Sustained and controlled release fertilizer with multi-layer degradable structure

Abstract

The utility model provides a sustained and controlled release fertilizer with a multi-layer degradable structure. Specifically, the slow / controlled-release fertilizer has a granular shape, and sequentially comprises a fertilizer core, a slow / controlled-release agent, a slow / controlled-release agent and a slow / controlled-release agent, a first degradable material layer; a fertilizer layer; a second degradable material layer; the first degradable material layer and the second degradable material layer are polylactic acid layers or polyvinyl alcohol layers, and the first inorganic structure layer is a fly ash layer, an attapulgite layer or a diatomite layer. According to the slow and controlled release fertilizer with the multilayer degradable structure, the effective controlled release of the fertilizer can be realized, and the slow and controlled release of the fertilizer can be realized within 1-5 months of a common crop growth period.

Description

Technical Field

[0001] The utility model relates to the technical field of slow-release fertilizers, and in particular to a slow-release fertilizer with a multi-layer degradable structure. Background Art

[0002] Fertilizer is an indispensable input in agricultural production, and plays a key role in increasing crop yields and improving the quality of agricultural products. However, there are many problems in the use of traditional fertilizers. For a long time, the excessive use and unreasonable application of traditional chemical fertilizers have been common. On the one hand, excessive fertilization leads to a large amount of nutrients that cannot be effectively absorbed and utilized by crops, resulting in low fertilizer utilization. According to statistics, the average utilization rate of chemical fertilizers in my country in the current season is only about 30%-35%, which is far lower than the level of developed countries. This not only means that the large amount of fertilizer costs invested by farmers are wasted, but also the nutrients that are not absorbed remain in the soil and are lost to water bodies through rainwater erosion and other channels, causing eutrophication of water bodies, triggering algae proliferation, and destroying the ecological balance of water bodies; seepage into the ground may pollute groundwater and pose a threat to drinking water safety. On the other hand, the release rate of traditional fertilizers is difficult to accurately match the fertilizer demand law during the crop growth cycle. In the early stage of crop growth, the rapid release of fertilizers may cause seedling burns, affecting crop growth; in the later stage of growth, insufficient fertilizer supply may limit the improvement of crop yield and quality. In addition, the long-term and large-scale use of traditional fertilizers will also cause problems such as soil compaction and acidification, destroy soil structure, reduce soil aeration, water retention and fertilizer retention, and thus affect the structure and activity of soil microbial communities, causing soil fertility to gradually decline, forming a vicious circle, and ultimately causing serious obstacles to the sustainable development of agriculture.

[0003] In order to solve a series of problems brought by traditional fertilizers, slow-release fertilizer technology came into being. Slow-release fertilizer refers to a type of fertilizer that uses various regulatory mechanisms to make the fertilizer nutrients in accordance with the set release mode (such as slow release, controlled release, etc.) in coordination with the fertilizer requirements during the crop growth cycle. In recent years, slow-release fertilizer technology has been widely studied and developed at home and abroad, and its preparation methods mainly include chemical methods, physical methods and biochemical methods. The chemical method forms a layer of insoluble protective film on the surface of fertilizer particles through chemical reactions to control the dissolution rate of nutrients; the physical method mainly uses physical processes such as coating and wrapping to change the release characteristics of fertilizers; the biochemical method uses biological materials or microorganisms to regulate nutrient release. Although slow-release fertilizer technology has made certain progress, it still faces some challenges. For example, among the existing slow-release fertilizers, the slow-release effect of some products is not ideal, and it is difficult to release nutrients continuously and stably over a long period of time (such as 1-5 months of crop growth). Some fertilizers may release nutrients suddenly in the early stage, and then the release rate drops rapidly, which cannot meet the needs of the crop throughout the entire growth cycle. At the same time, the cost of some slow-release fertilizers is relatively high, mainly because their coating materials are expensive or the preparation process is complicated, which limits their large-scale application in agricultural production. In addition, some coating materials are difficult to degrade in the natural environment, and will remain in the soil after long-term use, causing potential pollution to the soil environment and is not conducive to the sustainable development of the agricultural ecosystem.

