A method of applying fertilizer without follow-up application to improve wheat yield

Abstract

This invention provides a method for increasing wheat yield without topdressing, using a compound fertilizer in granular form, comprising, from the inside out: an inner core containing fast-acting nitrogen fertilizer, a urease inhibitor, and a nitrification inhibitor; a middle layer containing slow-release nitrogen fertilizer and enzyme activating substances; and an outer layer containing controlled-release nitrogen fertilizer and sugar-enhancing substances. The inner, middle, and outer layers form a functional spatiotemporal coupling structure, matching nitrogen release with the nitrogen requirements of wheat during its growth period, with an effective fertilizer period of 110-120 days. In the inner core, the urease inhibitor is selected from NBPT (n-butylthiophosphoric triamine) or its derivatives, and the nitrification inhibitor is selected from DMPP (3,4-dimethylpyrazole phosphate) or DCD (dicyandiamide). This invention's compound fertilizer provides effective nitrogen supply for 110-120 days, covering the entire wheat growth period, achieving a single basal application and eliminating the need for topdressing throughout the entire growth period, reducing fertilization operations by 2-3 times and significantly lowering labor costs.

Description

Technical Field

[0001] This invention relates to the field of wheat fertilization technology, specifically to a method for applying fertilizer without topdressing that can increase wheat yield. Background Technology

[0002] Wheat is one of my country's major grain crops, with a long growth cycle and high fertilizer requirements. The proper supply of nitrogen fertilizer, in particular, plays a decisive role in yield and quality. Traditional wheat fertilization typically employs a "basal fertilizer + topdressing" model, applying basal fertilizer before sowing and then applying topdressing 1-2 times during the greening or jointing stages. This model has the following problems: First, the timing of topdressing depends on weather and soil moisture, resulting in a short window of opportunity and requiring significant manual or mechanical input, leading to high production costs. Second, topdressing is mostly applied topically, making nitrogen easily lost through ammonia volatilization, leaching, and denitrification, with nitrogen utilization rates generally only 30%-40%. Third, improper matching of topdressing time with the peak nitrogen demand period of wheat can easily lead to excessive early growth or nutrient deficiency in the later stages, affecting yield and quality.

[0003] Current technologies lack solutions that address the nitrogen requirements of wheat throughout its entire growth cycle, employing a synergistic design of spatial stratification and temporal release to achieve 110-120 days without topdressing while significantly improving nitrogen use efficiency. Existing products still largely rely on single technological approaches, making it difficult to simultaneously meet the comprehensive needs of "long-term supply, nutrient synergy, and rhizosphere regulation."

[0004] Therefore, developing a compound fertilizer and its application method that can eliminate the need for topdressing throughout the entire wheat growth period, improve nitrogen utilization, synergistically activate soil nutrients, and promote grain filling in the later stages is of great practical significance and application value. Summary of the Invention

[0005] In order to overcome the problems existing in the background art, the present invention provides a fertilization method that can improve wheat yield without topdressing, which can effectively increase wheat yield and eliminate the need for topdressing, while reducing workload.

[0006] To achieve the above objectives, the invention is implemented through the following technical solution: A compound fertilizer for increasing wheat yield without topdressing, characterized in that the compound fertilizer is granular and comprises, from the inside out: The inner core contains fast-acting nitrogen fertilizer, urease inhibitors, and nitrification inhibitors; The middle layer contains slow-release nitrogen fertilizer and enzyme-activating substances; The outer layer contains controlled-release nitrogen fertilizer and sugar-enhancing substances; The inner, middle and outer layers form a functional spatiotemporal coupling structure, which matches the nitrogen release with the nitrogen requirement of wheat during its growth period, and the fertilizer effect lasts for 110-120 days.

[0007] Preferably, in the inner core, the urease inhibitor is selected from NBPT (n-butylthiophosphoric triamine) or its derivatives, and the nitrification inhibitor is selected from DMPP (3,4-dimethylpyrazole phosphate) or DCD (dicyandiamide); the fast-acting nitrogen fertilizer accounts for 25-35% of the total nitrogen; the urease inhibitor and the nitrification inhibitor work synergistically to extend the retention time of ammonium nitrogen in the soil to 40-50 days; during this window period, the activity of the enzyme activating substance increases by 30-50%, forming a synergistic effect of "inhibition to promote activation"; In the middle layer, the slow-release nitrogen fertilizer is coated urea or stable urea, accounting for 35-45% of the total nitrogen; the enzyme activating substance includes at least one of phytase and alkaline phosphatase, as well as humic acid or fulvic acid. In the outer layer, the controlled-release nitrogen fertilizer is polymer-coated urea, accounting for 25-35% of the total nitrogen content; the sugar synergist includes at least one of seaweed oligosaccharide, mannitol, and γ-aminobutyric acid.

