Simplified nitrogen fertilizer application rate recommendation method for crops based on nitrogen balance standard

Abstract

A nitrogen fertilizer application rate recommendation method for crops based on a nitrogen balance standard, comprising the following steps: 1) determining a soil nitrogen supply grade for a target plot; 2) determining a nitrogen balance standard for the target plot; 3) determining the aboveground nitrogen uptake amount of rice in the target plot; and 4) calculating a recommended nitrogen fertilizer application rate for the rice in the target plot. The method only requires knowledge of crop yield and soil fertility grade to recommend a nitrogen fertilizer application rate, and can minimize nitrogen surplus in soil to the greatest extent while ensuring crop yield, thereby reducing environmental losses of reactive nitrogen and promoting high-yield, high-efficiency, sustainable, and healthy agricultural development.

Description

A simplified method for recommending nitrogen fertilizer application rates for crops based on nitrogen balance standards Technical Field

[0001] This invention relates to the field of agricultural resource and environmental technology, and in particular to a simplified method for recommending nitrogen fertilizer application rates for crops based on nitrogen balance standards. Background Technology

[0002] Wheat, rice, and corn are major crops, and excessive application of nitrogen fertilizer is a common problem in their cultivation. This excessive application not only wastes fertilizer resources but also triggers a series of environmental problems, such as increased ammonia volatilization, leaching, and runoff losses, exacerbating air and water pollution. Furthermore, the nitrification-denitrification process in rice cultivation leads to greenhouse gas emissions, becoming a significant source of global nitrogen pollution.

[0003] Currently, the recommended methods for crop nitrogen fertilizer application are mainly based on soil nutrient testing, fertilizer effect functions, and crop or soil models. However, these methods have obvious limitations: on the one hand, under the smallholder farming model, most farmers do not have the professional equipment, technology, and capital investment required for soil testing and fertilization, and crop rotation is tight (such as summer corn and double-cropping rice), which leads to problems such as untimely soil test results; on the other hand, farmers have long relied on experience for fertilization, and unreasonable fertilization is common, resulting in low nitrogen fertilizer utilization efficiency and prominent pressure to save fertilizer and reduce emissions.

[0004] Therefore, developing a scientific, reasonable, simple, efficient, and applicable method for recommending nitrogen fertilizer application rates for crops has become an urgent need to promote efficient nitrogen fertilizer application and ensure the coordinated development of food security and the ecological environment. Summary of the Invention

[0005] The purpose of this invention is to provide a simplified method for recommending nitrogen fertilizer application rates for crops based on nitrogen balance standards, in order to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a simplified method for recommending nitrogen fertilizer application rates for crops based on nitrogen balance standards, comprising the following steps:

[0008] Step 1): Determine the nitrogen supply level of the soil in the target plot: In nitrogen fertilizer recommendations, soil fertility is mainly reflected in the soil's nitrogen supply capacity.

[0009] This invention provides four methods for determining soil nitrogen supply levels:

[0010] Method 1: Determine the amount of nitrogen absorbed by the aboveground parts of crops in the target plot without applying nitrogen fertilizer.

[0011] This invention collects and summarizes field fertilization trial data from major rice, corn, and winter wheat producing areas in China, and establishes a database. The top 25%, middle 25%-75%, and bottom 25% of the nitrogen uptake data of the above-ground parts of these crops under nitrogen-free conditions in the database are used as the criteria for classifying soil nitrogen supply as high, medium, and low (Tables 1-3).

[0012] Table 1

[0013]

[0014] Table 2

[0015]

[0016] Table 3

[0017]

[0018] Method 2: Determine the yield based on the crop yield of the target plot without applying nitrogen fertilizer.

[0019] Based on the Method 1 database, the top 25%, middle 25%-75%, and bottom 25% of crop yield datasets under no nitrogen fertilizer conditions were used as the criteria for classifying soil nitrogen supply as high, medium, and low (Tables 4-6).

[0020] Table 4

[0021]

[0022] Table 5

[0023]

[0024] Table 6

[0025]

[0026] Method 3: If soil test results are available for the target plot, classify it according to soil organic matter content (Table 7); specifically:

[0027] Soil nitrogen supply level is based on soil organic matter content as the basis for nitrogen supply level assessment, and soil hydrolyzable nitrogen is used as the adjustment factor: when soil hydrolyzable nitrogen ≥180 mg / kg, the low supply capacity of soil nitrogen supply level is adjusted to medium supply capacity; when soil hydrolyzable nitrogen ≤100 mg / kg, the high supply capacity of soil nitrogen supply level is adjusted to medium supply capacity.

