Multi-element synergistic compound fertilizer for fruits and vegetables and preparation method thereof

Abstract

The application discloses a kind of multi-element synergistic effect type fruit and vegetable special-purpose compound fertilizer and preparation method thereof, belong to compound fertilizer production technical field.The compound fertilizer is with urea, monoammonium phosphate, potassium sulfate as the basis of macroelement, chelated with citric acid state trace element, compound mineral source fulvic acid potassium, compound amino acid powder, seaweed powder form ternary synergistic system;When preparing, first chelate with trace element in the form of solution form, realize nutrient uniform distribution with synergistic component premix process.The chelated trace element of product accounts for ≥60% of total trace element mass ratio, nitrogen, phosphorus and potassium field utilization rate is 10%-15% higher than that of conventional same nutrient compound fertilizer;After applying to facility fruit and vegetable, yield is increased by 8%-12%, soluble solid content of fruit is increased by 1.5-2.5 percentage points;Product sphericity is ≥90%, particle compressive strength is ≥10N, process can be directly adapted to existing compound fertilizer production line, suitable for industrialized large-scale production.

Description

Technical Field

[0001] This invention relates to the field of compound fertilizer production technology, and in particular to a multi-element synergistic compound fertilizer for fruits and vegetables and its preparation method. Background Technology

[0002] Fruit and vegetable crops have short growth cycles and high yields. They have comprehensive and concentrated nutrient requirements. In addition to macronutrients such as nitrogen, phosphorus, and potassium, micronutrients such as calcium, magnesium, boron, zinc, and iron directly participate in fruit development, photosynthetic metabolism, and stress resistance processes, playing an irreplaceable role in improving the yield and quality of fruits and vegetables.

[0003] Currently, commercially available compound fertilizers for fruits and vegetables are developing towards specialization and functionality, but three technical shortcomings still exist, making it difficult to meet the needs of green and efficient production of greenhouse fruits and vegetables. First, the availability of micronutrients is low. Most existing products directly mix borax and sulfate-based micronutrients into the compound fertilizer in the form of inorganic salt dry powder. Iron, zinc, and other metallic elements easily form insoluble compounds in the soil, while calcium and magnesium are easily adsorbed by colloids. At the same time, high concentrations of phosphorus antagonize zinc and iron ions, resulting in a micronutrient utilization rate generally below 20% in the current season. Even if soil nutrient test values ​​meet standards, crops are still prone to physiological deficiency diseases such as blossom-end rot in tomatoes, flower and fruit drop in cucumbers, and yellowing of new shoots. Second, the synergistic components are singular, and the multi-component synergistic mechanism is lacking. Existing products mostly add only humic acid substances, which can only improve the soil to a limited extent and have a weak effect on promoting crop root growth and active nutrient absorption. Components with physiological regulatory functions, such as compound amino acids and seaweed active substances, are rarely used and have not formed a scientific compound system with humic acid, failing to achieve multi-dimensional synergy of "soil improvement - nutrient activation - crop growth promotion," resulting in limited quality and yield improvement. Thirdly, the preparation process and functional components have poor compatibility, leading to insufficient product quality stability. Mainstream rotary drum granulation processes mostly use all-dry powder mixing granulation, with small amounts of micronutrients added. Direct mixing easily leads to material segregation and poor uniformity, and excessively high local concentrations can easily cause seedling burn. If pre-prepared chelated micronutrient dry powder is added, it is not only costly, but the chelated structure is also prone to dissociation under high temperature and humidity conditions during granulation. At the same time, conventional products have low particle strength and are prone to clumping and pulverization, affecting the uniformity of mechanized fertilization.

[0004] In summary, developing a compound fertilizer specifically for fruits and vegetables that features high availability of micronutrients, synergistic effects from multiple components, compatibility with existing industrial production lines, and stable quality is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a multi-element synergistic compound fertilizer for fruits and vegetables and its preparation method, solving the problems of low micronutrient availability, poor nutrient synergy, low crop absorption and utilization rate in existing fruit and vegetable compound fertilizers, as well as poor micronutrient mixing uniformity and unstable product granulation quality during the preparation process.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A multi-element synergistic compound fertilizer for fruits and vegetables, by weight, comprises the following components: The total weight of the raw materials is 100 parts, including 35-65 parts of macronutrients, 4-12 parts of mesonutrients, 0.8-3.5 parts of chelated micronutrients, 6-18 parts of a synergistic system, and 3-10 parts of a binder. The macronutrients consist of urea, monoammonium phosphate, and potassium sulfate. The final product contains ≥45% nitrogen, phosphorus pentoxide, and potassium oxide, and the nitrogen-phosphorus-potassium ratio can be adjusted according to different growth stages of fruits and vegetables. The mesonutrients consist of a mixture of calcium nitrate tetrahydrate and magnesium sulfate heptahydrate, used to supplement calcium, magnesium, and sulfur, and to prevent physiological diseases such as fruit cracking and leaf yellowing in fruits and vegetables. The chelated trace element raw materials are prepared by chelating at least two of zinc sulfate heptahydrate, ferrous sulfate heptahydrate, and manganese sulfate monohydrate with citric acid; the raw materials also include borax as a boron nutrient component, and citric acid is a common industrial-grade raw material. Chelation can reduce the risk of soil fixation. The synergistic effect system is composed of mineral-derived potassium humate, compound amino acid powder, and seaweed powder in a mass ratio of (3-5):(2-4):1. The three components work synergistically to activate soil nutrients, promote root absorption, and enhance crop stress resistance.

