Organic-inorganic compound fertilizer for improving sandy soil and preparation method thereof
By combining organic components, inorganic components, natural mineral materials, biodegradable polymers, and microorganisms, the problem of rapid nutrient loss in sandy soils has been solved, achieving dual stability of soil structure and fertility, as well as a healthy microecology.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-24
- Publication Date
- 2026-03-10
AI Technical Summary
In existing technologies, inorganic nutrients are easily leached away quickly with rainfall or irrigation, and organic components are also decomposed more rapidly due to the high permeability of sandy soil, resulting in a rapid decline in soil fertility after nutrient loss in a short period of time.
It combines organic components such as humic acid, organic compost, and plant residues with inorganic components such as ammonium nitrate, potassium dihydrogen phosphate, and potassium chloride, and adds natural mineral materials and biodegradable polymers. It also incorporates nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, and growth-promoting microorganisms. Through the action of slow-release materials and microorganisms, it regulates soil fertility and structure and promotes the continuous release of nutrients.
It effectively prevents rapid nutrient loss, ensures a stable supply of fertilizer throughout the entire growth cycle, enhances the health of the soil microbial community, achieves dual stability of soil structure and fertility, and avoids the phenomenon of short-term effectiveness after improvement but subsequent rebound.
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Figure CN121627447A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of agricultural technology, in particular to an organic-inorganic compound fertilizer for improving sandy soil and a preparation method thereof. BACKGROUND
[0002] Sandy soil is prone to problems such as crop water and fertilizer deficiency and growth restriction in agricultural production due to its large inter-particle gap, weak water and fertilizer retention capacity, and low organic matter content. Therefore, improving sandy soil to enhance its structural stability and fertility level is a key requirement for ensuring sustainable agricultural development in sandy soil areas. Organic-inorganic compound fertilizer, which can take advantage of both organic and inorganic components, has become an important technical carrier for sandy soil improvement. Through the synergistic effect of organic and inorganic components, it can theoretically achieve soil structure optimization and nutrient supply at the same time. However, the existing technology has not fully utilized the improvement potential of this type of fertilizer.
[0003] Currently, the organic-inorganic compound fertilizer technology for sandy soil is mostly prepared by directly mixing organic raw materials such as decomposed straw and livestock and poultry manure with inorganic fertilizers such as urea, superphosphate, and potassium chloride. Some technologies add a small amount of natural minerals such as montmorillonite and kaolin to slightly enhance water and fertilizer retention. However, in use, inorganic nutrients are easily leached with rainfall or irrigation, and organic components are also accelerated in decomposition due to the strong permeability of sandy soil, leading to rapid decline in soil fertility after short-term nutrient loss. SUMMARY
[0004] To solve the problem in the prior art that inorganic nutrients are easily leached with rainfall or irrigation, and organic components are also accelerated in decomposition due to the strong permeability of sandy soil, leading to rapid decline in soil fertility after short-term nutrient loss, the present application provides an organic-inorganic compound fertilizer for improving sandy soil and a preparation method thereof.
[0005] In a first aspect, the present application provides an organic-inorganic compound fertilizer for improving sandy soil, which is composed of the following raw materials by weight: Humic acid 10-25 parts, organic compost 20-40 parts, plant residues 10-30 parts, ammonium nitrate 1.5-5 parts, potassium dihydrogen phosphate 1-3 parts, potassium chloride 1.5-4 parts, calcium oxide 0.5-2 parts, magnesium oxide 0.3-1 part, nitrogen-fixing bacteria 0.5-3 parts, phosphorus-solubilizing bacteria 0.5-3 parts, growth-promoting microorganisms 0.5-3 parts, natural mineral materials 5-20 parts, biodegradable polymers 2-10 parts, zinc sulfate 0.1-0.3 parts, sodium selenite 0.02-0.1 parts, and ammonium molybdate 0.01-0.05 parts.
[0006] The above technical solution utilizes organic components such as humic acid, organic compost, and plant residues, combined with inorganic components such as ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide, and magnesium oxide. This is achieved through slow-release materials made from natural minerals and biodegradable polymers, along with biological components including nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms. This effectively regulates soil fertility and structure, improves soil water retention and aeration, promotes healthy crop roots, improves soil structure, and prevents rapid nutrient loss. Through the slow-release materials, nutrients are continuously released, preventing rapid fertilizer consumption in the short term and ensuring a stable supply of fertilizer throughout the entire growth cycle. Simultaneously, microorganisms enhance nutrient transformation and cycling in the soil, improve the health of the soil microbial community, and prevent short-term soil microecological rebound. This effectively ensures the dual stability of sandy soil structure and fertility, avoiding the phenomenon of short-term effectiveness followed by later rebound, and ensuring the health of the soil microecology.
[0007] Preferably, the nitrogen-fixing bacteria are *Azotobacter chrysophagus*, with a viable count of 1 × 10⁻⁶. 6 –1×10 9 CFU / g, phosphate-solubilizing bacteria used: Bacillus subtilis, viable count 1×10⁻⁶ 6 –1×10 9 CFU / g, the growth-promoting microorganism used is Trichoderma harzianum, viable count 1×10⁻⁶ 6 –1×10 9 CFU / g.
