CN116773744B - Crop water deficiency diagnosis method based on soil moisture and meteorological monitoring - Google Patents
Crop water deficiency diagnosis method based on soil moisture and meteorological monitoring Download PDFInfo
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Abstract
The invention discloses a crop water deficiency diagnosis method based on soil moisture and meteorological monitoring, and relates to the technical field of soil detection and precise irrigation. Comprising the following steps: monitoring the soil moisture content, solar radiation, air temperature and relative humidity of the root zone of crops, and then calculating response coefficients of different environmental variables: soil water stress response coefficient, water stress hysteresis response coefficient, solar radiation response coefficient, temperature response coefficient and humidity response coefficient; and then, calculating a plant water deficit index PWDI by combining the Jarvis leaf stomata conductivity correction model and the P-M model, so as to diagnose the water deficit degree of crops. The invention provides a crop water deficiency degree assessment method with stronger mechanization and systemicity from the water migration process and mechanism of a soil-plant-atmosphere continuous system, can reflect the crop water deficiency condition more accurately, and can provide an effective tool for precise management of the crop water in dry fields.
Description
Technical Field
The invention relates to the technical field of soil detection and precise irrigation, in particular to a crop water deficiency diagnosis method based on soil moisture and meteorological monitoring.
Background
In dry-land farmlands, soil drought is a major obstacle to limiting crop root absorption, growth and development, and yield improvement. The soil moisture condition of the root zone of the crops is regulated and controlled timely through irrigation, so that the soil moisture and nutrient absorption and utilization of the crops are facilitated, ineffective losses such as soil surface evaporation and deep seepage can be reduced, and the soil moisture and nutrient absorption and utilization method is particularly important for realizing water conservation, stable yield and yield increase. Rational irrigation must be based on an accurate assessment of crop water deficit, which is often reflected in the Plant Water Deficit Index (PWDI).
In the prior art, PWDI is most evaluated based on soil moisture conditions. The root zone water soil moisture status is generally expressed by the root zone arithmetic average water soil matrix potential (or water content) and is used as a irrigation control index, for example, irrigation is started when the root zone water soil matrix potential is lower than a certain critical value, and irrigation is stopped until the root zone water soil matrix potential reaches a certain target value suitable for crop growth. The latest research improves and perfects the arithmetic average method by further considering the relative distribution relation between soil moisture and root systems, namely, the relative root length density is used as a weight factor to weight the soil moisture, and the root system weighted average soil water matrix potential is obtained through calculation, so that the influence of soil water stress on crop transpiration water consumption and water deficiency is represented.
The defects of the prior art are as follows: the influence of the current soil water stress is considered, and the important influence of early water stress hysteresis effect and meteorological condition change on the transpiration water consumption of crops is ignored. On the one hand, the heavier the water stress on the crop in the earlier stage, the larger the hysteresis effect on the water state of the crop, and the PWDI evaluation is likely to deviate to some extent by neglecting the hysteresis effect; on the other hand, the meteorological conditions are important factors for controlling crop transpiration, even under the condition that the soil moisture condition is kept constant, the crop transpiration (or the moisture deficiency degree) is continuously changed along with the change of meteorological factors such as solar radiation, air temperature, humidity and the like, and the influence of the change is completely not considered, so that the diagnosis of the crop moisture deficiency is extremely uncertain, and particularly, the diagnosis is obvious when the meteorological conditions are severely changed. Therefore, the existing crop water deficiency degree assessment method has obvious defects in science and rationality, and the assessment result is difficult to accurately reflect the actual water deficiency condition of crops, so that the farmland irrigation precision is reduced.
Disclosure of Invention
In view of the above, it is desirable to provide a method for diagnosing crop water deficiency based on soil moisture and meteorological monitoring.
