Growth-promoting slow-release organic compound fertilizer for rice and preparation method thereof

Abstract

The invention belongs to the technical field of agricultural organic fertilizers, and particularly relates to a growth-promoting slow-release organic compound fertilizer for rice and a preparation method of the growth-promoting slow-release organic compound fertilizer. The soil conditioner is prepared from the following raw materials in parts by weight: 55 to 65 parts of organic matter matrix, 10 to 14 parts of porous carrier, 14 to 20 parts of mineral micropowder, 10 to 12 parts of pore-foaming agent, 7 to 10 parts of adhesive solution, 3 to 4 parts of sodium alginate, 2 to 4 parts of CaCl2, 0.8 to 1.6 parts of MgCl2, 0.1 to 0.15 part of sodium tetraborate, 4 to 6 parts of coating emulsion and 0.5 to 1 part of natural polyphenol solution. According to the invention, fertilizer supply, interface and mechanical properties are optimized by means of hierarchical synergy of core microcell-middle layer cross-linking-outer layer coating; mineral micro-powder and a porous carrier are embedded in the inner core organic matter, so that release of ammonium and potassium is controlled, and loss is inhibited; the middle layer is subjected to pore-forming and sodium alginate ternary crosslinking, initial release is controlled, and the slow-release rhythm is stabilized; and the outer layer is directionally coated to reduce flux and is eco-friendly.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural organic fertilizer, and particularly relates to a growth-promoting slow-release organic compound fertilizer for rice and a preparation method thereof. BACKGROUND

[0002] In the field of fertilizer technology, slow-release organic fertilizer refers to a kind of fertilizer taking organic matter as the main raw material, which is treated by physical, chemical or biological technology, so that the contained nutrients can be released at a slow and controllable rate, thereby more effectively meeting the nutrient demand of crops in the whole growth period. Its core value lies in combining the inherent soil improvement function of organic material with the sustained supply capacity of nutrients, aiming to achieve multiple goals of improving fertilizer utilization rate, cultivating soil fertility and reducing environmental pollution. As the main food crop, rice is an ideal object for applying slow-release organic fertilizer due to its unique flooded planting environment and long growth period. Under anaerobic conditions in paddy fields, conventional chemical fertilizers, especially nitrogen, are prone to be lost in large quantities through ammonia volatilization, nitrification-denitrification and other ways, and the utilization rate is generally low. Slow-release organic fertilizer can significantly reduce the rapid dissolution and leaching of nutrients in irrigation water through its slow-release characteristics, ensuring that the nutrient supply is more matched with the fertilizer demand law of each key growth stage of rice. At the same time, its rich organic matter can effectively improve the soil compaction caused by long-term flooding, promote root development, and help maintain a healthy rice field microbial community, which is crucial for the steady growth and high yield of rice. However, the slow-release organic fertilizer under the prior art still has several defects to be solved. First, the release process of its nutrients mainly depends on the decomposition activity of microorganisms, and the activity of microorganisms is significantly affected by environmental factors such as soil temperature, humidity and pH value, which leads to high uncertainty and unpredictability of the rate and mode of nutrient release, making it difficult to achieve precise synchronization with the crop fertilizer demand curve. Secondly, the particles composed of organic materials often have the problem of insufficient mechanical strength, which are easy to powder and caking during transportation, storage and mechanized spreading, affecting the commodity nature and application effect of the product. In addition, some composite processes introduced to achieve slow-release function often face the problem of poor compatibility with existing large-scale fertilizer granulation production lines, resulting in high production cost and high energy consumption, which restricts its large-scale application in field crops. SUMMARY

[0003] In view of the defects of the prior art, the purpose of the present application is to provide a growth-promoting slow-release organic compound fertilizer for rice and a preparation method thereof.

[0004] The technical effect of the present application is realized by the following technical scheme: a growth-promoting slow-release organic compound fertilizer for rice, which comprises the following raw materials in parts by weight: 55-65 parts of organic matter matrix, 10-14 parts of porous carrier, 15-20 parts of mineral micro powder, 10-12 parts of pore-forming agent, 7-10 parts of binder solution, 3-4 parts of sodium alginate, 2-4 parts of CaCl2, 0.8-1.6 parts of MgCl2, 0.1-0.15 parts of sodium tetraborate, 4-6 parts of coating emulsion, and 0.5-1 part of natural polyphenol solution.