[0008] Through the above technical solution, the addition of *Azotobacter chrysophagus* (nitrogen-fixing bacteria), *Bacillus subtilis* (phosphate-solubilizing bacteria), and *Trichoderma harzianum* (growth-promoting microorganisms) effectively promotes the transformation and cycling of nutrients in fertilizers. Nitrogen-fixing bacteria convert atmospheric nitrogen into nitrogen sources that can be absorbed by crops, improving the nitrogen supply in the soil; phosphate-solubilizing bacteria convert insoluble phosphorus sources in the soil into usable phosphorus, increasing the phosphorus content in the soil and ensuring the phosphorus requirements of crops during growth; growth-promoting microorganisms promote root growth, enhance the crop's ability to absorb nutrients and water, and improve the crop's resistance to stress. Through synergistic action, the nutrients in the fertilizer are ensured to be stably supplied to the soil in the long term, and the health of the soil's microbial community is improved. The interaction between microorganisms and fertilizers ensures the stable release of fertilizers throughout the crop growth cycle, while reducing the rebound effect caused by excessive short-term nutrient release, thereby ensuring the health of the microecology in sandy soils, achieving dual stability of structure and fertility, and avoiding the phenomenon of short-term effectiveness followed by a rebound after improvement.
[0009] Preferably, the natural mineral material includes one or more of montmorillonite, kaolin, zeolite, and diatomite.
[0010] Through the above technical solutions, the combination of natural mineral materials such as montmorillonite, kaolin, zeolite, and diatomaceous earth with biodegradable polymers such as polylactic acid or polyvinyl alcohol can effectively control the nutrient release rate in fertilizers. The addition of natural mineral materials enhances the water retention capacity of fertilizers and soil permeability, helping to form a stable nutrient supply system in the soil while preventing excessive loss of water-soluble nutrients.
[0011] Preferably, the biodegradable polymer is polylactic acid or polyvinyl alcohol.
[0012] Through the aforementioned technical solutions, the addition of biodegradable polymers allows the nutrient release rate of fertilizers to be adjusted according to the needs of soil and crops, thereby avoiding excessive nutrient release in the short term. This ensures the stability of both the fertilizer's structure and fertility, effectively preventing a rebound effect after high-efficiency short-term use, reducing nutrient loss, and maintaining long-term fertilizer effectiveness. Furthermore, the combination of natural mineral materials and biodegradable polymers also helps improve the soil's micro-ecological environment, ensuring a healthy micro-ecology in sandy soils and providing continuous and stable nutrient support for crop growth.
[0013] On the other hand, this application provides a method for preparing an organic-inorganic compound fertilizer for improving sandy soil, comprising the following steps: S1: Raw material pretreatment; S2: Mix the organic raw materials and inorganic nutrients in the pretreated raw materials to prepare a basic mixture; S3: Mix microorganisms with a protective agent and incubate to prepare a microbial mixture; S4: Mix the base mixture, microbial mixture, natural mineral materials, biodegradable polymers and trace elements to prepare a composite mixture; S5: After molding, drying, and packaging the composite mixture, store it.
[0014] Through the above technical solutions, raw material pretreatment helps remove impurities and improve the physical properties of the raw materials, providing a high-quality foundation for subsequent mixing steps. The mixing of organic raw materials and inorganic nutrients combines the long-term fertility of organic matter with the rapid action of inorganic fertilizers, thus ensuring the stability of both soil structure and fertility, and preventing nutrient rebound after short-term effectiveness. The mixed incubation of microorganisms and protectants can protect the activity of microorganisms, ensuring their survival rate in the fertilizer and their interaction with the soil, thereby enhancing soil microecological health and improving nutrient conversion efficiency. The mixing of the base mixture, microbial mixture, natural mineral materials, biodegradable polymers, and trace elements allows each component to work synergistically, ensuring the slow-release characteristics of nutrients. Simultaneously, the precise supplementation of trace elements avoids nutrient over- or under-nutrients, promoting healthy crop growth. Finally, through molding, drying, and packaging, the stability and microbial activity of the fertilizer are maintained, ensuring its long-term effectiveness and sustainability.
[0015] Preferably, the preprocessing in step S1 includes: Plant residues are crushed to a particle size of 0.1–0.5 mm and piled at 50℃–60℃ for 7–10 days to decompose. During the decomposition process, the moisture content is controlled at 50%–60%, and a decomposition agent is added. The decomposition agent is composed of Aspergillus oryzae and yeast in a 3:1 weight ratio. Crush the organic compost to a particle size of 0.2–0.8 mm and pass it through an 80-mesh sieve.
[0016] The above technical solution effectively increases the organic matter content of plant residues by crushing and composting them, promoting rapid decomposition and increasing the effective organic components of the fertilizer. Controlling the moisture content and adding composting agents during the composting process accelerates the process, ensuring that organic matter is fully decomposed and converted into usable nutrients. Furthermore, using Aspergillus oryzae and yeast composting agents further improves composting efficiency, ensures the stability of raw material quality, and avoids the impact of uncomposted materials on fertilizer effectiveness. The crushing and screening of organic compost ensures particle uniformity and fineness, facilitating subsequent mixing with other raw materials, ensuring fertilizer consistency and operability, and fully preparing the organic matter in the raw materials. This enhances the fertilizer's effectiveness and stability, ultimately guaranteeing a long-term, stable effect of both structure and fertility during use.
[0017] Preferably, in step S2, the organic compost and plant residues pretreated in step S1 are mixed and then ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide and magnesium oxide are added. The mixture is stirred using a spiral stirrer at a temperature of 20℃–35℃, a stirring speed of 50–100 rpm and a stirring time of 30–60 minutes.
[0018] The above technical solution, by mixing organic compost and plant residues with ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide, and magnesium oxide, ensures the uniform distribution of organic and inorganic nutrients in the fertilizer. This ensures the coordinated release of organic matter and inorganic nutrients, thereby enhancing fertilizer stability and providing a continuous nutrient supply to crops. Using a spiral mixer to mix the fertilizer, controlling temperature and stirring speed, prevents nutrient loss or fertilizer component stratification due to excessively high temperatures or speeds, thus ensuring nutrient uniformity and preventing fertilizer rebound during use.
