Assessing UAS Mounted Imaging Sensors for the Evaluation of Zea Mays Nitrogen Status.

Improved efficiency of Nitrogen (N) fertilizer applications is an issue of importance for the agricultural community. The environmental and economic considerations of optimizing N input to yield ratios warrant research in topics including optimal timing of fertilization and effectiveness of variable rate applications for improving Nitrogen Use Efficiency (NUE). Remote sensing (RS) techniques have been shown to be able to detect the onset and spatial variability of N stress. A new generation of compact multispectral imaging sensors opens possibilities for rapid acquisition of crop imagery at high spatial resolution utilizing unmanned aircraft systems (UAS). An experiment was conducted at the Beltsville Agricultural Research Service in Maryland in which N treatment, irrigated vs rain fed, and thinned plots induced biophysical variability in the corn canopy. Biophysical and remote sensing measurements were conducted at multiple growth stages to determine the effectiveness of UAS borne RS instruments to detect this variability. UAS RS techniques can produce imagery with spatial resolutions on the order of square centimeters that can be filtered to exclude background, glare and shadow pixels. Removing this “noise” masking the signal of the plants chlorophyll status may improve results when compared to lower resolution imagery whose pixels contain a greater mixture of plant, soil, and lighting conditions. The effect of scale and potential for filtering multispectral imagery pixels that contain minimal crop information and to improve the assessment of the spatial variability of corn N status was investigated through the acquisition of UAS RS data at multiple altitudes.