Coupling simulation method of soil water, heat and salt transport and crop growth on heterogeneous underlying surface

Abstract

The present application proposes a method for simulating the coupling of soil water, heat and salt migration and crop growth on a non-uniform underlying surface, including the following steps: constructing a two-dimensional soil water, heat and salt migration model that takes into account a partially covered non-uniform underlying surface and crop growth, and setting the initial conditions and boundary conditions for the operation of the two-dimensional soil water, heat and salt migration model; connecting the aboveground crop growth and the underground soil water, heat and salt migration through root water absorption and soil water, heat and salt stress, solving the two-dimensional soil water, heat and salt migration model based on the input soil information, meteorological data, crop growth data and required parameters, and obtaining the water, heat and salt distribution characteristics and crop growth indicators on the two-dimensional soil profile at the specified time. The present application considers the effects of the dynamic changes in crop root water absorption, crop canopy coverage and the warming and moisture retention effects of film covering on soil water, heat and salt migration in the traditional two-dimensional soil water, heat and salt migration model, making it more suitable for simulating water, heat and salt migration and crop growth processes in salinized soils of drip-irrigated farmland under film.

Description

Technical Field

[0001] The present application relates to the field of agricultural engineering, and in particular to a method for simulating the coupling of soil water, heat and salt migration and crop growth on a non-uniform underlying surface. Background Art

[0002] Existing two-dimensional soil water, heat and salt simulation models have not yet considered the growth and development process of crops above the ground. As for root water absorption, Hydrus-2d simulates crop root water absorption by defining the root range within the simulation area; for some film-covered areas, Hydrus-2d sets the film-covered area as a zero flux boundary, which serves as the upper boundary condition for two-dimensional soil water, heat and salt migration.

[0003] However, the current two-dimensional soil water, heat and salt transport model based on dynamic processes ignores crop growth and development, fails to consider the impact of root dynamic development on root water absorption and crop canopy coverage on soil evaporation, and is difficult to describe the spatiotemporal changes in soil water, heat and salt under the growth and development of crops and their influence. In addition, the film-covered drip irrigation technology for row-sown farmland, which has been widely promoted in the arid areas of northwest my country, has changed the uniformity of the underlying surface. The simulation of water, heat and salt transport under film-covered conditions based on HYDRUS-2D software is mostly simplified to zero flux boundary processing, ignoring the water and heat transfer between the soil under the film and the air above the film in the film-covered farmland, and cannot accurately describe the effect of film-covering on warming and moisture retention of the surface soil. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the purpose of this application is to propose a coupled simulation method for soil water, heat and salt migration and crop growth on a non-uniform underlying surface, so as to consider the influence of crop growth and development, such as dynamic root development, canopy coverage, etc., on the basis of the traditional two-dimensional soil water, heat and salt model, and on the basis of energy balance, consider the influence of partial film covering and canopy coverage on the upper boundary conditions of model moisture and temperature.

[0006] To achieve the above-mentioned purpose, the embodiment of the present application proposes a method for coupling simulation of soil water, heat and salt migration and crop growth on a non-uniform underlying surface, which is characterized by comprising the following steps:

[0007] Construct a two-dimensional soil water, heat and salt transport model that takes into account the partially covered non-uniform underlying surface and crop growth, and set the initial conditions and boundary conditions for the operation of the two-dimensional soil water, heat and salt transport model;

[0008] The aboveground crop growth and underground soil water, heat and salt migration are connected through root water absorption and soil water, heat and salt stress. The two-dimensional soil water, heat and salt migration model is solved according to the input soil information, meteorological data, crop growth data and required parameters to obtain the water, heat and salt distribution characteristics and crop growth indicators on the two-dimensional soil profile at a specified time.

[0009] Optionally, before constructing a two-dimensional soil water, heat and salt transport model that considers partially covered non-uniform underlying surface and crop growth, it also includes:

[0010] Collect soil data, weather data, irrigation data, and crop growth data for conventional weather data-driven models;

[0011] Determine soil hydraulic parameters, heat transfer parameters, solute transport parameters, crop growth parameters, and evaporation / transpiration stress parameters;

[0012] According to the data and parameters obtained above, the simulation range and time of soil profile and crop growth are determined and the simulation area is divided into triangular grids.

[0013] Optionally, when calculating the net radiation of the soil surface, the two-dimensional soil water, heat and salt migration model considers four underlying surface conditions: bare soil without cover, bare soil covered by a canopy, covered soil, and covered soil covered by a canopy, and performs energy distribution calculation based on FAO-56 and the mixed dual-source theory. The calculation process includes:

[0014] Net radiation from bare soil surface without covering The calculation method is:

[0015]

[0016] In the formula, is the net shortwave radiation, is the net longwave radiation, is the incident solar radiation, is the soil surface reflectivity;

[0017] Divide the net radiation of the bare soil surface into latent heat flux and sensible heat flux , which is calculated as follows:

[0018]

[0019]

[0020]

[0021] In the formula, , , They are the evaporation resistance of the soil surface, the air resistance between the soil surface and the canopy height, and the air resistance between the canopy height and the reference height. is the air density, is the specific heat of air at normal pressure, is the hygrometer constant, is the soil surface vapor pressure, is the vapor pressure at the reference height, is the soil surface temperature, is the air temperature at the reference altitude;

[0022] The calculation method of soil surface evaporation and temperature without shielding is:

[0023]

[0024]

[0025] In the formula, is the latent heat of evaporation, is the slope of the saturated vapor pressure-temperature curve, is the saturated water vapor pressure at the reference height;

[0026] Net radiation on bare soil surface under vegetation canopy cover The calculation method is:

[0027]

[0028] In the formula, is the crop canopy reflectance, is the crop coefficient, is the leaf area index;

[0029] Net radiation of bare soil surface under vegetation canopy cover Latent heat flux and sensible heat flux The calculation process is similar to the net radiation partition calculation process of bare soil surface without cover. The calculation method of soil surface evaporation and temperature under vegetation canopy cover is:

[0030]

[0031]

[0032] In the formula, , , They are the evaporation resistance of the soil surface under the canopy coverage scenario, the air resistance between the soil surface and the canopy height, the air resistance between the canopy height and the reference height, is the evaporation rate of bare soil surface under canopy cover, is the surface temperature of bare soil under canopy cover;

[0033] Net radiation on the surface of film-covered soil The calculation method is:

[0034]

[0035] In the formula, is the short-wave reflectivity of the film, is the long-wave transmittance of the film, is the long-wave radiation emitted by the film;

[0036] Under the film covering condition, the film is regarded as an impermeable layer, and the water vapor transmission between the soil under the film and the air above the film is ignored. The net radiation obtained by the soil under the film is all used to increase the soil temperature, that is:

[0037]

[0038] in, is the soil sensible heat flux under film covering conditions;

[0039] Soil temperature under film covering The calculation method is:

[0040]

[0041] In the formula, is the contact thermal resistance between the film and the soil;

[0042] When the vegetation canopy and film exist at the same time, the net radiation of the film-covered soil surface under the vegetation canopy Calculation method:

[0043]

[0044] Since the net radiation obtained by the film-covered soil surface under the vegetation canopy is all used to increase the soil temperature, the soil sensible heat flux for:

[0045]

[0046] The soil temperature under the vegetation canopy is The calculation method is:

[0047]

[0048] In the formula, is the thermal contact resistance between the film and the soil.