[0028] Table 7

[0029]

[0030] Method 4: Determine based on the apparent characteristics of the soil texture and color of the target plot (Table 8).

[0031] Table 8

[0032]

[0033] Step 2): Determine the nitrogen balance standard for the target plot.

[0034] Based on the aforementioned database, this invention establishes a relationship between nitrogen yield response (i.e., the increase in crop yield in the nitrogen fertilizer treatment compared to the no-nitrogen fertilizer treatment in the target plot) and apparent soil nitrogen balance (i.e., the difference between the amount of nitrogen applied and the amount absorbed and removed by crops). While ensuring crop yield and minimizing nitrogen surplus in the soil, this invention proposes nitrogen balance standards for high, medium, and low soil nitrogen supply levels using a maximum economic benefit algorithm.

[0035] Meanwhile, this invention compares the differences in apparent nitrogen balance in soil under various fertilization modes, including conventional nitrogen fertilizer application, controlled-release nitrogen fertilizer, deep mechanical application of nitrogen fertilizer, combined application of organic fertilizer, and straw return to the field, and proposes reference standards for nitrogen balance under different fertilization modes (Table 5).

[0036] Based on the soil nitrogen supply level and nitrogen fertilizer application pattern identified in step 1), refer to Tables 9 to 11 to determine the nitrogen balance standard of the target plot.

[0037] Table 9

[0038]

[0039] Table 10

[0040]

[0041] Table 11

[0042]

[0043] Step 3) Determine the nitrogen uptake of crop plants in the target plot:

[0044] The nitrogen uptake of aboveground crop plants, considering both grain nitrogen uptake and straw nitrogen uptake, can be calculated using formula (1):

[0045] N uptake = N grain + N straw = Y grain X grain + Y straw X straw (1)

[0046] Where, N uptake N grain N straw These represent the nitrogen uptake by the aboveground parts of crops, the nitrogen uptake by crop grains, and the nitrogen uptake by crop straw in the target plot (kg N / ha), respectively; Y grain and Y straw X represents crop grain yield and crop straw biomass (kg / ha), respectively; grain and X straw These represent the nitrogen content of crop grains and the nitrogen content of crop straw (mg / kg), respectively.

[0047] Specifically, Y grain The yield was determined based on the average crop yield of the target plot over the past 3-5 years when there were no biological stresses.

[0048] Y straw If no measured data is available, it can be obtained using formula (2):

[0049] Y straw =Y grain a (2)

[0050] Where 'a' represents the conversion coefficient between crop grain yield and crop straw biomass, with reference values ​​shown in Tables 6-1 to 6-3.

[0051] X grain If there is no measured data, then N grain Obtained through formula (3):

[0052] N grain = Y grain b 0.001 (3)

[0053] Where b represents the conversion coefficient between crop grain yield and crop grain nitrogen uptake, and the reference values ​​are shown in Tables 6-1 to 6-3.

[0054] X straw If there is no measured data, then N straw Obtained through formula (4):

[0055] N straw = Y straw c 0.001 (4)

[0056] Where c represents the conversion coefficient between crop straw biomass and rice straw nitrogen uptake, and the reference values ​​are shown in Tables 12 to 14.

[0057] Table 12

[0058]

[0059] Note: The numbers in parentheses are the sample sizes.

[0060] Table 13

[0061]

[0062] Table 14

[0063]

[0064] Step 4) Calculate the nitrogen fertilizer application rate for crops in the target plot: Based on the nitrogen uptake of the aboveground parts of the crops in the target plot and the nitrogen balance standard, predict the recommended nitrogen fertilizer application rate, which is obtained through formula (5):

[0065] N=N uptake +N balance (5)

[0066] Wherein, N represents the recommended nitrogen fertilizer application rate (kg N / ha) for the target plot; N uptake The aboveground nitrogen uptake (kg N / ha) of the crops in the target plot is represented by step 3); N balance The nitrogen balance standard (kg N / ha) of the target plot is obtained from steps 1) and 2).

