Modified bio-based coated controlled-release fertilizer and preparation method thereof

Abstract

The invention discloses a modified bio-based coated controlled-release fertilizer and a preparation method thereof, and belongs to the technical field of bio-organic fertilizers. The fertilizer comprises two parts, namely a coating prepared from a modified bio-based coating material and a fertilizer core prepared from organic and inorganic nutrient substances. The modified bio-based material is used as the coating layer, so that the slow release performance of the fertilizer is remarkably improved, and the problem of environmental pollution caused by a traditional petroleum-based polymer coating material is effectively solved. The natural biomass material is chemically modified, so that the mechanical strength and water resistance of the coating material are improved, and meanwhile, good biodegradability is reserved. Agricultural wastes such as pineapple leaves are efficiently utilized, so that cyclic utilization of resources is realized, and the pressure of the wastes on the environment is also reduced. Compared with the prior art, the degradation speed of the fertilizer in soil is more balanced, and potential damage to the soil structure can be avoided while the slow release effect is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of bio-organic fertilizers, and particularly relates to a modified bio-based coated controlled-release fertilizer and a preparation method thereof. Background Art

[0002] Agriculture is the lifeblood of the national economy, and fertilizers are the foundation of agricultural production. However, traditional fertilizers have low nutrient utilization rates. Fertilizer nutrient loss not only wastes resources and increases agricultural production costs, but also harms the environment. To alleviate this problem, slow-release fertilizers are gaining increasing attention in modern agricultural development. Slow-release fertilizers have become a leading trend in fertilizer development. They are environmentally friendly, highly nutrient-efficient, and time- and labor-saving, making them a key path to achieving "zero growth" in chemical fertilizer use in agricultural production.

[0003] Slow-release fertilizers are modified through coatings or additives to align their release rate with crop nutrient requirements. Coated slow-release fertilizers, prepared by combining inorganic or polymeric materials with fertilizers, are the most widely studied and fastest-growing type of slow-release fertilizer and have become a key research focus. Coated slow-release fertilizers are based on granulated fertilizers. A coating material is evenly applied to the surface of the fertilizer particles to form a slow-release film. This film inhibits the diffusion of water molecules from the soil into the fertilizer core, slowing the release rate and achieving the desired slow-release effect, thereby improving fertilizer utilization.

[0004] However, traditional coating materials are mostly petroleum-based polymers (such as polyolefins and epoxy resins). Although they have good controlled-release effects, they are expensive and difficult to degrade. Long-term use can cause serious "white pollution" and damage soil structure. To address the environmental problems caused by traditional coating materials, researchers have begun to explore renewable and degradable bio-based materials as coating substances in recent years. Bio-based materials are derived from natural resources such as starch, cellulose, and chitosan, and have good biodegradability and environmental friendliness. By physically or chemically modifying these natural materials, their mechanical properties, thermal stability, and hydrophobicity can be improved, thereby meeting the performance requirements of coated slow-release fertilizers.

[0005] For example, Chinese patent application CN202110483089.1 discloses a bio-based polymer coating material, a coated controlled-release fertilizer, and a preparation method thereof. The bio-based polymer coating material is formulated according to the following weight percentages: 50-70% hydroxyl-containing component and 30-50% isocyanate MDI; the hydroxyl-containing component is composed of 50-90% hydroxyl-terminated prepolymer, 2-10% additive, 7-50% polyol, and 1-10% small molecule chain extender; the hydroxyl-terminated prepolymer is prepared by reacting 80-100% biomass liquefaction product with 0-20% isocyanate MDI. The bio-based polymer coated controlled-release fertilizer consists of a core and a membrane shell.

[0006] Although it uses biomass prepared from corn starch, potato starch, wheat starch, sweet potato starch, green bean starch, corn straw, corn cob, rice straw, wheat straw, peanut shell and cotton straw, etc. as raw materials. However, there are still some deficiencies in practical application. For example, still use a variety of organic raw materials, the problem of soil pollution has not been effectively solved. At the same time, in the slow-release performance of fertilizer, although the use of bio-based materials can achieve slow release of nutrients to some extent, but the stability and durability of the release rate need to be further improved to better meet the nutrient needs of crops in the whole growth cycle. In addition, the degradation rate of this coating material in the soil may be affected by many factors, such as soil pH, temperature, humidity, and microorganism species and quantity, etc. If it degrades too fast, it may affect the slow-release effect of the fertilizer; if it degrades too slowly, it may have potential impact on the soil environment. Therefore, it is necessary to further research and improve the existing modified bio-based coated controlled-release fertilizer and its preparation method. SUMMARY

[0007] The present application provides a novel bio-based coated controlled-release fertilizer and its preparation method to solve the problems in the prior art.

[0008] The fertilizer uses modified bio-based materials as the coating layer, which not only significantly improves the slow-release performance of the fertilizer, but also effectively solves the environmental pollution problem caused by traditional petroleum-based polymer coating materials. The core innovation lies in the chemical modification of natural biomass materials, which improves the mechanical strength and water resistance of the coating material, while retaining good biodegradability. In addition, the fertilizer shows higher stability and controllability in nutrient release rate.

[0009] Another advantage of the present application is that the preparation process is simple and environmentally friendly, the raw materials are widely available, the cost is relatively low, and it is suitable for large-scale production. Through efficient utilization of agricultural waste such as pineapple leaves, not only the resource recycling is realized, but also the environmental pressure of waste is reduced. Compared with the prior art, the degradation rate of the fertilizer in the soil is more balanced, which can ensure the slow-release effect while avoiding potential damage to the soil structure.

[0010] To achieve the above technical purposes, the technical scheme adopted by the present application is: A modified bio-based coated controlled-release fertilizer, which comprises a coating made of modified bio-based coating material and a fertilizer core composed of organic and inorganic nutrients.

[0011] Further, the fertilizer core composed of organic and inorganic nutrient substances comprises the following components in parts by weight: fermented livestock and poultry manure 30-52 parts, urea 15-25 parts, diammonium phosphate 8-15 parts, potassium chloride 5-10 parts, humic acid 5-8 parts, trace element additive 2-4 parts.

[0012] Further, the trace element additive comprises one or more of iron, zinc, boron, molybdenum, copper and manganese, and exists in the form of oxide or sulfate.