[0008] As a preferred technical solution of the present invention, the nitrogen source is agricultural urea with a nitrogen content of ≥46%, the phosphorus source is powdered monoammonium phosphate with an effective phosphorus pentoxide content of ≥55%, and the potassium source is agricultural grade potassium sulfate with a potassium oxide content of ≥50%; the mass ratio of urea, monoammonium phosphate, and potassium sulfate is (2-3):(1-1.5):(2-2.5), which is suitable for the high potassium requirements of fruits and vegetables during the fruit expansion period.

[0009] As a preferred embodiment of the present invention, the medium-element raw material is composed of calcium nitrate tetrahydrate and magnesium sulfate heptahydrate mixed in a mass ratio of (2-3):1; the total mass of the medium-element raw material accounts for 2%-5% of the total mass of the compound fertilizer based on oxides.

[0010] As a preferred embodiment of the present invention, the chelated trace element raw material is composed of borax, zinc sulfate heptahydrate, and ferrous sulfate heptahydrate in a mass ratio of (2-3):(1-2):(1-1.5); the mass ratio of citric acid to total trace element salt in the chelation reaction is (0.5-1):1, and the proportion of chelated trace elements in the final product is ≥60% of the total trace element mass.

[0011] As a preferred embodiment of the present invention, the bonding carrier is calcium-based bentonite or attapulgite; the compound fertilizer is spherical granules with a particle size range of 2 to 4.75 mm and a moisture content of ≤2.0%.

[0012] The present invention also provides a method for preparing the above-mentioned multi-element synergistic compound fertilizer for fruits and vegetables, including the following steps: (1) Raw material pretreatment: crush the macro-element raw materials and medium-element raw materials to 60-80 mesh respectively, put them into a mixer for premixing according to the ratio, and obtain basic mixed powder; (2) Chelation reaction: dissolve citric acid and trace element salts in water according to the ratio, adjust the pH of the system to 5.0-6.0, keep warm and stir to react, and obtain chelated micro-fertilizer solution; (3) Synergistic premix: mix each component of the synergistic system with some dry powder of binder carrier evenly to obtain synergistic premix, avoiding the segregation problem that occurs when a small amount of synergistic components are directly mixed; (4) Rotary drum granulation: send the basic mixed powder and synergistic premix into a rotary drum granulator, spray the chelated micro-fertilizer solution and binder aqueous solution at the same time, and roll granulate to obtain wet granules; (5) Post-treatment molding: dry, cool and screen the wet granules in sequence, and the qualified granules after screening are coated to obtain finished compound fertilizer.

[0013] Further, in step (1), a horizontal ribbon mixer is used for premixing, with a spindle speed of 30-40 r / min, a mixing time of 8-15 min, and a mixing uniformity variation coefficient of ≤5%; in step (2), the solid-liquid mass ratio in the reactor is 1:(3-5), the pH is adjusted with dilute sulfuric acid or ammonia, the chelation reaction temperature is 55-65℃, the stirring speed is 60-80 r / min, and the reaction time is 40-70 min.

[0014] Further, in step (3), a double-spiral conical mixer is used for mixing, with a revolution speed of 10-15 r / min, a rotation speed of 20-30 r / min, and a mixing time of 5-10 min; the amount of the binder used is 30%-50% of the total mass of the binder; in step (4), the cylinder of the rotary drum granulator has an inclination angle of 3°-5°, a rotation speed of 18-28 r / min, a granulation material temperature controlled at 45-55℃, a total amount of spray liquid used is 8%-15% of the total mass of the powder, and a spray pressure of 0.2-0.4 MPa.