[0005] Preferably, the organic matter matrix is obtained by dry mixing humic acid and sodium lignosulfonate, spraying into a 10wt% sodium lignosulfonate aqueous solution, turning while spraying, until the mass fraction of >2mm agglomerates is 5-10%, and then drying with hot air at 45-55℃ until the water content is 8-10%, and then lightly crushing and passing through a 200 mesh screen; Preferably, the porous carrier is any one of zeolite, bentonite, and biochar; Preferably, the mineral micro powder is composed of 11-13 parts of urea micro powder, 3-4.5 parts of ammonium phosphate micro powder, and 1-2.5 parts of potassium chloride micro powder; Preferably, the pore-forming agent is composed of 5-6 parts of sodium bicarbonate and 5-6 parts of citric acid monohydrate; Preferably, the binder solution is obtained by compounding sodium lignosulfonate and molasses at a mass ratio of 7-8:2-3, adding deionized water to adjust to 40wt% solid content, adjusting the pH to neutral, and standing to remove bubbles; Preferably, the coating emulsion is obtained by compounding 30wt% hydrophobized dextrin aqueous solution and 50wt% rosin pentaerythritol ester dispersion at a volume ratio of 6:4, adding 2% 5wt% hydroxypropyl methylcellulose aqueous solution and 0.2-0.4% polydimethylsiloxane, adding water to 20wt% solid content, adjusting the pH to 6.5-7.5, and shearing and dispersing at 1000-2000rpm for 10-15min; Preferably, the hydrophobized dextrin is octenyl succinic anhydride esterified dextrin, which is obtained by reacting dextrin with a molecular weight of 5-30kDa in 1wt% Na2CO3 alkaline aqueous phase at 30-40℃ for 2-3h; the amount of octenyl succinic anhydride is 1.5-3% of the mass of dry dextrin; Preferably, the natural polyphenol solution is obtained by compounding tannic acid and catechin at a mass ratio of 1:1, and adding deionized water to adjust to a concentration of 2wt%; Preferably, another aspect of the present application provides a preparation method of a growth-promoting slow-release organic compound fertilizer for rice, comprising the following steps: S1: sequentially add organic matrix, porous carrier and mineral micro-powder into a stirring machine, dry mix at 40-60 rpm for 6-8 min, then pan granulation to obtain inner core; S2: staggered spray 30 wt% citric acid solution and 8 wt% sodium bicarbonate solution to the inner core of step S1, hot air drying at 45-55 °C for 90-120 min, hot air speed 0.8-1.5 m / s, to obtain sprayed particles; S3: cyclically spray 1.8 wt% sodium alginate solution, 5 wt% CaCl2 solution and 2 wt% MgCl2 solution, 0.5 wt% sodium tetraborate solution to the sprayed particles of step S2, to obtain cross-linked coated particles; S4: spray coating emulsion to the cross-linked coated particles of step S3, then spray natural polyphenol solution; light pressure at 0.05-0.2 MPa for 30-60 s, stand at 25 °C for 24 h, dry at 40-50 °C until the moisture content is less than 2%; sieve to retain 2-4 mm particles, to obtain slow-release organic compound fertilizer; Preferably, in step S1, the specific operation parameters of the pan granulation are: pan angle 48-52°; initial speed 45 rpm, later 38-42 rpm, spray in binder solution, spray speed 5-12 g / min, atomization pressure 0.2-0.4 MPa, spray distance 25-35 cm, target wet particle size 2.8-3.2 mm, bed apparent moisture content 14-18 wt%; Preferably, in step S2, the citric acid solution and sodium bicarbonate solution are prepared by dissolving citric acid monohydrate and sodium bicarbonate in deionized water from the pore-forming agent; Preferably, in step S2, the specific operation parameters of the staggered spray are: material temperature 30-35 °C, atomization air pressure 0.22-0.28 MPa, nozzle diameter 1-1.2 mm, spray angle 60°-80°, 30-40 cm above the pan surface, two guns staggered against each other, included angle 45°-60°, bed apparent moisture content 14-18 wt%; Preferably, in step S3, the specific operation parameters of the cyclic spray are: drum speed 9-11 rpm, loading coefficient 45-55%, material temperature 30 °C, spray sodium alginate solution 60-80 g / min, time 90 s; mixed spray Ca / Mg solution 50-60 g / min, time 60 s; spray sodium tetraborate solution 25-30 g / min, time 45 s, cycle interval 60-90 s; low-temperature deliquoring and shaping at hot air temperature 30-38 °C, air speed 0.8-1.5 m / s, speed 8-10 rpm, time 3-6 min, bed apparent moisture content 8-10 wt%; Preferably, in step S4, the specific parameters of spraying the coating emulsion are as follows: using a directional spray head and a hemispherical coverage on the material surface, the tangential angle between the spray gun and the material surface is 25-35°, the nozzle aperture is 1-1.2 mm, the atomization air pressure is 0.18-0.24 MPa, the spray distance is 30-40 cm; the roller rotation speed is 8-10 rpm, and the loading coefficient is 45-55%. Preferably, in step S4, the specific operation parameters of spraying the natural polyphenol solution are consistent with those of spraying the coating emulsion.

[0006] The beneficial effects of the present application are as follows: Compared with the prior art, the present application realizes the integrated optimization of fertilizer supply kinetics, interface flux and particle mechanics through hierarchical synergy of core microzone-middle layer crosslinking-outer layer selective coating. First, the organic matter matrix is used as a continuous phase, the mineral micro-powder with controlled particle size is embedded and dispersed cooperatively with the porous carrier, so that the nutrients are in a non-penetrating microzone structure; the adsorption and ion exchange sites of the porous carrier form temporary fixation with ammonium and potassium, which matches the physiological characteristics of rice preferring to absorb ammonium nitrogen, and inhibits surface ammonia volatilization and deep leaching; at the same time, it provides slow release and re-supply of potassium ions, which helps to maintain the mechanical strength of rice plants and the steady state potassium demand in the grain filling process; the complexation and slow release effect of the organic component is superimposed, which prolongs the water migration path and inhibits early burst release. On this basis, acid-alkali in-situ pore-forming is used to build a uniform and fine microporous network inside the particle, and the effective diffusion path of water entry and solute exit is determined by the tortuous channel and microzone distribution, realizing the physical shaping of the initial release rate. Then, the Ca / Mg / boron ternary synergistic crosslinking of sodium alginate is introduced to form a reversible multi-point network, which has a swelling / shrinking and complexation / decomplexation reversible response under different water content and ionic strength conditions, and has a gating effect on water transport and ion diffusion, thereby converting the release uncertainty driven by environmental fluctuations into a predictable slow release rhythm. The outermost layer adopts directional and trace coating on the high-nutrient exposed surface instead of full-surface thick coating, the hydrophobic phase emulsion enhances the local water-solid interface impedance, and the natural polyphenol (tannic acid and catechin) provides mild and metabolizable enzyme activity regulation, which reduces the early flux at the key interface and avoids long-term inhibition of rhizosphere microorganisms, and balances the release stability and ecological friendliness.