[0049] Optionally, when the vegetation canopy and the film exist simultaneously, the method further comprises:

[0050] Obtaining the net radiation intercepted by the crop canopy , the calculation formula is:

[0051]

[0052] Since the net radiation intercepted by the crop canopy is used for latent heat generation in the leaves and sensible heat consumption , then the following formula holds:

[0053]

[0054]

[0055]

[0056] After joint solution, the calculation formula of crop canopy potential transpiration rate is:

[0057]

[0058] In the formula, is the crop potential transpiration rate, is the canopy leaf temperature, for The canopy saturated water vapor pressure at temperature, is the transpiration resistance of leaf stomata, is the air resistance at the height of the leaves and the canopy.

[0059] Optionally, when simulating crop growth, the two-dimensional soil water, heat and salt transport model takes into account the interception of light energy by the canopy, the conversion of light energy into biomass, the calculation of yield based on biomass, and the process of water, heat and salt stress.

[0060] The simulation process of the crop growth part includes:

[0061] The simulation part of crop growth is based on days as the time step, and phenological development is based on daily heat units. Based on the calculation of the heat unit coefficient from 0 to 1, the crop is controlled The growth process from sowing to maturity is expressed as:

[0062]

[0063]

[0064] in, and They are The highest and lowest temperatures of the day, The base temperature for crop growth. It is the maximum heat unit value required for crops from sowing to maturity;

[0065] The simulation of leaf area is divided into two stages. The first stage is from sowing to the maximum leaf area, and the second stage is from the beginning of the decline of leaf area to crop maturity. The leaf area change process in the first stage is expressed as:

[0066]

[0067]

[0068] in, is the leaf area index, is the potential maximum leaf area index, is the heat unit factor, As the minimum crop stress factor, the soil water, heat and salt comprehensive stress factor is taken as and temperature stress factors The minimum value in is calculated by the following formulas:

[0069]

[0070]

[0071]

[0072] In the formula, and is the crop parameter, In order to consider the influence of soil water, heat and salt The actual evaporation of the day, For the Potential transpiration of crops per day, is the daily average temperature, The optimum growth temperature for crops;

[0073] The leaf area change process in the second stage is expressed as:

[0074]

[0075] In the formula, is the actual maximum leaf area index, is the leaf area senescence index, is the heat unit coefficient when the leaf area begins to age;

[0076] Plant height The simulation part is about the maximum plant height and heat unit factor The function is calculated as follows:

[0077]

[0078] Crop canopy width The simulated part and crop height The calculation formula is:

[0079]

[0080] In the formula, is the crop canopy parameter;

[0081] The simulation of crop root growth and root density distribution takes into account its dynamic changes in the two-dimensional profile. Days of crop root length The calculation formula is:

[0082]

[0083] In the formula, is a constant;

[0084] Crop root width Take it as half of the length, that is:

[0085]

[0086] No. The calculation formula for the two-dimensional distribution of crop root density on a given day is:

[0087]

[0088] In the formula, For the day's crop root area, is an arbitrarily specified distribution function, which can be described as follows:

[0089]

[0090] In the formula, , are the distances of the crop from the coordinate origin in the horizontal and vertical directions, , Respectively The maximum root width and depth of crops in horizontal and vertical directions during the day. For planting crops, , is the empirical coefficient, , Respectively The position of maximum water uptake by roots in horizontal and vertical directions during the day;

[0091] Optionally, the boundary conditions for running the two-dimensional soil water, heat and salt transport model include boundary conditions of water, temperature and salt in the two-dimensional soil profile, where:

[0092] The upper boundary of soil moisture exists in film, drip irrigation belt and bare soil at the same time, involving zero flux, variable flux and atmospheric boundary conditions. The left and right boundaries of soil moisture select zero flux boundary, and the lower boundary of soil moisture selects constant head, zero flux or free drainage boundary. Among them, for soil covered with film, the upper boundary of moisture is regarded as zero flux boundary; for soil under drip irrigation belt, the upper boundary of moisture is regarded as variable head boundary; for bare soil area without film coverage, the upper boundary of moisture is regarded as atmospheric boundary;

[0093] Each soil node of the soil temperature upper boundary adopts given temperature and constant temperature flux boundary conditions, the left and right boundaries of the soil temperature adopt given temperature or zero flux boundary conditions, and the middle boundary of the soil temperature adopts given temperature or constant temperature flux boundary conditions. Among them, there are four types of upper boundaries of given temperature under the given temperature upper boundary conditions, and the upper boundary type of each soil node can be automatically converted according to the crop growth status. Among them, the four types of upper boundaries of given temperature under the given temperature boundary conditions are the soil surface temperature under the film not covered by the canopy, the soil surface temperature under the film covered by the canopy, the bare soil surface temperature under the canopy covered, and the bare soil surface temperature not covered by the canopy;

[0094] The upper boundary of soil solute can select constant concentration, constant concentration flux or zero flux boundary conditions, the left and right boundaries of soil solute migration can select zero flux boundary conditions, and the lower boundary type of soil solute migration is the same as the upper boundary, and constant concentration, constant concentration flux or zero flux boundary conditions can be selected.

[0095] Optionally, the method of connecting the aboveground crop growth and the underground soil water, heat and salt migration through root water absorption and soil water, heat and salt stress includes:

[0096] The simulation of soil water movement adopts the two-dimensional mixed Richards equation considering root water absorption, which is expressed as:

[0097]

[0098] In the formula, is the soil volume moisture content, For time, is the soil matrix potential or pressure head, is the unsaturated hydraulic conductivity of the soil, , is the two-dimensional spatial coordinate, rightward and downward are positive, is the source-sink term;

[0099] The Van Genuchten-Mualem model is used to describe the soil hydraulic properties, in which the soil moisture content in the soil hydraulic properties is and hydraulic conductivity Matrix potential The relational expression is expressed as:

[0100]

[0101]

[0102]

[0103] In the formula, is the effective saturation of soil, is the residual moisture content of the soil, is the saturated moisture content of the soil, , and is the soil shape coefficient, and , is the saturated hydraulic conductivity of the soil, is the soil porosity correlation parameter;

[0104] The source and sink terms in the soil water transport equation are the crop root water absorption terms in the two-dimensional soil water, heat and salt transport model. The actual crop root water absorption rate calculation formula is:

[0105]

[0106] In the formula, is the width of the soil surface related to the transpiration process, is the potential transpiration rate, is the node coordinate The water-salt stress coefficient at is calculated as follows:

[0107]

[0108] in, , is an empirical parameter, is the osmotic potential, To ignore the pressure head that reduces the water absorption rate by 50% under the osmotic potential condition, The osmotic potential is the 50% reduction in water absorption rate when the soil matrix potential is ignored;

