A special compound fertilizer for lodging resistance of wheat and a preparation method thereof

Abstract

The application discloses a kind of wheat lodging-resistant special-purpose compound fertilizer and preparation method thereof, belong to compound fertilizer technical field.The fertilizer is according to dry basis weight parts, including macroelement base fertilizer 35~65, silicon calcium base medium element fertilizer 10~30, trace element premix 1~6, humic acid organic carrier 10~25, slow-release coating agent 3~10;Nitrogen source uses quick-acting and slow-release component compound, combined with coating to control nutrient release, silicon calcium component sets effective content lower limit.Preparation method includes pretreatment, mixing, drum granulation, drying screening, coating whole grain step.The present application nutrient release matches wheat growth period, can enhance stem strength, reduce lodging risk, raw material is general, adapts existing compound fertilizer production line.

Description

Technical Field

[0001] This invention relates to the field of compound fertilizer preparation technology, and in particular to a special compound fertilizer for wheat lodging prevention and its preparation method. Background Technology

[0002] According to agricultural production statistics, lodging during the wheat jointing to grain-filling stage typically results in a yield loss of 10% to 30%. Lodging also leads to insufficient grain filling, reduced thousand-grain weight, lower test weight, and an increased proportion of inferior wheat, directly impacting the quality of marketable grain. Furthermore, lodged plants with ears close to the ground are prone to sprouting and mold, significantly increasing the difficulty of mechanical harvesting and grain loss. Currently, preventing wheat lodging primarily involves optimizing fertilizer nutrient structure and release characteristics, regulating wheat stem development from the nutrient supply side—a crucial technical approach that balances yield improvement with lodging resistance cultivation.

[0003] Currently, the common wheat-specific compound fertilizers widely used in field operations are mainly designed to meet the basic yield requirements in terms of nitrogen, phosphorus, and potassium ratios. Nitrogen is mostly in a fast-acting form, with the peak release concentrated in the greening and jointing stage. This can easily lead to excessive elongation of the basal internodes, thinning of the stem walls, and insufficient development of mechanical tissues, thus creating a hidden danger for lodging later on. Existing improved fertilizers for lodging resistance generally suffer from the following shortcomings: First, nutrient regulation is singular, often relying solely on increasing potassium fertilizer application as the core method, neglecting the synergistic effects of cell wall structural elements such as silicon and calcium, resulting in limited improvement in stem mechanical strength; second, the slow-release system design is not well-matched to the wheat growth stage, and single-coating or single-slow-release nitrogen control modes cannot simultaneously meet the nutrient requirements for stable growth in the early stage, strong stems in the middle stage, and prevention of premature aging in the later stage; third, some products rely on niche and expensive raw materials such as chelated trace elements and special resin coating agents, resulting in high raw material procurement costs and poor supply chain stability, making it difficult to adapt to the fertilizer cost affordability of field crops; fourth, some preparation processes require the addition of special reaction and molding equipment, making it impossible to directly connect with the mainstream drum granulation production lines of existing compound fertilizer companies, resulting in high technical transformation costs for large-scale promotion.

[0004] Therefore, developing a lodging-resistant compound fertilizer with universal raw materials, balanced and synergistic nutrient ratios, slow-release properties adapted to the wheat growth period, and compatibility with existing compound fertilizer production processes is of great practical significance for stabilizing wheat yield and improving quality, and reducing planting risks. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a special compound fertilizer for wheat lodging resistance and its preparation method. It uses conventional bulk raw materials from the fertilizer industry and improves wheat stem strength and lodging resistance through optimization of nutrient structure and slow-release system. At the same time, the preparation process is highly compatible with existing compound fertilizer production lines, making it easy to promote and apply on a large scale.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a special compound fertilizer for preventing lodging in wheat, comprising the following components by dry weight: 35-65 parts of macro-element base fertilizer, 10-30 parts of silicon-calcium-based medium-element fertilizer, 1-6 parts of micro-element premix, 10-25 parts of humic acid organic carrier, and 3-10 parts of slow-release coating agent. The macro-element base fertilizer consists of a nitrogen source, a phosphorus source, and a potassium source, wherein the nitrogen source is composed of a readily available nitrogen source and a slow-release nitrogen source in a mass ratio of 4:6 to 6:4; the slow-release coating agent coats the outer layer of the fertilizer particles. In the silicon-calcium-based medium-element fertilizer, the effective silicon (SiO2) mass fraction is ≥20%, and the active calcium (CaO) mass fraction is ≥15%.

