A simulation and optimization method for water and fertilizer management in rice field based on tank model

Abstract

This invention belongs to the field of rice water and fertilizer management simulation and optimization technology, and discloses a method for simulating and optimizing paddy field water and fertilizer management based on a water tank model, including: S1: using historical rainfall, irrigation, drainage, field water level and water quality data of paddy fields in the study area to establish a water tank model, and calibrating the parameters of each sub-module in the water tank model, wherein the sub-modules include: a water module, a nitrogen module and a phosphorus module; S2: using the water module of the water tank model to simulate changes in paddy field water level; S3: using the nitrogen module of the water tank model to simulate changes in paddy field nitrogen concentration; S4: using the phosphorus module of the water tank model to simulate changes in paddy field phosphorus concentration, thereby solving the problem of simulating and optimizing water and fertilizer management patterns for rice cultivation.

Description

Technical Field

[0001] This invention belongs to the field of rice water and fertilizer management simulation and optimization technology, specifically involving a method for rice paddy water and fertilizer management simulation and optimization based on a water tank model. Background Technology

[0002] Model simulation is an effective method for studying soil moisture movement and nitrogen and phosphorus nutrient transformation and transport. Paddy field water and fertilizer simulation methods are of great reference value for optimizing water and fertilizer management patterns in rice cultivation, assessing environmental impacts, and responding to climate change. Currently, there are many models simulating soil moisture movement and nutrient transformation and transport in paddy fields, with ORYZA, HYDRUS, and DNDC being among the most widely used.

[0003] The ORYZA model is a crop growth simulation model specifically developed for rice. The model consists of multiple modules, including aboveground crop growth, transpiration and evaporation, nitrogen dynamics, and soil moisture balance. Using a daily time step, the model dynamically and quantitatively describes the growth, development, and yield formation of rice under potential production levels, water limitation levels, and nitrogen limitation levels, as well as the dynamic changes in soil moisture and nitrogen.

[0004] The HYDRUS model is based on the finite element method (FEM) to solve Richard's water transport equation and solute convection-dispersion equation. It is applicable to water, solute, and heat transport in one-dimensional, two-dimensional, and three-dimensional systems of varying complexity, and can be used to study paddy soil moisture conditions, rice water use efficiency, and nitrogen leaching in paddy fields. The model includes modules for water transport, heat and solute transport, root water uptake, profile information setup, simulation result post-processing, and parameter inversion.

[0005] The DNDC model was initially used to predict carbon capture and N2O release fluxes in farmland ecosystems. With continuous research and development, it has now become a geochemical cycle mathematical model for simulating and predicting crop growth, carbon capture, greenhouse gas emissions, nitrate leaching, and other processes in ecosystems such as drylands, wetlands, grasslands, and forests, or in specific ecological environments. The DNDC model comprises six interacting sub-modules: climate and soil, crop growth, decomposition, nitrification, denitrification, and fermentation processes. By integrating key crop growth algorithms into the model, a CROP-DNDC model has been developed that can simulate crop growth processes under water and nitrogen stress and optimize crop yield, soil nitrogen fixation, and trace gas emissions.

[0006] The shortcomings of commonly used paddy field water and fertilizer simulation models mainly include the following aspects: (1) The model is relatively complex, with many parameters and it is difficult to accurately obtain these parameters; (2) The data volume is large, requiring a large amount of high-quality soil, meteorological, crop and management data, and the model calculation volume is also large; (3) The parameter uncertainty is high, and inaccurate parameter estimation will reduce the reliability of model prediction. At the same time, changes in soil and climate conditions increase the difficulty of parameter estimation; (4) Model verification and calibration are difficult; (5) The model simulates water and nitrogen factors relatively comprehensively, but considers less or lacks nutrients such as phosphorus and potassium; (6) Poor local adaptability: after the model is calibrated in a specific area, it may not be applicable to other areas; (7) The model operation is complex, requiring high professional ability from users, which limits the use by non-professional users. Summary of the Invention

