Silicon-containing humic acid compound fertilizer for middle indica rice and preparation method thereof

Abstract

This invention provides a silicon-containing humic acid compound fertilizer for medium-grain indica rice and its preparation method. The compound fertilizer includes: urea; controlled-release synergistic urea; soluble silicon fertilizer; humic acid; monoammonium phosphate or diammonium phosphate; and potassium chloride. The total weight of the compound fertilizer comprises 40%–50% N, P2O5, and K2O, with a mass ratio of N, P2O5, and K2O of 1:(0.3–0.5):(0.6–0.7). The available silicon from the soluble silicon fertilizer, calculated as SiO2, accounts for 0.5%–2% of the total weight, and the humic acid accounts for 0.5%–2% of the total weight. By continuously supplying available silicon and humic acid, root growth and stem silicification are promoted, significantly improving the lodging resistance and high-temperature tolerance of rice. This compound fertilizer can be applied as a base fertilizer in a single application, saving labor and effort, and has a high fertilizer utilization rate, which is beneficial for the green and efficient production of medium-grain indica rice in the Jianghuai region.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer technology, and in particular to a silicon-containing humic acid compound fertilizer for medium-grain indica rice and its preparation method. Background Technology

[0002] The Jianghuai region is an important rice-producing area in my country, with hybrid indica rice being widely cultivated. The growth period of indica rice is typically 135-150 days. During its growth, the tillering and booting stages are two critical peak periods for nutrient demand, with a large and concentrated need for nitrogen. However, most conventional compound fertilizers are fast-acting, releasing nutrients too quickly and dissolving in large quantities shortly after application to the soil, resulting in a significant mismatch with the rice's nutrient requirements. This leads to an oversupply of nitrogen during the tillering stage, causing fertilizer waste and environmental pollution. By the booting stage, when the nutrient demand is even greater, the nitrogen in the soil is almost depleted, resulting in significant late-stage nutrient deficiency, severely impacting the number of grains per panicle and yield.

[0003] Furthermore, existing compound fertilizers typically lack systematic improvements to the lodging resistance and high-temperature tolerance of indica rice. In the Jianghuai region, frequent high-temperature heat damage during the booting to grain-filling stage (late July to early August) easily leads to pollen abortion and reduced seed setting rate. Simultaneously, under high-nitrogen cultivation, rice plants exhibit excessive vegetative growth, thinning stem walls, and reduced toughness, significantly increasing the risk of lodging. Conventional compound fertilizers cannot effectively enhance rice's resistance to these adverse factors from a physiological and morphological perspective, resulting in a high risk of yield reduction.

[0004] Therefore, developing a compound fertilizer product that can precisely match nitrogen supply with the fertilizer requirements of medium-grain indica rice during the tillering and booting stages, while systematically enhancing the lodging resistance and high-temperature tolerance of rice, is of great significance for the high-yield, stable-yield, and green and sustainable production of medium-grain indica rice in the Jianghuai region. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention provides a silicon-containing humic acid compound fertilizer for medium-grain indica rice and its preparation method, so as to solve the technical problem of mismatch between the nitrogen release of existing fertilizers and the fertilizer requirements of medium-grain indica rice.

[0006] To achieve the above and other related objectives, this invention provides a silicon-containing humic acid compound fertilizer for medium-grain indica rice. The compound fertilizer comprises: urea; controlled-release synergistic urea; soluble silicon fertilizer; humic acid; monoammonium phosphate or diammonium phosphate; and potassium chloride. The controlled-release synergistic urea is obtained by coating synergistic urea with a biodegradable coating material to form controlled-release particles. The synergistic urea is obtained by adding soluble silicon fertilizer and humic acid to the urea. Based on the total weight of the compound fertilizer, the total nutrients N, P2O5, and K2O account for 40% to 50% by mass, and the mass ratio of N, P2O5, and K2O is 1:(0.3 to 0.5):(0.6 to 0.7). The available silicon from the soluble silicon fertilizer, calculated as SiO2, accounts for 0.5% to 2% by mass, and the humic acid accounts for 0.5% to 2% by mass.

[0007] In one embodiment of the present invention, the controlled-release urea includes a first controlled-release urea with a controlled-release period of 30±5 days and a second controlled-release urea with a controlled-release period of 80±5 days. The nitrogen release peak of the first controlled-release urea is synchronized with the peak fertilizer requirement during the tillering stage of medium-grained rice, and the nitrogen release peak of the second controlled-release urea is synchronized with the peak fertilizer requirement during the booting stage of medium-grained rice.

