Full-biodegradable mulching film added with straw powder and microelement fertilizer as well as preparation method and application of full-biodegradable mulching film

Abstract

The invention relates to the field of agricultural environment-friendly materials, and discloses a full-biodegradable mulching film added with straw powder and a microelement fertilizer as well as a preparation method and application of the full-biodegradable mulching film. The mulching film is prepared from the following raw materials in parts by weight: 60-80 parts of polyadipic acid / butylene terephthalate (PBAT), 5-20 parts of polylactic acid (PLA), 5-15 parts of a blocking agent, 3-8 parts of a plasticizer, 3-10 parts of calcium carbonate powder (CaCO3), 1-7 parts of straw powder and 1-7 parts of a microelement fertilizer. The preparation process comprises the following steps: after drying the raw materials, carrying out melt blending and pelletizing through a twin-screw pelletizer (the first area is 140-170 DEG C, and the screw rotating speed is 100-300 RPM), and then forming a film through a film blowing machine (the first area is 90-130 DEG C, and the screw rotating speed is 15-45 RPM). The mulching film is used for agricultural covering, can improve crop trace element absorption, enhance stress resistance and improve soil fertility, solves the problems of insufficient mechanical properties, single function and low agricultural waste utilization rate of a traditional mulching film, has both environmental protection and yield increase benefits, realizes nutrient slow release in the degradation process, and promotes agricultural ecological sustainable development.

Description

Technical Field

[0001] This invention relates to the field of agricultural environmental protection materials technology, specifically to a fully biodegradable mulch film with added straw powder and micronutrients, its preparation method, and its application. Background Technology

[0002] Mulching technology, as an important component of modern agriculture, plays a significant role in heat preservation, moisture retention, and weed control. Traditional mulch films are mostly made of polyethylene (PE), whose non-degradable nature leads to the accumulation of residual film in the soil, causing environmental problems such as soil structure damage and reduced crop yields. In recent years, fully biodegradable mulch films have become a research hotspot. By using biodegradable polymers such as PBAT and PLA to prepare mulch films, the environmental pollution problems of traditional mulch films have been solved. However, existing technologies still have the following shortcomings: Insufficient utilization of agricultural waste resources; Commonly available biodegradable materials are polylactic acid (PLA) and polybutylene adipate / terephthalate (PBAT). To further reduce the manufacturing cost of biodegradable mulch films and accelerate their degradation rate, researchers often add natural plant fibers to PLA and PBAT. Straw, as an agricultural waste, has advantages such as low price, abundant raw materials, high specific modulus, and low processing energy consumption. Therefore, using straw as a reinforcing agent to form composite materials with these polymers has become a current research hotspot. Adding straw to mulch films can not only reduce costs and improve the resource utilization rate of straw waste, but also facilitate the implementation of straw return to the field. Currently, adding straw to mulch films faces many challenges. Due to the significant interfacial incompatibility between straw and the polymer substrate, and the high surface roughness of straw fibers, composite films with added straw generally have lower mechanical properties than commercially available biodegradable mulch films.

[0003] The challenge of balancing mechanical properties and degradation performance For example, the three-layer fully biodegradable composite membrane disclosed in Chinese invention patent publication number CN110091564A has optimized the barrier performance through the formulation design of different layers, but it does not involve the addition of straw powder and micro-fertilizer, and the preparation process is not optimized for agricultural waste treatment, so it cannot simultaneously meet the dual requirements of high strength of mulch film and soil improvement.

[0004] 3. Limitation due to single function Although Chinese invention patent publication number CN115260720A improved the compatibility of the blended material by adding compatibilizers, it did not introduce straw powder as a reinforcing material and micronutrients were not used as functional components. Therefore, it could not achieve the function of slow-release of nutrients during the degradation process and could not meet the needs of modern agriculture for improving soil fertility.

[0005] Furthermore, existing studies have shown that long-term mulching weakens crop absorption of micronutrients such as iron, copper, and manganese, leading to decreased yield and quality due to micronutrient deficiency. Micronutrient fertilizers, rich in elements like iron, zinc, boron, manganese, copper, and molybdenum, can improve soil fertility, increase crop yield and quality, and enhance crop resistance, making them a primary measure for supplementing crops with micronutrients. Adding micronutrient fertilizers to mulch film products can not only mitigate the adverse effects of long-term mulching on crop micronutrient absorption but also improve crop yield and quality, protecting the long-term stability of the agricultural ecological environment. However, methods for preparing mulch film with added micronutrient fertilizers have not yet been reported.