[0015] Furthermore, in step (5), the drying process adopts a two-stage drying process: the first stage drying temperature is 70-80℃ and the duration is 10-15min, which is used for surface moisture evaporation; the second stage drying temperature is 90-110℃ and the duration is 15-20min, which is used for deep dehydration; the moisture content of the particles after drying is ≤2.0%; the cooling adopts a counter-current air cooling method, and the material temperature after cooling is ≤40℃; the screening adopts a double-layer vibrating screen, with the upper screen hole being 4.75mm and the lower screen hole being 2mm, and the unqualified particles are returned to be crushed and re-granulated; the qualified particles after screening are also coated, sprayed with mineral oil coating agent and coated with talc powder, the amount of coating agent is 0.1%-0.3% of the total mass of particles, and the amount of talc powder is 0.2%-0.5%, which improves the anti-caking performance of the product.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Significantly improved nutrient absorption and utilization: Through citric acid chelation treatment, the proportion of chelated trace elements in the product is ≥60%, which can reduce the fixation and antagonism of trace elements in the soil; combined with the nutrient activation effect of the ternary synergistic system, the field utilization rate of nitrogen, phosphorus and potassium is increased by 10% to 15% compared with conventional compound fertilizers with the same nutrients; 2. The effects of improving the quality and increasing the yield of fruits and vegetables can be quantified: Field comparative trials of tomatoes and cucumbers in greenhouse cultivation have verified that, under the same nutrient application rate, the application of this product can increase the yield of fruits and vegetables by 8% to 12%, increase the soluble solids content of fruits by 1.5 to 2.5 percentage points, and reduce the incidence of physiological nutrient deficiency by more than 60%. 3. Stable and controllable product molding quality: The granulation method of solution spraying + dry powder premixing is adopted, and the product pelleting rate is ≥90%, the granule compressive strength is ≥10N, the particle size qualification rate is ≥90%, the moisture content is ≤2.0%, and it is not easy to pulverize and clump during storage and transportation, and the fertilizer application is uniform. 4. Strong industrial adaptability: All raw materials are common agricultural raw materials, and the preparation process does not require the addition of special equipment. It can be directly adapted to existing rotary drum granulation compound fertilizer production lines, and the overall production cost is ≤5% higher than that of conventional products with the same nutrients. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 is a schematic diagram of the preparation process of the multi-element synergistic compound fertilizer for fruits and vegetables according to the present invention, showing each step of the preparation process and the direction of material transfer; Figure 2 is a bar chart comparing the yield of greenhouse tomatoes per mu in various embodiments of the present invention with that in the comparative examples. The horizontal axis represents the experimental treatment group, and the vertical axis represents the tomato yield per mu, in kg. Figure 3 is a bar chart comparing the soluble solids content of tomato fruits in various embodiments and comparative examples of the present invention. The horizontal axis represents the experimental treatment group, and the vertical axis represents the mass fraction of soluble solids in the fruit, in units of _____. Detailed Implementation

[0018] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] In the attached diagram, all identical reference numerals refer to the same components.

[0020] Example 1: Preferred Formulation Example This embodiment is a preferred implementation of the present invention, and the preparation process corresponds completely to the process path in Figure 1.

[0021] 1. Raw material formula (by weight parts) All raw materials are common bulk raw materials used in the compound fertilizer industry, and their specifications all meet the corresponding agricultural-grade product standards: a total of 60 parts of macro-element raw materials: 25 parts of agricultural urea (compliant with GB 2440-2017, containing N≥46.4%), 12 parts of powdered monoammonium phosphate (compliant with GB 10205-2009, available P2O5≥45%, total N≥10%), and 23 parts of agricultural-grade potassium sulfate (compliant with GB20406-2017, K2O≥50%, powder); the mass ratio of the three is approximately 2.08:1:1.92, and the total nutrient content (N+P2O5+K2O) of the finished product is 46.2%.

[0022] The total amount of medium-quantity raw materials is 7 parts: 5 parts of calcium nitrate tetrahydrate (CaO≥23.4%) and 2 parts of magnesium sulfate heptahydrate (MgO≥16.2%), with a mass ratio of 2.5:1; the total mass of calcium and magnesium, calculated as oxides, accounts for 3.2% of the total mass of the finished product.

[0023] Chelated trace element raw materials: a total of 2.1 parts of trace element salts, including 1 part of industrial grade borax (compliant with GB / T537-2009, B2O3≥95%), 0.6 parts of zinc sulfate heptahydrate (compliant with HG / T 2326-2015, Zn≥21%), and 0.5 parts of ferrous sulfate heptahydrate (compliant with GB / T 664-2011, Fe≥19%), with a mass ratio of approximately 2:1.2:1; the chelating agent is 1.0 part of citric acid monohydrate (food grade, purity≥99%), with a mass ratio of citric acid to total trace element salts of approximately 0.48:1.

[0024] The synergistic effect system consists of 12 parts: 6 parts of mineral-derived potassium fulvicate (fulvic acid ≥50%, humic acid ≥70%), 4 parts of compound amino acid powder (free amino acids ≥40%, organic matter ≥30%), and 2 parts of seaweed powder (alginic acid ≥18%, organic matter ≥45%), with a mass ratio of 3:2:1.

[0025] Binder: 5 parts of calcium-based bentonite (blue absorption ≥25g / 100g, particle size 200 mesh).

[0026] 2. Preparation process (corresponding to Figure 1, full process flow) The entire preparation process uses general industrial equipment commonly used in the compound fertilizer industry: (1) Raw material pretreatment: Urea, monoammonium phosphate, potassium sulfate, calcium nitrate tetrahydrate, and magnesium sulfate heptahydrate are respectively fed into a hammer mill for crushing, and then screened through a 70-mesh standard inspection sieve. The material on the sieve is returned to the mill for secondary crushing, and the sieve pass rate of the powder is controlled to be ≥95%. The powder is weighed according to the formula ratio and put into a horizontal ribbon mixer with an effective volume of 1m³. The material filling coefficient is 60%, the main shaft speed is set to 35r / min, and the mixture is discharged after 10min to obtain the basic mixed powder. The mixing uniformity is determined by multi-point sampling according to GB / T 8571-2008 "Laboratory Sample Preparation of Compound Fertilizers". The coefficient of variation of the mixing uniformity is calculated to be 4.2%, indicating good mixing uniformity.

