Special bag-controlled fertilizer and method for increasing oxygen content of soil by using same

Abstract

The invention discloses a special bag-controlled fertilizer and a method for increasing the oxygen content of soil by using the same, and belongs to the technical field of agricultural planting soil improvement and fertilization. The special bag-controlled fertilizer comprises a bag body made of a polypropylene porous non-woven fabric and functional materials, the functional materials comprise a controlled-release fertilizer, perlite, a decomposed organic fertilizer and bentonite, and the controlled-release fertilizer is coated with a degradable polymer composite film. The composite film is prepared from polylactic acid, cassava starch and other raw materials through pretreatment, pre-crosslinking, melt mixing, modified blending, compounding, film forming liquid preparation, tape casting, drying and curing. During application, through soil pretreatment, special bag arrangement and later-period management, a bag body and a functional material cooperatively construct a ventilation channel. According to the invention, the synergistic interaction of oxygen supply and fertilizer control is realized, the oxygen content of a soil root layer can be stabilized, the root activity and nutrient utilization rate of crops are improved, the leaching loss of nutrients is reduced, the operation is simple and convenient, the adaptability is wide, the fertilizer can be repeatedly used, the soil pollution and degradation are avoided, and the fertilizer has both production benefits and ecological benefits.

Description

Technical Field

[0001] This invention relates to the field of agricultural planting soil improvement and fertilization technology, specifically to a special bag-controlled fertilizer and its application in increasing soil oxygen content. Background Technology

[0002] In agricultural production, soil oxygen content and nutrient supply are core factors affecting crop growth, yield, and quality. Their synergistic optimization is key to improving the quality and efficiency of modern agriculture and achieving sustainable development. Sufficient oxygen in the soil root zone is fundamental for crop root respiration, nutrient absorption, and metabolic activities; oxygen deficiency leads to decreased root vitality, root rot, and disease proliferation. Scientific nutrient supply must match the needs of the crop's growth stage while protecting soil structure and preventing soil degradation caused by improper fertilization. However, current soil oxygen supply and nutrient regulation technologies have long been disconnected, each facing insurmountable bottlenecks, failing to meet the needs of comprehensive soil environmental optimization.

[0003] In terms of soil oxygenation technology, traditional methods mainly involve deep tillage, adding coarse media, and laying aeration pipes. Deep tillage breaks up compacted layers mechanically, but irrigation, rainfall, and root growth quickly cause the soil to recompact, resulting in short-term aeration effects. This requires repeated operations, which are time-consuming, labor-intensive, and may damage the soil structure. Adding coarse media can improve permeability in the short term, but it is difficult to build continuous aeration channels, making them prone to clogging and extremely unstable. Aeration pipes are complex to install, costly, and difficult to maintain, making them only suitable for large-scale facility agriculture and difficult to popularize. More importantly, these single oxygenation technologies do not consider the impact of fertilization on soil aeration, and long-term use can easily lead to soil structural imbalance and exacerbate hypoxia.

[0004] In the field of nutrient regulation, traditional fertilizers release nutrients rapidly, which is mismatched with the nutrient requirements of crops, leading to severe nutrient leaching and loss. This not only results in low utilization rates but also causes soil acidification and salinization, damages soil aggregate structure, and indirectly reduces soil permeability. While existing controlled-release fertilizers regulate nutrient release through coatings, they do not consider soil aeration needs. Their coating materials either have poor degradability, leaving residues that pollute the soil, or degrade too quickly to provide long-term controlled release. Furthermore, the coating structure does not consider gas permeability, making it difficult to synergistically meet the needs of nutrient control and soil aeration. At the same time, the disconnect between controlled-release fertilizers and oxygen supply measures means that even with reasonable nutrient release, soil hypoxia can still significantly reduce crop nutrient absorption efficiency.

[0005] More significantly, the disconnect between oxygen supply and fertilizer control technologies creates a vicious cycle: oxygen supply alone cannot solve nutrient imbalances, exacerbating soil compaction and hypoxia; fertilizer control alone fails to address aeration, leading to soil structure degradation and further reducing aeration performance. Furthermore, different soil types and planting scenarios have significantly different needs for oxygen and nutrients, resulting in poor adaptability of existing technologies. Aeration enhancement is insufficient for heavy clay soils, and sandy soils struggle to balance water and fertilizer retention with aeration. The different nutrient requirements and root distribution patterns of various crops cannot be specifically addressed by existing technologies, demonstrating extremely poor versatility.

[0006] In the field of coating materials, traditional polylactic acid coatings are brittle and have difficult-to-control degradation rates, while starch-based coatings have poor film-forming properties and insufficient strength. Existing composite coating materials use single raw materials and lack scientific synergistic mechanisms, failing to simultaneously meet the requirements for film-forming properties, stability, controllable degradation, and air permeability. Furthermore, unreasonable design of preparation process parameters leads to large fluctuations in nutrient release from the membrane material and a mismatch between the degradation cycle and the crop growth period, thus restricting the application effect of controlled-release fertilizer technology.

[0007] In summary, existing technologies cannot achieve synergistic optimization of soil oxygen supply and nutrient supply, and suffer from many problems such as short-lived aeration effects, low nutrient utilization, easy soil degradation, and poor adaptability. There is an urgent need to develop a comprehensive technical solution that synergistically combines oxygen supply and fertilizer control, is long-lasting and stable, and has wide adaptability, in order to break through the technical bottleneck of modern agricultural soil environment optimization. Summary of the Invention

[0008] To address the aforementioned shortcomings, this invention provides a special bag for controlled-release fertilizer and its application in increasing soil oxygen content. By combining a porous bag with a composite membrane-coated controlled-release fertilizer, it solves the problems of short-lived oxygen supply, disconnect between controlled-release fertilizer and aeration, and easy soil degradation associated with existing technologies.

[0009] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0010] A special bag for controlled fertilization includes a porous, breathable bag body and a functional material filled inside the bag body;

[0011] The porous breathable bag is made of porous non-woven fabric with a porosity of 30%-40% and a thickness of 0.15-0.2mm. Multiple breathable holes are evenly opened on the bottom and sides of the bag.

[0012] The functional material is composed of the following raw materials in parts by weight: 70-85 parts controlled-release fertilizer, 3-5 parts lightweight breathable medium, 5-8 parts organic fertilizer, and 2-3 parts soil conditioner; the filling amount of the functional material is 70%-80% of the bag volume.

[0013] The controlled-release fertilizer is fertilizer granules coated with a biodegradable polymer composite membrane;

[0014] The biodegradable polymer composite film, by weight, is made from the following raw materials: 40-50 parts polylactic acid, 15-20 parts starch, 5-8 parts cellulose derivative, 3-5 parts plasticizer, 2-4 parts crosslinking agent, 1-3 parts nanofiller, 2.5-4 parts antibacterial agent, 3-6 parts dispersant, 1-2 parts anti-aging agent, 2-3 parts binder, 3-5 parts film-forming aid, 2-4 parts auxiliary plasticizer, 3.5-5 parts reinforcing fiber, and 1.5-2.5 parts degradation rate regulator.

[0015] Preferably, the porous nonwoven fabric is a polypropylene porous nonwoven fabric; the diameter of the air pores is 0.5-1cm, and the pore spacing is 5-8cm; the bag body dimensions are 30-40cm in length and 20-25cm in width.

[0016] Preferably, the lightweight, breathable medium is perlite with a particle size of 1-2 mm; the organic fertilizer is well-rotted organic fertilizer; and the soil conditioner is bentonite.