[0019] Preferably, in step S3, the specific steps for mixing and incubating the microorganisms with the protectant are as follows: Nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms are added to a microbial protectant and chitosan quaternary ammonium salt. The microbial protectant is composed of sodium alginate and sucrose in a weight ratio of 1:1–2:1. The chitosan quaternary ammonium salt has a degree of deacetylation of not less than 85% and a molecular weight of 5000–10000 Da. The mixture is incubated at 25℃–30℃ and 60%–70% humidity for 24–48 hours.
[0020] Through the above technical solution, precise ingredient ratios and strict incubation conditions, the high activity and biostability of nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms in fertilizers are ensured. The combination of microbial protectants and chitosan quaternary ammonium salts effectively protects the survival environment of microorganisms in fertilizers and enhances their stress resistance, ensuring their optimal function in the soil. The appropriate ratio of sodium alginate and sucrose provides a stable nutrient environment and enhances microbial activity; chitosan quaternary ammonium salts have excellent protective properties, helping microorganisms avoid adverse environmental conditions during application. Incubation allows microorganisms to fully multiply, ensuring their stability in fertilizers and enabling them to quickly interact with soil nutrients upon application, thereby promoting soil nutrient transformation and microecological balance. This step ensures the effectiveness of microorganisms in fertilizers and avoids the fertilizer's effects disappearing too quickly in the short term.
[0021] Preferably, in step S4, the specific steps for preparing the composite mixture are as follows: Add the microbial mixture prepared in step S3 to the basic mixture prepared in step S2, and stir at 40–60 rpm for 10–20 minutes until homogeneous; Then add natural mineral materials, biodegradable polymers, zinc sulfate, sodium selenite and ammonium molybdate, and stir at 30–60 rpm for 20–40 minutes at 25℃–40℃ until homogeneous.
[0022] The above technical solution, by combining the base mixture with the microbial mixture, ensures the uniform distribution of microorganisms and nutrients, guaranteeing the activity of microorganisms during application and their good synergistic effect with soil nutrients. The nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms contained in the microbial mixture are further evenly distributed in this step, contributing to improved nutrient transformation in the soil and crop growth. The addition of natural mineral materials, biodegradable polymers, zinc sulfate, sodium selenite, and ammonium molybdate improves the slow-release performance of the fertilizer, ensuring long-term nutrient release, reducing short-term nutrient loss, and enhancing soil fertility stability. The biodegradable polymers further optimize fertilizer solubility and the microbial environment, ensuring the long-term stable operation of microorganisms and nutrients in the soil.
[0023] Preferably, the specific steps for molding, drying, packaging, and storing the composite mixture in step S5 are as follows: First, the composite mixture prepared in step S4 is crushed to 100–200 mesh and then formed into granules by a twin-screw extruder. The particle size of the granules after forming is 3–8 mm. The shaped granules are then placed in a hot air circulating dryer for drying. During the drying process, the hot air velocity is 0.5–1.0 m / s, the temperature is 40℃–60℃, and the time is 4–8 hours. The granules are turned over every 1–2 hours. The dried granules are packed into polypropylene woven bags and stored in an environment with a temperature of 20℃–30℃ and a humidity of 40%–60%.
[0024] The above technical solution ensures the uniformity and stability of the granules by pulverizing the composite mixture to an appropriate particle size and forming it using a twin-screw extrusion granulator. This helps ensure that the fertilizer is evenly distributed and effectively releases nutrients during application. Drying the formed granules in a hot air circulating dryer ensures that moisture is properly removed, preventing nutrient loss and maintaining the activity and stability of microorganisms. Turning the granules ensures uniformity during the drying process, further guaranteeing fertilizer quality. Finally, the dried granules are packaged and stored under suitable temperature and humidity conditions, ensuring that the fertilizer is unaffected by changes in the external environment during storage and maintaining its long-term stability.
[0025] This application provides an organic-inorganic compound fertilizer for improving sandy soil and its preparation method. It has the following beneficial effects: 1. This application combines organic components such as humic acid, organic compost, and plant residues with inorganic nutrients such as ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide, and magnesium oxide, and uses the slow-release effect of natural mineral materials and biodegradable polymers to ensure that the nutrients in the fertilizer can be continuously released into the soil, avoiding the rapid consumption of nutrients in the short term and effectively preventing the rebound of nutrients after a short period of effectiveness.
[0026] 2. The addition of nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms in this application promotes the transformation and cycling of nutrients in the soil. By enhancing the activity and health of the soil microbial community, it ensures the synergistic effect between microorganisms and fertilizers, thereby maintaining the stability of the soil microecology. The microorganisms can work stably after fertilizer application, effectively improving the health of crop roots and ensuring the health of the microecology in sandy soils.
[0027] 3. This application ensures that the microorganisms are evenly distributed during application and work well with the nutrients in the soil by combining the basic mixture with the microbial mixture. In addition, the addition of natural mineral materials, biodegradable polymers, zinc sulfate and other trace elements optimizes the nutrient release rate of the fertilizer, so that the fertilizer effect can be maintained for a long time and at the same time enhances the stability of the fertilizer, ensuring a stable supply of fertilizer throughout the entire growth cycle. Attached Figure Description
[0028] Figure 1 This is a flowchart of a method for preparing an organic-inorganic compound fertilizer for improving sandy soil, as described in this application. Detailed Implementation
[0029] The present application will be further described in detail below with reference to embodiments and comparative examples.
