In-season variable rate nitrogen fertilizer application needs a fast and efficient determination of nitrogen status in crops. Common sensor-based monitoring of nitrogen status mainly relies on tractor mounted active or passive sensors. Over the last few years, researchers tested different sensors and indicated the potential of in-season monitoring of nitrogen status by unmanned aerial vehicles (UAVs) in various crops. However, the UAV-platforms and the available sensors are not yet accepted to monitor nitrogen status in farm practice. This study compares tractor-based spectrometer measurements with measurements from a UAV to assess the potential in estimating N uptake. Sensors on both platforms were technically identical. The UAV sensor was adapted to a UAV platform and its payload restriction. The sensors measured the reflectance in the spectral wavelength domain of 600-1100 nm and with a spectral resolution of 10 nm. Measurements were taken in a winter wheat field, which was split into 12 differently fertilized treatments. At three crop growth stages in 2015 (BBCH 31, 49, 59) crop scans were conducted, accompanied by destructive biomass samples to determine aboveground plant N uptake. Spectra from both sensing platforms showed comparable characteristics. Similar correlations between N uptake and a Simple Ratio vegetation index (SR) were observed for both platforms across the three growth stages, whereas the commonly observed saturation of the Normalized Difference Vegetation Index (NDVI) was less pronounced for the UAV based sensor with nadir view, resulting in a better correlation with N uptake compared to an NDVI calculated from tractor-based sensor spectra obtained at oblique view. The differences in explained variability between the systems were due to the different sensor viewing angles and footprints. N uptake can be monitored by spectral reflectance measurements with an acceptable accuracy for farming practice, irrespective of the platform (UAV or tractor-mounted) and the related viewing angle. Provided that crop and growth stage specific calibrations are developed, UAV-based spectral crop sensing, therefore, has the potential to supplement tractor based sensing where required.