[0008] In one embodiment of the present invention, the ratio of the effective nitrogen contribution of the urea and the monoammonium phosphate or diammonium phosphate, the effective nitrogen contribution of the first controlled-release synergistic urea, and the effective nitrogen contribution of the second controlled-release synergistic urea is 5:2:3.

[0009] In one embodiment of the present invention, the soluble silicon fertilizer is one or more of blast furnace silicon fertilizer, silicon-calcium-potassium fertilizer, or molten calcium-magnesium phosphate fertilizer.

[0010] In one embodiment of the present invention, the humic acid is activated humic acid derived from weathered coal or lignite.

[0011] In one embodiment of the present invention, the biodegradable coating material is selected from one or more of vegetable oil-based polyurethane, modified starch, and cellulose derivatives.

[0012] To achieve the above and other related objectives, the present invention also provides a method for preparing a silicon-containing humic acid compound fertilizer for medium-grain indica rice. The method includes: adding soluble silicon fertilizer and humic acid during urea production, followed by granulation to obtain enhanced urea granules; sieving the enhanced urea granules, and then coating them with a biodegradable coating material to obtain controlled-release enhanced urea granules; and mixing monoammonium phosphate or diammonium phosphate, potassium chloride, soluble silicon fertilizer, humic acid, urea, and the controlled-release... The enhanced urea granules are mixed evenly according to the formula to obtain the compound fertilizer, wherein the formula is such that the total nutrients N, P2O5 and K2O in the compound fertilizer account for 40%~50% by mass, and the mass ratio of N, P2O5 to K2O is 1:(0.3~0.5):(0.6~0.7), the effective silicon from the soluble silicon fertilizer accounts for 0.5%~2% by mass as SiO2, and the humic acid accounts for 0.5%~2% by mass.

[0013] In one embodiment of the present invention, soluble silicon fertilizer and humic acid are added during the urea production process, and granulation is performed to obtain enhanced urea granules. The process includes: crushing the soluble silicon fertilizer to a predetermined particle size; adding the crushed soluble silicon fertilizer and humic acid at a mass percentage of 1% to 7% during the urea production process, and adding a polymer composite binder at a mass percentage of 2% to 3%; feeding the mixture into a rotary drum granulator or a disc granulator, and spraying water vapor to perform agglomeration granulation; drying the granulated wet granules at a preset temperature until the moisture content is lower than a preset value, and then cooling and sieving to obtain the enhanced urea granules.

[0014] In one embodiment of the present invention, the predetermined particle size is 1~4mm, the predetermined temperature is 80~110℃, and the predetermined value is 2%.

[0015] In one embodiment of the present invention, the amount of water vapor injected during the agglomeration granulation process is determined by collecting the current ambient temperature T, relative humidity H, and initial moisture content M of the mixture in the workshop. init Calculate the ideal water vapor injection rate W using the following formula. ideal :W ideal =(M target -M init )+α(T-T0)-β(H-H0), where M target Let T0 be the preset target moisture content constant, H0 be the reference temperature, α be the temperature evaporation compensation coefficient, and β be the humidity absorption compensation coefficient; minimize |W steam -W ideal |With the goal of achieving 5% ≤ W steam Determine the actual water vapor injection rate W under the constraint of ≤8%. steam Among them, W steamThis indicates the percentage of water vapor injected relative to the dry basis mass of the material.

[0016] The beneficial effects of this invention are as follows: This invention proposes a silicon-containing humic acid compound fertilizer for medium-grain indica rice and its preparation method. This method achieves a dual-peak release of nitrogen by compounding urea with controlled-release synergistic urea. By controlling the controlled-release period of the synergistic urea, the nitrogen supply can be precisely synchronized with the two peak fertilizer demand periods of medium-grain indica rice. At the same time, the soluble silicon fertilizer and humic acid directly added to the compound fertilizer form a synergistic effect with the silicon and humic acid inside the synergistic urea, continuously supplying effective silicon and humic acid, promoting root growth and stem silicification, and significantly improving the lodging resistance and high-temperature resistance of rice. This compound fertilizer can be applied as a base fertilizer in one application, saving labor and effort, and has a high fertilizer utilization rate, which is beneficial to the green and efficient production of medium-grain indica rice in the Jianghuai region. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The accompanying drawings are incorporated in and constitute a part of this specification, illustrating embodiments consistent with this application, and are used together with the description to explain the principles of this application. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0018] Figure 1 This invention provides a method for preparing a silicon-containing humic acid compound fertilizer for medium-grain indica rice; Figure 2 This invention provides a method for preparing enhanced urea granules according to an embodiment of the present invention. Detailed Implementation

[0019] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art and the description of the present invention by those skilled in the art, any prior art methods, equipment, and materials similar to or equivalent to the methods, equipment, and materials in the embodiments of the present invention can be used to implement the present invention.

