Leaf spectrum-based corn nitrogen nutrition diagnosis method and water and fertilizer integrated fertilization device

Abstract

The invention discloses a leaf spectrum-based corn nitrogen nutrition diagnosis method and a water and fertilizer integrated fertilization device. Relates to the technical field of agriculture, in particular to a leaf spectrum-based corn nitrogen nutrition diagnosis method, which comprises the following steps of: constructing a critical nitrogen concentration dilution curve of corn leaves in Hetao region of an Inner Mongolia autonomous region; calculating NNI, and analyzing the influence of the NNI on the spectral information; constructing a brand new spectral index NTRI suitable for NNI prediction; constructing an NNI prediction model suitable for different varieties, places and years; verifying the prediction model by using the independent data set and verifying in large-area demonstration; a water and fertilizer integrated fertilization device comprises a base, a supporting mechanism, a storage cylinder and a filtering assembly. Based on the latest completely expanded leaf spectrum, the method can be used for corn nitrogen nutrition diagnosis in Hetao region of Inner Mongolia autonomous region; through the water and fertilizer integrated fertilization device, the water and fertilizer mixing effect is improved, and fertilization is stable.

Description

Technical Field

[0001] The present invention relates to the field of agricultural technology, and more particularly to a corn nitrogen nutrition diagnosis method based on leaf spectra and a water-fertilizer integrated fertilization device. Background Art

[0002] Nitrogen is one of the most important macronutrients for plants and has a significant impact on crop growth, productivity and quality. The determination of nitrogen in agriculture has been a subject of extensive discussion and research. A prerequisite for modern agriculture is proper nitrogen management. Only with adequate nitrogen supply and corresponding nitrogen uptake can optimal crop yields be obtained from high-quality grains. Therefore, fertilization is usually used to apply nitrogen in agricultural practice. Fertilization is often in oversupply because the actual uptake of nitrogen depends mainly on the current growing conditions, which are highly variable in both space and time. This overfertilization leads to plant stress and makes plants more susceptible to disease. On the other hand, nitrogen deficiency can lead to a decrease in the quantity and quality of crops in terms of photosynthesis and yield. In the process of corn cultivation in the Hetao region, farmers often cannot accurately judge whether corn is nitrogen-deficient when applying traditional fertilization, and lack the recommended fertilizer amount for the entire region. Long-term excessive nitrogen fertilizer application leads to a large amount of nitrogen residue in the soil. At present, water-fertilizer integration technology has been fully applied to corn cultivation in the Hetao region of Inner Mongolia Autonomous Region, which provides a guarantee for the implementation of topdressing for crops. However, there is a lack of a rapid and non-destructive method for nitrogen nutrition diagnosis in the corn cultivation process. Remote sensing technology is widely recognized for its importance and necessity in modern agricultural production, as it is fast, non-destructive, and has a wide range of advantages in monitoring crop nitrogen status. Currently, existing crop nitrogen diagnosis methods are basically based on the construction of dilution curves based on plant biomass and nitrogen concentration, and there is a lack of remote sensing estimation methods for nitrogen nutrition diagnosis at the leaf scale.

[0003] Water-fertilizer integration technology refers to a new agricultural technology that integrates irrigation and fertilization. Water-fertilizer integration is to use a pressure system (or natural terrain drop) to mix soluble solid or liquid fertilizers according to the soil nutrient content and the fertilizer requirements and characteristics of the crop types, and mix them with fertilizer liquid together with irrigation water, and supply water and fertilizer through a controllable pipeline system. After the water and fertilizer are mixed, sprinkler irrigation or drip irrigation is formed through pipelines and drippers to evenly, regularly and quantitatively infiltrate the root development and growth area of ​​the crop, so that the main root soil is always loose and suitable; at the same time, according to the fertilizer requirements of different crops, soil environment and nutrient content, the water requirements of crops in different growth periods, and the fertilizer requirements, the demand design for different growth periods is carried out, and water and nutrients are provided to crops directly in a regular and quantitative manner in proportion.

