Corn close planting and yield increasing method based on coordination of root zone targeted carbon supply and canopy carbon supplement

Abstract

The invention provides a corn close planting and yield increasing method based on coordination of root zone targeted carbon supply and canopy carbon supplement, and belongs to the technical field of crop production. The specific micromolecular carbon fertilizer (the molecular weight is 1t, 1000Da, and the carboxyl content is greater than or equal to 5mmol / g) is used to realize rapid leaf surface absorption and root activity activation (the bleeding sap flow rate in the R3 stage is increased by 20.7%), and the yield is not reduced when the micromolecular carbon fertilizer is cooperatively applied with urea / compound fertilizer. And through cooperative regulation and control of root zone targeted carbon supply and canopy unmanned aerial vehicle carbon supplementation, root system downward pricking can be remarkably promoted, root system activity can be maintained, leaf aging can be delayed, overall physiological optimization in the corn growth period is achieved, and high-yield and high-efficiency cultivation of close planting corn is achieved.

Description

Technical Field

[0001] This invention belongs to the field of crop production technology, and in particular relates to a method for increasing maize yield through dense planting based on the synergy of root zone targeted carbon supply and canopy carbon supplementation. Background Technology

[0002] Thanks to the breeding of high-yielding, high-density-tolerant varieties and the widespread application of supporting high-density planting technologies, maize planting density has increased significantly over the past few decades, becoming a major factor driving maize yield growth. Future increases in maize yield still require further exploration of the potential for higher density planting.

[0003] However, with increased planting density, competition for light among maize plants intensifies, leading to a 20%–40% decrease in overall photosynthetic efficiency. Studies show that of the carbon fixed by maize through photosynthesis, 60%–80% is allocated to the aboveground parts for respiration, stem and leaf development, and grain formation, while the remainder is allocated to the roots for growth. Under high-density planting conditions, the proportion of photosynthetic carbon allocated to the roots is significantly reduced, resulting in a lower root-to-shoot ratio. This is manifested in a significant decrease in root length, root biomass, number of nodes, and density and length of lateral roots. These changes severely limit root growth and nutrient absorption capacity, making it difficult to meet the nutrient demands of the aboveground parts. This not only hinders the achievement of increased yield through higher planting density but also increases reliance on excessive fertilization. As the "currency" for plant growth, carbon replenishment is crucial under high-density planting conditions.

[0004] Currently, the commonly used fertilization methods mainly include one-time basal application of chemical fertilizers or spraying with conventional foliar fertilizers. These methods are neither effective in alleviating the problem of decreased carbon assimilation capacity caused by canopy light competition, nor can they meet the specific carbon requirements of the root system. There is an urgent need for an efficient carbon supplementation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for increasing maize yield through dense planting based on the synergy of root zone targeted carbon supply and canopy carbon supplementation.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for increasing maize yield through dense planting based on the synergistic effect of root zone targeted carbon supply and canopy carbon supplementation, comprising the following steps: 1) Apply fertilizer at the early stage of jointing; 2) Apply foliar fertilizer during the V12 and R2 stages respectively; The location of the topdressing should be adjusted according to the planting density. The horizontal distance of the fertilization location is represented by D, in cm, and the planting density is represented by S, in plants / ha. The horizontal distance between the fertilization locations and the planting density satisfy the following relationship: D(cm)=15+0.1×(S-60000) / 1000; The topdressing in step 1) contains carbon fertilizer and urea. The amount of carbon fertilizer used is 120~150g / ha, and the mass ratio of carbon fertilizer to urea is carbon fertilizer: urea = 1:870~1330. The foliar fertilizer in step 2) for V12 or R2 stage contains carbon fertilizer and urea. The concentration of carbon fertilizer is 53~375mg / L, and the mass ratio of carbon fertilizer to urea is carbon fertilizer: urea = 1:870~1330. The application rate of foliar fertilizer during the V12 or R2 stage is 40~225 L / ha; The carbon fertilizer contains carbon nanotubes, graphene oxides, or carbon quantum dot materials.

[0007] Preferably, the molecular weight of the carbon fertilizer is <1000 Da.

