A multi-layer coated controlled-release fertilizer for supplying nutrients according to the growth period of crops, and a preparation method and application thereof

Abstract

The present application relates to the field of efficient fertilization and green agricultural technology, and particularly relates to a multi-layer coated controlled-release fertilizer for supplying nutrients according to crop growth stages, and a preparation method and application thereof.The multi-layer coated controlled-release fertilizer for supplying nutrients according to crop growth stages provided by the present application divides the whole growth period of crops into several stages through more than one layer of granulation or coating, each stage corresponds to one layer of fertilizer, and the nutrient types, ratio and release rate of each layer of fertilizer are customized and constructed according to the nutrient demand characteristics of the corresponding growth stage.The inner layer nutrients are released after the slow-release coating layer gradually degrades or ruptures, achieving the goal of "supplying on demand, precise control release and cross-season continuation".The present application fundamentally solves the problem that the nutrient supply of traditional fertilizers and existing controlled-release fertilizers is not synchronized with crop demand, and systematically solves the problems such as mismatch between the release period of existing controlled-release fertilizers and the growth period of crops, fixed layer structure, single function, insufficient function of the inner core and insufficient cooperation of microorganisms.

Description

Technical Field

[0001] This invention relates to the field of efficient fertilization and green agriculture technology, and in particular to a multi-layer coated controlled-release fertilizer that supplies nutrients according to the crop growth stage, its preparation method and application. Background Technology

[0002] Fertilizers are a crucial material foundation for ensuring global food security. Statistics show that global annual fertilizer consumption exceeds 200 million tons, with nitrogen fertilizer accounting for approximately 60%. However, traditional fertilizer application suffers from a mismatch between nutrient release rates and crop absorption needs, resulting in low fertilizer utilization rates. Large amounts of unabsorbed nutrients enter the environment through leaching, volatilization, and runoff, causing serious agricultural non-point source pollution problems such as water eutrophication, soil acidification, and greenhouse gas emissions.

[0004] Slow-release and controlled-release fertilizers refer to a class of fertilizers that use various regulatory mechanisms to match the nutrient release rate with the crop's absorption needs. According to the International Organization for Standardization (ISO), slow-release fertilizers have a nutrient release rate significantly lower than conventional fertilizers; controlled-release fertilizers have a nutrient release rate that can be regulated through specific mechanisms. Currently, slow-release and controlled-release fertilizers mainly include the following technical approaches: (1) Coated controlled-release fertilizers: Coated controlled-release fertilizers are currently the most widely used type of controlled-release fertilizer. They are produced by coating the fertilizer granules with one or more layers of semi-permeable or impermeable membrane material, utilizing the membrane's permeability to control nutrient release. The coating materials mainly include: 1) Inorganic coating materials: Sulfur-coated urea (SCU) is a representative example, where molten sulfur is sprayed onto the surface of urea particles to form a coating layer. Sulfur-coated urea has a lower cost, but it suffers from problems such as brittle coating, easy breakage, and unstable nutrient release. Other inorganic coating technologies include zeolite coating and silicate coating.

[0005] 2) Synthetic polymer coating materials: These include polyolefin resins (such as polyethylene and polypropylene), polyurethane (PU), and polylactic acid (PLA). Polyolefin resin-coated fertilizers have the characteristic that the nutrient release rate is only controlled by temperature, achieving an S-shaped release curve that closely matches the crop's absorption patterns. Polyurethane-coated fertilizers utilize a solvent-free in-situ reaction film-forming process, offering advantages such as uniform coating and stable controlled-release performance. However, synthetic polymer coating materials suffer from high cost, poor biodegradability, and environmental residues.

[0006] 3) Bio-based Coating Materials: In recent years, the use of bio-based materials such as starch, cellulose, lignin, and sodium alginate to replace petrochemical-based membrane materials has become a research hotspot. Professor Yang Yuechao's team at Shandong Agricultural University has developed a bio-based polyurethane-coated controlled-release fertilizer technology, overcoming global challenges such as the difficulty in forming bio-based films and the low matching degree between nutrient release and crop absorption. Bio-based coating materials have advantages such as being renewable, biodegradable, and environmentally friendly, but they also suffer from problems such as unstable controlled-release effects and insufficient mechanical strength.

[0007] (2) Chemically inhibited slow-release fertilizers: By adding urease inhibitors (such as NBPT and NBTPT) and nitrification inhibitors (such as DCD and DMPP), the hydrolysis of urea and the nitrification of ammonium nitrogen can be slowed down, thus extending the fertilizer's effective period. This technology is relatively inexpensive, but its inhibitory effect is greatly affected by environmental factors such as soil temperature, humidity, and pH, and its controlled-release precision is limited.

[0008] (3) Substrate-based slow-release fertilizers: This technology combines fertilizer nutrients with an adsorbent matrix (such as zeolite, bentonite, biochar, etc.), allowing the matrix to adsorb, complex, and exchange ions, thus delaying nutrient release. While this technology uses widely available and low-cost raw materials, its controlled-release effect is significantly influenced by the matrix properties and soil conditions, resulting in limited precision in nutrient control.

[0009] Despite significant progress in controlled-release fertilizer technology, the following prominent issues still exist with current technologies: (1) Insufficient precision of single-layer coating controlled release: Most existing coated controlled release fertilizers have a single-layer or double-layer coating structure, which makes it difficult to achieve precise nutrient supply at different stages of crop growth. The requirements of crops for nutrient types, quantities and proportions vary significantly at different growth stages (such as seedling stage, growth stage, flowering stage, grain filling stage and maturity stage), and single-layer coating is difficult to meet such dynamic changes.

[0010] (2) The design and preparation process of multilayer structures are not mature: Although some researchers have proposed the concept of multilayer coating, most of them are still in the laboratory research stage and lack systematic multilayer granulation, multilayer coating process and supporting equipment. There are technical bottlenecks in the multilayer coating process, such as weak interlayer bonding force, uneven membrane thickness and uncontrollable nutrient release.

[0011] (3) The contradiction between the environmental friendliness and controlled release performance of coating materials: Synthetic polymer coating materials have excellent controlled release performance but are difficult to degrade, while bio-based materials are degradable but have unstable controlled release performance. How to achieve the environmental friendliness of coating materials while ensuring the accuracy of controlled release remains a technical challenge.

[0012] (4) Lack of special fertilizers customized according to crop growth stage: Most existing controlled-release fertilizer products are general-purpose and do not fully consider the differences in nutrient requirements of different crops and different growth stages, making it difficult to achieve the goal of "on-demand supply" precise fertilization.

[0013] (5) Poor synchronization between nutrient release and crop absorption: The nutrient release curves of existing controlled-release fertilizers are mostly parabolic or L-shaped (linear), which are difficult to match precisely with the crop's S-shaped absorption curve, resulting in insufficient nutrient supply in the early stage or excessive supply in the later stage, affecting crop yield and quality.

[0014] (6) Problems with cross-seasonal nutrient utilization: For perennial crops or cross-year planting systems, nutrients that are not fully absorbed in the current season are often lost due to leaching, fixation and other reasons. There is a lack of technical means to lock in the remaining nutrients in the current season and continue to supply them in the next season.

[0015] In the field of multilayer coating technology, existing patents mostly focus on double-layer coating structures (such as an inner layer of sulfur and an outer layer of polymer). There is significant room for technological innovation in multilayer granulation and multilayer coating precision controlled-release technologies with three or more layers. In particular, technical solutions that combine multilayer coating structures with the precise matching of nutrient requirements during crop growth stages have not yet been systematically reported. Summary of the Invention

[0016] In view of this, the present invention provides a multi-layer coated controlled-release fertilizer that supplies nutrients according to the crop growth stage, its preparation method and application. The multi-layer coated controlled-release fertilizer that supplies nutrients according to the crop growth stage provided by the present invention can release corresponding fertilizers according to the growth cycle of different crops, thereby improving fertilizer utilization and reducing fertilizer application.

[0017] This invention provides a multi-layered coated controlled-release fertilizer, employing a concentric multi-layered alternating coating structure. From the inside out, it includes a core and a controlled-release fertilizer layer coating the surface of the core. The core includes a soil-improving nutrient core and a slow-release coating layer coating the surface of the soil-improving nutrient core. The controlled-release fertilizer layer is either a first controlled-release fertilizer layer or a second controlled-release fertilizer layer. The first controlled-release fertilizer layer includes an exogenous fertilizer layer and a slow-release coating layer coating the outer surface of the exogenous fertilizer layer. The second controlled-release fertilizer layer is a composite layer of the exogenous fertilizer layer and the slow-release coating layer. The number of controlled-release fertilizer layers is two or more.

[0018] Preferably, the components of the soil amendment nutrient core include one or more of the following: biochar, bio-organic fertilizer, fulvic acid, brown humic acid, black humic acid, biomass humic acid, macro-elements, micro-elements, and synergists.

[0019] Preferably, the biochar is corn stalk biochar.

[0020] Preferably, the bio-organic fertilizer includes one or both of chicken manure organic fertilizer and sheep manure organic fertilizer.

[0021] Preferably, the synergist is zeolite powder.

[0022] Preferably, the sustained-release coating layer in the core is made of the following raw materials in parts by weight: 80-120 parts polylactic acid, 10-35 parts starch, 10-25 parts biochar, 8-25 parts humic acid, 5-10 parts modified humic acid, 5-10 parts sorbitol, 5-15 parts maleic anhydride, 1-2 parts stearic acid and 1-2 parts oleic acid.

[0023] Preferably, the humic acid includes one or more of black humic acid, yellow humic acid and brown humic acid.

[0024] Preferably, the modified humic acid includes one or more of nitrofulvic acid, mineral-derived fulvic acid, nitrobrown humic acid, mineral-derived brown humic acid, nitroblack humic acid, and mineral-derived black humic acid.

[0025] Preferably, the slow-release coating layer in the core also includes functional additives; the functional additives include one or more of the following: antibacterial agents, stress-resistant factors, growth-regulating factors, flowering-promoting factors, fruit enlargement factors, quality-enhancing factors, and root-promoting factors.

[0026] Preferably, the thickness of the sustained-release coating layer in the core is 30-60 micrometers.

[0027] Preferably, in the first controlled-release fertilizer layer, the exogenous fertilizer layer includes one or more of the following: macro-elements, meso-elements, micro-elements, humic acid, modified humic acid, biomass humic acid, biochar, functional additives, and functional microbial agents.

[0028] Preferably, the humic acid includes one or more of black humic acid, yellow humic acid and brown humic acid.

[0029] Preferably, the molecular weight of nitrofulic acid or mineral-derived fulvic acid is 300-1000 Daltons; the molecular weight of nitrobrown humic acid or mineral-derived humic acid is 1000-5000 Daltons; and the molecular weight of nitroblack humic acid or mineral-derived black humic acid is 5000-100000 Daltons.

[0030] Preferably, the mass ratio of fulvic acid, brown humic acid and black humic acid is 2:3:5 to 4:3:3.

[0031] Preferably, the functional microbial agent includes one or more of Bacillus subtilis, Pseudomonas fluorescens, Bacillus amyloliquefaciens, and Trichoderma harzianum.

[0032] Preferably, the exogenous fertilizer layer comprises the following components in parts by weight: 2-25 parts urea, 1-20 parts monoammonium phosphate, 8-25 parts potassium sulfate, 8-22 parts humic acid, 3-12 parts modified humic acid, 5-45 parts biochar or bio-organic fertilizer, 5-15 parts biomass humic acid, 0.05-2 parts functional additives, and 0.3-2 parts functional microbial agents.

[0033] Preferably, in the first controlled-release fertilizer layer, the thickness of the exogenous fertilizer layer is 155~165 micrometers.

[0034] Preferably, in the first controlled-release fertilizer layer, the slow-release coating layer is made of the following raw materials in parts by weight: 80-120 parts polylactic acid, 10-35 parts starch, 10-25 parts biochar, 8-25 parts humic acid, 5-10 parts sorbitol, 5-15 parts maleic anhydride, 1-2 parts stearic acid and 1-2 parts oleic acid.

[0035] Preferably, the thickness of the slow-release coating layer in the first controlled-release fertilizer layer is 30-60 micrometers.

[0036] Preferably, the total mass fraction of the core is 50-120 parts; the total mass fraction of the single-layer exogenous fertilizer layer is 30-80 parts; and the total mass fraction of the single-layer sustained-release coating layer is 100-200 parts.

[0037] Preferably, the multi-layer coated controlled-release fertilizer is a two-layer granulation (second controlled-release fertilizer layer), a two-layer coating (first controlled-release fertilizer layer), a three-layer granulation, a three-layer coating, a four-layer granulation, a four-layer coating, a five-layer granulation, or a five-layer coating.

[0038] Preferably, the layers of the multi-layered controlled-release fertilizer release at the following times: the first layer (outermost layer) is released 7 to 30 days after the first application; the second layer is released 20 to 160 days after the first application; the third layer is released 35 to 180 days after the first application; the fourth layer is released 50 to 210 days after the first application; and the fifth layer (innermost layer, adjacent to the core) is released 20 to 300 days after the first application.

[0039] This invention also provides a method for preparing the above-described multi-layer coated controlled-release fertilizer, comprising the following steps: (1) Preparation of soil-amortized nutrient core: The raw materials of soil-amortized nutrient core are mixed and extruded into granules to obtain soil-amortized nutrient core; (2) Preparation of raw materials for exogenous fertilizer layers: According to the needs of crops at different growth stages, the raw materials for each exogenous fertilizer layer are prepared separately, including macro-elements, meso-elements, micro-elements, humic acid, functional additives and functional microbial agents; the selection of humic acid follows the following principles: First layer (outermost layer) and second layer: Add nitrofulic acid or mineral-derived fulvic acid, with a molecular weight of 300~1000 Daltons, and the amount added accounts for 3%~8% of the total weight of the exogenous fertilizer layer; The third and fourth layers: Add nitro humic acid or mineral-derived humic acid, with a molecular weight of 1000~5000 Daltons, and the amount added accounts for 5%~10% of the total weight of the exogenous fertilizer layer. Fifth layer (innermost layer): Add nitrohumic acid or mineral-derived humic acid, with a molecular weight of 5,000 to 100,000 Daltons, accounting for 5% to 12% of the total weight of the exogenous fertilizer layer; (3) Preparation of sustained-release coating solution: Mix the raw materials of the sustained-release coating layer with the solvent to obtain the sustained-release coating solution; (4) Fluidized bed coating: Through fluidized bed coating, a slow-release coating liquid is sprayed onto the surface of the soil-improved nutrient core, dried, and cooled to obtain the core; (5) Rotary drum granulation to coat exogenous fertilizer layer: The raw materials of exogenous fertilizer layer are mixed with the core and fed into the rotary drum granulator. At the same time, binder and water are sprayed for granulation, drying, and cooling to obtain composite granules. (6) Granulation and coating: The controlled-release coating material is added simultaneously with the raw materials of the exogenous fertilizer layer, and the coating is achieved during the granulation process; (7) Repeat steps (4) to (6) to alternately spray, granulate and coat according to the target number of layers to obtain multi-layer coated controlled-release fertilizer.

[0040] This invention also provides the application of the above-described multi-layer coated controlled-release fertilizer in the field of agricultural planting.

[0041] Preferred multi-layer coated controlled-release fertilizers are suitable for field crops, fruit crops, cash crops, or vegetable crops.

[0042] Compared with the prior art, the present invention has achieved the following beneficial effects: This invention provides a multi-layered coated controlled-release fertilizer that supplies nutrients according to the crop's growth stage. Through multi-layer granulation or coating, the entire crop growth period is divided into several stages, with each stage corresponding to a single layer of fertilizer. The nutrient types, ratios, and release rates of each fertilizer layer are customized according to the nutrient requirements of that growth stage. The slow-release coating gradually degrades or ruptures, releasing the inner layer nutrients, achieving the goals of "on-demand supply, precise controlled release, and cross-seasonal continuity." This fundamentally solves the problem of nutrient supply not synchronizing with crop needs in traditional fertilizers and existing controlled-release fertilizers. It systematically addresses technical issues such as the mismatch between the release cycle and crop growth stage of existing controlled-release fertilizers, fixed layer structure, single function, insufficient core function, insufficient microbial synergy, limited application of humic acid, environmentally unfriendly coating materials, cumbersome processes, inconvenient use of water-soluble foliar fertilizers, and lack of targeted addition of functional components.

[0043] I. Product Structure: The multi-layered coated controlled-release fertilizer provided by this invention, which supplies nutrients according to the crop's growth stage, has a soil-improving nutrient core produced by extrusion granulation. It is primarily potassium-based with small amounts of nitrogen and phosphorus, mainly promoting fruit growth while protecting the soil, increasing soil organic matter, preventing soil acidification and salinization, and fixing unabsorbed nutrients for the next crop. The core is then coated with an exogenous fertilizer layer and a slow-release coating layer, each containing nutrients. The release time and nutrient ratio are precisely controlled according to the needs of different crops at different growth stages. The exogenous fertilizer layer contains differentiated amounts of nitrofulvic acid or mineral-derived nitro-brown humic acid or mineral-derived brown humic acid, or nitro-black humic acid or mineral-derived black humic acid, following the principle of "increasing molecular weight, decreasing activity, and increasing soil-improving function from the outside in," forming a multi-functional synergistic system of "microorganisms-humic acid-biochar." Multi-layer coated controlled-release fertilizers can replace water-soluble fertilizers or foliar fertilizers. Water-soluble and foliar fertilizers are added to the appropriate controlled-release fertilizer layers according to the crop's nutrient requirements during its growth stage. Multi-layer coated controlled-release fertilizers can have two, three, four, five, or more layers of granulation, achieving the effects of "providing nutrients according to the crop's growth stage, precise controlled release, one function per layer, and effectiveness throughout the entire growth process."