[0027] (2) Chelation Reaction: Citric acid, borax, zinc sulfate heptahydrate, and ferrous sulfate heptahydrate were added to a stainless steel reactor equipped with a jacketed heating system, mechanical stirring, and online pH monitoring. Deionized water was added at a solid-liquid mass ratio of 1:4. Stirring was started first until the citric acid was completely dissolved, and then trace element salts were added in batches, with stirring continued until all materials were dissolved. The pH of the system was adjusted to 5.5 with 5% sulfuric acid by mass, and hot water was introduced to raise the temperature to 60°C at a rate of 2°C / min. The stirring speed was controlled at 70 r / min, and the chelation reaction was maintained at this temperature for 50 min. After the reaction, samples were taken, and the chelation rate was determined by cation exchange resin separation: free metal ions were adsorbed by cation exchange resin, and the total metal ion and free metal ion contents were titrated separately after elution. It was calculated that the chelated trace elements accounted for 66% of the total trace element mass, which met the reaction endpoint requirement. A clear chelated micronutrient fertilizer solution was then discharged.

[0028] (3) Enhanced premixing: Potassium humate from mineral source, compound amino acid powder, seaweed powder, and 2 parts of calcium-based bentonite are added to a double-helix conical mixer with an effective volume of 0.3 m³. The revolution speed is set to 12 r / min and the rotation speed to 25 r / min. After mixing for 8 minutes, the material is discharged to obtain the enhanced premix. This process uses carrier dilution premixing to avoid particle size segregation caused by a small amount of enhanced components being directly mixed with a large amount of powder, ensuring that the enhanced components are evenly distributed in the finished product.

[0029] (4) The basic mixed powder and the synergistic premix are synchronously fed into the rotary drum granulator via a metering screw. The drum inclination angle is set at 4°, the rotation speed at 22 r / min, the feed rate of the basic powder is 1 t / h, and the synergistic premix is ​​fed synchronously according to the proportion. The front end of the granulator is equipped with a dual-channel atomizing nozzle to spray the chelated micro-fertilizer solution and the bentonite binder liquid, respectively. The total spray mass is controlled to be 11% of the total powder mass, and the spray pressure is 0.3 MPa. The temperature of the material in the granulation zone is controlled to be stable at 50°C by introducing 45°C hot air for heat compensation. The material rolls and agglomerates in the drum, gradually growing larger. Online sampling and testing show that the wet granule pelleting rate is 92%, and wet granules are discharged.

[0030] (5) The wet granules are conveyed to a rotary drum dryer via belt conveyor and dried using a two-stage counter-current hot air drying process: The first stage is low-temperature drying: drying temperature 75℃, hot air velocity 1.2m / s, and particle residence time 12min, mainly removing free water from the particle surface to prevent rapid surface crusting that would prevent internal moisture from escaping; the second stage is high-temperature drying: drying temperature 100℃, hot air velocity 1.0m / s, and particle residence time 18min, deeply removing bound water from the particles. After drying, samples are taken and tested according to the vacuum oven method of GB / T 8576-2010, and the moisture content of the granules is 1.8% by mass.

[0031] (6) The dried particles after cooling and screening are sent to a counter-current cooler with a cooling air volume of 8000 m³ / h. The cold air exchanges heat with the particles in a counter-current contact, and the particle temperature drops to 35℃ after cooling. After cooling, the particles enter a double-layer linear vibrating screen with an upper screen aperture of 4.75 mm and a lower screen aperture of 2 mm. After screening, 93% of the particles are qualified with a size of 2-4.75 mm. Oversized particles and fine powder are collected and returned to the crushing process for re-granulation.

[0032] (7) The qualified coated particles are fed into the rotary coating drum and the drum speed is set to 15 r / min. First, the mineral oil coating agent is sprayed through the atomizing nozzle at a dosage of 0.2% of the total mass of the particles. The drum is rolled for 1 min to make the oil film evenly coated. Then, talc powder is added at a dosage of 0.3% of the total mass of the particles. The drum is rolled for another 3 min before being discharged to obtain the final product.

[0033] 3. Testing of the physical and chemical properties of the finished product The following tests were conducted according to the standard methods specified in GB / T 15063-2020 "Compound Fertilizers", and the results are as follows:

[0034] Example 2: Boundary Parameter Verification Example This embodiment selects the low to medium values ​​of the formula and process parameters of the present invention to verify the universality and repeatability of the scheme.

[0035] 1. Raw material formula (by weight parts) The total amount of macro-element raw materials is 45 parts: 18 parts of agricultural urea, 9 parts of powdered monoammonium phosphate, and 18 parts of agricultural-grade potassium sulfate, with a mass ratio of 2:1:2 and a total nutrient content of 45.5%.

