Preparation method of special controlled-release organic fertilizer for eucalyptus

Abstract

The invention discloses a preparation method of a controlled release organic fertilizer special for eucalyptus, which comprises the following steps: uniformly mixing decomposed farmyard manure, compound fertilizer, clay, borax and zinc sulfate according to the nutritional requirements of the eucalyptus in different growth stages to obtain a base fertilizer; the preparation method comprises the following steps: mixing urea, monoammonium phosphate, calcium superphosphate, potassium chloride, clay, manganese sulfate, diammonium phosphate, potassium sulfate, magnesium potassium sulfate, borax, zinc sulfate and other raw materials according to different proportions, granulating, and respectively spraying with a polyurethane coating liquid and an epoxy resin coating liquid, polyurethane coating layers and epoxy resin coating layers with different thicknesses are sprayed on the through holes to obtain slow release fertilizers with different slow release periods, the slow release fertilizers with different slow release periods are mixed in proportion and then applied to planting holes at one time when eucalyptus is planted, and the slow release fertilizers are released in different growth periods of the eucalyptus; the proportion of various nutrient substances is regulated and controlled to meet the nutritional requirements of the eucalyptus in different growth stages, so that the fertilization frequency is greatly reduced, and the problem that the fertilization cost is relatively high is solved.

Description

A method for preparing a controlled-release organic fertilizer specifically for eucalyptus trees Technical Field

[0001] This invention belongs to the field of eucalyptus organic fertilizer technology, specifically relating to a method for preparing a controllable release organic fertilizer for eucalyptus. Background Technology

[0002] Eucalyptus is a collective term for plants in the genera *Eucalyptus*, *Eucalyptus*, and *Eucalyptus* within the Myrtaceae family. Most are evergreen trees, and there are many varieties. Eucalyptus trees are characterized by wide adaptability, strong resistance, drought tolerance, tolerance to poor soil, rapid growth, and good trunk shape. They can be used in industries such as pulp and paper making, engineered wood products, and construction. They can also be used as biomass energy and can produce forest by-products such as eucalyptus oil and eucalyptus polyphenols.

[0003] Eucalyptus trees require a large amount of water and fertilizer, especially in the first three years after planting, when multiple fertilizations are needed annually, often through hole-drilling, resulting in high fertilization costs. While slow-release fertilizers can reduce fertilization frequency and lower manual fertilization costs, existing eucalyptus organic fertilizers typically have a release period of 60-180 days, a relatively short period. Therefore, two fertilizations are still required annually for the first three years, keeping fertilization costs high during this initial period. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention discloses a method for preparing a controlled-release organic fertilizer specifically for eucalyptus trees. This method combines multiple slow-release fertilizers with different release cycles, significantly reducing the number of fertilization applications and solving the problem of high fertilization costs.

