glycol at 15% of the mass of the compound penetrant, and stir until homogeneous to obtain the compound penetrant.

[0083] Step 7: Prepare foliar fertilizer. Add 100 parts of fast-acting chelated micronutrient premix and 7 parts of potassium silicate to 200 parts of deionized water, and stir at 300 rpm for 30 minutes at 25°C. Add 1.5 parts of γ-aminobutyric acid and continue stirring for 10 minutes. Add 22 parts of fish protein hydrolysate peptide powder, 15 parts of earthworm protein hydrolysate antimicrobial peptide powder, 8 parts of alginate oligosaccharide, and 5 parts of carboxymethyl chitosan, and stir until completely dissolved. Finally, add 12 parts of modified magnesium-loaded porous slow-release microparticles and 3.5 parts of compound penetrant, and stir evenly to obtain the areca nut anti-yellowing foliar fertilizer with compound fish protein and earthworm protein.

[0084] Comparative Example 1: The foliar fertilizer formula and preparation method provided in Example 1 were used, except that: no modified magnesium-loaded porous slow-release microparticles were added, and magnesium was replaced with magnesium sulfate heptahydrate in an equal amount of magnesium and dissolved in deionized water along with the fast-acting chelated trace element premix. All other components and operations were the same as in Example 1.

[0085] Comparative Example 2: The foliar fertilizer formula and preparation method provided in Example 1 were used, except that earthworm protease hydrolysed antimicrobial peptide powder was not added, and an equal amount of fish protease hydrolysed polypeptide powder was used to make up the difference. All other components and operations were the same as in Example 1.

[0086] Comparative Example 3: The foliar fertilizer formula and preparation method provided in Example 1 were used, except that: no alginate oligosaccharide and carboxymethyl chitosan were added, and an equal amount of deionized water was used to make up the difference. All other components and operations were the same as in Example 1.

[0087] Comparative Example 4: The foliar fertilizer formula and preparation method provided in Example 1 were used, except that: when preparing the modified magnesium-loaded porous slow-release microparticles, commercially available ordinary potassium humate was used instead of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate. The remaining components and operations were the same as in Example 1.

[0088] test:

[0089] Experiment 1: Test on the effect of yellowing recovery in areca seedlings.

[0090] Areca nut seedlings with uniform growth, 2 years old, and exhibiting magnesium deficiency chlorosis were selected as test materials. There were no significant differences in the SPAD values ​​of functional leaves before treatment among the treatment groups, with an average value of 24.5. The SPAD value of healthy control plants was 46.0. Each treatment was replicated in triplicate, with 5 plants per replicate, arranged in a randomized block design. The foliar fertilizers obtained in Examples 1-3 and Comparative Examples 1-4 were diluted 500 times with deionized water and sprayed evenly on both sides of the areca nut leaves on sunny evenings until the leaves were moist but not dripping. Spraying was repeated once every 7 days for a total of 3 applications. The blank control was sprayed with an equal amount of deionized water. Seven days after the final spray, the SPAD value of functional leaves for each treatment was measured using a portable chlorophyll meter. Three measurements were taken for each leaf, and the average value was recorded. Simultaneously, functional leaves were collected, chopped, mixed, and 0.200g of fresh leaves were weighed, ground and extracted with 80% acetone, filtered, and diluted to 25mL. Using 80% acetone as a blank, absorbance was measured at 663nm and 645nm using a UV-Vis spectrophotometer. Chlorophyll content was calculated using the Arnon method. The chlorosis recovery rate was calculated using the following formula:

[0091] Yellowing recovery rate = (SPAD value after treatment - SPAD value before treatment) ÷ (SPAD value of healthy controls - SPAD value before treatment) × 100%

[0092] The results are as follows:

[0093] Table 1

[0094] Example 1 42.0 81.4 2.28 Example 2 41.1 77.2 2.21 Example 3 42.8 85.1 2.35 Comparative Example 1 35.6 51.6 1.82 Comparative Example 2 37.8 61.9 1.95 Comparative Example 3 36.2 54.4 1.86 Comparative Example 4 34.8 47.9 1.76 Blank Control 26.1 7.4 1.13 Healthy Control 46.0 — 2.61

