Cow dung organic controlled-release fertilizer and preparation method thereof

Abstract

The invention provides a cow dung organic controlled-release fertilizer and a preparation method thereof. The preparation method comprises the following steps: preparing porous cow dung biochar; preparing a cow dung organic fertilizer; uniformly mixing and stirring the porous cow dung biochar, the natural fibers in the treated cow dung and the cow dung organic fertilizer, and extruding and granulating in a granulator at normal temperature; drying to obtain the composite porous cow dung biochar with the sea urchin structure; preparing a hydrogel membrane solution, soaking the composite porous cow dung biochar with the sea urchin structure in the hydrogel membrane solution, and drying to obtain the cow dung organic controlled-release fertilizer. The cow dung organic controlled-release fertilizer formed by wrapping the cellulose hydrogel film layer with the composite porous cow dung biochar with the sea urchin structure is adopted, the porous cow dung biochar retains organic matter and nutritional ingredients in cow dung, and meanwhile moisture and pathogenic microorganisms are reduced through the carbonization process; the organic fertilizer is suitable for release and utilization of long-acting nutrient substances, the cow dung organic fertilizer is slowly released and utilized firstly, and the cow dung biochar is released and utilized for a long time.

Description

Technical Field

[0001] The invention relates to the technical field of organic fertilizers, and in particular to a cow dung organic controlled-release fertilizer and a preparation method thereof. Background Art

[0002] China is a large agricultural country and the world's largest fertilizer producer and consumer. Chemical fertilizers are the largest material input in agricultural production. According to statistics from the Food and Agriculture Organization of the United Nations, chemical fertilizers account for 40-60% of the increase in yield. However, production practice shows that due to the combined effects of the properties of chemical fertilizers themselves, soil environmental conditions, and agricultural measures, the utilization rate of chemical fertilizers is very low. The waste of nutrient resources caused by the low utilization rate of fertilizer nutrients in China is very alarming. According to statistics, China produces and applies about 20 million tons of nitrogen fertilizers each year, and its utilization rate in the current season is only 30-50%, and the cumulative utilization rate is 45-60%. The direct economic losses caused by the low utilization rate of nitrogen fertilizers are equivalent to RMB 23.94 billion. How to improve the utilization rate of fertilizers, reduce environmental pollution caused by improper fertilization, and sustainable development of efficient agriculture has become a common concern of countries around the world. Since the 1970s, the development and application of controlled-release fertilizers have proposed new ideas for solving this problem. The development of controlled-release fertilizers has become a hot spot in fertilizer research around the world. According to statistics, a cow excretes about 20 kilograms of excrement a day, and the daily excretion of cow dung is as high as about 300,000 tons. The accumulation of a large amount of cow dung can easily cause environmental pollution, mainly manifested in soil pollution, water pollution and air pollution. Using cow dung as organic fertilizer not only increases its value but also reduces pollution. Summary of the invention

[0003] Technical problem to be solved: The purpose of the present invention is to provide a cow dung organic controlled-release fertilizer and a preparation method thereof, which adopts a cow dung organic controlled-release fertilizer composed of a composite porous cow dung biochar with a sea urchin structure wrapped with a cellulose hydrogel film layer. The porous cow dung biochar retains the organic matter and nutrients in the cow dung, and at the same time reduces moisture and pathogenic microorganisms through the carbonization process, which is suitable for the release and utilization of long-term nutrients. The cow dung organic fertilizer is first slowly released and utilized, and the cow dung biochar is released and utilized for a long time. At the same time, the porous structure of the cow dung biochar can also improve the soil's ability to retain water and fertilizer, promote the development of plant roots, thereby increasing crop yield and quality.

