Slow-release long-acting compound fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of compound fertilizers, in particular to a slow-release long-acting compound fertilizer and a preparation method thereof. According to the slow-release long-acting compound fertilizer, N-isopropylacrylamide modified carrageenan-humic acid is used as a carrier material to wrap a nitrogen-phosphorus-potassium fertilizer to form an inner-layer compound, and an outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material. After being applied into soil, the outer layer material is slowly degraded to form micropores under the action of pH value, water and microorganisms, and water permeates into the micropores. N-isopropylacrylamide in the inner layer has temperature responsiveness, molecular chains shrink at high temperature to accelerate release of nutrients, and the molecular chains stretch at low temperature to slow release. The outer molecular sieve can temporarily store nutrient ions, and hydroxyapatite is degraded to release phosphate ions. A hydrogen bond network is formed between the inner and outer layers to enhance structural stability and regulate nutrient release. In the release process, nutrient ions need to break through a hydrogen bond network and generate reversible ion exchange with the molecular sieve, and accurate regulation and control of nutrient release are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of compound fertilizers, and in particular to a slow-release long-acting compound fertilizer and a preparation method thereof. Background Art

[0002] Traditional quick-acting fertilizers often have problems such as large nutrient loss and low utilization rate, while slow-release long-acting compound fertilizers can better solve these problems. Its mechanism of action is to regulate nutrient release by controlling the degradation rate of the coating material or the breaking rate of chemical bonds, so that the fertilizer can continuously and stably supply the nutrients such as nitrogen, phosphorus, and potassium required for crop growth, and achieve slow release and continuous supply of nutrients. The advantage of this type of fertilizer is that it can extend the effective period of fertilizer, reduce the number of fertilization times, improve fertilizer utilization, and reduce the risk of environmental pollution.

[0003] In actual applications, slow-release long-acting compound fertilizers usually only need to be applied once to continuously supply nutrients for 3 to 6 months or even longer, reducing the labor intensity of farmers in fertilizing. This type of fertilizer is particularly suitable for crops with long growth cycles such as rice, corn, and cash crops. It is also widely used in facility agriculture and fruit tree planting. Since the nutrient release is relatively uniform, it can avoid the problem of excess nutrients in the early stage and insufficient nutrients in the later stage of traditional fertilizers, which is conducive to the balanced growth of crops and the improvement of yield quality.

[0004] However, the current slow-release and long-acting compound fertilizers still face some application difficulties. The most prominent problem is that the accuracy and stability of nutrient release need to be improved. Due to the influence of environmental factors, such as temperature changes, fluctuations in soil moisture content, etc., the nutrient release rate will become unstable. Especially under extreme weather conditions, there may be a phenomenon of too fast release in the early stage or insufficient release in the later stage, which makes it difficult to fully match the differentiated nutrient needs of crops at different growth stages. This mismatch between nutrient supply and crop demand not only affects the efficiency of fertilizer use, but may also affect the growth and development of crops. In addition, factors such as soil microbial activity and pH value will also affect the degradation rate of the coating material, thereby affecting the stability of nutrient release. The existence of these problems makes the slow-release and long-acting compound fertilizers still have certain uncertainties in practical applications, and it is necessary to further optimize product performance and improve application technology. Summary of the invention

[0005] (1) Technical issues to be solved

[0006] The object of the present invention is to provide a slow-release long-acting compound fertilizer and a preparation method thereof, so as to solve the problem of inaccurate nutrient release.

[0007] (2) Technical solution

[0008] To achieve the above object, on the one hand, the present invention provides a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 15 to 20 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 50 to 60 parts of nitrogen, phosphorus and potassium fertilizers, and 25 to 30 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0009] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0010] Furthermore, the preparation method of the N-isopropylacrylamide modified carrageenan-humic acid comprises:

[0011] S11. dissolving k-carrageenan in deionized water and stirring in a water bath at 60 to 70° C. for 2 to 3 hours to obtain a carrageenan solution;

[0012] S12. Weigh humic acid and add it to deionized water, adjust the pH to 7.0-7.5, and stir magnetically for 1-2 hours to obtain a humic acid solution;

