Fig. 9. Failure of growth stage (GS)-30 N uptake to distinguish between N deficient and N sufficient sample locations. Data are identical to those shown in Fig. 5 and 8; however, filled symbols represent sample locations with N deficiency based on the critical value of 39.5 g kg^-1 for GS-30 whole-plant N concentration (Scharf et al., 1993). Open symbols represent sample locations with sufficient N also based on 39.5 g kg^-1 for GS-30 whole-plant N concentration. (A) NDVI vs. GS-30 N uptake; (B) PredNRate_NUptakeBased calculated from GS-30 N uptake (Eq. [8]) vs. NDVI.