Summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology

Abstract

The invention discloses a summer corn nitrogen nutrition diagnosis method based on an infrared thermal imaging technology, and is applied to the technical field of summer corn nitrogen nutrition diagnosis. Comprising the following steps: respectively acquiring summer corn canopy thermal imaging data under different height, angle and time shooting modes in different growth periods; synchronously measuring the plant biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorptive photosynthetically active radiation component of the overground part of the summer corn in different growth periods; analyzing summer corn canopy temperature image information difference and a relationship between the summer corn canopy temperature image information difference and a nitrogen nutrition index; the influence effect of the shooting mode on the canopy temperature is judged, and the optimal shooting mode is determined; the critical temperature is determined according to the relation between the canopy temperature and the relative yield, a summer corn nitrogen fertilizer real-time topdressing model with different canopy temperatures in different growth periods is constructed, and theoretical support and thought reference are provided for application and development of near-earth infrared thermal imaging precise diagnosis of summer corn nitrogen nutrition.

Description

Technical Field

[0001] The invention relates to the technical field of summer corn nitrogen nutrition diagnosis, and more particularly to a summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology. Background Art

[0002] Nitrogen is the most demanded nutrient element in the growth and development of crops. It is also a basic component element of the secondary metabolism and signal transduction substances of crops. It plays an important role in biological inheritance, protein synthesis, and the storage and transportation of photosynthetic substances. When plants are deficient in nitrogen, they usually show symptoms such as short plant shape, decreased biomass accumulation, chlorophyll synthesis and photosynthesis, and premature senescence of leaves. Excess nitrogen can easily cause crops to be greedy for green and late maturity, poor stress resistance, and "luxurious absorption" of nutrients. At present, in order to continuously increase crop yields, excessive application of nitrogen fertilizers is still common in production practice. In addition to reducing crop yields and deteriorating quality, excessive nitrogen application will also cause a large amount of nitrogen residue in the soil, causing groundwater and atmospheric environmental pollution, which will then endanger human health and the sustainable development of the ecological environment. Therefore, sufficient and reasonable nitrogen supply is crucial to promoting crop growth, yield formation, quality construction and green development of agriculture.

[0003] Real-time and precise nitrogen management is one of the most critical nutrient management measures in crop production with the goal of high crop yield and high nutrient efficiency. Rapid monitoring and precise diagnosis of nitrogen nutrition status using crop light and temperature response specificity has always been a research hotspot in smart agriculture and real-time field nutrient integrated management and application. At present, traditional crop nitrogen nutrition monitoring is mainly based on laboratory chemical analysis. Although this method can obtain relatively accurate results, it is time-consuming, expensive, and difficult to implement on a macro scale due to the process of field sample collection, preliminary processing, and indoor analysis, which affects the timeliness and objectivity of agricultural decision-making. At present, infrared thermal imaging technology, as one of the most convenient tools for thermal infrared remote sensing, has been rapidly developed and widely used due to its advantages of rapidity, non-destructiveness, and precision. However, the application of thermal imaging technology to crop nitrogen nutrition diagnosis is easily affected by factors such as meteorology and operation methods (such as shooting time, shooting height, shooting angle, etc.), and the acquisition of crop canopy thermal infrared images is mainly carried out using fixed or original recommended methods. There are relatively few studies on the standardization of instrument shooting parameters and the construction of quantitative diagnostic models. How to obtain more accurate thermal infrared image information of crop canopies is the key to using this technology to monitor crop nitrogen nutrition in real time, and obtaining high-quality temperature images is the premise and guarantee for establishing nitrogen nutrition parameters and quantitative diagnostic models. Summer corn is a nitrogen-responsive sensitive crop with a short growing period and significant changes in group structural indicators such as biomass, leaf area index, and canopy width, which in turn causes large differences in nitrogen nutrition and canopy temperature information in different growing periods. When using infrared thermal imaging technology to carry out precise monitoring of summer corn nitrogen nutrition, the canopy structure changes caused by the difference in nitrogen nutrition and growth period effects, the standardization of inversion parameters, and the internal plant nutrition-spectral informatics mechanism should be fully considered. Therefore, how to provide a summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology is a problem that technicians in this field urgently need to solve. Summary of the invention

[0004] In view of this, the present invention provides a summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology, which obtains the canopy temperature of summer corn through infrared thermal imaging technology and then obtains the summer corn nitrogen nutrition real-time diagnosis equation.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology comprises the following steps:

[0007] S1. Acquire summer corn canopy thermal imaging data at different heights, angles and time shooting modes at different growth stages; the heights are 0.5m, 1.5m and 2.5m, the angles are 30°, 60° and 90°, and the times are 9:00, 12:00, 14:00 and 16:00 respectively;

[0008] S2. Synchronously measure the aboveground plant biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn at different growth stages;

[0009] S3. Analyze the relationship between nitrogen fertilizer application and yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn to determine the effect of nitrogen fertilizer application on the growth and development of summer corn;

[0010] S4. Analyze the relationship between canopy temperature and nitrogen fertilizer application, yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn under different shooting modes, determine the impact of different shooting modes on canopy temperature and determine the best shooting mode;

[0011] S5. Determine the critical temperature at different growth stages based on the relationship between canopy temperature and relative yield of summer corn under the optimal shooting mode;

[0012] S6. Construct a real-time nitrogen topdressing model based on canopy temperature at different growth stages under the optimal shooting mode for summer corn.

