Spectral index constructing method for detecting carbon nitrogen ratios of canopy leaves of crops

Abstract

The invention discloses a spectral index constructing method for detecting carbon nitrogen ratios of canopy leaves of crops. The method comprises the following steps: (1) obtaining hyperspectral original reflectivity data of crop canopies within the waveband range of 500-910 nm; (2) figuring out a relative reflectivity by using the obtained original reflectivities of the crop canopies; (3) figuring out gradients of a relative reflectivity spectrum curve within three sub waveband ranges of 500-550 nm, 680-760 nm and 760-910 nm; and (4) constructing a spectral index RCN for detecting the carbon nitrogen ratios of the canopy leaves of the crops. Through the adoption of the spectral index constructed according to the invention in detecting the carbon nitrogen ratios of the canopy leaves of the crops, the influences of lighting condition differences on the detection of the carbon nitrogen ratios can be eliminated and the problem that adjacent wavelength reflectivities of the existing spectral index are related in height can be also avoided.

Description

technical field [0001] The invention relates to a spectral index construction method, in particular to a spectral index construction method for detecting the carbon-nitrogen ratio of crop canopy leaves. Background technique [0002] Carbon and nitrogen are two basic elements of crop plants, and their metabolic status has an important impact on the formation of crop yield and quality. The carbon-nitrogen ratio of crop leaves (the ratio of leaf carbon content to nitrogen content) can explain the metabolic status of carbon and nitrogen, and is an important indicator for comprehensive diagnosis of carbon-nitrogen balance, nutritional status, growth activity and disease resistance in crop plants. Therefore, real-time, effective and accurate detection of crop leaf carbon-nitrogen ratio is of great significance for field crop growth diagnosis and cultivation management. [0003] Conventional detection of the carbon-nitrogen ratio of crop canopy leaves is usually achieved by field ...

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Problems solved by technology

[0004] At present, there are many spectral index methods for detecting nitrogen content in crop leaves using hyperspectral technology, but there are few reports on spectral index methods for detecting carbon-nitrogen ratio. The few reported spectral index methods for detecting carbon-nitrogen ratio , and most of them are obtained by simple mathematical operations using the original reflectance of two or three characteristic wavelengths. However, due to the small number of wavelengths used, there is a high correlation between the original reflectance of adjacent wavelengths, so that the constructed spectral index can be used for carbon Lack of proper stability in nitrogen ratio detection

In addition, the existing spectral index uses the original reflectance information, but in practical applications, when obtaining the spectrum of crop canopy in the field, it is vulnerable to temporary or occasional occlusion by local cloud spots and shadows in the sky, as well as changes in the sun's altitude angle at different times of the day Due to the influence of differences in lighting conditions caused by factors such as the original reflectance, the spectral index often carries certain measurement errors, and unnecessary detection errors will inevitably occur when used for the detection of crop leaf carbon-nitrogen ratio.

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