[0017] Preferably, the starch is tapioca starch; the cellulose derivative is hydroxypropyl methylcellulose; the plasticizer is glycerol; the crosslinking agent is tannic acid; the antibacterial agent is chitosan; the anti-aging agent is phytosterol; the binder is sodium alginate; the film-forming aid is polyvinyl alcohol; the auxiliary plasticizer is sorbitol; the reinforcing fiber is microcrystalline cellulose; the degradation rate regulator is calcium lactate; and the nanofiller includes nano-silica and a light stabilizer.

[0018] Preferably, the light stabilizer is titanium dioxide; the weight ratio of tannic acid to calcium lactate is 1:(0.5-1); and the weight ratio of titanium dioxide to nano-silica is 1:(1-2).

[0019] A method for producing a biodegradable polymer composite film includes the following steps:

[0020] (1) Raw material pretreatment: Weigh each raw material according to the ratio; dry polylactic acid; dry starch and sieve; dissolve chitosan in acid solution to prepare chitosan solution; sieve microcrystalline cellulose for later use;

[0021] (2) Preparation of pre-crosslinked liquid: Tannic acid, calcium lactate and a portion accounting for 30%-50% of the total weight of plasticizer and auxiliary plasticizer are mixed and stirred under heating conditions to obtain pre-crosslinked liquid;

[0022] (3) Melting and mixing of basic materials: Pretreated polylactic acid, starch, hydroxypropyl methylcellulose, polyvinyl alcohol and microcrystalline cellulose are mixed and melt-blended under heating and stirring to obtain a basic mixture;

[0023] (4) Modified blending: The remaining plasticizer and auxiliary plasticizer, dispersant, nanofiller and light stabilizer are added to the base mixture, and the mixture is blended and modified under stirring to obtain a modified blend;

[0024] (5) Preparation of composite and film-forming solution: Add the chitosan solution, phytosterol, sodium alginate and the pre-crosslinking solution to the modified blend and stir to mix; then add water to adjust the solid-liquid mass ratio of the system to 1:(3-5), stir at constant temperature and filter to obtain a uniform film solution;

[0025] (6) Casting and drying: The film liquid is cast on the substrate and the wet film thickness is controlled; preliminary drying is performed first, and then balanced curing is performed to obtain a biodegradable polymer composite film of the target thickness.

[0026] Preferably, in step (2), the total amount of plasticizer and auxiliary plasticizer used to prepare the pre-crosslinked liquid accounts for 30%-50% of its total weight; in step (6), the wet film thickness is 0.1-0.16 mm, the initial drying temperature is 40-50°C, the equilibrium curing conditions are temperature 25°C, relative humidity 50%-60%, time 24-48 hours, and the resulting composite film thickness is 0.05-0.08 mm.

[0027] A method for improving soil oxygen content through controlled fertilization using specialized bags includes the following steps:

[0028] (1) Soil pretreatment: The soil of the target plot is crushed and screened, the soil bulk density, moisture content and pH value are adjusted, and the soil is tilled;

[0029] (2) Deployment of special bags: Determine the spacing of the bags according to the planting type, dig planting trenches or planting holes in the soil, lay the special bags at the set depth, cover the soil and compact them;

[0030] (3) Crop planting and management: Plant crops in the area where the special bags have been laid, irrigate, and regularly check the ventilation holes of the bags.

[0031] Preferably, in step (1), the soil bulk density is adjusted to 1.1-1.3 g / cm³. 3 The soil moisture content is adjusted to 20%-25%, and the pH value is adjusted to 6.0-7.5. In step (2), the row spacing for open field planting is 30-40cm and the plant spacing is 25-30cm, while the row spacing for facility planting is 25-35cm and the plant spacing is 20-25cm. The laying depth is 15-20cm. In step (3), the irrigation frequency is once every 3-5 days to maintain the soil moisture content at 30%-35%, and the frequency of checking the air vents is once every 15-20 days.

[0032] Preferably, the method further includes a bag treatment step after crop harvest: recycling the porous breathable bag, removing the consumed functional material remaining in the bag, and replenishing the bag with new functional material of the same composition as the functional material described in this invention.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] I. Synergistic effect of oxygen supply and fertilizer control, breaking the technical barriers

[0035] In existing technologies, soil oxygen supply and nutrient regulation are independent, making it difficult to meet both needs simultaneously, resulting in a vicious cycle of "oxygen deficiency - hindered nutrient absorption - soil degradation." This invention innovatively integrates a porous, breathable bag with a composite membrane-coated controlled-release fertilizer to construct a synergistic system of "aeration - controlled fertilization - soil conditioning": the bag and lightweight, breathable medium work together to create a continuous and stable deep aeration channel, providing sustained oxygen to the roots; the composite membrane controlled-release fertilizer precisely matches the crop's nutrient requirements, achieving scientific nutrient supply. The two work in a positive feedback loop: sufficient oxygen strengthens root vitality and improves nutrient absorption efficiency; reasonable nutrient supply promotes healthy root growth, inhibits anaerobic metabolism of harmful microorganisms, optimizes the soil aeration environment, and achieves simultaneous optimization of soil oxygen content and nutrient supply.

[0036] II. Comprehensive performance upgrade of composite membranes, overcoming the defects of traditional coatings.

[0037] Traditional biodegradable coatings suffer from poor film-forming properties, insufficient mechanical properties, difficulty in controlling degradation rates, and an imbalance between air permeability and controlled release. This invention's composite membrane achieves a performance breakthrough through scientific raw material formulation and process design: using polylactic acid and tapioca starch as base materials, combined with cellulose derivatives and reinforcing fibers to enhance mechanical strength and toughness, solving the problem of easy breakage of traditional coatings; plasticizers and auxiliary plasticizers synergistically optimize flexibility; crosslinking agents and degradation rate regulators precisely match the degradation cycle with the crop's growth period; nanofillers and light stabilizers optimize pore structure and enhance anti-aging properties; antibacterial agents inhibit disordered coating degradation, achieving a comprehensive balance between film-forming properties, controllable degradation, and controlled release permeability.

[0038] Third, it has wide adaptability and is easy to operate, adapting to diverse planting needs.

[0039] Existing technologies suffer from poor adaptability, complex operation, and difficulty in widespread adoption. This invention, through modular design, allows for adjustments to parameters such as bag porosity, media addition, and composite membrane performance to adapt to different soil types (heavy clay, sandy soil, etc.) and various planting scenarios (open field, greenhouse, etc.). The raw materials for the specialized bags are readily available and cost-effective; deployment requires no complex equipment and can be completed manually, adapting to different planting scales. Post-harvest management only requires routine irrigation and ventilation hole checks, eliminating the need for frequent soil loosening and fertilization. After harvest, the bags are recyclable and reusable; the organic fertilizer and soil conditioner in the functional materials improve soil structure and prevent soil degradation, providing both production and ecological benefits.

[0040] IV. Long-lasting and stable ventilation effect, overcoming the shortcomings of traditional oxygen supply systems.

[0041] Traditional methods of oxygenation, such as deep tillage and the addition of coarse media, are short-lived and prone to failure, requiring repeated operations. This invention utilizes the structural stability of a polypropylene porous nonwoven bag, combined with the elastic ventilation space formed by breathable pores and a lightweight, breathable medium, to resist soil compaction and pore blockage, constructing a long-lasting, continuous ventilation channel. This system maintains stable ventilation throughout the crop's entire growth period, eliminating the need for repeated soil loosening. This reduces labor input and avoids damage to soil structure caused by loosening. Simultaneously, it works synergistically with soil conditioners to promote aggregate formation, achieving an organic combination of short-term ventilation and long-term soil improvement. Detailed Implementation

[0042] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0043] A special bag for controlled fertilization includes a porous, breathable bag body and a functional material filled inside the bag body;

[0044] The porous breathable bag is made of porous non-woven fabric with a porosity of 30%-40% and a thickness of 0.15-0.2mm. Multiple breathable holes are evenly opened on the bottom and sides of the bag.

