A slow-release fertilizer formula specifically designed for the growth period of guava

Abstract

This invention relates to the field of agricultural fertilizer technology, and in particular to a slow-release fertilizer formula suitable for the growth period of guava. By weight, the core layer comprises 30-40 parts potassium sulfate, 5-8 parts calcium nitrate, and 3-5 parts magnesium sulfate; the middle layer comprises 15-20 parts ammonium dihydrogen phosphate, 1-2 parts borax, and 0.5-1 parts zinc sulfate; the outer layer comprises 20-25 parts urea, 10-15 parts potassium humate, and 3-5 parts amino acid chelate powder; and the coating material comprises 2-4 parts bio-based polyurethane and 0.5-2 parts modified paraffin. This invention employs a core layer, middle layer, and outer layer structure. The outer layer provides fast-acting nutrients that are rapidly released after fertilization, meeting the nitrogen requirements of guava during its budding and shoot-growing stage. The middle layer releases nutrients in large quantities 45-60 days after fertilization, matching the phosphorus, boron, and zinc requirements during the flowering and fruit-setting stage. The core layer provides long-acting, slow-release nutrients that are gradually released during the fruit enlargement stage, meeting the high potassium, calcium, and magnesium requirements. This invention achieves a high degree of consistency between the nutrient release curve and the physiological nutrient requirement curves of guava during shoot growth, flowering, and fruit enlargement.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer technology, and in particular to a slow-release fertilizer formula suitable for the growth period of guava. Background Technology

[0002] Guava is a typical evergreen fruit tree in tropical and subtropical regions, with the biological characteristics of flowering and fruiting year-round. Its nutrient requirements throughout its growth period show significant stage-specific differences: during the budding and shoot emergence period, nitrogen is required in large quantities, as nitrogen is the core element for promoting shoot growth and leaf photosynthesis; during the flowering and fruit setting period, it is sensitive to the requirements of phosphorus and boron, as phosphorus promotes flower bud differentiation and fruit setting, while boron can effectively prevent fruit malformation; during the fruit enlargement period, the demand for potassium and calcium increases sharply, as potassium enhances the sweetness and taste of the fruit, while calcium reduces fruit cracking.

[0003] Currently, most fertilizers for guava on the market are ordinary compound fertilizers. The nutrient release of ordinary compound fertilizers is out of sync with the nutrient requirements of guava. Ordinary compound fertilizers release nutrients too quickly, and in tropical and subtropical rainy areas, they are easily leached away by water. On the other hand, single-rate controlled-release fertilizers cannot adapt to the drastic changes in the ratio of nitrogen, phosphorus, and potassium nutrients required by guava from shoot emergence to fruit setting, which can easily lead to nutrient excess in one growth stage and nutrient deficiency in another. Therefore, it is necessary to design a slow-release fertilizer formula that is suitable for the growth period of guava. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a slow-release fertilizer formula suitable for the growth period of guava.

[0005] The technical solution adopted in this invention is as follows: a slow-release fertilizer formula suitable for the growth period of guava, wherein the fertilizer, by weight, consists of a core layer, a middle layer, an outer layer, and a coating material; the core layer comprises 30-40 parts potassium sulfate, 5-8 parts calcium nitrate, and 3-5 parts magnesium sulfate; the middle layer comprises 15-20 parts ammonium dihydrogen phosphate, 1-2 parts borax, and 0.5-1 parts zinc sulfate; the outer layer comprises 20-25 parts urea, 10-15 parts potassium humate, and 3-5 parts amino acid chelate powder; and the coating material comprises 2-4 parts bio-based polyurethane and 0.5-2 parts modified paraffin.

[0006] As a further description of the above technical solution: The core layer also includes 0.1-0.3 parts of EDTA chelated iron, which is of the EDTA-Fe-13 type and has an iron content of ≥13%.

[0007] As a further description of the above technical solution: The potassium humate is one of mineral-derived potassium humate, biochemical potassium humate, or compound potassium humate, with a humic acid content ≥55% and a potassium content of 8%-11%.

[0008] As a further description of the above technical solution: The amino acid chelated powder is a plant-derived amino acid chelated powder, which is produced by microbial fermentation of soybean meal, rapeseed meal and cottonseed meal, and has a total amino acid content of ≥40%.

