Table 9.

Coefficient of determination (R2) and root mean square error (RMSE) between the calculated vegetation indices and the nitrogen content (g m⁻²) within variation.

Vegetation Index	Year	Soil Management	N Content
			g m−2
			R2	RMSE 1
ARVI	2018	NT 2	0.80 ***	0.61
		CT 3	0.08	0.68
	2019	NT	0.73 **	1.48
		CT	0.48 *	1.53
MSAVI2	2018	NT	0.96 ***	0.28
		CT	0.70 **	0.39
	2019	NT	0.84 ***	1.15
		CT	0.42 *	1.61
NDRE	2018	NT	0.88 ***	0.47
		CT	0.59 **	0.45
	2019	NT	0.95 ***	0.62
		CT	0.76 **	0.04
VDVI	2018	NT	0.61 **	0.84
		CT	0.15	0.65
	2019	NT	0.13	1.98
		CT	0.11	2.67
WDRVI	2018	NT	0.78 **	0.64
		CT	0.01	0.71
	2019	NT	0.80 ***	1.28
		CT	0.44 *	1.59
Mean	2018	NT	0.81	0.57
		CT	0.31	0.58
	2019	NT	0.69	1.44
		CT	0.45	1.35

¹ RMSE: root mean square error; ² NT: no tillage; ³ CT: conventional tillage; *: significant at p < 0.05%; **: significant at p < 0.01%; ***: Significant at p < 0.001%.