[0045] The functional material is composed of the following raw materials in parts by weight: 70-85 parts controlled-release fertilizer, 3-5 parts lightweight breathable medium, 5-8 parts organic fertilizer, and 2-3 parts soil conditioner; the filling amount of the functional material is 70%-80% of the bag volume.

[0046] The controlled-release fertilizer is fertilizer granules coated with a biodegradable polymer composite membrane;

[0047] The biodegradable polymer composite film, by weight, is made from the following raw materials: 40-50 parts polylactic acid, 15-20 parts starch, 5-8 parts cellulose derivative, 3-5 parts plasticizer, 2-4 parts crosslinking agent, 1-3 parts nanofiller, 2.5-4 parts antibacterial agent, 3-6 parts dispersant, 1-2 parts anti-aging agent, 2-3 parts binder, 3-5 parts film-forming aid, 2-4 parts auxiliary plasticizer, 3.5-5 parts reinforcing fiber, and 1.5-2.5 parts degradation rate regulator.

[0048] The porous nonwoven fabric is a polypropylene porous nonwoven fabric; the diameter of the air pores is 0.5-1cm, and the pore spacing is 5-8cm; the bag body dimensions are 30-40cm in length and 20-25cm in width.

[0049] The lightweight, breathable medium is perlite with a particle size of 1-2 mm; the organic fertilizer is well-rotted organic fertilizer; and the soil conditioner is bentonite.

[0050] The starch is tapioca starch; the cellulose derivative is hydroxypropyl methylcellulose; the plasticizer is glycerol; the crosslinking agent is tannic acid; the antibacterial agent is chitosan; the anti-aging agent is phytosterol; the binder is sodium alginate; the film-forming aid is polyvinyl alcohol; the auxiliary plasticizer is sorbitol; the reinforcing fiber is microcrystalline cellulose; the degradation rate regulator is calcium lactate; and the nanofiller includes nano-silica and a light stabilizer.

[0051] The light stabilizer is titanium dioxide; the weight ratio of tannic acid to calcium lactate is 1:(0.5-1); the weight ratio of titanium dioxide to nano-silica is 1:(1-2).

[0052] A method for producing a biodegradable polymer composite film includes the following steps:

[0053] (1) Raw material pretreatment: Weigh each raw material according to the ratio; dry polylactic acid; dry starch and sieve; dissolve chitosan in acid solution to prepare chitosan solution; sieve microcrystalline cellulose for later use;

[0054] (2) Preparation of pre-crosslinked liquid: Tannic acid, calcium lactate and a portion accounting for 30%-50% of the total weight of plasticizer and auxiliary plasticizer are mixed and stirred under heating conditions to obtain pre-crosslinked liquid;

[0055] (3) Melting and mixing of basic materials: Pretreated polylactic acid, starch, hydroxypropyl methylcellulose, polyvinyl alcohol and microcrystalline cellulose are mixed and melt-blended under heating and stirring to obtain a basic mixture;

[0056] (4) Modified blending: The remaining plasticizer and auxiliary plasticizer, dispersant, nanofiller and light stabilizer are added to the base mixture, and the mixture is blended and modified under stirring to obtain a modified blend;

[0057] (5) Preparation of composite and film-forming solution: Add the chitosan solution, phytosterol, sodium alginate and the pre-crosslinking solution to the modified blend and stir to mix; then add water to adjust the solid-liquid mass ratio of the system to 1:(3-5), stir at constant temperature and filter to obtain a uniform film solution;

[0058] (6) Casting and drying: The film liquid is cast on the substrate and the wet film thickness is controlled; preliminary drying is performed first, and then balanced curing is performed to obtain a biodegradable polymer composite film of the target thickness.

[0059] In step (2), the total amount of plasticizer and auxiliary plasticizer used to prepare the pre-crosslinked liquid accounts for 30%-50% of its total weight; in step (6), the wet film thickness is 0.1-0.16 mm, the initial drying temperature is 40-50℃, the equilibrium curing conditions are temperature 25℃, relative humidity 50%-60%, time 24-48 hours, and the resulting composite film thickness is 0.05-0.08 mm.

[0060] A method for improving soil oxygen content through controlled fertilization using specialized bags includes the following steps:

[0061] (1) Soil pretreatment: The soil of the target plot is crushed and screened, the soil bulk density, moisture content and pH value are adjusted, and the soil is tilled;

[0062] (2) Deployment of special bags: Determine the spacing of the bags according to the planting type, dig planting trenches or planting holes in the soil, lay the special bags at the set depth, cover the soil and compact them;

[0063] (3) Crop planting and management: Plant crops in the area where the special bags have been laid, irrigate, and regularly check the ventilation holes of the bags.

[0064] In step (1), the soil bulk density is adjusted to 1.1-1.3 g / cm³. 3 The soil moisture content is adjusted to 20%-25%, and the pH value is adjusted to 6.0-7.5. In step (2), the row spacing for open field planting is 30-40cm and the plant spacing is 25-30cm, while the row spacing for facility planting is 25-35cm and the plant spacing is 20-25cm. The laying depth is 15-20cm. In step (3), the irrigation frequency is once every 3-5 days to maintain the soil moisture content at 30%-35%, and the frequency of checking the air vents is once every 15-20 days.

[0065] It also includes a bag treatment step after crop harvest: recycling the porous breathable bag, removing the consumed functional materials remaining in the bag, and replenishing the bag with new functional materials of the same composition as the functional materials described in this invention.

[0066] The working mechanism of this invention is as follows:

[0067] I. Raw material pretreatment: laying the foundation for uniform dispersion of components

[0068] Raw material pretreatment is a prerequisite for ensuring the stable performance of composite membranes. Its core function is to eliminate the impact of defects in the raw materials themselves on the subsequent film formation quality, creating conditions for the synergistic effect of each component. Drying polylactic acid removes moisture, preventing air bubbles from forming during melting due to moisture vaporization, ensuring a dense membrane structure, and preventing controlled-release performance failure caused by abnormal pores. Sieving dried cassava starch breaks up particle agglomeration, improving its compatibility with other raw materials and preventing uneven local performance of the membrane caused by starch particle aggregation. Dissolving chitosan in an acid solution to create a homogeneous solution solves the problem of poor dispersion of chitosan in the solid state, allowing it to be evenly distributed in the membrane and fully exert its antibacterial effect. Sieving microcrystalline cellulose ensures its uniform length, avoiding internal defects in the membrane caused by long fiber agglomeration, and providing a guarantee for enhancing the mechanical properties of the membrane. This step, through targeted treatment of key raw materials, ensures from the source that each component can fully contact and synergistically act in the subsequent process, laying a solid foundation for improving the overall performance of the composite membrane.

[0069] II. Preparation of Pre-crosslinking Solution: Constructing a Controllable Crosslinking Core System

[0070] The preparation of the pre-crosslinked solution is a crucial step in achieving precise control over the degradation rate and structural stability of the composite membrane. Tannic acid, acting as a crosslinking agent, synergistically forms a basic crosslinked network under heating and stirring conditions. This network serves as the framework for the subsequent three-dimensional structure of the composite membrane, enhancing membrane strength and allowing for precise matching of the membrane's degradation cycle with the crop's growth stage through the regulatory effect of calcium lactate. The addition of some plasticizers and auxiliary plasticizers improves the system's fluidity in the early stages of the crosslinking reaction, promoting a uniform reaction between tannic acid and calcium lactate and preventing excessive or insufficient crosslinking in certain areas. This step, by constructing the crosslinking core in advance, lays the foundation for subsequent composites with other components, achieving pre-optimization of the crosslinking reaction and degradation rate control. It solves the problem of balancing crosslinking and degradation performance in traditional processes, resulting in a synergistic effect of structural stability and controllable degradation.

