Abstract
Leaf nitrogen content (LNC) is a significant factor which can be utilized to monitor the status of paddy rice and it requires a reliable approach for fast and precise quantification. This investigation aims to quantitatively analyze the correlation between fluorescence parameters and LNC based on laser-induced fluorescence (LIF) technology. The fluorescence parameters exhibited a consistent positive linear correlation with LNC in different growing years (2014 and 2015) and different rice cultivars. The R2 of the models varied from 0.6978 to 0.9045. Support vector machine (SVM) was then utilized to verify the feasibility of the fluorescence parameters for monitoring LNC. Comparison of the fluorescence parameters indicated that F740 is the most sensitive (the R2 of linear regression analysis of the between predicted and measured values changed from 0.8475 to 0.9226, and REs ranged from 3.52% to 4.83%) to the changes in LNC among all fluorescence parameters. Experimental results demonstrated that fluorescence parameters based on LIF technology combined with SVM is a potential method for realizing real-time, non-destructive monitoring of paddy rice LNC, which can provide guidance for the decision-making of farmers in their N fertilization strategies.
Highlights
laser induced fluorescence (LIF) technology can be employed to monitor the alterations of leaf N content (LNC)
A close linear positive correlation was observed between fluorescence parameters and LNC for different paddy rice cultivars (Japonica rice, Hsien rice, and Yangliangyou 6) and different growing years (2014 and 2015)
support vector machine (SVM) was utilized to verify if LNC can be evaluated on the basis of the fluorescence parameters (F685, F740, and F740/F685)
Summary
Numerous investigations utilized fluorescence technology to analyze the N status of triticale, soybean, paddy rice, and cotton[24,25,26] These investigations revealed that leaf fluorescence parameters can be implemented to estimate the LNC of crops. These investigations mainly utilized fluorescence kinetics, minimum fluorescence intensity after short dark adaptation (Fo), maximum fluorescence intensity after short dark adaptation (Fm), and quantum efficiency of photosystem II9 as the indicators of the nutrient stress of crops. These studies discussed the effect of different nutrient stress values on fluorescence parameters in wheat, corn, and spring triticale[9,27]. The main objectives of this investigation are as follows: (1) to discuss the influence of different paddy rice cultivars and growing years on the relationship between fluorescence parameters (fluorescence intensity and fluorescence ratio) and LNC and (2) to compare the performance of fluorescence parameters with the help of support vector machine (SVM) to quantitatively evaluate LNC in paddy rice
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