[0044] II. Preparation method: The preparation method provided by this invention allows the controlled-release fertilizer layer to be an exogenous fertilizer layer and a slow-release coating layer covering the outer surface of the exogenous fertilizer layer, or a composite layer of the exogenous fertilizer layer and the slow-release coating layer, combining the two into one. Granulation is coating, achieving the same purpose of controlled release. This invention uses fluidized bed spraying and rotary drum granulation alternately, or an integrated granulation and coating method. By controlling the thickness of the controlled-release fertilizer layer, the material ratio, and functional additives, precise controlled release for different release cycles can be achieved. The preparation method provided by this invention involves continuous alternating granulation and coating, completing the coating of all layers in a single production process. During the coating process, each layer forms interlayer physical interlocking and chemical bonding, making the multi-layer coated controlled-release fertilizer of this invention a single, indivisible particle.

[0045] III. Functional Components: In this invention, the three types of humic acid are added following the principle of "increasing molecular weight, decreasing activity, and increasing soil-improving function from the outside to the inside," such as... Figure 5 As shown: (1) Nitrofulic acid or mineral-derived fulvic acid (molecular weight 300~1000Da): mainly added to the first (outermost) and second exogenous fertilizer layers for promoting root growth, stabilizing seedlings, resisting stress, and enhancing nutrient efficiency during the vegetative growth period. It has the smallest molecular weight, the highest activity, the strongest water solubility and mobility, and can be directly absorbed and utilized by crop roots and leaves. It has the strongest cation exchange capacity, chelation capacity and adsorption capacity, and can quickly activate plant enzyme activity and promote cell division and growth.

[0046] (2) Nitro-based or mineral-derived humic acid (molecular weight 1000~5000 Da): mainly added to the third and fourth exogenous fertilizer layers for soil improvement and nutrient slow release synergy during flowering and fruit setting, fruit enlargement, or panicle differentiation. It has a medium molecular weight, medium activity, and medium translocation within plants, and has a strong ability to improve soil aggregate structure. It can promote the release of fixed nutrients in the soil, improve nutrient availability, and improve soil aeration and water retention.

[0047] (3) Nitrohumic acid or mineral-derived humic acid (molecular weight 5000~100000Da): mainly added to the fifth (innermost) exogenous fertilizer layer or soil amendment nutrient core, used for soil heavy metal passivation, long-term carbon sequestration and soil structure improvement during the mature harvest period, overwintering period or next season's crops. It has the largest molecular weight, the lowest activity, and slow translocation in plants, but its solid pore structure and large specific surface area have a strong adsorption and passivation effect on soil heavy metals, and can exist stably in the soil for a long time, providing a continuous soil improvement effect.

[0048] IV. Controlled release mechanism: The multi-layered coated controlled-release fertilizer provided by this invention allows each layer to release nutrients at the following times: the first layer (outermost layer) releases nutrients 7-30 days after sowing (or after agricultural operations such as transplanting, harvesting, pruning, etc.); the second layer releases nutrients 20-160 days after sowing; the third layer releases nutrients 35-180 days after sowing; the fourth layer releases nutrients 50-210 days after sowing; and the fifth layer (innermost layer) releases nutrients 20-300 days after sowing. Different release times meet the nutrient requirements of different crop growth stages. This invention achieves precise controlled release within any release period of 7-300 days by adjusting the ratio of polylactic acid and starch, the content of biochar and humic acid, the thickness of the membrane layers, and the granulation / coating parameters in each layer.

[0049] V. Application Methods: The multi-layer coated controlled-release fertilizer provided by this invention is suitable for field crops such as rice, wheat, corn, soybeans, and rapeseed, or fruits such as apples, citrus, grapes, nectarines, pears, peaches, apricots, cherries, and lychees, as well as cash crops such as peanuts, and can also be used for vegetable crops. The multi-layer coated controlled-release fertilizer provided by this invention requires an application rate of 50% to 70% of that of traditional chemical fertilizers, achieving multiple goals of reducing fertilizer use, increasing crop yield, and improving quality. The multi-layer coated controlled-release fertilizer is applied in a single, indivisible granule form, providing nutrient supply throughout the entire growth period with a single application.

[0050] VI. Soil Protection: The multi-layered coated controlled-release fertilizer provided by this invention has the function of preventing soil problems such as salinization, heavy metal pollution, farmland degradation, acidification and compaction, and reduction of soil organic matter. This invention integrates soil improvement and nutrient supply through biochar adsorption of salt, humic acid regulation of ion balance, fulvic acid enhancement of buffering capacity, and salt-tolerant microorganisms improvement of soil microecology. After the fertilizer's effective period ends, the residual coating, biochar, and humic acid form a residual soil-improving layer, continuously exerting its soil remediation effect.

[0051] VII. Comprehensive Technology Development and Protection: This invention achieves comprehensive development of multi-layer coated controlled-release fertilizers from the dimensions of product structure, preparation process, application method, functional components, controlled-release mechanism, and alternative solutions. Any scheme that achieves the same or equivalent technical effect as this invention by separately producing single-layer controlled-release fertilizer, single-layer slow-release fertilizer, or single-layer compound fertilizer, and then physically mixing or compounding them according to the proportions and release times of the components of this invention, falls within the protection scope of this invention. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of this invention, the accompanying drawings used in the embodiments of this invention or in the prior art are briefly described below. For those skilled in the art, other drawings can be derived from the following drawings without creative effort, and all such drawings are within the protection scope of this invention.

[0053] Figure 1 This is a schematic diagram of the structure of the multi-layer coated controlled-release fertilizer provided by the present invention; wherein, 1 is the soil-improving nutrient core, 2 is the first slow-release coating layer, 3 is the first exogenous fertilizer layer, 4 is the second slow-release coating layer, 5 is the second exogenous fertilizer layer, 6 is the third slow-release coating layer, 7 is the third exogenous fertilizer layer, 8 is the fourth slow-release coating layer, 9 is the fourth exogenous fertilizer layer, and 10 is the slow-release coating layer of the core (the fifth slow-release coating layer). Figure 2 A schematic diagram illustrating the relationship between the multi-layer coated controlled-release fertilizer provided by this invention and the fertilizer release time at different crop growth stages; Figure 3 This is a process flow diagram of the preparation method of the multi-layer coated controlled-release fertilizer of the present invention; Figure 4 This is a schematic diagram of the functional additives in the multi-layer coated controlled-release fertilizer of the present invention, showing the zoned loading. Figure 5 This is a schematic diagram of the humic acid gradient configuration of the multi-layer coated controlled-release fertilizer of the present invention; Figure 6 This is a three-dimensional cross-sectional structural diagram of the multi-layer coated controlled-release fertilizer of the present invention. Detailed Implementation

[0054] This invention provides a multi-layered coated controlled-release fertilizer, employing a concentric multi-layered alternating coating structure. From the inside out, it includes a core and a controlled-release fertilizer layer coating the surface of the core. The core includes a soil-improving nutrient core and a slow-release coating layer coating the surface of the soil-improving nutrient core. The controlled-release fertilizer layer is either a first controlled-release fertilizer layer or a second controlled-release fertilizer layer. The first controlled-release fertilizer layer includes an exogenous fertilizer layer and a slow-release coating layer coating the outer surface of the exogenous fertilizer layer. The second controlled-release fertilizer layer is a composite layer of the exogenous fertilizer layer and the slow-release coating layer. The number of controlled-release fertilizer layers is two or more.

[0055] In this invention, the components of the soil amendment nutrient core include one or more of the following: biochar, bio-organic fertilizer, fulvic acid, brown humic acid, black humic acid, biomass humic acid, macro-elements, micro-elements, and synergists.

[0056] In this invention, the biochar can be corn stalk biochar.

[0057] In this invention, the bio-organic fertilizer may include one or both of chicken manure organic fertilizer and sheep manure organic fertilizer.

[0058] The core of this invention has two main functions: 1) providing the nutrients required for crop maturity; 2) soil improvement: by optimizing soil physical structure, balancing chemical nutrients, and activating microbial activity, it achieves long-term soil improvement and fertility maintenance. In summary, the core's functions are soil nourishment, soil improvement, and fertilization. Unlike the core, the controlled-release fertilizer film primarily provides fertilization, while also nourishing and improving the soil.

[0059] The soil-improving nutrient core of this invention uses biochar and bio-organic fertilizer as core matrix materials to provide soil improvement functions, increase soil organic matter content, and improve soil aggregate structure; brown humic acid, as a soil conditioner and nutrient activator, promotes the release of fixed nutrients in the soil and improves nutrient availability; black humic acid, as a soil water and fertilizer retention agent and microbial growth factor, enhances soil buffering capacity and prevents soil acidification and salinization; and biomass humic acid, as a core component of soil improvement, promotes the formation of soil aggregate structure, enhances soil aeration and water retention, and prevents farmland degradation, acidification and compaction, and reduction of soil organic matter.

[0060] The nutrient ratio of the soil-improving nutrient core in this invention is mainly potassium, with small amounts of nitrogen and phosphorus. The potassium content accounts for 60% to 75% of the total nutrients in the core, the nitrogen content accounts for 5% to 25%, and the phosphorus content accounts for 5% to 15%, mainly playing a role in promoting fruit growth. The soil-improving nutrient core has the function of fixing various nutrients that have not been absorbed in the current season. Through the adsorption of biochar, the complexation of humic acid, and the chelation of fulvic acid, nitrogen, phosphorus, potassium, medium elements, and trace elements are fixed and stored for continued absorption and utilization by the next season's crops, realizing "one season of fertilization, multiple seasons of benefit". After the fertilizer effect cycle ends, the soil-improving nutrient core continues to play a role in soil improvement, preventing soil problems such as salinization, heavy metal pollution, farmland degradation, acidification and compaction, and reduction of soil organic matter. It also promotes the improvement of desertified soils and barren grasslands.

[0061] In this invention, the synergist can be zeolite powder.

[0062] In this invention, the core, the sustained-release coating layer may be made of the following raw materials in parts by weight: 80-120 parts polylactic acid, 10-35 parts starch, 10-25 parts biochar, 8-25 parts humic acid, 5-10 parts modified humic acid, 5-10 parts sorbitol, 5-15 parts maleic anhydride, 1-2 parts stearic acid and 1-2 parts oleic acid.

[0063] In this invention, humic acid may include one or more of black humic acid, yellow humic acid, and brown humic acid.

[0064] In this invention, the modified humic acid may include one or more of nitrofulvic acid, mineral-derived fulvic acid, nitrobrown humic acid, mineral-derived brown humic acid, nitroblack humic acid, and mineral-derived black humic acid.

[0065] In this invention, the core, the slow-release coating layer may further include functional additives; the functional additives may include one or more of the following: antibacterial agents, stress-resistant factors, growth-regulating factors, flowering-promoting factors, fruit enlargement factors, quality-enhancing factors, and root-promoting factors.

[0066] In this invention, the thickness of the sustained-release coating layer in the core can be 30-60 micrometers, specifically 40-55 micrometers.

[0067] In this invention, the exogenous fertilizer layer in the first controlled-release fertilizer layer may include one or more of the following: macro-elements, medium-element elements, micro-elements, humic acid, modified humic acid, biomass humic acid, biochar, functional additives, and functional microbial agents.

[0068] In this invention, macroelements include nitrogen, phosphorus, and potassium, and their proportions are adjusted according to the needs of different growth stages of the crop; mesoelements include calcium, magnesium, and sulfur, and their proportions are adjusted according to the needs of different growth stages of the crop; microelements may include one or more of iron, manganese, zinc, copper, boron, and molybdenum, and are selectively added according to the needs of different growth stages of the crop.

[0069] In this invention, humic acid may include one or more of black humic acid, fulvic acid, and brown humic acid. Fulvic acid serves as a nanocarrier to load functional microbial agents, while biochar provides a growth environment as a habitat carrier; brown humic acid serves as a soil aggregate structure improver and nutrient slow-release carrier; black humic acid serves as a soil heavy metal adsorption and passivation agent and a long-term carbon sink material; the three humic acids, together with the functional microbial agents and biochar, form a multi-element synergistic system to improve fertilizer bioavailability, enhance soil buffering capacity, and prevent soil acidification and salinization.

[0070] In this invention, the molecular weight of nitrofulvic acid or mineral-derived fulvic acid can be 300-1000 Daltons. Nitrofulvic acid or mineral-derived fulvic acid is soluble in acids, alkalis, water, acetone, or ethanol, and contains functional groups such as carboxyl, phenolic hydroxyl, methoxy, ketone, and sulfonic acid groups. It has the highest hydrophilicity and oxidative activity, and the strongest cation exchange capacity, chelating capacity, and adsorption capacity. It is rapidly transported within plants, has a strong stimulating effect, and can be directly absorbed and utilized by crop roots and leaves. It is mainly added to the outermost and second-to-outermost exogenous fertilizer layers for promoting root growth, stabilizing seedlings, resisting stress, promoting growth, and enhancing nutrient efficiency during the vegetative growth period.

[0071] In this invention, the molecular weight of nitro-brown humic acid or mineral-derived humic acid can be 1000-5000 Daltons, specifically 2000-20000 Daltons. Nitro-brown humic acid or mineral-derived humic acid is soluble in alkali, acetone, and ethanol, but insoluble in water and acid; it contains a relatively high amount of carbon and nitrogen, with oxygen mostly in the cyclic structure (ether bonds, carboxyl groups, quinone groups, methoxy groups, amide groups, carbonyl groups, etc.); it exhibits moderate translocation within plants and moderate stimulating effect; it has a strong soil-improving ability, promotes the formation of soil aggregates, and improves soil aeration and water retention; it is mainly added to the third and fourth exogenous fertilizer layers for soil improvement and nutrient slow-release synergy during the flowering and fruit-setting period, fruit enlargement period, or panicle differentiation period.

[0072] In this invention, the molecular weight of nitrohumic acid or mineral-derived humic acid can be 5,000 to 100,000 Daltons, specifically 10,000 to 100,000 Daltons. Nitrohumic acid or mineral-derived humic acid is only soluble in alkalis and insoluble in water, acids, acetone, and ethanol; it contains fewer active functional groups such as hydroxyl groups, but its solid pore structure and large specific surface area have a strong adsorption and passivation effect on soil heavy metals; it translocates slowly within plants, has a slow stimulating effect, is easily adsorbed by the plant surface, and promotes root growth; it is mainly added to the fifth (innermost) exogenous fertilizer layer or the soil amendment nutrient core for soil heavy metal passivation, long-term carbon sequestration, and soil structure improvement during the mature harvest period, overwintering period, or the next crop season.

[0073] In this invention, the three humic acids—fulvic acid, brown humic acid, and black humic acid—can be synergistically combined and optimized, specifically including: Synergistic effect of fulvic acid and humic acid: fulvic acid provides fast-acting nutrient chelation and root-promoting stress resistance, while humic acid provides medium-efficiency soil aggregate structure improvement. The ratio of the two is fulvic acid: humic acid = 3:7~7:3 (mass ratio), which is suitable for crops with light soil compaction and requiring rapid seedling growth during their growth period. Synergistic effect of fulvic acid and humic acid: fulvic acid provides fast-acting nutrient transport and biostimulation, while humic acid provides long-lasting soil heavy metal passivation and carbon sequestration. The ratio of the two is fulvic acid: humic acid = 2:8~5:5 (mass ratio), which is suitable for crop planting in soils contaminated with heavy metals. Synergistic effect of brown humic acid and black humic acid: Brown humic acid provides medium-efficiency soil structure improvement function, while black humic acid provides long-term soil water and fertilizer retention function. The compound ratio of the two is brown humic acid: black humic acid = 4:6~6:4 (mass ratio), which is suitable for crop planting in arid and semi-arid areas. The three humic acids work synergistically: fulvic acid: brown humic acid: black humic acid = 2:3:5~4:3:3 (mass ratio), which is suitable for saline-alkali land or heavy metal polluted farmland with severe soil degradation that requires comprehensive improvement; the synergistic compounding ratio is dynamically adjusted according to soil type, crop type, growth stage and target function to achieve precise configuration and maximize the function of humic acid.

[0074] In this invention, nitrofulvic acid, nitrobrown humic acid, or nitroblack humic acid can be prepared by the following nitration method: Preparation method of nitrofulvic acid: Using weathered coal or lignite as raw material, a mixed acid oxidation extraction method is adopted (the mass ratio of sulfuric acid to nitric acid is 7:3, the mass ratio of raw coal to mixed acid to water is 1:0.3:6, oxidation is carried out at 70℃ for 40 min, and stirring reaction is carried out at 60℃ for 1 h), which increases the fulvic acid extraction rate to 25%~35%. The molecular weight of the obtained nitrofulvic acid is 300~800 Daltons, the nitrogen content is increased by 5%~25%, and the number of functional groups is increased by 20%~30%. Preparation method of nitrobrown humic acid: using weathered coal or lignite as raw material, the method of alkali dissolution-hydrogen peroxide oxidation-acid precipitation is adopted (NaOH concentration 1%~3%, hydrogen peroxide concentration 5%~10%, oxidation temperature 60~80℃, oxidation time 2~4h). The resulting nitrobrown humic acid has a molecular weight of 1000~5000 Daltons, an increase of 8%~28% in oxygen-containing functional groups, and an improvement in soil aggregate structure of 25%~40%. Preparation method of nitrohumic acid: Using weathered coal or lignite as raw material, a high-temperature and high-pressure hydrothermal oxidation method is adopted (temperature 80~220℃, pressure 2~5MPa, reaction time 4~8h, oxidant is hydrogen peroxide or potassium permanganate). The resulting nitrohumic acid has a molecular weight of 8000~50000 Daltons, a specific surface area increase of 30%~50%, and a heavy metal adsorption capacity increase of 35%~50%. The nitration method in this invention improves the activity, number of functional groups and functional specificity of humic acid, and significantly enhances the synergistic effect of the three humic acids in multilayer controlled-release fertilizers.