[0013] S13. Weigh N-isopropylacrylamide and N,N'-methylenebisacrylamide, dissolve them in deionized water, and then introduce N2 for 15 to 20 minutes to obtain a mixed solution A;

[0014] S14. mixing the carrageenan solution and the humic acid solution, and then adding the mixed solution A to obtain a mixed solution B, passing N2 into the mixed solution B for 10 to 20 minutes to obtain a mixed solution C, adding ammonium persulfate and tetramethylethylenediamine to the mixed solution C to obtain a mixed solution D, and reacting the mixed solution D at 25 to 35° C. for 4 to 6 hours to obtain a reaction solution A;

[0015] S15. The reaction solution A is dialyzed for 3 to 4 days, and the water is changed 3 to 4 times a day to obtain a dialyzed product. The dialyzed product is freeze-dried for 36 to 48 hours to obtain N-isopropylacrylamide-modified carrageenan-humic acid.

[0016] Furthermore, the preparation method of the nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material comprises:

[0017] S21. Add nano-hydroxyapatite to anhydrous ethanol, then add γ-aminopropyltriethoxysilane to obtain a mixed solution A, ultrasonicate the mixed solution A for 30 to 40 minutes to obtain a mixed solution A after ultrasonication, reflux and stir the mixed solution A after ultrasonication at 80 to 90° C. for 4 to 5 hours to obtain a mixed solution A after reaction, filter the mixed solution A after reaction to obtain a filtered product A, wash the filtered product A with ethanol for 3 to 4 times to obtain a washed product A, and vacuum dry the washed product A at 60 to 70° C. for 12 to 24 hours to obtain a product A;

[0018] S22. Activate the ZSM-5 molecular sieve at 100-120° C. for 4-5 hours to obtain an activated molecular sieve, cool the activated molecular sieve to room temperature and add γ-aminopropyltriethoxysilane to obtain a mixed solution B, stir the mixed solution B at room temperature for 2-3 hours to obtain a stirred mixed solution B, filter the stirred mixed solution B to obtain a filtered product B, wash the filtered product B with ethanol for 3-4 times to obtain a washed product B, and vacuum dry the washed product B at 70-80° C. for 6-8 hours to obtain a product B;

[0019] S23. Add product A and product B to xylene, and then ultrasonicate for 1 to 1.5 hours to obtain a suspension, dissolve phenyl silicone resin in xylene to obtain solution C, add solution C to the suspension to obtain solution D, mechanically stir solution D for 30 to 40 minutes to obtain a stirred solution D, and ultrasonicate the stirred solution D for 30 to 40 minutes to obtain a uniform slurry;

[0020] S24. Pour the uniform slurry into a mold and pre-cure it at room temperature for 2 to 3 hours to obtain a pre-cured slurry, cure the pre-cured slurry at 80 to 90°C for 2 to 3 hours to obtain a first cured slurry, post-cure the first cured slurry at 120 to 130°C for 2 to 3 hours to obtain a second cured slurry, cool the second cured slurry to room temperature to obtain a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0021] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing a slow-release long-acting compound fertilizer, which is applied to the slow-release long-acting compound fertilizer, and comprises the following steps:

[0022] S31. dissolving carrageenan-humic acid modified with N-isopropylacrylamide in deionized water to obtain solution A, heating solution A in a water bath at 60 to 70° C. with stirring for 2 to 3 hours to obtain solution B, cooling solution B to 30 to 40° C. to obtain cooled solution B, adding nitrogen, phosphorus and potassium compound fertilizer to the cooled solution B, and mechanically stirring for 30 to 40 minutes to obtain solution C, and ultrasonically treating solution C for 15 to 30 minutes to obtain a mixture;

[0023] S32. The mixture was spray dried at an inlet temperature of 180 to 200°C, an outlet temperature of 85 to 100°C, an atomization pressure of 0.2 to 0.3 MPa, and a feed rate of 10 to 15 mL / min to obtain inner layer composite particles;

[0024] S33. The nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material is dissolved in xylene and stirred for 10 to 15 minutes to obtain a coating solution;

[0025] S34. The inner layer of the composite particles was added to the fluidized bed, the bed temperature was 40 to 45 ° C, the spraying rate was 10 to 15 mL / min, the atomization pressure was 0.1 to 0.15 MPa, the fluidizing air temperature was 40 to 50 ° C, and the coating was obtained;

[0026] S35. The coated material is dried at 60 to 70 ° C for 2 to 3 hours to obtain a dried coated material, the dried coated material is heated to 80 to 90 ° C for 1 to 2 hours to obtain a solidified material, and the solidified material is cooled to room temperature to obtain a cooled material;

[0027] S36. The cooled material is sieved, and a particle size of 0.5 to 2 mm is selected to obtain a sieved material, and the sieved material is vacuum dried for 12 to 24 hours to obtain a slow-release long-acting compound fertilizer.

