Amino acid synergistic fertilizer and unmanned aerial vehicle variable spraying synergistic nitrogen and phosphorus emission reduction method

Abstract

This invention discloses a method for nitrogen and phosphorus emission reduction through the synergistic application of amino acid-enhanced fertilizer and variable-rate spraying by drones. The method includes: acquiring NDVI / NDRE distribution maps using a multispectral drone before the rice tillering stage to generate a variable-rate fertilizer prescription map; preparing an amino acid-enhanced compound granular fertilizer containing urea, monoammonium phosphate, potassium fertilizer, compound amino acid powder, γ-polyglutamic acid, humic acid, and urease inhibitor, and applying it via drone according to the prescription map; acquiring multispectral information again before the rice booting or heading stage to generate a variable-rate spraying prescription map; preparing an amino acid-nitrogen-phosphorus compound foliar fertilizer containing compound amino acids, urea, potassium dihydrogen phosphate, γ-polyglutamic acid, fucoidan oligosaccharide, and brassinolide, and applying it via drone according to the prescription map. This invention significantly improves nitrogen and phosphorus fertilizer utilization efficiency, reduces nitrogen and phosphorus concentrations in field surface water and runoff loss through the synergistic application of both broadcasting and spraying pathways, achieving fertilizer reduction and yield increase while controlling agricultural non-point source pollution at its source.

Description

Technical Field

[0001] This invention belongs to the field of agricultural fertilization and non-point source pollution control technology, specifically involving a nitrogen and phosphorus emission reduction method that combines amino acid-enhanced fertilizer with variable-rate spraying by drones. Background Technology

[0002] Rice is my country's largest grain crop, with a planting area consistently around 450 million mu (approximately 30 million hectares). While rice production involves a large input of chemical fertilizers, nitrogen and phosphorus utilization rates remain consistently low. Statistics show that nitrogen fertilizer utilization rates in my country's rice industry are generally between 30% and 35%, while phosphorus fertilizer utilization rates are less than 20%. Unabsorbed nitrogen and phosphorus enter water bodies through surface runoff, seepage, and leaching, becoming a major source of agricultural non-point source pollution. The "First National Pollution Source Census Bulletin" indicates that agricultural non-point source pollution contributes 57.2% of the total nitrogen and 67.3% of the total phosphorus in national water bodies. Therefore, improving fertilizer utilization and reducing nitrogen and phosphorus loss at the source are urgent issues that need to be addressed in rice cultivation and non-point source pollution control.

[0003] To address the aforementioned issues, numerous studies in recent years have attempted breakthroughs in two directions: enhanced fertilizer efficiency and precision fertilization. For example, CN115259959A discloses a special polypeptide enhanced fertilizer for hybrid indica rice during the heading stage and its drone-based precision fertilization method. This fertilizer is made into granules using urea, potassium chloride, natural peat moss, and polypeptide enhancers (such as gamma-aminobutyric acid or polyaspartic acid) as raw materials, and is applied via aerial spraying using drones. This method only targets topdressing during the heading stage of rice (jointing to heading stage), has a single formulation, and only involves solid granule application. It does not address differentiated fertilization during the tillering, booting, or heading stages, nor does it employ foliar spraying.

[0004] CN103449886A provides a compound microbial fertilizer for rice, whose raw materials include rare earth humic acid, polyaspartic acid, silicon-calcium-magnesium fertilizer, amino acid fertilizer, nitrogen-phosphorus-potassium fertilizer and fermented organic matter. Although it has added synergistic ingredients such as amino acids and polyaspartic acid, the fertilizer application is still mainly based on traditional manual or mechanical spreading, without combining drone variable operation, and without designing different formulations and application methods according to different growth stages.

[0005] CN111620739A discloses a rice-specific fertilizer that synergistically enhances the effect of returning wheat straw to the field and its application method. The fertilizer contains nitrogen, phosphorus, potassium, trace elements, compound amino acids, alginic acid, etc. It is applied as topdressing during the tillering stage, but the application method is still conventional broadcasting. It does not use drone variable broadcasting or spraying technology, nor does it have a foliar spraying plan for the booting stage or heading stage.

[0006] In addition, recent studies have attempted to combine UAV multispectral remote sensing diagnostics with variable fertilization technology. For example, CN116602106A discloses a UAV-based variable fertilization method for paddy fields. This method uses UAVs to acquire NDRE images, combines them with a nitrogen fertilizer optimization algorithm (NFOA) to calculate the topdressing amount and generate a prescription map, and then uses the UAV to apply urea in a variable manner. While this method achieves variable application based on remote sensing diagnostics, it still has the following shortcomings: First, it only uses conventional urea for application without adding any synergistic ingredients, leaving nitrogen still facing a high risk of ammonia volatilization and runoff loss. Second, it only focuses on solid particle application and does not address foliar spraying schemes during the rice booting and heading stages. After the booting stage, when the plant closes in, foliar spraying can bypass soil fixation and volatilization loss channels, resulting in higher absorption efficiency. Third, it does not design differentiated fertilizer formulations and application methods for different growth stages of rice, lacking a systematic approach.