[0067] The nitrogen fertilizer application recommendation method based on the nitrogen balance standard of this invention is a simplified recommendation method that can be used with or without soil test results. Ordinary farmers with a certain scientific knowledge only need to understand the rice yield level of the target plot, identify the soil fertility level, and then perform a simple calculation process to achieve a scientific and reasonable nitrogen fertilizer recommendation. Compared with existing technologies, it is more suitable for small farmers who do not have the conditions for soil testing and formula fertilization or other fertilization techniques that require professional testing equipment and personnel.

[0068] This invention not only provides standard nitrogen balance parameters for conventional nitrogen fertilizer products and application methods, but also provides parameter calibration for high-efficiency fertilization scenarios such as controlled-release fertilizers, deep mechanical application of nitrogen fertilizers, combined application of organic fertilizers, and straw return to the field. Therefore, compared with existing technologies, this invention is more applicable to the diverse nitrogen fertilizer application scenarios for crops today.

[0069] This invention generates relevant nitrogen fertilizer recommendation parameters based on big data from field trials, rather than on the results of individual or a few trials, thus possessing broad representativeness. Furthermore, this invention uses crop yield response as a response indicator to changes in nitrogen balance, rather than directly using crop yield. This is because yield response is the increase in yield of the nitrogen-applied treatment relative to the non-nitrogen-applied treatment, and the yield of the non-nitrogen-applied treatment represents the soil fertility level of the plot. Therefore, this invention minimizes the bias in recommended fertilization parameters caused by differences in soil fertility levels at different test sites. Consequently, the nitrogen balance standard provided by this invention is suitable for different crop types, varieties, and soil and climate conditions.

[0070] This invention's method only requires knowledge of crop yield and soil fertility level to recommend nitrogen fertilizer application based on relevant parameters. It is applicable to various nitrogen fertilizer application scenarios, including conventional nitrogen fertilizer, controlled-release fertilizer, deep mechanical application of nitrogen fertilizer, organic fertilizer application, and straw return to the field. Based on extensive field trial data from different rice-growing regions, the nitrogen fertilizer application recommended by this invention is essentially equivalent to the recommendations for soil testing and formula fertilization, significantly reducing application compared to farmers' conventional methods. This achieves the goals of simplified, efficient, and scientific fertilization, making it particularly suitable for smallholder farmers who lack access to soil testing and formula fertilization techniques or other scientific fertilization technologies.

[0071] The present invention discloses the following technical effects:

[0072] This invention proposes a method for recommending nitrogen fertilizer application rates for crops based on nitrogen balance standards. This method only requires knowledge of crop yield and soil fertility level to recommend nitrogen fertilizer application rates. It can minimize nitrogen surplus in the soil while ensuring crop yield, thereby reducing environmental loss of reactive nitrogen and promoting high-yield, high-efficiency, and sustainable agricultural development. Detailed Implementation

[0073] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0074] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0075] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0076] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0077] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0078] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0079] Example 1

[0080] To verify the feasibility of applying the nitrogen fertilizer application recommendation method based on nitrogen balance standards to rice, this invention utilizes extensive field trial data from different rice-growing regions to conduct recommended fertilization practices and compares the results with those of local farmers' habitual fertilization and other widely accepted scientific fertilization methods to verify the rationality of the recommendations.

[0081] Field trials were conducted from 2017 to 2020 in single-season rice producing areas of Heilongjiang and Jilin provinces, mid-season rice producing areas of Hubei and Anhui provinces, and early / late double-season rice producing areas of Hunan and Jiangxi provinces. The recommended nitrogen fertilizer application method based on nitrogen balance standards was validated, involving a total of 136 experimental plots. The number of trials and regions validating different fertilization methods are shown in Table 15. Based on the nitrogen uptake of aboveground rice in the no-nitrogen-fertilizer treatment of each experimental plot, the soil nitrogen supply level of that plot was determined using the standards provided in Table 1 (Table 15). Based on the fertilization method and soil nitrogen supply level of each experimental plot, the nitrogen balance standard of that plot was determined using the standards provided in Table 9 (Table 15). The highest measured value of aboveground nitrogen uptake in rice among all treatments was used as the target nitrogen uptake. The recommended nitrogen fertilizer application (OPT) for the rice plot was predicted by formula (5) and compared with the local farmers' habitual nitrogen fertilizer application (FP), the local soil testing and formula fertilization recommended nitrogen fertilizer application (ST), and the nutrient expert method recommended nitrogen fertilizer application (NE) based on the same plot (Table 16).