[0004] Therefore, the development of a slow-release fertilizer that can effectively slow-release fertilizers during the growing period of crops, is cost-effective and environmentally friendly has become a research hotspot and development direction in the current agricultural fertilizer field, and has an urgent practical need to ensure the efficient, green and sustainable development of agricultural production. Utility Model Content

[0005] Based on the technical problems described above, one of the purposes of the utility model is to provide a slow-release fertilizer with a multi-layer degradable structure, which can achieve effective controlled release of fertilizer and can slowly release fertilizer within 1-5 months of the normal crop growth period.

[0006] Specifically, according to one aspect of the utility model, a slow-release fertilizer having a multi-layer degradable structure is provided, characterized in that the slow-release fertilizer has a granular shape and comprises, from the inside to the outside:

[0007] Fertilizer cores;

[0008] a first degradable material layer;

[0009] Fertilizer layer;

[0010] a second degradable material layer; and

[0011] A first inorganic structural layer, wherein:

[0012] The first degradable material layer and the second degradable material layer are polylactic acid layers or polyvinyl alcohol layers, and

[0013] The first inorganic structural layer is a fly ash layer, an attapulgite layer or a diatomaceous earth layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A cross-sectional view showing a slow-release fertilizer having a multi-layer degradable structure according to one embodiment of the present invention; and

[0015] Figure 2 A cross-sectional view of a slow-release fertilizer having a multi-layer degradable structure according to another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0016] The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It will be appreciated that other embodiments are contemplated and may be implemented without departing from the scope or spirit of the present invention. Therefore, the following detailed description is non-restrictive.

[0017] Unless otherwise indicated, all numbers used in the specification and claims to represent feature sizes, quantities and physicochemical properties should be understood as being modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters listed in the above specification and the attached claims are approximate values, and those skilled in the art can use the teachings disclosed herein to seek to obtain the desired properties and appropriately change these approximate values. The use of numerical ranges expressed as endpoints includes all numbers within the range and any range within the range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4 and 5, etc.

[0018] As mentioned above, the utility model aims to solve many problems existing in traditional fertilizers. Excessive use of traditional fertilizers leads to low utilization rate, nutrient loss and environmental pollution, and the release rate is difficult to match with the fertilizer requirement of crops, and also causes soil compaction, etc. At the same time, existing slow-release fertilizers have problems such as unsatisfactory slow-release effect, high cost, and difficult degradation of coating materials. The utility model aims to provide a slow-release fertilizer with a multi-layer degradable structure. Through a specific structural design, it can achieve effective slow-release of fertilizers during the 1-5 month crop growth period, improve fertilizer utilization, reduce costs, reduce environmental pollution, and promote sustainable agricultural development.

[0019] Specifically, the utility model provides a slow-release fertilizer with a multi-layer degradable structure, wherein the slow-release fertilizer has a granular shape and comprises, from the inside to the outside:

[0020] Fertilizer cores;

[0021] a first degradable material layer;

[0022] Fertilizer layer;

[0023] a second degradable material layer; and

[0024] A first inorganic structural layer, wherein:

[0025] The first degradable material layer and the second degradable material layer are polylactic acid layers or polyvinyl alcohol layers, and

[0026] The first inorganic structural layer is a fly ash layer, an attapulgite layer or a diatomaceous earth layer.

[0027] Figure 1 FIG. 1 shows a cross-sectional view of a slow-release fertilizer 100 having a multi-layer degradable structure according to an embodiment of the present invention. Figure 1 As shown in the figure, the slow-release fertilizer 100 has a granular shape and includes, from the inside to the outside,: a fertilizer core 1; a first degradable material layer 2; a fertilizer layer 3; a second degradable material layer 4; and a first inorganic structure layer 5, wherein: the first degradable material layer 2 and the second degradable material layer 4 are polylactic acid layers or polyvinyl alcohol layers, and the first inorganic structure layer 5 is a fly ash layer, a attapulgite layer or a diatomaceous earth layer.