[0004] In the process of corn planting, the existing integrated water and fertilizer fertilization methods mainly include drip irrigation, sprinkler irrigation and micro-spraying, etc. The existing drip irrigation integrated water and fertilizer fertilization device has the problem of uneven mixing of water and fertilizer in the storage cylinder, and cannot ensure uniform spraying during drip irrigation, affecting the fertilization effect; the existing integrated water and fertilizer fertilization device needs to improve the mixing effect of water and fertilizer in the storage cylinder to avoid water and fertilizer precipitation, resulting in clogging of the water pump or nozzle, affecting the stable performance of the drip irrigation effect.

[0005] Therefore, how to provide a remote sensing estimation method for nitrogen nutrition diagnosis at the leaf scale, improve the water-fertilizer mixing effect, and stabilize drip irrigation fertilization, a corn nitrogen nutrition diagnosis method based on leaf spectra, and an integrated water-fertilizer fertilization device are problems that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of this, the present invention provides a corn nitrogen nutrition diagnosis method based on leaf spectrum and a water-fertilizer integrated fertilization device, aiming to solve one of the problems in the above-mentioned background technology, a remote sensing estimation method for nitrogen nutrition diagnosis at the leaf scale, improves the water-fertilizer mixing effect, and stabilizes drip irrigation fertilization.

[0007] In order to achieve the above object, the present invention adopts the following technical solution: A method for diagnosing nitrogen nutrition of corn based on leaf spectrum comprises the following steps: S1. Construct the critical nitrogen concentration dilution curve of maize leaves in the Hetao region of Inner Mongolia Autonomous Region based on multi-year multi-point and multi-variety data; S2, calculate NNI based on the critical nitrogen concentration dilution curve of corn leaves and analyze its influence on spectral information; S3, construct a new spectral index NTRI suitable for NNI prediction based on the spectral information of the latest fully expanded leaves; S4. Construct NNI prediction models based on NTRI index suitable for different varieties, locations and years; S5. Validate the prediction model using independent datasets and verify it on large-scale demonstrations.

[0008] Furthermore, a Bayesian statistical model was used in S1 to construct the leaf critical nitrogen concentration dilution curve of the commonly grown corn varieties in the Hetao region.

[0009] Furthermore, the calculation formula of nitrogen nutrition index NNI based on the critical nitrogen concentration dilution curve of corn leaves in Hetao region in S2 is: NNI=N / N C , where N is the measured leaf nitrogen concentration, N C is the critical nitrogen concentration; When NNI=1, nitrogen nutrition is considered to be optimal; when NNI<1, nitrogen nutrition is considered to be insufficient; and when NNI>1, nitrogen nutrition is considered to be excessive.

[0010] Furthermore, the band range of the new spectral index design was set to 680–750 nm in S3, and the spectral reflectance of 680–750 nm was transformed by the first-order derivative, and the cross-section between the area enclosed by the first-order derivative spectral curve and the red line area was related to the biomass, N, and chlorophyll contents.

[0011] On the other hand, the present invention provides a water-fertilizer integrated fertilization device, which is applicable to the corn planting fertilization operation in the above-mentioned corn nitrogen nutrition diagnosis method based on leaf spectrum, comprising: Base; The supporting mechanism comprises a hydraulic cylinder, a mounting seat and a fixing assembly, wherein the hydraulic cylinder and the mounting seat are arranged on the base relative to each other, the fixing assembly is arranged on the top of the hydraulic cylinder, and a buffer block and a driving motor are arranged on the top of the mounting seat; A storage cylinder, a feed port is provided on the side wall of the storage cylinder, a sealing plug is provided at the feed port, a rotating rod is provided at one end of the storage cylinder, the rotating rod is connected to the output end of the driving motor, a fertilizer discharge pipe is provided at the other end of the storage cylinder, the fertilizer discharge pipe is arranged on the fixing assembly, a valve is provided at one end of the fertilizer discharge pipe away from the storage cylinder, a slag discharge port is provided at one end of the storage cylinder close to the mounting seat, the slag discharge port is located below the rotating rod, a water pump is provided in the storage cylinder, and the water pump is connected to the fertilizer discharge pipe; The filter assembly comprises a filter barrel and a funnel. The filter barrel is detachably arranged at the feed port. Limiting blocks are respectively arranged on both sides of the filter barrel. The funnel is arranged on the top of the filter barrel.