[0008] Preferably, a transition layer is provided between the inner core and the middle layer, and between the middle layer and the outer layer. The thickness of the transition layer is 5-15 μm, and it contains the functional components of the two adjacent layers to form a functional gradient interface.

[0009] Preferably, the outer layer of controlled-release nitrogen fertilizer uses a pH-responsive or temperature-responsive bio-based polyurethane coating material, and the release rate of the coating material adaptively accelerates when the rhizosphere pH decreases or the soil temperature increases.

[0010] Preferably, the compound fertilizer has an NPK mass ratio of 29-6-7 and is compounded with plant potential stimulating substances and trace organic carbon synergists. The plant potential activating substance is located in the middle layer in the form of sodium alginate-chitosan microcapsules; The trace organic carbon synergist is located in the outer layer in the form of polylactic acid microcapsules; The plant potential activating substances and trace organic carbon synergists are released sequentially during the wheat jointing and grain-filling stages, respectively. The sugar-enhancing substance has both physiological enhancement and microecological regulation functions: Physiological enhancement: Promotes wheat sugar synthesis and photosynthetic product transport, and activates crop immunity; Microecological regulation: As a carbon source regulator for rhizosphere microorganisms, it selectively promotes the proliferation of ammonia-oxidizing bacteria-inhibiting microorganisms, forming a synergistic chemical-biological dual-pathway nitrification inhibition with the nitrification inhibitors.

[0011] A method for applying fertilizer without topdressing to increase wheat yield, characterized by the following steps: S1. Before sowing, soil urease activity and nitrification potential are tested, and the amount of inhibitor in the compound fertilizer described in claim 2 is dynamically adjusted. S2, When sowing, apply the compound fertilizer described in claim 2 at one time, using the method of sowing the seed and fertilizer at the same time or applying it from the side, with a fertilization depth of 8-10 cm; no topdressing is required during the entire growth period of wheat.

[0012] Preferably, by adjusting the thickness of the three layers of the compound fertilizer, the coating material, and the ratio of inhibitors to activators, the spatiotemporal matching coefficient STMC is controlled between 0.85 and 1.15 during the wheat tillering, jointing, booting, and grain-filling stages. The spatiotemporal matching coefficient STMC = nitrogen requirement of wheat at each growth stage / nitrogen release from fertilizer during the corresponding period; The application rate of the compound fertilizer is 40-60 kg / mu, which is 12-18 kg / mu in terms of pure nitrogen.

[0013] Preferably, the specific method for dynamically adjusting the dosage of inhibitor in the compound fertilizer according to any one of claims 1-9 includes: (1) Soil urease activity and nitrification potential were measured before sowing; (2) When the soil urease activity is ≤15 μg NH4⁺-N·g⁻¹·h⁻¹, the dosage of urease inhibitor is 80% of the standard dosage; when the soil urease activity is 15-30 μg NH4⁺-N·g⁻¹·h⁻¹, the dosage of urease inhibitor is 100% of the standard dosage; when the soil urease activity is ≥30 μg NH4⁺-N·g⁻¹·h⁻¹, the dosage of urease inhibitor is 120% of the standard dosage. (3) When the soil nitrification potential is ≤5 mg NO2⁻-N·kg⁻¹·d⁻¹, the dosage of nitrification inhibitor is 70% of the standard dosage; when the soil nitrification potential is 5-15 mg NO2⁻-N·kg⁻¹·d⁻¹, the dosage of nitrification inhibitor is 100% of the standard dosage; when the soil nitrification potential is ≥15 mg NO2⁻-N·kg⁻¹·d⁻¹, the dosage of nitrification inhibitor is 130% of the standard dosage. (4) The standard dosage of the urease inhibitor is 0.5% of the total mass of the inner core, and the standard dosage of the nitration inhibitor is 0.8% of the total mass of the inner core.