The embodiment of the invention provides a crop water deficiency diagnosis method based on soil moisture and meteorological monitoring, which comprises the following steps:
acquiring the soil water content monitored in real time, and calculating the root weighted average soil water matrix potential h according to the soil water content monitored in real time RW Then weighting and averaging the soil water matrix potential h according to the root system RW Calculating soil water stress response coefficient f W And a water stress hysteresis response coefficient f Re ；
Solar radiation R for acquiring automatic monitoring of weather station s Air temperature T, relative humidity RH, wind speed u z And calculate the water vapor pressure difference D, the saturated water vapor pressure curve slope delta, the aerodynamic resistance r a Solar radiation response coefficient f Rs Temperature response coefficient f T And a humidity response coefficient f D ；
Response coefficient f to soil water stress W Hysteresis response coefficient f of water stress Re Solar radiation response coefficient f Rs Temperature response coefficient f T And a humidity response coefficient f D Inputting Jarvis blade air hole air conductivity correction model to obtain actual blade air hole air conductivity g s Potential blade air hole conductivity g under condition of full water supply of soil s0 The method comprises the steps of carrying out a first treatment on the surface of the Air hole conductivity g of actual blade s And potential blade air hole conductance g s0 Inputting into a P-M model to obtain the actual transpiration rate T of the blade a And potential transpiration rate T p ；
Actual transpiration rate T of the leaves a And potential transpiration rate T p The original formula of the plant water deficit index PWDI is substituted, and the crop water deficit degree is diagnosed through the plant water deficit index PWDI.
In addition, the root system weighted average soil water matrix potential h is calculated RW Comprising the following steps:
wherein h is RW The weighted average soil water matrix potential of the root system is given by cm, k is the number of layers of soil subdivision in the root zone, h i Is the water matrix potential of the ith layer of soil, cm, z ri For the relative depth of each layer of soil, L nrd (z ri ) Δz as relative root length density ri The relative thickness of each layer of soil.
In addition, the method calculates the soil water stress response coefficient f W And a water stress hysteresis response coefficient f Re Comprising the following steps:
wherein f W Is the response coefficient of soil water stress, h RW Weighting and averaging soil water matrix potential, cm and h of root system W And h L Respectively, the wilting coefficient and the lower limit of the soil water matrix potential suitable for crop growth, cm, k W Fitting parameters for soil water stress response, f Re Is the hysteresis response coefficient of water stress, k Re Fitting parameters for water stress hysteresis response.
In addition, the water vapor pressure difference D, the saturated water vapor pressure curve slope Δ includes:
wherein D is waterThe steam pressure difference, kPa, delta is the slope of a saturated water steam pressure curve, kPa DEG C -1 ，T mean Mean air temperature, DEG C, RH mean For average relative humidity,%.
In addition, the calculated aerodynamic resistance r a Comprising the following steps:
wherein r is a For aerodynamic drag, s m -1 Z is the meteorological observation height, m, H c Is plant height, m, d is zero plane displacement, m, z 0 For the length of the momentum transfer roughness, m, K is von Karman constant, u z For wind speed at z-height, m s -1 。
In addition, the calculation of the solar radiation response coefficient f Rs Temperature response coefficient f T Coefficient of humidity response f D Comprising the following steps:
wherein f Rs For solar radiation response coefficient, R s For solar radiation Wm -2 ，R sH For maximum solar radiation, wm -2 ，k Rs Fitting parameters for solar radiation responses;
f T ＝1-k T (25-T) 2
wherein f T Is the temperature response coefficient, T is the air temperature, DEG C, k T Fitting parameters for temperature response;
f D ＝1-k D D
wherein f D Is the humidity response coefficient, D is the water vapor pressure difference, kPa, k D Fitting parameters for humidity response.
In addition, the air hole conductivity g of the actual blade is obtained s Potential blade air hole conductivity g under condition of full water supply of soil s0 Comprising the following steps:
g s ＝g s0 f W f Re
wherein g s M s for the air hole conductivity of the actual blade -1 ，g s0 For blade air hole conductivity when the soil moisture condition is optimal, m s -1 ，g smax Maximum blade air hole conductivity when the soil moisture and the meteorological conditions are optimal, m s -1 ，f W Is the response coefficient of soil water stress, f Re Is the hysteresis response coefficient of water stress, f Rs For solar radiation response coefficient, f T F is the temperature response coefficient D Is the humidity response coefficient.
