A stable fertilizer for preventing and treating peanut rhizome rot and a preparation method thereof

Abstract

This invention relates to the field of fertilizers, specifically to a stable fertilizer for preventing and controlling peanut root and stem rot and its preparation method. The fertilizer comprises, from the inside out, a fertilizer core layer, a nano-microbial metabolite layer, and a microbial protective layer. The stable fertilizer for preventing and controlling peanut root and stem rot provided by this invention utilizes a dual nitrification inhibition system constructed from humic acid-encapsulated inhibitors and *Trichoderma harzianum* metabolites. The two work synergistically to reduce nitrification, improve nitrogen fertilizer utilization, and reduce non-point source pollution.

Description

Technical Field

[0001] This invention relates to the field of fertilizers, specifically to a stable fertilizer for preventing and controlling peanut root and stem rot and its preparation method. Background Technology

[0002] Peanuts are a major oilseed crop in my country, second only to soybeans and rapeseed, and play a vital role in national economic development and food and oil security. Statistics show that in 2023, my country's peanut planting area was approximately 71.97 million mu (about 5.4 million hectares), with a yield of 19.231 million tons, accounting for 49.8% of the total oilseed crop output. However, in recent years, my country's edible oil self-sufficiency rate has been only 34%, and the contradiction between oilseed supply and demand has intensified. To ensure food and oil security and promote agricultural efficiency and farmers' income, improving the yield and quality of peanut kernels has become a key means to solve this problem. Fertilizer application is an important factor affecting peanut yield and quality, but in pursuit of higher yields, farmers often overuse chemical fertilizers. Excessive application of chemical fertilizers stimulates microbial-driven nitrification, which not only reduces nitrogen use efficiency in farmland soil but also increases the economic burden on farmers and causes environmental pollution. Nitrification is the main cause of nitrogen loss from the soil ecosystem, and the leaching of nitrate nitrogen causes groundwater and surface water pollution, while also increasing emissions of N2O, one of the three major greenhouse gases. Existing technologies often employ nitrification inhibitors to suppress the activity of soil nitrifying microorganisms, thereby slowing down nitrification in the soil. These inhibitors include hydrocarbons and their derivatives, sulfur-containing compounds, nitrogen-containing heterocyclic compounds, cyanamides, acetylene (C2H2), 2-chloro-6-trichloromethylpyridine (Nitrapyrin), 3,4-methylpyrazole phosphate (DMPP), and dicyandiamide (DCD). Although nitrification inhibitors can effectively improve fertilizer efficiency and reduce nitrogen loss through leaching and denitrification of nitrate and nitrite nitrogen, existing technologies suffer from limitations such as high cost, unstable efficacy due to inhibitor inactivation, and potential environmental pollution. Peanut root and stem rot is a common fungal disease in peanut fields. The pathogens of peanut root rot include *Fusarium solani*, *Fusarium oxysporum*, *Fusarium rosenbergii*, *Fusarium trifidum*, and *Fusarium moniliforme*. The pathogen of peanut stem rot is *Dispora alopecuroides*. Both diseases are soil-borne and seed-borne. The pathogens mainly overwinter as mycelia or conidia in the soil, diseased plant debris, or seeds, and their strong survival ability makes them sources of infection for the following year. Infection causes plant death, missing seedlings, seed rot, and pod rot, leading to reduced peanut yield and lower quality. Applying pesticides is considered one of the most convenient and efficient methods for controlling peanut root and stem rot. However, excessive pesticide use can cause serious environmental pollution, including soil degradation, water pollution, and air pollution, while also harming human health, leading to acute poisoning and even increasing the risk of cancer. Furthermore, excessive pesticide use can damage ecosystems, cause pests to develop resistance, and reduce biodiversity. Summary of the Invention

[0003] To address the problems of high cost, unstable efficacy, and environmental pollution caused by chemical nitrification inhibitors, which negatively impact the sustainable development of farmland ecosystems, this invention provides a stable fertilizer for controlling peanut root and stem rot and its preparation method. It utilizes a dual nitrification inhibition system composed of humic acid inhibitor encapsulated with inhibitors and Trichoderma chloroticulata metabolites, achieving a stable increase in soil nitrogen use efficiency. Simultaneously, the combination of microbial immobilization microsphere technology further enhances the control effect of peanut root and stem rot.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] In a first aspect, the present invention provides a stable fertilizer for preventing and controlling peanut root and stem rot, wherein the fertilizer comprises, from the inside out, a fertilizer core layer, a nano-microbial metabolite layer, and a microbial protective layer.

[0006] Preferably, the raw materials for the fertilizer core layer, by weight, include:

[0007] The ingredients are: 80-120 parts of humic acid inhibitor capsules, 180-380 parts of urea, 150-340 parts of monoammonium phosphate, 220-320 parts of potassium sulfate, 20-80 parts of calcium nitrate, 6-25 parts of magnesium sulfate, 6-25 parts of sulfur powder, 0.6-1.2 parts of sodium borate, 0.1-0.3 parts of ammonium molybdate, and 100-160 parts of fermented peanut shells.