[0013] Further, the preparation method of the fermented livestock and poultry manure is as follows: mixing livestock and poultry manure with straw powder at a weight ratio of 3:1, adding EM bacterial agent accounting for 2% of the mass of the mixture, and carrying out fermentation at a temperature of 35-40℃ for 15-20 days, followed by drying, crushing and sieving to obtain the fermented livestock and poultry manure, which is brownish-brown powder, has a water content of less than 15% and an organic matter content of greater than 45%.

[0014] A preparation method of a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) preparing fermented livestock and poultry manure: (2) preparing a fertilizer core composed of organic and inorganic nutrient substances: uniformly mixing fermented livestock and poultry manure with urea, diammonium phosphate, potassium chloride, humic acid and trace element additive in proportion, and then granulating, drying and sieving to obtain a fertilizer core with uniform particle size; (3) preparing a modified bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean and dry, then crush the pineapple leaves into fiber powder with a crusher; b. Then, mix 60-80g of fiber powder, 30-40g of ethylene glycol and 360-380g of polyethylene glycol with 10-12g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected with a condensing device; continuously stir at a speed of 800-1000 r / min for 2-4h at 160-170℃, and finally cool to ambient temperature, filter to remove solid unreacted substances, and vacuum evaporate to remove excess water to obtain liquefied pineapple leaf-based biomass; c. Mix palm oil and organosiloxane at a mass ratio of 1:1 to obtain a composite modifier, then uniformly mix the composite modifier with the liquefied pineapple leaf-based biomass in a high-speed mixer, add isocyanate MDI, and react at 80-85℃ for 3 hours to form a modified bio-based coating material; (4) Place the prepared fertilizer core in a coating device, uniformly spray the modified bio-based coating material on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer, and obtain the modified bio-based coated controlled-release fertilizer after cooling.

[0015] In the preparation of the modified bio-based coating material, the abandoned pineapple leaves are used as raw materials, and the acid catalysis is used to make the polysaccharides, lignin and other high molecular components in the pineapple leaf fibers degrade and alcoholysis, so as to form liquefied pineapple leaf-based biomass with relatively small molecular weight and certain fluidity. Subsequently, palm oil and organosiloxane are mixed in a mass ratio of 1:1 to obtain a composite modifier. The palm oil contains unsaturated fatty acids and other components, and the organosiloxane contains siloxane bonds and other special structures. After mixing, a variety of functional groups can be introduced for subsequent reactions. The -NCO groups in the added isocyanate MDI have high reactivity, which can react with the hydroxyl groups (-OH) in the liquefied pineapple leaf-based biomass, the active groups (such as silanol groups) provided by the organosiloxane in the composite modifier, and other chemical bonds such as urethane bonds are formed, and crosslinking reaction occurs. This crosslinking reaction makes the originally relatively independent molecular chains connected with each other to form a three-dimensional network structure, thereby improving the strength, toughness and other properties of the material, and finally forming a modified bio-based coating material with certain performance.

[0016] Further, the mass ratio of the composite modifier, the liquefied pineapple leaf-based biomass and the isocyanate MDI is 1:1.5:0.8.

[0017] Further, the organosiloxane in the composite modifier is vinyl hydroxyl silicone oil, and the viscosity is 25-40 mPa·s.

[0018] Further, in the coating process, the spraying amount of the coating material is controlled to be 3%-5% of the mass of the fertilizer core, so as to ensure that a coating layer with uniform thickness and dense structure is formed.

[0019] Advantages (1) The fertilizer core of the present application is based on fermented livestock and poultry manure, and is compounded with inorganic nitrogen, phosphorus and potassium, humic acid and trace elements. It not only provides comprehensive nutrients combining quick-acting and slow-acting, but also effectively improves the soil aggregate structure, enhances the soil water and fertilizer retention capacity and microbial activity, realizes the combination of "fertilization" and "soil improvement", and provides persistent and effective nutrient substances for crops, thereby improving the fertilization efficiency.

[0020] (2) Using pineapple leaf liquefaction product as a bio-based main body, combined with palm oil + organic silane composite modifier to prepare a coating material. The introduction of organosiloxane significantly enhances the hydrophobicity, thermal stability and mechanical strength of the coating material, so that it can withstand the mechanical stress in the coating process and the soil environment. Palm oil provides excellent flexibility to prevent the coating from cracking. The synergistic effect of the two overcomes the defects of single bio-based material such as poor film forming property and easy cracking, and realizes the ideal balance of strength and toughness, controlled release and degradation. Through the composite modification of palm oil and organosiloxane, a coating layer with dense structure, strong hydrophobicity and moderate crosslinking degree is constructed. The coating can effectively regulate the water infiltration rate in the soil and the nutrient diffusion rate outward, so that the release curve of fertilizer nutrients is more consistent with the nutrient demand of crops in different growth stages, significantly improves the nutrient utilization rate, reduces the frequency and total amount of fertilization, and reduces the cost of agricultural production.

[0021] (3) In addition, this modified bio-based coating material can degrade at a more balanced rate in the soil, avoiding adverse effects on the soil environment due to excessive or insufficient degradation. In practical application, this fertilizer not only significantly reduces nutrient loss, but also reduces the frequency of fertilization, reducing the labor intensity of farmers. At the same time, since the raw materials are mainly derived from agricultural waste and renewable resources, the production cost is greatly reduced, and the preparation process is green and environmentally friendly, without harmful by-products.

[0022] (4) In summary, through the efficient use of pineapple leaves and other agricultural wastes, the present application realizes the resource utilization of waste, reduces environmental pollution problems caused by burning or landfill, and helps to improve the rural ecological environment. Combined with its excellent slow-release performance and environmental protection characteristics, this fertilizer is especially suitable for economic crop planting areas that require long-term stable fertilizer supply, such as orchards, tea gardens and facility agriculture, etc., and has a broad market prospect and promotion value. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Fertilizer particle sample diagram obtained by the present application example 1; Figure 2 Rape planting experiment effect diagram; Figure 3 Rape total nitrogen content of different treatment groups; Figure 4 Rape total phosphorus content of different treatment groups; Figure 5 Rape total potassium content of different treatment groups. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be further described below in conjunction with specific examples, but are not limited thereto.

[0025] Example 1 A modified bio-based coated controlled-release fertilizer, which comprises a coated layer made of a modified bio-based coating material and a fertilizer core composed of organic-inorganic nutrient substances.

