Corn zonewise precision fertilization method suitable for high-density planting in black soil of northeast cold region

Abstract

The application discloses a corn zonewise precision fertilization method suitable for high-density planting in black soil in northeast cold regions, belongs to the technical field of high-density cultivation in northeast cold regions, and solves the technical problems that, when facing the high-density planting conditions in northeast cold regions, the fertilizer utilization rate is low, the yield increasing potential is limited, and the regional farmland ecological environment is threatened, and the like. Step 1, a planting function zone is divided for a target planting area; step 2, based on the division result of the planting function zone, routine element fertilization is carried out on different planting function zones in the whole growth period; and step 3, based on the division result of the planting function zone, base fertilization and growth period topdressing of medium and trace elements are carried out on different planting function zones, so that the corn zonewise precision fertilization is realized. The application is used for realizing the corn zonewise precision fertilization.

Description

Technical Field

[0001] This invention relates to the field of high-density cultivation technology in the cold regions of Northeast China, specifically to a method for precise fertilization of maize in strips for high-density planting in the black soil of the cold regions of Northeast China. Background Technology

[0002] The Northeast Plain is a major corn-producing region in my country, its core advantage lying in its unique cold-region black soil resources. The deep black soil layer, high organic matter content, and good soil structure provide a natural fertility foundation for high and stable corn yields. In recent years, with the advancement of initiatives to increase corn yield per unit area, high-density cultivation has become the core approach to tapping the region's production potential.

[0003] In the cold, black soil region of Northeast China, maize fertilization methods are diverse, with a common practice under rainfed conditions: a single, concentrated basal application. This method easily leads to exacerbated nitrogen loss, manifesting as non-productive losses such as ammonia volatilization and nitrate leaching due to excess inorganic nitrogen in the soil during the early growth stage, and premature senescence and nutrient deficiency induced by nitrogen supply shortages in the later growth stage, resulting in a decline in both yield and quality. Even in some areas where topdressing is used in the Northeast cold-region planting scenario, the nitrogen conversion rate is slowed by spring drought, low temperatures, and freeze-thaw cycles, with significant losses occurring through ammonia volatilization and nitrate leaching. This not only reduces fertilizer utilization but also poses a potential threat to the regional farmland ecosystem. Furthermore, high-density planting in the Northeast cold-region introduces population structure stress, further amplifying the spatial and temporal misalignment of fertilizer supply and demand, leading to a further decrease in the efficiency of conventional fertilization strategies.

[0004] In summary, existing technologies suffer from low fertilizer utilization and limited yield potential when faced with high-density planting conditions in the cold regions of Northeast China, and also pose a potential threat to the regional farmland ecological environment. Summary of the Invention

[0005] This invention solves the technical problems of low fertilizer utilization, limited yield potential, and potential threats to the regional farmland ecological environment when facing high-density planting conditions in the cold Northeast region.

[0006] The method for precise fertilization of maize in strips for high-density planting in the cold black soil of Northeast China, as described in this invention, includes the following steps: Step 1: Divide the target planting area into functional planting zones; Step 2: Based on the results of the planting functional zone division, apply conventional element fertilization throughout the entire growth period to different planting functional zones; Step 3: Based on the results of the planting functional zone division, apply micronutrients as basal fertilizer and top dressing during the growth period to different planting functional zones to achieve precise fertilization of corn by zone.

[0007] Furthermore, in one embodiment of the present invention, the division of the target planting area into planting functional zones in step 1 specifically involves: Step 11: Obtain the multi-parameter soil dataset for the target planting area; Step 12: Calculate the soil comprehensive fertility index (SFI) based on the soil multi-parameter dataset; Step 13: Complete the division of planting functional zones based on the Soil Fertility Index (SFI).

[0008] Furthermore, in one embodiment of the present invention, the comprehensive fertility index SFI in step 12 specifically refers to: ; Wherein, Nnorm, Pnorm, Knorm, and pHnorm are the standardized parameter values ​​of available nitrogen, available phosphorus, available potassium, and pH, respectively. These are the weighting coefficients. It is a fast-acting nitrogen, For available phosphorus, It is a fast-acting potassium. This refers to pH level.

[0009] Furthermore, in one embodiment of the present invention, step 13, which involves dividing planting functional zones based on the Soil Fertility Index (SFI), specifically includes: When SFI≥0.6, it is designated as the core maize growth zone; When 0.4 ≤ SFI < 0.6, it is designated as a buffer zone for maize growth; When 0.2 ≤ SFI < 0.4, it is classified as a marginal zone; When SFI < 0.2, it is designated as an ecological protection zone.

[0010] Furthermore, in one embodiment of the present invention, step 2 involves applying conventional elemental fertilization throughout the entire growth period to different planting functional zones, specifically as follows: For areas designated as core maize growing zones, apply 345-375 kg of pure nitrogen, 195-225 kg of P2O5, and 150-225 kg of K2O per hectare throughout the entire growth period. For areas designated as buffer maize growing zones, apply 285-315 kg of pure nitrogen, 165-195 kg of P2O5, and 120-165 kg of K2O per hectare throughout the entire growth period. For areas designated as marginal zones, apply 195-225 kg of pure nitrogen, 120-150 kg of P2O5, and 90-120 kg of K2O per hectare throughout the entire growth period.

[0011] Furthermore, in one embodiment of the present invention, in the conventional element fertilization throughout the entire growth period, the pure nitrogen applied as base fertilizer is selected as slow-release nitrogen fertilizer, and a phosphorus-solubilizing and potassium-solubilizing bacterial agent is mixed and added to the base fertilizer.

[0012] Furthermore, in one embodiment of the present invention, the application of micronutrients to different planting functional zones in step 3 specifically includes: During the land preparation stage before sowing, zinc, boron, silicon-calcium, magnesium, and iron fertilizers should be applied at the first benchmark rate for areas designated as core maize growing zones. For areas designated as buffer maize growing zones, silicon-calcium fertilizer should be applied at a rate 20%-30% higher than the first benchmark rate, and zinc and boron fertilizers should be applied at a rate 10%-15% higher than the first benchmark rate. For areas designated as edge zones, zinc and boron fertilizers should be applied at a rate 30% to 50% higher than the first benchmark rate, iron fertilizer at a rate 50% to 100% higher than the first benchmark rate, and magnesium fertilizer at a rate 25% to 35% higher than the first benchmark rate. No micronutrient fertilizers should be applied to areas designated as ecological protection zones.