[0030] Example 1 This application provides an organic-inorganic compound fertilizer for improving sandy soil, comprising the following raw materials in parts by weight: 10 parts humic acid, 20 parts organic compost, 10 parts plant residue, 1.5 parts ammonium nitrate, 1 part potassium dihydrogen phosphate, 1.5 parts potassium chloride, 0.5 parts calcium oxide, 0.3 parts magnesium oxide, 0.5 parts nitrogen-fixing bacteria, 0.5 parts phosphate-solubilizing bacteria, 0.5 parts growth-promoting microorganisms, 5 parts natural mineral materials, 2 parts biodegradable polymer, 0.1 parts zinc sulfate, 0.02 parts sodium selenite, and 0.01 parts ammonium molybdate; The nitrogen-fixing bacteria used are *Azotobacter chrysophagus*, with a viable count of 1 × 10⁻⁶. 6 CFU / g; Phosphate-solubilizing bacteria used: Bacillus subtilis, viable count 1×10⁻⁶ 6 CFU / g; the growth-promoting microorganism used was *Trichoderma harzianum*, with a viable count of 1×10⁻⁶. 6 CFU / g; the natural mineral material includes montmorillonite; the biodegradable polymer is polylactic acid.
[0031] The above-mentioned method for preparing an organic-inorganic compound fertilizer for improving sandy soil includes the following steps: S1: Raw material pretreatment; The process involves crushing plant residues to a particle size of 0.1 mm, piling them at 50°C for 7 days to decompose, controlling the moisture content at 50% during the decomposition process, and adding a decomposition agent; crushing organic compost to a particle size of 0.2 mm and passing it through an 80-mesh sieve; and using a decomposition agent composed of Aspergillus oryzae and yeast in a 3:1 weight ratio.
[0032] S2: Mix the organic raw materials and inorganic nutrients in the pretreated raw materials to prepare a basic mixture; In this process, the organic compost and plant residues pretreated in step S1 are mixed together and then ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide and magnesium oxide are added. The mixture is then stirred using a spiral mixer at a temperature of 20°C, a stirring speed of 50 rpm and a stirring time of 30 minutes.
[0033] S3: Mix microorganisms with a protective agent and incubate to prepare a microbial mixture; In this process, nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms are added to a microbial protectant and chitosan quaternary ammonium salt, and the mixture is incubated for 24 hours at 25°C and 60% humidity. The microbial protectant is composed of sodium alginate and sucrose in a 1:1 weight ratio. The degree of deacetylation of the chitosan quaternary ammonium salt is not less than 85% and the molecular weight is 5000 Da.
[0034] S4: Mix the base mixture, microbial mixture, natural mineral materials, biodegradable polymers and trace elements to prepare a composite mixture; In this process, the microbial mixture prepared in step S3 is added to the basic mixture prepared in step S2 and stirred at 40 rpm for 10 minutes until homogeneous; then natural mineral materials, biodegradable polymers, zinc sulfate, sodium selenite and ammonium molybdate are added and stirred at 30 rpm for 20 minutes at 25°C until homogeneous.
[0035] S5: After molding, drying, and packaging the composite mixture, store it. First, the composite mixture prepared in step S4 is pulverized to 100 mesh and granulated into particles using a twin-screw extruder, resulting in particles with a diameter of 3 mm. The granules are then dried in a hot air circulating dryer at a speed of 0.5 m / s, a temperature of 40°C, and a drying time of 4 hours, with the particles being turned over every 2 hours. The dried particles are then packed into polypropylene woven bags and stored in an environment with a temperature of 20°C and a humidity of 40%. Example 2 This application provides an organic-inorganic compound fertilizer for improving sandy soil, comprising the following raw materials in parts by weight: 17.5 parts humic acid, 30 parts organic compost, 20 parts plant residue, 3.25 parts ammonium nitrate, 2 parts potassium dihydrogen phosphate, 2.75 parts potassium chloride, 1.25 parts calcium oxide, 0.65 parts magnesium oxide, 1.75 parts nitrogen-fixing bacteria, 1.75 parts phosphate-solubilizing bacteria, 1.75 parts growth-promoting microorganisms, 12.5 parts natural mineral materials, 6 parts biodegradable polymers, 0.2 parts zinc sulfate, 0.06 parts sodium selenite, and 0.03 parts ammonium molybdate.
[0036] The nitrogen-fixing bacteria used are *Azotobacter chrysophagus*, with a viable count of 1 × 10⁻⁶. 7 . 5 CFU / g; Phosphate-solubilizing bacteria used: Bacillus subtilis, viable count 1×10⁻⁶ 7 . 5 CFU / g; the growth-promoting microorganism used was *Trichoderma harzianum*, with a viable count of 1×10⁻⁶. 7 . 5 CFU / g; the natural mineral materials include montmorillonite and kaolin; the biodegradable polymer is polyvinyl alcohol; The above-mentioned method for preparing an organic-inorganic compound fertilizer for improving sandy soil includes the following steps: S1: Raw material pretreatment; The process involves crushing plant residues to a particle size of 0.3 mm, composting them at 55°C for 8.5 days, controlling the moisture content at 55% during composting, and adding composting microbial agents; crushing organic compost to a particle size of 0.5 mm and passing it through an 80-mesh sieve; and using composting microbial agents composed of Aspergillus oryzae and yeast in a 3:1 weight ratio.
[0037] S2: Mix the organic raw materials and inorganic nutrients in the pretreated raw materials to prepare a basic mixture; In this process, the organic compost and plant residues pretreated in step S1 are mixed and then ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide and magnesium oxide are added. The mixture is then stirred using a spiral mixer at a temperature of 27.5℃, a stirring speed of 75 rpm and a stirring time of 45 minutes.