[0020] It should be understood that the terminology used in the embodiments of this invention is for describing specific implementations and not for limiting the scope of protection of this invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0021] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In some embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0022] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functions, and operations that may be implemented in the methods and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0023] An embodiment of the present invention provides a silicon-containing humic acid compound fertilizer for medium-grain indica rice. The compound fertilizer includes: urea; controlled-release synergistic urea; soluble silicon fertilizer; humic acid; monoammonium phosphate or diammonium phosphate; and potassium chloride. The controlled-release synergistic urea is obtained by coating synergistic urea with a biodegradable coating material to obtain controlled-release granules. The synergistic urea is obtained by adding soluble silicon fertilizer and humic acid to urea. Based on the total weight of the compound fertilizer, the total nutrients N, P2O5, and K2O account for 40%~50% by mass, and the mass ratio of N, P2O5 to K2O is 1:(0.3~0.5):(0.6~0.7). The available silicon from the soluble silicon fertilizer, calculated as SiO2, accounts for 0.5%~2% by mass, and the humic acid accounts for 0.5%~2% by mass.

[0024] In this compound fertilizer, the enhanced urea is a granular product made by directly adding soluble silicon fertilizer and humic acid during the urea production process. Silicon and humic acid are evenly distributed within the granules, forming the core of the fertilizer's functionalization. The controlled-release enhanced urea is made by coating the enhanced urea granules with a biodegradable coating material. By adjusting the coating thickness and material composition, the release rate of nitrogen, as well as the internal silicon and humic acid, can be precisely controlled. This compound fertilizer simultaneously contains urea (as part of the readily available nitrogen source) and coated controlled-release enhanced urea, forming a nitrogen supply hierarchy of "quick-acting + medium-acting + long-acting." This structural design ensures sufficient readily available nitrogen to promote tillering in the early stages of rice growth, while the different controlled-release granules ensure nitrogen supply in the middle and later stages, avoiding the problem of nutrient deficiency in the later stages of traditional fertilizers. In addition, the soluble silicon fertilizer and humic acid directly added to the compound fertilizer further replenish the available silicon and organic matter in the soil, forming a complementary effect with the functional components in the controlled-release urea, and synergistically enhancing the effect. This systematically improves the stress resistance and yield potential of rice from two levels: the internal physiological mechanism of crop growth (root vitality, leaf photosynthetic efficiency) and the external morphological structure (stem wall thickness, degree of silicification).

[0025] In a specific embodiment of the present invention, the mass ratio of N, P2O5, and K2O is 1:0.4:0.6. This preferred mass ratio of 1:0.4:0.6 fully considers the absorption ratio and intensity of nitrogen, phosphorus, and potassium in indica rice during the tillering, jointing, and booting stages in the Jianghuai region. This ratio, while ensuring sufficient nitrogen supply, appropriately increases the proportion of potassium, which is beneficial for enhancing the toughness of rice stems and lodging resistance. Simultaneously, an adequate supply of phosphorus ensures early root development and energy metabolism, laying the foundation for later grain filling. This preferred ratio is a further optimization based on conventional fertilizer formulations, better aligning with the nutrient requirements of the target crop, and contributing to efficient nutrient utilization and stable, high yields.

[0026] In a specific embodiment of the present invention, the controlled-release urea includes a first controlled-release urea with a controlled-release period of 30±5 days and a second controlled-release urea with a controlled-release period of 80±5 days. The nitrogen release peak of the first controlled-release urea is synchronized with the peak fertilizer requirement during the tillering stage of medium-grained rice, and the nitrogen release peak of the second controlled-release urea is synchronized with the peak fertilizer requirement during the booting stage of medium-grained rice.