[0006] Against this backdrop, developing a functional, fully biodegradable mulch film with added straw powder and micronutrients would not only reduce the cost of biodegradable mulch films and improve the utilization rate of straw resources, but also be of great significance for improving the quality of agricultural products, promoting the use of biodegradable mulch films, and protecting the agricultural ecological environment. Summary of the Invention

[0007] The purpose of this invention is to provide a fully biodegradable mulch film with added straw powder and micro-fertilizer, its preparation method and application. By optimizing the raw material formula and innovating the preparation process, this invention solves the problems of insufficient mechanical properties, single function and low resource utilization rate of agricultural waste in existing mulch films, and achieves high strength, full biodegradability and soil improvement function of the mulch film.

[0008] To address the shortcomings of existing technologies, this invention provides a fully biodegradable mulch film with added straw powder and micronutrients, comprising the following raw material components in parts by weight: 60-80 parts polybutylene adipate / terephthalate (PBAT), 5-20 parts polylactic acid (PLA), 5-15 parts barrier agent, 3-8 parts plasticizer, 3-10 parts calcium carbonate powder (CaCO3), 1-7 parts straw powder, and 1-7 parts micro-fertilizer.

[0009] Furthermore, the barrier agent is polypropylene carbonate (PPC).

[0010] Further, the plasticizer is at least one of epoxidized soybean oil (ESO), ATBC, DOP, glycerin, sorbitol, xylitol, glycerol, white oil or polyethylene glycol, preferably epoxidized soybean oil (ESO).

[0011] Furthermore, the calcium carbonate powder is light calcium carbonate with a particle size of 1000-5000 mesh.

[0012] Furthermore, the straw powder is corn straw powder with a particle size of 1000-3000 mesh, and its preparation method includes: After chopping the corn stalks, dry them at 105℃ for 12 hours, then pulverize them to 60-100 mesh. The material is finely crushed to a mesh size of over 1000 using a high-pressure pulse crusher, and then screened to a mesh size of 1000-3000 using an ultrasonic vibrating screen.

[0013] Furthermore, the micro-fertilizer is a concentrated white micro-fertilizer powder rich in iron, zinc, boron, manganese, copper, and molybdenum elements, with a particle size of 1000-3000 mesh, and its preparation method includes: (1) Dry the micro-fertilizer in an oven at 40-60℃ for 8 hours; (2) The material is finely crushed to a mesh size of 1000 or more by a high-pressure pulse crusher and then screened to a mesh size of 1000-3000 by an ultrasonic vibrating screen.

[0014] By adopting the above technical solutions, polybutylene adipate terephthalate (PBAT) exhibits excellent flexibility and processing fluidity, but its rigidity and heat resistance are insufficient. Polylactic acid (PLA), as a high-strength bio-based material, possesses outstanding rigidity and biocompatibility, but suffers from poor toughness and high brittleness. By compounding PBAT and PLA in a specific ratio as a mulch film substrate, and controlling the content of both (60-80 parts PBAT, 5-20 parts PLA), a synergistic structure of "rigid skeleton - flexible toughening" can be formed: PLA provides mechanical support, PBAT improves the brittleness of the film material, and the synergistic effect of the ester bonds between their molecular chains accelerates the hydrolysis reaction during degradation, thereby balancing the mechanical properties and degradation rate of the mulch film.

[0015] Straw powder, as an agricultural waste reinforcing agent, possesses natural interfacial compatibility between its cellulose structure and the polymer matrix. After being crushed to 1000-3000 mesh under high pressure pulse, it can be uniformly dispersed in the PBAT / PLA matrix, forming a physical cross-linked network. This significantly improves the tensile load (up to 4.09N longitudinally and 3.49N transversely, far exceeding the national standard of 2.20N) and tensile strain (427% longitudinally and 290% transversely) of the mulch film. Simultaneously, the lignin component in the straw powder can adsorb heavy metal ions in the soil, helping to improve the soil environment.