[0008] Preferably, the humic acid inhibitor capsule comprises humic acid, sodium alginate, maleic anhydride, inhibitor, and curing agent; wherein the mass ratio of humic acid to sodium alginate is 3:1, the mass percentage of inhibitor is 5%-15%, and the curing agent is a CaCl2 solution.

[0009] Preferably, the raw materials for the nano-microbial metabolic layer, by weight, include:

[0010] 20-30 parts of Trichoderma yellow-green fermentation broth, 1-1.5 parts of nano-silica, and 0.02-0.03 parts of sodium polyacrylate.

[0011] Preferably, the particle size of the nano-silica is 20-50 nm.

[0012] Preferably, the raw materials for the microbial protective layer, by weight, include:

[0013] 20-50 parts of microbial solidified microspheres and 1-2.5 parts of adhesive.

[0014] Preferably, the microbial solidified microspheres comprise Trichoderma harzianum fermentation broth, Bacillus subtilis fermentation broth, trehalose, and sodium alginate, wherein the viable cell count of the Trichoderma harzianum fermentation broth is (1×10⁻⁶)⁻¹. 8CFU / g), the viable count of Bacillus subtilis BS-5 fermentation broth was (5×10⁻⁶ CFU / g). 8 CFU / g).

[0015] Preferably, the adhesive is polyvinyl alcohol, and the molecular weight range of polyvinyl alcohol is 0.5K-10K.

[0016] Preferably, the preparation method of the humic acid inhibitor capsule includes the following steps:

[0017] S1: Mix 3g of humic acid with 1g of sodium alginate, add 100mL of deionized water, and stir until completely dissolved under pH=6.5-7.0 conditions to obtain a colloidal solution;

[0018] S2: Add maleic anhydride (MPA) gradually to the colloidal solution. The amount added is 2%-4% of the mass of the colloidal solution. Adjust the pH of the solution to 8.0-10.0, and then stir in the dark for 15-30 hours. After the reaction is completed, place it in a dialysis bag and dialyze it in water. The molecular weight cutoff of the dialysis bag is 15-18 kDa. After dialysis for 5-7 days, vacuum dry to obtain the gel matrix. Prepare the gel matrix solution with deionized water.

[0019] S3: Add the inhibitor to the gel matrix solution, stir evenly, add 20 mL of 0.1 mol / L CaCl2 solution dropwise for cross-linking and curing, react at 23-27℃ for 25-40 min to obtain a gel microsphere suspension;

[0020] S4: Humic acid inhibitor capsules were obtained after spray drying.

[0021] Preferably, the inhibitor includes dicyandiamide (DCD) and / or nitration inhibitor DMPP, and the particle size of the inhibitor powder is 40-60 μm.

[0022] Preferably, the humic acid is one of weathered coal humic acid and lignite humic acid.

[0023] Preferably, the inlet air temperature of the spray dryer is 70-80℃, and the outlet air temperature is 40-45℃.

[0024] Preferably, the diameter of the humic acid inhibitor capsule is 0.5-1.2 mm.

[0025] Preferably, the method for preparing the microbial immobilized microspheres includes the following steps:

[0026] P1: Trichoderma harzianum spore suspension and Bacillus subtilis fermentation broth were mixed in a 2:1 ratio, and 5% trehalose freeze-drying protectant was added to obtain a mixed bacterial solution.

[0027] P2: Mix the mixed bacterial solution with 2wt% sodium alginate solution, spray it into 0.3mol / L CaCl2 solution through an electrostatic atomization device, and react at 23-27℃ for 20-30 min to obtain a microbial solidified microsphere suspension;

[0028] P3: Drying at a temperature below 40°C yields microbial-solidified microspheres.

[0029] Secondly, the present invention provides a method for preparing the stabilized fertilizer, comprising the following steps:

[0030] Step (1): Mix calcium nitrate, magnesium sulfate and sulfur powder evenly to obtain calcium magnesium sulfur complex. Then add urea, monoammonium phosphate, potassium sulfate, decomposed peanut shell powder and humic acid inhibitor capsules and mix evenly. Add polyaspartic acid as a binder and granulate to obtain fertilizer core layer.

[0031] Step (2): Mix sodium alginate solution and chitosan solution, add glycerin and stir until no bubbles are formed to form a film liquid, spray it on the surface of the fertilizer core layer to form a thin film, spray CaCl2 solution, and let it stand to solidify to obtain fertilizer particles pre-coated with biofilm.

[0032] Step (3): Prepare a mixture of nano-silica and sodium polyacrylate to obtain a nano-silica suspension. Immerse the pre-coated biofilm fertilizer particles in the nano-silica suspension, stir, remove and drain naturally to obtain silica-loaded fertilizer particles.