[0082] Table 15

[0083]

[0084] Table 16

[0085]

[0086] Table 16 summarizes the average nitrogen fertilizer application results of four fertilization methods on relevant plots of the same rice-growing region type and soil fertility level. The results show that for single-season rice, the average OPT nitrogen fertilizer application rate under high, medium, and low soil fertility levels was 171 kg N / ha, which was 6.7% lower than the average FP nitrogen fertilizer application rate, and basically equivalent to the ST recommendation result. For mid-season rice, the average OPT nitrogen fertilizer application rate under the three soil fertility levels was 185 kg N / ha, which was 2.8% lower than the average OPT nitrogen fertilizer application rate, but higher than the ST and NE application rates. This is mainly because the method of this invention has a higher recommendation result in low-fertility soils in order to ensure the target yield level. For early and late rice, the average OPT application rate was 184 kg N / ha and 194 kg N / ha, respectively. The OPT application rate was lower than the FP application rate in late rice, but higher than the FP application rate in early rice, which also shows a higher recommendation result in low-fertility soils.

[0087] Example 2

[0088] To verify the feasibility of applying the nitrogen fertilizer application recommendation method based on nitrogen balance standards to maize, this invention utilizes extensive field trial data from different maize planting seasons to conduct recommended fertilization practices and compares the results with local farmers' habitual fertilization practices and other widely accepted scientific fertilization methods to verify the rationality of the recommendations.

[0089] Field trials were conducted from 2017 to 2020 in 124 plots across major spring maize producing regions such as Heilongjiang, Jilin, and Inner Mongolia, and major summer maize producing provinces such as Hebei and Shanxi. The trials validated the recommended nitrogen fertilizer application methods based on nitrogen balance standards. The number of trials and regions validating different fertilization methods are shown in Table 17. Based on the aboveground nitrogen uptake of maize in the no-nitrogen-fertilizer treatment in each plot (Table 17), the soil nitrogen supply level of that plot was determined using the standards provided in Table 2 (Table 17). Based on the fertilization method and soil nitrogen supply level of each plot, the nitrogen balance standard of that plot was determined using the standards provided in Table 10 (Table 18). The highest aboveground nitrogen uptake of maize in all treatments was used as the target nitrogen uptake. The recommended nitrogen fertilizer application (OPT) for the maize plot was predicted using formula (5) and compared with the local farmers' habitual nitrogen fertilizer application (FP), the local soil testing and formula fertilization recommended nitrogen fertilizer application (ST), and the nutrient expert method recommended nitrogen fertilizer application (NE) based on the same plot (Table 18).

[0090] Table 17

[0091]

[0092] Table 18

[0093]

[0094] Table 18 summarizes the nitrogen requirements of maize under different planting seasons and soil fertility levels, along with recommended application rates for four fertilization methods. The results show that in all spring maize plots, the average application rate of OPT nitrogen fertilizer was 220 kg N / ha, a decrease of 6.4% compared to the average application rate of FP nitrogen fertilizer, but an increase of 8.6%–13.1% compared to the recommended rates of ST and NE. This is mainly because in low-fertility soils, due to the lower background nitrogen supply capacity, this method requires a higher amount of exogenous nitrogen fertilizer to ensure yield levels. In all summer maize plots, the average application rate of OPT nitrogen fertilizer was 185 kg N / ha, which is basically the median of the recommendations from ST and NE methods, and a decrease of 20.8% compared to the average application rate of FP nitrogen fertilizer.

[0095] Example 3

[0096] To verify the feasibility of applying the nitrogen fertilizer application recommendation method based on the nitrogen balance standard to wheat, this invention utilizes extensive field trial data from major wheat-producing areas in China to conduct recommended fertilization practices and compares the results with those of local farmers' habitual fertilization and other widely accepted scientific fertilization methods to verify the rationality of the recommendations.

