A value-added water-soluble compound fertilizer and a preparation method and application thereof

Abstract

This invention relates to the field of agricultural technology, and in particular to a value-added water-soluble compound fertilizer, its preparation method, and its application. The raw materials for its preparation include: urea, powdered ammonium sulfate, crystalline monoammonium phosphate, potassium sulfate, biochemical potassium humate, neutral mineral-derived potassium humate, aminobutyric acid, nitrification inhibitor DMPP, citric acid chelate, and polyglutamic acid. The water-soluble fertilizer obtained by this invention is suitable for various fertilization methods such as water-soluble fertigation, drip irrigation, and foliar application in field crops, cash crops, and greenhouse cultivation. Under the background of reducing nitrogen application, it can achieve equivalent or better yields and quality with lower nitrogen application intensity, balancing economic efficiency and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and in particular to a value-added water-soluble compound fertilizer, its preparation method, and its application. Background Technology

[0002] Most existing water-soluble fertilizers are based on mineral nutrients (such as urea, ammonium sulfate, monoammonium phosphate, potassium sulfate, etc.). Although they dissolve quickly and are convenient for irrigation, they generally have the following shortcomings: (1) Low nitrogen utilization rate: After application, ammonium nitrogen is prone to nitrification and denitrification, and nitrate is lost due to irrigation and rainfall; at the same time, ammonia volatilization causes losses, resulting in a short fertilizer effect period and increased environmental risks.

[0003] (2) Single function: Conventional water-soluble fertilizers focus on "nutrient supply" and have limited effect on crop stress resistance, rhizosphere water retention and soil aggregate structure improvement; micronutrients are easily antagonized or precipitated, and their utilization rate is not high.

[0004] (3) Difficult to be compatible with bioactive components: When small molecules (such as aminobutyric acid, GABA) or biomacromolecules (such as polysaccharides, high molecular weight water-retaining agents) with plant physiological regulatory functions are introduced into the formulation, they are often degraded and deactivated due to heat / oxygen / metal ion catalysis; coexistence with strong inorganic salts can easily cause activity decay or decrease the clarity of the solution.

[0005] (4) The storage stability of granular water-soluble fertilizer is poor: granules containing highly hygroscopic components such as humic acid, amino acids, and polyglutamic acid are prone to absorbing moisture, clumping, powdering, and browning during storage; if the raw materials from the fermentation source are not properly processed, microbial reactivation may occur, causing slight gas production, which affects the appearance and applicability of the product.

[0006] (5) Suppressing the fragmentation of nitrogen transformation technology: Although nitrification inhibitors (such as DMPP) can delay nitrification when used alone, they are significantly affected by soil moisture content, porosity and adsorption of organic colloids. Their effective period and stability fluctuate greatly under different soils and irrigation regimes, and they lack structured synergy with organic-polymer matrices.

[0007] Therefore, there is an urgent need for a value-added water-soluble compound fertilizer technology that integrates nutrient supply, high nitrogen efficiency, stress resistance and growth promotion, water retention and soil improvement, stable granulation, and good storage properties. This technology should achieve functional and structural synergy without sacrificing water solubility and process feasibility, and solve long-standing problems such as easy deactivation of active ingredients, easy granule agglomeration, and easy nitrogen loss. Summary of the Invention

[0008] This invention provides a method for preparing a value-added water-soluble compound fertilizer. The fertilizer combines the functions of rapid nutrient supply, high nitrogen efficiency, activity regulation, stress resistance and growth promotion, and storage stability. It is produced by fermenting soybeans with GABA and polysaccharides, polyglutamic acid, biochemical / mineral potassium humate, and DMPP, and then granulating them in synergy with various water-soluble mineral nutrients. This method solves the problems of existing water-soluble fertilizers, such as single function, serious nitrogen loss, unstable active ingredients, and easy clumping during storage.

[0009] To solve the above technical problems, the present invention provides a method for preparing a value-added water-soluble compound fertilizer, the steps of which are as follows: (1) The complexing agent and 1,2-dimethylpropylphosphonic acid were mixed to obtain pretreated product 1; (2) Ferment soybeans to obtain fermented product; mix the fermented product with citric acid chelate salt and neutral mineral potassium humate evenly to obtain premix 1; (3) Mix urea and potassium sulfate evenly to obtain premix 2; (4) Mix ammonium sulfate and monoammonium phosphate, add the pretreated material 1, premix 1 and premix 2 obtained in the above steps; then granulate to obtain the value-added water-soluble compound fertilizer.

[0010] In one embodiment of the present invention, in step (1), the complexing agent is polyglutamic acid.

[0011] As one embodiment of the present invention, the detailed steps of step (1) are as follows: 1) PGA is dissolved in deionized water to prepare a PGA solution; 2) Dissolve DMPP in a small amount of 20 v / v% alcohol-water to form a pre-solution, then pour it into the PGA solution. The resulting PGA-DMPP solution has a solid content of 4-6%. 3) Prepare a 1.0 w / v% CaCl2·2H2O aqueous solution and maintain the temperature at 20–25℃; 4) PGA-DMPP solution is continuously atomized and dripped into CaCl2·2H2O aqueous solution through a nozzle with a diameter of 80-200 μm, a pump speed of 0.5-5 mL / min, a nozzle distance of 5-20 cm from the liquid surface, and stirring at 50-150 rpm. 5) Solidify in CaCl2·2H2O aqueous solution for 1–5 min; then collect microspheres using a filter with a mesh size of 40–200 µm; immediately rinse once with deionized water and then send the wet microspheres into a fluidized bed for vacuum dehydration and drying, with the temperature controlled at ≤50℃, and gradually reduce the water content to ≤0.3%.

