Slow-release activated phosphate fertilizer based on roller extrusion granulation and preparation method thereof

Abstract

The application provides a slow-release activated phosphate fertilizer based on roller extrusion granulation and a preparation method thereof, and belongs to the technical field of novel slow-release fertilizer preparation. The fertilizer comprises, by weight, 45-55 parts of superphosphate, 20-30 parts of humic acid, 8-12 parts of bentonite, 4-6 parts of starch and 8-12 parts of wood vinegar; all the solid materials are sieved to 80-100 meshes, the wood vinegar is sprayed after dry mixing, and the product is formed through roller extrusion under the conditions of an extrusion pressure of 18-22 MPa, a roller gap of 0.5-1.5 mm and a pressure roller rotating speed of 10-20 r / min, and then the product is dried at a low temperature of 42-48 DEG C to obtain the finished product. The application constructs a compact organic-inorganic integrated particle skeleton through high-pressure extrusion, simultaneously activates soil inert phosphorus by using humic acid-wood vinegar compound, reduces secondary phosphorus fixation, improves the utilization rate of phosphate fertilizer, reduces agricultural non-point source pollution, and is suitable for industrialized extrusion granulation production.

Description

Technical Field

[0001] This invention relates to the field of novel controlled-release fertilizer preparation technology, specifically to a controlled-release activated phosphate fertilizer based on roller extrusion granulation and its preparation method. Background Technology

[0002] Phosphorus is an essential macronutrient for crop cell division, photosynthesis, and yield formation. The level of available phosphorus supply in the root zone of farmland directly determines arable land productivity. Conventional phosphate fertilizer application results in significant soil fixation losses. Soluble phosphates applied to the soil readily react with iron, aluminum, calcium oxides, and clay minerals in the soil, undergoing precipitation and fixation reactions. Over 70% of exogenous phosphorus is converted into inert phosphorus that crops cannot directly absorb, resulting in a phosphate fertilizer utilization rate of only 10%-25% in the current season. Excessive phosphate fertilizer application in agricultural production has long accelerated the depletion of phosphate rock resources. Accumulated phosphorus in the topsoil enters water bodies through runoff and leaching, causing eutrophication and exacerbating agricultural non-point source pollution. Developing modified phosphate fertilizers with both slow-release phosphorus supply and soil-residual phosphorus activation functions is a crucial pathway to improve phosphorus resource utilization efficiency and achieve green and sustainable agricultural development.

[0003] Existing technologies for improving phosphate fertilizer utilization efficiency can be mainly divided into three categories: The first category is coated slow-release phosphate fertilizer. For example, Chinese patent CN120842020A (publication date 2025-10-28) discloses a coated slow-release high-efficiency micronized phosphate fertilizer, which obtains slow-release micronized phosphate fertilizer by coating carboxymethyl cellulose after core modification. However, coated fertilizers rely solely on physical coating to delay phosphorus dissolution, the coating layer is easily damaged, it cannot activate the inert phosphorus stored in the soil, and some coating materials are difficult to degrade, posing a risk of soil accumulation.

[0004] The second category is organic chelated phosphate fertilizer. For example, Chinese patent CN103044144B (authorization announcement date 2014-05-07) discloses a method for preparing organic chelated fertilizer, which uses a humic liquid-compound amino acid system to achieve nutrient chelation and stability. This type of technology generally has complex processes and high production costs; the products lack physical barrier structures, are prone to phosphorus burst release and loss in the early stage, and the slow release and activation functions are difficult to coordinate.

[0005] The third category involves applying activators alone or in simple combinations with phosphate fertilizers. Humic acid and wood vinegar can activate and fix phosphorus through complexation and acidification; however, phosphorus activated by short-term activating components is easily re-fixed by minerals, and long-term components provide insufficient phosphorus supply during the seedling stage. When activators are simply mixed with superphosphate, a stable organic-inorganic interface is lacking, and phosphorus and activating components are rapidly lost upon contact with water, resulting in limited long-term synergistic effects.