[0008] In a preferred embodiment of the present invention, the mass ratio of nitrogen, phosphorus pentoxide, and potassium oxide in the macronutrient-based fertilizer is (12-18):(8-15):(15-22), based on pure nutrients, wherein potassium oxide accounts for no less than 35% of the total pure nitrogen, phosphorus, and potassium nutrients. The readily available nitrogen source is one or a combination of urea, ammonium sulfate, and ammonium chloride in any proportion; the slow-release nitrogen source is one or a combination of urea-formaldehyde and sulfur-coated urea in any proportion; the phosphorus source is one or a combination of monoammonium phosphate, diammonium phosphate, superphosphate, and calcium magnesium phosphate in any proportion; and the potassium source is one or a combination of potassium sulfate and potassium chloride in any proportion, wherein potassium sulfate accounts for no less than 60% of the total potassium source mass.

[0009] As a preferred embodiment of the present invention, the silicon-calcium based medium-element fertilizer is composed of silicon-calcium-magnesium phosphate fertilizer and light calcium carbonate in a mass ratio of (3-5):1; wherein the effective silicon is 20%-35% by mass of SiO2, the active calcium is 15%-25% by mass of CaO, and the mass ratio of effective silicon to active calcium is (1.2-1.8):1.

[0010] As a preferred embodiment of the present invention, the micronutrient premix comprises, by weight, 0.5-2 parts zinc fertilizer, 0.3-1.5 parts boron fertilizer, and 0.2-2.5 parts magnesium fertilizer. The zinc fertilizer is zinc sulfate heptahydrate, the boron fertilizer is borax or boric acid, and the magnesium fertilizer is magnesium sulfate heptahydrate. Based on pure elements, the mass ratio of boron to zinc is 1:(1.5-3), and magnesium accounts for 10%-30% of the total elemental mass of the premix.

[0011] As a preferred embodiment of the present invention, the humic acid organic carrier is composed of weathered coal humic acid and potassium fulvate in a mass ratio of (2-3):1, wherein the dry basis mass fraction of humic acid is ≥50% and the mass fraction of free humic acid is ≥30%. The slow-release coating agent is one of sulfur-polymer composite coating material and epoxy resin coating agent; the coating integrity rate of fertilizer granules is ≥95%. Under static water conditions at 25℃, the initial nitrogen release rate of the finished fertilizer is ≤10%, the cumulative release rate after 28 days is ≤30%, and the cumulative release time of 80% nitrogen nutrients is 90-120 days.

[0012] This invention also provides a method for preparing the above-mentioned wheat lodging-resistant compound fertilizer, comprising the following steps: (1) Raw material pretreatment: The macro-element base fertilizer, silicon-calcium based medium-element fertilizer, micro-element premix, and humic acid organic carrier are crushed and sieved respectively, and the moisture content of the raw materials is adjusted to 2% to 5% to obtain the base powder. (2) Mixing and batching: Weigh each base powder, micro-element premix and humic acid organic carrier according to the ratio, put them into the mixer and mix to obtain a mixed powder with a uniformity variation coefficient ≤ 5%. (3) Rotary drum granulation: The mixed powder is fed into a rotary drum granulator, saturated steam is introduced, and the material is agglomerated into granules under the conditions of material moisture content of 10% to 15% and material temperature of 55 to 70℃ to obtain wet base fertilizer granules. (4) Drying, cooling and screening: The wet base fertilizer granules are dried in stages, cooled in countercurrent and then screened to obtain base fertilizer granules with a particle size of 2.0 to 4.0 mm. (5) Coating and granulation: The basic fertilizer granules are fed into a roller coating machine and sprayed with a molten slow-release coating agent at an environment of 60-75℃. After spraying, the granules are kept warm and matured, cooled and screened to obtain the finished compound fertilizer.

[0013] As a preferred technical solution of the present invention, in step (1), the material is crushed and passed through an 80-100 mesh standard sieve, with the proportion of undersize material ≥95%; the moisture content of the raw material is controlled by low-temperature hot air at 40-60℃. In step (2), the mixing time is 12-20 min, and the deviation rate of single nutrient content of the mixed material is ≤3%.

