Fig 1.
Experimental plots and total cultivars of kenaf used in this study.
Table 1.
UAV aerial images acquisition during growing seasons (June to August).
Table 2.
Parameters of the Pix4D processing used in this study.
Fig 2.
(A) Calibration targets within the experimental field; (B) Standard reflectance spectrum of the calibration targets; (C) Empirical Line Method (ELM) sample of the red, green and blue band mounted on the UAV (22 June 2019).
Table 3.
Results of the exponential regression model on each flight date.
Table 4.
Formulas of vegetation indices.
Fig 3.
Growth of kenaf (Hibiscus cannabinus L.) entry traits affecting biomass production at two different growth stages.
(A) Surface of the individual plant (cm2), (B) Expected plant height (mm), (C) Stem diameter (mm), and (D) Number of nodes of 20 kenaf entries at two different growth stages. Set 1 and Set 2 measured June 22 and August 31.
Fig 4.
Variation of traits among kenaf (Hibiscus cannabinus L.) entry two growth stage.
(A) Surface of the individual plant (cm2), (B) Expected plant height (mm), (C) Stem diameter (mm), and (D) Number of nodes of 20 kenaf entries at two different growth stages. Set 1 and Set 2 measured June 22 and August 31. The black bar and letter represent set 1, and the grey bar and letter represent set 2. Different letters on the bar are significantly different by Dunn test with Bonferroni adjustment. Non-parametric rank data were used for the statistical analysis; however, untransformed data are represented.
Table 5.
Kruskal-Wallis rank sum test at two growth stages.
Fig 5.
VIs of 20 kenaf entries at two different growth stages.
(A) EXG, (B) EXGR, (C) EXR, (D) GLI, (E) NDI, and (F) VARI of 20 kenaf entries at two different growth stages. Set 1 and Set 2 measured June 22 and August 31.
Fig 6.
Variation of VIs among kenaf (Hibiscus cannabinus L.) entry two growth stage.
(A) EXG, (B) EXGR, (C) EXR, (D) GLI, (E) NDI, and (F) VARI of 20 kenaf cultivars at two different growth stages. Set 1 and Set 2 measured June 22 and August 31. The black bar and letter represent set 1, and the grey bar and letter represent set 2. Different letters on the bar are significantly different by Dunn test with Bonferroni adjustment. Non-parametric rank data were used for the statistical analysis; however, untransformed data are represented.
Table 6.
Spearman’s rank correlation among surface of an individual plant, estimated plant height, actual plant height, stem diameter, number of nodes, EXG, EXGR, EXR, GLI, NDI, and VARI in kenaf germplasm at two growth stages.
Fig 7.
PCA analysis of 20 kenaf entries at two different growth stages.
(A) PCA analysis by surface of individual plant, expected plant height, stem diameter, number of nodes, EXG, EXGR, EXR, GLI, NDI, and VARI; (B) PCA analysis by surface of individual plant, expected plant height, stem diameter, and number of nodes; (C) PCA analysis by EXG, EXGR, EXR, GLI, NDI, and VARI. Set 1, and set 2 measured June 22, and August 31.
Table 7.
The eigenvalues of the correlation matrix for four Growth Traits (GT) and 5 RGB-based growth index (RGB-VI) on 20 entries of kenaf.