Gradient canopy measurement method for non-equal-line-spacing corn planting

Abstract

The invention provides a gradient canopy measurement method for non-equal-row-spacing corn planting, which comprises the following steps: performing measurement in a corn tasseling spinning or filling stage, selecting a wide row area and a narrow row area in non-equal row spacing as a wide row measurement area and a narrow row measurement area, and selecting a transition area between the wide row area and the narrow row area as a transition measurement area; measuring points are selected in the three measuring areas respectively, then predicted measuring points are selected in a corn field according to photosynthetically active radiation values and leaf area indexes of four vertical layers in the height direction of the corn, and the corn field is predicted on the basis of a photosynthetically active radiation prediction model and a leaf area index prediction model. And predicting a photosynthetically active radiation value and a leaf area index of the predicted measurement point. According to the method, the photosynthetically active radiation values and the leaf area indexes of four vertical layers of corn are measured, the complete gradient of light distribution of corn canopies is covered, and the photosynthetically active radiation and the leaf area indexes of non-equal-line-spacing corn planting fields are accurately predicted by adopting the data.

Description

Technical Field

[0001] This invention belongs to the field of canopy measurement technology, specifically relating to a gradient canopy measurement method for corn planted with non-equidistant row spacing. Background Technology

[0002] Traditional maize planting methods mostly employ uniform ridge planting, and the methods for measuring maize canopy structure are relatively simple and mature. However, with increasing demands for maize yield, planting methods have become more diversified. In recent years, asymmetrical and high-density maize planting methods have developed rapidly, such as alternating wide and narrow row planting and double-row drip irrigation with integrated water and fertilizer technology. These methods can fully utilize growing space, improve ventilation and light penetration in maize fields, and increase light energy utilization.

[0003] In maize planting patterns with non-equidistant row spacing, the vertical structure of the maize canopy is complex, and the light gradient distribution from the ground to the canopy varies between wide and narrow rows. This leads to significant spatial heterogeneity in the light distribution of the maize canopy. Traditional uniform point measurement cannot take into account the special spatial structure of wide and narrow rows in this planting pattern. If traditional uniform point measurement is used to measure population indicators such as photosynthetically active radiation and leaf area of ​​the maize canopy in this planting pattern, it will have problems such as failing to reflect the light distribution characteristics of the maize population and ignoring the photosynthetic characteristics of key functional leaf layers such as ear-side leaves. Furthermore, the calculation results of the measured data will have large deviations. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a gradient canopy measurement method for maize with non-equidistant row spacing. This measurement method is mainly designed for maize with non-equidistant row spacing, taking into account the heterogeneity of light distribution in the transition zone between wide and narrow rows. It delineates three measurement zones: a wide row measurement zone, a narrow row measurement zone, and a transition zone. Measurement points are selected within these three zones, and a composite point layout scheme is designed. During measurement, both horizontal and vertical measurements are performed to accurately capture the asymmetric canopy light distribution. Simultaneously, the measured values ​​of photosynthetically active radiation (PARadia) and leaf area index (LAI) at each measurement point in the wide row measurement zone, narrow row measurement zone, and transition zone are obtained from four vertical levels. Finally, based on the established PARadia prediction model and LAI prediction model, the PARadia and LAI at the measurement points are comprehensively predicted.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for measuring the gradient canopy of maize planted with non-equidistant row spacing, characterized in that the non-equidistant row spacing of maize refers to a planting method that combines wide rows and narrow rows, and the method is as follows: S1. Take measurements during the corn's tasseling, silking, or grain-filling stages. Select the wide and narrow row areas in the non-equal row spacing as the wide row measurement area and the narrow row measurement area, and select the transition area between the wide and narrow row areas as the transition measurement area. S2. Select measurement points in the wide row measurement area, narrow row measurement area and transition measurement area respectively, and use a plant canopy analyzer to measure the photosynthetically active radiation value and leaf area index of the four vertical layers in the corn height direction at the measurement points. The measured values ​​of photosynthetically active radiation and leaf area index of each measurement point in the wide row measurement area, narrow row measurement area and transition area are as follows: The four vertical layers, from bottom to top, are the surface layer, the layer 1m from the surface, the ear leaf layer, and the canopy layer; S3. Based on the photosynthetically active radiation prediction model and the leaf area index prediction model, and combined with the measured values ​​of photosynthetically active radiation and leaf area index at various measurement points in the wide-row measurement area, narrow-row measurement area and transition area, the photosynthetically active radiation value and leaf area index at the measurement points in S2 are predicted.