[0004] Technical solution: A cow dung organic controlled-release fertilizer, which is composed of a composite porous cow dung biochar with a sea urchin structure wrapped with a cellulose hydrogel film layer. Furthermore, the particle size of the composite porous cow dung biochar with sea urchin structure is 0.5-0.8 mm. The method for preparing the above-mentioned cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Add bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 600-700°C at a heating rate of 5-8°C / min, and pyrolyze for 1.5-2.5h under anoxic conditions; S4: cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar; S5: Take fresh cow dung, clean out the debris, screen out the natural fiber in the cow dung, wash and dry it for later use, and compost and ferment the remaining cow dung to obtain cow dung organic fertilizer; S6: taking the porous cow dung biochar, the natural fiber in the treated cow dung and the cow dung organic fertilizer, mixing them evenly, and placing them in a granulator for extrusion and granulation at room temperature; S7: after drying, a composite porous cow dung biochar with sea urchin structure was obtained; S8: taking part of the natural fibers in S5, adding deionized water, placing in a pressure reactor, reacting at 90° C. for 60 min, taking out, washing, and drying to obtain cellulose; S9: Take the ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add cellulose and mix evenly, place it in a 100℃ oil bath and stir to dissolve for 3h; S10: Add bentonite nanosheets and stir evenly; S11: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S12: taking out and vacuum freeze-drying to obtain the cow dung organic controlled-release fertilizer. Furthermore, the mass ratio of the cow dung particles to the bacterial cellulose is 100:(3-7). Furthermore, the specific composting fermentation method of the cow dung organic fertilizer is as follows: S51: taking fresh cow dung, cleaning out the debris, screening out the natural fiber in the cow dung, adjusting the moisture content of the remaining cow dung to 50-55%, adding the composite bacterial agent, turning and mixing 3-4 times, and making a fermentation pile with a height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning. The compost will ferment for 8-12 days to obtain cow dung organic fertilizer. Furthermore, the composite bacteria is composed of the following strains in parts by weight: 10-20 parts of Bacillus licheniformis, 10-20 parts of Bacillus coagulans, 10-15 parts of Streptococcus thermophilus, 5-10 parts of Trichoderma reesei, 1-6 parts of Chaetomium and 1-3 parts of lactic acid bacteria. Furthermore, the addition amount of the composite bacterial agent is 0.2-0.5wt.‰ of the cow dung after adjusting the water content. Furthermore, the mass ratio of the porous cow dung biochar, the natural fiber in the treated cow dung, and the cow dung organic fertilizer is 5:(1-2):(5-10). Furthermore, the natural fibers in the treated cow dung are processed by cutting and screening to obtain fibers with a length of 1.0-1.3 mm and a diameter of 50-130 μm. Furthermore, the mass ratio of the ionic liquid BmimCl, cellulose and bentonite nanosheets is 50:2:(2-5). Beneficial effects: 1. The present invention adopts a cow dung organic controlled-release fertilizer composed of a cellulose hydrogel film layer wrapped with a composite porous cow dung biochar with a sea urchin structure. The porous cow dung biochar retains the organic matter and nutrients in the cow dung, and reduces moisture and pathogenic microorganisms through the carbonization process, which is suitable for the release and utilization of long-term nutrients. The cow dung organic fertilizer is first slowly released and utilized, and the cow dung biochar is released and utilized for a long time. At the same time, the porous structure of the cow dung biochar can also improve the soil's ability to retain water and fertilizer, promote the development of plant roots, and thus improve the yield and quality of crops. 2. The present invention prepares composite porous cow dung biochar into a sea urchin structure, extracts fibers from cow dung, and the fiber length is greater than the particle size of the composite porous cow dung biochar. Therefore, during the granulation and drying process, the fibers are pulled out of the pellets to form a sea urchin structure. Ordinary spherical fertilizers are easily lost from the soil under conditions such as rain, while the sea urchin structure can firmly grasp the soil, improve the binding property with the soil, and is not easy to lose. At the same time, the fiber content in cow dung is high and is not easy to be fermented. After the fibers are screened out, the fermentation efficiency of the cow dung biofertilizer can be improved, killing two birds with one stone. 3. The present invention wraps a cellulose hydrogel film layer on the outside of the composite porous cow dung biochar with a sea urchin structure, which can increase the moisture content of the soil, increase the effectiveness of soil moisture, and achieve the effect of soil water retention and water release. At the same time, the entry of water can promote the dissolution of fertilizers to achieve a slow-release effect; however, the mechanical properties of hydrogels prepared from cellulose alone are often poor, and the hydrogels are easy to break, and cannot achieve a good slow-release effect. Bentonite nanosheets have a very high in-plane elastic modulus and a rich surface of exposed bonding sites, which can improve the mechanical properties of the hydrogels. At the same time, bentonite nanosheets also have the functions of fixing nitrogen, potassium and organic matter, reducing the loss of fertilizers in the soil, controlling the release of nutrients in fertilizers, and improving the utilization rate of fertilizers; bentonite nanosheets can also absorb water and swell, making the soil structure loose, achieving the effect of water retention and fertilizer retention. DETAILED DESCRIPTION Example 1 The specific composting and fermentation methods of cow dung organic fertilizer are as follows: S51: Take fresh cow dung, clean out the debris, sieve out the natural fiber in the cow dung, adjust the moisture content of the remaining cow dung to 50%, add 0.2wt.‰ of the composite bacterial agent of the cow dung after the moisture content is adjusted, the composite bacterial agent is composed of the following strains in parts by weight: 10 parts of Bacillus licheniformis, 15 parts of Bacillus coagulans, 13 parts of Streptococcus thermophilus, 10 parts of Trichoderma reesei, 3 parts of Chaetomium and 2 parts of lactic acid bacteria, turn and mix 4 times, and make a fermentation pile with a pile height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning it over. Compost and ferment to obtain cow dung organic fertilizer. Example 2 The specific composting and fermentation methods of cow dung organic fertilizer are as follows: S51: Take fresh cow dung, clean out the debris, sieve out the natural fiber in the cow dung, adjust the moisture content of the remaining cow dung to 52%, add 0.3wt.