[0075] In this invention, the modified humic acid may include one or more of nitrofulvic acid, mineral-derived fulvic acid, nitrobrown humic acid, mineral-derived brown humic acid, nitroblack humic acid, and mineral-derived black humic acid.

[0076] In this invention, functional additives may include one or more of the following: antibacterial agents, stress-resistance factors, growth-regulating factors, flowering-promoting factors, fruit enlargement factors, quality-enhancing factors, and root-promoting factors. The functional additives are applied in zones according to the functional requirements of each layer, rather than being added to every layer. Figure 4 As shown.

[0077] Root-promoting factors: Added to the first layer (outermost layer), suitable for seedling and transplanting stages, promoting root development; Antibacterial agents: Added to the first layer, suitable for seedling stabilization and high disease incidence periods, controlling soil-borne diseases; Stress-resistance factors: Added to the first or second layer, suitable for adverse conditions (high temperature, low temperature, drought), enhancing crop stress resistance; Growth-regulating factors: Added to the second or third layer, suitable for the vegetative growth period, preventing excessive vegetative growth; Flower-promoting factors: Added to the third or second layer, suitable for the flowering and fruit-setting period, promoting flower bud differentiation and fruit setting; Fruit enlargement factors: Added to the fourth or fifth layer, third or second layer, suitable for the fruit enlargement period, promoting fruit enlargement; Quality-enhancing factors: Added to the fifth or fourth layer, third or second layer, suitable for the mature harvest period, increasing fruit sugar content and vitamin C content, and reducing nitrate content; Functional additives such as root-promoting and stress-resistance additives are precisely added to the corresponding layers according to crop needs, achieving precise supply of "one function per layer".

[0078] In this invention, the functional microbial agent may include one or more of Bacillus subtilis, Pseudomonas fluorescens, Bacillus amyloliquefaciens, and Trichoderma harzianum. This invention employs zoned loading based on the functional requirements of each layer. Each exogenous fertilizer layer is loaded with a functional microbial agent, and one or more of nitrofulvic acid or mineral-derived fulvic acid, nitrobrown humic acid or mineral-derived humic acid, or nitroblack humic acid or mineral-derived black humic acid are added according to the different needs of different growth stages, forming a multi-element synergistic system of "microorganism-humic acid-biochar," which can achieve precise microbial regulation of "one microorganism per layer."

[0079] Bacillus subtilis: produces proteases, amylases, and cellulases to break down large organic molecules into smaller molecules that are easily absorbed by crops, while also producing antimicrobial peptides to inhibit soil-borne pathogens; Pseudomonas fluorescens: produces siderophores, antibiotics, and plant growth promoters to inhibit soil-borne pathogens, promote crop root growth, and enhance crop resistance; Bacillus amyloliquefaciens: produces a variety of antimicrobial substances to prevent and control crop diseases and promote crop growth; Trichoderma harzianum: produces chitinase and glucanase to inhibit soil-borne fungal diseases and promote crop root development.

[0080] In this invention, the exogenous fertilizer layer may specifically include the following components in parts by weight: 2-25 parts urea, 1-20 parts monoammonium phosphate, 8-25 parts potassium sulfate, 8-22 parts humic acid, 3-12 parts modified humic acid, 5-45 parts biochar or bio-organic fertilizer, 5-15 parts biomass humic acid, 0.05-2 parts functional additives, and 0.3-2 parts functional microbial agents. When the above components are adjusted within the specified ranges in this invention, their functional positioning and relative proportions remain unchanged, achieving the same technical effect.

[0081] In this invention, the thickness of the exogenous fertilizer layer in the first controlled-release fertilizer layer can be 155-165 micrometers, specifically 158 micrometers, 162 micrometers or 163 micrometers.

[0082] In this invention, the first controlled-release fertilizer layer may be made of the following raw materials in parts by weight: 80-120 parts polylactic acid, 10-35 parts starch, 10-25 parts biochar, 8-25 parts humic acid, 5-10 parts sorbitol, 5-15 parts maleic anhydride, 1-2 parts stearic acid and 1-2 parts oleic acid.

[0083] In this invention, the thickness of the slow-release coating layer in the first controlled-release fertilizer layer can be 30-60 micrometers.

[0084] In this invention, the second controlled-release fertilizer layer is a composite layer of an exogenous fertilizer layer and a slow-release coating layer. The slow-release coating layer can also be integrated with the nutrients, achieving controlled release through granulation. Specifically, the slow-release coating layer is added simultaneously with the exogenous fertilizer raw materials during the granulation process. Through extrusion granulation or drum granulation, the coating material is uniformly coated onto the surface of the nutrient particles, forming an integrated structure of "granulation as coating." This integrated process simplifies the traditional two-step process of "granulation first, then coating," reducing equipment investment and energy consumption, and improving production efficiency. In the granulation-as-coating structure, the coating material is tightly bound to the nutrient particles. By controlling the ratio of the coating material to the nutrients, granulation pressure, and temperature, precise controlled release for different release cycles can be achieved. The granulation-as-coating process is suitable for the preparation of the innermost soil amendment nutrient core and the granulation process of each exogenous fertilizer layer.

[0085] In this invention, each exogenous fertilizer layer contains nutrient ratios adjusted according to the needs of different crop growth stages and is loaded with functional microbial agents. Modified humic acid is added to each exogenous fertilizer layer according to the needs of different growth stages, forming a multi-element synergistic system of "microorganisms-humic acid-biochar". The selection of humic acid is differentiated according to the crop growth stage, soil type, and target function. The addition of the three types of humic acid in the multi-layer structure follows the principle of "increasing molecular weight, decreasing activity, and increasing soil improvement function from the outside to the inside," achieving a gradient synergistic effect of "rapid-medium-long-lasting effect."

[0086] The slow-release coating layer, made of bio-based biodegradable materials, coats the surface of the exogenous fertilizer layer. By adjusting the coating thickness, material ratio, and functional additives, precise controlled release at different release cycles can be achieved. The slow-release coating layer can also be integrated with the nutrients; granulation itself forms the coating, achieving controlled release. The exogenous fertilizer layer and the slow-release coating layer alternately, forming a multi-layered structure. Each layer contains nutrients, which are released sequentially according to the needs of different crop growth stages, achieving "nutrient supply according to crop growth stage and precise controlled release." Multi-layered coated controlled-release fertilizers can prevent or treat soil problems such as salinization, heavy metal pollution, organic pollution, industrial pollution, farmland degradation, acidification and compaction, and reduction of soil organic matter. They also promote the improvement of desertified soils and barren grasslands.

[0087] In this invention, the outermost controlled-release fertilizer layer of the multi-layer coated controlled-release fertilizer can be a physical composite layer of humic acid and a slow-release coating layer; the humic acid can be one or both of fulvic acid and palmitic acid. The outermost controlled-release fertilizer layer is similar to applying a slurry to a multi-layer coated controlled-release fertilizer, by fully mixing the raw materials of the humic acid and the slow-release coating layer simultaneously.

[0088] In this invention, the total mass fraction of the core can be 50-120 parts; the total mass fraction of the single-layer exogenous fertilizer layer can be 30-80 parts; and the total mass fraction of the single-layer sustained-release coating layer can be 100-200 parts.

[0089] In this invention, the particle size of the multi-layer coated controlled-release fertilizer can be 3-7 mm, specifically 4 mm, 5 mm or 6 mm (the number of layers and particle size of the controlled-release fertilizer layer are different).

[0090] In this invention, the multilayer coated controlled-release fertilizer can be a two-layer granulation (second controlled-release fertilizer layer), a two-layer coating (first controlled-release fertilizer layer), a three-layer granulation, a three-layer coating, a four-layer granulation, a four-layer coating, a five-layer granulation, a five-layer coating, or more layers, such as... Figure 1 and Figure 6 As shown, the selection can be flexibly made based on the length of the crop's growth period and the complexity of its nutrient requirements: Two-layer granulation and two-layer coating: suitable for crops with short growth periods and relatively simple nutrient requirements, such as leafy vegetables like lettuce and spinach, with a total controlled-release cycle of 20-160 days; Three-layer granulation and three-layer coating: determined according to crop, soil conditions and climate characteristics, it is suitable for crops with medium growth period and nutrient requirements in three stages, such as strawberry, tomato and other melon and fruit crops, with a total controlled release period of 35 to 180 days. Four-layer granulation and four-layer coating: suitable for field grain crops with long growth periods and four stages of nutrient requirements, such as northern wheat, southern wheat, rice, corn, soybeans, rapeseed, etc., with a total controlled release cycle of 50~210 days. Five-layer granulation and five-layer coating: suitable for cash crops or perennial crops with long growth periods and nutrient requirements in five stages, such as peppers, tea, nectarines, grapes, apples, citrus, lychees, pears, peaches, apricots, cherries, etc., with a total controlled release period of 20 to 300 days; Multiple layers: Based on the specific growth stage requirements of crops, six or more layers can be constructed to achieve more precise nutrient supply throughout the growth period. The release time of multi-layered coated controlled-release fertilizers varies depending on the crop, region, and climate, but all fall within the aforementioned time range. The composition of each controlled-release fertilizer layer can be adjusted to adapt to different soil types and crops.

[0091] In this invention, the multi-layer coated controlled-release fertilizer can be granulated in two layers or coated in two layers, three layers or coated in three layers, four layers or coated in four layers, or five layers or coated in five layers. The difference lies in that the core and the outermost controlled-release fertilizer layer are fixed, while 1 to 3 layers of controlled-release fertilizer layer can be set between the core and the outermost controlled-release fertilizer layer. According to the crop growth cycle, controlled-release fertilizer layers with different release cycles can be selectively matched to achieve precise fertilization of crops and precise adjustment of soil nutrients, which has broad application prospects.

[0092] This invention selects different layer structures and release times based on the growth period characteristics of different crops. For example... Figure 2As shown, taking a 5-layer controlled-release fertilizer as an example, each layer of the multi-layer coated controlled-release fertilizer releases nutrients at the following times, with different release times meeting the nutrient requirements of different crop growth stages: The first layer (outermost layer): After sowing (or transplanting, harvesting, pruning, cutting and other agricultural operations), it is released 7 to 30 days after the first application of fertilizer during the growing season. It provides corresponding nutrients according to different crops to meet their needs in the early stage of growth, such as stabilizing seedlings, promoting root growth, preventing diseases and pests, and promoting shoot growth. The second layer: released from day 20 to 160, providing corresponding nutrients according to different growth stages of different crops to meet their needs during the vegetative growth stage or early reproductive growth stage, such as promoting growth, preventing excessive growth, promoting flower bud differentiation, promoting strong shoots and controlling excessive growth, etc., suitable for overwintering crops in the north and non-overwintering crops in the south. The third layer: released from day 35 to 180, providing corresponding nutrients according to different crops to meet their needs during the flowering and fruit setting period or the ear differentiation period, such as promoting flowering and fruit setting, and protecting ear differentiation; The fourth layer is released from day 50 to 210, providing corresponding nutrients according to different crops to meet their needs during the fruit enlargement or grain filling stages, such as fruit enlargement and grain filling. The fifth layer (the innermost layer, adjacent to the kernel, for soil nourishment, improvement, and fertilization): released between the 20th and 300th day, providing corresponding nutrients according to different crops to meet their needs during the maturity and harvest period or overwintering period, such as fruit strengthening and quality improvement, prevention of premature aging, post-harvest recovery, and overwintering nutrient reserves. It is suitable for crops of all growth stages.

[0093] The multi-layer coated controlled-release fertilizer provided by this invention uses the starting point of each layer's release time as a benchmark based on agricultural operations (sowing, transplanting, harvesting, pruning, etc.), and can be flexibly adjusted according to the growth characteristics of different crops. This multi-layer coated controlled-release fertilizer is suitable for major field crops such as rice, wheat, corn, soybeans, and rapeseed, as well as major fruits in both northern and southern China such as apples, citrus, grapes, nectarines, pears, peaches, apricots, cherries, and lychees, and cash crops such as peanuts, and various vegetable crops. The application rate of this multi-layer coated controlled-release fertilizer is 70%–85% of the traditional fertilizer application rate in the first year and 50%–70% of the traditional fertilizer application rate in the second year, achieving multiple goals of fertilizer reduction, crop yield increase, and quality improvement.

[0094] In this invention, the slow-release coating layer is located in the innermost layer (immediately adjacent to the soil amendment nutrient core), and is not present in every layer, but each layer retains a corresponding residual function after release, specifically including: After the first layer (outermost layer) is released: the residual membrane forms a protective shell for the soil, preventing soil fertility degradation, improving soil aggregate structure, and enhancing soil aeration and water retention. After the second layer is released: the residual membrane and the unreleased nutrients form a nutrient fixation layer, which adsorbs and fixes the nitrogen, phosphorus and potassium components that are not absorbed and utilized by the crop in the current period, reducing nutrient loss; After the third layer is released: the residual membrane and functional microorganisms form a microbial habitat layer, providing a habitat and carbon source for beneficial soil microorganisms and improving soil microbial diversity; After the fourth layer is released: the residual coating and humic acid form a soil improvement transition layer, gradually releasing the soil improvement components and promoting the formation of soil aggregate structure; After the fifth layer (innermost layer) is released: the residual coating, biochar, and humic acid form a soil improvement residual layer, which continues to play a role in soil remediation after the fertilizer effect cycle ends, preventing salinization, heavy metal pollution, farmland degradation, acidification and compaction, and reduction of soil organic matter. Biochar and humic acid provide a habitat and carbon source for beneficial soil microorganisms, and the fixed and stored nutrients are available for crop absorption and utilization in the next release cycle, thus achieving the goal of reducing chemical fertilizer use.

[0095] The multi-layered coated controlled-release fertilizer provided by this invention has the function of preventing soil problems, specifically including: preventing salinization: biochar adsorbs salt, humic acid regulates ion balance, fulvic acid enhances buffering capacity, and salt-tolerant microorganisms (such as Haloxylon ammodendron) improve soil microecology; preventing heavy metal pollution: biochar adsorbs and passivates heavy metals, humic acid complexes and fixes heavy metals, reduces the biological activity of heavy metals, and reduces crop absorption; preventing farmland degradation: increasing soil organic matter, improving aggregate structure, enhancing microbial diversity, and strengthening soil biological activity; preventing acidification and compaction: humic acid buffers pH, biochar improves aeration, biomass humic acid promotes aggregate formation, and enhances soil buffering capacity; preventing the reduction of soil organic matter: biochar provides long-term carbon sequestration, bio-organic fertilizer replenishes organic matter, humic acid promotes humification, and microorganisms decompose organic matter.

[0096] The multi-layer coated controlled-release fertilizer provided by this invention is a green fertilizer that is soil-friendly and can completely replace traditional fertilizers, achieving the following goals: fertilizer reduction: application rate is reduced by 30-50% compared to traditional fertilizers; crop yield increase: crop yield increases by 20-40%; quality improvement: fruit sugar content increases, vitamin C content increases, and nitrate content decreases; soil protection: preventing soil degradation, compaction, acidification, and salinization, and preventing heavy metal pollution; environmental friendliness: reducing eutrophication pollution of water bodies caused by nitrogen, phosphorus, and potassium loss, and reducing agricultural non-point source pollution; sustainable agriculture: achieving an integrated cycle of "fertilization-improvement-remediation-reuse" through soil improvement and nutrient core.

[0097] The multi-layer coated controlled-release fertilizer provided by this invention can replace water-soluble fertilizers and foliar fertilizers. Water-soluble and foliar fertilizers are added to corresponding controlled-release layers according to the nutrient requirements of the crop at different growth stages. Specifically, water-soluble fertilizer nutrients (such as urea, potassium dihydrogen phosphate, potassium nitrate, etc.) are added to corresponding exogenous fertilizer layers according to the needs of different crop growth stages, achieving slow release through the control of the coating layer, replacing the multiple applications of traditional water-soluble fertilizers; foliar fertilizer nutrients (such as amino acids, trace elements, humic acid, etc.) are added to corresponding exogenous fertilizer layers according to the needs of different crop growth stages, achieving rhizosphere release through the control of the coating layer, replacing the multiple sprayings of traditional foliar fertilizers. This multi-layer coated controlled-release fertilizer integrates the functions of rhizosphere and foliar fertilization, reducing the number of fertilizations and labor costs, and achieving precise nutrient supply for the entire season with a single application.

[0098] The preparation method provided by this invention employs a continuous alternating granulation-coating process, completing the coating of all controlled-release fertilizer layers in a single production flow. It prohibits the separate granulation and coating of each controlled-release fertilizer layer followed by physical mixing. The continuous alternating granulation-coating process includes: core extrusion granulation; fluidized bed spray coating; drum granulation coating of exogenous fertilizer layers; repeating the above steps until all controlled-release fertilizer layers are coated. During the coating process, each controlled-release fertilizer layer forms interlayer physical interlocking and chemical bonding, making the multi-layer coated controlled-release fertilizer a single, indivisible particle. The multi-layer coated controlled-release fertilizer provided by this invention is applied in the form of a single, indivisible particle, achieving nutrient supply throughout the entire growth period with a single application.