[0014] As a preferred technical solution of the present invention, in step (3), the granulation pelleting rate is ≥85%; during the granulation process, a sodium humate solution with a mass fraction of 0.5% to 1% is sprayed simultaneously, and the spraying amount is 2% to 5% of the total mass of the mixed powder. In step (4), the unqualified particles generated by screening are crushed and returned to the granulation process as return material, and the proportion of return material to the total feed mass is controlled at 15% to 25%.

[0015] As a preferred technical solution of the present invention, in step (4), the segmented drying is divided into a low-temperature pre-drying section and a high-temperature shaping section: the inlet air temperature of the low-temperature pre-drying section is 60-80℃, and the inlet air temperature of the high-temperature shaping section is 90-110℃; the moisture content of the dried particles is ≤2.0%. The grading and screening adopts a double-layer vibrating screen, with an upper screen aperture of 4.0mm and a lower screen aperture of 2.0mm.

[0016] As a preferred technical solution of the present invention, in step (5), the slow-release coating agent is pre-melted at a constant temperature of 80-90℃, and the total spraying mass of the slow-release coating agent is 3%-10% of the mass of the base fertilizer granules. After spraying, the granules are kept warm and rolled for 5-10 minutes, and then cooled to room temperature; the compressive strength of the finished granules is ≥15N, the particle size qualification rate is ≥90%, and the moisture content is ≤2.0%.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The nitrogen fertilizer uses a combination of fast-acting and slow-release components, combined with an outer coating structure. The nutrient release rate matches the fertilizer requirements of wheat throughout its entire growth period, which can moderate the intensity of nitrogen supply in the early stage and reduce excessive elongation of the basal internodes of wheat. Field plot trials have verified that, compared with ordinary compound fertilizer of the same nutrient content as a control, the length of the second basal internode of wheat is shortened by 8% to 12%, effectively reducing the risk of lodging. 2. Optimizing the ratio and effective content of silicon and calcium, the medium elements can provide silicon and calcium nutrients for wheat stem development, and increase the thickness of stem cell walls and mechanical support strength. Experimental results show that the stem wall thickness at the base of mature wheat is 10%–16% higher than that of the control, and the stem bending resistance is 12%–18% higher. 3. Combined with humic acid and trace elements such as zinc, boron, and magnesium, it can promote wheat root growth and vascular bundle development, enhance the plant's root system's ability to hold its weight, and synergistically improve lodging resistance with nutrient regulation and stem strengthening effects; field trial results show that the lodging index of wheat at maturity is reduced by 12% to 19% compared with the control. 4. All raw materials are conventional bulk raw materials in the fertilizer industry, and the preparation process can be directly adapted to the existing compound fertilizer rotary drum granulation production line without the need for additional special equipment, which facilitates large-scale production and field application. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 is a schematic diagram of the preparation process of the wheat lodging-resistant compound fertilizer of the present invention; Figure 2 is a comparison of the cumulative nitrogen release curves of Example 1 and the comparative fertilizer under static water conditions at 25°C. Figure 3 is a bar chart comparing the flexural strength and lodging index of wheat stems at maturity under the various embodiments and comparative treatments; Detailed Implementation The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0019] In the attached diagram, all identical reference numerals refer to the same components.

[0020] The overall preparation process of the wheat lodging-resistant compound fertilizer of the present invention is shown in Figure 1. It includes, in sequence, a raw material pretreatment process, a mixing and batching process, a drum granulation process, a drying, cooling and screening process, and a coating and granulation process. Each process is connected in sequence. The unqualified materials generated by screening are crushed and returned to the drum granulation process for recycling.

[0021] Example 1 As shown in Figure 1, the wheat lodging-resistant compound fertilizer of this invention is prepared using a conventional compound fertilizer rotary drum granulation production line. The entire process consists of nine major steps: raw material pretreatment → metering and batching → biaxial mixing → rotary drum granulation → segmented drying → countercurrent cooling → grading and screening → drum coating → cooling and granulation → finished product packaging. Among them, the oversized particles produced by grading and screening are crushed and returned to the rotary drum granulation process inlet along with the undersize fine powder as recycled material, forming a closed-loop production system. Large-scale production can be achieved without the need for additional special equipment.