[0028] According to certain preferred embodiments of the utility model, the fertilizer core is a urea fertilizer core, which is spherical in shape. Urea, as a commonly used nitrogen fertilizer, can provide nitrogen elements for crops. The spherical shape is selected because it has good dispersibility in the soil and is convenient for subsequent coating operations. Preferably, the average particle size of the fertilizer core is controlled within the range of 2 mm to 6 mm. The setting of this range has a certain flexibility and can be selected according to the root characteristics of different crops. For example, for shallow-rooted crops such as vegetables, a particle size of 2-3 mm can be selected, which can enable the roots to quickly contact the fertilizer; for deep-rooted crops such as fruit trees, a particle size of 4-6 mm can reduce the contact area between the fertilizer core and the outside world, delay the release of nutrients, and better meet the nutrient needs of different crops during the growth cycle.

[0029] According to certain preferred embodiments of the utility model, commercially available urea granules can be used, screened using a vibrating screen, and particles that do not meet the particle size requirements can be removed through a screen with a suitable aperture to obtain fertilizer cores with uniform particle size.

[0030] According to certain preferred embodiments of the utility model, the thickness of the first degradable material layer is in the range of 0.1 mm to 1 mm, preferably 0.3 mm to 0.8 mm. The setting of this thickness range has an important influence on the slow-release performance of the fertilizer. The appropriate thickness can ensure that the first degradable material layer effectively controls the release rate of nutrients in the fertilizer core within a certain period of time, and gradually degrades during the growth period of crops, so that the nutrients in the fertilizer layer can be released.

[0031] According to certain preferred embodiments of the utility model, the fertilizer layer is a urea fertilizer layer. Preferably, the thickness of the fertilizer layer is in the range of 0.5 mm to 1.2 mm, preferably 0.8 mm to 1 mm. This thickness range helps to adjust the nutrient content and release rate of the fertilizer as a whole, ensure that the right amount of nutrients is provided to the crops at different growth stages, and avoid imbalance in nutrient supply due to too thick or too thin a fertilizer layer.

[0032] According to certain preferred embodiments of the utility model, the thickness of the second degradable material layer is in the range of 0.1 mm to 1 mm, preferably 0.3 mm to 0.8 mm. Similar to the first degradable material layer, the thickness of the second degradable material layer also affects the release characteristics and degradation cycle of the fertilizer. By controlling the thickness of the second degradable material layer in the range of 0.1 mm to 1 mm, while ensuring effective regulation of the nutrient release of the fertilizer layer, the degradability of the fertilizer layer in the soil environment is achieved.

[0033] According to certain preferred embodiments of the utility model, the first degradable material layer and the second degradable material layer are polyvinyl alcohol layers. Polyvinyl alcohol has good water solubility and biodegradability, and can be degraded at a certain rate in the soil, thereby achieving a slow-release effect of the fertilizer. In addition, since the first degradable material layer and the second degradable material layer are both composed of polyvinyl alcohol, the production process of the slow-release fertilizer can be simplified.