[0006] Extrusion molding technology has been used in fertilizer granulation, but existing extruded phosphate fertilizer formulation systems are relatively simple, mostly using starch and bentonite as single binders, lacking a technical approach to pressure-controlled molecular interface interactions. Current research only conducts simple material mixing molding and phosphorus release performance testing, without forming a complete verification chain of molecular interface, particle internal structure, soil phosphorus component transformation, and crop absorption. It is difficult to simultaneously solve the problems of phosphorus burst release in ordinary superphosphate, secondary phosphorus fixation in soil, and activation of existing phosphorus. There is a lack of low-cost, all-natural, biodegradable, and industrially compatible integrated slow-release activated phosphate fertilizer preparation solutions. Summary of the Invention

[0007] In view of the above-mentioned prior art, the purpose of this invention is to provide a slow-release activated phosphate fertilizer based on roller extrusion granulation and its preparation method.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this invention provides a slow-release activated phosphate fertilizer based on roller extrusion granulation, comprising the following raw material components by weight: 45-55 parts superphosphate, 20-30 parts humic acid, 8-12 parts bentonite, 4-6 parts potato starch, and 8-12 parts wood vinegar; wherein the superphosphate has a P2O5 content of ≥12%; all solid raw materials pass through an 80-100 mesh sieve; the fertilizer is formed into granules by roller extrusion, and the granules are free of hollow or cracked defects.

[0009] In a second aspect, the present invention provides a method for preparing a slow-release activated phosphate fertilizer based on roller extrusion granulation, the steps of which include: (1) Mixing raw materials: crush superphosphate, humic acid, bentonite and potato starch separately, and pass them all through an 80-100 mesh standard sieve to remove large particles of impurities; weigh the solid powder according to the weight ratio, dry mix and stir for 5-10 min; spray wood vinegar in batches and stir continuously for 8-12 min to obtain a moist composite mixture. (2) Roller extrusion molding: The wet composite mixture is fed into a double-roller extrusion granulator. The roller pressure is 18-22 MPa, the roller gap is 0.5-1.5 mm, and the roller speed is 10-20 r / min. The fertilizer preform is obtained by extrusion. The mechanical pressure shortens the intermolecular distance, strengthens the hydrogen bond and surface complexation between organic and inorganic components, and constructs a dense integrated particle skeleton. (3) Low-temperature drying and shaping: The green body is placed in an oven at 42-48℃ and dried to constant weight, and then screened to obtain the finished slow-release activated phosphate fertilizer.

[0010] It should be noted that the shape of the fertilizer preform in this invention is determined by the die cavity of the roller extrusion granulator, and this invention is not limited to columnar particles. By changing the roller die cavity with different structures, other shapes of fertilizer particles such as pillow-shaped, oblate, and square strips can also be obtained. As long as the raw material formula defined in this invention is used, and dense particles without hollows or cracks are obtained under extrusion conditions of 18-22 MPa, the technical effects of phosphorus slow release and activation of inert phosphorus in the soil can still be achieved, even if the particle shape is changed. The embodiments of this invention only use columnar cavities to prepare columnar particles, which is a preferred embodiment of this invention and does not constitute a limitation on the particle shape. The beneficial effects of this invention are: 1. The formula of this invention achieves a functional combination of long-acting activating component humic acid and fast-acting activating component wood vinegar. Bentonite and potato starch form a mineral-organic dual barrier carrier. Unlike simple physical mixing, it forms a dense, crack-free integrated granular skeleton through high-pressure extrusion within a limited pressure range, which reduces the water penetration rate, changes the fertilizer phosphorus release kinetics, and inhibits the explosive release of water-soluble phosphorus from ordinary superphosphate.