[0033] Step (4): Centrifuge and concentrate the Trichoderma chlorophyllum fermentation broth, add β-cyclodextrin and mix evenly, immerse the silica-loaded fertilizer particles in it, shake, take them out and drain, solidify, and obtain fertilizer particles coated with nano-microbial metabolite layer.

[0034] Step (5): Mix the microbial solidified microspheres with a polyvinyl alcohol solution, spray the mixture onto the surface of the particles to form a microbial coating, and dry until the moisture content of the particles is less than 5%;

[0035] Step (6): Irradiate the surface of the particles with ultraviolet light to kill surface bacteria, and dry at low temperature to obtain the stable fertilizer for preventing peanut root and stem rot.

[0036] Preferably, the ultraviolet lamp has a wavelength of 254nm, a dose of 30mJ / cm², and an irradiation duration of 20-30s.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. The stable fertilizer for preventing peanut root and stem rot provided by this invention uses a dual nitrification inhibition system constructed by encapsulating inhibitors in humic acid material and Trichoderma chloroticum metabolites. The two work synergistically to reduce nitrification, improve nitrogen fertilizer utilization, and reduce non-point source pollution.

[0039] 2. Microbial-solidified microspheres form an outer protective layer on the surface of fertilizer granules. Trichoderma harzianum and Bacillus subtilis not only effectively inhibit the growth of root and stem rot pathogens but also induce plant immune responses, enhancing peanut disease resistance. Furthermore, these functional microorganisms promote peanut root development by secreting plant hormones, thereby increasing peanut yield and quality.

[0040] 3. This invention incorporates a humic acid inhibitor capsule into the core. This capsule, based on the synergistic effect of humic acid and biological inhibitors, is used to improve fertilizer utilization. The capsule uses humic acid and sodium alginate as initial raw materials. First, the hydroxyl groups (-OH) in humic acid and sodium alginate combine with the anhydride groups (-O-CO-O-) of maleic phellodendron anhydride to form a gel matrix. Then, it undergoes a solidification treatment with calcium chloride to obtain a structurally stable three-dimensional network gel structure.

[0041] 4. Maleic pine anhydride is a derivative of rosin. As a ternary crosslinking agent, it connects sodium alginate molecular chains through ester bonds to form a crosslinked three-dimensional network structure. This crosslinking improves the stability and water resistance of the capsule material while retaining the pH sensitivity of sodium alginate, giving the capsule material stronger swelling-shrinkage behavior, thereby achieving a better controlled-release effect. Attached Figure Description

[0042] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0043] Figure 1 The results show the dynamic changes in ammonium nitrogen content in the soil during the later stages of peanut growth treated with fertilizers prepared in Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0045] Trichoderma aureoviride and Trichoderma harzianum were purchased from Ningbo Mingzhou Biotechnology Co., Ltd., and Bacillus subtilis was purchased from Beijing Solarbio Technology Co., Ltd.

[0046] The present invention will be further described below with reference to the following embodiments.

[0047] Example 1

[0048] A stable fertilizer for preventing peanut root and stem rot, the fertilizer comprising, from the inside out, a fertilizer core layer, a nano-microbial metabolite layer, and a microbial protective layer.

[0049] The raw materials for the fertilizer core layer, by weight, include:

[0050] 100 parts of humic acid inhibitor capsules, 180 parts of urea, 300 parts of monoammonium phosphate, 270 parts of potassium sulfate, 30 parts of calcium nitrate, 10 parts of magnesium sulfate, 10 parts of sulfur powder, 0.6 parts of sodium borate, 0.1 parts of ammonium molybdate, and 100 parts of fermented peanut shells.

[0051] The raw materials for the nano-microbial metabolic layer, by weight, include:

[0052] 20 parts of Trichoderma yellow-green fermentation broth, 1 part of nano-silica, and 0.02 parts of sodium polyacrylate.

[0053] The raw materials for the microbial protective layer, by weight, include:

[0054] 20 parts of microbial solidified microspheres and 1 part of polyvinyl alcohol.

[0055] The preparation method of humic acid inhibitor capsules includes:

[0056] S1: Mix 3g of weathered coal humic acid with 1g of sodium alginate, add 100mL of deionized water, and stir until completely dissolved under pH=7.0 conditions to obtain a colloidal solution;

[0057] S2: Maleic pine anhydride (MPA) was gradually added to the colloidal solution at a rate of 3% of the colloidal solution mass. The pH of the solution was adjusted to 9.0, and then stirred in the dark for 25 hours. After the reaction was completed, the solution was placed in a dialysis bag and dialyzed in water. The molecular weight cutoff of the dialysis bag was 16 kDa. After dialysis for 7 days, the solution was vacuum dried to obtain the gel matrix. A 5 wt% gel matrix solution was prepared with deionized water.