[0022] The raw material composition of each embodiment and comparative example is summarized in the table below: Table 1. Composition of each raw material for processing (parts by dry weight)

[0023] Example 1 (Preferred Example) 1. Raw material composition and specifications The raw material ratios in this embodiment correspond to the column of Example 1 in Table 1, and the specific specifications of each component are as follows: Basic fertilizer containing macronutrients: Based on pure nutrients, N:P2O5:K2O=15:10:18, with potassium oxide accounting for 39.1% of the total macronutrient mass; the nitrogen source is a mixture of agricultural-grade urea (total nitrogen ≥46.4%) and urea-formaldehyde (slow-release nitrogen ≥38%, activity index 52%) in a mass ratio of 5:5; the phosphorus source is agricultural-grade monoammonium phosphate (total nitrogen ≥11.0%, available P2O5 ≥44.0%); the potassium source is a combination of potassium sulfate (K2O ≥50.0%) and potassium chloride (K2O ≥60.0%) in a mass ratio of 7:3, with potassium sulfate accounting for 70% of the total potassium source mass.

[0024] Silicon-calcium based medium-element fertilizer: It is composed of silicon-calcium-magnesium phosphate fertilizer (effective SiO2≥20.0%, CaO≥25.0%) and light calcium carbonate (CaO≥52.0%) in a mass ratio of 4:1; after compounding, the effective silicon is 28% by mass as SiO2, the active calcium is 20% by mass as CaO, and the mass ratio of effective silicon to active calcium is 1.4:1.

[0025] Trace element premix: Composed of 1.2 parts of zinc sulfate heptahydrate (Zn≥21.0%), 0.8 parts of borax (B≥11.0%), and 1.0 part of magnesium sulfate heptahydrate (Mg≥9.8%); On a pure element basis, the mass ratio of boron to zinc is 1:2, and magnesium accounts for 22% of the total element mass of the premix.

[0026] Humic acid organic carrier: It is composed of weathered coal humic acid (humic acid dry basis ≥50%) and potassium fulvate (fulvic acid ≥50%) in a mass ratio of 2.5:1. After compounding, the dry basis mass fraction of humic acid is 55% and the mass fraction of free humic acid is 35%.

[0027] Slow-release coating agent: Sulfur-polymer composite coating material is used, and the final product coating integrity rate is 96%.

[0028] 2. Preparation process steps (1) Raw material pretreatment: The macro-element basic fertilizer and silicon-calcium-based medium-element fertilizer are respectively fed into a hammer mill for crushing. After crushing, they are passed through a 90-mesh standard inspection sieve, and the proportion of the sieve material is 96%. Low temperature hot air at 40~60℃ is used to control the moisture of the powder. Finally, the moisture of the raw material is stabilized at 3.5%, and a basic powder with uniform particle size is obtained for use.

[0029] (2) Metering and mixing: Weigh each basic powder, trace element premix and humic acid organic carrier according to the weight ratio, and feed them into the horizontal twin-shaft zero-gravity mixer at a uniform speed through the automatic metering and batching bin; first add the bulk basic powder for premixing for 3 minutes, then add the trace element premix and continue mixing for 12 minutes, for a total mixing time of 15 minutes; after mixing, the coefficient of variation of material uniformity is 4.2%, and the deviation rate of single nutrient content is 2.5%, thus obtaining uniformly mixed powder.

[0030] (3) Rotary drum granulation: The mixed powder is continuously fed into a rotary drum granulator with an inclination angle of 3° and a drum rotation speed of 15 r / min; 0.3 MPa saturated steam is introduced through the nozzle at the front end of the granulator and sprayed evenly into the material bed, controlling the material moisture content to 12% and the material temperature to 62℃; during the granulation process, a sodium humate solution with a mass fraction of 0.8% is sprayed simultaneously as an auxiliary binder, and the spraying amount is 3.5% of the total mass of the mixed powder; the material agglomerates into balls as the drum rotates, with a residence time of 10 min, and the final granulation balling rate is 88%, resulting in wet-based fertilizer granules.