[0095] As shown in Table 1, after spraying in Examples 1-3, the SPAD value of areca seedlings recovered to above 41, the yellowing recovery rate reached over 77%, and the chlorophyll content reached over 2.2 mg / g, significantly higher than the comparative examples. This indicates that the foliar fertilizer of this invention can effectively promote the regreening of yellowed leaves. Comparative Example 1 used fast-acting magnesium sulfate heptahydrate instead of modified magnesium-loaded porous slow-release microparticles. Magnesium was rapidly dissolved and lost after spraying, resulting in insufficient magnesium supply in the later stages, and the yellowing recovery rate was only 51.6%. Comparative Example 4 used ordinary potassium humate to prepare magnesium-loaded microparticles, resulting in poor mesoporous structure development and poor magnesium slow-release performance, leading to the lowest yellowing recovery rate of 47.9%. Comparative Example 2 lacked earthworm protease hydrolysed antibacterial peptide powder, reducing the total amount of small molecule peptide nutrients and lacking antibacterial substances, resulting in a significantly lower yellowing recovery rate than the examples. Comparative Example 3 lacked alginate oligosaccharides and carboxymethyl chitosan, resulting in the loss of immune induction and film-forming moisturizing effects, shortening the retention time of nutrients on the leaf surface, and also significantly lower than the examples.

[0096] Experiment 2: Magnesium slow-release performance and foliar retention test.

[0097] Magnesium cumulative release rate test: 0.500 g of each of the modified magnesium-loaded porous sustained-release microparticles prepared in Examples 1-3 and Comparative Example 4 were weighed. The modified magnesium-loaded porous sustained-release microparticles used in Comparative Examples 2 and 3 were the same as those in Example 1, and 0.500 g were weighed in each case. For Comparative Example 1, the same amount of magnesium heptahydrate magnesium sulfate was weighed. All samples were placed in 250 mL Erlenmeyer flasks, 100 mL of deionized water was added, and the flasks were kept at 25 °C. The supernatant was collected on days 7 and 28, filtered through a 0.45 μm microporous membrane, and the magnesium ion concentration was measured at 285.2 nm using an atomic absorption spectrophotometer. The total magnesium content in each sample was determined separately by nitric acid digestion and atomic absorption spectrophotometry. The cumulative magnesium release rate was calculated using the following formula:

[0098] Cumulative magnesium release rate = (Mass of magnesium in the released solution ÷ Total mass of magnesium in the sample) × 100%

[0099] Foliar efficacy test: The foliar fertilizers obtained in Examples 1-3 and Comparative Examples 1-4 were diluted 500 times with deionized water and sprayed evenly on both sides of the leaves of uniformly growing areca palm seedlings in the evening on a sunny day until the leaves were moist but not dripping. Functional leaves were collected on the 7th and 28th days after spraying. After rinsing with deionized water, blanching at 105℃, drying, and pulverizing, 0.500g of each leaf was weighed and digested using the nitric acid-perchloric acid wet digestion method. After volume adjustment, the total magnesium content of the leaves was determined using an atomic absorption spectrophotometer. The results are as follows:

[0100] Table 2

[0101] Example 1 42.5 79.8 2960 2150 Example 2 35.6 73.4 2880 2060 Example 3 39.4 76.5 3050 2280 Comparative Example 1 96.8 98.9 2710 690 Comparative Example 2 42.5 79.8 2890 1980 Comparative Example 3 42.5 79.8 2910 2010 Comparative Example 4 71.3 93.6 2780 1240

[0102] As shown in Table 2, the cumulative magnesium release rate of Examples 1-3 was 35.6%-42.5% over 7 days and 73.4%-79.8% over 28 days, exhibiting typical slow-release characteristics. The magnesium content in the leaves remained above 2000 mg / kg 28 days after spraying, demonstrating a long nutrient retention period. Comparative Example 1 used fast-acting magnesium sulfate heptahydrate, achieving a cumulative release rate of 96.8% over 7 days. However, the magnesium content in the leaves plummeted to 690 mg / kg 28 days after spraying, indicating rapid magnesium dissolution and loss, insufficient supply in the later stages, and poor nutrient retention. Comparative Example 4 used ordinary potassium humate to prepare magnesium-loaded microparticles, which did not form a good mesoporous structure and complex coating layer. The cumulative magnesium release rate was 71.3% over 7 days and 93.6% over 28 days, showing significantly inferior slow-release performance compared to the examples. The magnesium content in the leaves was only 1240 mg / kg 28 days after spraying. The modified magnesium-loaded porous slow-release microparticles used in Comparative Examples 2 and 3 were the same as those in Example 1, and the cumulative magnesium release rate was consistent with that in Example 1. However, due to the overall growth of the plants, the magnesium content in the leaves was slightly lower than that in Example 1 28 days after spraying.

[0103] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A compound foliar fertilizer for areca nut anti-chlorosis, containing fish protein and earthworm protein, characterized in that, The product is composed of the following components by weight: 15-28 parts fish protein hydrolysate peptide powder; 10-20 parts earthworm protein hydrolysate antimicrobial peptide powder; 8-16 parts modified magnesium-loaded porous slow-release microparticles; 5-12 parts alginate oligosaccharide; 3-8 parts carboxymethyl chitosan; 55-150 parts fast-acting chelated trace element premix; 4-10 parts potassium silicate; 2-5 parts compound penetrant; 0.8-2.5 parts γ-aminobutyric acid; and 150-260 parts deionized water.

2. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The fast-acting chelated trace element premix is ​​composed of sugar alcohol magnesium, EDTA-Fe, EDTA-Zn, EDTA-Mn and sodium octaborate tetrahydrate, wherein the mass ratio of Mg, Fe, Zn, Mn and B is 3.0-7.0: 0.8-2.0: 0.3-0.8: 0.2-0.6: 0.1-0.3, respectively.

3. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The preparation method of the modified magnesium-loaded porous sustained-release microparticles includes the following steps: A1 calcium source preparation: After washing and drying the seashells, calcine them at 950-1050℃ for 1.5-3.0h to obtain calcium oxide. Then, treat the calcium oxide and water at 80-90℃ for 30-60min at a mass ratio of 1:5 to 1:8 to prepare a calcium hydroxide suspension. A2 soft template complexation involves dissolving citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate in deionized water to prepare a 3%–8% (w / v) solution. Then, 4%–10% of the theoretical hydroxyapatite mass is added to the calcium hydroxide suspension from step A1. The mixture is stirred at 30–40°C and 200–400 rpm for 40–60 min to allow the humic acid carboxyl groups to react with the Ca2+. 2+ Pre-complexation forms a soft template; A3 coprecipitation: Under conditions of 60–75℃ and pH 10.0–11.0 throughout, 0.3–0.6 mol / L phosphoric acid solution was added dropwise to the A2 system at a Ca / P molar ratio of 1.62–1.70 at a dropping rate of 2–5 mL / min. After the addition was complete, the reaction continued for 2–4 h, and then aged at room temperature for 12–24 h. The solid and liquid were separated and washed until the conductivity of the filtrate was ≤200 μS / cm, and then dried to obtain the precursor. A4 calcination to create pores involves calcining the precursor from step A3 at 350–450°C for 1.5–3.0 h to remove the soft template agent and form a mesoporous structure, thus obtaining mesoporous hydroxyapatite. A5 involves a two-stage negative pressure impregnation and coating process. In the first stage, a magnesium impregnation solution containing magnesium nitrate is prepared, with a metal ion concentration of 0.4–0.8 mol / L. 2%–4% (by mass of mesoporous hydroxyapatite) of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate is added, along with the mesoporous hydroxyapatite from step A4 at a liquid-to-solid ratio of (6–12) mL:1g. Impregnation is carried out at 40–55℃ and a negative pressure of -0.06–-0.09 MPa for 2–5 hours. After restoring to normal pressure, solid-liquid separation is performed, followed by vacuum drying at 40–50℃ until the moisture content is ≤3%, forming a magnesium-rich outer shell precursor. In the second stage, a mixed iron-zinc-manganese impregnation solution containing ferrous sulfate, zinc sulfate, and manganese sulfate is prepared, with a total metal ion concentration of 0.5–1.0 mol / L and a Fe:Zn:Mn molar ratio of (10–18). Add 3%–6% of citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate and 0.2%–0.5% ascorbic acid to the mesoporous hydroxyapatite by mass of 5–9 and add the first-stage precursor at a liquid-solid ratio of (8–15) mL:1g. Impregnate for 2–5 h at 40–55 °C and -0.06–-0.09 MPa negative pressure. After restoring normal pressure, continue stirring for 1–2 h. Separate the solid and liquid, vacuum dry at 40–50 °C until the water content is ≤3%, and air-jet pulverize to D90≤5μm. Finally, disperse the obtained powder in a 1%–3% γ-polyglutamic acid aqueous solution at a solid-liquid ratio of 1:3–1:5, coat at 40–50 °C for 60–90 min, and spray dry to obtain the modified magnesium-loaded porous slow-release microparticles.

4. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 3, characterized in that, The preparation method of the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate includes the following steps: B1 swelling involves dissolving potassium humate from weathered coal in deionized water to prepare a suspension with a mass-volume concentration of 8%–15%, adjusting the pH to 9.0–10.0 with potassium hydroxide, and stirring at 60–70°C for 40–60 minutes to allow it to fully swell, thereby obtaining a potassium humate swollen solution. The potassium humate from the weathered coal has a humic acid content ≥60%, a K2O content ≥8%, and a weight-average molecular weight of 8000–15000 Da. B2 acidification and Fenton-like oxidative depolymerization: Citric acid (4%–10% by dry weight of potassium humate) is added to the swelling solution from step B1 to adjust the pH to 4.0–5.