[0058] S3: Add the inhibitor DCD with a particle size of 60 μm to the gel matrix solution, stir evenly, add 20 mL of 0.1 mol / L CaCl2 solution dropwise for cross-linking and curing, react at 25 °C for 30 min to obtain a gel microsphere suspension;

[0059] S4: Spray drying was carried out at an inlet air temperature of 75℃ and an outlet air temperature of 40℃ to obtain humic acid inhibitor capsules; the total mass fraction of DCD in the humic acid inhibitor capsules was 10%.

[0060] The preparation methods of microbial immobilized microspheres include:

[0061] P1: The viable bacterial count is 1×10⁻⁶ 8 The CFU / g Trichoderma harzianum spore suspension had a viable count of 5 × 10⁻⁶. 8 CFU / g Bacillus subtilis fermentation broth was mixed in a 2:1 ratio, and 5wt% trehalose was added as a protectant to obtain a mixed bacterial solution.

[0062] P2: Mix the mixed bacterial solution with 2wt% sodium alginate solution evenly, spray it into 0.3mol / L CaCl2 solution through an electrostatic atomization device, and react at 25℃ for 25min to obtain microbial solidified microsphere suspension;

[0063] P3: Dry at 38℃ to obtain microbial solidified microspheres.

[0064] The preparation methods for the stabilized fertilizers used to prevent peanut root and stem rot include:

[0065] Step (1): Mix 30 parts calcium nitrate, 10 parts magnesium sulfate, and 10 parts sulfur powder, then add 180 parts urea, 300 parts monoammonium phosphate, 270 parts potassium sulfate, 100 parts decomposed peanut shell powder, 80 parts humic acid inhibitor capsules, 0.6 parts sodium borate, and 0.1 parts ammonium molybdate and mix evenly. Add 0.5 wt% polyaspartic acid as a binder. The moisture content is 12-14%. Granulate at below 45℃ to obtain the fertilizer core layer.

[0066] Step (2): Mix 2wt% sodium alginate solution and 1wt% chitosan solution, add 0.5wt% glycerol and stir until no bubbles are formed to form a film solution. Spray the film solution onto the surface of the fertilizer core layer to form a thin film. Spray 2% CaCl2 solution and let it stand for 10 minutes to solidify to obtain fertilizer particles pre-coated with biofilm.

[0067] Step (3): Prepare a mixture of 5wt% nano silica and 0.1wt% sodium polyacrylate to obtain a nano silica suspension. Immerse the pre-coated fertilizer particles with biofilm into the nano silica suspension and stir at 40°C for 30 minutes. After removing them, let them drain naturally for 30 minutes to obtain silica-loaded fertilizer particles.

[0068] Step (4): Ferment the cultured Trichoderma chloroticum in PD culture medium for 4 days to obtain a spore concentration of 1×10⁻⁶. 8 CFU / g *Trichoderma huanglvensis* fermentation broth; the fermentation broth was centrifuged at 5000 rpm for 20 min at 4℃, the supernatant was concentrated to 50 g / L, 0.5 wt% β-cyclodextrin was added and mixed evenly, and then silica-loaded fertilizer granules were immersed in the mixture, shaken at room temperature for 1 hour, drained, and solidified at room temperature to obtain fertilizer granules coated with a nano-microbial metabolite layer; previous studies have shown that *Trichoderma huanglvensis* prefers ammonium nitrogen sources and can slow down nitrification to NO3 production. - This process reduces N2O release. It can produce a large number of active secondary metabolites, effectively reducing the abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in the soil, thereby inhibiting the soil nitrification process;

[0069] Step (5): Mix 20 parts of microbial solidified microspheres with 5wt% polyvinyl alcohol (1K) solution and spray the mixture onto the surface of the particles to form a microbial coating;

[0070] Step (6): Irradiate the particle surface with a 254nm wavelength ultraviolet lamp at a concentration of 30mJ / cm. 2 At the specified dosage, irradiation for 20 seconds kills surface bacteria, followed by low-temperature drying to obtain fertilizer.

[0071] Example 2

[0072] A stable fertilizer for preventing peanut root and stem rot, the fertilizer comprising, from the inside out, a fertilizer core layer, a nano-microbial metabolite layer, and a microbial protective layer.

[0073] The raw materials for the fertilizer core layer, by weight, include:

[0074] 100 parts of humic acid inhibitor capsules, 320 parts of urea, 180 parts of monoammonium phosphate, 230 parts of potassium sulfate, 24 parts of calcium nitrate, 8 parts of magnesium sulfate, 8 parts of sulfur powder, 0.8 parts of sodium borate, 0.2 parts of ammonium molybdate, and 100 parts of fermented peanut shells.

[0075] The raw materials for the nano-microbial metabolic layer, by weight, include:

[0076] 25 parts of Trichoderma yellow-green fermentation broth, 1.25 parts of nano-silica, and 0.025 parts of sodium polyacrylate.

