BLUE-GREEN FLUORESCENCE AND VISIBLE-INFRARED REFLECTANCE OF CORN (ZEA-MAYS L) GRAIN FOR IN-SITU FIELD DETECTION OF NITROGEN SUPPLY

The sensing of spectral attributes of corn (Zea mays L.) grain from si te specific areas of the field during the harvest process may be usefu l in managing agronomic inputs and production practices on those areas of the field in subsequent growing seasons. Eight levels of nitrogen (N) fertilization were applied to field grown corn at Beltsville, Mary land. These N treatments produced a range of chlorophyll levels, bioma ss and physiological condition in the live plant canopies. After harve st. spectra were obtained in the laboratory on whole grain samples. Fl uorescence emissions were acquired from 400 to 600 nm and percent refl ectance were measured in the visible (VIS) near infrared (NIR) and mid -infrared (MIR) regions from 400 nm to 2400 nm. A ultraviolet (UV) exc itation band centered at 385 nm was the most effective in producing fl uorescence emission differences in the blue-green region of the fluore scence spectrum with maxima centered from 430-470 nm in the blue and w ith an intense shoulder centered at around 530-560 nm in the green reg ion. Reflectance showed the most spectral differences in the NIR and M IR (970-2330 nm) regions.