[0031] (4) Drying, cooling, and screening: The wet-based granules are fed into a rotary drum dryer for segmented gradient drying: the inlet air temperature of the low-temperature pre-drying section is 70℃, and the material stays for 8 minutes to remove free water from the surface of the granules and prevent granule disintegration; the inlet air temperature of the high-temperature shaping section is 100℃, and the material stays for 20 minutes to solidify the internal structure of the granules; the moisture content of the dried granules is 1.6%. The dried granules are then fed into a counter-current cooler for forced cooling, with a cooling air velocity of 2.0 m / s and a cooling time of 14 minutes. The temperature of the cooled granules is 3℃ higher than the ambient temperature. The cooled material enters a double-layer vibrating screen for grading, with an upper screen aperture of 4.0 mm and a lower screen aperture of 2.0 mm, to obtain basic fertilizer granules with a particle size of 2.0~4.0 mm; the unqualified granules produced by screening are crushed and returned to the granulation process as return material, accounting for 20% of the total feed mass.

[0032] (5) Coating and Granulation: The base fertilizer granules are fed into an insulated roller coating machine, and 68℃ circulating hot air is introduced to maintain the material temperature. The slow-release coating agent is pre-placed in a constant-temperature melting tank and heated to 85℃ until completely melted. It is then uniformly sprayed onto the surface of the granules through a pressure atomizing nozzle at a pressure of 0.4MPa and a spraying rate of 1.0kg / min. The total spraying mass is 9% of the mass of the base fertilizer granules. After spraying, the granules are kept warm and rolled in the coating machine for 7 minutes to mature. Then, room temperature cold air is introduced to cool them to room temperature. After granulation and sieving, the finished compound fertilizer is obtained. The compressive strength of the finished granules is 18N, the particle size qualification rate is 92%, and the moisture content is 1.5%.

[0033] 3. Product sustained-release performance testing The cumulative nitrogen release rate of fertilizer was determined according to the static water extraction method in GB / T 23348-2009 "Slow-Release Fertilizers" under constant temperature conditions of 25℃. Each treatment was performed in triplicate, and the average value was taken. The specific data are shown in the table below, and the release curve is shown in the figure. Figure 2 As shown.

[0034] Table 2. Results of cumulative nitrogen release rate (still water at 25℃)

[0035] As shown in Table 2 and Figure 2, the initial nitrogen release rate of the fertilizer in this embodiment is 8.1% ≤ 10%, the cumulative release rate over 28 days is 26.4% ≤ 30%, and the cumulative release time for 80% of the nutrients is 105 days, which falls entirely within the range of the slow-release index defined in the claims. In contrast, the initial release rate of ordinary compound fertilizer (comparative example) is over 35%, and the fertilizer is basically fully released within 28 days. The nutrient release cycle of this embodiment is highly matched with the entire growth period of winter wheat (approximately 110 days from sowing to grain filling). Nitrogen supply is moderate during the greening and jointing stage to avoid excessive vegetative growth, and continuous nitrogen supply during the grain filling stage prevents premature aging.

[0036] 4. Field verification of lodging resistance effect The experiment was conducted at an experimental base in the Huang-Huai-Hai wheat region during the 2025-2026 wheat growing season. The experimental field soil was alluvial soil, with the following basic fertility in the 0-20cm soil layer: organic matter 12.8 g / kg, total nitrogen 1.05 g / kg, available phosphorus 18.6 mg / kg, available potassium 125 mg / kg, and pH 7.2. The tested wheat variety was Jimai 22, sown on October 15, 2025, at a seeding rate of 12 kg / mu, with a row spacing of 20 cm, and harvested on June 10, 2026. The experiment adopted a randomized block design, with three replicates per treatment. The plot area was 20 m² (4 m × 5 m). The fertilizer application rates for each treatment were 15 kg / mu of pure nitrogen, 10 kg / mu of phosphorus pentoxide, and 18 kg / mu of potassium oxide, all applied as a single basal fertilizer. No further topdressing was applied during the growing season. Other field management practices were consistent with local field production practices.

[0037] Test items and methods: Stem morphology: During the flowering period, 10 plants with uniform growth were randomly selected from each plot, and the length and wall thickness of the second internode at the base were measured, and the average value was taken. Stem bending strength: At the milk stage, the bending strength of the middle part of the second internode at the base was measured using a plant stem strength tester. Ten plants were used in each plot, and the average value was taken. Lodging index: Calculated using the formula Lodging index = (fresh weight of a single stem / stem bending strength) × 100. The smaller the value, the stronger the lodging resistance. Yield: The actual yield per plot is 2m² at maturity. After threshing and drying, the yield is calculated per mu (unit of land area).