[0016] Micronutrient fertilizer (rich in trace elements such as Fe, Zn, B, and Mn) is introduced into the mulch film system at a ratio of 1-7 parts. The particle size is controlled to 1000-3000 mesh through ultrasonic sieving to ensure uniform distribution during melt blending. The hydroxyl groups on the surface of the micronutrient fertilizer particles form hydrogen bonds with the PBAT / PLA molecular chains, which not only avoids agglomeration but also allows the micronutrients to be released synchronously with the degradation of the mulch film under the action of soil microorganisms. This solves the problem of crop nutrient deficiency caused by long-term mulching and improves crop resistance (such as drought resistance and lodging resistance) and fruit quality.

[0017] The synergistic effect of barrier agent polypropylene carbonate (PPC) and plasticizer epoxidized soybean oil (ESO) further optimizes the performance of the mulch film: PPC enhances the barrier performance of the film material against oxygen and water vapor through the molecular chain entanglement effect, reducing the impact of environmental humidity on the degradation rate; ESO, as a bio-based plasticizer, can be inserted between PBAT / PLA molecular chains, lowering the glass transition temperature, improving processing fluidity, and avoiding the migration and contamination problems of traditional plasticizers.

[0018] This invention also provides a method for preparing a fully biodegradable mulch film with added straw powder and micronutrients, comprising the following steps: (1) Dry PBAT, PLA, calcium carbonate powder, straw powder, and micronutrients at 30-50℃ for 8 hours; (2) The dried raw materials, barrier agent and plasticizer are added to a twin-screw mixer and granulator, melt-blended and then pelletized to obtain mixed plastic granules; (3) The mixed plastic granules are dried at 40-60℃ for 8 hours and blown into a film by a blown film machine to obtain a nutrient-type fully biodegradable mulch film with added straw powder and micro-fertilizer.

[0019] Furthermore, the process parameters of the twin-screw mixing granulator are as follows: Zone 1 temperature 140-170℃, Zone 2 temperature 140-170℃, Zone 3 temperature 160-190℃, Zone 4 temperature 160-190℃, screw speed 100-300RPM, hopper feed speed 2-8Hz, pelletizer speed 1-6Hz.

[0020] Furthermore, the process parameters of the blown film machine are as follows: Zone 1 temperature 90-130℃, Zone 2 temperature 100-150℃, Zone 3 temperature 100-150℃, screw speed 15-45RPM, traction speed 5-15RPM, winding speed 5-15RPM.

[0021] By adopting the above technical solutions, the four-zone temperature gradient design of the twin-screw granulator (zone 1 140-170℃, zone 2 140-170℃, zone 3 160-190℃, zone 4 160-190℃) ensures that the raw materials are fully melted and blended. The screw speed of 100-300 RPM, combined with the hopper feed speed of 2-8 Hz, allows for adjustable shear force, preventing excessive crushing of straw powder and thus reducing the reinforcing effect. During the film blowing process, the low-temperature melting zone of 90-130℃ in zone 1 reduces the heat loss of trace elements in the micronutrient fertilizer, while the setting temperature of 100-150℃ in zone 3 ensures the stability of the film bubble, ultimately forming a mulch film product with uniform thickness and excellent mechanical properties.

[0022] The present invention also provides an application of a fully biodegradable mulch film with added straw powder and micronutrients. The mulch film is used for ground cover in agricultural planting, which can improve the absorption of micronutrients by crops, enhance stress resistance and improve soil fertility.

[0023] In summary, the present invention has the following beneficial effects: 1. Excellent Mechanical Properties: The fully biodegradable mulch film prepared by this invention meets all the mechanical property requirements of the national standard GB / T35795-2017 "Fully Biodegradable Agricultural Ground Cover Film". From the mechanical property test results of the examples, the tensile load reaches 4.09N in the longitudinal direction and 3.49N in the transverse direction, both far exceeding the national standard requirement of 2.20N; the breaking strain is 427% in the longitudinal direction and 290% in the transverse direction, better than the national standard requirements of 200% in the longitudinal direction and 280% in the transverse direction; the right-angle tensile load is 2.48N in the longitudinal direction and 2.64N in the transverse direction, also higher than the national standard requirement of 1.20N, thus meeting the mechanical strength requirements of mulch film in agricultural production.

[0024] 2. Reduce costs and improve resource utilization: Utilizing agricultural waste: Processing agricultural waste such as corn stalks into straw powder and adding it to mulch film realizes the resource utilization of straw, reduces environmental pollution from agricultural waste, and turns waste into treasure, thereby increasing the economic value of straw.

[0025] Reduced material costs: Straw is inexpensive and abundant, and can replace some polymers, thus reducing the production cost of biodegradable mulch film and promoting its use.