[0013] Furthermore, in one embodiment of the present invention, the first reference amount is 5-8 kg of zinc fertilizer, 2-3 kg of boron fertilizer, 75-120 kg of silicon-calcium fertilizer, 30-45 kg of magnesium fertilizer and 10-15 kg of iron fertilizer per hectare.

[0014] Furthermore, in one embodiment of the present invention, the topdressing during the growth period in step 3 is applied during the growth period of the core maize growing zone, specifically as follows: During the corn seedling stage, apply 450-600 liters / hectare of zinc sulfate solution with a concentration of 0.1%-0.2% and 450 liters / hectare of manganese sulfate solution with a concentration of 0.5%-1.0% as foliar sprays. During the jointing stage of corn, apply 40-75 kg / ha of silicon-calcium fertilizer as top dressing, and spray 450 liters / ha of magnesium sulfate solution with a concentration of 1%-2% on the leaves. During the corn's tasseling stage, apply 450 liters / hectare of a 0.1%-0.2% borax solution and 450 liters / hectare of a 0.5% sodium silicate solution as foliar sprays.

[0015] Furthermore, in one embodiment of the present invention, when the local temperature is below 5°C, the SFI inclusion threshold of the core maize growing zone is lowered to 0.50; when the local temperature is between 5°C and 10°C, the SFI inclusion threshold of the core maize growing zone is lowered to 0.55; when the local temperature rises to above 10°C, the SFI inclusion threshold of the core maize growing zone remains unchanged at 0.60.

[0016] The specific beneficial effects of this invention include: 1. This invention proposes a precise fertilization method for corn in high-density planting in the cold black soil of Northeast China. By dynamically dividing the planting functional zones through the comprehensive soil fertility index under ground temperature correction, and combining it with the basal application of slow-release nitrogen fertilizer, the fertilizer can continuously and stably supply nutrients throughout the corn's growth process, significantly improving fertilizer utilization efficiency and reducing potential threats to the regional farmland ecological environment. 2. This invention proposes a method for precise fertilization of maize in strips for high-density planting in the cold black soil of Northeast China. By adopting a differentiated fertilization strategy in strips, it effectively alleviates the contradiction of nutrient supply and demand mismatch between plants under dense planting conditions, and makes fertilizer supply and population demand more matched in space and time, thereby breaking through the technical bottleneck of low fertilizer utilization and limited yield potential under high-density cultivation mode. 3. This invention proposes a precise fertilization method for maize grown in high-density black soil in the cold region of Northeast China, establishes a differentiated micronutrient supplementation mechanism for different zones, and constructs a long-term slow-release basal application and topdressing system for micronutrients throughout the entire growth period, so that the supply of micronutrients meets the needs of maize at all growth stages in the cold region, and further improves fertilizer utilization efficiency and crop yield and quality. 4. This invention proposes a method for precise fertilization of maize in strips for high-density planting in the cold black soil of Northeast China. It introduces a freeze-thaw risk correction mechanism to dynamically expand the buffer distance of the ecological protection zone along the river and lake shoreline in areas with high freeze-thaw intensity and concentrated snowmelt runoff. This controls the lateral migration of non-point source pollutants to water bodies during the freeze-thaw period from the source, achieving both increased yield from high-density planting and ecological protection of the black soil. Attached Figure Description

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of the precision fertilization method for high-density planting of corn in the cold black soil of Northeast China, as described in Implementation Method 1. Detailed Implementation

[0018] Various embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] Implementation Method 1: A precise fertilization method for high-density corn planting in the cold black soil of Northeast China, comprising the following steps: Step 1: Divide the target planting area into functional planting zones; Step 2: Based on the results of the planting functional zone division, apply conventional element fertilization throughout the entire growth period to different planting functional zones; Step 3: Based on the results of the planting functional zone division, apply micronutrients as basal fertilizer and top dressing during the growth period to different planting functional zones to achieve precise fertilization of corn by zone.

[0020] Current technologies, when faced with high-density planting conditions in the cold regions of Northeast China, suffer from low fertilizer utilization rates, limited yield potential, and exacerbate potential threats to the regional farmland ecological environment. Meanwhile, while the black soil of Northeast China has relatively high basic fertility, the long-term reliance on nitrogen, phosphorus, and potassium (the "old three") fertilization practices has led to increasingly prominent soil nutrient imbalances and degradation. The long-term excessive application of macronutrient fertilizers, neglecting the supplementation of micronutrients, results in deficiencies in the soil, limiting crop yield and quality, weakening plant resistance, and damaging soil aggregate structure, leading to compaction and reduced water and fertilizer retention capacity.

[0021] To address the aforementioned technical issues, this embodiment proposes a precise fertilization method for maize grown in strips on high-density black soil in the cold regions of Northeast China, specifically including the following steps: Step 1: Divide the target planting area into functional planting zones; By combining high-precision positioning using the Global Navigation Satellite System (GNSS) with multi-parameter soil sensors, the planting area is divided into different levels of maize planting zones based on soil fertility and ecological function.

[0022] Step 11, High-precision positioning and placement. Establish a spatial benchmark to ensure that each soil monitoring point has centimeter-level spatial coordinates, providing accurate geographical reference for subsequent spatial interpolation and boundary delineation.

[0023] Step 111, GNSS System Selection Employing RTK-GNSS (Real-time Dynamic Differential Positioning) technology, positioning accuracy can reach the centimeter level (horizontal error ≤2cm, elevation error ≤3cm). It supports multi-system fusion (GPS, BeiDou, GLONASS, Galileo) to ensure stable high-precision coordinate acquisition even in signal-blocked areas such as forest edges and valleys in the cold regions of Northeast China.

[0024] Step 112, Sampling Grid Design The basic grid unit is 30m×30m or 50m×50m, covering the entire target planting area. In areas with significant soil variation (such as transitional zones and undulating terrain), the grid is densified to 15m×15m to improve the spatial resolution of boundary identification. Permanent GNSS control stakes are deployed at the four corners and center of the area for coordinate registration and data fusion during multi-period monitoring.