[0008] Preferably, the foliar fertilizer further includes components at the following concentrations: Potassium dihydrogen phosphate 222~6250 mg / L, sugar alcohol calcium boron fertilizer 444~5000 mg / L, sugar alcohol zinc / chelated zinc 111~3750 mg / L.

[0009] Preferably, the application depth of the topdressing is 15-22 cm.

[0010] Preferably, the method for increasing corn yield through dense planting further includes applying basal fertilizer, wherein the amount of basal fertilizer is as follows: N 120~147kg / ha, P2O5 90~110kg / ha, K2O 90~120kg / ha.

[0011] Preferably, the foliar fertilizer is applied using either a drone or a spray boom.

[0012] Preferably, the UAV operates at a flight speed of 3-5 m / s, a flight altitude of 2-4.5 m, and sprays pesticide droplets with a droplet size of 80-120 μm and a coverage density of 30-40 drops / cm². 2 .

[0013] Preferably, the boom height is 1.5~2.5m, the working pressure is 2.0~2.5bar, and the spraying speed is ≤4km / h.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for increasing maize yield through dense planting based on the synergistic effect of root zone targeted carbon supply and canopy carbon supplementation. By using a specific small-molecule carbon fertilizer (molecular weight <1000 Da, carboxyl content ≥5 mmol / g), it achieves rapid foliar absorption and root vitality activation (increasing sap flow rate by 20.7% in the R3 stage), and its synergistic application with urea / compound fertilizer does not reduce yield. Furthermore, through the synergistic regulation of root zone targeted carbon supply and canopy UAV carbon supplementation, it can significantly promote root penetration, maintain root vitality, and delay leaf senescence, achieving overall physiological optimization of maize's growth cycle and enabling high-yield and high-efficiency cultivation of densely planted maize. Attached Figure Description

[0015] Figure 1 For the significance analysis of the difference in green leaf area index between Example 1 and Comparative Example 1 at different growth stages; Figure 2 To analyze the significant differences in relative chlorophyll content (SPAD) of leaves at different growth stages between Example 1 and Comparative Example 1; Figure 3 For the significance analysis of the differences in root length of individual plants at different growth stages between Example 1 and Comparative Example 1; Figure 4 For the significance analysis of the root-shoot ratio difference between Example 1 and Comparative Example 1 at different growth stages; Figure 5 For the analysis of the significant differences in the root length ratio of each soil layer from 0 to 60 cm during the silking stage between Example 1 and Comparative Example 1; Figure 6 For the analysis of the significant difference in root sap flow rate between Example 1 and Comparative Example 1 at different growth stages; Figure 7 For the significance analysis of the differences in green leaf area index between Example 2 and Comparative Examples 2 and 3 at different growth stages; Figure 8 For the significance analysis of the difference in relative chlorophyll content (SPAD) of leaves at different growth stages between Example 2 and Comparative Examples 2 and 3; Figure 9 For the analysis of the significant difference in root length of individual plants at the silking stage between Example 2 and Comparative Examples 2 and 3; Figure 10 For the analysis of the significant differences in the root length ratio of each soil layer from 0 to 60 cm during the silking stage between Example 2 and Comparative Examples 2 and 3; Figure 11 For the analysis of the significant difference in root sap flow rate between Example 2 and Comparative Examples 2 and 3 at different growth stages; Figure 12 A schematic diagram of targeted carbon supply to the root region and carbon replenishment to the canopy. Detailed Implementation

[0016] This invention provides a method for increasing maize yield through dense planting based on the synergistic effect of root zone targeted carbon supply and canopy carbon supplementation, comprising the following steps: 1) Apply fertilizer at the early stage of jointing; 2) Apply foliar fertilizer during the V12 and R2 stages respectively; In this invention, it is preferred to apply basal fertilizer at the time of sowing. The basal fertilizer preferably includes N, P2O5 and K2O. The application rate of N is preferably 120~147 kg / ha, more preferably 110~130 kg / ha, and even more preferably 120 kg / ha. The application rate of P2O5 is preferably 70~120 kg / ha, more preferably 90~110 kg / ha, and even more preferably 100 kg / ha. The application rate of K2O is preferably 70~120 kg / ha, more preferably 90~110 kg / ha, and even more preferably 100 kg / ha.