[0077] The raw materials for the microbial protective layer, by weight, include:

[0078] 30 parts of microbial solidified microspheres and 1.5 parts of polyvinyl alcohol.

[0079] The preparation method of humic acid inhibitor capsules includes:

[0080] S1: Mix 3g of lignite humic acid with 1g of sodium alginate, add 100mL of deionized water, and stir until completely dissolved under pH=7.0 conditions to obtain a colloidal solution;

[0081] S2: Maleic pine anhydride (MPA) was gradually added to the colloidal solution at a rate of 3% of the colloidal solution mass. The pH of the solution was adjusted to 9.0, and then stirred in the dark for 25 hours. After the reaction was completed, the solution was placed in a dialysis bag and dialyzed in water. The molecular weight cutoff of the dialysis bag was 16 kDa. After dialysis for 7 days, the solution was vacuum dried to obtain the gel matrix. A 5 wt% gel matrix solution was prepared with deionized water.

[0082] S3: Add DMPP with a particle size of 60 μm to the gel matrix solution, stir evenly, add 20 mL of 0.1 mol / L CaCl2 solution dropwise for cross-linking and curing, react at 23℃ for 25 min to obtain a gel microsphere suspension;

[0083] S4: Spray drying was carried out at an inlet air temperature of 70℃ and an outlet air temperature of 40℃ to obtain humic acid inhibitor capsules; the total mass fraction of DMPP in the humic acid inhibitor capsules was 5%.

[0084] The preparation methods of microbial immobilized microspheres include:

[0085] P1: The viable bacterial count is 1×10⁻⁶ 8 The CFU / g Trichoderma harzianum spore suspension had a viable count of 5 × 10⁻⁶. 8 CFU / g Bacillus subtilis fermentation broth was mixed in a 2:1 ratio, and 5% trehalose protectant was added to obtain a mixed bacterial solution;

[0086] P2: Mix the mixed bacterial solution with 2% sodium alginate solution evenly, spray it into 0.3 mol / L CaCl2 solution through an electrostatic atomization device, and react at 27℃ for 20 min to obtain a microbial solidified microsphere suspension;

[0087] P3: Dry at room temperature to obtain microbial solidified microspheres.

[0088] The preparation methods for the stabilized fertilizers used to prevent peanut root and stem rot include:

[0089] Step (1): Mix 30 parts calcium nitrate, 10 parts magnesium sulfate, and 10 parts sulfur powder evenly, then add 200 parts urea, 300 parts monoammonium phosphate, 300 parts potassium sulfate, 100 parts decomposed peanut shell powder, 80 parts humic acid microcapsules, 0.8 parts sodium borate, and 0.1 parts ammonium molybdate and mix evenly. Add 0.5% polyaspartic acid as a binder. The moisture content is 12-14%. Granulate at 45℃ to obtain the fertilizer core layer.

[0090] Step (2): Mix 2% sodium alginate solution and 1% chitosan solution, add 0.5% glycerol and stir until no bubbles are formed to form a film liquid. Spray it on the surface of the fertilizer core layer to form a thin film. Spray 2% CaCl2 solution and let it stand for 10 minutes to solidify to obtain fertilizer particles pre-coated with biofilm.

[0091] Step (3): Prepare a mixture of 5% nano silica and 0.1% sodium polyacrylate to obtain a nano silica suspension. Immerse the pre-coated fertilizer particles with biofilm into the nano silica suspension and stir at 40°C for 30 minutes. After removing them, let them drain naturally for 30 minutes to obtain the silica-loaded fertilizer particles.

[0092] Step (4): Centrifuge 25 portions of Trichoderma chloroticum fermentation broth at 8000 rpm for 20 min at 4℃, take the supernatant and concentrate it to 50 g / L, add 0.5% β-cyclodextrin and mix evenly, immerse the silica-loaded fertilizer particles in it, shake at room temperature for 1 hour, take them out and drain, solidify at room temperature to obtain fertilizer particles coated with nano-microbial metabolite layer;

[0093] Step (5): Mix 30 parts of microbial solidified microspheres with 5% polyvinyl alcohol (1K) and spray the mixture onto the surface of the particles to form a microbial coating;

[0094] Step (6): Irradiate the surface of the particles with a 254nm wavelength ultraviolet lamp for 20s at a dose of 30mJ / cm² to kill surface bacteria, and then dry at low temperature to obtain fertilizer.

[0095] Example 3

[0096] A stable fertilizer for preventing peanut root and stem rot, the fertilizer comprising, from the inside out, a fertilizer core layer, a nano-microbial metabolite layer, and a microbial protective layer.

[0097] The raw materials for the fertilizer core layer, by weight, include:

[0098] 80 parts of humic acid inhibitor capsules, 200 parts of urea, 300 parts of monoammonium phosphate, 300 parts of potassium sulfate, 30 parts of calcium nitrate, 10 parts of magnesium sulfate, 10 parts of sulfur powder, 1 part of sodium borate, 0.1 parts of ammonium molybdate, and 100 parts of fermented peanut shells.