[0038] S3: Mix microorganisms with a protective agent and incubate to prepare a microbial mixture; In this process, nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms are added to a microbial protectant and chitosan quaternary ammonium salt, and the mixture is incubated for 36 hours at 27.5℃ and 65% humidity. The microbial protectant is composed of sodium alginate and sucrose in a weight ratio of 1.5:1. The degree of deacetylation of chitosan quaternary ammonium salt is not less than 85% and the molecular weight is 7500 Da.
[0039] S4: Mix the base mixture, microbial mixture, natural mineral materials, biodegradable polymers and trace elements to prepare a composite mixture; In step S2, the microbial mixture prepared in step S3 is added to the basic mixture and stirred at 50 rpm for 15 minutes until homogeneous. Then, natural mineral materials, biodegradable polymers, zinc sulfate, sodium selenite and ammonium molybdate are added and stirred at 32.5°C at 45 rpm for 30 minutes until homogeneous.
[0040] S5: After molding, drying, and packaging the composite mixture, store it. First, the composite mixture prepared in step S4 is pulverized to 150 mesh and granulated into particles using a twin-screw extruder. The particle size of the granules after granulation is 5.5 mm. Then, the granules are dried in a hot air circulating dryer. During the drying process, the hot air velocity is 0.75 m / s, the temperature is 50°C, and the time is 6 hours. The granules are turned over every 1.5 hours. The dried granules are then packed into polypropylene woven bags and stored in an environment with a temperature of 25°C and a humidity of 50%.
[0041] Example 3 This application provides an organic-inorganic compound fertilizer for improving sandy soil, comprising the following raw materials in parts by weight: 25 parts humic acid, 40 parts organic compost, 30 parts plant residue, 5 parts ammonium nitrate, 3 parts potassium dihydrogen phosphate, 4 parts potassium chloride, 2 parts calcium oxide, 1 part magnesium oxide, 3 parts nitrogen-fixing bacteria, 3 parts phosphate-solubilizing bacteria, 3 parts growth-promoting microorganisms, 20 parts natural mineral materials, 10 parts biodegradable polymers, 0.3 parts zinc sulfate, 0.1 parts sodium selenite, and 0.05 parts ammonium molybdate; The nitrogen-fixing bacteria used are *Azotobacter chrysophagus*, with a viable count of 1 × 10⁻⁶. 9 CFU / g; Phosphate-solubilizing bacteria used: Bacillus subtilis, viable count 1×10⁻⁶ 9 CFU / g; the growth-promoting microorganism used was *Trichoderma harzianum*, with a viable count of 1×10⁻⁶. 9 CFU / g; the natural mineral materials include zeolite and diatomaceous earth; the biodegradable polymer is polylactic acid; The above-mentioned method for preparing an organic-inorganic compound fertilizer for improving sandy soil includes the following steps: S1: Raw material pretreatment; The process involves crushing plant residues to a particle size of 0.5 mm, composting them at 60°C for 10 days, controlling the moisture content at 60% during composting, and adding composting microbial agents; crushing organic compost to a particle size of 0.8 mm and passing it through an 80-mesh sieve; and using composting microbial agents composed of Aspergillus oryzae and yeast in a 3:1 weight ratio.
[0042] S2: Mix the organic raw materials and inorganic nutrients in the pretreated raw materials to prepare a basic mixture; In this process, the organic compost and plant residues pretreated in step S1 are mixed and then ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide and magnesium oxide are added. The mixture is then stirred using a spiral mixer at a temperature of 35°C, a stirring speed of 100 rpm and a stirring time of 60 minutes.
[0043] S3: Mix microorganisms with a protective agent and incubate to prepare a microbial mixture; In this process, nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and growth-promoting microorganisms are added to a microbial protectant and chitosan quaternary ammonium salt, and the mixture is incubated at 30°C and 70% humidity for 48 hours. The microbial protectant is composed of sodium alginate and sucrose in a 2:1 weight ratio. The degree of deacetylation of the chitosan quaternary ammonium salt is not less than 85% and the molecular weight is 10,000 Da.
[0044] S4: Mix the base mixture, microbial mixture, natural mineral materials, biodegradable polymers and trace elements to prepare a composite mixture; In this process, the microbial mixture prepared in step S3 is added to the basic mixture prepared in step S2 and stirred at 60 rpm for 20 minutes until homogeneous; then natural mineral materials, biodegradable polymers, zinc sulfate, sodium selenite and ammonium molybdate are added and stirred at 60 rpm for 40 minutes at 40°C until homogeneous.
[0045] S5: After molding, drying, and packaging the composite mixture, store it. First, the composite mixture prepared in step S4 is pulverized to 200 mesh and granulated into particles using a twin-screw extruder. The granules have a particle size of 8 mm. Then, the granules are dried in a hot air circulating dryer at a hot air velocity of 1.0 m / s, a temperature of 60°C, and a drying time of 8 hours, with the particles being turned over every hour. The dried particles are then packed into polypropylene woven bags and stored in an environment with a temperature of 30°C and a humidity of 60%. Comparative Example 1 The only difference from Example 2 is that nitrogen-fixing bacteria are missing from the raw materials; the composition of the other raw materials, preparation steps and parameters are the same as in Example 2.
[0046] Comparative Example 2 The only difference from Example 2 is that the nitrogen-fixing bacteria species is replaced by brown azotocinus instead of chrysozoicus. The other raw material composition, preparation steps and parameters are the same as in Example 2.