[0109] According to the actual crop root water absorption rate, the actual crop transpiration rate is calculated using the following formula:

[0110]

[0111] In the formula, To consider the actual transpiration under the influence of soil water and salt stress;

[0112] Ignoring the effect of water vapor diffusion, the two-dimensional heat conduction equation for the soil temperature simulation is:

[0113]

[0114] In the formula, and are the volumetric heat capacities of the porous medium and the liquid phase, is the soil temperature, is the sensible thermal conductivity of soil, , are the single-width flow rates in the horizontal and vertical directions, respectively. The volumetric heat capacity is defined as the product of the volumetric heat capacity and the mass heat capacity:

[0115]

[0116] in, Indicates volume ratio, subscript , , They represent solid phase, organic matter and liquid phase respectively;

[0117] Soil sensible thermal conductivity Calculated by the following formula:

[0118]

[0119] In the formula, , are the longitudinal and transverse thermal diffusivities, is the absolute value of Darcy flux density, thermal conductivity Reflects the tortuosity of porous media, and its expression is:

[0120]

[0121] in, , , All are empirical coefficients;

[0122] The two-dimensional solute transport in soil is based on the advection-diffusion equation, and the calculation formula of the advection-diffusion equation is:

[0123]

[0124] In the formula, is the solute mass concentration, is the soil dry bulk density, is the adsorption concentration, is the source-sink term in the water transport equation, is the solute source and sink term, is the saturated-unsaturated hydrodynamic diffusion coefficient, and its calculation formula is:

[0125]

[0126] In the formula, is the liquid phase bending coefficient, is the diffusion coefficient of solute molecules in water, , are the lateral and longitudinal solute diffusivities, respectively.

[0127] Optionally, before solving the two-dimensional soil water, heat and salt transport model, the method further includes:

[0128] According to the input soil information samples, meteorological data samples, crop growth data samples and required parameter samples, a numerical algorithm is run to calculate the daily crop growth and soil evaporation, plant transpiration and soil surface temperature to update the upper boundary conditions of the two-dimensional soil water, heat and salt migration model.

[0129] Optionally, solving the two-dimensional soil water, heat and salt migration model includes:

[0130] The finite element method is used to solve the discrete moisture, temperature and salt control equations. The simulation stops when the last set time point is reached, and the spatiotemporal distribution of moisture, temperature and salt as well as the crop growth status and final yield are obtained.

[0131] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0132] 1. Conventional meteorological data can be used to drive the model, avoiding the difficulty of obtaining non-uniform ground water, heat and salt boundary data. In addition, crop growth and development can be considered on the basis of the traditional two-dimensional soil water, heat and salt model, and the mutual feedback between crop growth and two-dimensional soil water, heat and salt migration can be considered.

[0133] 2. The addition of the effects of film covering and crop canopy covering on soil water and heat transfer can make up for the deficiency of the existing model in temperature simulation that cannot reflect the warming effect of film covering, and more carefully depict plant transpiration and soil evaporation, which is conducive to truly reflecting the soil water, heat and salt migration process in drip irrigation farmland under film.

[0134] 3. In the simulation of two-dimensional soil water, heat and salt migration and crop growth, the coupling and mutual feedback mechanism between crop root water absorption and soil water, heat and salt conditions is considered, which more accurately and comprehensively describes the two-dimensional distribution of soil water, heat and salt and the crop growth process during farmland production, laying the foundation for precision irrigation and targeted desalination.

[0135] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0136] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0137] Figure 1 It is a flow chart of a method for coupling simulation of soil water, heat and salt migration and crop growth on a non-uniform underlying surface according to an embodiment of the present application;

[0138] Figure 2 is an operation flow chart of a two-dimensional soil water, heat and salt migration model according to an embodiment of the present application;

[0139] Figure 3 is a structural diagram of a two-dimensional soil water, heat and salt migration model according to an embodiment of the present application;

[0140] Figure 4 It is a schematic diagram of upper boundary type conversion according to an embodiment of the present application. DETAILED DESCRIPTION

[0141] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0142] The following describes a method for coupling simulation of soil water, heat and salt migration and crop growth on a non-uniform underlying surface according to an embodiment of the present application with reference to the accompanying drawings.

[0143] Existing water-salt transport models are mostly aimed at the water-heat-salt transport in one-dimensional soils. They are unable to consider the impact of field management measures such as crop row sowing and film mulching on the energy balance and water-heat transport of the underlying surface, and are difficult to fully reflect processes such as soil evaporation, plant transpiration, temperature transfer and salt accumulation in two-dimensional profiles. The commonly used two-dimensional soil water-heat-salt simulation software HYDRUS-2D only involves the simulation of water-heat-salt transport in soils. For film-mulched soils, it often simplifies the simulation by using zero flux conditions as the upper boundary, and is unable to describe in detail the impact of crop growth and development and the warming and moisture-retaining effects of film mulching on the water-heat-salt transport in two-dimensional soils.

[0144] Therefore, the present invention proposes a coupled simulation method for soil water, heat and salt migration and crop growth on a non-uniform underlying surface, which takes into account soil water, heat and salt migration and crop growth processes under the influence of non-uniform underlying surfaces (such as crop row sowing, partial film covering, drip irrigation, etc.). The main problems solved by this method include: considering the influence of crop growth and development, such as root system dynamic development, canopy coverage, etc., on the basis of the traditional two-dimensional soil water, heat and salt model; and considering the influence of partial film covering and canopy coverage on the upper boundary conditions of model moisture and temperature on the basis of energy balance.

[0145] Figure 1 FIG. 1 is a flow chart of a method for coupling simulation of soil water, heat and salt migration and crop growth on a non-uniform underlying surface according to an embodiment of the present application. Figure 1 As shown, the method comprises the following steps:

[0146] Step 101, construct a two-dimensional soil water, heat and salt migration model that takes into account the partially covered non-uniform underlying surface and crop growth, and set the initial conditions and boundary conditions for the operation of the two-dimensional soil water, heat and salt migration model.

[0147] It should be noted that when constructing the two-dimensional soil water, heat and salt migration model line, it is necessary to first determine the data and parameters, so as to determine the simulation range and simulation time of the soil profile and crop growth and divide the simulation area into triangular grids, including:

[0148] Collect soil data, meteorological data, irrigation data, and crop growth data for conventional meteorological data-driven models; determine soil hydraulic parameters, heat conduction parameters, solute transport parameters, crop growth parameters, and evaporation / transpiration stress parameters; based on the above data and parameters, determine the simulation range and simulation time of the soil profile and crop growth and divide the simulation area into triangular grids.

[0149] The embodiment of the present application avoids the difficulty of obtaining non-uniform ground water, heat and salt boundary data by adopting conventional meteorological data to drive the model.

[0150] In some embodiments of the present application, the two-dimensional soil water, heat and salt transport model is constructed based on FAO-56 and the mixed dual-source theory, taking into account the interaction between energy distribution and non-uniform underlying surfaces (such as row crops, partial film covering, etc.). The calculation methods of the net radiation, sensible heat flux and latent heat flux of the soil surface under different underlying surface conditions are described in detail, and the calculation methods of the soil evaporation rate and temperature of bare soil without cover, bare soil under canopy cover, film covered soil and film covered soil under canopy cover are given through formula derivation.