In addition, the actual transpiration rate T is obtained a And potential transpiration rate T p Comprising the following steps:
wherein the actual transpiration rate T when the soil water supply is sufficient a Reaching potential level T p ：
Wherein T is a For the actual transpiration rate, mm d -1 ，T p For potential transpiration rate, mm d -1 Lambda is the latent heat of vaporization, MJ kg -1 Delta is the slope of the water vapor pressure curve and kPa DEG C -1 ，R n For net radiation, MJm -2 d -1 G is soil heat flux, MJm -2 d -1 ，ρ a The average density of air at normal pressure is kg m -3 ，C p MJ kg for specific heat of air under normal pressure -1 ℃ -1 D is the water vapor pressure difference, kPa, gamma is the hygrometer constant, kPa DEG C -1 ，r a For aerodynamic drag, s m -1 ，g s M s for the air hole conductivity of the actual blade -1 ，g s0 Potential leaf pore conductance under conditions sufficient to supply water to the soil, m s -1 。
Additionally, the original formula for substituting the plant water deficit index PWDI includes:
wherein T is a For the actual transpiration rate, mm d -1 ，T p For potential transpiration rate, mm d -1 Delta is the slope of the water vapor pressure curve and kPa DEG C -1 Gamma is hygrometer constant, kPa DEG C -1 ，r a For aerodynamic drag, s m -1 ，g s M s for the air hole conductivity of the actual blade -1 ，g s0 Potential leaf pore conductance under conditions sufficient to supply water to the soil, m s -1 。
In addition, the diagnosing the degree of crop water deficit by the plant water deficit index PWDI includes:
wherein f W Is the response coefficient of soil water stress, f Re G is the hysteresis response coefficient of water stress smax Maximum blade air hole conductivity when the soil moisture and meteorological conditions are optimal, m s -1 ，r a For aerodynamic drag, s m -1 Delta is the slope of the water vapor pressure curve and kPa DEG C -1 Gamma is hygrometer constant, kPa DEG C -1 ，f Rs For solar radiation response coefficient, f T F is the temperature response coefficient D Is the humidity response coefficient;
the change of the plant water deficit index PWDI value ranges from 0 to 1, and when the plant water deficit index PWDI tends to be 1, the plant water deficit index PWDI is more serious; in contrast, when the plant water deficit index PWDI is more toward 0, it means that the crop water deficit is less severe.
Compared with the prior art, the crop water deficiency diagnosis method based on soil moisture and meteorological monitoring has the following beneficial effects:
the invention starts from the water migration process and mechanism of a soil-plant-atmosphere continuous system, comprehensively considers the transient effect, the hysteresis effect and the influence of different meteorological environment variables of soil water stress to correct a Jarvis leaf pore air permeability correction model, and couples the Jarvis leaf pore air permeability correction model with a Penman-Monteth (P-M) model to calculate the leaf transpiration rate; and substituting the transpiration rate obtained by the calculation of the coupling model into an original formula of a plant water deficit index PWDI, and diagnosing the crop water deficit degree through the plant water deficit index PWDI. The crop water deficiency diagnosis method provided by the invention reflects the relationship between the crop water condition and the environment more systematically, can more accurately represent the crop water deficiency degree, and can provide an effective tool for realizing accurate irrigation, water saving and yield increasing targets of farmlands in arid regions.
Drawings
FIG. 1 is a graph of soil water stress, water stress hysteresis, solar radiation, air temperature, humidity (differential water vapor pressure) response coefficient as a function of a crop water deficiency diagnostic method based on soil moisture and meteorological monitoring provided in one embodiment;
FIG. 2 is a flow chart of a crop water deficit diagnostic method based on soil moisture and meteorological monitoring, provided in one embodiment;
FIG. 3 is a field test scenario diagram of a crop water deficit diagnostic method based on soil moisture and meteorological monitoring, provided in one embodiment;
fig. 4 is a graph showing a comparison between PWDI obtained by evaluation of two different irrigation treatments (T1 and T2) based on the method proposed by the present invention and measured values in a field test of a crop water deficiency diagnosis method based on soil moisture and meteorological monitoring, provided in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
First, the principle of calculating the plant water deficit index PWDI according to the present invention will be described.