[0013] Optionally, S1 specifically includes: setting different summer corn canopy vertical heights as shooting heights, setting different shooting times, setting different angles between the infrared thermal imager and the horizontal plane as shooting angles, and shooting at the jointing stage, large trumpet stage, silking stage and filling stage of summer corn respectively.

[0014] Optionally, S2 is specifically:

[0015] Four representative maize plants were selected from each planting plot at the jointing stage, trumpet stage, silking stage and grain filling stage of summer maize, and the plants were sterilized at 105℃ for 30min and dried at 75℃ to constant weight. The aboveground biomass was calculated. The maize samples dried at each growth stage were crushed and sieved, digested by H2SO4-H2O2 method, and the nitrogen content of the plants was determined by AA3 flow injection analyzer. The nitrogen accumulation of the plants was calculated. 2 Take continuous plots, thresh and air-dry until constant weight, and calculate the grain yield;

[0016] All the leaves of corn plants collected at each growth stage were picked and laid flat on a black background cloth, with a 10cm×10cm standard white board placed at each corner. The leaf area index was calculated after taking photos with a digital camera.

[0017] In each planting plot at each growth stage, 10 corn plants with similar growth were selected and planted continuously. The SPAD values ​​of their leaves were measured using a daily chlorophyll meter, and the average value of the test results of each planting plot was calculated.

[0018] The photosynthetically active radiation of the summer maize canopy and base was measured by a canopy analyzer at each growth stage, and the absorbed photosynthetically active radiation component was calculated.

[0019] Optionally, the absorbed photosynthetically active radiation component is calculated as follows:

[0020]

[0021] In the formula, FPAR is the absorbed photosynthetically active radiation component, PAR ci is the canopy incident photosynthetically active radiation, PAR cr PAR is the photosynthetically active radiation reflected by the canopy. gi is the incident photosynthetically active radiation at the base, PAR gr Reflects photosynthetically active radiation to the base.

[0022] Optional, S3 is:

[0023] The Person correlation analysis method was used to quantitatively analyze the relationships between nitrogen fertilizer application and yield of summer corn, nitrogen fertilizer application and aboveground biomass, nitrogen fertilizer application and nitrogen accumulation, nitrogen fertilizer application and leaf area index, nitrogen fertilizer application and leaf SPAD value, nitrogen fertilizer application and absorbed photosynthetically active radiation component, and nitrogen fertilizer application and summer corn canopy temperature, and the changing trends of each parameter with the increase of nitrogen fertilizer application were analyzed.

[0024] Optionally, S4 is specifically:

[0025] The Person correlation analysis method was used to quantitatively analyze the relationships between summer maize canopy temperature and nitrogen fertilizer application, yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value, and absorbed photosynthetically active radiation component at different shooting angles, different shooting heights, and different shooting times. The optimal shooting angle, optimal shooting height, and optimal shooting time for summer maize in different growth stages were determined based on the correlation coefficient and determination coefficient.

[0026] Optionally, S5 is specifically:

[0027] A quadratic equation was used to fit the canopy temperature of summer maize at each growth stage and its relative yield at maturity under the optimal shooting mode. The critical value was determined according to the fitting classification standard. The relative yield was calculated as the ratio of the summer maize yield at maturity for each nitrogen fertilizer treatment to its maximum yield. 95% of the relative yield was taken as the critical value. A value below 95% indicated nitrogen fertilizer deficiency, and a value above 95% indicated nitrogen fertilizer abundance. The critical temperature value for each growth stage was determined in this way.

[0028] Optionally, S6 is specifically:

[0029] The relationship between nitrogen fertilizer application and yield in each growth period of summer corn was fitted by a quadratic equation, and the fitting relationship between total nitrogen fertilizer application and yield in the whole growth period was obtained. The partial derivative of the fitting relationship was obtained to obtain the maximum yield and the corresponding nitrogen fertilizer application amount. The nitrogen fertilizer application amount was used as the reference value of the total amount of nitrogen fertilizer topdressing. The nitrogen topdressing amount was:

[0030] N top =N c -N fer

[0031]

[0032] Where N top N is the amount of nitrogen added c is the reference value of the total amount of nitrogen fertilizer applied, N fer is the current nitrogen fertilizer level, T ca The current canopy temperature, a, b, c are constants, and the a, b, c values ​​of each growth period are substituted into the calculation equation for the amount of nitrogen topdressing to obtain the calculation equation for the amount of nitrogen topdressing in each growth period.