[0047] Comparative Example 3 The only difference from Example 2 is that natural mineral materials are missing from the raw materials; the composition of the other raw materials, preparation steps and parameters are the same as in Example 2.
[0048] Comparative Example 4 The only difference from Example 2 is that the biodegradable polymer is replaced with polyethylene instead of polyvinyl alcohol; the other raw material composition, preparation steps and parameters are the same as in Example 2.
[0049] Comparative Example 5 The only difference from Example 2 is that no composting agent is added during the pretreatment in step S1, while the composition of the other raw materials, preparation steps and parameters are the same as in Example 2.
[0050] Comparative Example 6 The only difference from Example 2 is that chitosan quaternary ammonium salt is not added in step S3, while the composition of other raw materials, preparation steps and parameters are the same as in Example 2.
[0051] Comparative Example 7 The only difference from Example 2 is that the amount of zinc sulfate added is 0.4 parts, while the composition of other raw materials, preparation steps and parameters are the same as in Example 2.
[0052] Comparative Example 8 The only difference from Example 2 is that the temperature is controlled at 45°C during the mixing process in step S2. The other raw material composition, preparation steps and parameters are the same as in Example 2.
[0053] Comparative Example 9 The only difference from Example 2 is that the biodegradable polymer is missing from the raw materials, while the composition of the other raw materials, preparation steps and parameters are the same as in Example 2.
[0054] Comparative Example 10 The only difference from Example 2 is that the viable count of nitrogen-fixing bacteria is 1×10⁻⁶. 5 The CFU / g ratio, as well as the composition of the remaining raw materials, preparation steps, and parameters, are consistent with those in Example 2.
[0055] I. Dual Stability Test of Soil Structure and Fertility Experimental content: Samples of improved sandy soil organic-inorganic compound fertilizer from Examples 1-3 and Comparative Examples 1-10 were selected. One pot experiment was conducted for each type of sample. The pots were Φ25cm × H30cm, and each pot contained 5kg of the tested sandy soil with an initial organic matter content of 0.85% and a bulk density of 1.52g / cm³. 3 Available nitrogen 35.2 mg / kg. The dosage of each compound fertilizer was calculated based on a pure nitrogen content of 0.2 g / kg soil. It was applied as a single basal application 5 cm below the soil surface. A blank control group was included, receiving no fertilizer. Each group was replicated three times. Potted plants were placed in natural light, maintaining soil moisture content at 60% ± 5% of field capacity, for a cultivation period of 180 days.
[0056] Soil samples were collected at 30, 90, and 180 days of cultivation. Soil bulk density was determined using the ring cutter method (NY / T1121.4-2006). Total porosity was calculated using the formula: Total porosity (%) = (1 - Soil bulk density / 2.65) × 100. The content of water-stable aggregates was determined using the wet sieving method (NY / T1121.12-2006). Available nitrogen in the soil was determined using the alkaline hydrolysis diffusion method (NY / T1121.7-2014), available phosphorus was determined using the molybdenum-antimony colorimetric method (NY / T1121.8-2014), and available potassium was determined using the flame photometry method (NY / T1121.13-2006). The nutrient retention rate and structural rebound rate at 180 days compared to 30 days were calculated.
[0057] The soil structure and fertility stability test data of Examples 1-3 and Comparative Examples 1-10 are shown in Table 1.
[0058] Table 1. Data from the dual stability test of soil structure and fertility
[0059] II. Testing of Soil Microecological Health and Preparation Process Effectiveness Experimental content: Compound fertilizer samples from Examples 1-3 and Comparative Examples 1-10 were selected. Soil microecological health tests were conducted: Soil samples from the above-mentioned potted plants were taken for 30 days, 90 days, and 180 days. The number of microorganisms was determined by the dilution plate count method, and the urease activity was determined by the indophenol blue colorimetric method and the phosphatase activity was determined by the disodium phenyl phosphate colorimetric method. The change rate of the number of microorganisms and the change rate of enzyme activity were calculated from 180 days to 30 days.
[0060] The soil microecological health data of Examples 1-3 and Comparative Examples 1-10 are shown in Table 2.
[0061] Table 2 Soil microecological health test data
[0062] Based on the test data results of the above embodiments and comparative examples, the following conclusions are drawn: 1. Based on Examples 1-3 and Comparative Example 1, and in conjunction with Table 1, it can be seen that nitrogen-fixing bacteria are a key biological component for maintaining the dual stability of sandy soil structure and fertility. They can indirectly optimize soil aggregate structure by promoting soil nitrogen cycling, while also helping to maintain nutrient balance. If this component is removed, the 180-day bulk density change rate increases from -0.8% to 0.0% in the examples to +5.1%, the water-stable aggregate change rate decreases from -0.9% to +1.0% to -12.2%, and the available nitrogen retention rate decreases from 91.9% to 92.5% to 81.4%. Soil structure rebounds significantly, fertility stability decreases significantly, and the synergistic stability of structure and fertility cannot be achieved.
[0063] 2. Based on Examples 1-3 and Comparative Example 2, and in conjunction with Table 2, it can be seen that *Azotobacter chrysotrichum* is a specific microorganism that ensures the health of the soil microecology. It can promote the reproduction of soil bacteria and actinomycete communities through its own metabolic activities, while also increasing soil enzyme activity. If it is replaced by *Azotobacter chrysotrichum*, the 180-day bacterial count change rate decreases from +1.6% to +1.9% in the examples to -16.7%, the actinomycete count change rate decreases from +4.0% to +5.0% to -33.3%, and the urease and phosphatase activity change rates decrease from -2.6% to 3.1% and -3.8% to 4.5% to -21.4% and -26.3%, respectively. The soil microecology is unbalanced and cannot maintain a long-term healthy state.