[0071] III. Melting and mixing of basic materials: forming a stable film-forming substrate

[0072] The core of the melt blending of basic materials is to construct a film-forming substrate that combines stability and processability, optimizing substrate performance through the synergistic effect of each component. Polylactic acid (PLA) and tapioca starch, as basic substrates, are melt-blended under heating and stirring. PLA provides structural stability, while tapioca starch ensures biodegradability, forming a complementary system. The addition of hydroxypropyl methylcellulose (HMC) and polyvinyl alcohol (PVA) binds to the substrate backbone through hydrogen bonds, improving film uniformity and flexibility, and avoiding the defects of high brittleness and easy cracking associated with single substrates. Microcrystalline cellulose, as a reinforcing fiber, is uniformly dispersed in the melt system, forming a physical reinforcing network, further enhancing the mechanical strength of the substrate. This step, through melt blending, fully integrates the basic components, achieving a synergistic improvement in structural stability, biodegradability, flexibility, and mechanical strength, providing a high-performance substrate foundation for subsequent modified blending and film formation.

[0073] IV. Modified Blending: Multifunctional Synergistic Optimization of Membrane Material Properties

[0074] The modified blending step introduces functional components to synergistically improve multiple properties of the membrane material, including breathability, anti-aging, and dispersion uniformity. The remaining plasticizer and auxiliary plasticizer further optimize the system's flexibility, working in tandem with the previously added plasticizer to ensure the membrane maintains good processing performance and durability throughout the process. The addition of dispersants promotes the uniform dispersion of nanofillers and light stabilizers, preventing uneven membrane performance caused by agglomeration. Nano-silica, as a nanofiller, constructs a reasonable pore structure within the membrane, balancing oxygen permeability and nutrient control. Light stabilizers enhance the membrane's anti-aging properties and delay degradation caused by sunlight and microorganisms in the soil environment. The synergistic effect of these components enables the membrane to maintain structural stability while possessing multifunctional properties such as breathability and anti-aging adaptability to the soil environment, overcoming the limitations of traditional single-function membrane materials.

[0075] V. Preparation of Composite and Film-Forming Solutions: Integration of Functional Components and Homogenization

[0076] The core of this step is to fully integrate the functional components with the base system and prepare a uniform and stable membrane solution, ensuring the smooth casting process. The addition of chitosan solution ensures uniform dispersion of the antibacterial components, forming a synergistic antibacterial system with the membrane substrate, inhibiting the disorderly degradation of the membrane material by harmful microorganisms. Phytosterols (anti-aging agents) and sodium alginate (binder) work synergistically; phytosterols enhance the membrane's aging resistance, while sodium alginate strengthens the adhesion between the membrane and fertilizer particles, preventing coating detachment. The addition of pre-crosslinking liquid deeply integrates the previously constructed crosslinking network with the base system, forming a complete three-dimensional structure and precisely controlling the membrane degradation rate. Adding water to adjust the solid-liquid ratio and maintaining a constant temperature while stirring and filtering removes impurities, ensuring a uniform and fine membrane solution and preventing defects after film formation. This step, through deep integration and homogenization of multiple components, achieves the synergistic integration of antibacterial, anti-aging, adhesive, and controllable degradation functions, guaranteeing the quality of the membrane solution.

[0077] VI. Casting and Drying Curing: Precise Control of Membrane Material Structure and Properties

[0078] Casting and drying / curing are crucial steps determining the final performance of the composite membrane. Precise matching of membrane structure and performance is achieved through the control of process parameters. Casting controls the wet film thickness, laying the foundation for a rational structure during subsequent drying and curing. Precise selection of the initial drying temperature allows the membrane to form a gradient pore structure during drying; a dense surface layer ensures controlled nutrient release, while a porous inner layer facilitates later degradation. The equilibration curing process allows the membrane to complete structural adjustments in a stable environment, eliminating internal stress and ensuring stable membrane performance. This step, through the coordinated control of process parameters and the film-forming process, achieves a precise match between membrane structure, controlled release performance, and degradation performance, solving the problems of uneven membrane structure and unstable performance in traditional film-forming processes. Ultimately, a composite membrane with advantages such as precise controlled release, controllable degradation, and structural stability is obtained.

[0079] To make the present invention more fully disclosed, more specific embodiments are described below.

[0080] I. Experimental Materials and Instruments

[0081] (a) Experimental materials

[0082] Polylactic acid (molecular weight 80,000-100,000), tapioca starch (industrial grade), hydroxypropyl methylcellulose (HPMC, viscosity 10,000 mPa·s), glycerol (analytical grade), tannic acid (analytical grade), nano silica (particle size 20-50 nm), chitosan (degree of deacetylation ≥90%), polyethylene glycol 400 (analytical grade), phytosterols (purity ≥95%), sodium alginate (industrial grade), polyvinyl alcohol (PVA, degree of polymerization 1750±50), and other ingredients. Precipitol (analytical grade), microcrystalline cellulose (particle size 50-100 μm), calcium lactate (analytical grade), titanium dioxide (anatase type, particle size 10-20 nm); polypropylene porous nonwoven fabric (porosity 30%-40%), perlite (particle size 1-2 mm), well-rotted organic fertilizer (organic matter content ≥45%), bentonite (industrial grade); nitrogen, phosphorus, and potassium compound fertilizer granules (N:P2O5:K2O=15:10:12); test soil (clay loam, initial bulk density 1.45 g / cm³). 3 The test crop was a tomato (variety: Pink Cherry No. 1, adapted to the hot and rainy climate of South China). The test ingredients were triphenyltetrazolium chloride (TTC, analytical grade), phosphate buffer (pH=7.0), ethyl acetate (analytical grade), and sulfuric acid (analytical grade).

[0083] (II) Experimental Instruments

[0084] Vacuum drying oven, high-speed mixer, melt blender, casting machine, forced-air drying oven, electronic universal testing machine, air permeability tester, biodegradation instrument, soil oxygen content analyzer, ultraviolet-visible spectrophotometer.

[0085] Supplementary notes on root activity determination: The determination was performed using the national standard TTC reduction method specified in "Experimental Guide to Plant Physiology" in conjunction with a UV-Vis spectrophotometer. The core principle is that root dehydrogenase can reduce colorless TTC to red formazan. The absorbance of formazan at a wavelength of 485nm is directly proportional to the dehydrogenase activity (i.e., root activity). The root activity value (unit: U / g·h) was obtained by conversion through a standard curve.

[0086] II. Implementation Examples

[0087] Example 1

[0088] (I) Preparation of biodegradable polymer composite membranes

[0089] 1. Raw material pretreatment: Weigh out 45 parts polylactic acid, 17 parts tapioca starch, 6 parts hydroxypropyl methylcellulose, 4 parts glycerol, 3 parts tannic acid, 2 parts nano silica, 3 parts chitosan, 4 parts polyethylene glycol 400, 1.5 parts phytosterol, 2.5 parts sodium alginate, 4 parts polyvinyl alcohol, 3 parts sorbitol, 4 parts microcrystalline cellulose, 2 parts calcium lactate, and 1 part titanium dioxide according to the following weight: Dry polylactic acid in a vacuum drying oven at 65℃ for 5 hours; dry tapioca starch at 105℃ for 2.5 hours, pulverize and pass through a 100-mesh sieve; dissolve chitosan in 1% acetic acid solution to prepare a 5% chitosan solution; pass microcrystalline cellulose through a 100-mesh sieve for later use.