[0036] The total amount of medium-quantity raw materials is 5 parts: 3.5 parts of calcium nitrate tetrahydrate and 1.5 parts of magnesium sulfate heptahydrate, with a mass ratio of approximately 2.33:1.

[0037] Chelated trace element raw materials: 1.2 parts total of trace element salts: 0.5 parts of borax, 0.35 parts of zinc sulfate heptahydrate, 0.35 parts of ferrous sulfate heptahydrate; 0.8 parts of citric acid, with a mass ratio of citric acid to trace element salts of 0.67:1.

[0038] The synergistic effect system consists of 8 parts: 4 parts of mineral-derived potassium humate, 2.5 parts of compound amino acid powder, and 1.5 parts of seaweed powder, with a mass ratio of approximately 2.67:1.67:1.

[0039] Bonding carrier: 4 parts of attapulgite soil.

[0040] 2. Preparation process The preparation process is the same as shown in Figure 1. The core process parameters are selected in the lower range: (1) The raw material is crushed to 60 mesh and the sieve rate is ≥95%; the main shaft speed of the horizontal ribbon mixer is 32 r / min, and the mixing time is 12 min. The coefficient of variation of the mixing uniformity is 4.7%. (2) The solid-liquid mass ratio of the chelation reaction is 1:3.5. The pH is adjusted to 5.2 with 5% dilute ammonia water. The reaction temperature is 58℃, the stirring speed is 65 r / min, and the reaction time is 60 min. The proportion of chelated trace elements is 63%. (3) 1.6 parts of attapulgite clay are premixed with the synergistic component. The double spiral conical mixer revolves at 10 r / min and rotates at 22 r / min. The mixing time is 7 min. (4) The drum granulator has a cylinder inclination angle of 3.5°, a rotation speed of 20 r / min, a total spray liquid volume of 9.5% of the powder, a spray pressure of 0.25 MPa, and a material temperature of 48℃. The pelleting rate is 90.5%. (5) Two-stage drying: the first stage is dried at 70℃ for 15 minutes, and the second stage is dried at 95℃ for 20 minutes; the moisture content after drying is 1.9%. (6) Countercurrent air cooling to 38℃, double-layer vibrating screen screening, particle size qualification rate is 91%; no coating treatment is performed in this embodiment.

[0041] 3. Finished product testing results The average compressive strength of the particles is 11.2 N, the moisture content is 1.9%, and the proportion of chelated trace elements is 63%. All indicators meet the product performance requirements of this invention, proving that the parameter range of this invention has good versatility and repeatability, and the boundary parameters can stably produce qualified products.

[0042] Example 3: Optimized Example of High Anti-caking Coating This embodiment optimizes the coating process parameters based on Embodiment 1 to verify the effect of the coating process on improving the storage and transportation performance of the product.

[0043] 1. Basic Formulation and Preliminary Processes The basic raw material formula and all parameters from raw material pretreatment to cooling and screening are completely consistent with those in Example 1, except that the parameters of the coating process are optimized.

[0044] 2. Optimized coating process Qualified granules are fed into a rotary coating drum, with the drum speed set at 18 r / min. First, mineral oil coating agent is sprayed through a high-pressure atomizing nozzle, with the dosage increased to 0.25% of the total granule mass and the spraying pressure at 0.4 MPa, so that the oil film can more evenly coat the surface of the granules. After rolling for 1 minute, 1250 mesh talc powder is added in two batches, with a total dosage of 0.4% of the total granule mass. After rolling for a total of 5 minutes, the granules are discharged.

[0045] 3. Anti-caking performance testing Agglomeration tests were conducted according to the constant temperature and pressure briquetting method specified in GB / T 10516-2012: Samples were placed in a dedicated test mold, a constant pressure of 0.05 MPa was applied, and the samples were placed in a constant temperature and humidity chamber at 54℃ and 70% relative humidity for 72 hours. After removal, the samples were allowed to cool naturally to room temperature, and then vibrated on a 2mm standard sieve for 2 minutes. The mass of agglomerated material on the sieve was weighed, and the agglomeration rate was calculated. Test results: In Example 1, the agglomeration rate of the basic coated sample was 8.7%, while the agglomeration rate of the optimized coated sample in this example was 3.2%, representing a reduction of 63.2%, significantly improving the product's storage and transportation stability.

[0046] Comparative analysis of existing conventional compound fertilizers with the same nutrients Prepared using an industry-standard all-dry drum granulation process, this invention serves as a comparison with existing technologies to quantitatively verify the technological advancements of the present invention. Formula: Total nutrients 46.0%, NPK ratio is the same as in Example 1; Borax, zinc sulfate heptahydrate, and ferrous sulfate heptahydrate are added directly in the form of inorganic salt dry powder, the dosage is the same as in Example 1, without chelation treatment; no mineral-derived potassium humate, compound amino acid powder, and seaweed powder synergistic system are added; the binder is 5 parts of calcium-based bentonite.