[0026] The fertilizer core composed of organic-inorganic nutrient substances comprises the following components in parts by weight: fermented livestock and poultry manure 30 parts, urea 15 parts, diammonium phosphate 8 parts, potassium chloride 5 parts, humic acid 5 parts, trace element additive 2 parts.

[0027] The trace element additive comprises iron, zinc, boron, molybdenum, copper and manganese, and exists in the form of oxide or sulfate.

[0028] The preparation method of the fermented livestock and poultry manure is as follows: livestock and poultry manure is mixed with straw powder at a weight ratio of 3:1, EM bacterial agent is added in an amount of 2% of the mass of the mixture, and fermentation is carried out at a temperature of 35-40℃ for 15 days, followed by drying, crushing and sieving to obtain the fermented livestock and poultry manure, which is in the form of brownish red powder, has a water content of less than 15% and an organic matter content of greater than 45%. The EM bacterial agent can be a commercially available bacterial agent, and the EM bacterial agent used in the present application is produced by Weifang Yihao Biotechnology Co., Ltd.

[0029] A preparation method of a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) preparing fermented livestock and poultry manure: (2) preparing a fertilizer core composed of organic-inorganic nutrient substances: fermenting livestock and poultry manure is uniformly mixed with urea, diammonium phosphate, potassium chloride, humic acid and trace element additive in proportion, and then granulated, dried and sieved to obtain a fertilizer core with uniform particle size; (3) preparing a modified bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean and dry, then crush the pineapple leaves into fiber powder with a crusher; b. Then, fiber powder 60g, ethylene glycol 30g and polyethylene glycol 360g are reacted with concentrated sulfuric acid 10g as a catalyst in a three-necked round-bottom flask connected with a condensing device; the reaction is continuously stirred at a speed of 800-1000 r / min for 2h at 160-170℃, and finally cooled to ambient temperature, filtered to remove solid unreacted substances, and vacuum evaporated to remove excess water to obtain liquefied pineapple leaf-based biomass; c. Palm oil and organosiloxane are mixed in a mass ratio of 1:1 to obtain a composite modifier, and then the composite modifier is uniformly mixed with the liquefied pineapple leaf-based biomass in a high-speed mixer, isocyanate MDI is added, and the reaction is carried out at 80-85℃ for 3 hours to form a modified bio-based coating material; (4) Put the prepared fertilizer core into the coating equipment, and uniformly spray the modified bio-based coating material on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80 DEG C to form a complete and dense coating layer, and the modified bio-based coated controlled-release fertilizer is obtained after cooling.

[0030] The mass ratio of the composite modifier, liquefied pineapple leaf-based biomass and isocyanate MDI is 1:1.5:0.8.

[0031] The organosiloxane in the composite modifier is vinyl hydroxyl silicone oil, and the viscosity is 25-40 mPa s.

[0032] In the coating process, the spraying amount of the coating material is controlled to be 3% of the mass of the fertilizer core to ensure that a coating layer with uniform thickness and dense structure is formed.

[0033] Example 2 A modified bio-based coated controlled-release fertilizer, which comprises a coating made of a modified bio-based coating material and a fertilizer core composed of organic and inorganic nutrients.

[0034] The fertilizer core composed of organic and inorganic nutrients comprises the following components in parts by weight: fermented livestock and poultry manure 35 parts, urea 18 parts, diammonium phosphate 10 parts, potassium chloride 7 parts, humic acid 6 parts, trace element additive 3 parts.

[0035] The trace element additive comprises iron, zinc, boron, molybdenum, copper and manganese, and exists in the form of oxide or sulfate.

[0036] The preparation method of the fermented livestock and poultry manure is as follows: the livestock and poultry manure is mixed with straw powder at a weight ratio of 3:1, EM bacterial agent is added in an amount of 2% of the mass of the mixture, and fermentation is carried out at a temperature of 35-40 DEG C for 15 days, followed by drying, crushing and sieving to obtain the fermented livestock and poultry manure, which is brownish-brown powder, has a water content of less than 15% and an organic matter content of more than 45%.

[0037] A preparation method of a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) Preparation of fermented livestock and poultry manure: (2) Preparation of a fertilizer core composed of organic and inorganic nutrients: the fermented livestock and poultry manure is uniformly mixed with urea, diammonium phosphate, potassium chloride, humic acid and trace element additive in proportion, and then granulated, dried and sieved to obtain a fertilizer core with uniform particle size; (3) Preparation of a modified bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean and dry them, then crush the pineapple leaves into fiber powder with a crusher; b. Then the fiber powder 70g, ethylene glycol 35g and polyethylene glycol 370g were reacted with concentrated sulfuric acid 11g as catalyst in a three-necked round-bottom flask connected with a condenser; the reaction was continuously stirred at 800-1000 r / min for 3h at 160-170℃, and finally cooled to ambient temperature, the solid unreacted material was removed by filtration, and the excess water was removed by vacuum evaporation to obtain liquefied pineapple leaf-based biomass; c. The palm oil and organosiloxane were mixed in a mass ratio of 1:1 to obtain a composite modifier, and then the composite modifier was uniformly mixed with the liquefied pineapple leaf-based biomass in a high-speed mixer, isocyanate MDI was added, and the reaction was carried out at 80-85℃ for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core was placed in a coating device, and the modified bio-based coating material was uniformly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer, and the modified bio-based coated controlled-release fertilizer was obtained after cooling.

[0038] The mass ratio of the composite modifier, the liquefied pineapple leaf-based biomass and the isocyanate MDI is 1:1.5:0.8.

[0039] The organosiloxane in the composite modifier is vinyl hydroxyl silicone oil with a viscosity of 25-40 mPa·s.

[0040] In the coating process, the spraying amount of the coating material is controlled to be 4% of the mass of the fertilizer core to ensure the formation of a coating layer with uniform thickness and dense structure.

[0041] Example 3 A modified bio-based coated controlled-release fertilizer, which comprises a coating made of a modified bio-based coating material and a fertilizer core composed of organic and inorganic nutrients.

[0042] The fertilizer core composed of organic and inorganic nutrients comprises the following components by weight: fermented livestock and poultry manure 40 parts, urea 20 parts, diammonium phosphate 12 parts, potassium chloride 8 parts, humic acid 7 parts, and trace element additive 3 parts.