[0005] The present invention is achieved by the following technical solution: a method for preparing a controllable release organic fertilizer for eucalyptus trees, comprising the following steps: (1) taking well-rotted farmyard manure, compound fertilizer, clay, borax and zinc sulfate and mixing them evenly to obtain a base fertilizer, wherein the base fertilizer comprises the following components by mass fraction: organic matter 15-25%, total nitrogen 8-12%, P2O5 15-18%, K2O 12-15%, borax 0.05-0.1%, zinc sulfate 0.2-0.5%, and the remainder being clay; (2) taking urea, monoammonium phosphate, superphosphate, potassium chloride, clay and manganese sulfate and mixing them to granulate to obtain fertilizer granules I, and then spraying the surface of fertilizer granules I with polyurethane coating liquid to obtain slow-release fertilizer I; wherein fertilizer granules I comprises the following components by mass fraction: total nitrogen 10-15%, P2O5 10-15%, K2O 10-15%, manganese sulfate 0.2-0.3%, the remainder is clay; the thickness of the polyurethane coating of the slow-release fertilizer I is 15-25 μm; (3) Take urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax and zinc sulfate, mix them and granulate them to obtain fertilizer granules II, and then spray the surface of fertilizer granules II with polyurethane coating liquid to obtain slow-release fertilizer II; the fertilizer granules II include the following components by mass fraction: total nitrogen 15-18%, P2O5 3-5%, K2O 12-15%, borax 0.05-0.1%, zinc sulfate 0.2-0.5%, the remainder being clay; the thickness of the polyurethane coating of the slow-release fertilizer I is 45-55 μm; (4) Take urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax, and zinc sulfate, mix them, and granulate them to obtain fertilizer granules III. The fertilizer granules III include the following components in mass fraction: total nitrogen 8-12%, P2O5 8-12%, K2O 15-18%, borax 0.02-0.05%, zinc sulfate 0.1-0.2%, the remainder being clay; (5) Take two equal amounts of fertilizer granules III, spray one portion of fertilizer granules III with epoxy resin coating liquid to obtain slow-release fertilizer III, mix slow-release fertilizer III and calcium carbonate evenly to obtain fertilizer granules IV, spray the surface of fertilizer granules IV with polyurethane coating liquid to obtain slow-release fertilizer IV, mix slow-release fertilizer IV and another portion of fertilizer granules III evenly to obtain fertilizer granules V, and use The surface of fertilizer granules V is sprayed with epoxy resin coating liquid to obtain slow-release fertilizer V; the polyurethane coating thickness of the slow-release fertilizer IV is 10-15 μm; the epoxy resin coating thickness of the slow-release fertilizer III and slow-release fertilizer V is 50-70 μm; (6) Take base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V, and mix them evenly according to the weight ratio of base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V of 2:(1-2):(1-1.5):(1-1.2) to obtain eucalyptus-specific controlled-release organic fertilizer.

[0006] Furthermore, the particle size of fertilizer granules I, II, and III is 2–4 mm.

[0007] Furthermore, in step (1), the base fertilizer contains one of lime, sulfur powder, or aluminum sulfate to adjust the soil pH to 5.5-6.5.

[0008] Furthermore, in step (5), an epoxy resin coating solution is prepared using an epoxy resin with an equilibrium swelling degree of less than 120% and a glass transition temperature (Tg) greater than 150°C.

[0009] Furthermore, in step (5), slow-release fertilizer III and calcium carbonate are uniformly mixed in a mass ratio of (5-10):1 to obtain fertilizer granules IV. The simultaneous release of calcium carbonate and slow-release fertilizer III helps to regulate the soil pH, which is beneficial for maintaining a suitable soil pH for eucalyptus growth.

[0010] Furthermore, in step (6), the eucalyptus-specific controlled-release organic fertilizer is applied once during eucalyptus planting, and is mixed with the soil at a ratio of 0.3 to 0.6 kg per planting hole before being backfilled into the planting hole.

[0011] Compared with existing technologies, this technical solution has the following advantages: 1. This invention mixes base fertilizer and slow-release fertilizer with different slow-release periods in a certain proportion and applies it all at once when planting eucalyptus trees, thereby reducing the number of topdressings during the first three years of eucalyptus growth and lowering the cost of manual fertilization. Simultaneously, the nutrient ratios in different slow-release fertilizers are specifically adjusted according to different slow-release periods to ensure that eucalyptus trees receive the necessary nutrients at different stages of growth, avoiding nutritional imbalances.