[0009] As a further description of the above technical solution: The modified paraffin is one of oxidized microcrystalline wax and oxidized polyethylene wax.

[0010] As a further description of the above technical solution: It also includes 0.5-1 part of Bacillus subtilis agent, wherein the Bacillus subtilis agent is a microcapsule-encapsulated powder and is dispersed between the middle layer and the outer layer.

[0011] As a further description of the above technical solution: The Bacillus subtilis agent is uniformly sprayed onto the surface of the intermediate layer using a 0.5% xanthan gum dilution as a bio-adhesive, forming an agent adhesion layer with a thickness of 10-20 μm.

[0012] As a further description of the above technical solution: In the coating material, bio-based polyurethane and modified paraffin are in a molten mixed state, forming a dense composite coating layer with a thickness of 20-30 μm on the outer layer of fertilizer particles.

[0013] As a further description of the above technical solution: The special fertilizer is in the form of spherical granules with a particle size of 2.0-2.5 mm.

[0014] The present invention has the following beneficial effects: 1. This invention adopts a core layer, middle layer, and outer layer structure. The fast-acting nutrients in the outer layer can be released quickly after fertilization to meet the nitrogen requirements of guava during the budding and shoot growth stage. The nutrients in the middle layer are released in large quantities 45-60 days after fertilization, which is suitable for the phosphorus, boron, and zinc requirements during the flowering and fruit setting stage. The nutrients in the core layer are long-acting and slow-release, which are gradually released during the fruit enlargement stage to meet the high potassium, calcium, and magnesium requirements. This invention achieves a high degree of consistency between the nutrient release curve and the physiological fertilizer requirement curve of guava during shoot growth, flowering, and fruit enlargement, fundamentally solving the problem of the disconnect between the supply and demand of nutrients in existing fertilizers.

[0015] 2. The double-layer coating structure of bio-based polyurethane and modified paraffin in this invention effectively controls the nutrient release rate and avoids leaching loss caused by the rapid release of nutrients in ordinary compound fertilizers. At the same time, the adsorption effect of potassium humate can fix nitrogen and potassium ions in the soil and prevent nutrient loss. The nutrient utilization rate of this invention is higher than that of traditional guava compound fertilizer, reducing the amount of chemical fertilizer applied, and lowering planting costs and environmental pressure.

[0016] 3. The Bacillus subtilis agent added to the formula of this invention can colonize in the soil and secrete antibacterial substances, effectively inhibiting the reproduction of pathogens of soil-borne diseases such as guava root rot and wilt, and reducing the incidence of guava root rot; at the same time, potassium humate can activate the activity of various enzymes in the crop, enhance the tree's adaptability to adverse conditions such as drought and high temperature, and enhance its resistance. Detailed Implementation

[0017] This invention provides a slow-release fertilizer formula suitable for the growth period of guava. By weight, this fertilizer consists of a core layer, a middle layer, an outer layer, and a coating material, with the following design for each component: The core layer consists of 30-40 parts potassium sulfate, 5-8 parts calcium nitrate, and 3-5 parts magnesium sulfate. 0.1-0.3 parts EDTA chelated iron can also be added to provide high potassium, calcium, and magnesium nutrients during the guava fruit enlargement and ripening stages. Potassium promotes sugar accumulation in the fruit, while calcium and magnesium reduce fruit cracking and increase fruit firmness. EDTA chelated iron is a chelated trace element that avoids fixation in acidic soil, preventing yellowing of the tree leaves and ensuring normal photosynthesis.

[0018] The middle layer consists of 15-20 parts ammonium dihydrogen phosphate, 1-2 parts borax, and 0.5-1 parts zinc sulfate. This provides phosphorus, boron, and zinc nutrients for the flowering and fruit setting period of guava. Phosphorus promotes flower bud differentiation and fruit setting, boron prevents deformed fruit, and zinc promotes auxin synthesis to ensure normal flower development. Additionally, 0.5-1 parts of Bacillus subtilis agent are added between the middle and outer layers to release nutrients while inhibiting soil-borne diseases such as guava root rot.

[0019] Outer layer: 20-25 parts urea, 10-15 parts potassium humate, and 3-5 parts amino acid chelate powder. It provides fast-acting nitrogen and organic active substances for guava during the budding and shoot emergence period. Urea quickly replenishes nitrogen and promotes shoot growth, while mineral-derived potassium humate and plant-derived amino acid chelate powder can immediately improve the rhizosphere microenvironment and activate soil nutrients.