[0025] Step 12, in-situ data collection using multi-parameter soil sensors. Key soil parameters at each sampling point are acquired in real time, and a multi-parameter soil dataset of the target planting area is obtained, providing a data foundation for functional zone division.

[0026] Step 121, Sensor Selection and Deployment Portable or stationary soil multi-parameter sensors can be used to measure parameters simultaneously: Table 1

[0027] Step 122, Data Acquisition Strategy Data collection during critical growth periods: Systematic data collection was conducted three times, before sowing, at the jointing stage, and after harvest.

[0028] Stratified sampling: Measurements were taken at two layers, 0–20 cm and 20–40 cm, to identify the distribution characteristics of nutrients in the topsoil and sub-topsoil layers.

[0029] In-situ measurement: The sensor is directly inserted into the soil for in-situ measurement, avoiding data lag and errors during sampling, transportation and laboratory analysis.

[0030] Steps 1, 2, and 3: Real-time data upload The sensor transmits measurement data and GNSS coordinates wirelessly via Bluetooth, 4G / 5G or LoRa, uploading them to the cloud data center in real time to form a three-dimensional data matrix of space, time and parameters.

[0031] Step 13, Functional band classification based on cold-region adaptability threshold Based on soil fertility and ecological function, the grid units are divided into different levels of maize planting zones and ecological protection zones.

[0032] Step 131, Calculation of Comprehensive Fertility Index The division of maize planting zones is based on the Soil Fertility Index (SFI), which is calculated by weighting available nitrogen, available phosphorus, available potassium, and pH value. Specifically: ; Wherein, Nnorm, Pnorm, Knorm, and pHnorm are the standardized parameter values ​​of available nitrogen, available phosphorus, available potassium, and pH, respectively. These are the weighting coefficients. It is a fast-acting nitrogen, For available phosphorus, It is a fast-acting potassium. For pH, the stated and The values ​​are 0.4, 0.3, 0.2, and 0.1 respectively. When the planting density of corn is ≥60,000 plants / hectare, the weighting coefficient of available potassium is adjusted. Adjusted to 0.25.

[0033] The pH value mentioned in this embodiment is the pH value of the soil. In the formula for calculating the comprehensive soil fertility index, the four parameters (available nitrogen, available phosphorus, available potassium, and pH) must be weighted and summed on the same scale. However, their original dimensions are completely different: 1) Available nitrogen: mg / kg, range 0-100; 2) Available phosphorus: mg / kg, range 0-80; 3) Available potassium: mg / kg, range 50-400; 4) pH value: dimensionless, with a value range of 0-14, and has a central optimum characteristic (neither higher nor lower is better).

[0034] If the raw values ​​are not standardized and the SFI is calculated directly, the contribution of pH to the total score will be affected by the values ​​of available nitrogen, available phosphorus and available potassium, and the correction effect of pH will be lost. Therefore, this implementation method maps the raw data of different dimensions to a unified range of [0,1], so that the SFI will eventually become a dimensionless comprehensive evaluation value with a value range of [0,1].

[0035] In this implementation, the weighting coefficients are determined based on the nutrient requirements of maize in the cold black soil of Northeast China and the actual risks of high-density planting. Nitrogen has the highest weight (0.4) because nitrogen is the primary limiting factor for maize yield; a low weight would lead to incorrect zoning of nitrogen-deficient areas, resulting in reduced yields. Phosphorus has the second highest weight (0.3) because phosphorus is crucial for root and grain development; a high weight would mask nitrogen deficiency, while a low weight would ignore the role of phosphorus. Potassium has a relatively low base weight (0.2) because black soil has abundant potassium, which is sufficient for demand at normal densities, but the potassium weight needs to be increased to prevent lodging risks during high-density planting. pH has the lowest weight (0.1) as a correction for nutrient availability; a weight of zero would ignore the impact of acid-base barriers on nutrient uptake. This set of weights is set according to the primary and secondary nutrient limitations, and a dynamic adjustment of the potassium weight is introduced for high-density scenarios. Using other values ​​would lead to inaccurate zoning or underestimation of specific risks. The specific reasons are as follows: First, in the four-factor weighted model, if the weight of a certain factor exceeds 0.5, the combined contribution of the remaining three factors (wP=0.3, wK=0.2, wpH=0.1) is compressed to 0.5 or 0.4. At this time, the SFI calculation result will be highly similar to the single nitrogen index, and the SFI difference between zones mainly reflects the difference in nitrogen rather than the difference in comprehensive soil fertility. The "comprehensive" value of zone division is severely weakened. Second, the phosphorus weight (wP=0.3) will be relatively devalued when wN=0.5 (the actual contribution is only 60% of nitrogen). However, the key role of phosphorus in root development (early stage) and grain filling (late stage) is equally important in the cold Northeast region (root elongation is hindered at low temperatures and sufficient phosphorus nutrition is required). Finally, the total SFI weight = 1. If wN=0.4, then wP+wK+wpH=0.6. If wN is increased to 0.5, the sum of the remaining three factors is 0.5, which means that the sum of wP=0.3, wK=0.2, and wpH=0.1 is 0.6, which is greater than 0.5 and exceeds the allowable range. If wN=0.6, then wP+wK+wpH=0.4, with an average of only 0.133 per factor, which completely fails to reflect the hierarchical difference between phosphorus and potassium as the main nutrient elements and pH as the correction factor.

[0036] When corn planting density reaches a certain threshold, the plants become denser, significantly intensifying competition for nutrients, water, and light among the corn plants. Conventional soil fertility evaluation methods typically assign fixed weights to each nutrient, without considering planting density. Potassium plays a crucial role in the robustness and breakage resistance of corn stalks. Insufficient potassium supply makes densely planted corn more prone to weak stalks and excessively long internodes, ultimately impacting yield. Therefore, this implementation method adjusts the weighting coefficient for available potassium to prioritize potassium supply in subsequent fertilization plans, ensuring fertilizer allocation better meets the actual needs of densely planted corn.