[0011] 2. Wood vinegar acts as a liquid-phase wetting and cross-linking medium, achieving rapid activation. After being applied to the soil, small-molecule organic acids dissolve rapidly, locally reducing the rhizosphere pH and dissolving insoluble phosphates, thus enabling rapid phosphorus supply during the seedling stage. Humic acid macromolecules continuously exert their effects of complexing metal ions, competing for mineral adsorption sites, and colloidal coating, protecting already activated phosphorus, inhibiting secondary phosphorus closure and fixation, continuously activating the soil's inherent inert phosphorus, enhancing the Resin-P and NaHCO3-P active phosphorus pools, and reducing HCl-P inert phosphorus.

[0012] 3. The extrusion process strengthens the interfacial bonding between humic acid, wood vinegar, superphosphate, bentonite, and starch, preventing the rapid leaching and loss of activated components upon contact with water; all raw materials are naturally biodegradable and will not produce persistent residues in the soil; the process relies on existing extrusion granulation equipment, the raw materials are readily available, and the process parameters have a wide operating window, making it suitable for industrial production.

[0013] 4. The fertilizer of this invention simultaneously achieves slow release of phosphorus from the fertilizer itself and continuous activation of inert phosphorus in the soil, thereby improving the utilization rate of phosphate fertilizer in the current season, reducing the risk of phosphorus runoff leaching, and mitigating agricultural non-point source pollution. Attached Figure Description

[0014] Figure 1 Photograph of the finished slow-release activated phosphate fertilizer granules obtained by this invention.

[0015] Figure 2 SEM-EDS morphology and elemental surface distribution mapping of fertilizer samples from Example 1 and Comparative Examples 1 and 2 of this invention; Figure 3Characterization spectra of the samples of Example 1 and Comparative Example 2 of this invention; in the figure, A is the FT-IR infrared spectrum, B is the XRD spectrum, C is the XPS full spectrum scan spectrum of the comparative example 2 sample, D is the XPS full spectrum scan spectrum of the sample of Example 1, E is the C1s high-resolution peak spectrum of the comparative example 2 sample, and F is the C1s high-resolution peak spectrum of the sample of Example 1. Figure 4 Example 1 of the present invention: Micro-CT microstructure characterization diagram of fertilizer particles; A in the figure is a schematic diagram of three-dimensional reconstruction of particles, B is a cross-sectional morphology diagram of particles, C is a statistical diagram of particle size distribution, D is a box plot of single particle volume, E is a scatter plot of particle density-sphericity, and F is a schematic diagram of three-dimensional spatial distribution of particles. Figure 5 Example 1 of this invention: Compressive mechanical properties curve of fertilizer granules; A1-A3 in the figure are mechanical curves of sample 2 in comparative example, and B1-B3 are mechanical curves of physical mixture sample 1 in example; Figure 6 Photographs of the above-ground and underground growth states of radishes after harvest in a pot experiment of this invention; Detailed Implementation The following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0016] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0017] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels. Experimental methods without specified detailed conditions are performed according to conventional test methods or the supplier's recommended operating instructions. Wherein: All fertilizer raw materials used in this invention were purchased from Taobao Mall. Among them, superphosphate was purchased from an agricultural supplies and green plant gardening store, in bulk granular form of Fengle phosphate fertilizer, 1.5 kg; humic acid was purchased from Qingyan Youxuan store, in 25 kg; bentonite was purchased from a laboratory supplies direct sales store, in 200 mesh form, 2.5 kg; potato starch was purchased from a Dingxi specialty store, in 2.5 kg; and wood vinegar was purchased from Taobao Laile Youxuan store.

[0018] Example 1: A slow-release activated phosphate fertilizer (SAPF) based on roller extrusion granulation 1. Fertilizer composition: By weight: 50 parts superphosphate (P2O5≥12%), 25 parts humic acid, 10 parts bentonite, 5 parts potato starch, and 10 parts wood vinegar.