[0047] Process: All raw material dry powders are directly mixed and then transferred to a rotary drum granulator, where they are sprayed with clean water for granulation; conventional single-stage drying, cooling and sieving are then performed to obtain the finished product, without any synergistic premixing, chelation, or coating processes.

[0048] Finished product testing: average compressive strength of particles 7.2N, particle size qualification rate 82%, moisture 2.3%, all trace elements are inorganic free state, chelated state accounts for 0%; constant temperature agglomeration rate 15.6%.

[0049] Field application effect test A small-plot comparative experiment was conducted using greenhouse tomatoes as the experimental crop, and the experimental data correspond one-to-one with Figures 2 and 3.

[0050] 1. Basic experimental conditions Experimental location: A tomato growing greenhouse in a facility, with alluvial soil; Basic soil fertility: 0-20cm soil layer contains 14.2g / kg organic matter, 98.6mg / kg available nitrogen, 32.5mg / kg available phosphorus, 186mg / kg available potassium, and pH 7.2; The test crop was Pink Crown No. 1 tomato, which was transplanted on February 15, 2025, and pulled up on June 20, with a total growth period of 125 days. Cultivation method: High ridges covered with film, drip irrigation under the film, single-stem pruning, topped with 4 fruit clusters, planting density of 3500 plants / acre.

[0051] 2. Experimental Design Four fertilization treatments were set up, and one unfertilized control was set up to calculate nutrient utilization rate. Each treatment was replicated three times and arranged in a randomized block design. The plot area was 20m², and 105 plants were planted in each plot. A 0.5m wide protective row was left between plots, and a 2m wide protective row was set around the experimental field.

[0052] Treatment 1: Apply the product from Example 1 Treatment 2: Applying the product from Example 2 Treatment 3: Apply the product from Example 3 Treatment 4: Apply comparative product (conventional compound fertilizer) Blank control: No fertilizer applied. Fertilization plan: The total amount of nitrogen, phosphorus and potassium applied in all fertilization treatments was exactly the same. The total amount of pure N was 22 kg, P2O5 was 10 kg and K2O was 25 kg per mu throughout the entire growth period. Among them, 40% of the total nutrients were applied as base fertilizer, and 30% of the total nutrients were applied as top dressing during the first fruit set period and the third fruit expansion period. The blank control plot was only irrigated with the same amount of water, and the rest of the field management was exactly the same.

[0053] 3. Measurement Items and Methods (1) Yield determination: Harvest each ear of fruit in batches when it reaches commercial maturity, record the weight of the fruit harvested in each plot each time, accumulate the total yield of the whole growth period, convert it into yield per mu, and take the average of 3 replicates. (2) Soluble solids determination: During the peak harvest period of the 2nd and 3rd ears of fruit, randomly select 20 fruits of uniform size and maturity from each plot, extract juice from the equatorial part of the fruit, and measure it with a handheld refractometer. Each sample is measured 3 times, and the average value is taken. (3) Nutrient utilization rate calculation: During the harvest period, take 5 representative plants from each plot, dry and crush the roots, stems, leaves and fruits, and measure the total nitrogen, total phosphorus and total potassium content respectively, and calculate the total nutrient absorption of the crop; use the difference method to calculate the apparent nutrient utilization rate, the formula is: apparent nutrient utilization rate (%) = (nutrient absorption in the fertilized area - nutrient absorption in the blank area) / nutrient application in the fertilized area × 100 The average value of the utilization rates of nitrogen, phosphorus and potassium is taken to obtain the comprehensive utilization rate. (4) Nutrient deficiency incidence survey: During the third fruit enlargement stage, 100 plants were surveyed in each plot, the number of plants with blossom-end rot was counted, and the disease incidence rate was calculated.

[0054] 4. Experimental Results and Analysis The results of field trials for each treatment are shown in the table below. A direct comparison of yield and soluble solids content corresponds to the following values:Figure 2 Figure 3:

[0055] The above data can verify that: Significant yield increase: The products in the three examples showed a yield increase of 8.2% to 11.4% compared to conventional compound fertilizers, with the overall increase remaining stable in the range of 8% to 12%.

[0056] Significant quality improvement: The soluble solids content of the fruit increased by 1.6 to 2.0 percentage points compared with the control group, demonstrating the clear effect of the synergistic effect system on improving fruit quality.

[0057] Improved nutrient utilization: The comprehensive utilization rate of nitrogen, phosphorus and potassium is 10.2% to 15.1% higher than that of the control group. Chelated trace elements and synergistic systems can effectively reduce soil nutrient fixation and loss.

[0058] The effect of nutrient deficiency control is outstanding: the incidence of blossom-end rot is reduced by more than 61% compared with the control group, and the availability of chelated trace elements is significantly improved, which can effectively prevent physiological nutrient deficiency diseases in fruits and vegetables.