[0034] According to some preferred embodiments of the utility model, the first degradable material layer is a polylactic acid layer, and the second degradable material layer is a polyvinyl alcohol layer. In a preferred embodiment of the multi-layer degradable slow-release fertilizer of the utility model, the polylactic acid layer with more difficult biodegradability is used as the first polymer layer, and is arranged next to the fertilizer core. This design is of great significance. In the initial stage after the fertilizer is applied to the soil, due to the slow degradation of the polylactic acid layer, it can effectively form a barrier to prevent the rapid release of nutrients in the fertilizer core. It is difficult for moisture and microorganisms in the soil to quickly penetrate the polylactic acid layer to reach the fertilizer core, thereby significantly delaying the nutrient release of the fertilizer core. The polyvinyl alcohol layer located outside the fertilizer layer begins to degrade after a certain period of time due to its relatively fast degradation rate. At this time, the polylactic acid layer is still playing a blocking role, but over time, the degradation of the polyvinyl alcohol layer will gradually expose the fertilizer layer, creating conditions for the release of nutrients in the fertilizer layer. With the further degradation of the polyvinyl alcohol layer, the contact area between the fertilizer layer and the external environment gradually increases, and nutrients begin to diffuse outward from the fertilizer layer. When the polylactic acid layer finally begins to degrade, the nutrients in the fertilizer core will gradually be released, thus achieving a slow-release effect of the fertilizer over a long period of time (1-5 months of crop growth period). This layered structure and the combination of polymer layers with different degradation rates accurately regulate the release time of fertilizer nutrients, ensuring that the fertilizer can continuously and stably supply nutrients according to the fertilizer demand rules during the crop growth cycle, avoiding the problems of sudden nutrient release in the early stage and insufficient supply in the later stage of traditional fertilizers, improving the utilization rate of fertilizers, and reducing the pollution caused by nutrient loss to the environment. At the same time, the degradable material layer can naturally decompose in the soil after completing its slow-release function, and will not cause long-term adverse effects on the soil environment, which is conducive to the sustainable development of agriculture.

[0035] According to certain preferred embodiments of the utility model, the thickness of the first inorganic structure layer is in the range of 0.5 mm to 0.8 mm. The first inorganic structure layer in this thickness range can effectively enhance the structural stability of the fertilizer particles without affecting the overall performance of the fertilizer, and at the same time, use its own characteristics to fine-tune the release of fertilizer nutrients, and work together with the degradable material layer to achieve effective slow and controlled release of the fertilizer during the growth period of crops.

[0036] According to certain preferred embodiments of the present invention, the slow-release fertilizer further includes a second inorganic structure layer, and the second inorganic structure layer is located between the first degradable material layer and the fertilizer layer.

[0037] Figure 2A cross-sectional view of a slow-release fertilizer 200 having a multi-layer degradable structure according to another embodiment of the present invention is shown. Specifically, the slow-release fertilizer 200 has a granular shape and includes, from the inside to the outside, a fertilizer core 1; a first degradable material layer 2; a second inorganic structure layer 6; a fertilizer layer 3; a second degradable material layer 4; and a first inorganic structure layer 5.

[0038] According to certain preferred embodiments of the present invention, the first degradable material layer 2 and the second degradable material layer 4 are polylactic acid layers or polyvinyl alcohol layers.

[0039] According to some preferred embodiments of the present invention, the first inorganic structure layer 5 and the second inorganic structure layer 6 are fly ash layers, attapulgite layers or diatomaceous earth layers. These materials have their own unique physical and chemical properties, can play a role in regulating nutrient release and improving soil environment in fertilizers, and meet the requirements of environmental protection and resource utilization.

[0040] Preferably, the thickness of the second inorganic structure layer is in the range of 0.5 mm to 0.8 mm. This thickness range helps the second inorganic structure layer to play its due function in the fertilizer structure, cooperate with other layers, ensure that the fertilizer releases nutrients stably and continuously during the crop growth cycle, and further increase the integrity and performance stability of the fertilizer particles.

[0041] There is no particular restriction on the method for producing the slow-release fertilizer with a multi-layer degradable structure according to the utility model. The core material and materials of all material layers constituting the multi-layer degradable structure can be commercially obtained, and the slow-release fertilizer described above can be made according to conventional methods known in the chemical industry.

[0042] For example, the slow-release fertilizer can be prepared by combining a spraying method with a drum method.

[0043] Specifically, the preparation process may include the following aspects:

[0044] Fertilizer core preparation

[0045] Commercially available urea granules are selected as the raw materials for fertilizer cores. First, the urea granules are screened using a vibrating screen, and particles that do not meet the particle size requirements (2 mm to 6 mm) are removed through a sieve with a suitable aperture, thereby obtaining spherical urea fertilizer cores with uniform particle size for later use.