[0026] 3. Improve soil fertility and crop quality: Supplementing micronutrients: The micronutrients added to the mulch film are rich in elements such as iron, zinc, boron, manganese, copper, and molybdenum. They can be slowly released into the soil, improving the problem of reduced absorption of micronutrients by crops under long-term mulching conditions, and preventing crop yield and quality decline due to lack of micronutrients.

[0027] Enhancing crop resistance to stress: The addition of micronutrients helps to enhance the crop's resistance to stress, making it more adaptable to adverse environmental conditions and improving crop growth stability and yield.

[0028] 4. Environmentally friendly: It uses biodegradable materials such as PBAT and PLA as the base material, and the added straw powder and micro-fertilizer are all natural or environmentally friendly ingredients. The mulch film is biodegradable in the soil and will not leave long-term residues that damage the soil structure like traditional PE mulch film, which is conducive to the long-term stable development of agricultural ecological environment protection.

[0029] 5. Uniform component distribution: As can be seen from the magnified image under a microscope, the straw powder and micronutrients are distributed relatively evenly in the film. This helps to ensure the stability of the mulch film's performance and allows it to perform the same function in different areas, such as uniformly supplementing micronutrients and uniformly enhancing mechanical properties. Attached Figure Description

[0030] Figure 1 This is a comparison chart of the available nutrients (A) and micronutrients (B) in soil with and without micronutrient (WWF) mulch film; Figure 2 This is a product image of the fully biodegradable mulch film prepared in the example; Figure 3 These are magnified microscopic images of the fully biodegradable mulch film prepared in the examples. From left to right, they are the original image, magnified 40 times, magnified 100 times, and magnified 400 times. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the scope described.

[0033] A fully biodegradable mulch film with added straw powder and micronutrients, comprising the following raw material components in parts by weight: 60-80 parts polybutylene adipate / terephthalate (PBAT), 5-20 parts polylactic acid (PLA), 5-15 parts barrier agent, 3-8 parts plasticizer, 3-10 parts calcium carbonate powder (CaCO3), 1-7 parts straw powder, and 1-7 parts micro-fertilizer.

[0034] Furthermore, the barrier agent is polypropylene carbonate (PPC).

[0035] Further, the plasticizer is at least one of epoxidized soybean oil (ESO), ATBC, DOP, glycerin, sorbitol, xylitol, glycerol, white oil or polyethylene glycol, preferably epoxidized soybean oil (ESO).

[0036] Furthermore, the calcium carbonate powder is light calcium carbonate with a particle size of 1000-5000 mesh.

[0037] Furthermore, the straw powder is corn straw powder with a particle size of 1000-3000 mesh, and its preparation method includes: After chopping the corn stalks, dry them at 105℃ for 12 hours, then pulverize them to 60-100 mesh. The material is finely crushed to a mesh size of over 1000 using a high-pressure pulse crusher, and then screened to a mesh size of 1000-3000 using an ultrasonic vibrating screen.

[0038] Furthermore, the micro-fertilizer is a concentrated white micro-fertilizer powder rich in iron, zinc, boron, manganese, copper, and molybdenum elements, with a particle size of 1000-3000 mesh, and its preparation method includes: (1) Dry the micro-fertilizer at 40-60℃ for 8 hours; (2) The material is finely crushed to a mesh size of 1000 or more by a high-pressure pulse crusher and then screened to a mesh size of 1000-3000 by an ultrasonic vibrating screen.

[0039] A method for preparing a fully biodegradable mulch film with added straw powder and micronutrients includes the following steps: (1) Dry PBAT, PLA, calcium carbonate powder, straw powder, and micronutrients at 30-50℃ for 8 hours; (2) The dried raw materials, barrier agent and plasticizer are added to a twin-screw mixer and granulator, melt-blended and then pelletized to obtain mixed plastic granules; (3) The mixed plastic granules are dried at 40-60℃ for 8 hours and blown into a film by a blown film machine to obtain a nutrient-type fully biodegradable mulch film with added straw powder and micro-fertilizer.

[0040] Furthermore, the process parameters of the twin-screw mixing granulator are as follows: Zone 1 temperature 140-170℃, Zone 2 temperature 140-170℃, Zone 3 temperature 160-190℃, Zone 4 temperature 160-190℃, screw speed 100-300RPM, hopper feed speed 2-8Hz, pelletizer speed 1-6Hz.