[0007] In the mechanics and storage side, the ternary crosslinking network gives the balance of wet adhesion and dry crack resistance, combined with light compaction to reduce the risk of pulverization and caking, short-time low-temperature setting to ensure the stable combination of coating and crosslinking network, and to avoid subsequent cracks and delamination caused by high-temperature embrittlement. In the process, the sequential process of dry mixing nucleation, in-situ pore formation, wet crosslinking, selective coating, densification polishing and low-temperature setting, concentrates the key variables in the three on-line monitoring nodes of atomization, crosslinking and coating, facilitating batch consistency and scale-up replication; the raw materials and equipment paths used are compatible with conventional compound fertilizer granulation lines, reducing the modification cost and energy consumption. In summary, the multi-scale coupling of micro-geometric constraints, pore tortuosity regulation and reversible crosslinking gating makes the nutrient release from an "environment-driven random process" to a "structure-dominated engineered process", achieving stable slow release, good mechanical adaptation and overall optimization of unit nutrient cost without relying on thick coating. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is the N release curve diagram of the fertilizer obtained by example 1 and comparative examples 1-4 of the present application in water-based slow release test; Figure 2 is the P release curve diagram of the fertilizer obtained by example 1 and comparative examples 1-4 of the present application in water-based slow release test; Figure 3 is the K release curve diagram of the fertilizer obtained by example 1 and comparative examples 1-4 of the present application in water-based slow release test; Figure 4 is the N release curve diagram of the fertilizer obtained by example 1 and comparative examples 1-4 of the present application in salt-based slow release test; Figure 5 is the P release curve diagram of the fertilizer obtained by example 1 and comparative examples 1-4 of the present application in salt-based slow release test; Figure 6 is the K release curve diagram of the fertilizer obtained by example 1 and comparative examples 1-4 of the present application in salt-based slow release test. DETAILED DESCRIPTION

[0009] The technical solutions of the present application will be described in detail below in combination with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments; unless otherwise specified, the raw materials involved in the present application are purchased through conventional commercial channels; the experimental methods without specific conditions are the conventional methods and conventional conditions familiar to the field, or according to the conditions recommended by the instrument manufacturer.

[0010] Embodiment 1: A growth-promoting slow-release organic compound fertilizer for rice, which comprises the following raw materials by weight parts: 60 parts of organic matter matrix, 12 parts of porous carrier, 18 parts of mineral powder, 11 parts of pore-forming agent, 8 parts of binder solution, 3.5 parts of sodium alginate, 3 parts of CaCl2, 1.2 parts of MgCl2, 0.12 parts of sodium tetraborate, 5 parts of coating emulsion, and 0.8 parts of natural polyphenol solution.

[0011] 1. The organic matter matrix is obtained by dry mixing humic acid and sodium lignosulfonate, then spraying into 10wt% sodium lignosulfonate aqueous solution, and turning while spraying until the mass fraction of >2mm agglomerates is 8%, and then drying with hot air at 50℃ until the water content is 9%, and then lightly crushing and passing through a 200 mesh screen; 2. The mineral powder is composed of 12 parts of urea powder, 4 parts of ammonium phosphate powder, and 2 parts of potassium chloride powder by weight parts; 3. The pore-forming agent is composed of 5.5 parts of sodium bicarbonate and 5.5 parts of citric acid monohydrate by weight parts; 4. The binder solution is obtained by compounding 7.5g of sodium lignosulfonate and 2.5g of molasses, adding deionized water to make up to 25mL to adjust to 40wt% solid content, adjusting the pH to neutral, and standing to remove bubbles; 5. The coating emulsion is obtained by compounding 60mL of 30wt% hydrophobized dextrin aqueous solution and 40mL of 50wt% rosin pentaerythritol ester dispersion, adding 2mL of 5wt% hydroxypropyl methylcellulose aqueous solution and 0.3mL of polydimethylsiloxane, making up water to 20wt% solid content, adjusting the pH to 7, and shearing and dispersing at 1500rpm for 12min; 6. The hydrophobized dextrin is octenyl succinic anhydride esterified dextrin, which is obtained by reacting 10g of dextrin with a molecular weight of 5-30kDa in 100mL of 1wt% Na2CO3 alkaline aqueous phase at 35℃ for 2.5h; 7. The natural polyphenol solution is obtained by compounding 1g of tannic acid and 1g of catechin, adding deionized water to make up to 100mL to adjust to a concentration of 2wt%; 8. The preparation of the growth-promoting slow-release organic compound fertilizer for rice comprises the following steps: S1: Add the organic matter matrix, zeolite, and mineral powder into a blender in sequence, dry mix at 50rpm for 7min, then disc granulation with a disc angle of 50°; the initial speed is 45rpm, and the later speed is 40rpm; spray the binder solution at a speed of 10g / min, with an atomization pressure of 0.3MPa, a spraying distance of 30cm, a target wet particle size of 3mm, and a bed apparent water content of 15wt%; obtain the core; S2: Spray 30wt% citric acid solution and 8wt% sodium bicarbonate solution alternately into the core of step S1 using atomized spraying. The material temperature is 32℃, the atomizing air pressure is 0.25MPa, the nozzle orifice diameter is 1.1mm, the spray angle is 70°, and the nozzle is 35cm above the disc surface. The two nozzles spray alternately at an angle of 50°. The apparent water content of the bed is 15wt%. Dry with hot air at 50℃ for 100min at a hot air velocity of 1.2m / s to obtain sprayed particles. S3: 1.8wt% sodium alginate solution, 5wt% CaCl2 solution, 2wt% MgCl2 solution, and 0.5wt% sodium tetraborate solution are circulated and sprayed onto the particles from step S2. The drum speed is 10 rpm, the loading coefficient is 50%, the material temperature is 30℃, the sodium alginate solution is sprayed at 70 g / min for 90 s, the Ca / Mg solution is mixed and sprayed at 55 g / min for 60 s, the sodium tetraborate solution is sprayed at 28 g / min for 45 s, and the circulation interval is 80 s. The hot air temperature is 35℃, the wind speed is 1 m / s, the rotation speed is 9 rpm, and the time is 5 min for low-temperature dehydration and shaping. The apparent water content of the bed is 9wt%. Cross-linked coated particles are obtained. S4: Spray the coating emulsion onto the cross-linked coated particles from step S3, then spray the natural polyphenol solution. Use a directional nozzle and a hemispherical covering method on the material surface. The tangential angle between the spray gun and the material surface is 30°, the nozzle orifice diameter is 1.1 mm, the atomizing air pressure is 0.2 MPa, and the spray distance is 35 cm. The drum speed is 9 rpm, the loading coefficient is 50%, and the material is lightly pressed at 0.1 MPa for 50 seconds. Let it stand at 25°C for 24 hours, and dry it at 45°C until the moisture content is less than 2%. Screen the particles to retain 2-4 mm particles to obtain slow-release organic compound fertilizer.