[0019] 2. Preparation method: (1) Mixing raw materials: Take superphosphate, humic acid, bentonite and potato starch and crush them separately. Pass them through a 100-mesh standard sieve to remove large particles of impurities. Weigh superphosphate, humic acid, bentonite and potato starch according to the proportion, put them into the mixing tank, dry mix for 10 min, and mix the powder evenly. Spray wood vinegar solution in batches and continue to stir for 10 min to obtain a moist composite mixture. (3) Roller extrusion molding: The wet composite mixture is conveyed to the roller extrusion granulator, the roller pressure is set to 20MPa, the roller gap is 1mm, the roller speed is 15r / min, and columnar fertilizer blanks are produced by extrusion; the mechanical pressure shortens the molecular distance, and each component forms a dense integrated skeleton by hydrogen bond and surface complexation, and there are no hollows or cracks inside the particles. (4) Low-temperature drying and shaping: The columnar fertilizer blanks are placed in a 45℃ oven and dried to constant weight. They are then sieved to obtain a finished slow-release activated phosphate fertilizer with uniform particle size, such as... Figure 1 As shown.

[0020] Example 2: 1. Fertilizer composition: By weight: 45 parts superphosphate, 30 parts humic acid, 8 parts bentonite, 6 parts potato starch, and 12 parts wood vinegar. 2. Preparation method: The preparation method is the same as in Example 1.

[0021] Example 3: 1. Fertilizer composition By weight: 55 parts superphosphate, 20 parts humic acid, 12 parts bentonite, 4 parts potato starch, and 8 parts wood vinegar. 2. Preparation method: The preparation method is the same as in Example 1.

[0022] Comparative Example 1 (Superphosphate only control group, SSP) Superphosphate (P2O5≥12%) was used directly as is. After being crushed, it was passed through a 100-mesh sieve. No other excipients were added to this control group. No extrusion granulation or drying treatment was performed.

[0023] Comparative Example 2 (Simple physical mixing, no extrusion molding, raw material mixture) The raw material weight ratio is exactly the same as in Example 1; after the solid powder is dry-mixed evenly, it is sprayed with an equal mass of refined wood vinegar and stirred; without roller pressing, it is directly dried at 45°C to obtain the mixed fertilizer sample.

[0024] Comparative Example 3 (without wood vinegar, the rest of the formulation and process are the same as in Example 1) Raw materials by weight: 50 parts superphosphate, 25 parts humic acid, 10 parts bentonite, 5 parts potato starch; no wood vinegar added; extruded at 20 MPa and dried at 45℃.

[0025] Comparative Example 4 (humic acid removed, the rest of the formulation and process are the same as in Example 1) Raw materials by weight: 50 parts superphosphate, 10 parts bentonite, 5 parts potato starch, 10 parts wood vinegar; no humic acid added; extruded at 20 MPa and dried at 45℃.

[0026] Comparative Example 5 (Control group where humic acid and wood vinegar were removed simultaneously, and only the substrate was squeezed) Raw materials by weight: 50 parts superphosphate, 10 parts bentonite, 5 parts potato starch; no humic acid or wood vinegar added; extruded at 20 MPa, dried at 45°C, and the rest of the process is consistent with Example 1.

[0027] Experimental Example 1: Test on the slow-release performance of fertilizer phosphorus This experiment conducted in vitro intermittent static water extraction tests on samples from Examples 1-3 and Comparative Examples 1-5 to evaluate the sustained-release performance of phosphorus in each sample.

[0028] 1. Test method: Accurately weigh 2.00 g (accurate to 0.01 g) of whole granular fertilizer sample and place it in a sealed extraction container. Add 200 mL of deionized water and perform intermittent extraction at a constant temperature of 25℃. Sampling was carried out at time points 1, 3, 7, 10, 14, 21, and 28 days. During sampling, all extracts were filtered through a 0.45 μm filter membrane, and the phosphorus concentration of the filtrate was determined using the molybdenum antimony spectrophotometric method. After sampling, 200 mL of fresh deionized water was added back to the extraction container, and extraction was continued at a constant temperature. Each treatment was tested in triplicate, and the average value of the results was taken.