[0099] This invention also provides a method for preparing the above-described multi-layer coated controlled-release fertilizer, comprising the following steps: (1) Preparation of soil-amortized nutrient core: The raw materials of soil-amortized nutrient core are mixed and extruded into granules to obtain soil-amortized nutrient core; (2) Preparation of raw materials for exogenous fertilizer layers: According to the needs of crops at different growth stages, the raw materials for each exogenous fertilizer layer are prepared separately, including macro-elements, meso-elements, micro-elements, humic acid, functional additives and functional microbial agents; the selection of humic acid follows the following principles: First layer (outermost layer) and second layer: Add nitrofulic acid or mineral-derived fulvic acid, with a molecular weight of 300~1000 Daltons, and the amount added accounts for 3%~8% of the total weight of the exogenous fertilizer layer; The third and fourth layers: Add nitro humic acid or mineral-derived humic acid, with a molecular weight of 1000~5000 Daltons, and the amount added accounts for 5%~10% of the total weight of the exogenous fertilizer layer. Fifth layer (innermost layer): Add nitrohumic acid or mineral-derived humic acid, with a molecular weight of 5,000 to 100,000 Daltons, accounting for 5% to 12% of the total weight of the exogenous fertilizer layer; (3) Preparation of sustained-release coating solution: Mix the raw materials of the sustained-release coating layer with the solvent to obtain the sustained-release coating solution; (4) Fluidized bed coating: Through fluidized bed coating, a slow-release coating liquid is sprayed onto the surface of the soil-improved nutrient core, dried, and cooled to obtain the core; (5) Rotary drum granulation to coat exogenous fertilizer layer: The raw materials of exogenous fertilizer layer are mixed with the core and fed into the rotary drum granulator. At the same time, binder and water are sprayed for granulation, drying, and cooling to obtain composite granules. (6) Granulation and coating: The controlled-release coating material is added simultaneously with the raw materials of the exogenous fertilizer layer, and the coating is achieved during the granulation process; (7) Repeat steps (4) to (6) to alternately spray, granulate and coat according to the target number of layers to obtain multi-layer coated controlled-release fertilizer.

[0100] The process flow of the preparation method of the multi-layer coated controlled-release fertilizer provided by this invention is as follows: Figure 3 As shown, it has the following innovative features: Fluidized bed spraying and rotary drum granulation alternating process: Fluidized bed spraying is used to achieve uniform coating of the slow-release coating layer, and rotary drum granulation is used to achieve dense coating of the exogenous fertilizer layer. The two processes are carried out alternately to ensure tight bonding between the layers. Granulation and coating integrated process: Controlled-release coating material and exogenous fertilizer raw materials are added simultaneously, and coating is achieved during the granulation process, which simplifies the process and reduces equipment investment and energy consumption; Multi-layer granulation and multi-layer coating: Through multiple granulation and coating processes, a multi-layer structure is formed, with nutrients in each layer, achieving "nutrient supply according to the crop's growth stage"; Bio-based biodegradable materials: Replacing traditional petroleum-based polymers with bio-based materials such as polylactic acid, starch, biochar, and humic acid; the coating material is biodegradable and leaves no microplastic residue after the fertilizer effect cycle ends; Functional factor zoning: According to crop needs, functional components such as antibacterial agents, stress resistance factors, growth regulators, flowering promoters, fruit enlargement factors, quality improvement factors, and root-promoting factors are added to each layer to achieve "one function per layer". Functional microbial agents are loaded in different zones: according to crop needs, different functional microbial agents are loaded in each layer to achieve precise microbial regulation of "one agent per layer"; Humic acid gradient configuration: Based on the principle of "increasing molecular weight, decreasing activity, and increasing soil improvement function from the outside to the inside", fulvic acid, brown humic acid, and black humic acid are added in different layers to achieve a gradient synergistic effect of "quick-acting-medium-acting-long-acting". Precise control of release time: By adjusting the polylactic acid / starch ratio, biochar / humic acid content, membrane thickness, and granulation / coating process parameters in each layer, precise controlled release can be achieved for any release period within the range of 7 to 300 days.

[0101] This invention also provides the application of the above-described multi-layer coated controlled-release fertilizer in the field of agricultural planting.

[0102] The multi-layer coated controlled-release fertilizer provided by this invention can be applied in the following ways, which still fall within the protection scope of this invention: (1) Fertilizer products produced separately are combined and applied by physical mixing or mechanical compounding in an attempt to achieve the same or equivalent technical effect as the present invention: "segmented nutrient supply and precise controlled release according to crop growth period"; (2) Some layers of the multi-layer coated controlled-release fertilizer provided by the present invention are separated and produced independently as single or multiple fertilizer products. Regardless of the product name, packaging form, brand logo or sales method, they are then combined and applied after physical mixing or mechanical compounding to cover the crop growth stage that is the same as or overlaps with the multi-layer structure of the multi-layer coated controlled-release fertilizer provided by the present invention. (3) The fertilizer products produced independently as described in (1) or (2) above are packaged under the names of “formula combination”, “nutrient package”, “phased management plan”, “full-process fertilization technology” or any other name, and applied once or multiple times in an attempt to achieve the same or equivalent technical effect as the multi-layer coated controlled-release fertilizer of the present invention, namely “segmented supply of nutrients according to crop growth period and precise controlled release”. Among them, the fertilizer products produced independently include: single-layer controlled-release fertilizer, single-layer slow-release fertilizer, and single-layer compound fertilizer that have similar characteristics to any dimension of any layer or part of the layer combination of the present invention in terms of nutrient type, release kinetic characteristics, controlled-release / slow-release time window, and crop growth period correspondence; and double-layer, multi-layer, or non-full-layer controlled-release fertilizer, slow-release fertilizer, or compound fertilizer that have similar characteristics to some layers of the present invention.

[0103] The scope of protection of this invention covers the following circumvention behaviors: (1) Take the single-layer controlled-release fertilizer, single-layer slow-release fertilizer, single-layer compound fertilizer or any combination of the above fertilizers produced independently, and combine them according to the technical parameters that are similar to those of each layer in the multi-layer coated controlled-release fertilizer of the present invention in any dimension of nutrient type, functional positioning, release kinetic characteristics, controlled-release / slow-release time window, and crop growth period correspondence, through physical mixing, mechanical compounding, layered granulation and then mixing, core and outer coating, surface coating or co-granulation, in order to try to achieve the same or equivalent technical effect of "segmented nutrient supply according to crop growth period and precise controlled release" as the present invention. (2) After one or more layers in the multilayer structure of the multilayer coated controlled-release fertilizer of the present invention are produced independently, regardless of the name, packaging, brand, or sales channel of the product, they can be combined by any process to cover the same or overlapping crop growth stages as the present invention, even if the number of layers is less than the number of layers described in the present invention, even if it is claimed to be a "formula combination", "nutrient package", "phased management plan", "full-process fertilization technology" or any other name; (3) To attempt to circumvent the exclusive protection of this invention by packaging the behaviors described in (1) or (2) above as technical services, fertilization programs, management packages, brand alliances, channel cooperation or any other business model; The “similar technical parameters” are determined based on the release curve data of each layer of the multi-layered granules in the multi-layered coated controlled-release fertilizer described in this specification.

[0104] When determining whether a technical solution falls within the protection scope of this invention, if the technical solution is applied in a non-single, indivisible granule form, and its actual nutrient absorption curve of the crop is substantially similar to the nutrient demand curve of the corresponding crop growth period recorded in the specification of this invention, then regardless of the name, packaging, brand, or business model of the technical solution, the technical solution falls within the protection scope of this invention. The determination of "substantial similarity" is based on the release curve comparison experimental data recorded in the specification of this invention, and is not affected by product name, packaging form, brand logo or sales pitch.

[0105] Overall, the present invention achieves the following beneficial effects: (1) Supply nutrients according to the crop growth period and make precise matching: Based on the growth period characteristics of different crops, this invention precisely designs the release time and nutrient ratio of each layer to achieve "supply nutrients according to the crop growth period" and avoid nutrient waste and nutrient deficiency.

[0106] (2) The number of layers is flexible and adjustable to suit a variety of crops: This invention can be two-layer granulation / two-layer coating, three-layer granulation / three-layer coating, four-layer granulation / four-layer coating, five-layer granulation / five-layer coating or more layers, respectively adaptable to different crops such as lettuce (two layers), strawberry (three layers), wheat (four layers), soybean, rapeseed, corn (four layers), chili pepper (five layers), tea (five layers), apple, citrus, grape, nectarine (five layers), etc., to achieve flexible production of "one process, multiple products".

[0107] (3) Each layer contains nutrients and is effective throughout the process: Each exogenous fertilizer layer of the present invention contains a nutrient ratio designed according to the needs of different growth stages of crops, so as to achieve “each layer contains nutrients and is effective throughout the process”.

[0108] (4) One layer, one function, functional zoning load: According to the needs of crops, the present invention adds functional components to each layer to achieve multiple functions such as stabilizing seedlings and preventing diseases and pests, promoting root growth and resisting stress, promoting growth and preventing excessive growth, promoting flowering and fruit setting, expanding and strengthening fruit, strengthening fruit and improving quality and preventing premature aging, thus avoiding waste of functional components.

[0109] (5) One layer, one microorganism, microbial synergy: The present invention loads different functional microbial agents in different layers and adds three kinds of humic acid in a differentiated manner to form a multi-dimensional synergistic system of "microorganism-humic acid-biochar", realizing precise microbial regulation of "one layer, one microorganism" and improving the bioavailability of fertilizer.

[0110] (6) Humic acid gradient configuration for maximum functionality: This invention innovatively configures three components—fulvic acid, brown humic acid, and black humic acid—in a multi-layered structure based on the principle of "increasing molecular weight, decreasing activity, and increasing soil improvement function from the outside to the inside." Fulvic acid (outer layer) provides fast-acting root-promoting and stress-resistance functions, brown humic acid (middle layer) provides medium-efficiency soil improvement and nutrient slow-release synergistic functions, and black humic acid (inner layer) provides long-term heavy metal passivation and soil structure improvement functions. The three humic acids work synergistically to achieve a gradient effect of "fast-acting - medium-efficiency - long-efficiency," improving the effect by 30% to 50% compared to the application of single humic acid.

[0111] (7) Core improves soil, one season of fertilization benefits multiple seasons: The soil improvement nutrient core of the present invention uses biochar or bio-organic fertilizer, palm humic acid, black humic acid and biomass humic acid as the main components. It adopts extrusion granulation process, which not only provides nutrients for fruit growth, but also protects the soil, increases soil organic matter, prevents soil acidification and salinization, and fixes various nutrients that are not fully absorbed in the current season for continued supply to crops in the next season.

[0112] (8) Granulation is coating, simplifying the process: The controlled-release coating material of the present invention can be combined with nutrients, and granulation is coating, which simplifies the traditional two-step process of "granulation first and then coating", reduces equipment investment and energy consumption, and improves production efficiency.

[0113] (9) Replace water-soluble fertilizer and foliar fertilizer, apply once for the whole season: This invention adds water-soluble fertilizer and foliar fertilizer into the corresponding controlled-release layer according to the nutrient requirements of the crop growth period, replacing the multiple irrigations of traditional water-soluble fertilizer and the multiple sprays of foliar fertilizer, reducing the number of fertilizations and labor costs.

[0114] (10) Bio-based biodegradable materials, green and environmentally friendly: This invention uses bio-based materials such as polylactic acid, starch, biochar, and humic acid to replace traditional petroleum-based polymers. The coating material is biodegradable and there are no microplastic residues after the fertilizer effect cycle ends.

[0115] (11) Preventing soil problems and protecting arable land: This invention has the function of preventing soil problems such as salinization, heavy metal pollution, arable land degradation, acidification and compaction, and reduction of soil organic matter. It is achieved through synergistic mechanisms such as biochar adsorption, humic acid complexation, fulvic acid buffering, and microbial improvement.

[0116] (12) Reduced fertilizer use, increased crop yield and improved quality: This invention achieves a 20% to 40% increase in nitrogen, phosphorus and potassium (NPK) utilization, a 30% to 50% reduction in fertilizer application, a 20% to 40% increase in crop yield, increased fruit sugar content, increased vitamin C content and decreased nitrate content.

[0117] (13) Comprehensive protection of technology: This invention achieves comprehensive development and protection of fertilizer technology from the dimensions of product structure, adjustable number of layers, release time, microbial synergy, core composition, nutrient design, granulation and coating, replacement of water-soluble foliar fertilizer, preparation method, controlled-release nutrient core, application field, functional zoning load, soil problem prevention, green target, process innovation, humic acid synergistic optimization, nitrated humic acid preparation, adjustable components, core ratio, general range, continuous alternating process, application method avoidance, product protection avoidance, and absolute protection scope.

[0118] To further illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments.

[0119] In a specific embodiment of the present invention, nitrofulvic acid, nitrobrown humic acid, or nitroblack humic acid are prepared by the following nitration method: Preparation method of nitrofulvic acid: Using weathered coal or lignite as raw material, a mixed acid oxidation extraction method is adopted (the mass ratio of sulfuric acid to nitric acid is 7:3, the mass ratio of raw coal to mixed acid to water is 1:0.3:6, oxidation is carried out at 70℃ for 40 min, and stirring reaction is carried out at 60℃ for 1 h), which increases the fulvic acid extraction rate to 25%~35%. The molecular weight of the obtained nitrofulvic acid is 300~800 Daltons, the nitrogen content is increased by 5%~25%, and the number of functional groups is increased by 20%~30%. Preparation of nitrobrown humic acid: Using weathered coal or lignite as raw material, an alkaline dissolution-hydrogen peroxide oxidation-acid precipitation method was adopted (NaOH concentration 1wt%, hydrogen peroxide concentration 8wt%, oxidation temperature 70℃, oxidation time 3 h). The resulting nitrobrown humic acid has a molecular weight of 1000~5000 Daltons, an increase of 8%~28% in oxygen-containing functional groups, and an improvement in soil aggregate structure of 25%~40%. Preparation of nitrohumic acid: Using weathered coal or lignite as raw material, a high-temperature and high-pressure hydrothermal oxidation method is adopted (temperature 150℃, pressure 3 MPa, reaction time 6 h, oxidant is hydrogen peroxide or potassium permanganate). The resulting nitrohumic acid has a molecular weight of 8000~50000 Daltons, a specific surface area increase of 30%~50%, and a heavy metal adsorption capacity increase of 35%~50%.

[0120] In a specific embodiment of the present invention, the biochar is commercially available corn stalk biochar; the bio-organic fertilizer is commercially available chicken manure organic fertilizer; and the biomass humic acid is fruit and vegetable bio-humic acid raw material organic fertilizer from Gansu Sudi Fertilizer Co., Ltd.

[0121] In a specific embodiment of the present invention, the preparation method of the multi-layer coated controlled-release fertilizer includes the following steps: (1) Preparation of soil-improving nutrient core: Biochar or bio-organic fertilizer, brown humic acid, black humic acid, biomass humic acid, potassium fertilizer, a small amount of nitrogen fertilizer and phosphorus fertilizer are mixed in proportion and extrusion granulation process is adopted to obtain a soil-improving nutrient core with a particle size of 2.0~3.0 mm and a dense structure; extrusion granulation makes the core structure dense and continuously releases nutrients. (2) Preparation of raw materials for exogenous fertilizer layers: According to the needs of crops at different growth stages, the raw materials for each exogenous fertilizer layer are prepared separately, including macro-elements, meso-elements, micro-elements, humic acid, functional additives and functional microbial agents; the selection of humic acid follows the following principles: First layer (outermost layer) and second layer: Nitrofulic acid or mineral-derived fulvic acid with a molecular weight of 300~1000 Daltons is added preferentially, and the amount added accounts for 3%~8% of the total weight of the exogenous fertilizer layer in this layer, which is used to promote root growth, stabilize seedlings, resist stress, and enhance nutrient efficiency during the vegetative growth period. The third and fourth layers: Nitro humic acid or mineral-derived humic acid with a molecular weight of 1,000 to 5,000 Daltons are added preferentially, accounting for 5% to 10% of the total weight of the exogenous fertilizer layer in this layer, and are used for soil improvement and nutrient slow release synergy during the flowering and fruit setting period and the fruit enlargement period. The fifth layer (innermost layer) or soil improvement nutrient core: prioritize the addition of nitro humic acid or mineral-derived humic acid, with a molecular weight of 5,000 to 100,000 Daltons, and the amount added accounts for 5% to 12% of the total weight of the core source fertilizer. It is used for soil heavy metal passivation, long-term carbon sequestration and soil structure improvement during the mature harvest period and overwintering period. (3) Preparation of sustained-release coating solution: Mix the raw materials of each sustained-release coating layer with the solvent to obtain the sustained-release coating solution; (4) Fluidized bed spray coating: Using fluidized bed coating technology, a slow-release coating liquid is sprayed onto the soil amendment nutrient core or the surface of the previous layer of particles, dried and cooled to obtain coated particles; (5) Rotary drum granulation with exogenous fertilizer layer: The exogenous fertilizer layer raw material and the coated particles are mixed and fed into the rotary drum granulator. At the same time, binder and water are sprayed for granulation, drying and cooling to obtain composite particles. (6) Granulation and coating integrated process: The controlled-release coating material and the exogenous fertilizer layer raw material are added at the same time, and the coating is achieved during the granulation process, which simplifies the two-step process of "granulation first and coating later" and achieves the purpose of controlled release; (7) Repeat steps (4) to (6), and perform multiple alternating spraying, granulation and coating according to the target number of layers to obtain a multi-layer coated controlled-release fertilizer with a multi-layer structure; (8) Finished product screening and packaging: The obtained multi-layer coated controlled-release fertilizer is screened to remove unqualified particles and then packaged for moisture protection.