[0006] Preferably, the photosynthetically active radiation prediction model is as follows: ; Where (x, y, z) are the predicted spatial coordinates of the measurement point, and the predicted measurement point lies within the x-axis coordinate range of (...). L1 represents the spacing between wide rows of corn; the y-axis coordinate range is ( L2 represents the plant spacing of maize; z takes values ​​of 0, 1, 2, and 3 along the z-axis, where z=0 indicates the location is at the ground surface, z=1 indicates the location is 1m above the ground, z=2 indicates the location is at the ear-leaf layer, and z=3 indicates the location is in the canopy layer; PAR(x,y,z) represents the predicted value of photosynthetically active radiation at the measurement point; PAR i λ represents the measured value of photosynthetically active radiation at the i-th measurement point, and n is the number of measurement points; the predicted measurement points and the actual measurement points belong to the same measurement area and are located at the same vertical level; λ i Let i be the kriging weight of the i-th measurement point; The leaf area index prediction model is as follows: LAI(x,y,z) Among them, PAR above (x,y,z) represents the photosynthetically active radiation value in the vertical layer adjacent to and above the predicted measurement point; PAR below (x,y,z) represents the photosynthetically active radiation value in the vertical layer adjacent to and below the predicted measurement point; K (z) represents the highly correlated extinction coefficient, which is a constant; CF represents the aggregation correction factor, which is a constant.

[0007] Preferably, the measurement in S1 is taken during the corn's tasseling, silking, or grain-filling stage, preferably after 10 a.m. on a sunny day.

[0008] Preferably, the number of measurement points in the wide row measurement area, narrow row measurement area and transition measurement area in S2 is multiple, and the average value is taken for each measurement point at the same vertical level.

[0009] Preferably, the distance between the wide-row measurement area, narrow-row measurement area and transition measurement area in S1 and the edge of the field exceeds 2m.

[0010] Preferably, the wide row measurement area, the narrow row measurement area, and the transition measurement area are all rectangular, with a length of 10 meters and a width of 5 meters.

[0011] Preferably, in S2, the selected measurement point in the wide row measurement area is located at the midline A between the two rows of corn in the wide row, the selected measurement point in the narrow row measurement area is located at the midline B between the two rows of corn in the narrow row, and the selected measurement point in the transition measurement area is located at the midline C between the midline A between the two rows of corn in the wide row and the midline B between the two rows of corn in the narrow row.

[0012] Preferably, each vertical layer measurement point is subjected to both vertical and horizontal measurements. Vertical measurement refers to the plant canopy analyzer measuring along the direction of the corn strip, while horizontal measurement refers to the plant canopy analyzer measuring in the direction perpendicular to the corn strip.

[0013] Preferably, λ i Solve using the following matrix equation: Where γ in the matrix ij γ is the semivariogram value between the i-th and j-th measurement points. 0i The semivariogram value is the predicted value between the measurement point and the i-th measurement point; If the predicted measurement point is located in the wide-row measurement area, ; ; Where a represents the sill value coefficient of the wide row; b represents the distance threshold at which the spatial correlation of the wide row significantly decreases; a and b are constants, (x i ,y i ) and (x j ,y j ) are the x and y coordinates of the i-th and j-th measurement points, respectively; (x, y) are the predicted x and y coordinates of the measurement points; If the predicted measurement point is located in a narrow measurement area, ; ; Where c represents the narrow row sill value coefficient; d represents the distance threshold at which the spatial correlation of the narrow row significantly decreases; c and d are constants; If the predicted measurement point is located in the transition measurement zone, ; ; Where ω is the weighting coefficient, ranging from 0 to 1, and is calculated using the following formula: ;d wide d is the predicted distance from the measurement point to the median line A. narrow This is the predicted distance from the measurement point to the median line B.

[0014] Preferably, an error field model is established to evaluate the reliability of the predicted photosynthetically active radiation (PAR) values ​​at the measurement points using the PAR prediction model. The error field model is represented by the prediction standard deviation, specifically: ε(x,y,z)= ; where σ 2 This represents the variance of photosynthetically active radiation measured at all measurement points.

