Dual-Platform Comparison of Canopy Reflectance on Corn Whole Plant and Leaf Tissue Nitrogen Status and Grain Yield.

The U.S. planted approximately 38 million hectares of corn in 2016; of this acreage 97% received fertilizer N inputs averaging 162.5 kg/ha. Alluvial soils typically vary spatially in residual available soil N due to within field variability in texture and drainage. Single-rate blanket application of fertilizer N can result in an over or under application of fertilizer N. Variable rate (VR) applications of fertilizer N tailored to actual crop demands can improve N use efficiency in spatially variable fields. The objective of this study was to compare and improve relationships derived between corn canopy reflectance acquired with both tractor and aerial mounted sensors. The study plots were 12 rows (0.97m spacing) by 38.1m. Fertilizer N rates of 0 kg/ha, 89 kg/ha, 178 kg/ha, and 269 kg/ha were split applied 50% at V1-2 and 50% at V5-6 using a urea-ammonium-nitrate solution (32% N) and all treatments were replicated four times. Sensing and biophysical sampling was taken throughout the growing season for analysis and comparison to calculated VIs. Preliminary results show strong relationships between VIs calculated with both tractor and aerial mounted sensors, with the strongest relationships found using VI’s that incorporate the red edge (720 nm) wavelength. Results from this study are expected to demonstrate the utility of using remote sensing technologies to more accurately predict corn N status for eventual use in VR prescription development.