[0099] The raw materials for the nano-microbial metabolic layer, by weight, include:

[0100] 30 parts of Trichoderma yellow-green fermentation broth, 1.5 parts of nano-silica, and 0.03 parts of sodium polyacrylate.

[0101] The raw materials for the microbial protective layer, by weight, include:

[0102] 50 parts of microbial solidified microspheres and 2.5 parts of polyvinyl alcohol.

[0103] The preparation method of humic acid inhibitor capsules includes:

[0104] S1: Mix 3g of weathered coal humic acid with 1g of sodium alginate, add 100mL of deionized water, and stir until completely dissolved under pH=6.5 conditions to obtain a colloidal solution;

[0105] S2: Maleic pine anhydride (MPA) was gradually added to the colloidal solution at a rate of 3% of the colloidal solution mass. The pH of the solution was adjusted to 9.0, and then stirred in the dark for 25 hours. After the reaction was completed, the solution was placed in a dialysis bag and dialyzed in water. The molecular weight cutoff of the dialysis bag was 16 kDa. After dialysis for 7 days, the solution was vacuum dried to obtain the gel matrix. A 5 wt% gel matrix solution was prepared with deionized water.

[0106] S3: Add DMPP and DCD with a particle size of 60μm to the gel matrix solution, stir evenly, add 20mL of 0.1mol / L CaCl2 solution dropwise for cross-linking and curing, react at 27℃ for 30min to obtain a gel microsphere suspension;

[0107] S4: Spray drying was carried out at an inlet air temperature of 75℃ and an outlet air temperature of 40℃ to obtain humic acid inhibitor capsules; the total mass fraction of DMPP and DCD in the humic acid inhibitor capsules was 8%, and the mass ratio of DMPP to DCD was 1:1.

[0108] The preparation methods of microbial immobilized microspheres include:

[0109] P1: The viable bacterial count is 1×10⁻⁶ 8 The CFU / g Trichoderma harzianum spore suspension had a viable count of 5 × 10⁻⁶. 8 CFU / g Bacillus subtilis fermentation broth was mixed in a 2:1 ratio, and 5% trehalose protectant was added to obtain a mixed bacterial solution;

[0110] P2: Mix the mixed bacterial solution with 2% sodium alginate solution evenly, spray it into 0.3 mol / L CaCl2 solution through an electrostatic atomization device, and react at 25℃ for 25 min to obtain a microbial solidified microsphere suspension;

[0111] P3: Dry at room temperature to obtain microbial solidified microspheres.

[0112] The preparation methods for the stabilized fertilizers used to prevent peanut root and stem rot include:

[0113] Step (1): Mix 30 parts calcium nitrate, 10 parts magnesium sulfate, and 10 parts sulfur powder evenly, then add 200 parts urea, 300 parts monoammonium phosphate, 300 parts potassium sulfate, 100 parts decomposed peanut shell powder, 80 parts humic acid microcapsules, 1 part sodium borate, and 0.1 parts ammonium molybdate and mix evenly. Add 0.5% polyaspartic acid as a binder. The moisture content is 12-14%. Granulate at 45℃ to obtain the fertilizer core layer.

[0114] Step (2): Mix 2% sodium alginate solution and 1% chitosan solution, add 0.5% glycerol and stir until no bubbles are formed to form a film liquid. Spray it on the surface of the fertilizer core layer to form a thin film. Spray 2% CaCl2 solution and let it stand for 10 minutes to solidify to obtain fertilizer particles pre-coated with biofilm.

[0115] Step (3): Prepare a mixture of 5% nano silica and 0.1% sodium polyacrylate to obtain a nano silica suspension. Immerse the pre-coated fertilizer particles with biofilm into the nano silica suspension and stir at 40°C for 30 minutes. After removing them, let them drain naturally for 30 minutes to obtain the silica-loaded fertilizer particles.

[0116] Step (4): Centrifuge 30 portions of Trichoderma chloroticum fermentation broth at 4℃ for 20 min at 5000 rpm, take the supernatant and concentrate it to 50 g / L, add 0.5% β-cyclodextrin and mix evenly, immerse the silica-loaded fertilizer particles in it, shake at room temperature for 1 hour, take them out and drain, solidify at room temperature to obtain fertilizer particles coated with nano-microbial metabolite layer;

[0117] Step (5): Mix 50 parts of microbial solidified microspheres with 5% polyvinyl alcohol (1K) and spray the mixture onto the surface of the particles to form a microbial coating;

[0118] Step (6): Irradiate the particle surface with a 254nm wavelength ultraviolet lamp at a concentration of 30mJ / cm. 2 At the specified dosage, irradiation for 20 seconds kills surface bacteria, followed by low-temperature drying to obtain fertilizer.