[0012] In one embodiment of the present invention, the concentration of the PGA solution is 0.5–3 w / v.

[0013] As one embodiment of the present invention, the detailed steps of step (2) are as follows: 1) Soak soybeans at a water-to-soybean mass ratio of 3:1 (v / w) at room temperature for 8–24 hours, changing the water every 6 hours, and changing the water again in the last 6 hours, adding 0.05 wt% CaCl2. 2) Spread the soaked soybeans evenly on the sprouting cloth, keeping the thickness ≤5cm. Keep them at a temperature of 25-30℃, relative humidity of 85-95%, and in the dark for 24-48 hours, spraying 5ml of water at the same temperature every 12 hours. 3) Put the sprouted soybeans into a grinder, add deionized water, and grind them into a paste at a solid-liquid ratio of 1:4 (w / v); 4) Transfer the pulp to the fermentation tank, adjust the pH to 4.8–5.0, and maintain the temperature at 35℃; add: Glucose 10–30 g / L, pyridoxal 0.05–0.1 g / L, yeast extract 1–5 g / L, citrate-sodium citrate buffer 1–5 g / L, humic acid powder 1–5 g / L, seed culture 5–10% (v / v); ensure uniform suspension at 50–200 rpm; fermentation conditions: 32–35℃, pH maintained at 4.5–5.2, fermentation time: 24–72 h; after fermentation, heat the fermentation broth to 70–75℃ for 10–15 min, then cool to room temperature. 5) Centrifuge to remove solid residue, take the supernatant, and vacuum concentrate to a solid content of 20-40%; adjust the pH of the concentrated fermentation broth to 5.8, slowly add citric acid chelate salt to the concentrated fermentation broth, and stir for 10-30 minutes; then slowly add neutral mineral potassium humate while stirring; adjust the total solid content to 20-40% to obtain premix 1.

[0014] In one embodiment of the present invention, in step 4), the seed solution is: Lactobacillus short-lived seed solution and Saccharomyces cerevisiae seed solution; the bacterial cell concentration of the seed solution is (1-2). 10 8 CFU / mL.

[0015] In one embodiment of the present invention, the mass ratio of *Lactobacillus shortiflora* to *Saccharomyces cerevisiae* is 2:1.

[0016] A second aspect of the present invention provides a value-added water-soluble compound fertilizer, which is prepared by the method for preparing the value-added water-soluble compound fertilizer.

[0017] As one embodiment of the present invention, the raw materials for preparing the value-added water-soluble compound fertilizer include: urea, powdered ammonium sulfate, crystalline monoammonium phosphate, potassium sulfate, biochemical potassium humate, neutral mineral potassium humate, aminobutyric acid, nitrification inhibitor dmpp, citric acid chelate, and polyglutamic acid.

[0018] As one embodiment of the present invention, the aforementioned value-added water-soluble compound fertilizer is applied to crop cultivation.

[0019] By adopting the above technical solution, the present invention has the following beneficial effects: The value-added water-soluble compound fertilizer provided by this invention uses the GABA-rich component obtained from soybean fermentation as the core, combined with its associated extracellular polysaccharides and polyglutamic acid to construct a hydrophilic colloidal structure. This structure forms a multi-point complex / hydrogen bond interpenetrating structure with biochemical potassium fulvate and neutral mineral potassium fulvate. In the soil in which it is applied, it can form a "water-retaining and pesticide-carrying" function, buffer salt osmotic pressure, and facilitate root absorption.

[0020] At the same time, it provides a physical adsorption and open shielding environment for DMPP, slowing down its migration and deactivation, making nitration inhibition more persistent and uniform; the citric acid chelate salt stabilizes the valence state of trace elements, reduces precipitation and antagonism, and improves the clarity of the formulation and the bioavailability of trace elements.

[0021] The enzyme-inhibiting effect of DMPP, in synergy with the colloidal network of fulvic acid / polyglutamic acid, delays the conversion of ammonium nitrogen to nitrate nitrogen and weakens its rapid migration with the aqueous phase. Compared with systems using only DMPP, the spatial fixation and slow release of DMPP in this invention are superior, making it suitable for high-frequency water-soluble fertilizer application scenarios such as drip irrigation / fertigation, resulting in a longer ammonium retention period and a reduced risk of nitrate leaching.

[0022] Simultaneously employing wet granulation and low-temperature drying processes, the final moisture content of the granules is controlled below 8%, significantly inhibiting hygroscopic bridging. This is particularly effective for highly hygroscopic formulations containing fulvic acid / polyglutamic acid, balancing water solubility and strength.

[0023] Fulvic acid and polyglutamic acid enhance the aggregate structure and cation exchange capacity of the topsoil. Combined with the physiological regulatory effect of GABA, this results in more developed root systems and enhanced stress resistance. This comprehensive effect is particularly evident in sandy or secondary compacted soils.

[0024] The water-soluble fertilizer obtained by this invention is applicable to various fertilization methods such as water-soluble fertigation, drip irrigation, and foliar application in field, cash crops, and facility cultivation. Under the background of reducing nitrogen application, it can achieve equivalent or better yield and quality with lower nitrogen application intensity, taking into account both economic efficiency and environmental friendliness. Detailed Implementation

[0025] The present invention will be further explained below with reference to specific embodiments.