[0014] A method for preparing the compound fertilizer according to claim 5, characterized by comprising the following steps: (1) Core granulation: quick-acting nitrogen fertilizer is mixed with urease inhibitor and nitrification inhibitor, and then granulated to form inner core particles with a diameter of 1.0-1.5 mm; (2) Intermediate layer spraying: The inner core particles are fed into a fluidized bed coating machine and the intermediate layer slurry is sprayed at a fluidized air temperature of 40-50℃ until the intermediate layer thickness reaches 0.4-0.6 mm, and then dried and cured. (3) Transition layer spraying: After the intermediate layer is sprayed, a mixture of intermediate layer slurry and outer layer slurry is sprayed on the surface of the particles for 30-60 seconds to form a transition layer with a thickness of 5-15 μm. (4) Outer layer spraying: On the surface of the transition layer, the outer layer slurry is sprayed at 35-45°C until the outer layer thickness reaches 0.3-0.5 mm. After curing, the compound fertilizer is obtained. The middle layer slurry contains slow-release nitrogen fertilizer and enzyme-activating substances, while the outer layer slurry contains controlled-release nitrogen fertilizer and sugar-enhancing substances.

[0015] Preferably, the plant potential activating substance is pre-formed into 20-50 μm microcapsules in the form of sodium alginate-chitosan microcapsules and then mixed into the middle layer slurry; the trace organic carbon synergist is pre-formed into 20-50 μm microcapsules in the form of polylactic acid microcapsules and then mixed into the outer layer slurry.

[0016] The beneficial effects of this invention are: 1. The fertilizer effect period is significantly extended. The effective nitrogen supply period of the compound fertilizer of this invention is 110-120 days, covering the entire growth period of wheat, realizing one-time basal application and no need for topdressing throughout the growth period, reducing fertilization operations by 2-3 times and greatly reducing labor costs.

[0017] 2. Nitrogen fertilizer utilization rate is significantly improved. Through the synergistic effect of "dual inhibition-dual activation" and the three-layer spatiotemporal coupling structure, the nitrogen fertilizer utilization rate reaches 48.6%, which is 16.1 percentage points higher than conventional fertilization.

[0018] 3. Significantly improved yield and quality, with wheat yield reaching 8245 kg / ha, a 12.6% increase compared to conventional fertilization; grain protein content increased by 1.5 percentage points, achieving a synergistic improvement in both yield and quality.

[0019] 4. Ammonia volatilization loss was reduced by 14.3 percentage points, reducing nitrogen leaching and denitrification losses and lowering agricultural non-point source pollution.

[0020] 5. The combination of sugar-enhancing substances and nitrification inhibitors forms a chemical-biological dual-pathway nitrification inhibition, reducing the abundance of AOB in the rhizosphere by 41.2%, thereby reducing nitrogen transformation loss from a microbial ecological perspective. Attached Figure Description

[0021] Figure 1 This is a picture of the compound fertilizer of this invention.

[0022] Figure 2These are comparative photographs of wheat ears grown using the fertilization methods employed in the embodiments and comparative examples of this invention.

[0023] Figure 3 This is a comparison photo of wheat grains grown using the compound fertilizer and fertilization method of this invention (right) and wheat grains grown using ordinary fertilizer (left). Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. All raw materials used in the following embodiments are commercially available, and the fluidized bed coating equipment used is conventional equipment in the art.

[0025] I. Preparation of Compound Fertilizer Example 1 This embodiment provides a three-layer compound fertilizer, prepared using a fluidized bed layer-by-layer spraying method. The specific steps are as follows: (1) Core granulation Urea (containing 46% N), NBPT (n-butylthiophosphoric triamine, accounting for 0.5% of the total inner layer mass), and DMPP (3,4-dimethylpyrazole phosphate, accounting for 0.8% of the total inner layer mass) were mixed with bentonite binder and granulated into core particles with a diameter of 1.2-1.5 mm using a rotary granulator. The particles were then dried at 60℃ until the moisture content was ≤1.2%. The readily available nitrogen fertilizer in the inner core layer accounted for 30% of the total nitrogen content.

[0026] (2) Intermediate layer spraying The core particles are fed into a fluidized bed coating machine, with the fluidizing air temperature controlled at 45℃, and a middle layer slurry is sprayed on. The middle layer slurry formula is: 65% coated urea micropowder (containing 42% N), 2% phytase, 1% alkaline phosphatase, 10% humic acid, and 22% sodium alginate binder, with a solid content of 30%. The plant potential activating substance is pre-formed into 30-40 μm microcapsules in the form of sodium alginate-chitosan microcapsules and mixed into the middle layer slurry at a ratio of 5% of the total mass of the middle layer. The slurry is sprayed until the particle diameter reaches 2.2-2.5 mm (middle layer thickness approximately 0.5 mm), and then dried and cured with hot air at 40℃. The slow-release nitrogen fertilizer in the middle layer accounts for 40% of the total nitrogen content.