[0012] Furthermore, the fixing assembly includes a support plate, a rotating tube and a clamping plate, the support plate is arranged on the top of the hydraulic cylinder, the rotating tube is arranged on the support plate, the fertilizer outlet pipe is rotatably arranged in the rotating tube, two clamping plates are slidably arranged on the support plate, and the rotating tube is fixed between the two clamping plates by bolts.

[0013] Furthermore, it also includes a stirring component, which includes a rotating motor, a rotating shaft and a stirring rod. The rotating motor is arranged on the side wall of the storage cylinder, the rotating shaft is arranged in the storage cylinder, the rotating shaft is connected to the output end of the rotating motor, and a plurality of stirring rods are arranged at intervals in the horizontal direction, and the plurality of rotating rods are all arranged on the rotating shaft.

[0014] Furthermore, it also includes a support column, which is arranged on the base, the support column is located below the storage tube, the top of the support column is provided with an arc support, the support column and the arc support are connected through a universal joint, and the arc support is in contact with the bottom of the storage tube.

[0015] Furthermore, it also includes an aerator, which is arranged on the storage cylinder, the aerator is connected to the interior of the storage cylinder, and the aerator and the feed port are located on the same horizontal line.

[0016] Furthermore, a collecting groove is provided on one side of the mounting seat close to the storage cylinder, and the collecting groove is detachably arranged in the mounting seat.

[0017] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a corn nitrogen nutrition diagnosis method based on leaf spectra and a water-fertilizer integrated fertilization device, which has the following beneficial effects: 1. Through the corn nitrogen nutrition diagnosis method based on leaf spectra, a critical nitrogen dilution curve suitable for corn leaf scale in the Hetao region of Inner Mongolia Autonomous Region was established, and the nitrogen nutrition status of spring corn was estimated using the latest fully expanded leaf spectral information; a new spectral index was constructed to accurately diagnose the nitrogen status of spring corn; this not only provides a more accurate method for monitoring the nitrogen status of spring corn planting in the Hetao region, but also provides a new crop diagnosis strategy for strengthening crop sustainable management practices; 2. Through the integrated water-fertilizer fertilization device, the support mechanism can realize the rotation of the storage cylinder, thereby improving the water-fertilizer mixing effect in the storage cylinder and stabilizing drip irrigation fertilization; by setting a filtering component, the fertilizer can be filtered to prevent impurities in the fertilizer from causing water and fertilizer precipitation and affecting the water-fertilizer mixing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

[0019] Figure 1 A schematic diagram of the process of the corn nitrogen nutrition diagnosis method based on leaf spectrum provided by the present invention; Figure 2 The critical nitrogen concentration dilution curve of leaves of common corn varieties in the Hetao region of Inner Mongolia Autonomous Region provided by the present invention; Figure 3 The new spectral index construction idea provided by the present invention; Figure 4The NNI prediction model for corn in the Hetao region of Inner Mongolia Autonomous Region based on NTRI provided by the present invention; Figure 5 The validation results of the prediction model provided by the present invention under independent data sets; Figure 6 Verification of the critical nitrogen dilution curve model of corn by the nitrogen nutrition index provided by the present invention; Figure 7 The corn nitrogen nutrition diagnosis based on the nitrogen nutrition index provided by the present invention; Figure 8 A schematic diagram of the structure of the water-fertilizer integrated fertilization device provided by the present invention; Fig. 9 A schematic diagram of the structure of the water-fertilizer integrated fertilization device provided by the present invention (from another perspective); Fig.10 A schematic diagram of the internal structure of the storage cylinder provided by the present invention; Fig.11 This is a schematic diagram of the structure of the filter assembly provided by the present invention.