[0026] This invention provides a method for preparing a value-added water-soluble compound fertilizer, comprising the following steps: (1) The complexing agent and 1,2-dimethylpropylphosphonic acid were mixed to obtain pretreated product 1; (2) Ferment soybeans to obtain fermented product; mix the fermented product with citric acid chelate salt and neutral mineral potassium humate evenly to obtain premix 1; (3) Mix urea and potassium sulfate evenly to obtain premix 2; (4) Mix ammonium sulfate and monoammonium phosphate, add the pretreated material 1, premix 1 and premix 2 obtained in the above steps; then granulate to obtain the value-added water-soluble compound fertilizer.

[0027] Step (1) The detailed steps of step (1) are as follows: 1) PGA is dissolved in deionized water to prepare a 0.5-3 w / v% PGA solution; 2) Dissolve DMPP in a small amount of 20 v / v% alcohol-water to form a pre-solution, then pour it into the PGA solution. The resulting PGA-DMPP solution has a solid content of 4-6%. 3) Prepare a 1.0 w / v% CaCl2·2H2O aqueous solution and maintain the temperature at 20–25℃; 4) PGA-DMPP solution is continuously atomized and dripped into CaCl2·2H2O aqueous solution through a nozzle with a diameter of 80-200 μm, a pump speed of 0.5-5 mL / min, a nozzle distance of 5-20 cm from the liquid surface, and stirring at 50-150 rpm. 5) Solidify in CaCl2·2H2O aqueous solution for 1–5 min; then collect microspheres using a filter screen with a pore size of 40–200 µm; immediately rinse the microspheres once with deionized water and then send the wet microspheres into a fluidized bed for vacuum dehydration and drying, with the temperature controlled at ≤50℃, and gradually reduce the water content to ≤0.3%.

[0028] Since polyglutamic acid (PGA) is a high molecular weight polypeptide, when the concentration is too low (e.g., below 0.5%), its water retention, film formation, and chelation effects are insufficient, and it cannot play a role in protecting DMPP and granulation adhesion. When the concentration is too high (e.g., above 3%), it will significantly increase the viscosity of the solution, resulting in difficulty in stirring, poor uniformity, and problems such as sticking to the wall and difficulty in granulation when spray drying or mixing with powder.

[0029] To minimize activity loss during the drying process after encapsulation and to ensure the structural stability of the microspheres formed from droplets later, the concentration of the PGA solution is preferably 2.5 w / v.

[0030] Considering that DMPP phosphate derivatives may experience local supersaturation or trace hydrolysis during preparation, they are pre-prepared in alcohol and water to avoid later crystallization and clogging at the nozzle. The preferred PGA-DMPP solution has a solid content of 4.5%.

[0031] In addition, the negatively charged carboxyl group of PGA can react with Ca.2+ Through electrostatic and coordination cross-linking of ions, Ca gels into spheres. 2+ Too low a concentration leads to a thin gel layer, slow curing, and easy collapse of the spheres; too high a concentration causes the surface to instantly "skin-like," forming a dense outer shell while the interior is not fully cross-linked, resulting in hollow spheres or cracks. The inventors discovered that preparing a CaCl2·2H2O aqueous solution and controlling the concentration at 1.0 w / v% can achieve the formation of a uniform, dense gel skin within a short time (1-5 min) after the droplets are introduced into the liquid, but without preventing the core from being unable to cross-link; at the same time, combined with the nozzle diameter, pump speed, and nozzle distance from the liquid surface, a concentration of 1.0 w / v% facilitates the control of the microsphere single-pore yield and size distribution.

[0032] Step (2) The detailed steps of step (2) are as follows: 1) Soak soybeans at a water:bean mass ratio of 3:1 (v / w) at room temperature for 8-24 hours, changing the water every 6 hours, and changing the water again in the last 6 hours, adding 0.05wt% CaCl2. 2) Spread the soaked soybeans evenly on the sprouting cloth, with a thickness of ≤5cm. Keep them in the dark at a temperature of 25-30℃ and a relative humidity of 85-95% for 24-48 hours, spraying 5ml of water at the same temperature every 12 hours. 3) Put the sprouted soybeans into a grinder, add deionized water, and grind them into a paste at a solid-liquid ratio of 1:4 (w / v); 4) Transfer the pulp to the fermentation tank, adjust the pH to 4.8–5.0, and maintain the temperature at 35℃; add: Glucose 10–30 g / L, pyridoxal 0.05–0.1 g / L, yeast extract 1–5 g / L, citrate-sodium citrate buffer 1–5 g / L, humic acid powder 1–5 g / L, seed culture 5–10% (v / v); ensure uniform suspension at 50–200 rpm; fermentation conditions: 32–35℃, pH maintained at 4.5–5.2, fermentation time: 24–72 h; after fermentation, heat the fermentation broth to 70–75℃ for 10–15 min, then cool to room temperature. 5) Centrifuge to remove solid residue, take the supernatant, and vacuum concentrate to a solid content of 20-40%; adjust the pH of the concentrated fermentation broth to 5.8, slowly add citric acid chelate salt to the concentrated fermentation broth, and stir for 10-30 minutes; then slowly add neutral mineral potassium humate while stirring; adjust the total solid content to 20-40% to obtain premix 1.

[0033] In one embodiment of the present invention, in step 4), the seed solution is: *Lactobacillus brevis* seed solution and *Saccharomyces cerevisiae* seed solution; the cell concentrations of the *Lactobacillus brevis* seed solution and the *Saccharomyces cerevisiae* seed solution are (1-2) × 10⁻⁶, respectively. 8CFU / mL; and the mass ratio of the *Lactobacillus short-lived* seed culture to the *Saccharomyces cerevisiae* seed culture is 2:1.

[0034] In this invention, considering the storage and stability of the later products, the slurry in step 3) is first cooked (cooked at 95°C for 5-10 minutes) before entering the fermentation tank, so that the granules are easier to form in the later stage and less likely to cause pH fluctuations and granule deterioration.