[0037] Step 132, grading threshold The SFI threshold for planting zones is determined based on the actual soil fertility of the Northeast black soil. An SFI above 0.6 indicates sufficient soil nutrients, and conventional fertilization can meet the high-yield requirements; thresholds that are too high or too low will affect yield. An SFI between 0.4 and 0.6 indicates moderate soil fertility, requiring adjustments to fertilization strategies to compensate for deficiencies. An SFI between 0.2 and 0.4 indicates significant nutrient deficiency, limiting planting benefits. An SFI below 0.2 indicates extremely poor soil fertility, making it difficult to recover input costs; such areas are designated as ecological protection zones. Furthermore, areas with strong acid or alkalinity, steep slopes, or proximity to water bodies are also included in the protection zones. Considering the characteristics of cold regions, the core threshold is lowered to 0.55 in low-temperature zones to compensate for delayed nutrient release, and the water buffer zone is expanded to 100 meters in high-risk freeze-thaw zones to enhance nitrogen interception.

[0038] Table 2

[0039] Step 133, Standards for Delineating Ecological Protection Zones If any of the following adverse factors exist, such as extremely low soil productivity, acid-base imbalance, topographical risk, or water pollution risk, the site should not continue to be used as a high-yield agricultural input area, but should be primarily used for ecological restoration.

[0040] Table 3

[0041] Step 134, Cold-region adaptation threshold correction To address the issue of delayed soil nutrient release due to the slow rise in soil temperature in early spring in the cold regions of Northeast China, this implementation method introduces a soil temperature grading correction mechanism. The soil temperature at a depth of 5 cm before and after sowing is used as the criterion: when the soil temperature is below 5℃, the frozen soil layer has not completely thawed, and root absorption capacity is extremely weak; at this time, the soil nutrient availability (SFI) threshold for the core maize growth zone is lowered to 0.50. When the soil temperature is between 5℃ and 10℃, microbial activity is still inhibited, and nutrient release is slow; the threshold is lowered to 0.55. When the soil temperature rises above 10℃, soil nutrient availability is basically restored, and the threshold remains unchanged at 0.60. 5℃ and 10℃ are chosen as grading nodes because 10℃ is the critical temperature at which soil microbial activity begins to increase, while 5℃ is the inflection point where microbial activity significantly decreases; below these temperatures, there is no need to apply exogenous nitrogen. Without the above correction, if farmers apply fertilizer according to the conventional threshold, the fertilizer cannot be effectively absorbed due to the low soil temperature, resulting in yields far below expectations and a significant decrease in the input-output ratio.

[0042] To address the risk of non-point source pollution from snowmelt runoff during the spring freeze-thaw season in the cold regions of Northeast China, this implementation plan introduces a quantitative classification mechanism for freeze-thaw risk. Five indicators are used for comprehensive assessment: maximum annual freezing depth, number of annual freeze-thaw cycles, duration of runoff during the snowmelt season, annual non-point source pollutant input, and topographic features. Areas with a freezing depth exceeding 120 cm, more than 5 annual freeze-thaw cycles, less than 15 days of runoff duration, pollutant input exceeding 15 kg / hectare / year, or located in floodplains are classified as high-risk freeze-thaw zones, requiring prior adjustment of protection strategies. In late March each year, the freeze-thaw process in the cold regions of Northeast China is intense. The snowmelt process washes away topsoil particles and organic matter, and the nitrogen adsorbed on these particles enters water bodies, forming non-point source pollution. A standard 50-meter riverbank buffer zone can intercept the first peak runoff in normal years. However, in years with exceptionally heavy snowmelt, the runoff accounts for 40-50% of the total annual volume, and the second wave of pollution peaks extends to a range of 50-100 meters, with approximately 30-50% of the runoff directly entering water bodies. Referring to relevant domestic and international standards, the buffer zone for high-risk freeze-thaw zones will be dynamically expanded from 50 meters to 100 meters. This will comprehensively cover the pollution peak range in exceptionally high-risk years while providing a safety margin for interannual runoff fluctuations. Beyond 100 meters, the output of soil particles and organic matter significantly decreases, limiting the marginal benefits of further expansion. Therefore, in areas with high freeze-thaw intensity and concentrated snowmelt runoff, the buffer zone along river and lake shorelines will be expanded from 50 meters to 100 meters, and ecological protection zones will be strictly delineated.

[0043] Step 2: Based on the functional zone division results, apply conventional element fertilization throughout the entire growth period to different planting functional zones. The specific plan is as follows: 1. Core corn growing zone Fertilization strategy: Increase nitrogen, phosphorus and potassium application in a coordinated manner.

[0044] Table 4. Fertilizer application rate per hectare throughout the entire growth period of the core maize growing zone.

[0045] 2. Buffer zone for corn growth Fertilization strategy: Moderate reduction in fertilizer use.

[0046] Table 5. Fertilizer application rate per hectare throughout the entire growth period of the buffer maize growing zone.

[0047] 3. Border areas Fertilization strategy: reduce nitrogen, stabilize phosphorus, and increase organic matter.

[0048] Table 6. Fertilizer application rate per hectare throughout the entire growth period in marginal areas

[0049] With the implementation of engineering measures such as straw return to the field, increased application of organic fertilizer, and deep tillage, the soil fertility in this area is gradually being improved, transforming year by year into a buffer zone for corn growth and even a core zone for corn growth.

[0050] In this embodiment, a low-temperature response strategy is adopted: Slow-release fertilizers are selected as base fertilizers: resin-coated urea or stable fertilizers are used to slowly release nutrients according to changes in soil temperature and humidity. The release rhythm is more in line with the nutrient requirements of corn in cold regions during its growth period, effectively solving the contradiction of too rapid fertilization in the early stage and nutrient deficiency in the later stage, and achieving stable growth throughout the season with one application of fertilizer.

[0051] Synergistic effect of microbial agents: Adding phosphorus and potassium solubilizing agents (such as Bacillus megaterium and Bacillus spp.) to base fertilizer can maintain a certain level of activity even under low temperature conditions, promote the activation and transformation of insoluble phosphorus and potassium in the soil, and make up for the problem of insufficient microbial activity in cold regions at low temperatures.

