Applications of fluorescence sensing systems to the remote assessment of nitrogen supply in field corn (Zea mays L.)

Currently, leaf and canopy level fluorescence measurements are being explored as a means to non-destructively monitor plant productivity. Over the past few decades it has been established that changes in fluorescence characteristics of green vegetation can relate to both anthropogenic and naturally occurring plant stresses. The following studies were conducted to better define changes in fluorescence properties of field grown corn (Zea mays L.) as they relate to varying levels of nitrogen fertilization. Nitrogen was supplied in the form of urea at varying rates to obtain levels corresponding to 150, 125, 100, 75, 50, 25, 0% of the nitrogen required for optimal growth. The recommended rate for nitrogen fertilization on the field site consisting of a Codrous sandy loam soil was determined by the soil testing laboratory at the University of Maryland to be 162 kg N/ha. The field site consisted of seven nitrogen treatments in four randomized complete blocks. Fluorescence spectral measurements were obtained from the uppermost fully expanded leaves at the grain fill stage of growth. Florescence measurements were compared with the following physiological parameters: rate of photosynthesis, elemental composition, pigment and protein concentration, and grain yield. The goals of this study were to characterize leaf level fluorescence emissions as they relate physiological changes within the plant in response to nitrogen supply. Ultimately, this research is directed toward providing a remote non-destructive technique to distinguish inadequate and over fertilization of corn crops with nitrogen fertilizers.