[0035] Step (3) The detailed steps of step (3) are as follows: Powdered urea is ground to 60-120 mesh with a moisture content of less than 0.3% to avoid clumping; potassium sulfate is also pulverized to 80-150 mesh to ensure that its particle size is close to that of urea; then the two are mixed in a V-type mixer for 8 minutes at a speed of 15 rpm to obtain premix 2.

[0036] Step (4) Ammonium sulfate and crystalline monoammonium phosphate are mixed and added to pretreated material 1, premix 1, and premix 2 obtained in the above steps; then granulation is performed to obtain the value-added water-soluble compound fertilizer.

[0037] The detailed steps are as follows: (001) Material status Pretreatment material 1 should be kept with a moisture content of ≤0.3% and a particle size of 80~200 mesh. Premix 1 maintains a solid content of 20-40%; Premix 2 should maintain a moisture content of ≤0.3% and a particle size of 80~150 mesh.

[0038] Equipment: High shear granulator; Environmental conditions: Relative humidity in the granulation room ≤50%, material and equipment temperature 20~30℃.

[0039] (002) Add ammonium sulfate and monoammonium phosphate to a high shear granulator, and then mix thoroughly and evenly for 3-5 minutes at 120-180 rpm for the main impeller and 800-1200 rpm for the cutter; then add premix 2 and pretreated material 1 in sequence and dry mix at the same speed for 2-4 minutes. (003) Then, the premix 1 is first adjusted with deionized water to a solid content of 20-25% and the viscosity is controlled at 300-1000 mPa·s. Then, the liquid is sprayed with an online spray gun. The initial speed of the main propeller is 160-260 rpm, which can be reduced to 140-200 rpm as the particles grow. The cutter is 900-1500 rpm to break up large agglomerates and keep the particle size distribution narrow until the particle d50 reaches 2-3 mm.

[0040] Among them: spray parameters: nozzle: 0.7~1.0mm, spray rate: 0.5~2.0mL / min·kg dry powder, droplet: medium atomization (1.5~2.5bar); internal temperature: ≤35~40℃.

[0041] (004) The fertilizer granules are then dried in a fluidized bed to ensure that the moisture content is less than 7 wt%. After exiting the bed, 0.3 w / w% diatomaceous earth is sprayed on the granules (by uniformly spreading them on a low-speed drum at 6-10 rpm for 2-3 minutes). The granules are then cooled, homogenized, and packaged. The homogenization step involves placing the finished product in a chamber and letting it stand for 20-30 minutes until the moisture content and temperature are uniform.

[0042] In this invention, the premix contains GABA fermentation broth and humic acid, which have high viscosity and are prone to absorbing moisture and clumping. The cutting speed of 800~1200rpm is significantly higher than that of conventional inorganic fertilizer granulation (generally 500~800rpm), which can ensure that the nuclei are formed uniformly and not too large.

[0043] PGA is a polycarboxylic acid material and Ca 2+ The formation of ionic cross-linked gels can create diffusion resistance within the colloidal network of neutral and hydrophobic DMPP, significantly reducing the migration and inactivation of DMPP in high ionic strength water-soluble fertilizers.

[0044] DMPP was immobilized in PGA-Ca 2+ Within the gel microdomain, diffusion is restricted, slowing its migration in soil pores and the aqueous phase, resulting in a longer inhibition period and more uniform distribution; it is also less likely to be deactivated by adsorption of organic colloids / alkaline sites than untreated DMPP.

[0045] GABA, different fulvic acids, and citric acid chelates can form a multi-point complex / hydrogen bond interpenetrating network, which takes into account the stability of metal ions, film formation and adhesion, and water retention. This allows the particle formation and the post-application rhizosphere "water retention-drug loading" microenvironment to benefit simultaneously, which is a synergistic effect of multi-mechanism coupling (complexation, hydrogen bonding, colloidal adhesion).

[0046] Meanwhile, this invention first chelates and then adds mineral-derived fulvic acid, avoiding cross-precipitation of metal ions with humic / phosphate ions under a weakly acidic buffer of pH 5.5~6.0; thus achieving a transparent or low-turbidity water-soluble system.

[0047] In this invention, the citric acid chelate salt contains 4wt% Fe, 1.5wt% Cu, 15wt% Mn, 4wt% Mg, 2wt% B, and 0.1wt% Mo.

[0048] The following will provide a detailed description with reference to specific embodiments.

[0049] Example 1 This embodiment provides a value-added water-soluble compound fertilizer, the raw materials of which include: 92 parts urea, 66.84 parts powdered ammonium sulfate, 73 parts crystalline monoammonium phosphate, 171.6 parts potassium sulfate, 10 parts biochemical potassium humate, 5 parts neutral mineral potassium humate, 5 parts aminobutyric acid, 0.8 parts nitrification inhibitor dmpp, 10 parts citric acid chelate, and 5 parts polyglutamic acid.

[0050] This embodiment also provides a method for preparing a value-added water-soluble compound fertilizer, the preparation steps of which are as follows: Step (1): 1) PGA is dissolved in deionized water to prepare a 2.5 w / v% PGA solution; 2) Dissolve DMPP in a small amount of 20 v / v% alcohol-water to form a pre-solution, then pour it into the PGA solution. The resulting PGA-DMPP solution has a solid content of 4.5%. 3) Prepare a 1.0 w / v% CaCl2·2H2O aqueous solution and maintain the temperature at 25℃; 4) PGA-DMPP solution is continuously atomized and dripped into CaCl2·2H2O aqueous solution through a nozzle with a diameter of 120μm, a pump speed of 2mL / min, a nozzle distance of 10cm from the liquid surface, and stirring at 100rpm. 5) Solidify in CaCl2·2H2O aqueous solution for 4 min; then collect microspheres using a filter with a pore size of 80-150µm; immediately rinse once with deionized water and then send the wet bulbs into a fluidized bed for vacuum dehydration and drying, with the temperature controlled at ≤50℃, and gradually reduce the water content to ≤0.3%.