[0028] The mechanism of action of the above raw material components is as follows:

[0029] N-isopropylacrylamide modified carrageenan-humic acid: In the inner layer structure, N-isopropylacrylamide modified carrageenan-humic acid is used as a carrier material to encapsulate nitrogen, phosphorus and potassium fertilizers to form a stable complex. This design has unique advantages, mainly reflected in the significant temperature responsiveness of N-isopropylacrylamide. When the ambient temperature changes, its molecular chain segments will undergo a reversible conformational transition, causing the carrier network structure to contract or relax, thereby realizing intelligent regulation of the nutrient release rate. At the same time, the carrageenan-humic acid network structure has excellent water retention and natural slow-release properties, which can maintain a stable moisture environment and ensure the continuous and balanced release of nutrients.

[0030] Nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material: The nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material used in the outer layer further enhances the performance of the fertilizer. This composite material has a unique structural design, in which nano-hydroxyapatite can not only provide additional phosphorus source supplementation, but also enhance the mechanical strength of the material through its special crystal structure; the molecular sieve component has a regular pore structure and selective adsorption characteristics, which can effectively regulate the diffusion and release process of various nutrient ions; and the phenyl silicone resin provides excellent chemical stability and waterproof performance, effectively protecting the inner layer of the composite.

[0031] Nitrogen, phosphorus and potassium fertilizers: Fertilizers are three nutrients needed for plant growth.

[0032] (3) Beneficial effects

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The temperature-sensitive properties of N-isopropylacrylamide are used to match nutrient release with crop growth requirements. The release is accelerated at high temperatures (peak growth period) and slowed down at low temperatures (slow growth period), thereby improving fertilizer utilization efficiency.

[0035] 2. The composite structure of the inner and outer layers forms a control barrier. The reversible ion exchange effect of the outer molecular sieve and the inner hydrogen bond network jointly regulate the release of nutrients, avoiding the sudden loss of nutrients. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a physical picture of the slow-release long-acting compound fertilizer according to Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The test equipment and preparations of the examples described below are as follows:

[0039] Electronic balance (Sartorius, Germany), electric blast constant temperature dryer (Shanghai Fomar Experimental Equipment), electric constant temperature water bath (Jiangsu Kedao), pulverizer (Shandong Tianfang Machinery), magnetic stirrer (Shanghai Meiyingpu), vacuum shaping box (Qingdao Kunlun Haisu), ultrasonic cleaner (Shanghai Yingke), freeze dryer (Shanghai Shunzhi), spray dryer (Shanghai Jipu), fluidized bed (Changzhou Longtai); chemicals and reagents were purchased from Sigma-Aldrich.

[0040] Example 1: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 18 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 52 parts of nitrogen, phosphorus and potassium fertilizers, and 26 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0041] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0042] The slow-release long-acting compound fertilizer adopts a double-layer packaging structure design. Figure 1 As shown in the figure, the precise regulation and release of nutrients is achieved through the synergistic effect of the inner and outer layer materials. When this double-layer fertilizer particle is applied to the soil, first, the outer layer of nanohydroxyapatite-molecular sieve doped phenyl silicone resin composite material begins to slowly degrade in the soil environment. This degradation process is mainly affected by the soil pH, moisture content and microbial activity, and gradually forms micropore structures of varying sizes on the surface of the material. These pores not only provide channels for subsequent water penetration, but also serve as important diffusion paths for nutrient release. As the degradation process proceeds, soil moisture gradually penetrates into the inner layer through the formed microporous network and contacts with the carrageenan-humic acid carrier material modified with N-isopropylacrylamide. At this time, a series of structural changes begin to occur in the inner layer material: N-isopropylacrylamide will undergo a reversible conformational transition under the influence of temperature. At higher temperatures (such as the period of vigorous crop growth), the molecular chain will shrink, accelerating the release of nutrients; at lower temperatures (such as the period of slow crop growth), the molecular chain will stretch, slowing down the release rate. This temperature-responsive change cooperates with the network structure of carrageenan-humic acid to form a dynamic regulation system.