[0020] The coating material consists of 2-4 parts bio-based polyurethane and 0.5-2 parts modified paraffin wax (oxidized polyethylene wax). After being melted and mixed, the two form a dense composite coating layer on the outer layer of fertilizer granules. Bio-based polyurethane is the main film-forming substance, ensuring the density and mechanical strength of the coating. Oxidized polyethylene wax is a hydrophobic regulating substance that fills the pores of the polyurethane membrane and reduces the water permeation rate of the coating layer. The two work together to control the nutrient release rate. Furthermore, both bio-based polyurethane and modified paraffin wax are biodegradable, avoiding secondary soil pollution.

[0021] Example 1: The special fertilizer formula in this embodiment, by weight parts, is as follows: Core layer: 35 parts potassium sulfate, 6 parts calcium nitrate, 4 parts magnesium sulfate, 0.2 parts EDTA-Fe-13 chelated iron (iron content ≥13%); Intermediate layer: 18 parts ammonium dihydrogen phosphate, 1.5 parts borax, 0.8 parts zinc sulfate; Outer layer: 22 parts urea, 12 parts mineral-derived potassium humate (humic acid content 58%, K2O content 10%), 4 parts plant-derived amino acid chelate powder (total amino acid content 45%). Coating material: 3 parts bio-based polyurethane and 1 part modified paraffin.

[0022] The preparation method is as follows: Core layer granulation: The core layer components are fed into a disc granulator, and an appropriate amount of deionized water is added as a wetting agent. The granulator speed is adjusted to 30 r / min and the tilt angle is 45° to produce core layer particles with a particle size of 1.5 mm. The core layer particles are placed in a 40℃ hot air drying oven for pre-drying until the moisture content is ≤3%. After cooling to room temperature, they are sieved to remove fine powder and large particles, and then set aside for later use.

[0023] Intermediate layer coating: The core layer particles are fed into a fluidized bed coating machine, and the air conveying system is turned on. The suspension prepared by mixing the intermediate layer components with a 2% sodium carboxymethyl cellulose solution is evenly sprayed onto the surface of the core layer particles through a spray gun. The fluidized bed inlet air temperature is adjusted to 38℃, the outlet air temperature to 32℃, and the atomization pressure to 0.3MPa to achieve uniform coating and rapid film formation of the intermediate layer material. After coating, the material is dried until the moisture content is ≤2.5% to obtain core layer-intermediate layer composite particles for later use.

[0024] Adhesion of the outer layer of fast-acting nutrients: Add the outer layer nutrient mixture fine powder to the fluidized bed coating machine, keep the air conveying system running at low speed, so that the outer layer nutrient fine powder is evenly adhered to the surface of the middle layer; take samples for testing every 5 minutes during the adhesion process to ensure that the outer layer nutrient coating is complete and there is no exposure or peeling, so as to obtain core-shell multilayer basic particles.

[0025] Composite bio-based coating treatment: The core-shell multilayer basic particles are transferred into a special fluidized bed for coating. The composite coating solution is uniformly sprayed onto the outermost layer of the particles through a constant temperature spray gun (spray gun temperature 55℃). The inlet air temperature of the fluidized bed is adjusted to 45℃ and the atomization pressure is 0.4MPa. The spraying speed is controlled to form a dense composite coating layer with a thickness of 20μm on the particle surface. After coating, the particles are dried by air conveying until the coating layer is completely formed and there is no particle sticking.

[0026] Drying, cooling, and finished product packaging: The coated fertilizer granules are transferred to a low-temperature dryer and dried at 55℃ for 2.5 hours, controlling the moisture content of the finished product to ≤2%; then they are transferred to a cooling sieve and cooled to 25℃ under room temperature cold air, and passed through a 2.0mm standard sieve to remove fine powder, broken particles, and oversized particles; finally, they are vacuum-packed in moisture-proof woven bags and stored in a dry and ventilated warehouse at 15℃ and relative humidity ≤60%.