[0027] The selection of two controlled-release urea products with release periods of 30±5 days and 80±5 days was based on in-depth research into the growth stage and nutrient requirements of medium-grain indica rice. The first controlled-release urea product with a release period of 30±5 days had its nitrogen release curve designed to show the first release peak approximately 10-15 days after application. This period coincides with the beginning of tillering in medium-grain indica rice, providing timely and concentrated nitrogen nutrition for effective tillering, promoting early and rapid tillering, and increasing the panicle formation rate. The second controlled-release urea product with a release period of 80±5 days showed a second, more significant release peak approximately 40-60 days after application. This period coincides with the booting stage of medium-grain indica rice, a critical period determining the number of grains per panicle and the seed setting rate. Sufficient nitrogen supply promotes panicle differentiation, increases the number of grains per panicle, and stores nutrients for later grain filling. After this, nitrogen release tends to level off, avoiding excessive nitrogen in the later stages of grain filling that leads to premature vegetative growth and delayed maturity. This "dual-peak" release pattern achieves precise alignment between nitrogen supply and the two key peaks of nutrient demand in rice, fundamentally solving the problem of traditional fertilizers being "excessive in the early stage, deficient in the middle stage, and nonexistent in the later stage."

[0028] In a specific embodiment of the present invention, the ratio of the effective nitrogen contribution from urea and monoammonium phosphate or diammonium phosphate, the effective nitrogen contribution from the first controlled-release synergistic urea, and the effective nitrogen contribution from the second controlled-release synergistic urea is 5:2:3. The effective nitrogen contribution refers to the mass of nitrogen element that can be absorbed and utilized by crops in each nitrogen source component (urea, monoammonium phosphate / diammonium phosphate, and each controlled-release synergistic urea), and its value is equal to the mass of each component multiplied by its nitrogen mass percentage. In this invention, urea and monoammonium phosphate / diammonium phosphate are used as readily available nitrogen sources, and the ratio of their effective nitrogen contribution to the first and second controlled-release synergistic urea with controlled-release periods of 30 days and 80 days is designed to be 5:2:3. This ratio was obtained through extensive field trials and fertilizer requirement model simulation optimization. It allocates 50% of the total nitrogen supply to readily available nitrogen sources to meet the rapid and abundant nitrogen demand in the early stages of rice growth (especially the tillering stage), promoting early and rapid growth; 20% to medium-release nitrogen sources with a 30-day controlled-release period, used to bridge the nutrient transition from the late tillering stage to the jointing stage; and 30% to long-release nitrogen sources with an 80-day controlled-release period to ensure nitrogen supply during the peak fertilizer demand period of the booting stage. This ratio ensures that the nitrogen release curve closely matches the stage-specific fertilizer requirement pattern of indica rice, reducing nitrogen loss and volatilization while improving nitrogen fertilizer utilization efficiency and rice yield.

[0029] In a specific embodiment of the present invention, the soluble silicon fertilizer is one or more of blast furnace silicon fertilizer, silicon-calcium-potassium fertilizer, or molten calcium-magnesium phosphate fertilizer. Blast furnace silicon fertilizer, silicon-calcium-potassium fertilizer, and molten calcium-magnesium phosphate fertilizer are all typical soluble silicon fertilizers, sharing the common characteristics of high silicon availability and slow release. By selecting one or more for compounding, the silicon supply intensity can be flexibly adjusted according to different soil conditions and target yields. This type of silicon fertilizer not only provides sufficient silicon for rice but also simultaneously supplements other medium-quantity elements such as calcium, magnesium, and potassium, thus balancing soil nutrients and improving soil physicochemical properties. Furthermore, its relatively low cost makes it suitable for large-scale application.

[0030] In one specific embodiment of the present invention, the humic acid is activated humic acid derived from weathered coal or lignite. Humic acid derived from weathered coal or lignite, after activation treatment, has a small molecular weight, abundant active functional groups, and extremely strong ion exchange and complexing capabilities. Adding this type of activated humic acid to fertilizers can, on the one hand, complex metal ions in the soil, reduce phosphorus fixation, and improve the effectiveness of phosphate fertilizer; on the other hand, it can stimulate rice root growth and enhance the root system's ability to absorb water and nutrients. Simultaneously, humic acid can also act as a carrier for silicon migration, promoting the transport and deposition of silicon within the plant, thereby more effectively enhancing stem mechanical strength and improving lodging resistance and high-temperature resistance.

[0031] In one specific embodiment of the present invention, the biodegradable coating material is selected from one or more of plant oil-based polyurethane, modified starch, and cellulose derivatives. Plant oil-based polyurethane, modified starch, and cellulose derivatives are all biodegradable and environmentally friendly materials. Using these materials as coatings, after fertilizer is applied to the soil, the coating gradually degrades with the activity of soil microorganisms and the infiltration of water, requiring no manual recycling and causing no plastic pollution to the soil. Simultaneously, by adjusting the formulation of these materials and the coating thickness, the nitrogen release rate can be precisely controlled, achieving a controlled release period of 30 or 80 days. Compared to traditional polyolefin coating materials, biodegradable coating materials are more environmentally friendly and meet the requirements of sustainable development in modern agriculture.