[0007] CN118010648A discloses a multispectral diagnostic method for nitrogen nutrition in rice and wheat for precision fertilization by drones. Based on a critical nitrogen concentration dilution model, it calculates recommended nitrogen application rates and generates a digital prescription map to guide precision fertilization by drones. While this method establishes a relatively scientific fertilization decision-making model, it still has the following shortcomings: First, it does not address the enhancement and improvement of the fertilizer itself, still using conventional chemical fertilizers, and the nutrient loss problem is not solved at its source; second, it does not design differentiated fertilizer formulations and application methods for different growth stages of rice, especially failing to utilize the high absorption advantage of foliar spraying during the booting and heading stages; third, it does not provide specific fertilizer enhancement formulas, resulting in insufficient completeness and reproducibility of the technical solution.

[0008] In summary, existing technologies for rice fertilization still have some significant shortcomings. First, there is a lack of systematic consideration of the entire rice growth cycle. During the tillering stage, rice plants are small and suitable for broadcasting solid granular fertilizers, which are easily absorbed by the rhizosphere. After the booting stage, the plants close up, and the leaves are dense; at this time, foliar spraying is more effective because it allows for rapid absorption and bypasses soil fixation and volatilization. However, existing technologies do not systematically combine broadcasting and spraying based on the characteristics of these different growth stages. Second, drone fertilization technology currently mostly uses single-formula applications—either broadcasting solid granules or spraying liquid fertilizers—without forming a complete technology chain such as "variable-rate broadcasting of solid amino acid granular fertilizer during the tillering stage + variable-rate spraying of liquid amino acid foliar fertilizer during the booting / heading stage." Third, although some fertilizers contain added amino acids and polyaspartic acid, the application method is still mainly manual or mechanical broadcasting, lacking variable decision support based on multispectral remote sensing diagnosis. The amount of fertilizer applied often does not match the actual needs of the crop, resulting in a still high risk of nutrient loss and non-point source pollution.

[0009] Therefore, the technical problem that needs to be solved is to truly integrate amino acid-enhanced fertilizers with drone-based variable application and spraying technologies to form a comprehensive technical solution of "diagnosis-decision-application synergy" that addresses the different fertilizer requirements of rice throughout its entire growth cycle. Summary of the Invention

[0010] To address the aforementioned problems, this invention aims to provide a method for reducing nitrogen and phosphorus emissions from farmland that can significantly improve the utilization rate of nitrogen and phosphorus fertilizers, reduce nitrogen and phosphorus concentrations in field surface water and runoff loss, and reduce agricultural non-point source pollution at its source.

[0011] To achieve the above objectives, this invention provides a method for nitrogen and phosphorus emission reduction through the synergistic effect of amino acid-enhanced fertilizer and variable-rate spraying by drones, comprising the following steps: (1) 3-7 days before the tillering stage of rice, use multispectral UAV or satellite to obtain the spatial distribution map of normalized vegetation index (NDVI) and / or normalized red edge index (NDRE) of rice field, divide the field into multiple variable fertilization levels including at least high demand area, medium demand area and low demand area according to the spatial distribution map, and generate variable fertilization prescription map. (2) Prepare an amino acid-enhanced compound granular fertilizer for rice tillering stage, which includes the following by weight: 45-60 parts urea, 10-20 parts monoammonium phosphate, 5-15 parts potassium fertilizer, 8-15 parts compound amino acid powder, 2-6 parts γ-polyglutamic acid, 5-10 parts humic acid, 0.05-0.2 parts urease inhibitor, and 2-5 parts binder; (3) During the tillering stage of rice, an agricultural drone equipped with a solid particle variable broadcasting system is used to broadcast the amino acid enhanced compound granular fertilizer prepared in step (2) according to the variable fertilizer prescription map generated in step (1). The broadcasting amount is 10-20 kg per mu. (4) 3-5 days before the rice booting stage or heading stage, use a multispectral drone or satellite to obtain the spatial distribution map of NDVI and / or NDRE in the paddy field and generate a variable spraying prescription map. (5) Prepare an amino acid-nitrogen-phosphorus compound foliar fertilizer for rice during the booting or heading stage, which includes the following by weight: 20-30 parts compound amino acids, 8-15 parts urea, 10-18 parts potassium dihydrogen phosphate, 3-8 parts γ-polyglutamic acid, 2-5 parts alginic oligosaccharides, 0.001-0.005 parts brassinolide, 1-3 parts compound trace elements, 0.5-1.0 parts wetting and spreading agent, and deionized water to make up to 100 parts; (6) During the rice booting or heading stage, an agricultural drone equipped with a liquid variable spraying system is used to spray the amino acid-nitrogen-phosphorus compound foliar fertilizer prepared in step (5) according to the variable spraying prescription diagram generated in step (4). The spraying amount per mu is 2-4L.