[0007] The purpose of this invention is to solve the problem of simulating and optimizing water and fertilizer management models in rice cultivation, and to propose a method for simulating and optimizing water and fertilizer management in paddy fields based on a water tank model.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for simulating and optimizing paddy field water and fertilizer management based on a water tank model, the method comprising:

[0010] S1: Using historical rainfall, irrigation, drainage, field water level and water quality data of paddy fields in the study area, establish a double-layer water tank model, and calibrate the parameters of the double-layer water tank model and the parameters of each sub-module in the double-layer water tank model. The sub-modules of the double-layer water tank model include: water module, nitrogen module and phosphorus module.

[0011] S2: Use the water module to simulate changes in water level in paddy fields;

[0012] S3: Use the nitrogen module to simulate changes in nitrogen concentration in paddy fields;

[0013] S4: Use the phosphorus module to simulate changes in phosphorus concentration in paddy fields.

[0014] Furthermore, in S1, a two-layer water tank model was established using historical rainfall, irrigation, drainage, field water level, and water quality data of the paddy fields in the study area. Specifically, this included:

[0015] S11: Select a study area, select at least three typical paddy fields within the study area, and collect field test data consisting of rainfall, irrigation, drainage, field water level and water quality data for at least one year from at least three typical paddy fields;

[0016] S12: Establish a double-layer water tank model, which includes an upper water tank and a lower water tank; the upper water tank simulates the water layer in the paddy field, and the lower water tank simulates the cultivated layer in the paddy field. Corresponding water modules, nitrogen modules, and phosphorus modules are constructed in both the upper and lower water tanks.

[0017] The parameters of the double-layer water tank model include the initial depth of the paddy field water layer. Initial depth of topsoil water The height of the four water outlets on the side of the double-layer water tank model , , and Seepage of water layer in the field and deep leakage The specific heights of the four water outlets are: the height of the paddy field ridges in the study area. Farmer's drainage outlet height Lateral seepage height of water in the field and soil water lateral seepage height ;

[0018] And determine the parameters of the water module, nitrogen module, and phosphorus module;

[0019] S13: Using the field test data collected in S11, and combining the parameters of the water module, nitrogen module, and phosphorus module in the double-layer water tank model, calculate the average Nash efficiency coefficients of the water module, nitrogen module, and phosphorus module respectively, and adjust the values ​​of each parameter in the water module, nitrogen module, and phosphorus module so that the average Nash efficiency coefficients of the water module, nitrogen module, and phosphorus module are all greater than 0.8.

[0020] Furthermore, the parameters of the water module include: the flow coefficients corresponding to the four outlets on the side of the double-layer water tank model. , , , as well as the field water layer permeability coefficient and the deep water layer permeability coefficient and ;

[0021] The parameters of the nitrogen module include the urea hydrolysis rate constant. ammonia volatilization rate constant nitration rate constant Denitrification rate constant Initial field ammonia nitrogen load Initial field water nitrate nitrogen load Initial field water urea load PU Initial soil nitrate nitrogen load and initial soil urea load ;

[0022] The parameters of the phosphorus module include the soil retention coefficient. Phosphorus release base Phosphorus release coefficient Initial field water particulate phosphorus Initial field water soluble phosphorus Initial soil layer granular phosphorus and soluble phosphorus in the initial soil layer .

[0023] Furthermore, S2 specifically includes:

[0024] S21: Multiply the flow coefficients of each water module by the head of the corresponding outlet to calculate the outflow from each outlet of the double-layer water tank model; the outflow from each outlet includes rainfall runoff. ,drain Lateral seepage of water in the field Lateral seepage of soil water Field water seepage and deep leakage The calculation method for the outflow from each outlet is as follows:

[0025]

[0026] S22: Simulate field water level changes using a double-layer water tank model and the principle of water balance;

[0027] The formula for simulating field water level changes is:

[0028]

[0029]

[0030] in,

[0031] Indicates the initial depth of the water layer in the paddy field. Represents the initial depth of soil water in the topsoil layer. For rainfall, This represents the actual daily water requirement for rice. Indicates the amount of irrigation water. Indicates the amount of water drained during field drying. Indicates a specific day, It indicates the day after the current day.