[0032] Two specific examples of compound fertilizers are given below for reference. Example

[0033] Design goals: Total nutrients >40%, N:P2O5:K2O = 1:0.35:0.6, available silicon 1%, humic acid 1%.

[0034] Formula composition (for producing 1 ton of product): Urea (N≈46%): 173.63 kg; Controlled-release synergistic urea (N≈41%, controlled-release period 30 days, effective silicon and humic acid calculated at 3.5% each): 107.32 kg; Controlled-release synergistic urea (N≈41%, controlled-release period 80 days, effective silicon and humic acid calculated at 3.5% each): 160.98 kg; Diammonium phosphate (N≈18%, P2O5≈46%): 167.39 kg; Ordinary potassium chloride (K2O≈60%): 220.00 kg; soluble silicon fertilizer: 30.61 kg; Additives (bentonite): 140.07 kg; Total: Approximately 1000 kg.

[0035] Nutrient calculation: Total N≈22.0%, P2O5≈7.7%, K2O≈13.2%, total nutrients 42.9%, available silicon 1%, humic acid content 0.94%. Example

[0036] Design goals: Total nutrients >45%, N:P2O5:K2O = 1:0.35:0.7, available silicon 1.5%, humic acid 1%.

[0037] Formula composition (for producing 1 ton of product): Urea (N≈46%): 181.52 kg; Controlled-release synergistic urea (N≈41%, controlled-release period 30 days, effective silicon and humic acid calculated at 3.5% each): 112.20 kg; Controlled-release synergistic urea (N≈41%, controlled-release period 80 days, effective silicon and humic acid calculated at 3.5% each): 168.29 kg; Diammonium phosphate (N≈18%, P2O5≈46%): 175.00 kg; Ordinary potassium chloride (K2O≈60%): 268.33 kg; 50.18 kg of soluble silicon fertilizer; Additives (bentonite): 44.48 kg; Total: Approximately 1000 kg.

[0038] Nutrient calculation: Total N≈23.0%, P2O5≈8.05%, K2O≈16.1%, total nutrients 47.15%, available silicon 1.5%, humic acid content 0.98%.

[0039] It should be noted that Examples 1 and 2 above are merely two specific implementation schemes of the present invention and are not limitations on the formula ratio. In actual production, the specific addition quality of each component can be appropriately adjusted according to the target yield, soil fertility status, and rice variety characteristics, provided that the total nutrient content is 40%-50%, the ratio of N, P2O5 to K2O is within the range of 1:(0.3-0.5):(0.6-0.7), and the contents of available silicon and humic acid are both within the range of 0.5%-2%. For example, when the target total nutrient content is set at 45%, the input of each nitrogen, phosphorus, and potassium source can be increased accordingly; when the available silicon content in the soil is high, the addition amount of soluble silicon fertilizer can be appropriately reduced. As long as the various nutrient indicators of the final product meet the above ranges, it falls within the protection scope of the present invention.

[0040] Please see Figure 1 , Figure 1 An embodiment of the present invention provides a method for preparing the above-mentioned silicon-containing humic acid compound fertilizer for medium-grain indica rice, the method comprising steps S101 to S103.

[0041] Step S101: Add soluble silicon fertilizer and humic acid during urea production, and then granulate to obtain enhanced urea granules. This step is one of the core steps in preparing the compound fertilizer of this invention. By directly mixing silicon fertilizer and humic acid into urine or molten urea, the strong permeability and adhesion of the molten urea liquid are utilized to uniformly disperse silicon and humic acid inside the urea granules, forming "enhanced urea" with a functional core, rather than a simple physical mixture, thus ensuring the synchronous release of functional components and nitrogen.

[0042] Please see Figure 2 In a specific embodiment of the present invention, step S101 includes: S201, pulverizing the soluble silicon fertilizer to a predetermined particle size, which may be, for example, 1-4 mm; S202, during the urea production process, adding the pulverized soluble silicon fertilizer and humic acid at a mass percentage of 1%-7%, and adding a polymer composite binder at a mass percentage of 2%-3%; S203, feeding the mixture into a rotary drum granulator or a disc granulator, and spraying water vapor to agglomerate and granulate; S204, drying the granulated wet granules at a preset temperature until the moisture content is lower than a preset value, and then cooling and sieving to obtain enhanced urea granules, wherein the preset temperature may be, for example, 80-110°C, and the preset value of the moisture content may be, for example, 2%.