[0051] Step (2) The detailed steps of step (2) are as follows: 1) Soak soybeans at a water:bean mass ratio of 3:1 (v / w) at room temperature for 18 hours, changing the water every 6 hours, and changing the water again in the last 6 hours, adding 0.05wt% CaCl2. 2) Spread the soaked soybeans evenly on the sprouting cloth, with a thickness of ≤5cm. Keep them in the dark at a temperature of 25℃ and a relative humidity of 90% for 36 hours, spraying 5ml of water at the same temperature every 12 hours. 3) Put the sprouted soybeans into a grinder, add deionized water, with a solid-liquid ratio of 1:4 (w / v), grind into a paste, cook at 95℃ for 8 minutes and then cool. 4) Transfer the cooked pulp to a fermentation tank, adjust the pH to 4.8, and maintain the temperature at 35℃; add: Glucose 20 g / L, pyridoxal 0.1 g / L, yeast extract 2 g / L, citrate-sodium citrate buffer 2 g / L, humic acid powder 3 g / L, seed culture 9% (v / v); ensure uniform suspension at 100 rpm; fermentation conditions: 35℃, pH maintained at 4.5–5.2, fermentation time: 36 h; after fermentation, heat the fermentation broth to 75℃ for 10 min, then cool to room temperature. 5) Centrifuge to remove solid residue, take the supernatant, and vacuum concentrate to 30% solid content; adjust the pH of the concentrated fermentation broth to 5.8, slowly add citric acid chelate salt to the concentrated fermentation broth, and stir for 20 minutes; then slowly add neutral mineral potassium humate while stirring; adjust the total solid content to 30% and the pH to 5.8 to obtain premix 1.

[0052] The seed cultures were: *Lactobacillus brevis* seed culture and *Saccharomyces cerevisiae* seed culture; the cell concentrations of the *Lactobacillus brevis* seed culture and the *Saccharomyces cerevisiae* seed culture were 1.5 × 10⁻⁶ cells / mL, respectively. 8 CFU / mL; and the mass ratio of the *Lactobacillus short-lived* seed culture to the *Saccharomyces cerevisiae* seed culture is 2:1.

[0053] Step (3) Powdered urea was ground to 100 mesh with a moisture content of less than 0.3%; potassium sulfate was also pulverized to 120 mesh. The two mixtures were then mixed in a V-type mixer for 8 minutes at a speed of 15 rpm to obtain premix 2.

[0054] Step (4) The detailed steps are as follows: (001) Material status Pretreatment material 1 should be kept with a moisture content of ≤0.3% and a recommended particle size of 120 mesh; Premix 1 maintains a solid content of 20-40%; Premix 2 should maintain a moisture content of ≤0.3% and a particle size of 100~150 mesh.

[0055] Equipment: High shear granulator; Environmental conditions: Relative humidity in the granulation room ≤50%, material and equipment temperature 25℃.

[0056] (002) Add ammonium sulfate and monoammonium phosphate to a high shear granulator, and then mix thoroughly and evenly for 3 minutes at 150 rpm for the main impeller and 1000 rpm for the cutter; then add premix 2 and pretreated material 1 in sequence and dry mix at the same speed for 3 minutes. (003) Then the premix 1 is first controlled with deionized water to achieve a viscosity of 600 mPa·s; then it is sprayed with an online spray gun. The initial speed of the main propeller is 200 rpm, which can be reduced to 180 rpm as the particles grow. The cutter is 1200 rpm to break up large agglomerates and maintain a narrow particle size distribution until the particle d50 reaches 2.5 mm.

[0057] Among them: spray parameters: nozzle: 0.8mm, spray rate: 1.0mL / min·kg dry powder, droplet: medium atomization (pressure 2.0bar); internal temperature of the vessel is less than 38℃.

[0058] (004) The fertilizer granules were then dried in a fluidized bed to ensure that the moisture content was less than 6 wt%. After exiting the fluidized bed, 0.3 w / w% diatomaceous earth was sprayed on the granules (method: uniformly spread on a roller at low speed of 8 rpm for 2 min), followed by cooling, homogenization, and packaging. The homogenization step refers to placing the finished product in a chamber and letting it stand for 25 min until the moisture content and temperature are uniform.

[0059] Example 2 The difference between this embodiment and Embodiment 1 is that step (1) is changed to PGA concentration of 0.5 w / v% and PGA-DMPP solution solid content of 3.5%.

[0060] Example 3 The difference between this embodiment and Example 1 is that step (1) is changed to PGA concentration of 3.0 w / v% and PGA-DMPP solution solid content of 6%.

[0061] Example 4 The only difference between this embodiment and Example 1 is that the CaCl2 solution concentration is 0.3 w / v, and the curing time is extended to 8 min.

[0062] Example 5 The only difference between this embodiment and Embodiment 1 is that the CaCl2 solution concentration is 2.0 w / v%, and the curing time is shortened to 2 min.

[0063] Example 6 The difference between this embodiment and embodiment 1 is only that step 5) in step (2) is: centrifuge to remove solid residue, take the supernatant, and vacuum concentrate to a solid content of 30%; adjust the pH of the concentrated fermentation liquid to 5.8, slowly add neutral mineral potassium humate to the concentrated fermentation liquid, and stir for 20 minutes; then slowly add citric acid chelate salt under stirring; adjust the total solid content to 30% and the pH to 5.8 to obtain premix 1.