[0046] The first degradable material layer is coated (by spraying method)

[0047] Place the selected fertilizer cores in a drum device, turn on the drum and rotate it slowly to ensure that the fertilizer cores can roll evenly in the drum. Prepare a solution of polylactic acid or polyvinyl alcohol (if polylactic acid is used, the polylactic acid can be dissolved in an appropriate organic solvent such as chloroform, with a concentration of 10% by weight - 20% by weight; if polyvinyl alcohol is used, its aqueous solution is directly used). Spray the solution evenly on the surface of the rotating fertilizer core through a spray device. During the spraying process, control the spraying speed so that the solution can be evenly attached to the fertilizer core and avoid the solution from accumulating to form droplets. For example, the spraying speed can be controlled at 10-20 ml / min, which is adjusted according to the size of the drum and the number of fertilizer cores. While spraying, turn on the heating device to heat the drum. This helps the solvent to volatilize, so that the polylactic acid or polyvinyl alcohol quickly forms a film on the surface of the fertilizer core to form a first degradable material layer. The heating time is determined according to the actual situation, generally 10-20 minutes, to ensure that the solvent is basically evaporated and the first degradable material layer is initially solidified. Stop heating and spraying, and continue to rotate the drum for 5-10 minutes to allow the first degradable material layer to be further evenly distributed and solidified on the surface of the fertilizer core, thereby obtaining a fertilizer core intermediate coated with the first degradable material layer.

[0048] Second inorganic structure layer coating (optional step, using spraying method)

[0049] If there is a second inorganic structure layer in the design, the fertilizer core intermediate obtained above is continued to remain in the drum, and the drum speed is adjusted to 3-5 rpm. Prepare a suspension of fly ash, attapulgite or diatomite (the inorganic material is dispersed in water, and the concentration is 15% by weight-25% by weight). The suspension is evenly sprayed on the surface of the fertilizer core intermediate by a spraying device, and the spraying speed is controlled at 8-15 ml / min. After spraying, stop spraying, continue to rotate the drum for 10-15 minutes, so that the inorganic material is evenly attached to the surface of the first degradable material layer and preliminarily dried to form a second inorganic structure layer. Then, appropriate drying treatment can be carried out as needed, and the temperature is controlled at 60-80°C for 10-15 minutes to ensure the stability and dryness of the second inorganic structure layer.

[0050] Fertilizer layer coating (by spraying method)

[0051] The fertilizer core intermediate coated with the first degradable material layer (and the second inorganic structure layer, if present) is placed in a rotary drum again, and the rotary drum speed is adjusted to 8-12 rpm. Prepare urea fertilizer solution (urea is dissolved in water, and the concentration is 20% by weight-30% by weight), and the urea solution is evenly sprayed on the surface of the fertilizer core intermediate by a spraying device, and the spraying speed is controlled at 15-25 ml / min. During the spraying process, the inclination angle (such as 5 °-10 °) of the rotary drum can be appropriately adjusted so that the urea solution can cover the surface of the fertilizer core intermediate more comprehensively and form a uniform fertilizer layer. After spraying, continue to rotate the rotary drum for 15-20 minutes to preliminarily solidify the fertilizer layer. Then low temperature drying can be carried out, and the temperature is controlled at 40-60 ° C for 15-20 minutes, and the fertilizer layer is further dried to obtain a fertilizer granule intermediate coated with a fertilizer layer.

[0052] Second degradable material layer coating (using spraying method)

[0053] The above-mentioned fertilizer granule intermediate is left in the rotary drum, and the rotary drum speed is adjusted to 6-9 rpm. According to the preparation method of the first degradable material layer, a polylactic acid or polyvinyl alcohol solution is prepared, and the solution is evenly sprayed on the surface of the fertilizer granule intermediate by a spraying device, and the spraying speed is controlled at 12-20 ml / min. After spraying, heat treatment is performed, and the temperature is controlled at 40-60 ° C for 10-15 minutes to solidify the second degradable material layer on the surface of the fertilizer layer. Then continue to rotate the rotary drum for 5-10 minutes to further evenly distribute the second degradable material layer and fully solidify to obtain fertilizer granules coated with the second degradable material layer.