[0032] Furthermore, S3 specifically includes:

[0033] S31: The nitrogen transformation process in paddy fields is represented as follows:

[0034]

[0035]

[0036]

[0037]

[0038] in, This indicates the ammonia nitrogen produced by hydrolysis. Urea, representing urea dissolved in paddy field water, This indicates volatile ammonia nitrogen. This indicates the initial field ammonia nitrogen load. This refers to nitrate nitrogen produced during nitration. This refers to the nitrogen produced by denitrification. Indicates the initial soil nitrate nitrogen load. , , , These are the rate constants for urea hydrolysis, volatilization, nitrification, and denitrification, respectively. It is a time interval;

[0039] S32: Combines the migration and transformation processes of nitrogen in paddy fields with various flow velocities simulated in the water module to simulate the nitrogen balance in paddy fields;

[0040] By combining the migration and conversion processes of nitrogen with various flow velocities simulated in the water module, the formula for calculating the nitrogen concentration index in field water is as follows:

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] in, This is the plant absorption correction factor. , , These represent the dissolved urea, initial ammonia nitrogen load, and initial nitrate nitrogen load in paddy field water, respectively. , , These represent the concentrations of total nitrogen, ammonia nitrogen, and nitrate nitrogen in field water, respectively.

[0048] Furthermore, S4 specifically includes:

[0049] S41: Calculate the amount of phosphorus retained in the soil and the amount of phosphorus released due to rainwater erosion; the formulas for calculating the amount of phosphorus retained in the soil and the amount of phosphorus released due to rainwater erosion are as follows:

[0050]

[0051]

[0052] in, This indicates the amount of phosphorus that has seeped into the soil layer from the ground. This represents the total amount of phosphorus entering the soil layer, and s represents the soil interception coefficient. This indicates the amount of phosphorus released by rainfall or irrigation. To release the base, R represents the release coefficient, and R represents the daily rainfall.

[0053] S42: The migration and transformation process of phosphorus in paddy fields is combined with various flow velocities simulated in the water module to simulate the phosphorus balance in paddy fields;

[0054] The formula for calculating the change in total phosphorus concentration in field water is:

[0055]

[0056]

[0057] in, This is the plant absorption correction factor. Indicates the total phosphorus load in field water. This represents the total phosphorus concentration in field water. This refers to the water level in the field.

[0058] The present invention provides an intuitive and relatively accurate simulation of the alternating anaerobic and aerobic states during the flooding-drying process in paddy fields. The water and fertilizer simulation method is flexible and convenient, allowing for the adjustment and modification of various parameters based on the actual conditions of the simulated area. It can even change the number of water tanks or add coupling modules as needed. It requires no complex mechanistic assumptions, has high data utilization efficiency, and its calculations are simple and easy to understand. It can quickly respond to dynamic changes in water and fertilizer conditions in the field and update data. Attached Figure Description

[0059] Figure 1 The flowchart shows a simulation method for paddy field water and fertilizer management based on a water tank model.

[0060] Figure 2 A schematic diagram of a double-layer water tank model for paddy fields;

[0061] Figure 3 A schematic diagram of nitrogen migration and transformation in a double-layer water tank model of a paddy field;

[0062] Figure 4 This is a schematic diagram of phosphorus migration and transformation in a double-layer water tank model of a paddy field. Detailed Implementation

[0063] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0064] Model simulation is an effective method for studying soil moisture movement and nitrogen and phosphorus nutrient transformation and transport. Paddy field water and fertilizer simulation methods have significant reference value for optimizing water and fertilizer management patterns in rice cultivation, assessing environmental impacts, and addressing climate change. Currently, there are many models simulating soil moisture movement and nutrient transformation and transport in paddy fields, such as HYDRUS and ORYZA. However, these models are complex, have numerous parameters, and require substantial data and computational resources, making model validation and calibration challenging. Compared to other models, paddy field water and fertilizer simulation methods based on water tank models are flexible, convenient, and computationally simple. Furthermore, various parameters can be adjusted and modified according to the actual conditions of the simulation area, and even the number of water tanks or the addition of coupling modules can be changed as needed. Therefore, paddy field water and fertilizer simulation methods based on water tank models have significant application value for optimizing paddy field water and fertilizer regulation patterns and improving water and fertilizer use efficiency.