From the definition, the Plant Water Deficit Index (PWDI) indicates the water deficit (T) of crops caused by water stress p –T a ) Moisture demand (T) p ) Is prepared from the following components in proportion:
wherein: t (T) a For the actual transpiration rate, mm d -1 ，T p For potential transpiration rate, mm d -1 . From [1]]It can be seen that the key to estimating PWDI is to accurately obtain the relative transpiration rate T a /T p . However, due to numerous factors affecting transpiration and complicated interrelation, T is required to be quickly and accurately obtained under field conditions a And T p Thereby utilizing [1]]Direct calculation of PWDI remains a significant challenge.
Based on a classical Penman-Monteth (P-M) model and a common Jarvis leaf stomata conductivity model, the quantitative relation between PWDI and soil moisture, weather and physiological characteristics of crops is deduced, and the quantitative relation is briefly described as follows:
based on P-M model, actual transpiration rate T of crop leaves a Can be characterized as:
wherein: t (T) a For the actual transpiration rate, mm d -1 Lambda is the latent heat of vaporization, MJkg -1 Delta is the slope of the steam pressure curve, kPa℃ -1 ，R n For net radiation, MJm -2 d -1 G is soil heat flux, MJm -2 d -1 ，ρ a The average density of air at normal pressure is kg m -3 ，C p MJkg as specific heat of air under normal pressure -1 ℃ -1 D is the water vapor pressure difference, kPa, gamma is the hygrometer constant, kPa DEG C -1 ，r a For aerodynamic drag, s m -1 ，g s M s for the air hole conductivity of the actual blade -1 ，g s0 Potential leaf pore conductance under conditions sufficient to supply water to the soil, m s -1 。
When the water supply to the soil is sufficient, the amount of water lost by transpiration of the crop leaves depends on the atmospheric distillation spring (the air hole conductivity of the leaves at this time is recorded as g s0 ) Will g s0 Instead of [2]]G of (3) s Obtaining potential transpiration rate T under the condition of fully supplying water to soil p The method comprises the following steps:
substituting the formula [2] and the formula [3] into the formula [1], and simplifying the arrangement to obtain:
from [4]]It can be seen that the air hole conductance g of the blade s (g s0 ) Is an important variable for evaluating PWDI, and is evaluated by adopting a common Jarvis continuous multiplication model. It should be noted that the traditional Jarvis continuous multiplication model pair g s When the evaluation is carried out, the influence of factors such as the soil moisture amount, solar radiation, air temperature, relative humidity and the like is mainly considered, but the relative distribution relation of the soil moisture and the root system and the hysteresis effect of water stress are still lacked to be considered. Therefore, the invention considers the influence of the relative distribution relation of soil moisture and root system by introducing root system weighted soil water matrix potential and considers the water stress hysteresis effect by introducing water stress hysteresis response coefficient by referring to the latest research, thereby correcting and finishing the Jarvis continuous multiplication modelIs good. The modified Jarvis continuous multiplication model is used for evaluating the air hole conductivity of the blade as follows:
g s ＝g s0 f W f Re [5]
wherein: g s M s for the air hole conductivity of the actual blade -1 ，g s0 For blade air hole conductivity when the soil moisture condition is optimal, m s -1 ，f W Is the response coefficient of soil water stress, f Re G is the hysteresis response coefficient of water stress smax Maximum blade air hole conductivity when the soil moisture and the meteorological conditions are optimal, m s -1 ，f Rs For solar radiation response coefficient, f T F is the temperature response coefficient D Is the humidity response coefficient.
Substituting the formula [5] and the formula [6] into the formula [4], and obtaining the comprehensive expression of PWDI after finishing and simplifying:
[7]]Not only consider the current soil moisture conditions (from f W Description) while also taking into account early water stress (from f Re Description), meteorological conditions (by f Rs 、f T 、f D Description) and physiological properties of crops themselves (from g) smax Description), and the like, the influence of factors on the transpiration of the leaves more comprehensively and systematically reflects the relationship between the water shortage degree of crops and the environment, and the quantitative relationship between the water shortage condition of crops and the change of the resistance of the air holes of the leaves is reflected on physiological mechanisms, thereby having strict physical and physiological basis. To more clearly present the estimation process of PWDI, the following equation [7]]The evaluation method of each intermediate variable involved in the process is stated one by one:
soil water stress response coefficient f W Description of the "concave-convex" function:
wherein: h is a RW Weighting average soil water matrix potential for root systemcm，h W Is wilting coefficient, cm, h L The lower limit of the water matrix potential of the soil suitable for crop growth is cm, k W Fitting parameters for soil water stress response. FIG. 1a shows, f W Along with h RW The higher the soil water matrix potential, the less the weakening effect of soil water stress on leaf stomata conductivity and transpiration.