[0012] 2. This invention uses a mixture of well-rotted farmyard manure, compound fertilizer, clay, borax, and zinc sulfate in a specific ratio to prepare base fertilizer. The organic matter improves the rhizosphere soil, creating a favorable microbial environment and enhancing water and fertilizer retention capacity. It also replenishes soil fertility, providing readily available nutrients to newly planted eucalyptus seedlings, promoting new root growth, and increasing survival rate. Next, this invention uses a mixture of urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate to prepare fertilizer granules I. The surface of fertilizer granules I is then sprayed with a polyurethane coating solution to obtain slow-release fertilizer I. The thickness of the polyurethane coating layer is controlled at 15–25 μm, ensuring the slow-release fertilizer... Fertilizer I provides a 3-month slow-release period, offering high nitrogen and phosphorus nutrients in the early stages of eucalyptus planting to promote root growth and seedling development. Meanwhile, fertilizer granules II are prepared by mixing urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax, and zinc sulfate. The surface of fertilizer granules II is then coated with a polyurethane coating solution to create slow-release fertilizer II. The thickness of the polyurethane coating layer is controlled at 45–55 μm, allowing fertilizer II to achieve a slow-release period of approximately 9 months. Over 6–9 months after eucalyptus planting, the release of nutrients gradually increases, shifting from high nitrogen and phosphorus to high nitrogen and potassium, thus promoting growth.

[0013] 3. This invention uses a mixture of urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax, and zinc sulfate, which is then granulated to obtain fertilizer granules III. These granules are then coated with an epoxy resin layer with a thickness of 50-70 μm to meet the nutrient requirements of eucalyptus trees in the first 1-2 years after planting, promoting lignification and improving resistance. The multi-layer coating method allows the slow-release fertilizer to achieve a slow-release effect of about 2 years. Specifically, some fertilizer granules III are first coated with an epoxy resin layer and then with a polyurethane layer, resulting in a longer slow-release period. Furthermore, to address the potential soil acidification after eucalyptus planting, calcium carbonate is mixed with fertilizer granules III and coated to regulate soil pH through the slow release of calcium carbonate, creating a suitable acid-base environment for eucalyptus growth. Detailed Implementation

[0014] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0015] Example 1: A method for preparing a controlled-release organic fertilizer for eucalyptus trees, comprising the following steps: (1) taking well-rotted farmyard manure, compound fertilizer, clay, borax, and zinc sulfate and mixing them evenly to obtain a base fertilizer, wherein the base fertilizer comprises the following components by mass fraction: 20% organic matter, 10% total nitrogen, 16% P2O5, 14% K2O, 0.08% borax, 0.3% zinc sulfate, and the remainder being clay; the base fertilizer contains lime to adjust the soil pH to 6.0; (2) taking urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate and mixing them to granulate to obtain fertilizer granules I with a particle size of 3mm, and then spraying the surface of fertilizer granules I with polyurethane coating liquid to obtain slow-release fertilizer I; wherein fertilizer granules I comprises the following components by mass fraction: 12% total nitrogen, 12% P2O5, 14% K2O, 0.08% borax, 0.3% zinc sulfate, and the remainder being clay; 12%, manganese sulfate 0.25%, the remainder is clay; the thickness of the polyurethane coating of the slow-release fertilizer I is 20μm; (3) Take urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax and zinc sulfate, mix them and granulate to obtain fertilizer particles II with a particle size of 3mm, and then spray the surface of fertilizer particles II with polyurethane coating liquid to obtain slow-release fertilizer II; the fertilizer particles II include the following components by mass fraction: total nitrogen 16%, P2O 54%, K2O 14%, borax 0.08%, zinc sulfate 0.3%, the remainder being clay; the thickness of the polyurethane coating of the slow-release fertilizer I is 50μm; (4) Take urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax, and zinc sulfate, mix them, and granulate them to obtain fertilizer particles III with a particle size of 3mm. The fertilizer particles III include the following components by mass fraction: total nitrogen 10%, P2O5 10%, K2O 16%, borax 0.03%, zinc sulfate 0.15%, the remainder is clay; (5) Take two equal amounts of fertilizer granules III, spray one part of fertilizer granules III with epoxy resin coating liquid to obtain slow-release fertilizer III, mix slow-release fertilizer III and calcium carbonate in a mass ratio of 8:1 to obtain fertilizer granules IV, spray the surface of fertilizer granules IV with polyurethane coating liquid to obtain slow-release fertilizer IV, mix slow-release fertilizer IV and another part of fertilizer granules III in a uniform manner to obtain fertilizer granules V, spray the surface of fertilizer granules V with epoxy resin coating liquid to obtain slow-release fertilizer V; the polyurethane coating thickness of the slow-release fertilizer IV is 1 2μm; the epoxy resin coating thickness of the slow-release fertilizer III and slow-release fertilizer V is 60μm; epoxy resin coating liquid is prepared using epoxy resin with a balance swelling degree of 110% and a glass transition temperature (Tg) of 135℃; (6) take base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V, and mix them evenly in a weight ratio of 2:1.5:1.2:1.05 to obtain eucalyptus-specific controlled-release organic fertilizer; the eucalyptus-specific controlled-release organic fertilizer is applied once when planting eucalyptus trees, and is mixed with soil and backfilled into the planting hole in a ratio of 0.5 kg per planting hole.