[0041] Furthermore, the process parameters of the blown film machine are as follows: Zone 1 temperature 90-130℃, Zone 2 temperature 100-150℃, Zone 3 temperature 100-150℃, screw speed 15-45RPM, traction speed 5-15RPM, winding speed 5-15RPM.

[0042] In this invention, the barrier agent is polypropylene carbonate (PPC).

[0043] The plasticizers mentioned can be commonly used commercially available ATBC, DOP, glycerin, sorbitol, xylitol, glycerol, epoxidized soybean oil, white oil, polyethylene glycol, etc., with epoxidized soybean oil (ESO) being the preferred choice.

[0044] The calcium carbonate powder is preferably light calcium carbonate, and the particle size should preferably be 1000-5000 mesh.

[0045] The straw used is preferably corn straw, which can be recycled from farmland or purchased from the market. The straw powder is processed by fine grinding using a pulse method.

[0046] The micro-fertilizer is a concentrated white powder rich in elements such as iron, zinc, boron, manganese, copper, and molybdenum, with a particle size of approximately 60-150 mesh. It is stable and resistant to high temperatures. Further fine grinding is performed using a pulse method.

[0047] The aforementioned PBAT, PLA, CaCO3 (light calcium carbonate), ESO, and PPC are all available on the market. Example 1

[0048] Step 1: Preparation of Corn Stalk Powder Fresh corn stalks are first washed clean with water, then chopped with scissors and dried in an oven at 105℃ for 12 hours to ensure sufficient dryness. After drying, they are first initially pulverized to 60-100 mesh using a pulverizer, and then finely pulverized to over 1000 mesh using a high-pressure pulse crusher. The resulting fine stalk powder is then screened through an ultrasonic vibrating sieve to a suitable mesh size, preferably 1000-3000 mesh.

[0049] Step 2: Preparation of Micronutrient Powder The micro-fertilizer powder is first dried in an oven at 40-60℃ for 8 hours, then finely crushed to a mesh size of over 1000 using a high-pressure pulse crusher. Finally, the finely ground micro-fertilizer powder is screened to a suitable mesh size, preferably 1000-3000 mesh, using an ultrasonic vibrating screen.

[0050] Step 3: Preparation of Mixed Plastic Particles PBAT, PLA, CaCO3, and the straw powder and micro-fertilizer powder obtained in steps one and two were all dried in an oven at 30-50℃ for 8 hours before mixing and granulation to ensure dryness. PBAT, PLA, CaCO3, PPC, ESO, straw powder, and micro-fertilizer powder were added to a twin-screw mixer and granulator, melt-blended, and then pelletized by a pelletizer to obtain mixed plastic granules. The weight proportions of each component are as follows: 80 parts PBAT (polybutylene adipate / terephthalate), 8 parts PLA (polylactic acid), 10 parts barrier agent, 8 parts plasticizer, 8 parts calcium carbonate powder (CaCO3), 8 parts straw powder, and 8 parts micro-fertilizer. The parameters of the twin-screw mixing granulator are as follows: the temperatures of zones one, two, three, and four are 140-170℃, 140-170℃, 160-190℃, and 160-190℃ respectively; the screw speed is 100-300 RPM; the hopper feed speed is 2-8 Hz; the conveyor belt speed is 1-6 revolutions / minute; and the pelletizer speed is 1-6 Hz.

[0051] Step 4: Film blowing The mixed plastic granules obtained in step three are first dried in an oven at 30-60℃ for 8 hours, then fed into a blown film machine for blowing and winding to obtain a nutrient-type fully biodegradable mulch film with added straw powder and micronutrients. The blown film machine parameters are as follows: zone 1 temperature is 90-130℃, zone 2 temperature is 100-150℃, and zone 3 temperature is 100-150℃, respectively; screw speed is 15-45 RPM; traction speed is 5-15 RPM; and winding speed is 5-15 RPM.

[0052] Comparative Example 1 (without straw powder):

[0053] The straw powder was removed from the formulation, while other conditions remained the same as in Example 1. Tensile strength increased by approximately 10%, and elongation at break also increased by approximately 10%, indicating that the addition of straw powder had a slight negative impact on mechanical properties.