[0090] 2. Preparation of pre-crosslinked liquid: Take 3 parts of tannic acid and 2 parts of calcium lactate, add 40% of the total weight of plasticizer (1.6 parts of glycerol) and auxiliary plasticizer (1.2 parts of sorbitol), and stir at 900 r / min for 40 min under heating at 85℃ to obtain the pre-crosslinked liquid.

[0091] 3. Melting and mixing of basic materials: 45 parts of pretreated polylactic acid, 17 parts of tapioca starch, 6 parts of hydroxypropyl methylcellulose, 4 parts of polyvinyl alcohol, and 4 parts of microcrystalline cellulose are added to a melt mixer and melt-mixed for 60 minutes at 160℃ and 500 r / min to obtain the basic mixture.

[0092] 4. Modified blending: Add the remaining plasticizer (2.4 parts glycerol), auxiliary plasticizer (1.8 parts sorbitol), 4 parts polyethylene glycol 400, 2 parts nano silica, and 1 part titanium dioxide to the base mixture, and blend and modify for 30 min at 150℃ and 600 r / min to obtain the modified blend.

[0093] 5. Preparation of composite and film-forming solution: Chitosan solution, 1.5 parts of phytosterol, 2.5 parts of sodium alginate and pre-crosslinking solution were added to the modified blend and stirred for 50 min at 90℃ and 400 r / min. Then deionized water was added to adjust the solid-liquid mass ratio of the system to 1:4. The mixture was stirred at 65℃ for 25 min and filtered through a 100-mesh sieve to obtain a uniform film solution.

[0094] 6. Casting and Drying Curing: The film solution is uniformly cast on a polytetrafluoroethylene plate, and the wet film thickness is controlled to be 0.13 mm. It is placed in a 45℃ forced-air drying oven for 9 hours and then placed in an environment of 25℃ and 55% relative humidity for 36 hours to equilibrate, resulting in a biodegradable polymer composite film with a thickness of 0.065 mm.

[0095] (II) Preparation of fertilizer control bag

[0096] Mix 78 parts of controlled-release fertilizer (coated with the above-mentioned composite film), 4 parts of perlite, 6 parts of decomposed organic fertilizer, and 2.5 parts of bentonite evenly, and fill the mixture into a bag made of polypropylene porous non-woven fabric (porosity 35%, thickness 0.17mm, length 35cm, width 22cm, with ventilation holes of 0.7cm in diameter and 6cm in spacing evenly opened on the bottom and sides of the bag). The filling amount is 75% of the bag volume. Seal the bag opening and leave a 1.5cm ventilation gap to make a special bag-type controlled fertilizer.

[0097] (III) Implementation of methods to increase soil oxygen content

[0098] 1. Soil pretreatment: The soil from the target site is crushed and passed through a 3mm sieve to adjust the soil bulk density to 1.2g / cm³. 3 The moisture content is 22% and the pH value is 6.8. It is dried for 1.5 days, during which it is plowed twice to a depth of 25cm.

[0099] 2. Placement of special bags: Adopt the facility planting mode with a row spacing of 30cm and a plant spacing of 22cm. Dig planting trenches, place special bags at a depth of 17cm, with each bag corresponding to one tomato plant, cover with soil and compact.

[0100] 3. Crop transplanting and management: Transplant tomato seedlings in the designated bag area and irrigate every 4 days to maintain soil moisture content at 32%; check the air vents of the bags every 17 days and remove any blockages; regularly measure soil oxygen content by inserting a soil oxygen content meter into the root zone (17cm deep); regularly measure tomato root vigor using the national standard TTC reduction method in conjunction with an ultraviolet-visible spectrophotometer.

[0101] 4. Post-harvest processing: After the tomatoes are harvested, the porous and breathable bags are recycled, the residual materials inside the bags are removed, and new functional materials are added for reuse.

[0102] Single-factor experimental design and results of key process parameters

[0103] (I) Experimental Design Principles

[0104] To screen key process parameters, the following single-factor experiments were designed. Each experiment changed only one parameter, while the other conditions were the same as the corresponding stage in Example 1.

[0105] (II) Summary of Single-Factor Experiment Results

[0106]

[0107] Conclusion and Analysis: The preparation temperature of the pre-crosslinking solution affects the performance and application effect of the composite membrane. As shown in Table 1, the overall trend is "increases first and then decreases". The optimal performance is achieved at 85℃, with a mechanical strength of 18.3 MPa, elongation at break of 42.7%, a degradation period of 4.5 months, and an air permeability coefficient of 2.3 × 10⁻⁶. -11 m 2 The soil oxygen content was 20.3%, and the tomato root activity was 28.7 U / g·h. Below 85℃, the cross-linking reaction between tannic acid and calcium lactate was incomplete, resulting in a loose cross-linking network. This led to poor mechanical properties of the composite film, a longer degradation cycle, and a lower air permeability coefficient. The synergistic effect of aeration and fertilizer control in the bag was also poor, resulting in insufficient soil oxygen content, inhibited root dehydrogenase activity, and low root activity. Above 85℃, the plasticizer volatilized more rapidly, and excessive cross-linking increased the film's brittleness, decreased mechanical properties, shortened degradation cycle, and impaired air permeability. The balance between aeration and controlled release was disrupted, leading to a decrease in both soil oxygen content and root activity.

[0108]

[0109] Conclusion and Analysis: The thickness of the cast wet film significantly affects the performance and application effect of the composite film. As shown in Table 2, the optimal thickness is 0.13 mm. At this thickness, the composite film has a mechanical strength of 18.3 MPa, an elongation at break of 42.7%, a degradation period of 4.5 months, and an air permeability coefficient of 2.3 × 10⁻⁶. -11 m 2 The soil oxygen content was 20.3%, and the tomato root activity was 28.7 U / g·h. When the thickness was less than 0.13 mm, the membrane material lacked structural integrity after drying, resulting in weak mechanical properties, a short degradation cycle, and an excessively high air permeability coefficient. This prevented precise controlled release, nutrient loss, and soil environmental imbalance, leading to suboptimal soil oxygen content and root activity. When the thickness was greater than 0.13 mm, internal stress accumulated in the membrane material, resulting in excessively high structural density, reduced air permeability, decreased ventilation, prolonged degradation cycle, insufficient nutrient supply, and a tendency for minor defects in the membrane material. Consequently, the mechanical properties decreased, and both soil oxygen content and root activity were reduced.

[0110]

[0111] Conclusion and Analysis: The melting and mixing temperature of the base materials has a regulatory effect on the performance and application effect of the composite membrane. As shown in Table 3, the optimal temperature is 160℃, at which the composite membrane has a mechanical strength of 18.3 MPa, an elongation at break of 42.7%, a degradation period of 4.5 months, and an air permeability coefficient of 2.3 × 10⁻⁶. -11 m 2 The soil oxygen content was 20.3%, and the tomato root activity was 28.7 U / g·h. When the temperature was below 160℃, the raw materials such as polylactic acid and cassava starch did not melt sufficiently, the components were not mixed evenly, there were many defects inside the membrane material, the mechanical properties were poor, the air permeability coefficient was low, the aeration-fertilization synergy effect was poor, the soil oxygen content was insufficient, and the root activity was low. When the temperature was above 160℃, the raw materials were prone to thermal degradation, molecular chain breakage, increased membrane brittleness, decreased mechanical properties, shortened degradation cycle, destruction of the coating structure, and disruption of the balance between air permeability and controlled release. Both soil oxygen content and root activity showed a downward trend.