Coefficient of water stress hysteresis response f Re The power function description is adopted:
wherein: [ f W ] t-1 Indicating the degree of relative water stress at the previous time, a higher value indicates that the water stress at the previous time is lighter, k Re Fitting parameters for water stress hysteresis response. FIG. 1b shows, f Re Along with [ f W ] t-1 Elevated, meaning that the lighter (heavier) the early water stress, the less (greater) it has a hysteresis effect on leaf stomatal conductance and transpiration.
Solar radiation response coefficient f Rs The following function description is used:
wherein: r is R s Wm is the actual solar radiation -2 ，R sH For maximum solar radiation, wm -2 ，k Rs Fitting parameters for solar radiation response. FIG. 1c shows f Rs And R is R s And the nonlinear positive correlation relation is formed.
Temperature response coefficient f T By using a secondaryDescription of the function:
f T ＝1-k T (25-T) 2 [11]
wherein: t is the air temperature, DEG C, k T Fitting parameters (> 0) for temperature response. f (f) T The relationship with T is shown in fig. 1 d.
Humidity response coefficient f D Describing by adopting a linear function:
f D ＝1-k D D[12]
wherein: d is the water vapor pressure difference, kPa, k D Fitting parameters (> 0) for humidity response. f (f) D Is inversely related to D (as shown in fig. 1 e).
The slope delta of the steam pressure curve is calculated as:
wherein: delta is the slope of saturated water vapor pressure curve and kPa DEG C -1 ，T mean The average air temperature, DEG C.
Aerodynamic resistance r a The calculation is as follows:
wherein: r is (r) a For aerodynamic drag, s m -1 Z is the meteorological observation height, m, H c Is plant height, m, d is zero plane displacement, m, z 0 For the length of the momentum transfer roughness, m, K is von Karman constant, u z For wind speed at z-height, m s -1 。
Having described the theoretical derivation and calculation of the PWDI of the present invention, the crop water deficit diagnostic method of the present invention based on soil moisture and weather monitoring is described below in a preferred embodiment. As shown in fig. 2, a flow chart of a crop water deficiency diagnosis method based on soil moisture and meteorological monitoring according to a preferred embodiment of the present invention is as follows:
in step S1: setting parameters including soil moisture characteristic curveParameter, wilting coefficient h W Lower limit h of water matrix potential of suitable growth soil L Fitting parameter k for soil water stress response W Fitting parameter k of water stress hysteresis response Re Maximum blade air hole conductance g smax Relative root length density L nrd Plant height H c Maximum solar radiation R sH Fitting parameter k of solar radiation response Rs Fitting parameter k of temperature response T Fitting parameter k of humidity response D ；
In step S2: the root zone soil moisture was monitored. One preferred measurement is: inserting a soil moisture sensor into the soil of the root zone perpendicular to the soil profile, thereby measuring the moisture content θ of each layer of soil i The method comprises the steps of carrying out a first treatment on the surface of the Monitoring meteorological conditions, including solar radiation R s Air temperature T, relative humidity RH, wind speed u z Etc.;
in step S3: according to the characteristic curve of soil moisture, the soil moisture content is converted into soil water matrix potential, and the relative root length density L is combined nrd Calculating the weighted average soil water matrix potential h of the root system RW ：Then based on h RW Calculating soil water stress response coefficient f W (as shown in [8 ]]Shown). Based on f W Calculating a water stress hysteresis response coefficient f Re (as shown in [9 ]]Shown). Based on solar radiation R s Calculating the solar radiation response coefficient f Rs (as shown in [10 ]]Shown). Calculating a temperature response coefficient f based on the air temperature T T (as shown in [11 ]]Shown). Calculating humidity response coefficient f based on water vapor pressure difference D D (as shown in [12 ]]Shown). Calculating the slope delta of the water vapor pressure curve based on the air temperature T (e.g. [13 ]]Shown). Based on wind speed u z And plant height H c Calculating aerodynamic resistance r a : (as shown in [14 ]]Shown). F to be calculated W 、f Re 、f Rs 、f T 、f D Air hole conductivity correction model substituted into Jarvis blade calculating the actual and potential air hole conductivity g s And g s0 (as shown in [5]]And [6]]Shown), g s And g s0 Substituting the actual and potential transpiration rates T into the P-M model a And T p 。
In step S4: actual and potential transpiration rate T calculated by coupling Jarvis blade air hole conductivity correction model and P-M model a And T p Substituting the plant water deficit index PWDI to obtain optimized comprehensive expression(as shown in [7]]Shown).