[0119] Comparative Example 1

[0120] A stable fertilizer for preventing peanut root and stem rot, differing from Example 2 in that the fertilizer consists of a fertilizer core layer and a microbial protective layer from the inside out, without introducing a nano-microbial metabolite layer, and without adding humic acid inhibitor capsules to the fertilizer core layer.

[0121] The raw materials for the fertilizer core layer, by weight, include:

[0122] 320 parts urea, 180 parts monoammonium phosphate, 230 parts potassium sulfate, 24 parts calcium nitrate, 8 parts magnesium sulfate, 8 parts sulfur powder, 0.8 parts sodium borate, 0.2 parts ammonium molybdate, and 100 parts roasted peanut shells.

[0123] Comparative Example 2

[0124] A stable fertilizer for preventing peanut root and stem rot is different from Example 2 in that the preparation method of the humic acid inhibitor capsule in the core layer of the fertilizer is different, while all other aspects are the same as Example 2.

[0125] The preparation method of humic acid inhibitor capsules includes:

[0126] S1: Mix 3g of lignite humic acid with 1g of sodium alginate, add 100mL of deionized water, and stir until completely dissolved under pH=7.0 conditions to obtain a colloidal solution;

[0127] S2: Add DMPP with a particle size of 60μm to the colloidal solution, stir evenly, add 20mL of 0.1mol / L CaCl2 solution dropwise for cross-linking and curing, react at 23℃ for 25min to obtain a gel microsphere suspension;

[0128] S3: Spray drying was carried out at an inlet air temperature of 70℃ and an outlet air temperature of 40℃ to obtain humic acid inhibitor capsules; the total mass fraction of DMPP in the humic acid inhibitor capsules was 5%.

[0129] Comparative Example 3

[0130] Commercially available potassium sulfate compound fertilizer (total nutrients 45%, N:P2O5:K2O ratio 15:15:15).

[0131] Experimental Example

[0132] Experiment location: Zhengyang County, Zhumadian City, Henan Province

[0133] The soil nutrient content was as follows: organic matter 1.2%, available nitrogen 157 mg / kg, available phosphorus (P2O5) 21 mg / kg, available potassium (K2O) 149 mg / kg, soil pH 6.5, and soil type yellow-brown soil.

[0134] Peanut variety tested: Yuanza 9102

[0135] Experimental Design: This experiment consisted of 6 treatments, each replicated 3 times, in a randomized block design. The experimental plot area was 111 m². 2All fertilizers were applied as base fertilizer in a single application at a rate of 50 kg / mu (approximately 667 square meters), broadcast before peanut sowing and then plowed into the soil. Single-seed sowing was adopted, with a plant spacing of 10-11 cm. Ridge cultivation with mulching was used, with two rows per ridge, each ridge being 30 m long and 85 cm wide, for a total of four ridges. Sowing took place on May 8, 2024, and harvesting on September 8, 2024. Other management practices followed conventional field management methods.

[0136] Soil samples were collected during the seedling, pegging, pod-setting, and maturity stages of peanut plants for analysis of soil ammonium nitrogen content. At harvest, 2m³ samples were taken from each plot. 2 Record the number of plants, harvest all pods, dry them, weigh them, and calculate the yield. Count the number of full pods, the number of empty pods, measure the weight of 100 pods, the weight of 100 kernels, and the incidence of root rot and stem rot. The results are as follows: Figure 1 See Table 1.

[0137] Table 1. Peanut yield and root and stem rot incidence in Examples 1-3 and Comparative Examples 1-3

[0138]

[0139] Depend on Figure 1 As can be seen, compared with Comparative Examples 1-3, the ammonium nitrogen content in the soil during the later stages of peanut growth was higher in the fertilizer treatments of Examples 1-3 than in other treatments, indicating that Examples 1-3 had a good inhibitory effect on the process of soil ammonium nitrogen being converted into nitrate nitrogen.

[0140] As shown in Table 1, Examples 1-3 increased peanut yield by 10.4%-14.5%, with root rot incidence at 2%-4% and stem rot incidence at 2%-5%. Their effects on increasing yield and preventing peanut root and stem rot were better than those of Comparative Examples 1-2.