[0016] Example 2: A method for preparing a controlled-release organic fertilizer for eucalyptus trees, comprising the following steps: (1) taking well-rotted farmyard manure, compound fertilizer, clay, borax, and zinc sulfate and mixing them evenly to obtain a base fertilizer, wherein the base fertilizer comprises the following components by mass fraction: 15% organic matter, 8% total nitrogen, 15% P2O5, 12% K2O, 0.05% borax, 0.2% zinc sulfate, and the remainder being clay; aluminum sulfate is added to the base fertilizer to adjust the soil pH to 5.5; (2) taking urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate and mixing them to granulate fertilizer particles I with a particle size of 2mm, and then spraying the surface of fertilizer particles I with polyurethane coating liquid to obtain slow-release fertilizer I; wherein fertilizer particles I comprise the following components by mass fraction: 10% total nitrogen, 10% P2O5, 10% K2O, 0.05% borax, 0.2% zinc sulfate, and the remainder being clay; aluminum sulfate is added to the base fertilizer to adjust the soil pH to 5.5; (3) taking urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate and mixing them to obtain fertilizer particles I with a particle size of 2mm, and then spraying the surface of fertilizer particles I with polyurethane coating liquid to obtain slow-release fertilizer I; fertilizer particles I comprise the following components by mass fraction: 10% total nitrogen, 10% P2O5, 10% K2O, 0.05% borax, 0.05% zinc sulfate, and the remainder being clay; 10%, manganese sulfate 0.2%, the remainder is clay; the polyurethane coating thickness of the slow-release fertilizer I is 15μm; (3) Take urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax and zinc sulfate and mix them to obtain fertilizer particles II with a particle size of 2mm. Then spray the surface of fertilizer particles II with polyurethane coating liquid to obtain slow-release fertilizer II; the fertilizer particles II include the following components in mass fraction: total nitrogen 15%, P2O5 3%, K2O 12%, borax 0.05%, zinc sulfate 0.2%, the remainder is clay; the polyurethane coating thickness of the slow-release fertilizer I is 45μm; (4) Take urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax and zinc sulfate and mix them to obtain fertilizer particles III with a particle size of 2mm. The fertilizer particles III include the following components in mass fraction: total nitrogen 8%, P2O5 8%, K2O 15%, borax 0.02%, zinc sulfate 0.1%, the remainder being clay; (5) Take two equal amounts of fertilizer granules III, spray one part of fertilizer granules III with epoxy resin coating liquid to obtain slow-release fertilizer III, mix slow-release fertilizer III and calcium carbonate in a mass ratio of 5:1 to obtain fertilizer granules IV, spray the surface of fertilizer granules IV with polyurethane coating liquid to obtain slow-release fertilizer IV, mix slow-release fertilizer IV and another part of fertilizer granules III in a uniform manner to obtain fertilizer granules V, spray the surface of fertilizer granules V with epoxy resin coating liquid to obtain slow-release fertilizer V; the slow-release The polyurethane coating thickness of fertilizer IV is 10 μm; the epoxy resin coating thickness of the slow-release fertilizer III and slow-release fertilizer V is 50 μm; an epoxy resin coating liquid is prepared using epoxy resin with an equilibrium swelling degree of 110% and a glass transition temperature (Tg) of 135℃; (6) take base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V, and mix them evenly in a weight ratio of 2:1:1:1 to obtain eucalyptus-specific controlled-release organic fertilizer; the eucalyptus-specific controlled-release organic fertilizer is applied once when planting eucalyptus trees, and the amount applied in each planting hole is 0.Mix 6 kg of the mixture with the soil and backfill it into the planting hole.