[0038] Example 2 (Medium-high nitrogen ratio scheme) 1. Raw material composition and specifications The raw material ratios in this embodiment correspond to column 2 of Table 1, and the specific specifications of each component are as follows: Basic fertilizer containing macronutrients: Based on pure nutrients, N:P2O5:K2O=16:12:20, with potassium oxide accounting for 41.7% of the total macronutrient mass; the nitrogen source is a mixture of urea and sulfur-coated urea in a mass ratio of 6:4; the phosphorus source is a combination of diammonium phosphate and superphosphate in a mass ratio of 3:1; and the potassium source is entirely potassium sulfate.

[0039] Silicon-calcium based medium-element fertilizer: It is composed of silicon-calcium-magnesium phosphate fertilizer and light calcium carbonate in a mass ratio of 3:1; the effective silicon is 22% by mass as SiO2, the active calcium is 18% by mass as CaO, and the mass ratio of effective silicon to active calcium is 1.22:1.

[0040] Trace element premix: composed of 0.8 parts zinc sulfate heptahydrate, 0.5 parts borax, and 0.7 parts magnesium sulfate heptahydrate; on a pure element basis, the mass ratio of boron to zinc is 1:2.2, and magnesium accounts for 25% of the total element mass of the premix.

[0041] Humic acid organic carrier: It is composed of weathered coal humic acid and potassium fulvate in a mass ratio of 2:1, with a dry basis mass fraction of 52% and a free humic acid mass fraction of 32%.

[0042] Sustained-release coating agent: Epoxy resin coating agent is used, and the integrity rate of the finished coating is 95.5%.

[0043] 2. Preparation process parameters After crushing, the raw materials were passed through an 80-mesh standard sieve, with 95.5% of the material passing through the sieve. The moisture content of the raw materials was adjusted to 2.8%. The mixing time was 12 minutes, the coefficient of variation for mixing uniformity was 4.5%, and the deviation rate of single nutrient was 2.8%. Granulation was carried out using 0.25 MPa saturated steam, with a material moisture content of 11% and a material temperature of 58℃. A 0.6% sodium humate solution was sprayed, with a spray volume of 2.8%, resulting in a pelleting rate of 86.5%. The material was dried in stages at low temperature (65℃) and high temperature (95℃), resulting in a moisture content of 1.8% and a return material ratio of 18%. The coating environment temperature was 65℃, the melting temperature of the coating agent was 82℃, the coating ratio was 8%, and the curing time was 6 minutes. The finished granules had a compressive strength of 16 N, a particle size qualification rate of 91%, and a moisture content of 1.7%.

[0044] 3. Performance and Field Effects The initial nitrogen release rate was 9.0%, the cumulative release rate over 28 days was 28.1%, and 80% of the nutrients were released over 98 days.

[0045] Example 3 (High Silicon-Calcium Ratio Formula) 1. Raw material composition and specifications The raw material ratios in this embodiment correspond to column 3 of Example 1 in Table 1, and the specific specifications of each component are as follows: Basic fertilizer containing macronutrients: Based on pure nutrients, N:P2O5:K2O=13:9:16, with potassium oxide accounting for 42.1% of the total macronutrient mass; the nitrogen source is a mixture of ammonium sulfate and urea-formaldehyde in a mass ratio of 4:6; the phosphorus source is calcium magnesium phosphate fertilizer; and the potassium source is a combination of potassium sulfate and potassium chloride in a mass ratio of 6:4.

[0046] Silicon-calcium based medium-element fertilizer: It is composed of silicon-calcium-magnesium phosphate fertilizer and light calcium carbonate in a mass ratio of 5:1; the effective silicon is 32% by mass as SiO2, the active calcium is 22% by mass as CaO, and the mass ratio of effective silicon to active calcium is 1.45:1.

[0047] Trace element premix: composed of 1.8 parts zinc sulfate heptahydrate, 1.2 parts borax, and 2.0 parts magnesium sulfate heptahydrate; on a pure element basis, the mass ratio of boron to zinc is 1:1.8, and magnesium accounts for 28% of the total element mass of the premix.

[0048] Humic acid organic carrier: It is composed of weathered coal humic acid and potassium fulvate in a mass ratio of 3:1, with a dry basis mass fraction of 58% and a free humic acid mass fraction of 38%.

[0049] Slow-release coating agent: Sulfur-polymer composite coating material is used, and the integrity rate of the finished coating is 95.2%.