[0027] (3) Transition layer spraying After the intermediate layer is coated, a mixture of intermediate and outer layer slurries (mass ratio 1:1) is sprayed onto the particle surface for 45 seconds to form a transition layer with a thickness of about 10 μm, which contains the functional components of both the intermediate and outer layers.

[0028] (4) Outer layer spraying On the surface of the transition layer, the outer layer slurry is sprayed on at 40°C. The outer layer slurry formula is: 70% polyurethane-coated urea (containing 42% N), 3% seaweed oligosaccharide, 2% γ-aminobutyric acid, 2% mannitol, and 23% polyacrylate emulsion, with a solid content of 35%. Trace organic carbon synergists are pre-formed into 30-40 μm microcapsules in the form of polylactic acid microcapsules and mixed into the outer layer slurry at a ratio of 4% of the total outer layer mass. Spraying is performed until the particle diameter reaches 2.8-3.2 mm (outer layer thickness approximately 0.4 mm), followed by hot air curing at 40°C to obtain the final compound fertilizer product. The controlled-release nitrogen fertilizer in the outer layer accounts for 30% of the total nitrogen content.

[0029] The resulting compound fertilizer had an NPK mass ratio of 29-6-7, an average particle size of 3.0 mm, and a fertilizer effect period of 115 days.

[0030] Example 2 This embodiment is basically the same as Embodiment 1, except that: In the inner core, the urease inhibitor is an NBPT derivative, the nitrification inhibitor is DCD (dicyandiamide), and the fast-acting nitrogen fertilizer accounts for 28% of the total nitrogen. In the middle layer, only phytase is used as the enzyme activator, humic acid is replaced with fulvic acid, and slow-release nitrogen fertilizer accounts for 42% of the total nitrogen. In the outer layer, the sugar-enhancing substance is only seaweed oligosaccharide, and the controlled-release nitrogen fertilizer uses a pH-responsive bio-based polyurethane coating material (which increases the release rate by 30% when pH≤5.5), accounting for 30% of the total nitrogen content; The transition layer is approximately 8 μm thick.

[0031] The resulting compound fertilizer granules had an average particle size of 3.1 mm and an effective period of 112 days.

[0032] Comparative Example 1 Ordinary compound fertilizer: NPK=29-6-7, no layered structure, no added inhibitors, activators, or synergists, prepared using conventional granulation process, with a particle size of 2.5-3.5 mm.

[0033] Comparative Example 2 Single-layer stable compound fertilizer: NPK=29-6-7, with added NBPT (0.5%) and DMPP (0.8%), no layered structure, no enzyme activating substances or sugar synergists, prepared using conventional granulation process.

[0034] Comparative Example 3 Double-layer compound fertilizer (without a transition layer): Composed of an inner layer and an outer layer. The inner layer contains fast-acting nitrogen and an inhibitor, while the outer layer contains controlled-release nitrogen and a sugar synergist. There is no middle layer containing enzyme activators, and no transition layer. It is prepared using a fluidized bed spraying method. The inner layer has a diameter of 1.5 mm, and the outer layer has a thickness of 0.6 mm.

[0035] II. Field Trials To verify the technical efficacy of the compound fertilizer of this invention, a field trial was conducted in a wheat-growing area in Kunming City, Yunnan Province, from October 2024 to June 2025. The wheat variety used was "Jimai 22", the soil type was alluvial soil, and the basic physicochemical properties were as follows: organic matter 12.5 g / kg, available nitrogen 68 mg / kg, available phosphorus 22 mg / kg, available potassium 95 mg / kg, and pH 7.6.

[0036] The experiment consisted of 6 treatments, each with 3 replicates, arranged in a randomized block design, with a plot area of ​​30 m². Processing Number Processing Name Fertilization methods Topdressing situation T1 Example 1 Compound Fertilizer Sow seeds and fertilizer simultaneously, with fertilizer applied at a depth of 8-10 cm. No additional fertilizer applied throughout the entire reproductive period T2 Example 2 Compound Fertilizer Sow seeds and fertilizer simultaneously, with fertilizer applied at a depth of 8-10 cm. No additional fertilizer applied throughout the entire reproductive period T3 Comparative Example 1 (Ordinary Compound Fertilizer) Base fertilizer + top dressing Apply urea at a rate of 150 kg / ha during the jointing stage. T4 Comparative Example 2 (Single-layer stable fertilizer) Base fertilizer + top dressing Apply 75 kg / ha of urea as top dressing during the jointing stage. T5 Comparative Example 3 (Double-layer without transition layer) Sow seeds and fertilizer simultaneously, with fertilizer applied at a depth of 8-10 cm. No additional fertilizer applied throughout the entire reproductive period T6 Blank control No fertilizer — The total nitrogen application rate remained consistent across all treatments (180 kg / ha of pure N). For treatments T3 and T4, the difference in total nitrogen compared to T1 was supplemented with topdressing. The application rate for T1, T2, and T5, based on a pure N of 180 kg / ha, was approximately 620 kg / ha of compound fertilizer (equivalent to approximately 41.3 kg / mu). Other field management practices remained consistent.