[0064] 3. Combining Examples 1-3 and Comparative Example 3 with Table 1, it can be seen that natural mineral materials are the core components for achieving slow nutrient release and soil structure improvement. The porous structure can adsorb nutrients to extend the supply cycle and optimize the soil pore distribution. If this component is removed, the 180-day available phosphorus retention rate drops sharply from 92.8%-93.2% in the examples to 68.2%, and the water-stable aggregate change rate drops to -16.5%, which is far lower than the level of the examples. Nutrients are rapidly lost, the soil structure rebounds severely, and the dual stability effect is destroyed.
[0065] 4. Based on Examples 1-3 and Comparative Example 4, and in conjunction with Table 1, it can be seen that biodegradable polymers are important slow-release components for regulating nutrient release rates. They can synergistically extend the nutrient supply cycle with natural mineral materials and adapt to the degradation characteristics of the soil environment. If they are replaced with non-biodegradable polyethylene, the 180-day available nitrogen retention rate drops from 91.9%-92.5% in the examples to 73.9%, and the water-stable aggregate change rate drops to -16.4%. Because polyethylene is non-degradable and cannot synergistically adsorb nutrients with natural minerals, nutrient loss is accelerated, soil structure deteriorates, and dual stability cannot be achieved.
[0066] 5. Based on Examples 1-3 and Comparative Example 5, and in conjunction with Table 1, it can be seen that the composting microbial agent is a process auxiliary component that enhances the effectiveness of raw materials, ensures the stability of soil structure and fertility, accelerates the conversion of organic matter from plant residues, and reduces the adverse effects of uncomposted substances on the soil. If this component is removed, the 180-day bulk density change rate increases from -0.8% to 0.0% in the examples to +4.4%, the water-stable aggregate change rate decreases from -0.9% to +1.0% to -11.5%, and the available nitrogen retention rate decreases from 91.9% to 92.5% to 82.3%. Insufficient composting of raw materials leads to a decline in both soil structure and fertility stability.
[0067] 6. Based on Examples 1-3 and Comparative Example 6, and in conjunction with Table 2, it can be seen that chitosan quaternary ammonium salt is a key protective component for maintaining microbial activity and ensuring soil microecological health. It can reduce the loss of nitrogen-fixing bacteria during storage and application, ensuring the function of microorganisms. If this component is removed, the bacterial count change rate over 180 days decreases from +1.6% to +1.9% in the examples to -17.8%, the actinomycete count change rate decreases from +4.0% to +5.0% to -31.6%, and the urease and phosphatase activity change rates decrease to -20.7% and -25.0%, respectively. Microbial survival and metabolism are inhibited, and soil microecological health deteriorates.
[0068] 7. Based on Examples 1-3 and Comparative Example 7, and in conjunction with Tables 1 and 2, it can be seen that the amount of zinc sulfate added needs to be controlled within a reasonable range of 0.1-0.3 parts to accurately supplement soil trace elements and help maintain microbial activity and nutrient balance. If the amount added is increased to 0.4 parts, the retention rate of available phosphorus after 180 days decreases from 92.8%-93.2% in the examples to 80.0%, and the bacterial count change rate decreases from +1.6%-+1.9% to -14.3%. Excessive trace elements lead to nutrient imbalance and decreased microbial activity, affecting the bistabilization and microecological health.
[0069] 8. Based on Examples 1-3 and Comparative Example 8, and in conjunction with Table 1, it can be seen that the mixing temperature in step S2 needs to be controlled within a reasonable range of 20℃-35℃. This temperature range can ensure that the organic raw materials and inorganic nutrients are mixed evenly, and avoid nutrient volatilization due to high temperature. If the temperature rises to 45℃, the 180-day available phosphorus retention rate drops from 92.8%-93.2% in the examples to 67.8%, and the bulk density change rate rises from -0.8%-0.0% to +5.0%. Nutrient volatilization intensifies, mixing uniformity decreases, and fertility stability and soil structure both rebound.
[0070] 9. Combining Examples 1-3 and Comparative Example 9 with Table 1, it can be seen that the slow-release system composed of biodegradable polymers and natural mineral materials has a synergistic effect. The two jointly adsorb nutrients to extend the supply cycle and optimize soil structure. If the biodegradable polymers are removed and only natural mineral materials are retained, the 180-day available phosphorus retention rate decreases from 92.8%-93.2% in the examples to 72.8%, and the water-stable aggregate change rate decreases to -16.4%. The slow-release and structural improvement capabilities of a single natural mineral are limited and cannot completely prevent nutrient loss and structural rebound.
[0071] 10. As can be seen from Examples 1-3 and Comparative Example 10, and Table 2, the viable count of nitrogen-fixing bacteria needs to be controlled at 1×10⁻⁶. 6 -1×10 9 The appropriate range of CFU / g ensures that viable bacteria effectively participate in soil nitrogen cycling and microecological construction; if the viable bacteria count drops to 1×10⁻⁶, it indicates a deficiency. 5 The CFU / g of the 180-day change rate of actinomycete count decreased from +4.0% to +5.0% in the previous example to -22.2%, and the change rate of phosphatase activity decreased from -3.8% to -4.5% to -21.1%. The microbial function was weakened and unable to maintain the health of the soil microecology and the balance of nutrient cycling.
[0072] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.