[0097] Field trials were conducted from 2017 to 2020 in major wheat-producing provinces including Henan, Shandong, Hebei, Shanxi, and Inner Mongolia. The recommended nitrogen fertilizer application method based on nitrogen balance standards was validated, involving a total of 44 experimental plots. The number of trials and regions validating different fertilization methods are shown in Table 19. Based on the aboveground nitrogen uptake of wheat in the no-nitrogen-fertilizer treatment in each experimental plot, the soil nitrogen supply level of that plot was determined using the standards provided in Table 3 (Table 19). Based on the fertilization method and soil nitrogen supply level of each experimental plot, the nitrogen balance standard of that plot was determined using the standards provided in Table 11 (Table 20). The highest aboveground nitrogen uptake of wheat in all treatments was used as the target nitrogen uptake. The recommended nitrogen fertilizer application (OPT) for the wheat plot was predicted by formula (5) and compared with the local farmers' habitual nitrogen fertilizer application (FP), the local soil testing and formula fertilization recommended nitrogen fertilizer application (ST), and the nutrient expert method recommended nitrogen fertilizer application (NE) based on the same plot (Table 20).

[0098] Table 19

[0099]

[0100] Table 20

[0101]

[0102] Table 20 summarizes the average nitrogen fertilizer application results for four fertilization methods on relevant plots with different soil fertility levels. The results show that in all experimental plots, the average nitrogen requirement for wheat was 171 kg N / ha, and the average application of OPT nitrogen fertilizer was 199 kg N / ha. This application rate falls between the recommended values ​​of the two scientific fertilization methods, ST and NE, thus ensuring the rationality of the recommendations. Compared to farmers' conventional fertilization practices, FP (nitrogen fertilizer) was reduced by 22.6%. In high-fertility plots, OPT nitrogen fertilizer application showed the greatest potential for reduction compared to FP, at 30.5%. Under low, medium, and high soil fertility levels, the average application of OPT nitrogen fertilizer was 191, 221, and 185 kg N / ha, respectively. The difference from the ST recommendation ranged from -3 to -41 kg N / ha, and the difference from the NE recommendation ranged from 7 to 24 kg N / ha.

[0103] In summary, the nitrogen fertilizer application recommendation method based on nitrogen balance standards proposed in this invention can significantly reduce the nitrogen fertilizer application habits of farmers. Under high fertility conditions, the recommended results are basically equivalent to those of soil testing and formula fertilization. Under medium and low fertility conditions, the recommended results are improved compared to the other two scientific fertilization methods. This is mainly because it aims to ensure the yield level of the plot by increasing the input of fertilizer nitrogen, while avoiding excessive consumption of soil organic matter. Therefore, the field verification test results show that the nitrogen fertilizer application recommendation method based on nitrogen balance standards proposed in this invention can be used for nitrogen fertilizer application decisions for crops.