[0141] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A stable fertilizer for preventing and controlling peanut root and stem rot, characterized in that, The fertilizer comprises, from the inside out, a fertilizer core layer, a nano-microbial metabolite layer, and a microbial protective layer; The raw materials for the fertilizer core layer, by weight, include: The ingredients are: 80-120 parts of humic acid inhibitor capsules, 180-380 parts of urea, 150-340 parts of monoammonium phosphate, 220-320 parts of potassium sulfate, 20-80 parts of calcium nitrate, 6-25 parts of magnesium sulfate, 6-25 parts of sulfur powder, 0.6-1.2 parts of sodium borate, 0.1-0.3 parts of ammonium molybdate, and 100-160 parts of fermented peanut shells. The preparation method of the humic acid inhibitor capsule includes the following steps: S1: Mix 3g of humic acid with 1g of sodium alginate, add 100mL of deionized water, and stir until completely dissolved under pH=6.5-7.0 conditions to obtain a colloidal solution; S2: Gradually add maleic anhydride to the colloidal solution, the amount added is 2%-4% of the mass of the colloidal solution, adjust the pH of the solution to 8.0-10.0, and then stir in the dark for 15-30 hours. After the reaction is completed, place it in a dialysis bag and dialyze it in water. The molecular weight cutoff of the dialysis bag is 15-18kDa. After dialysis for 5-7 days, vacuum dry to obtain the gel matrix, and prepare the gel matrix solution with deionized water. S3: Add the inhibitor to the gel matrix solution, stir evenly, add 20 mL of 0.1 mol / L CaCl2 solution dropwise for cross-linking and curing, react at 23-27℃ for 25-40 min to obtain a gel microsphere suspension; S4: Humic acid inhibitor capsules were obtained after spray drying; Of this, inhibitors account for 5%-15% of the total mass. The raw materials for the nano-microbial metabolic layer, by weight, include: 20-30 parts of Trichoderma yellow-green fermentation broth, 1-1.5 parts of nano-silica, and 0.02-0.03 parts of sodium polyacrylate.

2. The stable fertilizer for preventing peanut root and stem rot according to claim 1, characterized in that, The raw materials for the microbial protective layer, by weight, include: 20-50 parts of microbial solidified microspheres and 1-2.5 parts of adhesive.

3. The stable fertilizer for preventing peanut root and stem rot according to claim 2, characterized in that, The microbial solidified microspheres comprise Trichoderma harzianum fermentation broth, Bacillus subtilis fermentation broth, trehalose, and sodium alginate; wherein the viable cell count of the Trichoderma harzianum fermentation broth is 1 × 10⁻⁶. 8 The viable count of Bacillus subtilis fermentation broth was 5 × 10⁻⁶ CFU / g. 8 CFU / g.

4. The stable fertilizer for preventing peanut root and stem rot according to claim 2, characterized in that, The adhesive is polyvinyl alcohol, and the molecular weight range of polyvinyl alcohol is 0.5K-10K.

5. The stable fertilizer for preventing peanut root and stem rot according to claim 1, characterized in that, The inhibitors include dicyandiamide (DCD) and / or nitration inhibitor DMPP, with the inhibitor powder having a particle size of 40-60 μm.

6. The stable fertilizer for preventing peanut root and stem rot according to claim 1, characterized in that, Humic acid is one of the humic acids from weathered coal and lignite.

7. The stable fertilizer for preventing peanut root and stem rot according to claim 2, characterized in that, The preparation method of the microbial immobilized microspheres includes the following steps: P1: Trichoderma harzianum spore suspension and Bacillus subtilis fermentation broth were mixed in a 2:1 ratio, and 5% trehalose freeze-drying protectant was added to obtain a mixed bacterial solution. P2: Mix the mixed bacterial solution with 2wt% sodium alginate solution evenly, spray it into 0.3mol / L CaCl2 solution through an electrostatic atomization device, and react at 23-27℃ for 20-30 min to obtain a microbial solidified microsphere suspension; P3: Drying at a temperature below 40°C yields microbial-solidified microspheres.

8. A method for preparing the stabilized fertilizer according to claim 1, characterized in that, Includes the following steps: Step (1): Mix calcium nitrate, magnesium sulfate and sulfur powder evenly to obtain calcium magnesium sulfur complex. Then add urea, monoammonium phosphate, potassium sulfate, decomposed peanut shell powder and humic acid inhibitor capsules and mix evenly. Add polyaspartic acid as a binder and granulate to obtain fertilizer core layer. Step (2): Mix sodium alginate solution and chitosan solution, add glycerin and stir until no bubbles are formed to form a film liquid, spray it on the surface of the fertilizer core layer to form a thin film, spray CaCl2 solution, and let it stand to solidify to obtain fertilizer particles pre-coated with biofilm. Step (3): Prepare a mixture of nano-silica and sodium polyacrylate to obtain a nano-silica suspension. Immerse the pre-coated biofilm fertilizer particles in the nano-silica suspension, stir, remove and drain naturally to obtain silica-loaded fertilizer particles. Step (4): Centrifuge and concentrate the fermentation broth of Trichoderma chlorophyllum, add β-cyclodextrin and mix evenly, immerse the fertilizer particles loaded with silica into it, shake, take out and drain, solidify, and obtain fertilizer particles coated with nano-microbial metabolite layer. Step (5): Mix the microbial solidified microspheres with a polyvinyl alcohol solution, spray the mixture onto the surface of the particles to form a microbial coating, and dry until the moisture content of the particles is less than 5%; Step (6): Irradiate the surface of the particles with ultraviolet light to kill surface bacteria, and then dry at low temperature to obtain a stable fertilizer for preventing peanut root and stem rot.

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