[0012] Furthermore, in the composite amino acid powder described in step (2), the proportion of glutamic acid is ≥35%, the proportion of aspartic acid is ≥15%, and the proportion of glycine is ≥10%, and the molecular weight of the composite amino acid powder is ≤500 Da. This specific composition of composite amino acids can synergistically promote the absorption of nitrogen and phosphorus by rice: glutamic acid can activate the expression of nitrogen transport proteins, aspartic acid participates in nitrogen metabolism and promotes root development, and glycine has the effect of chelating trace elements.

[0013] Furthermore, the amino acid-enhanced compound granular fertilizer described in step (2) has a particle size of 3-5 mm and a specific gravity ≥ 1.2 g / cm³. 3 The particle size range is suitable for drone seeding systems. The higher specific gravity ensures that the particles can quickly sink to the surface of the paddy field soil, reducing uneven nutrient distribution caused by floating. Sufficient compressive strength prevents breakage in the drone feed hopper and during seeding.

[0014] Further, the potassium fertilizer in step (2) is potassium chloride or potassium sulfate; the urease inhibitor is NBPT (n-butylthiophosphoric acid triamine); and the binder is bentonite or starch. NBPT can inhibit urease activity and delay urea hydrolysis, thereby reducing ammonia volatilization loss.

[0015] Further, the composite trace element in step (5) is a water-soluble chelated trace element, including at least one of EDTA-Fe, EDTA-Zn, and boric acid. Preferably, the composite trace element is composed of EDTA-Fe, EDTA-Zn, and boric acid in a mass ratio of 1:1:1.

[0016] Furthermore, the complex amino acid in step (5) is an enzymatically hydrolyzed plant-derived amino acid with a molecular weight ≤500 Da, wherein glutamic acid accounts for ≥30%, aspartic acid accounts for ≥15%, and glycine accounts for ≥10%. Enzymatically hydrolyzed plant-derived amino acids have the characteristics of high activity, few impurities, and easy absorption by leaves.

[0017] Further, the wetting and spreading agent in step (5) is an organosilicon surfactant, which makes the surface tension of the amino acid-nitrogen-phosphorus compound foliar fertilizer ≤25mN / m; the pH value of the amino acid-nitrogen-phosphorus compound foliar fertilizer is 5.5-6.5, the total free amino acid content is ≥18%, the total nitrogen content is 4%-7%, the total phosphorus content is 3%-6%, and the total potassium content is 2%-5%. The lower surface tension can overcome the hydrophobicity of the rice leaf surface, promote droplet spreading and adhesion, and improve the leaf absorption rate.

[0018] Furthermore, the operational parameters for the variable-rate application of the drone in step (3) are: flight altitude 3-5m above the field surface, sowing width 6-10m, and operating speed 5-7m / s; the operational parameters for the variable-rate spraying of the drone in step (6) are: flight altitude 2-3m above the rice canopy, spray width 4-6m, droplet size 150-250μm, and operating speed 4-6m / s. These parameters, after optimization, can balance operational efficiency and fertilizer uniformity.

[0019] Furthermore, the operation time for the variable spraying by the drone in step (6) is 9-11 am or 4-6 pm; if there is rainfall within 4 hours after spraying, a supplementary spraying will be carried out.

[0020] Furthermore, the method also includes step (7): collecting field surface water samples and / or runoff samples on the 3rd, 7th and 14th days after topdressing, measuring the concentrations of total nitrogen, total phosphorus and ammonium nitrogen, and collecting rice plant samples to measure the nitrogen and phosphorus content in the aboveground parts, and evaluating the nitrogen and phosphorus emission reduction effect.