[0122] Example 1: Nutrient supply during the growth period of chili peppers (five layers): The growth period of chili peppers is about 150 days, which is divided into the seedling establishment period (7-10 days after transplanting), the vegetative growth period (10-40 days after transplanting), the flowering and fruit setting period (40-70 days after transplanting), the fruit enlargement period (70-100 days after transplanting), and the ripening and harvesting period (100-150 days after transplanting).

[0123] This embodiment prepares a five-layer, chili-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), fifth slow-release coating layer (10), fourth exogenous fertilizer layer (9), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0124] The raw material components of the fifth sustained-release coating layer (10), the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 22 parts starch, 15 parts biochar, 15 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 8 parts sorbitol, 8 parts maleic anhydride, 1 part stearic acid, 1 part oleic acid, and 0.5 parts quality improvement factor (potassium sulfate); the thickness of the fifth sustained-release coating layer can be 55 micrometers; the thickness of the fourth sustained-release coating layer can be 50 micrometers; the thickness of the third sustained-release coating layer can be 45 micrometers; the thickness of the second sustained-release coating layer can be 37 micrometers; and the thickness of the first sustained-release coating layer can be 30 micrometers.

[0125] Soil amendment nutrient core (1): 30 parts biochar, 25 parts bio-organic fertilizer, 15 parts palm humic acid, 15 parts black humic acid, 10 parts biomass humic acid, 20 parts potassium sulfate, 5 parts urea, and 3 parts monoammonium phosphate. Extrusion granulation, particle size 2.0~3.0 mm, dense structure.

[0126] First exogenous fertilizer layer (3) (seedling stabilization and disease / pest prevention layer, released 7-10 days after transplanting): 15 parts urea, 8 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.5 parts antibacterial agent (potassium dihydrogen phosphate), 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (phenylpeptide amino acid), 1 part Bacillus subtilis. NPK (mass ratio, the same below) = 18:10:15. Functions: promotes root growth, stabilizes seedlings, prevents diseases and pests, and enhances stress resistance; fulvic acid provides fast-acting root promotion and nutrient chelation functions.

[0127] Second exogenous fertilizer layer (5) (growth-promoting and anti-excessive growth layer, released 20-35 days after transplanting): 18 parts urea, 10 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.3 parts growth regulator (chlormequat chloride), 3 parts calcium and magnesium, 1 part Pseudomonas fluorescens. NPK=20:12:12. Functions: promotes growth and prevents excessive growth; fulvic acid provides nutrient enhancement and stress resistance.

[0128] The third exogenous fertilizer layer (7) (flowering and fruit setting layer, released 40-60 days after transplanting): 10 parts urea, 15 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part flower-promoting factor (boric acid), 1 part boron and zinc, and 1 part Bacillus amyloliquefaciens. NPK=12:18:15. Functions: promotes flowering and fruit setting; humic acid provides synergistic functions of improving medium-efficiency soil aggregate structure and slow-release nutrients.

[0129] Fourth exogenous fertilizer layer (9) (fruit enlargement and strengthening layer, released 70-100 days after transplanting): 8 parts urea, 10 parts monoammonium phosphate, 20 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.2 parts fruit enlargement factor (gibberellin), 2 parts calcium, and 1 part Trichoderma harzianum. NPK=10:12:22. Functions: enlarges and strengthens fruit; humic acid provides medium-efficiency soil improvement and nutrient fixation.

[0130] Fifth slow-release coating layer (10) (fruit strengthening, quality improvement and anti-premature aging layer, released 110-150 days after transplanting). Functions: fruit strengthening and quality improvement, anti-premature aging; black humic acid provides long-term soil heavy metal passivation and long-term carbon sequestration functions.

[0131] Controlled-release effect: Covers the entire growth period of chili peppers for 150 days, achieving "one application per year". Compared with traditional fertilizers, the amount of chemical fertilizer used is reduced by 40%, yield is increased by 35%, vitamin C content is increased by 28%, and nitrate content is reduced by 32%.

[0132] Example 2: Nutrient supply during the annual growth period of tea (five-layer structure): Tea is a perennial evergreen shrub with an annual growing season of about 300 days, which is divided into the spring tea sprouting period (February to March, after picking and pruning), the summer tea growing period (May to June), the autumn tea accumulation period (August to September), the winter tea rest period (October to November), and the overwintering nutrient storage period (December to January of the following year).

[0133] This embodiment prepares a five-layer structure for tea-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), fifth slow-release coating layer (10), fourth exogenous fertilizer layer (9), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0134] The raw material components of the fifth sustained-release coating layer (10), the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 20 parts starch, 18 parts biochar, 18 parts humic acid, 10 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 7 parts maleic anhydride, 1 part stearic acid, and 1 part oleic acid. The thickness of the fifth sustained-release coating layer can be 55 micrometers; the thickness of the fourth sustained-release coating layer can be 60 micrometers; the thickness of the third sustained-release coating layer can be 55 micrometers; the thickness of the second sustained-release coating layer can be 50 micrometers; and the thickness of the first sustained-release coating layer can be 55 micrometers.

[0135] Soil amendment nutrient core (1): 35 parts biochar, 30 parts bio-organic fertilizer, 12 parts palm humic acid, 12 parts black humic acid, 12 parts biomass humic acid, 15 parts potassium sulfate, 3 parts urea, and 2 parts monoammonium phosphate. Extrusion granulation, particle size 2.0~3.0 mm, dense structure.

[0136] First exogenous fertilizer layer (3) (spring tea bud-promoting layer, released 7-15 days after picking and pruning): 18 parts urea, 10 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.3 parts bud-promoting factor (gibberellin), 2 parts amino acids, 0.5 parts root-promoting factor (indoleacetic acid), and 1 part Bacillus subtilis. NPK=20:11:13. Functions: promotes bud and shoot growth, promotes root growth; fulvic acid provides fast-acting bud promotion and nutrient transport functions.

[0137] Second exogenous fertilizer layer (5) (Summer tea growth-promoting layer, released 20-40 days after spring tea harvest): 15 parts urea, 8 parts monoammonium phosphate, 15 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part heat-resistant factor (betaine), 0.5 parts stress-resistant factor (homosensitive factor), 2 parts calcium and magnesium, 1 part fluorescent Pseudomonas. NPK=16:9:16. Functions: promotes growth, resists high temperature and stress; fulvic acid provides rapid stress resistance and nutrient enhancement.

[0138] The third exogenous fertilizer layer (7) (autumn tea accumulation layer, released 35-60 days after summer tea harvest): 10 parts urea, 12 parts monoammonium phosphate, 18 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part quality-enhancing factor (tea polyphenol promoter), 0.5 parts selenium, and 1 part Bacillus amyloliquefaciens. NPK=12:14:19. Function: Quality accumulation; humic acid provides medium-efficiency soil improvement and nutrient slow-release function.

[0139] Fourth exogenous fertilizer layer (9) (winter tea rest layer, released 50-80 days after autumn tea harvest): 8 parts urea, 10 parts monoammonium phosphate, 20 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part cold-resistant factor (proline), 5 parts organic matter, and 1 part Trichoderma harzianum. NPK=10:12:22. Functions: cold resistance and rest; humic acid provides medium-efficiency soil water and fertilizer retention.

[0140] Fifth slow-release coating layer (10) (overwintering nutrient reserve layer, released 70-120 days into winter). Function: Overwintering nutrient reserve. Black humic acid provides long-term soil structure improvement and heavy metal passivation.

[0141] Controlled-release effect: Covering approximately 300 days of the tea's annual growth period, achieving "one application per year," it improves the quality of spring tea, stabilizes summer tea yield, ensures sufficient accumulation in autumn tea, allows winter tea to rest well, and provides ample nutrient reserves for overwintering. Fertilizer application is reduced by 45% compared to traditional fertilizers, while spring tea yield increases by 30%, tea polyphenol content increases by 18%, and amino acid content increases by 22%.

[0142] Example 3: Nutrient supply during the strawberry growth period (three-layer structure): Strawberries are perennial herbaceous plants, but are usually cultivated as annuals. Their growth period is about 120-150 days, which is divided into the seedling establishment period (7-10 days after transplanting), the vegetative growth period (10-40 days after transplanting), the budding and flowering period (40-60 days after transplanting), the fruit enlargement period (60-90 days after transplanting), and the ripening and harvesting period (90-120 days after transplanting).

[0143] This embodiment prepares a three-layer structure, strawberry-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0144] The raw material components of the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 25 parts starch, 15 parts biochar, 15 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 8 parts sorbitol, 9 parts maleic anhydride, 1 part stearic acid, 1 part oleic acid, and 0.5 parts quality improvement factor (earthworm fertilizer); the thickness of the third sustained-release coating layer can be 45 micrometers; the thickness of the second sustained-release coating layer can be 45 micrometers; and the thickness of the first sustained-release coating layer can be 30 micrometers.

[0145] Soil amendment nutrient core (1): 25 parts biochar, 20 parts bio-organic fertilizer, 10 parts brown humic acid, 10 parts black humic acid, 8 parts biomass humic acid, 18 parts potassium sulfate, 5 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0146] First exogenous fertilizer layer (3) (for seedling establishment and vegetative growth period, released 7-30 days after transplanting): 18 parts urea, 10 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.2 parts root-promoting factor (indoleacetic acid), 0.3 parts stress-resistant factor (alginic acid), 2 parts calcium, and 0.5 parts Bacillus subtilis. NPK=20:11:11. Functions: promotes rooting, stabilizes seedlings, and provides stress resistance. Fulvic acid provides fast-acting root promotion and nutrient chelation functions.

[0147] Second exogenous fertilizer layer (5) (released 35-90 days after transplanting during budding, flowering, and fruit enlargement): 10 parts urea, 15 parts monoammonium phosphate, 18 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part flower-promoting factor (boric acid), 0.3 parts fruit-enlarging factor (cytokinin), and 1 part Pseudomonas fluorescens. NPK=12:17:20. Functions: promotes flowering and fruit setting, and promotes fruit enlargement and growth. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0148] The third slow-release coating layer (6) (released 90-120 days after planting at maturity). Functions: promotes fruit growth and quality improvement, prevents premature aging. Black humic acid provides long-lasting soil improvement and heavy metal passivation.

[0149] Controlled-release effect: Covers the entire strawberry growth period of approximately 120 days, achieving "one application for the whole season," resulting in increased fruit yield, sugar content, firmness, and extended shelf life. Compared to traditional fertilizers, the amount of chemical fertilizer used is reduced by 35%, yield is increased by 28%, and sugar content is increased by 1.8 degrees Brix.

[0150] Example 4: Nutrient supply during the growth period of nectarines (five-layer structure): Nectarines are deciduous fruit trees with an annual growth period of about 280 to 300 days, which is divided into the budding period (March, after pruning), flowering period (March to April), fruit setting period (April to May), fruit enlargement period (May to June), fruit coloring and ripening period (June to July), post-harvest recovery period (July to August), flower bud differentiation period (August to September), and overwintering dormancy period (October to February of the following year).

[0151] This embodiment prepares a five-layer structure, a multi-layered coated controlled-release fertilizer specifically for nectarines, which consists of the following layers from the inside out: soil-improving nutrient core (1), fifth slow-release coating layer (10), fourth exogenous fertilizer layer (9), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0152] The raw material components of the fifth sustained-release coating layer (10), the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 18 parts starch, 20 parts biochar, 20 parts humic acid, 10 parts nitrohumic acid (molecular weight 10000~30000Da), 9 parts sorbitol, 6 parts maleic anhydride, 1 part stearic acid, and 1 part oleic acid; the thickness of the fifth sustained-release coating layer can be 55 micrometers; the thickness of the fourth sustained-release coating layer can be 60 micrometers; the thickness of the third sustained-release coating layer can be 55 micrometers; the thickness of the second sustained-release coating layer can be 55 micrometers; and the thickness of the first sustained-release coating layer can be 35 micrometers.

[0153] Soil amendment nutrient core (1): 30 parts biochar, 25 parts bio-organic fertilizer, 15 parts palm humic acid, 15 parts black humic acid, 10 parts biomass humic acid, 18 parts potassium sulfate, 4 parts urea, and 3 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0154] First exogenous fertilizer layer (3) (budding and flowering layer, released 7-15 days after pruning): 20 parts urea, 12 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part flowering factor (boric acid), 0.5 parts rooting factor (indoleacetic acid), 0.5 parts zinc, and 1 part Bacillus subtilis. NPK=22:13:11. Functions: promotes budding and flowering, and promotes root growth. Fulvic acid provides fast-acting budding and nutrient transport functions.

[0155] Second exogenous fertilizer layer (5) (fruit setting and stabilizing layer, released 20-40 days after flowering): 12 parts urea, 15 parts monoammonium phosphate, 15 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 2 parts fruit-setting factor (calcium), 0.5 parts stress-resistant factor (glutamate), 2 parts amino acids, 1 part Pseudomonas fluorescens. NPK=14:17:17. Functions: fruit setting and stabilizing, stress resistance. Fulvic acid provides rapid stress resistance and nutrient enhancement.

[0156] The third exogenous fertilizer layer (7) (fruit enlargement and strengthening layer, released 35-80 days after fruit set): 8 parts urea, 10 parts monoammonium phosphate, 22 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.2 parts fruit enlargement factor (gibberellin), 2 parts calcium, and 1 part Bacillus amyloliquefaciens. NPK=10:12:24. Function: Fruit enlargement and strengthening. Humic acid provides medium-efficiency soil improvement and slow-release nutrient function.

[0157] Fourth exogenous fertilizer layer (9) (coloring and ripening + post-harvest recovery layer, released 50-120 days after fruit enlargement): 6 parts urea, 8 parts monoammonium phosphate, 25 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.5 parts coloring factor (anthocyanin promoter), 0.5 parts quality improving factor (brassinolide), 5 parts organic matter, 1 part Trichoderma harzianum. NPK=8:10:26. Functions: coloring and sweetening, quality improvement, post-harvest recovery. Humic acid provides medium-efficiency soil improvement and nutrient fixation functions.

[0158] Fifth slow-release coating layer (10) (flower bud differentiation + overwintering layer, released 70-150 days in autumn). Functions: flower bud differentiation, overwintering nutrient storage. Black humic acid provides long-term soil structure improvement and heavy metal passivation.

[0159] Controlled-release effect: Covers approximately 300 days of the peach's annual growth period, achieving "one application per year." This results in uniform fruit coloring, high sugar content, good firmness, long shelf life, excellent flower bud differentiation, and safe overwintering. Compared to traditional fertilizers, fertilizer application is reduced by 50%, yield is increased by 32%, and sugar content is increased by 2.2 degrees Brix.

[0160] Example 5: Nutrient supply during the growth period of wheat in northern China (four-layer structure): The growth period of northern wheat (winter wheat) is about 240-270 days, which is divided into the seedling stage (7-10 days after sowing), tillering stage (30-50 days after sowing), overwintering stage (December to February of the following year), greening stage (March), jointing stage (April), booting stage (April-May), heading and flowering stage (May), and grain filling and ripening stage (May-June).

[0161] This embodiment prepares a four-layer structured multi-layered controlled-release fertilizer for northern wheat, consisting of the following layers from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0162] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 28 parts starch, 14 parts biochar, 14 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 10 parts maleic anhydride, 1.5 parts stearic acid, 1 part oleic acid, and 0.5 parts quality improvement factor (zinc element); the thickness of the fourth sustained-release coating layer can be 55 micrometers; the thickness of the third sustained-release coating layer can be 45 micrometers; the thickness of the second sustained-release coating layer can be 45 micrometers; and the thickness of the first sustained-release coating layer can be 40 micrometers.

[0163] Soil amendment nutrient core (1): 30 parts biochar, 25 parts bio-organic fertilizer, 12 parts brown humic acid, 12 parts black humic acid, 10 parts biomass humic acid, 15 parts potassium sulfate, 5 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0164] First exogenous fertilizer layer (3) (released 7-30 days after sowing during seedling emergence and tillering): 20 parts urea, 8 parts monoammonium phosphate, 8 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (brassinolide), 0.5 parts zinc, and 1 part Bacillus subtilis. NPK=24:10:10. Functions: promotes root growth, tillering, and stress resistance. Fulvic acid provides fast-acting root-promoting and nutrient-enhancing functions.

[0165] Second exogenous fertilizer layer (5) (greening-up and jointing stage, released 80-120 days after sowing, i.e., March-April of the following year): 18 parts urea, 12 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part lodging resistance factor (silicon), 0.2 parts growth regulator (mepiride), 2 parts calcium and magnesium, 1 part Pseudomonas fluorescens. NPK=20:13:11. Functions: greening-up and jointing stage, lodging resistance, and prevention of excessive growth. Humic acid provides medium-efficiency soil improvement and slow-release nutrient function.

[0166] The third exogenous fertilizer layer (7) (released 120-160 days after sowing, i.e., April-May, during the booting and flowering period): 12 parts urea, 18 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part flowering-promoting factor (boric acid), 0.3 parts molybdenum, and 1 part Bacillus amyloliquefaciens. NPK=14:20:13. Function: Promotes booting and flowering. Humic acid provides medium-efficiency soil improvement and nutrient fixation.

[0167] Fourth slow-release coating layer (8) (released 160-200 days after sowing, i.e., May-June, during the grain-filling and maturation period). Functions: Grain filling and quality improvement. Black humic acid provides long-lasting soil improvement and heavy metal passivation functions.