[0151] Specific, uncovered bare soil surface net radiation The calculation method is:

[0152]

[0153] In the formula, is the net shortwave radiation, is the net longwave radiation, is the incident solar radiation, is the soil surface reflectivity.

[0154] The net radiation of the bare soil surface is further divided into latent heat flux and sensible heat flux , which is calculated as follows:

[0155]

[0156]

[0157]

[0158] In the formula, , , They are the evaporation resistance of the soil surface, the air resistance between the soil surface and the canopy height, and the air resistance between the canopy height and the reference height. is the air density, is the specific heat of air at normal pressure, is the hygrometer constant, is the soil surface vapor pressure, is the vapor pressure at the reference height, is the soil surface temperature, is the air temperature at the reference altitude.

[0159] By solving the above formula, the calculation method of soil surface evaporation and temperature without shielding is obtained as follows:

[0160]

[0161]

[0162] In the formula, is the latent heat of evaporation, is the slope of the saturated vapor pressure-temperature curve, is the saturated water vapor pressure at the reference height, and the other parameters are the same as above.

[0163] Net radiation on bare soil surface under vegetation canopy cover The calculation method is:

[0164]

[0165] In the formula, is the crop canopy reflectance, is the crop coefficient, is the leaf area index;

[0166] Similarly, the net radiation of the bare soil surface under the vegetation canopy is Further divided into latent heat flux and sensible heat flux The calculation process is similar to the net radiation partition calculation process of bare soil surface without cover. The calculation method of soil surface evaporation and temperature under vegetation canopy cover is:

[0167]

[0168]

[0169] In the formula, , , They are the evaporation resistance of the soil surface under the canopy coverage scenario, the air resistance between the soil surface and the canopy height, the air resistance between the canopy height and the reference height, is the evaporation rate of bare soil surface under canopy cover, is the surface temperature of bare soil under canopy cover.

[0170] Net radiation on the surface of film-covered soil The calculation method is:

[0171]

[0172] In the formula, is the short-wave reflectivity of the film, is the long-wave transmittance of the film, is the long-wave radiation emitted by the film.

[0173] It can be understood that under the film covering condition, the film can be regarded as an impermeable layer, and the water vapor transmission between the soil under the film and the air above the film is ignored. The net radiation obtained by the soil under the film is all used to increase the soil temperature, that is:

[0174]

[0175] in, is the soil sensible heat flux under mulching conditions.

[0176] Soil temperature under film covering The calculation method is:

[0177]

[0178] In the formula, is the thermal contact resistance between the film and the soil.

[0179] When the vegetation canopy and film exist at the same time, the net radiation of the film-covered soil surface under the vegetation canopy Calculation method:

[0180]

[0181] Since the net radiation obtained by the film-covered soil surface under the vegetation canopy is all used to increase the soil temperature, the soil sensible heat flux for:

[0182]

[0183] The soil temperature under the vegetation canopy is The calculation method is:

[0184]

[0185] In the formula, is the thermal contact resistance between the film and the soil.

[0186] Furthermore, when the vegetation canopy and film exist at the same time, the net radiation intercepted by the crop canopy is The calculation formula is:

[0187]

[0188] Since the net radiation intercepted by the crop canopy is used for latent heat generation in the leaves and sensible heat consumption , then the following formula holds:

[0189]

[0190]

[0191]

[0192] After joint solution, the calculation formula of crop canopy potential transpiration rate is:

[0193]

[0194] In the formula, is the crop potential transpiration rate, is the canopy leaf temperature, for The canopy saturated water vapor pressure at temperature, is the transpiration resistance of leaf stomata, is the air resistance at the height of the leaves and the canopy.

[0195] In addition, when simulating crop growth, the two-dimensional soil water, heat and salt transport model takes into account the interception of light energy by the canopy, the conversion of light energy into biomass, the calculation of yield based on biomass, and the process of water, heat and salt stress.

[0196] Specifically, the crop growth simulation uses days as the time step, and the phenological development is based on daily heat units. Based on the calculation of the heat unit coefficient from 0 to 1, the crop is controlled The growth process from sowing to maturity is expressed as:

[0197]

[0198]

[0199] in, and They are The highest and lowest temperatures of the day, The base temperature for crop growth. It is the maximum heat unit value required for crops from sowing to maturity.

[0200] The simulation part of leaf area is divided into two stages. The first stage is from sowing to the maximum leaf area, and the second stage is from the beginning of leaf area decline to crop maturity.

[0201] Among them, the leaf area change process in the first stage is expressed as:

[0202]

[0203]

[0204] in, is the leaf area index, is the potential maximum leaf area index, is the heat unit factor, As the minimum crop stress factor, the soil water, heat and salt comprehensive stress factor is taken as and temperature stress factors The minimum value in is calculated by the following formulas:

[0205]

[0206]

[0207]

[0208] In the formula, and is the crop parameter, In order to consider the influence of soil water, heat and salt The actual evaporation of the day, For the Potential transpiration of crops per day, is the daily average temperature, It is the optimum growth temperature for crops.

[0209] The leaf area change process in the second stage is expressed as:

[0210]

[0211] In the formula, is the actual maximum leaf area index, is the leaf area senescence index, It is the heat unit coefficient when the leaf area begins to age.

[0212] Plant height The simulation part is about the maximum plant height and heat unit factor The function is calculated as follows:

[0213]

[0214] Crop canopy width The simulated part and crop height The calculation formula is:

[0215]

[0216] In the formula, is the crop canopy parameter.

[0217] The simulation of crop root growth and root density distribution takes into account its dynamic changes in the two-dimensional profile. Days of crop root length The calculation formula is:

[0218]

[0219] In the formula, is a constant.

[0220] In one possible embodiment, When the value is 2.5, the root system is The maximum value is reached when it is 0.4.

[0221] Crop root width Take it as half of the length, that is:

[0222]

[0223] No. The calculation formula for the two-dimensional distribution of crop root density on a given day is:

[0224]

[0225] In the formula, For the day's crop root area, is an arbitrarily specified distribution function.

[0226] In some embodiments of the present application, The description form can be:

[0227]

[0228] In the formula, , are the distances of the crop from the coordinate origin in the horizontal and vertical directions, , Respectively The maximum root width and depth of crops in horizontal and vertical directions during the day. For planting crops, , is the empirical coefficient, generally 1, , Respectively The position of maximum water absorption by the roots in the horizontal and vertical directions during the day.

[0229] In some embodiments of the present application, the initial conditions for setting the operation of the two-dimensional soil water, heat and salt migration model have been explained in the process of determining parameters in the previous text, and this application will not give detailed examples.

[0230] In addition, the initial conditions also include the set initial node information of soil moisture, temperature and salinity, as well as the meteorological data within a given simulation time.

[0231] In the embodiment of the present application, the boundary conditions set for the operation of the two-dimensional soil water, heat and salt migration model include the boundary conditions of moisture, temperature and salt in the two-dimensional soil profile.