[0064] Example 7 The only difference between this embodiment and Embodiment 1 is that the spraying rate is adjusted to 3.0 mL / min·kg.

[0065] Example 8 (Diatomaceous earth-free anti-caking) The difference between this embodiment and Embodiment 1 is that step (4) (004) is as follows: the fertilizer granules are then dried in a fluidized bed to ensure that the moisture content is less than 6 wt%; followed by cooling, homogenization, and packaging. The homogenization step refers to placing the finished product in a silo and letting it stand for 25 minutes until the moisture content and temperature are uniform.

[0066] Comparative Example 1 The difference between this embodiment and embodiment 1 is that step (1) is: PGA and DMPP are directly mixed, and the remaining steps are the same as in embodiment 1.

[0067] Comparative Example 2 The difference between this embodiment and embodiment 1 is that in step (2), the citric acid chelate and fulvic acid are added at once. Specifically, "after the fermentation broth is concentrated to 30% solid content, the citric acid chelate and potassium fulvic acid are added at once and stirred for 40 minutes, and the pH is adjusted to 5.8." The rest is the same as in embodiment 1.

[0068] Performance testing methods Test 1: Storage Stability Test The sample was stored at 40℃ and 75%RH for 30 days, and the agglomeration rate was measured (gravimetric method). Specific steps: 1.1 Pre-inspection: Gently pour the sample onto a 2.00mm sieve and observe whether there are any large pieces (>10mm) visible to the naked eye. If so, record a photo.

[0069] 1.2 Standard sieving: Load a 2.00mm sieve into a mechanical sieve separator and run it at 60 rpm for 2.0 min. If the sample contains a lot of powder, a receiving tray can be added under the sieve and covered with a polytetrafluoroethylene film to prevent sticking.

[0070] 1.3 Secondary dissociation verification: For the agglomerates still remaining on the 2.00mm sieve, a standardized light pressure was used to attempt dissociation. Hold a 100g weight and press it once with a force of about 10N on a glass plate using a 20mm diameter flat-headed pressure block; those that can be separated and pass through a 2.00mm sieve 100% are not considered as agglomerates; Those that remain on the 2.00mm sieve are counted as clumps (Mcake).

[0071] 1.4 Weighing: The particles and powder that pass through the sieve are combined and weighed, and recorded as Mpass; Weigh the remaining hardened lumps on the sieve and record them as Mcake; Verification: The mass conservation deviation of the sum of Mpass and Mcake from M0 is ≤0.5g.

[0072] Clumping rate = Mcake / M0 100%.

[0073] Aggregates that are difficult to disintegrate under mild mechanical force are defined as clumps. Three parallel mean and standard deviation (Mean ± SD) values ​​were taken for each sample.

[0074] Table 1 Test Results of Test 1

[0075] Test 2: Sustained-release performance test Evaluation of the NH4 content of the prepared granular water-soluble compound fertilizer in an aqueous phase at 25℃ + The release behavior of ammonium nitrogen and the dissolution / release kinetics of DMPP (nitration inhibitor) were used to obtain the cumulative release rate curve over time and to calculate T. 50 / T 80 Indicators such as these.

[0076] Ratio: 1.000g sample / 100.0mL deionized water (V0=100.0mL) Sample preparation: Weigh 1.0000±0.0005g (accurate to 0.001g) of the uniformly mixed finished fertilizer and place it in a 250mL Erlenmeyer flask with a cap. Perform three parallel tests.

[0077] Add solvent: Add 100.00 mL of 25.0℃ deionized water, immediately cover and shake gently for 5 seconds.

[0078] Place in a shaking chamber: Place the sample bottle in a shaker (100 rpm) and start timing (t=0 is 0 min after adding water).

[0079] Measurement: NH4 + Both DMPP and DMPP were determined by ion chromatography (IC). Initial frequent sampling to capture rapid release: 0.5h, 1h, 2h, 4h, 8h, 24h; later extended sampling to capture sustained release: 48h, 72h, 120h (5d), 168h (7d), 336h (14d), 504h (21d), 720h (30d).

[0080] The sampling endpoint can be shortened or extended depending on the target release window (e.g., if T is expected). 80 (Approximately 14 days, with a focus on days 0-21). Each sample should be taken in 5.0 mL volume.

[0081] A.NH4 + (Cation determination) Column type: Strongly acidic cation exchange column Mobile phase: 10 mM methanesulfonic acid Flow rate: 0.8 mL / min Testing: Conductivity testing Injection volume: 30µL Column temperature: 30℃ Calibration range: NH4 + : 0.1, 0.5, 1, 2, 5, 10, 20 mg / L (at least 5 linearity points) B. DMPP (phosphate esters / phosphonates, anion IC assay can be attempted) Column type: Strong anion exchange column (for organic acids / phosphates / phosphonates) Mobile phase: 10mM KOH Flow rate: 0.8 mL / min Detection: Suppressed conductivity detection Injection volume: 30µL Column temperature: 30℃ Calibration range: DMPP 0.01, 0.05, 0.1, 0.5, 1.0, 5.0 mg / L (set according to the actual content range) For each analytical batch, an external standard curve (at least 5 points) should be prepared, requiring R... 2 ≥0.995.

[0082] Table 2. DMPP sustained-release period (T80, days)

[0083] Test 3: Activity Retention Rate Samples were taken after 30 days of storage, and the GABA content (HPLC) and fulvic acid activity (UV spectrophotometry) were measured.

