标题：Modelling of crop chlorophyll content based on Dualex
作者：Li, Zhenhai ;Wang, Jihua ;He, Peng ;Zhang, Yongfeng ;Liu, Haiying ;Chang, Hong ;Xu, Xingang
作者机构：[Li, Zhenhai ;He, Peng ;Zhang, Yongfeng ;Liu, Haiying ;Chang, Hong ;Xu, Xingang ] Beijing Research Center for Information Technology in Agriculture, B 更多
来源：Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering
摘要：Real-time non-destructive and quick estimation of leaf chlorophyll content can provide important information about plant stress, nutritional state and relationships between plants and their environment, and therefore will be of great significance in agriculture field management. In this study, 2 hand-held chlorophyll absorbance meters, Dualex 4 and SPAD-502, for relative chlorophyll content, and standard chemical method by the spectrophotometric for absolute chlorophyll content in wheat and maize were used for analyzing the relationships between relative chlorophyll content and absolute chlorophyll content. The absolute chlorophyll content can be expressed in terms of chlorophyll mass per leaf mass (Chl-M, mg/g) and chlorophyll mass per leaf square (Chl-S, mg/dm2). The objective of this study was to establish chlorophyll content models, Chl-M model and Chl-S model, and evaluate whether these models could be as general models for estimating leaf chlorophyll content. Four field experiments were carried out, including 2 experiments with 3 winter wheat cultivars during the growing season from 2014 to 2015 and 2 experiments with 3 maize cultivars during the growing seasons in 2013 and 2015. Time-course measurements were taken on relative chlorophyll content and absolute chlorophyll content. Linear regression analyses between relative chlorophyll content (Dualex value or SPAD value) and absolute chlorophyll content (Chl-M or Chl-S) were conducted. Three statistical indicators including determination coefficient (R2), root mean square error (RMSE) and normalized root mean square error (nRMSE) were employed to evaluate the performance of each model. The results showed that the performances of Chl-M and Chl-S model using Dualex (R2values of 0.77 and 0.88, respectively) were better than those using SPAD (R2values of 0.66 and 0.79, respectively). Chl-S models using Dualex at each growing stage were superior to Chl-M models. The relationship between Chl-M and Dualex values at each growing stage should consider the influence of leaf thickness. A strong relationship between Chl-S and Dualex values was demonstrated, with the R2value of each Chl-S model ranging from 0.87 to 0.97 and the nRMSE value lower than 10%. The general model of Chl-S demonstrated a high performance, with the R2, RMSE, and nRMSE of 0.88, 4.80 mg/dm2, and 8.33%, respectively. The range of Chl-S was from 12.2 to 105.6 mg/dm2, and could be applied at any growing stage for winter wheat and maize. Therefore, this study proposes a consensus equation for the transformation of Dualex into leaf chlorophyll content of winter wheat and maize, achieves the real-time and non-destructive estimation of chlorophyll content, and provides theoretical basis and technical support for the acquisition of crop nutritional state and the field decision-making.
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