[0232] Among them, the upper boundary of soil moisture exists in film, drip irrigation belt and bare soil at the same time, involving zero flux, variable flux and atmospheric boundary conditions. The left and right boundaries of soil moisture select zero flux boundary, and the lower boundary of soil moisture selects constant head, zero flux or free drainage boundary. Among them, for soil covered with film, the upper boundary of moisture is regarded as zero flux boundary; for soil under drip irrigation belt, the upper boundary of moisture is regarded as variable head boundary; for bare soil area without film coverage, the upper boundary of moisture is regarded as atmospheric boundary.

[0233] Specifically, for film-covered soil, the upper boundary of moisture can be regarded as a zero flux boundary, that is:

[0234]

[0235] In the formula, , They are the coordinates of the nodes at both ends of the coating area.

[0236] For the soil under the drip irrigation belt, affected by the irrigation periodicity, the upper boundary of moisture is regarded as variable water head, that is:

[0237]

[0238] In the formula, , are the coordinates of the nodes at both ends of the wetted area of ​​the drip irrigation belt, is the irrigation water flux, which corresponds to the flux during the irrigation period and is 0 during the non-irrigation period.

[0239] For bare soil areas without film coverage, the upper boundary of moisture can be regarded as the variable water head boundary, but the impact of crop canopy coverage on evaporation and rainfall needs to be considered, that is:

[0240]

[0241]

[0242] In the formula, for The evaporation rate of the bare soil surface under the canopy cover at the moment is ; is the evaporation rate of bare soil surface without canopy cover at time t, which is ; is the rainfall rate; is the end point of the coating area, less than is the coating area, larger than It is a bare soil area; is the node coordinate corresponding to the widest point on the right side of the crop canopy, which changes with the growth and development of crops during the growth period and is smaller than is the canopy coverage area, greater than It is a bare soil area; are the side node coordinates of the bare soil area.

[0243] The left and right boundaries of soil moisture can be selected as zero flux boundaries, that is:

[0244]

[0245] The soil moisture lower boundary can be selected as constant head, zero flux or free drainage boundary, which are:

[0246]

[0247]

[0248]

[0249] In the formula, is the depth of the lower boundary; is the pressure head at the lower boundary; the other parameters are the same as above.

[0250] Among them, each soil node on the upper boundary of the boundary soil temperature adopts given temperature and constant temperature flux boundary conditions, the left and right boundaries of the soil temperature adopt given temperature or zero flux boundary conditions, and the middle boundary of the soil temperature adopts given temperature or constant temperature flux boundary conditions. Among them, there are four types of upper boundaries with given temperatures under the given temperature upper boundary conditions, and the upper boundary type of each soil node can be automatically converted according to the crop growth status. Among them, the four types of upper boundaries with given temperatures under the given temperature boundary conditions are the soil surface temperature under the film not covered by the canopy, the soil surface temperature under the film covered by the canopy, the bare soil surface temperature under the canopy covered, and the bare soil surface temperature not covered by the canopy.

[0251] Specifically, each soil node on the soil temperature upper boundary can adopt the given temperature and constant temperature flux boundary conditions. Under the given temperature boundary condition, the temperature difference caused by different underlying surface conditions in the horizontal direction and the influence of the dynamic changes of the crop canopy are considered. There can be 4 types of given temperature upper boundaries at the same time, namely:

[0252] (1) Soil surface temperature under the film without canopy cover: ;

[0253] (2) Soil surface temperature under film under canopy cover: ;

[0254] (3) Bare soil surface temperature under canopy cover: ;

[0255] (4) Surface temperature of bare soil not covered by canopy: .

[0256] In the embodiment of the present application, the two-dimensional soil water, heat and salt migration model can automatically convert the upper boundary type of each soil node according to the crop growth status.

[0257] In a possible embodiment, it is assumed that there are two crop planting points in the drip irrigation farmland under film and The node coordinates corresponding to the left and right ends of the canopy width are , , , , then in ( ) in the simulation area, the upper boundary conditions for a given temperature are:

[0258] : Soil surface temperature under the film without canopy cover ;

[0259] : Soil surface temperature under film under canopy cover ;

[0260] : Soil surface temperature under the film without canopy cover ;

[0261] : Soil surface temperature under film under canopy cover ;

[0262] : Bare soil surface temperature under canopy cover ;

[0263] : Bare soil surface temperature without canopy cover .

[0264] It can be understood that the canopy width can be 0. In this scenario, there are only two given temperature upper boundary types (1) and (2). When the canopy width changes with the simulation time, the upper boundary type corresponding to each soil node changes at the same time. When water is applied, the upper boundary type of the wet zone is converted from a given temperature boundary to a constant temperature flux boundary condition:

[0265]

[0266] In the formula, Irrigation water temperature.

[0267] The left and right boundaries of soil temperature can adopt given temperature or zero flux boundary conditions, which are:

[0268]

[0269]

[0270]

[0271] The soil temperature boundary can use a given temperature or a constant temperature flux boundary condition, which are:

[0272]

[0273]

[0274] In the formula, is the soil temperature at the lower boundary; is the moisture flux temperature at the lower boundary.

[0275] Among them, the upper boundary of soil solute selects constant concentration, constant concentration flux or zero flux boundary conditions, the left and right boundaries of soil solute migration select zero flux boundary conditions, and the lower boundary type of soil solute migration is the same as the upper boundary, selecting constant concentration, constant concentration flux or zero flux boundary conditions.

[0276] Specifically, the soil solute upper boundary can choose constant concentration, constant concentration flux or zero flux boundary conditions, which are:

[0277]

[0278]

[0279]

[0280] In the formula, is the upper boundary solute concentration; is the solute concentration of the upper boundary water flux.

[0281] Zero flux boundary conditions can be selected for the left and right boundaries of soil solute transport:

[0282]

[0283] The lower boundary type of soil solute transport is the same as the upper boundary, and both can select constant concentration, constant concentration flux or zero flux boundary conditions. Refer to the above formula, and this application will not repeat it here.

[0284] Step 102, connecting the aboveground crop growth and the underground soil water, heat and salt migration through root water absorption and soil water, heat and salt stress, solving the two-dimensional soil water, heat and salt migration model according to the input soil information, meteorological data, crop growth data and required parameters, and obtaining the water, heat and salt distribution characteristics and crop growth indicators on the two-dimensional soil profile at a specified time.

[0285] In the embodiment of the present application, the simulation part of soil water movement adopts a two-dimensional mixed Richards equation considering root water absorption, and its expression is:

[0286]

[0287] In the formula, is the soil volume moisture content, For time, is the soil matrix potential or pressure head, is the unsaturated hydraulic conductivity of the soil, , is the two-dimensional spatial coordinate, rightward and downward are positive, It is the source and sink term.