[0017] In this invention, the topdressing is applied at the beginning of the jointing stage, and the application location is adjusted according to the planting density. The horizontal distance of the fertilization location is represented by D, in cm, and the planting density is represented by S, in plants / ha. The horizontal distance between the fertilization locations and the planting density satisfy the following relationship: D(cm)=15+0.1×(S-60000) / 1000; Implementation Example: When the planting density is 65,000 plants / ha, the calculated distance D is 15 + 0.1 × (65,000 - 60,000) / 1000 = 15.5 cm; when the density is 70,000 plants / ha, D = 16 cm; when the density is 75,000 plants / ha, D = 16.5 cm. In actual operation, a deviation of ±1 cm in the horizontal distance D for fertilization is allowed, and this deviation will not affect the fertilization effect. The error in the spacing of the fertilization shovel should be controlled ≤ ±1 cm, and the coefficient of variation of fertilizer flow rate should be < 5%.

[0018] In this invention, the application depth of topdressing is preferably 15-22cm, more preferably 18-20cm, and even more preferably 19cm.

[0019] In this invention, the fertilizer used for topdressing comprises components in the following mass ratio: carbon fertilizer: urea = 1:870~1:1330, preferably carbon fertilizer: urea = 1:900~1300, more preferably carbon fertilizer: urea = 1:1100; the carbon fertilizer preferably contains carbon nanotubes, graphene oxide or carbon quantum dot materials, and the molecular weight of the carbon fertilizer is preferably <1000 Da.

[0020] The application rate of carbon fertilizer in the topdressing is 120-150 g / ha, dynamically adjusted according to the soil organic matter content. When the organic matter content is <15 g / kg, 140-150 g / ha is preferred, and more preferably 145 g / ha. When the organic matter content is 15-25 g / kg, 130-140 g / ha is preferred, and more preferably 135 g / ha. When the organic matter content is >25 g / kg, 120-130 g / ha is preferred, and more preferably 125 g / ha. When the density is ≥80,000 plants / ha, the above application rate is preferably increased by 40%-60%, more preferably 45%-55%, and even more preferably 50%.

[0021] In this invention, foliar fertilizer is applied during the V12 and R2 stages. The V12 stage (large trumpet stage) of maize is a crucial stage in its growth cycle, marked by the full unfolding of the twelfth true leaf. At this time, the plant enters the floret differentiation stage, and the silks of the female ear begin to differentiate, determining the number of kernels per ear. The most typical characteristic of the R2 stage (kernel formation stage) is that the kernels in the middle of the ear are basically formed, and the endosperm is clear and pulpy. At this time, the kernel moisture content is about 85%, and the internal liquid is clearly visible (water blister stage), marking a critical stage in kernel volume and endosperm development. The application methods for foliar fertilizer during the V12 or R2 stages include drone operation or boom spraying. If drones are used for application, the foliar fertilizer comprises components at the following concentrations: The preferred concentration of small molecule carbon fertilizer is 200~375 mg / L, more preferably 250~350 mg / L, and even more preferably 300 mg / L; The potassium dihydrogen phosphate concentration is preferably 833~6250 mg / L, more preferably 1500~4500 mg / L, and even more preferably 3000 mg / L; The sugar alcohol calcium boron fertilizer is preferably 1667~5000 mg / L, more preferably 2000~4000 mg / L, and even more preferably 3000 mg / L; The sugar alcohol zinc / chelated zinc concentration is preferably 417~3750 mg / L, more preferably 1000~3000 mg / L, and even more preferably 2000 mg / L; If boom spraying is used, a high-clearance boom sprayer or a vehicle-mounted stretcher sprayer is preferred. The foliar fertilizer comprises components of the following concentrations: The preferred concentration of small molecule carbon fertilizer is 53.3~100 mg / L, more preferably 65~90 mg / L, and even more preferably 75 mg / L; The potassium dihydrogen phosphate concentration is preferably 222~1667 mg / L, more preferably 500~1500 mg / L, and even more preferably 1000 mg / L; The sugar alcohol calcium boron fertilizer is preferably 444~1333 mg / L, more preferably 800~1100 mg / L, and even more preferably 1000 mg / L; The sugar alcohol zinc / chelated zinc concentration is preferably 111~1000 mg / L, more preferably 300~800 mg / L, and even more preferably 500 mg / L; The carbon fertilizer preferably comprises carbon nanotubes, graphene oxide, or carbon quantum dot materials, and the molecular weight of the carbon fertilizer is preferably <1000 Da.