[0012] Example 2: A slow-release organic compound fertilizer for rice growth promotion, comprising the following raw materials by weight: 55 parts organic matrix, 10 parts porous carrier, 14 parts mineral powder, 10 parts pore-forming agent, 7 parts binder solution, 3 parts sodium alginate, 2 parts CaCl2, 0.8 parts MgCl2, 0.1 parts sodium tetraborate, 4 parts coating emulsion and 0.5 parts natural polyphenol solution.

[0013] 1. The organic matrix is ​​obtained by dry mixing of humic acid and sodium lignosulfonate, followed by atomizing and spraying into a 10wt% sodium lignosulfonate aqueous solution while agitating until the agglomeration degree is 5%, expressed as the mass fraction of agglomerates >2mm; then drying with hot air at 45℃ to a water content of 10%, and lightly crushing and passing through a 200-mesh sieve. 2. The mineral powder is composed of 11 parts urea powder, 3 parts ammonium phosphate powder and 1 part potassium chloride powder by weight. 3. The pore-forming agent is composed of 5 parts sodium bicarbonate and 5 parts citric acid monohydrate by weight; 4. The binder solution is prepared by mixing 8 g of sodium lignosulfonate and 2 g of molasses, adding deionized water to make up to 25 mL to 40 wt% solid content, adjusting the pH to neutral, and standing to remove bubbles to obtain; 5. The coating emulsion is prepared by mixing 60 mL of 30 wt% hydrophobized dextrin aqueous solution and 40 mL of 50 wt% rosin pentaerythritol ester dispersion, adding 2 mL of 5 wt% hydroxypropyl methylcellulose aqueous solution and 0.2 mL of polydimethylsiloxane, adding water to make up to 20 wt% solid content, adjusting the pH to 7.5, and shearing and dispersing at 1000 rpm for 15 min to obtain; 6. The hydrophobized dextrin is octenyl succinic anhydride esterified dextrin, which is obtained by reacting 10 g of dextrin with a molecular weight of 5-30 kDa in 100 mL of 1 wt% Na2CO3 alkaline aqueous phase at 30°C for 2 h; 7. The natural polyphenol solution is prepared by mixing 1 g of tannic acid and 1 g of catechin, adding deionized water to make up to 100 mL to obtain a concentration of 2 wt%; 8. The preparation of the growth-promoting slow-release organic compound fertilizer for rice includes the following steps: S1: Add organic matter matrix, biochar and mineral powder into a stirring machine in sequence, dry mix at 40 rpm for 8 min, then disc granulation with a disc angle of 52°; the initial rotating speed is 45 rpm and the later rotating speed is 38 rpm; spray the binder solution at a spraying speed of 5 g / min, an atomization pressure of 0.2 MPa, a spraying distance of 35 cm, a target wet particle size of 2.8 mm, and a bed apparent water content of 18 wt%; obtain the inner core; S2: Interlacedly spray 30 wt% citric acid solution and 8 wt% sodium bicarbonate solution onto the inner core of step S1 at a material temperature of 30°C, an atomization air pressure of 0.22 MPa, a nozzle diameter of 1 mm, a spraying angle of 80°, 40 cm above the disc surface, and a bed apparent water content of 18 wt%; dry at a hot air temperature of 45°C for 120 min at a hot air speed of 0.8 m / s to obtain the sprayed particles; S3: Recirculate the sprayed particles of step S2 to spray 1.8 wt% sodium alginate solution, 5 wt% CaCl2 solution and 2 wt% MgCl2 solution, and 0.5 wt% sodium tetraborate solution; the rotating speed of the drum is 9 rpm, the charging coefficient is 45%, the material temperature is 30°C, the spraying speed of sodium alginate solution is 60 g / min, the time is 90 s; the mixed spraying speed of Ca / Mg solution is 50 g / min, the time is 60 s; the spraying speed of sodium tetraborate solution is 25 g / min, the time is 45 s, and the recirculation interval is 60 s; low-temperature liquid removal shaping at a hot air temperature of 30°C, a wind speed of 0.8 m / s, a rotating speed of 8 rpm, and a time of 3 min to obtain the cross-linked coated particles; S4: The crosslinked coated particles of step S3 are sprayed with a coating emulsion, and then sprayed with a natural polyphenol solution, using a directional spray head and a half-sphere covering method on the material surface, with a tangential angle of 35° between the spray gun and the material surface, a nozzle aperture of 1 mm, an atomization air pressure of 0.18 MPa, and a spray distance of 40 cm; the roller rotates at a speed of 8 rpm, and the loading coefficient is 45%; the particles are lightly pressed at 0.05 MPa for 30 s, and then left to stand at 25°C for 24 h, and then dried at 50°C until the moisture content is less than 2%; the particles with a size of 2-4 mm are obtained by sieving, and a slow-release organic compound fertilizer is obtained.