[0027] Example 2: The special fertilizer formula in this embodiment, by weight parts, is as follows: Core layer: 35 parts potassium sulfate, 6 parts calcium nitrate, 4 parts magnesium sulfate, 0.2 parts EDTA-Fe-13 chelated iron (iron content ≥13%); Intermediate layer: 18 parts ammonium dihydrogen phosphate, 1.5 parts borax, 0.8 parts zinc sulfate; Disease-resistant additives: 0.8 parts of Bacillus subtilis agent (effective viable count ≥20 billion / g, dispersed between the middle and outer layers); Outer layer: 22 parts urea, 12 parts mineral-derived potassium humate (humic acid content 58%, K2O content 10%), 4 parts plant-derived amino acid chelate powder (total amino acid content 45%). Coating material: 3 parts bio-based polyurethane and 1 part modified paraffin.

[0028] The preparation method is as follows: Core layer granulation: The core layer components are fed into a disc granulator, and an appropriate amount of deionized water is added as a wetting agent. The granulator speed is adjusted to 35 r / min and the tilt angle is 45° to produce core layer particles with a particle size of 2.0 mm. The core layer particles are placed in a 40℃ hot air drying oven for pre-drying until the moisture content is ≤3%. After cooling to room temperature, they are sieved to remove fine powder and large particles, and then set aside for later use.

[0029] Intermediate layer coating: The core layer particles are fed into a fluidized bed coating machine, and the air conveying system is turned on. The suspension prepared by mixing the intermediate layer components with a 2% sodium carboxymethyl cellulose solution is evenly sprayed onto the surface of the core layer particles through a spray gun. The fluidized bed inlet air temperature is adjusted to 40℃, the outlet air temperature to 32℃, and the atomization pressure to 0.4MPa to achieve uniform coating and rapid film formation of the intermediate layer material. After coating, the material is dried until the moisture content is ≤2.5% to obtain core layer-intermediate layer composite particles for later use.

[0030] Bacillus subtilis agent spraying: Keeping the parameters of the fluidized bed coating machine unchanged, mix Bacillus subtilis agent with 0.5% xanthan gum dilution at a weight ratio of 10:1, and spray it evenly on the surface of the composite particles through a low-pressure spray gun (atomization pressure 0.3MPa) to form an agent adhesion layer; during the spraying process, continue low-speed air conveying to avoid agent particle agglomeration. After the spraying is completed, directly transfer to the next process. The entire process time is controlled to be ≤30min.

[0031] Adhesion of the outer layer of fast-acting nutrients: Add the fine powder of the outer layer of nutrients to the fluidized bed coating machine, keep the air conveying system running at a low speed, and use the adhesiveness of xanthan gum to make the fine powder of the outer layer of nutrients evenly adhere to the surface of the bacterial agent layer; take samples for testing every 5 minutes during the adhesion process to ensure that the outer layer of nutrients is completely coated without any exposure or peeling, and obtain core-shell multilayer basic particles.

[0032] Composite bio-based coating treatment: The core-shell multilayer basic particles are transferred into a special fluidized bed for coating. The composite coating solution is uniformly sprayed onto the outermost layer of the particles through a constant temperature spray gun (spray gun temperature 60℃). The inlet air temperature of the fluidized bed is adjusted to 45℃ and the atomization pressure is 0.5MPa. The spraying speed is controlled to form a dense composite coating layer with a thickness of 30μm on the particle surface. After coating, the particles are dried by air until the coating layer is completely formed and there is no particle sticking.

[0033] Drying, cooling and finished product packaging: The coated fertilizer granules are transferred to a low-temperature dryer and dried at 60℃ for 2 hours, controlling the moisture content of the finished product to ≤2%; then transferred to a cooling sieve and cooled to 25℃ under room temperature cold air, and passed through a 2.5mm standard sieve to remove fine powder, broken particles and oversized particles; finally, they are vacuum packaged in moisture-proof woven bags and stored in a dry and ventilated warehouse at 20℃ and relative humidity ≤60%.

[0034] Comparative Example 1: Commercially available ordinary guava compound fertilizer We use commercially available 18-7-25 type guava-specific compound fertilizer, with a nitrogen content of 18%, a phosphorus content of 7%, and a potassium content of 25%, and no trace elements or soil conditioners.

[0035] Test site Guava planting base in Zhangzhou City, Fujian Province (tropical and subtropical climate, annual rainfall over 1500mm, soil type: red soil, pH 4.7, organic matter content 12.3g / kg, bulk density 1.56g / cm³). 3 (This is a typical acidified and compacted guava orchard).