[0043] This preparation process first pulverizes the soluble silicon fertilizer into fine particles of 1-4 mm, ensuring its uniform dispersion during subsequent mixing and granulation. Silicon fertilizer and humic acid are added at a mass ratio of 1%-7% to ensure the concentration of functional components in the enhanced urea core. Using a rotary drum or disc granulator with 2%-3% binder and an appropriate amount of steam forms dense, high-strength granules, preventing breakage during subsequent coating and transportation. Drying at 80-110℃ until the moisture content is below 2% effectively removes moisture to prevent granule agglomeration and avoids excessively high temperatures that could damage the activity of humic acid. The entire process is continuous, stable, and controllable, suitable for industrial production.

[0044] In a specific embodiment of the present invention, the amount of water vapor injected during the agglomeration granulation process is determined by the following method: (1) collecting the current ambient temperature T, relative humidity H, and initial moisture content M of the mixture in the workshop. init (2) Calculate the ideal water vapor injection rate W according to the following formula. ideal :W ideal =(M target -M init )+α(T-T0)-β(H-H0), where M target The preset target moisture content constant is T0, the reference temperature is H0, the reference humidity is α, the temperature evaporation compensation coefficient is β, and the humidity absorption compensation coefficient is α; (3) minimize |W steam -W ideal |With the goal of achieving 5% ≤ W steam Determine the actual water vapor injection rate W under the constraint of ≤8%. steam Among them, W steam This indicates the percentage of water vapor injected relative to the dry basis mass of the material.

[0045] Because the temperature and humidity in the workshop environment fluctuate daily, fixing the amount of water vapor injected will lead to unstable material moisture content during granulation, resulting in fluctuations in pelletizing rate and increased return material. The control algorithm introduced in this invention uses sensors to collect ambient temperature T, humidity H, and initial material moisture M in real time. init And use the formula to dynamically calculate the theoretical water demand W ideal Subsequently, through the objective function and process constraints (5%≤W) steam (≤8%) Automatic optimization, output the current best W steam The algorithm achieves closed-loop precise control of the water vapor injection amount during the granulation process. Even with drastic changes in ambient temperature and humidity, it ensures that the actual moisture content of the mixture remains stable near the ideal value for optimal pellet formation, thereby significantly improving the pelletizing rate and product quality consistency, and reducing energy consumption for return material processing.

[0046] Step S102: After sieving the enhanced urea granules, a biodegradable coating material is used to coat them, thus obtaining controlled-release enhanced urea granules. This step is crucial for achieving the "bimodal" release of nitrogen. First, the enhanced urea granules obtained in the previous step are sieved, and granules with uniform particle size (e.g., 2-4 mm) are selected as the coating core material to ensure consistent coating effect. Then, using fluidized bed equipment, the biodegradable coating material is uniformly sprayed onto the surface of the granules to form coating layers of different thicknesses. By precisely controlling the type, formulation, and coating amount of the coating material, two types of controlled-release enhanced urea granules with controlled-release periods of 30 days and 80 days can be prepared respectively. Fluidized bed coating technology features uniform coating, high efficiency, and suitability for large-scale production.

[0047] Step S103: Mix monoammonium phosphate or diammonium phosphate, potassium chloride, soluble silicon fertilizer, humic acid, urea and controlled-release urea granules evenly according to the ratio to obtain compound fertilizer. The ratio is such that the total nutrients N, P2O5 and K2O in the compound fertilizer account for 40%~50% by mass, and the mass ratio of N, P2O5 and K2O is 1:(0.3~0.5):(0.6~0.7). The effective silicon from the soluble silicon fertilizer, calculated as SiO2, accounts for 0.5%~2% by mass, and the humic acid accounts for 0.5%~2% by mass.