[0014] Example 3: A growth-promoting slow-release organic compound fertilizer for rice, which comprises the following raw materials in parts by weight: 65 parts of an organic matter matrix, 14 parts of a porous carrier, 20 parts of mineral micro-powder, 12 parts of a pore-forming agent, 10 parts of a binder solution, 4 parts of sodium alginate, 4 parts of CaCl2, 1.6 parts of MgCl2, 0.15 parts of sodium tetraborate, 6 parts of a coating emulsion, and 1 part of a natural polyphenol solution.

[0015] 1. The organic matter matrix is obtained by dry mixing humic acid and sodium lignosulfonate, spraying the mixture into a 10 wt% sodium lignosulfonate aqueous solution while stirring, until the mass fraction of >2 mm agglomerates is 10%; then drying at 55°C with hot air until the water content is 8%, and then lightly crushing and sieving through a 200-mesh screen to obtain the organic matter matrix; 2. The mineral micro-powder is composed of 13 parts of urea micro-powder, 4.5 parts of ammonium phosphate micro-powder, and 2.5 parts of potassium chloride micro-powder; 3. The pore-forming agent is composed of 6 parts of sodium bicarbonate and 6 parts of citric acid monohydrate; 4. The binder solution is obtained by compounding 7 g of sodium lignosulfonate and 3 g of molasses, adding deionized water to make up to 25 mL to adjust the solid content to 40 wt%, adjusting the pH to neutral, and then standing to obtain the binder solution; 5. The coating emulsion is obtained by compounding 60 mL of a 30 wt% hydrophobized dextrin aqueous solution and 40 mL of a 50 wt% rosin pentaerythritol ester dispersion, adding 2 mL of a 5 wt% hydroxypropyl methylcellulose aqueous solution and 0.4 mL of polydimethylsiloxane, adding water to make up to 20 wt% solid content, adjusting the pH to 6.5, and then shearing and dispersing at 2000 rpm for 10 min to obtain the coating emulsion; 6. The hydrophobized dextrin is obtained by reacting 10 g of dextrin with a molecular weight of 5-30 kDa with 0.3 g of octenyl succinic anhydride in 100 mL of a 1 wt% Na2CO3 alkaline aqueous phase at 40°C for 2 h to obtain the hydrophobized dextrin; 7. The natural polyphenol solution is obtained by compounding 1 g of tannic acid and 1 g of catechin, and then adding deionized water to make up to 100 mL to obtain a 2 wt% concentration; 8. The preparation of the growth-promoting slow-release organic compound fertilizer for rice comprises the following steps: S1: Organic matrix, bentonite and mineral micro-powder were added into a stirring machine in sequence, dry-mixed at 60 rpm for 6 min, and then disk granulated at a disk angle of 48°; the rotation speed was initially 45 rpm and later 42 rpm, the binder solution was sprayed in, the spraying speed was 12 g / min, the atomization pressure was 0.4 MPa, the spraying distance was 25 cm, the target wet particle size was 3.2 mm, and the bed apparent water content was 14 wt%; a core was obtained; S2: The core obtained in step S1 was interlacedly sprayed with 30 wt% citric acid solution and 8 wt% sodium bicarbonate solution, the material temperature was 35 °C, the atomization air pressure was 0.28 MPa, the nozzle aperture was 1.2 mm, the spraying angle was 60°, the distance above the disk surface was 30 cm, the two nozzles were interlacedly sprayed, the included angle was 45°, and the bed apparent water content was 14 wt%; the sprayed particles were obtained by drying at 55 °C for 90 min with a hot air speed of 1.5 m / s; S3: The sprayed particles obtained in step S2 were circularly sprayed with 1.8 wt% sodium alginate solution, 5 wt% CaCl2 solution, 2 wt% MgCl2 solution and 0.5 wt% sodium tetraborate solution, the drum rotation speed was 11 rpm, the filling coefficient was 55%, the material temperature was 30 °C, the spraying speed of sodium alginate solution was 80 g / min, the time was 90 s; the spraying speed of mixed Ca / Mg solution was 60 g / min, the time was 60 s; the spraying speed of sodium tetraborate solution was 30 g / min, the time was 45 s, the circular interval was 90 s; the crosslinked coated particles were obtained by low-temperature liquid removal shaping at a hot air temperature of 38 °C, a wind speed of 1.5 m / s, a rotation speed of 10 rpm, a time of 6 min and a bed apparent water content of 8 wt%; S4: The crosslinked coated particles obtained in step S3 were sprayed with a coating emulsion and then with a natural polyphenol solution, a directional nozzle and a material surface upper hemisphere covering method were used, the included angle of the spraying gun and the material surface was 25°, the nozzle aperture was 1.2 mm, the atomization air pressure was 0.24 MPa, and the spraying distance was 30 cm; the drum rotation speed was 10 rpm, the filling coefficient was 55%; the particles were obtained by light pressing at 0.2 MPa for 60 s, standing at 25 °C for 24 h, and drying at 40 °C until the moisture content was less than 2%; the 2-4 mm particles were screened out, and the slow-release organic compound fertilizer was obtained.