[0288] Furthermore, the Van Genuchten-Mualem model is used to describe the soil hydraulic properties, in which the soil moisture content in the soil hydraulic properties is and hydraulic conductivity Matrix potential The relational expression is expressed as:

[0289]

[0290]

[0291]

[0292] In the formula, is the effective saturation of soil, is the residual moisture content of the soil, is the saturated moisture content of the soil, , and is the soil shape coefficient, and , is the saturated hydraulic conductivity of the soil, It is the soil porosity correlation parameter, and its value is generally 0.5.

[0293] The source and sink terms in the soil water transport equation are the crop root water absorption terms in the two-dimensional soil water, heat and salt transport model. The actual crop root water absorption rate calculation formula is:

[0294]

[0295] In the formula, is the width of the soil surface related to the transpiration process, is the potential transpiration rate, is the node coordinate The water-salt stress coefficient at is calculated as follows:

[0296]

[0297] in, , is an empirical parameter, is the osmotic potential, which is related to the solute concentration. To ignore the pressure head that reduces the water absorption rate by 50% under the osmotic potential condition, The osmotic potential is the 50% reduction in water absorption rate when the soil matrix potential is ignored.

[0298] Furthermore, the actual transpiration rate of crops can be calculated based on the actual crop root water absorption rate. The calculation formula is:

[0299]

[0300] In the formula, To consider the actual transpiration under the influence of soil water and salt stress.

[0301] Ignoring the effect of water vapor diffusion, the two-dimensional heat conduction equation for the soil temperature simulation is:

[0302]

[0303] In the formula, and are the volumetric heat capacities of the porous medium and the liquid phase, is the soil temperature, is the sensible thermal conductivity of soil, , are the single-width flow rates in the horizontal and vertical directions, respectively. The volumetric heat capacity is defined as the product of the volumetric heat capacity and the mass heat capacity:

[0304]

[0305] in, Indicates volume ratio, subscript , , They represent solid phase, organic matter and liquid phase respectively.

[0306] Soil sensible thermal conductivity Calculated by the following formula:

[0307]

[0308] In the formula, , are the longitudinal and transverse thermal diffusivities, is the absolute value of Darcy flux density, thermal conductivity Reflects the tortuosity of porous media, and its expression is:

[0309]

[0310] in, , , All are empirical coefficients.

[0311] The two-dimensional solute transport in soil is based on the advection-diffusion equation, and the calculation formula of the advection-diffusion equation is:

[0312]

[0313] In the formula, is the solute mass concentration, is the soil dry bulk density, is the adsorption concentration, is the source-sink term in the water transport equation, is the solute source and sink term, is the saturated-unsaturated hydrodynamic diffusion coefficient, and its calculation formula is:

[0314]

[0315] In the formula, is the liquid phase bending coefficient, is the diffusion coefficient of solute molecules in water, , are the lateral and longitudinal solute diffusivities, respectively.

[0316] Furthermore, the dissolved concentration and adsorption concentration The non-equilibrium interaction between them is described by the linear isotherm adsorption equation:

[0317]

[0318]

[0319] In the formula, is an empirical parameter.

[0320] Therefore, the two-dimensional soil water, heat and salt migration model can be solved according to the input soil information, meteorological data, crop growth data and required parameters to obtain the water, heat and salt distribution characteristics and crop growth indicators on the two-dimensional soil profile at a specified time.

[0321] It can be understood that before solving the two-dimensional soil water, heat and salt migration model, it is necessary to run a numerical algorithm to calculate the daily crop growth and soil evaporation, plant transpiration and soil surface temperature based on the input soil information samples, meteorological data samples, crop growth data samples and required parameter samples, so as to update the upper boundary conditions of the two-dimensional soil water, heat and salt migration model.

[0322] As a possible implementation method, the specific steps for solving the two-dimensional soil water, heat and salt transport model are as follows:

[0323] Step 1: First, determine the simulation range of the soil profile, discretize it into spatial triangular grid nodes, and set the simulation time and step size;

[0324] Step 2: Set soil and crop parameter information, including soil hydraulic characteristic parameters, heat conduction parameters, solute transport parameters, and crop growth parameters;

[0325] Step 3: Set the initial node information of soil moisture, temperature and salinity, and the meteorological data within the given simulation time;

[0326] Step 4: Set the boundary conditions of moisture, temperature and salinity in the two-dimensional soil profile;

[0327] Step 5: Read meteorological data and crop growth parameters to determine the specific values ​​of upper and lower boundary conditions;

[0328] Step 6: Using finite element method to solve the discrete moisture, temperature and salt control equations;

[0329] Step 7: Repeat the above steps until the last simulation time point is reached, and the spatiotemporal distribution of water, temperature and salinity, as well as the crop growth status and final yield can be finally obtained.

[0330] Among them, steps 1 to 4 have been explained in the previous text and will not be repeated here.

[0331] Step 5 involves running a numerical algorithm to calculate daily crop growth and soil evaporation, plant transpiration and soil surface temperature based on input soil information, meteorological data, crop growth data and required parameters, and determining the specific values ​​of the upper and lower boundary conditions.

[0332] Step 6 involves the process of solving the discrete moisture, temperature and salt control equations using the finite element method. The finite element method is a numerical method widely used in engineering and scientific computing. It divides a complex physical problem into multiple simple small units, solves the approximate solution of each small unit separately, and then combines them to obtain an approximate solution to the overall problem. This application does not limit the specific algorithm of the finite element method.

[0333] In order to explain the above embodiment more clearly, Figure 2 and 3 As shown, this application shows the operation flow chart and structure diagram of the two-dimensional soil water, heat and salt migration model.

[0334] exist Figure 2 The operation flow chart shown in the figure first calculates the , root distribution and other crop growth indicators and potential transpiration / evaporation; then solve the upper boundary energy balance and near-surface water and heat transfer under the mulching condition to determine the two-dimensional water and heat conditions at the upper boundary; combine root water absorption and two-dimensional upper boundary water, heat and salt conditions to solve the two-dimensional spatiotemporal dynamic changes of soil water, heat and salt using the finite element method; calculate crop growth stress factors based on actual crop transpiration and potential transpiration, air temperature, etc., and proceed to the next period of solution; until the simulation time and operating accuracy are met, the cycle ends, the results are output, and the model simulation ends.

[0335] exist Figure 3The structure diagram shown shows the energy distribution and water and heat transfer process under the condition of non-uniform underlying surface in the model. The available energy reaches the soil after being intercepted by the canopy and reflected and transmitted by the film, resulting in the non-uniformity of the upper boundary. The model takes into account the energy balance between the atmosphere-canopy-film-soil. By solving the sensible heat exchange between the soil under the film and the film, the sensible heat and latent heat exchange between the canopy leaves and the reference height, and the water and heat transfer between the bare soil and the atmosphere, it provides the upper boundary of the two-dimensional soil water, heat and salt migration on the non-uniform underlying surface. The model also adds a crop growth module. The dynamic development of the crop canopy affects the ground energy balance and changes the upper boundary conditions. The root water absorption acts as a sink to cause soil water consumption and salt accumulation; soil temperature affects the process of crop growth period, and the root zone water, heat and salt stress affects the crop root water absorption. In general, the model takes into account the growth and development and energy balance of crops aboveground, the two-dimensional soil water, heat and salt migration and crop stress in the underground, and the two are mutually feedback, thus realizing the simulation of two-dimensional soil water, heat and salt migration and crop growth.