[0029] Calculate the cumulative phosphorus release rate of fertilizer at different time points: Cumulative phosphorus release rate (%) = Total mass of phosphorus released from the sample ÷ Total mass of phosphorus in the fertilizer sample × 100%.

[0030] The cumulative phosphorus release rates of each sample at different times are shown in Table 1.

[0031] Table 1. Cumulative phosphorus release rate of each sample at different times (unit: %) 2. Experimental Results: Table 1 shows that the pure superphosphate sample in Comparative Example 1 exhibited a significant phosphorus burst release phenomenon, with a cumulative release rate of 47.3% on the first day, indicating a rapid phosphorus release rate in the early stage. Comparative Example 2, which was only physically mixed without high-pressure extrusion, also showed a rapid phosphorus release in the early stage.

[0032] Examples 1-3 all adopted the formula and high-pressure extrusion process specified in this invention, which can significantly reduce the initial phosphorus release rate, and the release curve is flat, which is more in line with the quasi-secondary kinetic release characteristics and effectively inhibits the explosive release of phosphorus. Among them, Example 1 has the best slow-release effect. Examples 2 and 3 are the formula boundary examples, and their slow-release performance is slightly lower than that of Example 1, but significantly better than each comparative example.

[0033] Comparing the results of Comparative Examples 3 and 4, the slow-release performance decreased when either wood vinegar or humic acid was omitted alone; in Comparative Example 5, the slow-release effect worsened further due to the removal of both active components. Calculations showed that the times to reach 80% cumulative phosphorus release rate in Example 1 and Comparative Examples 3-5 were 21.0 d, 17.5 d, 15.8 d, and 13.8 d, respectively. Compared to Comparative Examples 3 and 4, the composite regulation system of Example 1 exhibited a significant synergistic slow-release effect, with the increase in time required to reach 80% cumulative phosphorus release rate exceeding the sum of the individual contributions of the two functional components, indicating a synergistic regulation of phosphorus release behavior between humic acid and wood vinegar. This proves that only through the synergistic effect of humic acid and wood vinegar, combined with a 18-22 MPa high-pressure extrusion process, can excellent phosphorus slow-release effects be achieved; there is a synergistic effect between each component and the extrusion process. The total phosphorus release at 28 days was similar for all samples, indicating that this invention does not reduce the total phosphorus release potential of fertilizers.

[0034] Experimental Example 2: Grading and Detection Experiment of Soil Phosphorus Components The test soil was collected from the 0-20cm topsoil layer of calcareous alluvial soil in farmland. The basic physicochemical properties of the soil were: pH (soil-water ratio 1:2.5) 8.12, organic matter 13.6 g / kg, total phosphorus 0.74 g / kg, and Olsen available phosphorus 7.8 mg / kg. The initial phosphorus composition of the soil was: Resin-P 3.1% of total phosphorus, NaHCO3-P 6.2% of total phosphorus, NaOH-P 14.7% of total phosphorus, HCl-P 28.3% of total phosphorus, and Residual-P 47.7% of total phosphorus. After collection, the soil was air-dried, stones and plant residues were removed, and the soil was passed through a 2mm standard sieve and thoroughly mixed before use.

[0035] 1. Test method: An indoor potted plant culture experiment was conducted, with 500g of dry soil in each pot. Fertilizers for each treatment were applied to the soil according to the principle of equal phosphorus nutrient content and thoroughly mixed. A blank control group (CK) without fertilizer was set up. The culture period was 60 days, and the soil moisture content was maintained at 60-70% of field capacity during the culture period. Each treatment had three biological parallel groups. After the culture was completed, soil samples were collected, air-dried, and sieved through a 2mm sieve. A modified Hedley sequential fractionation extraction method was used to determine different forms of phosphorus in the soil, extracting Resin-P, NaHCO3-P, NaOH-P, HCl-P, and Residual-P sequentially. The inorganic phosphorus content of each extract was determined using a molybdenum-antimony spectrophotometric method, and the percentage of each phosphorus form in the total soil phosphorus was calculated. The results are shown in Table 2.