[0054] The first inorganic structural layer is coated (using the drum method)

[0055] The fertilizer granules coated with the second degradable material layer are left in the rotary drum, and the rotary drum speed is adjusted to 10-15 rpm. A suspension of fly ash, attapulgite or diatomite is prepared (the inorganic material is dispersed in water, and the concentration is 15 wt %-25 wt %). The suspension is evenly sprayed on the surface of the fertilizer granules coated with the second degradable material layer by a spraying device, and the spraying speed is controlled at 8-15 ml / min. After spraying, spraying is stopped, and the rotary drum is continuously rotated for 10-15 minutes, so that the inorganic material is evenly attached to the surface of the second degradable material layer and is preliminarily dried to form the first inorganic structure layer.

[0056] Various exemplary embodiments of the present invention are further illustrated by the following list of embodiments, which should not be construed as unduly limiting the present invention:

[0057] Specific embodiment 1 is a slow-release fertilizer with a multi-layer degradable structure, characterized in that the slow-release fertilizer has a granular shape and includes, from the inside to the outside:

[0058] Fertilizer cores;

[0059] a first degradable material layer;

[0060] Fertilizer layer;

[0061] a second degradable material layer; and

[0062] A first inorganic structural layer, wherein:

[0063] The first degradable material layer and the second degradable material layer are polylactic acid layers or polyvinyl alcohol layers, and

[0064] The first inorganic structural layer is a fly ash layer, an attapulgite layer or a diatomaceous earth layer.

[0065] Specific embodiment 2 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the fertilizer core is a urea fertilizer core.

[0066] Specific embodiment 3 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the fertilizer core has a spherical shape and its average particle size is in the range of 2 mm to 6 mm.

[0067] Specific embodiment 4 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the thickness of the first degradable material layer is in the range of 0.1 mm to 1 mm.

[0068] Specific embodiment 5 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the fertilizer layer is a urea fertilizer layer.

[0069] Specific embodiment 6 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the thickness of the fertilizer layer is in the range of 0.5 mm to 1.2 mm.

[0070] Specific embodiment 7 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the thickness of the second degradable material layer is in the range of 0.1 mm to 1 mm.

[0071] Specific embodiment 8 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the first degradable material layer and the second degradable material layer are polyvinyl alcohol layers.

[0072] Specific embodiment 9 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the first degradable material layer is a polylactic acid layer, and the second degradable material layer is a polyvinyl alcohol layer.

[0073] Specific embodiment 10 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 1, characterized in that the thickness of the first inorganic structure layer is in the range of 0.5 mm to 0.8 mm.

[0074] Specific embodiment 11 is a slow-release fertilizer with a multi-layer degradable structure according to any one of specific embodiments 1-10, characterized in that the slow-release fertilizer also includes a second inorganic structure layer, and the second inorganic structure layer is located between the first degradable material layer and the fertilizer layer.

[0075] Specific embodiment 12 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 11, characterized in that the second inorganic structure layer is a fly ash layer, a attapulgite layer or a diatomaceous earth layer.

[0076] Specific embodiment 13 is a slow-release fertilizer with a multi-layer degradable structure according to specific embodiment 11, characterized in that the thickness of the second inorganic structure layer is in the range of 0.5 mm to 0.8 mm.

[0077] Compared with the shock absorbing parts in the prior art, the slow-release fertilizer with a multi-layer degradable structure according to the utility model has the following advantages:

[0078] 1. Effective controlled release: The slow-release fertilizer of the utility model can realize effective controlled release of fertilizer within 1-5 months of the normal crop growth period, which helps to coordinate with the fertilizer demand law during the crop growth cycle and improve the utilization rate of fertilizer.