[0065] like Figure 1 As shown, this invention provides a simulation and optimization method for paddy field water and fertilizer management based on a water tank model, comprising the following steps:

[0066] S1: Using historical rainfall, irrigation, drainage, field water level and water quality data of paddy fields in the study area, a double-layer water tank model was established, and the parameters of each module of the double-layer water tank model were calibrated.

[0067] S2: After calibrating the water module parameters of the double-layer water tank model, the water module is used to simulate the water level changes in the paddy field;

[0068] S3: After calibrating the nitrogen module parameters of the double-layer water tank model, the nitrogen module is used to simulate the changes in nitrogen concentration in paddy fields;

[0069] S4: After calibrating the phosphorus module parameters of the double-layer water tank model, the phosphorus module is used to simulate the changes in phosphorus concentration in paddy fields.

[0070] Further, step S1 includes the following sub-steps:

[0071] S11: Select a study area, select at least three typical paddy fields within the study area, and collect data on rainfall, irrigation, drainage, field water level and water quality for at least one year for the typical paddy fields;

[0072] S12: Establish a water tank model and initially determine the initial depth of the water layer in the paddy field. Initial depth of soil water The height of the four model outlets and the values ​​of each parameter of the water, nitrogen, and phosphorus modules in the model (the parameter values ​​recommended by the model can be used in actual simulations);

[0073] S13: Using the various data collected in S11, the model parameters are calibrated through trial calculations to ensure that the average Nash efficiency coefficient of the model simulation results is greater than 0.8.

[0074] Furthermore, such as Figure 2 As shown: In step S12, the heights of the four water outlets include:

[0075] The height of paddy field ridges in the study area Farmer's drainage outlet height Lateral seepage height of water in the field and soil water lateral seepage height ;

[0076] Water module parameters include flow coefficient , , , , and The range of values ​​is shown in Table 1.

[0077] Table 1. Parameter range of the water module in the double-layer water tank model.

[0078]

[0079] Furthermore, such as Figure 3 The nitrogen transformation process in the paddy field is illustrated as follows: In the upper water tank, urea hydrolysis, ammonia volatilization, and nitrification are the main processes; while in the lower water tank (i.e., the soil layer), which is covered by the water layer and considered a reducing layer, urea hydrolysis, denitrification, mineralization, solidification, and plant uptake mainly occur. Nitrogen migrates freely between the upper and lower water tanks in the form of ammonia nitrogen, nitrate nitrogen, and urea molecules. In this invention, total nitrogen only includes ammonia nitrogen, nitrate nitrogen, and nitrogen from urea molecules, excluding nitrite nitrogen and other dissolved organic nitrogen in the paddy field water besides urea molecules.

[0080] Nitrogen module parameters include the urea hydrolysis rate constant. ammonia volatilization rate constant nitration rate constant Denitrification rate constant Initial field ammonia nitrogen load Initial field water nitrate nitrogen load Initial field water urea load Initial soil nitrate nitrogen load and initial soil urea load The range of values ​​is shown in Table 2.

[0081] Table 2. Parameter range of the nitrogen module in the double-layer water tank model.

[0082]

[0083] Furthermore, such as Figure 4 The transformation process of phosphorus in the paddy field is shown as follows: In the upper water tank, the dissolution and precipitation of soluble and particulate phosphorus are the main processes; in the lower water tank, not only the dissolution and precipitation of soluble and particulate phosphorus occur, but also soil interception and plant absorption take place. Phosphorus in paddy fields is mainly carried by water and flows with the water, being exported through deep seepage, lateral seepage, artificial drainage, and surface storm runoff.