[0036] Table 2. Percentage of each phosphorus component in total phosphorus in soil after 60 days of cultivation (unit: %) 2. Experimental Results: As shown in Table 2, the proportions of active phosphorus Resin-P and NaHCO3-P in the soil of the blank CK group were the lowest, while the proportions of inert HCl-P and Residual-P were the highest.

[0037] In Comparative Example 1, the application of pure superphosphate resulted in phosphorus being easily fixed by soil calcium, iron, and aluminum ions, with limited increases in Resin-P and NaHCO3-P. A large amount of phosphorus was converted into HCl-P calcium-bound inert phosphorus.

[0038] Examples 1-3 all significantly increased the proportion of active phosphorus in soil Resin-P and NaHCO3-P, and decreased the proportion of inert phosphorus in HCl-P and Residual-P. Example 1 showed the best effect. Examples 2 and 3, as boundary examples of the formulation, had slightly lower activation effects than Example 1, but were better than all comparative examples.

[0039] Comparative Example 2, which involved only physical mixing without compression, and Comparative Examples 3-5, which lacked one or both of the components of humic acid and wood vinegar, showed weaker effects in enhancing soil active phosphorus compared to Examples 1-3. This indicates that the fertilizer of the present invention, on the one hand, slowly releases its own phosphorus, and on the other hand, relies on the synergistic effect of humic acid and wood vinegar to inhibit the conversion of exogenous phosphorus into inert phosphorus, while simultaneously activating the soil's inherent inert phosphorus and increasing the soil's available active phosphorus pool for crop utilization.

[0040] If either humic acid or wood vinegar is missing, the activation, inhibition, and fixation effects will be significantly reduced. This demonstrates that the dense particles prepared by high-pressure extrusion, along with the combination of humic acid and wood vinegar, are key to regulating the phosphorus form in the soil. It also verifies that the expected technical effects can be achieved within the weight range of the formula of this invention.

[0041] Experimental Example 3: Microstructure and Interface Characterization of Fertilizer The microstructure and interface of fertilizer samples from Example 1, Comparative Example 1, and Comparative Example 2 were characterized using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Micro-CT.

[0042] 1. Test method: SEM-EDS: Observe the microstructure of the sample, collect energy dispersive spectroscopy and elemental surface mapping, and analyze the elemental distribution of C, Si, P, Ca and Al. FT-IR infrared spectroscopy: testing 500-4000 cm⁻¹ -1 Range infrared absorption was used to analyze changes in hydrogen bonds of functional groups. XRD: Tests the crystalline phase structure of the sample; XPS: Determines the elemental binding state on the sample surface and analyzes organic-inorganic interface interactions; Micro-CT: Observe the internal porosity, cracks, and density of fertilizer particles, and statistically analyze particle size, sphericity, and particle volume distribution.

[0043] 2. Experimental Results: like Figure 2 As shown, SEM-EDS and element mapping indicate that in Comparative Example 1 (pure superphosphate, SSP), each element is independently distributed; in Comparative Example 2 (mixed without extrusion, Mix), the components are mixed together and do not form a tightly bound interface; in Example 1 (high-pressure extruded fertilizer, SAPF) sample, C (humic acid, starch, wood vinegar organic components) is intertwined with Ca, P, and Si elements, and the organic-inorganic components form a tightly bound interface.

[0044] like Figure 3 As shown in the FT-IR, XRD, and XPS spectra, the infrared characteristic peaks of the sample in Example 1 shifted. Figures C-F (XPS) show that the binding energies of CO and OC=O functional groups changed, proving that high-pressure extrusion induced hydrogen bonding and surface complexation between humic acid, wood vinegar, and superphosphate, thus changing the state of the interfacial functional groups. Figure B (XRD) shows that the extrusion process did not destroy the main crystalline phase of superphosphate.