[0016] Comparative Example 1: The raw materials and process of Comparative Example 1 were basically the same as those of Example 1, the main difference was that in step S4, 4 nozzles were used for surrounding, and the included angle of the spraying gun and the material surface was adjusted to 80°; the other steps and parameters were consistent with those of Example 1.

[0017] Comparative Example 2: The raw materials and process of Comparative Example 2 were basically the same as those of Example 1, the main difference was that in step S3, only CaCl2 solution was used for crosslinking of sodium alginate, and MgCl2 and sodium tetraborate were not added; in order to avoid interference caused by the difference in ionic strength, the ionic strength was compensated with an inert salt solution (NaCl) to be equivalent to that of Example 1; the other steps and parameters were consistent with those of Example 1.

[0018] Comparative Example 3: The raw materials and process of Comparative Example 3 are basically the same as those of Example 1, the main difference being that the step S2 does not perform the staggered atomization pore-forming treatment of 30wt% citric acid solution and 8wt% sodium bicarbonate solution, but is replaced by atomization spraying of equal volume of deionized water, and the spraying time and subsequent hot air drying parameters are kept consistent; the remaining steps and parameters are kept consistent with Example 1.

[0019] Comparative Example 4: The raw materials and process of Comparative Example 4 are basically the same as those of Example 1, the main difference being that the total amount of mineral powder in step S1 is increased from 16 parts to 26 parts, and the organic matter matrix is reduced by equal weight parts to maintain the total weight parts and particle size distribution close; the remaining steps and parameters are kept consistent with Example 1.

[0020] Performance test: Mechanical and stability test: The fertilizer particles obtained in Examples 1-3 and Comparative Examples 1-4 were sampled and loaded into aluminum-plastic composite bags with extremely low air permeability (200g per bag, the initial water content and particle size were recorded before sealing), and were divided into three groups for processing. Group A was subjected to accelerated heat and humidity storage: placed in a constant temperature and humidity chamber at 45°C / 75%RH for 14 days, and after equilibration to room temperature for 2h, the following tests were performed: ① single particle compressive strength and strength retention rate (%) = (average compressive strength after heat and humidity / average compressive strength before heat and humidity) x 100%; ② powder loss rate: the mass percentage (%) of fine powder less than 1mm after 5min of rotary cylinder screening; ③ moisture absorption weight gain rate (%) = (average weight after measurement-average weight before measurement) / average weight before measurement x 100%; ④ surface coating integrity: contact angle change (pre-test contact angle-post-test contact angle) and appearance microcrack ratio (%)(ratio of particles with microcracks). Group B was subjected to low temperature-reheat cycle: -10°C refrigeration for 7 days, then 25°C for 24h, and then the above ①-④ were measured. Group C was subjected to transportation simulation: bagged and placed on a vibration table (5Hz, displacement 5mm) for 1h and then subjected to 1.2m free drop for 3 times, and then ① single particle compressive strength and compressive strength retention rate and ② powder loss rate were measured. The test results of group A are shown in Table 1, the test results of group B are shown in Table 2, and the test results of group C are shown in Table 3.

[0021] Table 1. Summary of accelerated heat and humidity storage test results of example and comparative example fertilizer

[0022] Table 2. Summary of low temperature-reheat test results of example and comparative example fertilizer

[0023] Table 3. Summary of transportation simulation results of example and comparative example fertilizer

[0024] Based on the results in Tables 1-3, it can be seen that the fertilizer prepared in the embodiments of the present invention can still maintain compressive strength, low dust shedding, low moisture absorption, and coating integrity after heat and humidity and freeze-thaw cycles. All indicators form a consistent steady-state window, exhibiting excellent mechanical properties and stability. The main difference in Comparative Example 1 is that the S4 spraying was changed to a circumferential coating with an increased tangential angle of 80°, weakening selectivity and resulting in a more even distribution of the coating on non-critical surfaces. This leads to insufficient interfacial barriers in critical exposed micro-areas, a more significant decrease in contact angle and an increase in the proportion of microcracks after heat and humidity and rewarming, a slightly higher moisture absorption weight gain rate, and a marginal decrease in strength retention due to early interfacial degradation. However, its core and cross-linking system remain unchanged, and the overall compressive strength and dust shedding of the particles are still close to those of the embodiments. Comparative Example 2, in S3, only used Ca... 2+ Single-ion crosslinking and removal of Mg 2+ Coordination with boron disrupts the multi-point, reversible, and slow-release swelling network balance; under hot and humid conditions, the film layer is more prone to embrittlement and shrinkage imbalance, and the internal stress release is uneven after warming, manifested as a significant decrease in strength retention, an increase in the proportion of dust and microcracks, and a greater decrease in contact angle; in the transportation simulation, the compressive strength retention and wear resistance also deteriorate simultaneously. Comparative Example 3 eliminates the in-situ pore formation of S2, resulting in a denser core and reduced pore tortuosity; the dense structure brings positive effects on the mechanical side: in the three sets of tests, the single particle compressive strength is the highest, the dust loss is the lowest, and the microcracks are the fewest, indicating that the absence of pores improves the overall strength and wear resistance of the particles; however, correspondingly, the lack of a uniform and dense microporous network weakens the channel regulation and gating response of subsequent release. This result does not contradict the design expectation, and the mechanical properties are better, but it is not equivalent to better slow-release performance. Comparative Example 4 increased the mineral powder content in S1 to 26 parts, which easily triggered micro-island connectivity and increased the proportion of rigid phase. The risk of interconnection and phase boundary incompatibility caused internal stress concentration, and microcracks and brittle fracture were more likely to occur after heat and humidity and reheating. This was manifested as the lowest strength retention rate, the highest powder loss rate and microcrack ratio, and the greater contact angle decay. In the transportation simulation, the compressive strength retention and pulverization deteriorated simultaneously. This difference is directly caused by the geometric phase transition from non-connected to connected: once the threshold is exceeded, interface defects and brittleness dominate the failure mode.