[0021] The present invention also provides a system for implementing the above method, comprising: Multispectral information acquisition unit, used to acquire spatial distribution maps of NDVI and / or NDRE in paddy fields; A variable decision unit is used to generate a variable fertilization prescription map and / or a variable spraying prescription map based on the spatial distribution map. The rice-specific amino acid-enhanced fertilizer unit includes the aforementioned amino acid-enhanced compound granular fertilizer and amino acid-nitrogen-phosphorus compound foliar fertilizer; The drone variable application unit has a solid particle variable application mode and a liquid variable application mode, and can be selectively switched to the application mode or the application mode according to the rice growth stage.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly improved nitrogen and phosphorus fertilizer utilization: Through the synergistic effect of applying amino acid-enhanced granular fertilizer during the tillering stage (activating soil nutrients and inhibiting ammonia volatilization) and spraying amino acid foliar fertilizer during the booting / heading stage (direct absorption by leaves, bypassing soil fixation), the nitrogen fertilizer utilization rate of rice can be increased to over 43.4%-45.2% (an increase of 7.5-16.1 percentage points compared to the conventional method), and the phosphorus fertilizer utilization rate can be increased to over 22.5%-28.3% (an increase of 3.0-11.6 percentage points compared to the conventional method). The specific increase varies depending on soil conditions and variety.

[0023] 2. Significant reduction in nitrogen and phosphorus concentrations in field surface water: Due to the chelation effect of amino acids, the slow-release effect of urease inhibitors, and the fact that foliar spraying avoids field surface water, the peak concentration of ammonium nitrogen in field surface water after topdressing can be reduced by 27.3%-34.5%, and the peak concentration of total phosphorus can be reduced by 55.9%, thereby significantly reducing nitrogen and phosphorus loss caused by runoff and leaching, and controlling agricultural non-point source pollution from the source.

[0024] 3. Achieving fertilizer reduction and yield increase: While ensuring or increasing rice yield, nitrogen fertilizer application can be reduced by approximately 25%, and phosphorus fertilizer application by approximately 25%. Example data shows that rice yield can increase by 1.8%-8.8% compared to conventional fertilization.

[0025] 4. Precise variable application, matching fertilizer spatial distribution with crop needs: Using multispectral remote sensing to obtain NDVI / NDRE distribution maps of rice, generating variable fertilizer prescription maps, drones automatically adjust the application rate or spraying rate according to the prescription map, avoiding excessive fertilization in vigorous growth areas and insufficient fertilization in weak seedling areas, further improving fertilizer utilization efficiency.

[0026] 5. Full growth period coverage, combined broadcasting and foliar spraying: Targeting key nutrient demand windows such as the tillering stage, booting stage, and heading stage of rice, two modes are adopted: solid granule broadcasting and liquid foliar spraying, which give full play to the advantages of different fertilization methods and form a systematic technical solution. Attached Figure Description

[0027] Figure 1 This is a flowchart of a nitrogen and phosphorus emission reduction method for the synergistic use of amino acid-enhanced fertilizer and drone variable spraying according to the present invention; Figure 2 This is a schematic diagram illustrating the synergistic mechanism of the amino acid-enhanced fertilizer of the present invention in promoting absorption and reducing emissions in paddy fields, showing the synergistic effect of soil application and foliar spraying. Figure 3 This is a schematic diagram of the operation modes of the UAV variable application mode (a) and the UAV variable spraying mode (b) of the present invention; Figure 4 This is a comparison chart showing the dynamic changes of ammonium nitrogen (a) and total phosphorus (b) concentrations in field surface water over time under different fertilization modes of this invention; Figure 5 This is a schematic diagram comparing the nitrogen loss pathways and emission reduction effects in paddy fields under conventional fertilization (a) and the technology of this invention (b). Figure 6 Photos showing the growth of rice in the field during the tillering stage; Figure 7 Photos of rice growth in the field during the booting stage; Figure 8 Photos of agricultural drones operating in the field; Figure 9 These are photographs of rice at maturity after the application of the technology of this invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments. Figure 1 This is an overall flowchart of the technical solution of the present invention. The following embodiments are all based on... Figure 1 Perform the steps shown. Figure 2 This invention demonstrates the mechanism of action of its dual-path synergistic application (soil application + foliar spraying). Figure 3 The diagram illustrates the operational modes of drones at different reproductive stages. Figure 4 and Figure 5 The comparison shows the dynamic changes and loss pathways of nitrogen and phosphorus in field surface water.

[0029] Example 1:

[0030] Amino acid granular fertilizer is applied by drone during the rice tillering stage (see...) Figure 1 Mode 1 and Figure 3 a).

[0031] This embodiment follows Figure 1 The process involves "information collection → demand zoning → intelligent decision-making → fertilizer matching → variable-based operations → effect evaluation". Details are as follows: Field information: The rice variety is Xiangliangyou 900, the planting area is 100 mu, the soil type is river mud paddy, medium fertility. The previous crop was winter fallow.