[0033] It can be seen from the above technical scheme that compared with the prior art, the present invention provides a summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology, which has the following beneficial effects: the present invention deeply and systematically analyzes the influence and differential effects of factors such as shooting time, shooting height and shooting angle on the summer corn canopy temperature, and determines a convenient and accurate optimal acquisition method for summer corn canopy thermal images; constructs a summer corn nitrogen nutrition real-time diagnosis equation, in order to provide theoretical and practical references for real-time and accurate diagnosis of summer corn nitrogen nutrition and precise application of nitrogen fertilizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 The present invention is a flow chart of the summer corn nitrogen nutrition diagnosis method;

[0036] Figure 2 This is a schematic diagram of the nitrogen fertilizer dosage and yield analysis results in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of the analysis results of nitrogen fertilizer dosage and aboveground biomass in an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of the analysis results of nitrogen fertilizer dosage and nitrogen accumulation in the embodiment of the present invention;

[0039] Figure 5 This is a schematic diagram of the analysis results of nitrogen fertilizer dosage and leaf area index in an embodiment of the present invention;

[0040] Figure 6 This is a schematic diagram of the analysis results of nitrogen fertilizer dosage and leaf SPAD value in an embodiment of the present invention;

[0041] Figure 7 Schematic diagram of the analysis results of nitrogen fertilizer dosage and absorbed photosynthetically active radiation component in an embodiment of the present invention;

[0042] Figure 8 This is a schematic diagram of the fitting results of the relationship between canopy temperature and yield in an embodiment of the present invention;

[0043] Fig. 9 This is a schematic diagram of the fitting results of the relationship between nitrogen fertilizer dosage and yield in an embodiment of the present invention;

[0044] Fig.10 The thermal imaging images of summer corn canopy at different shooting heights in the embodiment of the present invention;

[0045] Fig.11 The thermal imaging images of summer corn canopy at different shooting angles in the embodiment of the present invention;

[0046] Fig.12 These are thermal images of summer corn canopies at different shooting times in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The embodiment of the present invention discloses a method for diagnosing nitrogen nutrition of summer corn based on infrared thermal imaging technology. Figure 1 As shown, the following steps are included:

[0049] S1. Acquire summer corn canopy thermal imaging data at different heights, angles and time shooting modes at different growth stages; the heights are 0.5m, 1.5m and 2.5m, the angles are 30°, 60° and 90°, and the times are 9:00, 12:00, 14:00 and 16:00 respectively;

[0050] S2. Synchronously measure the aboveground plant biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn at different growth stages;

[0051] S3. Analyze the relationship between nitrogen fertilizer application and yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn to determine the effect of nitrogen fertilizer application on the growth and development of summer corn;

[0052] S4. Analyze the relationship between canopy temperature and nitrogen fertilizer application, yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn under different shooting modes, determine the impact of different shooting modes on canopy temperature and determine the best shooting mode;

[0053] S5. Determine the critical temperature at different growth stages based on the relationship between canopy temperature and relative yield of summer corn under the optimal shooting mode;

[0054] S6. Construct a real-time nitrogen topdressing model based on canopy temperature at different growth stages under the optimal shooting mode for summer corn.

[0055] Furthermore, S1 is specifically as follows: setting different summer corn canopy vertical heights as shooting heights, setting different shooting times, setting different angles between the infrared thermal imager and the horizontal plane as shooting angles, and shooting at the jointing stage, large trumpet stage, silking stage and filling stage of summer corn respectively.

[0056] In one embodiment of the present invention, a field experiment on nitrogen fertilizer effect of summer corn was carried out for two consecutive years (2022-2023), and five treatments were set in both annual experiments, namely 0 (N0), 70 (N70), 140 (N140), 210 (N210) and 280 (N280) kg / hm 2 Each plot has an area of ​​30m 2 (5.0m×6.0m), repeated three times, and arranged in random blocks. The types of nitrogen, phosphorus, and potassium fertilizers were ordinary urea (N 46%), ESN resin coated urea (containing N 44%), superphosphate (P2O512%), and potassium chloride (K2O60%). Nitrogen fertilizer was applied at a ratio of 5:5 between ordinary urea and coated urea, and the amounts of phosphorus and potassium fertilizers were P2O590 kg / hm 2 and K2O75kg / hm 2 All fertilizers were applied as basal fertilizers at the five-leaf stage (V5) of summer maize to avoid the effects of fertilizer topdressing on the canopy temperature and nitrogen nutrition continuity of summer maize.