[0037] III. Test Indicators and Methods 1. Soil ammonium nitrogen and nitrate nitrogen content: Soil samples from the 0-20cm layer were collected at 7, 15, 30, 45, 60, 90, and 120 days after fertilization. Ammonium nitrogen was determined by potassium chloride extraction-indophenol blue colorimetric method, and nitrate nitrogen was determined by ultraviolet spectrophotometry.

[0038] 2. Nitrogen release period determination: The field bag burial method was adopted. The compound fertilizer of each treatment was put into a 300-mesh nylon mesh bag and buried in the soil layer of 10 cm. The remaining nitrogen content was measured periodically, and the cumulative nitrogen release rate was calculated. The time when the release rate was ≥80% was taken as the fertilizer effect period.

[0039] 3. Wheat yield and its components: At maturity, a 1 m² sampling point was randomly selected from each plot to measure the number of spikes, the number of grains per spike, and the weight of 1,000 grains, and the actual yield was calculated.

[0040] 4. Grain quality determination: The protein content of grains was determined using a near-infrared grain analyzer.

[0041] 5. Nitrogen fertilizer utilization rate: The difference method is used to calculate the nitrogen fertilizer utilization rate (%) = (amount of nitrogen absorbed by the aboveground parts of the nitrogen-applied area - amount of nitrogen absorbed by the aboveground parts of the blank area) / amount of nitrogen applied × 100%.

[0042] 6. Ammonia volatilization loss: The ammonia loss was measured daily for 1-15 days after fertilization using the intermittent vacuum method in a closed chamber, and then every 3 days thereafter until there was no significant volatilization.

[0043] IV. Test Results 4.1 Nitrogen release characteristics and fertilizer effect period The results of nitrogen release characteristics and fertilizer effect period determination of compound fertilizer for each treatment are shown in Table 1.

[0044] Table 1. Nitrogen release characteristics of compound fertilizers under different treatments deal with Number of days required for 80% cumulative nitrogen release. Release curve characteristics Nitrogen matching with wheat T1 115 Release is steady, with a bimodal pattern (release peaks occur at 30 days and 70 days). excellent T2 112 Smooth release, bi-peaked excellent T3 25 Rapid release in the early stage, single-peak pattern Difference T4 58 The early stage is fast, the middle stage is moderate, and the late stage is insufficient. middle T5 98 Release was low at the beginning and high at the end, with the later period being relatively high. middle The results showed that the compound fertilizers of Examples 1 and 2 of this invention had an effective period of 115 days and 112 days, respectively, which could cover the entire growth period of wheat (approximately 110-120 days). Furthermore, their release curves exhibited a bimodal characteristic, matching the two peak nitrogen demand periods of wheat: the tillering-jointing stage and the booting-grain-filling stage. While Comparative Example 3 extended the effective period, its release curve was low at the beginning and high at the end, which did not match the early nitrogen demand of wheat and could easily lead to nitrogen deficiency in the early stages.

[0045] 4.2 Soil ammonium nitrogen retention time and enzyme activity Table 2 shows the results of soil ammonium nitrogen content and phytase activity measurements for each treatment 30 days after fertilization.

[0046] Table 2 Soil ammonium nitrogen content and phytase activity 30 days after fertilization deal with Soil ammonium nitrogen content (mg / kg) Ammonium nitrogen retention time (days)* Soil phytase activity (U / g) Enzyme activity increase rate (%) T1 28.6 46 2.85 42.5 T2 27.9 44 2.76 38.0 T3 8.2 12 1.86 — T4 18.5 32 2.03 9.1 T5 22.3 38 2.21 18.8 *Note: Ammonium nitrogen retention time refers to the number of days required for the soil ammonium nitrogen content to drop to 50% of its peak value after fertilization.