[0032] Preparation before operation: On the 5th day after rice transplanting (before tillering), use a DJI Mavic 3M multispectral drone to acquire an NDVI distribution map of the rice paddy (corresponding to...). Figure 1 Step ①), flight altitude 60m, ground resolution 8cm. Import the acquired NDVI data into the intelligent decision-making system, dividing the field into three variable zones: high-demand zone (weak seedling area, NDVI < 0.55) 30%, medium-demand zone (normal area, NDVI 0.55-0.70) 50%, and low-demand zone (vigorous growth area, NDVI > 0.70) 20% (corresponding to...). Figure 1 Steps ② and ③).

[0033] Fertilizer formulation: Weigh out 50 parts by weight of urea, 15 parts by weight of monoammonium phosphate, 10 parts by weight of potassium chloride, 12 parts by weight of compound amino acid powder (38% glutamic acid, 16% aspartic acid, and 12% glycine, molecular weight ≤500 Da), 4 parts by weight of γ-polyglutamic acid, 8 parts by weight of humic acid, 0.1 parts by weight of NBPT, and 3 parts by weight of bentonite. After mixing, granulate to obtain particles with a diameter of 3-5 mm and a specific gravity of 1.25 g / cm³. 3 granular fertilizer with a compressive strength of 28N (corresponding to) Figure 1 Step 4 and Figure 2 Path A).

[0034] Drone operation: DJI T50 agricultural drones are used, equipped with a solid particle variable dispersing system (such as...). Figure 3 (As shown in a). Based on the variable fertilizer prescription diagram, the flight height was set to 4m above the field surface, the sowing width to 8m, and the operating speed to 6m / s. The application rate per mu was set as follows: 18kg for high-demand areas, 13kg for medium-demand areas, and 8kg for low-demand areas (corresponding to...). Figure 1 Step ⑤). The weather was sunny and the wind speed was level 2 on the day of the operation. In this embodiment, the rice was in the early tillering stage, the plants were small, and their growth in the field was as follows: Figure 6 As shown. During this period, the use of drones for variable-rate application of solid granular fertilizer is beneficial for the fertilizer granules to sink into the root zone, promoting early tillering.

[0035] Control setting: A conventional control area was set up in the same field, where 15 kg / mu of nitrogen fertilizer was applied manually, without the application of amino acid synergistic fertilizer, and other field management was the same.

[0036] Effect evaluation: Field water samples and plant samples were collected on the 3rd, 7th, and 14th days after topdressing (corresponding to...). Figure 1 Step ⑥). The dynamic changes of ammonium nitrogen and total phosphorus in field surface water are as follows: Figure 4 As shown, the peak concentration and duration of the treatment (amino acid fertilizer zone) of this invention were significantly lower than those of the conventional control. Comparison of nitrogen and phosphorus loss pathways, for example... Figure 5 As shown, the present invention significantly reduces ammonia volatilization, runoff, and leaching losses through a dual-pathway application of broadcasting and spraying.

[0037] Results: As shown in Table 1, compared with the conventional control, the nitrogen application rate in the treatment area of ​​Example 1 of this invention was reduced by 25%, the peak value of ammonium nitrogen in field water was reduced by 27.3%, the peak value of total phosphorus was reduced by 55.9%, the nitrogen fertilizer utilization rate was increased by 7.5 percentage points, the phosphorus fertilizer utilization rate was increased by 3.0 percentage points, and the yield was increased by 1.8%.

[0038] Table 1: Comparison of fertilizer effects and environmental indicators between Example 1 and the control. Example 2:

[0039] Amino acid foliar fertilizer sprayed by drone during the rice booting stage (see Figure 1 Mode 2 and Figure 3 b).

[0040] This embodiment follows Figure 1 The process of "information collection → intelligent decision-making → fertilizer matching → variable spraying" is repeated again, and adopts... Figure 2 Foliar spraying path B in the middle.

[0041] Field information: Same as in Example 1.

[0042] Operational Plan: On the 50th day after rice transplanting (booting stage), a multispectral UAV was used to acquire an NDRE distribution map, generating a variable spraying prescription map. Amino acid foliar fertilizer was prepared by weighing 25 parts by weight of enzymatically hydrolyzed plant-derived compound amino acids (32% glutamic acid, 16% aspartic acid, 11% glycine, molecular weight ≤500 Da), 10 parts by weight of urea, 15 parts by weight of potassium dihydrogen phosphate, 5 parts by weight of γ-polyglutamic acid, 3 parts by weight of fucoidan, 0.003 parts by weight of brassinolide, 2 parts by weight of compound trace elements (in this example, composed of EDTA-Fe, EDTA-Zn, and boric acid in a mass ratio of 1:1:1), 0.8 parts by weight of organosilicon wetting and spreading agent, and deionized water to a total of 100 parts. The mixture was stirred thoroughly, and the pH was measured to be 6.2, surface tension 22 mN / m, total free amino acids 20%, total nitrogen 5.2%, total phosphorus 4.8%, and total potassium 3.5%.