[0104] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A light and simple method for recommending the amount of nitrogen fertilizer for rice based on the standard of nitrogen balance, characterized by, Includes the following steps: (1) Determine the nitrogen supply level of the soil in the target plot using any one of methods 1-4: Method 1: Determine the soil nitrogen supply level of the target plot based on the nitrogen uptake of the aboveground parts of rice without nitrogen fertilizer, according to different rice varieties. Method 2: Determine the soil nitrogen supply level of the target plot based on the yield of rice without nitrogen fertilizer, according to different rice varieties: Method 3: Classify the soil nitrogen supply level of the target plot based on soil organic matter content: Soil nitrogen supply level is based on soil organic matter content as the basis for nitrogen supply level assessment, and soil hydrolyzable nitrogen is used as the adjustment factor: when soil hydrolyzable nitrogen ≥180 mg / kg, the low supply capacity of soil nitrogen supply level is adjusted to medium supply capacity; when soil hydrolyzable nitrogen ≤100 mg / kg, the high supply capacity of soil nitrogen supply level is adjusted to medium supply capacity. Method 4: Determine the soil nitrogen supply level of the target plot based on soil texture and apparent properties: (2) Based on the soil nitrogen supply level of the target plot determined in step (1), and in conjunction with the fertilization method, determine the nitrogen balance standard of the target plot according to the following table: (3) Obtain Y based on the target yield grain For the rice grain yield, the aboveground nitrogen uptake amount of the target plot of rice is determined in accordance with formula (a-1) or (a-2): N uptake = N grain + N straw (a-1) in: N uptake For the amount of nitrogen absorbed by the above-ground part of rice, kg N / ha; N grain Nitrogen uptake by rice grains, kg N / ha; N straw Nitrogen uptake by rice straw, kg N / ha; N uptake = Y grain X grain + Y straw X straw (a-2) in: N uptake Nitrogen uptake by the aboveground parts of rice, kg N / ha; Y grain Rice grain yield, kg / ha; Y straw Rice straw biomass, kg / ha; X grain Nitrogen content in rice grains, mg / kg; X straw For rice straw nitrogen content, mg / kg; (4) Calculate the recommended amount of nitrogen fertilizer for rice in the target plot according to formula (b): N=N uptake +N balance (b); Where N represents the recommended nitrogen fertilizer application rate for rice, kg N / ha; N uptake This indicates the amount of nitrogen absorbed by the aboveground parts of rice, expressed in kg N / ha; N balance Nitrogen balance standard, kg N / ha; If no actual measurement value is available for the rice straw biomass, it can be calculated according to formula (c): Y straw = Y grain a (c) Y straw Y represents rice straw biomass, kg / ha; grain denoted as rice grain yield, kg / ha; a represents the conversion coefficient between rice grain yield and rice straw biomass, with the conversion coefficients for different rice varieties shown in the table below; If no actual measurement data is available for nitrogen uptake in rice grains, it can be calculated using formula (d): N grain =Y grain b 0.001 （d） N grain Nitrogen uptake by rice grains, kg N / ha; Y grain denoted as rice grain yield (kg / ha); b represents the conversion coefficient between rice grain yield and nitrogen uptake by rice grains, where... The conversion coefficients for different rice varieties are shown in the table below; If no actual measurement data is available for the nitrogen uptake of rice straw, it can be calculated according to formula (e): N straw = Y straw c 0.001 （e） N straw Nitrogen uptake by rice straw, kg N / ha; Y straw The value is denoted as rice straw biomass, kg / ha; c represents the conversion coefficient between rice straw biomass and nitrogen uptake from rice straw, where... The conversion coefficients for different rice varieties are shown in the table below: 。 2. A simplified method for recommending nitrogen fertilizer application rates for corn based on nitrogen balance standards, characterized in that, Includes the following steps: (1) Determine the nitrogen supply level of the soil in the target plot using any one of methods 1-4: Method 1: Determine the soil nitrogen supply level of the target plot based on the nitrogen uptake of the aboveground parts of corn without nitrogen fertilizer, according to different corn varieties: Method 2: Determine the soil nitrogen supply level of the target plot based on the yield of corn without nitrogen fertilizer, according to different corn varieties: Method 3: Classify the soil nitrogen supply level of the target plot based on soil organic matter content: Soil nitrogen supply level is based on soil organic matter content as the basis for nitrogen supply level assessment, and soil hydrolyzable nitrogen is used as the adjustment factor: when soil hydrolyzable nitrogen ≥180 mg / kg, the low supply capacity of soil nitrogen supply level is adjusted to medium supply capacity; when soil hydrolyzable nitrogen ≤100 mg / kg, the high supply capacity of soil nitrogen supply level is adjusted to medium supply capacity. Method 4: Determine the soil nitrogen supply level of the target plot based on soil texture and apparent properties: (2) Based on the soil nitrogen supply level of the target plot determined in step (1), and in conjunction with the fertilization method, determine the nitrogen balance standard of the target plot according to the following table: (3) Obtain Y based on target output grain To determine the corn grain yield, the nitrogen uptake of the aboveground corn plant in the target plot is determined according to formula (a-1) or (a-2): N uptake = N grain + N straw (a-1) in: N uptake Nitrogen uptake by the aboveground