[0048] In actual production, firstly, based on the target total nutrient content (e.g., 45%) and the target N-P2O5-K2O ratio (e.g., 1:0.4:0.6), the required pure nutrient mass of N, P2O5, and K2O for producing 1 ton of compound fertilizer is calculated. Then, based on the nutrient content of the raw materials (e.g., urea contains approximately 46% N, diammonium phosphate contains approximately 18% N and 46% P2O5, potassium chloride contains approximately 60% K2O, and controlled-release urea contains approximately 41% N), and combined with the preset ratio (5:2:3) of the readily available nitrogen source and the two types of controlled-release nitrogen sources in the compound fertilizer, a system of multiple linear equations is established through material balance. Solving this system of equations yields the specific feed mass of urea, monoammonium phosphate or diammonium phosphate, potassium chloride, and the two types of controlled-release urea. During the solution process, the final content requirements for effective silicon and humic acid (0.5%-2%) must also be met. Based on this, the mass of additional soluble silicon fertilizer and humic acid that needs to be added can be calculated. For the remaining portion, it can be made up by auxiliary materials (such as bentonite). This process can be automatically completed by designing algorithms to accurately measure and mix each raw material.

[0049] To verify the effectiveness of the compound fertilizer in this invention, a field trial was conducted in Hefei City, Anhui Province, using locally grown hybrid indica rice (growing period of 145 days). The trial included the following treatments: T1, the compound fertilizer of this invention (single basal application, 750 kg / ha); T2, conventional compound fertilizer (equal total nutrient content, applied twice, as basal fertilizer and as panicle fertilizer).

[0050] Experimental results: Compared with T2, the T1 treatment increased the tillering and panicle formation rate of rice by 8%, the SPAD value (relative chlorophyll content) of leaves during the booting stage by 12%, the thickness of the second internode wall at the base of the stem increased by 12% at maturity, and the bending resistance was enhanced by 20%. Under temperatures above 35℃, the seed setting rate of T1 was 5 percentage points higher than that of T2. The final yield of T1 was 6.5% higher than that of T2. Therefore, the silicon-containing humic acid compound fertilizer provided by this invention can significantly improve the agronomic traits and physiological indicators of medium-grain indica rice compared with conventional compound fertilizers. Through precise biphasic nitrogen release, it increases the tillering and panicle formation rate and leaf chlorophyll content; through the synergistic effect of silicon and humic acid, it effectively enhances the mechanical strength of the stem and improves lodging resistance; under high-temperature stress, it exhibits a higher seed setting rate, ultimately achieving a significant yield increase of 6.5%. This fully demonstrates the outstanding technical effects of the compound fertilizer of this invention in promoting rice growth, enhancing stress resistance, and increasing yield.

[0051] In summary, the silicon-containing humic acid compound fertilizer for medium-grain indica rice and its preparation method provided by this invention have the following beneficial effects: First, precise fertilization. By scientifically combining fast-acting nitrogen sources with dual-peak controlled-release nitrogen sources with release periods of 30 days and 80 days, the nitrogen release curve is precisely synchronized with the two peak fertilizer demand periods of the tillering and booting stages of indica rice. This solves the problem of nutrient distribution in traditional fertilizers, which are "excessive in the early stage, deficient in the middle stage, and absent in the later stage," and significantly improves fertilizer utilization.

[0052] Secondly, it enhances resistance to adverse conditions and increases yield. The humic acid and available silicon in the fertilizer form a synergistic effect, promoting root growth and vitality while simultaneously increasing silicon deposition in stem epidermal cells, thus increasing stem wall thickness and bending strength. This systematically strengthens rice's resistance to lodging and its heat tolerance during the heading and booting stages. Field trials have shown that this fertilizer significantly improves tillering and panicle formation rate, stem strength, and grain filling rate, ultimately achieving stable and increased yields.

[0053] Third, it is labor-saving and efficient. This compound fertilizer has a high total nutrient content, a scientific nutrient ratio, and nitrogen has long-lasting and slow-release characteristics. It can be applied as a base fertilizer in one application, eliminating the need for topdressing in the middle and later stages, greatly reducing labor costs, and meeting the current needs of large-scale and simplified agricultural production.

[0054] Fourth, it is green and environmentally friendly. The coating material used is biodegradable and will not cause plastic accumulation pollution in the soil. At the same time, the precise nutrient supply reduces nitrogen leaching and volatilization losses, reducing the environmental burden on water bodies and the atmosphere, making it an environmentally friendly fertilizer.