[0057] The summer maize canopy temperature data were collected using the TiX640 infrared thermal imager (Fluke, TiX640, USA) produced by Fluke Company of the United States during the jointing stage, trumpet stage, silking stage and grain filling stage of summer maize. The instrument has a band range of 7.5um-14μm, an image resolution of 640×480 (307200 pixels), an IFOV (spatial resolution) of 0.8mRad, a thermal sensitivity of ≤0.03℃ at a target temperature of 30℃, and a field of view of 30.9°×23.1°. In order to obtain more representative canopy temperature information, the air temperature was obtained before and after shooting in each plot for correction;

[0058] In the embodiment of the present invention, different shooting modes are as follows:

[0059] 1) Shooting time: The vertical height from the summer corn canopy was 1.5 m, and the infrared thermal imager was adjusted to a 60° angle with the horizontal plane. Shooting was performed at 9:00, 12:00, 14:00, and 16:00 on the same day, and 3 photos were taken for each plot;

[0060] 2) The photos were taken between 12:00 and 14:00 during the above growth period, with the infrared thermal imager adjusted to a 60° angle with the horizontal plane, and the shooting heights were set to 0.5m, 1.5m and 2.5m from the summer corn canopy, and 3 photos were taken for each plot;

[0061] 3) The shooting angle was also between 12:00-14:00 during the above growth period, with a vertical height of 1.5m from the summer corn canopy. The infrared thermal imager was adjusted to 30°, 60° and 90° with the horizontal plane for shooting, and 3 photos were taken for each plot.

[0062] Furthermore, S2 is specifically:

[0063] Four representative maize plants were selected from each planting plot at the jointing stage, trumpet stage, silking stage and grain filling stage of summer maize, and the plants were sterilized at 105℃ for 30min and dried at 75℃ to constant weight. The aboveground biomass (kg / hm2) was calculated. 2 ), the dried corn samples at each growth stage were crushed and sieved, digested by H2SO4-H2O2 method, and the nitrogen content (%) of the plants was determined by AA3 flow injection analyzer (SEAL, Germany), and the nitrogen accumulation (kg / hm2) of the plants was calculated. 2 ), select 15m in each plot at the mature stage 2 The continuous plots were threshed and air-dried to constant weight, and the grain yield (kg / hm2) was calculated. 2 );

[0064] All the leaves of corn plants collected at each growth stage were picked and laid flat on a black background cloth, with a 10cm×10cm standard white board placed at each corner. The leaf area index (LAI) was calculated after taking photos with a digital camera.

[0065] In each planting plot at each growth stage, 10 corn plants with similar growth were selected and planted continuously. The SPAD values ​​of their leaves were measured using a daily chlorophyll meter, and the average value of the test results of each planting plot was calculated.

[0066] The photosynthetically active radiation of the summer maize canopy and base was measured by a canopy analyzer at each growth stage, and the fraction of absorbed photosynthetically active radiation (FPAR) was calculated.

[0067] Furthermore, the absorbed photosynthetically active radiation component is calculated as follows:

[0068]

[0069] In the formula, FPAR is the absorbed photosynthetically active radiation component, PAR ci is the canopy incident photosynthetically active radiation, PAR cr PAR is the photosynthetically active radiation reflected by the canopy. gi is the incident photosynthetically active radiation at the base, PAR gr Reflects photosynthetically active radiation to the base.

[0070] Furthermore, S3 is specifically:

[0071] The Person correlation analysis method was used to quantitatively analyze the relationships between nitrogen fertilizer application and yield of summer corn, nitrogen fertilizer application and aboveground biomass, nitrogen fertilizer application and nitrogen accumulation, nitrogen fertilizer application and leaf area index, nitrogen fertilizer application and leaf SPAD value, nitrogen fertilizer application and absorbed photosynthetically active radiation component, and nitrogen fertilizer application and summer corn canopy temperature, and the changing trends of each parameter with the increase of nitrogen fertilizer application were analyzed.

[0072] Microsoft Excel 2016 was used for basic data input and preliminary processing; SPSS 20.0 software was used for variance analysis and significance test (LSD method), and the significance level was set at P < 0.5;

[0073] In one embodiment of the present invention, the analysis results of nitrogen fertilizer application and yield of summer corn are as follows: Figure 2 As shown in Figure 2, the summer maize yields in N210 and N280 reached the highest values ​​of 12655 and 11707 kg / hm2, respectively. 2Compared with N0, the average increase in summer maize grain yield in 2022 and 2023 under nitrogen application was 30.7% and 30.9%, respectively, with significant effects. The fertilizer effect function was used to fit the nitrogen application rate and yield of summer maize, and the relationship between the two was in line with the "linear + platform" trend change, and the determination coefficient (R 2 ) were 0.849 and 0.941 respectively, and the optimum nitrogen application rates were 174 and 215 kg / hm 2 , the corresponding yields are 12589 and 11707 kg / hm 2 ;