[0079] 2. Multi-layer degradable structure: The slow-release fertilizer has a multi-layer structure including a fertilizer core, a first degradable material layer, a fertilizer layer, a second degradable material layer and a first inorganic structure layer from the inside to the outside. This structural design helps to achieve more precise nutrient release control.

[0080] 3. Environmentally friendly materials: The first degradable material layer and the second degradable material layer are polylactic acid layers or polyvinyl alcohol layers, which are biodegradable and help reduce the impact on the environment. The first inorganic structure layer is a fly ash layer, attapulgite layer or diatomaceous earth layer, which also have environmentally friendly characteristics.

[0081] 4. Reasonable cost: The materials and preparation process used in the slow-release fertilizer of the utility model are relatively simple, which helps to reduce costs, making the slow-release fertilizer more economical and convenient for large-scale application in agricultural production.

[0082] 5. Environmentally friendly: Due to the use of degradable materials and inorganic structural layers, no residue will remain in the soil after long-term use, reducing the potential pollution to the soil environment and is conducive to the sustainable development of the agricultural ecosystem.

[0083] 6. Improve fertilizer utilization: By controlling the release rate and pattern of fertilizers, nutrient loss is reduced, fertilizer utilization is improved, and environmental problems caused by excessive fertilization are reduced.

[0084] 7. Reduce soil problems: Due to the slow-release characteristics of fertilizers, it can reduce soil compaction, acidification and other problems caused by excessive use of traditional fertilizers, and protect soil structure and fertility.

[0085] 8. Adapt to different crop needs: The particle size of the fertilizer core can be adjusted according to the root depth of the crop to adapt to the needs of different crops, which helps to improve the targeting and efficiency of the fertilizer.

[0086] Obviously, those skilled in the art can make various changes and modifications to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, if these modifications and variations of the present disclosure fall within the scope of the claims of the present utility model and their equivalents, the present disclosure is also intended to include these modifications and variations.

Claims

1. A slow-release fertilizer with a multi-layer degradable structure, characterized in that: The slow-release fertilizer has a granular shape and comprises, from the inside to the outside: Fertilizer cores; a first degradable material layer; Fertilizer layer; a second degradable material layer; and A first inorganic structural layer, wherein: The first degradable material layer and the second degradable material layer are polylactic acid layers or polyvinyl alcohol layers, and The first inorganic structural layer is a fly ash layer, an attapulgite layer or a diatomaceous earth layer.

2. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The fertilizer core is a urea fertilizer core.

3. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The fertilizer core has a spherical shape and an average particle size thereof is in the range of 2 mm to 6 mm.

4. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The thickness of the first degradable material layer is in the range of 0.1 mm to 1 mm.

5. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The fertilizer layer is a urea fertilizer layer, or The thickness of the fertilizer layer is in the range of 0.5 mm to 1.2 mm.

6. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The thickness of the second degradable material layer is in the range of 0.1 mm to 1 mm.

7. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The first degradable material layer and the second degradable material layer are polyvinyl alcohol layers, or The first degradable material layer is a polylactic acid layer, and the second degradable material layer is a polyvinyl alcohol layer.

8. The slow-release fertilizer with a multi-layer degradable structure according to claim 1, characterized in that: The thickness of the first inorganic structure layer is in the range of 0.5 mm to 0.8 mm.

9. The slow-release fertilizer with a multi-layer degradable structure according to any one of claims 1 to 8, characterized in that: The slow-release fertilizer further includes a second inorganic structure layer, and the second inorganic structure layer is located between the first degradable material layer and the fertilizer layer.

10. The slow-release fertilizer with a multi-layer degradable structure according to claim 9, characterized in that: The second inorganic structural layer is a fly ash layer, an attapulgite layer or a diatomaceous earth layer, or The thickness of the second inorganic structure layer is in the range of 0.5 mm to 0.8 mm.

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