[0020] Among them: 1 is a base; 2 is a hydraulic cylinder; 3 is a mounting seat; 4 is a buffer block; 5 is a driving motor; 6 is a storage cylinder; 61 is a feed port; 62 is a sealing plug; 63 is a rotating rod; 64 is a fertilizer outlet pipe; 65 is a valve; 66 is a slag outlet; 67 is a water pump; 7 is a filter barrel; 8 is a funnel; 9 is a limit block; 10 is a support plate; 11 is a rotating tube; 12 is a clamping plate; 13 is a bolt; 14 is a rotating motor; 15 is a rotating shaft; 16 is a stirring rod; 17 is a support column; 18 is an arc support; 19 is an aerator; 20 is a collecting tank; 21 is a controller. DETAILED DESCRIPTION

[0021] 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.

[0022] See also Figure 1-11 The embodiment of the present invention discloses a method for diagnosing nitrogen nutrition of corn based on leaf spectrum, comprising: S1. Construct the critical nitrogen concentration dilution curve of maize leaves in the Hetao region of Inner Mongolia Autonomous Region based on multi-year multi-point and multi-variety data; S2, calculate NNI based on the critical nitrogen concentration dilution curve of corn leaves and analyze its influence on spectral information; S3, construct a new spectral index NTRI suitable for NNI prediction based on the spectral information of the latest fully expanded leaves; S4. Construct NNI prediction models based on NTRI index suitable for different varieties, locations and years; S5. Validate the prediction model using independent datasets and verify it on large-scale demonstrations; In this embodiment, a Bayesian statistical model is used in S1 to construct a leaf critical nitrogen concentration dilution curve of corn varieties commonly grown in the Hetao region, such as Figure 2 As shown, the commonly grown corn varieties in the Hetao region are Dika 159 (DK159), Xianyu 1331 (XY1331), and Heyu 12 (HY12).

[0023] In this embodiment, the nitrogen nutrition index NNI calculation formula based on the critical nitrogen concentration dilution curve of corn leaves in the Hetao region in S2 is: NNI=N / N C , where N is the measured leaf nitrogen concentration, N C is the critical nitrogen concentration; When NNI=1, nitrogen nutrition is considered to be optimal; when NNI<1, nitrogen nutrition is considered to be insufficient; and when NNI>1, nitrogen nutrition is considered to be excessive.

[0024] In this embodiment, the band range of the new spectral index design is set to 680-750nm in S3, and the spectral reflectance of 680-750nm is transformed by the first-order derivative to overcome the inevitable noise and other factors in the sampling process; the cross-section of the area surrounded by the first-order derivative spectral curve and the red line area is related to the biomass, N and chlorophyll content; the red edge area (680-750nm) is a special transition area between the strong pigment absorption and the internal structural characteristics of the leaves, which contains rich absorption and reflection information and plays a key role in estimating the chlorophyll content and N status of the leaves; especially considering the advantages of the red edge area in monitoring the vertical distribution of plant nitrogen, this study assumes that the spectral index constructed based on the first-order derivative surface of the red edge area can be used for corn NNI monitoring; in order to reduce the influence of the chlorophyll absorption surface on the accuracy of NNI estimation, a new spectral index is established on the basis of fully considering the spectral response characteristics of the red edge area; finally, two new spectral indices, namely the nitrogen nutrition triangular index (NTI) and the nitrogen nutrition triangular ratio index (NTRI), are calculated, as shown in Figure 3 shown.