0. Ferrous sulfate and a 30% hydrogen peroxide solution are then added sequentially, wherein Fe... 2+ The molar ratio of potassium humate to H2O2 is 1:25 to 1:50, the amount of hydrogen peroxide solution is 10% to 20% of the dry weight of potassium humate, and the oxidation and depolymerization is carried out at 55 to 65℃ for 90 to 150 min. B3 is used to terminate and reduce the reaction. The temperature is raised to 85-90℃ and held for 20-30 minutes to decompose the residual hydrogen peroxide. Then, sodium metabisulfite (0.5%-1.5% by dry weight of potassium humate) is added and the reaction is continued for 10-15 minutes. B4 is end-capped and stabilized. The pH is adjusted to 8.0-9.0 with potassium hydroxide. Sodium tripolyphosphate is added at 1%-3% of the dry weight of potassium humate. The reaction is carried out at 50-60℃ for 40-60 min. B5 is dried by spray drying at an inlet air temperature of 160-180℃ and an outlet air temperature of 70-80℃ to obtain the citric acid-hydrogen peroxide synergistic depolymerization modified potassium humate.

5. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The preparation method of the fish protein hydrolysate peptide powder includes the following steps: C1 After homogenizing the fish processing by-products, add water at a material-to-water mass ratio of 1:1 to 1:2, adjust the pH to 8.5 to 9.5, add alkaline protease at 2000 to 4000 U / g substrate protein, and enzymatically hydrolyze at 52 to 56°C for 2.5 to 4.0 h, and inactivate the enzyme at 95°C for 10 min. C2 is cooled to 50℃ and the pH is adjusted to 6.5-7.

0. Papain is added at 1500-3000 U / g and flavor protease is added at 1000-2000 U / g. The enzyme is hydrolyzed at 50-54℃ for 1.5-2.5 h, the enzyme is inactivated at 95℃ for 10 min, and the supernatant is collected by centrifugation at 4000-6000 r / min for 15-20 min. C3 involves passing the supernatant through an ultrafiltration membrane with a molecular weight cutoff of 3000 Da at 0.15–0.25 MPa and 35–45 °C. The permeate is then desalted by nanofiltration and concentrated to 25%–35% solids. 0.5%–1.5% activated carbon and 1%–2% β-cyclodextrin are added, and the mixture is deodorized and debittered at 45–55 °C for 30–40 min. C4 spray drying, with an inlet air temperature of 170-185℃ and an outlet air temperature of 75-85℃, yields the fish protein hydrolysate peptide powder.

6. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The preparation method of the earthworm protease hydrolysate antibacterial peptide powder includes the following steps: D1 Take fresh Eisenia fetidae bodies and add 0.05-0.10 mol / L phosphate buffer solution with pH 6.8-7.2 at a material-to-liquid mass-to-volume ratio of 1:2 to 1:

4. Homogenize the mixture 2-3 times with a colloid mill and autolyze it at 45-50℃ with pH 6.5-7.0 for 6-10 hours. Adjust the pH to 8.0-8.5 with D2, add trypsin at 1500-2500 U / g and alkaline protease at 1500-2500 U / g, hydrolyze at 48-52℃ for 3-5 hours, inactivate the enzyme at 95℃ for 10 minutes, and centrifuge to collect the supernatant. The supernatant of D3 was ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 5000 Da, and 2% to 4% of β-cyclodextrin by weight of solids was added to the permeate for encapsulation and deodorization. D4 spray drying, with an inlet air temperature of 165-180℃ and an outlet air temperature of 70-80℃, yields the earthworm protease hydrolysed antimicrobial peptide powder.

7. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The alginate oligosaccharide has a degree of polymerization of 2 to 8, and the proportion of components with a degree of polymerization of 2 to 8 is ≥80%. It is obtained by enzymatic hydrolysis of alginate with alginate lyase at 40 to 50°C and pH 6.5 to 7.5 for 3 to 6 hours, followed by desalting and drying.

8. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The carboxymethyl chitosan is N,O-carboxymethyl chitosan with a degree of substitution ≥0.85, a degree of deacetylation ≥90%, and a viscosity of 1% aqueous solution at 25°C of 10–50 mPa·s.

9. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The compound penetrant is composed of rhamnolipin, polyether-modified trisiloxane, and propylene glycol.

10. The areca nut anti-chlorosis foliar fertilizer containing compound fish protein and earthworm protein according to claim 1, characterized in that, The mass ratio of rhamnolipin to polyether-modified trisiloxane is 1:1.5 to 1:3, and propylene glycol accounts for 10% to 20% of the mass of the compound penetrant.