We examined the correlation among 12 SPAD and 4 nitrogen (N) indicators in rice.
Normalized SPAD index of the fourth fully expanded leaf from top (NSI4) was selected to develop the single-stage and duration models from stem elongation to booting stages.
Two stable & general duration diagnostic models were developed between plant N accumulation (NA), N nutrition index (NNI) and NSI4.
The calibration showed the models can be used as suitable N diagnostic tools.