[0084] Phosphorus module parameters include soil retention coefficient. Phosphorus release base Phosphorus release coefficient Initial field water particulate phosphorus Initial field water soluble phosphorus Initial soil layer granular phosphorus and soluble phosphorus in the initial soil layer The range of values ​​is shown in Table 3.

[0085] Table 3. Parameter range of the phosphorus module in the double-layer water tank model.

[0086]

[0087] In step S13, the formula for calculating the Nash efficiency coefficient (NES) is as follows:

[0088]

[0089] in These are measured values. These are simulated values. This is the mean of the series of measured values. The number of data points in the measured sequence is used. The trial-and-error method involves adjusting each parameter multiple times until the simulation accuracy meets the standard. Field measurements include field water level, total nitrogen, ammonia nitrogen, nitrate nitrogen concentration, and total phosphorus concentration. The measured values ​​are then compared with the simulated values.

[0090] Further, step S2 includes the following sub-steps:

[0091] S21: Multiply the flow coefficient by the head of the corresponding outlet to calculate the outflow of each outlet of the water tank model;

[0092] S22: Simulate the process of water level change in the field using a water tank model and the principle of water balance.

[0093] Furthermore, in step S21, the outflow from each outlet includes rainfall runoff. Artificial drainage Lateral seepage of water in the field Lateral seepage of soil water Field water seepage and deep leakage The formulas for calculating each outflow rate are as follows:

[0094]

[0095] In step S22, the formula for simulating the field water level change process is:

[0096]

[0097]

[0098] in, This indicates the simulated water level in the field. The soil layer represents the water depth. For rainfall, This represents the actual daily water requirement for rice, calculated using methods referenced to the water requirements of other crops. Indicates the amount of irrigation water. This indicates the amount of water drained from the drying field.

[0099] Furthermore, step S3 includes the following sub-steps:

[0100] S31: Use equations to represent the main nitrogen transformation processes in the water portion of paddy fields;

[0101] S32: Combines the migration and transformation processes of nitrogen in paddy fields with various flow velocities simulated in the water module to simulate the nitrogen balance in paddy fields.

[0102] Furthermore, the migration and transformation processes of nitrogen are as follows: Figure 3 As shown,

[0103] In step S31, the main nitrogen transformation process in the paddy field is represented by the following equation:

[0104]

[0105]

[0106]

[0107]

[0108] in, This indicates the ammonia nitrogen produced by hydrolysis. Urea, representing urea dissolved in paddy field water, This indicates volatile ammonia nitrogen. This indicates the ammonia nitrogen content in field water. This refers to nitrate nitrogen produced during nitration. This refers to the nitrogen produced by denitrification. This indicates nitrate nitrogen in the soil layer. , , , These are the rate constants for urea hydrolysis, volatilization, nitrification, and denitrification, respectively. It is a time interval.

[0109] In step S32, after combining the nitrogen migration and conversion process with various flow velocities simulated in the water module, the formula for calculating the nitrogen concentration index in field water is as follows:

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] in, The value is the plant absorption correction coefficient, which is 10 one week after applying basal fertilizer, 5 one week after applying topdressing fertilizer, and 1 under normal circumstances. , , These represent the loads of urea, ammonia nitrogen, and nitrate nitrogen in the field water, respectively. , , These represent the concentrations of total nitrogen, ammonia nitrogen, and nitrate nitrogen in field water, respectively.

[0117] Furthermore, the migration and transformation processes of phosphorus, such as Figure 4 As shown,

[0118] Step S4 includes the following steps:

[0119] S41: Calculate the amount of phosphorus retained in the soil and the amount of phosphorus released from the soil due to rainwater erosion during each period of heavy rainfall;

[0120] S42: The migration and transformation of phosphorus in paddy fields is combined with various flow velocities simulated in the water module to simulate the phosphorus balance in paddy fields.