[0015] Compared with the prior art, the present invention has the following advantages: 1. Unlike existing canopy measurement methods that only measure the top of the canopy and the ground surface, this invention innovatively designs four vertical layers: the ground surface, a layer 1m away from the ground surface, the ear leaf layer, and the canopy, covering the complete gradient of light distribution in the maize canopy. In particular, the exclusive measurement of the ear leaf layer (the three leaves closest to the corn cob, which is the key photosynthetic functional zone) solves the problem of traditional methods neglecting the light environment of functional leaf layers.

[0016] 2. The gradient canopy measurement method of the present invention is mainly for maize with non-equidistant row spacing. Considering the heterogeneity of light distribution in the transition zone between wide and narrow rows, three measurement zones are defined: a wide row measurement zone, a narrow row measurement zone, and a transition measurement zone between wide and narrow rows. Measurement points are selected in the three measurement zones, and a composite point layout scheme is designed. During the measurement, bidirectional measurement is selected in both horizontal and vertical directions to achieve accurate capture of asymmetric canopy light distribution.

[0017] 3. The photosynthetically active radiation prediction model and leaf area index prediction model constructed in this invention can accurately predict the photosynthetically active radiation and leaf area index at the vertical level of the predicted measurement points in the measurement area.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the arrangement of the wide-row measurement area, the narrow-row measurement area, and the transition measurement area in Embodiment 1 of the present invention.

[0020] Figure 2Schematic diagrams of horizontal and vertical measurements of wide rows, narrow rows, and transition zones in Embodiment 1 of the present invention, as well as a three-dimensional measurement schematic diagram of four vertical levels in the height direction of corn. Detailed implementation manners

[0021] Embodiment 1 A gradient canopy measurement method for non-uniform row spacing corn planting disclosed in this embodiment. The experimental site is the experimental base in Qingshan Town, Taobei District, Baicheng, Jilin Province. The corn variety is Xiangyu 998, and the planting method is wide and narrow row planting. The wide row planting spacing is L1, and in this embodiment, L1 = 80 cm. The narrow row planting spacing is L2, and in this embodiment, L2 = 40 cm. The planting density is 70,000 plants per hectare. The measurements are carried out on August 18, 2023 and August 30, 2024 respectively. It is sunny from 10:00 to 16:00. The plant canopy analyzer used is the Sun Scan canopy analysis system (produced by Delta Company, UK). This gradient canopy measurement method is as follows: S1. Conduct measurements during the tasseling, silking, or filling stage of corn, starting after 10 am on a sunny day. Select the wide row area and narrow row area in the corn field as the wide row measurement area and narrow row measurement area respectively, and select the transition area between the wide row area and narrow row area as the transition measurement area. Among them, as Figure 1 shown, in this embodiment, three rectangular areas with a "pin" shape structure are selected in the corn field as replicates. The length of the rectangular area is 10 meters and the width is 5 meters. To avoid marginal effect errors, the distance between the boundary of the rectangular area and the edge of the corn field exceeds 2 m. Wide row measurements, narrow row measurements, and transition canopy index measurements are carried out on each rectangular area respectively.

[0022] S2. Select multiple measurement points in the wide row measurement area, narrow row measurement area, and transition measurement area respectively. The measurement points selected in the wide row measurement area are located on the middle line A of the two rows of corn in the wide row. The middle line A is specifically the middle line of the 80 cm wide row. The measurement points selected in the narrow row measurement area are located on the middle line B of the two rows of corn in the narrow row. The middle line B is specifically the middle line of the 40 cm narrow row. The measurement points selected in the transition measurement area are located on the middle line C between the middle line A and the middle line B. The middle line C is specifically the middle line A of the 80 cm wide row (40 cm away from the corn row where the wide row area and narrow row area share a row, as Figure 2 shown) to the middle line B of the 40 cm narrow row (20 cm away from the corn row where the wide row area and narrow row area share a row, as Figure 2 shown) of the middle line c (30 cm away from both the middle line A and the middle line B, as Figure 2 shown).