Claims
1. An organic-inorganic compound fertilizer for improving sandy soil, characterized in that, The composition comprises the following raw materials by weight: humic acid 10-25 parts, organic compost 20-40 parts, plant residues 10-30 parts, ammonium nitrate 1.5-5 parts, potassium dihydrogen phosphate 1-3 parts, potassium chloride 1.5-4 parts, calcium oxide 0.5-2 parts, magnesium oxide 0.3-1 part, nitrogen-fixing bacteria 0.5-3 parts, phosphorus solubilizing bacteria 0.5-3 parts, growth-promoting microorganisms 0.5-3 parts, natural mineral materials 5-20 parts, biodegradable polymers 2-10 parts, zinc sulfate 0.1-0.3 parts, sodium selenite 0.02-0.1 parts, and ammonium molybdate 0.01-0.05 parts.
2. The organic-inorganic compound fertilizer for improving sandy soil according to claim 1, characterized by comprising: The nitrogen-fixing bacteria used are *Azotobacter chrysophagus*, with a viable count of 1 × 10⁻⁶. 6 –1×10 9 CFU / g, phosphate-solubilizing bacteria used: Bacillus subtilis, viable count 1×10⁻⁶ 6 –1×10 9 CFU / g, the growth-promoting microorganism used is Trichoderma harzianum, viable count 1×10⁻⁶ 6 –1×10 9 CFU / g.
3. The organic-inorganic compound fertilizer for improving sandy soil according to claim 1, characterized by comprising: The natural mineral material comprises one or more of montmorillonite, kaolin, zeolite, and diatomite.
4. The organic-inorganic compound fertilizer for improving sandy soil according to claim 1, characterized by comprising: The biodegradable polymer is polylactic acid or polyvinyl alcohol.
5. A method for preparing an organic-inorganic compound fertilizer for improving sandy soil, characterized in that, The improved organic-inorganic compound fertilizer for sandy soil in claims 1-4 comprises the following steps: S1: raw material pretreatment; S2: mixing the organic raw material and inorganic nutrients in the pretreated raw material to prepare a base mixture; S3: mixing and incubating the microorganisms with a protective agent to prepare a microbial mixture; S4: mixing the base mixture, microbial mixture, natural mineral material, biodegradable polymer, and trace elements to prepare a composite mixture; S5: molding, drying, and packaging the composite mixture for storage.
6. The method of claim 5, wherein the organic-inorganic compound fertilizer for improving sandy soil is prepared by mixing 1 part by weight of the organic material, 1 part by weight of the inorganic material, and 0.1 to 0.5 parts by weight of the clay material. The pretreatment in S1 comprises: crushing the plant residues to a particle size of 0.1-0.5 mm, composting at 50-60°C for 7-10 days to decompose, controlling the moisture content during the decomposition process at 50-60%, and adding a decomposition agent, wherein the decomposition agent is composed of Aspergillus oryzae and yeast bacteria at a weight ratio of 3:1; crushing the organic compost to a particle size of 0.2-0.8 mm and passing through an 80-mesh sieve.
7. The method of claim 5, wherein the organic-inorganic compound fertilizer for improving sandy soil is prepared by mixing 1 part by weight of the organic material, 1 part by weight of the inorganic material, and 0.1 to 0.5 parts by weight of the clay material. In S2, after mixing the pretreated organic compost and plant residues in S1, ammonium nitrate, potassium dihydrogen phosphate, potassium chloride, calcium oxide, and magnesium oxide are added, and a spiral stirrer is used for mixing, with a temperature of 20-35°C, a stirring speed of 50-100 rpm, and a stirring time of 30-60 minutes.
8. The method of claim 5, wherein the organic-inorganic compound fertilizer for improving sandy soil is prepared by mixing 1 part by weight of the organic material, 1 part by weight of the inorganic material, and 0.1 to 0.5 parts by weight of the clay material. In S3, the specific steps for mixing and incubating the microorganisms with a protective agent are as follows: adding nitrogen-fixing bacteria, phosphorus solubilizing bacteria, and growth-promoting microorganisms to a microbial protective agent and chitosan quaternary ammonium salt, wherein the microbial protective agent is composed of sodium alginate and sucrose at a weight ratio of 1:1-2:1, the chitosan quaternary ammonium salt has a degree of deacetylation of not less than 85% and a molecular weight of 5000-10000 Da, and the mixture is incubated at 25-30°C and a humidity of 60-70% for 24-48 hours.
9. The method of claim 5, wherein the organic-inorganic compound fertilizer for improving sandy soil is prepared by mixing 1 part by weight of the organic material, 1 part by weight of the inorganic material, and 0.1 to 0.5 parts by weight of the clay material. In S4, the specific steps for preparing the composite mixture are as follows: adding the microbial mixture prepared in S3 to the base mixture prepared in S2, stirring at 40-60 rpm for 10-20 minutes until uniform; then adding the natural mineral material, biodegradable polymer, zinc sulfate, sodium selenite, and ammonium molybdate, stirring at 30-60 rpm at 25-40°C for 20-40 minutes until uniform.
10. The method of claim 5, wherein the organic-inorganic compound fertilizer for improving sandy soil is prepared by mixing 10-30 parts by weight of the organic material, 10-30 parts by weight of the inorganic material, and 40-60 parts by weight of the clay material. In S5, the specific steps for molding, drying, and packaging the composite mixture for storage are as follows: First, the composite mixture prepared in the S4 step is crushed to 100-200 mesh, and formed into granules by a double screw extrusion granulator. After forming, the granule particle size is 3-8 mm; Then, the formed granules are placed in a hot air circulating dryer for drying. During the drying process, the hot air speed is 0.5-1.0 m / s, the temperature is 40°C-60°C, the time is 4-8 hours, and the granules are turned over every 1-2 hours; The dried granules are loaded into a polypropylene woven bag and stored in an environment with a temperature of 20°C-30°C and a humidity of 40%-60%.