Abstract
Leaf nitrogen concentration (LNC) is a major biochemical parameter for estimating photosynthetic efficiency and crop yields. Laser-induced fluorescence, which is a promising potential technology, has been widely used to estimate the growth status of crops with the help of multivariate analysis. In this study, a fluorescence index was proposed based on the slope characteristics of fluorescence spectrum and was used to estimate LNC. Then, the performance of different fluorescence characteristics (proposed fluorescence index, fluorescence ratios, and fluorescence characteristics calculated by principal component analysis (PCA)) for LNC estimation was analyzed based on back-propagation neural network (BPNN) model. The proposed fluorescence index exhibited more stability and reliability for LNC estimation than fluorescence ratios and characteristics calculated by PCA. In addition, the effect of different kernel functions and hidden layer sizes of BPNN model on the accuracy of LNC estimation was discussed for different fluorescence characteristics. The optimal train functions “trainrp,” “trainbr,” and “trainlm” were then selected with higher R2 and lower standard deviation (SD) values than those of other train functions. In addition, experimental results demonstrated that the hidden layer size has a smaller impact on the accuracy of LNC estimation than the kernel function of the BPNN model.
Highlights
The photosynthesis ability of vegetation is closely related to vegetation growth status, which is influenced by biochemical concentrations
leaf nitrogen concentration (LNC) can serve as a major indicator for monitoring crop growth status based on passive or active technology in the field of remote sensing [2,3], wherein related investigations have been conducted by many researchers
The fluorescence peak spectrum at 685 nmshows is less aintensive that at with 740 nm because thereabsorption fluorescenceby characteristic peaks at nm and nm increased with the increasing of LNC.the the chlorophyll pigment at 685 nm is stronger than that at 740 nm [34]
Summary
The photosynthesis ability of vegetation is closely related to vegetation growth status, which is influenced by biochemical concentrations. The leaf nitrogen concentration (LNC) is one of the most important biochemical parameters closely related to the photosynthetic efficiency and crop yields [1]. LNC can serve as a major indicator for monitoring crop growth status based on passive or active technology in the field of remote sensing [2,3], wherein related investigations have been conducted by many researchers. For passive remote sensing technology, the reflectance spectrum of crops was measured, and the relationship between spectral characteristics and LNC or crop status was established. Numerous investigations regarding LNC estimation have been done due to the non-destructive, fast, and.
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