[0045] like Figure 4 As shown in the Micro-CT results, the fertilizer granules extruded in Example 1 have fewer internal pores and higher density, with no obvious hollows or cracks. Compared with the mixed materials, high-pressure extrusion reconstructs the internal microstructure of the granules, constructing a dense organic-inorganic integrated framework.

[0046] Experimental Example 4: Mechanical Properties Testing of Fertilizer Pellets 1. Test method: Randomly select complete cylindrical fertilizer granules from Example 1 and physical mixture granules from Comparative Example 2, and conduct single-particle compression tests using a materials mechanics testing machine to record the pressure, displacement, and strain data during the compression process.

[0047] 2. Experimental Results: like Figure 5 As shown, compared with the physically mixed fertilizer of Comparative Example 2, the extruded fertilizer granules of Example 1 have good mechanical strength, and there is a stress buffering stage during the compression process. The granules have a certain toughness and are not easy to break. This shows that the mechanical properties of the fertilizer granules produced by the process of the present invention meet the actual production and use requirements for packaging, transportation and application.

[0048] Experiment 5: Pot Crop Cultivation Experiment 1. Test method: A pot experiment was conducted on radishes, with a control group (CK), comparative example 1, comparative example 2, and fertilizer treatments from Example 1, to evaluate the effects of different fertilizers on crop growth. The soil used in the experiment was the same as in Example 2. The amount of phosphorus fertilizer applied to each treatment was kept consistent, except for the control group (CK), which was not treated with phosphorus fertilizer. Radishes were planted in pots with uniform water and fertilizer management, and the growth cycle was 60 days. After harvest, the growth of the aboveground and underground parts of the radishes was observed.

[0049] 2. Experimental Results: like Figure 6 As shown, the radish growth in the CK (control group) was the weakest; the growth of radishes treated with Comparative Example 1 (pure superphosphate, SSP) was improved, but the improvement was limited; the crop growth in Comparative Example 2 (mixed without compression, Mix) was stronger than that in Comparative Example 1, but weaker than that in Example 1; Example 1 showed the best growth. This demonstrates that the slow-release activated phosphate fertilizer of this invention can effectively promote crop growth while achieving slow-release of phosphorus and activation of soil phosphorus.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A slow-release activated phosphate fertilizer based on roller extrusion granulation, characterized in that, The raw materials, by weight, include: 45-55 parts superphosphate, 20-30 parts humic acid, 8-12 parts bentonite, 4-6 parts potato starch, and 8-12 parts wood vinegar.

2. The slow-release activated phosphate fertilizer according to claim 1, characterized in that, The slow-release activated phosphate fertilizer has the following particle shapes: columnar, pillow-shaped, oblate, square, or flaky.

3. The slow-release activated phosphate fertilizer according to claim 1, characterized in that, The superphosphate contains ≥12% P2O5.

4. The method for preparing slow-release activated phosphate fertilizer according to claim 1 or 2, characterized in that, Includes the following steps: (1) Mixing raw materials: crush superphosphate, humic acid, bentonite and potato starch separately; weigh the solid powder according to the weight ratio, dry mix and stir for 5-10 min until the powder is uniform; spray wood vinegar in batches and stir continuously for 8-12 min to obtain a moist composite mixture. (2) Roller extrusion molding: The wet composite mixture is fed into a double roller extrusion granulator and extruded to obtain fertilizer preforms; (3) Low-temperature drying and shaping: The fertilizer blank is dried at 42-48℃ to constant weight and then screened to obtain the finished slow-release activated phosphate fertilizer.

5. The preparation method according to claim 3, characterized in that, In step (1), the raw materials are crushed and then passed through an 80-100 mesh standard sieve.

6. The preparation method according to claim 3, characterized in that, In step (1), the wood vinegar solution is sprayed 8-12 times.

7. The preparation method according to claim 3, characterized in that, In step (3), the pressure of the double roller extrusion granulator is 18-22 MPa, the roller gap is 0.5-1.5 mm, and the roller speed is 10-20 r / min.

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