[0043] At the same time, the molecular sieve components in the outer layer can temporarily intercept and store some of the nutrient ions (such as NH 4+ , K + This selective adsorption is equivalent to an ion reservoir, which can effectively prevent the sudden release of nutrients and make the release process more gentle. During the degradation process, nano-hydroxyapatite will gradually release phosphate ions, which not only replenishes the effective phosphorus content in the soil, but also forms a balanced supply of nutrients with nitrogen, potassium and other nutrients released from the inner layer.

[0044] In the whole system, an interfacial interaction network is formed between the inner layer of humic acid and the outer layer of nano-hydroxyapatite. A dense hydrogen bond network is formed between the large number of oxygen-containing functional groups (such as -COOH, -OH) in the humic acid molecules and the hydroxyl groups on the surface of nano-hydroxyapatite. This hydrogen bond network not only enhances the physical bonding strength between the inner and outer layers and prevents interlayer separation, but also participates in regulating the transmission and release of nutrient ions through the dynamic formation and breaking process of hydrogen bonds. At the same time, the carboxyl groups in the humic acid molecules can also form coordination complexes with calcium ions on the surface of nano-hydroxyapatite, further stabilizing the interface structure.

[0045] When the nutrient ions in the inner layer (such as NH 4+ , K + When the ions begin to release under the action of temperature response, they first need to break through the barrier of the hydrogen bond network and then interact with the exchangeable cations (such as Na +) ion exchange occurs. This multiple mass transfer resistance and exchange process effectively slows down the release rate of nutrients. At the same time, the ion exchange process of the molecular sieve is reversible and can automatically adjust the exchange rate according to the changes in the surrounding ion concentration, which further optimizes the release kinetics of nutrients. N-isopropylacrylamide-modified carrageenan-humic acid and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composites can achieve corresponding functions in any ratio.

[0046] The preparation method of the N-isopropylacrylamide modified carrageenan-humic acid comprises:

[0047] S11. dissolving k-carrageenan in deionized water and stirring in a water bath at 60 to 70° C. for 2 to 3 hours to obtain a carrageenan solution;

[0048] S12. Weigh humic acid and add it to deionized water, adjust the pH to 7.0-7.5, and stir magnetically for 1-2 hours to obtain a humic acid solution;

[0049] S13. Weigh N-isopropylacrylamide and N,N'-methylenebisacrylamide, dissolve them in deionized water, and then introduce N2 for 15 to 20 minutes to obtain a mixed solution A;

[0050] S14. mixing the carrageenan solution and the humic acid solution, and then adding the mixed solution A to obtain a mixed solution B, passing N2 into the mixed solution B for 10 to 20 minutes to obtain a mixed solution C, adding ammonium persulfate and tetramethylethylenediamine to the mixed solution C to obtain a mixed solution D, and reacting the mixed solution D at 25 to 35° C. for 4 to 6 hours to obtain a reaction solution A;

[0051] S15. The reaction solution A is dialyzed for 3 to 4 days, and the water is changed 3 to 4 times a day to obtain a dialyzed product. The dialyzed product is freeze-dried for 36 to 48 hours to obtain N-isopropylacrylamide-modified carrageenan-humic acid.