[0074] The analysis results of nitrogen fertilizer application and aboveground biomass are as follows: Figure 3 As shown in the figure, the aboveground biomass of summer maize at each growth stage was significantly affected by the amount of nitrogen fertilizer. With the increase of nitrogen application, the aboveground biomass in each period showed a trend of first increasing and then slightly decreasing, reaching a peak at N210, and there was no significant difference between N210 and N280. A comprehensive analysis of the two years showed that compared with no nitrogen application (N0), the average increase in aboveground biomass at the jointing stage, trumpet stage, silking stage, grain filling stage and maturity stage after nitrogen application was 57.87%, 51.86%, 41.71%, 52.07% and 50.61%, respectively. During the growth period, the average aboveground biomass at the jointing stage, trumpet stage, silking stage, grain filling stage and maturity stage was 2009.9, 5794.2, 8828.9, 18183.6 and 22049.5 kg / hm, respectively. 2 ;

[0075] The analysis results of nitrogen fertilizer application and nitrogen accumulation are as follows: Figure 4 As shown in the figure, consistent with the biomass change trend, the nitrogen accumulation of summer maize aboveground plants also increased significantly with the increase of nitrogen fertilizer application, and during the growth period, it first increased and then stabilized as the growth period progressed. In 2022, the average nitrogen accumulation of the aboveground parts of the plants in the jointing stage, trumpet stage, silking stage, grain filling stage and maturity stage was 48.1, 164.1, 182.1, 265.3 and 234.9 kg / hm2, respectively. 2 In 2023, they will be 83.5, 98.9, 163.5, 270.5 and 314.9 kg / hm2 respectively. 2 Among the treatments, the average nitrogen accumulation of summer corn plants in the 2022 nitrogen application treatment was 192.7 kg / hm 2 , 55.70% higher than N0 treatment; 207.7kg / hm in 2023 2 , an increase of 106.83% compared with N0.

[0076] The analysis results of nitrogen fertilizer application and leaf area index are as follows: Figure 5As shown, with the advancement of the growth period, the LAI of summer maize showed an overall trend of first increasing and then decreasing. Among the treatments, the LAI of summer maize with different nitrogen application rates was significantly different. In 2022 and 2023, the N210 and N280 treatments had the most significant effects. Compared with N0, the average increase in LAI in each period in 2022 was 13.51%-47.39%, 12.01%-34.83%, 10.24%-29.84% and 15.13%-41.27%, respectively; in 2023, the LAI in each period increased by 26.58%-85.47%, 25.78%-65.09%, 9.07%-28.34% and 26.91%-60.88%, respectively;

[0077] The analysis results of nitrogen fertilizer application and leaf SPAD value are as follows: Figure 6 As shown, with the growth period, the SPAD values ​​of summer corn in 2022-2023 were all in the order of filling period > silking period > trumpet period > jointing period. Different nitrogen fertilizer application rates also had a significant effect on the SPAD value of summer corn leaves. With the increase of nitrogen fertilizer application rate, the leaf SPAD value first increased and then tended to stabilize. In both years, N210 and N280 were significantly higher than other treatments, and the increase in nitrogen application treatments compared with N0 in each period in 2022 was 4.18%-16.85%, 4.34%-14.67%, 4.26%-18.54% and 3.33%-12.25%, respectively; the increase in each period in 2023 compared with N0 treatment was 4.19%-14.01%, 6.03%-21.41%, 4.49%-13.34% and 5.97%-13.92%, respectively;

[0078] The analysis results of nitrogen fertilizer application and absorbed photosynthetically active radiation are as follows: Figure 7 As shown in the figure, the FPAR value of summer maize canopy is significantly affected by the nitrogen fertilizer effect, and there are certain differences in different growth periods. Among the different nitrogen fertilizer application rates, the FPAR values ​​of the two test years first increased and then tended to stabilize with the increase of nitrogen fertilizer application. Comprehensive analysis of the nitrogen fertilizer effect in each period, the nitrogen fertilizer application rates of the two test years were 0, 70, 140, 210 and 280 kg / hm 2 The canopy FPAR values ​​were 0.700, 0.739, 0.779, 0.820 and 0.827, respectively. During the growth period, the canopy FPAR values ​​at the jointing stage, trumpet stage, silking stage, grain filling stage and maturity stage in the experimental years (2022 and 2023) were 0.674, 0.778, 0.823 and 0.817, respectively, with large differences;

[0079] The analysis results of nitrogen fertilizer application and summer corn canopy temperature at different shooting heights are shown in Table 1. The thermal imaging images of summer corn canopy are shown in Fig.10As shown; it can be seen that with the increase of shooting height, the average canopy temperature in 2022 showed a gradual downward trend. When the shooting height was 0.5m, 1.5m and 2.5m, the average canopy temperature was 29.63, 29.51 and 29.47℃ respectively; the average canopy temperature in 2023 showed a trend of first decreasing and then increasing with the increase of shooting height. The average temperatures at shooting heights of 0.5m, 1.5m and 2.5m were 31.13, 31.04 and 31.18℃ respectively.