[0043] Using the XAG P100 Pro drone, equipped with a variable spraying system (such as...) Figure 3 (As shown in b). Flight altitude 2.5m above the canopy, spray width 5m, droplet size 180μm, operating speed 5m / s, spraying rate 3L per acre. Operating time: 5 PM. Figure 7 As shown, the rice plants in the booting stage have basically closed the canopy, with dense foliage and high field density. At this stage, using drones for variable-rate foliar fertilizer application can bypass soil fixation and ammonia volatilization losses, enabling rapid absorption by the leaves.

[0044] Control setting: A conventional control area was set up in the same field, and 10 kg / mu of compound fertilizer (15-15-15) was manually applied during the booting stage.

[0045] Results: As shown in Table 2, the number of grains per ear in the treatment area of ​​Example 2 of this invention was 190, which was 14 more than the control (176 grains per ear), an increase of 8.0%; the thousand-grain weight was 24.9g, which was 0.5g more than the control (24.4g), an increase of 2.0%; the peak total nitrogen in the field surface water was 11.8mg / L, which was 5.9mg / L less than the control (17.7mg / L), a decrease of 33.3%; and the yield was 593kg / mu, which was 48kg / mu more than the control (545kg / mu), an increase of 8.8%.

[0046] Table 2: Comparison of yield and environmental indicators between Example 2 and the control Example 3:

[0047] The "spraying + spraying" combination model throughout the entire reproductive period (see...) Figure 1 Full process and Figure 2 (Dual-path collaboration).

[0048] This embodiment is executed completely. Figure 1The complete process shown includes application path A during the tillering stage and spraying path B during the heading / heading stage, achieving... Figure 2 The dual-path synergistic emission reduction effect is shown.

[0049] Field information: Feixi County, Hefei, Anhui Province; rice variety Fengliangyou No. 4; area: 100 mu; fertility: medium.

[0050] Work plan: Tillering stage (8 days after transplanting): Amino acid granular fertilizer prepared in Example 1 was applied by drone according to the method described in Example 1. Figure 3 a), apply 12 kg per mu.

[0051] During the booting stage (48 days after transplanting): the amino acid foliar fertilizer prepared in Example 2 was applied by drone variable-rate spraying according to the method in Example 2. Figure 3 b), spray 3L per mu.

[0052] Heading stage (72 days after transplanting): The amino acid foliar fertilizer prepared in Example 2 was applied again via drone variable-rate spraying at a rate of 2.5 L per acre. This example involved three drone variable-rate operations throughout the entire growth period (one application and two applications of spraying). The on-site operation details are as follows: Figure 8 As shown, the drone automatically adjusts the amount of seeding or spraying liquid according to the prescription map, achieving precise variable fertilization.

[0053] Control set: conventional three topdressings (10 kg / mu of urea during the tillering stage, 10 kg / mu of compound fertilizer during the booting stage, and 5 kg / mu of urea during the heading stage).

[0054] Results: As shown in Table 3, the nitrogen fertilizer utilization rate in the treatment area of ​​this invention increased by 16.1 percentage points, the phosphorus fertilizer utilization rate increased by 11.6 percentage points, the weighted average concentration of total nitrogen in field surface water decreased by 61.0%, the weighted average concentration of total phosphorus decreased by 64.0%, and the yield increased by 6.9%. Figure 4 and Figure 5 The above emission reduction effects were confirmed from the perspectives of dynamic changes and loss paths, respectively.

[0055] Table 3: Comparison of overall effects between Example 3 and the control Example 4:

[0056] Comparison of different formulations of amino acid granular fertilizer.

[0057] To verify the composition of the compound amino acids and the effects of γ-polyglutamic acid and urease inhibitor, the following comparative formulations were set up (all applied according to the method in Example 1, with a nitrogen application rate of 11.25 kg / mu): Formula A (this invention): 50 parts urea, 15 parts monoammonium phosphate, 10 parts potassium chloride, 12 parts compound amino acid powder (38% glutamic acid, 16% aspartic acid, 12% glycine), 4 parts γ-PGA, 8 parts humic acid, 0.1 parts NBPT, and 3 parts bentonite.

[0058] Formula B (lacking γ-PGA): Same as Formula A, but without adding γ-PGA.

[0059] Formula C (lacking NBPT): Same as Formula A, but without adding NBPT.

[0060] Formula D (Ordinary Amino Acids): Same as Formula A, but the compound amino acid powder is an equal amount of ordinary compound amino acids (glutamic acid 20%, aspartic acid 8%, glycine 5%).