[0052] The preparation method of the nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material comprises:

[0053] S21. Add nano-hydroxyapatite to anhydrous ethanol, then add γ-aminopropyltriethoxysilane to obtain a mixed solution A, ultrasonicate the mixed solution A for 30 to 40 minutes to obtain a mixed solution A after ultrasonication, reflux and stir the mixed solution A after ultrasonication at 80 to 90° C. for 4 to 5 hours to obtain a mixed solution A after reaction, filter the mixed solution A after reaction to obtain a filtered product A, wash the filtered product A with ethanol for 3 to 4 times to obtain a washed product A, and vacuum dry the washed product A at 60 to 70° C. for 12 to 24 hours to obtain a product A;

[0054] S22. Activate the ZSM-5 molecular sieve at 100-120° C. for 4-5 hours to obtain an activated molecular sieve, cool the activated molecular sieve to room temperature and add γ-aminopropyltriethoxysilane to obtain a mixed solution B, stir the mixed solution B at room temperature for 2-3 hours to obtain a stirred mixed solution B, filter the stirred mixed solution B to obtain a filtered product B, wash the filtered product B with ethanol for 3-4 times to obtain a washed product B, and vacuum dry the washed product B at 70-80° C. for 6-8 hours to obtain a product B;

[0055] S23. Add product A and product B to xylene, and then ultrasonicate for 1 to 1.5 hours to obtain a suspension, dissolve phenyl silicone resin in xylene to obtain solution C, add solution C to the suspension to obtain solution D, mechanically stir solution D for 30 to 40 minutes to obtain a stirred solution D, and ultrasonicate the stirred solution D for 30 to 40 minutes to obtain a uniform slurry;

[0056] S24. Pour the uniform slurry into a mold and pre-cure it at room temperature for 2 to 3 hours to obtain a pre-cured slurry, cure the pre-cured slurry at 80 to 90°C for 2 to 3 hours to obtain a first cured slurry, post-cure the first cured slurry at 120 to 130°C for 2 to 3 hours to obtain a second cured slurry, cool the second cured slurry to room temperature to obtain a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0057] A method for preparing a slow-release long-acting compound fertilizer, which is applied to the slow-release long-acting compound fertilizer, comprises the following steps:

[0058] S31. dissolving carrageenan-humic acid modified with N-isopropylacrylamide in deionized water to obtain solution A, heating solution A in a water bath at 60 to 70° C. with stirring for 2 to 3 hours to obtain solution B, cooling solution B to 30 to 40° C. to obtain cooled solution B, adding nitrogen, phosphorus and potassium compound fertilizer to the cooled solution B, and mechanically stirring for 30 to 40 minutes to obtain solution C, and ultrasonically treating solution C for 15 to 30 minutes to obtain a mixture;

[0059] S32. The mixture was spray dried at an inlet temperature of 180 to 200°C, an outlet temperature of 85 to 100°C, an atomization pressure of 0.2 to 0.3 MPa, and a feed rate of 10 to 15 mL / min to obtain inner layer composite particles;

[0060] S33. The nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material is dissolved in xylene and stirred for 10 to 15 minutes to obtain a coating solution;

[0061] S34. The inner layer of the composite particles was added to the fluidized bed, the bed temperature was 40 to 45 ° C, the spraying rate was 10 to 15 mL / min, the atomization pressure was 0.1 to 0.15 MPa, the fluidizing air temperature was 40 to 50 ° C, and the coating was obtained;

[0062] S35. The coated material is dried at 60 to 70 ° C for 2 to 3 hours to obtain a dried coated material, the dried coated material is heated to 80 to 90 ° C for 1 to 2 hours to obtain a solidified material, and the solidified material is cooled to room temperature to obtain a cooled material;

[0063] S36. The cooled material is sieved, and a particle size of 0.5 to 2 mm is selected to obtain a sieved material, and the sieved material is vacuum dried for 12 to 24 hours to obtain a slow-release long-acting compound fertilizer.

[0064] Example 2: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 15 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 50 parts of nitrogen, phosphorus and potassium fertilizers, and 25 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0065] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0066] The preparation method of the N-isopropylacrylamide modified carrageenan-humic acid and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0067] Example 3: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 20 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 60 parts of nitrogen, phosphorus and potassium fertilizers, and 30 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0068] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0069] The preparation method of the N-isopropylacrylamide modified carrageenan-humic acid and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0070] Example 4: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 17 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 55 parts of nitrogen, phosphorus and potassium fertilizers, and 28 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0071] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0072] The preparation method of the N-isopropylacrylamide modified carrageenan-humic acid and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0073] Control group 1: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 18 parts of carrageenan-humic acid, 52 parts of nitrogen, phosphorus and potassium fertilizers, and 26 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0074] The slow-release long-acting compound fertilizer uses carrageenan-humic acid as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0075] The preparation method of the carrageenan-humic acid and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0076] Control group 2: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 18 parts of carrageenan modified with N-isopropylacrylamide, 52 parts of nitrogen, phosphorus and potassium fertilizers, and 26 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material;