[0043] The trace element additive includes iron, zinc, boron, molybdenum, copper and manganese, and exists in the form of oxide or sulfate.

[0044] The preparation method of the fermented livestock and poultry manure is as follows: livestock and poultry manure is mixed with straw powder at a weight ratio of 3:1, EM bacterial agent is added in an amount of 2% of the mass of the mixture, and fermentation is carried out at a temperature of 35-40℃ for 20 days, followed by drying, crushing and sieving to obtain the fermented livestock and poultry manure. The fermented livestock and poultry manure is brownish-brown powder with a water content of less than 15% and an organic matter content of more than 45%.

[0045] A preparation method of a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) preparing fermented livestock and poultry manure: (2) preparing a fertilizer core composed of organic and inorganic nutrients: uniformly mixing fermented livestock and poultry manure with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in proportion, and then granulating, drying and screening to obtain a fertilizer core with uniform particle size; (3) preparing a modified bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean and dry them, then crush the pineapple leaves into fiber powder with a pulverizer; b. Then, 80g of fiber powder, 40g of ethylene glycol and 380g of polyethylene glycol are reacted with 12g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected to a condensing device; the reaction is continuously stirred at 800-1000 r / min for 2h at 160-170℃, and finally cooled to ambient temperature, filtered to remove solid unreacted substances, and vacuum evaporated to remove excess water to obtain liquefied pineapple leaf-based biomass; c. Mixing palm oil and organosiloxane at a mass ratio of 1:1 to obtain a composite modifier, then uniformly mixing the composite modifier with the liquefied pineapple leaf-based biomass in a high-speed mixer, adding isocyanate MDI, and reacting at 80-85℃ for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core is placed in a coating device, and the modified bio-based coating material is uniformly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer, and the modified bio-based coated controlled-release fertilizer is obtained after cooling.

[0046] The mass ratio of the composite modifier, liquefied pineapple leaf-based biomass and isocyanate MDI is 1:1.5:0.8.

[0047] The organosiloxane in the composite modifier is vinyl hydroxy silicone oil with a viscosity of 25-40 mPa·s.

[0048] During the coating process, the spraying amount of the coating material is controlled to be 4% of the mass of the fertilizer core to ensure the formation of a coating layer with uniform thickness and dense structure.

[0049] Example 4 A modified bio-based coated controlled-release fertilizer, which comprises a coating made of a modified bio-based coating material and a fertilizer core composed of organic and inorganic nutrients.

[0050] The fertilizer core composed of organic and inorganic nutrients includes the following components by weight: fermented livestock and poultry manure 52 parts, urea 25 parts, diammonium phosphate 15 parts, potassium chloride 10 parts, humic acid 8 parts, and trace element additives 4 parts.

[0051] The trace element additive includes iron, zinc, boron, molybdenum, copper and manganese, and exists in the form of oxide or sulfate.

[0052] The preparation method of the fermented livestock and poultry manure is as follows: the livestock and poultry manure is mixed with straw powder at a weight ratio of 3:1, 2% of EM microbial agent is added to the mixture, and fermentation is carried out at a temperature of 35-40℃ for 20 days, followed by drying, crushing and sieving to obtain the fermented livestock and poultry manure, which is brown and powdery, has a water content of less than 15% and an organic matter content of more than 45%.

[0053] A preparation method of a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) preparing fermented livestock and poultry manure: (2) preparing a fertilizer core composed of organic and inorganic nutrients: the fermented livestock and poultry manure is uniformly mixed with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in proportion, and then granulated, dried and sieved to obtain a fertilizer core with uniform particle size; (3) preparing a modified bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean and dry them, then crush the pineapple leaves into fiber powder with a crusher; b. Then, 80g of the fiber powder, 40g of ethylene glycol and 380g of polyethylene glycol are reacted with 12g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected to a condensing device; the reaction is carried out at 160-170℃ with continuous stirring at a speed of 800-1000 r / min for 4h, and finally cooled to ambient temperature, filtered to remove solid unreacted substances, and vacuum evaporated to remove excess water to obtain liquefied pineapple leaf-based biomass; c. The palm oil and organosiloxane are mixed at a mass ratio of 1:1 to obtain a composite modifier, and then the composite modifier is uniformly mixed with the liquefied pineapple leaf-based biomass in a high-speed mixer, and isocyanate MDI is added, and the reaction is carried out at 80-85℃ for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core is placed in a coating device, and the modified bio-based coating material is uniformly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer, and the modified bio-based coated controlled-release fertilizer is obtained after cooling.

[0054] The mass ratio of the composite modifier, the liquefied pineapple leaf-based biomass and the isocyanate MDI is 1:1.5:0.8.

[0055] The organosiloxane in the composite modifier is vinyl hydroxyl silicone oil with a viscosity of 25-40 mPa·s.

[0056] In the process of coating, the spraying amount of the coating material is controlled to be 5% of the mass of the fertilizer core to ensure the formation of a uniform-thickness and dense-structure coating layer.

[0057] Comparative Example 1 In this comparative example, the steps and raw materials are the same as those in Example 1 except that the composite modifier is not used. A bio-based coated controlled-release fertilizer, which comprises a coating made of bio-based coating material and a fertilizer core composed of organic and inorganic nutrients.

[0058] A method for preparing a bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) Preparation of fermented livestock manure: (2) Preparation of a fertilizer core composed of organic and inorganic nutrients: the fermented livestock manure is uniformly mixed with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in proportion, and then granulated, dried and sieved to obtain a fertilizer core with uniform particle size; (3) Preparation of bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean and dry, then crush the pineapple leaves into fiber powder with a pulverizer; b. Then, 60 g of fiber powder, 30 g of ethylene glycol and 360 g of polyethylene glycol are reacted with 10 g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected to a condensing device; the reaction is carried out at 160-170℃ with continuous stirring at a speed of 800-1000 r / min for 2h, and finally cooled to ambient temperature, filtered to remove solid unreacted substances, and vacuum evaporated to remove excess water to obtain liquefied pineapple leaf-based biomass; c. The liquefied pineapple leaf-based biomass is placed in a high-speed mixer and isocyanate MDI is added, and the reaction is carried out at 80-85℃ for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core is placed in a coating device, and the bio-based coating material is uniformly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer, and the bio-based coated controlled-release fertilizer is obtained after cooling.