‰ of the composite bacterial agent of the cow dung after the moisture content is adjusted, the composite bacterial agent is composed of the following strains in parts by weight: 13 parts of Bacillus licheniformis, 10 parts of Bacillus coagulans, 15 parts of Streptococcus thermophilus, 8 parts of Trichoderma reesei, 4 parts of Chaetomium and 3 parts of lactic acid bacteria, turn and mix 4 times, and make a fermentation pile with a pile height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning it over. Compost and ferment to obtain cow dung organic fertilizer. Example 3 The specific composting and fermentation methods of cow dung organic fertilizer are as follows: S51: Take fresh cow dung, clean out the debris, sieve out the natural fiber in the cow dung, adjust the moisture content of the remaining cow dung to 53%, add 0.4wt.‰ of the composite bacterial agent of the cow dung after the moisture content is adjusted, the composite bacterial agent is composed of the following strains in parts by weight: 15 parts of Bacillus licheniformis, 20 parts of Bacillus coagulans, 11 parts of Streptococcus thermophilus, 5 parts of Trichoderma reesei, 6 parts of Chaetomium and 3 parts of lactic acid bacteria, turn and mix 4 times, and make a fermentation pile with a pile height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning it over. Compost and ferment to obtain cow dung organic fertilizer. Example 4 The specific composting and fermentation methods of cow dung organic fertilizer are as follows: S51: Take fresh cow dung, clean out the debris, sieve out the natural fiber in the cow dung, adjust the moisture content of the remaining cow dung to 54%, add 0.4wt.‰ of the composite bacterial agent of the cow dung after adjusting the moisture content, the composite bacterial agent is composed of the following strains in parts by weight: 18 parts of Bacillus licheniformis, 15 parts of Bacillus coagulans, 15 parts of Streptococcus thermophilus, 5 parts of Trichoderma reesei, 2 parts of Chaetomium and 1 part of lactic acid bacteria, turn and mix 4 times, and make a fermentation pile with a pile height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning it over. Compost and ferment to obtain cow dung organic fertilizer. Example 5 The specific composting and fermentation methods of cow dung organic fertilizer are as follows: S51: Take fresh cow dung, clean out the debris, sieve out the natural fiber in the cow dung, adjust the moisture content of the remaining cow dung to 55%, add 0.5wt.‰ of the composite bacterial agent of the cow dung after adjusting the moisture content, the composite bacterial agent is composed of the following strains in parts by weight: 20 parts of Bacillus licheniformis, 13 parts of Bacillus coagulans, 10 parts of Streptococcus thermophilus, 9 parts of Trichoderma reesei, 5 parts of Chaetomium and 2 parts of lactic acid bacteria, turn and mix 4 times, and make a fermentation pile with a pile height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning it over. Compost and ferment to obtain cow dung organic fertilizer. Determination of seed germination index: Place 20 rapeseed seeds in a culture dish covered with filter paper, and add 5 mL of cow dung organic fertilizer extract to the culture dish. Use distilled water as a control. Repeat the experiment 3-4 times for each sample. After culturing in a seed germination box at 25°C for 96 hours, calculate the germination rate and measure the root length, and then calculate the seed germination index according to the following formula. Germination index GI / % = (germination rate of treated seeds × root length of treated seeds) / (germination rate of control seeds × root length of control seeds) × 100%; Determination of the number of effective live bacteria in cow dung organic fertilizer: The plate dilution live bacteria counting method is adopted according to the determination method in the Chinese Agricultural Microbial Agent Standard (NY / T 884-2021). Table 1 After comprehensive comparison of various properties of cow dung organic fertilizer, Example 4 was selected for subsequent tests. Example 6 The method for preparing porous cow dung biochar comprises the following steps: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Take 100 parts of cow dung pellets, add 3 parts of bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 650°C at a heating rate of 7°C / min, and pyrolyze for 2 h under anoxic conditions; S4: Cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar. Example 7 The method for preparing porous cow dung biochar comprises the following steps: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Take 100 parts of cow dung pellets, add 5 parts of bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 650°C at a heating rate of 7°C / min, and pyrolyze for 2 h under anoxic conditions; S4: Cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar. Example 8 The method for preparing porous cow dung biochar comprises the following steps: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Take 100 parts of cow dung pellets, add 7 parts of bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 650°C at a heating rate of 7°C / min, and pyrolyze for 2 h under anoxic conditions; S4: Cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar. Example 9 The method for preparing porous cow dung biochar comprises the following steps: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Take 100 parts of cow dung pellets, add 5 parts of bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 600°C at a heating rate of 7°C / min, and pyrolyze for 2.5h under anoxic conditions; S4: Cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar. Example 10 The method for preparing porous cow dung biochar comprises the following steps: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Take 100 parts of cow dung pellets, add 5 parts of bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 700°C at a heating rate of 7°C / min, and pyrolyze for 1.5h under anoxic conditions; S4: Cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar. The pore size and porosity of the porous cow dung biochar prepared in the above example were measured, and the results are shown in Table 2 below: Table 2 Average pore size (nm) <![CDATA[Specific surface area (m 2 / g)]]> Example 6 20.68 20.64 Example 7 18.42 20.89 Example 8 17.13 21.18 Example 9 20.35 18.45 Example 10 17.17 22.07 After comprehensive comparison of the average pore size and specific surface area of ​​porous cow dung biochar, Example 8 was selected for subsequent experiments. Embodiment 11 A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 1 part of the natural fiber in the treated cow dung and 8 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fiber