[0047] As shown in Table 2, the ammonium nitrogen retention times in Examples 1 and 2 of this invention reached 46 days and 44 days, respectively, significantly longer than those in the comparative example. Simultaneously, the prolonged retention of ammonium nitrogen created a suitable microenvironment for enzyme activation (increased root secretion of organic acids and decreased rhizosphere pH), resulting in phytase activity increasing by 42.5% and 38.0% compared to Comparative Example 1, respectively, confirming the synergistic effect of "inhibition promoting activation."

[0048] 4.3 Regulatory Effects of Sugar-Enhancing Substances on Rhizosphere Microorganisms The community structure of ammonia-oxidizing bacteria (AOB) in the rhizosphere soil was analyzed by high-throughput sequencing 45 days after fertilization. The results are shown in Table 3.

[0049] Table 3. Relative abundance of ammonia-oxidizing bacteria (AOB) in rhizosphere soil deal with AOB relative abundance (%) Changes compared to Comparative Example 1 T1 1.82 Reduced by 41.2% T2 1.95 Reduced by 37.1% T3 3.10 — T4 2.56 Reduced by 17.4% T5 2.38 Decreased by 23.2% The results showed that the relative abundance of AOB in the rhizosphere soil of Examples 1 and 2 of this invention was significantly reduced, indicating that sugar-enhancing substances, as carbon source regulators, selectively inhibited the proliferation of nitrification-related microorganisms and formed a "chemical-biological dual pathway" synergistic inhibition with chemical nitrification inhibitors, further reducing the conversion loss of ammonium nitrogen to nitrate nitrogen.

[0050] 4.4 Wheat yield and nitrogen fertilizer utilization rate The results of wheat yield, yield components, and nitrogen fertilizer utilization rate measurements for each treatment are shown in Table 4.

[0051] Table 4. Wheat yield, yield components, and nitrogen fertilizer utilization rate under different treatments deal with Number of ears (10,000 ears / ha) Number of grains per ear (grains) 1000-grain weight (g) Yield (kg / ha) Increase in production compared to T3 (%) Nitrogen fertilizer utilization rate (%) T1 682.5 38.6 46.8 8245 12.6 48.6 T2 675.2 38.2 46.5 8120 10.9 47.2 T3 625.3 35.8 43.2 7320 — 32.5 T4 638.7 36.5 44.1 7580 3.6 38.7 T5 645.2 36.9 44.8 7785 6.4 41.2 T6 485.6 30.2 38.5 5250 — — As shown in Table 4, the wheat yield of the treatment in Example 1 of this invention reached 8245 kg / ha, an increase of 12.6% compared with Comparative Example 1 (ordinary compound fertilizer + topdressing), an increase of 8.8% compared with Comparative Example 2 (single-layer stable fertilizer + reduced topdressing), and an increase of 5.9% compared with Comparative Example 3 (double-layer fertilizer without transition layer, no topdressing). The nitrogen fertilizer utilization rate reached 48.6%, an increase of 16.1 percentage points compared with Comparative Example 1, an increase of 9.9 percentage points compared with Comparative Example 2, and an increase of 7.4 percentage points compared with Comparative Example 3.

[0052] Figure 2 These are comparative photographs of wheat ears planted using the fertilization methods employed in the embodiments and comparative examples of the present invention. It can be seen that the wheat ears planted using the compound fertilizer and fertilization method of the present invention in Examples 1 and 2 are significantly larger and have a higher yield than those planted using ordinary fertilizer.

[0053] Figure 3 The image shows a comparison of wheat grains grown using the compound fertilizer and fertilization method of this invention (right) and wheat grains grown using ordinary fertilizer (left). It can be seen that the average diameter of wheat grains grown using the compound fertilizer and fertilization method of this invention is significantly larger than that of wheat grains grown using ordinary fertilizer. Therefore, wheat grown using the compound fertilizer and fertilization method of this invention has a higher yield.

[0054] 4.5 Grain Quality The results of the protein content determination of seeds in each treatment are shown in Table 5.

[0055] Table 5 Protein content of grains under different treatments deal with Protein content (%) Improved by (percentage points) compared to T3 T1 14.8 1.5 T2 14.6 1.3 T3 13.3 — T4 13.8 0.5 T5 14.0 0.7 The protein content of the grains treated in Example 1 of this invention reached 14.8%, which was significantly higher than that in Comparative Example 1, indicating that the release of sugar-enhancing substances during the grain-filling period promoted the synergistic effect of carbon and nitrogen metabolism and improved grain quality.

