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Chinese Agricultural Science Bulletin ›› 2023, Vol. 39 ›› Issue (1): 123-132.doi: 10.11924/j.issn.1000-6850.casb2021-1212

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Estimation Model of Cotton Leaf Phosphorus Content Based on Hyperspectral Reflectance

MA Yuanhua1,2(), YIN Caixia1, WANG Hongyu1, LIU Yuxuan1, LIU Qiantong1, ZHANG Ze1()   

  1. 1. Agricultural College of Shihezi University/ Key Laboratory of Oasis Ecological Agriculture of Xinjiang Production and Construction Corps, Shihezi, Xinjiang 832000
    2. College of Agronomy, Northwest A & F University, Yangling, Shaanxi 712100
  • Received:2021-12-28 Revised:2022-11-10 Online:2023-01-05 Published:2022-12-27
  • Contact: ZHANG Ze E-mail:1162392907@qq.com;zhangze1227@163.com

Abstract:

The changes of chlorophyll content in cotton leaves under different phosphorus application rates were studied, aiming to establish an estimation model of leaf phosphorus content based on hyperspectrum to realize the rapid monitoring of phosphorus content in cotton leaves. Pot experiments were conducted, the chlorophyll content and phosphorus content of cotton functional leaves were determined under different phosphorus application rates, and the spectral variables of phosphorus content were constructed by using the correlation between vegetation index and chlorophyll content, thus achieving the quantitative monitoring of phosphorus content in cotton leaves by using hyperspectrum. The following results were obtained. (1) About 100 days after sowing, leaf phosphorus content and chlorophyll content has a significant relationship (R2=0.96). (2) The spectral variables of phosphorus content in the first leaf, the second leaf, the third leaf and the fourth leaf from the top are constructed by the correlation between vegetation index (X) and chlorophyll content (I). Each blade of the optimal model is shown as follows: for the first leaf from the top (L1): I1=2.6131XRENDVI-0.4275, the XRENDVI represents red edge normalized difference vegetation index, R2 and root mean square error (RMSE) reach 0.71 and 0.20, respectively; for the second leaf from the top (L2): I5 =0.0142XTVI+0.3274, the XTVI represents triangular vegetation index, R2 and RMSE reach 0.76 and 0.09, respectively; for the third leaf from the top (L3): I9=-0.3445XARI+0.4996, the XARI represents anthocyanin reflectance index, R2 and RMSE reach 0.47 and 0.15, respectively; and for the fourth leaf from the top (L4): I10=-0.5082XARI+0.3484, R2 and RMSE reach 0.82 and 0.10, respectively. (3) The inversion model of leaf phosphorus content of cotton is constructed based on spectral variables, and the R2 and RMSE reach 0.75 and 0.04, respectively. Therefore, the leaf phosphorus content of cotton can be effectively monitored based on the correlation between leaf vegetation index and chlorophyll content at different leaf positions, and the liner relationship between chlorophyll content and leaf phosphorus content.

Key words: cotton, hyperspectrum, leaf position, chlorophyll, leaf phosphorus content