[0050] 2. Preparation process parameters After crushing, the raw materials were passed through a 100-mesh standard sieve, with 97% of the material passing through the sieve. The moisture content of the raw materials was adjusted to 4.2%. The mixing time was 18 minutes, the coefficient of variation for mixing uniformity was 3.8%, and the deviation rate of single nutrient was 2.2%. Granulation was carried out using 0.35 MPa saturated steam, with a material moisture content of 14% and a material temperature of 68℃. A 0.9% sodium humate solution was sprayed on the material at a spray rate of 4.5%, resulting in a pelleting rate of 87%. The material was dried in stages at 75℃ and 105℃, resulting in a moisture content of 1.5% and a return material ratio of 22%. The coating environment temperature was 72℃, the melting temperature of the coating agent was 88℃, the coating ratio was 5%, and the curing time was 9 minutes. The finished granules had a compressive strength of 17 N, a particle size qualification rate of 90.5%, and a moisture content of 1.4%.

[0051] 3. Performance and Field Effects The initial nitrogen release rate is 7.5%, the cumulative release rate over 28 days is 24.0%, and the 80% nutrient release time is 115 days.

[0052] V. Comparative Examples The ordinary wheat-specific compound fertilizer with the same nitrogen, phosphorus, and potassium pure nutrient content as in Example 1, with N:P2O5:K2O=15:10:18, uses ordinary urea as the nitrogen source, and does not add silicon-calcium based medium-element fertilizer, humic acid organic carrier, or slow-release coating agent. It is prepared using a conventional rotary drum granulation process, and the production parameters are the same as in Example 1.

[0053] The table below summarizes all the field test results for each embodiment and comparative example: Table 3 Comparison of lodging resistance indicators and yield at wheat maturity

[0054] As shown in Table 3 and Figure 3, the stem bending strength of the three examples was significantly higher than that of the comparative example, and the lodging index was significantly lower than that of the comparative example. Among them, Example 1 showed the best overall performance in terms of yield and lodging resistance, while Example 3 showed the best performance in terms of stem wall thickness and lodging index, which verified the stability of the lodging resistance improvement effect under different formulation schemes.

[0055] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A compound fertilizer specifically for preventing lodging in wheat, characterized in that, Based on dry weight, the fertilizer comprises the following components: 35-65 parts of macro-element base fertilizer, 10-30 parts of silicon-calcium-based medium-element fertilizer, 1-6 parts of micro-element premix, 10-25 parts of humic acid organic carrier, and 3-10 parts of slow-release coating agent. The macro-element base fertilizer consists of a nitrogen source, a phosphorus source, and a potassium source, wherein the nitrogen source is composed of a fast-acting nitrogen source and a slow-release nitrogen source in a mass ratio of 4:6 to 6:

4. The slow-release coating agent coats the outer layer of the fertilizer particles. In the silicon-calcium-based medium-element fertilizer, the effective silicon (SiO2) mass fraction is ≥20%, and the active calcium (CaO) mass fraction is ≥15%.

2. The wheat lodging-resistant compound fertilizer according to claim 1, characterized in that, In the aforementioned basic fertilizer containing macronutrients, the mass ratio of nitrogen, phosphorus pentoxide, and potassium oxide, based on pure nutrients, is (12-18):(8-15):(15-22), wherein potassium oxide accounts for no less than 35% of the total pure nutrients of nitrogen, phosphorus, and potassium; the readily available nitrogen source is one or a combination of urea, ammonium sulfate, and ammonium chloride in any proportion; the slow-release nitrogen source is one or a combination of urea-formaldehyde and sulfur-coated urea in any proportion; the phosphorus source is one or a combination of monoammonium phosphate, diammonium phosphate, superphosphate, and calcium magnesium phosphate in any proportion; and the potassium source is one or a combination of potassium sulfate and potassium chloride in any proportion, wherein potassium sulfate accounts for no less than 60% of the total potassium source mass.

3. The wheat lodging-resistant compound fertilizer according to claim 1, characterized in that, The silicon-calcium based medium-element fertilizer is composed of silicon-calcium-magnesium phosphate fertilizer and light calcium carbonate in a mass ratio of (3-5):1; wherein the effective silicon is 20%-35% by mass as SiO2, the active calcium is 15%-25% by mass as CaO, and the mass ratio of effective silicon to active calcium is (1.2-1.8):

1.