[0084] 3.1 Weigh approximately 0.5000g of finely powdered granular sample (accuracy 0.0001g) and place it in a 15mL centrifuge tube.

[0085] 3.2 Add 10.00 mL of 0.1 M HCl, sonicate for 15 min, and promote dissolution at 25 °C.

[0086] 3.3 Centrifugation: 12000 rpm, 10 min; collect the supernatant and filter it through a 0.22 µm filter membrane.

[0087] 3.4 Dilute to an appropriate range based on the estimated concentration (so that the peak area after derivatization falls within the range of the standard curve).

[0088] 3.5 Derivatization: Take 100µL of filtered sample solution, 100µL of carbonate buffer (pH9), and 20µL of LOPA solution, and mix at room temperature for 2 min.

[0089] 3.6 Inject 20 µL of sample into HPLC-FLD.

[0090] The peak area of ​​the sample was converted to concentration C (mg / L) using the external standard curve, and then converted to mg / g based on the extraction volume and sample mass. GABA (mg / g) = concentration C 100mL / 0.5g. GABA retention rate = content measured after storage for a certain period of time / initial GABA content. 100%.

[0091] fulvic acid activity 3.7 Weigh 1.0000g of the granular sample (accuracy 0.0001g).

[0092] 3.8 Add 10.00 mL of 0.1 M NaOH (solid-liquid ratio 1:10 w / v) and seal.

[0093] 3.9 Shake on a shaker for 2 hours (room temperature, 100 rpm).

[0094] 3.10 Centrifuge at 8000 rpm for 10 min; take the supernatant, pass it through a 0.45 µm filter, and make up to 25.00 mL. Record the volume Vext.

[0095] 3.11 Dilute appropriately by 1:5 based on the sample concentration.

[0096] The absorbance of the sample at 254 nm, 465 nm, and 665 nm was measured as A254, A465, and A665, respectively. The fulvic acid retention rate was then determined.

[0097] Table 3 Retention Rate

[0098] Test 4: Plant Growth Experiment I. Experimental Objective The effects of this invention's value-added water-soluble compound fertilizer (containing GABA, humic acid, PGA-DMPP microspheres, etc.) on maize growth, nutrient utilization, and yield under field conditions were verified, with a focus on evaluating: 1. Compare the yield-increasing effects of conventional water-soluble fertilizer / comparative treatment; 2. Nitrogen use efficiency (NUE) and emission reduction potential (indirect evaluation of nitrification inhibition effect); 3. Field correlation between crop physiological indicators (chlorophyll content, dry matter accumulation) and shelf stability.

[0099] II. Test Site and Soil Choose a corn-wheat rotation site with flat land, good drainage and irrigation, and complete historical fertilization records.

[0100] Before the experiment, soil samples of 1-20 cm were collected for basic soil physicochemical and nutrient analysis (pH, organic matter, total nitrogen, available phosphorus, available potassium, CEC, etc.). The location, latitude and longitude, and weather station data source were recorded.

[0101] III. Experimental Design Design type: Randomized block design (RCBD).

[0102] Processing (Example 6 processing, 3 repetitions): 3 repetitions per processing, for a total of 18 cells.

[0103] Community dimensions: 6m × 5m (30m) per community 2 Row spacing is 0.75m, plant spacing is 0.20m. A 1m boundary buffer zone is maintained.

[0104] Treatment setup (administered at the same total nitrogen level): CK: No fertilizer (subject to local regulations) Std: Conventional commercial water-soluble fertilizer (commercially available comparison, applying the same amount of nitrogen). IE1: Formulation of Example 1 IE2: Formulation of Example 6 REF1: Comparative Example 1 Formulation REF2: Comparative Example 2 Formula Total nitrogen dosage: 180 kg N / ha (can be divided into basal application and top dressing), but all treatments are equal in nitrogen. Record the date and amount of fertilization.

[0105] IV. Cultivation and Fertilization Management All treatments were calculated based on equal nitrogen amounts: total nitrogen was allocated as follows: 50% for basal application and 50% for topdressing (or multiple topdressings were applied at different stages: seedling stage, jointing stage, and heading stage); water-soluble fertilizer (this invention and control) was applied by drip irrigation.

[0106] V. Measurement Indicators and Time Points Sampling should be representative and standardized.

[0107] A. Key observation points during the reproductive period Record seedling survival rate during the emergence period (V2–V3) Plant height and leaf SPAD (chlorophyll) were measured during the jointing stage (V6–V8). Measure the same index again before the grouting period (before R1). Yield and yield components measured in pre-maturity (R6) harvested plots B. Specific Measurement Methods Plant height: Ten parallel plants (marked) were randomly selected from each effective plot, and the height from the ground to the top of the ear (cm) was measured. The measurement was taken three times at each key growth stage and the average was taken.

[0108] Chlorophyll (SPAD): Using a portable SPAD meter (such as Minolta / SPAD), measure the chlorophyll content of the 3rd to 4th mature, complete leaves (middle of the leaf, between the veins) on the main stem, taking the average of 3 measurements per plant, and then calculate the average for 10 plants. Aboveground dry matter weight (biomass).

[0109] During the sampling period (e.g., the jointing stage and grouting stage), a 1m sample is randomly taken from the effective area. 2 To obtain samples, cut above-ground plant material and weigh it fresh; then dry it in an oven at 70℃ until constant weight (48~72h) to obtain the dry weight (g / m³). 2 ), converted to t / ha.

[0110] Yield and yield components: Harvest the entire effective area at maturity (measure the number of ears / plant, thousand-grain weight, and moisture content), thresh the grains, and weigh the grains to convert the yield (kg / ha). Grain weight is corrected for standardized moisture content.