[0112]

[0113] Conclusion and Analysis: The ratio of plasticizer to auxiliary plasticizer in the pre-crosslinking solution affects the performance and application effect of the composite membrane. As shown in Table 4, the optimal ratio is 40%, at which point the composite membrane has a mechanical strength of 18.3 MPa, an elongation at break of 42.7%, a degradation period of 4.5 months, and an air permeability coefficient of 2.3 × 10⁻⁶. -11 m 2 The soil oxygen content was 20.3%, and the tomato root activity was 28.7 U / g·h. When the plasticizer content was below 40%, the plasticizing effect was insufficient, the membrane material had poor flexibility, low elongation at break, the cross-linked network was too dense, the air permeability coefficient was low, the aeration effect was poor, and the soil oxygen content and root activity did not reach the optimal level. When the plasticizer content was above 40%, the excess plasticizer was prone to migration and precipitation, the mechanical strength of the membrane material decreased, the structural stability deteriorated, the degradation cycle was shortened, the air permeability fluctuated, the balance between aeration and controlled release was broken, and the soil oxygen content and root activity both decreased to varying degrees.

[0114] Example 2

[0115] (I) Preparation of biodegradable polymer composite membranes

[0116] 1. Raw material pretreatment: Weigh out 45 parts polylactic acid, 17 parts tapioca starch, 6 parts hydroxypropyl methylcellulose, 4 parts glycerol, 3 parts tannic acid, 2 parts nano silica, 2.5 parts chitosan, 4 parts polyethylene glycol 400, 1.5 parts phytosterol, 2.5 parts sodium alginate, 4 parts polyvinyl alcohol, 3 parts sorbitol, 3.5 parts microcrystalline cellulose, 1.5 parts calcium lactate, and 1 part titanium dioxide according to the following weight: Dry polylactic acid in a vacuum drying oven at 65℃ for 5 hours; dry tapioca starch at 105℃ for 2.5 hours, pulverize, and pass through a 100-mesh sieve; dissolve chitosan in 1% acetic acid solution to prepare a 5% chitosan solution; pass microcrystalline cellulose through a 100-mesh sieve for later use.

[0117] 2. Preparation of pre-crosslinked liquid: Take 3 parts of tannic acid and 1.5 parts of calcium lactate, add 40% of the total weight of plasticizer (1.6 parts of glycerol) and auxiliary plasticizer (1.2 parts of sorbitol), and stir at 900 r / min for 40 min under heating at 85℃ to obtain the pre-crosslinked liquid.

[0118] 3. Melting and mixing of basic materials: 45 parts of pretreated polylactic acid, 17 parts of tapioca starch, 6 parts of hydroxypropyl methylcellulose, 4 parts of polyvinyl alcohol, and 3.5 parts of microcrystalline cellulose were added to a melt mixer and melt-mixed for 60 minutes at 160°C and 500 r / min to obtain the basic mixture.

[0119] 4. Modified blending: Add the remaining plasticizer (2.4 parts glycerol), auxiliary plasticizer (1.8 parts sorbitol), 4 parts polyethylene glycol 400, 2 parts nano silica, and 1 part titanium dioxide to the base mixture, and blend and modify for 30 min at 150℃ and 600 r / min to obtain the modified blend.

[0120] 5. Preparation of composite and film-forming solution: Chitosan solution (containing 2.5 parts chitosan), 1.5 parts phytosterol, 2.5 parts sodium alginate and pre-crosslinking solution were added to the modified blend and stirred for 50 min at 90℃ and 400 r / min. Then deionized water was added to adjust the solid-liquid mass ratio of the system to 1:4. The mixture was stirred at 65℃ for 25 min and filtered through a 100-mesh sieve to obtain a uniform film solution.

[0121] 6. Casting and Drying Curing: The film solution is uniformly cast on a polytetrafluoroethylene plate, and the wet film thickness is controlled to be 0.13 mm. It is placed in a 45℃ forced-air drying oven for 9 hours and then placed in an environment of 25℃ and 55% relative humidity for 36 hours to equilibrate, resulting in a biodegradable polymer composite film with a thickness of 0.065 mm.

[0122] (II) Preparation and application methods of special bag-based controlled fertilization

[0123] Same as Example 1.

[0124] Example 3

[0125] (I) Preparation of biodegradable polymer composite membranes

[0126] 1. Raw material pretreatment: Weigh out 45 parts polylactic acid, 17 parts tapioca starch, 6 parts hydroxypropyl methylcellulose, 4 parts glycerol, 3 parts tannic acid, 2 parts nano silica, 4 parts chitosan, 4 parts polyethylene glycol 400, 1.5 parts phytosterol, 2.5 parts sodium alginate, 4 parts polyvinyl alcohol, 3 parts sorbitol, 5 parts microcrystalline cellulose, 2.5 parts calcium lactate, and 1 part titanium dioxide according to the following weight: Dry polylactic acid in a vacuum drying oven at 65℃ for 5 hours; dry tapioca starch at 105℃ for 2.5 hours, pulverize, and pass through a 100-mesh sieve; dissolve chitosan in 1% acetic acid solution to prepare a 5% chitosan solution; pass microcrystalline cellulose through a 100-mesh sieve for later use.

[0127] 2. Preparation of pre-crosslinked liquid: Take 3 parts of tannic acid and 2.5 parts of calcium lactate, add 40% of the total weight of plasticizer (1.6 parts of glycerol) and auxiliary plasticizer (1.2 parts of sorbitol), and stir at 900 r / min for 40 min under heating at 85℃ to obtain the pre-crosslinked liquid.

[0128] 3. Melting and mixing of basic materials: 45 parts of pretreated polylactic acid, 17 parts of tapioca starch, 6 parts of hydroxypropyl methylcellulose, 4 parts of polyvinyl alcohol, and 5 parts of microcrystalline cellulose are added to a melt mixer and melt-mixed for 60 minutes at 160°C and 500 r / min to obtain the basic mixture.

[0129] 4. Modified blending: Add the remaining plasticizer (2.4 parts glycerol), auxiliary plasticizer (1.8 parts sorbitol), 4 parts polyethylene glycol 400, 2 parts nano silica, and 1 part titanium dioxide to the base mixture, and blend and modify for 30 min at 150℃ and 600 r / min to obtain the modified blend.

[0130] 5. Preparation of composite and film-forming solution: Chitosan solution (containing 4 parts chitosan), 1.5 parts phytosterol, 2.5 parts sodium alginate and pre-crosslinking solution were added to the modified blend and stirred for 50 min at 90℃ and 400 r / min. Then deionized water was added to adjust the solid-liquid mass ratio of the system to 1:4. The mixture was stirred at 65℃ for 25 min and filtered through a 100-mesh sieve to obtain a uniform film solution.

[0131] 6. Casting and Drying Curing: The film solution was uniformly cast onto a polytetrafluoroethylene plate, controlling the wet film thickness to 0.13 mm. It was then dried in a 45℃ forced-air drying oven for 9 hours, followed by equilibration at 25℃ and 55% relative humidity for 36 hours to obtain a biodegradable polymer composite film with a thickness of 0.065 mm. (II) Preparation and Application Method of Special Bag Fertilizer Control

[0132] Same as Example 1.

[0133] Example 4

[0134] (I) Preparation of biodegradable polymer composite membranes

[0135] 1. Raw material pretreatment: Same as in Example 1.

[0136] 2. Preparation of pre-crosslinked liquid: Same as in Example 1.

[0137] 3. Melting and mixing of basic materials: Same as in Example 1.

[0138] 4. Modified blending: Same as Example 1.

[0139] 5. Preparation of composite and film-forming solution: Same as in Example 1.