[0055] It should be noted that the steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they contain the same logical relationship, they are all within the scope of protection of this application. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, but without changing the core design of the algorithm and process, are also within the scope of protection of this patent.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A silicon-containing humic acid compound fertilizer for medium-grain indica rice, characterized in that, The compound fertilizer includes: Urea; Controlled-release synergistic urea; soluble silicon fertilizer; Humic acid; Monoammonium phosphate or diammonium phosphate; and Potassium chloride; The controlled-release synergistic urea is a controlled-release particle obtained by coating synergistic urea with a biodegradable coating material. The synergistic urea is a particle obtained by adding soluble silicon fertilizer and humic acid to the urea. Based on the total weight of the compound fertilizer, the total nutrients N, P2O5 and K2O account for 40% to 50% by mass, and the mass ratio of N, P2O5 to K2O is 1:(0.3 to 0.5):(0.6 to 0.7). The effective silicon from the soluble silicon fertilizer, calculated as SiO2, accounts for 0.5% to 2% by mass, and the humic acid accounts for 0.5% to 2% by mass.

2. The silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 1, characterized in that, The controlled-release urea includes a first controlled-release urea with a controlled-release period of 30±5 days and a second controlled-release urea with a controlled-release period of 80±5 days. The nitrogen release peak of the first controlled-release urea is synchronized with the peak fertilizer requirement during the tillering stage of medium-grain indica rice, and the nitrogen release peak of the second controlled-release urea is synchronized with the peak fertilizer requirement during the booting stage of medium-grain indica rice.

3. The silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 2, characterized in that, The ratio of the effective nitrogen contribution of the urea and the monoammonium phosphate or diammonium phosphate, the effective nitrogen contribution of the first controlled-release synergistic urea, and the effective nitrogen contribution of the second controlled-release synergistic urea is 5:2:

3.

4. The silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 1, characterized in that, The soluble silicon fertilizer is one or more of blast furnace silicon fertilizer, silicon-calcium-potassium fertilizer, or molten calcium-magnesium phosphate fertilizer.

5. The silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 1, characterized in that, The humic acid is activated humic acid derived from weathered coal or lignite.

6. The silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 1, characterized in that, The biodegradable coating material is selected from one or more of vegetable oil-based polyurethane, modified starch, and cellulose derivatives.

7. A method for preparing a silicon-containing humic acid compound fertilizer for medium-grain indica rice as described in any one of claims 1 to 6, characterized in that, The method includes: Adding soluble silicon fertilizer and humic acid during urea production and then granulating the mixture yields enhanced urea granules. After sieving the enhanced urea granules, they are coated with a biodegradable coating material to obtain controlled-release enhanced urea granules. Monoammonium phosphate or diammonium phosphate, potassium chloride, soluble silicon fertilizer, humic acid, urea, and the controlled-release urea granules are mixed evenly in a certain proportion to obtain the compound fertilizer. The proportion is such that the total nutrients N, P2O5, and K2O in the compound fertilizer account for 40% to 50% by mass, and the mass ratio of N, P2O5, and K2O is 1:(0.3 to 0.5):(0.6 to 0.7). The available silicon from the soluble silicon fertilizer, calculated as SiO2, accounts for 0.5% to 2% by mass, and the humic acid accounts for 0.5% to 2% by mass.

8. The method for preparing the silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 7, characterized in that, Adding soluble silicon fertilizer and humic acid during urea production, followed by granulation, yields enhanced urea granules, including: The soluble silicon fertilizer is pulverized to a predetermined particle size; In the urea production process, pulverized soluble silicon fertilizer and humic acid are added at a mass percentage of 1% to 7%, and a polymer composite binder is added at a mass percentage of 2% to 3%. The mixture is fed into a rotary drum granulator or a disc granulator, and steam is injected to agglomerate and granulate it. The granulated wet granules are dried at a preset temperature until the moisture content is lower than a preset value, then cooled and sieved to obtain the enhanced urea granules.

9. The method for preparing the silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 8, characterized in that, The predetermined particle size is 1~4mm, the predetermined temperature is 80~110℃, and the predetermined value is 2%.

10. The method for preparing the silicon-containing humic acid compound fertilizer for medium-grain indica rice according to claim 8, characterized in that, In the agglomeration granulation process, the amount of water vapor injected is determined in the following way: Collect the current ambient temperature T, relative humidity H, and initial moisture content M of the mixture in the workshop. init ; The ideal steam injection rate W is calculated using the following formula. ideal : W ideal =(M target -M init )+α(T-T0)-β(H-H0), In the formula, M target The preset target moisture content constant is T0, the reference temperature is H0, the reference humidity is α, the temperature evaporation compensation coefficient is β, and the humidity absorption compensation coefficient is α. To minimize |W steam -W ideal |With the goal of achieving 5% ≤ W steam Determine the actual water vapor injection rate W under the constraint of ≤8%. steam Among them, W steam This indicates the percentage of water vapor injected relative to the dry basis mass of the material.

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