Orchard evapotranspiration differentiation method and device based on differential changes in soil moisture

Abstract

The present invention relates to the field of evapotranspiration calculation, and specifically relates to a method and device for differentiating orchard evapotranspiration based on differential changes in soil moisture, which greatly reduces the observation cost of evapotranspiration components. The solution includes: performing two sets of short-term soil moisture measurements (7-10 days) under conditions not affected by precipitation. The first set measures the soil moisture profile curve in the existing state, and the second set measures the soil moisture profile curve under the starting covering condition; at the initial moment of measurement, the change curves of the soil moisture of the two sets with depth in the longitudinal section are the same, denoted as SWC1 * ; at the second moment during the measurement process, the curve of the soil moisture change with depth of the first set is denoted as SWC1, and the curve of the soil moisture change with depth of the second set is denoted as SWC2. According to the water balance principle, the evapotranspiration amount is the soil moisture consumption of the corresponding test. Then, the evapotranspiration amounts in both the first case and the second case are transpiration amounts, that is, #imgabs1#. During the set time period, the soil evaporation amount E = ET1 - ET2. The present invention is applicable to differentiating evapotranspiration.

Description

Technical Field

[0001] The present invention relates to the field of evapotranspiration calculation, and particularly to a method and device for differentiating orchard evapotranspiration based on differential changes in soil moisture. Background Art

[0002] Water plays an important role in the material cycle and energy flow. Especially in the farmland system, nearly 90% of the water volume is consumed in the form of evapotranspiration. ET (evapotranspiration) includes two major components: transpiration T and evaporation E. T and E respectively reflect the productive and unproductive water losses of biological and physical processes. Specifically, E refers to the evaporation that occurs on the soil surface, which is a physical process affected by meteorological factors (such as temperature, humidity, wind speed, and solar radiation) and soil conditions (soil texture, soil color, soil water content, etc.), and has no direct relationship with vegetation productivity. Therefore, it is considered unproductive water consumption. On the contrary, T refers to the water lost through the stomata of plant leaves, which is closely related to the growth, development, yield, and fruit quality of crops. Therefore, it is considered productive water consumption.

[0003] In the context of modern agriculture's pursuit of efficient water conservation and precise irrigation, reducing unproductive water consumption is the focus of modern water-saving agriculture. At the same time, this also means that the traditional criteria for formulating irrigation systems based on ET measurement need to be reexamined and adjusted. T directly participates in the physiological metabolism process of crops, while E has little impact on the growth and development of crops. Therefore, accurately differentiating E and T is crucial for optimizing irrigation strategies and agricultural water resource management, timely diagnosing crop water deficit conditions, improving water use efficiency, and promoting the development of high-water-efficiency agriculture.

[0004] ET differentiation methods can be roughly divided into two categories: field measurement methods and model estimation methods. Among them, field measurement methods include the ET component field measurement method and the ET ratio method. Specifically, the ET component field measurement method mainly includes the combined use of micro-lysimeters and sap flow meters, the eddy covariance method, and the combined use of sap flow meters, etc.; while the ET ratio method is a method for estimating the proportion of ET components in different ways, such as calculating T / ET using the water-carbon flux coupling relationship after observing ET with an eddy covariance system, or estimating T / ET by observing the stable isotope composition of E and T. The measurement cost of field measurement methods is high, the measurement data is discontinuous, and the spatial and temporal scales of measurement often do not meet the requirements of precise irrigation. Relatively speaking, the model method is more suitable for differentiating ET at a large regional scale. The model method can be divided into estimation methods based on traditional physical models, estimation methods based on remote sensing models, and empirical model methods based on vegetation characteristics. Most models rely on physical processes, are limited by simplified assumptions, have high requirements for the spatio-temporal parameters of vegetation physiological variables, the simulation results highly depend on the accuracy of input data and model parameters, and the calculation program is complex. In addition, the time resolution of the ET differentiation estimation method based on the remote sensing model is 8 days, and the spatial resolution is several meters or dozens of meters or even hundreds of meters. The ET differentiation method based on remote sensing cannot meet the requirements of crop precise irrigation decision-making. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an orchard evapotranspiration differentiation method and device based on the differential change of soil moisture, which greatly reduces the observation cost of ET components, simplifies the ET differentiation method, improves the ET differentiation efficiency, and can effectively guide orchard precise irrigation.

[0006] The present invention adopts the following technical solutions to achieve the above purpose. On the one hand, the present invention provides an orchard evapotranspiration differentiation method based on the differential change of soil moisture, including:

[0007] Conduct two groups of measurements under the condition of not being affected by precipitation. The first group measures the soil moisture profile curve in the existing non-covered state, and the second group measures the soil moisture profile curve under the starting covering condition; at the initial moment of measurement, the change curves of the soil moisture of the two groups with depth in the longitudinal section are the same, denoted as SWC1 * ; at the second moment of the measurement process, the curve of the soil moisture change with depth of the first group is denoted as SWC1, and the curve of the soil moisture change with depth of the second group is denoted as SWC2. According to the water balance principle, the evapotranspiration amount is the soil moisture consumption of the corresponding test. Then the evapotranspiration amount in the first group of cases In the second group of cases, due to the covering restricting soil evaporation, the evapotranspiration amount is all transpiration amount, that is Then E = ET1 - ET2, indicating that the soil moisture difference under the two groups of measurement conditions is caused by the unevaporated water volume.