[0052] In one embodiment of this method, the soil fertility index (SFI) in the high-altitude cold region of northern Heilongjiang Province was 0.22, the pH was 5.8, the organic matter content was 28 grams per kilogram, the available phosphorus was only 18 milligrams per kilogram, and the available potassium was only 85 milligrams per kilogram, classifying it as a typical low-fertility marginal zone. Before sowing, 120 kg of pure nitrogen, 45 kg of phosphorus pentoxide, and 30 kg of potassium oxide were applied per hectare as basal fertilizer, along with 1800 kg of organic fertilizer. Simultaneously, a phosphorus- and potassium-solubilizing agent, a 1:1 mixture of Bacillus megaterium and Bacillus mucilaginosus, was applied at a rate of 30 kg per hectare. 15 kg was spread with the basal fertilizer and then lightly tilled into the soil, while the remaining 15 kg was applied as topdressing. After one harvest, the available phosphorus in the topsoil increased to 36 milligrams per kilogram, and the available potassium increased to 142 milligrams per kilogram, resulting in a corn yield increase of approximately 10% compared to the control group without the agent.

[0053] In this embodiment, population control under high-density planting is adopted: Under high-density planting conditions (planting density ≥ 60,000 plants / hectare), chemical regulation is needed to control plant height in this area to prevent lodging and disease risks caused by overcrowding. Topdressing should mainly consist of nitrogen fertilizer, but the amount must be strictly controlled to avoid excessive vegetative growth.

[0054] Table 7 Examples of plant height control using chemical regulation

[0055] 4. Ecological Protection Area Fertilization strategies: nitrogen reduction and pollution control, as well as ecological isolation.

[0056] Table 8 shows the nitrogen reduction and pollution control strategies implemented in ecological protection areas: applying only phosphorus and potassium fertilizers and no or little nitrogen fertilizer to control agricultural non-point source pollution from the source.

[0057] Table 8

[0058] Establish physical isolation zones (≥5m wide) between ecological protection zones and other planting zones (planting alfalfa or other green manure crops) to reduce lateral nutrient migration and protect water quality.

[0059] Step 3: Based on the results of the planting functional zone division, apply micronutrients as basal fertilizer and top dressing during the growing season to different planting functional zones.

[0060] The black soil of Northeast China has relatively high basic fertility, but the long-standing reliance on nitrogen, phosphorus, and potassium fertilization has led to a growing deficiency of micronutrients. Therefore, this implementation plan designs a systematic micronutrient supplementation scheme: Table 9

[0061] Step 31, Supplementation of medium-quantity elements (Ca, Mg, S, Si) Calcium (Ca): Applying 75-120 kg of quicklime or gypsum per hectare can regulate soil acidity, enhance root activity, and promote crop absorption of nitrogen and phosphorus.

[0062] Magnesium (Mg): Apply 30-45 kg / ha of magnesium sulfate heptahydrate as a base fertilizer, and spray the leaves with a 1%–2% magnesium sulfate solution during the jointing stage to supplement the magnesium element necessary for chlorophyll synthesis.

[0063] Sulfur (S): Apply sulfur or ammonium sulfate as a base fertilizer at a rate of 30-45 kg / ha to supplement the sulfur element required for protein synthesis and to regulate soil pH.

[0064] Silicon (Si): Applying silicon-calcium fertilizer, with a benchmark amount of 75-120 kg / ha in the core corn growth zone, can enhance stem strength and significantly improve lodging resistance, which is especially important for high-density planting. Apply 40-75 kg / ha of silicon-calcium fertilizer during the corn jointing stage, and spray the leaves with a 0.5% sodium silicate solution during the corn tasseling stage.

[0065] Iron (Fe): For areas designated as marginal zones, apply iron fertilizer at a rate 25% to 40% higher than the first baseline amount.

[0066] Table 10

[0067] Step 32, Micronutrient supplementation (Zn, B, Mn, Cu) Zinc (Zn): Apply zinc sulfate as a base fertilizer, with a baseline application rate of 5-8 kg / ha in the core maize growing zone, and spray 0.1%-0.2% zinc sulfate solution on the leaves when maize is at the 3-5 leaf stage. Zinc is a cofactor of carbonic anhydrase and is crucial for low temperature resistance and nitrogen metabolism.

[0068] Boron (B): Apply borax as a base fertilizer, with a standard application rate of 2-3 kg / ha in the core maize growing zone, and foliar spray with 0.1%-0.2% borax solution during the large trumpet stage to promote pollen tube elongation and increase seed setting rate.

[0069] Manganese (Mn): During the seedling stage of corn, foliar spraying with manganese sulfate solution (concentration 0.5%-1.0%) has a significant effect on enhancing leaf photosynthesis and improving stress resistance.

[0070] Copper (Cu): In copper-deficient areas, applying 3-5 kg / ha of copper sulfate as a base fertilizer or foliar spray can improve crop disease resistance.

[0071] Table 11

[0072] In this implementation, the dosage of each micronutrient was specifically adjusted based on the actual needs of high-density planting in cold regions, rather than directly adopting empirical values ​​from conventional production areas. In early spring, soil temperatures are low in cold regions, significantly reducing zinc availability. The basal application rate in the core area is set at 5-8 kg per hectare, while in the peripheral areas with even worse soil conditions, it is increased by 30-50%. Simultaneously, foliar zinc supplementation during the seedling stage is applied to prevent white bud symptoms. Boron availability in cold soils is already low, and the demand for boron during female ear development is further increased under high-density planting. The basal application rate in the peripheral areas is increased to 3-5 kg ​​per hectare, with an additional foliar spray at the large trumpet stage to reduce the risk of flowering without fruit set. The buffer zone experiences the greatest lodging pressure in high-density planting. The basal application rates of calcium and silicon are 20-30% higher than conventional rates, with silicon applied twice more during the jointing and large trumpet stages. The total silicon usage throughout the entire growth period is approximately two to three times that of conventional densities. The soil in the peripheral areas is alkaline, making iron easily fixed. The basal application rate of iron is significantly higher than conventional rates, and foliar spraying is used to correct yellowing when it occurs. Magnesium absorption efficiency decreases under low temperature conditions, and high-density populations with large leaf areas consume more magnesium. The amount of basal application should be increased by 30% to 100% compared to the conventional method, and foliar application should be carried out during the jointing stage.

[0073] In this embodiment, according to the National Standard for Cultivated Land Quality (GB / T 33469-2016), the soil organic matter content is classified as follows: Table 12

[0074] In agricultural practice, an organic matter content of ≥ 2.0% is generally considered to be at a high level, which is also the basic fertility characteristic of the Northeast Black Soil Region (the organic matter content of black soil is generally between 2% and 5%).