[0025] Slow-release curve test: 10g of fertilizer granules obtained in Example 1 and Comparative Examples 1-4 were randomly sampled (total N, P, and K content was recorded), and 200mL of deionized water (temperature sensitive; representative of paddy fields in summer) and 1mM CaCl2 solution were added respectively (the combined effect of temperature and salt). The samples were kept at 35°C with constant temperature and gentle vibration at 80rpm under dark conditions. On days 1, 3, 7, and 14, 10mL samples were quickly taken from each sample and filtered through a 0.45µm filter. The filtrate was immediately acidified with H2SO4 solution to pH < 2 and stored at 4°C in the dark for testing. An equal volume of deionized water was added after each sampling to maintain a constant volume. N was determined by the Kjeldahl method; P was determined by the ammonium molybdate-ascorbic acid colorimetric method; and K was determined by flame photometry. The test curves are shown below. Figure 1 , Figure 2 , Figure 3 ,Figure 4 , Figure 5 and Figure 6 As shown, where Figures 1-3 It is a slow-release curve of deionized water. Figures 4-6 This is a slow-release curve in CaCl2 solution.

[0026] based on Figures 1-6 The results show that Example 1 of the present invention exhibits the best performance in multiple performance indicators, specifically the lowest release rate on day 1 and the smallest slope of the release curve from day 7 to day 14, indicating the most stable release behavior; in a medium containing 1 mM CaCl2, exogenous Ca 2+ A slight re-crosslinking effect was produced on the alginate network, but the release curves of N and K in Example 1 only showed a slight shift, demonstrating excellent ion interference stability. Comparative Example 1 used an 80° four-nozzle surround spraying structure, resulting in an overly uniform distribution of the outer coating material on the particle surface, failing to form effective interface reinforcement in highly exposed areas. Consequently, the ability to control the flux of N and K decreased in the early stages of release, and the release amounts on days 1 and 3 increased significantly. Although no runaway occurred in the later stages of release due to the presence of the core and crosslinking layer structure, its plateau slope remained consistently higher than that of Example 1. Under CaCl2 conditions, the selective coating deficiency caused by this spraying structure could not be corrected by the salt effect, thus exhibiting a consistent performance difference in both media. Comparative Example 2 used only Ca... 2+ As a single crosslinking ion, no Mg was introduced. 2+ Boron participates in coordination; due to the fewer network nodes and concentrated energy distribution formed by single-ion crosslinking, the material exhibits an imbalance between wet toughness and dry crack resistance, resulting in a higher tendency for microcrack formation and powder shedding in mechanical and migration simulations; during the mid-release phase, the system shows significant insufficient controlled-release capacity, with a significantly increased release slope from 3 to 14 days; exogenous Ca 2+The re-crosslinking of the existing pure calcium network has limited improvement effect, and its salt sensitivity coefficient is even increased; in 1 mM CaCl2 medium, the release behavior of N and K in 1-3 days cannot be stabilized as in Example 1, and the low strength retention rate after freeze-thaw can be attributed to the lack of reversible synergy mechanism in the crosslinked network. Comparative Example 3 cancels the in-situ pore-forming process, although the apparent porosity of the obtained structure is reduced and the texture is more compact, due to the lack of controllable fine and tortuous channels, water permeates unevenly in the particle interior, and a direct path is formed locally; after the swelling is established and part of the path is connected, the late diffusion coefficient rises rapidly, resulting in the average release rate and cumulative release amount in 7-14 days exceeding those of Example 1. Comparative Example 4 increases the mineral micro-island content to above the percolation threshold, forming a higher probability of connected paths at the statistical geometric level, which is equivalent to building shorter and straighter migration channels in the particle interior; although the outer layer and crosslinked structure still exist, the direct flow that cannot be effectively inhibited in the early stage leads to an overall increase in the release rate on the first and third days, and the release endpoint approaches the highest level by the 14th day; the inhibitory effect of CaCl2 on N release is limited, while the release of K is intensified due to the ion competition replacement effect, making the release difference in 1-3 days more obvious; this group of samples also shows a lower strength retention rate and a higher micro-crack ratio in the hot and humid and migration tests, which is consistent with the trend of faster release throughout, indicating that the through-type structure not only weakens the mechanical properties but also intensifies the internal material migration.

[0027] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A growth promoting slow release organic compound fertilizer for rice, characterized by, The composition comprises the following raw materials by weight parts: 55-65 parts of organic matter matrix, 10-14 parts of porous carrier, 15-20 parts of mineral powder, 10-12 parts of pore forming agent, 7-10 parts of binder solution, 3-4 parts of sodium alginate, 2-4 parts of CaCl2, 0.8-1.6 parts of MgCl2, 0.1-0.15 parts of sodium tetraborate, 4-6 parts of coating emulsion and 0.5-1 parts of natural polyphenol solution.