[0054] Comparative Example 2 (without micronutrients):

[0055] Micronutrients were removed from the formula, and other conditions were the same as in Example 1. Figure 1 The results of the field experiment on soil nutrients show that the addition of micronutrients to the mulch film can significantly increase the content of zinc, iron, manganese, boron and available potassium, with an increase of about 10%. This indicates that the addition of micronutrients has practical application value in supplementing farmland soil with micronutrients and readily available nutrients.

[0056] Table 1 shows the mechanical property test results of the fully biodegradable mulch films of Example 1, Comparative Example 1, and Comparative Example 2. The results all meet the national standard requirements stipulated in GB / T 35795-2017 Fully Biodegradable Agricultural Ground Cover Film.

[0057] Table 1. Mechanical property test results of fully biodegradable mulch films in Example 1, Comparative Example 1, and Comparative Example 2.

[0058] Example 1: Sample of finished mulch film Figure 2 As shown, the magnified image under the microscope is as follows: Figure 3 As shown. From Figure 2 As can be seen, the nutrient-type fully biodegradable mulch film produced by this invention, which incorporates straw powder and micronutrients, has a uniform texture and is a light yellow, semi-transparent film. From... Figure 2 The distribution of straw powder and micronutrients in the finished product sample of the example can be seen, and the components are distributed relatively evenly.

[0059] 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 fully biodegradable mulch film containing added straw powder and micronutrients, characterized in that, The raw material components include the following parts by weight: 60-80 parts polybutylene adipate / terephthalate (PBAT), 5-20 parts polylactic acid (PLA), 5-15 parts barrier agent, 3-8 parts plasticizer, 3-10 parts calcium carbonate powder (CaCO3), 1-7 parts straw powder, and 1-7 parts micro-fertilizer.

2. The fully biodegradable mulch film according to claim 1, characterized in that: The barrier agent is polypropylene carbonate (PPC).

3. The fully biodegradable mulch film according to claim 1, characterized in that: The plasticizer is at least one of epoxidized soybean oil (ESO), ATBC, DOP, glycerin, sorbitol, xylitol, glycerol, white oil, or polyethylene glycol.

4. The fully biodegradable mulch film according to claim 1, characterized in that: The calcium carbonate powder is light calcium carbonate with a particle size of 1000-5000 mesh.

5. The fully biodegradable mulch film according to claim 1, characterized in that: The straw powder is corn straw powder with a particle size of 1000-3000 mesh, and its preparation method includes: After chopping the corn stalks, dry them at 105℃ for 12 hours, then pulverize them to 60-100 mesh. The material is finely crushed to a mesh size of over 1000 using a high-pressure pulse crusher, and then screened to a mesh size of 1000-3000 using an ultrasonic vibrating screen.

6. The fully biodegradable mulch film according to claim 1, characterized in that: The micro-fertilizer is a powder rich in iron, zinc, boron, manganese, copper, and molybdenum, with a particle size of 1000-3000 mesh. Its preparation method includes: (1) Dry the micro-fertilizer in an oven at 40-60℃ for 8 hours; (2) The material is finely crushed to a mesh size of 1000 or more by a high-pressure pulse crusher and then screened to a mesh size of 1000-3000 by an ultrasonic vibrating screen.

7. The method for preparing the fully biodegradable mulch film according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Dry PBAT, PLA, calcium carbonate powder, straw powder, and micronutrients at 30-50℃ for 8 hours; (2) The dried raw materials, barrier agent and plasticizer are added to a twin-screw mixer and granulator, melt-blended and then pelletized to obtain mixed plastic granules; (3) Dry the mixed plastic granules at 40-60℃ for 8 hours, and blow them into a film using a blown film machine.

8. The preparation method according to claim 7, characterized in that: The process parameters of the twin-screw mixer granulator are as follows: Zone 1 temperature 140-170℃, Zone 2 temperature 140-170℃, Zone 3 temperature 160-190℃, Zone 4 temperature 160-190℃, screw speed 100-300RPM, hopper feed speed 2-8Hz, pelletizer speed 1-6Hz.

9. The preparation method according to claim 7, characterized in that: The process parameters of the blown film machine are as follows: Zone 1 temperature 90-130℃, Zone 2 temperature 100-150℃, Zone 3 temperature 100-150℃, screw speed 15-45RPM, traction speed 5-15RPM, winding speed 5-15RPM.

10. The application of the fully biodegradable mulch film according to any one of claims 1-6, characterized in that: The mulch film is used for ground covering in agricultural planting, which can improve the absorption of trace elements by crops, enhance their resistance to stress, and improve soil fertility.

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