[0022] In this invention, when the drone is operating, its flight speed is preferably 3-5 m / s, more preferably 4 m / s; its flight altitude is preferably 2-4.5 m, further preferably 2.5-4 m, and even more preferably 3 m; the droplet size of the sprayed pesticide is preferably 80-120 μm, more preferably 90-110 μm, and even more preferably 100 μm; and the coverage density is preferably 30-40 drops / cm³. 2 Further preferred is 32~38 drops / cm 2 A further preferred value is 35 drops / cm 2 When using drones, the application rate of foliar fertilizer is 40-60 L / ha, preferably 45-55 L / ha, and even more preferably 50 L / ha. It is recommended to add a spraying aid to improve droplet settling and anti-evaporation performance. Ensure an input of 12-15 g of carbon fertilizer per hectare, and 50-250 g / ha of potassium dihydrogen phosphate, 100-200 g / ha of sugar alcohol calcium boron fertilizer, and 25-150 g / ha of sugar alcohol zinc / chelated zinc, with synergistic concentrations of all components to prevent precipitation, suitable for the low-volume, high-concentration spraying characteristics of drones.

[0023] In this invention, when using a spray boom, the preferred height of the spray boom is 1.5-2.5m, more preferably 1.7-2.2m, and even more preferably 2m. The preferred working pressure of the spray boom is 2.0-2.5bar, more preferably 2.1-2.4bar, and even more preferably 2.3bar. The preferred spraying speed is ≤4km / h. When using a spray boom, the preferred application rate of foliar fertilizer in the V12 or R2 stage is 150-225 L / ha, more preferably 180-200 L / ha, and even more preferably 190 L / ha. This ensures that the carbon fertilizer input per hectare is 12-15 g, and the amounts of potassium dihydrogen phosphate (50-250 g / ha), sugar alcohol calcium boron fertilizer (100-200 g / ha), and sugar alcohol zinc / chelated zinc (25-150 g / ha) are consistent with the total nutrient content in the drone scenario. Furthermore, the concentrations of each component are adapted to the volumetric spray characteristics of the spray boom machine, avoiding nozzle clogging and excessive nutrient application. The preferred spraying rate for high ground clearance boom sprayers is 150~225 L / ha, more preferably 180~200 L / ha, and can be adjusted to 225~300 L / ha in special dense crop scenarios.

[0024] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment is designed for smallholder farming conditions in Heilongjiang Province and implemented in the main corn-producing area of ​​Harbin City, Heilongjiang Province. The locally dominant, high-density-tolerant variety, Xianyu 335, was selected, with a planting density set at 70,000-75,000 plants / hectare, representing the upper limit of planting density currently achievable by farmers. The experimental field was typical meadow black soil with the following basic soil fertility: organic matter content 29.4 g / kg, total nitrogen 1.4 g / kg, available phosphorus 40.4 mg / kg, and available potassium 137.2 mg / kg. The previous crop was corn, sown on May 1st, using a 65cm equal row spacing planting pattern.

[0027] Specific technical measures: Fertilizer application: The total nitrogen fertilizer application should be controlled at 180 kg pure nitrogen / ha, of which 2 / 3 should be applied as basal fertilizer, applied in one go at sowing using a seed-fertilizer co-seeder; the remaining 1 / 3 of the nitrogen fertilizer should be applied as topdressing in the early jointing stage (V6 stage, when the 6th fully expanded leaf) in conjunction with deep tillage. Phosphorus and potassium fertilizers should be applied entirely as basal fertilizers, with phosphate fertilizer (P2O5) at a rate of 90-100 kg / ha and potassium fertilizer (K2O) at a rate of 90-100 kg / ha.