[0059] 5. Industrialization Cost Accounting Based on the formulation of Example 1, the cost per ton of product was calculated for an annual production scale of 100,000 tons: all raw materials are common agricultural raw materials with no special or scarce components; the preparation process can be directly adapted to existing rotary drum granulation compound fertilizer production lines, requiring only the addition of one 0.5m³ small chelation reactor and a matching spray system, resulting in low equipment modification costs. Calculations show that the comprehensive production cost per ton of this product is approximately 4.2% higher than that of conventional compound fertilizers with the same nutrient content, demonstrating strong industrial applicability.

[0060] Example 4: Pot Experiment for Screening Synergistic Effect System Ratio To determine the optimal compounding ratio of mineral-derived potassium humate, compound amino acid powder, and seaweed powder, and to verify the technical effect of the ratio range specified in the claims, a pot screening experiment was conducted using greenhouse tomatoes as the test crop.

[0061] Experimental materials: Test crop: Pink Crown No. 1 tomato, transplanted from seedling to the four-leaf-one-heart stage; Test substrate: peat moss + vermiculite + perlite mixed in a volume ratio of 3:1:1, with consistent basic nutrients; Basic fertilizer: the same macro-elements + meso-elements + chelated micro-elements as in Example 1, with the total nutrient application amount being completely consistent in each treatment.

[0062] The experiment consisted of 8 treatments, with 10 replicates per treatment and 1 plant per pot. All treatments had the same basic nutrient dosage, differing only in the proportions of the synergistic effect system components. The total amount of the synergistic effect system added was uniformly 12% of the total fertilizer mass, consistent with Example 1.

[0063] Treatment A (blank control): No synergistic components added. Treatment B: Adding only mineral-derived potassium humate Processing C: Adding compound amino acid powder Treatment D: Add seaweed powder alone Process E: Mass ratio 2:1:1 (the proportion of mineral-derived potassium humate is lower than the lower limit of the claims) Processing F: Mass ratio 3:2:1 (lower limit of claim scope) Processing G: Mass ratio 4:3:1 (mean value within the scope of claims) Treatment H: Mass ratio 6:5:1 (the proportion of mineral-derived potassium humate and compound amino acids exceeds the upper limit of the claims). The potted plants are cultivated for 60 days, with uniform water and fertilizer management. Various indicators are measured after the cultivation period ends.

[0064] Measurement Indicators and Methods Dry weight of the whole plant: blanching at 105℃ for 30 minutes, drying at 75℃ to constant weight and weighing. Total nitrogen, phosphorus and potassium uptake by plants: After digestion, nitrogen was determined by Kjeldahl method, molybdenum antimony colorimetric method and flame photometry, respectively. Root activity: determined using the TTC reduction method; Soil available nutrient content: After harvest, rhizosphere soil samples were taken to determine the contents of available nitrogen, available phosphorus, and available potassium.

[0065] Experimental results:

[0066] Note: Soil available nutrient activation rate = (Soil available nutrient content in treatment group - Control group) / Control group × 100% Results Analysis The synergistic effects of the single components were significantly lower than those of the compound group, proving that the combination of the three components has a synergistic effect. When the compound ratio is within the range of (3-5):(2-4):1 as defined in the claims (treatments F and G), the plant dry matter, nutrient uptake, root activity, and soil nutrient activation rate are all at a high level, with an increase of more than 25% compared to the single component, and an increase of more than 11% compared to treatment E where the ratio exceeds the lower limit; When the proportion of a component exceeds the upper limit of the claim (process H), the synergistic effect does not continue to increase with the increase of the proportion of the component, but instead decreases slightly. At the same time, it increases the production cost of the product and significantly reduces the cost-effectiveness. In summary, when potassium humate from mineral sources, compound amino acid powder, and seaweed powder are mixed in a mass ratio of (3-5):(2-4):1, the optimal synergistic effect of "soil nutrient activation - root growth and absorption promotion - crop stress resistance enhancement" can be achieved. This ratio range is the optimal range verified by experiments.

[0067] Summary of Implementation Examples The product formula of this invention is reasonable, and the raw materials are all common bulk materials in the industry. By combining chelated trace elements with a ternary synergistic enhancement system, it can effectively improve nutrient availability and crop absorption efficiency.

[0068] The preparation process is highly controllable with a wide parameter range, and can be directly adapted to existing industrial production lines. The product has a high pelletizing rate, good particle strength, low moisture content, and stable storage and transportation performance.

[0069] Field application verification shows that this product can improve the quality and yield of fruits and vegetables, increase fertilizer utilization, reduce physiological nutrient deficiency diseases, and has significant comprehensive economic benefits, making it worthy of large-scale promotion and application.

[0070] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-element synergistic compound fertilizer for fruits and vegetables, characterized in that, The raw materials, by weight, comprise the following components: 100 parts by weight, including 35-65 parts of macronutrient raw materials, 4-12 parts of medium-nutrient raw materials, 0.8-3.5 parts of chelated trace element raw materials, 6-18 parts of a synergistic enhancement system, and 3-10 parts of a binder; the macronutrient raw materials consist of urea, monoammonium phosphate, and potassium sulfate, with the final product containing ≥45% total nitrogen, phosphorus pentoxide, and potassium oxide by mass; the medium-nutrient raw materials consist of a mixture of calcium nitrate tetrahydrate and magnesium sulfate heptahydrate; the chelated trace element raw materials are obtained by chelating at least two of zinc sulfate heptahydrate, ferrous sulfate heptahydrate, and manganese sulfate monohydrate with citric acid; the raw materials also include borax as a boron nutrient component; the synergistic enhancement system is a compound of mineral-derived potassium humate, compound amino acid powder, and seaweed powder in a mass ratio of (3-5):(2-4):

1.

