Estimation of Chlorophyll Content in Winter Wheat Based on UAV Hyperspectral
FENG Hai-kuan1, 2, TAO Hui-lin1, ZHAO Yu1, YANG Fu-qin3, FAN Yi-guang1, YANG Gui-jun1*
1. Key Laboratory of Quantitative Remote Sensing in Agriculture of Ministry of Agriculture and Rural Affairs, Information Technology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
2. National Engineering and Technology Center for Information Agriculture, Nanjing Agricultural University, Nanjing 210095, China
3. College of Civil Engineering, Henan University of Engineering, Zhengzhou 451191, China
Abstract：Chlorophyll content (SPAD) is a vital index for crop growth evaluation, which can monitor the growth of crops and is crucial for agricultural management, so it is important to estimate SPAD quickly and accurately. In this study, the remote sensing images of the jointing, flagging, and flowering stages were acquired using UAV hyperspectral for winter wheat. The vegetation indices and red edge parameters were extracted to explore the ability of vegetation indices and red edge parameters to estimate SPAD. Firstly, the vegetation indices and red edge parameters were correlated with the SPAD of different fertility stages. Then, the SPAD was estimated based on the vegetation indices, vegetation indices combined with red edge parameters , and using partial least square regression (PLSR) method. Finally, the SPAD distribution map was produced to verify the validity of the model. The results showed that (1) most of the vegetation indices and red edge parameters were correlated with SPAD at highly significant levels (0.01 significant) in all three major reproductive stages; (2) the SPAD estimation model constructed from individual vegetation index had the best performance for LCI among vegetation indexes (best R2=0.56, RMSE=2.96, NRMSE=8.14%) and Dr/Drmin performed best (best R2=0.49, RMSE=3.18, NRMSE=8.76%); (3) SPAD estimation model based on vegetation indices combined with red edge parameters was the best and better than SPAD estimation model based on vegetation indices only. Meanwhile, both models reached the highest accuracy at the flowering stage as the fertility stage progressed, with R2 of 0.73 and 0.78, RMSE of 2.49 and 2.22, and NRMSE of 5.57% and 4.95%, respectively. Therefore, based on the vegetation indices combined with the red edge parameters, using the PLSR method can improve the estimation effect of SPAD, which can provide a new method for SPAD monitoring based on UAV remote sensing, and also provide a reference for agricultural management.
Key words：Winter wheat; Chlorophyll content; Vegetation index; Red edge parameter; Partial least squares regression
冯海宽，陶惠林，赵 钰，杨福芹，樊意广，杨贵军. 利用无人机高光谱估算冬小麦叶绿素含量[J]. 光谱学与光谱分析, 2022, 42(11): 3575-3580.
FENG Hai-kuan, TAO Hui-lin, ZHAO Yu, YANG Fu-qin, FAN Yi-guang, YANG Gui-jun. Estimation of Chlorophyll Content in Winter Wheat Based on UAV Hyperspectral. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(11): 3575-3580.
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