[0028] Carbon fertilizer supplementation plan: At the early jointing stage (V6 stage, the 6th fully expanded leaf), apply commercially available small-molecule carbon fertilizer simultaneously at a rate of 120 g / ha, mixed with the nitrogen fertilizer and applied using a modified fertilizer applicator. At the 12-leaf stage (V12) and the water-bubble stage (R2) of corn, use a plant protection drone for foliar spraying. The composition and ratio are: 250 mg / L small-molecule carbon fertilizer, 3000 mg / L potassium dihydrogen phosphate, 3000 mg / L sugar alcohol calcium boron fertilizer, and 1500 mg / L sugar alcohol zinc / chelated zinc. The drone operation rate is 50 L / ha. After mixing the components according to the above concentration ratio, dilute with water to the target volume. See the detailed diagram of root zone targeted carbon supply and canopy carbon supplementation. Figure 12 .

[0029] Key technical parameters: The location of topdressing is dynamically adjusted according to planting density. The calculation formula is: Row-to-side distance (cm) = 15 + 0.1 × (Actual density - 60000) / 1000. The fertilization depth is controlled at 18 cm to ensure that the fertilizer is applied to the main root distribution area. Drone operation parameters: Flight altitude 3 meters, speed 5 meters / second, droplet size 120 μm. Note: During actual mechanical operation, the row-to-side distance is allowed to be adjusted within ±1 cm. This deviation is within the normal operating error range of agricultural machinery.

[0030] Example 2

[0031] This example was implemented in the Hongxinglong Administration Bureau of Heilongjiang State Farms, using the high-density cultivar Dika 186, with a planting density increased to 85,000-90,000 plants / hectare. The experimental field was black soil with the following basic soil fertility: organic matter content 25.1 g / kg, total nitrogen 1.3 g / kg, available phosphorus 15.1 mg / kg, and available potassium 148.7 mg / kg. The previous crop was corn, sown on May 1st, using a dense planting method with a row spacing of 110 cm.

[0032] Specific technical measures: Fertilizer application: The total amount of nitrogen fertilizer should be maintained at 200 kg of pure nitrogen per hectare, of which 2 / 3 should be applied as basal fertilizer and 1 / 3 should be applied as top dressing at the early jointing stage (V6 stage, when the 6th fully expanded leaf). Phosphorus and potassium fertilizers should be applied entirely as basal fertilizer, with the following application rates: 100 kg / ha of P2O5 and 110 kg / ha of K2O, respectively.

[0033] Carbon fertilizer supplementation plan: The amount of carbon fertilizer applied to the root zone is increased by 50% based on Example 1, reaching 180 grams / ha. The amount of carbon supplemented by the leaves is increased by 30% simultaneously, with 16 grams / ha per spray each time.

[0034] Key technical parameters: Topdressing position 18 cm to the side of the row, depth 20 cm. A Case Magnum 340 tractor paired with a Haofeng 2BQM-6 fertilizer applicator is used, with an operating speed of 6 km / h. The drone flies at an altitude of 3 meters. In actual operation, the fertilizer application position can be adjusted within ±1 cm of the calculated value, which meets the requirements of agricultural machinery operation standards.

[0035] Comparative Example 1

[0036] Conventional model for farmers: Experimental Design: Representing the traditional smallholder farming methods in Heilongjiang Province, the experiment was conducted on the same plot of land in Songbei District, Harbin. The planting density was 50,000-55,000 plants / hectare, and the variety was Xianyu 335.

[0037] Management measures: The total nitrogen fertilizer application rate is 180 kg of pure nitrogen per hectare, all applied as a single basal application using compound fertilizer (N:P2O5:K2O=28-10-12, purchased from Heilongjiang Beifeng Agricultural Materials Group Co., Ltd.), without any topdressing. Field management includes only weeding during the seedling stage (atrazine + acetochlor) and later-stage control of corn borers (high-efficiency cyhalothrin). No foliar fertilizers or carbon fertilizers are applied.

[0038] Growth period performance: During the silking stage (July 30), the leaf SPAD value was only 51.2; the root dry weight was 5.8g / plant; the final yield was 7.8 tons / hectare, the grain moisture content was 28% (requires drying), and the barren tip rate was as high as 15%.

[0039] Comparative Example 2

[0040] Farm Standard Mode: Experimental Design: Representing the current standard management model of the state-owned farm system, implemented in the Hongxinglong Administration Bureau. Planting density: 80,000-85,000 plants / hectare; Variety: Dika 186.