in the treated cow dung has a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 4 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Example 12 A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 2 parts of the natural fibers in the treated cow dung, and 8 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fibers in the treated cow dung have a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 4 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Example 13 A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 2 parts of the natural fibers in the treated cow dung, and 5 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fibers in the treated cow dung have a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 4 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Embodiment 14 A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 2 parts of the natural fibers in the treated cow dung, and 10 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fibers in the treated cow dung have a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 4 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Embodiment 15 A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 2 parts of the natural fibers in the treated cow dung, and 8 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fibers in the treated cow dung have a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 2 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Example 16 A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 2 parts of the natural fibers in the treated cow dung, and 8 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fibers in the treated cow dung have a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 5 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Comparative Example 1 The difference between this comparative example and Example 12 is that no natural fiber in the treated cow dung is added, specifically as follows: A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8 and 8 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; S3: After drying, composite porous cow dung biochar with a particle size of 0.5-0.8 mm is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 4 parts of bentonite nanosheets and stir evenly; S7: impregnating the composite porous cow dung biochar, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Comparative Example 2 The difference between this comparative example and Example 12 is that no bentonite nanosheets are added, specifically as follows: A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 5 parts of the porous cow dung biochar prepared in Example 8, 2 parts of the natural fibers in the treated cow dung, and 8 parts of the cow dung organic fertilizer prepared in Example 4, mix and stir evenly, and place them in a granulator for extrusion and granulation at room temperature; the natural fibers in the treated cow dung have a length of 1.0-1.3 mm and a diameter of 50-130 μm; S3: After drying, a composite porous cow dung biochar with a particle size of 0.5-0.8 mm and a sea urchin structure is obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S7: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Comparative Example 3 The difference between this comparative example and Example 12 is that the cow dung organic fertilizer is directly used for granulation, which is as follows: A method for preparing a cow dung organic controlled-release fertilizer comprises the following steps: S1: Take fresh cow dung, clean out the debris, screen out the natural fibers in the cow dung, wash and dry for later use; S2: Take 8 portions of the cow dung organic fertilizer prepared in Example 4, adjust the moisture, and place in a granulator for extrusion granulation at room temperature; S3: After drying, the cow dung organic fertilizer particles with a particle size of 0.5-0.8 mm are obtained; S4: taking part of the natural fibers in S1, adding deionized water, placing in a pressure reactor, reacting at 90°C for 60 minutes, taking out, washing and drying, and obtaining cellulose; S5: Take 50 parts of ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add 2 parts of cellulose and mix well, place it in a 100℃ oil bath and stir to dissolve for 3h; S6: Add 4 parts of bentonite nanosheets and stir evenly; S7: soaking the cow dung organic fertilizer particles therein, cooling to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S8: Take out and vacuum freeze-dry to obtain the cow dung organic controlled-release fertilizer. Cow dung organic controlled-release fertilizer nutrient release determination: Take 5.0g of cow dung organic controlled-release fertilizer and place it in a wide-mouth bottle filled with 100mL of deionized water, incubate at 25°C and take samples at intervals, repeat 3 times; each time sampling, pour out all the leachate in the wide-mouth bottle, add 100mL of deionized water and continue incubation. Use a conductivity meter to measure the sample conductivity value to characterize the cumulative nutrient release rate. The results are shown in Table 3 below: Table 3 The cow dung organic controlled-release fertilizer prepared in each embodiment was applied to wheat planting, and yield determination and seed testing were carried out. After the winter wheat was physiologically mature, 1 m 2 For wheat yield measurement, 20 wheat plants were selected to measure plant height, number of grains per ear and number of ears. 2 The aboveground biomass, yield and harvest index of wheat. The harvest index (HI) refers to the ratio of economic yield (grains, fruits, etc.) to biological yield at the time of crop harvest, reflecting the distribution ratio of crop assimilation products in grains and nutritional organs. The results are shown in Table 4 below: Table 4 <![CDATA[Aboveground biomass (t / hm 2 )]]> <![CDATA[Yield (t / hm 2 )]]> Harvest Index HI Embodiment 11 21.42 10.66 0.62 Example 12 22.17 10.94 0.64 Example 13 20.23 10.15 0.58 Embodiment 14 22.34 11.06 0.64 Embodiment 15 21.78 10.75 0.62 Example 16 22.20 10.92 0.65 Comparative Example 1 20.65 10.04 0.58 Comparative Example 2 20.16 10.11 0.56 Comparative Example 3 17.94 9.27 0.50 Commercially available controlled release fertilizer 16.27 8.37 0.48 The above embodiments are intended to provide a clear and complete description of the technical solution, and are partial implementations of the present invention, rather than all implementations. However, the implementations of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations or simplifications that do not deviate from the spirit and principle of the present invention shall be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A cow dung organic controlled-release fertilizer, characterized in that: The cow dung organic controlled-release fertilizer is composed of a cellulose hydrogel film layer wrapped with composite porous cow dung biochar having a sea urchin structure.