[0080] With the increase of shooting height, the average canopy temperature in 2022 showed a gradual downward trend. When the shooting heights were 0.5m, 1.5m and 2.5m, the average canopy temperatures were 29.63, 29.51 and 29.47℃, respectively. In 2023, the average canopy temperature first decreased and then increased with the increase of shooting height. The average temperatures at shooting heights of 0.5m, 1.5m and 2.5m were 31.13, 31.04 and 31.18℃, respectively.

[0081] Table 1 Nitrogen fertilizer application and summer corn canopy temperature at different shooting heights

[0082]

[0083] The analysis results of nitrogen fertilizer application and summer corn canopy temperature under different shooting angles are shown in Table 2. The thermal imaging images of summer corn canopy are shown in Fig.11 As shown; it can be seen that at the same shooting angle, with the increase of nitrogen fertilizer application, the canopy temperature of summer corn in each growth period of the two years showed a downward trend. Taking 60° as an example, the average canopy temperature of summer corn in each growth period of N0, N70, N140, N210 and N280 was 30.47, 29.95, 29.44, 28.92 and 28.79°C, respectively. Under the same nitrogen application level, with the increase of shooting angle, the canopy temperature of summer corn in the two years showed a trend of first decreasing and then increasing, and was the lowest at 60°. The average temperatures in 2022 and 2023 were 29.51°C and 31.04°C, respectively. Taking N210 as an example, the average canopy temperatures at 30°, 60° and 90° were 28.93, 28.92 and 28.98°C, respectively.

[0084] Table 2 Nitrogen fertilizer application and summer corn canopy temperature at different shooting angles

[0085]

[0086] The analysis results of nitrogen fertilizer application and summer corn canopy temperature at different shooting times are shown in Table 3. The thermal imaging images of summer corn canopy are shown in Fig.12As shown in the figure, it can be seen that the temperature of the summer corn canopy shows a trend of first rising and then falling with the shooting time during the day. Overall, the summer corn canopy temperature is lowest at 9:00 in the morning and highest at 14:00. Compared with 9:00, the average temperature of the summer corn canopy in 2022 increased by 11.38%, 17.03% and 14.03% at the shooting time of 12:00, 14:00 and 16:00 respectively. The trend in 2023 is the opposite, and the average temperature of the summer corn canopy increased by 3.91%, 5.46% and 3.38% respectively. The results in 2022 show that with the increase of nitrogen application, the summer corn canopy temperature at the shooting time of 12:00 gradually decreases and then tends to stabilize, while there is no consistent change pattern at other shooting times; in 2023, the summer corn canopy temperature at different shooting times shows a trend of gradually decreasing and then tending to stabilize with the increase of nitrogen fertilizer application.

[0087] Table 3 Nitrogen fertilizer application and summer corn canopy temperature at different shooting times

[0088]

[0089]

[0090] With the increase of nitrogen fertilizer application, the canopy temperature of summer corn first decreased and then gradually stabilized, and the rate of decrease slowed down between N210 and N280. Compared with the N0 treatment, the average canopy temperature of nitrogen fertilizer treatments N70, N140, N210 and N280 decreased by 0.48, 0.95, 1.44 and 1.55℃ respectively in 2022; the average canopy temperature of nitrogen fertilizer treatments in 2023 decreased by 0.52, 1.17, 2.18 and 2.52℃ respectively;

[0091] Furthermore, S4 is specifically:

[0092] The Person correlation analysis method was used to quantitatively analyze the relationships between summer maize canopy temperature and nitrogen fertilizer application, yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value, and absorbed photosynthetically active radiation component at different shooting angles, different shooting heights, and different shooting times. The optimal shooting angle, optimal shooting height, and optimal shooting time for summer maize in different growth stages were determined based on the correlation coefficient and determination coefficient.

[0093] In one embodiment of the present invention, the relationship between the average canopy temperature of summer corn and the nitrogen nutrition index at different shooting heights almost reached an extremely significant level (P<0.01). The determination coefficient (R) between the canopy temperature and the nitrogen fertilizer application and yield in two years when the shooting heights were 0.5m, 1.5m and 2.5m respectively 2) were 0.898, 0.916, 0.894 and 0.779, 0.807, 0.789, respectively. During the growth period, the canopy temperature correlation was better when the shooting height was 0.5m during the jointing stage, 2.5m was the best during the trumpet stage, and 1.5m was the best during the silking stage to the grain filling stage. Comprehensive analysis found that R 2 The value is the highest at 1.5m, with an average of 0.826. Therefore, the embodiment of the present invention selects 1.5m as the optimal shooting height;