[0023] The number of measurement points is set according to the size of the cornfield. In this embodiment, three measurement points are selected in each of the wide row measurement area, narrow row measurement area and transition measurement area. The sensors of the plant canopy analyzer are respectively deployed at the measurement points in each measurement area, and the photosynthetically active radiation value and leaf area index are measured in four vertical layers in the corn height direction. The measured values ​​of photosynthetically active radiation and leaf area index at each measurement point in the wide row measurement area, narrow row measurement area and transition measurement area are obtained. like Figure 2 As shown, the four vertical layers from bottom to top are the surface layer H0, the layer 1m from the surface H1, and the ear-leaf layer H... s and canopy H t ; In specific measurements, multiple measurements are taken at the same vertical level for each measurement point, and the average value is used to represent the measured values ​​of photosynthetically active radiation and leaf area index at that vertical level of the measurement point. S3. Construct a predictive model for photosynthetically active radiation and a predictive model for leaf area index; S3-1. A photosynthetically active radiation (PAR) prediction model is constructed based on the Kriging interpolation method to predict the PAR value at a measurement point with spatial coordinates (x, y, z). The core is to calculate the predicted PAR value at the measurement point by using the known measured values ​​and spatial correlation. The predicted measurement point is set as the x-axis in the forward direction of the spatial coordinates, and the coordinate range of the predicted measurement point on the x-axis is (…). L1 represents the spacing between wide rows of corn; the coordinate range on the y-axis is ( L2 represents the plant spacing of corn; in this embodiment, the coordinate range of the x-axis is -40~40cm, and the coordinate range of the y-axis is -35~35cm. The measurement point and the predicted measurement point are set as the z-axis with the direction perpendicular to the ground. z takes 0, 1, 2, 3, representing four vertical layers. z=0 indicates that it is located at the ground surface, z=1 indicates that it is located at the layer 1m away from the ground surface, z=2 indicates that it is located at the ear leaf layer, and z=3 indicates that it is located at the canopy layer. The photosynthetically active radiation prediction model is as follows: ; Where PAR(x,y,z) represents the predicted value of photosynthetically active radiation at the measurement point; PAR i The measured value of photosynthetically active radiation at the i-th measurement point, in μmol·m⁻¹. -2 ・s -1λ represents the number of measurement points; the predicted measurement point and the i-th measurement point belong to the same measurement area and are located at the same vertical level. That is, when the predicted measurement point is located in the wide-row measurement area and the ear leaf layer, the measurement point is selected from the wide-row measurement area and the ear leaf layer; when the predicted measurement point is located in the narrow-row measurement area and the canopy layer, the measurement point is selected from the narrow-row measurement area and the canopy layer; when the predicted measurement point is located in the transition measurement area and 1m from the ground surface, the measurement point is selected from the transition measurement area and 1m from the ground surface. i λ is the Kriging weight for the i-th measurement point; i Solve using the following matrix equation: Where γ in the matrix ij γ is the semivariogram value between the i-th and j-th measurement points. 0i The semivariogram value is the predicted value between the measurement point and the i-th measurement point; If the predicted measurement point is located in the wide-row measurement area, ; ; Where a represents the sill value coefficient of the wide row; b represents the distance threshold at which the spatial correlation of the wide row significantly decreases; a and b are constants, (x i ,y i ) and (x j ,y j ) are the x and y coordinates of the i-th and j-th measurement points, respectively; (x, y) are the predicted x and y coordinates of the measurement points; If the predicted measurement point is located in a narrow measurement area, ; ; Where c represents the narrow row sill value coefficient; d represents the distance threshold at which the spatial correlation of the narrow row significantly decreases; c and d are constants; If the predicted measurement point is located in the transition measurement zone, ; ; Where ω is the weighting coefficient, ranging from 0 to 1, and is calculated using the following formula: ;d wide d is the predicted distance from the measurement point to the median line A. narrow This is the predicted distance from the measurement point to the median line B; S3-2, The leaf area index prediction model is: LAI(x,y,z) Where LAI(x,y,z) represents the predicted leaf area index at the predicted measurement point located at the vertical level represented by z, where z takes values ​​of 1 and 2; PAR above (x,y,z) represents the photosynthetically active radiation value in the vertical layer adjacent to and above the predicted measurement point; PAR below (x,y,z) represents the photosynthetically active radiation value in the vertical layer adjacent to and below the predicted measurement point; PAR above (x,y,z), PAR below (x, y, z) were all predicted and calculated using a photosynthetically active radiation (PAR) prediction model. The PAR prediction model is based on parameters such as total radiative flux above the canopy, solar altitude angle, and atmospheric transmittance, and is established in conjunction with radiative transfer theory. It can accurately predict the PAR intensity at different spatial locations, providing key data support for analyzing radiation distribution within the canopy. PAR below (x,y,z) and PAR above (x, y, z) together constitute the radiation boundary conditions of the vertical layer where the measurement point is located, which is used to quantify the energy attenuation during the radiation penetration process inside the canopy, and thus help to analyze the actual light-receiving level of leaves in different parts of the canopy.