[0059] The mass ratio of liquefied pineapple leaf-based biomass to isocyanate MDI is 1.5:0.8.

[0060] In the process of coating, the spraying amount of the coating material is controlled to be 5% of the mass of the fertilizer core to ensure the formation of a uniform-thickness and dense-structure coating layer.

[0061] Comparative Example 2 In this comparative example, the steps and raw materials are the same as those in Example 1 except that the composite modifier is not used. A method for preparing a modified bio-based coated controlled-release fertilizer comprises the following steps: (1) Preparation of fermented livestock and poultry feces: (2) preparing a fertilizer core composed of organic and inorganic nutrients: mixing fermented livestock and poultry manure with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in a proportion, followed by granulation, drying and sieving to obtain a fertilizer core with uniform particle size; (3) Preparation of modified bio-based coating materials: a. First, collect the discarded pineapple leaves, clean them and dry them, then use a grinder to crush the pineapple leaves into fiber powder; b. Then 60g of fiber powder, 30g of ethylene glycol and 360g of polyethylene glycol were reacted with 10g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected to a condensing apparatus; the reaction was stirred continuously at a speed of 800-1000 r / min for 2h at 160-170 ° C, and finally cooled to ambient temperature, the solid unreacted material was filtered out, and the excess water was evaporated in vacuo to obtain liquefied pineapple leaf-based biomass; c. The palm oil and liquefied pineapple leaf-based biomass were uniformly mixed in a high-speed mixer, and isocyanate MDI was added and reacted at 80-85°C for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core is placed in a coating device, and the modified bio-based coating material is evenly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80 ° C to form a complete and dense coating layer. After cooling, the modified bio-based coated controlled-release fertilizer is obtained.

[0062] The mass ratio of palm oil, liquefied pineapple leaf-based biomass and isocyanate MDI is 1:1.5:0.8.

[0063] Comparative Example 3 In this comparative example, except that only organosiloxane was used as the composite modifier, the remaining steps and raw materials were the same as those in Example 1. A method for preparing a modified bio-based coated controlled-release fertilizer comprises the following steps: (1) Preparation of fermented livestock and poultry feces: (2) preparing a fertilizer core composed of organic and inorganic nutrients: mixing fermented livestock and poultry manure with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in a proportion, followed by granulation, drying and sieving to obtain a fertilizer core with uniform particle size; (3) Preparation of modified bio-based coating materials: a. First, collect the discarded pineapple leaves, clean them and dry them, then use a grinder to crush the pineapple leaves into fiber powder; b. Then the fiber powder 60g, ethylene glycol 30g and polyethylene glycol 360g were reacted with concentrated sulfuric acid 10g as catalyst in a three-necked round-bottom flask connected with a condensing device; the reaction was continuously stirred at 800-1000 r / min for 2h at 160-170℃, and finally cooled to ambient temperature, the solid unreacted material was removed by filtration, and the excess water was removed by vacuum evaporation to obtain liquefied pineapple leaf-based biomass; c. The organosiloxane and the liquefied pineapple leaf-based biomass were uniformly mixed in a high-speed mixer, isocyanate MDI was added, and the mixture was reacted at 80-85℃ for 3h to form a modified bio-based coating material; (4) The prepared fertilizer core was placed in a coating device, and the modified bio-based coating material was uniformly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer. After cooling, a modified bio-based coated controlled-release fertilizer was obtained.

[0064] The mass ratio of organosiloxane, liquefied pineapple leaf-based biomass and isocyanate MDI was 1:1.5:0.8.

[0065] The organosiloxane in the composite modifier was vinyl hydroxy silicone oil with a viscosity of 25-40 mPa·s.

[0066] Comparative Example 4 In this comparative example, the composition ratio of palm oil and organosiloxane in the composite modifier was changed, and the remaining steps and raw materials were the same as in Example 1. That is: A method for preparing a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) Preparation of fermented livestock and poultry manure: (2) Preparation of a fertilizer core composed of organic and inorganic nutrients: The fermented livestock and poultry manure was uniformly mixed with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in proportion, and then granulated, dried and sieved to obtain a fertilizer core with uniform particle size; (3) Preparation of a modified bio-based coating material: a. First, the discarded pineapple leaves were collected, washed and dried, and then crushed into fiber powder using a crusher; b. Then the fiber powder 60g, ethylene glycol 30g and polyethylene glycol 360g were reacted with concentrated sulfuric acid 10g as catalyst in a three-necked round-bottom flask connected with a condensing device; the reaction was continuously stirred at 800-1000 r / min for 2h at 160-170℃, and finally cooled to ambient temperature, the solid unreacted material was removed by filtration, and the excess water was removed by vacuum evaporation to obtain liquefied pineapple leaf-based biomass; c. The palm oil and organosiloxane are mixed in a mass ratio of 2:1 to obtain a composite modifier, which is then uniformly mixed with the liquefied pineapple leaf-based biomass in a high-speed mixer, isocyanate MDI is added, and the mixture is reacted at 80-85°C for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core is placed in a coating device, the modified bio-based coating material is uniformly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80°C to form a complete and dense coating layer, and the modified bio-based coated controlled-release fertilizer is obtained after cooling.

[0067] The mass ratio of the composite modifier, the liquefied pineapple leaf-based biomass, and isocyanate MDI is 1:1.5:0.8.

[0068] The organosiloxane in the composite modifier is vinyl hydroxyl silicone oil with a viscosity of 25-40 mPa·s.