[0075] Step 33: Differentiated application of micronutrient base fertilizers in different planting zones Table 13

[0076] Core corn growing zone: Maintain basic supplementation with micronutrient fertilizers to ensure high yield and quality, and apply according to standard dosage.

[0077] Buffering the corn growing zone: Based on the standard dosage, the dosage of Ca and Si is specifically increased to cope with the risk of lodging in high-density planting. The increase is determined based on the effect value of field trials (the contribution rate of Ca and Si to lodging resistance is about 15%–25%).

[0078] Marginal areas: The soil has low basic fertility and poor root activity. Micronutrients and trace elements should be added to correct the long-term nutrient imbalance, while organic fertilizers should be used to improve soil biological activity.

[0079] Incremental baseline: The standard usage of each element in the core area is taken as 100% baseline.

[0080] Quantitative explanation of different trace elements: 1. Zinc (Zn) Zinc is a cofactor for carbonic anhydrase and is crucial for low-temperature resistance and nitrogen metabolism. In buffer maize growing zones, a moderate increase of 10%–15% (6–8 kg / ha) is recommended, while in peripheral zones, a significant increase of 30%–50% (7–12 kg / ha) is advised. In the cold regions of Northeast China, early spring low temperatures significantly reduce zinc availability; increasing basal zinc application can compensate for absorption barriers caused by low temperatures.

[0081] 2. Boron (B) Boron promotes pollen tube elongation and ear development. Increase boron application by 10%–15% (2.5–3.5 kg / ha) in the buffer zone of maize growth, and by 30%–50% (3–5 kg / ha) in the marginal zones. In marginal zones with low soil organic matter content, the risk of boron leaching is higher, requiring appropriately increased application rates.

[0082] 3. Calcium (Ca) and Silicon (Si) – Key Enhancements for Buffering Corn Growth Zone Calcium: Apply 75–150 kg / ha of lime as basal fertilizer to the core maize growing zone (to adjust soil acidity); increase by 20%–30% to 90–150 kg / ha for the buffer maize growing zone, while also taking into account the need for improvement of acidic black soil.

[0083] Silicon: Apply 75–120 kg / ha of silicon-calcium fertilizer to the core maize growing zone; increase to 90–150 kg / ha by 20%–30% in the buffer maize growing zone. Silicon's lodging resistance can improve stem penetration strength by 8%–15%, which is especially important for high-density planting (≥60,000 plants / ha).

[0084] 4. Iron (Fe) and Magnesium (Mg) – Key supplements for peripheral areas Iron (Fe): The soil pH in marginal areas is high (alkaline), and the availability of iron is low. Therefore, apply 15–25 kg / ha of ferrous sulfate as a base fertilizer and spray 450–600 liters / ha of 0.3%–0.5% ferrous sulfate solution on the leaves during the seedling to jointing stage to correct iron deficiency chlorosis.

[0085] Magnesium (Mg): The organic matter content in the peripheral areas is low, and the risk of magnesium leaching is high. Therefore, apply 40-60 kg / ha of magnesium sulfate heptahydrate as a base fertilizer (25%-35% more than in the core area) and supplement with foliar spraying.

[0086] 5. Ecological protection zone (SFI<0.2) – No micronutrient fertilizers should be applied. Ecological reserves are primarily designed to restore soil fertility and ecological functions. Excessive human input of nutrients may disrupt the ecological balance, therefore micronutrient fertilizers are not applied.

[0087] Table 14. Full-cycle fertilization history of micronutrient fertilizers (example)

[0088] Step 4, Dynamic Optimization of Topdressing By combining the vegetation index inversion results from UAV remote sensing at the jointing and tasseling stages, growth status diagnosis was conducted on the maize growth zone, and variable-rate topdressing was implemented: Step 41, Acquisition of UAV Remote Sensing Data During the corn's jointing stage (6-8 unfolded leaves) and the large trumpet stage (10-15 days before tasseling), select sunny, windless weather (10:00-14:00, during periods of stable sunlight) to conduct low-altitude remote sensing data collection using a drone equipped with a multispectral sensor. The flight altitude is typically set at 30-80 meters, with a forward overlap of ≥70% and a lateral overlap of ≥60%, achieving a ground resolution of 2-5 cm / pixel.

[0089] Step 42, Vegetation index inversion and growth diagnosis After preprocessing, vegetation indices for each field or grid cell are extracted from the original images: NDVI (Normalized Difference Vegetation Index) reflects crop greenness and cover; GNDVI (Green Normalized Difference Vegetation Index) is sensitive to nitrogen changes; and NDRE (Red Normalized Difference Vegetation Index) is suitable for diagnosis under high nitrogen levels.

[0090] The extraction of vegetation indices involves four steps. First, remote sensing imagery is acquired using a drone equipped with a multispectral sensor. During clear, cloudless morning to afternoon hours, the drone flies at an altitude of 30 to 80 meters, ensuring a forward overlap of at least 70% and a lateral overlap of at least 60%, acquiring high-resolution images encompassing five bands: blue, green, red, red-edge, and near-infrared. Second, radiometric, atmospheric, and geometric corrections are performed. The raw sensor values ​​are converted into surface reflectance, and orthorectification is applied to the images using RTK positioning data, ensuring each pixel corresponds to precise geographic coordinates. Third, band calculations are performed, calculating the Normalized Difference Vegetation Index (NDVI), Green NDVI, and Red-edge NDVI pixel by pixel. NDVI reflects crop cover and vigor, GNDVI is sensitive to nitrogen changes, and NDRE is suitable for diagnosing high nitrogen levels. Finally, spatial aggregation is performed, which overlays the pixel-level vegetation index with the field boundary vector, extracts the average, median and tenth percentile of all effective pixels in each field or grid cell, and outputs statistical values ​​representing the overall growth of the area after quality control such as cloud shadow masking and boundary smoothing, for subsequent topdressing decisions.