[0024] K (z) The extinction coefficient, representing the high correlation, is a constant; K (z) The value characterizes the attenuation of photosynthetically active radiation during vertical transport within the canopy, and its value dynamically varies with vertical height (z). Specifically, when z=1, the measurement height is 1m above the ground, in the middle transition zone of the canopy, where leaf density and radiation shading effect are enhanced, K... (z) = 0.88; When z=2, the measurement height is located at the ear level, where the canopy leaves are most densely packed, resulting in significant radiation interception and the attenuation coefficient reaching its peak. K (z) = 0.91; When z=3, the measurement height is located in the canopy. Due to the sparse leaf distribution and the influence of the external environment, the radiation attenuation capacity is reduced. (z) = 0.82.

[0025] K at different measurement heights (z) The values ​​are based on long-term field trial data. Nonlinear regression analysis is used to fit the radiation attenuation characteristics of different height layers, providing important parameters for accurately calculating the PAR distribution within the canopy. Accurate measurement and reasonable values ​​of each parameter are key to precisely assessing the crop canopy's light interception capacity, thus providing a scientific basis for optimizing crop management strategies under wide-narrow row planting patterns. CF represents the aggregation correction factor, which is set to 1.12.

[0026] In the leaf area index prediction model, the z-axis coordinates of the selected measurement points do not include the case where z=0; S4. In step one, select a measurement point from the wide-row measurement area, narrow-row measurement area, and transition measurement area as the predicted measurement point. Based on the photosynthetically active radiation prediction model and leaf area index prediction model constructed in S3, and combined with the measured values ​​of photosynthetically active radiation and leaf area index of each measurement point in the wide-row measurement area, narrow-row measurement area, and transition area, predict the photosynthetically active radiation and leaf area index of the predicted measurement point, and obtain the predicted values ​​of photosynthetically active radiation and leaf area index of the predicted measurement point.

[0027] In this embodiment, an error field model is also established to evaluate the reliability of the predicted photosynthetically active radiation at the measurement point, and the uncertainty of spatial interpolation is reflected by calculating the prediction standard deviation. The formula for predicting standard deviation is: ε(x,y,z)= Where, σ 2 This represents the variance of photosynthetically active radiation measured at all measurement points, in units of (μmol·m⁻²). 2 ・s⁻ 1 ) 2 .

[0028] In this embodiment, each vertical layer measurement point is measured vertically and horizontally. Vertical measurement refers to the plant canopy analyzer measuring along the direction of the corn strip, and horizontal measurement refers to the plant canopy analyzer measuring in the direction perpendicular to the corn strip. Specifically, the BF5 sensor of the plant canopy analyzer is fixed on the center line A, center line B and center line C. The probe (1 meter long) of the plant canopy analyzer performs vertical and horizontal measurements respectively. The vertical measurement is placed along the center line A (center line B or center line C), and the horizontal measurement is placed perpendicular to the center line A (center line B or center line C). The ear leaf measurement point is often overlooked in existing methods. By adopting a measurement method with four vertical levels, the complete gradient of light distribution in the maize canopy is covered. In particular, the dedicated measurement of the ear leaf measurement point (the three leaves closest to the corn cob, the key photosynthetic functional zone) solves the problem of traditional methods neglecting the light environment of functional leaf layers.

[0029] It should be noted that when using the constructed photosynthetically active radiation (PARF) prediction model and leaf area index (LAI) prediction model to predict the lateral PARF and LAI values ​​at a certain vertical level of the measurement point, the actual measured values ​​at the measurement point are the actual measured values ​​at the lateral level of that vertical level. When using the constructed PARF prediction model and LAI prediction model to predict the longitudinal PARF and LAI values ​​at a certain vertical level of the measurement point, the actual measured values ​​at the measurement point are the actual measured values ​​at the longitudinal level of that vertical level.

[0030] In this embodiment, the number of measurement points is chosen based on the time intervals that arise from sequential measurements at each point. The angle and intensity of sunlight vary at different times; minimizing these time intervals helps ensure the accuracy of the measurement results. Increasing the number of measurement points allows for a corresponding increase in the number of staff. More measurement points result in a larger sample size and higher accuracy. Furthermore, a single measurement point can simultaneously collect multiple values, such as 10 data points, which also helps increase the sample size.