[0061] Formula E (conventional urea): Apply only 11.25 kg / mu of urea.

[0062] The results (Table 4) showed that Formula A had the lowest peak ammonium nitrogen in field water (27.9 mg / L) and the highest nitrogen fertilizer utilization rate (43.4%). After the absence of γ-PGA or NBPT, the peak ammonium nitrogen in field water increased to 32.5 mg / L and 36.1 mg / L, respectively, while the nitrogen fertilizer utilization rates decreased to 39.7% and 38.2%, respectively, indicating that γ-PGA and NBPT had a synergistic effect in inhibiting nitrogen loss. Formula D, using common amino acids, had a peak ammonium nitrogen in field water of 33.8 mg / L and a nitrogen fertilizer utilization rate of 40.1%, lower than Formula A, indicating that the compound amino acid with specific components (high glutamic acid, aspartic acid, and glycine) had a better synergistic effect.

[0063] Table 4: Comparison of the effects of different granular fertilizer formulations.

[0064] Example 5:

[0065] Comparison of operating parameters for different drones.

[0066] Using the fertilizer and conditions of Example 1, different combinations of drone application parameters were set to examine the uniformity of application (expressed as coefficient of variation CV%). The results are shown in Table 5. When the flight altitude was 3-5m, the spreading width was 6-10m, and the speed was 5-7m / s, the coefficient of variation for uniformity was ≤12%. Excessive flight altitude (>6m) or excessive speed (>8m / s) led to a significant decrease in uniformity (CV>18%); excessively wide spreading width (>12m) resulted in insufficient application in the edge areas.

[0067] Table 5: Effect of UAV application parameters on uniformity Rice paddies using the technical solution of this invention exhibit uniform growth patterns, large panicles, and full grains at maturity. Figure 9 As shown, this intuitively demonstrates the positive effect of reducing weight without reducing production, and increasing production and efficiency.

[0068] In summary, the technical solution of this invention was verified in paddy field trials in Changsha, Hunan Province and Feixi County, Anhui Province. Variable-rate application of amino acid granular fertilizer during the tillering stage, compared with conventional urea application, resulted in a 27.3% reduction in peak ammonium nitrogen in field water and a 55.9% reduction in peak total phosphorus, with nitrogen fertilizer utilization increasing by 7.5 percentage points and phosphorus fertilizer utilization increasing by 3.0 percentage points, leading to a 1.8% increase in yield, all under the condition of a 25% reduction in nitrogen. Foliar application of amino acid fertilizer during the booting stage increased the number of grains per panicle by 8.0%, yield by 8.8%, and reduced the peak total nitrogen in field water by 33.3%. Under the "broadcast + foliar spray" combination mode throughout the entire growth period, total nitrogen application was reduced by 32%, total phosphorus application by 38%, and the weighted average concentrations of total nitrogen and total phosphorus in field water decreased by 61% and 64%, respectively, resulting in a 6.9% increase in yield. Formula comparison experiments showed that γ-polyglutamic acid and NBPT have a synergistic effect in inhibiting nitrogen loss, and the synergistic effect of the specific compound amino acid composition is superior to that of ordinary amino acids. The optimization test of UAV operation parameters showed that when the flight altitude was 3-5m, the sowing width was 6-10m, and the speed was 5-7m / s, the coefficient of variation of sowing uniformity was ≤12%.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reducing nitrogen and phosphorus emissions by synergizing amino acid synergistic fertilizer with variable spraying by unmanned aerial vehicle, characterized in that, Includes the following steps: (1) 3-7 days before the tillering stage of rice, use multispectral UAV or satellite to obtain the spatial distribution map of the normalized vegetation index NDVI and / or normalized red edge index NDRE of the paddy field. Based on the spatial distribution map, divide the field into multiple variable fertilization levels, including at least weak seedling area, normal area and vigorous growth area, and generate variable fertilization prescription map. (2) Prepare an amino acid-enhanced compound granular fertilizer for rice tillering stage, which includes the following by weight: 45-60 parts urea, 10-20 parts monoammonium phosphate, 5-15 parts potassium fertilizer, 8-15 parts compound amino acid powder, 2-6 parts γ-polyglutamic acid, 5-10 parts humic acid, 0.05-0.2 parts urease inhibitor, and 2-5 parts binder; (3) During the tillering stage of rice, an agricultural drone equipped with a solid particle variable broadcasting system is used to broadcast the amino acid enhanced compound granular fertilizer prepared in step (2) according to the variable fertilizer prescription map generated in step (1). The broadcasting amount is 10-20 kg per mu. (4) 3-5 days before the rice booting stage or heading stage, use a multispectral drone or satellite to obtain the spatial distribution map of NDVI and / or NDRE in the paddy field and generate a variable spraying prescription map. (5) Prepare an amino acid-nitrogen-phosphorus compound foliar fertilizer for rice during the booting or heading stage, which includes the following by weight: 20-30 parts compound amino acids, 8-15 parts urea, 10-18 parts potassium dihydrogen phosphate, 3-8 parts γ-polyglutamic acid, 2-5 parts alginic oligosaccharides, 0.001-0.005 parts brassinolide, 1-3 parts compound trace elements, 0.5-1.0 parts wetting and spreading agent, and deionized water to make up to 100 parts; (6) During the rice booting or heading stage, an agricultural drone equipped with a liquid variable spraying system is used to spray the amino acid-nitrogen-phosphorus compound foliar fertilizer prepared in step (5) according to the variable spraying prescription diagram generated in step (4). The spraying amount per mu is 2-4L.