[0008] Furthermore, the covering condition in the second group of measurements is the film covering condition. Under the film covering condition, the air permeability of the film is greater than the set value and can inhibit soil evaporation, and the reflectivity is within the set range compared with the reflectivity of the ground surface in the existing non-covered state.

[0009] Furthermore, a soil sensor is used to measure the change value of soil moisture, and the measurement interval is less than the set threshold.

[0010] On the other hand, the present invention provides an orchard evapotranspiration differentiation device based on the differential change of soil moisture. The device includes:

[0011] A first measurement module for measuring the evapotranspiration amount ET1 in the existing non-covered state, ET1 = E + T, where E represents the evaporation amount and T represents the transpiration amount; at the initial measurement moment, the change curves of the soil moisture of the two groups with depth in the longitudinal section are the same, denoted as SWC1 * , at the second moment during the measurement process, the curve of the first group of soil moisture changing with depth is denoted as SWC1;

[0012] A second measurement module for measuring the evapotranspiration amount ET2 under the covering condition. Since the covering restricts soil evaporation E, then ET2 = T, and the curve of the soil moisture changing with depth in the second group of measurements is denoted as SWC2;

[0013] A data processing module for calculating according to the data of the first measurement module and the second measurement module. The calculation process is as follows: Then the evaporation amount E during this time period = ET1 - ET2.

[0014] Furthermore, the covering condition is the film covering condition. Under the film covering condition, the air permeability of the film is greater than the set value and can inhibit soil evaporation, and the difference in reflectivity from the reflectivity of the ground surface in the existing non-covered state is within the set range.

[0015] Furthermore, the first measurement module and the second measurement module use a soil sensor to measure the change value of soil moisture.

[0016] The beneficial effects of the present invention are as follows:

[0017] The present invention differentiates ET only through soil moisture data. The measurement cost of soil moisture data is relatively low, the measurement method is relatively simple, the operation procedure and calculation are simple, the spatio-temporal scale adaptability is strong, and it has the characteristics of real-time diagnosis of water consumption of different components in the orchard, providing an important way for the evaluation of the water-saving irrigation potential of the orchard and economic and timely irrigation diagnosis. Description of the Drawings

[0018] Figure 1 It is a flowchart of a method for differentiating orchard evapotranspiration based on the differential change of soil moisture provided by an embodiment of the present invention. Detailed Embodiments

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] The present invention measures the change of soil moisture based on the principle of water balance. The equation of the water balance principle is as follows:

[0021] W t -W0 = W r +P0 + K + M - ET, W t represents the soil planned wetting layer water content at the end of the time period, W0 represents the soil planned wetting layer water content at the beginning of the time period, W r represents the increased water content due to the increase of the planned wetting layer, P0 represents the effective rainfall stored in the soil planned layer, K represents the groundwater recharge amount during the time period, M represents the irrigation water amount during the time period, and ET represents the evapotranspiration amount during the time period.

[0022] In the expression of the water balance principle, when the influence of other factors (such as rainfall, irrigation, groundwater recharge, etc.) is small and can be basically ignored, the above formula can be simplified to W t -W0 = W r -ET. Since the calculation time period adopted in the present invention is short and the depth of the planned wetting layer basically does not change, the item of W r is 0. Therefore, based on the water balance principle, it can be obtained that W t -W0 = -ET. In short, ET is numerically equal to the change value of the soil planned wetting layer water content. The water for evapotranspiration ultimately comes from soil moisture, so the evapotranspiration amount is equal to the soil water consumption. Considering the main root distribution length and root water absorption of different crops, the total soil water consumption will be calculated by the stratified method, and accumulated layer by layer with a gradient of 10 cm until the soil depth is 80 cm.

[0023] The present invention provides a method for distinguishing orchard evapotranspiration based on the differential change of soil moisture, such as Figure 1As shown, the method is divided into two groups of experiments. One group measures the soil moisture profile curve under the existing state (non-mulched), and the other group measures the soil moisture profile curve under the mulched condition. Both groups of experiments are carried out under the condition of not being affected by precipitation, and in the experiment, the soil moisture is measured by a soil sensor to obtain the change value of soil water content at different depths (generally, the depth interval does not exceed 10 cm). Among them, for the mulched experiment, it is required that the film has good air permeability but can well inhibit soil evaporation. If the air permeability is greater than the set value, it is considered that the air permeability is good. This set value is generally obtained through experiments, and this experiment should consider both the air permeability and the situation of inhibiting soil evaporation. The reflectivity is basically the same as that of the non-mulched ground surface, ensuring that the energy received by the ground surface is basically the same. At the initial moment T1, the change of soil moisture with depth in the longitudinal section is denoted as SWC1 * (Under ideal conditions, the soil moisture at the initial moment in Experiments 1 and 2 is considered to be undifferentiated); at the moment T2, the curve of the change of soil moisture with depth in Experiment 1 is denoted as SWC1, and the curve of the change of soil moisture with depth in Experiment 2 is denoted as SWC2. In the experiment, the evapotranspiration under the existing state is ET1 = E + T, and the evapotranspiration under the mulched condition is ET2 = T (no evaporation). Since the two groups of experiments are in the same atmospheric environment and the transpiration rate of the fruit tree canopy is the same, then E = ET1 - ET2. In the experiment, ET1 is the change value of the soil moisture in Experiment 1 from the moment T1 to the moment T2, and ET2 is the change value of the soil moisture in Experiment 2 from the moment T1 to the moment T2. Since the soil moisture in Experiments 1 and 2 is basically the same at the moment T1, E represents the difference in soil moisture between the two groups of experiments at the moment T2. The specific calculation formula is as follows:

[0024]

[0025] Thus, the evapotranspiration in the orchard is distinguished based on the differential changes in soil moisture at different depths in the non-covered / covered areas,

[0026] Based on the above method, the present invention also provides a distinguishing device, which includes:

[0027] The first measurement module is used to measure the evapotranspiration amount ET1 under the existing non-covered state, ET1 = E + T, where E represents the evaporation amount and T represents the transpiration amount; measure that at the initial moment, the curves of the change of the soil moisture of the two groups with depth in the longitudinal section are the same, denoted as SWC1 * , and at the second moment during the measurement process, the curve of the change of the soil moisture of the first group with depth, denoted as SWC1;

[0028] The second measurement module is used to measure the evapotranspiration amount ET2 under the covered condition. Since the cover restricts the soil evaporation E, then ET2 = T, and the curve of the change of the soil moisture in the second group of measurements is denoted as SWC2;

[0029] A data processing module, which is used to calculate according to the data of the first measurement module and the second measurement module. The calculation process is as follows: Then the evaporation amount E during this time period is E = ET1 - ET2.

[0030] The above are only the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And the changes and alterations made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. A method for differentiating orchard evapotranspiration based on the differential change of soil moisture, characterized in that, The method includes: Two sets of measurements are carried out under the condition of not being affected by precipitation. The first set measures the soil moisture profile curve in the existing uncovered state, and the second set measures the soil moisture profile curve under the starting covering condition. At the initial moment of measurement, the variation curves of the soil moisture of the two sets with depth in the longitudinal section are the same, denoted as SWC1 * ; At the second moment of the measurement process, the curve of the soil moisture variation with depth in the first set is denoted as SWC1, and the curve of the soil moisture variation with depth in the second set is denoted as SWC2. According to the principle of water balance, the evapotranspiration of the orchard is the soil moisture consumption of the corresponding test. Then the evapotranspiration in the first set of cases In the second set of cases, due to the covering restricting soil evaporation, the evapotranspiration is all transpiration, that is Then E = ET1 - ET2, indicating that the difference in soil moisture under the two sets of measurement conditions is caused by the water volume that has not been evaporated. Among them, h1 is the depth of the planned wetting layer of the soil. The covering condition in the second set of measurements is the film covering condition. Under the film covering condition, the air permeability of the film is greater than the set value and can inhibit soil evaporation, and the difference in reflectivity from the reflectivity of the ground surface in the existing uncovered state is within the set range.

2. The method for differentiating orchard evapotranspiration based on the differential change of soil moisture according to claim 1, wherein Using soil sensors with different depths to measure the change value of soil moisture, and the depth interval does not exceed the set threshold.

3. An orchard evapotranspiration differentiation device based on differential changes in soil moisture, which is used to implement the orchard evapotranspiration differentiation method based on differential changes in soil moisture as described in claim 1 or 2, characterized in that, The device includes: The first measurement module is used to measure the evapotranspiration ET1 in the existing non-covered state, where ET1 = E + T, E represents the evaporation amount, and T represents the transpiration amount; at the measurement initial moment, the variation curves of the two groups of soil moisture with depth in the longitudinal section are the same, denoted as SWC1 * , at the second moment of the measurement process, the curve of the first group of soil moisture varying with depth is denoted as SWC1; A second measurement module for measuring the evapotranspiration ET2 under the covering condition. Since the covering restricts soil evaporation E, then ET2 = T, and the curve of soil moisture varying with depth in the second group of measurements is denoted as SWC2; A data processing module, which is used to calculate according to the data of the first measurement module and the second measurement module. The calculation process is as follows: Then the evaporation amount E during this time period is E = ET1 - ET2.

4. The orchard evapotranspiration differentiation device based on the differential change of soil moisture according to claim 3, characterized in that, The covering condition is the film covering condition, the air permeability of the film is greater than the set value and can inhibit soil evaporation, and the difference in reflectivity from the reflectivity of the ground surface in the existing non-covered state is within the set range.

5. The orchard evapotranspiration differentiation device based on the differential change of soil moisture according to claim 3, wherein, The first measurement module and the second measurement module use soil sensors to measure the change value of soil moisture, and the depth interval does not exceed the set threshold.

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