[0025] On the other hand, the present invention provides a water-fertilizer integrated fertilization device, which is applicable to the corn planting fertilization operation in the above-mentioned corn nitrogen nutrition diagnosis method based on leaf spectrum, comprising: Base 1; The supporting mechanism includes a hydraulic cylinder 2, a mounting seat 3 and a fixing assembly. The hydraulic cylinder 2 and the mounting seat 3 are relatively arranged on the base 1. The fixing assembly is arranged on the top of the hydraulic cylinder 2. A buffer block 4 and a driving motor 5 are arranged on the top of the mounting seat 3. By arranging the hydraulic cylinder 2, the height of one end of the storage tube 6 can be adjusted in cooperation with the fixing assembly. The buffer block 4 plays a buffering role on the rotating rod 63, and the storage tube 6 is driven to rotate by the driving motor 5, so as to improve the water-fertilizer mixing effect in the storage tube 6 and stably perform drip irrigation fertilization. The storage cylinder 6 has a feeding port 61 on its side wall, a sealing plug 62 at the feeding port 61, a rotating rod 63 at one end of the storage cylinder 6, the rotating rod 63 is connected to the output end of the driving motor 5, a fertilizer discharging pipe 64 is provided at the other end of the storage cylinder 6, the fertilizer discharging pipe 64 is arranged on the fixed assembly, a valve 65 is provided at the end of the fertilizer discharging pipe 64 away from the storage cylinder 6, a slag discharge port 66 is provided at the end of the storage cylinder 6 close to the mounting seat 3, the slag discharge port 66 is located below the rotating rod 63, a sealing plug 62 is also provided at the slag discharge port 66, a water pump 67 is provided in the storage cylinder 6, and the water pump 67 is connected to the fertilizer discharging pipe 64; by setting the rotating rod 63, the driving motor 5 drives the storage cylinder 6 to rotate, and the water and fertilizer sediment in the storage cylinder 6 is discharged through the slag discharge port 66 to avoid affecting the drip irrigation fertilization. Through the slag discharge port 66, the water and fertilizer in the storage cylinder 6 can be discharged when different fertilizers are replaced to avoid affecting the components of the water and fertilizer.

[0026] The filter assembly includes a filter barrel 7 and a funnel 8. The filter barrel 7 is detachably arranged at the feed port 61. Limit blocks 9 are respectively arranged on both sides of the filter barrel 7. The funnel 8 is arranged on the top of the filter barrel 7. By setting the filter assembly, the fertilizer can be filtered to prevent impurities in the fertilizer from causing water and fertilizer precipitation.

[0027] In this embodiment, the fixing assembly includes a support plate 10, a rotating tube 11 and a clamping plate 12. The support plate 10 is arranged on the top of the hydraulic cylinder 2, the rotating tube 11 is arranged on the support plate 10, the fertilizer discharge pipe 64 is rotatably inserted into the rotating tube 11, and two clamping plates 12 are slidably arranged on the support plate 10. The rotating tube 11 is fixed between the two clamping plates 12 by bolts 13; by setting the clamping plate 12, the rotating tube 11 is adjustable and clamped, so that the fertilizer discharge pipe 64 at one end of the storage tube 6 is not affected when rotating or adjusting the height.

[0028] In this embodiment, a stirring assembly is also included, which includes a rotating motor 14, a rotating shaft 15 and a stirring rod 16. The rotating motor 14 is arranged on the side wall of the storage barrel 6, and the rotating shaft 15 is arranged in the storage barrel 6. The rotating shaft 15 is connected to the output end of the rotating motor 14. A plurality of stirring rods 16 are arranged at intervals in the horizontal direction, and a plurality of rotating rods 63 are all arranged on the rotating shaft 15. The stirring assembly will reciprocately shake the storage barrel 6 while stirring the water and fertilizer inside the storage barrel 6, thereby improving the mixing effect of water and fertilizer in the storage barrel 6, avoiding the precipitation of water and fertilizer, and facilitating the smooth spraying of water and fertilizer.

[0029] In this embodiment, it also includes a support column 17, which is arranged on the base 1, and the support column 17 is located below the storage barrel 6. An arc support 18 is provided on the top of the support column 17. The support column 17 and the arc support 18 are connected by a universal joint, and the arc support 18 is in contact with the bottom of the storage barrel 6; the bottom of the storage barrel 6 is supported by arranging the support column 17 and the arc support 18, and the arc support 18 can be adjusted in position through the universal joint as the storage barrel 6 rotates or tilts.

[0030] In this embodiment, an aerator 19 is also included. The aerator 19 is arranged on the storage barrel 6. The aerator 19 is connected to the interior of the storage barrel 6, and the aerator 19 and the feed port 61 are located on the same horizontal line; the aerator 19 can stir the water and fertilizer in the storage barrel 6, prevent the fertilizer in the storage barrel 6 from settling, and improve the mixing effect of the water and fertilizer in the storage barrel 6.

[0031] In this embodiment, a collecting groove 20 is provided on one side of the mounting seat 3 close to the storage tube 6 , and the collecting groove 20 is detachably arranged in the mounting seat 3 ; the water and fertilizer sediment discharged from the storage tube 6 is collected by the collecting groove 20 .