[0336] In addition, the present application also proposes an embodiment for a schematic diagram of dynamic changes in the upper boundary conditions of the model temperature.

[0337] Taking some film-covered farmland as an example, Figure 3 The schematic diagram of the dynamic change of the upper boundary condition of the model temperature under this scenario is shown. As the growth period progresses, the crop canopy continues to develop, changing the upper boundary condition of the two-dimensional soil temperature transfer.

[0338] 1) In the early stage, the coverage of crop canopy is small and can be ignored. At this time, there are only two types of soil under film cover and bare soil without cover on the upper boundary;

[0339] 2) As crops develop, the canopy coverage effect cannot be ignored, but the canopy width does not reach the bare soil area. At this time, the upper boundary includes soil under film coverage, soil under canopy coverage, and bare soil without shelter;

[0340] 3) As the crop develops further, the canopy covers the bare soil area. At this time, there are four types of upper boundaries at the same time, namely, soil under canopy cover film, soil under film cover, bare soil under canopy cover, and bare soil without cover;

[0341] 4) When the crops grow to the peak period, the canopy covers all the soil in the mulched area and the bare soil area. At this time, the upper boundary types only have two types: soil under the mulched film and bare soil. According to the surface energy balance and aerodynamic principles, the soil temperature of different boundary types can be solved separately.

[0342] In summary, this model determines the upper boundary type according to the crop growth and development process and irrigation system, and realizes the function of dynamic conversion of boundary types of each simulation node on the upper boundary (including conversion to given temperature flux boundary conditions under irrigation conditions), which is more in line with production reality.

[0343] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this application can be executed in parallel, sequentially or in different orders, as long as the expected results of the technical solution of this application can be achieved, and this document is not limited here.

[0344] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A method for coupling simulation of soil water, heat and salt migration and crop growth on a non-uniform underlying surface, characterized in that: The following steps are involved: Construct a two-dimensional soil water, heat and salt transport model that takes into account the partially covered non-uniform underlying surface and crop growth, and set the initial conditions and boundary conditions for the operation of the two-dimensional soil water, heat and salt transport model; Connecting the aboveground crop growth and the underground soil water, heat and salt migration through root water absorption and soil water, heat and salt stress, solving the two-dimensional soil water, heat and salt migration model according to the input soil information, meteorological data, crop growth data and required parameters, and obtaining the water, heat and salt distribution characteristics and crop growth indicators on the two-dimensional soil profile at a specified time; The two-dimensional soil water, heat and salt migration model considers four underlying surface conditions: bare soil without cover, bare soil covered by a canopy, covered soil, and covered soil covered by a canopy when calculating the net radiation on the soil surface. The energy distribution calculation is performed based on FAO-56 and the mixed dual-source theory. The calculation process includes: Net radiation from bare soil surface without covering The calculation method is: In the formula, is the net shortwave radiation, is the net longwave radiation, is the incident solar radiation, is the soil surface reflectivity; Divide the net radiation of the bare soil surface into latent heat flux and sensible heat flux , which is calculated as follows: In the formula, , , They are the evaporation resistance of the soil surface, the air resistance between the soil surface and the canopy height, and the air resistance between the canopy height and the reference height. is the air density, is the specific heat of air at normal pressure, is the hygrometer constant, is the soil surface vapor pressure, is the vapor pressure at the reference height, is the soil surface temperature, is the air temperature at the reference altitude; The calculation method of soil surface evaporation and temperature without shielding is: In the formula, is the latent heat of evaporation, is the slope of the saturated vapor pressure-temperature curve, is the saturated water vapor pressure at the reference height; Net radiation on bare soil surface under vegetation canopy cover The calculation method is: In the formula, is the crop canopy reflectance, is the crop coefficient, is the leaf area index; Net radiation of bare soil surface under vegetation canopy cover Latent heat flux and sensible heat flux The calculation process is similar to the net radiation partition calculation process of bare soil surface without cover. The calculation method of soil surface evaporation and temperature under vegetation canopy cover is: In the formula, , , They are the soil surface evaporation resistance under the canopy coverage scenario, the air resistance between the soil surface and the canopy height, the air resistance between the canopy height and the reference height, is the evaporation rate of bare soil surface under canopy cover, is the surface temperature of bare soil under canopy cover; Net radiation on the surface of film-covered soil The calculation method is: In the formula, is the short-wave reflectivity of the film, is the long-wave transmittance of the film, is the long-wave radiation emitted by the film; Under the film covering condition, the film is regarded as an impermeable layer, and the water vapor transmission between the soil under the film and the air above the film is ignored. The net radiation obtained by the soil under the film is all used to increase the soil temperature, that is: in, is the soil sensible heat flux under film covering conditions; Soil temperature under film covering The calculation method is: In the formula, is the contact thermal resistance between the film and the soil; When the vegetation canopy and film exist at the same time, the net radiation of the film-covered soil surface under the vegetation canopy Calculation method: Since the net radiation obtained by the film-covered soil surface under the vegetation canopy is all used to increase the soil temperature, the soil sensible heat flux for: The soil temperature under the vegetation canopy is The calculation method is: In the formula, is the thermal contact resistance between the film and the soil.

2. The method according to claim 1, characterized in that Before constructing a two-dimensional soil water, heat and salt transport model that considers partially covered non-uniform underlying surfaces and crop growth, it also includes: Collect soil data, weather data, irrigation data, and crop growth data for conventional weather data-driven models; Determine soil hydraulic parameters, heat transfer parameters, solute transport parameters, crop growth parameters, and evaporation / transpiration stress parameters; According to the data and parameters obtained above, the simulation range and time of soil profile and crop growth are determined and the simulation area is divided into triangular grids.

3. The method according to claim 2, characterized in that When the vegetation canopy and the film exist simultaneously, the method further comprises: Obtaining the net radiation intercepted by the crop canopy , the calculation formula is: Since the net radiation intercepted by the crop canopy is used for latent heat generation in the leaves and sensible heat consumption , then the following formula holds: After joint solution, the calculation formula of crop canopy potential transpiration rate is: In the formula, is the crop potential transpiration rate, is the canopy leaf temperature, for The canopy saturated water vapor pressure at temperature, is the transpiration resistance of leaf stomata, is the air resistance at the height of the leaves and the canopy.

4. The method according to claim 3, characterized in that The two-dimensional soil water, heat and salt transport model takes into account the interception of light energy by the canopy, the conversion of light energy into biomass, the calculation of yield based on biomass, and the water, heat and salt stress process when simulating crop growth.