[0091] Step 43, Topdressing Decision and Precise Variable Operation The vegetation index is used in the diagnostic model to determine the nitrogen sufficiency or deficiency of the plots. The growth zone is divided into management units such as "weak seedling area," "normal area," and "vigorous growth area." For weak seedling plots below the critical threshold, a variable fertilizer prescription map is generated, recommending 75-150 kg / ha of urea at the jointing stage. The prescription map is imported into a drone fertilization system or a Beidou navigation variable fertilizer applicator, which performs automatic variable fertilizer application based on RTK-GNSS centimeter-level positioning and a preset flight path. In the normal area, the standard nitrogen application rate is followed: 75 to 90 kg / ha of urea at the jointing stage and 60 to 75 kg / ha at the large bell-shaped bud stage. The application method is the same as that for the weak seedling area, but the prescription rate is different. In the vigorous growth area, the vegetation index is high, indicating that the soil nitrogen is excessive. Continuing to apply the standard rate will lead to excessive vegetative growth, weak stems, increased risk of lodging, aggravated pests and diseases, and increased nitrogen leaching. Therefore, the application rate should be reduced or stopped. For mild vegetative growth, reduce the application rate by half, applying 30 to 45 kg per hectare; for moderate vegetative growth, reduce the application rate by 75%, applying 15 to 22 kg per hectare; for severe vegetative growth, skip the application. The variable-rate fertilizer applicator automatically applies zero or low-rate fertilizer according to the prescription map in the corresponding grid unit.

[0092] The diagnostic model was established based on measured data of spring maize in the cold regions of Northeast China, with the jointing stage and the large trumpet stage as two key diagnostic windows. At the jointing stage, a combined assessment was made using the normalized green light index (NRI) as the primary indicator and the normalized vegetation index (NVI) as a secondary indicator: a NRI below 0.12 or a NVI below 0.35 was considered a severely nitrogen-deficient weak seedling area, requiring topdressing with 120-150 kg of urea per hectare; a NRI between 0.12 and 0.18 or a NVI between 0.35 and 0.45 indicated mild nitrogen deficiency, requiring topdressing with 90-120 kg of urea per hectare; a NRI between 0.18 and 0.30 and a NVI between 0.45 and 0.65 indicated a nitrogen-suitable normal area, requiring topdressing with the standard amount of 75-90 kg; any index exceeding the upper limit indicated a vigorous growth area, requiring reduction to below 30 kg or cessation of application. During the large trumpet stage, the red-edge normalized vegetation index was replaced with the green light index for auxiliary judgment, and the threshold was adjusted accordingly. The standard nitrogen application rate in normal areas was reduced to 60-75 kg per hectare. For diagnosis, the average and 10th percentile of the vegetation index within a grid cell were extracted. After multi-index joint logical judgment, a variable fertilizer prescription map was generated. A gradual prescription was used in the boundary transition zone to avoid drastic fluctuations in fertilizer application rate over short distances. Before each growing season, samples with known nitrogen levels were selected in the field for localized threshold calibration, and plot trials were used to verify the yield response of nitrogen application rate.

[0093] Implementation Method 2: This implementation method aims to verify the effectiveness of the method described in Implementation Method 1 through comparative experiments.

[0094] The control group represents the current conventional fertilization method in the cold black soil region of Northeast China, namely a uniform fertilization scheme without zone division, differentiated quantitative application of micronutrients, or freeze-thaw risk correction. A uniform nitrogen, phosphorus, and potassium application rate was used throughout the region, and micronutrients were applied uniformly according to conventional empirical values. A fixed 50-meter buffer zone was used in the ecological protection area. This group reflects the actual performance of existing general technologies under high-density planting conditions.

[0095] Table 15

[0096] Regarding nitrogen fertilizer utilization rate, this invention achieved 48.5%, nearly 50% higher than the control's 32.5%. This increase mainly comes from two aspects: first, the use of slow-release nitrogen fertilizer as base fertilizer reduced ammonia volatilization losses during the early spring low-temperature period; second, the use of drone remote sensing for variable topdressing reduced waste caused by excessive nitrogen supply. Regarding phosphorus fertilizer utilization rate, this invention achieved 28.6%, more than 50% higher than the control's 18.5%. This increase mainly comes from the synergistic effect of the differentiated phosphorus application strategy and the phosphorus-solubilizing bacteria, the latter of which can still activate insoluble phosphorus in the soil under low-temperature conditions. In terms of yield and efficiency synergy, the control yielded 11,200 kg / ha with a total nitrogen application rate of 345 kg / ha, resulting in a nitrogen fertilizer utilization rate of only 32.5%, a typical high-input, low-efficiency model. This invention, by slightly increasing the total nitrogen application rate to 360 kg per hectare, achieves a dual increase in yield of 14,400 kg per hectare and nitrogen fertilizer utilization rate of 48.5% through precise zoning and variable topdressing, breaking through the bottleneck of difficulty in achieving both increased yield and increased efficiency in existing technologies.

[0097] Comparison of pollution control effectiveness in ecological protection areas: Table 16

[0098] Regarding nitrate nitrogen concentration in ecological zones, this invention achieved 8.5 mg / L, a reduction of over 50% compared to the control's 18.5 mg / L. This effect is primarily attributed to two factors: firstly, strict control of nitrogen fertilizer application within ecological protection zones, limiting it to no more than 75 kg per hectare; and secondly, the establishment of 100-meter buffer zones to effectively intercept lateral nutrient migration. In terms of nitrogen runoff reduction during freeze-thaw cycles, this invention achieved 72%, mainly due to the introduction of a freeze-thaw risk correction mechanism. In areas with high freeze-thaw intensity and concentrated snowmelt runoff, the buffer zone along river and lake shorelines was dynamically expanded to 100 meters, effectively controlling the migration of non-point source pollutants into water bodies during freeze-thaw cycles. Regarding the compliance rate of river and lake shoreline buffer zones, this invention achieved 96%, significantly higher than the control's 62%, thanks to the precise delineation of buffer zone boundaries using centimeter-level positioning technology, avoiding blind spots caused by human measurement errors.

