Table 4 Statistics of the calibration and validation results for estimating leaf nitrogen concentration (LNC, g kg ^-1 ) and SPAD with color index b ^* , SPAD and days after transplanting (DAT)

Calibration

Model 1 LNC = αSPAD + βDAT + γ

1.02 ± 0.07

-0.31 ± 0.01

7.01 ± 2.95

3.07 g kg^-1

0.78

Model 2 LNC = αb^* + βDAT + γ

-0.67 ± 0.06

-0.29 ± 0.01

69.27 ± 2.10

3.36 g kg^-1

0.71

Model 3 SPAD = αb^* + βDAT + γ

-0.60 ± 0.04

0.024 ± 0.007

59.66 ± 1.14

1.62

0.55

Model 4 SPAD = αb^* + γ

-0.60 ± 0.04

60.70 ± 1.12

1.62

0.53

Validation

Model 1

2.43 g kg^-1

0.75

1.19%

Model 2

2.59 g kg^-1

0.62

-1.32%

Model 3

2.01

0.46

-1.94%

Model 4

1.89

0.47

-2.00%