[0077] The slow-release long-acting compound fertilizer uses carrageenan modified with N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

[0078] The preparation method of the N-isopropylacrylamide modified carrageenan and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0079] Control group 3: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 18 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 52 parts of nitrogen, phosphorus and potassium fertilizers, and 26 parts of nano-hydroxyapatite-phenyl silicone resin composite material;

[0080] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-phenyl silicone resin composite material.

[0081] The preparation method of the N-isopropylacrylamide-modified carrageenan-humic acid and nano-hydroxyapatite-phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0082] Control group 4: This example discloses a slow-release long-acting compound fertilizer, comprising the following raw materials in parts by weight: 18 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 52 parts of nitrogen, phosphorus and potassium fertilizers, and 26 parts of molecular sieve-doped phenyl silicone resin composite materials;

[0083] The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified with N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a molecular sieve doped with phenyl silicone resin composite material.

[0084] The preparation method of the N-isopropylacrylamide modified carrageenan-humic acid and molecular sieve doped phenyl silicone resin composite material in this embodiment is consistent with that in Example 1. The preparation method of a slow-release long-acting compound fertilizer in this embodiment is consistent with that in Example 1.

[0085] Test verification:

[0086] 1. Nutrient release experiment under different temperature conditions

[0087] Prepare 3 constant temperature incubators, set the temperatures at 15°C, 25°C, and 35°C respectively, put the fertilizer samples of each embodiment group and the control group into a nylon mesh bag and seal it, put the nylon mesh bag containing the sample into a beaker containing 100 mL of deionized water, put the beaker into a constant temperature incubator of the corresponding temperature, and take samples regularly for measurement.

[0088] 2. Release experiments in soils with different pH values

[0089] 1. Collect natural soil samples, air-dry and sieve to 2 mm, adjust the soil pH to 5.5, 6.5, or 7.5 with dilute hydrochloric acid or sodium hydroxide, put the soil with adjusted pH into a plastic pot, evenly mix the fertilizer samples of each embodiment group and the control group into the soil, incubate at a constant temperature of 25° C., and regularly sample and determine the soluble nutrient content of the soil.

[0090] 3. Degradation experiments under different moisture conditions

[0091] The field water holding capacity of the soil was determined, and the moisture content corresponding to 40%, 60%, and 80% of the field water holding capacity was calculated. 300 g of air-dried soil was placed in a plastic basin, and the fertilizer samples of each embodiment group and the control group were added and evenly mixed. The calculated amount of water was added to the target water content, and water was regularly added to maintain the target water content. The soil was cultured at a constant temperature of 25° C., and samples were taken regularly to determine the degree of degradation.

[0092] 4. Dynamic light scattering particle size measurement experiment

[0093] The fertilizer samples of each embodiment group and the control group were prepared into a water dispersion, ultrasonically treated for 5 to 10 minutes, and the dispersion was transferred to a cuvette. A temperature gradient (15° C., 25° C., 35° C.) was set, and the measurement was performed after stabilization at each temperature point for 10 minutes.

[0094] Table 1 Cumulative nutrient release rate under different temperature conditions (%)

[0095]

[0096] Table 2 Cumulative nutrient release rate under different pH conditions (28 days, 25°C)

[0097] Sample Group pH 5.5 pH 6.5 pH 7.5 Example 1 58.4 63.8 67.2 Example 2 56.8 62.1 65.9 Example 3 56.2 61.5 65.1 Example 4 57.5 62.9 66.4 Control group 1 65.8 71.4 75.2 Control group 2 67.5 73.2 77.1 Control group 3 63.6 69.2 73.1 Control group 4 61.9 67.5 71.2

[0098] Table 3 Degradation rate of samples under different moisture conditions (28 days, 25°C)