[0056] 4.6 Ammonia Volatilization Loss and Environmental Benefits The results of the cumulative loss of ammonia volatilization in each treatment are shown in Table 6.

[0057] Table 6. Cumulative loss of ammonia volatilization under different treatments deal with Cumulative loss of ammonia due to volatilization (kg N / ha) Percentage of nitrogen applied (%) T1 12.8 7.1 T2 13.5 7.5 T3 38.5 21.4 T4 24.6 13.7 T5 18.2 10.1 In Example 1 of this invention, ammonia volatilization loss accounted for only 7.1% of the applied nitrogen amount, which was 14.3 percentage points lower than Comparative Example 1, 6.6 percentage points lower than Comparative Example 2, and 3.0 percentage points lower than Comparative Example 3. This indicates that the synergistic design of the three-layer structure and the dual inhibition-dual activation significantly reduced nitrogen gaseous loss and had good environmental benefits.

[0058] V. Verification of Spatiotemporal Matching Coefficients According to the spatiotemporal matching coefficient (STMC) described in claim 7, the nitrogen release and nitrogen requirement of the compound fertilizer in Example 1 at each growth stage of wheat were matched and analyzed, and the results are shown in Table 7.

[0059] Table 7. Spatiotemporal matching coefficient (STMC) of compound fertilizer in Example 1 reproductive period Nitrogen requirement percentage (%) Nitrogen release percentage (%) STMC Tillering stage (0-40 days) 28 26 0.93 Jointing period (40-65 days) 32 34 1.06 Spike incubation period (65-85 days) 22 24 1.09 Grouting period (85-110 days) 18 16 0.89 The STMC was controlled within the range of 0.85-1.15 at each growth stage, indicating that the nitrogen release of the compound fertilizer of this invention is precisely matched with the nitrogen requirement of wheat.

[0060] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A compound fertilizer for wheat that requires no topdressing and can increase wheat yield, characterized in that, The compound fertilizer is granular and comprises, from the inside out: The inner core contains fast-acting nitrogen fertilizer, urease inhibitors, and nitrification inhibitors; The middle layer contains slow-release nitrogen fertilizer and enzyme-activating substances; The outer layer contains controlled-release nitrogen fertilizer and sugar-enhancing substances; The inner, middle and outer layers form a functional spatiotemporal coupling structure, which matches the nitrogen release with the nitrogen requirement of wheat during its growth period, and the fertilizer effect lasts for 110-120 days.

2. The compound fertilizer according to claim 1, characterized in that, In the inner core, the urease inhibitor is selected from NBPT (n-butylthiophosphoric triamine) or its derivatives, and the nitrification inhibitor is selected from DMPP (3,4-dimethylpyrazole phosphate) or DCD (dicyandiamide); the fast-acting nitrogen fertilizer accounts for 25-35% of the total nitrogen; the urease inhibitor and the nitrification inhibitor work synergistically to extend the retention time of ammonium nitrogen in the soil to 40-50 days; during this window period, the activity of the enzyme activating substance increases by 30-50%, forming a synergistic effect of "inhibition to promote activation"; In the middle layer, the slow-release nitrogen fertilizer is coated urea or stable urea, accounting for 35-45% of the total nitrogen; the enzyme activating substance includes at least one of phytase and alkaline phosphatase, as well as humic acid or fulvic acid. In the outer layer, the controlled-release nitrogen fertilizer is polymer-coated urea, accounting for 25-35% of the total nitrogen content; the sugar synergist includes at least one of seaweed oligosaccharide, mannitol, and γ-aminobutyric acid.

3. The compound fertilizer according to claim 1, characterized in that, A transition layer is provided between the inner core and the middle layer, and between the middle layer and the outer layer. The thickness of the transition layer is 5-15 μm, and it contains the functional components of the two adjacent layers to form a functional gradient interface.

4. The compound fertilizer according to claim 2, characterized in that, The outer layer of controlled-release nitrogen fertilizer uses a pH-responsive or temperature-responsive bio-based polyurethane coating material, and the release rate of the coating material adaptively accelerates when the rhizosphere pH decreases or the soil temperature increases.