[0069] Comparative Example 5 In this comparative example, the composition ratio of palm oil and organosiloxane in the composite modifier is changed, and the remaining steps and raw materials are the same as in Example 1. That is: A method for preparing a modified bio-based coated controlled-release fertilizer, comprising the following preparation steps: (1) Preparation of fermented livestock manure: (2) Preparation of a fertilizer core composed of organic and inorganic nutrients: The fermented livestock manure is uniformly mixed with urea, diammonium phosphate, potassium chloride, humic acid, and trace element additives in a certain proportion, and then granulated, dried, and sieved to obtain a fertilizer core with uniform particle size; (3) Preparation of a modified bio-based coating material: a. First, collect discarded pineapple leaves, wash them clean, and dry them, then use a pulverizer to pulverize the pineapple leaves into fiber powder; b. Then, 60 g of fiber powder, 30 g of ethylene glycol, and 360 g of polyethylene glycol are mixed with 10 g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected to a condensing device; the reaction is carried out at 160-170°C with continuous stirring at a speed of 800-1000 r / min for 2h, and finally cooled to ambient temperature, filtered to remove solid unreacted substances, and vacuum evaporated to remove excess water to obtain liquefied pineapple leaf-based biomass; c. The palm oil and organosiloxane are mixed in a mass ratio of 2:1 to obtain a composite modifier, which is then uniformly mixed with the liquefied pineapple leaf-based biomass in a high-speed mixer, isocyanate MDI is added, and the mixture is reacted at 80-85°C for 3 hours to form a modified bio-based coating material; (4) Put the prepared fertilizer core into the coating equipment, and uniformly spray the modified bio-based coating material on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80℃ to form a complete and dense coating layer, and the modified bio-based coated controlled-release fertilizer is obtained after cooling.

[0070] The mass ratio of the composite modifier, liquefied pineapple leaf-based biomass and isocyanate MDI is 1:1.5:0.8.

[0071] The organosiloxane in the composite modifier is vinyl hydroxyl silicone oil, and the viscosity is 25-40 mPa·s.

[0072] Comparative Example 6 In this comparative example, the steps and raw materials are the same as those in Example 1 except that the coating material is a traditional slow-release material. A coated controlled-release fertilizer, which comprises a coated liquid and a fertilizer core composed of organic and inorganic nutrients.

[0073] The coating liquid used is prepared by heating epoxy resin to 80-95℃, adding the curing agent in a weight ratio of 8:2-4, and mixing uniformly.

[0074] The fertilizer core composed of organic and inorganic nutrients comprises the following components in parts by weight: fermented livestock and poultry manure 30 parts, urea 15 parts, diammonium phosphate 8 parts, potassium chloride 5 parts, humic acid 5 parts, trace element additive 2 parts.

[0075] A preparation method of a coated controlled-release fertilizer, comprising the following preparation steps: (1) Preparation of fermented livestock and poultry manure: (2) Preparation of a fertilizer core composed of organic and inorganic nutrients: uniformly mix fermented livestock and poultry manure with urea, diammonium phosphate, potassium chloride, humic acid and trace element additive in proportion, and then granulate, dry and sieve to obtain a fertilizer core with uniform particle size; (3) Put the prepared fertilizer core into the coating equipment, preheat in a rotating drum at 60℃ and 40 rmp for 15 minutes, raise the temperature to 70-90℃, and repeatedly add the coating liquid to the surface of the rolling urea particles, and obtain the controlled-release fertilizer after curing, with a curing time of 10-30 min.

[0076] In the coating process, the spraying amount of the coating liquid is controlled to be 3% of the mass of the fertilizer core to ensure the formation of a coating layer with uniform thickness and dense structure.

[0077] Performance test The preparation of the film coating material was carried out according to the method of the embodiment and the comparative example of the present application, and the physical and chemical properties of the film coating material were tested after curing. The specific method is as follows: after the film coating liquid is prepared, a uniform thin film is scraped on a glass plate, and it is placed in an oven for heating and curing.

[0078] Water absorption rate test of film coating material: prepare three kinds of film shell materials with a certain size (2 cm x 2 cm x 0.5 mm) and place them in 300 mL deionized water. After incubation at ambient temperature of 25°C for 24 h, the film shell was taken out and the excess water on the surface of the film shell was removed with absorbent paper. The weight of each water-swollen film shell was recorded. Each treatment was repeated three times. The calculation formula is as follows: Water absorption rate = wherein W1 is the dry film shell weight, and W2 is the water-swollen film shell weight.

[0079] Contact angle measurement: the water contact angle (WCA) of all samples was determined using a JC2000C1 contact angle meter (China, POWEREACH). Three repeated measurements were performed at room temperature using a drop of water (5 μL), and the average contact angle was determined.

[0080] The microstructure of the film material was observed using a scanning electron microscope (Hitachi Regulus 8100 field).

[0081] Degradation rate determination of film material: The prepared film layer of the film coating material was cut into 20 x 20 mm square pieces, accurately weighed using an electronic balance, and the weight was recorded as M0. The sample was placed in an 80-mesh 100 x 100 mm nylon mesh bag, the bag opening was tightly tied, and the label was attached. The sample was buried in soil with a depth of 20 cm, and three replicates were set for each group. The experimental site was the soil of the Stanley Agricultural Group Planting Demonstration Garden, and the experimental period was from April to June 2024. Samples were taken at 30 d and 200 d, and the soil on the surface of the film material was washed clean with ultrapure water. The sample was dried in a 40°C oven, and the weight was recorded as M1. The degradation rate (D) was calculated according to the following formula: Degradation rate (D) = (M0 - M1) / M0 x 100%.

[0082] Table 1: Test results of physical and chemical properties of film material From the experimental data in Table 1, it can be seen that the film materials prepared by the embodiments (1-4) of the present application are excellent in all aspects, and have low water absorption, indicating that by compounding and modifying palm oil and organosiloxane at a ratio of 1:1, film materials with high mechanical strength, wear resistance and good hydrophobicity are successfully obtained, which can meet the requirements of film-coated fertilizer processing and use. The degradation rates of the film materials are all less than 20% at 30 days, indicating that they can maintain structural integrity in the early stage of crop growth and effectively play a controlled release role. At 200 days, the degradation rates of the film materials of the present application all reach more than 85%, showing good final biodegradability.

[0083] The comparative examples 1-6 change the film materials, and the properties of all of them decrease to different degrees. In comparative example 1, no compounding modifier is used, the water absorption is as high as 45.6%, and the degradation is too fast, with a degradation rate of 30.6% at 30 days. In comparative example 2, only palm oil is used as a modifier, and the material properties are improved compared with comparative example 1. In comparative example 3, organosiloxane is used as the only modifier, although the contact angle is increased to 105°, showing a certain degree of hydrophobicity, but the water absorption is as high as 20.1%, and the degradation rate at 200 days is only 58.5%, which is far lower than that of the embodiment group. Comparative examples 4 and 5 adjust the ratio of palm oil to organosiloxane, but neither of them achieves the ideal effect. This further verifies the importance of compounding and modifying palm oil and organosiloxane at a ratio of 1:1 in a synergistic balance. Only in this ratio can the best balance of hydrophobicity, mechanical strength and degradation performance be achieved.