2. The method according to claim 1, characterized in that, In step (2), the composite amino acid powder contains ≥35% glutamic acid, ≥15% aspartic acid, and ≥10% glycine, and the molecular weight of the composite amino acid powder is ≤500 Da.

3. The synergistic nitrogen and phosphorus emission reduction method of amino acid fertilizer and unmanned aerial variable spraying according to claim 1, characterized in that, The amino acid synergistic compound granular fertilizer in step (2) has a particle size of 3-5 mm, a specific gravity of ≥1.2 g / cm 3 , a compressive strength of ≥25 N, and a moisture content of ≤2%.

4. The method according to claim 1, characterized in that, The potassium fertilizer in step (2) is potassium chloride or potassium sulfate; the urease inhibitor is NBPT; and the binder is bentonite or starch.

5. The method according to claim 1, wherein the amino acid synergistic fertilizer is cooperated with the unmanned aerial vehicle variable spraying to reduce nitrogen and phosphorus emissions. The operating parameters for the variable application of the UAV in step (3) are: flight height 3-5m above the field surface, sowing width 6-10m, and operating speed 5-7m / s; the operating parameters for the variable spraying of the UAV in step (6) are: flight height 2-3m above the rice canopy, spray width 4-6m, droplet size 150-250μm, and operating speed 4-6m / s.

6. The method of claim 1, wherein the amino acid synergistic fertilizer is applied in coordination with the unmanned aerial vehicle variable application. The complex amino acids mentioned in step (5) are enzymatically hydrolyzed plant-derived amino acids with a molecular weight ≤500 Da, of which glutamic acid accounts for ≥30%, aspartic acid accounts for ≥15%, and glycine accounts for ≥10%.

7. The method according to claim 1, wherein the amino acid synergistic fertilizer is cooperated with the unmanned aerial vehicle variable spraying to reduce the emission of nitrogen and phosphorus. The wetting and spreading agent in step (5) is an organosilicon surfactant, which makes the surface tension of the amino acid-nitrogen-phosphorus compound foliar fertilizer ≤25mN / m; the pH value of the amino acid-nitrogen-phosphorus compound foliar fertilizer is 5.5-6.5, the total amount of free amino acids is ≥18%, the total nitrogen content is 4%-7%, the total phosphorus content is 3%-6%, and the total potassium content is 2%-5%.

8. The method according to claim 1, characterized in that, The operation time for the variable spraying by drone in step (6) is 9-11 am or 4-6 pm; if there is rainfall within 4 hours after spraying, re-spraying will be carried out.

9. The method according to claim 1, characterized in that, It also includes step (7): collecting field surface water samples and / or runoff samples on the 3rd, 7th and 14th days after topdressing, measuring the concentrations of total nitrogen, total phosphorus and ammonium nitrogen, and collecting rice plant samples to measure the nitrogen and phosphorus content in the aboveground parts, and evaluating the nitrogen and phosphorus emission reduction effect.

10. A system for implementing the nitrogen and phosphorus emission reduction method of synergistic application of amino acid-enhanced fertilizer and variable-rate spraying by unmanned aerial vehicles as described in any one of claims 1-9, characterized in that, include: Multispectral information acquisition unit, used to acquire spatial distribution maps of NDVI and / or NDRE in paddy fields; A variable decision unit is used to generate a variable fertilization prescription map and / or a variable spraying prescription map based on the spatial distribution map. A rice-specific amino acid-enhanced fertilizer unit, comprising the amino acid-enhanced compound granular fertilizer described in step (2) of claim 1 and the amino acid-nitrogen-phosphorus compound foliar fertilizer described in step (5) of claim 1; The drone variable application unit has a solid particle variable application mode and a liquid variable application mode, and can be selectively switched to the application mode or the application mode according to the rice growth stage.

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