[0032] In addition, in this embodiment, in S4, the growth period, variety and location are the main factors affecting the NNI estimation. The spectral index (NTRI) constructed by the present invention not only overcomes the influence of the growth period and variety on the NNI estimation, but also establishes a general model for the NNI estimation of corn in the Hetao area of ​​Inner Mongolia Autonomous Region: NNI=0.84×NTRI+0.32, and the determination coefficient (R 2 ) is 0.90.

[0033] In order to verify the precision and accuracy of the NTRI index in practical application, we verified the NNI of three maize varieties at three locations, as shown in Table 1; Table 1 Experimental treatment and sampling details:

[0034] from Figure 6 It can be seen that the amount of fertilizer applied is greater than 180kgNha -1, the nitrogen nutrition index (NNI) value is mostly above 1.1, nitrogen nutrition is in excess, and the fertilizer application amount is equal to 180kgNha -1 (OPT) NNI values ​​were mostly between 0.95 and 1.05, and the nitrogen nutrition level was just moderate; In order to increase the reliability of the model, we used an independent data set to independently verify the estimated model. The model verification results were good, with R2=0.88, RMSE=0.08, and RE=7.31%. The above results can prove that the model can accurately predict the NNI of corn at different ecological locations; it was verified by the data of the traditional planting plots of farmers around the recommended nitrogen application demonstration fields and the experimental fields. Figure 7 As shown, the results indicate that the latest fully expanded leaf spectrum can be used for nitrogen nutrition diagnosis of maize in the Hetao region of Inner Mongolia Autonomous Region.

[0035] It also includes a controller 21, which is arranged on the side wall of the mounting base 3. The controller 21 is electrically connected to the drive motor 5, the rotating motor 14, the water pump 67 and the valve 65. The controller 21 has a time reminder function, which cooperates with the valve 65 to control the fertilization process to avoid the fertilization time being too long and affecting the vegetation growth.

[0036] It also includes a fertilizer pipe, which is connected to the fertilizer outlet pipe 64. A nozzle is arranged on the fertilizer pipe, and the nozzle is close to the root of the plant for drip irrigation and fertilization.

[0037] Specific use process According to the corn nitrogen nutrition diagnosis method based on leaf spectrum, the nitrogen status of spring corn is judged and the required fertilizer is determined; Place the filter barrel 7 at the feed inlet 61 and add fertilizer to filter the fertilizer. Take out the filter barrel 7, add water, close the feed inlet 61 through the sealing plug 62, turn on the drive motor 5, drive the rotating rod 63 to rotate, drive the storage barrel 6 to rotate, and at the same time, turn on the rotating motor 14 to drive the stirring rod 16 on the rotating shaft 15 to stir the water and fertilizer. The stirring assembly will reciprocate and shake the storage barrel 6 while stirring the water and fertilizer inside the storage barrel 6 to fully mix the water and fertilizer. Turn on the water pump 67 to fertilize. After fertilization is completed, adjust the bolt 13, open the rotating clamp, remove the sealing plug 62 at the slag discharge port 66, and raise one end of the fertilizer discharge pipe 64 of the storage tube 6 through the hydraulic cylinder 2 to discharge the water fertilizer sediment in the storage tube 6 into the collection tank 20. In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0038] 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 method for diagnosing nitrogen nutrition of corn based on leaf spectra, characterized in that: The specific steps include: S1. Construct the critical nitrogen concentration dilution curve of maize leaves in the Hetao region of Inner Mongolia Autonomous Region based on multi-year multi-point and multi-variety data; S2, calculate NNI based on the critical nitrogen concentration dilution curve of corn leaves, and analyze its influence on spectral information; S3, construct a new spectral index NTRI suitable for NNI prediction based on the spectral information of the latest fully expanded leaves; S4. Construct NNI prediction models based on NTRI index for different varieties, locations and years; S5. Validate the prediction model using independent datasets and verify it on large-scale demonstrations.