[0084] Comparative example 6 uses traditional slow-release material epoxy resin for film coating, and its water absorption is the lowest, only 10.1%, and the contact angle reaches 115°, showing excellent hydrophobicity. However, in terms of degradation performance, the data of this group is obviously abnormal, with a degradation rate of only 0.3% at 30 days and 1.5% at 200 days. This shows that traditional materials are difficult to achieve environmental-friendly degradation while ensuring the controlled release effect, and long-term residues may pose a potential threat to soil ecology.

[0085] Fertilizer particle performance test: According to the embodiments and comparative examples, fertilizers are prepared. The particle compression strength and wear resistance of the coated fertilizers are determined by the determination method in the national standard GB / T23348-2009 for slow-release fertilizers.

[0086] Nutrient release determination: According to the national standard for slow-release fertilizers, the initial nutrient release rate refers to the cumulative nutrient release amount after the fertilizer sample is soaked for 24 hours. The cumulative nutrient release period of the fertilizer refers to the date corresponding to 80% cumulative nutrient release. The experiment is set in triplicate.

[0087] Table 2: Test results of fertilizer particle performance From the data in Table 2, we can see that the fertilizer particles prepared in Examples 1-4 all exhibit excellent performance in terms of compressive strength, wear resistance, and nutrient release control. Their compressive strength all exceeds 25N, and the mass loss rate is less than 1.2%, indicating that the particles have good mechanical strength and wear resistance, which can meet the requirements of modern agricultural mechanization fertilization. The initial nutrient release rate is controlled at about 10%, and the nutrient release period reaches 58-62 days, showing an ideal slow-release effect.

[0088] In contrast, the performance of the fertilizer particles in Comparative Examples 1-6 all shows different degrees of decline. In Comparative Example 1, the composite modified coating material is not used, resulting in a particle compressive strength of only 13.5N, poor wear resistance, a mass loss rate of up to 3.8%, and too fast nutrient release, with an initial release rate of 28.7% and a release period of only 32 days. Although Comparative Example 2 is improved by single palm oil modification, the various indicators are still significantly lower than those of the example group. In Comparative Example 3, organosiloxane is used as the only modifier, although the initial nutrient release rate is reduced, the release period is still too short.

[0089] Comparative Examples 4 and 5 have improved performance by adjusting the ratio of palm oil to organosiloxane, but still cannot reach the level of the example group. This again verifies the necessity of composite modification of palm oil and organosiloxane at a ratio of 1:1. Comparative Example 6 uses traditional epoxy resin coating material, although the mechanical properties are good, the mass loss rate is high, and there is an environmental friendliness problem, which is difficult to meet the requirements of modern agricultural sustainable development.

[0090] Planting experiment: Experimental site: The experiment was conducted in the Stanley Agricultural Demonstration Zone in Linyi City, Shandong Province, typical sandy soil was selected, and the test crop was rape.

[0091] Test soil: The test soil is sandy soil, after passing through a 2mm aperture sieve, half of the soil is weighed and placed in a No. 10 self-sealing bag, then the weighed test fertilizer is added, the fertilizer dosage is 30g per pot. The other half of the soil is weighed and placed in a plastic pot after mixing. The test pot is a plastic pot with specifications: upper diameter 21.5cm, bottom diameter 19.5cm, height 16.5cm. The soil in the pot is about 5kg. The irrigation water is tap water. Before sowing, water the soil thoroughly, sow 30 rape seeds per pot, cover with 1cm fine soil, cover with plastic film to prevent water evaporation, and space the seedlings to leave about 8. Every 3-4 days, water once. Spray pesticides and weeds about once every 3 weeks, a total of 2 times.

[0092] Experimental design: The experiment uses a completely randomized block design, a total of 7 treatments, each treatment is repeated 4 times, and the average value of all test results is taken.

[0093] CK: No fertilizer is applied, as a control group.

[0094] S1 : applying the fertilizer granules prepared in Example 1; S2: applying the fertilizer granules prepared in Comparative Example 1; S3: applying the fertilizer granules prepared in Comparative Example 2; S4: applying the fertilizer granules prepared in Comparative Example 3; S5: applying the fertilizer granules prepared in Comparative Example 4; S6: applying the fertilizer granules prepared in Comparative Example 5; S7: applying the fertilizer granules prepared in Comparative Example 6.

[0095] Test items and methods: Plant growth indicators: the plant height was measured by the distance between the stem base and the top of the rape plant using a ruler. The third true leaf of the rape was selected, and the relative chlorophyll content (SPAD) of the leaf was determined using a chlorophyll meter (SPAD-502, Minolta, Japan). The leaf area was measured using a YMJ-CHA3 leaf area meter.

[0096] Fresh and dry weights of the above-ground parts of the rape: after the rape was harvested, it was placed in an oven at 105°C for 1 hour for fixation, and then the oven was adjusted to 70°C to dry the rape to a constant weight, and the dry weight was measured.

[0097] Total nitrogen, total phosphorus, and total potassium contents of the rape: The dried above-ground parts of the rape were ground using a grinder and passed through a 60-mesh sieve. The plant samples were decomposed using a H2SO4-H2O2 combined digestion method, and then the total nitrogen was determined using a Kjeldahl nitrogen determination instrument (KDY-9820, Beijing Tongrunyuan Electromechanical Technology Co., Ltd.). The total phosphorus was determined using a vanadium-molybdenum yellow colorimetric method under a UV-visible spectrophotometer (Evolution 300, USA Thermo). The total potassium was determined using a flame spectrophotometer (M410, UK).

[0098] Total nitrogen, available phosphorus, and available potassium contents of the soil: After the rape was harvested, soil sampling was performed. Three points were taken from each pot and mixed as a sample, which was dried in the shade and then passed through a 60-mesh sieve. The total nitrogen was determined using a Kjeldahl nitrogen determination instrument (KDY-9820, Beijing Tongrunyuan Electromechanical Technology Co., Ltd.). The available phosphorus was determined using a vanadium-molybdenum yellow colorimetric method under a UV-visible spectrophotometer (Evolution 300, USA Thermo). The available potassium was determined using a flame spectrophotometer (M410, UK).