[0140] 6. Casting and Drying Curing: The film solution is uniformly cast on a polytetrafluoroethylene plate, and the wet film thickness is controlled to be 0.15 mm. It is placed in a 45℃ forced-air drying oven for 11 h, and then placed in an environment of 25℃ and 55% relative humidity for 42 h to equilibrate, so as to obtain a biodegradable polymer composite film with a thickness of 0.075 mm.

[0141] (II) Preparation and application methods of special bag-based controlled fertilization

[0142] Same as Example 1.

[0143] Example 5

[0144] (I) Preparation of biodegradable polymer composite membranes

[0145] 1. Raw material pretreatment: Same as in Example 1.

[0146] 2. Preparation of pre-crosslinked liquid: Same as in Example 1.

[0147] 3. Melting and mixing of basic materials: Same as in Example 1.

[0148] 4. Modified blending: Same as Example 1.

[0149] 5. Preparation of composite and film-forming solution: Same as in Example 1.

[0150] 6. Casting and Drying Curing: The film solution is uniformly cast on a polytetrafluoroethylene plate, and the wet film thickness is controlled to be 0.11 mm. It is then placed in a 45℃ forced-air drying oven for 7 hours and then placed in an environment of 25℃ and 55% relative humidity for 30 hours to equilibrate, resulting in a biodegradable polymer composite film with a thickness of 0.055 mm.

[0151] (II) Preparation and application methods of special bag-based controlled fertilization

[0152] Same as Example 1.

[0153] Example 6

[0154] (I) Preparation of biodegradable polymer composite membranes

[0155] 1. Raw material pretreatment: Same as in Example 1.

[0156] 2. Preparation of pre-crosslinked liquid: Same as in Example 1.

[0157] 3. Melting and mixing of basic materials: 45 parts of pretreated polylactic acid, 17 parts of tapioca starch, 6 parts of hydroxypropyl methylcellulose, 4 parts of polyvinyl alcohol, and 4 parts of microcrystalline cellulose are added to a melt mixer and melt-mixed for 50 minutes at 170°C and 500 r / min to obtain the basic mixture.

[0158] 4. Modified blending: Same as Example 1.

[0159] 5. Preparation of composite and film-forming solution: Same as in Example 1.

[0160] 6. Casting and drying / aging: Same as in Example 1.

[0161] (II) Preparation and application methods of special bag-based controlled fertilization

[0162] Same as Example 1.

[0163] III. Comparative Example

[0164] Comparative Example 1

[0165] 1. Soil pretreatment: Same as in Example 1, but deep tillage (25cm depth) is carried out every 10 days to improve soil aeration using traditional methods.

[0166] 2. Fertilization and planting: Conventional nitrogen, phosphorus and potassium compound fertilizer (N:P2O5:K2O=15:10:12) was applied in furrows at a rate of 30 kg per mu. The tomato planting density was the same as in Example 1, but the special bag-controlled fertilizer and composite film coating technology of this invention were not used.

[0167] 3. Field management: Same as in Example 1

[0168] Comparative Example 2

[0169] 1. Preparation of porous bag: The same polypropylene porous nonwoven bag as in Example 1 (porosity 35%, thickness 0.17mm, length 35cm, width 22cm, with ventilation holes of 0.7cm in diameter and 6cm in spacing evenly opened on the bottom and sides of the bag) is used. The interior is filled with only perlite, with a filling amount of 75%. No organic fertilizer, soil conditioner and controlled-release fertilizer are added. Only the ventilation function of the bag is retained.

[0170] 2. Laying out and planting: Lay out the porous bags according to the laying method of Example 1, and apply conventional nitrogen, phosphorus and potassium compound fertilizer in furrows (without using the composite film-coated controlled-release fertilizer of this invention). The rest of the operation is the same as in Example 1.

[0171] 3. Performance testing: Same as in Example 1.

[0172] Comparative Example 3

[0173] 1. Preparation of special bag: The same bag as in Example 1 (polypropylene porous non-woven bag) is used. The inside is filled with uncoated nitrogen, phosphorus and potassium compound fertilizer (N:P2O5:K2O=15:10:12), perlite, decomposed organic fertilizer and bentonite. The ratio is the same as in Example 1 (78 parts controlled-release fertilizer, 4 parts perlite, 6 parts decomposed organic fertilizer and 2.5 parts bentonite). However, the compound fertilizer is not coated with the biodegradable polymer composite film of this invention. It is just a conventional uncoated fertilizer.

[0174] 2. Layout and planting: Same as in Example 1.

[0175] Comparative Example 4

[0176] 1. Preparation of starch-based coated controlled-release fertilizer: Using cassava starch as the single coating material, adding glycerol as a plasticizer, the coating thickness is 0.065 mm. Without adding the cellulose derivatives, nanofillers, crosslinking agents and other components in the composite film of this invention, a traditional single starch-based coated controlled-release fertilizer is prepared.

[0177] 2. Planting and management: Apply the above-mentioned starch-based coated controlled-release fertilizer according to conventional planting methods (without using the porous breathable bag arrangement of the present invention), and the rest of the operation is the same as in Example 1.

[0178] 3. Performance testing: using Example 1.

[0179] Summary of experimental results:

[0180] (a) Test Results

[0181] The test results of Examples 1-6 and Comparative Examples 1-4 are shown in Table 5.

[0182]

[0183] (II) Data Comparison and Analysis

[0184] 1. Composite membrane performance analysis

[0185] As shown in Table 5, the composite membranes of Examples 1-6 have a mechanical strength range of 13.6-18.3 MPa, an elongation at break range of 31.8-42.7%, a degradation period range of 3.2-5.8 months, and an air permeability coefficient range of 1.5-2.7 × 10⁻⁶. -11 m 2Among them, the composite membrane of Example 1 exhibited the best performance in all aspects, with a mechanical strength of 18.3 MPa, an elongation at break of 42.7%, a degradation period of 4.5 months, and an air permeability coefficient of 2.3 × 10⁻⁶. -11 m 2 In contrast, none of the comparative examples used the biodegradable polymer composite film of the present invention (Comparative Examples 1, 2, and 3) or the traditional single starch-based coating (Comparative Example 4, whose composite film performance was not measured). Therefore, there is no corresponding composite film performance data. Furthermore, judging from the application effect, the coating effect of the latter is far inferior to that of the composite film of the present invention.

[0186] From a theoretical perspective, the performance advantages of the composite membrane of this invention stem from the synergistic effect of multiple components and precise process control: using polylactic acid and tapioca starch as the base materials, combined with cellulose derivatives such as hydroxypropyl methylcellulose, a matrix structure with both flexibility and rigidity is constructed; glycerol and sorbitol act as plasticizers and auxiliary plasticizers to improve the compatibility of the base material and enhance the toughness of the membrane; tannic acid and calcium lactate form a pre-crosslinking liquid to construct a stable crosslinking network and enhance the mechanical strength of the membrane; nano-silica and titanium dioxide work synergistically to refine the membrane grains and optimize air permeability and degradation rate; chitosan, phytosterols and other components further enhance the stability of the membrane, achieving a balance between mechanical properties, air permeability and degradation performance.