[0041] Management measures: The total nitrogen fertilizer application rate is 200 kg pure nitrogen / ha, with 2 / 3 applied as basal fertilizer and 1 / 3 applied as top dressing at the early jointing stage (V6 stage, when the 6th fully expanded leaf). All phosphorus and potassium fertilizers are applied as basal fertilizer. Foliar spray with 0.3% potassium dihydrogen phosphate twice; no additional carbon fertilizer is needed. Top dressing should be applied at the center of the row (27-28 cm away).

[0042] Comparative Example 3

[0043] Carbon supplementation control mode: In addition to the farm's regular management practices, carbon fertilizer supplementation is added, but the traditional fertilization location is maintained.

[0044] Management measures: When applying fertilizer to the root zone, apply 180 grams of carbon fertilizer per hectare in the middle of the row (27-28 cm away).

[0045] Foliar spraying does not supplement carbon; other management practices are the same as in control ratio 2.

[0046] Experimental Example 1

[0047] At the 9-leaf stage (V9), 12-leaf stage (V12), silking stage (R1), mid-grain-filling stage (R3), and late-grain-filling stage (R5), two uniformly growing, continuously growing plants were selected from the third row on the same side of each plot. The green area of ​​the plant was measured: the length and maximum width of each leaf were measured. Based on the formula: Green Leaf Area = Leaf Length × Maximum Leaf Width × 0.75, the Leaf Area Index (LAI) was calculated as: Leaf Area per Plant (m²) 2 () × Number of plants per unit area / hectare of land area.

[0048] The relative chlorophyll content (SPAD value) of maize was measured at the 9-leaf stage (V9), 12-leaf stage (V12), silking stage (R1), mid-grain-filling stage (R3), and late-grain-filling stage (R5). The newest fully expanded leaf or ear leaf of each maize plant was selected (ear leaf during silking and grain-filling stages). A SPAD-502 PLUS chlorophyll meter (Konica Minolta, Tokyo, Japan) was used for measurement. Three points were measured on each side of the middle of the leaf, avoiding the midrib. The average value was taken as the single-leaf SPAD value. Five plants were measured in each plot, and the plot average SPAD value was calculated to reflect the relative chlorophyll content level of the plant. The cultivation effects of Examples 1-2 and Comparative Examples 1-3 were compared, and the results are as follows: Figures 1-11 As shown: The results showed that Example 1 exhibited significant technical advantages throughout the entire growth period of maize. From V12 to R5, the mean leaf area index (LAI) increased by 10.6%–82.2% compared to Comparative Example 1 (P<0.05 or P<0.01); by the R5 waxy maturity stage, the SPAD value increased by 7.4% (P<0.01), effectively delaying leaf senescence. Regarding root development, the root length per plant was significantly lower in stage V9 than in Comparative Example 1 (P<0.05), but increased by 8.0% in stage R3 (P<0.01) and by 20.8% in stage R6 (P<0.01). The root-to-shoot ratio increased by 3.6%–25.0% compared to Comparative Example 1 in stages R1, R3, and R6 (P<0.01). Optimization of root vertical distribution during the silking stage (R1): The proportion of root length in the 0-20cm soil layer significantly decreased to 55.1% (compared to 59.2% in Comparative Example 1, P<0.01), while the proportion in the 20-40cm soil layer significantly increased to 24.6% (P<0.01). Sap flow rate significantly increased by 7.4% in stages V12 and R3 (P<0.01). Overall, this technology optimizes the overall physiological development of maize during its growth period by promoting root penetration, maintaining root vigor, and delaying leaf senescence. Example 2 significantly outperformed Comparative Example 1 with a yield of 15.1 tons / ha, representing an 11.9% increase. Example 1's yield was comparable to Comparative Example 2 / 3, but significantly better than Comparative Example 1. Regarding lodging rate, there was no significant difference between Example 2 (8.0%) and Comparative Example 2 / 3 (7.6%). The lodging rate of Example 1 (14.5%) was significantly lower than that of Comparative Example 1 (19.3%), but higher than that of Example 2.