4. The wheat lodging-resistant compound fertilizer according to claim 1, characterized in that, In the micronutrient premix, the proportions of zinc, boron, and magnesium, based on pure elements, are 0.5-2 parts by mass of zinc fertilizer, 0.3-1.5 parts by mass of boron fertilizer, and 0.2-2.5 parts by mass of magnesium fertilizer. The zinc fertilizer is zinc sulfate heptahydrate, the boron fertilizer is borax or boric acid, and the magnesium fertilizer is magnesium sulfate heptahydrate. Based on pure elements, the mass ratio of boron to zinc is 1:(1.5-3), and magnesium accounts for 10%-30% of the total element mass of the premix.

5. The wheat lodging-resistant compound fertilizer according to claim 1, characterized in that, The humic acid organic carrier is composed of weathered coal humic acid and potassium fulvate in a mass ratio of (2-3):1, wherein the dry basis mass fraction of humic acid is ≥50% and the mass fraction of free humic acid is ≥30%; the slow-release coating agent is one of sulfur-polymer composite coating material and epoxy resin coating agent; the coating integrity rate of fertilizer granules is ≥95%; under static water conditions at 25℃, the initial nitrogen release rate of the finished fertilizer is ≤10%, the cumulative release rate after 28 days is ≤30%, and the cumulative release time of 80% nitrogen nutrients is 90-120 days.

6. A method for preparing the wheat lodging-resistant compound fertilizer according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Raw material pretreatment: The macro-element basic fertilizer, silicon-calcium based medium-element fertilizer, micro-element premix, and humic acid organic carrier are crushed and sieved respectively, and the moisture content of the raw materials is adjusted to 2% to 5% to obtain basic powder; (2) Mixing and batching: Weigh each basic powder, micro-element premix and humic acid organic carrier according to the ratio, put them into the mixer and mix to obtain a mixed powder with a uniformity variation coefficient ≤ 5%; (3) Rotary drum granulation: The mixed powder is fed into a rotary drum granulator, saturated steam is introduced, and the material is agglomerated into granules under the conditions of material moisture content of 10% to 15% and material temperature of 55 to 70℃ to obtain wet base fertilizer granules; (4) Drying, cooling and screening: The wet base fertilizer granules are dried in stages, cooled in countercurrent and then screened to obtain a particle size of 2.0 to 4.0 mm. (5) Coating and granulation: The basic fertilizer granules are fed into a roller coating machine and a slow-release coating agent in molten state is sprayed at 60-75℃. After spraying, the granules are kept warm and matured, cooled and screened to obtain the finished compound fertilizer.

7. The preparation method according to claim 6, characterized in that, In step (1), after crushing, the material is passed through an 80-100 mesh standard sieve, and the proportion of the material passing through the sieve is ≥95%; the moisture content of the raw material is controlled by low temperature hot air at 40-60℃; in step (2), the mixing time is 12-20 min, and the deviation rate of single nutrient content of the mixed material is ≤3%.

8. The preparation method according to claim 6, characterized in that, In step (3), the granulation pelleting rate is ≥85%; during the granulation process, a sodium humate solution with a mass fraction of 0.5% to 1% is sprayed simultaneously, and the spraying amount is 2% to 5% of the total mass of the mixed powder; after the unqualified particles generated by screening in step (4) are crushed, they are returned to the granulation process as return material, and the proportion of return material to the total feed mass is controlled at 15% to 25%.

9. The preparation method according to claim 6, characterized in that, In step (4), the segmented drying is divided into a low-temperature pre-drying section and a high-temperature shaping section: the inlet air temperature of the low-temperature pre-drying section is 60-80℃, and the inlet air temperature of the high-temperature shaping section is 90-110℃; the moisture content of the dried particles is ≤2.0%; the grading and screening adopts a double-layer vibrating screen with an upper screen aperture of 4.0mm and a lower screen aperture of 2.0mm.

10. The preparation method according to claim 6, characterized in that, In step (5), the slow-release coating agent is preheated to 80-90℃ and the total spraying mass of the slow-release coating agent is 3%-10% of the mass of the base fertilizer granules. After spraying, the granules are kept warm and rolled for 5-10 minutes, and then cooled to room temperature. The finished granules have a compressive strength ≥15N, a particle size qualification rate ≥90%, and a moisture content ≤2.0%.

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