In order to verify the key technology of the invention, the irrigation test of a winter wheat field lysimeter is specially adopted (the test scene is shown in figure 3): the test involved two different irrigation treatments: t1 and T2. T1 is irrigated for 4 times in the key growth period (namely, the period from the rising period to the maturing period, which corresponds to 185 to 245d after sowing) of winter wheat, the irrigation time corresponds to 196d, 207d, 222d and 234d after sowing, and the irrigation quota corresponds to 73mm, 67mm, 81mm and 81mm; t2 is irrigated 2 times in the same period, the irrigation time corresponds to 213d and 233d after sowing, and the irrigation quota corresponds to 96mm and 97mm. During the test, the data of soil water content, solar radiation, air temperature, relative humidity, wind speed, plant height, actual and potential transpiration rate of the leaves and the like are monitored at the same moment every day. Based on the above measured data, the PWDI is calculated by adopting the estimation method (formula 7) and the original definition (formula 1), and the rationality and reliability of the PWDI estimation method are verified by comparing the two. The PWDI estimation flow or process is as follows:
firstly, setting parameters, wherein the soil to be tested in the field test can be divided into three layers with different properties: 0-30cm, 30-80cm, 80-150cm, saturated water content theta of each layer of soil s 0.495, 0.541, 0.548cm 3 cm -3 Residual moisture content θ r 0.029, 0.068, 0.060cm 3 cm -3 The fitting parameters alpha of the soil moisture characteristic curves are 0.014, 0.013 and 0.020, and the parameters n are 1.315, 1.245 and 1.177; wilting coefficient h W -15000cm; lower limit h of soil water matrix potential suitable for crop growth L -400cm; soil water stress response fitting parameter k W =0.797, water stress hysteresis response mimicsParameters k of the combination Re =0.515; maximum blade air hole conductance g smax ＝0.012m s -1 Relative root length density L nrd (z r )＝p(1-z r ) p-1 (winter wheat p is 3.85); maximum solar radiation R sH ＝210Wm -2 Fitting parameter k of solar radiation response Rs =3.724, temperature response fitting parameter k T =0.0016, humidity response fitting parameter k D =0.346; the above parameters can be obtained by actual measurement (e.g. θ s 、θ r 、g smax 、R sH ) Or can be determined by least squares optimization (e.g., alpha, n, k Re 、k Rs 、k T 、k D ) Reasonable recommendation can also be made by consulting references (e.g. h W 、h L 、p)。
Based on the model parameters and the actual measured soil water content theta in the test i Solar radiation R s Air temperature T, relative humidity RH, wind speed u z Plant height H c The data are that firstly, the water content theta of each layer of soil is determined by utilizing the characteristic curve of soil water content i Is converted into soil water matrix potential h i Based on the relative root length density distribution L nrd (z r ) Calculating the weighted average soil water matrix potential h of the root system RW Then sequentially, the formula [8 ] is adopted]Calculating soil water stress response coefficient f W The method comprises the steps of carrying out a first treatment on the surface of the By means of [9 ]]Calculating a water stress hysteresis response coefficient f Re The method comprises the steps of carrying out a first treatment on the surface of the By means of [10 ]]Calculating the solar radiation response coefficient f Rs The method comprises the steps of carrying out a first treatment on the surface of the By means of [11 ]]Calculating a temperature response coefficient f T The method comprises the steps of carrying out a first treatment on the surface of the By means of [12 ]]Calculating humidity response coefficient f D The method comprises the steps of carrying out a first treatment on the surface of the By means of [13 ]]Calculating the slope delta of the steam pressure curve; by means of [14 ]]Calculating aerodynamic resistance r a The method comprises the steps of carrying out a first treatment on the surface of the Finally, based on formula [7]]Plant water deficit index PWDI was calculated and compared with the measured value (formula [1]]Obtained) and the results are shown in fig. 4. The figure shows that: whether the irrigation treatment T1 (FIG. 4 a) or T2 (FIG. 4 b) is carried out, the PWDI estimated based on the method of the invention is basically consistent with the measured value, the correlation coefficient r between the PWDI and the measured value is 0.90 and 0.88 respectively, the root mean square error RMSE is 0.07 and 0.07 respectively, and the PWDI and the RMSE are within acceptable ranges, which indicates that the plant water deficiency index P provided by the inventionThe WDI evaluation method can evaluate the water shortage condition of crops more accurately and can provide reference for reasonable irrigation of farmlands.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.