[0168] Controlled-release effect: Covering the entire growth period of wheat in northern regions for approximately 240 days, achieving "one sowing for the whole season," increasing the number of tillers, the number of grains per ear, the thousand-grain weight, and the yield. Compared with traditional fertilizers, the amount of chemical fertilizer applied is reduced by 40%, the yield is increased by 30%, the protein content is increased by 1.8 percentage points, and the wet gluten content is increased by 3.5 percentage points.

[0169] Example 6: Nutrient supply during the growth period of wheat in southern China (four-layer structure): Southern wheat (spring or winter wheat) has a growth period of approximately 80-20 days, divided into the emergence stage (7-10 days after sowing), tillering stage (20-40 days after sowing), jointing stage (60-80 days after sowing), booting stage (90-110 days after sowing), heading and flowering stage (110-130 days after sowing), and grain-filling and ripening stage (130-170 days after sowing). Southern wheat has a shorter growth period than northern wheat due to higher temperatures and a faster pace of nutrient demand.

[0170] This embodiment prepares a four-layer structured multi-layered controlled-release fertilizer for southern wheat, which consists of the following layers from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0171] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 30 parts starch, 12 parts biochar, 12 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 11 parts maleic anhydride, 1.5 parts stearic acid, 1.5 parts oleic acid, and 0.5 parts quality improvement factor (iron element); the thickness of the fourth sustained-release coating layer can be 35 micrometers; the thickness of the third sustained-release coating layer can be 35 micrometers; the thickness of the second sustained-release coating layer can be 35 micrometers; and the thickness of the first sustained-release coating layer can be 30 micrometers.

[0172] Soil amendment nutrient core (1): 28 parts biochar, 22 parts bio-organic fertilizer, 12 parts brown humic acid, 12 parts black humic acid, 10 parts biomass humic acid, 16 parts potassium sulfate, 5 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0173] First exogenous fertilizer layer (3) (released 7-25 days after sowing during seedling emergence and tillering): 22 parts urea, 8 parts monoammonium phosphate, 8 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (sodium nitrophenolate), 0.5 parts zinc, and 1 part Bacillus subtilis. NPK=26:10:10. Functions: promotes root growth, tillering, and stress resistance. Fulvic acid provides fast-acting root promotion and nutrient enhancement.

[0174] Second exogenous fertilizer layer (5) (released 50-80 days after sowing during the jointing stage): 16 parts urea, 14 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part lodging resistance factor (silicon), 0.2 parts growth regulator (mepiride), 2 parts calcium and magnesium, and 1 part Pseudomonas fluorescens. NPK=18:15:11. Functions: Promotes strong stem growth, lodging resistance, and prevents excessive growth. Humic acid provides medium-efficiency soil improvement and slow-release nutrient function.

[0175] The third exogenous fertilizer layer (7) (released 90-30 days after sowing during the booting and flowering period): 10 parts urea, 20 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part flowering-promoting factor (boric acid), 0.3 parts molybdenum, and 1 part Bacillus amyloliquefaciens. NPK=12:22:13. Function: Promotes booting and flowering. Humic acid provides medium-efficiency soil improvement and nutrient fixation.

[0176] Fourth slow-release coating layer (8) (released 130-180 days after sowing during the grain-filling and maturation period). Functions: Grain filling and quality improvement. Black humic acid provides long-lasting soil improvement and heavy metal passivation.

[0177] Controlled-release effect: Covers the entire growth period of wheat in southern China for approximately 180 days, achieving "one sowing for the whole season," adapting to the hot and rainy climate of the south, with a rapid nutrient release pace, full grain filling, and increased yield. Compared with traditional fertilizers, the amount of chemical fertilizer used is reduced by 35%, the yield is increased by 25%, and the protein content is increased by 1.5 percentage points.

[0178] Example 7: Nutrient supply during the rice growth period (four-layer structure): The growth period of rice varies depending on the variety and planting region. Early rice takes about 90-120 days, mid-season rice about 120-150 days, and late rice about 130-160 days. It is divided into the seedling stage (0-30 days after sowing), tillering stage (10-30 days after transplanting), jointing stage (30-50 days after transplanting), booting stage (50-70 days after transplanting), heading and flowering stage (70-90 days after transplanting), and grain filling and ripening stage (90-120 days after transplanting).

[0179] This embodiment takes medium-grain rice as an example and prepares a four-layer structure rice-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0180] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 32 parts starch, 10 parts biochar, 10 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 12 parts maleic anhydride, 2 parts stearic acid, and 1.5 parts oleic acid; the thickness of the fourth sustained-release coating layer can be 40 micrometers; the thickness of the third sustained-release coating layer can be 38 micrometers; the thickness of the second sustained-release coating layer can be 39 micrometers; and the thickness of the first sustained-release coating layer can be 32 micrometers.

[0181] Soil amendment nutrient core (1): 32 parts biochar, 28 parts bio-organic fertilizer, 10 parts brown humic acid, 10 parts black humic acid, 10 parts biomass humic acid, 12 parts potassium sulfate, 6 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0182] First exogenous fertilizer layer (3) (released 7-20 days after transplanting during the greening and tillering stage): 22 parts urea, 8 parts monoammonium phosphate, 8 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (ethephon), 0.5 parts zinc, 1 part silicon, and 1 part Bacillus subtilis. NPK=26:10:10. Functions: promotes rooting, tillering, and stress resistance. Fulvic acid provides fast-acting root promotion and nutrient enhancement functions.

[0183] Second exogenous fertilizer layer (5) (jointing and booting stage, released 25-60 days after transplanting): 15 parts urea, 18 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.3 parts booting factor (cytokinin), 0.5 parts lodging resistance factor (silicon), 2 parts calcium and magnesium, 1 part Pseudomonas fluorescens. NPK=17:20:11. Functions: jointing and booting stage, lodging resistance. Humic acid provides medium-efficiency soil improvement and slow-release nutrient function.

[0184] The third exogenous fertilizer layer (7) (released 60-110 days after transplanting during the heading and flowering + grain-filling stage): 10 parts urea, 12 parts monoammonium phosphate, 20 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part anti-premature aging factor (betaine), 0.5 parts quality-enhancing factor (zinc), 0.3 parts selenium, and 1 part Bacillus amyloliquefaciens. NPK=12:14:23. Functions: Grain filling, anti-premature aging, and quality enhancement. Humic acid provides medium-efficiency soil improvement and nutrient fixation.

[0185] Fourth slow-release coating layer (8) (released 110-150 days after transplanting during the late stage of grain filling and maturity). Functions: Grain filling and quality improvement. Black humic acid provides long-term soil improvement and heavy metal passivation functions.

[0186] Controlled-release effect: Covering the entire growth period of mid-season rice for approximately 150 days, achieving "one planting for the whole season", increasing the number of effective tillers, the number of grains per panicle, the seed setting rate, the thousand-grain weight, and the yield. Compared with traditional fertilizers, the amount of chemical fertilizer applied is reduced by 40%, the yield is increased by 28%, the head rice rate is increased by 6 percentage points, and the chalkiness is reduced by 2.5 percentage points.

[0187] Example 8: Nutrient supply during lettuce growth period (two-layer structure): Lettuce is a leafy vegetable with a growing period of about 60-80 days, divided into seedling stage (0-15 days after sowing), rosette stage (15-35 days after sowing), head formation stage (35-60 days after sowing), and harvest stage (60-80 days after sowing). Lettuce has a short growing period, relatively simple nutrient requirements, and is suitable for a two-tiered structure.

[0188] This embodiment prepares a two-layer structure for lettuce-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0189] Soil amendment nutrient core (1): 20 parts biochar, 15 parts bio-organic fertilizer, 8 parts palm humic acid, 8 parts black humic acid, 6 parts biomass humic acid, 15 parts potassium sulfate, 5 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0190] The raw material components of the second sustained-release coating layer (4) or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 30 parts starch, 12 parts biochar, 12 parts humic acid, 6 parts nitrohumic acid (molecular weight 10000~30000Da), 8 parts sorbitol, 10 parts maleic anhydride, 1 part stearic acid, 1 part oleic acid, and 0.3 parts quality improvement factor (iron element); the thickness of the second sustained-release coating layer can be 42 micrometers; the thickness of the first sustained-release coating layer can be 50 micrometers.

[0191] First exogenous fertilizer layer (3) (seedling stage + rosette stage, released 7-20 days after sowing): 20 parts urea, 10 parts monoammonium phosphate, 8 parts potassium sulfate, 8 parts fulvic acid, 3 parts nitrofulvic acid (molecular weight 300-500 Da), 6 parts biochar, 0.5 parts root-promoting factor (indoleacetic acid), 0.3 parts stress-resistant factor (xylooligosaccharides), 1 part calcium, 0.5 parts Bacillus subtilis. NPK=24:12:10. Functions: promotes root growth, stabilizes seedlings, and resists stress. Fulvic acid provides fast-acting root promotion and nutrient enhancement functions.

[0192] Second slow-release coating layer (4) (released 35-70 days after sowing during the heading and harvesting periods). Functions: Improves head quality and promotes fuller heading. Black humic acid provides long-lasting soil improvement.

[0193] Controlled-release effect: Covers the entire growth period of lettuce for approximately 70 days, achieving "one sowing for the whole season," resulting in thicker leaves, firmer heads, increased yield, and reduced nitrate content. Compared to traditional fertilizers, fertilizer application is reduced by 30%, yield is increased by 22%, vitamin C content is increased by 25%, and nitrate content is reduced by 28%.

[0194] Example 9: Nutrient supply during maize's growth period (four-layer structure): The growth period of maize varies depending on the variety and planting region. Spring maize takes about 120-150 days, while summer maize takes about 90-110 days. It is divided into the seedling stage (0-30 days after sowing), the jointing stage (30-50 days after sowing), the large trumpet stage (50-70 days after sowing), the tasseling and flowering stage (70-90 days after sowing), and the grain-filling and ripening stage (90-130 days after sowing).

[0195] This embodiment takes spring corn as an example and prepares a four-layer structure corn-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0196] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 30 parts starch, 12 parts biochar, 12 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 11 parts maleic anhydride, 1.5 parts stearic acid, and 1.5 parts oleic acid; the thickness of the fourth sustained-release coating layer can be 44 micrometers; the thickness of the third sustained-release coating layer can be 45 micrometers; the thickness of the second sustained-release coating layer can be 48 micrometers; and the thickness of the first sustained-release coating layer can be 46 micrometers.

[0197] Soil amendment nutrient core (1): 30 parts biochar, 25 parts bio-organic fertilizer, 12 parts palm humic acid, 12 parts black humic acid, 10 parts biomass humic acid, 16 parts potassium sulfate, 5 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0198] First exogenous fertilizer layer (3) (seedling stage, released 7-25 days after sowing): 20 parts urea, 8 parts monoammonium phosphate, 8 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (silicon fertilizer), 0.5 parts zinc, 1 part Bacillus subtilis. NPK=24:10:10. Functions: promotes root growth, strengthens seedlings, and enhances stress resistance. Fulvic acid provides fast-acting root-promoting and nutrient-enhancing functions.

[0199] Second exogenous fertilizer layer (5) (jointing + large trumpet stage, released 30-60 days after sowing): 18 parts urea, 15 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part lodging resistance factor (silicon), 0.2 parts growth regulator (paclobutrazol), 2 parts calcium and magnesium, 1 part Pseudomonas fluorescens. NPK=20:16:11. Functions: Promotes strong stem growth, lodging resistance, and prevents excessive growth. Humic acid provides medium-efficiency soil improvement and slow-release nutrient function.

[0200] The third exogenous fertilizer layer (7) (released 60-110 days after sowing during the tasseling and flowering + grain-filling stage): 10 parts urea, 12 parts monoammonium phosphate, 20 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part anti-premature aging factor (potassium dihydrogen phosphate), 0.5 parts quality-enhancing factor (boron fertilizer), 0.3 parts selenium, and 1 part Bacillus amyloliquefaciens. NPK=12:14:23. Functions: Grain filling, anti-premature aging, and quality enhancement. Humic acid provides medium-efficiency soil improvement and nutrient fixation.

[0201] Fourth slow-release coating layer (8) (released 110-150 days after sowing during the late grain-filling and maturation stage). Functions: Grain filling and quality improvement. Black humic acid provides long-term soil improvement and heavy metal passivation.

[0202] Controlled-release effect: Covers the entire growth period of spring corn for approximately 150 days, achieving "one-plant-full-season" benefits. It promotes well-developed root systems, robust stalks, large ears with full kernels, increased thousand-kernel weight, and higher yield. Compared to traditional fertilizers, fertilizer application is reduced by 40%, yield is increased by 30%, and thousand-kernel weight is increased by 8%.

[0203] Example 10: Nutrient supply during grape growing season (five-layer structure): Grapes are perennial deciduous vines with an annual growing season of about 200-240 days, which is divided into the budding period (March-April, after pruning), the new shoot growth period (April-May), the flowering and fruit setting period (May-June), the fruit enlargement period (June-July), the fruit coloring and ripening period (July-September), the post-harvest recovery period (September-October), and the overwintering dormancy period (November to February of the following year).

[0204] This embodiment prepares a five-layer structure grape-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), fifth slow-release coating layer (10), fourth exogenous fertilizer layer (9), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0205] The raw material components of the fifth sustained-release coating layer (10), the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 18 parts starch, 20 parts biochar, 20 parts humic acid, 10 parts nitrohumic acid (molecular weight 10000~30000Da), 9 parts sorbitol, 6 parts maleic anhydride, 1 part stearic acid, and 1 part oleic acid; the thickness of the fifth sustained-release coating layer can be 45 micrometers; the thickness of the fourth sustained-release coating layer can be 40 micrometers; the thickness of the third sustained-release coating layer can be 40 micrometers; the thickness of the second sustained-release coating layer can be 45 micrometers; and the thickness of the first sustained-release coating layer can be 42 micrometers.

[0206] Soil amendment nutrient core (1): 32 parts biochar, 28 parts bio-organic fertilizer, 10 parts palm humic acid, 10 parts black humic acid, 12 parts biomass humic acid, 15 parts potassium sulfate, 4 parts urea, and 3 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0207] First exogenous fertilizer layer (3) (budding and shoot-promoting layer, released 7-15 days after pruning): 18 parts urea, 10 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.3 parts bud-promoting factor (gibberellin), 0.5 parts root-promoting factor (indoleacetic acid), 0.5 parts zinc, and 1 part Bacillus subtilis. NPK=20:11:11. Function: promotes budding, shoot growth, and root development. Fulvic acid provides fast-acting bud promotion and nutrient transport functions.

[0208] Second exogenous fertilizer layer (5) (flowering and fruit setting layer, released 20-40 days after bud break): 10 parts urea, 18 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part fruit-preserving factor (boric acid), 0.5 parts stress-resistant factor (arginine), 2 parts calcium, 1 part Pseudomonas fluorescens. NPK=12:20:13. Functions: flowering and fruit setting, stress resistance. Fulvic acid provides rapid stress resistance and nutrient enhancement.

[0209] The third exogenous fertilizer layer (7) (fruit enlargement and strengthening layer, released 35-80 days after fruit set): 8 parts urea, 10 parts monoammonium phosphate, 22 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.3 parts fruit enlargement factor (cytokinin), 2 parts calcium, and 1 part Bacillus amyloliquefaciens. NPK=10:12:24. Function: Fruit enlargement and strengthening. Humic acid provides medium-efficiency soil improvement and slow-release nutrient function.

[0210] Fourth exogenous fertilizer layer (9) (coloring and ripening + post-harvest recovery layer, released 50-120 days after fruit enlargement): 6 parts urea, 8 parts monoammonium phosphate, 25 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.5 parts coloring factor (anthocyanin promoter), 0.5 parts quality improvement factor (magnesium element), 5 parts organic matter, 1 part Trichoderma harzianum. NPK=8:10:26. Functions: coloring and sweetening, quality improvement, post-harvest recovery. Humic acid provides medium-efficiency soil improvement and nutrient fixation functions.

[0211] Fifth slow-release coating layer (10) (overwintering layer, released 70-150 days in autumn). Function: Overwintering nutrient storage. Black humic acid provides long-term soil structure improvement and heavy metal passivation.

[0212] Controlled-release effect: Covering the grapevines for approximately 240 days throughout the entire growing season, achieving "one application per year," resulting in uniform fruit coloring, high sugar content, moderate acidity, and rich flavor. Post-harvest vine vigor recovery is excellent, and overwintering is safe. Compared to traditional fertilizers, fertilizer application is reduced by 45%, yield increased by 28%, and sugar content increased by 2.0 degrees Brix.

[0213] Example 11: Nutrient supply during the tomato growth period (three-layer structure): Tomatoes are annual herbaceous plants with a growth period of about 120 to 150 days, which is divided into the seedling stage (0 to 30 days after sowing), the flowering and fruit setting stage (30 to 60 days after sowing), the fruit enlargement stage (60 to 90 days after sowing), and the ripening and harvesting stage (90 to 120 days after sowing).

[0214] This embodiment prepares a three-layer structure tomato-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0215] The raw material components of the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 28 parts starch, 14 parts biochar, 14 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 9 parts sorbitol, 10 parts maleic anhydride, 1 part stearic acid, and 1 part oleic acid; the thickness of the third sustained-release coating layer can be 36 micrometers; the thickness of the second sustained-release coating layer can be 36 micrometers; and the thickness of the first sustained-release coating layer can be 33 micrometers.