2. The corn nitrogen nutrition diagnosis method based on leaf spectrum according to claim 1, characterized in that: In S1, a Bayesian statistical model was used to construct the leaf critical nitrogen concentration dilution curve of the commonly grown corn varieties in the Hetao region.

3. The corn nitrogen nutrition diagnosis method based on leaf spectrum according to claim 1, characterized in that: The calculation formula of nitrogen nutrition index NNI based on the critical nitrogen concentration dilution curve of corn leaves in Hetao region in S2 is: NNI=N / N C , where N is the measured leaf nitrogen concentration, N C is the critical nitrogen concentration; When NNI=1, nitrogen nutrition is considered to be optimal; when NNI<1, nitrogen nutrition is considered to be insufficient; and when NNI>1, nitrogen nutrition is considered to be excessive.

4. The corn nitrogen nutrition diagnosis method based on leaf spectrum according to claim 1, characterized in that: In S3, the band range of the new spectral index design was set to 680–750 nm, and the spectral reflectance of 680–750 nm was transformed by the first-order derivative. The cross-section of the area enclosed by the first-order derivative spectral curve and the red line area was related to the biomass, N, and chlorophyll contents.

5. A water-fertilizer integrated fertilization device, applied to corn planting fertilization operations in a corn nitrogen nutrition diagnosis method based on leaf spectrum as described in any one of claims 1-4, characterized in that: include: Base; The supporting mechanism comprises a hydraulic cylinder, a mounting seat and a fixing assembly, wherein the hydraulic cylinder and the mounting seat are arranged on the base relative to each other, the fixing assembly is arranged on the top of the hydraulic cylinder, and a buffer block and a driving motor are arranged on the top of the mounting seat; A storage cylinder, a feed port is provided on the side wall of the storage cylinder, a sealing plug is provided at the feed port, a rotating rod is provided at one end of the storage cylinder, the rotating rod is connected to the output end of the driving motor, a fertilizer discharge pipe is provided at the other end of the storage cylinder, the fertilizer discharge pipe is arranged on the fixing assembly, a valve is provided at one end of the fertilizer discharge pipe away from the storage cylinder, a slag discharge port is provided at one end of the storage cylinder close to the mounting seat, the slag discharge port is located below the rotating rod, a water pump is provided in the storage cylinder, and the water pump is connected to the fertilizer discharge pipe; The filter assembly comprises a filter barrel and a funnel. The filter barrel is detachably arranged at the feed port. Limiting blocks are respectively arranged on both sides of the filter barrel. The funnel is arranged on the top of the filter barrel.

6. The water-fertilizer integrated fertilization device according to claim 5, characterized in that: The fixing assembly comprises a support plate, a rotating tube and a clamping plate, wherein the support plate is arranged on the top of the hydraulic cylinder, the rotating tube is arranged on the support plate, the fertilizer outlet pipe is rotatably arranged in the rotating tube, two clamping plates are slidably arranged on the support plate, and the rotating tube is fixed between the two clamping plates by bolts.

7. The water-fertilizer integrated fertilization device according to claim 5, characterized in that: It also includes a stirring component, which includes a rotating motor, a rotating shaft and a stirring rod. The rotating motor is arranged on the side wall of the storage cylinder, the rotating shaft is arranged in the storage cylinder, the rotating shaft is connected to the output end of the rotating motor, and a plurality of stirring rods are arranged at intervals along the horizontal direction, and the plurality of rotating rods are all arranged on the rotating shaft.

8. The water-fertilizer integrated fertilization device according to claim 5, characterized in that: It also includes a support column, which is arranged on the base, the support column is located below the storage cylinder, the top of the support column is provided with an arc support, the support column and the arc support are connected through a universal joint, and the arc support is in contact with the bottom of the storage cylinder.

9. The water-fertilizer integrated fertilization device according to claim 5, characterized in that: It also includes an aerator, which is arranged on the storage cylinder, the aerator is communicated with the interior of the storage cylinder, and the aerator and the feed port are located on the same horizontal line.

10. The water-fertilizer integrated fertilization device according to claim 5, characterized in that: A collecting groove is provided on one side of the mounting seat close to the storage cylinder, and the collecting groove is detachably arranged in the mounting seat.

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