[0111] Table 4 Results of Performance Test 4

[0112] Table 5 Residual NO3 in Soil - -N (0~20cm, at harvest)

[0113] The residual NO3 in IE1 was significantly lower than that in Std / REFs and close to the CK level, indicating that DMPP had a good nitrification suppression effect in IE1, improved root assimilation, and reduced soil nitrate nitrogen accumulation.

[0114] Compared with commercially available conventional water-soluble fertilizers, the preferred formulation of this invention (Example 1) showed significant improvement in field trials—yield increased by approximately 11.5% (8700 vs 7800 kg / ha). Comparative trials further demonstrated that removal of PGA-DMPP or alteration of the chelation sequence led to increased yield and soil nitrate accumulation.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A value-added water-soluble compound fertilizer, characterized in that, The raw materials for its preparation include: urea, powdered ammonium sulfate, crystalline monoammonium phosphate, potassium sulfate, biochemical potassium humate, neutral mineral potassium humate, aminobutyric acid, nitration inhibitor dmpp, citrate chelate, and polyglutamic acid.

2. A method for preparing a value-added water-soluble compound fertilizer, characterized in that, The steps are as follows: (1) The complexing agent and 1,2-dimethylpropylphosphonic acid were mixed to obtain pretreated product 1; (2) Ferment soybeans to obtain fermented product; mix the fermented product with citric acid chelate salt and neutral mineral potassium humate evenly to obtain premix 1; (3) Mix urea and potassium sulfate evenly to obtain premix 2; (4) Mix ammonium sulfate and monoammonium crystalline powder, add the pretreated material 1, premix 1 and premix 2 obtained in the above steps; then granulate to obtain the value-added water-soluble compound fertilizer.

3. The method for preparing a value-added water-soluble compound fertilizer according to claim 2, characterized in that, In step (1), the complexing agent is polyglutamic acid.

4. The method for preparing a value-added water-soluble compound fertilizer according to claim 3, characterized in that, The detailed steps of step (1) are as follows: 1) PGA is dissolved in deionized water to prepare a PGA solution; 2) Dissolve DMPP in a small amount of 20 v / v% alcohol-water to form a pre-solution, then pour it into the PGA solution. The resulting PGA-DMPP solution has a solid content of 4-6%. 3) Prepare a 1.0 w / v% CaCl2·2H2O aqueous solution and maintain the temperature at 20–25℃; 4) PGA-DMPP solution is continuously atomized and dripped into CaCl2·2H2O aqueous solution through a nozzle with a diameter of 80-200 μm, a pump speed of 0.5-5 mL / min, a nozzle distance of 5-20 cm from the liquid surface, and stirring at 50-150 rpm. 5) Solidify in CaCl2·2H2O aqueous solution for 1–5 min; then collect microspheres using a filter with a mesh size of 40–200 µm; immediately rinse once with deionized water and then send the wet microspheres into a fluidized bed for vacuum dehydration and drying, with the temperature controlled at ≤50℃, and gradually reduce the water content to ≤0.3%.

5. The method for preparing a value-added water-soluble compound fertilizer according to claim 4, characterized in that, The concentration of the PGA solution is 0.5–3 w / v.

6. The method for preparing a value-added water-soluble compound fertilizer according to claim 2, characterized in that, The detailed steps of step (2) are as follows: 1) Soak soybeans at a water:bean mass ratio of 3:1 (v / w) at room temperature for 8-24 hours, changing the water every 6 hours, and changing the water again in the last 6 hours, adding 0.05wt% CaCl2. 2) Spread the soaked soybeans evenly on the sprouting cloth, keeping the thickness ≤5cm. Keep them at a temperature of 25-30℃, relative humidity of 85-95%, and in the dark for 24-48 hours, spraying 5ml of water at the same temperature every 12 hours. 3) Put the sprouted soybeans into a grinder, add deionized water, and grind them into a paste at a solid-liquid ratio of 1:4 (w / v). 4) Pour the pulp into the fermentation tank, adjust the pH to 4.8-5.0, and the temperature to 35℃; Add to: Glucose 10–30 g / L, pyridoxal 0.05–0.1 g / L, yeast extract 1–5 g / L, citrate-sodium citrate buffer 1–5 g / L, humic acid powder 1–5 g / L, seed culture 5–10% (v / v); ensure uniform suspension at 50–200 rpm; fermentation conditions: 32–35℃, pH maintained at 4.5–5.2, fermentation time: 24–72 h; after fermentation, heat the fermentation broth to 70–75℃ for 10–15 min, then cool to room temperature. 5) Centrifuge to remove solid residue, take the supernatant, and vacuum concentrate to a solid content of 20-40%; adjust the pH of the concentrated fermentation broth to 5.8, slowly add citric acid chelate salt to the concentrated fermentation broth, and stir for 10-30 minutes; then slowly add neutral mineral potassium humate while stirring; adjust the total solid content to 20-40% to obtain premix 1.

7. The method for preparing a value-added water-soluble compound fertilizer according to claim 6, characterized in that, In step 4), the seed solution is: Lactobacillus short-lived seed solution and Saccharomyces cerevisiae seed solution; the bacterial cell concentration of the seed solution is (1-2). 10 8 CFU / mL.

8. The method for preparing a value-added water-soluble compound fertilizer according to claim 7, characterized in that, The mass ratio of *Lactobacillus shortiflorus* to *Saccharomyces cerevisiae* is 2:

1.

9. A value-added water-soluble compound fertilizer, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

10. A value-added water-soluble compound fertilizer according to claim 2, characterized in that, It is used in the cultivation of medicinal plants.

Images