[0094] The correlation between summer corn canopy temperature and eight nitrogen nutrition indicators at three shooting angles of 30°, 60° and 90° was extremely significant (P<0.01). 2 The correlation was the highest at 0.830; the correlation was best when the shooting angle was 90° in 2023. Based on the two-year test results and the growth of summer corn in the field, 60°-90° was selected as the best shooting angle;

[0095] The canopy temperature of crops is affected by air temperature, which causes the canopy temperature to change over time within a day. In 2022, when the shooting time was 12:00, the relationship between the canopy temperature of summer corn and nitrogen nutrition indicators reached an extremely significant level (P<0.01); when the shooting time was 14:00, the canopy temperature of summer corn in the jointing stage could reach a significant correlation level, while the correlation between other shooting times and other indicators was not significant. In 2023, the correlation between different shooting times and nitrogen nutrition indicators reached a significant level, among which the correlation between the canopy temperature of summer corn and its indicators was the highest when the shooting time was 12:00. The average R 2 Based on the results of the two-year experiment, 12:00 noon was determined to be the best shooting time for thermal imaging diagnosis of nitrogen nutrition of summer corn.

[0096] Furthermore, S5 is specifically:

[0097] A quadratic equation was used to fit the canopy temperature of summer maize at each growth stage and its relative yield at maturity under the optimal shooting mode. The critical value was determined according to the fitting classification standard. The relative yield was calculated as the ratio of the summer maize yield at maturity for each nitrogen fertilizer treatment to its maximum yield. 95% of the relative yield was taken as the critical value. A value below 95% indicated nitrogen fertilizer deficiency, and a value above 95% indicated nitrogen fertilizer abundance. The critical temperature value for each growth stage was determined in this way.

[0098] In one embodiment of the present invention, the fitting result of the relationship between summer corn canopy temperature and yield is as follows: Figure 8As shown, the critical canopy temperatures of summer corn at the jointing stage, trumpet stage, silking stage and grain filling stage are 30.0℃, 31.0℃, 30.5℃ and 28.3℃ respectively; when the canopy temperature is higher than the critical temperature, it indicates that the nitrogen fertilizer supply is insufficient and nitrogen fertilizer should be applied.

[0099] Furthermore, S6 is specifically:

[0100] A quadratic equation was used to fit the relationship between nitrogen fertilizer application and yield at each growth stage of summer corn, such as Fig. 9 As shown in the figure, the fitting relationship between the total nitrogen fertilizer application during the whole growth period and the yield was obtained. The partial derivative of the fitting relationship was calculated to obtain the maximum yield and the corresponding nitrogen fertilizer application amount. The nitrogen fertilizer application amount was used as the reference value of the total amount of nitrogen fertilizer topdressing. The nitrogen topdressing amount was:

[0101] N top =N c -N fer

[0102]

[0103] Where N top N is the amount of nitrogen added c is the reference value of the total amount of nitrogen fertilizer applied, N fer is the current nitrogen fertilizer level, T ca The current canopy temperature, a, b, c are constants, and the a, b, c values ​​of each growth period are substituted into the calculation equation for the amount of nitrogen topdressing to obtain the calculation equation for the amount of nitrogen topdressing in each growth period.

[0104] In one embodiment of the present invention, the fitting result of the relationship between the amount of nitrogen fertilizer used and the yield of summer corn at each growth stage is as follows: Fig.12 As shown, the highest yield is 12244.7 kg / hm 2 , corresponding to nitrogen fertilizer dosage of 299.6kg / / hm 2 , 299.6kg / / hm 2 It is the total nitrogen application amount of summer corn during the whole growth period, which can be used as a reference value for the total amount of nitrogen fertilizer topdressing;

[0105] Based on the above calculation results, the calculation equation for nitrogen topdressing is:

[0106]

[0107] Substituting the a, b and c values ​​corresponding to each growth period into the above equation, we finally obtained the recommended nitrogen fertilizer application model corresponding to each growth period. The a, b and c values ​​corresponding to each growth period are shown in Table 4.

[0108] Table 4 a, b and c values ​​corresponding to each growth period

[0109]

[0110] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0111] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology, characterized in that: The following steps are involved: S1. Acquire summer corn canopy thermal imaging data at different heights, angles and time shooting modes at different growth stages; the heights are 0.5m, 1.5m and 2.5m, the angles are 30°, 60° and 90°, and the times are 9:00, 12:00, 14:00 and 16:00 respectively; S2. Synchronously measure the aboveground plant biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn at different growth stages; S3. Analyze the relationship between nitrogen fertilizer application and yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn to determine the effect of nitrogen fertilizer application on the growth and development of summer corn; S4. Analyze the relationship between canopy temperature and nitrogen fertilizer application, yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value and absorbed photosynthetically active radiation component of summer corn under different shooting modes, determine the impact of different shooting modes on canopy temperature and determine the best shooting mode; S5. Determine the critical temperature at different growth stages based on the relationship between canopy temperature and relative yield of summer corn under the optimal shooting mode; S6. Construct a real-time nitrogen topdressing model based on canopy temperature at different growth stages under the optimal shooting mode for summer corn.

2. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 1, characterized in that: S1 specifically includes: setting different summer corn canopy vertical heights as shooting heights, setting different shooting times, setting different angles between the infrared thermal imager and the horizontal plane as shooting angles, and shooting summer corn at the jointing stage, the large bell mouth stage, the silking stage and the grain filling stage respectively.

3. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 1, characterized in that: S2 is specifically: Four representative maize plants were selected from each planting plot at the jointing stage, trumpet stage, silking stage and grain filling stage of summer maize, and the plants were sterilized at 105℃ for 30min and dried at 75℃ to constant weight. The aboveground biomass was calculated. The maize samples dried at each growth stage were crushed and sieved, digested by H2SO4-H2O2 method, and the nitrogen content of the plants was determined by AA3 flow injection analyzer. The nitrogen accumulation of the plants was calculated. 2 Take continuous plots, thresh and air-dry until constant weight, and calculate the grain yield; All the leaves of corn plants collected at each growth stage were picked and laid flat on a black background cloth, with a 10cm×10cm standard white board placed at each corner. The leaf area index was calculated after taking photos with a digital camera. In each planting plot at each growth stage, 10 corn plants with similar growth were selected and planted continuously. The SPAD values ​​of their leaves were measured using a daily chlorophyll meter, and the average value of the test results of each planting plot was calculated. The photosynthetically active radiation of the summer maize canopy and base was measured using a canopy analyzer at each growth stage, and the absorbed photosynthetically active radiation component was calculated.

4. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 3 is characterized in that: The calculation of absorbed photosynthetically active radiation is as follows: In the formula, FPAR is the absorbed photosynthetically active radiation component, PAR ci is the canopy incident photosynthetically active radiation, PAR cr PAR is the photosynthetically active radiation reflected by the canopy. gi is the incident photosynthetically active radiation at the base, PAR gr Reflects photosynthetically active radiation to the base.

5. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 1, characterized in that: S3 is specifically: The Person correlation analysis method was used to quantitatively analyze the relationships between summer corn nitrogen fertilizer application and yield, nitrogen fertilizer application and aboveground biomass, nitrogen fertilizer application and nitrogen accumulation, nitrogen fertilizer application and leaf area index, nitrogen fertilizer application and leaf SPAD value, nitrogen fertilizer application and absorbed photosynthetically active radiation component, and nitrogen fertilizer application and summer corn canopy temperature, and the changing trends of each parameter with the increase of nitrogen fertilizer application were analyzed.

6. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 1, characterized in that: S4 is specifically: The Person correlation analysis method was used to quantitatively analyze the relationships between summer maize canopy temperature and nitrogen fertilizer application, yield, aboveground biomass, nitrogen accumulation, leaf area index, leaf SPAD value, and absorbed photosynthetically active radiation component at different shooting angles, different shooting heights, and different shooting times. The optimal shooting angle, optimal shooting height, and optimal shooting time for summer maize in different growth stages were determined based on the correlation coefficient and determination coefficient.

7. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 1, characterized in that: S5 is specifically: A quadratic equation was used to fit the canopy temperature of summer maize at each growth stage and its relative yield at maturity under the optimal shooting mode. The critical value was determined according to the fitting classification standard. The relative yield was calculated as the ratio of the summer maize yield at maturity for each nitrogen fertilizer treatment to its maximum yield. 95% of the relative yield was taken as the critical value. A value below 95% indicated nitrogen fertilizer deficiency, and a value above 95% indicated nitrogen fertilizer abundance. The critical temperature value for each growth stage was determined in this way.

8. The summer corn nitrogen nutrition diagnosis method based on infrared thermal imaging technology according to claim 1, characterized in that: S6 is specifically: The relationship between nitrogen fertilizer application and yield in each growth period of summer corn was fitted by a quadratic equation, and the fitting relationship between total nitrogen fertilizer application and yield in the whole growth period was obtained. The partial derivative of the fitting relationship was obtained to obtain the maximum yield and the corresponding nitrogen fertilizer application amount. The nitrogen fertilizer application amount was used as the reference value of the total amount of nitrogen fertilizer topdressing. The nitrogen topdressing amount was: N top =N c -N fer Where N top N is the amount of nitrogen added c is the reference value of the total amount of nitrogen fertilizer applied, N fer is the current nitrogen fertilizer level, T ca The current canopy temperature, a, b, c are constants, and the a, b, c values ​​of each growth period are substituted into the calculation equation for the amount of nitrogen topdressing to obtain the calculation equation for the amount of nitrogen topdressing in each growth period.

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