[0099] Table 2 Physiological indicators of rape Table 3 Soil indicators of different treatment groups As can be seen from Table 2-3, the fertilizers of Examples 1-4 showed significant advantages in the rape planting experiments. The plant growth indicators showed that the plant height of rape using the Example fertilizers was all more than 20 cm, 4-6 cm higher than the control group, and the chlorophyll content was maintained at about 50 mg / g, significantly higher than the 35-44 mg / g of the control group. The above-ground dry weight data showed that the dry weight of each rape plant in the Example group reached 18-20 g, indicating that the fertilizer nutrients were effectively absorbed and utilized. The total nitrogen, total phosphorus and total potassium contents of rape in different treatment groups Figures 3-5 It can also be seen that the Example fertilizers significantly improved the nutrient absorption efficiency of rape. The total nitrogen content determination results showed that the above-ground total nitrogen content of rape applying the Example fertilizers was higher than that of the control group and the control group, indicating that the slow-release characteristics could continuously provide stable nitrogen source for crops. The total phosphorus and total potassium contents also showed obvious advantages, which was closely related to the long nutrient release period of 58-62 days. In contrast, the control group had a significant nutrient supply bottleneck in the late growth period of rape due to too fast or insufficient nutrient release, affecting the absorption of phosphorus and potassium elements by crops.

[0100] The soil index data further verified the superiority of the Example fertilizers. After applying the Example fertilizers, the total nitrogen, available phosphorus and available potassium contents in the soil were maintained at a high level, and were significantly better than those of the control group. This not only shows that the Example fertilizers have good nutrient controlled-release effect, but also shows that they help to improve the soil fertility and reduce nutrient loss.

[0101] From the overall experimental results, the Example fertilizers showed excellent performance in promoting rape growth, improving nutrient utilization rate and improving soil environment. This is mainly due to the successful application of palm oil and organosiloxane at a ratio of 1:1 to modify the coating material, which achieves an ideal balance between mechanical strength, hydrophobicity and degradation characteristics. The control group lacks this balance, and the performance of plant growth, nutrient absorption and soil improvement is inferior to the Example group, further highlighting the advancement of the technical solution of the present application.

[0102] It should be noted that the above examples are only part of the preferred modes of implementing the present application, not all. Obviously, based on the above examples of the present application, all other examples obtained by a person of ordinary skill in the art without creative labor should fall within the scope of protection of the present application.

Claims

1. A modified bio-based coated controlled-release fertilizer, characterized in that: The fertilizer comprises two parts: a coating made of modified bio-based coating material and a fertilizer core composed of organic and inorganic nutrients.

2. The modified bio-based coated controlled-release fertilizer according to claim 1, characterized in that: The fertilizer core composed of organic and inorganic nutrients includes the following components in parts by weight: 30-52 parts of fermented livestock and poultry manure, 15-25 parts of urea, 8-15 parts of diammonium phosphate, 5-10 parts of potassium chloride, 5-8 parts of humic acid, and 2-4 parts of trace element additives.

3. The modified bio-based coated controlled-release fertilizer according to claim 2, characterized in that: The trace element additive includes one or more of iron, zinc, boron, molybdenum, copper and manganese, and exists in the form of oxides or sulfates.

4. The modified bio-based coated controlled-release fertilizer according to claim 2, characterized in that: The preparation method of the fermented livestock and poultry manure comprises: mixing the livestock and poultry manure with straw powder in a weight ratio of 3:1, adding 2% of the EM bacterial agent by weight of the mixture, fermenting at a temperature of 35-40°C for 15-20 days, and then drying, crushing, and sieving to obtain the fermented livestock and poultry manure. The fermented livestock and poultry manure is in a brown powdery form, has a moisture content of less than 15%, and an organic matter content of greater than 45%.

5. A method for preparing the modified bio-based coated controlled-release fertilizer according to any one of claims 1 to 4, characterized in that: The method comprises the following preparation steps: (1) Preparation of fermented livestock and poultry feces: (2) preparing a fertilizer core composed of organic and inorganic nutrients: mixing fermented livestock and poultry manure with urea, diammonium phosphate, potassium chloride, humic acid and trace element additives in a proportion, followed by granulation, drying and sieving to obtain a fertilizer core with uniform particle size; (3) Preparation of modified bio-based coating materials: a. First, collect the discarded pineapple leaves, clean them and dry them, then use a grinder to crush the pineapple leaves into fiber powder; b. Then 60-80g of fiber powder, 30-40g of ethylene glycol and 360-380g of polyethylene glycol were reacted with 10-12g of concentrated sulfuric acid as a catalyst in a three-necked round-bottom flask connected to a condensing apparatus; the reaction was stirred continuously at a speed of 800-1000 r / min for 2-4h at 160-170 ° C, and finally cooled to ambient temperature, the solid unreacted material was removed by filtration, and the excess water was evaporated in vacuo to obtain liquefied pineapple leaf-based biomass; c. Palm oil and organosiloxane were mixed in a mass ratio of 1:1 to obtain a composite modifier, and then the composite modifier was uniformly mixed with liquefied pineapple leaf-based biomass in a high-speed mixer, and isocyanate MDI was added. The mixture was reacted at 80-85°C for 3 hours to form a modified bio-based coating material; (4) The prepared fertilizer core is placed in a coating device, and the modified bio-based coating material is evenly sprayed on the surface of the fertilizer core at a rolling speed of 20-30 rpm at 60-80 ° C to form a complete and dense coating layer. After cooling, the modified bio-based coated controlled-release fertilizer is obtained.

6. The method for preparing the modified bio-based coated controlled-release fertilizer according to claim 5, characterized in that: The mass ratio of the composite modifier, liquefied pineapple leaf-based biomass and isocyanate MDI is 1:1.5:0.

8.

7. The method for preparing the modified bio-based coated controlled-release fertilizer according to claim 5, characterized in that: The organic siloxane in the composite modifier is vinyl hydroxy silicone oil with a viscosity of 25-40 mPa·s.

8. The method for preparing the modified bio-based coated controlled-release fertilizer according to claim 5, characterized in that: During the coating process, the spraying amount of the coating material is controlled to be 3%-5% of the mass of the fertilizer core to ensure the formation of a coating layer with uniform thickness and dense structure.

Images