5. The compound fertilizer according to claim 1 or 2, characterized in that, The compound fertilizer has an NPK mass ratio of 29-6-7 and is also formulated with plant potential stimulating substances and trace organic carbon synergists. The plant potential activating substance is located in the middle layer in the form of sodium alginate-chitosan microcapsules; The trace organic carbon synergist is located in the outer layer in the form of polylactic acid microcapsules; The plant potential activating substances and trace organic carbon synergists are released sequentially during the wheat jointing and grain-filling stages, respectively. The sugar-enhancing substance has both physiological enhancement and microecological regulation functions: Physiological enhancement: Promotes wheat sugar synthesis and photosynthetic product transport, and activates crop immunity; Microecological regulation: As a carbon source regulator for rhizosphere microorganisms, it selectively promotes the proliferation of ammonia-oxidizing bacteria-inhibiting microorganisms, forming a synergistic chemical-biological dual-pathway nitrification inhibition with the nitrification inhibitors.

6. A method for applying fertilizer without topdressing to increase wheat yield, characterized in that, Includes the following steps: S1. Before sowing, soil urease activity and nitrification potential are tested, and the amount of inhibitor in the compound fertilizer described in claim 2 is dynamically adjusted. S2, When sowing, apply the compound fertilizer described in claim 2 at one time, using the method of sowing the seed and fertilizer at the same time or applying it from the side, with a fertilization depth of 8-10 cm; no topdressing is required during the entire growth period of wheat.

7. The method according to claim 6, characterized in that, By adjusting the thickness of the three layers of the compound fertilizer, the coating material, and the ratio of inhibitors to activators, the spatiotemporal matching coefficient STMC was controlled between 0.85 and 1.15 during the wheat tillering, jointing, booting, and grain-filling stages. The spatiotemporal matching coefficient STMC = nitrogen requirement of wheat at each growth stage / nitrogen release from fertilizer during the corresponding period; The application rate of the compound fertilizer is 40-60 kg / mu, which is 12-18 kg / mu in terms of pure nitrogen.

8. The method according to claim 6, characterized in that, The specific method for dynamically adjusting the dosage of inhibitor in the compound fertilizer according to claim 2 includes: (1) Soil urease activity and nitrification potential were measured before sowing; (2) When the soil urease activity is ≤15 μg NH4⁺-N·g⁻¹·h⁻¹, the dosage of urease inhibitor is 80% of the standard dosage; when the soil urease activity is 15-30 μg NH4⁺-N·g⁻¹·h⁻¹, the dosage of urease inhibitor is 100% of the standard dosage; when the soil urease activity is ≥30 μg NH4⁺-N·g⁻¹·h⁻¹, the dosage of urease inhibitor is 120% of the standard dosage. (3) When the soil nitrification potential is ≤5 mg NO2⁻-N·kg⁻¹·d⁻¹, the dosage of nitrification inhibitor is 70% of the standard dosage; when the soil nitrification potential is 5-15 mg NO2⁻-N·kg⁻¹·d⁻¹, the dosage of nitrification inhibitor is 100% of the standard dosage; when the soil nitrification potential is ≥15 mg NO2⁻-N·kg⁻¹·d⁻¹, the dosage of nitrification inhibitor is 130% of the standard dosage. (4) The standard dosage of the urease inhibitor is 0.5% of the total mass of the inner core, and the standard dosage of the nitration inhibitor is 0.8% of the total mass of the inner core.

9. A method for preparing the compound fertilizer according to claim 5, characterized in that, Includes the following steps: Core granulation: Quick-acting nitrogen fertilizer is mixed with urease inhibitors and nitrification inhibitors, and then granulated to form inner core particles with a diameter of 1.0-1.5 mm. Intermediate layer coating: The inner core particles are fed into a fluidized bed coating machine, and the intermediate layer slurry is sprayed at a fluidized air temperature of 40-50℃ until the intermediate layer thickness reaches 0.4-0.6 mm, and then dried and cured. Transition layer spraying: After the intermediate layer spraying is completed, a mixture of intermediate layer slurry and outer layer slurry is sprayed onto the surface of the particles for 30-60 seconds to form a transition layer with a thickness of 5-15 μm. Outer layer spraying: On the surface of the transition layer, the outer layer slurry is sprayed at 35-45℃ until the outer layer thickness reaches 0.3-0.5 mm. After curing, the compound fertilizer is obtained. The middle layer slurry contains slow-release nitrogen fertilizer and enzyme-activating substances, while the outer layer slurry contains controlled-release nitrogen fertilizer and sugar-enhancing substances.

10. The method according to claim 9, characterized in that, The plant potential activating substance is pre-formed into 20-50 μm microcapsules in the form of sodium alginate-chitosan microcapsules and then mixed into the middle layer slurry; the trace organic carbon synergist is pre-formed into 20-50 μm microcapsules in the form of polylactic acid microcapsules and then mixed into the outer layer slurry.

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