5. The method according to claim 4, characterized in that The simulation process of the crop growth part includes: The simulation part of crop growth is based on days as the time step, and phenological development is based on daily heat units. Based on the calculation of the heat unit coefficient from 0 to 1, the crop is controlled The growth process from sowing to maturity is expressed as: in, and They are The highest and lowest temperatures of the day, The base temperature for crop growth. It is the maximum heat unit value required for crops from sowing to maturity; The simulation of leaf area is divided into two stages. The first stage is from sowing to the maximum leaf area, and the second stage is from the beginning of the decline of leaf area to crop maturity. The leaf area change process in the first stage is expressed as: in, is the leaf area index, is the potential maximum leaf area index, is the heat unit factor, is the minimum crop stress factor, and the soil water, heat and salt comprehensive stress factor is taken as and temperature stress factors The minimum value in is calculated by the following formulas: In the formula, and is the crop parameter, In order to consider the influence of soil water, heat and salt The actual evaporation of the day, For the Potential transpiration of crops per day, is the daily average temperature, The optimum growth temperature for crops; The leaf area change process in the second stage is expressed as: In the formula, is the actual maximum leaf area index, is the leaf area senescence index, is the heat unit coefficient when the leaf area begins to age; Plant height The simulation part is about the maximum plant height and heat unit factor The function is calculated as follows: Crop canopy width The simulated part and crop height The calculation formula is: In the formula, is the crop canopy parameter; The simulation of crop root growth and root density distribution takes into account its dynamic changes in the two-dimensional profile. Root length of crops The calculation formula is: In the formula, is a constant; Crop root width Take it as half of the length, that is: No. The calculation formula for the two-dimensional distribution of crop root density on a given day is: In the formula, For the day's crop root area, is an arbitrarily specified distribution function, which can be described as follows: In the formula, , are the distances of the crop from the coordinate origin in the horizontal and vertical directions, , Respectively The maximum root width and depth of crops in horizontal and vertical directions during the day. For planting crops, , is the empirical coefficient, , Respectively The position of maximum water absorption by the roots in the horizontal and vertical directions during the day.

6. The method according to claim 5, characterized in that The boundary conditions for the operation of the two-dimensional soil water, heat and salt transport model include the boundary conditions of water, temperature and salt in the two-dimensional soil profile, among which: The upper boundary of soil moisture exists in film, drip irrigation belt and bare soil at the same time, involving zero flux, variable flux and atmospheric boundary conditions. The left and right boundaries of soil moisture select zero flux boundary, and the lower boundary of soil moisture selects constant head, zero flux or free drainage boundary. Among them, for soil covered with film, the upper boundary of moisture is regarded as zero flux boundary; for soil under drip irrigation belt, the upper boundary of moisture is regarded as variable head boundary; for bare soil area without film coverage, the upper boundary of moisture is regarded as atmospheric boundary; Each soil node of the soil temperature upper boundary adopts given temperature and constant temperature flux boundary conditions, the left and right boundaries of the soil temperature adopt given temperature or zero flux boundary conditions, and the middle boundary of the soil temperature adopts given temperature or constant temperature flux boundary conditions. Among them, there are four types of upper boundaries of given temperature under the given temperature upper boundary conditions, and the upper boundary type of each soil node can be automatically converted according to the crop growth status. Among them, the four types of upper boundaries of given temperature under the given temperature boundary conditions are the soil surface temperature under the film not covered by the canopy, the soil surface temperature under the film covered by the canopy, the bare soil surface temperature under the canopy covered, and the bare soil surface temperature not covered by the canopy; The upper boundary of soil solute can select constant concentration, constant concentration flux or zero flux boundary conditions, the left and right boundaries of soil solute migration can select zero flux boundary conditions, and the lower boundary type of soil solute migration is the same as the upper boundary, and constant concentration, constant concentration flux or zero flux boundary conditions can be selected.

7. The method according to claim 6, characterized in that The method of connecting the aboveground crop growth and the underground soil water, heat and salt migration through root water absorption and soil water, heat and salt stress includes: The simulation of soil water movement adopts the two-dimensional mixed Richards equation considering root water absorption, which is expressed as: In the formula, is the soil volume moisture content, For time, is the soil matrix potential or pressure head, is the unsaturated hydraulic conductivity of the soil, , is the two-dimensional spatial coordinate, rightward and downward are positive, is the source-sink term; The Van Genuchten-Mualem model is used to describe the soil hydraulic properties, in which the soil moisture content in the soil hydraulic properties is and hydraulic conductivity Matrix potential The relational expression is expressed as: In the formula, is the effective saturation of soil, is the residual moisture content of the soil, is the saturated moisture content of the soil, , and is the soil shape coefficient, and , is the saturated hydraulic conductivity of the soil, is the soil porosity correlation parameter; The source and sink terms in the soil water transport equation are the crop root water absorption terms in the two-dimensional soil water, heat and salt transport model. The actual crop root water absorption rate calculation formula is: In the formula, is the width of the soil surface related to the transpiration process, is the potential transpiration rate, is the node coordinate The water-salt stress coefficient at is calculated as follows: in, , is an empirical parameter, is the osmotic potential, To ignore the pressure head that reduces the water absorption rate by 50% under the osmotic potential condition, The osmotic potential is the 50% reduction in water absorption rate when the soil matrix potential is ignored; According to the actual crop root water absorption rate, the actual crop transpiration rate is calculated using the following formula: In the formula, To consider the actual transpiration under the influence of soil water and salt stress; Ignoring the effect of water vapor diffusion, the two-dimensional heat conduction equation for the soil temperature simulation is: In the formula, and are the volumetric heat capacities of the porous medium and the liquid phase, is the soil temperature, is the sensible thermal conductivity of soil, , are the single-width flow rates in the horizontal and vertical directions, respectively. The volumetric heat capacity is defined as the product of the volumetric heat capacity and the mass heat capacity: in, Indicates volume ratio, subscript , , They represent solid phase, organic matter and liquid phase respectively; Soil sensible thermal conductivity Calculated by the following formula: In the formula, , are the longitudinal and transverse thermal diffusivities, is the absolute value of Darcy flux density, thermal conductivity Reflects the tortuosity of porous media, and its expression is: in, , , All are empirical coefficients; The two-dimensional solute transport in soil is based on the advection-diffusion equation, and the calculation formula of the advection-diffusion equation is: In the formula, is the solute mass concentration, is the soil dry bulk density, is the adsorption concentration, is the source-sink term in the water transport equation, is the solute source and sink term, is the saturated-unsaturated hydrodynamic diffusion coefficient, and its calculation formula is: In the formula, is the liquid phase bending coefficient, is the diffusion coefficient of solute molecules in water, , are the lateral and longitudinal solute diffusivities, respectively.

8. The method according to claim 7, characterized in that Before solving the two-dimensional soil water, heat and salt transport model, it also includes: According to the input soil information samples, meteorological data samples, crop growth data samples and required parameter samples, a numerical algorithm is run to calculate the daily crop growth and soil evaporation, plant transpiration and soil surface temperature to update the upper boundary conditions of the two-dimensional soil water, heat and salt migration model.

9. The method according to claim 8, characterized in that The method of solving the two-dimensional soil water, heat and salt migration model comprises: The finite element method is used to solve the discrete moisture, temperature and salt control equations. The simulation stops when the last set time point is reached, and the spatiotemporal distribution of moisture, temperature and salt as well as the crop growth status and final yield are obtained.

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