[0099] Sample Group 40% field capacity 60% field capacity 80% field capacity Example 1 32.5 45.8 58.4 Example 2 31.2 44.2 56.9 Example 3 30.8 43.6 56.1 Example 4 31.9 45.1 57.6 Control group 1 38.6 52.4 65.8 Control group 2 39.8 53.9 67.2 Control group 3 37.2 50.8 63.9 Control group 4 36.1 49.2 62.1

[0100] Table 4 Average particle size at different temperatures (nm)

[0101] Sample Group 15℃ 25℃ 35℃ Example 1 285 245 198 Example 2 292 252 205 Example 3 298 258 212 Example 4 289 248 202 Control group 1 312 285 245 Control group 2 325 295 258 Control group 3 308 278 238 Control group 4 302 272 232

[0102] By analyzing the above experimental data, the differences in nutrient release control and material properties between the embodiment group and the control group can be clearly observed. In the temperature responsiveness experiment, the cumulative release rates of Example 1 at 15°C, 25°C and 35°C after 28 days were 48.3%, 63.8% and 78.2%, respectively, showing an ideal temperature dependence, while the release rates of Control Groups 1 and 2 under the same conditions were generally 10 to 15 percentage points higher, indicating that the lack of N-isopropylacrylamide modification or humic acid components would significantly reduce the controlled release effect of the material. The results of the pH response experiment showed that the release rate of Example 1 in the pH range of 5.5 to 7.5 changed less (58.4%-67.2%), while the release rate of the control group changed more dramatically, confirming the improvement of pH adaptability by the double-layer structure design. In terms of moisture responsiveness, the degradation rate of Example 1 at different field water holding capacities (32.5%-58.4%) was significantly lower than that of the control group (36.1%-67.2%), indicating that the modified material has better moisture tolerance. The dynamic light scattering experimental data can best reflect the intelligent response characteristics of the material. When the temperature rises from 15°C to 35°C, the particle size of Example 1 decreases from 285nm to 198nm, and the shrinkage rate reaches 30.5%, while the particle size change of the control group is only 21.5%-22.8%, which fully confirms that the N-isopropylacrylamide modification gives the material excellent temperature-sensitive properties. By comparing the data of Examples 1-4, it can be found that when the amount of carrageenan-humic acid modified by N-isopropylacrylamide is 18 parts, nitrogen, phosphorus and potassium fertilizer is 52 parts, and nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material is 26 parts, the best synergistic effect can be achieved, which not only ensures sufficient fertilizer loading, but also achieves precise controlled release effect.

[0103] Finally, it should be noted that: Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A slow-release long-acting compound fertilizer, characterized in that: The method comprises the following raw materials in parts by weight: 15 to 20 parts of carrageenan-humic acid modified with N-isopropylacrylamide, 50 to 60 parts of nitrogen, phosphorus and potassium fertilizers, and 25 to 30 parts of nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material; The slow-release long-acting compound fertilizer uses carrageenan-humic acid modified by N-isopropylacrylamide as a carrier material to wrap nitrogen, phosphorus and potassium fertilizers to form an inner layer composite material, and the outer layer is a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

2. A slow-release long-acting compound fertilizer as claimed in claim 1, characterized in that: The preparation method of the N-isopropylacrylamide modified carrageenan-humic acid comprises: S11. dissolving k-carrageenan in deionized water and stirring in a water bath at 60 to 70° C. for 2 to 3 hours to obtain a carrageenan solution; S12. Weigh humic acid and add it to deionized water, adjust the pH to 7.0-7.5, and stir magnetically for 1-2 hours to obtain a humic acid solution; S13. Weigh N-isopropyl acrylamide and N,N'-methylenebisacrylamide and dissolve them in deionized water, then introduce N2 for 15 to 20 minutes to obtain a mixed solution A; S14. mixing the carrageenan solution and the humic acid solution, and then adding the mixed solution A to obtain a mixed solution B, passing N2 into the mixed solution B for 10 to 20 minutes to obtain a mixed solution C, adding ammonium persulfate and tetramethylethylenediamine to the mixed solution C to obtain a mixed solution D, and reacting the mixed solution D at 25 to 35° C. for 4 to 6 hours to obtain a reaction solution A; S15. The reaction solution A is dialyzed for 3 to 4 days, and the water is changed 3 to 4 times a day to obtain a dialyzed product. The dialyzed product is freeze-dried for 36 to 48 hours to obtain N-isopropylacrylamide-modified carrageenan-humic acid.