[0187] The performance differences among the embodiments stem from adjustments to core process parameters: In Embodiment 2, increasing the pre-crosslinking liquid preparation temperature leads to excessive crosslinking reaction, increased membrane brittleness, decreased mechanical strength and elongation at break, and a shortened degradation cycle; In Embodiment 3, decreasing the pre-crosslinking liquid preparation temperature results in incomplete crosslinking reaction, loose membrane structure, poor mechanical properties, and a prolonged degradation cycle; In Embodiment 4, increasing the thickness of the cast wet film increases membrane density, decreases air permeability, prolongs the degradation cycle, and initially increases then decreases mechanical properties; In Embodiment 5, decreasing the thickness of the cast wet film results in insufficient membrane structural integrity, decreased mechanical strength, increased air permeability, and a shortened degradation cycle; In Embodiment 6, increasing the melting and mixing temperature of the base materials leads to molecular chain breakage due to thermal degradation of the raw materials, resulting in decreased membrane mechanical properties and a shortened degradation cycle.

[0188] 2. Analysis of oxygen content in the soil root zone

[0189] As shown in Table 5, the oxygen content in the soil root layer of Examples 1-6 ranged from 17.9% to 20.3%, with Example 1 having the highest oxygen content at 20.3%. In contrast, the highest oxygen content in the soil root layer of Comparative Examples 1-4 was only 17.3%. The oxygen content of Example 1 was 42.9% higher than that of Comparative Example 1, 23.0% higher than that of Comparative Example 2, 17.3% higher than that of Comparative Example 3, and 34.4% higher than that of Comparative Example 4, demonstrating a significant advantage.

[0190] This performance advantage stems from the structural design and functional synergy of the special bag for fertilizer control in this invention: the porous and breathable bag body, combined with the bag's vents, creates an efficient air-permeable channel, promoting gas exchange between the soil and the air; the perlite inside the bag serves as a lightweight air-permeable medium, further optimizing the air-permeable structure and preventing soil compaction from clogging the air-permeable channels; the permeability coefficient of the biodegradable polymer composite membrane is precisely controlled, ensuring gas flow while preventing excessive nutrient loss, forming a synergistic effect of "air permeability-fertilizer control," and steadily increasing the oxygen content of the soil root zone.

[0191] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A special bag for controlled fertilization, characterized in that, Includes a porous, breathable bag body and functional materials filled within the bag body; The porous breathable bag is made of porous non-woven fabric with a porosity of 30%-40% and a thickness of 0.15-0.2mm. Multiple breathable holes are evenly opened on the bottom and sides of the bag. The functional material is composed of the following raw materials in parts by weight: 70-85 parts controlled-release fertilizer, 3-5 parts lightweight breathable medium, 5-8 parts organic fertilizer, and 2-3 parts soil conditioner; the filling amount of the functional material is 70%-80% of the bag volume. The controlled-release fertilizer is fertilizer granules coated with a biodegradable polymer composite membrane; The biodegradable polymer composite film, by weight, is made from the following raw materials: 40-50 parts polylactic acid, 15-20 parts starch, 5-8 parts cellulose derivative, 3-5 parts plasticizer, 2-4 parts crosslinking agent, 1-3 parts nanofiller, 2.5-4 parts antibacterial agent, 3-6 parts dispersant, 1-2 parts anti-aging agent, 2-3 parts binder, 3-5 parts film-forming aid, 2-4 parts auxiliary plasticizer, 3.5-5 parts reinforcing fiber, and 1.5-2.5 parts degradation rate regulator.

2. The special bag for controlled fertilization according to claim 1, characterized in that, The porous nonwoven fabric is a polypropylene porous nonwoven fabric; the diameter of the air pores is 0.5-1cm, and the pore spacing is 5-8cm; the bag body dimensions are 30-40cm in length and 20-25cm in width.

3. The special bag for controlled fertilization according to claim 1, characterized in that, The lightweight, breathable medium is perlite with a particle size of 1-2 mm; the organic fertilizer is well-rotted organic fertilizer; and the soil conditioner is bentonite.

4. The special bag for controlled fertilization according to claim 1, characterized in that, The starch is tapioca starch; the cellulose derivative is hydroxypropyl methylcellulose; the plasticizer is glycerol; the crosslinking agent is tannic acid; the antibacterial agent is chitosan; the anti-aging agent is phytosterol; the binder is sodium alginate; the film-forming aid is polyvinyl alcohol; the auxiliary plasticizer is sorbitol; the reinforcing fiber is microcrystalline cellulose; the degradation rate regulator is calcium lactate; and the nanofiller includes nano-silica and a light stabilizer.

5. The special bag for controlled fertilization according to claim 4, characterized in that, The light stabilizer is titanium dioxide; the weight ratio of tannic acid to calcium lactate is 1:(0.5-1); the weight ratio of titanium dioxide to nano-silica is 1:(1-2).

6. A method for preparing a biodegradable polymer composite film for use in the special bag-based fertilizer control system according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Raw material pretreatment: Weigh each raw material according to the ratio; dry polylactic acid; dry starch and sieve; dissolve chitosan in acid solution to prepare chitosan solution; sieve microcrystalline cellulose for later use; (2) Preparation of pre-crosslinked liquid: Tannic acid, calcium lactate and a portion accounting for 30%-50% of the total weight of plasticizer and auxiliary plasticizer are mixed and stirred under heating conditions to obtain pre-crosslinked liquid; (3) Melting and mixing of basic materials: Pretreated polylactic acid, starch, hydroxypropyl methylcellulose, polyvinyl alcohol and microcrystalline cellulose are mixed and melt-blended under heating and stirring to obtain a basic mixture; (4) Modified blending: The remaining plasticizer and auxiliary plasticizer, dispersant, nanofiller and light stabilizer are added to the base mixture, and the mixture is blended and modified under stirring to obtain a modified blend; (5) Preparation of composite and film-forming solution: Add the chitosan solution, phytosterol, sodium alginate and the pre-crosslinking solution to the modified blend and stir to mix; then add water to adjust the solid-liquid mass ratio of the system to 1:(3-5), stir at constant temperature and filter to obtain a uniform film solution; (6) Casting and drying: The film liquid is cast on the substrate and the wet film thickness is controlled; preliminary drying is performed first, and then balanced curing is performed to obtain a biodegradable polymer composite film of the target thickness.

7. The method for producing a biodegradable polymer composite film according to claim 6, characterized in that, In step (6), the thickness of the wet film is 0.1-0.16 mm, the initial drying temperature is 40-50℃, the equilibrium curing conditions are 25℃ temperature, 50%-60% relative humidity, and 24-48 hours, and the thickness of the resulting composite film is 0.05-0.08 mm.

8. A method for increasing soil oxygen content by using the special bags described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Soil pretreatment: The soil of the target plot is crushed and screened, the soil bulk density, moisture content and pH value are adjusted, and the soil is tilled; (2) Deployment of special bags: Determine the spacing of the bags according to the planting type, dig planting trenches or planting holes in the soil, lay the special bags at the set depth, cover the soil and compact them; (3) Crop planting and management: Plant crops in the area where the special bags have been laid, irrigate, and regularly check the ventilation holes of the bags.

9. The method for controlling fertilizer use with special bags to improve soil oxygen content according to claim 8, characterized in that, In step (1), the soil bulk density is adjusted to 1.1-1.3 g / cm³. 3 The soil moisture content is adjusted to 20%-25%, and the pH value is adjusted to 6.0-7.

5. In step (2), the row spacing for open field planting is 30-40cm and the plant spacing is 25-30cm, while the row spacing for facility planting is 25-35cm and the plant spacing is 20-25cm. The laying depth is 15-20cm. In step (3), the irrigation frequency is once every 3-5 days to maintain the soil moisture content at 30%-35%, and the frequency of checking the air vents is once every 15-20 days.

10. The method for controlling fertilizer use with special bags to improve soil oxygen content according to claim 8, characterized in that, It also includes a bag treatment step after crop harvest: recycling the porous breathable bag, removing the consumed functional materials remaining in the bag, and replenishing the bag with new functional materials of the same composition as the functional materials described in this invention.

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