[0121] Furthermore, in step S41, the formulas for calculating the amount of phosphorus retained by the soil and the amount of phosphorus released due to rainwater erosion are as follows:

[0122]

[0123]

[0124] in, This indicates the amount of phosphorus that has seeped into the soil layer from the ground. This represents the total amount of phosphorus entering the soil layer, and s represents the soil interception coefficient. This represents the amount of phosphorus released by rainfall or irrigation, where m is the base amount of release and n is the release coefficient. This indicates the amount of rainfall on that day.

[0125] In step S42, the formula for calculating the change in total phosphorus concentration in field water is:

[0126]

[0127]

[0128] in, The value is a plant absorption correction factor, which is 20 within one week after the application of base fertilizer; 5 when the phosphorus concentration is higher than 1 mg / L; and 1 under normal conditions. Indicates the total phosphorus load in field water. This represents the total phosphorus concentration in field water. This refers to the water level in the field.

[0129] The purpose of this invention is:

[0130] (1) Based on field measurement data, this invention constructs a water tank model and calibrates the water module parameters, which can be used for multi-scenario simulation of paddy field water management and optimize paddy field water management mode;

[0131] (2) After the nitrogen module parameters are calibrated, the present invention can be used for multi-scenario simulation of nitrogen fertilizer management in paddy fields, optimize the nitrogen fertilizer management mode in paddy fields, and reduce the amount of nitrogen loss in paddy fields;

[0132] (3) After the phosphorus module parameters are calibrated in this invention, it can be used for multi-scenario simulation of phosphate fertilizer management in paddy fields, optimize the phosphate fertilizer management mode in paddy fields, and reduce the amount of phosphorus loss in paddy fields;

[0133] In summary, this invention, through scenario simulation and analysis, can optimize the water and fertilizer management and control mode of paddy fields, save irrigation water, improve the utilization rate of nitrogen and phosphorus nutrients, and reduce non-point source pollution of farmland caused by nitrogen and phosphorus loss from the source.

[0134] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for simulating and optimizing paddy field water and fertilizer management based on a water tank model, characterized in that, The method includes: S1: Using historical rainfall, irrigation, drainage, field water level, and water quality data of paddy fields in the study area, a double-layer water tank model is established, and the parameters of the double-layer water tank model and the parameters of each sub-module in the double-layer water tank model are calibrated. The sub-modules of the double-layer water tank model include: a water module, a nitrogen module, and a phosphorus module. In S1, using historical rainfall, irrigation, drainage, field water level, and water quality data of paddy fields in the study area, the double-layer water tank model is established, specifically including: S11: Select a study area, select at least three typical paddy fields within the study area, and collect field test data consisting of rainfall, irrigation, drainage, field water level and water quality data for at least one year from at least three typical paddy fields; S12: Establish a double-layer water tank model, which includes an upper water tank and a lower water tank; the upper water tank simulates the water layer in the paddy field, and the lower water tank simulates the cultivated layer in the paddy field. Construct corresponding water modules, nitrogen modules, and phosphorus modules in both the upper and lower water tanks. The parameters of the double-layer water tank model include the initial depth of the paddy field water layer. Initial depth of topsoil water The height of the four water outlets on the side of the double-layer water tank model , , and Seepage of water layer in the field and deep leakage The specific heights of the four water outlets are: the height of the paddy field ridges in the study area. Farmer's drainage outlet height Lateral seepage height of water in the field and soil water lateral seepage height ; And determine the parameters of the water module, nitrogen module, and phosphorus module; The parameters of the water module include: the flow coefficients corresponding to the four outlets on the side of the double-layer water tank model. , , , as well as the field water layer permeability coefficient and the deep water layer permeability coefficient and ; The parameters of the nitrogen module include the urea hydrolysis rate constant. ammonia volatilization rate constant nitration rate constant Denitrification rate constant Initial field ammonia nitrogen load Initial field water nitrate nitrogen load Initial field water urea load PU Initial soil nitrate nitrogen load and initial soil urea load ; The parameters of the phosphorus module include the soil retention coefficient. Phosphorus release base Phosphorus release coefficient Initial field water particulate phosphorus Initial field water soluble phosphorus Initial soil layer granular phosphorus and soluble phosphorus in the initial soil layer ； S13: Using the field test data collected in S11, combined with the parameters of the water module, nitrogen module and phosphorus module in the double-layer water tank model, calculate the average Nash efficiency coefficient of the water module, nitrogen module and phosphorus module respectively, and adjust the values ​​of each parameter in the water module, nitrogen module and phosphorus module so that the average Nash efficiency coefficient of the water module, nitrogen module and phosphorus module is greater than 0.