parts of maize, kg N / ha; N grain Nitrogen uptake by corn kernels, kg N / ha; N straw Nitrogen uptake by corn stalks, kg N / ha; N uptake = Y grain X grain + And straw X straw (a-2) in: N uptake Nitrogen uptake by the aboveground parts of maize, kg N / ha; Y grain Corn kernel yield, kg / ha; Y straw Corn stalk biomass, kg / ha; X grain Nitrogen content of corn kernels, mg / kg; X straw Nitrogen content in corn stalks, mg / kg; (4) Calculate the recommended amount of nitrogen fertilizer for maize in the target plot according to formula (b): N=N uptake +N balance (b); Where N represents the recommended nitrogen fertilizer application rate for corn, kg N / ha; N uptake This indicates the amount of nitrogen absorbed by the aboveground parts of maize, expressed in kg N / ha; N balance Nitrogen balance standard, kg N / ha; The biomass of the corn stalks is calculated according to formula (c): AND straw = And grain a (c) Y straw Y represents corn stalk biomass, kg / ha; grain denoted as corn kernel yield, kg / ha; 'a' represents the conversion coefficient between corn kernel yield and corn straw biomass. The conversion coefficients for different corn varieties are shown in the table below. The nitrogen uptake of corn kernels is calculated according to formula (d): N grain =Y grain b 0.001 （d） N grain Nitrogen uptake by corn kernels, kg N / ha; Y grain denoted as corn kernel yield (kg / ha); b represents the conversion coefficient between corn kernel yield and corn kernel nitrogen uptake, where... The conversion coefficients for different maize varieties are shown in the table below: The nitrogen uptake of corn stalks is calculated according to formula (e): N straw = And straw c 0.001 （e） N straw Nitrogen uptake by corn stalks, kg N / ha; Y straw The value is: ... The conversion coefficients for different maize varieties are shown in the table below: 。 3. A simplified method for recommending nitrogen fertilizer application rates for winter wheat based on nitrogen balance standards, characterized in that, Includes the following steps: (1) Determine the nitrogen supply level of the soil in the target plot using any one of methods 1-4: Method 1: Determine the soil nitrogen supply level of the target plot based on the nitrogen uptake of the aboveground parts of wheat without nitrogen fertilizer, according to different wheat planting areas: Method 2: Determine the soil nitrogen supply level of the target plot based on the wheat yield without nitrogen fertilizer, according to different wheat-growing areas. Method 3: Classify the soil nitrogen supply level of the target plot based on soil organic matter content: Soil nitrogen supply level is based on soil organic matter content as the basis for nitrogen supply level assessment, and soil hydrolyzable nitrogen is used as the adjustment factor: when soil hydrolyzable nitrogen ≥180 mg / kg, the low supply capacity of soil nitrogen supply level is adjusted to medium supply capacity; when soil hydrolyzable nitrogen ≤100 mg / kg, the high supply capacity of soil nitrogen supply level is adjusted to medium supply capacity. Method 4: Determine the soil nitrogen supply level of the target plot based on soil texture and apparent properties: (2) Based on the soil nitrogen supply level of the target plot determined in step (1), and in conjunction with the fertilization method, determine the nitrogen balance standard of the target plot according to the following table: (3) Obtain Y based on target output grain This refers to wheat grain yield. The nitrogen uptake of the aboveground wheat in the target plot is determined according to formula (a-1) or (a-2): N uptake = N grain + N straw (a-1) in: N uptake Nitrogen uptake by wheat aboveground parts, kg N / ha; N grain Nitrogen uptake by wheat grains, kg N / ha; N straw For wheat straw nitrogen uptake, kg N / ha; N uptake = Y grain X grain + Y straw X straw (a-2) in: N uptake For the aboveground nitrogen uptake of wheat, kg N / ha; Y grain For wheat grain yield, kg / ha; Y straw Wheat straw biomass, kg / ha; X grain For wheat grain nitrogen content, mg / kg; X straw For wheat straw nitrogen content, mg / kg; (4) Calculate the recommended amount of nitrogen fertilizer for wheat in the target plot according to formula (b): N=N uptake +N balance (b); where N represents the recommended amount of nitrogen fertilizer for wheat, kg N / ha; N uptake represents the nitrogen uptake of the above-ground part of wheat, kg N / ha; N balance represents the nitrogen balance standard, kg N / ha; If no actual measurement value is available for the wheat straw biomass, it can be calculated according to formula (c): AND straw = And grain a (c) Y straw is the wheat straw biomass, kg / ha; Y grain is the wheat grain yield, kg / ha; a represents the conversion factor of the wheat grain yield and the wheat straw biomass, wherein the conversion factors of different wheat varieties are shown in the following table; If no measured value is available for nitrogen uptake in wheat grains, it can be calculated using formula (d): N grain =Y grain b 0.001 （d） N grain Nitrogen uptake by wheat grains, kg N / ha; Y grain denoted as wheat grain yield (kg / ha); b represents the conversion coefficient between wheat grain yield and wheat grain nitrogen uptake, where... The conversion coefficients for different wheat varieties are shown in the table below; If no actual measurement data is available for the nitrogen uptake of wheat straw, it can be calculated according to formula (e): N straw = Y straw c 0.001 （e） N straw Nitrogen uptake by wheat straw, kg N / ha; Y straw The value is: wheat straw biomass, kg / ha; c represents the conversion coefficient between wheat straw biomass and wheat straw nitrogen uptake, where... The conversion coefficients for different wheat varieties are shown in the table below: 。

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