3. A slow-release long-acting compound fertilizer as claimed in claim 1, characterized in that: The preparation method of the nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material comprises: S21. Add nano-hydroxyapatite to anhydrous ethanol, then add γ-aminopropyltriethoxysilane to obtain a mixed solution A, ultrasonicate the mixed solution A for 30 to 40 minutes to obtain a mixed solution A after ultrasonication, reflux and stir the mixed solution A after ultrasonication at 80 to 90° C. for 4 to 5 hours to obtain a mixed solution A after reaction, filter the mixed solution A after reaction to obtain a filtered product A, wash the filtered product A with ethanol for 3 to 4 times to obtain a washed product A, and vacuum dry the washed product A at 60 to 70° C. for 12 to 24 hours to obtain a product A; S22. Activate the ZSM-5 molecular sieve at 100-120° C. for 4-5 hours to obtain an activated molecular sieve, cool the activated molecular sieve to room temperature and add γ-aminopropyltriethoxysilane to obtain a mixed solution B, stir the mixed solution B at room temperature for 2-3 hours to obtain a stirred mixed solution B, filter the stirred mixed solution B to obtain a filtered product B, wash the filtered product B with ethanol for 3-4 times to obtain a washed product B, and vacuum dry the washed product B at 70-80° C. for 6-8 hours to obtain a product B; S23. Add product A and product B to xylene, and then ultrasonicate for 1 to 1.5 hours to obtain a suspension, dissolve phenyl silicone resin in xylene to obtain solution C, add solution C to the suspension to obtain solution D, mechanically stir solution D for 30 to 40 minutes to obtain a stirred solution D, and ultrasonicate the stirred solution D for 30 to 40 minutes to obtain a uniform slurry; S24. Pour the uniform slurry into a mold and pre-cure it at room temperature for 2 to 3 hours to obtain a pre-cured slurry, cure the pre-cured slurry at 80 to 90°C for 2 to 3 hours to obtain a first cured slurry, post-cure the first cured slurry at 120 to 130°C for 2 to 3 hours to obtain a second cured slurry, cool the second cured slurry to room temperature to obtain a nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material.

4. A method for preparing a slow-release long-acting compound fertilizer, which is used to prepare a slow-release long-acting compound fertilizer as claimed in any one of claims 1 to 3, characterized in that: The method comprises the following steps: S31. dissolving carrageenan-humic acid modified with N-isopropylacrylamide in deionized water to obtain solution A, heating solution A in a water bath at 60 to 70° C. with stirring for 2 to 3 hours to obtain solution B, cooling solution B to 30 to 40° C. to obtain cooled solution B, adding nitrogen, phosphorus and potassium compound fertilizer to the cooled solution B, and mechanically stirring for 30 to 40 minutes to obtain solution C, and ultrasonically treating solution C for 15 to 30 minutes to obtain a mixture; S32. The mixture was spray dried at an inlet temperature of 180 to 200°C, an outlet temperature of 85 to 100°C, an atomization pressure of 0.2 to 0.3 MPa, and a feed rate of 10 to 15 mL / min to obtain inner layer composite particles; S33. The nano-hydroxyapatite-molecular sieve doped phenyl silicone resin composite material is dissolved in xylene and stirred for 10 to 15 minutes to obtain a coating solution; S34. The inner layer of the composite particles was added to the fluidized bed, the bed temperature was 40 to 45 ° C, the spraying rate was 10 to 15 mL / min, the atomization pressure was 0.1 to 0.15 MPa, the fluidizing air temperature was 40 to 50 ° C, and the coating was obtained; S35. The coated material is dried at 60 to 70 ° C for 2 to 3 hours to obtain a dried coated material, the dried coated material is heated to 80 to 90 ° C for 1 to 2 hours to obtain a solidified material, and the solidified material is cooled to room temperature to obtain a cooled material; S36. The cooled material is sieved, and a particle size of 0.5 to 2 mm is selected to obtain a sieved material, and the sieved material is vacuum dried for 12 to 24 hours to obtain a slow-release long-acting compound fertilizer.

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