2. The multi-element synergistic compound fertilizer for fruits and vegetables according to claim 1, characterized in that, Among the aforementioned macro-element raw materials, the nitrogen source is agricultural urea with a nitrogen content of ≥46%, the phosphorus source is powdered monoammonium phosphate with an effective phosphorus pentoxide content of ≥45%, and the potassium source is agricultural-grade potassium sulfate with a potassium oxide content of ≥50%; the mass ratio of urea, monoammonium phosphate, and potassium sulfate is (2-3):(1-1.5):(2-2.5).

3. The multi-element synergistic compound fertilizer for fruits and vegetables according to claim 1, characterized in that, The medium-quantity element raw material is composed of calcium nitrate tetrahydrate and magnesium sulfate heptahydrate mixed in a mass ratio of (2-3):1; the total mass of medium-quantity elements accounts for 2%-5% of the total mass of the compound fertilizer, based on oxides.

4. The multi-element synergistic compound fertilizer for fruits and vegetables according to claim 1, characterized in that, The chelated trace element raw material is composed of borax, zinc sulfate heptahydrate, and ferrous sulfate heptahydrate in a mass ratio of (2-3):(1-2):(1-1.5); the chelated trace element raw material is obtained by chelating citric acid and total trace element salt in a mass ratio of (0.5-1):1, and the proportion of chelated trace elements in the final product is ≥60% of the total trace element mass.

5. The multi-element synergistic compound fertilizer for fruits and vegetables according to claim 1, characterized in that, The bonding carrier is calcium-based bentonite or attapulgite; the compound fertilizer is spherical granules with a particle size range of 2 to 4.75 mm and a moisture content of ≤2.0%.

6. A method for preparing the multi-element synergistic compound fertilizer for fruits and vegetables according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Raw material pretreatment: The macro-element raw materials and medium-element raw materials are crushed to 60-80 mesh and put into the mixer according to the ratio to premix and obtain basic mixed powder; (2) Chelation reaction: Citric acid and trace element salts are dissolved in water according to the ratio, the pH of the system is adjusted to 5.0-6.0, and the reaction is carried out by stirring and keeping warm to obtain chelated micro-fertilizer solution; (3) Synergistic premix: The components of the synergistic system are mixed evenly with some dry powder of binder carrier to obtain synergistic premix; (4) Rotary drum granulation: The basic mixed powder and synergistic premix are fed into the rotary drum granulator, and the chelated micro-fertilizer solution and binder aqueous solution are sprayed simultaneously and rolled to granulate to obtain wet granules; (5) Post-treatment molding: The wet granules are dried, cooled and screened in sequence. The qualified granules after screening are coated to obtain finished compound fertilizer.

7. The preparation method according to claim 6, characterized in that, Step (1) Premixing is carried out using a horizontal ribbon mixer with a spindle speed of 30-40 r / min and a mixing time of 8-15 min. The coefficient of variation of the mixing uniformity is ≤5%. In step (2), the solid-liquid mass ratio in the reactor is 1:(3-5). Dilute sulfuric acid or ammonia is used to adjust the pH. The chelation reaction temperature is 55-65℃, the stirring speed is 60-80 r / min, and the reaction time is 40-70 min.

8. The preparation method according to claim 6, characterized in that, Step (3) Use a double-helix conical mixer for mixing. The revolution speed is 10-15 r / min, the rotation speed is 20-30 r / min, and the mixing time is 5-10 min. The amount of binder used is 30%-50% of the total mass of the binder. Step (4) The cylinder of the rotary drum granulator has an inclination angle of 3°-5°, a rotation speed of 18-28 r / min, and the granulation material temperature is controlled at 45-55℃. The total amount of spray liquid is 8%-15% of the total mass of the powder, and the spray pressure is 0.2-0.4 MPa.

9. The preparation method according to claim 6, characterized in that, In step (5), the drying process adopts a two-stage drying process: the first stage drying temperature is 70-80℃ and the duration is 10-15min; the second stage drying temperature is 90-110℃ and the duration is 15-20min; the moisture content of the dried particles is ≤2.0%; the cooling adopts a counter-current air cooling method, and the material temperature is ≤40℃ after cooling; the screening adopts a double-layer vibrating screen with an upper screen hole of 4.75mm and a lower screen hole of 2mm. Unqualified particles are returned to be crushed and re-granulated; the qualified particles after screening are also coated by spraying mineral oil coating agent and coating with talc powder. The amount of coating agent is 0.1%-0.3% of the total mass of particles, and the amount of talc powder is 0.2%-0.5%.

Images