[0017] Example 3: A method for preparing a controlled-release organic fertilizer for eucalyptus trees, comprising the following steps: (1) taking well-rotted farmyard manure, compound fertilizer, clay, borax, and zinc sulfate and mixing them evenly to obtain a base fertilizer, wherein the base fertilizer comprises the following components by mass fraction: organic matter 22%, total nitrogen 9%, P2O5 16%, K2O 13%, borax 0.06%, zinc sulfate 0.4%, and the remainder being clay; the base fertilizer contains sulfur powder to adjust the soil pH to 5.8; (2) taking urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate and mixing them to granulate to obtain fertilizer granules I with a particle size of 3mm, and then spraying the surface of fertilizer granules I with polyurethane coating liquid to obtain slow-release fertilizer I; wherein fertilizer granules I comprise the following components by mass fraction: total nitrogen 13%, P2O5 11%, K2O 11%, manganese sulfate 0.28%, the remainder is clay; the polyurethane coating thickness of the slow-release fertilizer I is 20μm; (3) Take urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax and zinc sulfate and mix them to obtain fertilizer particles II with a particle size of 3mm. Then, spray the surface of fertilizer particles II with polyurethane coating liquid to obtain slow-release fertilizer II; the fertilizer particles II include the following components by mass fraction: total nitrogen 17%, P2O5 4%, K2O 13%, borax 0.08%, zinc sulfate 0.4%, the remainder is clay; the polyurethane coating thickness of the slow-release fertilizer I is 50μm; (4) Take urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax and zinc sulfate and mix them to obtain fertilizer particles III with a particle size of 3mm. The fertilizer particles III include the following components by mass fraction: total nitrogen 10%, P2O5 10%, K2O 17%, borax 0.03%, zinc sulfate 0.12%, the remainder is clay; (5) Take two equal amounts of fertilizer granules III, spray one part of fertilizer granules III with epoxy resin coating liquid to obtain slow-release fertilizer III, mix slow-release fertilizer III and calcium carbonate in a mass ratio of 6:1 to obtain fertilizer granules IV, spray the surface of fertilizer granules IV with polyurethane coating liquid to obtain slow-release fertilizer IV, mix slow-release fertilizer IV and another part of fertilizer granules III in a uniform manner to obtain fertilizer granules V, spray the surface of fertilizer granules V with epoxy resin coating liquid to obtain slow-release fertilizer V; the slow-release fertilizer I The polyurethane coating thickness of V is 12 μm; the epoxy resin coating thickness of the slow-release fertilizer III and slow-release fertilizer V is 65 μm; an epoxy resin coating liquid is prepared using epoxy resin with an equilibrium swelling degree of 110% and a glass transition temperature (Tg) of 135℃; (6) take base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V, and mix them evenly in a weight ratio of 2:1.8:1.1:1.1 to obtain eucalyptus-specific controlled-release organic fertilizer; the eucalyptus-specific controlled-release organic fertilizer is applied once when planting eucalyptus trees, and the amount applied in each planting hole is 0.Mix 4 kg of the mixture with the soil and backfill it into the planting hole.