2. A cow dung organic controlled-release fertilizer according to claim 1, characterized in that: The particle size of the composite porous cow dung biochar with sea urchin structure is 0.5-0.8 mm.

3. A method for preparing a cow dung organic controlled-release fertilizer according to any one of claims 1-2, characterized in that: The following steps are involved: S1: Take fresh cow dung, clean out the debris, naturally air-dry and crush, pass through an 80-mesh sieve to obtain cow dung particles; S2: Add bacterial cellulose, stir evenly, and place in an oven to dry; S3: Place in a muffle furnace, heat to 600-700°C at a heating rate of 5-8°C / min, and pyrolyze for 1.5-2.5h under anoxic conditions; S4: cooling, crushing, and passing through a 100-sieve to obtain porous cow dung biochar; S5: Take fresh cow dung, clean out the debris, screen out the natural fiber in the cow dung, wash and dry it for later use, and compost and ferment the remaining cow dung to obtain cow dung organic fertilizer; S6: taking the porous cow dung biochar, the natural fiber in the treated cow dung and the cow dung organic fertilizer, mixing them evenly, and placing them in a granulator for extrusion and granulation at room temperature; S7: after drying, a composite porous cow dung biochar with sea urchin structure was obtained; S8: taking part of the natural fibers in S5, adding deionized water, placing in a pressure reactor, reacting at 90° C. for 60 min, taking out, washing, and drying to obtain cellulose; S9: Take the ionic liquid BmimCl and melt it into a transparent liquid at room temperature, add cellulose and mix evenly, place it in a 100℃ oil bath and stir to dissolve for 3h; S10: Add bentonite nanosheets and stir evenly; S11: impregnating the composite porous cow dung biochar with sea urchin structure, cooling it to room temperature, and adding distilled water to replace the ionic liquid BmimCl; S12: taking out and vacuum freeze-drying to obtain the cow dung organic controlled-release fertilizer.