[0036] Test materials The guava variety used in the test was Pearl Guava. Plants that were 3 years old, had uniform growth, and were free from pests and diseases were selected, with a plant spacing of 3.5m × 3m.

[0037] Experimental Groups The experiment included three treatments: Example 1, Example 2, and Comparative Example 1, with three trees per treatment and three replicates in a randomized block design. The fertilizer application rate for each treatment was 2 kg / tree, applied as a single basal application, while other field management practices (pruning, watering, and control of non-soil-borne diseases and pests) remained consistent.

[0038] Measurement Indicators and Methods Nutrient release pattern: The soil culture dissolution method (NY / T 2272-2012) was used to determine the amount of available nitrogen, available phosphorus, and available potassium dissolved in the soil at 7, 15, 30, 45, 60, 75, 90, and 120 days after fertilization, and the cumulative nutrient release rate was calculated. Guava fertilizer requirements: The fertilizer requirements and proportion of each stage of the guava were determined during the budding and shoot growth period (1-30 days), flowering and fruit setting period (31-60 days), and fruit enlargement period (61-120 days). Nutrient utilization rate: The total nutrient utilization rate of nitrogen, phosphorus, and potassium was determined by the difference method; Tree growth indicators: The length of new shoots was measured 90 days after fertilization. Ten new shoots were randomly selected from each tree, and the average value was taken. Fruit quality indicators: After the fruit matures, 10 disease-free fruits are randomly selected from each plant, and the single fruit weight, soluble solids content (ATAGO digital display saccharimeter), deformed fruit rate, and cracked fruit rate are measured. Soil parameters: 120 days after fertilization, rhizosphere soil samples were collected to determine soil pH, organic matter content, and soil bulk density. Disease incidence rate: The incidence rate of guava root rot during the growing season is statistically analyzed.

[0039] Table 1 shows the relevant data on the cumulative nutrient release rate (%) of the special fertilizer in Example 2.

[0040] Table 1 Table 2 shows the relevant data on the percentage of nitrogen, phosphorus, and potassium fertilizer requirements for guava at different growth stages.

[0041] Table 2 Combining Tables 1 and 2, it can be seen that the nutrient release and fertilizer requirement patterns are highly matched: the cumulative release rate of effective nitrogen in Example 2 was 91.2% over 30 days, the cumulative release rate of effective phosphorus over 60 days was 88.6%, and the cumulative release rate of available potassium over 90 days was 89.7%. These figures are precisely matched with the proportion of nitrogen fertilizer requirement during the guava budding and shoot growth period (89.5%), the proportion of phosphorus fertilizer requirement during the flowering and fruit setting period (87.3%), and the proportion of potassium fertilizer requirement during the fruit enlargement period (40.3%). This achieves a gradient release pattern of nitrogen first, phosphorus second, and potassium third, which is highly consistent with the fertilizer requirement curve of guava throughout its entire growth period.

[0042] Table 3 shows the relevant data from the comprehensive test.

[0043] Table 3 Experimental Analysis 1. Nutrient utilization rate: As shown in Table 3, the nutrient utilization rates of Example 1 and Example 2 reached 68.5% and 70.2% respectively, which are much higher than the 32.3% of Comparative Example 1 and more than 35% higher than traditional fertilizers. This indicates that the multi-layer gradient coating structure of the present invention effectively controls the nutrient release rate and reduces leaching loss. The adsorption effect of potassium humate further improves the nutrient utilization rate and solves the problem of easy nutrient loss of guava fertilizer in tropical rainy areas.

[0044] 2. Tree growth: As shown in Table 3, the new shoot lengths of Example 1 and Example 2 were 48.6 cm and 50.2 cm, respectively, which were 54.3% and 59.4% higher than those of Comparative Example 1. This indicates that the outer layer of fast-acting nitrogen in the formula of this invention can quickly meet the nutrient requirements of guava during the shoot emergence period, and the chelated iron effectively prevents leaf yellowing, ensuring normal photosynthesis. The tree growth is significantly better than that of ordinary compound fertilizer treatment.