[0018] Example 4: A method for preparing a controlled-release organic fertilizer for eucalyptus trees, comprising the following steps: (1) taking well-rotted farmyard manure, compound fertilizer, clay, borax, and zinc sulfate and mixing them evenly to obtain a base fertilizer, wherein the base fertilizer comprises the following components by mass fraction: 25% organic matter, 12% total nitrogen, 18% P2O5, 15% K2O, 0.1% borax, 0.5% zinc sulfate, and the remainder being clay; the base fertilizer contains lime to adjust the soil pH to 6.5; (2) taking urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate and mixing them to granulate fertilizer particles I with a particle size of 4mm, and then spraying the surface of fertilizer particles I with polyurethane coating liquid to obtain slow-release fertilizer I; wherein fertilizer particles I comprise the following components by mass fraction: 15% total nitrogen, 15% P2O5, 15% K2O, 0.1% borax, 0.5% zinc sulfate, and the remainder being clay; 15%, manganese sulfate 0.3%, the remainder is clay; the polyurethane coating thickness of the slow-release fertilizer I is 25μm; (3) Take urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax and zinc sulfate and mix them to granulate to obtain fertilizer particles II with a particle size of 4mm. Then, spray the surface of fertilizer particles II with polyurethane coating liquid to obtain slow-release fertilizer II; the fertilizer particles II include the following components in mass fraction: total nitrogen 18%, P2O5 5%, K2O 15%, borax 0.1%, zinc sulfate 0.5%, the remainder is clay; the polyurethane coating thickness of the slow-release fertilizer I is 55μm; (4) Take urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax and zinc sulfate and mix them to granulate to obtain fertilizer particles III with a particle size of 4mm. The fertilizer particles III include the following components in mass fraction: total nitrogen 12%, P2O5 12%, K2O 18%, borax 0.05%, zinc sulfate 0.2%, the remainder being clay; (5) Take two equal amounts of fertilizer granules III, spray one part of fertilizer granules III with epoxy resin coating liquid to obtain slow-release fertilizer III, mix slow-release fertilizer III and calcium carbonate in a mass ratio of 10:1 to obtain fertilizer granules IV, spray the surface of fertilizer granules IV with polyurethane coating liquid to obtain slow-release fertilizer IV, mix slow-release fertilizer IV and another part of fertilizer granules III in a uniform manner to obtain fertilizer granules V, spray the surface of fertilizer granules V with epoxy resin coating liquid to obtain slow-release fertilizer V; the slow-release fertilizer The polyurethane coating thickness of IV is 15 μm; the epoxy resin coating thickness of the slow-release fertilizer III and slow-release fertilizer V is 70 μm; an epoxy resin coating liquid is prepared using epoxy resin with an equilibrium swelling degree of 110% and a glass transition temperature (Tg) of 135℃; (6) take base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V, and mix them evenly in a weight ratio of 2:2:15:1.2 to obtain eucalyptus-specific controlled-release organic fertilizer; the eucalyptus-specific controlled-release organic fertilizer is applied once when planting eucalyptus trees, and the amount applied in each planting hole is 0.Mix 3 kg of the mixture with the soil and backfill it into the planting hole.

[0019] Experimental Example: A eucalyptus planting experiment was conducted on February 25, 2025, in a forest farm in Fangchenggang, Guangxi. The spacing between plants was 2.5m × 3.0m. 0.5 kg of fertilizer was applied per planting hole. Experimental Group 1: Only the base fertilizer prepared in Example 1 was applied once at the time of planting. Experimental Group 2: Equal parts of the base fertilizer prepared in Example 1, slow-release fertilizer I, and slow-release fertilizer II were mixed and applied once at the time of planting. Experimental Group 3: Eucalyptus-specific controlled-release organic fertilizer was applied once at the time of planting. The tree height and diameter at breast height (DBH) of the eucalyptus trees were monitored at different time points. Specific results are shown in Table 1.