[0049] Example 2 demonstrated significant technical advantages at different growth stages of maize: at stage V9, the LAI (Leaf Intake) decreased by 10.9% compared to Comparative Example 2 (P<0.05), but significantly increased by 14.2-15.4% by stage R5 (P<0.01). Regarding chlorophyll retention, the SPAD value at stage R3 increased by 4.7% compared to Comparative Example 2 (P<0.05), and by 9%-11% at stage R5 (P<0.01). Significant advantages were also observed in root growth: at stage V12, the root length per plant increased by 12.2%-12.7% compared to Comparative Examples 2 and 3 (P<0.01), by 9.5%-11.4% at stage R1 (P<0.05), by 28.0%-29.7% at stage R3 (P<0.01), and by 23.6%-25.8% at stage R6 (P<0.01). Optimization of root vertical distribution during the silking stage (R1) significantly reduced the proportion of root length in the 0-20cm soil layer by 2.4%-2.7% (P<0.05). Regarding root vigor, sap flow rate increased by 8.9%-9.6% in R1 (P<0.01) and by 20.7%-21.2% in R3 (P<0.05). Overall, Example 2 achieved a mid-to-late growth advantage for maize by dynamically regulating LAI, enhancing chlorophyll retention, promoting root growth, and optimizing root distribution. Example 2 significantly outperformed Comparative Example 1 with a yield of 15.1 tons / ha, representing an 11.9% increase. Example 1's yield was comparable to Comparative Example 2 / 3, but significantly better. Regarding lodging rate, there was no significant difference between Example 2 (8.0%) and Comparative Example 2 / 3 (7.6%). Example 1's lodging rate (14.5%) was significantly lower than Comparative Example 1 (19.3%), but higher than Example 2.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for increasing maize yield through dense planting based on the synergy of root zone targeted carbon supply and canopy carbon supplementation, characterized in that, Includes the following steps: 1) Apply fertilizer at the early stage of jointing; 2) Apply foliar fertilizer during the V12 and R2 stages respectively; The location of the topdressing should be adjusted according to the planting density. The horizontal distance of the fertilization location is represented by D, in cm, and the planting density is represented by S, in plants / ha. The horizontal distance between the fertilization locations and the planting density satisfy the following relationship: D(cm)=15+0.1×(S-60000) / 1000; The topdressing in step 1) contains carbon fertilizer and urea. The amount of carbon fertilizer used is 120~150g / ha, and the mass ratio of carbon fertilizer to urea is carbon fertilizer: urea = 1:870~1330. The foliar fertilizer in step 2) for the V12 or R2 stage contains carbon fertilizer, and the concentration of carbon fertilizer is 53~375 mg / L; The application rate of foliar fertilizer in the V12 or R2 stage is 40~225L / ha; The carbon fertilizer contains carbon nanotubes, graphene oxides, or carbon quantum dot materials.

2. The method for increasing maize yield through dense planting according to claim 1, characterized in that, The molecular weight of the carbon fertilizer is <1000 Da.

3. The method for increasing maize yield through dense planting according to claim 1, characterized in that, The foliar fertilizer also includes components at the following concentrations: Potassium dihydrogen phosphate 222~6250 mg / L, sugar alcohol calcium boron fertilizer 444~5000 mg / L, sugar alcohol zinc / chelated zinc 111~3750 mg / L.

4. The method for increasing maize yield through dense planting according to claim 1, characterized in that, The application depth of the topdressing fertilizer is 15-22cm.

5. The method for increasing maize yield through dense planting according to claim 1, characterized in that, The method for increasing corn yield through dense planting also includes the application of basal fertilizer, the amount of which is as follows: N 120~147kg / ha, P2O5 90~110kg / ha, K2O 90~120kg / ha.

6. The method for increasing maize yield through dense planting according to claim 1, characterized in that, The application methods for the foliar fertilizer include drone operation or boom spraying.

7. The method for increasing maize yield through dense planting according to claim 6, characterized in that, The drone operates at a speed of 3-5 m / s and a flight altitude of 2-4.5 m. The sprayed pesticide droplets have a diameter of 80-120 μm and a coverage density of 30-40 drops / cm². 2 .

8. The method for increasing maize yield through dense planting according to claim 6, characterized in that, During the operation of the boom sprayer, the boom height is 1.5~2.5m, the working pressure of the boom sprayer is 2.0~2.5bar, and the spraying speed is ≤4km / h.

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