[0216] Soil amendment nutrient core (1): 25 parts biochar, 20 parts bio-organic fertilizer, 10 parts brown humic acid, 10 parts black humic acid, 8 parts biomass humic acid, 18 parts potassium sulfate, 5 parts urea, and 4 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0217] First exogenous fertilizer layer (3) (seedling stage + flowering and fruit setting stage, released 7-40 days after sowing): 18 parts urea, 12 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.8 parts flowering-promoting factor (boric acid), 0.5 parts root-promoting factor (indoleacetic acid), 0.3 parts stress-resistant factor (silicon fertilizer), 2 parts calcium, 1 part Bacillus subtilis. NPK=20:13:11. Functions: promotes rooting, promotes flowering, and resists stress. Fulvic acid provides fast-acting root promotion and nutrient enhancement functions.

[0218] Second exogenous fertilizer layer (5) (released 40-100 days after sowing during fruit enlargement and ripening harvest): 8 parts urea, 10 parts monoammonium phosphate, 22 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.2 parts fruit enlargement factor (gibberellin), 0.5 parts quality improvement factor (lycopene promoter), and 1 part Pseudomonas fluorescens. NPK=10:12:24. Functions: fruit enlargement and quality improvement. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0219] The third slow-release coating layer (6) (released 100-140 days after sowing during the late stage of maturity and harvest). Functions: Improves quality during maturity and prevents premature aging. Black humic acid provides long-term soil improvement and heavy metal passivation.

[0220] Controlled-release effect: Covers the entire tomato growth period of approximately 140 days, achieving "one-plant-full-season" results in increased fruit yield, sugar content, lycopene content, and extended shelf life. Compared to traditional fertilizers, fertilizer application is reduced by 35%, yield is increased by 25%, sugar content is increased by 1.5 degrees, and lycopene content is increased by 20%.

[0221] Example 12: Nutrient supply during soybean growth period (four-layer structure): The growth period of soybeans varies depending on the variety and planting region. Spring soybeans take approximately 120-140 days, while summer soybeans take approximately 90-110 days. It is divided into the seedling stage (0-25 days after sowing), branching stage (25-45 days after sowing), flowering and pod-setting stage (45-70 days after sowing), and grain-filling and ripening stage (70-120 days after sowing). Soybeans are a legume crop with nitrogen-fixing capabilities, requiring relatively little nitrogen but having higher requirements for phosphorus and potassium.

[0222] In this embodiment, taking spring soybean as an example, a four-layer structure soybean-specific multi-layer coated controlled-release fertilizer was prepared, which consists of the following layers from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0223] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 32 parts starch, 10 parts biochar, 10 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 12 parts maleic anhydride, 2 parts stearic acid, and 1.5 parts oleic acid; the thickness of the fourth sustained-release coating layer can be 30 micrometers; the thickness of the third sustained-release coating layer can be 30 micrometers; the thickness of the second sustained-release coating layer can be 32 micrometers; and the thickness of the first sustained-release coating layer can be 30 micrometers.

[0224] Soil amendment nutrient core (1): 30 parts biochar, 25 parts bio-organic fertilizer, 12 parts palm humic acid, 12 parts black humic acid, 10 parts biomass humic acid, 18 parts potassium sulfate, 3 parts urea, and 6 parts monoammonium phosphate. Extrusion granulation process is used, with a particle size of 2.0~3.0 mm and a dense structure. The phosphorus content is relatively high to promote pod formation.

[0225] First exogenous fertilizer layer (3) (seedling stage + branching stage, released 7-25 days after sowing): 12 parts urea, 15 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (silicon), 0.5 parts molybdenum (promotes nitrogen fixation), 1 part Bacillus subtilis. NPK=14:17:11. Functions: promotes rooting, branching, stress resistance, and nitrogen fixation. Fulvic acid provides fast-acting root-promoting and nutrient-enhancing functions.

[0226] Second exogenous fertilizer layer (5) (released 25-60 days after sowing during flowering and pod formation): 8 parts urea, 20 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part pod-protecting factor (boric acid), 0.5 parts stress-resistance factor (brassinolide), 2 parts calcium and magnesium, and 1 part Pseudomonas fluorescens. NPK=10:22:13. Functions: flowering and pod formation, pod protection, and stress resistance. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0227] The third exogenous fertilizer layer (7) (released 60-110 days after sowing during the grain-filling and maturation period): 6 parts urea, 12 parts monoammonium phosphate, 22 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1 part anti-premature aging factor, 0.5 parts quality-enhancing factor (molybdenum), 0.3 parts selenium, and 1 part Bacillus amyloliquefaciens. NPK=8:14:24. Functions: Grain filling, anti-premature aging, and quality enhancement. Humic acid provides medium-efficiency soil improvement and nutrient fixation.

[0228] Fourth slow-release coating layer (8) (released 110-140 days after sowing during the late stage of grain filling and maturation). Function: To fill and improve the quality of mature grains. Black humic acid provides long-term soil improvement and heavy metal passivation.

[0229] Controlled-release effect: Covers the entire growth period of spring soybeans for approximately 140 days, achieving "one sowing for the whole season," resulting in well-developed root systems, increased pod number, higher grain weight, increased protein content, and higher yield. Compared to traditional fertilizers, fertilizer application is reduced by 35%, yield is increased by 25%, and protein content is increased by 2.0 percentage points.

[0230] Example 13: Nutrient supply during the rapeseed growth period (four-layer structure): The growth period of rapeseed is approximately 180-220 days (autumn-sown type), divided into the seedling stage (0-40 days after sowing), budding stage (40-80 days after sowing), flowering stage (80-120 days after sowing), and pod development and maturation stage (120-200 days after sowing). Key characteristics of rapeseed include: high boron requirement (boric acid should be added during flowering); and high potassium requirement during the pod development stage.

[0231] This embodiment prepares a four-layer structured multi-layered controlled-release fertilizer for rapeseed, which consists of the following layers from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0232] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 30 parts starch, 12 parts biochar, 12 parts humic acid, 8 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 11 parts maleic anhydride, 1.5 parts stearic acid, 1.5 parts oleic acid, and 0.5 parts quality improvement factor (magnesium element); the thickness of the fourth sustained-release coating layer can be 40 micrometers; the thickness of the third sustained-release coating layer can be 43 micrometers; the thickness of the second sustained-release coating layer can be 40 micrometers; and the thickness of the first sustained-release coating layer can be 38 micrometers.

[0233] Soil amendment nutrient core (1): 30 parts biochar, 25 parts bio-organic fertilizer, 12 parts palm humic acid, 12 parts black humic acid, 10 parts biomass humic acid, 18 parts potassium sulfate, 4 parts urea, and 5 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0234] First exogenous fertilizer layer (3) (seedling stage, released 7-30 days after sowing): 18 parts urea, 10 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part root-promoting factor (indoleacetic acid), 0.5 parts stress-resistant factor (amino acid ester), 0.5 parts zinc, 1 part Bacillus subtilis. NPK=20:11:11. Functions: promotes root growth, strengthens seedlings, and enhances stress resistance. Fulvic acid provides fast-acting root-promoting and nutrient-enhancing functions.

[0235] Second exogenous fertilizer layer (5) (released 40-75 days after sowing during the budding and bolting stage): 15 parts urea, 15 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.2 parts growth regulator, 0.5 parts lodging resistance factor (silicon), 2 parts calcium and magnesium, and 1 part Pseudomonas fluorescens. NPK=16:16:13. Functions: promotes bolting and strong stems, resists lodging, and prevents excessive growth. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0236] The third exogenous fertilizer layer (7) (released 80-115 days after sowing during the flowering period): 8 parts urea, 18 parts monoammonium phosphate, 15 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 1.5 parts flowering-promoting factor (boric acid), 0.5 parts molybdenum, and 1 part Bacillus amyloliquefaciens. NPK=10:22:16. Functions: Promotes flowering and preserves fertility, improves fruit set rate. Humic acid provides medium-efficiency soil amendment and nutrient fixation functions.

[0237] Fourth slow-release coating layer (8) (released 120-200 days after sowing during silique development and maturation). Functions: Siliques are plumped and oil content is increased. Humic acid provides long-lasting soil amendment and heavy metal passivation.

[0238] Controlled-release effect: Covers the entire growth period of rapeseed for approximately 200 days, achieving "one sowing for the whole season," increasing the number of effective branches, pods, thousand-grain weight, and oil content. Compared with traditional fertilizers, the amount of chemical fertilizer applied is reduced by 35%, while the yield increases by 22% and the oil content increases by 1.5 percentage points.

[0239] Example 14: Nutrient supply during the apple growing season (five-layer structure): Apples are deciduous fruit trees with an annual growth period of approximately 200-240 days, divided into the budding period (March, 7-15 days after pruning), flowering period (March-April, 20-40 days after budding), fruit enlargement period (May-July, 35-90 days after fruit set), coloring and ripening period (July-September, 60-140 days after fruit enlargement), and post-harvest recovery period + overwintering period (September to February of the following year, 70-150 days in autumn). Key characteristics of apples include: absorbing 60% of nitrogen during fruit enlargement, requiring a large amount of calcium, and needing boron and zinc during flower bud differentiation.

[0240] This embodiment prepares a five-layer structured multi-layered controlled-release fertilizer for apples, which consists of the following layers from the inside out: soil-improving nutrient core (1), fifth slow-release coating layer (10), fourth exogenous fertilizer layer (9), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0241] The raw material components of the fifth sustained-release coating layer (10), the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 18 parts starch, 20 parts biochar, 20 parts humic acid, 10 parts nitrohumic acid (molecular weight 10000~30000Da), 9 parts sorbitol, 6 parts maleic anhydride, 1 part stearic acid, and 1 part oleic acid; the thickness of the fifth sustained-release coating layer can be 45 micrometers; the thickness of the fourth sustained-release coating layer can be 36 micrometers; the thickness of the third sustained-release coating layer can be 36 micrometers; the thickness of the second sustained-release coating layer can be 35 micrometers; and the thickness of the first sustained-release coating layer can be 32 micrometers.

[0242] Soil amendment nutrient core (1): 35 parts biochar, 30 parts bio-organic fertilizer, 12 parts brown humic acid, 12 parts black humic acid, 12 parts biomass humic acid, 18 parts potassium sulfate, 4 parts urea, and 3 parts monoammonium phosphate. The mixture is produced using an extrusion granulation process, with a particle size of 2.0~3.0 mm and a dense structure.

[0243] First exogenous fertilizer layer (3) (budding and flowering layer, released 7-15 days after pruning): 20 parts urea, 12 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.3 parts budding factor (gibberellin), 0.5 parts rooting factor (indoleacetic acid), 0.5 parts zinc, 0.3 parts boron, and 1 part Bacillus subtilis. NPK=22:13:11. Functions: promotes budding and flowering, promotes rooting, and prevents small leaf disease. Fulvic acid provides fast-acting budding and nutrient transport functions.

[0244] Second exogenous fertilizer layer (5) (released 20-45 days after bud break during flowering and young fruit development): 12 parts urea, 18 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part fruit-preserving factor (boric acid), 2 parts fruit-preserving factor (calcium), 0.5 parts stress-resistant factor (Bihu), 2 parts amino acids, and 1 part Pseudomonas fluorescens. NPK=14:20:13. Functions: Preserves flowers and fruits, improves fruit set rate, and prevents bitter pit. Fulvic acid provides rapid stress resistance and nutrient enhancement.

[0245] The third exogenous fertilizer layer (7) (released 35-90 days after fruit set during the fruit enlargement period): 10 parts urea, 10 parts monoammonium phosphate, 22 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.3 parts fruit enlargement factor (cytokinin), 2 parts calcium, 1 part magnesium, and 1 part Bacillus amyloliquefaciens. NPK=12:12:24. Functions: enlarges and strengthens fruit, supplements calcium and prevents bitter pit. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0246] Fourth exogenous fertilizer layer (9) (coloring and ripening + post-harvest recovery layer, released 60-140 days after fruit enlargement): 6 parts urea, 8 parts monoammonium phosphate, 25 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 8 parts biochar, 0.5 parts coloring factor (anthocyanin promoter), 0.5 parts quality improvement factor (boron), 5 parts organic matter, 1 part Trichoderma harzianum. NPK=8:10:26. Functions: coloring and sweetening, quality improvement, post-harvest recovery. Humic acid provides medium-efficiency soil improvement and nutrient fixation functions.

[0247] Fifth slow-release coating layer (10) (flower bud differentiation + overwintering layer, released 70-150 days in autumn). Functions: flower bud differentiation, overwintering nutrient storage. Black humic acid provides long-term soil structure improvement and heavy metal passivation.

[0248] Controlled-release effect: Covers approximately 240 days of the apple's annual growth period, achieving "one application per year." This results in uniform fruit coloring, high sugar content, good firmness, long shelf life, excellent flower bud differentiation, and safe overwintering. Compared to traditional fertilizers, fertilizer application is reduced by 50%, yield increased by 30%, sugar content increased by 2.0 degrees Brix, and the proportion of fruits with a diameter of 80mm or more increased by 15%.

[0249] Example 15: Nutrient supply during the citrus growth period (five-layer structure): Citrus is an evergreen fruit tree with an annual growing season of approximately 300 days, divided into four phases: spring shoot emergence (February-March), flowering (March-April), young fruit stage (April-May), fruit enlargement stage (June-August), fruit coloring and ripening stage (September-November), post-harvest recovery stage (November-December), and overwintering stage (December-February of the following year). Key characteristics of citrus include: acidic soils in the south, requiring the addition of limestone materials to adjust the pH; and a high magnesium requirement to prevent magnesium deficiency and chlorosis.

[0250] This embodiment prepares a five-layer structure citrus-specific multi-layer coated controlled-release fertilizer, which consists of the following layers from the inside out: soil-improving nutrient core (1), fifth slow-release coating layer (10), fourth exogenous fertilizer layer (9), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0251] The raw material components of the fifth sustained-release coating layer (10), the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 18 parts starch, 20 parts biochar, 20 parts humic acid, 10 parts nitrohumic acid (molecular weight 10000~30000Da), 9 parts sorbitol, 6 parts maleic anhydride, 1 part stearic acid, and 1 part oleic acid; the thickness of the fifth sustained-release coating layer can be 45 micrometers; the thickness of the fourth sustained-release coating layer can be 40 micrometers; the thickness of the third sustained-release coating layer can be 40 micrometers; the thickness of the second sustained-release coating layer can be 40 micrometers; and the thickness of the first sustained-release coating layer can be 40 micrometers.

[0252] Soil amendment nutrient core (1): 35 parts biochar, 30 parts bio-organic fertilizer, 12 parts brown humic acid, 12 parts black humic acid, 12 parts biomass humic acid, 8 parts calcareous material (calcium carbonate), 15 parts potassium sulfate, 4 parts urea, and 3 parts monoammonium phosphate. Extrusion granulation process is used, with a particle size of 2.0~3.0 mm and a dense structure. The calcareous material is used to adjust the pH of acidic soils in southern regions.

[0253] First exogenous fertilizer layer (3) (released during spring shoot emergence and flowering period, February to April): 18 parts urea, 12 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 0.3 parts shoot-promoting factor (gibberellin), 0.5 parts root-promoting factor (indoleacetic acid), 1 part magnesium, 0.5 parts zinc, 0.5 parts boron, and 1 part Bacillus subtilis. NPK=20:13:11. Functions: promotes shoot and flower development, promotes root development, and prevents magnesium deficiency chlorosis. Fulvic acid provides fast-acting shoot promotion and nutrient transport functions.

[0254] Second exogenous fertilizer layer (5) (released during the young fruit stage, April-May): 12 parts urea, 18 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts fulvic acid, 4 parts nitrofulvic acid (molecular weight 300-500 Da), 8 parts biochar, 1 part fruit-preserving factor (boric acid), 2 parts fruit-preserving factor (calcium), 0.5 parts stress-resistance factor (amino acids), 2 parts amino acids, 1 part Pseudomonas fluorescens. NPK=14:20:13. Functions: Fruit preservation and stabilization, stress resistance. Fulvic acid provides rapid stress resistance and nutrient enhancement.

[0255] The third exogenous fertilizer layer (7) (released during fruit enlargement period, June to August): 8 parts urea, 10 parts monoammonium phosphate, 22 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500~3000Da), 8 parts biochar, 0.3 parts fruit enlargement factor (cytokinin), 2 parts calcium, 1 part magnesium, and 1 part Bacillus amyloliquefaciens. NPK=10:12:24. Functions: enlarges and strengthens fruit, supplements calcium and magnesium. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0256] Fourth exogenous fertilizer layer (9) (coloring and ripening + post-harvest recovery layer, released from September to December): 6 parts urea, 8 parts monoammonium phosphate, 25 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500~3000Da), 8 parts biochar, 0.5 parts coloring factor (anthocyanin promoter), 0.5 parts quality improvement factor (seaweed), 5 parts organic matter, 1 part Trichoderma harzianum. NPK=8:10:26. Functions: coloring and sweetening, quality improvement, post-harvest recovery. Humic acid provides medium-efficiency soil improvement and nutrient fixation functions.

[0257] Fifth slow-release coating layer (10) (overwintering layer, released during winter 70-120 days). Function: Overwintering nutrient storage. Black humic acid provides long-term soil structure improvement and heavy metal passivation.

[0258] Controlled-release effect: Covering the citrus growing season for approximately 300 days, achieving "one application per year," resulting in uniform fruit coloring, high sugar content, moderate acidity, and rich flavor. Post-harvest tree vigor recovery is excellent, and overwintering is safe. Compared to traditional fertilizers, the amount of chemical fertilizer applied is reduced by 45%, yield is increased by 25%, sugar content is increased by 1.8 degrees, and the effect of preventing magnesium deficiency chlorosis is significant.