8. S2: Use the water module to simulate changes in water level in paddy fields; S3: Simulate changes in nitrogen concentration in paddy fields using the nitrogen module; S3 specifically includes: S31: The nitrogen transformation process in paddy fields is represented as follows: ， ， ， ， in, This indicates the ammonia nitrogen produced by hydrolysis. Urea, representing urea dissolved in paddy field water, This indicates volatile ammonia nitrogen. This indicates the initial field ammonia nitrogen load. This refers to nitrate nitrogen produced during nitration. This refers to the nitrogen produced by denitrification. Indicates the initial soil nitrate nitrogen load. , , , These are the rate constants for urea hydrolysis, volatilization, nitrification, and denitrification, respectively. It is a time interval; S32: Combines the migration and transformation processes of nitrogen in paddy fields with various flow velocities simulated in the water module to simulate the nitrogen balance in paddy fields; By combining the migration and conversion processes of nitrogen with various flow velocities simulated in the water module, the formula for calculating the nitrogen concentration index in field water is as follows: ， ， ， ， ， ， in, This is the plant absorption correction factor. , , These represent the dissolved urea, initial ammonia nitrogen load, and initial nitrate nitrogen load in paddy field water, respectively. , , These represent the concentrations of total nitrogen, ammonia nitrogen, and nitrate nitrogen in field water, respectively. S4: Simulate changes in phosphorus concentration in paddy fields using the phosphorus module; S4 specifically includes: S41: Calculate the amount of phosphorus retained in the soil and the amount of phosphorus released due to rainwater erosion; the formulas for calculating the amount of phosphorus retained in the soil and the amount of phosphorus released due to rainwater erosion are as follows: ， ， in, This indicates the amount of phosphorus that has seeped into the soil layer from the ground. This represents the total amount of phosphorus entering the soil layer, and s represents the soil interception coefficient. This indicates the amount of phosphorus released by rainfall or irrigation. To release the base, R represents the release coefficient, and R represents the daily rainfall. S42: The migration and transformation processes of phosphorus in paddy fields are combined with various flow velocities simulated in the water module to simulate the phosphorus balance in paddy fields; The formula for calculating the change in total phosphorus concentration in field water is: ， ， in, This is the plant absorption correction factor. Indicates the total phosphorus load in field water. This represents the total phosphorus concentration in field water. This refers to the water level in the fields. Indicates a specific day, Indicates the day after the current day. For rainfall runoff, For drainage, Lateral seepage of water in the field This is due to water seepage from the field.

2. The method for simulating and optimizing paddy field water and fertilizer management based on a water tank model according to claim 1, characterized in that, S2 specifically includes: S21: Multiply the flow coefficients of each water module by the head of the corresponding outlet to calculate the outflow from each outlet of the double-layer water tank model; the outflow from each outlet includes rainfall runoff. ,drain Lateral seepage of water in the field Lateral seepage of soil water Field water seepage and deep leakage The calculation method for the outflow from each outlet is as follows: ， S22: Simulate field water level changes using a double-layer water tank model and the principle of water balance; The formula for simulating field water level changes is: ， in, Indicates the initial depth of the water layer in the paddy field. Represents the initial depth of soil water in the topsoil layer. For rainfall, This represents the actual daily water requirement for rice. Indicates the amount of irrigation water. Indicates the amount of water drained during field drying. Indicates a specific day, It indicates the day after the current day.

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