. 2019 Jul 23;10:948. doi: 10.3389/fpls.2019.00948

TABLE 3.

The coefficient of determination (R²) of the linear relationship between the studied vegetation indices and crop total biomass dry weight, sugar release, and theoretical ethanol yield as affected by the three temporal scenarios (TSs) studied.

	Single dates, in DAS (TS-1)^*							Combined dates^*
Bioethanol-related variable/vegetation index	94	104	119	130	143	161	175	On anthesis (TS-2)	Full crop development (TS-3)
Total biomass
Visible
ExG	0.18^*	0.22^*	0.16^*	0.15^*	0.11			0.16^*	0.17
VIgreen	0.19^*	0.23^*	0.16^*	0.19^*	0.14^*	0.27^*		0.22^*	0.23^*
TCI	0.29^*	0.30^*	0.25^*	0.17^*	0.21^*	0.15	0.33^*	0.19	0.37^*
Visible and NIR
NDVI	0.41^*	0.41^*	0.40^*	0.35^*	0.45^*	0.50^*	0.34^*	0.54^*	0.58^*
GNDVI	0.40^*	0.40^*	0.40^*	0.39^*	0.49^*	0.51^*	0.35^*	0.57^*	0.59 ^*
MCARI	0.39^*	0.39^*	0.41^*	0.39^*	0.47^*	0.48^*	0.40^*	0.41^*	0.58^*
MSR	0.30^*	0.32^*	0.37^*	0.35^*	0.40^*	0.41^*	0.41^*	0.52^*	0.56^*
Sugar release
Visible
ExG	0.29^*	0.43^*	0.45^*	0.48^*	0.47^*	0.39^*		0.57 ^*	0.51^*
VIgreen	0.28^*	0.42^*	0.43^*	0.46^*	0.46^*	0.36^*		0.52^*	0.48^*
TCI	0.18^*	0.44^*	0.47^*	0.43^*	0.39^*	0.32^*	0.12	0.52^*	0.48^*
Visible and NIR
NDVI	0.18^*	0.41^*	0.42^*	0.45^*	0.45^*	0.24^*		0.34^*	0.44^*
GNDVI	0.17^*	0.28^*	0.26^*	0.26^*	0.25^*			0.20	0.23^*
MCARI	0.16^*	0.35^*	0.33^*	0.37^*	0.45^*	0.17^*		0.37^*	0.39^*
MSR	0.13	0.29^*	0.31^*	0.32^*	0.45^*	0.22^*		0.25^*	0.39^*
Theoretical ethanol yield
Visible
ExG	0.26^*	0.35^*	0.28^*	0.27^*	0.24^*	0.21^*		0.32^*	0.32^*
VIgreen	0.27^*	0.36^*	0.28^*	0.32^*	0.27^*	0.39^*		0.37^*	0.37^*
TCI	0.36^*	0.42^*	0.37^*	0.27^*	0.32^*	0.27^*	0.33^*	0.34^*	0.51^*
Visible and NIR
NDVI	0.46^*	0.51^*	0.48^*	0.46^*	0.54^*	0.55^*	0.34^*	0.62^*	0.66 ^*
GNDVI	0.43^*	0.47^*	0.45^*	0.45^*	0.53^*	0.45^*	0.28^*	0.58^*	0.61^*
MCARI	0.45^*	0.50^*	0.50^*	0.48^*	0.54^*	0.49^*	0.35^*	0.53^*	0.65^*
MSR	0.37^*	0.42^*	0.48^*	0.44^*	0.52^*	0.48^*	0.37^*	0.57^*	0.65^*

Significant R² values at p ≤ 0.001 are marked with an asterisk, while insignificant R² values are not shown. White, gray, and black cells indicate low (R² < 0.50), moderate (0.50 ≤ R² < 0.60) and high (R² ≥ 0.60) correlations, respectively. The bold numbers and the underlined numbers enphasize the best result of each VI and each TS, respectively. ^*Dataset: 234 samples for each date of TS-1, 495 samples for the combined dates of TS-2, and 1638 samples for the combined dates of TS-3.