2. The growth promoting slow release organic compound fertilizer for rice according to claim 1, characterized in that, The organic matter matrix is obtained by dry mixing humic acid and sodium lignosulfonate, spraying into 10wt% sodium lignosulfonate aqueous solution, turning while spraying, until the mass fraction of >2mm agglomerates is 5-10%, then hot air drying at 45-55℃ until the water content is 8-10%, and lightly crushing and passing through a 200 mesh screen.

3. The growth promoting slow release organic compound fertilizer for rice according to claim 2, characterized in that, The porous carrier is any one of zeolite, bentonite and biochar.

4. The growth promoting slow release organic compound fertilizer for rice according to claim 3, characterized in that, The mineral powder is composed of 11-13 parts of urea powder, 3-4.5 parts of ammonium phosphate powder and 1-2.5 parts of potassium chloride powder by weight parts; the pore forming agent is composed of 5-6 parts of sodium bicarbonate and 5-6 parts of citric acid monohydrate by weight parts.

5. The growth promoting slow release organic compound fertilizer for rice according to claim 4, characterized in that, The binder solution is compounded by sodium lignosulfonate and molasses at a mass ratio of 7-8:2-3, deionized water is added to adjust to 40wt% solid content, the pH is adjusted to neutral, and it is obtained by standing and defoaming; the natural polyphenol solution is compounded by tannic acid and catechin at a mass ratio of 1:1, and deionized water is added to adjust to 2wt% concentration.

6. The growth promoting slow release organic compound fertilizer for rice according to claim 5, characterized in that, The coating emulsion is compounded by 30wt% hydrophobicized dextrin aqueous solution and 50wt% rosin pentaerythritol ester dispersion at a volume ratio of 6:4, 2% 5wt% hydroxypropyl methylcellulose aqueous solution and 0.2-0.4% polydimethylsiloxane are added, water is added to 20wt% solid content, the pH is adjusted to 6.5-7.5, and it is obtained by shearing and dispersing at 1000-2000rpm for 10-15min; the hydrophobicized dextrin is obtained by reacting dextrin with a molecular weight of 5-30kDa in 1wt% Na2CO3 alkaline aqueous phase at 30-40℃ for 2-3h with octenyl succinic anhydride; the amount of octenyl succinic anhydride is 1.5-3% of the mass of dry dextrin.

7. A method for preparing the growth promoting slow release organic compound fertilizer for rice according to any one of claims 1-6, characterized in that, The following steps are included: S1: organic matter matrix, porous carrier and mineral powder are added to a mixer in turn, dry mixed at 40-60rpm for 6-8min, then pan granulated to obtain the inner core; S2: 30wt% citric acid solution and 8wt% sodium bicarbonate solution are staggered and sprayed on the inner core of step S1, hot air dried at 45-55℃ for 90-120min, hot air speed is 0.8-1.5m / s, to obtain sprayed particles; S3: 1.8wt% sodium alginate solution, 5wt% CaCl2 solution and 2wt% MgCl2 solution, and 0.5wt% sodium tetraborate solution are sprayed on the sprayed particles of step S2 to obtain cross-linked coated particles; S4: coating emulsion is sprayed on the cross-linked coated particles of step S3, and then natural polyphenol solution is sprayed. 0.05-0.2 MPa light pressure for 30-60 s, 25℃ standing for 24 h, 40-50℃ drying until moisture content is less than 2%; screening to retain 2-4 mm particles to obtain slow-release organic compound fertilizer.

8. The method for preparing the growth-promoting slow-release organic compound fertilizer for rice according to claim 7, characterized in that, In step S1, the specific operation parameters of the disc granulation are: disc angle 48-52°; initial speed 45 rpm, later 38-42 rpm, spraying binder solution, spraying speed 5-12 g / min, atomization pressure 0.2-0.4 MPa, spraying distance 25-35 cm, target wet particle size 2.8-3.2 mm, bed apparent moisture content 14-18 wt%.

9. The method for preparing the growth-promoting slow-release organic compound fertilizer for rice according to claim 8, characterized in that, In step S2, the specific operation parameters of the staggered atomization spraying are: material temperature 30-35℃, atomization air pressure 0.22-0.28 MPa, nozzle diameter 1-1.2 mm, spraying angle 60°-80°, 30-40 cm above the disc surface, two guns staggered and sprayed, included angle 45°-60°, bed apparent moisture content 14-18 wt%; in step S3, the specific operation parameters of the circulating spraying are: drum speed 9-11 rpm, loading coefficient 45-55%, material temperature 30℃, spraying sodium alginate solution 60-80 g / min, time 90 s; mixing spraying Ca / Mg solution 50-60 g / min, time 60 s; spraying sodium tetraborate solution 25-30 g / min, time 45 s, circulating interval 60-90 s; low-temperature deliquoring and shaping at hot air temperature 30-38℃, air speed 0.8-1.5 m / s, speed 8-10 rpm, time 3-6 min, bed apparent moisture content 8-10 wt%. In step S4, the specific parameters of the spraying and coating emulsion are: using directional nozzle and half-sphere covering on the material surface, tangential included angle of the spraying gun and the material surface 25°-35°, nozzle diameter 1-1.2 mm, atomization air pressure 0.18-0.24 MPa, spraying distance 30-40 cm; drum speed 8-10 rpm, loading coefficient 45-55%; the specific operation parameters of spraying natural polyphenol solution are consistent with those of spraying and coating emulsion.

10. The method for preparing the growth-promoting slow-release organic compound fertilizer for rice according to claim 9, characterized in that, ​

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