4. The method for preparing a cow dung organic controlled-release fertilizer according to claim 3, characterized in that: The mass ratio of the cow dung particles to the bacterial cellulose is 100:(3-7).

5. The method for preparing a cow dung organic controlled-release fertilizer according to claim 3, characterized in that: The specific composting fermentation method of the cow dung organic fertilizer is as follows: S51: taking fresh cow dung, cleaning out the debris, screening out the natural fiber in the cow dung, adjusting the moisture content of the remaining cow dung to 50-55%, adding the composite bacterial agent, turning and mixing 3-4 times, and making a fermentation pile with a height of 80 cm and a flat top; S52: Measure the temperature of the pile twice a day, turn the pile every 3 days, and return it to its original shape after turning. The compost will ferment for 8-12 days to obtain cow dung organic fertilizer.

6. The method for preparing a cow dung organic controlled-release fertilizer according to claim 5, characterized in that: The composite bacterial agent is composed of the following bacterial species in parts by weight: 10-20 parts of Bacillus licheniformis, 10-20 parts of Bacillus coagulans, 10-15 parts of Streptococcus thermophilus, 5-10 parts of Trichoderma reesei, 1-6 parts of Chaetomium and 1-3 parts of lactic acid bacteria.

7. The method for preparing a cow dung organic controlled-release fertilizer according to claim 5, characterized in that: The amount of the composite bacteria added is 0.2-0.5wt.‰ of the cow dung after adjusting the water content.

8. The method for preparing a cow dung organic controlled-release fertilizer according to claim 3, characterized in that: The mass ratio of the porous cow dung biochar, the natural fiber in the treated cow dung and the cow dung organic fertilizer is 5:(1-2):(5-10).

9. The method for preparing a cow dung organic controlled-release fertilizer according to claim 3, characterized in that: The method for processing the natural fibers in the treated cow dung is to cut and screen the natural fibers to have a length of 1.0-1.3 mm and a diameter of 50-130 μm.

10. The method for preparing a cow dung organic controlled-release fertilizer according to claim 3, characterized in that: The mass ratio of the ionic liquid BmimCl, cellulose and bentonite nanosheets is 50:2:(2-5).

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