[0099] In summary, under high-density planting conditions in the cold black soil of Northeast China, this invention has produced the following technical effects: First, it synergistically improves yield and efficiency, with both nitrogen fertilizer utilization and yield significantly higher than the control, breaking through the bottleneck of conventional nitrogen reduction strategies where increasing yield and efficiency are difficult to achieve simultaneously. Second, it significantly improves phosphorus fertilizer utilization, mainly due to the synergistic effect of phosphorus- and potassium-solubilizing bacteria under low-temperature conditions, promoting the activation and transformation of insoluble phosphorus in the soil. Third, it significantly controls nitrogen pollution in the ecological zone, with a marked reduction in nitrate nitrogen concentration and effective reduction in nitrogen runoff during the freeze-thaw period. This is due to the dynamic expansion of the buffer zone under the freeze-thaw risk correction mechanism and the strict nitrogen control strategy in the ecological zone. Compared with conventional technologies, this invention addresses the problem of decreased zinc availability caused by low temperatures in early spring in cold regions by increasing zinc application in marginal areas and combining it with foliar spraying during the seedling stage to effectively prevent zinc deficiency symptoms; it addresses the risk of lodging at high densities by increasing calcium and silicon application in the buffer zone to enhance stem lodging resistance; it addresses non-point source pollution in the ecological zone by dynamically expanding the buffer zone and implementing nitrogen reduction and pollution control; and it addresses the difficulty of phosphorus activation at low temperatures by significantly improving phosphorus fertilizer utilization efficiency through the synergistic effect of bacteria. The achievement of the above effects depends on the targeted design for the special conditions of cold black soil, the consideration of high-density stress, and the synergistic combination of strip fertilization and variable topdressing.

[0100] The above provides a detailed description of the precision fertilization method for high-density planting of maize in the cold black soil of Northeast China proposed in this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for precise fertilization of maize grown in high-density areas of cold, black soil in Northeast China, characterized by: Includes the following steps: Step 1: Divide the target planting area into functional planting zones; Step 1 involves dividing the target planting area into functional zones, specifically as follows: Step 11: Obtain the multi-parameter soil dataset for the target planting area; Step 12: Calculate the soil comprehensive fertility index (SFI) based on the soil multi-parameter dataset; Step 13: Complete the division of planting functional zones based on the Soil Fertility Index (SFI). Step 2: Based on the results of the planting functional zone division, apply conventional element fertilization throughout the entire growth period to different planting functional zones; In step 2, conventional element fertilization is applied throughout the entire growth period for different planting functional zones, specifically as follows: For areas designated as core maize growing zones, apply 345-375 kg of pure nitrogen, 195-225 kg of P2O5, and 150-225 kg of K2O per hectare throughout the entire growth period. For areas designated as buffer maize growing zones, apply 285-315 kg of pure nitrogen, 165-195 kg of P2O5, and 120-165 kg of K2O per hectare throughout the entire growth period. For areas designated as marginal zones, apply 195-225 kg of pure nitrogen, 120-150 kg of P2O5, and 90-120 kg of K2O per hectare throughout the entire growth period; Step 3: Based on the results of the planting functional zone division, apply micronutrients as basal fertilizer and top dressing during the growth period to different planting functional zones to achieve precise fertilization of corn by zone. In step 3, the application of micronutrients to different planting functional zones is specifically as follows: During the land preparation stage before sowing, for areas designated as the core maize growing zone, apply zinc, boron, silicon-calcium, magnesium, and iron fertilizers at the first benchmark rate; for areas designated as the buffer maize growing zone, apply silicon-calcium fertilizer at a rate 20%-30% higher than the first benchmark rate, and apply zinc and boron fertilizers at a rate 10%-15% higher than the first benchmark rate; for areas designated as the edge zone, apply zinc and boron fertilizers at a rate 30% to 50% higher than the first benchmark rate, apply iron fertilizer at a rate 50% to 100% higher than the first benchmark rate, and apply magnesium fertilizer at a rate 25% to 35% higher than the first benchmark rate; for areas designated as ecological protection zones, do not apply micronutrient fertilizers. In step 3, the topdressing during the growth period is applied within the core maize growth zone, specifically as follows: During the corn seedling stage, apply 450-600 liters / hectare of zinc sulfate solution with a concentration of 0.1%-0.2% and 450 liters / hectare of manganese sulfate solution with a concentration of 0.5%-1.0% as foliar sprays. During the jointing stage of corn, apply 40-75 kg / ha of silicon-calcium fertilizer as top dressing, and spray 450 liters / ha of magnesium sulfate solution with a concentration of 1%-2% on the leaves. During the corn's tasseling stage, apply 450 liters / hectare of a 0.1%-0.2% borax solution and 450 liters / hectare of a 0.5% sodium silicate solution as foliar sprays.

2. The method for precise fertilization of maize in strip planting in high-density black soil of Northeast China according to claim 1, characterized in that, The comprehensive fertility index SFI in step 12 is specifically as follows: ； Wherein, Nnorm, Pnorm, Knorm, and pHnorm are the standardized parameter values ​​of available nitrogen, available phosphorus, available potassium, and pH, respectively. These are the weighting coefficients. It is a fast-acting nitrogen, For available phosphorus, It is a fast-acting potassium. This refers to pH level.

3. The method for precise fertilization of maize in strip planting in high-density black soil of Northeast China according to claim 1, characterized in that, In step 13, the planting functional zones are divided according to the Soil Fertility Index (SFI). Specifically: When SFI≥0.6, it is designated as the core maize growth zone; When 0.4 ≤ SFI < 0.6, it is designated as a buffer zone for maize growth; When 0.2 ≤ SFI < 0.4, it is classified as a marginal zone; When SFI < 0.2, it is designated as an ecological protection zone.

4. The method for precise fertilization of maize in strip planting in high-density black soil of Northeast China according to claim 1, characterized in that, In the conventional element fertilization throughout the entire growth period, the pure nitrogen applied as base fertilizer is selected as slow-release nitrogen fertilizer, and phosphorus and potassium solubilizing bacteria are mixed into the base fertilizer.

5. The method for precise fertilization of maize in strip planting in high-density black soil of Northeast China according to claim 1, characterized in that, The first benchmark amount is 5-8 kg of zinc fertilizer, 2-3 kg of boron fertilizer, 75-120 kg of silicon-calcium fertilizer, 30-45 kg of magnesium fertilizer and 10-15 kg of iron fertilizer per hectare.

6. The method for precise fertilization of maize in strip planting in high-density black soil of Northeast China according to claim 3, characterized in that, When the local temperature is below 5℃, the SFI inclusion threshold for the core maize growing zone will be lowered to 0.50; when the local temperature is between 5℃ and 10℃, the SFI inclusion threshold for the core maize growing zone will be lowered to 0.55; when the local temperature rises above 10℃, the SFI inclusion threshold for the core maize growing zone will remain unchanged at 0.60.

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