[0031] The method in this embodiment is used to predict the lateral and vertical photosynthetically active radiation values ​​of the four vertical layers at each measurement point. The sum of the predicted lateral photosynthetically active radiation values ​​and the predicted vertical photosynthetically active radiation values ​​(divided by two) is taken as the average value to represent the photosynthetically active radiation value of that vertical layer. The sum of the predicted photosynthetically active radiation values ​​of the four vertical layers (divided by four) is taken as the average value to represent the photosynthetically active radiation value of that measurement point. The sum of the predicted photosynthetically active radiation values ​​of all measurement points (9 points) (divided by nine) is taken as the average value to represent the photosynthetically active radiation value of the cornfield obtained in this embodiment.

[0032] The method in this embodiment is used to predict the horizontal and vertical leaf area index (LAI) values ​​of the four vertical layers at each measurement point, specifically the layer 1m from the ground surface (z=1) and the ear leaf layer (z=2). The average of the measured values ​​of the horizontal and vertical LAI values ​​of the ground / canopy layers is used to represent the LAI value of the ground / canopy layer at that measurement point. The average of the predicted values ​​of the horizontal and vertical LAI values ​​of the layer 1m from the ground surface / ear leaf layer is also used to represent the LAI value of the layer 1m from the ground surface / ear leaf layer at that measurement point. Then, the LAI values ​​of the four vertical layers at that measurement point are summed (divided by four) and averaged to represent the LAI value of that measurement point. Finally, the LAI values ​​of all nine measurement points are summed (divided by nine) and averaged to represent the LAI value of the cornfield obtained in this embodiment.

[0033] In this embodiment, photosynthetically active radiation (PAR) in the cornfield was measured using a conventional method. The main process was as follows: Three measurement points were selected in the cornfield, located on the center line C. At each measurement point, a plant canopy analyzer was used to measure two vertical layers (top and bottom). Only the horizontal PAR and leaf area index (LAI) values ​​were measured. Three measurements were taken at the top or bottom layer of each measurement point, and the average was calculated to represent the PAR and LAI values ​​at that point. The sum of the PAR values ​​at the top or bottom layer was then averaged to represent the PAR value at that measurement point. The sum of the PAR values ​​from all three measurement points was then averaged to represent the PAR value of the cornfield obtained using the conventional method. Following the same process as obtaining the PAR value of the cornfield, the LAI values ​​from all three measurement points were obtained, and then the sums were averaged to obtain the LAI value of the cornfield using the conventional method.

[0034] Based on literature records on agricultural (maize) cultivation, the optimal range of photosynthetically active radiation values ​​for (high-yield maize cultivation) is as follows: The optimal leaf area index range is 4.3-4.8 m. 2 / m 2 Then, the median value is taken, and the median value is compared with the photosynthetically active radiation value and leaf area index value obtained by this embodiment and the traditional method. Then, the absolute value of the error value is obtained. The results are shown in Table 1, which is used to evaluate the measurement method of the traditional method and this embodiment.

[0035] Table 1. Photosynthetically active radiation and leaf area index values ​​obtained by traditional methods and in this embodiment. The gradient canopy measurement method provided by this invention ultimately yields photosynthetically active radiation (PAR) values ​​and leaf area index values ​​within the optimal range for high-yield maize cultivation. The values ​​are close to the median, meaning that the error between the photosynthetically active radiation value and the leaf area index value obtained by the traditional method and the median value is smaller. This indicates that the method of the present invention is more reliable and better meets the canopy measurement needs of cornfields with non-equal spacing.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for measuring the gradient canopy of maize planted with non-equidistant row spacing, characterized in that, The non-equidistant row spacing corn planting refers to a planting method that combines wide rows and narrow rows. The method is as follows: S1. Take measurements during the corn's tasseling, silking, or grain-filling stages. Select the wide and narrow row areas in the non-equal row spacing as the wide row measurement area and the narrow row measurement area, and select the transition area between the wide and narrow row areas as the transition measurement area. S2. Select multiple measurement points in the wide row measurement area, narrow row measurement area and transition measurement area respectively, and use a plant canopy analyzer to measure the photosynthetically active radiation value and leaf area index of each measurement point in the four vertical layers in the direction of corn height, so as to obtain the measured values ​​of photosynthetically active radiation and leaf area index of each measurement point in the wide row measurement area, narrow row measurement area and transition area. The four vertical layers, from bottom to top, are the surface layer, the layer 1m from the surface, the ear leaf layer, and the canopy layer; S3. Based on the photosynthetically active radiation prediction model and the leaf area index prediction model, and combined with the measured values ​​of photosynthetically active radiation and leaf area index at various measurement points in the wide-row measurement area, narrow-row measurement area and transition area, the photosynthetically active radiation value and leaf area index at the measurement points in S2 are predicted.

2. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 1, characterized in that, The photosynthetically active radiation prediction model is as follows: ; in,( x , y , z ( ) represents the predicted spatial coordinates of the measurement point, where the predicted measurement point is located. x The range of axis coordinates is L1 represents the spacing between wide rows of corn; y The range of axis coordinates is L2 represents the plant spacing of corn; in z axial direction z Choose 0, 1, 2, or 3. z =0 indicates that it is located on the Earth's surface. z =1 indicates that it is located at a depth of 1m from the Earth's surface. z =2 indicates that it is located in the ear leaf layer. z =3 indicates that it is located in the canopy; PAR ( x , y , z () represents the predicted value of the photosynthetically active radiation at the measurement point; PAR i For the first i The measured value of photosynthetically active radiation at each measurement point, in μmol·m⁻²·s⁻¹, where n is the number of measurement points; the predicted measurement points and the measured points belong to the same measurement area and are located at the same vertical level; λ i For the first i Kriging weights for each measurement point; The leaf area index prediction model is as follows: ; in, PAR above ( x , y , z This represents the photosynthetically active radiation value in the vertical layer adjacent to and above the measurement point. PAR below ( x , y , z This represents the photosynthetically active radiation value in the vertical layer adjacent to and below the measurement point. K (z) The extinction coefficient, representing the high correlation, is a constant. CF This represents the aggregation correction factor, which is a constant.

3. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 1, characterized in that, The S2 measurement area, narrow measurement area and transition measurement area have multiple measurement points, and each measurement point is measured multiple times at the same vertical level and the average value is taken.

4. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 1, characterized in that, The distance between the wide-row measurement area, narrow-row measurement area, and transition measurement area described in S1 and the edge of the field exceeds 2m.

5. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 1, characterized in that, In S2, the selected measurement point in the wide row measurement area is located at the midline A between the two rows of corn in the wide row; the selected measurement point in the narrow row measurement area is located at the midline B between the two rows of corn in the narrow row; and the selected measurement point in the transition measurement area is located at the midline C between the midline A and the midline B.

6. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 1, characterized in that, Vertical and horizontal measurements were performed at each measurement point in each vertical layer. Vertical measurement refers to the measurement by the plant canopy analyzer along the direction of the corn strip, while horizontal measurement refers to the measurement by the plant canopy analyzer perpendicular to the direction of the corn strip.

7. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 2, characterized in that, λ i Solve using the following matrix equation: ; In the matrix γ ij For the first i The measurement point and the first j The semivariogram values ​​between measurement points γ 0i For the predicted measurement point and the first i The semivariogram values ​​between measurement points; If the predicted measurement point is located in the wide-row measurement area, ； in, a Indicates the coefficient of the wide row base value; b The distance threshold indicating a significant decrease in correlation in wide-space areas; a and b is a constant, ( x i , y i )and( x j , y j ) are respectively the first i The and the first j The x and y coordinates of each measurement point; x , y (x, y coordinates of the predicted measurement point) If the predicted measurement point is located in a narrow measurement area, ； in, c Indicates the narrow row sill value coefficient; d The distance threshold that indicates a significant decrease in correlation in narrow-space regions; c and d It is a constant; If the predicted measurement point is located in the transition measurement zone, ； Where ω is the weighting coefficient, with a value ranging from 0 to 1, and the calculation formula is: ; d wide The distance from the predicted measurement point to the median line A. d narrow This is the predicted distance from the measurement point to the median line B.

8. The method for measuring the gradient canopy of maize planted with non-equidistant row spacing according to claim 7, characterized in that, An error field model was established to evaluate the reliability of the predicted photosynthetically active radiation (PAR) values ​​at the measurement points using the PRA prediction model. The error field model uses the prediction standard deviation. ε ( x , y , z )express: ; in, σ 2 This represents the variance of photosynthetically active radiation measured at all measurement points.

Images