Claims (4)
1. A method for diagnosing water deficit in crops based on soil moisture and meteorological monitoring, comprising:
acquiring the soil water content monitored in real time, and calculating the root weighted average soil water matrix potential h according to the soil water content monitored in real time RW The root system weighted average soil water matrix potential h is calculated RW Comprising the following steps:
wherein h is RW The weighted average soil water matrix potential of the root system is given by cm, k is the number of layers of soil subdivision in the root zone, h i Is the water matrix potential of the ith layer of soil, cm, z ri For the relative depth of each layer of soil, L nrd (z ri ) Δz as relative root length density ri The relative thickness of each layer of soil;
according to the weighted average soil water matrix potential h of the root system RW Calculating soil water stress response coefficient f W And a water stress hysteresis response coefficient f Re The soil water stress response coefficient f is calculated W And a water stress hysteresis response coefficient f Re Comprising the following steps:
wherein f W Is the response coefficient of soil water stress, h RW Weighting and averaging soil water matrix potential, cm and h of root system W And h L Respectively, the wilting coefficient and the lower limit of the soil water matrix potential suitable for crop growth, cm, k W Fitting parameters for soil water stress response, f Re Is the hysteresis response coefficient of water stress, k Re Fitting parameters for water stress hysteresis response;
solar radiation R for acquiring automatic monitoring of weather station s Air temperature T, relative humidity RH, wind speed u z And calculate the water vapor pressure difference D, the saturated water vapor pressure curve slope delta and the aerodynamic resistance r a Solar radiation response coefficient f Rs Temperature response coefficient f T And a humidity response coefficient f D The method comprises the steps of carrying out a first treatment on the surface of the The calculating the water vapor pressure difference D, the saturated water vapor pressure curve slope delta comprises:
wherein D is the water vapor pressure difference, kPa, delta is the slope of saturated water vapor pressure curve, kPa DEG C -1 ，T mean Mean air temperature, DEG C, RH mean Average relative humidity,%;
the calculated aerodynamic resistance r a Comprising the following steps:
wherein r is a Is aerodynamic resistance，s m -1 Z is the meteorological observation height, m, H c Is plant height, m, d is zero plane displacement, m, z 0 For the length of the momentum transfer roughness, m, K is von Karman constant, u z For wind speed at z-height, m s -1 ；
Said calculating a solar radiation response coefficient f Rs Temperature response coefficient f T Coefficient of humidity response f D Comprising the following steps:
wherein f Rs For solar radiation response coefficient, R s For solar radiation Wm -2 ，R sH For maximum solar radiation, wm -2 ，k Rs Fitting parameters for solar radiation responses;
f T ＝1-k T (25-T) 2
wherein f T Is the temperature response coefficient, T is the air temperature, DEG C, k T Fitting parameters for temperature response;
f D ＝1-k D D
wherein f D Is the humidity response coefficient, D is the water vapor pressure difference, kPa, k D Fitting parameters for humidity response;
response coefficient f to soil water stress W Hysteresis response coefficient f of water stress Re Solar radiation response coefficient f Rs Temperature response coefficient f T And a humidity response coefficient f D Inputting Jarvis blade air hole air conductivity correction model to obtain actual blade air hole air conductivity g s Potential blade air hole conductivity g under condition of full water supply of soil s0 ；
The air hole conductivity g of the actual blade is obtained s Potential blade air hole conductivity g under condition of full water supply of soil s0 Comprising the following steps:
g s ＝g s0 f W f Re
g s0 ＝g smax f Rs f T f D
wherein g s M s for the air hole conductivity of the actual blade -1 ，g s0 For blade air hole conductivity when the soil moisture condition is optimal, m s -1 ，g smax Maximum blade air hole conductivity when the soil moisture and the meteorological conditions are optimal, m s -1 ，f W Is the response coefficient of soil water stress, f Re Is the hysteresis response coefficient of water stress, f Rs For solar radiation response coefficient, f T F is the temperature response coefficient D Is the humidity response coefficient;
air hole conductivity g of actual blade s And potential blade air hole conductance g s0 Inputting into a P-M model to obtain the actual transpiration rate T of the blade a And potential transpiration rate T p The method comprises the steps of carrying out a first treatment on the surface of the Actual transpiration rate T of the leaves a And potential transpiration rate T p The original formula of the plant water deficit index PWDI is substituted, and the crop water deficit degree is diagnosed through the plant water deficit index PWDI.
2. A method for diagnosing water deficit in crops based on soil moisture and meteorological monitoring as claimed in claim 1, wherein the actual transpiration rate T of leaves is obtained a And potential transpiration rate T p Comprising the following steps:
wherein the actual transpiration rate T when the soil water supply is sufficient a Reaching potential level T p ：
Wherein T is a For the actual transpiration rate, mm d -1 ，T p For potential transpiration rate, mm d -1 Lambda is the latent heat of vaporization, MJ kg -1 Delta is the slope of the water vapor pressure curve and kPa DEG C -1 ，R n For net radiation, MJ m -2 d -1 G is soil heat flux, MJ m -2 d -1 ，ρ a The average density of air at normal pressure is kg m -3 ，C p MJ kg for specific heat of air under normal pressure -1 ℃ -1 D is the water vapor pressure difference, kPa, gamma is the hygrometer constant, kPa DEG C -1 ，r a For aerodynamic drag, s m -1 ，g s M s for the air hole conductivity of the actual blade -1 ，g s0 Potential leaf pore conductance under conditions sufficient to supply water to the soil, m s -1 。
3. A method of diagnosing water deficit in crops based on soil moisture and meteorological monitoring as claimed in claim 2, wherein the original formula for substituting the plant water deficit index PWDI includes:
wherein T is a For the actual transpiration rate, mm d -1 ，T p For potential transpiration rate, mm d -1 Delta is the slope of the water vapor pressure curve and kPa DEG C -1 Gamma is hygrometer constant, kPa DEG C -1 ，r a For aerodynamic drag, s m -1 ，g s M s for the air hole conductivity of the actual blade -1 ，g s0 Potential leaf pore conductance under conditions sufficient to supply water to the soil, m s -1 。
4. A method of diagnosing water deficit in crops based on soil moisture and meteorological monitoring as claimed in claim 1, wherein diagnosing the level of water deficit in crops by a plant water deficit index PWDI includes:
wherein f W Is the response coefficient of soil water stress, f Re G is the hysteresis response coefficient of water stress smax Maximum blade air hole conductivity when the soil moisture and meteorological conditions are optimal, m s -1 ，r a For aerodynamic drag, s m -1 Delta is the slope of the water vapor pressure curve and kPa DEG C -1 Gamma is hygrometer constant, kPa DEG C -1 ，f Rs For solar radiation response coefficient, f T F is the temperature response coefficient D Is the humidity response coefficient;
the change of the plant water deficit index PWDI value ranges from 0 to 1, and when the plant water deficit index PWDI tends to be 1, the plant water deficit index PWDI is more serious; in contrast, when the plant water deficit index PWDI is more toward 0, it means that the crop water deficit is less severe.
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