[0259] Example 16: Multi-layer controlled-release fertilizer for saline-alkali land improvement (four-layer structure, general type): This embodiment describes the preparation of a four-layer structure multi-layer coated controlled-release fertilizer specifically designed for saline-alkali land improvement, suitable for crops such as corn, cotton, and sunflower in saline-alkali land. It focuses on preventing soil problems such as salinization, heavy metal pollution, farmland degradation, acidification and compaction, and reduction of soil organic matter.

[0260] The multi-layered coated controlled-release fertilizer of this embodiment consists of, from the inside out: soil-improving nutrient core (1), fourth slow-release coating layer (8), third exogenous fertilizer layer (7), third slow-release coating layer (6), second exogenous fertilizer layer (5), second slow-release coating layer (4), first exogenous fertilizer layer (3), and first slow-release coating layer (2).

[0261] The raw material components of the fourth sustained-release coating layer (8), the third sustained-release coating layer (6), the second sustained-release coating layer (4), or the first sustained-release coating layer (2) are: 100 parts polylactic acid, 30 parts starch, 15 parts biochar, 15 parts humic acid, 10 parts nitrohumic acid (molecular weight 10000~30000Da), 10 parts sorbitol, 10 parts maleic anhydride, 1.5 parts stearic acid, 1.5 parts oleic acid, and 0.5 parts quality-enhancing factor (amino acid); the thickness of the fourth sustained-release coating layer can be 39 micrometers; the thickness of the third sustained-release coating layer can be 36 micrometers; the thickness of the second sustained-release coating layer can be 35 micrometers; and the thickness of the first sustained-release coating layer can be 35 micrometers.

[0262] Soil amendment nutrient core (1): 35 parts biochar, 30 parts bio-organic fertilizer, 15 parts palm humic acid, 15 parts black humic acid, 15 parts biomass humic acid, 10 parts desulfurized gypsum, 8 parts zeolite powder, 12 parts potassium sulfate, 4 parts urea, and 4 parts monoammonium phosphate. Extrusion granulation process is used, with a particle size of 2.0~3.0 mm and a dense structure. The desulfurized gypsum and zeolite powder are used for saline-alkali land improvement and to regulate soil ion balance.

[0263] First exogenous fertilizer layer (3) (seedling stage + seedling stabilization stage, released 7-30 days after sowing): 18 parts urea, 10 parts monoammonium phosphate, 10 parts potassium sulfate, 10 parts fulvic acid, 5 parts nitrofulvic acid (molecular weight 300-500 Da), 10 parts biochar, 1 part root-promoting factor (indoleacetic acid), 1 part stress-resistance factor (salt tolerance inducer), 1 part salt-tolerant microorganism (Haloxymonas), 0.5 parts zinc, 1 part Bacillus subtilis. NPK=20:11:11. Functions: promotes root growth, stabilizes seedlings, and induces salt tolerance. Fulvic acid provides fast-acting root-promoting and stress-resistance functions, enhancing the survival ability of crops under saline-alkali conditions.

[0264] Second exogenous fertilizer layer (5) (released 30-70 days after sowing during the vegetative growth period): 15 parts urea, 15 parts monoammonium phosphate, 12 parts potassium sulfate, 10 parts humic acid, 4 parts nitrohumic acid (molecular weight 1500-3000 Da), 10 parts biochar, 0.3 parts growth regulator, 0.5 parts stress resistance factor, 0.5 parts salt-tolerant microorganisms (Haloxymonas), 3 parts calcium and magnesium, 1 part Pseudomonas fluorescens. NPK=16:16:13. Functions: promotes growth, prevents excessive growth, and enhances salt tolerance. Humic acid provides medium-efficiency soil aggregate structure improvement and salt adsorption functions.

[0265] The third exogenous fertilizer layer (7) (released 70-130 days after sowing during the reproductive growth period): 10 parts urea, 12 parts monoammonium phosphate, 20 parts potassium sulfate, 10 parts humic acid, 5 parts nitrohumic acid (molecular weight 1500-3000 Da), 10 parts biochar, 1 part flower-promoting factor (boric acid), 0.3 parts fruit-enlarging factor (gibberellin), 0.5 parts anti-premature aging factor, 0.5 parts salt-tolerant microorganisms (Haloxymonas), and 1 part Bacillus amyloliquefaciens. NPK=12:14:23. Functions: promotes flowering and fruit setting, promotes fruit enlargement and growth, and resists premature aging. Humic acid provides medium-efficiency soil improvement and slow-release nutrient functions.

[0266] Fourth slow-release coating layer (8) (released 130-180 days after sowing at the mature harvest period). Functions: improves quality during maturity and prevents premature aging. Black humic acid provides long-term passivation of heavy metals in the soil and long-term carbon sequestration, continuously improving the soil structure of saline-alkali land.

[0267] Controlled-release effect: Covers the entire crop growth period for approximately 180 days, achieving "one sowing for the whole season". Under saline-alkali soil conditions (salt content 0.3%~0.5%), the amount of chemical fertilizer applied is reduced by 40% compared to traditional chemical fertilizers, crop yield is increased by 20%~30%, soil pH value is reduced by 0.3~0.5 units, soil salinity is reduced by 15%~25%, soil organic matter content is increased by 15%~20%, and microbial diversity index is increased by 25%~30%.

[0268] Soil problem prevention effect: (1) Prevention of salinization: biochar adsorbs salt, humic acid regulates ion balance, fulvic acid enhances buffering capacity, desulfurized gypsum replaces sodium ions, and zeolite powder adsorbs and fixes salt. (2) Prevention of heavy metal pollution: biochar adsorbs and passivates heavy metals, humic acid complexes and fixes heavy metals, and zeolite powder immobilizes heavy metals through ion exchange. (3) Prevent farmland degradation: increase soil organic matter, improve soil aggregate structure, and enhance microbial diversity; (4) Prevention of acidification and compaction: Humic acid buffers pH, biochar improves aeration, and biomass humic acid promotes the formation of aggregates; (5) Preventing soil organic matter from decreasing: biochar provides long-term carbon sequestration, bio-organic fertilizer replenishes organic matter, and humic acid promotes humification.

[0269] Comparative Example 1: The preparation method of this comparative example is the same as that of Example 1 (chili pepper), except that the five-layer structure is changed to a three-layer structure (removing the fourth slow-release coating layer, the fourth exogenous fertilizer layer, and the fifth slow-release coating layer) for chili pepper cultivation.

[0270] The results showed that the application of fertilizers failed to cover the entire 150-day growth period of chili peppers, thus failing to achieve the goal of "one application per year." The amount of chemical fertilizer applied was basically the same as that of traditional chemical fertilizers, decreasing by 4.2%, while the yield remained basically unchanged, increasing by 3.5%. The vitamin C content remained basically stable, increasing by 2%, and the nitrate content decreased by 1.7%.

[0271] Comparative Example 2: The preparation method of this comparative example is the same as that of Example 2 (tea), except that the biochar, humic acid, black humic acid and biomass humic acid in the soil improvement nutrient core (1) are replaced with an equal mass of ordinary organic fertilizer for tea planting.

[0272] The results showed that the amount of chemical fertilizer applied was reduced by 20.4% compared with traditional chemical fertilizers, the yield of spring tea increased by 12.1%, the content of tea polyphenols increased by 4.8%, and the content of amino acids increased by 8.3%.

[0273] Comparative Example 3: The preparation method of this comparative example is the same as that of Example 5 (Northern Wheat), except that the bio-based coating material (polylactic acid, starch, biochar, humic acid) is replaced with an equal mass of petroleum-based polymer (polyethylene, polyurethane) for use in northern wheat cultivation.

[0274] The results showed that fertilizer components were not released in time and could not cover the entire growth period of wheat in northern China, resulting in a decrease in tiller number, number of grains per ear, thousand-grain weight, and yield. Compared with traditional fertilizers, the amount of chemical fertilizer applied increased by 175%, but the yield decreased by 1.5%, protein content decreased by 3.2 percentage points, and wet gluten content decreased by 2.6 percentage points.

[0275] Comparative Example 4: The preparation method of this comparative example is the same as that of Example 13 (rapeseed), except that: no nitrofulvic acid, nitrobrown humic acid, or nitroblack humic acid were added, only a mixture of common humic acids was added, and no functional components (all functional factors added to each layer) were loaded in separate sections for rapeseed cultivation.

[0276] The results showed that the number of effective branches remained unchanged, the number of siliques decreased, the thousand-grain weight decreased, and the oil content remained unchanged. Compared with traditional fertilizers, the amount of chemical fertilizer applied was reduced by 6%, the yield increased by 2.8%, and the oil content increased by 0.2 percentage points.

[0277] Comparative Example 5: The preparation method of this comparative example is the same as that of Example 16 (for saline-alkali land improvement), except that: no desulfurized gypsum, zeolite powder, salt-tolerant microorganisms and biomass humic acid were added, and the three types of humic acid were not differentiated (only mineral-derived fulvic acid was added), which was used for corn planting in saline-alkali land.

[0278] The results showed that under saline-alkali soil conditions (salt content 0.3%~0.5%), the amount of chemical fertilizer applied was reduced by 12% compared with traditional chemical fertilizers, the crop yield increased by 1.2~5.1%, the soil pH value decreased by 0.1~0.4 units, the soil salinity decreased by 6%~10%, the soil organic matter content increased by 6%~11%, and the microbial diversity index increased by 4%~9%.

[0279] The specific quantities listed in the embodiments of this invention are merely illustrative and not intended to limit the technical solutions. Those skilled in the art should understand that, while maintaining the functional positioning and relative proportions of each component, the content of each component can be adjusted within a range of ±50% to still achieve the technical effects of this invention.

[0280] The embodiments of the present invention have been described above; however, these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the above embodiments of the present invention without inventive effort are within the protection scope of the present invention.

Claims

1. A multi-layer coated controlled-release fertilizer, characterized in that, The system employs a concentric, multi-layered, alternating coating structure, comprising, from the inside out, a core and a controlled-release fertilizer layer covering the surface of the core. The core includes a soil-improving nutrient core and a slow-release coating layer covering the surface of the soil-improving nutrient core. The controlled-release fertilizer layer is either a first controlled-release fertilizer layer or a second controlled-release fertilizer layer. The first controlled-release fertilizer layer includes an exogenous fertilizer layer and a slow-release coating layer covering the outer surface of the exogenous fertilizer layer. The second controlled-release fertilizer layer is a composite layer of the exogenous fertilizer layer and the slow-release coating layer. The controlled-release fertilizer layer has two or more layers.

2. The multi-layer coated controlled-release fertilizer according to claim 1, characterized in that, The core components of soil amendment nutrients include one or more of the following: biochar, bio-organic fertilizer, fulvic acid, brown humic acid, black humic acid, biomass humic acid, macro-elements, micro-elements, and synergists.

3. The multi-layer coated controlled-release fertilizer according to claim 2, characterized in that, The biochar is made from corn stalks.

4. The multi-layer coated controlled-release fertilizer according to claim 2, characterized in that, Bio-organic fertilizer includes one or both of chicken manure organic fertilizer and sheep manure organic fertilizer.

5. The multi-layer coated controlled-release fertilizer according to claim 2, characterized in that, The synergist is zeolite powder.

6. The multi-layer coated controlled-release fertilizer according to claim 1, characterized in that, The core contains a sustained-release coating layer made from the following raw materials in parts by weight: 80-120 parts polylactic acid, 10-35 parts starch, 10-25 parts biochar, 8-25 parts humic acid, 5-10 parts modified humic acid, 5-10 parts sorbitol, 5-15 parts maleic anhydride, 1-2 parts stearic acid, and 1-2 parts oleic acid.

7. The multi-layer coated controlled-release fertilizer according to claim 6, characterized in that, Humic acids include one or more of black humic acid, yellow humic acid, and brown humic acid.

8. The multi-layer coated controlled-release fertilizer according to claim 6, characterized in that, Modified humic acids include one or more of the following: nitrofulvic acid, mineral-derived fulvic acid, nitrobrown humic acid, mineral-derived brown humic acid, nitroblack humic acid, and mineral-derived black humic acid.

9. The multi-layer coated controlled-release fertilizer according to claim 6, characterized in that, Within the core, the slow-release coating layer also includes functional additives; these functional additives include one or more of the following: antibacterial agents, stress-resistant factors, growth-regulating factors, flowering-promoting factors, fruit enlargement factors, quality-enhancing factors, and root-promoting factors.

10. The multi-layer coated controlled-release fertilizer according to claim 1, characterized in that, Within the core, the thickness of the sustained-release coating layer is 30-60 micrometers.

11. The multi-layer coated controlled-release fertilizer according to claim 6, characterized in that, In the first controlled-release fertilizer layer, the exogenous fertilizer layer includes one or more of the following: macro-elements, meso-elements, micro-elements, humic acid, modified humic acid, biomass humic acid, biochar, functional additives, and functional microbial agents.

12. The multi-layer coated controlled-release fertilizer according to claim 11, characterized in that, Humic acids include one or more of black humic acid, yellow humic acid, and brown humic acid.

13. The multi-layer coated controlled-release fertilizer according to claim 8, characterized in that, The molecular weight of nitrofulvic acid or mineral-derived fulvic acid is 300-1000 Daltons; the molecular weight of nitrobrown humic acid or mineral-derived brown humic acid is 1000-5000 Daltons; and the molecular weight of nitroblack humic acid or mineral-derived black humic acid is 5000-100000 Daltons.

14. The multi-layer coated controlled-release fertilizer according to claim 7, characterized in that, The mass ratio of fulvic acid, brown humic acid and black humic acid is 2:3:5~4:3:

3.

15. The multi-layer coated controlled-release fertilizer according to claim 11, characterized in that, Functional microbial agents include one or more of Bacillus subtilis, Pseudomonas fluorescens, Bacillus amyloliquefaciens, and Trichoderma harzianum.

16. The multi-layer coated controlled-release fertilizer according to claim 11, characterized in that, The exogenous fertilizer layer comprises the following components in parts by weight: 2-25 parts urea, 1-20 parts monoammonium phosphate, 8-25 parts potassium sulfate, 8-22 parts humic acid, 3-12 parts modified humic acid, 5-45 parts biochar or bio-organic fertilizer, 5-15 parts biomass humic acid, 0.05-2 parts functional additives, and 0.3-2 parts functional microbial agents.

17. The multi-layer coated controlled-release fertilizer according to claim 1, characterized in that, In the first controlled-release fertilizer layer, the thickness of the exogenous fertilizer layer is 155~165 micrometers.

18. The multi-layer coated controlled-release fertilizer according to claim 1, characterized in that, In the first controlled-release fertilizer layer, the slow-release coating layer is made of the following raw materials in parts by weight: 80-120 parts polylactic acid, 10-35 parts starch, 10-25 parts biochar, 8-25 parts humic acid, 5-10 parts sorbitol, 5-15 parts maleic anhydride, 1-2 parts stearic acid and 1-2 parts oleic acid.

19. The multi-layer coated controlled-release fertilizer according to claim 1, characterized in that, The thickness of the slow-release coating layer in the first controlled-release fertilizer layer is 30-60 micrometers.

20. The multi-layer coated controlled-release fertilizer according to claim 6, characterized in that, The total mass fraction of the core is 50-120 parts; the total mass fraction of the single-layer exogenous fertilizer layer is 30-80 parts; and the total mass fraction of the single-layer sustained-release coating layer is 100-200 parts.

21. The multi-layer coated controlled-release fertilizer according to claim 6, characterized in that, Multi-layer coated controlled-release fertilizers can be granulated in two layers, coated in two layers, granulated in three layers, coated in three layers, granulated in four layers, coated in four layers, granulated in five layers, or coated in five layers.

22. The multi-layer coated controlled-release fertilizer according to claim 21, characterized in that, The layers of the multi-layered controlled-release fertilizer release fertilizer at the following times: the first layer is released 7-30 days after the first application; the second layer is released 20-160 days after the first application; the third layer is released 35-180 days after the first application; the fourth layer is released 50-210 days after the first application; and the fifth layer is released 20-300 days after the first application.

23. A method for preparing a multi-layer coated controlled-release fertilizer, characterized in that, The multi-layer coated controlled-release fertilizer is the multi-layer coated controlled-release fertilizer according to any one of claims 1 to 22, comprising the following steps: (1) Preparation of soil-amortized nutrient core: The raw materials of soil-amortized nutrient core are mixed and extruded into granules to obtain soil-amortized nutrient core; (2) Preparation of raw materials for exogenous fertilizer layer: Prepare raw materials for each exogenous fertilizer layer according to the needs of different growth stages of crops; (3) Preparation of sustained-release coating solution: Mix the raw materials of the sustained-release coating layer with the solvent to obtain the sustained-release coating solution; (4) Fluidized bed coating: Through fluidized bed coating, a slow-release coating liquid is sprayed onto the surface of the soil-improved nutrient core, dried, and cooled to obtain the core; (5) Rotary drum granulation to coat exogenous fertilizer layer: The raw materials of exogenous fertilizer layer are mixed with the core and fed into the rotary drum granulator. At the same time, binder and water are sprayed for granulation, drying, and cooling to obtain composite granules. (6) Granulation and coating: The controlled-release coating material is added simultaneously with the raw materials of the exogenous fertilizer layer, and the coating is achieved during the granulation process; (7) Repeat steps (4) to (6) to alternately spray, granulate and coat according to the target number of layers to obtain multi-layer coated controlled-release fertilizer.

24. The application of a multi-layer coated controlled-release fertilizer in agricultural planting, characterized in that, The multi-layer coated controlled-release fertilizer is any one of the multi-layer coated controlled-release fertilizers according to claims 1 to 22.

25. The application according to claim 24, characterized in that, Multi-layer coated controlled-release fertilizers are suitable for field crops, fruit crops, cash crops, or vegetable crops.

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