[0045] 3. Fruit quality: As shown in Table 3, the single fruit weight of Example 1 and Example 2 groups increased by 17.2% and 19.6% respectively compared with Comparative Example 1, and the soluble solids content increased by 23.4% and 27.4% respectively. The rates of deformed fruit and cracked fruit were significantly reduced, indicating that the boron, calcium, zinc and other elements added in this invention effectively solved the problems of deformed and cracked guava fruit. The synergistic effect of potassium and potassium humate significantly improved the sweetness of the fruit and greatly improved the commercial quality of the fruit.

[0046] 4. Soil Improvement: As shown in Table 3, the soil pH values ​​in Example 1 and Example 2 increased from 4.7 to 5.6 and 5.8 respectively, the soil organic matter content increased from 12.3 g / kg to 21.5 g / kg and 22.8 g / kg respectively, and the soil bulk density increased from 1.56 g / cm³. 3 Reduced to 1.32 g / cm³ 3 and 1.28g / cm 3 In contrast, the soil pH value of Comparative Example 1 was further reduced, the organic matter content did not increase significantly, and the soil bulk density increased slightly. This indicates that the mineral-derived potassium humate in this invention effectively neutralized the soil acidity, improved the soil aggregate structure, and alleviated soil compaction, achieving the dual effects of nutrient supply and soil conditioning.

[0047] 5. Disease control: As shown in Table 3, the incidence of root rot in Example 2 group, which added Bacillus subtilis agent, was only 0.4%, which was 81.8% lower than that in Example 1 group and 93.0% lower than that in Comparative Example 1 group. This indicates that Bacillus subtilis agent can effectively inhibit the occurrence of root rot in guava. The incidence of root rot in Example 1 group was also lower than that in Comparative Example 1 group because potassium humate improved the soil microecology and enhanced the tree's resistance to stress.

[0048] In summary, the slow-release fertilizer formula of this invention, adapted to the growth period of guava, can achieve gradient release of nutrients, accurately match the nutrient requirements of guava at different growth stages, significantly improve nutrient utilization, significantly improve fruit quality, improve orchard soil structure, and inhibit soil-borne diseases. It is a high-efficiency, environmentally friendly, and multifunctional fertilizer specifically for guava, and has good promotion and application value.

[0049] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is 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 slow-release fertilizer formula suitable for the growth period of guava, characterized in that, The special fertilizer, by weight, consists of a core layer, a middle layer, an outer layer, and a coating material; the core layer comprises 30-40 parts potassium sulfate, 5-8 parts calcium nitrate, and 3-5 parts magnesium sulfate; the middle layer comprises 15-20 parts ammonium dihydrogen phosphate, 1-2 parts borax, and 0.5-1 parts zinc sulfate; the outer layer comprises 20-25 parts urea, 10-15 parts potassium humate, and 3-5 parts amino acid chelate powder; and the coating material comprises 2-4 parts bio-based polyurethane and 0.5-2 parts modified paraffin.

2. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, The core layer also includes 0.1-0.3 parts of EDTA chelated iron, which is of the EDTA-Fe-13 type and has an iron content of ≥13%.

3. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, The potassium humate is one of mineral-derived potassium humate, biochemical potassium humate, or compound potassium humate, with a humic acid content ≥55% and a potassium content of 8%-11%.

4. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, The amino acid chelated powder is a plant-derived amino acid chelated powder, which is produced by microbial fermentation of soybean meal, rapeseed meal and cottonseed meal, and has a total amino acid content of ≥40%.

5. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, The modified paraffin is one of oxidized microcrystalline wax and oxidized polyethylene wax.

6. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, It also includes 0.5-1 part of Bacillus subtilis agent, wherein the Bacillus subtilis agent is a microcapsule-encapsulated powder and is dispersed between the middle layer and the outer layer.

7. The slow-release fertilizer formula adapted to the growth period of guava according to claim 6, characterized in that, The Bacillus subtilis agent is uniformly sprayed onto the surface of the intermediate layer using a 0.5% xanthan gum dilution as a bio-adhesive, forming an agent adhesion layer with a thickness of 10-20 μm.

8. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, In the coating material, bio-based polyurethane and modified paraffin are in a molten mixed state, forming a dense composite coating layer with a thickness of 20-30 μm on the outer layer of fertilizer particles.

9. The slow-release fertilizer formula adapted to the growth period of guava according to claim 1, characterized in that, The special fertilizer is in the form of spherical granules with a particle size of 2.0-2.5 mm.

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