[0020] Table 1 Eucalyptus growth status

[0021] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a controlled-release organic fertilizer specifically for eucalyptus trees, characterized in that: Includes the following steps: (1) Take well-rotted farmyard manure, compound fertilizer, clay, borax, and zinc sulfate and mix them evenly to obtain base fertilizer. The base fertilizer includes the following components by mass fraction: organic matter 15-25%, total nitrogen 8-12%, P2O5 15-18%, K2O 12-15%, borax 0.05-0.1%, zinc sulfate 0.2-0.5%, and the remainder is clay; (2) Take urea, monoammonium phosphate, superphosphate, potassium chloride, clay, and manganese sulfate and mix them to granulate fertilizer granules I. Then, spray the surface of fertilizer granules I with polyurethane coating liquid to obtain slow-release fertilizer I. The fertilizer granules I include the following components by mass fraction: total nitrogen 10-15%, P2O5 10-15%, K2O 10-15%, manganese sulfate 0.2-0.3%, the remainder is clay; the thickness of the polyurethane coating of the slow-release fertilizer I is 15-25 μm; (3) Take urea, monoammonium phosphate, potassium nitrate, potassium sulfate, clay, borax and zinc sulfate, mix them and granulate them to obtain fertilizer granules II, and then spray the surface of fertilizer granules II with polyurethane coating liquid to obtain slow-release fertilizer II; the fertilizer granules II include the following components by mass fraction: total nitrogen 15-18%, P2O5 3-5%, K2O 12-15%, borax 0.05-0.1%, zinc sulfate 0.2-0.5%, the remainder being clay; the thickness of the polyurethane coating of the slow-release fertilizer I is 45-55 μm; (4) Take urea, monoammonium phosphate, diammonium phosphate, potassium sulfate, potassium magnesium sulfate, clay, borax, and zinc sulfate, mix them, and granulate them to obtain fertilizer granules III. The fertilizer granules III include the following components in mass fraction: total nitrogen 8-12%, P2O5 8-12%, K2O 15-18%, borax 0.02-0.05%, zinc sulfate 0.1-0.2%, the remainder being clay; (5) Take two equal amounts of fertilizer granules III, spray one portion of fertilizer granules III with epoxy resin coating liquid to obtain slow-release fertilizer III, mix slow-release fertilizer III and calcium carbonate evenly to obtain fertilizer granules IV, spray the surface of fertilizer granules IV with polyurethane coating liquid to obtain slow-release fertilizer IV, mix slow-release fertilizer IV and another portion of fertilizer granules III evenly to obtain fertilizer granules V, and use The surface of fertilizer granules V is sprayed with epoxy resin coating liquid to obtain slow-release fertilizer V; the polyurethane coating thickness of the slow-release fertilizer IV is 10-15 μm; the epoxy resin coating thickness of the slow-release fertilizer III and slow-release fertilizer V is 50-70 μm; (6) Take base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V, and mix them evenly according to the weight ratio of base fertilizer, slow-release fertilizer I, slow-release fertilizer II and slow-release fertilizer V of 2:(1-2):(1-1.5):(1-1.2) to obtain eucalyptus-specific controlled-release organic fertilizer.

2. The method for preparing eucalyptus-specific controlled-release organic fertilizer according to claim 1, characterized in that: The particle size of fertilizer granules I, II and III is 2-4 mm.

3. The method for preparing eucalyptus-specific controlled-release organic fertilizer according to claim 1, characterized in that: In step (1), the base fertilizer contains one of lime, sulfur powder, or aluminum sulfate to adjust the soil pH to 5.5-6.

5.

4. The method for preparing eucalyptus-specific controlled-release organic fertilizer according to claim 1, characterized in that: In step (5), epoxy resin coating solution is prepared using epoxy resin with an equilibrium swelling degree of less than 120% and a glass transition temperature (Tg) greater than 150°C.

5. The method for preparing eucalyptus-specific controlled-release organic fertilizer according to claim 1, characterized in that: In step (5), slow-release fertilizer III and calcium carbonate are mixed evenly in a mass ratio of (5-10):1 to obtain fertilizer granules IV.

6. The method for preparing eucalyptus-specific controlled-release organic fertilizer according to claim 1, characterized in that: In step (6), the eucalyptus-specific controlled-release organic fertilizer is applied once when planting eucalyptus trees, and is mixed with the soil at a ratio of 0.3 to 0.6 kg per planting hole before being backfilled into the planting hole.

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